Reactions Of Hydrocarbons Research Articles

(Invited) Computational Predictions of Site-Dependent Reactivities for Complex Reactions in Confinement

It is well known that the relatively high overpotentials for oxygen evolution reactions arise from similar binding energies for HO* and HOO* intermediates that tend to move in lockstep on different catalysts. A strategy to break this scaling limitation is through differential stabilization of the two intermediates by engineering the reaction environment. Nanoporous materials such as zeolites and metal-organic frameworks provide such a possibility through their well-defined pore space that presents microscopically tunable reaction environments. Yet the predictive understanding of catalytic actions in these heterogeneous catalysts requires the ability to describe not only the electronic structure at the active site, but also how the extended environment interacts with the reacting species through individually weak yet collectively significant non-covalent interactions. In this talk, we present a new computational procedure that couples quantum-chemical methods and forcefield-based sampling to enable a consistent calculation of local activation energies for articulated reactants. As a first application, we studied hydrocarbon reactions in four different zeolites and showed how the method allows for the estimation of transition-state entropy and for the systematic calculation of site-dependent activation energies. The latter can be used to derive rigorous ensemble-averaged barriers for comparison with experiments, as well as guiding future strategies for controlling Al distributions during zeolite synthesis.

Exploration of NH3 and NH3/DME laminar flame propagation in O2/CO2 atmosphere: Insights into NH3/CO2 interactions

Cofiring with reactive hydrocarbon and oxygenated fuels is an effective approach to enhance ammonia (NH3) combustion, which raises growing interest in understanding CN interactions. Among these fuels, dimethyl ether (DME, CH3OCH3) has attracted extensive attention due to its renewable nature and potential for large-scale synthesis from CO2 feedstock. This work reports an experimental and modeling investigation on the laminar flame propagation of NH3 and NH3/DME in O2/CO2 atmosphere, with an emphasis on evaluating the enhanced NH3/CO2 interactions under flame conditions. Laminar burning velocities (LBVs) were measured at elevated pressures up to 5 atm in a constant-volume combustion vessel. A kinetic model was developed and can well reproduce the measured LBVs in this work, as well as the LBVs and speciation data in literature. Modeling analyses and the modified fictitious diluent gas method were used to explore the effects of DME cofiring, pressure and CO2 dilution on LBVs. The results reveal that the chemical effect plays a crucial role in promoting the laminar flame propagation of NH3 with DME cofiring, while the reduction of LBVs with CO2 dilution is predominantly influenced by the thermal effect. LBVs of NH3/DME present a stronger pressure dependency than that of pure NH3, which is attributed to the enhanced pressure-sensitive three-body reactions, including CH3 + H (+M) = CH4 (+M) and H + O2 (+M) = HO2 (+M). Phenomenological analysis of LBVs was conducted by varying the diluent gas from pure N2 to pure CO2, complemented by modeling analyses with adjusted rate constants, to provide insights into NH3/CO2 interactions. The results show that CO2 reduction reactions, including NH + CO2 = HNO + CO and CO + OH = CO2 + H, compete for reactive radicals like H and NH with chain-branching reactions H + O2 = OH + H and consequently prohibit the laminar flame propagation.

Effects of transition metal doping on the properties and catalytic performance of ZSM-5 zeolite catalyst on ethanol-to-hydrocarbons conversion

In this study, the effects of transition metal-doping on the physicochemical properties and catalytic performance of HZSM-5 catalysts for the conversion of ethanol to hydrocarbons are investigated using experimental data and secondary data from the literature. Hydrothermally synthesized novel ZSM-5 catalysts were modified with different concentrations (0.5 and 10 wt%) of transition metals (Co, Fe, Ni). Characterizations, including X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, particle size distribution, N2 adsorption and NH3 temperature-programmed desorption, revealed the changes in catalyst properties. The introduction of transition metals affected the surface area, particle size and acidity without altering the MFI structures. In particular, a reduction in surface area was observed, ranging from 2.6 to 23 %, corresponding to the different metal loading of 0.5–10 wt% compared to the surface area of the pure catalyst (397.5 m²/g). In addition, metal-doping led to an increase in Lewis acid sites, accompanied by a decrease in strong acid sites. Catalytic evaluation at 350 °C and a space velocity of 12 h−1 showed improved performance in metal-doped ZSM-5 catalysts, which exhibited high selectivity towards fuel-range hydrocarbons, compared to the unmodified catalyst. Catalysts with low metal doping showed optimal catalytic activity, while high metal doping led to increased coke deposition and deactivation of the catalyst due to an increased concentration of strong acids. These results underline the suitability of metal-modified ZSM-5 for hydrocarbon reactions and provide valuable insights for the optimization of catalysts for ethanol conversion to fuel-range hydrocarbons.

