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[Display omitted] The process of propane cracking in the presence of rare earth vanadites was explored. It was shown that the samples can be attributed to mesoporous catalysts, which also contain a small amount of micropores. It was revealed that the propane conversion and the yield of light olefins grew up with an increase in the molecular weight of a catalyst, while the ethylene and propylene selectivities were enhanced; the propane conversion reached a maximum value of 96.5% with ethylene and propylene selectivities of 69.4 and 26.5%, respectively, when europium vanadite was used as a catalyst. [ABSTRACT FROM AUTHOR]

Thermal cracking of complex organic matter can occur under many geological settings. However, the role of thermal cracking vs. other chemistries (e.g., metallic catalysis or Fischer-Tropsch-type reactions) in petroleum formation remains controversial. Realistic modeling of isotope effects in chemical reaction networks involving thermal cracking might shed light on this problem, especially given the recent progress on measurements of intramolecular stable isotope distributions in organic compounds. Previously published models of thermal cracking in petroleum formation are incapable of predicting the intramolecular isotope patterns of products because they do not incorporate realistic precursors, elementary reactions and patterns of inheritance. In this study, we develop a kinetic Monte-Carlo (kMC) model to address this problem. We simulate thermal breakdown of different types of organic matter that is represented by molecular models. At the onset of each simulation, we initialize the model parent organic molecules with isotopic substitutions, and then subject them to free radical chain reactions in a many-step process. Every simulation captures a possible route of thermal degradation and tallies the numbers of each unique isotopologue of all product molecules at the end. Although this model produces data that contain information for all molecules and isotopic forms, in this study we focus on the proportions of many of the isotopologues of all of the C 1 -C 7 n -alkanes. We use two chemistry schemes that differ in complexity. The basic scheme (scheme A) includes only homolytic cleavage and capping of metastable radicals by hydrogen atoms. The more sophisticated scheme (scheme B) includes most reactions of importance in the free radical chain mechanism of thermal cracking. We find significant differences between the schemes A and B in predicted molecular and isotopic compositions of products. Scheme B is more consistent with natural data than scheme A, suggesting that full radical mechanisms should be considered in models of thermal cracking in natural hydrocarbon formation. Our model is further validated by reproducing results from hydrous pyrolysis experiments. For simulating natural petroleum formation, we found that the kMC model is acceptable at low maturity, but cannot match compositions and time estimates of mature gas formation, suggesting the influence of alternative mechanisms in late-stage, high-thermal-maturity catagenesis. Using our model, we provide mechanistic explanations for some of the existing observations, such as the evolution of intramolecular and intermolecular carbon isotope compositions with thermal maturity. Our study also makes predictions of intramolecular isotope compositions for higher-order alkanes (C 4 +) that have been little studied to date but present attractive targets for future measurements. [ABSTRACT FROM AUTHOR]

• The effect of CNTs on the thermal expansion coefficient (CTE) of FSC at early age was investigated. • A time-varying model of FSC at early age CTE was developed based on maturity theory. • The time-varying CTE can reflect the actual thermal cracking situation of FSC. • The addition of 0.1 wt% CNTs can reduce the early CTE of FSC and improve its crack resistance. Temperature stresses are a major cause of thermal cracking in face slab concrete (FSC) at an early age. Time-varying coefficient of thermal expansion (CTE) can reflect the real thermal cracking of FSC. Carbon nanotubes (CNTs) can improve the mechanical properties of concrete, but its thermal cracking performance is rarely reported. In this study, CTE of FSC at an early age was investigated based on the maturity theory. The mechanism of CNTs on the CTE of FSC at early age was revealed, and a time-varying model for CTE at early age was developed. The results showed that CNTs can effectively reduce the CTE of FSC at an early age and can significantly improve the cracking resistance of FSC at early age. [ABSTRACT FROM AUTHOR]

Compared with conventional pyrolysis, microwave pyrolysis has superior heat transfer performance and promotes the decomposition of organic matter. The paper focuses on the harmless treatment and resource utilization of pharmaceutical sludge (PS) by microwave heating and conventional heating methods. The experimental results showed that the conventional pyrolysis gas is dominated by CO 2 , CO and H 2. For microwave pyrolysis gas, the "microwave effect" promoted secondary cracking of volatile fractions and increases the content of CH 4 , C x H y , H 2 and CO through condensation, aromatization, and dehydrogenation. Conventional pyrolysis oils contained the highest percentage of oxygenated compounds. However, high-temperature microwave radiation accelerated the cleavage of polar oxygenated molecular bonds and long-chain hydrocarbons, thereby increasing the aromatics content of pyrolysis oils. The solid residues obtained from microwave pyrolysis is highly graphitized and porous, with a surface area of 146.2 m2/g. Furthermore, the solid residue was rich in pyridine-N and pyrrole-N that could be utilized for adsorption and catalysis. The MA-600 removes up to 99% of tetracycline (TC) in 6 h. It was also found that the adsorption process of TC by the two pyrolysis residues was consistent with the proposed secondary and Freundlich models. [Display omitted] • Microwave pyrolysis oil has a smaller carbon number. • Hot spots and dehydrogenation are key factors in increasing C x H y yields. • Microwave pyrolysis residue surfaces are dominated by pyrrole nitrogen. • Porosity of microwave pyrolysis residues facilitates TC adsorption. [ABSTRACT FROM AUTHOR]

Several studies conducted at industrial sites have documented the infiltration of dense non-aqueous phase liquids (DNAPLs) into clay layers, a phenomenon potentially influenced by the coexistence of chemicals like surfactants in some common pollutants. Bentonite (Ben), monochlorobenzene (MCB), and Tween 80 (T80) were selected as reference components to investigate the influences of nonionic surfactants on DNAPLs migration in clays. Results showed that T80 promotes MCB dissolution and encourages MCB adsorption on Ben. This process reduces the hydrophilicity of Ben, resulting in water loss and shrinkage, which creates cracks and facilitates the migration of MCB within the clay. Tw80 notably enhances MCB solubility, as indicated by a molar solubilization ratio of 7.80. The MCB adsorption on Ben (Q MCB) displays a linear increase with raising the T80 adsorption on Ben (Q T80), especially when Q T80 are below the thresholds, e.g., 408.4 mg/g at pH 3 and 339.3 mg/g at pH 7; however, Q MCB is decreased with increasing adsorbed T80 further. The average fracture ratio, crack length, and crack width of cracked samples in the cracking experiments were 0.794%, 11.29 mm, and 0.209 mm, respectively. The findings here contribute to understanding the role of surfactants in VOC transport in contaminated sites. [Display omitted] • Tween 80 and MCB mutually enhance their adsorption onto bentonite. • Dissolved and adsorbed T80 has a competitive effect on MCB adsorption. • Upon Tween 80 or MCB adsorption, the hydrophilicity of bentonite is reduced. • Tween 80 induce cracks in bentonite to facilitate the migration of MCB. [ABSTRACT FROM AUTHOR]

In the present study, we pyrolyzed a waste tire at various temperatures under an N 2 atmosphere and a water environment in an autoclave reactor to investigate the effect of water on tire degradation. The analysis involved a comparison of product distribution, char properties, oil composition, and the behavior of heteroatom elements (especially oxygen, nitrogen, and sulfur) under different atmospheres. Elemental analysis, functional-group identification, and chemical state analysis of sulfur were performed for chars. In addition, the chemical composition, elemental composition, and molecular weight of the produced oils were evaluated. The heavy fraction of oils, not detectable by gas chromatography-mass spectrometry (GC-MS), was analyzed through Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The findings revealed that high temperatures promoted oil cracking, resulting in the formation of light oils in both pyrolysis and hydrolysis processes. Compared to pyrolysis, hydrolysis generated a higher yield of low molecular–weight oil. Elevated hydrolysis temperatures promoted aromatization, yielding an oil with a low H/C ratio and a high double bond equivalent number. Consequently, the concentration of aromatics in the light fraction of oils generated from the hydrolysis process exceeded that in oils from the pyrolysis process. Temperature exhibited a limited impact on oil composition during the pyrolysis process. Hydrolysis promoted the release of heteroatom-containing compounds at low temperatures. During pyrolysis, nitrogen was gradually released from the solid phase, whereas nitrogen-containing compounds were released early during hydrolysis, with gas-phase nitrogen accounting for more than 50 wt% at 320 °C. A maximum D-limonene yield of 45.58% was obtained at 360 °C within 0 min of hydrolysis, with the potential conversion of D-limonene into aromatics at higher hydrolysis temperatures. These results contribute to the understanding of tire valorization via hydrolysis. [Display omitted] • Higher temperatures can promote the formation of aromatics. • Hydrolysis promote the early release of nitrogen-containing compounds. • Higher hydrolysis temperatures can promote the formation of sulfide. • Temperature has a weak effect on oil composition for pyrolysis process. • Extensive of NxOy, NxOySz, NxSy, Nx and Ox classes formed. [ABSTRACT FROM AUTHOR]

