Altering bio-oil composition by catalytic treatment of pinewood pyrolysis vapors over zeolites using an auger - packed bed integrated reactor system

Abstract

Pine wood pyrolysis vapors were catalytically treated using zeolite catalysts. An auger fed reactor was used for the pine wood pyrolysis while a packed bed reactor mounted on the top of the auger reactor housed the catalyst for the treatment of pine wood pyrolytic vapors. The pyrolytic vapors produced at 450 ^oC were passed through zeolite catalysts maintained at 425 ^oC at a weight hourly space velocity (WHSV) of 12 h^-1. Five zeolites, including ZSM-5, mordenite, ferrierite, zeolite-Y, and zeolite-beta (all in H form), were used to study the effect of catalyst properties such as acidity, pore size, and pore structure on catalytic cracking of pine wood pyrolysis vapors. Product bio-oils were analyzed for their chemical composition (GC-MS), water content, density, viscosity, acid value, pH, and elemental compositions. Thermogravimetric analysis (TGA) was performed to analyze the extent of coking on zeolite catalysts. Application of catalysis to biomass pyrolysis increased gas product yields at the expense of bio-oil yields. While all the zeolites deoxygenated the pyrolysis vapors, ZSM-5 was found to be most effective. The ZSM-5 catalyzed bio-oil, rich in phenolics and aromatic hydrocarbons, was less viscous, had relatively lower acid number and high pH, and possessed oxygen content nearly half that of un-catalyzed bio-oil. Brønsted acidity, pore size, and shape-selective catalysis of ZSM-5 catalyst proved to be the determining factors for its activity. TGA results implied that the pore size of catalysts highly influenced coking reactions. Regeneration of the used catalysts was successfully completed at 700 ^oC.