Cellulose dehydration and depolymerization reactions during pyrolysis in the presence of phosphoric acid

The low-temperature pyrolysis process and dehydration reactions of cellulose impregnated with phosphoric acid (1–10 wt.%) have been studied. Based on the yield of pyrolytic water and alterations of glucopyranose units of cellulose, it has been confirmed that dehydrated cyclic structures are formed in the solid phase during cellulose pyrolysis in the temperature interval 200–250°C. Phosphoric acid also catalyzes the subsequent depolymerization process of the dehydrated cellulose giving rise to 20% (on cellulose) of levoglucosenone. The yield of levoglucosenone depends on the amount of phosphoric acid and the time of pyrolysis. Thus, the pathway of dehydration reactions can be controlled by variation of these two parameters.