The catalytic conversion of carbon dioxide to methanol is of great practical and scientific importance in the concept of reducing CO2 emissions. Moreover, it can partially solve the problem of human dependence on nonrenewable resources. The development of selective and active catalysts for CO2 hydrogenation is a key point due to the strong thermodynamic limitations and high chemical stability of CO2. In this work, the influence of the nature of the mesoporous supports, as well as the method of introducing the active component, on the catalytic properties of Cu-Zn catalysts in the CO2 hydrogenation to methanol were investigated. A series of bimetallic Cu-Zn catalysts deposited on mesoporous MCM-41 and SBA-15 supports were prepared by two methods: encapsulation and incipient wetness impregnation. The obtained catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), and thermogravimetry-differential thermal analysis (TG-DTA) methods. The highest CO2 conversion and methanol spacetime yield were observed over the encapsulated Cu-Zn catalyst based on the MCM-41 support. The optimal process temperature was 280 degrees C, at which a high selectivity of 92% methanol formation was achieved while maintaining the best CO2 conversion. The study demonstrates the prospects of using bimetallic Cu-Zn catalysts encapsulated in MCM-41 for direct CO2 hydrogenation for "green" methanol production.

Herein N2O decomposition over LaMO3 (M: Fe, Co, Ni) mixed oxides with perovskite structures has been optimized. The influence of the organic additive and the additive to (La3+ + Co2+) molar ratio on phase composition, particle aggregate size, textural properties, and catalytic activity of LaCoO3 has been determined for the first time. Glycine improved the phase purity of LaCoO3, enhanced the specific surface area and pore volume, and shifted the pore size distribution to the wider mesopore and macropore regions. LaCoO3 showed better activity than LaFeO3 and LaNiO3 owing to the greater reducibility of Co3+ and its large specific surface area, and correlations between the La3+:Co2+ molar ratio, particle aggregate size, pore volume for pores larger than 25 nm, and N2O decomposition activity for LaCoO3 have been determined. Changes in the LaCoO3 textural properties following catalytic experiments with 10% water vapor added to the feed have also been analyzed here-in.

The study of Fe-containing catalytic systems in the carbon dioxide hydrogenation reaction was conducted. A series of systems on the basis of iron oxide Fe2O3 wiśthout the addition of a second component and with the addition of aluminum (Al2O3), cerium (CeO2), zirconium (ZrO2) or silicon (SiO2) oxides was synthesized. Each system was synthesized by two methods, analogous to mesoporous molecular sieves synthesis methods for MCM-41 and SBA-15 with the use of cetyltrimethylammonium bromide and Pluronic 123 templates. The resulting samples had a uniform distribution of components on the surface with a component ratio close to 1:1 and iron oxide crystallite sizes ranging from 7 to 23 nm. The highest activity in the reaction of hydrogenation of carbon dioxide was demonstrated by the sample Fe/Al with Pluronic 123 as a template, the conversion was 11.5

Zeolites are widely used in oil processing and environmental protection, especially in abatement of toxic compounds and greenhouse gases, like nitrous oxide (N2O). Ferrierite zeolites are among the perspective but least studied zeolites. Conventional synthesis includes hydrothermal autoclave treatment during 30–60 h. New approaches to the fast synthesis of ferrierite are needed. In the present work, ferrierite zeolite (FER) was synthesized by different methods: microwave-assisted, hydrothermal and hydrothermal + seeds. The structure, texture and acidic properties of the samples were investigated by XRD, low-temperature adsorption–desorption of N2, scanning electron microscopy and DRIFT spectroscopy using adsorption of CD3CN as a probe molecule. Fe-FER catalysts were prepared by the incipient wetness impregnation method using Fe(III) acetylacetonate as an iron precursor. The catalytic performances of the prepared materials were studied in the N2O decomposition reaction. The FER-MW-6 sample prepared by the microwave-assisted method exhibited better physicochemical and catalytic characteristics.

