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Alkane dehydrogenation to alkene represents a promising alternative route for conventional petroleum cracking processes heavily reliant on fossil resources. This Concept outlines the latest advancements of novel alkane dehydrogenation routes that offer potential solutions to intrinsic problems existing in routine direct dehydrogenation or oxidative dehydrogenation reactions, including CO2 assisted alkane dehydrogenation, chemical looping alkane oxidative dehydrogenation, dual‐path dehydrogenation and auto‐accelerated multiple alkane dehydrogenation route. These novel reaction routes exhibit unique advantages in enhancing the activity, selectivity and stability of the alkane dehydrogenation reaction system. The rational design of novel catalysts and proper choice of the reaction condition that well‐fitted these reaction routes is the key for achieving highly efficient and stable alkane dehydrogenation process. These present examples in this manuscript also highlight the importance of fundamental in‐depth understandings on the mechanism and structure‐function relations, which is the foundation for developing novel alkane dehydrogenation routes for practical applications. [ABSTRACT FROM AUTHOR]

The influence of different modification methods of oyster shells on phosphorus adsorption properties were studied. The effect of different modified concentrations of AlCl3 on phosphorus removal in oyster shells was compared. The results showed that the phosphorus removal rate of 0.5 mol/L AlCl3 modified oyster shells was as high as 90%, and the phosphorus concentration of residual sewage after treatment was 0.05 mg/L. The study compared the treatment effects of natural oyster shells, hot-modified oyster shells and AlCl3 modified oyster shells on low-concentration phosphorus containing wastewater. The TP removal rate were 63% ~ 68%, 61% ~ 72% and 83% ~ 90%, respectively, and the TP removal rate of AlCl3 modified oyster shells were the highest. The adsorption of natural oyster shells, thermal modified oyster shells and AlCl3 modified oyster shells conforms to the quasi-second-order kinetic model and Freundlich isothermal adsorption model, and the adsorption process includes both physical adsorption and chemical adsorption. In the Freundlich isothermal adsorption model, parameter n values of natural oyster shell, hot-modified oyster shell and AlCl3 modified oyster shell were 1.205, 1.168 and 2.611, respectively, indicating that the adsorption reaction of phosphorus on AlCl3 modified oyster shell was easier than that on natural oyster shell and hot-modified oyster shell. [ABSTRACT FROM AUTHOR]

The effects of different hot air speeds and temperatures on the drying characteristics of half-ripe rice paper were investigated by hot air convection drying experiments. The thin-layer drying experiments were carried out at three different combinations of air speeds of 1.97 m/s, 3.00 m/s, and 3.90 m/s and temperatures of 85 °C, 100 °C and 115 °C. The results show that among the 10 drying kinetic models selected, the Modified Page model is the most suitable model to describe the drying characteristics of the thin layer of half-ripe rice paper; the whole drying process exists obvious ascending, constant and descending processes; the effective moisture diffusion coefficient of half-ripe rice paper is in the range of 1.52656 × 10−9 m2/s–3.15816 × 10−9 m2/s, whose size increases with the increase of the hot wind speed and temperature. Its magnitude increases with the increase of wind speed and temperature; the drying activation energy of half-ripe rice paper is 6.55 kJ/mol calculated by Arrhenius equation. [ABSTRACT FROM AUTHOR]

Introduction: The occurrence of mixed fracture mechanisms in mechanical elements is frequent, due to the action of multiple factors that intervene during their design, manufacturing and operation. Objective: To establish the causes of failures in tripod columns on trucks, based on the characterization of the base metal and the welded joints in the failure region. Materials and Methods: Visual inspection of the failures, chemical and microstructural characterization by optical microscopy of the columns, as well as tensible test of the base material were carried out. Results and Discussion: The integrated visual inspection analysis and the results of chemical and metallographic characterization reveal that the material of the columns is not recommended for welded structures and that measures such as preheating and thermal treatment after welding were not taken. Due to the characteristics of the steel and the location of the detected cracks, they may be associated with diffusible hydrogen cracking. Conclusions: The failure of the columns was the result of a combination of several factors, highlighting design and manufacturing errors in the selection of a non-recommended material and the non-execution of attenuation measures during the execution of the welding, also linked to factors such as, possible overloads or improper operation of the equipment. [ABSTRACT FROM AUTHOR]

