Is it possible to increase the oil yield of catalytic pyrolysis of biomass? A study using commercially-available acid and basic catalysts in ex-situ and in-situ modus

Catalytic pyrolysis of woody biomass and cellulosic materials has been investigated by analyzing the effect of catalysts on aqueous phase (sugar rich) and oil phase (lignin rich) organics produced by the preceding thermal pyrolysis. Tests were done in a downer reactor using ZSM-5 and Na2O/gamma-Al2O3 as typical commercially available catalysts. Both catalysts converted the aqueous phase organics to coke, water and gas, and deoxygenated and cracked the oil phase organics. The maximum yield of oil phase organics when applying the catalysts never exceeded the corresponding oil yield of thermal pyrolysis (similar to 22% on carbon basis). Analysis of new results of ex- situ with in-situ catalysis, in combination with earlier reported data, indicates that a path forward to obtain higher oil yields is not expected to come from process improvements. The development of catalysts that can convert the aqueous phase organics (potentially similar to 35% on carbon basis) into organic phase ones, instead of cracking and polymerizing them to respectively gas and char, should be considered.