This study quantitatively and fundamentally evaluated the effects of B and Hf on weld solidification cracking susceptibility for 247LC superalloy, and the behavior was compared with that of 247LC's original composition. To this end, the transverse-Varestraint test was performed by measuring the cracking temperature during weld solidification. The solidification brittle temperature range (BTR) values of the Boron (B)- and Hafnium (Hf)-free 247LC alloys were 206 and 172 K, respectively, which were significantly lower than that of the original 247LC alloy (400 K). Contrastingly, the minimum strain for solidification cracking ε min was similar in both alloys. The metallurgical mechanism for the largely reduced BTR (from 400 K to 172 K) was elucidated especially for the Hf-free 247LC alloy, which was highly dependent on its weld mushy zone range (170 K) calculated by non-equilibrium weld solidification. It was attributed to the suppression of carbide (MC + M 23 C 6) formation for Hf-free 247LC (area fraction: 0.15%) as compared with that of 247LC (area fraction: 4.72%) by direct identifying the solidification cracking surfaces. • Solidification cracking susceptibilities of 247LC and Hf,B-free alloys studied. • Brittle temperature range (BTR) reduced from 400 K to 170 K by nonaddition of Hf. • The reduced BTR attributed to suppressed carbide formation. [ABSTRACT FROM AUTHOR]

Recently, sp2-hybridized single-layer SiC, analogous to graphene, has received much attention in nanoelectronics and nanoelectromechanical systems because of its remarkable thermal, electrical, and mechanical properties. However, the unique properties and related applications strongly depend on the growth of a single-crystal and large-area two-dimensional SiC. The majority of synthesized SiC monolayers exhibit a natural polycrystalline structure, comprising single-crystalline grains with diverse sizes and orientations. Moreover, the emergence of structural defects, including cracks and notches, poses challenges that are difficult to overcome during both the fabrication and subsequent processing stages. In this paper, we explore the atomistic details of grain, crack, and notch effect on the mechanical behaviors and fracture mechanisms of single-layer SiC using molecular dynamics simulations. Increasing grain size from 2 nm to 35 nm gradually increases the elastic modulus and fracture strength, which fits well with the inverse Pseudo Hall-Petch relationship. However, an anomalous trend of decreasing as well as increasing fracture strain is observed with the increasing grain size. For polycrystalline SiC with a 2 nm grain size, the elastic modulus and fracture strength are roughly 87% and 41% of those observed in single-crystalline SiC. Notably, when comparing the impact of rectangular crack and circular notch defects, the circular notch exhibited a more pronounced effect in diminishing mechanical behavior under both armchair and zigzag orientational loading. The circular notch produces considerable amorphization around the notch, but the rectangular crack does not show any significant dislocation or amorphization around the crack. The critical stress intensity factor, energy release rate, radial distribution function, and potential energy per atom are calculated to explain all the fracture properties. The effect of temperature and strain rate is also investigated for all the defect-induced samples. Overall, our results provide new insight and understanding of the mechanical behavior and fracture mechanisms of polycrystalline, crack- and notch-induced SiC, and set a standard for making and designing new nanodevices and nanostructures made of SiC. [Display omitted] • Grain, crack, and notch effects on the mechanical behavior of 2D SiC are studied. • The MEAM potential is used to describe the atomistic interactions of monolayer SiC. • 2D SiC shows an inverse pseudo-hall-petch relation with increasing grain size. • Notch creates a higher decrease in mechanical properties than crack defects. • Fracture toughness and energy release rate are estimated to define defect actions. [ABSTRACT FROM AUTHOR]

A major drawback in the application of AlCoCrFeNiCu high-entropy alloy (HEA) coatings is a susceptibility to hot-cracking, which is closely related to a grain boundary segregation due to the low melting point Cu component. Reducing or eliminating the grain boundary segregation of Cu is an effective means of reducing cracking in the HEA coating. In this study, blended and partial pre-alloyed powders were used as feedstock to fabricate the AlCoCrFeNiCu coating. The application of electron beam (EB) cladding to partial pre-alloyed powders, prepared by resistance seam welding (RSEW), resulted in an appreciable reduction of crack density in the coating. This response is attributed to the formation of Ni 3 Al and Al 4 Cu 9 promoted by the relatively low heat generated during the RSEW process. In subsequent EB cladding, nanoscale Me 3 Al (Me = Cu, Ni) replaced the Cu-rich phase at grain boundaries. The hardness and wear resistance of coatings using partially pre-alloyed powders were 17.2 % and 15.8 % higher, respectively, than blended powders. The findings of this study indicate that the use of partial pre-alloyed powders can offer a new effective approach to reducing the hot cracks in EB cladding AlCoCrFeNiCu HEA coatings. [Display omitted] • AlCoCrFeNiCu coatings were fabricated by blended and partial pre-alloyed powders. • Cracks were reduced using partial pre-alloyed powders by electron beam cladding. • Ni 3 Al and Al 4 Cu 9 phases reduced the interdendritic segregation of Cu in RE coatings. • Wear resistance of RE coating was optimal 20.4 % higher than EB coating. [ABSTRACT FROM AUTHOR]

In this study, anodized aluminum oxide (AAO) films were fabricated in situ on the surface of a high-strength and robust 2024 aluminum alloy using step voltage and constant voltage modes, respectively. Our study included examination of the microstructure, thickness, microhardness, and electrochemical characteristics of the AAO films. Cross-sectional morphology analysis revealed that the AAO film produced via the step-voltage approach exhibited remarkable density, uniformity, and good quality. In contrast, conspicuous cracks were observed in the AAO film generated under constant-voltage conditions when applied to the 2024 aluminum alloy substrate. Notably, the microhardness of the AAO film prepared using the step voltage method surpassed that of its constant-voltage counterpart. Specifically, the microhardness of the AAO film produced at 30 V via the step voltage reached 289 HV, whereas the equivalent AAO film produced at a constant voltage of 30 V registered only 174 HV. Furthermore, the self-corrosion potential and polarization resistance of the AAO films created using the step voltage were markedly higher than those achieved using a constant voltage. Specifically, the AAO films produced under step voltage conditions, specifically at 30 V and 60 min, exhibited the highest self-corrosion potential and polarization resistance values of namely −0.52 V and 34,888.6 Ω, respectively. In contrast, AAO films prepared under constant voltage conditions displayed values of −0.61 V and 23,292.0 Ω, respectively. Conducting AC impedance measurements and subsequent fitting calculations, the maximum thickness of the AAO film generated via step voltage and constant voltage methods amounted to 132.43 nm and 106.70 nm, respectively. Overall, the microstructure and corrosion resistance of the AAO film formed on the surface of the 2024 aluminum alloy using the step voltage approach demonstrated that it outperformed that of the AAO layer prepared under constant-voltage conditions. Chinese library classification number:TG178 Document ID:A Article ID. • A new method and new idea for preparing anodic oxide film on aluminum alloy surface were explored. • Anodic oxide film produced using the step voltage approach exhibited a dense and uniform microstructure, forming a strong bond with the 2024 aluminum alloy substrate. • Anodic oxide film prepared the step voltage method exhibited a thinner thickness while demonstrating higher microhardness. • The corrosion resistance of the anodic oxide film prepared using the step voltage technique substantially exceeded that of the film produced using constant voltage. [ABSTRACT FROM AUTHOR]

Highlights • Hydrocracking and hydrotreating reactions kinetics are based on lumping technique. • The industrial model is validated with the performance of an experimental reactor. • Axial and radial dispersions are used to represent the slurry-phase reactor dynamic's. • Dynamic and steady-state simulations for hydrocracking of heavy oils are presented. • A sensitivity analysis of model parameters and operating conditions is presented. Abstract Modeling and simulation of a commercial size unit for hydrocracking of an atmospheric residue (312 °C+) in a slurry-phase reactor are reported. The model of the industrial reactor is formulated taking into account axial and radial gradients of the state variables: composition and temperature. The mathematical model was partially discretized with finite central differences in the positional derivatives generating a matrix system of ordinary differential equations which was solved by a Runge-Kutta method. The hydrocracking reaction kinetic model is based on lumping technique and hydrotreating reactions kinetics are described by Langmuir-Hinshelwood and power-law approaches. All the intrinsic kinetic parameters and correlations used in the simulations were taken from the literature. Dynamic and steady-state simulations were performed with the objective to find a distribution of composition and temperature in the reactor as a function of time. Also a parametric sensitivity study was elaborated in order to analyze the effects of uncertainties of model parameters in the dynamic and steady-state model responses. [ABSTRACT FROM AUTHOR]

Highlights • Effect of wall-effect, and fibre orientation and content on tensile strength of SFRC. • MCST is a multi-axial cube splitting test used to get post-crack properties of SFRC. • An approach for the determination of fibre orientation using MCST is proposed. • MCST method was verified to be a good method of determining the orientation of fibre. Abstract The post-cracking behaviour of steel fibre reinforced concrete (SFRC) are significantly influenced by the distribution of steel fibre in the concrete, while steel fibre distribution is further affected by wall-effect and fibre content. A series of three-point bending tests, cube splitting tests, and Brazilian splitting tests were conducted to analyze the influence of wall-effect and fibre content on the post-cracking tensile strength of SFRC. Furthermore, the influence of wall-effect and fibre content on fibre distribution was determined by conducting inductive tests on cubic SFRC specimens. To directly determine the relationship between fibre content and orientation, and the post-cracking mechanical properties of SFRC, this paper proposes a multi-axial cube splitting test (MCST test). Furthermore, this paper also proposes a method which utilizes the MCST test to measure fibre orientation based on the relationship between post-cracking peak load and toughness, and steel fibre orientation. Therefore, MCST method can be adapted for using with any type of fibre reinforced concrete, while the inductive test can only be used for concrete that is reinforced with metallic fibre. The MCST method is verified by comparing the similarity of the fibre orientations that were obtained using the inductive tests and MCST tests. [ABSTRACT FROM AUTHOR]

