Catalytic Composition Research Articles

Novel insight into calcium-catalyzed steam gasification behaviors of lignite

Lignite is a low-rank coal with abundant reserves, and direct combustion causes serious environmental pollution. Calcium-catalyzed steam gasification is a cleaner technology that can convert lignite into high-value fuels and chemicals. However, the detailed structural evolution of calcium species during lignite steam gasification remains inadequately understood. The present work addresses this issue by subjecting the calcium-catalyzed steam gasification process of lignite to a detailed analysis, focusing on both the pyrolysis and gasification stages. The transitions in the chemical structures of the lignite and calcium catalysts during the pyrolysis stage were investigated in situ by Fourier Transform Infrared Spectroscopy. The morphological and chemical characterization of chars was performed using SEM-EDS, Raman spectroscopy, XPS, and N2 adsorption/desorption. The catalytic performance and gas composition were investigated by TGA and a fixed-bed reactor during the gasification stage. The results verify that the calcium catalyst reduced the initial gasification temperature of lignite by 150 °C, resulting in a 13.91% increase in the H2 concentration of the synthesis gas and an improvement of the H2/CO ratio to 20.96. The active Ca-C site and intermediate Ca-O-C formed during the co-pyrolysis stage increase the defect density of char, and the transformation of organic calcium species catalyzes the gasification of lignite. The enhanced concentration of H2 in the syngas can be attributed to the catalytic effect of CaO on the water–gas shift reaction during the gasification process. These results are expected to guide efforts in supporting catalytic conversion processes and promoting the efficient utilization of low-rank coal.

Machine Learning Big Data Set Analysis Reveals C-C Electro-Coupling Mechanism.

Carbon-carbon (C-C) coupling is essential in the electrocatalytic reduction of CO2 for the production of green chemicals. However, due to the complexity of the reaction network, there remains controversy regarding the underlying reaction mechanisms and the optimal direction for catalyst material design. Here, we present a global perspective to establish a comprehensive data set encompassing all C-C coupling precursors and catalytic active site compositions to explore the reaction mechanisms and screen catalysts via big data set analysis. The 2D-3D ensemble machine learning strategy, developed to target a variety of adsorption configurations, can quickly and accurately expand quantum chemical calculation data, enabling the rapid acquisition of this extensive big data set. Analyses of the big data set establish that (1) asymmetric coupling mechanisms exhibit greater potential efficiency compared to symmetric coupling, with the optimal path involving the coupling CHO with CH or CH2, and (2) C-C coupling selectivity of Cu-based catalysts can be enhanced through bimetallic doping including CuAgNb sites. Importantly, we experimentally substantiate the CuAgNb catalyst to demonstrate actual boosted performance in C-C coupling. Our finding evidence the practicality of our big data set generated from machine learning-accelerated quantum chemical computations. We conclude that combining big data with complex catalytic reaction mechanisms and catalyst compositions will set a new paradigm for accelerating optimal catalyst design.

STUDY OF CATALYTIC BEHAVIOURS OF THE SPINEL STRUCTURE NdxMg1- xAl2O4 COMPOSITION WITH ZSM-5 ZEOLITE IN ETHYLBENZENE DISPROPORTIONATION

Nanosized (10–15 nm) powders of spinel structures NdxMg1–xAl2O4 were obtained by low-temperature combustion of aluminium, magnesium, neodymium nitrate solutions, diethylmalonate, and hydrazine monohydrate with further calcination of nanopowders at 1000 °C, which were used in the preparation of catalytic compositions with ZSM-5 zeolite. The obtained catalytic compositions were characterized by X-ray diffraction, pyridine adsorption, and low-temperature nitrogen adsorption. The acidic properties and porosity of the catalysts were altered by controlling the concentration of nanopowder (1.0–7.0 wt.%) in the catalytic composition. The interaction of the modifier with HZSM-5 zeolite leads to a decrease in specific surface area and pore volume, as well as reduse of strong Bronsted acid sites (B) and an increase in the concentration of medium Lewis acid sites (L), resulting in a change in the B/L ratio from 3.61 to 0.23. The ongoing variations contributed mainly to an enhancement of the para-selectivity of the catalytic composition in the ethylbenzene disproportionation reaction. The catalytic composition of 5% Nd0.1Mg0.9Al2O4 with a pore volume of 0.15 cm3/g and an acid site B/L ratio of 0.27 demonstrates a maximum selectivity to p-diethylbenzene of 75.6% with a conversion of ethylbenzene of 23.7%.

