Upgrading of Bio-oil over Aluminum Silicate in Supercritical Ethanol

Abstract

The crude bio-oil from fast pyrolysis of rice husk was upgraded in supercritical ethanol using aluminum silicate as a catalyst. The results showed that the supercritical upgrading process performed effectively and the components of upgraded bio-oil were optimized greatly. Acidic aluminum silicate facilitates esterification in supercritical ethanol to convert most acids contained in crude bio-oil into various kinds of esters. The amount of phenols that exist extensively in crude bio-oil decreased during the supercritical upgrading process. Aldehydes, such as furfural and vanillin, which are typically present in crude bio-oil, were removed during the supercritical upgrading process and not detected in upgraded bio-oil. The residue of distillated upgraded bio-oil decreased evidently compared to that of distillated crude bio-oil. The density and kinematical viscosity of upgraded bio-oil decreased compared to that of crude bio-oil. The pH value and heating value of upgraded bio-oil increased compared to that of crude bio-oil. The changes of these properties showed that the quality of upgraded bio-oil was improved.