Interpretable Machine Learning with Physics-Based Feature Engineering: Application to the Catalytic Cracking Reaction of Polycyclic Aromatic Hydrocarbons

Interpretable Machine Learning with Physics-Based Feature Engineering: Application to the Catalytic Cracking Reaction of Polycyclic Aromatic Hydrocarbons

Effect of iron on the soot formation of different model compounds pyrolysis

Control soot generation among hydrocarbon fuels efficient and clean utilization process is a significant challenge. This paper presents the physical and chemical characteristics of soot samples derived from model compounds (biphenyl, naphthalene, anthracene, and pyrene) mixed with ferric nitrate pyrolysis in an inert atmosphere. Characterization was conducted with transmission electron microscopy(TEM), Raman spectrometer, X-ray diffractometer(XRD), X-ray photoelectron spectroscopy(XPS), and infrared spectroscopy (FTIR). The results indicate that the soot indicates that four model compounds have similar primary diameters. The size of microcrystals in soot was proportional to the number of aromatic rings of the model compounds. The addition of fer ric nitrate induces a 7–20 % decrease in the diameter of soot primary particles. Meanwhile, the size of the microcrystals in the primary particles increased and the curvature decreased but did not affect the stacking distance of the crystallites. With the number of aromatic rings of the model compound increasing, the content of aliphatic chains in soot formation under the same conditions tends to rise. This suggests that the ring-opening reaction of polycyclic aromatic hydrocarbons is an essential process in soot formation. Additionally, the involvement of iron led to the production of more aliphatic functional groups and the generation of oxygen-containing functional groups.

Protolysis of five-membered metallacyclocumulene complexes of zirconocene and hafnocene

The reactions of the five-membered metallacyclocumulene complexes Cp2M[η4ButC4But] (M = Zr, Hf) with an equimolar amount of HCl in dioxane at 20 °C result in linear complexes Cp2M(Cl)–C(But)=CH–CCBut, whereas the reaction with an excess of HCl affords Cp2MCl2 and trans-ButCH=CH–CCBut. The reaction of the latter hydrocarbon with an equivalent amount of the bis(trimethylsilyl)acetylene complex of zirconocene Cp2Zr(Me3SiC2SiMe3)(Py) leads to bis(trimethylsilyl)acetylene and a five-membered zircona-cycloallene complex. This complex can also be obtained in ‘one-pot’ via the reactions of five-membered zircona-cyclocumulene with two equivalents of HCl and subsequent treatment with magnesium in THF.

Insight into reactive oxygen plasma characteristics and reaction mechanism on SRF accelerator plasma cleaning

Reactive oxygen plasma treatment is an effective technique to eliminate hydrocarbon and improve the performance of superconducting radio frequency (SRF) cavities. This work investigated the reaction mechanism between reactive oxygen plasma and hydrocarbon, surface reaction kinetics, and cleaning process optimization through experiments, analytical models, and numerical simulations. The experimental results declare that the reaction between oxygen plasma and hydrocarbon is dominated by ion-assisted chemical sputtering, and the hydrocarbon attenuates exponentially, increasing the work function exponentially. To study the surface reaction kinetic process in-depth, we proposed a plasma cleaning rate model based on the Langmuir–Hinshelwood theory. This study found that the plasma cleaning rate primarily depends on the sheath potential, electron temperature, O atoms density, O+ ions, and Ar+ ions densities. Furthermore, we did a control-parameter simulation and found that increasing gas pressures or O2 ratios are conducive to enhancing the chemical reaction rate between O atoms and hydrocarbon. Also, the power increase can enhance the physical effect of ions. It shows that increasing the gas pressure and power and reducing the oxygen content can achieve a better cleaning effect while reducing the radio frequency power loss caused by the oxide. Those results provide valuable guidance for optimizing the cleaning process, deepening the understanding of the cleaning mechanism, and improving the performance of SRF cavities.

