Sustainable Synthesis of Pyridine Bases from Glycerol

Abstract

Catalytic processes have been developed to obtain pyridine bases from glycerol, either by direct conversion or with acrolein as an intermediate. When producing acrolein as an intermediate, the reaction may proceed in a single reactor at temperatures above 400°C in co-feeding with ammonia. A system of two interconnected reactors can also be used: one reactor performs the catalytic dehydration of glycerol to acrolein, while in the second reactor acrolein reacts with ammonia to form pyridine bases. Both processes require the use of solid acid catalysts, for which ZSM-5 zeolite-based catalysts are the most studied. In the direct reaction between glycerol and ammonia, the most active catalysts were Cu/HZSM-5 and the composite zeolite HZSM-5/11. In the two-step systems, the dehydration of glycerol to acrolein over a HZSM-5 zeolite modified by alkali treatment or over a HZSM-22 zeolite modified by an alkali-acid treatment as catalysts in the first reactor, in combination with a Zn impregnated acid-treated-HZSM-5 zeolite have shown to be efficient catalyst pairs for the synthesis of pyridine bases from glycerol in two-step processes. When using acrolein or acrolein diacetals, the most active catalysts were a 4.6%Cu–1.0%Ru/HZSM-5 zeolite in the presence of hydrogen, and a ZnO/HZSM-5-At-acid zeolite.