Multicomponent Oxide Catalysts Research Articles

A Highly Active and Reusable Multicomponent high Entropy Metal Oxide Catalyst for Nitroarenes Hydrogenation

It is well known that multicomponent catalysts can improve catalytic performance, however their rational design and precise control of catalytic activities by varying the composition of the elements is challenging. Herein, we present a facile and scalable synthetic strategy for production of senary and septenary metal oxide nanoparticles with a chemical composition of MSbOx and MSb2Ox (M: Fe, Ni, Co, Cu, and Zn). All samples were formed in a tetragonal crystal structure with space group 136 and crystallographic symmetry P42/mnm while the details of their constituent unit cells are different, belonging to rutile or trirutile structures. These nanocomposites have an oxygen vacancy-rich construction with uniform elemental distributions that produce various surface functionalities. They showed instantaneous hydrogenation catalytic performance for reduction of 4-nitrophenol to 4-aminophenol at room temperature. Among our samples, the senary catalyst with MSbOx chemical composition showed better durability and reusability owning to its morphological and microstructural properties. It showed 100% conversion of 4-nitrophenol to 4-aminophenol within 4 min at the 18th run without any by-products.

Catalytic activity of Co, Cu and Mn oxide catalysts synthesized by the sol-gel combustion method in the low-temperature oxidation of carbon oxide

The synthesis of catalysts based on cobalt, copper and manganese oxides by sol-gel method with combustion was carried out, and their catalytic activity was studied in the reaction of low-temperature oxidation of carbon monoxide to dioxide. Oxides of cobalt, copper and manganese, as well as their double oxides (Co–Mn, Cu–Mn and Co–Cu) were synthesized. X-ray phase analysis showed the formation of manganites and oxides of corresponding metals in the Co–Mn and Cu–Mn systems. It was revealed that in the Co–Cu system only oxides of separate metals are formed. It was found that cobaltmanganese and copper-manganese oxide systems synthesized by sol-gel combustion method exhibit high catalytic activity in the low-temperature (110–140 0C) conversion of carbon monoxide into dioxide. One-step synthesis of Cu–Mn/Al2O3 catalytic system was also carried out by sol-gel method with burning precursors with binder hydrogel (Al2O3), and its high activity in low-temperature conversion of carbon monoxide was revealed. The catalytic systems were investigated by X-ray diffraction, IR spectral methods, BET, SEM. The results obtained show the possibility of obtaining active multicomponent oxide catalysts in low-temperature oxidation of carbon monoxide by technologically simple sol-gel combustion method.

Bifunctional keel flower-like Ni-Co-V multicomponent oxide catalyst with enhanced electron transport for accelerating overall water splitting

Heteroatom doping is considered a typical method for improving the electrochemical properties of composites. In this work, the multi-component oxide catalyst (Ni(VO3)2 and Co2V2O7 on Ni foam, referred to as NiCoVOx@NF) is formed by hydrothermal doping of V element into NiCo-based precursors followed by co-oxidation. In the catalyst NiCoVOx@NF, all three components of Ni, Co and V are particularly tightly coordinated, exhibiting an integrated structure of keel flower-like arrays. The catalyst NiCoVOx@NF’s contact surface with water is increased thanks to this unusual structure, exposing a high number of active sites. Furthermore, NiCoVOx@NF owns efficient electronic pathways, which greatly enhances the electron transport ability. To generate a current density of 10 mA cm−2 for hydrogen evolution reaction, just a 107 mV overpotential is required. The electrode exhibits a low overpotential of 217 mV to deliver 50 mA cm−2 for oxygen evolution reaction. In addition, the total water splitting performance of NiCoVOx@NF is also excellent, which could be achieved by only one 1.5 V AA battery. This study provides a feasible heteroatom doping route to design bifunctional catalysts with improved performances.

Insight into the selective oxidation of isobutene to methacrolein over Ce-accelerated Mo-Bi-Fe-Co-K-O catalyst

Understanding the mechanism of multi-component metal oxide catalyst for the selective oxidation of isobutene to methacrolein has long been challenging for its complexity. Herein, the key role of Ce on the Mo-Bi-Fe-Co-K-O catalysts for accelerating the selectivity of methacrolein was revealed. It was suggested that the Ce addition could replace the Bi3+ and then generate defects which changed the transformation of electron and the migration mobility of ions: Ⅰ. the production of Ce3+/Ce4+ and Co2+/Co3+ redox couples regulated the catalytic redox ability; and Ⅱ. the interaction effect between Ce and Co enhanced the storage capacity and mobility of oxygen which could benefit the adsorption and activation ability for isobutene molecules. Interestingly, it was found that adding appropriate amount of Ce adjusted the molar ratio of the catalytically active lattice oxygen and defect oxygen species. Therefore, proper amount of Ce addition to the catalyst significantly accelerated the methacrolein selectivity from 47.9% to 70.6%.