Analisis Miskonsepsi Siswa XI MIA 1 SMA Negeri 1 Pangkajene pada Materi Pokok Hidrokarbon

This descriptive research aims to analyze the student’s misconceptions on hydrocarbon subject that have been learned by STAD Type of Cooperative Learning Model. The subjects in research are 31 students of SMA Negeri 1 Pangkajene class XI MIA 1. The data was collected by 7 items essay test and intensified by interviews. The data was analyzed by descriptive statistic method to obtain percentage of the misconseption. The result of this research shows that student’s misconception is low category, 17% in determining C atom of primary, secondary, tertiary, and quaternary. In naming of alkanes, alkenes, and alkyne’s structure, is low category, average 24,5%. In understanding addition and subtitusi reaction of hydrocarbon is low category, 22,4%. And low category, average 21,3% on misconception of hydrocarbon in generallydisciplining teachers and motivating them to comply with the foundation's policies is a problem that must be immediately found a solution. This research uses a qualitative approach, data sources obtained through interviews through zoom applications, documentation, and observation. This article found that PAUD al Ashriyyah Principal Nurul Iman in improving teacher discipline used autocratic style to be the dominant style, not seen other styles played by principals in the leadership model. The principal in improving the work discipline of his teachers does not always run smoothly, the obstacles and obstacles

Abatement of photochemical smog precursors through complete hydrocarbon oxidation over commercial Pd catalysts under fuel-lean conditions with NO promoting effect

Currently, severe environmental issues have led to a great transition in the automotive industry from internal combustion engine vehicles to electric vehicles, but this transition will take time more than 10 years, which still requires the use of internal combustion engine vehicles. However, these vehicles emit a significant amount of hydrocarbons, in addition to nitrogen oxides (NOx), due to incomplete fuel combustion. They contribute to the formation of photochemical smog when they react with NOx in the presence of sunlight. To effectively remove these hydrocarbons from the exhaust gas of turbo-gasoline engines or diesel engines, we investigated the abatement of propane and iso-pentane, two typical hydrocarbons. In particular, we studied commercial Pd catalysts and revealed how the Pd loading and aging process simulating 4k and 100k mileage affected hydrocarbon abatement abilities, and their phases were identified using characterization technique, including CO chemisorption, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM). We also suggested the reaction pathway for the complete oxidation of propane over Pd catalyst based on the reaction orders of propane and oxygen: Propane adsorbs on O atoms of PdO, and the kinetically relevant C–H bond cleavage step occurs by the interaction with abundant neighboring O atoms of PdO. Finally, the propane and iso-pentane abatement ability of the Pd catalyst aged for 100k mileage were evaluated under realistic exhaust gas conditions, and the effect of each gas component in the realistic exhaust gas was identified; water inhibits the catalytic reaction of hydrocarbons by occupying the active sites, whereas NO catalyzes the hydrocarbon oxidation reaction by either changing the reaction pathway or active sites under fuel-lean conditions. These findings enable us to effectively reduce environmental pollution and facilitate a smoother transition from internal combustion engine vehicles to electric vehicles.

Study on the cooling and drag reduction characteristics of multi-port injector array film cooling using gaseous hydrocarbon fuel as coolant

Supersonic film cooling utilizing gaseous hydrocarbon fuel is an effective method to meet the thermal protection and drag reduction requirements inside a scramjet engine. The film injection scheme for film cooling using gaseous hydrocarbon fuel is crucial in determining the thermal protection and drag reduction performance of the film with oxidative cracking reaction. In this paper, a numerical study is conducted to compare the thermal protection and drag reduction performance of gaseous hydrocarbon fuel film under the slot injector film cooling structure and the multi-port injector array film cooling structure. The results show that the multi-port injector array film cooling utilizing gaseous hydrocarbon fuel as a coolant improves both thermal protection and drag reduction performance compared to the slot injector film cooling structure. The chemical reaction of hydrocarbon fuel expands the cooling range and low resistance area of a single discrete hole. The reason is that the multi-port injector array film cooling intermittently interrupts the oxidation and heat release process of the hydrocarbon fuel in the boundary layer, resulting in higher cooling efficiency in the film cooling injection area. It also improves the spatial distribution of the hydrocarbon fuel film, allowing for effective utilization of the chemical heat sink of the hydrocarbon fuel, which improves the thermal protection performance and expands the effective cooling area. Furthermore, the enhanced mixing of the multi-port injector array film cooling in the film injection area improves drag reduction performance through combustion inside the boundary layer, resulting in a significant drag reduction of 36.6%. The multi-port injector array film cooling also effectively distributes the low skin-friction resistance region due to the low molecular viscosity after the secondary cooling flow injection. Moreover, under supersonic mainstream conditions, the mixing efficiency of the multi-port injector array film cooling structure and the slot injector film cooling structure both decreases, and the difference gradually decreases.