The research progress of heavy oil catalytic cracking technology at home and abroad is summarized from three aspects: the research survey of reaction mechanism of heavy oil catalytic cracking, the analysis and comparison of molecular sieve catalytic materials for heavy oil catalytic cracking, the technical characteristics and industrial application of different heavy oil catalytic cracking processes. Firstly, modified molecular sieve catalyst materials, small-crystal molecular sieves, hierarchical pore molecular sieves have become hot spots in current research and application, so as to strengthen the hydrothermal stability of catalyst, the intracrystalline diffusion and the graded cracking of heavy oil macromolecules in the hierarchical pores of the heavy oil catalytic cracking catalyst; secondly, based on the research of the carbonium ion mechanism and the free radical mechanism of the catalytic cracking reaction and the like, the reaction severity of heavy oil catalytic cracking technologies such as DCC, CPP, HCC, RTC and HSFCC is continuously improved, and in order to match the optimal reaction environment for different feeds, new reactor or multi-reactor combination technology has become the main direction of process technology research, which has achieved the purpose of improving the yield and selectivity of light olefins. [ABSTRACT FROM AUTHOR]

C2+ hydrocarbons, especially C2+ olefins, as important basic chemical raw materials, mainly come from petroleum cracking. With the increasing scarcity of petroleum resources, the search for new olefins production routes has become the focus of research, and the production of olefins by the oxidative coupling of methane (OCM) process has attracted extensive attention. The OCM route is an important alternative to the production of olefins from petroleum resources and is also an important direction for the development of efficient and clean utilization of natural gas. In this paper, the mechanism, catalysts, and other key factors for the production of olefins by methane oxidative coupling are reviewed. The mechanism of OCM, including the reaction pathway and the formation of intermediate products, is introduced. Then, commonly used catalysts, such as alkali metal/alkaline earth metal oxides, rare earth metal oxides, composite metal oxides with special structures, and classical catalysts Mn/Na2WO4/SiO2, and their mechanisms of action in the reaction are discussed. In addition, the application of chemical looping oxidative coupling of methane (CLOCM) in olefin production is also investigated, which is a promising alternative way due to the high selectivity of olefins and the low cost of catalysts owing to the excellent performance of the catalyst recycling. These studies will help to further understand the mechanism of OCM for olefin production and provide guidance and support for applications in related fields. [ABSTRACT FROM AUTHOR]

The concrete deck at the negative bending moment region of a continuous steel-concrete composite girder bridge is the weakest part of the structure. Introducing ultra-high performance concrete (UHPC) to the hogging region may overcome the shortage and break through the bottleneck. This paper explores the cracking performance of steel-concrete composite girders with concrete slabs topped by a thin layer of UHPC subjected to a negative bending moment. A real continuous composite girder bridge is briefly introduced as the engineering background, and the cracking characteristic of the concrete deck over the middle piers of the bridge is numerically modeled. Approaches to strengthen the cracking performance of the concrete deck at the hogging region through topping UHPC overlays are proposed. The effectiveness of the approaches is examined by conducting a series of numerical and experimental tests. Numerical results indicate that the normal concrete (NC) deck near the middle forums of the bridge would crack due to the large tensile stress from negative bending moments. Replacing the top concrete with an identical-thick UHPC overlay can increase the cracking resistance of the deck under the moment. As the thickness of the UHPC overlay increased from 6.0 cm to 12.0 cm, the maximum shear stress at the UHPC overlay-to-NC substrate interface under different load combinations was decreased by 56.3%-65.3%. Experimental results show that the first-cracking load of the composite beam using an NC-UHPC overlaid slab was 2.1 times that using an NC slab. The application of a UHPC overlaid deck can significantly improve the crack performance of the steel-concrete composite girder bridge. [ABSTRACT FROM AUTHOR]

