Complex Oxide Catalysts Research Articles

Effect of Adding Phosphorus on Crystal Structure of W-V-Nb Complex Oxide and Catalytic Selective Oxidation of Acrolein.

The changes in the crystal structure of the W-V-Nb complex oxide with phosphorus addition to the hydrothermal synthesis process are investigated. The effect of the constituent units and crystal structure of phosphorus-added W-V-Nb complex oxide catalysts on the activity and selectivity for selective oxidation of acrolein is discussed. Phosphorus addition to the hydrothermal synthesis process promotes the formation of orthorhombic and trigonal W-V-Nb complex oxides. Orthorhombic and trigonal W-V-Nb complex oxide catalysts give higher acrylic acid selectivity in acrolein oxidation compared to poorly crystalline catalysts that only have {M6O21} pentagonal units and 7-membered rings.

Complex-Oxide Catalysts in Cracking of Propane

Complex-Oxide Catalysts in Cracking of Propane

Design strategies for MOFs-derived Ce10-xZrxOy catalysts with polyhedral coordination to enhance soot combustion

Various cerium-based metal–organic frameworks (Ce-MOFs and Ce10-xZrx-MOFs) and their derivatives (Ce10-xZrxOy complex oxide catalysts) with different structures and properties by modulating the organic ligands (i.e., trimesic acid (BTC), 1,2,4,5-benzenetetracarboxylic acid (PMA), and terephthalic acid (BDC)) and transition metal elements via the solvothermal method. The performance of these catalysts was tested in the diesel soot oxidation reaction. In contrast, morphology engineering and the introduction of heteroatom zirconium to modify CeO2 can significantly improve the catalytic activity and stability of the catalyst. Among them, the best Ce5Zr5Oy-BDC shows remarkable catalytic performance for soot oxidation, converting 90% of soot particles into CO2 at about 410 °C. A series of characterization results demonstrate that the engineering of morphology provides a highly active polycrystalline surface for the adhesion of reactants, and the electron transfer system caused by Zr doping weakens the Ce-O bond. With the help of their combined action, the exposed polycrystal surfaces greatly enhance the oxygen vacancy content and the ability to generate reactive oxygen species. The DFT investigations shows that the presence of Zr can weaken the Ce-O link, result in favorable defect structures, and the reactive oxygen species of formation were promoted. This study provides an idea for the design of non-precious metal catalysts with high activity and stability.

Golub N.P., Golub E.O., Kozma A.A., Hlebena H.F., Mikhalchuk H.M., Kuznietsova A.O. SYNTHESIS AND RESEARCH OF A COMPLEX MANGANESE-NICKELPHOSPHATE CATALYTIC SYSTEM

Individual Mn2P2O7 and Ni3(PO4)2 phosphate catalysts were synthesized. A new synthesis technique was developed and a new complex catalytic system хMn2P2O7×yNi3(PO4)2 was obtained based on them (К-1 – К-7), which has the predicted physicochemical properties. The composition of these phosphates in the structure of the catalyst was varied in the range of 0,5 – 99,5 wt.%. It was established that the conditions of synthesis of catalysts significantly influence the process of forming the composition, structure, and corresponding physicochemical parameters of the synthesized catalysts. On the thermogram of the differential thermal analysis of an individual manganese-phosphate catalyst, three endo-effects at 148°С, 220°С and 353°С and one exo-effect at 460°С are observed. The thermogram of individual Ni3(PO4)2 shows two endo-effects at 210°С and 372°С and one exo-effect at 803°С. The synthesized double manganese-containing systems are characterized by a significant difference in DTA curves for samples K-1 - K-7. All obtained air-dry samples are crystal hydras with different numbers of water molecules. The structure of the obtained series of complex manganese-nickel phosphate catalysts contains various forms of water. The process of dehydration contributes to its separation from the structure of the samples and leads to the occurrence of characteristic endothermic effects. On all synthesized complex samples, the transition of manganese (II) orthophosphate to its pyrophosphate is observed when the final heat treatment temperature is reached. Firing samples of synthesized catalysts above 700oC leads to their complete dehydration with the formation of anhydrous salts. DTA results for all synthesized manganese-nickel phosphate samples are in good agreement with their X-ray diffraction, IR spectroscopy, and surface acidity results. They confirmed the correct choice of the modifying ion to improve the structure and physicochemical parameters of the manganese (II) phosphate catalyst. It can be predicted that the synthesized new complex oxide catalysts will show improved catalytic properties (activity and selectivity) in the processes of partial oxidation of n-alkanes into valuable products. The synthesized double manganese-containing systems are characterized by a significant difference in DTA curves for samples K-1 - K-7. All obtained air-dry samples are crystal hydras with different numbers of water molecules. The structure of the obtained series of complex manganese-nickel phosphate catalysts contains various forms of water. The process of dehydration contributes to its separation from the structure of the samples and leads to the occurrence of characteristic endothermic effects. On all synthesized complex samples, the transition of manganese (II) orthophosphate to its pyrophosphate is observed when the final heat treatment temperature is reached. Firing samples of synthesized catalysts above 700oC leads to their complete dehydration with the formation of anhydrous salts. DTA results for all synthesized manganese-nickel phosphate samples are in good agreement with their X-ray diffraction, IR spectroscopy, and surface acidity results. They confirmed the correct choice of the modifying ion to improve the structure and physicochemical parameters of the manganese (II) phosphate catalyst. It can be predicted that the synthesized new complex oxide catalysts will show improved catalytic properties (activity and selectivity) in the processes of partial oxidation of n-alkanes into valuable products.
 Keywords: catalysis; catalyst; catalytic systems; complex oxides; heterogeneous catalysis; phosphates; oxidation; n-alkanes; hydrocarbons; ethane; ethylene; differential thermal analysis.

