Vanadium Loading Research Articles

An Efficient Vanadia Supported SrTiO3 Nanocatalyst for the Selective Oxidation of Benzylalcohol to Benzaldehyde

AbstractIn the present study, SrTiO3 (STO) was synthesized using oxalate method. A series of V2O5 nanoparticles supported on SrTiO3 (V2O5 / STO) with the vanadia content ranging from 0.5 to 2 wt. % was synthesized by wet impregnation method. Physicochemical properties of the synthesized catalysts were determined by X‐ray diffraction, Fourier transform infrared spectroscopy, Transmission electron microscopy, N2 physisorption and X‐ray photoelectron spectroscopy and acidity by pyridine adsorption method. XPS studies of the catalysts reveal that vanadium is in +5 oxidation state. Particle size of the catalysts calculated from TEM image analysis was found to be in the range of 86–92 nm. Pyridine adsorption studies reveals presence of Lewis acidity in the catalysts and the number of Lewis acid sites increase with vanadium content of the catalysts. Their catalytic activity was evaluated for the liquid phase oxidation of benzyl alcohol to benzaldehyde. STO is found to be least active and highly selective for the formation of benzaldehyde product where as V2O5/STO catalysts were found to be highly active and selective for the oxidation of benzyl alcohol reaction. Among all the catalysts the one with 1 wt. % loading of vanadia contains a greater number of active sites is found to be highly efficient heterogeneous catalyst system for selective oxidation of benzyl alcohol with 100 % benzaldehyde selectivity. The catalytic activity of the catalysts was correlated with the physico‐chemical properties of the catalysts.

Green synthesis and characterisation of novel [1,3,4]thiadiazolo/benzo[4,5]thiazolo[3,2-a]pyrimidines via multicomponent reaction using vanadium oxide loaded on fluorapatite as a robust and sustainable catalyst.

We synthesised materials with different loadings of vanadia on fluorapatite (V2O5/FAp), fully characterised their structural properties using various spectral techniques including TEM, BET, XRD, FT-IR, SEM and EDX and assessed their prowess as catalysts. The 2.5% V2O5/FAp exhibited excellent activity for the synthesis of novel [1,3,4]thiadiazolo[3,2-a]pyrimidines and benzo[4,5]thiazolo[3,2-a]pyrimidines. The one-pot three-component fusion reaction between chosen substrates of 1,3,4-thiadiazole-amines or 2-amino-benzothiazole, aldehydes and active methylene compounds in ethanol solvent at room temperature gave an excellent yield of products (90–97%) in a swift reaction (25–30 min). The advantages of this protocol are rapid synthesis, mild reaction conditions, green solvent, easy work-up, eco-friendliness, reusability of catalyst and no need for column chromatography.

Oxidative dehydrogenation of propane on silica-supported vanadyl sites promoted with sodium metavanadate

[VO4]/SiO2 promoted with NaVO3 polymorphs (α or β) shows higher initial activity in oxidative dehydrogenation of propane (increase by 30 and 125%, respectively) compared to that of unpromoted [VO4]/SiO2 at similar vanadium loadings.

Ce-Doped V2O5-WO3/TiO2 with Low Vanadium Loadings as SCR Catalysts and the Resistance of H2O and SO2

The promoting effect of Ce on V-W/Ti catalyst for selective catalytic reduction (SCR) of NOx by NH3 was studied. Compared with the original V-W/Ti samples, addition of Ce contributed better NH3-SCR performance. The H2O and SO2 resistance of Ce modified V-W/Ti catalyst was improved by the different impregnation sequence of Ce. The catalysts were characterized by NH3-temperature programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and H2-temperature programmed reduction (H2-TPR) techniques. The results showed that the impregnation sequence of W and Ce influenced the NH3 adsorption capacity of the catalysts. In comparison to 0.2V-5Ce-5W/Ti and 0.2V-(5Ce5W)/Ti, 0.2V-5W-5Ce/Ti catalyst contributed better H2O and SO2 resistance, with the highest Ce3+/(Ce4+ + Ce3+) value of 36.6%. Besides, a catalytic mechanism of SCR reactions over Ce-doped V-W/Ti catalysts was proposed.

