(30a) Acid-Base Bi-Functional Catalysis for Deoxygenation during Cellulose Fast Pyrolysis

Catalytic fast pyrolysis of cellulose was performed in a micropyrolyzer coupled with online product analysis by GC-MS/FID. Acid, base, transitional metal oxide and acid-base bi-functional catalyst were evaluated relative to their deoxygenation performance. The bi-functional catalyst was prepared by acid treatment of a natural mixed metal oxide, serpentine. Temperature programmed desorption measurement was used to evaluate the acid and base properties of the catalytic materials. The natural serpentine was basic, while medium and strong acid sites were introduced through acid treatment.  Using the same number of acid/base sites, all of the catalytic materials were used in pyrolysis for deoxygenation comparison.  The results showed the bi-functional catalyst achieved the best balance between deoxygenation and bio-oil yield among the tested materials. For the best catalytic material, the oxygen content of the condensed product from cellulose was decreased by 27 % and its high heating value increased from 15.41 MJ kg^-1 to 22.78 MJ kg^-1, with 60 % of the initial energy content remaining in the condensed product. It appeared that during catalysis, the acidic sites primarily promoted dehydration while the basic sites mainly promoted fragmentation reactions. Compared to a physical mixture of acid and base materials, the bi-functional catalyst appeared to promote deoxygenation reactions more effectively presumably due to the presence of adjacent acid and base sites.