Product Distribution and Deactivation of Y-zeolite Based Catalyst in the Catalytic Cracking of Biomass Pyrolysis Oil

Abstract

The valorization of bio-oil by catalytic cracking is a promising route for producing hydrocarbon fuels as an alternative to oil. This work addresses the cracking of bio-oil over HY zeolite catalyst (Si/Al = 15) in a continuous reaction system composed of two-step on line (thermal + catalytic). The effect that temperature has on the bio-oil conversion and the distribution of reaction products is studied. The catalyst was synthetized by agglomerating the zeolite powder with inert filler and binder, and the raw bio-oil was stabilized by adding 20 wt% MeOH. Operating condition were: 500 oC (thermal unit); 400-500 oC and space-time, 0.7 gcatalysth/gfeed (fluidized bed reactor). Attention is also paid to the catalyst deactivation, analyzing the spent catalyst samples by different techniques (N2 adsorption-desorption, adsorption/cracking/desorption of t-BA, and TGA-TPO). The results evidence a significant influence of temperature on the yield and composition of products. Although the LPG (C3-C4) hydrocarbons are the main products at 400 oC, the increase in temperature notably promotes the conversion of oxygenates into C5+ hydrocarbons, which are the majority products above 450 oC. Operation at 500 oC has the advantages of both maximizing the production of a liquid fuel composed of 74 % C5-C12 gasoline fraction (rich in 1-ring aromatics and C6-C7 cycloalkanes), and also attenuating the catalyst deactivation. Furthermore, the catalyst deactivation at 400 oC and 450 oC is faster than that observed at 500 oC, despite the lower formation of coke. This fact is explained by the different nature and location of the coke deposited in the porous structure of the catalyst.