V–Al–O catalysts prepared by flame pyrolysis for the oxidative dehydrogenation of propane to propylene

Abstract

A flame pyrolysis (FP) procedure has been set up for the preparation of V/Al/O catalysts to be employed for the oxidative dehydrogenation of propane to propylene. The samples have been characterised by means of various techniques (FT-IR, Raman, EPR, ICP-MS, TGA, XRD, SEM) and their catalytic activity has been evaluated in two different operating modes, i.e. under anaerobic conditions and by co-feeding oxygen. The particle size distribution became progressively more homogeneous with increasing V concentration, due to the catalytic effect of the V ions during the FP synthesis. Some V2O5 segregation was observed even at low V loading. However, higher V dispersion was attained with respect to a reference sample prepared by impregnation of the FP-prepared alumina support. 2The increase of V concentration always led to an improvement of propane conversion, though selectivity showed different trends depending on the operating conditions. The comparison with the sample prepared by impregnation showed similar catalytic activity, with a bit higher selectivity for the FP-prepared sample under anaerobic conditions.

EPR enlightening some aspects of propane ODH over VOx–SiO2 and VOx–Al2O3

“…More detailed data have been reported elsewhere [20][21]. For both the preparation methods the conversion was lower, but the selectivity was higher with SiO2-than with Al2O3-supported catalysts.…”

“…The feeding solutions have been prepared as described in [20,21], using Al(NO3)3*9H2O, tetra-ethyl-orthosilicate (TEOS) and V oxi-acetyl-acetonate as precursors.…”

“…We applied such a synthesis procedure to the preparation of silica-and alumina-supported V samples, which were tested as catalysts for the ODH of propane [20,21]. On the basis of such results, it can be hypothesised that, at least for FP-prepared silica-supported samples, V was more easily inserted into the support matrix, leading to a higher dispersion of the active sites, at difference with samples of similar composition prepared by different…”

“…An extensive description of the catalytic performance and physical-chemical properties of these samples has been reported elsewhere [20,21]. In the present investigation we concentrated on their characterisation by Electron Paramagnetic Resonance (EPR), a powerful tool to address the local structure of V 4+ sites.…”

Hydrogen Production by Photoreforming of Renewable Substrates

“…Flame pyrolysis is a preparation method allowing to obtain single or mixed oxides in nanosized form [153][154][155][156][157]. Titania was also prepared for photocatalytic applications.…”