Oxidative dehydrogenation of propane over vanadium and niobium oxides supported catalysts (original) (raw)
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Oxidative dehydrogenation of propane over vanadium oxide based catalysts
Catalysis Today, 2000
The oxidative dehydrogenation of propane was investigated using vanadia type catalysts supported on Al 2 O 3 , TiO 2 , ZrO 2 and MgO. The promotion of V 2 O 5 /Al 2 O 3 catalyst with alkali metals (Li, Na, K) was also attempted. Evaluation of temperature programmed reduction patterns showed that the reducibility of V species is affected by the support acid-base character. The catalytic activity is favored by the V reducibility of the catalyst as it was confirmed from runs conducted at 450-550 • C. V 2 O 5 /TiO 2 catalyst exhibits the highest activity in oxydehydrogenation of propane. The support's nature also affects the selectivity to propene; V 2 O 5 supported on Al 2 O 3 catalyst exhibits the highest selectivity. Reaction studies showed that addition of alkali metals decreases the catalytic activity in the order non-doped>Li>Na>K. Propene selectivity significantly increases in the presence of doped catalysts.
Oxidative dehydrogenation of propane over niobia supported vanadium oxide catalysts
Catalysis Today, 1996
Oxidative dehydrogenation (ODH) of propane is examined over a series of catalysts, which include Nb,O, supported monolayer VzO, catalysts, bulk vanadia-niobia with different vanadium oxide loadings and prepared by four different methods, VzO, and NbzO,. The intrinsic activity (TOF) of the samples studied indicates that vanadium containing active sites are indispensable for catalytic oxidative dehydrogenation of propane. Variations in the chemical environment of the vanadium ion do not cause significant changes in activity per site and, hence, all samples show similar TOF when the rates are normalised to the concentration of V on the surface. Selectivity to propene on the other hand strongly depends on the nature of the catalyst because readsorption and interaction of propene with the acid sites leads to total oxidation. Optimization of the weak sorption of propane is, therefore, concluded to be the key factor for the design of selective oxidative dehydrogenation catalysts.
Catalysis Letters, 2010
Novel vanadium oxide based catalyst derived from the open-framework solid, [Co 3 V 18 O 42 (H 2 O) 12 (XO 4)]Á24 H 2 O (X = V, S) (1) catalyses oxidative dehydrogenation of propane to propylene. Catalyst activity was evaluated in the temperature range 250-400°C with varying gas hourly space velocity (GHSV). At 350°C and GHSV of 9786 h-1 and at 1.3% propane conversion the selectivity to propylene was 36.8%. The major products obtained were propylene and CO x (CO 2 and CO). The ratio of the propylene to CO x depended directly on the catalytic sites present. Thus, as the amount of the catalyst was decreased, the conversion decreased with an increase in the propylene selectivity and a decrease in the selectivity to carbon oxides-CO x. The catalyst has been characterized by temperature programmed reduction and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).
Applied Catalysis A: General, 2004
In this paper, the effect of the oxide support for supporting the vanadium oxide phase is studied by estimating the reaction parameters for the oxidative dehydrogenation of propane. To achieve this objective, several V 2 O 5 /Al 2 O 3 and V 2 O 5 /TiO 2 catalysts were synthesized by an incipient-wetness-impregnation technique. The supported vanadium oxide catalysts were characterized and the surface area, monolayer coverage and reducibility were determined. The surface area of the catalyst samples was not significantly affected with supported vanadium oxide loading. It was observed that the catalysts contain only molecularly dispersed vanadium oxide species below monolayer coverage, and molecularly dispersed and crystalline V 2 O 5 above monolayer coverage. TPR studies revealed that the V 2 O 5 /Al 2 O 3 samples were more difficult to reduce relative to the V 2 O 5 /TiO 2 samples. The monolayer or near-monolayer catalysts, 10% V 2 O 5 /Al 2 O 3 and 4% V 2 O 5 /TiO 2 , were selected for detailed kinetic analysis. A Mars-van Krevelen (MVK) model containing eight parameters was chosen for this purpose. The parameters were estimated using a genetic algorithm (GA), which optimizes a suitable objective function for a non-linear multi-response system. From the parameters estimated, it was determined that a similar catalytic cycle occurs independent of the oxide support. However, the rate at which the catalytic cycle occurs appears to be much faster on the more reducible titania support compared to the rate on the less reducible alumina support. The degree of reduction varies along the length of the reactor and depends on the support. Thus, the support has a significant effect on the reaction parameters for the oxidative dehydrogenation of propane over supported vanadium oxide catalysts.