Development of Nb-based alloy membranes with improved resistance to corrosion by H2S

At present, the interest in non-Pd hydrogen permeation membranes mainly focuses on group 5 B metals (Nb, V, Ta) and their alloys. To solve the problem of easy oxidation and weak dissociation of hydrogen molecules, a "Pd catalytic layer" needs to be deposited on the membrane surface. Due to its limited stability towards sulfur, issues of irreversible poisoning by sulfur compounds must be addressed. To this end, Pd-, Pd65Ag35-, Pd90Cu10-, Pd80Au20-, and Pd55Ag35Au10-coated Nb30Hf35Co35 membranes were firstly synthesised by magnetron sputtering, and their hydrogen permeation behaviour in pure H2 and/or in different H2/H2S mixtures for up to 1000 ppm at 673 K were evaluated. At these conditions, the permeabilities of the Pd-coated membranes decrease rapidly with increasing the H2S concentration and cannot recover after removal of H2S from the feed mixtures. In comparison, the Pd–Ag-containing membrane greatly increases the pure H2 permeability, whereas the membrane doped with Au can effectively improve the response to H2S. Specifically, the Pd65Ag35-coated membrane shows the highest pure H2 permeability, but it loses maximum permeability value on exposure to H2/H2S feed mixtures. In contrast, Pd80Au20-containing membranes exhibit good tolerance of H2S poisoning and displayed a high fractional recovery (∼83%) of initial H2 permeability. The degradation of permeability for Pd- or Pd65Ag35-coated membranes after the H2S exposure can be ascribed to the deterioration of the structure caused by the possible formation of bulk Pd4S, which has been corroborated with EDS analysis, XRD, and XPS after testing. Finally, to improve both permeability and chemical tolerance, a Pd55Ag35Au10-coated membrane was successfully fabricated, and it possesses excellent comprehensive performance with respect to the permeability and H2S response. At 120 ppm H2S in the feed, the H2 flux equals ca. 43% of its original value at 673 K and can be stable for at least 166 h. Bulk sulfides did not form on the membrane surface after the testing. This paper not only developed a new type of group 5 B alloy membrane with improved resistance to corrosion by H2S, but also further confirmed the feasibility of improving H2S corrosion resistance by adjusting the catalytic layer type or composition of the outermost coating.

Activity of Platinum-Based Cathode Electrocatalysts in Oxygen Redaction for Proton-Exchange Membrane Fuel Cells: Influence of the Ionomer Content

Studying the ORR activity of platinum-based electrocatalysts is an urgent task in the development of materials for proton-exchange membrane fuel cells. The catalytic ink composition and the formation technique of a thin layer at the RDE play a significant role in studying ORR activity. The use of a polymer ionomer in the catalytic ink provides viscosity as well as proton conductivity. Nafion is widely used as an ionomer for research both at the RDE and in the MEA. The search for ionomers is a priority task in the development of the MEA components to replace Nafion. The study also considers the possibility of using the LF4-SK polymer as an alternative ionomer. The comparative results on the composition and techniques of applying the catalytic layer using LF4-SK and Nafion ionomers are presented, and the influence of the catalytic ink composition on the electrochemical characteristics of commercial platinum–carbon catalysts and a highly efficient platinum catalyst based on an N-doped carbon support is assessed.

Ni-Fe bimetallic catalysts with high dispersion supported by SBA-15 evaluated for the selective oxidation of benzyl alcohol to benzaldehyde.