Highlights • A novel hierarchical millisecond gas-phase catalytic cracking process was proposed. • Five catalysts were compared to study the selectivity of C 2 -C 4 hydrocarbons and BTX. • The maximum light olefins yield was obtained with 30% calcium aluminat/70% ZSM-5. • A bench-scale was used to verify the potential application of VR to chemicals. Abstract In order to enhance the production of light olefins from vacuum residue (VR), a novel hierarchical millisecond gas-phase catalytic cracking (HM-GCC) process was proposed. The process integrated the pyrolysis of VR and the catalytic cracking of the pyrolysis oil in the gas phase. Firstly, the effects of reaction temperature on the millisecond pyrolysis behavior of VR were investigated, and the results showed that the increase of C 2 -C 4 hydrocarbons content was not obvious when increasing the temperature from 600 to 750 °C. However, the thermal cracking as a pretreatment process converted the VR macromolecule into the low molecular pyrolysis oil. After that, five different catalysts calcium aluminate, FCC catalyst, and ZSM-5 zeolites (Z-40, Z-80, and Z-200) were investigated to evaluate their activities in catalytic cracking of pyrolysis oil, and among them Z-40 showed the highest selectivity for C 2 -C 4 hydrocarbons and BTX. For further study, the relative contents of C 2 -C 4 hydrocarbons were higher for the combination of calcium aluminate and Z-40 (Z + C-cat) than that of the pure Z-40 catalyst. This result was attributed to the fact that Z + C-cat facilitated the cracking of macromolecules and inhibited hydrogen transfer reactions. Finally, the conversion of VR and pyrolysis oil was studied in the bench scales with calcium aluminate and Z-40 catalyst. The yield of ethylene, propylene and butenes increased by 4.69, 7.87 and 3.37 wt% respectively in the presence of Z-40. [ABSTRACT FROM AUTHOR]

Highlights • Enhancing cracking process based on synergy improvement among radial field profiles. • Quantitatively analyzing the suitable arrangement of internals based on fluid mechanics principle. • A novel concept of mass transfer synergy angle was derived to explain the mass transfer enhancing mechanism. Abstract A novel insert-hollow cross disk (HCD) combined with twisted tape is embedded in a cracking coil to enhance the propane cracking process by positive constructing of synergetic flowing field. Quantitative analysis of appropriate insert arrangement has been conducted based on contrastive CFD simulation results in the bare and novel coil. The characteristic exchanging flow between the central zone and the near wall area induced by inserts in the novel coil can play an effective role in improving the radial synergy among heat, mass and velocity. This leads to an obvious yield increase of 0.50% and 10.23% of ethylene and propylene comparing with the bare coil. And the average tube skin temperature is declined by 28.45 k. Moreover, the Nu and Sh are increased by 10.96% and 2.98% respectively and the overall PEC factor has a rise of 8.00% in the novel coil. This confirms the effective strengthening effect by the novel coil. Furthermore, the field synergy theory is applied to evaluate the synergy improvement for the heat and mass transfer process. Comparing with the bare coil, the synergy angles for heat as well as mass transfer in the novel coil have a maximum decrease of 21.76% and 23.14% in the downstream of the twisted tape (z/L = 0.23) and HCD insert (z/L = 0.60), respectively. This could explain the enhanced heat and mass transfer as well as the product distribution due to the synergic flow field in the novel coil with the assemble inserts group. [ABSTRACT FROM AUTHOR]

Highlights • A new six-lump kinetics scheme was developed. • New six-lump activation energies, frequency factors and heat of reactions developed. • The estimated parameters can be used to simulate any type of FCC riser. Abstract In this work a simulation of detailed steady state model of an industrial fluid catalytic cracking (FCC) unit with a newly proposed six-lumped kinetic model which cracks gas oil into diesel, gasoline, liquefied petroleum gas (LPG), dry gas and coke. Frequency factors, activation energies and heats of reaction for the catalytic cracking kinetics and a number of model parameters were estimated using a model based parameter estimation technique along with data from an industrial FCC unit in Sudan. The estimated parameters were used to predict the major riser fractions; diesel as 0.1842 kg-lump/kg-feed with a 0.81% error while gasoline as 0.4863 kg-lump/kg-feed with a 2.71% error compared with the plant data. Thus, with good confidence, the developed kinetic model is able to simulate any type of FCC riser with six-lump model as catalyst-to-oil (C/O) ratios were varied and the results predicted the typical riser profiles. [ABSTRACT FROM AUTHOR]

Highlights • The two breakdown types of coal by HVEP in air environment were found. • Liquid nitrogen adsorption, SEM and 3D-XRM results suggest that HVEP is a potential method for CBM extraction. • A new method for fracturing and permeability enhancing is proposed combining with the hydraulic fracturing and HVEP. Abstract In order to enhance the gas extraction rate of low-permeability coal seams, a study was made on variation characteristics of pore structure of the coal saturated by NaCl solution under the effect of high-voltage electrical pulses (HVEP) by adopting a self-designed experimental system of fracturing and permeability enhancing of the coal with HVEP. In addition, current waveforms in the process of electrical breakdown were also investigated. The results revealed the two types of electrical breakdown of the coal in air environment, namely, surface breakdown and internal breakdown with three forms of breakage, namely, complete comminution, breakage from one side and cracks on the surface. Furthermore, the coal was broken due to internal tension under the influence of HVEP. Based on energy dispersive spectroscopy (EDS) analysis, the coal underwent both physical and chemical changes where the current flowed. Results of scanning electron microscope (SEM) demonstrated that the higher the breakdown voltage, the more the fissures in coal, and the better the breakage effect. Fissures in the coal were observed via the 3D-XRM to extend radially from the center to boundary areas with the breakage effect weakening gradually from anode to cathode when needle electrode discharged. Besides, these fissures were interconnected with each other. The result of liquid nitrogen adsorption suggested that electrical breakdown could effectively boost gas desorption by improving fissures as well as pores and micropores in the coal. Characteristics of the current waveform showed that great thermal expansion stress was caused by huge energy injected into the coal in an instant. During the electrical breakdown of coal with the same voltage, the peak current was different which increased with the growing of breakdown voltage. [ABSTRACT FROM AUTHOR]

Abstract The main purpose of this study is to elucidate the effect of catalyst on asphaltene molecular structure during hydrocracking of C 5 -isolated asphaltene. Remained asphaltene and coke were obtained after hydrothermal and catalytic hydrothermal cracking of C 5 -isolated asphaltene at 380–430 °C, using 1000 ppm Mo from Mo-octoate precursor. XRD and NMR analyses were used to investigate the change of molecular structure of asphaltene during the reaction. It was revealed that aggregation of asphaltene increased with increasing the reaction severity resulted in coke formation. The presence of catalyst reduced the aggregation of asphaltene molecules in comparison with the hydrothermal cracking. It was also observed that the average number of stacked polyaromatic sheets in the remained asphaltene decreased with increasing the reaction temperature because of the transformation of high stacked asphaltene into coke during the reaction. Moreover, it was confirmed that the main reason for asphaltene aggregation was the reduction of steric hindrance of asphaltene molecules by the change in molecular structure of asphaltenes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Development of a novel cracking catalyst for deoxygenation from earth abundant kaolin. • Characterization of the deoxygenation active sites on catalyst for the first time. • Correlation of the catalyst deoxygenation ability to its density of weak Lewis acids. • Study of the effects of density of Bronsted acids on triglyceride dehydrogenation. • The total amount of Bronsted acids determines the cracking capability of a catalyst. Abstract This work presents a cost-effective abundant kaolin-based cracking catalyst that has high deoxygenation, mild cracking, and low dehydrogenation performances for waste cooking oil (WCO) upgraded into organic liquid products (OLPs). Acid treated kaolin (ATK) exhibited high yield of 74.4% and high quality liquid products with high oxygen removal of 93.8% and low aromatic contents of 22.5%. The reference catalyst, a commercial petroleum catalyst (CC) could eliminate the most of oxygen (90.8%) but produced too many unexpected aromatics (55.8%). The density of weak Lewis acids was related to the deoxygenation capability. The density of Bronsted acids contributed to hydrogen transfer reactions. The total amount of Bronsted acids was correlated to cracking capability. The cracking by CC primarily followed carbonium ion reaction mechanism, whereas those by the kaolin-based catalysts complied more with free radical reaction mechanism. The deoxygenation active sites were characterized by CH 3 COOH-TPD for the first time. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Heat transfer performance is investigated at the presence of hollow-cross disk as a vortex generator for the cracking coil. • The vortical flow induced by HCD couples with CVPs and hairpin-like vortex, efficiently enhancing the heat transfer locally and globally. • The heat transfer mechanism is studied by field synergy theory, which indicates superior synergy near the wall weighs higher for the cracking flow. Abstract A novel comprehensive vortex generator, hollow-cross disk (HCD) which comprises a special sinusoidal wave structure, has been proposed to modify the configuration for cracking coil. The effects of HCD on the turbulent flow patterns, heat transfer characteristics and micro-mixing efficiency of the flow are investigated by CFD modelling in the present work. The numerical results demonstrate that in the test range of flow rates, the vorticial flow induced by HCD couples with CVPs and hairpin-like vortex, efficiently enhancing the convective heat transfer locally and globally. In contrast, although the global swirling flow induced by a twisted-tape can enhance the turbulence intensity, larger pressure drop taking place in the coil leads to relatively poor comprehensive heat transfer performance and lower micro-mixing efficiency. Moreover, the mechanisms of heat transfer enhancement for the cases with inserts have been investigated by the synergy regulation and the synergy between the temperature gradient and velocity has been discussed. The results indicate that better synergy occurring in the vicinity of coil surface is a key factor to enhance heat transfer for the cracking process. The obtained results can be used as a guidance for the design and optimization of the inserts for the cracking process. [ABSTRACT FROM AUTHOR]

