Vanadium-containing Catalysts Research Articles

EFFECT OF PHASE PROPERTIES OF W-V-O CATALYSTS ON THEIR ACTIVITY IN THE ETHANOL OXIDATION REACTION

The activity of binary tungsten-vanadium oxide catalysts in the reaction of ethanol oxidation was studied in this work. Ethylene and acetic acid have been found to be the main products of the vapor-phase oxidation of ethanol on tungsten-vanadium oxide catalysts. Depending on the reaction temperature, acetaldehyde and carbon dioxide are also formed in significant quantities. It is shown that acetic acid is the main product of ethanol oxidation at low reaction temperatures, while ethylene is the main product at high temperatures. The influence of the composition of binary tungsten-vanadium oxide catalysts on their activity in the ethanol oxidation reaction has been studied. The studies performed have shown that with an increase in the atomic ratio of tungsten to vanadium, the yield of acetic acid decreases, while the yields of acetaldehyde and ethylene increase. X-ray diffraction studies of binary vanadium-containing catalysts have been carried out. It has been established that three phases are formed in the W-V-O system: two modifications of WO3 and one V2O5. The degrees of crystallinity of the studied catalysts were also calculated. The degrees of crystallinity and activity of binary tungsten-vanadium oxide catalysts in the ethanol oxidation reaction are compared. It has been established that an increase in the degree of crystallinity of the catalyst contributes to a change in the direction of the ethanol oxidation reaction towards the formation of ethylene and acetaldehyde. Keywords: ethanol, acetic acid, ethylene, binary catalysts, vanadium oxide, tungsten oxide

Extraction of valuable components from spent cadmium and vanadium-containing catalysts

With the help of water-acid leaching methods, studies were carried out on the extraction of vanadium (V) oxide from spent vanadium-containing catalysts of Maksam-Chirchik JSC, AGMK JSC and Ammophos-Maxam JSC. A new, resource-saving technology for the extraction of vanadium compounds from spent vanadium catalysts has been proposed. In order to reduce the consumption of sulfuric acid in the leaching process, a three-stage aqueous acid leaching was proposed, as a result of which the degree of extraction of vanadium into the solution is more than 98%.

The Impact of 3-(trihydroxysilyl)-1-propanesulfonic Acid Treatment on the State of Vanadium Incorporated on SBA-15 Matrix

Bifunctional catalysts—e.g., those with acidic and redox sites—are of particular importance, especially in the cascade processes, including the one-pot transformation of glycerol to acrylic acid. In this study, we explore one aspect of the preparation of a vanadium-containing catalyst, which can be further modified with 3-(trihydroxysilyl)-1-propanesulfonic acid (TPS). The state of vanadium species loaded on mesoporous ordered silica of SBA-15 type was investigated before and after treatment with TPS, which can also be applied for the generation of acidic centers. Two vanadium sources, i.e., ammonium metavanadate and vanadium(IV) oxide sulfate, were applied to generate redox sites on SBA-15. The structure of materials obtained was analyzed using N2 adsorption/desorption and XRD measurements. For the estimation of the amount of vanadium and characterization of its state, the following techniques were applied: ICP, UV-Vis, XPS, ESR and FTIR combined with pyridine adsorption. The treatment of vanadium containing SBA-15 with TPS was found to lead to the oxidation of V4+ to V5+ and the partial removal of vanadium species, leading to a decrease in the number of penta-coordinated vanadium species. These features should be taken into account in the design of bifunctional catalysts with vanadium-active centers and SO3H acidic sites coming from TPS.

Theoretical study on molecular mechanism of aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformyfuran catalyzed by VO2 + with counterpart anion in N,N-dimethylacetamide solution.

Vanadium-containing catalysts exhibit good catalytic activity toward the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformyfuran (DFF). The aerobic oxidation mechanism of HMF to DFF catalyzed by VO2+ with counterpart anion in N,N-dimethylacetamide (DMA) solution have been theoretically investigated. In DMA solution, the stable VO2+-containing complex is the four-coordinated [V(O)2(DMA)2]+ species. For the gross reaction of 2HMF + O2 → 2DFF + 2H2O, there are three main reaction stages, i.e., the oxidation of the first HMF to DFF with the reduction of [V(O)2(DMA)2]+ to [V(OH)2(DMA)]+, the aerobic oxidation of [V(OH)2(DMA)]+ to the peroxide [V(O)3(DMA)]+, and the oxidation of the second HMF to DFF with the reduction of [V(O)3(DMA)]+ to [V(O)2(DMA)2]+. The rate-determining reaction step is associated with the C–H bond cleavage of –CH2 group of the first HMF molecule. The peroxide [V(O)3(DMA)]+ species exhibits better oxidative activity than the initial [V(O)2(DMA)2]+ species, which originates from its narrower HOMO–LUMO gap. The counteranion Cl− exerts promotive effect on the aerobic oxidation of HMF to DFF catalyzed by [V(O)2(DMA)2]+ species.