A wetness impregnation method was used to impregnate the substrate with a substantial quantity of oleic acid together with a metal precursor, leading to significantly dispersed Ni-Fe bimetallic catalysts based on mesoporous SBA-15. Using a wide variety of characterization methods, such as XRD, BET, and TEM Analysis, the physiochemical properties of the catalyst were determined. The addition of the metal does not have any effect on the structural characteristics of the SBA-15 catalyst, as validated by transmission electron microscopy (TEM), which shows that the prepared SBA-15 supported catalyst has a hexagonal mesoporous structure. The catalytic capabilities of the Ni-Fe-SBA-15 catalysts were evaluated in the conversion of BzOH using tert-butyl hydroperoxide (TBHP) as an oxidant and acetonitrile as a solvent. The Ni/Fe-SBA-15 (NFS-15) catalytic composition is the best of the developed catalysts, with a maximum conversion of 98% and a selectivity of 99%. In-depth investigations were conducted into the molar ratio of TBHP to BzOH, the dosage of the catalyst, the reaction rate, temperature, and solvent. The recycling investigations indicate that the synthesized Ni/Fe-SBA-15 (NFS-15) catalyst seems to be more durable up to seven successive cycles.

Production of light olefins from methanol using catalytic fixed bed reactor with different catalytic bed composition

Methanol to olefin conversion has captured the attention of the industry as olefins are feed material to many polymer industries. In this work methanol conversion to olefins was investigated over beds of (i) physical mixture of metal oxides with ZSM-5 (PMB) and (ii) metal impregnated over ZSM-5 (MLB). ZSM-5 used in the current study was pre modified by boric acid treatment for modifying catalytic active site composition. Two different metals from alkaline series: calcium and magnesium & from transition metal series: iron and copper were selected. PMB studies were performed on 1:1 (by weight) metal oxides and BZSM-5 whereas for MLB studies, 10 % metal was loaded. Performance studies of the two different bed composition were performed at 500°C, 100 ml/min N2 flow with 1 g catalyst in a fixed bed reactor. 100 % conversion was obtained on MLB studies in presence of Cu, Mg and Fe whereas in PMB studies, 100 % conversion could be obtained over FeO+BZSM-5 bed. The order of olefins yield obtained was in the following order: BZSM-5 > Mg/BZSM-5 > Cu/BZSM-5 > CuO+BZSM-5 > CaO+BZSM-5 > Fe/BZSM-5 > FeO+BZSM-5 > CaO+BZSM-5 > MgO+BZSM-5. It was observed that maximum methane yield was obtained in presence of physical mixture. Gaseous products other than olefins with high composition of C1–C4 hydrocarbons were formed in presence of Mg and Ca whereas the metal impregnated modified-ZSM-5 produced higher content of olefins with Cu loaded catalysts in both bed composition. Metal impregnated catalysts as well as physical mixtures were characterized by BET, FTIR and XRD, FESEM for surface area, topology, crystallinity etc. Spent catalysts were characterized for coke deposition using TGA.

Rational regulation of 3D N-doped carbon macro-architectures toward low-temperature plasma catalysis: The roles of nitrogen content and hierarchical porous structure

The application of low-temperature plasma technology with optimized catalysts in water treatment has shown a good application prospect. However, the relationships between catalytic performance and composition (N atom-doping) and structure (hierarchical porous) of catalysts is still unclear. Here, 3D N-doped carbon macro-architectures is designed by thermolysis of energetic Zn-MOF, where triazole ligand with ultra-high nitrogen content provided the possibility for effective nitrogen doping and creation of hierarchical porous structure. In the DBD system, a series of energetic MOF-derived carbon (EMC-x) catalysts with different pyrolysis temperatures (from 700 to 1000 °C) were prepared, and the composition/structure-effective relationship was investigated in detail. Degradation mechanisms and pathways were analyzed by bursting experiments, quantitative detection of H2O2 and O3, three-dimensional excitation-emission matrix spectroscopy (3D-EEM), LC-MS. The results confirmed that EMC-10 with high nitrogen content and hierarchical porous structure has a wide range of applications in synergistic plasma removal of TTCH from water bodies.

Spectroscopic determination of metal redox and segregation effects during CO and CO/NO oxidation over silica-supported Pd and PdCu catalysts

We report the effects of alloying Cu into silica supported Pd nanoparticles on the catalytic activity, surface composition, and particle structure during CO oxidation Pd is highly active for CO oxidation but is inhibited by relevant competitive reagents (e.g. NO) at low temperatures (< 150 °C). By alloying Cu into Pd nanoparticles, NO inhibition is suppressed without any CO oxidation activity loss. Infrared spectroscopy illustrates the formation of surface nitrosyl (NO-Pd) is eliminated in the PdCu alloy catalyst, preventing CO oxidation inhibition by NO. X-ray absorption spectroscopy studies show that Pd in the monometallic catalyst forms a surface oxide after light-off. Conversely, in the PdCu catalyst, Pd remains metallic during reaction, independent of temperature, whereas the Cu oxidizes when the catalyst becomes active, after light-off. Furthermore, DRIFTS studies show that the Cu segregates to the surface as the catalyst becomes active for diesel oxidation, presumably becoming the O2 adsorption site.

