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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 • 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 • 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]

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]

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]

Thermal cracking processes such as visbreaking are used in the petroleum industry to reduce the viscosity of heavy feedstocks, such as atmospheric and vacuum residues, without forming coke or unstable asphaltenes. Thermal cracking offers a potential method to reduce the viscosity of heavy oils and bitumen, enabling their pipeline transportation with less solvent addition. Viscosity is the most important property for transportation of crude oils, but this property also has a highly non-linear dependence on temperature and composition. In this work, we used a lumped-kinetic model, based on boiling point pseudo-components, coupled with a fluid property model, to correlate the viscosity of two heavy oils subjected to thermal cracking reactions at different severities, and assess the impact of the chemical transformations on the behavior of the heaviest fraction. The properties of these pseudo-components were estimated by validated correlations, and tuned with experimental values. By assuming that after the reactions these properties remained invariable in each boiling point pseudo-component, we could estimate the viscosity of the liquid products from the recombination of these individual properties using mixing rules available in literature. The results indicated that the vacuum residue fractions (>524 °C) undergo chemical transformations that alter their fluid properties. By using adjusting factors dependant on conversion, we were able to make estimations of viscosities at different temperatures with absolute average deviations lower than 25%. [ABSTRACT FROM AUTHOR]

Thermal cracking of Athabasca vacuum residue (AVR) and Athabasca bitumen (AB) and their maltene fraction was investigated at 400 °C in a closed system, i.e. autoclave. The effect of the following variables on the product yield and the properties of the liquid fraction and its maltene extract was evaluated: residence time, pressure of the reactor unit, stirring, temperature and asphaltenes content of the feedstock. The yield of the different fractions, the total energy consumption, the pressure buildup in the batch reactor and the °API gravity and viscosity of the liquid fraction and its maltene extract were used to evaluate the impact of a given parameter. In addition, high-temperature simulated distillation (HTSD) analysis of the liquid product and gas chromatography (GC) analysis for gas product were performed. The effect of reaction time, mixing and pressure on the yield of toluene insolubles (TI) depended on the presence of asphaltenes in the feedstock. TI yield increased at the expense of the asphaltenic fraction when reaction time, mixing and pressure increased. There is an inverse relationship between the initial asphaltenes content in the feedstock and the overall asphaltenes yield base on the parent feedstock. Moreover, increasing asphaltenes content of the feedstock did not introduce significant changes in the total energy input to the reactor. [ABSTRACT FROM AUTHOR]

In situ catalytic upgrading of heavy oil offers significant cost savings and overcomes logistical challenges associated with the high viscosity, low API gravity and high molecular weight fractions of unconventional hydrocarbon resources. The THAI-CAPRI process (toe-to-heel air injection – catalytic upgrading process in situ) offers one such route to upgrading through the use of high surface area transition metal cracking catalysts surrounding the production well. Here, we describe the catalytic upgrading of heavy oil in a stirred batch reactor by a biogenic nanoscale magnetite (BnM; Fe 3 O 4 ). A 97.8% decrease in viscosity relative to the feed oil was achieved and coking was lower compared to thermal cracking alone (6.9 wt% versus 10.2 wt%). The activity of this catalyst was further enhanced by a simple one-step addition of surface associated Pd to achieve loadings of 4.3, 7.1 and 9.5 wt% Pd. This led to significant decreases in viscosity of up to 99.4% for BnM loaded with 9.5 wt% Pd. An increment of 7.8° in API gravity with respect to the feed oil was achieved for 9.5 wt% Pd-BnM, compared with thermal cracking alone (5.3°). Whilst this level of upgrading was comparable to commercially available and previously tested catalysts, significant decreases in the coke content (3 wt% for 9.5 wt% Pd-BnM versus 10 wt% for thermal cracking) and associated increases in liquid content (∼90 wt% for 9.5 wt% Pd-BnM versus ∼79 wt% for thermal cracking) demonstrate the potential for the use of Pd-augmented biogenic magnetite as a catalyst in the THAI CAPRI process. [ABSTRACT FROM AUTHOR]