Synergistic Effect between Fe<sup>4+</sup> and Co<sup>4+</sup> on Oxygen Evolution Reaction Catalysis for CaFe<sub>1−</sub><i><sub>x</sub></i>Co<i><sub>x</sub></i>O<sub>3</sub>

Chemical substitution is an effective way to improve electrocatalytic properties in transition metal oxides. We investigate the synergistic effect between Fe4+ and Co4+ ions on the catalytic activity for oxygen evolution reaction (OER) in the Fe-Co-mixed perovskite oxide CaFe1–xCoxO3. The OER activity of CaFe1–xCoxO3 is substantially increased by small amounts of Co (Fe) doping into CaFeO3 (CaCoO3), leading to the superiority compared to the pure Fe and Co perovskite oxides. The x dependences of the OER overpotential and specific activity for CaFe1–xCoxO3 (0.05 ≦ x ≦ 0.95) are expressed by constant offset from the weighted average between CaFeO3 and CaCoO3, which can be interpreted to be the synergistic effect between Fe4+ and Co4+ ions on OER activity. The absence of the optimum x for the highest activity for CaFe1–xCoxO3 contrasts with the volcano-like plots reported in various mixed-metal oxides. First-principle calculations using the special quasirandom structure models on CaFe1–xCoxO3 (x = 0.03–0.5) demonstrate that about half the amount of Fe4+ is electronically activated to possess smaller charge-transfer energies, corroborating the enhancement of catalytic activity in CaFe1–xCoxO3. These findings provide new insight into the synergistic effects in complex transition metal oxide catalysts.

Efficient and stable Ni-supported novel porous Ca-Mg-Al complex oxide catalyst for catalytic pyrolysis of oleic acid into gasoline-kerosene rich production using methanol as a hydrogen donor: Synthesis methods and process optimization

In this study, a series of cost-effective and eco-friendly Ca-Mg-Al and Ni-modified Ca-Mg-Al catalysts were successfully synthesized with different methods (coprecipitation, impregnation and mechanical mixing method) and applied to catalytic pyrolysis vapor upgrading of oleic acid (OA) to produce gasoline-kerosene rich production using methanol as a hydrogen donor. In addition, the effects of the process parameters (catalyst type, OA to methanol ratio, pyrolysis/catalytic temperature, catalyst loading, feedstock injection volume) on the product yield and selectivity were explored, and the reuse properties and deactivation mechanism were also evaluated. Active Ni species coupled with methanol were more conducive to enhancing the catalyst activity and OA conversion and obviously increased the selectivity toward the gasoline-kerosene product. The impregnation method was favorable for the formation of NiAl2O4 species, and coprecipitation method suppressed the formation of NiAl2O4 species. The enhanced activity and deoxygenation selectivity of the coprecipitation method (NiCaMgAl) at lower pyrolysis temperatures was attributed to the abundant higher specific surface area and pore size, higher active metal oxide (Ni2+) and well-active Ni dispersion with a smaller particle size, as well as the lower acidity and partially oxidized Ni, which suppressed the NiAl2O4 spinel phase formation compared with the Ni/Ca-Mg/Al (impregnation) and Ca-Mg-Al (mixing) catalysts, which was beneficial to the decarbonylation/ decarboxylation reaction and inhibited the hydrocracking reaction of CC. Therefore, 100% conversion, 97.12% hydrocarbon yield, 54.53% gasoline and 58.80% kerosene content over NiCaMgAl catalyst were obtained under optimal conditions (pyrolysis/catalytic temperature = 450/500°C, catalyst loading = 1.5 g, feedstock injection volume = 0.1 ml/min and OA to methanol ratio = 3:1). Moreover, NiCaMgAl catalyst also demonstrated good reusability and hydrothermal stability performance due to the lower amount of coke deposition with a lower graphitized structure, which suppressed sintering.

