Abstract
Oxidative dehydrogenation (ODH) of light alkanes to olefins—in particular, using vanadium-based catalysts—is a promising alternative to the dehydrogenation process. Here, we investigate how the activity of the vanadium phase in ODH is related to its dispersion in porous matrices. An attempt was made to synthesize catalysts in which vanadium was deposited on a microporous faujasite zeolite (FAU) with the hierarchical (desilicated) FAU as supports. These yielded different catalysts with varying amounts and types of vanadium phase and the porosity of the support. The phase composition of the catalysts was confirmed by X-ray diffraction (XRD); low temperature nitrogen sorption experiments resulted in their surface area and pore volumes, and reducibility was measured with a temperature-programmed reduction with a hydrogen (H2-TPR) method. The character of vanadium was studied by UV-VIS spectroscopy. The obtained samples were subjected to catalytic tests in the oxidative dehydrogenation of propane in a fixed-bed gas flow reactor with a gas chromatograph to detect subtract and reaction products at a temperature range from 400–500 °C, with varying contact times. The sample containing 6 wt% of vanadium deposited on the desilicated FAU appeared the most active. The activity was ascribed to the presence of the dispersed vanadium ions in the tetragonal coordination environment and support mesoporosity.
Highlights
As a basic raw material, low-carbon olefins such as ethylene and propylene play an important role in the petrochemical industry
The activity of the reported catalysts is the interplay of three parameters: vanadium location, porosity of the samples, and their acidity
The higher selectivity of the Vx FAUdes catalysts should be mainly ascribed to the presence of the dispersed vanadium ions in the tetragonal coordination environment, as seen by the performed Ultra-Violet Visible Spectroscopy (UV-VIS) spectroscopy measurements
Summary
As a basic raw material, low-carbon olefins such as ethylene and propylene play an important role in the petrochemical industry. Ethane and propane are the most important lower alkanes and are widely used in the industry. Ethane is mainly derived from the gaseous product of the cracking gas of the ethylene production unit, while propane is mainly obtained from the gaseous products of the delayed coking and catalytic cracking unit. To efficiently convert low-carbon alkanes to olefins, a dehydrogenation (DH) catalyst is required. There are mainly two types of catalysts for the industrial dehydrogenation of lower alkanes to olefins: Pt-based catalysts and Cr-based catalysts [1]. They are widely used, they exhibit certain disadvantages. Pt-based catalysts are expensive, and the active components are prone to sintering during the reaction process
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