Influence of Reaction Parameters on the Catalytic Performance of Alkaline-Treated Zeolites in the Novel Synthesis of Pyridine Bases from Glycerol and Ammonia

Abstract

This work presented a novel route for the synthesis of pyridine bases from glycerol and ammonia. The whole process consisted of the dehydration of glycerol to acrolein and the subsequent condensation of acrolein and ammonia to pyridine bases, with the two reactions being conducted either simultaneously over a single catalyst in a conventional fixed-bed reactor (single-stage reactor mode) or separately over two different catalysts, namely, a catalyst pair, in a series-connected fixed-bed reactor (two-stage reactor mode). Under the optimized conditions, a 32.18% total yield of pyridine bases was achieved over the HZSM-5-At-acid catalyst, while a 62.25% and 60.85% total yield of pyridine bases, without the formation of 4-picoline, could be afforded over the catalyst pairs (HZSM-5-At + ZnO/HZSM-5-At-acid) and (HZSM-22-At-acid + ZnO/HZSM-5-At-acid), respectively. The catalyst pair (HZSM-22-At-acid + ZnO/HZSM-5-At-acid) exhibited the greatest stability with time-on-stream. This was attributed to the fact that the above-mentioned two reactions were affected differently by the texture and acid properties of the catalyst, and they could be simultaneously promoted to the greatest extent over two different suitable catalysts in a two-stage reactor mode but not over a single catalyst in the single-stage reactor mode. This novel route was shown to be more green and efficient relative to those employed currently in both industrial production and the literature.