Thermochemical Conversion of Biomass: Acid Catalysed Pathways and Kinetics of Cellulose Pyrolysis

Abstract

Cellulose thermal degradation can proceed via transglycosylation and beta-elimination to produce anhydrosaccharides and other light organics. Here, we have studied the qualitative, quantitative and kinetic effects of acids and alkalis on the yield of anhydrosaccharides. The extent of cellulose conversion via beta-elimination depends on the amount and strength of acid infused within the cellulose matrix. However, the beta-elimination route could also be suppressed/controlled by a neutralising species (OH- ions). The apparent activation energy of the conversion was also increased to ca. 250 kJ/mol by acids and decreased to ca. 180 kJ/mol by alkalis signifying the predominance of beta-elimination and transglycosylation respectively. For conversion of cellulose in alkaline sulfolane, anhydrosaccharide yields increased by ca. 20 % and indicated an optimal H+ ion concentration. Hence, a new method towards the selective production of chiral intermediates (anhydrosaccharides) via manipulation of H+ ion level has been demonstrated.