新規固定化金属錯体・金属ナノ粒子・金属酸化物触媒の創製とオペランド放射光X線解析

新規固定化金属錯体・金属ナノ粒子・金属酸化物触媒の創製とオペランド放射光X線解析

Preparation and application of ZrO2–SiO2 complex oxide for efficient biocrude generation by hydrothermal liquefaction of Spirulina

Catalysts act a pivotal part in hydrothermal liquefaction (HTL), which is a efficient technology for converting biomass into bioenergy. Herein, atom-doped ZrO2–SiO2 complex oxide catalysts were prepared for HTL of Spirulina to produce biocrude. In this study, sol–gel method was adopted to prepare the catalysts. Calcination temperature, surfactant type and dosage, ratio of SiO2 to ZrO2 were analyzed for optimizing biocrude yield. Physicochemical properties of ZrO2–SiO2 catalysts were conducted by X-ray diffraction, thermogravimetric analysis, N2 adsorption–desorption and infra-red spectroscopy of pyridine adsorption. The result showed that the catalysts that calcinated at 700°C with the ratio of SiO2:ZrO2 = 10:1, 5g polyethylene glycol applied in the sol precursor achieved the best performance: specific surface area reached 461.86m2g−1 and the density of total acid site was up to 53.98mmolg−1, thereby it provided the highest biocrude yield as 55.8%, which contained the largest hydrocarbon content. Accordingly, ZrO2–SiO2 demonstrated promising catalyst ability in the field of HTL and could inspire related researchers screening HTL catalysts from certain aspects.

THE DIFFERENTIAL THERMAL ANALYSIS OF COMPLEX CATALYTIC SYSTEM OF 50%Cu3(PO4)2•50%Ni3(PO4)2

The catalytic system of 50% Cu3(PO4)2∙50% Ni3(PO4)2 based on Copper (II) and Nickel (II) orthophosphates was synthesized by the coprecipitation method according to the method developed at the Department of Physical and Colloid Chemistry of Uzhhorod National University. The synthesized system was investigated by the method of differential thermal analysis. The obtained results can be interpreted in favor of the formation of a new phase, which is formed due to the equiatomic interaction of the initial components. Thus, a number of thermal effects different from Cu3(PO4)2∙3H2O and Ni3(PO4)2∙8H2O are observed on the corresponding thermogram. The only endothermic effect at 117 ° C is not recorded on the thermograms of the starting components. In the case of a solid solution or a simple mixture of phases based on starting phosphates, this effect should be observed at intermediate temperatures in the range from 129°C to 268°C. Probably, the newly formed phase, by the number of moles of water of crystallization, differs from the original individual orthophosphates. Information about a more accurate number of molecules of chemically bound water in hydrated forms of the synthesized complex copper-nickel phosphate catalyst will allow to establish the results of additional studies by derivatographic or gravimetric analyzes, which were not performed in this work. After dehydration with a further increase in temperature, no endothermic effect for a complex catalytic system is observed. Instead, four exothermic effects are recorded at once: the first two - at 456ºС and 564ºС (both insignificant in area), and the next two at slightly higher temperatures - 658ºС and 777ºС (larger in area). The effects at 564ºC and 658ºC can be attributed to the crystallization of dehydrated Cu3(PO4)2. The exoeffect at 777°C corresponds to the formation of the structure of dehydrated orthophosphate Nickel Ni3(PO4)2. Thus, the obtained experimental data of differential thermal analysis confirm the effective modifying role of Ni2+ ions on the structure, phase formation and a number of physicochemical properties of copper (II) phosphate in the synthesis of a complex oxide catalyst. This made it possible to obtain a new cheap and active complex acid catalyst with improved catalytic properties of 50 % Cu3(PO4)2∙50 % Ni3(PO4)2, which can be used for the process of converting natural gas components into valuable products of the chemical industry.
 Keywords: differential thermal analysis (DTA); catalysts; сopper (II) orthophosphate; nickel (II) orthophosphate; catalytic 50 % Cu3(PO4)2∙50 % Ni3(PO4)2 system.

