Unexpected events in sulfated zirconia catalyst during glycerol-to-acrolein conversion

The aim of the work was the analysis of the phenomena occurring during glycerol dehydration in the presence of sulfated zirconia used as solid acid catalysts; the attention was focused on catalyst deactivation. A close correlation between the sulfate content and catalytic behavior was found. In addition to the accumulation of carbon residues on the catalyst surface, there were other phenomena contributing to catalyst deactivation: (i) the self-reduction of sulfuric into sulfurous groups – an event which occurred, however, only in samples with the higher S content under anaerobic conditions – and (ii) the leaching of S from catalysts, due to the hydrolysis of sulfate groups and the formation of volatile esters. These findings are of general interest in relation to both the transformation of glycerol into acrolein by means of gas-phase dehydration and the use of sulfated zirconia catalysts for high-temperature, acid-catalyzed reactions.

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► Sulfated zirconia catalysts deactivate during glycerol dehydration into acrolein.
► The catalytic behavior of sulfated zirconia is affected by sulfate loading.
► Accumulation of heavy compounds is not the main reason for deactivation.
► Deactivation is mainly due to the self-reduction of S(VI) and to the loss of S.
► With catalysts having high S loading, O2 co-feeding limits catalyst deactivation.