Abstract The paper examines the proposed approach of using T-matrix model to convert dynamic moduli (Young's modulus and Poisson's ratio) determined by sonic well logging to values equivalent to values of static moduli (called effective moduli). The chosen approach is particularly suitable for rock masses consisting of solid rocks with irregular local cracking. The proposed approach is based on the fact that for intact rock with Young's modulus values on the order of several tens of GPa and strength σ c on the order of several tens of MPa, the values of static and dynamic moduli are equivalent. Any fractures in the rock will cause the elastic behaviour to cease being linear and a difference will appear between the values of static and dynamic moduli. It is possible to approximate this difference using the T-matrix model. The starting point for creating a T-matrix model is a simplified layered geological model of a borehole profile. Added to this are values of static moduli determined by a uniaxial compression test on representative samples of the borehole core. Additional input data for calculating the T-matrix model include porosity determined from well logging measurements, and the presence of cracks as interpreted from an acoustic scan of the borehole wall. The given approach is demonstrated in the experimental measurement of a borehole in Silurian limestone. The procedure was verified by comparing the calculated effective moduli with values of static moduli, measured on control samples prepared from borehole core outside the collection intervals of samples used as input for calculation of the T-matrix model. This comparison showed that for majority of samples there was a decrease in the difference from nearly 40% (dynamic moduli) to under 10% (effective moduli). Highlights • Use of a T-matrix model made it possible to approximate static moduli from dynamic moduli. • The curves calculated by the model are significantly more detailed than the original well logging. • The calculated effective values can be used for calculations instead of the static values. [ABSTRACT FROM AUTHOR]

Highlights • Large number of scenarios (10) shows impact of various practical variations. • Broad bandwidth of production cost; choice of vegetable oil being the most decisive. • Power-to-gas adds 26–34% to costs compared to conventional hydrogen provision. • High cracking rate for jet leads to high production of low-value hydrocarbons. • Diesel-mode is 30% cheaper than jet-mode. Abstract A techno-economic assessment of a novel biorefinery concept is carried out. It combines the hydrotreatment of vegetable oils (HEFA) with a power-to-gas (PTG) unit that provides the required hydrogen. Several scenarios are examined: the electricity supply for the PTG unit is varied from a grid-based supply to a renewable island solution; the hydrogen supply is varied from a PTG unit to conventional steam reforming; the utilised vegetable oil is varied from jatropha to rapeseed, palm and used cooking oil; the main product is varied from jet fuel to diesel. The HEFA-plant is assumed to process 500 kt of vegetable oil annually. In the reference scenario, jatropha oil is used as feedstock producing 227 kt a−1 of jet fuel. Per ton of processed oil, 1910 kWh el are used to produce 35.7 kg of hydrogen required for its treatment. By using different vegetable oils, both hydrogen demand and fuel output vary in a range of about ±10%. The overall energetic efficiency towards jet fuel is 41.6%. With a bandwidth between 1295 and 1800 EUR t−1 of jet fuel, the specific production costs are three to four times higher than the market price for fossil jet fuel. Operating the refinery in diesel-mode could lower the production costs by ca. 30%. More high-value, long-chained fuels are produced this way due to a lower cracking rate compared to the jet-mode. Investments of around 132 million EUR are required for the HEFA-plant in all scenarios. Investments for the PTG-plant lie around 82 million EUR if there is a constant electricity supply from the grid. They reach 246 million EUR if electricity is supplied in an island-solution based on fluctuating renewables demanding much higher hydrogen production and storage capacities. Total investments in the biorefinery reach 378 million EUR in this case. Despite high capital costs, the largest cost item is vegetable oil – similarly to a conventional HEFA plant. Supporting policy instruments such as subsidies or quotas for renewable jet fuel seem indispensable for an introduction of the PTG-HEFA technology in the short to medium term. [ABSTRACT FROM AUTHOR]

Abstract Steam crackers convert hydrocarbon feedstock (e.g., natural gas liquids) to light olefins via thermal cracking and produce hydrogen as a by-product during the process. Benefiting from the shale gas boom in recent years, the overall production capacity of U.S. steam crackers, as well as the potential of by-product hydrogen production, is continuously growing. We estimate that 3.5 million tonne/year of by-product hydrogen can be produced from steam crackers, almost doubling the size of the existing U.S. merchant hydrogen market. We also find that producing hydrogen from steam crackers creates less (15%–91%) life-cycle greenhouse gas emissions than the conventional centralized steam methane reforming (SMR) pathway. For criteria air pollutants, life-cycle emissions reduction benefits vary greatly (−75% – +85%), depending on the co-product treatment scenario (substitution or allocation) and air pollutant type. The substitution scenario generally results in an increase of criteria air pollutants emissions, mainly due to the requirement of substitutive natural gas fuel. We estimate that the cost of purified by-product hydrogen fuel from steam crackers is $0.9–1.1/kg, reducing hydrogen production costs by 30% compared to the conventional central SMR pathway. Furthermore, using by-product hydrogen from steam crackers can generate credits of $1.8–2.5/kg under California's low-carbon fuel standard. Graphical abstract Image 1 Highlights • By-product hydrogen production capacity from steam crackers: 3.5 million tonne/year. • Cost of by-product hydrogen from steam crackers is lower compared to steam methane reforming. • Different co-product allocation methods (mass and market value) are evaluated. • Using by-product hydrogen from steam crackers provides greenhouse gas emission reductions. • Criteria air pollutants emission reduction benefits depend on allocation approach. [ABSTRACT FROM AUTHOR]

With the increasing interest in unconventional resource plays, there have been important changes in the way how reservoirs and their attributes are assessed and characterized. Of particular relevance to the development of unconventional plays has been the focus on the assessment of organic porosity. A review of the available literature reveals contradictions with respect to where organic porosity develops (kerogen, bitumen, or pyrobitumen), when it develops with respect to hydrocarbon generation and cracking (within the oil window or beyond), its mode of formation (inherited or authigenic), the influence of organic carbon content, and the importance of organic porosity with respect to hydrocarbon storage and production. Many of these apparent contradictions appear to result from the nature of the data sets upon which the studies are based. Organic pore size generally limits the role that organic porosity plays in liquid-rich plays. From the available literature, it has become clear that there are number of issues that need to be clarified when addressing organic porosity. One such issue is terminology. There appears to be confusion in the usage of the terms kerogen, bitumen, and pyrobitumen. This confusion exists in the literature and reports prepared by various service providers for those engaged in the exploration and exploitation of unconventional resources. Another issue is the observed differences in the morphology of the organic pores (e.g., spongy, isolated bubbles, or fractures). Differences in pore morphology indicate multiple mechanisms for formation and/or growth of organic pores, suggesting more complexity to organic porosity development than often implied. For example, the spongy appearance of organic pores in some systems could reflect the amorphous character of some oil-prone kerogen, whereas the bubble pore character could be the result of degassing during the transition from the oil window into the gas window or an artifact of decompression and degassing as bitumen solidifies during core retrieval. Similarly, fractures could be a result of the conversion of oil to gas and the inability of the gas to escape or could be desiccation cracks, possibly formed after sample retrieval. Organic pores, if present in situ, increase space for hydrocarbon storage and increase surface area resulting in higher absorption capacity. However, the connectivity of these pores may be somewhat limited and may be dependent on the nature of the organic network, thus limiting their impact on permeability. A challenge when studying organic porosity is its observed variability within an individual reservoir. Very different spatial distribution of pores can occur between adjacent organic particles (e.g., macerals, solid bitumen) as well as within individual “macerals”. It has been suggested that this could be, in part, a result of organic–inorganic interactions although alternative interpretations have also been proposed. Further complicating the scientific understanding of organic porosity is the possibility that the act of studying the samples containing these pores may result in alteration of the rocks and the pores themselves. Therefore, observed organic pores may not be reflective of native conditions. The lack of a clear understanding of organic porosity development in unconventional mudstone reservoirs is by no means a surprise. Porosity and its development in conventional reservoirs have been studied since Sorby began the examination of sandstone thin sections in 1850 and is still under examination, while organic porosity has been studied for less than a decade. The focus of this study is to provide a review of porosity associated with the organic fraction, which may, in some shale-reservoirs, play a key role in hydrocarbon storage, migration, and production. [ABSTRACT FROM AUTHOR]