Partial oxidation of methane to formaldehyde over copper–molybdenum complex oxide catalysts

The Cu3Mo2O9 catalyst forms formaldehyde selectively in the methane oxidation with O2 in the presence of water.

Oxidative Dehydrogenation of But-1-ene to Buta-1,3-diene with V–Mg Complex Oxide Catalysts

Oxidative Dehydrogenation of But-1-ene to Buta-1,3-diene with V–Mg Complex Oxide Catalysts

The Latest Research Progress of NH3-SCR in the SO2 Resistance of the Catalyst in Low Temperatures for Selective Catalytic Reduction of NOx

The selective catalytic reduction (SCR) has been widely used in industrial denitrification owing to its high denitrification efficiency, low operating costs, and simple operating procedures. However, coal containing a large amount of sulfur will produce SO2 during combustion, which makes the catalyst easy to be deactivated, thus limiting the application of this technology. This review summarizes the latest NH3-SCR reaction mechanisms and the deactivation mechanism of catalyst in SO2-containing flue gas. Some strategies are summarized for enhancing the poison-resistance through modification, improvement of support, the preparation of complex oxide catalyst, optimizing the preparation methods, and acidification. The mechanism of improving sulfur resistance of catalysts at low temperatures is summarized, and the further development of the catalyst is also prospected. This paper could provide a reference and guidance for the development of SO2 resistance of the catalyst at low temperatures.

Effect of Cerium Addition to Bismuth–molybdenum Complex Oxide Catalyst for Partial Oxidation of Propylene to Acrolein

The effect of Ce addition to a Bi–Mo complex oxide catalyst supported on SiO2 was examined on the partial oxidation of propylene to acrolein. The catalyst consisted of an oxygen-supply phase in which the lattice oxygen in Mo-oxide was doped with transition metals such as Fe, Ni and Co and was supported by SiO2 and a catalytic-active phase that involved hydrogen abstraction from a reactant in the Bi-center of Bi–Mo oxide, which was supported by the oxygen-supply phase. In the present study, Ce was added to the oxygen-supply phase to enhance its redox nature. Ce addition was advantageous particularly under oxygen-rich conditions in the feed stream. For example, at P(C3H8) = 10.1 kPa and P(O2) = 15.5 kPa at 623 K, the yield of acrolein was slightly enhanced from 57.6 % with 0 % Ce doping to 65.3 % with 20 % Ce doping at 6 h on-stream. However, under more oxygen-rich conditions at P(C3H8) = 10.1 kPa and P(O2) = 31.0 kPa at 623 K, the yield of acrolein was approximately doubled from 27.7 % with 0 % Ce doping to 61.8 % with 20 % Ce doping at 6 h on-stream. Analysis using XPS of the previously used catalysts for the reaction in the absence of gaseous oxygen confirmed the unique redox behavior between the catalytic-active phase and the oxygen-supply phase as the lattice oxygen in the catalytic-active phase was replenished from the oxygen-supply phase to maintain the surface properties of the catalytic-active phase. The XPS results and the remarkable effect of Ce addition to the oxygen-supply phase under oxygen-rich conditions confirmed the validity of the concept of the catalyst preparation consisting of an oxygen-supply phase and a catalytic-active phase.

