Catalytic pyrolysis of cellulose and hemicellulose: Investigation on furans selectivity with different zeolite structures at microporous scale

Furans, as high-value chemicals, are very important target products for catalytic pyrolysis of biomass. In this work, the comparative performance of several different zeolites (SAPO18, SAPO11, SAPO34, and SSZ13 with different Si/Al ratios) for catalytic pyrolysis of cellulose and hemicellulose to generate furan compounds was investigated. SSZ13 was firstly found to improve the selectivity of the catalytic conversion of cellulose and hemicellulose to furans with up to 51.83% and 70.03%, respectively. The high selectivity of SSZ-13 was attributed to its smaller crystal size and higher total acid. SAPO11 was found for the first time to have a positive effect on the conversion of 5-HMF to 5-MFF. Correlation analysis suggested that isomerization was the limiting step in converting the cellulose to furans, while dehydration may be the determining step for hemicellulose. GCMS results indicated the compound in the inner surface after pyrolysis was dominated by polycyclic aromatics and no furans were detected, supporting the hypothesis that the furans were formed on the external surface of zeolite. The difference in mass transfer rates formed on the inner and outer surfaces of the microporous zeolites contributed to the generation and transfer of furans. Compared to complex multifunctional catalysts, simple zeolite structures may have more application potential.