A thermal cracking experimental equipment of hydrocarbon fuels was built to study n-heptane pyrolysis and the effect of reaction conditions on this reaction process. The main species were measured and the change rules were analyzed on the range of temperature 873–1073 K and pressure 0.1–3.5 MPa. The total content of alkenes products was more than alkanes on this pyrolysis process. Compared to alkenes with same number carbons, the alkanes were more easy to decompose with temperature but more conducive to formation with pressure increasing. The content of ethylene is usually the most on above reaction conditions, but its descent is also the fastest with pressure increasing. A mechanism model of n-heptane pyrolysis (44 species and 166 reactions) was constructed and validated by experiments on different conditions. Compared with n-heptane oxidation detailed model of Version 3.1 from Lawrence Livermore National Laboratory (LLNL), the pyrolysis model present a better accordant with experiment results on a range of temperature and pressure. The kinetic reaction of n-heptane pyrolysis was analyzed with present pyrolysis model, and the pyrolysis reaction pathway for the main products was obtained. The formation of alkenes are mainly through C C bond dissociation reaction, especiallyβ-C dissociation, and small alkanes are formed mainly by radical metathetical or synthesis reaction, the former are endothermic reactions, but the latter are mostly exothermal reactions. The properties of some main reactions have a critical role for the change of product content with temperature and pressure, which is the main reason for the variety of products selectivity under different conditions. Pressure increased the pyrolysis residence time and mass density but it does not significantly affect the reaction energy, so its contribution to conversion rate of fuels thermal cracking is limited, although it changes the reaction pathway greatly. However, the temperature can increase obviously the reaction activation energy, even though the residence time and concentration is decreased, the conversion rate of n-heptane pyrolysis still increased. [ABSTRACT FROM AUTHOR]

In order to improve the quality of bio-oil and reduce the coking and deactivation of HZSM-5 molecular sieve catalyst in the catalytic cracking of bio-oil upgrading process, Non-Thermal Plasma (NTP) assisted HZSM-5 technical scheme was proposed, online upgrading of rape straw vacuum pyrolytic vapors were conducted in a fixed bed reactor to verify the effectiveness of the technology. In the research, the influence of catalyzing temperature, catalyst bed height, discharge power on the physicochemical properties of refined bio-oil were studied, and the yield of refined bio-oil was regarded as evaluation index, response surface methodology was adopted to optimize upgrading processing parameters. Chemical composition of the refined bio-oil which was obtained under optimized parameters was analyzed by GC–MS, and using thermogravimetric analysis, the impact of NTP on catalyst anti-coking property was evaluated. Research results indicates that catalyzing temperature, catalyst bed height and discharge power have significance effect on yield and physicochemical properties of refined bio-oil. With the optimized processing parameters of 392 °C catalyzing temperature, 34 mm catalyst bed height and 23.7 W discharge power, the oxygen content, high heating value and pH of refined bio-oil were respectively 19.79%, 33.14 MJ/kg and 4.98. Compared with original HZSM-5 catalytic upgrading method, the quality of refined bio-oil was improved obviously, and the amount of catalyst coke deposit reduced from 5.88% to 2.14%, the feasibility of NTP assisted HZSM-5 online upgrading bio-oil was confirmed. [ABSTRACT FROM AUTHOR]

Figuring out the mining-crack-evolution characteristics of overburden strata is very important to roof control, gas drainage, disaster prevention and high efficient mining. In order to obtain the mining-crack-evolution characteristics of overburden strata in deep coal mining with large dip, in this study, No.1221 coal mining face of Zhao coal mine is chosen as the research object to establish an in-house experiment system of similarity simulation. The experiments could measure the stress and displacement of overburden strata, which can provide useful information to investigate the mining-crack-evolution characteristics, displacement variations and movement characteristics of overburden strata associated the coal mining face. Experimental results show that with the advancing of coal mining face, the scope of gob increases gradually, and formation of the false roof of overburden strata basically reflects the evolution process of collapsing. The overburden strata weight is constantly transferred to the front and rear of coal mining face, which forms the supporting pressures on both sides of coal pillars, and causes the gangue's collapsing in gob. The large dip of coal seam results in pressure disequilibrium in stress-increasing zone. Thus, the stress on the underside of gob becomes larger and larger, while the stress on upper side of gob decreases. The strata separation appears in the overburden strata of roof. Pressure-relief zone is mainly concentrated in the side of outlet roadway. Along the inclination direction of coal mining face, the crack development and strata separation are obvious, which create the passages for gas flow and migration. The similarity simulation results provide fundamental information for better understanding those mining-crack-evolution characteristics of overburden strata, which has become more and more important to control the roadway stability in coal mining and optimize the layout of gas drainage boreholes for improving mining safety. [ABSTRACT FROM AUTHOR]

The ethylene cracking furnace system is crucial for an olefin plant. Multiple cracking furnaces are used to convert various hydrocarbon feedstocks to smaller hydrocarbon molecules, and the operational conditions of these furnaces significantly influence product yields and fuel consumption. This paper develops a multiobjective operational model for an industrial cracking furnace system that describes the operation of each furnace based on current feedstock allocations, and uses this model to optimize two important and conflicting objectives: maximization of key products yield, and minimization of the fuel consumed per unit ethylene. The model incorporates constraints related to material balance and the outlet temperature of transfer line exchanger. The self-adaptive multiobjective teaching-learning-based optimization algorithm is improved and used to solve the designed multiobjective optimization problem, obtaining a Pareto front with a diverse range of solutions. A real industrial case is investigated to illustrate the performance of the proposed model: the set of solutions returned offers a diverse range of options for possible implementation, including several solutions with both significant improvement in product yields and lower fuel consumption, compared with typical operational conditions. [ABSTRACT FROM AUTHOR]

Natural fractures commonly exist in unconventional reservoirs such as shale and tight gas sandstone, which are mostly cemented (or sealed) with minerals and not able to contribute to reservoir storage or rock permeability. However, during hydraulic fracture stimulation, these cemented natural fractures will be encountered and influence hydraulic fracture geometry greatly and, thereby, gas production. In this work, hydraulic fracture propagation in rock with cemented natural fracture is investigated using our recently developed and validated hydro-mechanical coupled LBM-DEM model. The numerical results show that both the strength ratio (between cemented natural fracture and host rock) and the approach angle (between hydraulic and cemented natural fracture) significantly affect the hydraulic fracture propagation. A larger strength contrast or a smaller approach angle will be more conducive to deflection, which is consistent with experimental observation. For rocks with weakly cemented natural fractures, deflection is mainly caused by shear failure in weakly cemented fracture. However, for rocks with strongly cemented natural fractures, deflection happens accompanying with tensile failure in host rock along the cement wall, which cannot be captured by the previous numerical models where the cemented natural fracture is treated as a bonded interface. In addition, complex fracture network is more easily formed if multiple weakly cemented natural fractures are orthogonal to the hydraulic fracture propagation direction. [ABSTRACT FROM AUTHOR]

The hydrocarbon resources of shale gas and tight oil have made a significant impact on North American energy reserves over the past decade. The production of so-called “unconventional” natural gas from U.S shales like the Barnett, Haynesville, Fayetteville, Marcellus, and Utica, and Canadian shales like the Muskwa, Montney, and Duvernay have saturated North American gas markets, boosted Canada's exports, and turned the U.S. into a net exporter of natural gas. Tight oil production from the Bakken Shale has made important contributions to the economy of the Canadian province of Saskatchewan. North Dakota has become the second largest oil producing state in the U.S. thanks to production from the Bakken. It trails only the state of Texas, which maintains first place because of equally prolific hydrocarbon liquids production from the Eagle Ford Shale and shales in the Permian basin. It is difficult to overstate the importance of these shale gas and oil resources to the U.S., North American, and world energy economies. North American shale development blossomed in the United States between 2005 and 2010, driven by high natural gas and oil prices, the availability of favorable lease positions on shale plays, and the application of drilling and stimulation technology that could successfully produce commercial quantities of hydrocarbons from these formations at economical costs. Development in Canada began a bit later, and some development has also taken place on shales in Mexico. Many people who express surprise at the apparent “overnight” success of shale gas and oil production were simply not paying attention. The truth is that a historic and protracted engineering struggle was required to identify, modify, and apply the right technology for economically-viable production. Modern assessments of the resource potential of these rocks began in the late 1970s, as did the first systematic engineering attempts to drill directional wells and hydraulically fracture shale. Success was elusive for nearly two decades, however, until the right combination of economics and technology came along. The ability of some visionary people to recognize the applications of that technology led directly to the current success of shale gas and tight oil production. Other countries considering development of their own shale resources are looking to the North American example for leadership. The success of shale resource development has not been without controversy. Public fear of the hydraulic fracturing process, or “fracking” has been amplified by shale gas opponents, leading to restrictions against shale development in many areas, and outright bans in some locations like New York and Quebec. The “boomtown” nature of the early development, and the lack of definitive environmental risk data has added to the negative perceptions, resulting in a backlash against some exploration and production ventures. Researchers have been gradually reducing the amount of uncertainty with respect to environmental risks, and as operators have gained more experience, the frequency of incidents has fallen. Many operators now recognize that obtaining a “social license” from the community is a necessary first step for successful shale gas development. [ABSTRACT FROM AUTHOR]

Additives to a zeolite-containing cracking catalyst were synthesized and studied in order to enhance the resistance to the poisoning effect of nitrogen compounds (in particular indole) upon cracking of n-undecane as the model FCC hydrocarbon. The additives were represented by acid-activated clays and mixed oxides. The activation of clays in the catalyst by 5% sulfuric acid solutions was shown to enhance the resistance to nitrogen. The introduction of Mg, Al – mixed oxides in the catalytic system in the amount of 10 wt% increased its activity and resistance to indole. The highest resistance was observed for the systems containing magnesium‑aluminum oxides with a Me 2 + to Me 3 + molar ratio equal to 0.5: 1. Cobalt modification of these mixed oxides enhanced the activity and nitrogen resistance of the cracking catalysts. Use of such nitrogen-resistant catalysts will allow cracking of heavy raw materials. [ABSTRACT FROM AUTHOR]