Oxidative Dehydrogenation of Propane over Vanadium Catalyst Supported on Alkali-Modifiedx-Al2O3
Chemical science international journal, 2021
The propane oxidative dehydrogenation (ODH) reaction has been considered as an alternative method for propene production owing to its exothermic nature, which renders it environmentally friendly. The use of alkaline promoters for supported V catalysts can increase propene selectivity and partially inhibit the formation of CO and CO2. Our goal was to evaluate the promoting effect of K and Na and the support effect using gibbsite as precursor for the propane ODH reaction. Catalysts were prepared via co-impregnation of V and alkali metals on a previously prepared alumina support and were characterized using N2 adsorption-desorption, X-ray diffraction, temperature-programmed reduction, and isopropanol decomposition tests to evaluate their acid-base properties. The activity of the synthesized catalysts for the propane ODH reaction was evaluated at the O2:C3H8:He molar ratios of 5:2:4, 6:1:4, and 4:3:4. The addition of alkali metals to the V catalysts increased propane conversion and propene selectivity; moreover, both parameters increased with increasing molar fraction of O2 in the reactants. K doping increased the propene selectivity of the doped catalysts, because it inhibited a large fraction of catalytic surface acidic sites. A high molar fraction of O2 in the reactants facilitated the regeneration of the catalyst, whereas a high reoxidation rate improved catalytic activity and propene selectivity.
Catalysis Today, 2006
The effect of the nature and distribution of VO x species over amorphous and well-ordered (MCM-41) SiO 2 as well as over g-Al 2 O 3 on their performance in the oxidative dehydrogenation of propane with O 2 and N 2 O was studied using in situ UV-vis, ex situ XRD and H 2-TPR analysis in combination with steady-state catalytic tests. As compared to the alumina support, differently structured SiO 2 supports stabilise highly dispersed surface VO x species at higher vanadium loading. These species are more selective over the latter materials than over V/g-Al 2 O 3 catalysts. This finding was explained by the difference in acidic properties of silica-and alumina-based supports. C 3 H 6 selectivity over V/g-Al 2 O 3 materials is improved by covering the support fully with well-dispersed VO x species. Additionally, C 3 H 6 selectivity over all materials studied can be tuned by using an alternative oxidising agent (N 2 O). The improving effect of N 2 O on C 3 H 6 selectivity is related to the lower ability of N 2 O for catalyst reoxidation resulting in an increase in the degree of catalyst reduction, i.e. spatial separation of active lattice oxygen in surface VO x species. Such separation favours selective oxidation over CO x formation.
Propane Oxidative Dehydrogenation on Vanadium-Based Catalysts under Oxygen-Free Atmospheres
Catalysts, 2020
Catalytic propane oxidative dehydrogenation (PODH) in the absence of gas phase oxygen is a promising approach for propylene manufacturing. PODH can overcome the issues of over-oxidation, which lower propylene selectivity. PODH has a reduced environmental footprint when compared with conventional oxidative dehydrogenation, which uses molecular oxygen and/or carbon dioxide. This review discusses both the stoichiometry and the thermodynamics of PODH under both oxygen-rich and oxygen-free atmospheres. This article provides a critical review of the promising PODH approach, while also considering vanadium-based catalysts, with lattice oxygen being the only oxygen source. Furthermore, this critical review focuses on the advances that were made in the 2010–2018 period, while considering vanadium-based catalysts, their reaction mechanisms and performances and their postulated kinetics. The resulting kinetic parameters at selected PODH conditions are also addressed.
Oxydehydrogenation of Propane over Vanadium Oxide Supported on Kieselguhr or MCM-41
The Journal of Engineering Research [TJER]
Supported vanadium oxide (5 wt%) on either Kieselguhr or mesoporous MCM-41 was prepared using impregnation method and tested as a catalyst in propane oxidative dehydrogenation (POD). The catalyst samples were characterized using X-ray elemental analysis, Brunauer-Emmett-Teller (BET) physisorption, and Z-ray Photoelectron Spectroscopy (XPS). After impregnation, the catalyst surface area decreased compared with that of the support. More drastic decrease was observed in the case of MCM-41 (77%) than the Kieselguhr supported sample (48%). There are also different degrees of vanadium oxide-support interaction as reflected by the XPS result. Si-O binding energy of 531.5 eV was observed on MCM-41-supported sample compared with 529.5 eV for the Kieselguhr-supported sample. The catalyst tests were conducted at atmospheric pressure, with a propane to oxygen ratio of 0.7 - 3.6 and a reaction temperature of 400 - 700 °C. Oxidative dehydrogenation and combustion products were observed. Minor cr...