The catalytic properties of Cu–Zn catalysts are investigated on such commercial supports as Al2O3, SiO2, ZrO2(La), TiO2, ZnO, and activated carbon in the reaction of CO2 hydrogenation with the production of methanol. CuZn/Al2O3 catalyst displays the highest conversion of CO2. The highest selectivities toward methanol (99 and 97.5

In the oxidative dehydrogenation of propane in the presence of CO2, supported monometallic M/SiO2 (M = Zn, Cu) and bimetallic MCr/SiO2 oxide catalytic systems were studied in the temperature range 600–700°C. The catalytic systems were characterized by TG–DTG–DTA, SEM–EDX, and UV–Vis diffuse reflectance spectroscopy. It was revealed that the addition of a second metal leads to a decrease in propane conversion to 32

A series of chromium oxide catalysts supported on SiO2 with 5 wt

This work uses green sustainable reactions twice. Firstly, it is microwave synthesis: 2,4,6-tribiphenyl-4-yl-1,3,5-triazine and similar compounds were prepared in a closed microwave reactor in n-octane by the Friedel-Crafts reaction. Second, a hybrid electrocatalyst for the highly demanded electrochemical reaction of nitrate reduction to ammonia (NO3RR) was prepared based on this material. This reaction has great potential to replace the energy-intensive Haber-Bosch process, and in addition, has independent value for the elimination of nitrate contamination of water resources. As shown in the work, microwave synthesis is an eco-friendly method for the synthesis of complex organic compounds; fast, selective and with a high yield of the target product. The electrocatalyst deposited on the graphite electrode consisted of a layer of 2,4-bis([1,1 '-biphenyl]-4-yl)-6-hydroxy-1,3,5-triazine and related compounds coated with cobalt oxide. The hybrid catalyst was firmly retained on the graphite electrode during NO3RR and the material showed impressive stability with almost no decrease in catalytic activity even after the fifth cycle. Both 2,4-bis([1,1 '-biphenyl]-4-yl)-6-hydroxy-1,3,5-triazine and the catalyst based on this substance were characterized by SEM, XPS, XRD, UV-vis spectra, cyclic (and linear) voltammetry, and chronoamperometry. This work can serve as a starting point for the development of stable and durable electrocatalysts for NO3RR using triazine derivatives. The paper studies the process of eco-friendly microwave assisted synthesis of a material based on triazine compounds and the possibility of its use as part of a hybrid catalyst for the electrochemical synthesis of ammonia under mild conditions by the NO3RR reaction. image

Ferrierite zeolite (FER) was synthesized under microwave conditions while varying the microwave exposure time from 6 to 12h. For comparison, commercial FER and a FER zeolite synthesized by the conventional hydrothermal synthesis (72h) were studied. The structure, texture, and acidic properties of the samples were investigated by XRD, low-temperature N2 adsorption, ICP-AES, SEM, and DRIFT spectroscopy using adsorption of CO, CD3CN and pyridine as probe molecules. The catalytic characteristics of the obtained zeolites were studied in the cyclocondensation reaction of 1,2-phenylenediamine and acetone to produce 1,5-benzodiazepine. The activity of the zeolites in this reaction was found to increase with increasing microwave exposure time. The FER-MW sample synthesized in 12h showed the best results.

The green and sustainable electrocatalytic conversion of nitrogen-containing compounds to ammonia is currently in high demand in order to replace the eco-unfriendly Haber–Bosch process. Model catalysts for the nitrate reduction reaction were obtained by electrodeposition of metal Co, Fe, and bimetallic Fe/Co nanoparticles from aqueous solutions onto a graphite substrate. The samples were characterized by the following methods: SEM, XRD, XPS, UV–vis spectroscopy, cyclic (and linear) voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. In addition, the determination of the electrochemically active surface was also performed for all electrocatalysts. The best electrocatalyst was a sample containing Fe-nanoparticles on the layer of Co-nanoparticles, which showed a Faradaic efficiency of 58.2% (E = −0.785 V vs. RHE) at an ammonia yield rate of 14.6 μmol h−1 cm−2 (at ambient condition). An opinion was expressed to elucidate the mechanism of coordinated electrocatalytic action of a bimetallic electrocatalyst. This work can serve primarily as a starting point for future investigations on electrocatalytic conversion reactions to ammonia using model catalysts of the proposed type.