The new designs or new materials used in foundries for sand casting products in Vietnam now often rely on experience and adopt the try-to-fix method to gradually find the best implementation. This method is very time-consuming, and the product is often unsatisfactory in the first many castings. This study developed a casting simulation model to compare experimental and simulated results using the Fenotec molding technology for the RV95 engine body. The 3D simulation model that was used to simulate the casting process with the same boundary conditions as the experiment also gave similar results. The results show that when making new castings for the first time from experience, there are many casting defects such as cracking, metal deficiency, porosity, etc. In order to improve the casting results, the pouring gate, the arrangement of additional risers and the size of the runner were studied on the simulation to improve the defect results on the casting. After that, the parameters in the simulation model used in the experiment reveal that the molded product meets the required quality and no longer has defects. This molded product, after checking the mechanical and geometric parameters, can be put into mass production. [ABSTRACT FROM AUTHOR]

Zr based metallosilicalites, especially Zr‐ß, is promising catalyst for the conversion of ethanol to 1,3‐butadiene, which is considered to be a sustainable alternative to petroleum steam cracking. However it is suffering from deactivation derived from coking and unsatisfied catalytic activity derived from deficient Lewis acidity. For these issues, a dissolution‐recrystallization process through tetraethyl ammonium hydroxide treatment (TEAOH) for enhancing porosity and Lewis acidity of Zr‐ß zeolite was developed in this study. A balance of dissolution and recrystallization existed in this process, which was produced by OH− etching and templating of TEA+ ions, creating additional mesoporosity. Zirconium active sites maintained tetrahedral coordination, while the Lewis acidity was enhanced by creating higher proportion open sites in framework. The recrystallized Zr‐ß exhibited higher catalytic activity and stability in the conversion of ethanol‐acetaldehyde to butadiene due to the compromise of microporosity and mesoporosity, as well as the appropriate enhancement of Lewis acidity. [ABSTRACT FROM AUTHOR]

Bulk chemical 2‐methyl‐2‐butene, one of the main C5 distillates of the petrochemical industry, has scarcely been utilized directly in synthesizing high‐value‐added fine chemicals. Herein, we use 2‐methyl‐2‐butene as the starting material to develop a palladium‐catalyzed highly site‐ and regio‐selective C‐3 dehydrogenation reverse prenylation of indoles. This synthetic method features mild reaction conditions, a broad substrate scope, atom‐ and step‐economies. [ABSTRACT FROM AUTHOR]

Sand production in Wells is the main contradiction facing the explo让ation of unconsolidated sandstone oil and gas reservoirs・ Resin consolidated artificial wellbore is the most widely used chemical sand control method in oil fields at present because of its excellent effect on fine sand control, which can achieve screen-free sand control under complex well conditions ・ The extended finite element method (XFEM) was used to simulate the crack passing through a single particle, a pair of particles and a plurality of evenly distributed particles, and the influence of nanoparticles on the crack growth path and damage dissipation energy was studied・ It was found that the influence range of nano-SiO2 on the crack was 5 nanoparticle diameters, and the best mass fraction of nano-SiO2 was 3% of the resin matrix. The results of measuring the impact strength of resin spline and the compressive strength of resin sand control body show that when the mass fraction of nano-SiO2 is 3%, the impact strength of resin spline increases about 39% and the compressive strength of resin sand control body increases about 36%, which significantly improves the mechanical properties of phenolic resin. [ABSTRACT FROM AUTHOR]

[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]

In order to explore the effect of temperature on the cracking reaction system of 1, 1, 2-trichloro-ethane, the thermodynamic simulation calculation of the system was carried out. The reactor module RG・ ibbs in Aspen Plus VI1 was adopted and combined with the sensitivity model analysis tool to calculate the equilibrium yield of each product at 150 ~300 °C under three conditions of single component, no polymerization reaction and polymerization reaction. The thermodynamic simulation results show that under standard cond让ions, the main reaction of dehydrochlorination of 1, 1, 2・trichloroethane to produce vinylidene chloride and the side reaction of producing cis-1, 2-dichloroethylene and trans-1, 2-dichloroethylene cannot be spontaneous・ The main and side reactions are endothermic reactions・ When the temperature is 150 °C, the equilibrium conversion of the side reactions to produce trans-1, 2-dichloroethylene and cis-1, 2-dichloroethylene is the lowest and the highest, respectively・ The equilibrium conversion of 1, 1, 2-trichlo-roethane cracking reaction is directly proportional to the temperature・ When the temperature reaches 300 °C, the equilibrium conversion is close to 100%. The thermodynamic properties of related substances were verified by the DMol-3 module of Materials Stu dio. [ABSTRACT FROM AUTHOR]