Highly efficient electrooxidation of 5-hydroxymethylfurfural (HMF) by Cu regulated Co carbonate hydroxides boosting hydrogen evolution reaction

The biomass electrochemical oxidation has attracted worldwide attention owning to its carbon-neutral and sustainable nature. Here, different morphologies of CoCu-carbonate hydroxides (CH) electrodes are prepared through one-step hydrothermal method for 5-hydroxymethylfurfural electrocatalytic oxidation (HMF-ECO) to high-valued 2,5-furandicarboxylic acid (FDCA) for the first time. The results illustrate that Cu can regulate CoCu–CH morphologies from 1D nanorods to 2D ultra-thin nanosheets besides modulating the catalytic compositions. The optimal Co1Cu1–CH exhibits hybrid nanostructures containing the 1D nanorods and 2D ultra-thin nanosheets, which has the largest ECSA and specific surface area, as well as the smallest Tafel slope and impedance. The oxidation potential of HMF-ECO is 1.42 V vs RHE with the conversion of HMF 99.57%, the selectivity for FDCA 99.91%, and the FE 98.88%. In addition, Cu can promote the conversion of Co2+ to the favorable Co3+ for HMF-ECO on the catalyst surface. Density functional theory calculation indicates that Cu can improve charges transfer to HMF and lower its adsorption energy. In situ Raman spectra tests indicate that cobalt species is the active site for HMF-ECO. Furthermore, at 1.42 V vs RHE, the coupling of HMF-ECO and hydrogen evolution reaction shows that the cathodic hydrogen evolution rate is 92.33 L h−1 m−2, which is 3.69 times more than water splitting. This work provides a special structures material to process intensification of HMF electrooxidation coupling hydrogen production.

Thermal deactivation mechanism of the commercial Pt/Pd/Rh/CeO2-ZrO2/Al2O3 catalysts aged under different conditions for the aftertreatment of CNG-fueled vehicle exhaust

Commercial three-way catalysts with high-activity and long-term durability are critical for the aftertreatment of compressed natural gas vehicle exhausts to meet increasingly stringent policy requirements, but high concentrations of CH4 and H2O in the exhaust gas make the catalyst susceptible to deactivation. In this work, a series of commercially deactivated and aged honeycomb Pt/Pd/Rh/CeO2-ZrO2/Al2O3 catalysts were obtained by dry-aging, hydrothermal-aging and engine bench-aging methods, and the effects of aging conditions on catalytic performance, surface composition and microstructure evolution were investigated. The combinations of H2-TPR, XRD, Raman, HRTEM, XPS and in situ DRIFTS of CO/CH4 characterizations confirmed that the stability of CeO2-ZrO2 solid solution structure is a key factor affecting the catalytic activity and durability. Hydrothermally-aged catalyst has a relatively stable CeO2-ZrO2 solid solution structure, which ensures a high dispersion of precious metal particles in the form of small particles on the catalyst surface. Dry-aged catalyst shows that more CeO2 crystals have been segregated from CeO2-ZrO2 solid solution, resulting in most precious metal particles in the form of agglomerates. For the deactivated catalysts after engine bench aging, the microstructure was significantly changed with a large number of CeO2 crystals detached from CeO2-ZrO2 solid solution, resulting in more active sites of Platinum Group Metal (PGM) being encapsulated. In situ DRIFTS of CH4 experiments showed that the process of generation and depletion of intermediate species (e.g., methoxy, formate and bicarbonate species) is a matching process. For the deactivated catalysts with fewer active sites, the subsequent reaction steps of these intermediate species to CO2 and H2O are hindered by the accumulation of stable formate and bicarbonate intermediate species.