Hydrogen production by methane cracking over a set of demineralised Xiaolongtan lignite chars, with and without the addition of various inorganic species, has been studied using a fixed bed reactor at atmospheric pressure and 1123 K in order to study the catalytic effect of mineral matter on methane cracking. The raw lignite char was prepared by pyrolysing a Xiaolongtan lignite sample in nitrogen in the fixed bed reactor at 1173 K for 30 min. Of the two demineralised chars, one (Char 1) was prepared by washing the parent lignite sequentially with 5 N HCl, 29 N HF and 12 N HCl before pyrolysis while the other (Char 2) was prepared by washing the raw lignite char. For comparison, a variety of inorganic species were added into Char 1 via incipient impregnation. NaCl was added into Char 1 at a sodium content varying from 0.1 wt% to 0.3 wt%. CaCl 2 , FeCl 3 , KCl, and MgCl 2 were also added into Char 1, respectively, with the corresponding metal content being 0.1 wt% in the chars. The methane cracking experiments showed that hydrogen was the primary gas product. The demineralised chars were less effective in catalysing methane cracking than the raw char, suggesting that the mineral matter indeed promoted methane cracking. Char 2 showed higher catalytic activity than Char 1, due to its relatively higher mineral matter content and greater BET surface area. Carbon deposition during methane cracking resulted in deactivation of the chars by blocking the pores and reducing the surface areas. The added inorganic species at trace amounts in the demineralised Char 1 also enhanced the methane conversion and hydrogen yield. With increasing sodium addition up to 0.3 wt%, the catalytic effect of the char increased first and then decreased. In terms of the methane conversion, the catalytic effect of the inorganic species added into Char 1 followed the order of NaCl > CaCl 2 ≈ FeCl 3 > MgCl 2 ≈ KCl. However, the various inorganics showed no difference in enhancing hydrogen yield. [ABSTRACT FROM AUTHOR]

Unsupported Ni Pt metal catalyst with Ni/Pt molar ratio of 88/12 is prepared by water-in-oil (W/O) microemulsion method in this study. Compared to monometallic Ni and Pt catalysts, the Ni Pt catalyst exhibits superior activity and stability for methane cracking. By XRD (X-ray powder diffraction), XPS (X-ray photoelectron spectroscopy) and TEM (Transmission electron microscopy) analyses, the formation of Ni (0) Pt (0) alloy is believed to be the main reason for the reactivity improvement of this catalyst. Carbon nano tube (CNT) with Ni (0) Pt (0) particles anchored on the top of tube are found for the Ni Pt catalyst. [ABSTRACT FROM AUTHOR]

With the aim of enhancing oil refining processes based on fluid catalytic cracking (FCC), the catalytic cracking of polycyclic aromatic hydrocarbons (PAHs) was investigated using an FCC catalyst consisting of a rare earth ion exchanged USY zeolite. In these trials, model PAHs were dissolved in n -hexadecane and were fed into a fixed bed microactivity test reactor operating at 516 °C. Reaction product analysis indicated very little cracking of the 2-ring PAH over the FCC catalyst, while in contrast the 3-ring PAH was highly reactive, and was rapidly converted into monocyclic aromatic hydrocarbons, 2-ring PAHs and coke. Tests using FCC catalysts with different rare earth loadings revealed that the loading amount has little effect on the conversion of the 3-ring PAH. In addition, catalysts containing USY zeolites with comparable unit cell sizes, and thus having comparable hydrogen transfer activities, exhibited similar catalytic activities for 3-ring PAH conversion, even though they contained different amounts of the rare earth metal oxide. This result suggests that the hydrogen transfer reaction plays an important role in 3-ring PAH conversion and that the main effect of rare earth loading is to maintain the hydrogen transfer activity of the catalyst by stabilizing the USY zeolite against steam deactivation. In summary, this study successfully demonstrated a potential FCC process for converting PAHs into useful light fractions without the necessity of employing a pressurized hydrogen atmosphere. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive kinetic model for thermal cracking of waste cooking oil using monomolecular lumped kinetics. The chemical lumps were classified on the basis of carbon number range of the hydrocarbons and a first order irreversible monomolecular cracking kinetics was considered for finding the product concentration in a reactor. Arrhenius kinetic law was applied for determining temperature dependency of the apparent kinetic constants included in the model. The parameter reduction was performed by calculating the preexponential factors through transition state theory and statistical thermodynamics concepts. The activation energy of the reactions was estimated through hybrid optimization using experimental data available in the literature. The proposed kinetic model for thermal cracking of waste cooking oil exhibits good agreement with the experimental data. Furthermore, the present kinetic analysis reveals that all parallel reactions from waste cooking oil are dominant for producing hydrocarbons in a product lump as compared to reactions in series and further cracking of product lumps. [ABSTRACT FROM AUTHOR]