Cold-rolling oily sludge is a typical hazardous solid waste in the iron and steel industry. Clarifying the basic characteristics of cold-rolled sludge helps to realize the resource utilization and harmless disposal of it. The basic characteristics of cold-rolling oily sludge and its oil and solid phases were studied by scanning electron microscopy， thermogravimetric analysis and rheological analysis … etc. The results showed that cold-rolling oily sludge was a high viscosity emulsion formed by mixing oil， water and solids and the mass fractions of oil， water and solid phases were 47.28%， 27.15% and 25.57%， respectively. The viscosity of cold-rolling oily sludge was 1.439 Pa·s at 25℃ and 100 s-1. The pyrolysis process of it included the evaporation of moisture， desorption of adsorbed gas, decomposition of light fatty acid organic compounds, cracking of heavy organic compounds and reduction of iron oxides with carbon residues. The mass fractions of saturates, aromatics， resins and asphaltenes in oil phase were 8.030%, 0.394%, 86.436% and 5.139%, respectively， while the resins were mainly composed of long-chain fatty acids such as palmitic acid, oleic acid, and stearic acid, and the distillation range of it was 300～500℃. The solid phase contained magnetite and iron metal (Fe)，and the mass fraction of Fe element was 66.08%. The average particle size of the solid phase was 503.622 μm. [ABSTRACT FROM AUTHOR]

Y Zeolite plays an irreplaceable role in many important applications due to its unique physicochemical properties, which has attracted extensive attention from researchers. Response surface methodology (RSM) was used to optimize the process parameters for the hydrothermal synthesis of Y zeolite using kaolin activated by microwave heating. The best relative crystallinity was 108.17% could be achieved at the condition: the aging temperature of guiding agent was 65 ℃, the crystallization temperature was 100 ℃, the crystallization time was 24 h. In addition, the aging temperature of guiding agent was the most important influence factor. Under the optimal condition, the SiO2/Al2O3 ratio of synthesized Y zeolite was 4.54, 90% of the particle size was less than 60 μm, and the specific surface area of Y zeolite was 479 m2/g. The successful preparation of Y zeolite with high crystallinity is expected to provide reference for the application of wastewater treatment, CO2 sequestration and fluid catalytic cracking for petroleum. [ABSTRACT FROM AUTHOR]

Introduction: The finite element method has become popular to determine fracture mechanics parameters, but this type of numerical analysis may or not lead to accurate results, depending on the model quality and the implementation of the established methods. Objective: Implement and validate the calculation of the stress intensity factor and the J integral through the displacement extrapolation, domain integral and interaction integral methods, through finite element modeling of cracked part problems in 2D and 3D. Materials and methods: The stress intensity factor and the integral J were calculated in a compact cracked specimen and a plate with a semi-circumferential surface crack, by means of 2D and 3D finite element models, and these results were verified with those obtained by means of published analytical expressions. Results and Discussion: The error of the results provided by the finite element models does not exceed 3% for the two-dimensional models and 7% for the three-dimensional ones, which demonstrates their quality and precision. Conclusions: The implementation of the calculation of the fracture mechanics parameters is considered validated, which makes it possible to extend its use in the future for constructions and equipment that present cracking in service. [ABSTRACT FROM AUTHOR]

Fluid catalytic cracking (FCC) waste catalysts produced by petroleum cracking contain many harmful substances, such as heavy metals, and improper treatment can lead to environmental pollution. To solve this problem, this study investigated four types of FCC (LM, SH, A, SL) waste catalyst as a substitute filler for limestone mineral powder and examined their interactions with asphalt and fillers. The X-ray fluorescence (XRF), scanning electron microscope and specific surface area tests were conducted to compare the performance of FCC waste catalyst and fillers. Meanwhile, the effects of FCC waste catalyst on asphalt mastic composed of limestone mineral powder and asphalt were evaluated using surface energy, interaction parameters, and FTIR. Results show that there is little difference in the main components of the four waste FCC catalysts and limestone mineral powder. However, the surface roughness and specific surface area of the FCC catalysts are significantly greater than those of limestone. Moreover, the addition of FCC waste catalyst can improve the adhesion of asphalt with fillers and aggregates, and significantly enhance the interaction capabilities between the filler and the base asphalt, especially for SH. FTIR analysis confirms that the aforementioned improvements are achieved through physical interactions. This study reveals the effects of different FCC waste catalysts on asphalt mortar, and provides a theoretical basis for promoting the practical application of FCC waste catalysts in road engineering. [ABSTRACT FROM AUTHOR]