In this paper the effect of the iron precursors nature (iron (III) nitrate nonahydrate, iron (II) acetate, iron (III) citrate, and ammonium trioxalatoferrate (III)) on alumina-supported catalysts activity in CO2 conversion was studied. The CO2 conversion was carried out at temperatures range from 300 degrees C to 380 degrees C and atmospheric pressure. The structure of the samples was investigated using TPR-H2, SEM-EDX, ICP-AES, XRD, UV-VIS, and XPS methods. It was discovered that depending on the type of Fe precursor the dispersion of the supported iron and the interaction between the deposited component and the carrier in the catalyst can drastically change. During the preparation a mixed phase of iron and aluminum oxides was formed which occurred to be catalytically inactive in CO2 conversion. The formation of this phase prevents the deep reduction of iron and the activation of hydrogen under the reaction conditions, which significantly reduces the activity of the catalyst.

A carbazole-based linker 9-(carboxymethyl)carbazole-3,6-dicarboxylic acid (H3cbzac) was synthesized for the first time. Its structure was confirmed via 1H NMR and Powder X-Ray Difraction (PXRD) methods. A novel calcium-based 2D MOF Ca(H2cbzac)2(DMF)2 (ZIOC-10) was synthesized via a solvothermal procedure. It was found that the obtained framework undergoes several structural changes upon heating, which lead to the formation of a new framework Ca(H2cbzac)2 (ZIOC-10a). Noteworthy, ZIOC-10 transforms into the permanent porous (524 m2/g) 3D framework, which can absorb methane, ethane, propane, and carbon dioxide at room temperature.

The effect of the support nature (SiO 2 , Al 2 O 3 , SiO 2 -Al 2 O 3 ) on the catalytic performance of Ni-based catalysts prepared by the incipient wetness method was explored in the dry reforming of methane reaction, and the catalysts were characterized by TG-DTA, SEM-EDX, XRD and UV-VIS methods. The results demonstrate that NiO supported on SiO 2 -modified Al 2 O 3 exhibits superior catalytic performance in methane dry reforming in the temperature range of 650-700 degrees C.

Download This Paper Open PDF in Browser Add Paper to My Library Share: Permalink Using these links will ensure access to this page indefinitely Copy URL Copy DOI

The processes of dispersion hardening of the cobalt-niobium and cobalt-tantalum alloys belonging to the fccsolid solution based on cobalt jointly alloyed with rhenium are studied using scanning electron microscopy, local X-ray spectrum analysis, X-ray phase analysis, transmission electron microscopy, differential scanning calorimetry, and Vickers hardness measurements. Alloying with rhenium significantly increases the hardness of the cobalt-niobium and cobalt-tantalum alloys with the fcc-structure, since rhenium stabilizes the Co3Nb and Co3Ta phases and prevents the growth of their particles, thereby contributing to the preservation of the reticulated nanoscale structure. It is shown, that decomposition of the gamma Co-solid solution at 1200 K is accompanied by formation and growth of the Guinier-Preston zones, occurrence of the Suzuki atmospheres and subsequent formation of the metastable nanoscale Co3Nb and Co3Ta particles with the Mg3Cd-type of the crystal structure.