To improve the selectivity performance of CoMoS catalysts applied to the hydrodesulfurization (HDS) of fluid catalytic cracking (FCC) gasoline, a series of CoMoS/Al 2 O 3 catalysts was prepared with alumina of different pore structures, and their HDS performance was evaluated with a real FCC gasoline. This study indicated that CoMoS/Al 2 O 3 catalysts prepared with micro- or meso-porous alumina possessed high HDS activity but low selectivity, whereas macro-porous alumina enhanced the selectivity of CoMoS catalysts. The enhanced HDS selectivity was due to the tuning of the MoS 2 slabs and the weakening of the internal diffusion resistance. Based on the above results, the optimal CoMoS/Al 2 O 3 catalyst was prepared with the alumina of the tri-modal pore distribution at approximately 5–8 nm, 15–20 nm, and 90–100 nm. The optimal catalyst displayed a balanced HDS activity and selectivity in contrast to the reference catalyst prepared with K- and P-modified Al 2 O 3 . [ABSTRACT FROM AUTHOR]

Highlights: [•] This study investigates the effects of thermal cracking on asphaltene molecules. [•] An increase in cracking severity decreases the size of asphaltene molecules. [•] An increase in cracking severity increases the aromaticity. [•] An increase in cracking severity decreases the H/S ratio. [•] An increase in cracking severity concentrates the metals in polyaromatic entities. [Copyright &y& Elsevier]

Highlights: [•] VRs were thermally cracked simulating the Eureka process. [•] VRs consist to 95wt% of alkyl-aromatics with 50% aliphatic carbon. [•] Cracking results in cracked oil, off-gas, and pitch. [•] Oil contains about 4wt% S, aliphatic to aromatic carbon is about 3, and mono- or di-aromatics prevail. [•] Pitch consists of peri-condensed aromatics with ≈47wt% to ≈24wt% aliphatic carbon. [ABSTRACT FROM AUTHOR]

Highlights: [•] The understanding of antifoaming degradation is essential for silicon speciation. [•] PDMS degradation under thermal cracking of hydrocarbons was achieved. [•] Volatile siloxanes, silanes and silanol were characterized by GC/TOFMS. [•] A breakthrough in silicon speciation to understand silicon poisoning in gas cuts. [Copyright &y& Elsevier]

Abstract: Vacuum residues derived from three Kuwaiti crude oils, both conventional and heavy, were thermally cracked in a pilot-scale semi-batch reactor that simulates the cracking operation performance in the Eureka process. The thermal cracking of the vacuum residues resulted in three products: cracked oil, off-gas, and pitch. The effect of operating conditions (i.e. reaction temperature and residence time) on the quality of the products and yield distribution has been investigated. The study also determines the kinetic parameters from the experimental data and compares them with the ones predicted from a previously developed five-lumps discrete kinetic model [1]. The stabilities of the thermally cracked oils were also evaluated using the oxidation stability test while their compatibility with the crude oils were assessed using the Oil Compatibility Model of Exxon. [Copyright &y& Elsevier]

Abstract: Heat transfer and thermal cracking behaviors of kerosene are investigated in a thermal experiment and simulation. A flat-plane reactor of aviation kerosene with a rectangular channel is built. The heat sink and thermal cracking characteristics at subcritical and supercritical pressures are measured and compared. A one-step thermal cracking global reaction is established from the proportional product distribution and a gaseous-product experiment. The flow, heat transfer and cracking reaction of kerosene in a flat-plane reactor are coupled to simulate the two-phase flow and thermal cracking. The wall temperature predicted with a one-step thermal cracking model is in good agreement with the experimental data. The thermal cracking plays an important role in the endothermic process as the fuel temperature exceeds approximately 500°C. The rate of the variation in the overall heat sink increases with fuel temperature owing to the endothermic process of thermal cracking. An increase in pressure promotes the thermal cracking reaction. [Copyright &y& Elsevier]

Abstract: This work presents the development of a kinetic model for the thermal cracking of vacuum residues in a pilot-scale semi-batch reactor, which simulates the cracking operation performed in the Eureka process. The vacuum residues were derived from three Kuwaiti crude oils, both conventional and heavy. Experimental data was obtained at three cracking temperatures (400, 415, and 430°C) and three reaction times (30, 50, and 60min). The proposed thermal cracking kinetic model is based on the discrete lumping approach. The reaction scheme consisted of five lumps: the four cracked products and residual unconverted oil. The cracked products represent the product slates obtained from the commercial Eureka process, namely, the off-gases (<150°C), cracked light oil (150–370°C), cracked heavy oil (370–538°C), and demister oil (>538°C). The analysis of the results revealed that the thermal cracking of vacuum residue follows first order kinetics. The proposed model predicted the kinetic parameters for the thermal cracking of different residual feedstock and provided a good fit to the experimental data. [Copyright &y& Elsevier]