The vacuum residue thermal cracking reaction (nitrogen atmosphere) at different temperatures were explored using vacuum residue as raw material. And the asphaltene samples were extracted from the vacuum residue and its thermal cracking residues, which were further characterized by elemental analysis, infrared spectroscopy, Raman spectroscopy, scanning electron microscopy to reveal the content, composition and microstructure changes of asphaltene molecules under thermal stress. The results show that the asphaltene content of the thermally cracked residue experienced an increasing trend followed by a steady decline that was accompanied by a gradual increase in the yield of the insoluble toluene with an increase in the operating temperature. The molar ratio of hydrogen to carbon decreases significantly with the increase of reaction temperature, while the CH2/CH3 in asphaltene molecules decreases slightly. The aromaticity index [IAr=I3 047 /(I3 047+I2 918)] increased from 0.021 to 0.097, which indicates the thermal treatment promotes the aromaticity of asphaltene.In addition, the thermal treated asphaltene have more loose surface and shows irregular pore structure. [ABSTRACT FROM AUTHOR]

Hot tearing is one of the most serious defects during the casting solidification process. In this study, a new type of multichannel "cross" hot tearing device was designed. The hot cracks initiation and propagation were predicted by the relationship between temperature, shrinkage force and solidification time during the casting solidification process. The reliability and practicability of the multichannel "cross" hot tearing device were verified by casting experiments and numerical simulations. The theoretical calculation based on Clyne-Davies model and numerical simulation results show that the hot tearing tendency decreases in the order: 2024 Al alloy>Al-Cu alloy>Al-Si alloy at a pouring temperature of 670 °C and a mold temperature of 25 °C. Feeding of liquid films at the end of solidification plays an important role in the propagation process of hot tearing. The decrease of hot tearing tendency is attributed to the feeding of liquid film and intergranular bridging. [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]

Ethylene is an essential platform chemical with a conjugated double bond, which can produce many secondary chemical products through copolymerisation. At present, ethylene production is mainly from petroleum fractionation and cracking, which are unsustainable in the long term, and harmful to our environment. Therefore, a hot research field is seeking a cleaner method for ethylene production. Based on the model ethylene-forming enzyme (Efe) AAD16440.1 (6vp4.1.A) from Pseudomonas syringae pv. phaseolicol, we evaluated five putative Efe protein sequences using the data derived from phylogenetic analyses and the conservation of their catalytic structures. Then, pBAD expression frameworks were constructed, and relevant enzymes were expressed in E. coli BL21. Finally, enzymatic activity in vitro and in vivo was detected to demonstrate their catalytic activity. Our results show that the activity in vitro measured by the conversion of α-ketoglutarate was from 0.21–0.72 μmol ethylene/mg/min, which varied across the temperatures. In cells, the activity of the new Efes was 12.28–147.43 μmol/gDCW/h (DCW, dry cellular weight). Both results prove that all the five putative Efes could produce ethylene. [ABSTRACT FROM AUTHOR]

In order to explore the effect of nano-SiO2 on asphalt properties, modified asphalt mixtures with different nano-SiO2 doping contents were prepared. The properties of nano-SiO2 modified asphalt mixtures were characterized by rutting test, water immersion Marshall test, freeze-thaw splitting test and low temperature cracking resistance test. The results show that the modified asphalt with 5wt% doping content of nano-SiO2 has the lowest penetration and higher softening point and viscosity. Compared with the base asphalt, the rutting depth of 5% (mass fraction) nano-SiO2 modified asphalt mixture was reduced by 45.90% and 52.27% at 45 and 60 min, respectively, the dynamic stability was improved by 60.57%, and the residue was stable after immersion in water for 48 h. The tensile strength is up to 90.69%, the freeze-thaw splitting strength ratio is up to 91.24%, the flexural tensile strength is increased by 17.70%, the maximum flexural tensile strain is increased by 11.36%, and the bending stiffness modulus is increased by 8.86%. On the whole, the high temperature performance, water stability and low temperature crack resistance of 5wt% nano-SiO2 modified asphalt mixture have been significantly improved, and it has good road performance and application prospects. [ABSTRACT FROM AUTHOR]

