Influence of Niobium Precursor and Calcination Temperature On the Dehydration of Glycerol

The purpose of this study is to produce value added products by the dehydration of glycerol over niobium catalysts such as niobic acids and niobia phosphates. Niobium catalysts were prepared by calcinations of a niobium oxalate and niobia phosphate products from CBMM(Brazil) in the temperature range of 400~700°C. Catalysts were characterized by XRD and TPD of ammonia. Dehydration of glycerol was conducted in a stainless steel autoclave at the controlled reaction temperatures under corresponding pressure. Reactant was aqueous solution of 10 wt % glycerol. The gas products were condensed and analyzed by GC-MS. Acrolein was the main product and other useful products such as acetaldehyde, methanol, etc. were produced either in the catalytic reaction. When niobia phosphate catalyst was used in the reaction, glycerol conversions were generally higher than those of niobic acid catalyst. The higher catalytic performance of niobia phosphate than niobic acid could be related to the higher acidity of its surface. The performance of niobium catalysts for the dehydration reaction is affected by the catalyst calcination temperature that induces the changes in surface acidity and crystallization of niobium catalysts.