Bio-DEE Synthesis and Dehydrogenation Coupling of Bio-Ethanol to Bio-Butanol over Multicomponent Mixed Metal Oxide Catalysts

Within the Waste2Fuel project, innovative, high-performance, and cost-effective fuel production methods from municipal solid wastes (MSWs) are sought for application as energy carriers or direct drop-in fuels/chemicals in the near-future low-carbon power generation systems and internal combustion engines. Among the studied energy vectors, C1-C2 alcohols and ethers are mainly addressed. This study presents a potential bio-derived ethanol oxidative coupling in the gas phase in multicomponent systems derived from hydrotalcite-containing precursors. The reaction of alcohol coupling to ethers has great importance due to their uses in different fields. The samples have been synthesized by the co-precipitation method via layered double hydroxide (LDH) material synthesis, with a controlled pH, where the M(II)/M(III) ≈ 0.35. The chemical composition and topology of the sample surface play essential roles in catalyst activity and product distribution. The multiple redox couples Ni2+/Ni3+, Cr2+/Cr3+, Mn2+/Mn3+, and the oxygen-vacant sites were considered as the main active sites. The introduction of Cr (Cr3+/Cr4+) and Mn (Mn3+/Mn4+) into the crystal lattice could enhance the number of oxygen vacancies and affect the acid/base properties of derived mixed oxides, which are considered as crucial parameters for process selectivity towards bio-DEE and bio-butanol, preventing long CH chain formation and coke deposition at the same time.

Oxidative Transformations of Ethane and Ethylene on VMoTeNbO Catalysts

Comparative studies of oxidative transformations of ethane and ethylene were performed on multi-component oxide catalysts of the preset cationic composition, V0.3Mo1Te0.23Nb0.12, differing in the final calcination temperature. The highest (∼74%) ethylene yield in oxidative dehydrogenation of ethane is reached on the catalysts calcined in the temperature interval 550–650°C, which is due to the formation of the maximal amount of the active M1 phase.

Intelligent Optimization of Na−Mn−W/SiO2 Catalysts for the Oxidative Coupling of Methane

AbstractOptimizing the performance and understanding the mechanism of metal oxide catalysts in the oxidative coupling of methane (OCM) is one of the most important projects in industrial catalysis. Here, we report an intelligent approach to screen Na−Mn−W/SiO2 catalysts for the OCM reaction via ink‐jet printing and multidimensional group testing. The ink‐jet‐printing‐assisted (IJP‐A) synthetic methodology ensured a fast synthesis of 1536 catalysts that were evaluated in 24 tests via a multidimensional group testing strategy (m‐GT). After two‐round synthesis‐and‐screening processes, several excellent groups with different composition space were screened out. Among the excellent catalysts, the OCM performance of Na−Mn−W/SiO2 catalyst with higher Na, Mn and W content (G3 and G7) was less sensitive to its constituent than that of Na−Mn−W/SiO2 catalyst with lower Na, Mn and W content (G1). These results indicated the sensitivity of performance to its Na, Mn and W content decreased in larger Na, Mn and W spaces, consistent with the complex homogeneous/heterogeneous reaction mechanism and multi‐active sites. A series of Na−Mn−W/SiO2 formulas with good performance also provide a reasonable explanation to its excellent stability for the OCM reaction. In addition, this intelligent optimization in total space offers a pathway to study the multicomponent metal oxide catalyst in the OCM reaction.

Ab Initio Thermodynamic Investigation of Monolayer Stability of Multicomponent Metal Oxides: MxOy/ZnO(0001) and MxOy/TiO2(110) (M = Pd, Ru, Ni, Pt, Au, Zn)

Multicomponent metal oxide catalysts can offer a tunable redox capacity and chemical reactivity. These materials are used in fuel cells, in gas sensors, and as heterogeneous catalysts. The large number of possible combinations of different mixed-metal oxides and their metastability make the experimental discovery of such systems very inefficient. Herein, we develop an ab initio thermodynamic framework using density functional theory to accelerate this discovery process by predicting stable monolayer metal oxides that can be subjected to further computational study or experimental investigation. As an example of the application of this framework, we present our stability analysis of ZnO(0001)–Zn terminated and rutile TiO2(110) surfaces with epitaxial MxOy (M = Pd, Ru, Ni, Pt, Au, Zn) monolayers. Metastability is predicted relative to segregated particle structures of varying radii. We predict that NiO can form a metastable monolayer with the same stoichiometry as the support, ZnO(0001). A PdO and RuO2 mono...