Thermodynamic approach for hydrogen production from the steam reforming reaction of aromatic hydrocarbons (BTX)

This study investigates the preferred reaction conditions through thermodynamic analysis to produce hydrogen from the steam reforming of BTX, a mixture of benzene (C6H6), toluene (C7H8), and xylene (C8H10). A thermodynamic equilibrium analysis employing the minimization of Gibbs free energy was used to investigate the effects of temperatures (200–1000 °C), S/C ratios (0.5–4.0), and pressure (1–20 atm) on the molar fraction at equilibrium, conversion (C6H6, C7H8, C8H10), selectivity (C, CO, CO2, CH4), moles (H2 and CH4), and H2 yield. The steam reforming of BTX is a complex process that involves various reactions such as steam reforming, cracking, carbon formation, and water-gas shift reactions. It was confirmed that cracking does not occur above 700 °C, and carbon deposition does not form with S/C ratio higher than 3.0. In addition, the steam reforming reaction of BTX was found to be favorable at low pressure. To minimize undesirable reactions, such as cracking and carbon deposition, and enhance hydrogen production, the optimal conditions were identified as S/C ratio of 3.0, temperature of at least 700 °C, and atmospheric pressure. This research contributes valuable insights into the steam reforming of BTX, highlighting the optimal conditions that maximize hydrogen production while minimizing unwanted reactions. By identifying these conditions, the study underlines the importance and innovation in the hydrogen production field, potentially guiding future research and industrial applications.

Enhanced conversion of syngas to high-quality gasoline hydrocarbons over ZnZrOx coupled SAPO-11 nanosheets bifunctional catalyst

Syngas is a key precursor for synthesizing gasoline (C5-C11) hydrocarbons, offering an efficient route for utilizing non-petroleum carbon sources. However, the conventional Fischer-Tropsch synthesis (FTS) process faces a constraint with a maximum 45% selectivity for C5-C11, attributed to the Anderson-Schultz-Flory (ASF) distribution. Herein, bifunctional catalysts comprising ZnZrOx with different Zr/Zn ratios along with SAPO-11 zeolite sieves featuring varied morphologies like nanosheets (SA-A), petals (SA-B), and spheres (SA-C) have been effectively formulated and employed for the syngas-to-gasoline hydrocarbons (STG) reaction. Notably, the selectivity toward C5-C11 far exceeded the ASF limits. Under identical reaction parameters, the Zn1Zr4Ox/SA-A catalyst demonstrated notable enhancements of 6.6% and 26.2% in CO conversion, along with 4.6% and 7.6% increases in C5-C11 selectivity, as compared to that of Zn1Zr4Ox/SA-B and Zn1Zr4Ox/SA-C catalysts, respectively. Furthermore, under the ideal conditions (380 °C, 4.5 MPa and gas hourly space velocity (GHSV) of 2400 mL min−1 g−1), Zn1Zr4Ox/SA-A exhibited an exceptional C5-C11 selectivity of 69.8% (CO2-free) alongside a single-pass CO conversion of 30.4%. Impressively, isoparaffin constituted 39.2% of the total composition, with the iso/n-paraffin ratio reaching 11.8. Even after 100 h, the catalyst maintained its remarkable catalytic activity, with the CO conversion and C5-C11 selectivity maintaining levels of 27.5% and 66.85%, respectively.

Methanol diffusion and dynamics in zeolite H-ZSM-5 probed by quasi-elastic neutron scattering and classical molecular dynamics simulations.