AQUEOUS-PHASE HYDROGENATION OF FURFURAL IN THE PRESENCE OF SUPPORTED METALLIC CATALYSTS OF DIFFERENT TYPES. A REVIEW

Hydrogenation of furfural in the presence of heterogeneous catalysts has recently attracted increased interest as a method for the synthesis of oxygen-containing compounds of various classes based on renewable raw materials. The composition of the catalyst and the conditions of its preparation essentially determine which of the routes of reductive conversions during the hydrogenation of furfural will be predominant. The present review summarizes and analyzes methods for controlling the physicochemical and functional properties of various metal catalysts with an emphasis on Pd-, Ni-, Co, and Cu-containing catalytic compositions, as the most common and practically significant in the hydrogenation of furfural. Many examples show the influence of the nature of the support, the composition of the active metal precursor, and the conditions for the formation of metal nanoparticles on the activity and selectivity of supported catalysts in the reductive conversions of furfural under aqueous-phase hydrogenation conditions. Promising directions of research on the development of methods for the synthesis of efficient catalysts with controlled functional properties in the hydrogenation of furfural are considered. The bibliography includes 127 references.

Magnetically-separable quasi-homogeneous catalyst: Brush-type ionic liquid polymer coated magnetic polymer microspheres for tandem reactions to produce 4H-pyrans/biodiesel

Employing magnetic polystyrene microspheres as the core and brush-type alkaline imidazolium ionic liquid polymers as the covalent bonds, a robust magnetically-separable quasi-homogeneous magnetic brush-type ionic liquid polymers ([Im][OH]/MP-B) was synthesized. Due to the features of brush-type ionic liquid polymer (BILPs), [Im][OH]/MP-B demonstrated high catalytic activity. With a broad variety of substrates, [Im][OH]/MP-B was applied in Knoevenagel-Michael tandem reactions for the synthesis of 4 H-pyrans (achieving 99.99% conversion and 93.6% yield) and transesterification tandem reactions for sustainable biodiesel production (achieving 99.9% conversion and 95.2% yield). Furthermore, the catalytic performance of [Im][OH]/MP-B was superior to that of [Im][OH]/MP-CL and [Im][OH]/MP-L and comparable with that of homogeneous catalysts. The reasonable and feasible reaction mechanism of magnetic ionic liquid polymers catalyzing tandem reactions was explored in-depth based on the catalytic performance and kinetics, which clearly demonstrated the catalytic activity and stability of [Im][OH]/MP-B. Notably, [Im][OH]/MP-B was effortlessly recovered by magnetic separation and reutilized numerous times with no evident change in catalytic performance, composition, or microstructure, indicating promising possibilities for ecologically friendly procedures. This work provides a potential strategy for the synthesis of magnetic BILPs for tandem reactions, which could serve as a platform for ecologically friendly and sustainable chemistry.

Bimetallic Catalysts for Sustainable Chemistry: Surface Redox Reactions For Tuning The Catalytic Surface Composition

AbstractThe development of a bimetallic catalyst for a given reaction requires not only the selection of the appropriate metals M1 and M2 but also the control as far as possible of the distribution of the two metals together and at the support surface in the case of supported catalysts. Preparation methods using redox reactions specifically enable the deposition of a second metal M2 at the surface of monometallic M1 nanoparticles, leading in most cases to core‐shell nanoparticles with strong metal‐metal interactions. Various methods are possible depending on the electrochemical potentials of the species involved: either a direct redox reaction, also named galvanic replacement, or the reduction of an intermediate reducing agent activated at the surface of M1. In this minireview, the fundamental bases of the preparation of bimetallic catalysts by both types of redox reactions and the recent advances in that domain are described.

Study of Catalytic Properties of the HoxMg1-xAl2O4 Modified HZSM-5 Zeolite in Conversion of Methanol to C2-C4 Alkenes and p-Xylene