• EU-1 zeolite crystal sizes are shortened to nanoscale with the presence of TPOAC. • EU-1 nano zeolite aggregates expose more external acid sites and accessible volume. • Refining of EU-1 crystal sizes improves the accessibility and utilization degree of acid sites. • EU-1 nano zeolite aggregates show higher n-hexane cracking activity than parent EU-1. One-dimensional microporous zeolite, EU-1, exhibits more favorable selectivity of propylene in cracking of petroleum components. However, it faced the problem of low catalytic activity for the poor utilization of active sites. In this work, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC) was used to functionalize protozeolitic units and inhibit the excessive growth of crystals by the long hydrophobic alkyl chain. The introduction of TPOAC decreased the crystal sizes into nanoscale, enhanced the mesoporous volume of EU-1 zeolite, and exposed more external acid sites. Moreover, TPOAC could interact with Al species, and in this case, fewer Al atoms were incorporated into the zeolite framework, reducing the acid strength and amount. Intelligent gravitation analyzer test indicated that the zeolite prepared with the presence of 0.30 g TPOAC exhibited the largest accessible volumes in n-hexane adsorption, and the highest accessibility of acid sites, which synergistically promoted cracking of n-hexane for the production of light olefins. [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]

Unfilled elastomers often suffer from poor fracture resistance at high temperature where viscoelastic dissipation is low. A molecular design based on multiple interpenetrating networks composed of a brittle filler network isotropically prestretched to a value λ0 by swelling it in an extensible matrix leads to a dramatic increase of fracture energy Γc, typically attributed to sacrificial bond scission creating a dissipative damage zone ahead of the propagating crack. However, the molecular mechanisms controlling the size of the damage zone when the crack propagates are currently unknown. Here, we combine fluorogenic mechanochemistry with quantitative confocal mapping and mechanical testing to characterize both and the extent of bond scission in the sacrificial network detected on the fracture surfaces for different stretch rates and temperatures. We find that increasing the prestretch λ0 of the filler network leads to a large increase in Γc mainly at temperatures well above the glass transition temperature of the elastomers, where viscoelasticity is inactive, but also at lower temperatures where both mechanisms are coupled. Yet, we show that there is no direct linear relation between the extent of filler network scission and Γc. We mainly attribute the large increase in Γc to the dilution of highly stretched strands in the entangled and unstretched matrix, which delocalizes stress upon bond scission and effectively protects the matrix network from scission and the material from crack growth. Delaying the localization of bond scission by network design is a promising strategy that will guide molecular designs able to toughen elastomers even in the absence of viscoelastic dissipation. [ABSTRACT FROM AUTHOR]

Bimodal silica and aluminosilicate materials containing mesopores and macropores were synthesized by hydrothermal method using sodium silicate, aluminum nitrate, P123 triblock copolymer, n-decane, hydrochloric acid and water. The uncalcined silica compound was previously characterized by thermogravimetry, and the calcined materials were characterized by X-ray diffraction, infrared absorption spectroscopy, and scanning electron microscopy. The obtained materials have bimodal characteristics with mesopores and macropores in their structures, which pores are ideal for processing bulky molecules, such as hydrocarbons present in heavy oil. In this work, the synthesized silica and aluminosilicate were used as materials for distillation and cracking of a petroleum sample with oAPI = 17.4. The process was evaluated by thermogravimetry, in the temperature range from 25 to 900 °C, in a nitrogen atmosphere. The determination of activation energies (Ea) as a function of the degree of conversion was obtained by using the Ozawa–Flynn–Wall kinetic model and at heating rates of 5, 10 and 20 °C min−1. It was observed that the catalytic cracking of the oil presented Ea of 196 kJ mol−1 for 90% conversion. At the same conversion, for the oil containing 10% of Si-MBB catalyst, the Ea decreased to 170 kJ mol−1 and for AlSi-BMM, the Ea was 155 kJ mol−1, showing the efficiency of bimodal materials containing mesopores and macropores in its structure for processing of heavy oil. [ABSTRACT FROM AUTHOR]