Zeolite ZSM-5 is a key catalyst in commercially relevant processes including the widely studied methanol to hydrocarbon reaction, and molecular diffusion in zeolite pores is known to be a crucial factor in controlling catalytic reactions. Here, we present critical analyses of recent quasi-elastic neutron scattering (QENS) data and complementary molecular dynamics (MD) simulations. The QENS experiments show that the nature of methanol diffusion dynamics in ZSM-5 pores is dependent both on the Si/Al ratio (11, 25, 36, 40 and 140), which determines the Brønsted acid site density of the zeolite, and that the nature of the type of motion observed may vary qualitatively over a relatively small temperature range. At 373 K, on increasing the ratio from 11 to 140, the observed mobile methanol fraction increases and the nature of methanol dynamics changes from rotational (in ZSM-5 with Si/Al of 11) to translational diffusion. The latter is either confined localized diffusion within a pore in zeolites with ratios up to 40 or non-localized, longer-range diffusion in zeolite samples with the ratio of 140. The complementary MD simulations conducted over long time scales (1 ns), which are longer than those measured in the present study by QENS (≈1-440 ps), at 373 K predict the occurrence of long-range translational diffusion of methanol in ZSM-5, independent of the Si/Al ratios (15, 47, 95, 191 and siliceous MFI). The rate of diffusion increases slightly by increasing the ratio from 15 to 95 and thereafter does not depend on zeolite composition. Discrepancies in the observed mobile methanol fraction between the MD simulations (100% methanol mobility in ZSM-5 pores across all Si/Al ratios) and QENS experiments (for example, ≈80% immobile methanol in ZSM-5 with Si/Al of 11) are attributed to the differences in time resolutions of the techniques. This perspective provides comprehensive information on the effect of acid site density on methanol dynamics in ZSM-5 pores and highlights the complementarity of QENS and MD, and their advantages and limitations. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

Green synthesis of shaped nano-ZSM-5 toward more efficient methanol-to-hydrocarbon conversion

Commonly, in the synthesis of zeolites, calcination is necessary prior to ion exchange to remove organic templates. Herein, shaped nano-ZSM-5 was successfully prepared with the assistance of template-free nano-aggregate seed without the calcination step before ion exchange. This synthesis method dramatically increased mesopores volume compared with the one calcined prior to ion exchange. Besides, employing nano-aggregate as seed gave the synthesized ZSM-5 a markedly smaller particle size and higher yield than the one prepared with conventional silicate-1 as seed, and simultaneously accelerated the crystallization process by providing more nuclei. A possible formation mechanism of the shaped nano-ZSM-5 zeolites was proposed. The shaped nano-ZSM-5 possessed the smallest crystal size, largest mesopore volume, most acid sites and strongest acid strength, which endowed it highest catalytic activity and longest lifetime in methanol to hydrocarbons reaction. This work could attract more attention on the application of nanoscale ZSM-5 catalyst to industry.

Selective Valorization of CO2 towards Valuable Hydrocarbons through Methanol‐mediated Tandem Catalysis

AbstractThe thermocatalytic conversion of carbon dioxide (CO2) into valuable hydrocarbons presents a promising solution for mitigating anthropogenic CO2 emissions while producing drop‐in replacements for fossil‐derived products. Among the two tandem mechanisms for the direct hydrogenation of CO2, the methanol synthesis coupled with the methanol to hydrocarbon (MTH) reaction offers an improvement over the reverse water‐gas shift coupled with Fischer‐Tropsch synthesis reaction (RWGS‐FTS), as it is not limited by Anderson‐Schulz‐Flory distribution and yields higher selectivity towards specific products (e. g., olefins, aromatics, higher hydrocarbons). Herein, we focus on the recent progress achieved through this pathway and outline the existing knowledge gaps. We discuss the challenges involved in the process and highlight the key descriptors in the selection of catalyst components. Finally, we present several potential solutions to circumvent the current challenges, aiming to expedite the advancement of this route toward an efficient CO2 hydrogenation process.