Abstract: Fluid Catalytic Cracking (FCC) catalysts are based on combinations of two main active phases, the HY and the HZSM-5 (additive) zeolites, but previous studies only concerned the phenol influence on these pure zeolites. Therefore, n-heptane was transformed in presence of phenol over mechanical mixtures of HY and HZSM-5 zeolites, at 450°C, to evaluate the FCC catalysts behaviour during phenolic-rich bio-oils/conventional FCC feedstocks co-processing. Phenol induces an additional deactivation of the zeolites mixtures from the beginning of the reaction because increases the carbon deposition, as for pure zeolites. However, mixing the zeolites, the impact of phenol on HZSM-5 seems to not be as strong as for HZSM-5 alone due to an initial preferential adsorption of phenol on HY, as suggested by the adsorption energies of phenol on these catalysts calculated by Density Functional Theory (DFT), −80kJmol−1 for HY and −60kJmol−1 for HZSM-5. This agrees with the initial products distribution, which points out an enhancement of 14–20% in the paraffins/olefins molar ratio and of about 40% in the amount of branched species on the effluent in presence of phenol, as for pure HY. The HZSM-5 further resistance against phenol, when mixed with HY, decreases by increasing phenol content from 1.2wt.% to 4wt.%. Hence, at an industrial level, the FCC catalyst should suffer a lower effect of phenol on the ZSM-5 additive function than expected, which would be certainly dependent on the amount of each zeolite in the FCC catalysts formulations and on the fraction of phenolic species in the FCC feedstock. [Copyright &y& Elsevier]

Abstract: To shed light into the influences of the shape of the main hydrocarbon families constituting FCC feedstocks (naphthenes and alkanes) and of the phenolic molecules size on the MFI additive function during bio-oils and traditional Fluid Catalytic Cracking feedstocks co-processing, the transformations of n-heptane in presence of phenol and guaiacol were performed over an HMFI zeolite, at 350 and 450°C. For phenol, the results were compared with those previously obtained with methylcyclohexane. A lower impact of phenol was noticed for n-heptane than for methylcyclohexane due to the easier linear alkanes diffusion into the zeolite channels, which reveals that the phenolic molecules influence on the MFI additive function could not be as critical as envisaged for a purely naphthenic feedstock. Whatever the reactant, higher temperatures do not overcome phenol deactivating effect because, once inside the zeolite structure, phenol polar molecules diffusion is very limited. An increase of the coke molecules ramification and aromaticity was observed for the n-heptane transformation in presence of phenol, instead of a reduction of the coke production from the reactant, as noticed for methylcyclohexane. Therefore, for n-heptane the further HMFI deactivation due to phenol mainly proceeds by pore blocking, contrarily to that verified for methylcyclohexane. Furthermore, the greater the size of the phenolic molecules present in the hydrotreated bio-oils, the lower their effect on the MFI additive action. In fact, bulky oxygenated molecules are preferential adsorbed close to the zeolite outer surface, from which they are more easily removed at higher temperatures. This explains the lower guaiacol deactivating effect at 450°C, when compared with phenol. [ABSTRACT FROM AUTHOR]

Abstract: Experiments were carried out with a woody waste fraction using a two-stage gasifier consisting of a fluidized bed zone and a tar cracking zone that was filled with activated carbon. In the experiments, the effects of experimental conditions such as the temperature and the equivalence ratio were investigated. In addition, the results of the experiments with virgin activated carbon, without activated carbon, and with spent activated carbon were compared. The producer gases that were obtained in the experiments were analyzed using GCs (FID and TCD) and a GC–MS system. The producer gas obtained with the application of activated carbon at an ER of 0.2 had high H2 content (16vol.%, N2-free), and its lower heating value was above 10MJ/Nm3. In addition, the total amount of the tar captured by the scrubbers and the electrostatic precipitator was reduced sixfold when activated carbon was applied. [ABSTRACT FROM AUTHOR]