Selective conversion of methanol to C2-C4 alkenes and p-xylene is one of the appealing chemical routes. Currently, there are no effective catalysts for the co-production of C2-C4 alkenes and p-xylene from methanol. To date, modified medium-pore ZSM-5 zeolites are considered one of the excellent candidates for the development of selective catalysts for the conversion of methanol to lower alkenes and aromatic hydrocarbons. In this paper, nanosized (30-33nm) powders of HoхMg1-хAl2O4 spinel structure were obtained by the method of combustion of nitrate solutions of aluminium, magnesium, holmium, diethylmalonate and hydrazine monohydrate with the further calcination of nanopowders at 1000 °C. Obtained nanopowders used in the preparation of a solid-phase catalytic composition of HoхMg1-хAl2O4-HZSM-5. Various physico-chemical properties of the catalytic composition were investigated using X-ray diffraction (XRD), pyridine adsorption (BİO-RAD FTS 3000 MX) and low-temperature nitrogen adsorption (BET) techniques. The textural properties and acidity of the catalysts were altered by adjusting the nanopowder concentration (1.0-5.0 wt.%) in the catalytic composition. The conversion of methanol in the presence of the catalytic compositions was carried out in flow-type fixed-bed catalytic reactor at 400 °C, in the presence of nitrogen carrier gas with 1.0 h-1 flow rate. A correlation between the selectivity to C2-C4 alkenes and p-xylene with a ratio of Lewis (L) and Brønsted (B) acid sites and the volume of the catalyst pore, the amount of the modifier in the catalytic system has been established. As the amount of HoхMg1-хAl2O4 nanopowder increases, the ratio of B/L acid sites and the volume of the catalyst pore decrease, which play a significant role in the increase of the selectivity to C2-C4 alkenes and p-xylene. Maximum yield of C2-C4 alkenes (31.6%) and selectivity to p-xylene (80.5%) is achieved on a catalytic composition containing 5.0 wt.% HoxMg1-xAl2O4. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Esterase Sequence Composition Patterns for the Identification of Catalytic Triad Microenvironment Motifs.

Ester hydrolysis is of wide biomedical interest, spanning from the green synthesis of pharmaceuticals to biomaterials' development. Existing peptide-based catalysts exhibit low catalytic efficiency compared to natural enzymes, due to the conformational heterogeneity of peptides. Moreover, there is lack of understanding of the correlation between the primary sequence and catalytic function. For this purpose, we statistically analyzed 22 EC 3.1 hydrolases with known catalytic triads, characterized by unique and well-defined mechanisms. The aim was to identify patterns at the sequence level that will better inform the creation of short peptides containing important information for catalysis, based on the catalytic triad, oxyanion holes and the triad residues microenvironments. Moreover, fragmentation schemes of the primary sequence of selected enzymes alongside the study of their amino acid frequencies, composition, and physicochemical properties are proposed. The results showed highly conserved catalytic sites with distinct positional patterns and chemical microenvironments that favor catalysis and revealed variations in catalytic site composition that could be useful for the design of minimalistic catalysts.

The Contribution of Proton-Donor pKa on Reactivity Profiles of [FeFe]-hydrogenases.

The [FeFe]-hydrogenases are enzymes that catalyze the reversible activation of H2 coupled to the reduction–oxidation of electron carriers. Members of the different taxonomic groups of [FeFe]-hydrogenases display a wide range of preference, or bias, for H2 oxidation or H2 production reactions, despite sharing a common catalytic cofactor, or H-cluster. Identifying the properties that control reactivity remains an active area of investigation, and models have emerged that include diversity in the catalytic site coordination environments and compositions of electron transfer chains. The kinetics of proton-coupled electron transfer at the H-cluster might be expected to be a point of control of reactivity. To test this hypothesis, systematic changes were made to the conserved cysteine residue that functions in proton exchange with the H-cluster in the three model enzymes: CaI, CpII, and CrHydA1. CaI and CpII both employ electron transfer accessory clusters but differ in bias, whereas CrHydA1 lacks accessory clusters having only the H-cluster. Changing from cysteine to either serine (more basic) or aspartate (more acidic) modifies the sidechain pKa and thus the barrier for the proton exchange step. The reaction rates for H2 oxidation or H2 evolution were surveyed and measured for model [FeFe]-hydrogenases, and the results show that the initial proton-transfer step in [FeFe]-hydrogenase is tightly coupled to the control of reactivity; a change from cysteine to more basic serine favored H2 oxidation in all enzymes, whereas a change to more acidic aspartate caused a shift in preference toward H2 evolution. Overall, the changes in reactivity profiles were profound, spanning 105 in ratio of the H2 oxidation-to-H2 evolution rates. The fact that the change in reactivity follows a common trend implies that the effect of changing the proton-transfer residue pKa may also be framed as an effect on the scaling relationship between the H-cluster di(thiolmethyl)amine (DTMA) ligand pKa and Em values of the H-cluster. Experimental observations that support this relationship, and how it relates to catalytic function in [FeFe]-hydrogenases, are discussed.