Application of photocatalytic proxone process for petrochemical wastewater treatment

Industrial wastewaters are different from sanitary wastewaters, and treatment complications due to their unique characteristics, so biological processes are typically disrupted. High chemical oxygen demand, dye, heavy metals, toxic organic and non-biodegradable compounds present in petroleum industry wastewater. This study intends to optimize the photocatalytic proxone process, utilizing a synthesized ZnO–Fe3O4 nanocatalyst, for petroleum wastewater treatment. The synthesis of ZnO–Fe3O4 was done by air oxidation and layer-by-layer self-assembly method and XRD, SEM, EDAX, FT-IR, BET, DRS, and VSM techniques were used to characterize the catalyst. Central composite design (CCD) method applied to investigated the effect of pH (4–8), reaction time (30–60 min), ozone gas concentration (1–2 mg/L-min), hydrogen peroxide concentration (2–3 mL/L) and the amount of catalyst (1–0.5 g/L) on the process. In the optimal conditions, biological oxygen demand (BOD5) and total petroleum hydrocarbon (TPH) removal, reaction kinetic, and synergistic effect mechanisms on the process were studied. Based on the ANOVA, a quadratic model with R2 = 0.99, P-Value = 0.0001, and F-Value = 906.87 was proposed to model the process. Based on the model pH = 5.7, ozone concentration = 1.8 mg/L-min, hydrogen peroxide concentration = 2.5 mL/L, reaction time = 56 min, and the catalyst dose = 0.7 g/L were proposed as the optimum condition. According to the model prediction, an efficiency of 85.3% was predicted for the removal of COD. To evaluate the accuracy of the prediction, an experiment was carried out in optimal conditions, and experimentally, a 52% removal efficiency was obtained. Also, at the optimum condition, BOD5 and TPH removal were 91.1% and 89.7% respectively. The reaction kinetic follows the pseudo-first-order kinetic model (R2 = 0.98). Also, the results showed that there is a synergistic effect in this process. As an advanced hybrid oxidation process, the photocatalytic proxone process has the capacity to treat petroleum wastewater to an acceptable standard.

Potential production of carbon nanotubes from liquid aromatic hydrocarbons over Fe and Ni on alumina powder via catalytic chemical vapor deposition

In this study, liquid aromatic hydrocarbons of benzene C6H6, toluene C7H8, and xylene C8H10 (BTX), which can be abundantly found in industrial waste oil and pyrolysis products of waste plastics, were used as carbon sources to produce carbon nanotubes (CNTs). CNTs were firstly synthesized from liquid benzene over powdered alumina (Al2O3) supported Fe and Ni catalysts at 700 to 850 °C via catalytic chemical vapor deposition (CCVD) method. It was found that, CNTs synthesized from Fe/Al2O3 resulted in significantly higher carbon yields at 1.0–5.6 wt% with relatively higher graphitization analyzed by Raman spectroscopy compared to those of Ni/Al2O3 with the yields only at 0.6–2.8 wt%. However, smaller sizes of CNTs at 20–29 nm could be produced from Ni/Al2O3 compared to 30–38 nm obtained from Fe/Al2O3 due to its smaller crystallite size of the initial catalyst confirmed by X-ray diffraction (XRD) analysis. For both catalysts, with increasing CCVD temperature, the yields tended to increase with a slight increase in CNT diameter and graphitization degree. The temperature of 800 °C was then chosen for further preliminary investigation on potential mass production of CNTs from BTX. By doubling the amount of catalysts, the CNT yield could be approximately twice achieved by maintaining its uniformity and quality because of remaining active sites of the catalysts. In addition, increasing the carbon atoms of aromatic hydrocarbons resulted in improved yields without changing the quality of CNTs. Finally, kinetic mechanisms of CNT growth from BTX decomposition using Fe/Al2O3 catalyst were simply investigated by varying reaction time from 10 to 60 min. At feeding flow of 0.5 ml/min, optimum reaction time was achieved at 30 min in order to produce uniform CNTs at high yields without carbon loss, unreacted BTX, and undesired by-products, which possibly occurred by hydrogenation, catalyst deactivation, and/or side reactions of as-produced gaseous hydrocarbons during CCVD reaction.