Effect of Vanadium Oxides Composition Loaded on γAl2O3 Catalyst for Oxidative Dehydrogenation of Propane to Propylene

AbstractThe catalysts were prepared by impregnation method, and the mass fraction of vanadium on γAl2O3 was 3%, 6%, 9%, 12%, 15%, respectivley (denoted as 3 V‐γAl2O3, 6 V‐γAl2O3, 9 V‐γAl2O3, 12 V‐γAl2O3 and 15 V‐γAl2O3). X‐ray diffraction(XRD), Raman spectroscopy(Raman), cyclic voltammetry(CV) and in‐situ infrared spectroscopy (FT‐IR) were used to study the properties of series of vanadium oxides composition loaded on γAl2O3 catalyst for oxidative dehydrogenation of propane to propylene. The results show that the V−O‐Al bond and the V=O bond are formed at the 3 V‐γAl2O3 and 6 V‐γAl2O3 catalysts, and the vanadium oxides are uniformly dispersed on γAl2O3. With the increasing of vanadium loading, for 9 V‐γAl2O3, 12 V‐γAl2O3 and 15 V‐γAl2O3 catalysts, except V−O‐Al and V=O bond, there was appeared V−O‐V bond, indicating the formation of V2O5 crystal supported on γAl2O3 obviously. The uniform dispersion for low vanadium loading on γAl2O3, is favorable for the selectivity of propylene, and for high vanadium loading catalysts, the V2O5 crystal will accelerate the deep oxidation of propane. At 500°C, the propylene selectivity of the 3 V‐γAl2O3 catalyst was 75.9%, and the propane conversion was 12.5%. Whereas the propylene selectivity of the 15 V‐γAl2O3 catalyst was 67.3%, and the propane conversion was 10.7%.

Effect of vanadia loading on acidic and redox properties of VOx/TiO2 for the simultaneous abatement of PCDD/Fs and NOx

The effect of vanadia loading on the acidic and redox properties of VOx/TiO2 catalyst and their role in the simultaneous reduction of NO with NH3 and oxidation of o-DCB is studied. Catalyst samples with different proportions of VOx species, ranging from monomerics to V2O5 octahedral crystals have been prepared. A relationship between VOx species and their acidic and redox properties was found. At low temperature, o-DCB is adsorbed mainly on Lewis sites, associated to monomeric species, but at high temperature, o-DCB and NH3 compete for Brønsted sites associated to polymeric species.

Dmetallization of Iraqi Crude oil by Using Zeolite A

ABSTRACTIn present work, the removal of vanadium (V) from Iraqi crude oil using zeolite A was investigated. Different operating parameters such as adsorbent loading, vanadium loading, and operating time were studied for their effects on metal removal efficiency. Results of the adsorption test showed that the Langmuir isotherm predicted well the experimental data and the maximum zeolite A uptake was 30 mg V/1 g zeolite. XRD, SEM, and EDX analyses revealed the noticeable uptake of zeolite for V. In crude oil, experimental results indicated that for zeolite loading at 1 g/100 mL oil and within approximately 5 h, the removal efficiencies of V were 60, 45, and 33% at vanadium loadings of 75, 85, and 95 ppm respectively. While at 10, 20, 40, and 50 h the removal efficiency was 68, 75, 78 and 78% at 75 ppm of vanadium loading. At vanadium loading of 75 ppm, the equilibrium concentration of V in crude oil was obtained after 40 h of operation. Long-term tests revealed the high stability of zeolite A for vanadium removal. Experimental results depicted that zeolite A could be advantageous for the removal of V in the crude oil hydrotreating units.