Acidic bentonite clay was obtained through surface modification of bentonite clay using hydrochloric acid as acidic precursor to increase the acidity of the bentonite. The modified catalyst was examined via X-ray fluorescence (XRF), XRD analysis, Brunauer Emmett and Teller surface area (BET), FTIR analysis and temperature-programmed desorption (TPD) analysis. XRF analysis showed that the acid modification of bentonite clay results in an increase in the silica content and lower abundance of metal oxides, due to the dissolve of Fe 2 O 3 , MnO, CaO, Na 2 O. Ca 2+ , Na + cations from the interlayer and octahedral sheets. FTIR spectroscopy showed that the acid activation decreased the intensity of the absorption bands at 915, 875 and 836 cm −1 which arise from the binding modes of OH groups. NH 3 -TPD analysis showed a considerable increase in the moderate and strong Bronosted acid cites on the modified bentonite compared to the native clay. The modified bentonite was evaluated as economic and efficient heterogeneous catalyst in catalytic cracking process of two nonedible vegetable oils to obtain the corresponding biofuels at moderate processing temperature of 250–280 °C. It was observed that the catalytic conversion was preceded under mild temperature and obtained efficient biofuels with approved physical and fuel properties according to ASTM specifications. The role of the catalyst ratio was considerable on the yield percent and the properties of the obtained biofuels. The catalytic activity-reaction mechanism was discussed based on NH 3 -TPD analysis. [ABSTRACT FROM AUTHOR]

The global production of residual feedstock has reached 150 million metric tons per annum and is expected to increase in the future due to the progressively increasing heavier nature of the crudes. Petroleum coke (petcoke), one of these residues, is a solid-rich carbon typically produced during the upgrading of heavy oil and delay coking of vacuum residue in the refinery. Finding an alternative technique to treat this massive amount of petcoke is highly needed as the conventional processes like gasification and combustion have limitations in terms of efficiency and environmental friendliness. In this study, an oxy-cracking technique, which is a combination of cracking and oxidation reactions, is conducted as an alternative approach for petcoke utilization. The reaction is conducted in a Parr reactor where petcoke particles are solubilized in an aqueous alkaline medium and partially oxidized under mild operating temperature and pressure. Several operating conditions on petcoke oxy-cracking were investigated, such as temperature, oxygen pressure, reaction time, particle size and mixing rate to optimize the solubility and selectivity of oxy-cracked products. The results showed that the temperature and the residence time are the two major important parameters that affect the reaction conversion and selectivity. This enabled us to propose a reaction pathway based on the radical mechanism to describe the kinetic behavior of petcoke. Reaction kinetics indicated that petcoke oxidation undergoes a parallel-consecutive reaction in which an oxidative decomposition took place in the first step producing different oxidized intermediates. The oxy-cracked petcoke was characterized by FTIR, XPS and NMR analyses. The oxy-cracked products were found to contain carboxylic, carbonyl, phenolic, and sulfonic functions. Moreover, the elemental analysis showed that most of the metals remained in the residue, suggesting that the proposed technique could be employed for petcoke demineralization. [ABSTRACT FROM AUTHOR]

Fracking to approach permeability enhancement is indispensable to enhance coalbed methane recovery, which can significantly reduce greenhouse gas emissions and produce substantial clean energy. To access efficient fracking, samples of Permian low permeable coal reservoir were cracked into different sizes or scales of blocks and particles with liquid nitrogen cryogenic freeze fracturing (FF) by maximizing the underlying heterogeneity of coal. To investigate the crack efficacy, this study systematically examined the permeability evolution and mesoscopic cracking behaviors of coal with different water contents and cleat–fracture systems in the context of cryogenic FF. Results showed that the permeability enhancement and microcracking tended to occur with increasing water content of coal sample; and the efficacy of cryogenic FF on the tighter coal sample was more remarkable. However, the permeability does not strictly increase with the cycles of cryogenic FF and has a close relationship with water content, structural plane direction, efficacy of cryogenic FF, and porosity compaction. The mesoscopic cracking behaviors indicate that numerous smaller pores are iteratively, not strictly sequentially, cracked and become connective in this process. The permeability evolution of coal sample is identified as significantly associated with the mesoscopic cracking behaviors. Notably, the first cycle of cryogenic FF acted on the detected several scales of pores and micro fissures, and partially caused these structures to be opened and interconnected to be permeable. Two main changes were observed in the microcracking of the coal samples in this study: 1) nonuniform shrinkage deformation and micro fissure expansion; and 2) pores opening mostly in the macropore and mesopore scale. It is reasoned that thermal cracking and intermittent opening of seepage pores due to the phase transition of free water in pores or micro fissures ultimately contribute to the permeability enhancement in low permeable and heterogeneous coal. [ABSTRACT FROM AUTHOR]

The direct cracking of crude oil is an interesting option for producing cheaply large amounts of petrochemicals. This may be carried out with catalyst and equipment similar to that of catalytic cracking, but at a temperature range between that of standard catalytic cracking and steam cracking. Thermal cracking will play a role in the conversion, but is rarely disclosed in experimental or modeling work. Thus, a crude oil and its fractions were thermally cracked and the products yields were modeled using a 9 lumps cracking scheme. It was found that heavy fraction cracks twice as fast as diesel fraction and ten times faster than gasoline fraction, with activation energies in the 140–200 kJ/mol range. Selectivity to ethylene, propylene and butenes were found similar in the operating range explored. [ABSTRACT FROM AUTHOR]

According to the chemical, carbon isotopic, and hydrogen isotopic compositions and 3 He/ 4 He ratios of 127 natural gas samples, the natural gas in the Tarim Basin is mainly composed of gaseous alkanes dominated by methane. The contents of the gaseous alkanes decrease with the increase of their carbon numbers. The δ 13 C values of CH 4 , C 2 H 6 and C 3 H 8 in the platform area of the Tarim Basin vary in the range of −54.4‰∼-24.4‰ (an average value of −39.2‰), −43.1‰∼-26.7‰ (an average value of −36.1‰) and −37.9‰∼-21.6‰ (an average value of −31.8‰), respectively. The overall carbon isotopic composition of the alkanes follows the trend of δ 13 C 1 < δ 13 C 2 < δ 13 C 3 < δ 13 C 4 and in some cases varies with δ 13 C 1 >δ 13 C 2 or δ 13 C 3 > δ 13 C 4 . The lower carbon isotope values of methane (δ 13 C 1 < δ 13 C 2 ) may be attributed to thermal sulfate reduction (TSR), and the higher propane value (δ 13 C 3 > δ 13 C 4 ) was caused by the mixing of the natural gases of the same genetic type formed at different stages. The methane hydrogen isotopes (δ 2 H-C 1 ) of the natural gases in the Tarim Basin are in the range of −195‰∼-122‰ with an average value of −156‰. The 3 He/ 4 He ratios of the natural gases are in the range of 2.3 × 10 −8 ∼66.8 × 10 −8 , suggesting that there is no deep mantle-derived gas in the platform area of the Tarim Basin. The carbon isotope fractionation of alkane gases (δ 13 C 2 <−28‰ and δ 13 C 3 <−25‰) indicates that the natural gas in the platform area of the Tarim Basin is oil-type. The modified plots of lnC 1 /C 2 vs. lnC 2 /C 3 and C 2 /C 3 vs. δ 13 C 2 -δ 13 C 3 of the natural gases indicate that the oil-type gas in the Tarim Basin has different predominant formation processes, including kerogen-cracking, oil-cracking, oil- and gas-cracking, secondary gas-cracking and mixing of the kerogen-cracking and oil-cracking gases. The gas evolved from gas-cracking gas, to oil- and gas-cracking gas and oil-cracking gas along the direction from the west side of the Manjar Sag to the central Tarim Basin. The natural gases in some areas of Tazhong are the mixtures of the kerogen-cracking and oil-cracking gases. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an alternative way to estimate volumetric vapour: liquid ratio of gaseous or light-petroleum inclusions without fluorescence using regularly-shaped inclusions to estimate volumetric vapour: liquid ratios through geometric methods. The method was applied to the inclusions from the rock samples of the Lower Triassic Feixianguan and Jialingjiang Formations, NE Sichuan (China). The trapping pressures of inclusion fluids were calculated by integrating PVT simulation software, volumetric liquid: vapour ratios determined by the proposed method and homogenization temperatures measured by microthermometry. Fluid densities and gas-oil ratios (GOR) were also estimated. The estimated trapping pressures and temperatures are slightly lower for the Jialingjiang formation (29.69–31.33 MPa, 93.5–105.2 °C) than for the Feixianguan Formation (31.02–34.38 MPa, 98–148 °C), and the trapping time of the inclusions in the Jialingjiang Formation and Feixianguan Formation were estimated at about 173–170 Ma and 178-168 Ma, respectively. The distribution of high pressures correlates with the presence of pyro-bitumen in the reservoir rocks, suggesting the migrated fluid is derived mainly from the secondary cracking of oil. The modeled fluid density and GOR correspond to a typical light oil or condensate, suggesting an origin for the trapped hydrocarbons as an intermediate product in this process. [ABSTRACT FROM AUTHOR]

