Production of hydrocarbons by catalytic upgrading of a fast pyrolysis bio-oil. Part II: Comparative catalyst performance and reaction pathways

Abstract

Abstract Catalysts, namely, HZSM-5, H-mordenite H-Y, silicalite and silica-alumina which were used for the upgrading of Pyrolysis bio-oil in Part I of this study were examined for their relative performance in the production of organic distillate fraction (ODF), hydrocarbon formation and minimization of char, coke and tar formation. A catalyst effectiveness criterion based on yield and selectivity for each product was defined and correlated with the performance of each catalyst. Amongst the five catalysts studied, HZSM-5 was the most effective catalyst for the production of ODF, overall hydrocarbons and aromatic hydrocarbons. Also, it provided the least coke formation. Silica-alumina catalyst was most effective for minimizing the char formation and H-Y catalyst was superior in minimizing tar formation as well as maximizing the production of aliphatic hydrocarbon. Reaction pathways were proposed for the conversion of bio-oil. It was postulated that bio-oil conversion proceeded as a result of thermal effects followed by thermocatalytic effects. The thermal effects produced separation of bio-oil to light organics and heavy organics and polymerization of bio-oil to char. The thermocatalytic effects produced coke, tar, gas, water and the desired organic distillate fraction. Deoxygenation, cracking, cyclization, aromatization, isomerization and polymerization were the main thermocatalytic reactions.