Fast Optimization of LiMgMnOx/La2O3 Catalysts for the Oxidative Coupling of Methane.

The development of efficient catalyst for oxidative coupling of methane (OCM) reaction represents a grand challenge in direct conversion of methane into other useful products. Here, we reported that a newly developed combinatorial approach can be used for ultrafast optimization of La2O3-based multicomponent metal oxide catalysts in OCM reaction. This new approach integrated inkjet printing assisted synthesis (IJP-A) with multidimensional group testing strategy (m-GT) tactfully takes the place of conventionally high-throughput synthesis-and-screen experiment. Just within a week, 2048 formulated LiMgMnOx-La2O3 catalysts in a 64·8·8·8·8 = 262 144 compositional space were fabricated by IJP-A in a four-round synthesis-and-screen process, and an optimized formulation has been successfully identified through only 4·8 = 32 times of tests via m-GT screening strategy. The screening process identifies the most promising ternary composition region is Li0-0.48Mg0-6.54Mn0-0.62-La100Ox with an external C2 yield of 10.87% at 700 °C. The yield of C2 is two times as high as the pure nano-La2O3. The good performance of the optimized catalyst formulation has been validated by the manual preparation, which further prove the effectiveness of the new combinatorial methodology in fast discovery of heterogeneous catalyst.

Application of Oxide Copper Chromium Catalysts for the Purification of Exhaust Gases

Results of the development of multicomponent oxide catalysts based on Ni, Cu, and Cr supported on 2 % Ce/?-Al2O3 by varying the concentration of the active phase of catalyst are presented in paper. It was found that the highest degree of toluene conversion (up to 98.8 %) is observed on the three- component Ni-Cu-Cr/2% Ce/?-Al2O3 catalyst with optimal metal ratio Ni : Cu : Cr = 1.0 : 3.0 : 0.1 at GHSV = 5×103 h-1 and a temperature of 723 - 773 K. The presence of CeO2 crystals, X-ray amorphous clusters (d = 20 – 100 A) of variable valence metal oxides NiO and CuO as well as solid metal solutions CuO (NiO) was detected on the surface of optimum catalyst calcined at 873 K using XRD and electron microscopy methods.

Oxidative conversion of ethane over VMoTeNb oxide catalyst

The oxidative conversion of ethane over a multicomponent oxide catalyst with the composition V0.3Mo1Te0.23Nb0.12 was studied in the temperature range of 360–450°C. It was found that temperature did not affect the contribution from the parallel and consecutive paths of reaction product formation. The obtained data could be useful in developing applications for the process, particularly in choosing the type and design of a reactor (tubular fixed bed, fluidized bed, and so on).

Oxidative Conversion of Ethane to Ethylene over VMoTeNb Oxide Catalyst

Oxidative conversion of ethane to ethylene and COx over a multicomponent oxide catalyst V0,3Mo1Te0,23Nb0,12 was studied at 360–450 °C. No influence of temperature on the proportion of parallel and consecutive pathways towards the reaction products was established. Low temperature response of the selectivity to the reaction products will be taken into account in choosing the reactor type for scaling-up the process of oxidative conversion of ethane.

Oxidative Dehydrogenation of n-Butenes to 1,3-Butadiene over Bismuth Molybdate and Ferrite Catalysts: A Review

1,3-Butadiene, an important raw material for a variety of chemical products, can be produced via the oxidative dehydrogenation (ODH) of n-butenes over multicomponent oxide catalysts based on bismuth molybdates and ferrites. In this review, the basic concept, reaction mechanism, and catalysts typically used in an ODH reaction are discussed.

Atomic-Scale View of VOX–WOX Coreduction on the α-Al2O3 (0001) Surface

The catalytic activity of oxide-supported vanadium oxide is improved by the presence of tungsten oxide for the selective catalytic reduction of nitric oxides. We propose a mechanism for V–W synergy through studies of the reduction–oxidation behavior of near-monolayer VOX and WOX species grown by atomic layer deposition on the α-Al2O3 (0001) single crystal surface. In situ X-ray standing wave measurements reveal an overlayer of W6+ species that is correlated with the substrate lattice as well as a redox-reversible shift from uncorrelated V5+ to correlated V4+. X-ray photoelectron spectroscopy and electronic structure calculations show a partial reduction of W6+ in the presence of V4+, improving the Bronsted acidity in mixed V–W catalyst systems. This mechanism of V–W synergy suggests that control of W d-states might be used as a design parameter for Bronsted acid sites in multicomponent oxide catalysts.