Switchable Catalytic Polyoxometalate-Based Systems for Biomass Conversion to Carboxylic Acids.

We present the Keggin-type polyoxometalate H6[PV3Mo9O40] as a switchable catalyst being able to catalyze the transformation of both glucose and glyceraldehyde to formic acid (42%) and lactic acid (40%), respectively, within 1 h reaction time by simply changing the reaction atmosphere at 160 °C from oxygen to nitrogen in one reactor setup. In detail, we report the influence of different gas atmospheres and reaction temperatures on various vanadium-containing catalysts in the selective transformation of several biogenic substrates to carboxylic acids with a special emphasis on reaction pathways and switchability of the catalyst systems. All investigations were carried out in parallel using either an oxygen or a nitrogen atmosphere of 20 bar performing time-resolved experiments between 0.25 and 5 h and a temperature variation from 160 to 200 °C. Furthermore, a catalyst and a substrate variation led to the reaction system consisting of glyceraldehyde and the Keggin-type polyoxometalates (POM) H6[PV3Mo9O40] as the best switchable reaction system under the applied conditions. This study shows interesting potential for using both Keggin-type and Lindqvist-type POMs as switchable catalysts for selective biomass conversion to platform chemicals.

Vanadium-containing electro and photocatalysts for the oxygen evolution reaction: a review

This review summarizes the recent progress in vanadium-containing catalysts, including the synthesis strategies and performance in electrocatalytic and photocatalytic oxygen evolution.

Operando Electrical Conductivity and Complex Permittivity Study on Vanadia Oxidation Catalysts

The electrical conductivity and its real and imaginary permittivity parameters were studied over two vanadium-containing catalysts for the selective oxidation of n-butane to maleic anhydride. Parameter variation under isothermal conditions allowed determination of multiple steady-state conditions for catalytic performance and charge carrier dynamics. One sample was the n-type semiconductor V2O5–x with low selectivity, and the other sample was the p-type semiconductor vanadyl pyrophosphate (VPP) with high selectivity for the target product. Well-resolved conductivity parameters supported by in situ UV–vis studies allowed correlations between performance and charge carrier dynamics. A concept for interpreting the trends is presented, and consequences for further analytical work as well as for material design are derived.

VOx/Fe2O3 Shell\u2013Core Catalysts for the Selective Oxidation of Methanol to Formaldehyde

Efficient oxidation catalysts are important in many current industrial processes, including the selective oxidation of methanol to formaldehyde. Vanadium-containing catalysts have been shown to be effective selective oxidation catalysts for certain reactions, and research continues to examine their applicability to other reactions of interest. Several VOx/Fe2O3 shell–core catalysts with varying VOx coverage have been produced to investigate the stability of VOx monolayers and their selectivity for methanol oxidation. Catalyst formation proceeds via a clear progression of distinct surface species produced during catalyst calcination. At 300 °C the selective VOx overlayer has formed; by 500 °C a sandwich layer of FeVO4 arises between the VOx shell and the Fe2O3 core, inhibiting iron cation participation in the catalysis and enhancing catalyst selectivity. The resulting catalysts, comprising a shell–subshell–core system of VOx/FeVO4/Fe2O3, possess good catalytic activity and selectivity to formaldehyde.

The structure-property relationship of oxovanadium(IV) complexes in the wall framework of PMOs and their catalytic applications

Oxovanadium(IV) species could be considered as effective active sites in the catalytic oxidation reactions, but in the traditional vanadium-containing catalysts, the unstable and undispersible status of these active sites cause great limitation in their application. In this study, we present a novel approach to utilize the co-condensation of the silica source with oxovanadium organic complexes through the liquid-crystal templating (LCT) process introducing the vanadium species into the framework of periodically meosporous organosilicas (PMOs). Oxovanadium organic complexes are successfully obtained by the coordination effect between vanadium species and organic complexes. Thus the vanadium-containing PMOs catalysts are accordingly synthesized; the model structure of as-prepared catalysts is proposed and further verified by different characterization measurements. These vanadium-containing PMOs catalysts display the extremely stable and well-dispersed oxovanadium(IV) species in the framework, and due to this advanced structure, the corresponding excellent catalytic properties of these catalysts in styrene oxidation reaction are obtained.

Structure-Reactivity Correlations in Vanadium-Containing Catalysts for One-Pot Glycerol Oxidehydration to Acrylic Acid.