CALCULATION OF THERMODYNAMIC AND KINETIC PARAMETERS OF CATALYTIC CRACKING REACTIONS ON LEWIS AND BRØNSTED ACID SITES

Link for citation: Nazarova G.Y., Ivashkina E.N., Maltsev V.V. Calculation of thermodynamic and kinetic parameters of catalytic cracking reactions on Lewis and Brønsted acid sites. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 214-225. In Rus. The relevance of the research is caused by the emerging necessity of developing a mathematical model to optimize the heterogeneous process of catalytic cracking. This tools should take into account both the chemical transformations of a wide range of hydrocarbon groups (different feedstock types), as well as the stages of adsorption, reactants diffusion, conversion of hydrocarbons on the catalyst surface, acid characteristics and pore size of the catalysts. The study of the hydrocarbon conversion patterns on Lewis or Brønsted acid sites using quantum-chemical modeling methods allow us to quantify the thermodynamic parameters of reactants adsorption, the kinetic parameters of carbocations formation and cracking on acid sites. These results are necessary to develop a mathematical model based on the of heterogeneous catalytic reaction mechanism. The aim of this work is to identify the level of quantum chemical theory and to determine the thermodynamic and kinetic parameters of reactants adsorption, carbenium ions formationand hydrocarbons cracking on Lewis and Brønsted acid sites. Methods: quantum-chemical modeling methods to optimize the molecular geometry of reactants and products of catalytic cracking reactions, calculate vibrational frequencies, thermodynamic parameters of adsorption and catalytic cracking of hydrocarbons and heteroatomic compounds with the participation of Bronsted and Lewis acid sites. Results. The chosen level of quantum-chemical theory allowed obtaining the results that are consistent with the laws of the process and the experimental reactivity of hydrocarbons in cracking reactions on acid catalysts. The thermodynamic parameters of the adsorption of C6–C16 hydrocarbons and thiophenes on Lewis and Brønsted acid sites were identified. We found that during the cracking of n-hexane on the Lewis acid site, the reaction is limited by the carbenium ion formation stage.The activation energy of this stage was 281,3 kJ/mol whereas the value for the cracking stage was 277,2 kJ/mol. Further study shows that the activation energy of carbenium ion formation from izohexane and C8–C10 alkanes with normal structure on the Lewis acid site was 257,6 and 279,2…277,9 kJ/mol. The most energetically favorable is the formation of carbocation from hexene at Brønsted acid sites (76,59 kJ/mol). The results of the work will be used to create a mathematical model of a heterogeneous process based on the Langmuir–Hinshelwood equations.

Steam reforming of butanol-ethanol mixture for H2 production over Ru catalysts

The present work investigates the steam reforming of butanol – ethanol mixtures for H2 production over Ru-based catalysts. Α 5 wt% Ru/Al2O3 and a 5 wt% Ru/MgO-Al2O3 catalysts were synthesized via the wet impregnation method and physicochemically characterized with various techniques. Catalytic activity tests were carried out using a ButOH/EtOH/H2O mixture between 550 and 700 °C. The ButOH and EtOH conversion as well as H2 selectivity were found to be equal to ca. 100 % for all tested catalysts at 700 °C. The superior performance of Ru/Al2O3 compared to its Ru/MgO-Al2O3 counterpart was mainly attributed to the higher Ru metal dispersion achieved in the former case. The presence of MgO appears to suppress the H2 selectivity in favor of hydrocarbon reaction intermediates production. The higher activity and H2 selectivity of the Ru/Al2O3 is accompanied by remarkable stability after 45 h of exposure to the reaction mixture at 700 °C. Our work suggests that Ru-based catalysts may outperform Pt-based ones in technically challenging steam reforming processes involving alcohol mixtures toward H2 production.

Biodegradation of phenanthrene by piezotolerant Bacillus subtilis EB1 and genomic insights for bioremediation

A marine strain B. subtilis EB1, isolated from Equator water, showed excellent degradation towards a wide range of hydrocarbons. Degradation studies revealed dense growth with 93 % and 83 % removal of phenanthrene within 72 h at 0.1 and 20 MPa, respectively. The identification of phenanthrene degradation metabolites by GC–MS combined with its whole genome analysis provided the pathway involved in the degradation process. Whole genome sequencing indicated a genome size of 3,983,989 bp with 4331 annotated genes. The genome provided the genetic compartments, which includes monooxygenase, dioxygenase, dehydrogenase, biosurfactant synthesis catabolic genes for the biodegradation of aromatic compounds. Detailed COG and KEGG pathway analysis confirmed the genes involved in the oxygenation reaction of hydrocarbons, piezotolerance, siderophores, chemotaxis and transporter systems which were specific to adaptation for survival in extreme marine habitat. The results of this study will be a key to design an optimal bioremediation strategy for oil contaminated extreme marine environment.