The hot-tearing susceptibility (HTS) of Mg-6Zn-xGd (x=0.5, 1, 2, 3, 4, 6) alloys was evaluated using a constrained rod casting (CRC) method. The results show that the HTS curve follows a typical "Λ" shape with the increase of Gd content. The Mg-6Zn-2Gd alloy has the highest while Mg-6Zn-6Gd alloy has the lowest HTS value. The hot-tearing behavior characteristics of Mg-6Zn-xGd alloys were further studied through a multifunctional hot-tearing test device. According to the dendrite contact point inferred from the stress curve, the Clyne-Davies criterion was modified and found to be accurate in predicting the HTS of Mg-6Zn-xGd alloys. Microstructure observation reveals that the grain size and the volume of eutectic liquid are the two key factors affecting HTS of Mg-6Zn-xGd alloys. The large grain with columnar structure can easily promote initiation and propagation of hot-tearing due to the poor feeding and coordinating deformation capability, which have a harmful effect on HTS. A higher volume fraction of eutectic phase can refill the cracking and provide continuous feeding channels by dendrite bridge and thicker liquid film, thus increase the hot-tearing resistance. [ABSTRACT FROM AUTHOR]

Because thermowells are prone to fatigue damage in petroleum cracking gas pipelines, in this paper, the LES method is used to simulate the flow around thermowells through two-way thermal-fluid-solid coupling, the internal causes of thermowell damage are explored, and measures for improving the thermowell safety are proposed. According to this study, when high-speed, high-temperature gas passes the thermocouple bushing, the main factors affecting the structural safety of the thermocouple bushing are the alternating stress caused by the vortex falling off, the thermal stress cycle due to the temperature gradient, and the pressure gradient impacted by the gas. Furthermore, this paper proposes improving the thermowell safety by installing the interference devices and optimizing the installation angle. The improvement measures were studied by conducting a two-way thermal fluid-structure coupling simulation. The results of this study show that after installing the interference device and optimizing the installation angle the displacement deformation of the thermowell and the equivalent stress is reduced by 57.2% and 72.1%, respectively, which indicates the safety improvement of the thermowell structure and the effectiveness of the method. The research contents of this paper can provide guidance for the installation and use of thermocouple bushing. [ABSTRACT FROM AUTHOR]

The article discusses the main methods of modeling processes of skew rollers. Factors influencing the formation of internal cracks are discussed. The tendency of a material to crack in skew rolling processes decreases as the temperature of material increases, the number of rolling cycles decreases, and the number of rolls increases. In two-roll skew rolling, internal cracks appear around a central axial zone of a rolled specimen. The size and density of inclusions in a metal sample directly affect the formation of internal cracks. [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]

Steel ingot with a large height-to-diameter ratio is utilized to produce multiple products by one stock in practice. Water cooling is a usual way to enhance production efficiency. However, the combination of the two factors will generate internal defects, such as shrinkage porosity and hot crack. The characteristic of internal shrinkage crack in a 10 t water-cooled steel ingot with a large height-to-diameter ratio was examined by an ultrasonic test. A slice was sectioned from the ingot middle part where billets containing star-like crack were further extracted. The billets were examined by X-ray high energy industrial CT, and the compactness was reconstructed in three dimensions. Microstructure near the crack was observed using scanning electron microscopy, and the solidification process and grain size were studied by high temperature confocal microscopy. Moreover, thermomechanical simulation and post-processing were carried out to analyze the formation of shrinkage porosity and hot crack. A new criterion considering mushy zone mechanical behavior in brittle temperature as well as grain size distribution was proposed to evaluate hot cracking potential in the ingot. The results show that a deep shrinkage porosity band easily forms in the center line of such an ingot with a large height-to-diameter ratio, and water-cooling further generates excessive tensile stress tearing the liquid films around the porosities. Then, hot cracks begin to propagate along grain boundaries. The grain size in the upper and center of the ingot is large, which leads to an inverted cone shape defects zone in the ingot center. [ABSTRACT FROM AUTHOR]