The design of suitable catalysts for the one-pot conversion of glycerol into acrylic acid (AA) is a complex matter, as only fine-tuning of the redox and acid properties makes it possible to obtain significant yields of AA. However, fundamental understanding behind the catalytic phenomenon is still unclear. Structure-reactivity correlations are clearly behind these results, and acid sites are involved in the dehydration of glycerol into acrolein with vanadium as the main (or only) redox element. For the first time, we propose an in-depth study to shed light on the molecular-level relations behind the overall catalytic results shown by several types of V-containing catalysts. Different multifunctional catalysts were synthesized, characterized (>X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, temperature-programmed reduction, and temperature-programmed desorption of ammonia), and tested in a flow reactor. Combining the obtained results with those acquired from an in situ FTIR spectroscopy study with acrolein (a reaction intermediate), it was possible to draw conclusions on the role played by the various physicochemical features of the different oxides in terms of the adsorption, surface reactions, and desorption of the reagents and reaction products.

Catalytic oxidation of biomass to formic acid in aqueous solutions using vanadium-containing catalysts

Formic acid (FA) is an important material in the chemical industry, and the preparation of FA from biomass could provide a sustainable strategy for the large-scale production of FA. Vanadium (V)-containing catalysts have recently been reported to catalyze the conversion of biomass to FA with a high level of selectivity under aqueous conditions using molecular O 2 as an oxidant. These catalysts mainly include V-containing heteropoly acid, NaVO 3 /H 2 SO 4 and VOSO 4 . In this article, we have provided a detailed review of the performances of these three catalytic systems for the conversion of biomass into FA. This review is mainly focused on four key areas of research, including the mechanisms associated with this transformation, the relationships between various reactions, methods for the separation of FA from the aqueous solution and the recyclability of the catalytic systems. Vanadium-containing catalytic systems can be used to generate FA from numerous bio-based carbohydrates, including sugars, cellulose and hemicellulose, with a high level of selectivity. The active catalytic species in these processes is known to be V 5+ , and these processes can be explained in terms of an electron transfer-oxygen transfer mechanism, where the vanadium species (including V-containing heteropoly acid and VO 2 + ) receives two electrons from the substrate in exchange for one oxygen atom to form FA. Among the various reactions occurring in the catalytic system, the hydrolysis of the biomass and the selective oxidation of the biomass to FA are competitive, and variations in the main reaction parameters can lead to significant changes in the balance between these two reactions. The direct separation of FA from the aqueous reaction mixture by distillation is difficult, and the extraction of FA by organic solvents is by far a relatively feasible method. Among the extraction agents evaluated for this purpose, n-butyl ether and ethyl ether have been reported to be useful for the extraction of FA from catalytic systems using V-containing heteropoly acid and NaVO 3 /H 2 SO 4 as catalysts, respectively. In terms of the recyclability of the NaVO 3 /H 2 SO 4 system, the activity remained largely unchanged after several runs when cellulose and real lignocellulose were employed as substrates. Finally, the problems associated with this process for the conversion of biomass were analyzed and several new strategies have been proposed to further develop the processes involved in the preparation of FA from biomass. Research towards developing a better understanding of the reaction mechanism associated with this process has focused predominantly on the oxidation of potential model compounds and ambiguous inferences. Further studies on the mechanism should focus on the detection of the real coordinated complex formed by the catalyst and substrate through various testing methods. Research on real lignocellulose has so far been inefficient, because of the lack of studies towards lignin conversion and the effect of ash. The separation of FA from an aqueous solution still represents a significant challenge to the industrial application of biomass for production of FA.

Vapor-phase oxidation of β-picoline to nicotinic acid on V2O5 and modified vanadium oxide catalysts

Modification of V2O5 with Ti, Sn, Zr, Nb, and Al oxides improves the activity and selectivity of the vanadium oxide catalyst in vapor-phase oxidation of β-picoline to give nicotinic acid. It is shown that the conversion of β-picoline and the yield of nicotinic acid on two-component V2O5-TiO2, V2O5-SnO2, V2O5-ZtrO2, V2O5-Nb2O5, and V2O5-Al2O3 catalysts may be several times those on the V2O5 catalyst. It was found that, on passing from V2O5 to double-component vanadium-containing catalysts, the proton affinity of active oxygen bonded to vanadium, calculated by the quantum-chemical method, grows simultaneously with the increase in the activity of the catalysts in the oxidation reaction.

Role of vanadium in Keggin heteropoly molybdate supported on titania catalysts for oxidation reactions

Vanadium-incorporated molybdophosporic acid catalysts supported on titania were prepared and characterized by FT-IR, X-ray diffraction and laser Raman spectroscopy. Characterization data reveals the incorporation of vanadium into the primary structure of Keggin ion of MPA. Catalysts activities were evaluated for oxidation of 1,2 benzenedimethanol using H2O2 and O2 as oxidants. Vanadium-containing catalysts showed high activity compared to their parent heteropoly acids. Oxidation ability depended on the number of V atoms present in Keggin heteropoly molybdate. Effect of reaction parameters on the oxidation ability was also evaluated.

