Production of acrolein and acrylic acid through dehydration and oxydehydration of glycerol with mixed oxide catalysts

Dehydration of glycerol solution and further oxidation have been investigated with different mixed oxide catalysts. Among them, iron phosphates were found to be highly active and selective toward acrolein. Glycerol conversion was nearly complete and acrolein yields reach 80–90% after 5 h of test. Fresh and used catalysts were also characterized by different techniques (XRD, SEM, BET and TGA-DSC). Pure and well-defined structures were found more stable than relatively poor crystalline phase. Distribution of products changes during the deactivation of the catalyst, leading to by-products such as acetol, propanal and coke deposit on the surface of the catalyst, indicating a modification of the mechanism. Introducing some oxygen in the feed allowed decreasing the amount of those by-products, but oxidation products appeared such as acetic acid or COx on detriment of the yield in acrolein. Using appropriate mixed oxide catalysts such as molybdenum/tungsten vanadium based catalysts showed interesting performances to obtain acrylic acid directly from glycerol.