Low Temperature Catalytic Performance of Manganese and Cerium Complex Oxide Catalyst towards Toluene

A series of MnOX(X)–CeO2 complex oxide catalysts with various Mn/Ce mole ratios were prepared successfully by sol-gel method and were characterized by BET, XRD, SEM, H2-TPR and XPS techniques, and the catalytic activity towards toluene were tested. The results showed that MnOX(X)–CeO2 complex oxide catalysts presented superior low temperature catalytic activity than pure CeO2 and MnOx, MnOx(0.6)-CeO2 exhibited the highest catalytic activity with T50=125°C and T99=197°C under the condition of GHSV of 10000h−1 and toluene concentration of 100ppm. The characterization results also indicated that the catalytic activity was relavant closely with specific surface area, catalyst morphology and valence of manganese oxides. Also, MnOX(X)–CeO2 formed solid solution with fluorite structure after the introduction of manganese, and produced quantities of manganese species, atom adsorbed oxygen and crystal oxygen, which promoted the adsorption and activation of gaseous oxygen and the mobility and transfer of active oxygen.

Discovery of crystal structure–stability correlation in iridates for oxygen evolution electrocatalysis in acid

We provide general descriptions regarding the structure–stability correlations of iridium-based complex-oxide catalysts for oxygen evolution reaction in acid media.

Single-Site Vanadyl Species Isolated within Molybdenum Oxide Monolayers in Propane Oxidation

The cooperation of metal oxide subunits in complex mixed metal oxide catalysts for selective oxidation of alkanes still needs deeper understanding to allow for a rational tuning of catalyst perform...

Understanding the Impact of Defects on Catalytic CO Oxidation of LaFeO3-Supported Rh, Pd, and Pt Single-Atom Catalysts.

Understanding the intrinsic catalytic properties of perovskite materials can accelerate the development of highly active and abundant complex oxide catalysts. Here, we performed a first-principles density functional theory study combined with a microkinetics analysis to comprehensively investigate the influence of defects on catalytic CO oxidation of LaFeO3 catalysts containing single atoms of Rh, Pd, and Pt. La defects and subsurface O vacancies considerably affect the local electronic structure of these single atoms adsorbed at the surface or replacing Fe in the surface of the perovskite. As a consequence, not only the stability of the introduced single atoms is enhanced but also the CO and O2 adsorption energies are modified. This also affects the barriers for CO oxidation. Uniquely, we find that the presence of La defects results in a much higher CO oxidation rate for the doped perovskite surface. A linear correlation between the activation barrier for CO oxidation and the surface O vacancy formation energy for these models is identified. Additionally, the presence of subsurface O vacancies only slightly promotes CO oxidation on the LaFeO3 surface with an adsorbed Rh atom. Our findings suggest that the introduction of La defects in LaFeO3-based environmental catalysts could be a promising strategy toward improved oxidation performance. The insights revealed herein guide the design of the perovskite-based three-way catalyst through compositional variation.

Oxidative Dehydrogenation of n‐Butene with V–Mg Complex Oxide with Added Trivalent Metal Oxide

AbstractOxidative dehydrogenation (ODH) of n‐butene with V−Mg complex oxide catalysts was carried out with a fixed‐bed flow reactor at 480 °C. In order to improve the catalytic performance of V−Mg complex oxide, we examined the effect of added metal oxide on the ODH of n‐butene. When Fe was added to the V−Mg complex oxide, the reactivity of lattice oxygen in the V−Mg complex oxide increased. V−Mg‐Fe(20:30:10) prepared at a molar ratio of V:Mg:Fe=20:30:10 showed high conversion (53.9%) and buta‐1,3‐diene (BD) yield (20.3%) in the ODH with the lattice oxygen. To continuously produce BD, ODH under O2 flow was also investigated. The V−Mg‐Fe(20:30:10) catalyst exhibited higher BD yield than the V−Mg catalyst, and it was indicated that the high reactivity of the lattice oxygen affected the ODH under O2 flow. Moreover, the V−Mg‐Fe(20:30:10)‐800 catalyst calcined at 800 °C showed highly stable ODH activity, and the BD yield (11%) was maintained for 420 min. XRD analysis results of the catalyst showed that the maintenance of the ODH activity could be attributed to the maintenance of the crystalline structure of V−Mg‐Fe(20:30:10)‐800 during the reaction.

The Merits of In situ Environmental STEM for the Study of Complex Oxide Catalysts at Work

The Merits of In situ Environmental STEM for the Study of Complex Oxide Catalysts at Work

Characterization of an Iron-Oxide-Based Catalyst Used for Catalytic Cracking of Heavy Oil with Steam

Characterization of a complex metal oxide catalyst (Fe, Zr, and Al) used for catalytic cracking of petroleum residual oil with steam was examined. Heavy oil fractions were oxidatively cracked on th...