Abstract: A mixture of hospital post-commercial polymer waste (LDPE/HDPE/PP/PS) was pyrolyzed over various catalysts using a fluidized-bed reactor operating isothermally at ambient pressure. The yield of volatile hydrocarbons with zeolitic catalysts (ZSM-5>MOR>USY) were higher than with non-zeolitic catalysts (MCM-41>ASA). MCM-41 with large mesopores and ASA with weaker acid sites resulted in a highly olefinic product mixture with a wide carbon number distribution, whereas USY yielded a saturate–rich product mixture with a wide carbon number distribution and substantial coke levels. The systematic experiments discussed in this paper show that the use of various catalysts improves the yield of hydrocarbon products and provide better selectivity in the product distributions. A novel developed model based on kinetic and mechanistic considerations which take into account chemical reactions and catalyst deactivation for the catalytic degradation of commingled polymer waste has been investigated. This model represents the benefits of product selectivity for the chemical composition such as alkanes, alkenes, aromatics and coke in relation to the performance and the particle size selection of the catalyst used as well as the effect of the fluidizing gas and reaction temperature. [Copyright &y& Elsevier]

Abstract: To minimize tar in the producer gas from birch gasification at 700, 750 and 800°C, four Chinese dolomites (Zhenjiang, Nanjing, Shanxi, Anhui) and a Swedish dolomite (Sala) used as reference were studied in a laboratory-scale atmospheric fluidized bed gasifier. The gasifier was equipped with a downstream fixed catalyst bed. The results imply that all dolomites but Anhui dolomite effectively decompose tar into gases. Anhui dolomite showed a low catalytic capacity to crack tar produced at 700 and 800°C. The influence of various ratios of steam to biomass on tar content in the producer gas after passing over dolomite was studied. The tar cracking efficiency of the dolomites did not improve significantly with the ratio of steam to biomass in the region 0.11–0.52. [Copyright &y& Elsevier]

Abstract: This paper provides a kinetics model for thermal cracking of various oils over time frames which correspond to the long term storage at temperatures up to those experienced in an in situ combustion process. The model describes detailed kinetic mechanisms and concentration changes of individual species during the thermal cracking reactions. Also the modeling results are compared with the experimental data to verify their validity. [Copyright &y& Elsevier]

Abstract: Gasification of meat and bone meal followed by thermal cracking of tar was carried out at atmospheric pressure using a two-stage fixed bed reaction system in series. The first stage was used for the gasification and the second stage was used for thermal cracking of tar. In this work, the effects of temperature (650–850°C) of both stages, equivalence ratio (actual O2 supply/stoichiometric O2 required for complete combustion) (0.15–0.3) and the second stage packed bed height (40–100mm) on the product (char, tar and gas) yield and gas (H2, CO, CO2, CH4, C2H4, C2H6, C3H6, C3H8) composition were studied. It was observed that the two-stage process increased hydrogen production from 7.3 to 22.3vol.% (N2 free basis) and gas yield from 30.8 to 54.6wt.% compared to single stage. Temperature and equivalence ratio had significant effects on the hydrogen production and product distribution. It was observed that higher gasification (850°C) and cracking (850°C) reaction temperatures were favorable for higher gas yield of 52.2wt.% at packed bed height of 60mm and equivalence ratio of 0.2. The residence time of tar and product gases was varied by varying the packed bed height of second stage. The tar yield decreased from 18.6wt.% to 14.2wt.% and that of gas increased from 50.6wt.% to 54.6wt.% by changing the packed bed height of second stage from 40 to 100 mm while the gross heating value (GHV) of the product gas remained almost constant (16.2–16.5MJ/m3). [Copyright &y& Elsevier]

Abstract: In order to study the catalysis of solid acid for the liquefaction of coal, a series of solid acids were synthesized by the method of precipitation–impregnation. The catalytic behaviours of the solid acids for the hydro-liquefaction of Shenhua coal and model compounds, such as diphenylmethane, bibenzyl and phenyl ethyl ether, were investigated. In addition, non-catalytic liquefaction and the catalytic liquefaction under N2 were further compared with the catalytic liquefaction under H2 in order to understand the catalytic mechanism of solid acid. The results indicate that hydro-liquefaction conversions of coal and model compounds are related to the strength, amount and nature of acid sites on the surface of , and the strong acid site responds to their catalytic activities. The solid acid catalyzes mainly the hydro-cracking, ring-opening and hydrogenation reactions of coal to produce oil and gas during the coal liquefaction. The hydro-cracking reactions in the liquefaction of model compounds and coal catalyzed by involved via carbenium ion intermediate instead of traditional radicals intermediate. [Copyright &y& Elsevier]