The article presents the results of processing heavy oil residues initiated by atmospheric oxygen. We found that the introduction of a small amount of atmospheric oxygen (2–6%) in the thermo cracking reactor (thermo-oxidative cracking) significantly increases the yields of light fractions. E.g. A thermo cracking of vacuum residue (visbreacking) with the air supply to the soaker camera gives twice more light fractions than traditional visbreacking process (36% of petrol and diesel fractions compared to 10–15% in conventional process). Thermo-oxidative cracking of atmospheric residue gives up to 60% of light fractions. In order to obtain a mathematical description of the process needed for its subsequent industrial implementation we conducted experiments on thermo-oxidative cracking of atmospheric and vacuum residues in a continuous flow reactor with a wide variation of the process parameters. Based on the analysis of the experimental data a common scheme for thermo-oxidative cracking, a mathematical model of the process and its parameters were established. The model adequately describes all the experimental data obtained in the temperature range 430–460 °C, pressure 2–8 atm, retention times 4–33 min and relations oxygen/raw material 0,9–2,5 % wt. Industrial implementation of thermo-oxidative cracking needed just minimal modification of the existing thermal installations through the organization of air supply in the soaker chamber. This modification will increase the output of light fractions in the thermal processing heavy oil residues in 2–3 times with minimal capital investments. [ABSTRACT FROM AUTHOR]

‘Chemical Looping Combustion’ (CLC) is an emerging clean combustion technology which offers an efficient route for fossil fuel combustion with inherent CO 2 capture. Beyond combustion, chemical looping is also applicable to selective oxidation of fuels to synthesis gas or olefins. In all these applications, the main advantage of chemical looping lies in the inherent air separation, which allows conversion of the fuel without nitrogen dilution. In the present work, we extend this inherent separation principle to separation of the product stream by demonstrating the formation of fully separated syngas streams from methane, i.e. the production of separate, high-purity CO and H 2 streams via (non-oxidative) methane cracking. CH 4 is first cracked catalytically over Ni, producing gaseous H 2 and solid carbon. The carrier is then periodically regenerated by burning off the carbon using CO 2 as oxidant, thus enabling the reduction of CO 2 to CO. Importantly, the Ni carrier is never oxidized during this cycle and hence acts as a “carbon carrier” rather than as an oxygen carrier as typical in chemical looping processes to-date. Autothermal process configurations are discussed, which allow reconciling the use of abundant natural gas reserves with the demand for clean, carbon-free energy production. [ABSTRACT FROM AUTHOR]

Heat transfer and reaction behavior of aviation kerosene were investigated numerically and experimentally at a supercritical pressure. A global thermal cracking and catalytic reforming reaction model were modified and developed based on the experimental data. A set of surrogate components for aviation kerosene was built and its thermodynamic properties were predicted. Interactions among heat transfer, cracking and catalytic steam reforming reactions were simulated in a micro-channel reactor. Comparison between calculation and experiment showed that the numerical model can predict the wall and outlet fuel temperatures with an error not exceeding 5%. The conversion rate of kerosene and water were also in good agreement with experimental data. Heat transfer deterioration phenomenon can be observed when fuel contains water. Fuel with catalytic steam reforming reactions had the advantage of weakening the heat transfer deterioration and obvious promotion in heat sink. Heat transfer process can be divided into four sub-regions: entrance, gasification, transition and interactive reaction regions. The two kinds of reactions occurring in the reaction region significantly improve the heat sink of hydrocarbon fuel. Interactions between cracking and reforming reactions illustrated that the reaction region were considerably moved ahead due to the existing of steam reforming reactions, resulting in lower fuel temperature which led to a lower rate of thermal cracking and conversion. Thermal cracking reaction was inhibited by catalytic steam reforming reactions. [ABSTRACT FROM AUTHOR]

With the aim of investigating the solutions of ethane shortage in a commercial ethylene plant, addition of propane as supplementary feedstock and increasing steam to hydrocarbon ratio were proposed as possible strategies. These strategies were proposed to compensate for the ethane shortage in the thermal cracking unit of the commercial plant. Run length, ethylene yield, and propylene yield were considered as the determining factors to appraise the strategies. The major contribution of present work would be the investigation of effect of feed shift on the run length of the steam cracker. Regarding this, five different cases were investigated in real plant condition. To include all the aspects of process, a mathematical model with reasonable assumptions was developed and then validated against the real plant data. Based on the obtained results, increasing propane concentration leads to increase in propylene yield and decrease in ethylene yield. Besides, run length of process was obtained to be longer in the cases with higher propane content in the feed stream. [ABSTRACT FROM AUTHOR]

The Chemical structures of oil sand bitumen (OSB) derived from Buton and Xinjiang oil sands were determined by elemental analysis, FTIR and 1 H NMR. The thermal cracking behaviors and evolving characteristics of gaseous products of Buton and Xinjiang OSBs were investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR). Additionally, the composition and distribution of volatile products formed from the fast thermal cracking process of these two OSBs were evaluated via pyrolysis gas chromatography-time of flight mass spectrometry (Py-GC/TOF-MS). Results indicated that Xinjiang OSB featured stronger polarity and contained more aliphatic structures with shorter chain length and larger branching degree compared to Buton OSB. Whereas Buton OSB possessed a larger amount of aromatic structures and its condensation degree was lower than that of Xinjiang OSB. The thermal cracking process of these two OSBs were both mainly consisted of two reaction stages, including volatilization stage and main reaction stage. The coke yields for Buton and Xinjiang OSBs were 15.51% and 16.76%, respectively. CO 2 , CO, CH 4 , C 2 H 4 , light C 2+ aliphatic hydrocarbons and light aromatics were the typical gaseous products released from the main reaction stages of both two OSBs. The evolving behavior of each of the typical gaseous products except for CO 2 and light aromatics during the thermal cracking process of Buton and Xinjiang OSB featured good similarity. The volatile products formed during the fast thermal cracking process of Buton and Xinjiang OSBs were mainly divided into five types of compounds, including alkenes (1-alkenes, iso-alkenes and cycloalkenes), alkanes (n-alkanes, iso-alkanes and cycloalkanes), diolefins, aromatics and sulfur compounds. Among of them, alkenes was the most predominant type in volatile products and 1-alkenes were the most abundant products for both two OSB. Furthermore, Buton OSB has higher selectivities of 1-alkenes and n-alkanes compared to Xinjiang OSB. [ABSTRACT FROM AUTHOR]

A series of nickel catalysts i.e. nickel sulfide (NiS), nickel phosphide (NiP) and nickel carbide (NiC) was investigated for hydrotreating of spent coffee oil to produce bio-hydrotreated fuel (BHF). Catalytic tests were carried out at 375–425 °C and 20–40 bar of initial H 2 pressure (before heating) with reaction time of 0–3 h. The activity of the catalysts are in the order of NiC > NiP > NiS; however NiC tended to promote cracking reaction resulting in high gasoline and gaseous yields. On the other hand, although NiS gives the lowest oil conversion, it is favorable to diesel yield with lowest methanation and cracking activity. Compared with decarboxylation (DCO 2 ) and hydrodeoxygenation (HDO), decarbonylation (DCO) was the major route for deoxygenation of coffee oil for all the catalysts. The ratio of (DCO + DCO 2 ) to HDO (as represented by C n-1 /C n ) decreased in the order NiS > NiC > NiP. Ketones as intermediate products (ca. 3 wt%) were detected in case of NiP. They could be generated via rearrangement of alcohol and keto-enol tautomerism. Significant amount of aromatics (4 wt%) with some isomerization products (0.9 wt%) can also be observed in NiS catalyzed liquid products while trace amount of these compounds were detected for NiP and NiC catalysts. Physiochemical analysis of the diesel fraction exhibited satisfactory properties. The density and kinematic viscosity were consistent with the specification of commercial bio-hydrogenated diesel, NExBTL. Since main products are straight chain hydrocarbons, high cetane index (>110) could be achieved. [ABSTRACT FROM AUTHOR]

This study examined the effects of microwave (MW) and ultrasonic (US) waves on an heavy crude oil sample from a reservoir in southwest Iran. The waves irradiated the sample from two to 10 min at two-minute steps. MW caused the temperature of the crude-oil sample to rise by selective heating of polar components and creation of hot zones; under US, heating was accompanied by a cavitation effect. MW at 2 and 4 min reduced the sample’s viscosity by inducing hot zones. At 2 min, the viscosity declined 16% due to cracking of heavy components such as asphaltenes, which have a higher capacity to absorb MW. As the radiation time increased after 4 min, the viscosity increased because light components escaped from the sample. However, US reduced the viscosity of the heavy crude oil sample at all time durations. The greatest reduction of viscosity was around 19%, at 4 min. The viscosity increased with irradiation time and then remained constant. Ultrasonic waves altered the viscosity by creating bubbles, which disintegrated the resin intermolecular bonds and cracked the large molecular particles of the asphaltene. The reduction in sulfur content under US was much greater than under MW. At all time durations, sulfur content fell as radiation time increased. Due to its high potential to absorb MW, creates active sulfur that can be emitted from the crude oil as sulfide and hydrogen sulfide, with the sulfur level falling to 0.39%. Furthermore, US waves also reduced sulfur content to around 0.46% as the asphaltene flocks disintegrated. Reduction of sulfur content from asphaltene agglomerates under MW and US was observed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In addition to reducing the effect of sulfur by affecting its nitrogen and oxygen elements, irradiation also reduced the polarity of the asphaltene particles and prevented reaggregation of cracked particles. Results of SARA (saturation, aromatic, resin and asphaltene) analysis showed that asphaltene particles have a higher capacity to absorb MW than resin components, as after the amount of asphaltene components declined in the early stages of irradiation, resin components began to change, falling to 34% at 10 min. The decrease in asphaltene content in samples under US was more evident, reaching 34% at 8 min. According to Fourier transform infrared (FTIR) spectra results, MW irradiation caused cracking of large-chain molecules and drove light components from heavy crude sample. These two phenomena are a function of radiation time. The rate of cracking of heavy components was continuously greater than the rate of light components leaving the sample at early time intervals; ultimately, this resulted in an upgraded heavy oil. In some cases, despite cracking of large-chain molecules and creation of light components, the output values of light components were higher. Under US, the cracking of large-chain molecules occurred, but due to the departure of heavy components from the crude oil, peak intensities increased and the resulting crude oil had purer components. [ABSTRACT FROM AUTHOR]