Evidences for Different Reaction Sites for Dehydrogenation and Dehydration of Ethanol over Vanadia Supported on Titania

Vanadia supported on titania were prepared with increasing vanadia loadings up to 20 wt % to study the effect of the vanadia loading on catalytic reactivity. A competitive decomposition of ethanol into ethylene (dehydration) and acetaldehyde (dehydrogenation) over the catalyst occurs over the vanadia supported on TiO2. Dehydrogenation is generally favored over dehydration over a wide range of the vanadia loadings up to 20 wt % due to a lower energy barrier for the dehydrogenation channel. Both dehydration and dehydrogenation rates are enhanced in proportion to the vanadia loadings up to about 2 wt %. At higher vanadia loadings (>2 wt %), however, the dehydration rate decreases while the dehydrogenation rate saturates. X‐ray photoelectron spectroscopic analysis reveals that reduced V and Ti species are formed at the low vanadia contents and act as strong dissociative adsorption sites for H2O, while extended VOx clusters as well as three‐dimensional V2O5 islands formed at high vanadia loadings prevent the formation of such sites. Thus, the observed difference between the two reaction channels can be explained from the structural transition of the vanadia overlayers from highly dispersed small VOx clusters into larger polyvanadates or islands. At low vanadia loadings (<2 wt %), both the edge sites and the surface sites of the small VOx clusters grow in proportion to the loadings as the number of the clusters increases. Thus, both reaction channels are enhanced as well. At higher vanadia loadings (>2 wt %), however, the transformation into larger islands reduces the edge sites or the boundaries between the clusters and TiO, not the surface area. This implies that the active sites for the dehydrogenation are on the surfaces of the vanadia overlayers, while those for the dehydration are on the boundaries between the VOx and TiO2. Our results provide an additional insight into the active sites for dehydration and dehydrogenation reactions over the titania‐supported vanadia catalysts.

Activated Bentonite for Removal Nickle and Vanadium from Petroleum Distillates

The present work is to investigate the feasibility of removal vanadium (V) and nickel (Ni) from Iraqi heavy gas oil using activated bentonite. Different operating parameters such as the degree of bentonite activation, activated bentonite loading, and operating time was investigated on the effect of heavy metal removal efficiency. Experimental results of adsorption test show that Langmuir isotherm predicts well the experimental data and the maximum bentonite uptake of vanadium was 30 mg/g. The bentonite activated with 50 wt% H2SO4 shows a (75%) removal for both Ni and V. Results indicated that within approximately 5 hrs, the vanadium removal efficiencies were 33, 45, and 60% at vanadium loadings of 10, 30, and 40 ppm respectively. Further processing of heavy gas oil with 10 ppm vanadium shows a continuous slight increase in metal removal with operating time. At 10, 20, 40, and 50 hrs the removal efficiency was 68, 75, 78 and 78% respectively. Results indicated that an equilibrium concentration of the 10 ppm of vanadium was attained after 30 hrs while for Nickel at a loading of 4 and 7 ppm the equilibrium achieved after 40 hrs. Results depicted that activated bentonite has higher selectivity towards Vanadium. Results depict that activated bentonite (ACB) has a remarkable capacity for removal of (V) and (Ni) from heavy gas oil.

Selective Catalytic Reduction of NOx with Ammonia and Hydrocarbon Oxidation Over V2O5–MoO3/TiO2 and V2O5–WO3/TiO2 SCR Catalysts

The NH3-SCR performance in the presence of short and long chain hydrocarbons (propylene and dodecane) as well as of formaldehyde was investigated for a series of V2O5–MoO3/TiO2 (VMoTi) and V2O5–WO3/TiO2 (VWTi) catalysts. The results demonstrate that vanadium oxides act as the main catalytically active component for NOx conversion, hydrocarbon (HC) and formaldehyde oxidation. Among VMoTi and VWTi materials with different vanadium loading, the catalysts containing 3 wt% V2O5 lead to the highest catalytic activity. The ability to simultaneously remove NOx, HC and HCHO over VMoTi is inferior to that of the conventional WO3-based catalyst. However, VMoTi exhibits higher CO2 selectivity, especially during oxidation of long-chain HCs, which represents an important advantage for a possible multifunctional catalyst. Apart from CO, formaldehyde was detected as byproduct during HC oxidation for both catalyst formulations.