High Nb-TiAl (Ti-44Al-8Nb-0.2W-0.2B-0.5Y, at.%) ingot was fabricated by vacuum arc remelting (VAR). The as-cast ingot was hot-isostatic pressed (HIP) and homogenizing annealing processed. The influence of heat treatment temperature and thermomechanical processing on the microstructure and tensile property of the alloy was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and tensile tests. It was found that the high Nb-TiAl alloy after HIP and annealing was mainly composed of coarse α2/γ lamellae, β/B2 phase and γ phase and the solidification path of this alloy was: L→L+β→β→α+β→α→α+β+γ→α2+β+γ. The water quenching results showed that the alloy was in α single phase region at 1,340 °C. After heating at 1,340 °C for 30 min followed by furnace cooling, the alloy showed a full lamellar microstructure and its ultimate tensile strength was about 538 MPa, with an elongation of 0.3% at room temperature. Free-crack forged pancakes with fine-grained fully lamellar structure (FFLS) were obtained with an initial deformation temperature of 1,340 °C and the ultimate tensile strength of forged alloy was about 820 MPa, with an elongation of 0.9% at room temperature, which was much higher than that of alloy after HIP and annealing because of microstructural refinement. [ABSTRACT FROM AUTHOR]

During fire investigation, gasoline, as a common accelerant, is produced by petroleum cracking. However, the pyrolysis residues of other petrochemicals may interfere with gasoline identification. Polymerised styrene butadiene rubber (SBR) 1502 has combustion characteristics highly consistent with those of gasoline, thus having a great effect on gasoline identification. This study investigated the pyrolysis process of SBR 1502 by using thermogravimetric–differential scanning calorimetry (TG–DSC) and gas chromatography–mass spectrometry (GC–MS) to examine the residues during combustion stages, including pyrolysis and nonpyrolysis stages. The results indicated that 2,3-dimethylnaphthalene in the pyrolysis residues of SBR 1502 in pyrolysis stages 2 and 3 was lacked. However, when SBR 1502 only undergoes the first pyrolysis stage or even earlier (Nonpyrolysis stage), the characteristic components in the residue are similar to gasoline. In addition, mathematical methods were applied to analyse relevance and differences between SBR 1502 and gasoline. The conclusion was that the Pearson product-moment correlation was > 0.990, which may interfere with the identification, and principal component analysis could efficiently distinguish them. The current results can provide an accurate and feasible basis for fire investigation. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms of petroleum thermal cracking is critical to develop more efficient and eco-friendly petroleum cracking processes. Asphaltenes are the main component of petroleum subjected to cracking processes. Thermal cracking mechanisms of petroleum were explored by computational methods using 1,2-diphenylethane (DPE) as a model molecule in this study. The overall mechanisms were divided into four steps including initiation, H-transfer reaction, H-ipso reaction, and termination represented by seven reactions. We carried out extensive quantum chemistry calculations at high levels of theory to accurately explore the minimum energy pathways as the mechanisms of the proposed reactions. The reaction energy and barriers in terms of enthalpy and free energy and their temperature dependence were calculated in the vacuum and in both polar and nonpolar solvents using the polarizable continuum model (PCM) method. The temperature dependence of the target reaction barriers are characterized in different environments and provides computational guidance for future development for petroleum thermal cracking. As the first reported systematic investigation of petroleum cracking mechanisms, this study provided a comprehensive theoretical description of petroleum cracking processes with valuable information about temperature and solvent dependence. [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]

The adsorption and reaction properties of heterogeneous zeolite catalysts (e.g. for catalytic cracking of petroleum, partial oxidation of natural gas) depend strongly on the types and distributions of Al heteroatoms in the aluminosilicate frameworks. The origins of these properties have been challenging to discern, owing in part to the structural complexity of aluminosilicate zeolites. Herein, combined solid‐state NMR and synchrotron X‐ray powder diffraction analyses show the Al atoms locate preferentially in certain framework sites in the zeolite catalyst Al‐SSZ‐70. Through‐covalent‐bond 2D 27Al{29Si} J‐correlation NMR spectra allow distinct framework Al sites to be identified and their relative occupancies quantified. The analyses show that 94 % of the Al atoms are located at the surfaces of the large‐pore interlayer channels of Al‐SSZ‐70, while only 6 % are in the sub‐nm intralayer channels. The selective siting of Al atoms accounts for the reaction properties of catalysts derived from SSZ‐70. [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]