Particle agglomeration can occur in heavy oil upgrading hydroprocessors due to the formation of carbonaceous mesophase, a secondary liquid phase which results from an increased rate of thermal cracking relative to the hydrogenation rate. A cold-flow slurry bubble column operated at atmospheric pressure with an internal diameter of 0.152 m was used to examine particle agglomeration behavior and the overall fluid dynamics in a gas-liquid-liquid-solid system. The experimental system consisted of biodiesel (organic continuous phase), aqueous glycerol solutions (immiscible secondary phase), glass beads and nitrogen. The impacts of the secondary liquid loading, secondary liquid viscosity, and particle diameter on the fluid dynamics were established. Particle agglomeration was studied by measuring the axial solid holdup profiles while varying the superficial gas velocity and secondary liquid loading. Enhanced particle agglomeration was observed when increasing the secondary liquid loading, based on the increased solid holdups at the bottom of the column. Three sparger designs (six-legged spider sparger, perforated plate and conical perforate plate) were compared. Following the glycerol addition, the spider sparger was less effective based on the particle sedimentation at lower liquid/solid ratios when compared to the other sparger designs. A Revolution Powder Analyzer (RPA) was also used for complementary measurements to examine whether operational difficulties due to particle agglomeration can be anticipated using a simplified system. [ABSTRACT FROM AUTHOR]

Refining of high acid crudes (HACs) is seriously limited by extensive corrosion of refinery equipment due to the presence of intrinsic naphthenic acids (NAs). Herein, in the absence of a catalyst or external hydrogen, effective removal of the NAs contained in HACs was achieved using methanol at moderate temperature and moderate pressure. Several process variables, including the temperature, crude concentration, and reaction time are explored to optimize the removal of NAs from HACs. At 250 °C, 6.4 MPa, and 33.3 wt% crude, a very low total acid number (TAN) of 0.08 mg-KOH/g-oil (96.9% reduction efficiency) with a high oil yield (95 wt%) is achieved. During the reduction of the TAN using methanol, some fraction of the resins and asphaltenes in the crude oil crack to form low-molecular-weight aromatic compounds. Compared to deacidification using methanol, pyrolysis (without methanol) results in a much lower TAN reduction efficiency (38.6%). The major deacidification mechanism using methanol is esterification, while that of pyrolysis (without methanol) is decarboxylation. [ABSTRACT FROM AUTHOR]

In this research, hydrogen induced cracking (HIC) behavior of an API X70 pipeline steel has been studied. In order to create HIC cracks, an electrochemical hydrogen charging experiment was carried out on X70 steel by using 0.2 M sulfuric acid and 3 g/l ammonium thiocyanate for 8 h. Moreover, SEM, EDS and EBSD techniques were used to characterize the as-received (AR) steel and investigate the different aspects of HIC phenomenon as well. The results showed that the inclusions and precipitates which play a key role in HIC phenomenon have been distributed randomly through the cross-section of tested steel. However, the concentration of them was higher at the center of cross-section than other areas. All HIC cracks initiated and propagated through the center of thickness where center segregation of elements has occurred. It is also observed that HIC cracks were initiated from several special types of inclusions and precipitates such as manganese sulphide and carbonitride precipitates. EBSD results showed that the dominant local texture of center of thickness in RD-TD plane was {001}//ND and {111}//ND. Moreover, HIC cracks propagate through differently oriented grains where the local texture is random. [ABSTRACT FROM AUTHOR]

Vacuum residue cracking has been successfully conducted under supercritical water condition in presence of various metal oxide nanocalysts, namely NiO, CuO, ZnO, Co 2 O 3 , and Cr 2 O 3 synthesized at supercritical water. The cracking experiments were carried out at 450 °C. Three species of cracking: maltene, asphaltene, and coke were then weighed and their corresponding speciation was defined. Gas chromatography-mass spectrometry (GC–MS), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), and elemental analysis (CHNS) tests were utilized to prove the performance of upgrading reactions. It was revealed that NiO showed the best performance among other catalyst, in which its activity and stability in catalytic cracking changed slightly. According to the results obtained from GC–MS, NMR, TGA, and CHNS anlyses, it was confirmed that the proportion of heavy hydrocarbons of products (i.e. non-catalytic and catalytic reactions) was lower than that of feedstock. [ABSTRACT FROM AUTHOR]

Significant amount of different maturity kerogen in Bazhenov oil-shale formation are reserves of hydrocarbons to be recovered by enhanced oil recovery methods in nearest future when the conventional oil field development drops crucially. A technology of in-situ kerogen conversion into synthetic oil in Bazhenov formation opens broad perspectives in development of Bazhenov formation, West Siberia, Russia. Laboratory investigation of in-situ kerogen conversion process in the presence of supercritical water performed on Bazhenov formation rocks is presented in this study. A feasibility of the tertiary hydrous pyrolysis hydrocarbons (HC) recovery method was accessed. Study helped to obtain reliable data to validate the numerical simulation model for that enhanced oil recovery method. First tests of hydrous pyrolysis extraction were conducted on crushed oil shale samples at temperatures of 300, 350, 400 and 480 °C and under formation pressure of 30 MPa. Liquid HC extraction from sample started from 400 °C. The secondary hydrocarbons conversion process was detected at reaction temperature of 480 °C. Second stage of laboratory tests allowed to find optimal parameters for in-situ kerogen conversion – optimal conversion temperature, time of the conversion. The experiments on Bazhenov formation cores with low kerogen maturity were conducted in closed vessel at formation pressure and in temperature range of 250–400 °С. It was found that oil synthesis starts at 300 °С. Amount of liquid products increased at temperatures above 350 °С, but the secondary cracking processes had been observed also. It was discovered that hydrous pyrolysis and cracking caused an increase in rock porosity and permeability. Results obtained in this study were used in numerical simulation. [ABSTRACT FROM AUTHOR]

Thermal cracking of canola oil was investigated in a continuously operating pilot plant. The influence of different cracking temperatures (450 °C to 580 °C) on the product was observed with a final objective of maximizing LCO (light cycle oil). LCO can be used as diesel blend if a required quality is achieved. The pilot plant was constructed as a reaction/regeneration system with an internal circulating fluidized bed design. All experiments were conducted with canola oil at a feed rate of 2.5 kg/h. Silica sand was used as bed material. A 6-lump model was used for product characterization. The composition of gas ( C 1 – C 4 ), gasoline (saturated hydrocarbons, olefins, aromatics) and LCO (aromatics) was analyzed. In addition, the oxygen content of the liquid products was determined at cracking temperatures of 450 °C and 580 °C. The experiments show that the product distribution is heavily dependent on the cracking temperature. With increasing cracking temperature gas, gasoline and carbon oxides increase, whereas LCO, residue and coke decrease. At a cracking temperature of 450 °C 8.6 wt% gas, 21.1 wt% gasoline, 47.5 wt% LCO, 15.8 wt% residue, 3.7 wt% coke and 3.3 wt% carbon oxides are formed. The liquid product contains high amounts of oxygenates. [ABSTRACT FROM AUTHOR]

The bio-oil from rice hull fast pyrolysis was distillated under reduced pressure at 0.005 Mpa, then mixed with ethanol (2:3 by weight). The mixture was subjected to catalytic co-cracking over Ni-ZSM-5/MCM-41 molecular sieves in a fixed-bed at 500 °C and 3.75 h −1 of the WHSV. The distillation results showed the distilled bio-oil, compared with raw bio-oil, contained lower oxygen content (decreased from 45.91 wt.% in raw bio-oil to 33.74 wt.%), higher (H/C) eff ratio (0.35) and HHV value (22.81 MJ/kg). The ethanol was involved in the ketonization, esterification, aromatization and dehydration during the catalytic co-cracking of distilled bio-oil and ethanol. The Ni loaded on ZSM-5/MCM-41 molecular sieves reduced char formation compared with ZSM-5/MCM-41. The ZSM-5/MCM-41 catalyst exhibited higher activity in the esterification and aromatization, which converted acids in upgraded bio-oil to esters, aromatics or phenols. The Ni-ZSM-5/MCM-41 catalysts showed excellent activity that transformed acids to ketones by ketonization process. The 6% Ni-ZSM-5/MCM-41 catalyst performed the good activity with the minimum char formation (7.3 wt.%) and higher upgraded bio-oil (40.8 wt.%). Moreover, the acid content in the upgraded bio-oil dropped to 0.1 wt.% and the total concentration of CO 2 and CO in the gas products was 36.8 vol.%. [ABSTRACT FROM AUTHOR]