[Display omitted] • Ultra-low hydrogen content PAHs observed in the processed petroleum bottoms. • The H 10 molecules can be rationalized by the corannulene-based PAHs. • Highly curved bowl-shaped PAH structures proposed for H 8 , H 6 and H 4 molecules. • H 8 , H 6 and H 4 PAHs do not obey the "isolated pentagon rule" as do H 10 PAHs. • Strain energies of the PAHs are lower than that of fullerenes of the same C number. • The bowl-shaped PAHs are likely formed in the catalytic cracking of the petroleums. In the ultra-high resolution mass spectrometric analysis of processed petroleums (fossil materials), we observed species with ultra-low hydrogen content (e.g. H/C ratio from 0.1 to 0.4). Some of the observed chemical formula (C 20-40 H 10) can be rationalized by the known corannulene-based peri -condensed Polycyclic Aromatic Hydrocarbons (PAHs). Other formulas (such as C 20-40 H 8 , C 20-40 H 6 and C 20-40 H 4) cannot be rationalized with any known structures. We proposed highly curved non-planar PAHs involving multiple connected five member aromatic rings. These structures do not obey the isolated pentagon rule (IPR). The stabilities of the proposed structures were evaluated by density functional theory. Strain energies were calculated based on hypothetical isodesmic conversion of planar structures to the curved non-planar structures. Results showed that the strain energies of the proposed structures are lower than that of fullerenes of the same carbon number, confirming stabilities of the non-IPR structures. The low hydrogen content species are likely formed in the thermal and/or catalytic cracking of the petroleums. They are possible intermediate molecules on the path toward the formation of fullerenes (buckyballs) and other nano-carbon materials [ABSTRACT FROM AUTHOR]

Athabasca bitumen vacuum bottom (ABVB) was fractionated into 66.9% maltenes (n-pentane-solubles), 32.2% asphaltenes (n-pentane-insolubles), and 0.9% coke (toluene-insolubles). The maltenes were subsequently split into four sub-fractions: 5.6% saturates (MF1), 2.6% mono and diaromatics (MF2), 38.2% polyaromatics (MF3), and 20.3% polars (MF4). Yield maximization of the desirable light MF1 and MF2 sub-fractions was explored according to three catalytic (Mo) scenarios: (i) a one-step ABVB hydrocracking with light products recovery; (ii) two-step process consisting of ABVB hydrocracking followed by the hydrocracking of the maltenic MF3+MF4 sub-fractions; and (iii) one-step ABVB hydrocracking with specific pretreatment procedures to enhance contacting between Mo-based catalyst and the heavy oil. The products yield distribution was mapped according to a severity parameter combining temperature and time. Coke and gas formation increased with increased severity while asphaltenes and total maltenes decreased. For scenario (i), the optimum severity factor for the highest light products yield was 7.2. At this severity the ensemble of saturates, plus mono and diaromatics reached 32.7%. For scenario (ii), the optimum severity factors were 6.9 and 7.0 for the first and second hydrocracking steps, respectively, resulting in a total light products yield of 45.4%. In scenario (iii) where options such as increasing the catalyst concentration, removal of oil-borne coke before hydrocracking and ultrasonic mixing, the maximum MF1+MF2 yield reached 50.8% on raw ABVB weight basis at a severity factor of 7.2. [Copyright &y& Elsevier]

This study investigated the deposition of coke in a fractionation tower following thermal cracking of heavy feedstocks. A simple microscopic technique was used to determine whether the coke formed in situ in the fractionator or was formed elsewhere (e.g. in the reactor vessel) and was subsequently entrained in the vapour phase. The reflectance of coke types, mode of occurrence, and distributions from the bottom to the top of the fractionator were used to interpret the range of temperatures responsible for coke formation. Both isotropic and anisotropic (mosaic) coke was observed in the samples. The anisotropic textural features indicated that asphaltenes carry-over was a minor problem and that the vast majority of the isotropic coke precursors were the maltenes present in the gas phase that entered the fractionator. The formation of perfectly spherical mesophase was attributed to the gas oil stream itself used to quench the vapours exiting the thermal cracking vessel. Microscopic evidence, along with metals concentration in the coke at various locations of the operation provided useful information as to the nature of the coke precursors. [Copyright &y& Elsevier]