Heterogeneous catalytic oxidative conversion of ethane to ethylene

Multicomponent and multiphase oxide catalysts with a uniform composition Mo1V0.3Te0.23Nb12 but different phase contents were studied in the oxidative conversion of ethane to ethylene and characterized by X-ray diffraction analysis. The phase composition of the samples was varied by modifying such conditions of catalyst preparation as the pH of raw precursor, the drying of the wet precursor, and the conditions of solid precursor calcination. The content of the detected phase is determined via Rietveld refinement. The catalytic activity of MoVTeNb oxide catalysts studied in the oxidative conversion of ethane was found to be determined by the content of the orthorhombic M1 phase (the layered four-component compound (TeO)0.23(Mo,V,Nb)5O14).

Synthesis of Mesoporous Composite Oxides for the Catalysis of NH$lt;inf$gt;3$lt;/inf$gt;-SCR

A novel mesoporous ZrO2-TiO2 (ZT) based multi-component composite oxide catalyst V2O5-WO3-CuO-Al2O3/ZrO2-TiO2 (VWCuAl/ZT) was successfully synthesized by one-pot hydrothermal method using both Brij-35 and P123 as composite template. The results indicated that the active species of V2O5, WO3, CuO and Al2O3 could be homogeneously dispersed into mesoporous ZrO2-TiO2 catalyst carrier. Compared with the reference samples of non-mesoporous I-VWCuAl/ZT and the traditional commercial catalyst V2O5-WO3/TiO2(V-W/Ti), the prepared VWCuAl/ZT showed a superior low-temperature catalytic activity and high stability over the reaction of NH3-SCR of NO, especially high catalytic efficacy for NO reduction within a wide temperature range of between 200 degrees C to 500 degrees C.

Enhanced soot combustion over partially substituted hydrotalcite-drived mixed oxide catalysts CoMgAlLaO

A series of hydrotalcite-derived multicomponent oxide catalysts Co2.5Mg0.5Al1–x%Lax%O (denoted as CMALax, x=0, 5, 8, 10 or 15) with different La contents were synthesized by co-precipitation, and employed for catalytic soot combustion and NOx storage at lean condition. It is found that the La-substituted catalysts are more active than the one without La for soot combustion and NOx storage. Among all the catalysts CMALax, CMALa10 (x=10) exhibits the highest catalytic performance, showing the largest NOx storage capacity (300μmol/g) and the lowest temperature for the maximal soot oxidation rate (Tm=388°C). The results of H2-TPR and O2-TPD indicate that the La-substitution can enhance the redox properties and increase the amount of surface lattice oxygen species of the catalysts. The results of soot combustion kinetics show that the apparent activation energy of CMALa10 is the lowest (92.75kJ/mol). Based upon the catalytic performance and in situ DRIFTS characterization, a nitrate and/or NO2 enhanced soot combustion mechanism over CMALa10 was proposed. It is revealed that at low temperature the stored nitrate can directly promote soot ignition, while at high temperature the NO2 species arising from NO oxidation or nitrate decomposition act as the main active species for soot combustion.

Oxidative dehydrogenation of butenes to butadiene over Bi–Fe–Me(Me = Ni, Co, Zn, Mn and Cu)–Mo oxide catalysts

BiFe0.65Me0.05Mo oxide catalysts promoted with different metals (Me=Ni, Co, Zn, Mn and Cu) were prepared and the effects of the transition metal addition based on multicomponent BiFeMo oxide catalysts have been investigated for the oxidative dehydrogenation of butenes to 1,3-butadiene. It has been found that the catalytic activity of BiFe0.65Me0.05Mo oxide catalysts depends on the nature of the metals employed, varying in the order of Ni>Co>Zn>Mn>Cu. Temperature-programed re-oxidation measurements revealed that the catalytic activity of the BiFe0.65Me0.05Mo oxide catalysts was well correlated with the oxygen mobility of the catalysts.

Creation of Oxidation Catalysts Based on Molybdenum Oxides with Structural Variety

Complex metal oxide catalysts active for gas-phase selective oxidations of olefins and alkanes are usually constructed with molybdenum oxide as a main and key component with various metal elements. Two catalytic systems, multicomponent Mo-Bi oxide catalysts for propylene selective oxidation and crystalline Mo-V oxide-based catalysts for alkane selective oxidation have been described in details in terms of catalytic component collaboration sustained by high dimensional catalyst structures.

The partial oxidation of propane on mixed metal oxides—A short overview

Recently much attention has been paid to the partial oxidation of propane to acrylic acid on multi-component mixed oxide catalysts in view of the development of a one-step industrial process. Much progress has been made in the understanding of the different parameters of the reacting systems but sufficient performance of the catalysts has still not been attained. The actual situation is described in a short overview and the remaining problems are pointed out.