Thermal desorption of toluene from Vanadium-containing catalysts coated onto various carriers

Thermal desorption of toluene from Vanadium-containing catalysts coated onto various carriers

Morphology and activity of vanadium-containing catalysts for the selective oxidation of benzene to maleic anhydride

The morphology and activity of vanadium catalysts are studied using a number of physicochemical methods: electron microscopy, electron paramagnetic resonance, and infrared spectroscopy. It is found that the active agent of the conversion of benzene to maleic anhydride over modified vanadium catalysts is the V4+ ion in the vanadyl configuration.

Одержання метакрилової кислоти на ванадійвмісних каталізаторах в газовій фазі

У статті розглянуто закономірності одержання метакрилової кислоти альдольною конденсацією пропіонової кислоти з формальдегідом на B 2 O 3 – P 2 O 5 – V 2 O 5 каталізаторах в газовій фазі

Decavanadate-intercalated Ni–Al hydrotalcites as precursors of mixed oxides for the oxidative dehydrogenation of propane

Two nickel–aluminum hydrotalcite type precursors were synthesized with molar ratio Ni/Al=3, using hydroxyl and carbonate as compensation anions. These precursors were intercalated by 30% (theoretical) decavanadate anion. The catalysts were obtained after calcination at 550°C and their performance was evaluated in propane oxidative dehydrogenation at 400°C using space velocities of 100, 150, 200 and 400mlg−1min−1 under conditions of oxygen deficiency and oxygen excess. Catalysts derived from nickel–aluminum-hydroxyl precursors attained an excellent performance under oxygen deficiency conditions promoting high propene selectivity and conversion. Under oxygen excess conditions the catalyst was more active but its selectivity was lower. Vanadium-containing catalysts showed improved selectivity under this operation condition. The formation of the hydrotalcite phase in precursors and mixed oxides in the catalysts was evidenced by X-ray diffraction (XRD). Analyses of textural and reduction properties were carried-out with nitrogen adsorption and temperature programmed reduction techniques respectively. Structural studies were performed by X-ray absorption spectroscopy for materials that showed best performance in the oxidative dehydrogenation reaction.

Lignocellulosic-derived mesoporous materials: An answer to manufacturing non-expensive catalysts useful for the biorefinery processes

The synthesis procedure and characterization of a mesoporous carbon obtained from biomass waste by a simple method, generating a low-cost material, with the corresponding waste revaluation are described. The use of phosphoric acid during the activation of the waste material induces the presence of stable phosphate groups, with acid characteristics, on the surface of the mesoporous carbon, which could find many applications as an acid solid catalyst. In addition, such phosphate groups increase the stability of the carbon material under oxidizing conditions at relatively high temperatures, increasing the range of catalytic applications in which this material could be used. This paper also shows how the redox functionality can be incorporated on the surface of this carbon material by impregnation with vanadium oxide species. The corresponding carbon supported vanadium oxide catalyst is active and relatively selective in the propylene partial oxidation to oxygenates. It is also discussed how the catalytic behavior of such vanadium-containing catalysts can be improved by the use of Zr as dopant.

A Thermodynamic Investigation of the Redox Properties of VPO Catalysts

The redox properties of a vanadium phosphorus oxide (VPO) catalyst with a V:P ratio of one were inves- tigated using Coulometric Titration at 873 K. Equilibrium between (VO)2P2O7 and VOPO4 exists at a P(O2 )o f 3 9 10 -4 atm, corresponding to DG of -60 kJ/mol O2. This value for VPO is significantly lower than that mea- sured with other vanadium-containing catalysts that have been studied. Furthermore, compared to other vanadium catalysts, V ?4 was stabilized against further reduction at lower P(O2). These redox thermodynamics may help to explain the unique catalytic properties of VPO catalysts for partial oxidation of butane to maleic anhydride.

Determination of the chemical composition of supported vanadium-containing oxide catalysts by the differential dissolution method

The results of the application of the stoichiographic method of differential dissolution (DD) in the determination of the chemical composition of vanadium-containing catalysts are presented. In the studied catalyst series, amounts of vanadium were deposited onto TiO2, SiO2, Al2O3, ZrO2, and Nb2O5. The catalysts were prepared by the impregnation method or by the spray drying method and thermally treated at different temperatures. The DD method was used for the precise correction of the phase composition of the V2O5/TiO2 catalyst samples in order to determine the nature of the active component of these catalysts and obtain the correct information on their structure using the NMR method.