Abstract
The deposition of V-based catalysts for the oxidative dehydrogenation of propane to propene on cordierite honeycomb monoliths was optimised as a strategy to decrease the contact time in a structured reactor with respect to a conventional fixed bed one. 10 wt% VOx supported over SiO2 or Al2O3 were used as catalysts, deposed over the monolith using silica or alumina as primer, respectively. Both the alumina supported catalyst and the bohemite primer precursor were effectively deposed by dip-coating from stable powder suspensions, whereas insufficient adhesion was obtained when loading pre-synthesised SiO2 over the cordierite. A new method based on sol-gel production of SiO2 from tetraethylortosilicate (TEOS) over the monolith surface was set up. A correlation was derived for the prevision of the amount of silica deposed depending on the amount of TEOS. Both primer and catalyst loading were optimised as for uniformity and stability of the coating and resulted 0.5–1 wt % primer and 0.15 wt % of catalyst. Activity testing confirmed the strong improvement of propene productivity by increasing the time factor (i.e. Ncm3 of flowing reactant/min gcat), which ended in a one order of magnitude increase of productivity for the honeycomb-supported samples with respect to the fixed bed configuration.
Highlights
Low molecular weight olefins (C2–C4) are obtained mainly from steam cracking and catalytic cracking processes of natural gas and various oil fractions
We have investigated catalysts prepared by flame pyrolysis (FP), a peculiar method for the synthesis of solids that allows obtaining a nanometric powder, high surface area, and thermally stable materials [19,23,28,29]
The decrease of contact time improved propene productivity in fixed bed configuration and this suggested to support the active phase over a cordierite honeycomb to improve its dispersion and to lower by orders of magnitude the catalyst loading, so increasing the time factor
Summary
Low molecular weight olefins (C2–C4) are obtained mainly from steam cracking and catalytic cracking processes of natural gas and various oil fractions. From an application point of view, olefins are more interesting than their corresponding paraffins, since they are used as intermediates in various sectors of the basic chemical industry, especially in the polymers one [1,2]. It is advantageous to transform compounds of low market price into products with higher added value. An important example is the dehydrogenation of isobutane to isobutene, whose demand on the market is constantly increasing, above all thanks to its application in the synthesis of methyltertbutylether (MTBE). The dehydrogenation of paraffins is an important way to obtain specific olefins for use in the polymer and intermediates industries. The Oxidative Dehydrogenation (ODH) route is an interesting alternative, though not yet commercial, because it operates at a lower
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