Upgrading biomass pyrolysis oil model compound via esterification with ethanol over a heteropoly acid

Abstract

ABSTRACTUpgrading of bio-oil, which is produced from the fast pyrolysis of biomass, has gained increasing attention as an alternative carbon-neutral liquid fuel. In this work, esterification of the bio-oil model compound from fast pyrolysis of jatropha cake with ethanol catalyzed by tungstosilicic acid (heteropoly acid [HPA]) was investigated. Response surface methodology in cooperation with the central composite design of experiments was utilized to investigate and optimize the process variables, including reaction temperature, molar ratio of alcohol to acid, catalyst loading, and reaction time to obtain the highest acid conversion for esterification. The result showed that the HPA catalyst was effective in the bio-oil upgrading with the esterification process. The highest conversion obtained was almost 85% at 73°C with a molar ratio of alcohol to acid of 9.1:1 and catalyst loading of 10% by weight for 9.1 h as the optimum condition. The fuel properties of the oil model compound representing jatropha cake pyrolysis oil were improved with the total acid number decreased from 307 to 50 mgKOH/gOil.