Enhancement of renewable N-heterocycles production via catalytic co-pyrolysis of glycerol and cellulose over HZSM-5 under ammonia atmosphere

Abstract

Catalytic pyrolysis of biomass for efficient N-heterocycles production is highly promising but extremely challenging. Herein, catalytic co-pyrolysis of glycerol and cellulose under ammonia atmosphere was proposed to enhance the N-heterocycles yield. First, a solvolysis effect of glycerol, which could improve the thermal depolymerization of cellulose, was observed in thermogravimetric analysis (TGA). After that, the major influential factors, including Si/Al ratio, reaction temperature, and glycerol-to-cellulose (Gly:Cel) ratio, were investigated systematically. The N-heterocycles yield, as well as the comprehensive synergies of feedstocks, reached their maximum value under the conditions of Si/Al = 85, 550 ℃, and Gly:Cel = 5:1. The best synergistic extents for pyrroles, pyridines, and indoles were 105.3%, 71.3%, and 38.8%, respectively. The mechanism insight showed that, the thermal decomposition of cellulose was promoted while the coking of oxygenated molecules was suppressed during the catalytic co-pyrolysis process. Consequently, more oxygenated molecules were generated and retained for further catalytic conversion into imine intermediates and N-heterocycles.