The promotion effect of ceria on high vanadia loading NH3-SCR catalysts

A high vanadia loading (5 wt%) catalyst was modified by ceria to improve the NH3-SCR performance. CeVO4 was generated after the addition of ceria to 5 wt% V2O5/TiO2, result not seen in the case of low-loading vanadia samples. CeVO4 presented stable Brønsted acid sites for NH3 adsorption and moderate redox sites for NH3 activation rather than polymeric VOx for the V-based catalyst. These properties effectively suppressed formation of N2O and NO (side reactions). Therefore, ceria preserved the low-temperature activity of V2O5/TiO2 and improved its high-temperature N2 selectivity. Furthermore, ceria promoted the resistance of V2O5/TiO2 to SO2 and H2O poisoning.

Electrospun vanadium oxide based submicron diameter fiber catalysts. Part I: Preparation procedure and propane ODH application

V-Zr-O submicron diameter fibers have been prepared by electrospinning of V and Zr containing solutions in only one calcination step. This is a simple and versatile synthesis method, easy to scale up, that produces porous solids, with fibrous morphology and with VOx catalytically active species, being these solids attractive for alkane partial oxidation reactions, since the catalysts with fibrous morphology present several advantages with respect powered ones. With the new proposed method, at low vanadium loadings (V% w/w<6.4), surface dispersed VOx were found in the zirconia fiber as shown by Raman spectroscopy analysis, whereas crystalline ZrV2O7 was observed when the V content was increased (V% w/w>6.4). These fibers were very active for the propane oxidative dehydrogenation (ODH) catalytic reaction, showing very promising results since the fibrous morphology of submicrometric diameter makes these solids quite suitable for fixed-bed catalytic reactors.

New insight into alkali resistance and low temperature activation on vanadia-titania catalysts for selective catalytic reduction of NO

A series of vanadia-titania catalysts with different vanadia loadings for the selective catalytic reduction (SCR) of NO by ammonia was prepared via incipient impregnation method. The alkali resistance and SCR activity at low temperature has been investigated on the prepared catalysts. Increasing the vanadia loading from 1% to 10%, the NO removal efficiency of the catalysts gained a 70% growth at 200 °C. With the increase of the vanadia loading, the high loading vanadia-titania catalysts exhibited higher ratio of V5+/(V4++V5+), which enhanced the oxidation of NH3 at high temperatures and also improved the standard SCR performance at low temperature. After doping with potassium, V4/Ti catalyst (V2O5 = 4 wt%) displayed the best performance over which 80% initial activity was retained from 300 °C to 400 °C. More acid sites and active vanadium species were retained in the high loading vanadia-titania catalysts, which made them exhibit better low temperature alkali resistance. However, when vanadia content was higher than 4%, the competition of NH3 oxidation severely deactivated the catalytic activity above 250 °C. Additionally, in the presence of SO2 and H2O the SCR performance of the high loading vanadia-titania catalysts were also studied in order to investigate the influence of the actual working conditions.

VOx/γ‐Al2O3 Catalysts for Propane Dehydrogenation Prepared by “Impregnation‐Solid Phase Reaction” Method with Aluminum Hydroxide as Support Precursor

AbstractThe alumina supported vanadium oxide catalysts (VOx/γ‐Al2O3) were prepared by wet impregnation‐solid phase reaction method with aluminum hydroxide as support precursor. The prepared catalysts were characterized by N2 adsorption–desorption, UV–vis, X‐ray photoelectron spectroscopy and Raman spectroscopy. The performances of the catalysts were tested for propane dehydrogenation (PDH) reaction. The results indicate that the loading of vanadium on the aluminum hydroxide can influence the surface morphology of the catalysts and greatly improve the specific surface area of the resulted VOx/γ‐Al2O3 compared to pure γ‐Al2O3 support. The vanadium content markedly influences the polymerization degree of surface VOx species and catalytic performances of VOx/γ‐Al2O3 catalysts for PDH. Among all samples, the 2.9VOX/γ‐Al2O3 catalyst (vanadium content is 2.9 wt.%) possesses the maximum specific surface area and harmonious polymerization degree of VOX species. It exhibits the best catalytic performances during the 8 h of PDH reaction. Meanwhile, the 2.9VOx/γ‐Al2O3 catalyst possesses high regeneration stability and the highest TOF (turnover frequencies) value of 9.0×10−3 s−1, which is evidently higher those of previous works. After 7 reaction–regeneration cycles, the initial activity and propene selectivity can be almost restored.