In this study a comprehensive analysis of the influence of synthesis route of CuFe2O4 2 O 4 spinel mixed oxides on their catalytic performance in the N2O 2 O decomposition was carried out. A co-precipitation technique allowed one to obtain the CuFe2O4 2 O 4 spinel with a higher specific surface area and pore volume compared to the synthesis with the application of organic additives. This resulted in better catalytic performance of the CuFe2O4 2 O 4 samples prepared by co-precipitation. The microwave activation step with the duration of 1 min during the co-precipitation synthesis led to the formation of the CuFe2O4 2 O 4 spinel with a higher content of oxygen vacancies per 1 m2 2 in comparison with the sample obtained without the microwave activation. This fact caused a significantly higher specific activity of the CuFe2O4 2 O 4 spinel synthesized with the application of 1 min microwave activation. The increase of the microwave treatment time led to the fast growth of the contents of the CuO and alpha-Fe2O3 2 O 3 phases, which are less active in the N2O 2 O decomposition, resulting in the activity drop.

In this work a detailed comparison of the N2O decomposition catalytic performance of LaCoO3 perovskite-like mixed oxides supported over different commercial materials was conducted. Zirconia-, silica- and gamma-alumina-based supports were studied. Zirconia-based supports turned out to be the most applicable because of the formation of the pure LaCoO3 perovskite phase on their surface. Among these supports, ZrO2-La revealed to possess the best activity owing to the highest Co2+/Co3+ (0.82) and O-ads./O-L (0.67) ratios on its surface. The raw of activities was as follows: LaCoO3(20 %)/ZrO2-La > LaCoO3(20 %)/ZrO2 > LaCoO3((2)0 %)/ZrO2-W. When the LaCoO3 content in LaCoO3/ZrO2-La was 20 wt%, the maximum of activity was observed - 94.78 mmol(N2O)/[g(cat.)h] at 450 degrees C. This fact was in accordance with the highest Co2+/Co3+ (0.82) and O-ads./O-L (0.67) ratios at the 20 wt% LaCoO3 content. Coordinatively unsaturated Co2+, forming Lewis acid-base pairs, were proposed to be the active sites of the zirconia-based LaCoO3 catalysts in the N2O decomposition.

For the first time, kinetic data on the decomposition of N2O 2 O over mixed oxide LaCoO3 3 with a perovskite structure have been obtained. Bulk LaCoO3 3 synthesized using microwave activation exhibited an increased intrinsic reaction rate with a 30 kJ mol-1 -1 lower activation energy. Perovskite samples supported on ZrO2-La 2-La demonstrated lower intrinsic reaction rates due to the lower content of the LaCoO3 3 phase, but the activation energies were also lower by 50-80 kJ mol-1. -1 .

Electrocatalytic methods for producing ammonia from nitrates represent a promising and environmentally friendly alternative to the traditional Haber-Bosch synthesis. An important criterion for assessing the efficiency of a reduction reaction is the Faraday efficiency of the reaction. It is determined by the choice of catalyst electrode and its properties. Nanocatalysts offer advantages over conventional metal catalysts by increasing catalyst activity by controlling particle size and reducing catalyst production costs. Currently, the electrocatalytic activity of metal cobalt, its oxides, and mixed catalysts based on it are being actively studied. In this study, the electrocatalytic ability of electrodeposited and metallic cobalt in the reduction of nitrate to ammonia was investigated. The nanocatalysts were synthesized by electrodeposition of cobalt onto a graphite substrate from an aqueous solution of sodium sulfate at a deposition time of 5–30 min. The surface of the resulting catalysts represents a dense and thin layer of cobalt particles with a diameter of 20-100 nm. The efficiency of nanocatalysts was assessed using Faraday efficiency (FE) data. The best results for electrodeposited cobalt were 50 to 60% FE. The electroreduction reaction of nitrates deserves further study and discussion of its prospects for industrial application. Further research will be aimed at optimizing reaction conditions and developing new electrocatalysts with high efficiency and selectivity, including the addition of particles of other metals to cobalt (Fe, Cu, Ni). Figure 1