The effect of iron oxide content in bentonite clay in the catalytic composition on the distribution of sulfur in the cracking products of the model sulfur-containing feedstock

The study revealed the effect of a clay with different content of iron oxides introduced into the cracking catalyst composition on the distribution of feedstock sulfur in the products and on the amount of sulfur oxides formed upon regeneration of the coked catalyst after cracking of the model sulfur-containing feedstock with a sulfur content of 10 000 ppm from 2-methylthiophene or benzothiophene. The use of a sulfur compound with a higher molecular weight increased the fraction of the feedstock sulfur passing into liquid products and coke. When iron oxidecontent in the catalyst was increased from 0.61 to 1.53 wt.% upon cracking of the model feedstock, the yield of liquid products increased, the conversion of model hydrocarbon decreased, and the yield of coke on the catalyst grew from 3.8 to 5.2 wt.%; in the process, the fraction of the feedstock sulfur that passed into SO2 increased fourfold.

Automation and Control of the Electrocatalytic Layers Formation Using a Two-Dimensional Coordinate Spraying Machine

The paper describes the developed automated device for the formation of electrocatalytic layers used in electrochemical systems, and the issues of development of the sputtering technology, which allows to obtain the best parameters of the formed active layers. The general scheme of the automated device includes a system of automatic positioning of the spraying head according to two coordinates, driven by stepper motors controlled by a personal computer, an ultrasonic mini-disperser, a spraying head, ultrasonic generators for the ultrasonic mini-disperser, and the ultrasonic spraying head. Stepper motors were controlled by microprocessor system based on 8-bit Atmel AT90S2313 single-chip microcontroller and standard buffer microcircuits. The key actuating element of the device and the process is the developed atomizing head with an integrated ultrasonic homogenizer that prevents sedimentation of the catalytic composition. The overall automation circuit designed and reproduced to control all electronic devices was described in detail. It differed by application of Attiny2313 microprocessor for the control, availability of communication with personal computer via RS-485 interface that allowed not only to switch the disperser on/off, but also to control its working frequency directly from the personal computer. It was envisaged both manual control of stepper motor controller via control buttons and control from external personal computer, which had the opportunity to control spraying program step by step. In this case all the sequence of steps is contained in the personal computer memory, it is transmitted to the stepper motor controller step-by-step as the program is being executed. Algorithms for moving the spraying head that provide the best drying of catalytic composition in the process of its application have been developed. The effectiveness of the developed automated device has been shown by comparing it with manual application by a specialist according to such criteria as the rate of application of electrocatalytic layers and their quality. The created device, algorithms of its operation, software and scientific and technological advance, in general, can be used for the formation of various coatings both in electrochemical technologies and in other fields.

Silver catalysts for the partial oxidation of alcohols

The review analyzes state of the art in the partial oxidation of alcohols to carbonyl compounds over Ag catalysts, including the partial oxidation of methanol to formaldehyde, oxidation of ethylene glycol to glyoxal, and oxidation of ethanol to acetaldehyde. For the methanol oxidation process, conditions for implementing the BASF and ICI technologies are considered and the entire chain of transformations from natural gas to formaldehyde is estimated in terms of exergy. When considering modern kinetic studies for the partial oxidation of alcohols on silver, some recent publication are analyzed, particularly those devoted to the application of a ring-shaped reactor to suppress the homogeneous steps of formaldehyde decomposition, the development of a new approach to simulation of the process taking into account different reactivity of the catalyst, and the creation of a simulator to calculate the methanol oxidation process using a neural network with a genetic algorithm. Main steps in the development of a technology for the partial oxidation of ethylene glycol to glyoxal on Ag catalysts are briefly described. The author analyzes modern experimental and theoretical works devoted to the formation mechanisms of oxygencontaining active sites on the silver surface and their involvement in the conversion of alcohols to carbonyl compounds, as well as the new Ag-containing catalytic compositions.