Characteristics of Vanadium-Based Coal Gasification Slag and the NH3-Selective Catalytic Reduction of NO

In order to realize the resource utilization of coal gasification slag (CGS) and to effectively control the emission of nitrogen oxides (NOx) in coke oven gas, the effect of the reaction conditions and vanadium loading over the CGS catalysts was carried out for the selective catalytic reduction (SCR) of NO by NH3. The various vanadium loaded CGS catalysts were prepared using impregnation methods. The addition of 1% vanadium to the CGS catalyst (V1/CGS) significantly enhanced the NO conversion at a wide temperature range of 180–290 °C. The catalysts were characterized by N2 adsorption/desorption, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, NH3-temperature programmed desorption, Inductively coupled plasma optical emission spectrometer (ICP-OES), thermo gravimetric analyses (TGA), Fourier Transform infrared spectroscopy (FTIR), Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS), and X-ray powder diffraction (XRD). The experimental results show the following: That (1) the NO removal efficiency of the sample CGS3 was the best, and it could be up to 100% under the experimental conditions; (2) The NO removal efficiency of the catalysts was higher in the atmosphere with SO2 than that without SO2; (3) The XRD results indicated the active component of vanadium was homogeneously dispersed over CGS and the active component of catalyst was V2O5 according to the XPS results. In particular, the NH3-TPD spectra of the vanadium loaded CGS catalyst showed that vanadium produced more acid sites, and the Lewis acid sites on the vanadium species were the active sites for the catalytic reduction of NO at 240–290 °C.

Synthesis of Vanadium Catalysts Supported on Cerium Containing TiO2 Nanotubes for the Oxidative Dehydrogenation of Propane

Cerium containing TiO2 nanotubes (CeTNTs) were successfully synthesized through the hydrothermal method and applied as support for vanadium catalyst in the oxidative dehydrogenation of propane. The impregnation method was employed to load 2, 5 and 8 wt % vanadium on the CeTNT surface. The catalysts were labeled as xV/CeTNT which x refers to the amount of vanadium loading. For a comparison, pure TNT was also synthesized and impregnated with 5 wt % vanadium. Based on TGA, XRD and TEM analyses, it was concluded that the addition of Ce increased the thermal stability of TNT. The Raman results showed that the 5V/CeTNT sample with a higher surface area hosted a higher number of monomeric VOx species compared to 5V/TNT. On the other hand, it was shown that the population of monomeric VOx species decreased as the vanadium loading increased. Catalytic results showed that propane conversion increased while propylene selectivity decreased as the vanadium loading increased. The best catalytic performance belonged to the 5V/CeTNT sample with propylene yield of about 10.6 wt % at the reaction temperature of 500°C.

Vanadium and nickel deposition on FCC catalyst: Influence of residual catalyst acidity on catalytic products

Abstract The alteration of catalytic activity and selectivity of the cracking catalyst by porphyrinic metallic elements present in heavy crude oil fractions is a subject that requires serious attention. In this study, the effects of the two most deleterious of the metals (vanadium and nickel) and how they shift the product selectivity of the catalytic cracking are discussed, with a key focus on the catalytic behavior of the residual acidity consequent upon metal deactivation. Increasing loadings of vanadium and nickel were deposited on the FCC catalyst and subjected to a simulated FCC regeneration unit conditions. It is found that at loadings greater than 0.3 wt%, vanadium is 4–5 times as destructive as nickel on the crystalline structure of the catalyst. Catalytic evaluation results revealed correlations between residual surface acidity, catalyst activity and amount of coke formed on the catalyst at a constant catalyst-to-oil ratio (CTO). This result is in slight contrast with the widely reported enhanced coking activity of vanadium on FCC catalyst consequent upon dehydrogenation reaction. An alternative coke formation pathway based on the residual catalyst acidity is advanced for the observed coking behavior of high vanadium laden catalyst. In addition, a vanadium control measure relying on the acid-base chemistry and hydrothermal stability of a mixed-metal oxide is demonstrated as an effective method to limit the mobility of vanadium into the framework of the catalyst, the action that initiates vanadium deleterious effects. This study is expected to renew interest in the research on the coking behavior of metal poison catalysts.

Ordered mesoporous alumina-supported vanadium oxides as an efficient catalyst for ethylbenzene dehydrogenation to styrene with CO2

Ordered mesoporous alumina (OMA)-supported vanadia catalysts with different vanadium loading (denoted as nV/OMA) were employed for ethylbenzene dehydrogenation to styrene with CO2 as soft oxidant, and a commercial γ-Al2O3-supported vanadia catalyst for comparison. The catalytic behavior depends strongly on the vanadium loading and the support properties. With an optimal V loading of 0.8 mmol/g-support, 0.8 V/OMA catalyst exhibits superior catalytic performance than that of 0.8 V/γ-Al2O3, which can be attributed to the excellent structural, textual, and surface properties of OMA support. The important roles played by OMA lies in stabilizing highly dispersed V5+ active species and preventing the coke formation.

The Reducibility and Cluster Size of Vanadium Oxide as Potential Descriptors of Its Catalytic Activity in the Partial Oxidation of Ethanol

Abstract A series of vanadium oxide (VOx) catalysts prepared using three different supports were tested for the partial oxidation of ethanol to acetaldehyde. Optical absorption spectroscopy and Temperature Programmed reductions experiments indicate that the reducibility and average domain size of the vanadia clusters anchored on the supports are very sensitive to vanadia loading. The catalytic activity results were modeled using a pseudo steady state approximation using the ethanol hydrogen abstraction step as rate limiting. The results obtained strongly suggest that catalytic activity can be correlated to both average vanadia cluster size and the ability of vanadia to uptake hydrogen during TPR experiments.

Low-Temperature Pyrolysis–Catalysis Coupled System for Efficient Tetrachlorobenzene Removal: Condition Optimization and Decomposition Mechanism

The decomposition of tetrachlorobenzene (TeCB) emitted from simulated fly ash was studied in a low-temperature pyrolysis–catalysis coupled system. The influences of catalyst support, active component type, active phase-to-assistant ratio, vanadium loading, and catalyst calcination temperature on TeCB conversion were comprehensively investigated. The optimal catalyst composition and preparation conditions were determined through single-factor experiments. Moreover, the effects of reaction temperature, space velocity, and pollutant initial concentration on TeCB decomposition efficiency were explored by orthogonal experiments. The possible mechanism for PeCB decomposition over prepared V2O5–WO3/TiO2 catalysts was proposed based on reaction-byproduct composition and distribution. It is found that the TeCB decomposition efficiency is positively correlated with reaction temperature while being negatively correlated with gas hourly space velocity (GHSV) and TeCB initial concentration. GHSV has the most significant effect on TeCB decomposition, followed by reaction temperature and TeCB concentration. Under optimal conditions of space velocity of 600 h–1, reaction temperature of 350 °C, and TeCB initial concentration of 0.5 volume percent, the TeCB conversion can reach up to 94.1%. The key substeps of TeCB decomposition are aromatic pollutant adsorption, nucleophilic substitution, and intermediate electrophilic substitution. The TeCB molecules were first adsorbed on catalyst surface and then decomposed into low-chlorination aromatics and aromatic and aliphatic hydrocarbons as phenolates, benzoquinone, aldehydes, and carboxylic acids.