Influence of catalysts on bio-oil yield and quality: a review

The catalytic production of bio-oil can potentially solve the impending fossil fuel depletion crisis. Two practical problems related to bio-oil are the yield and quality, which are determined by the catalyst. Until recently, little work has focused on the relationship between biomass, catalyst, yield, and quality. To cover this deficiency, this work reviews the influence of metal oxides and zeolites on the yields and qualities of bio-oil derived from woody, herbaceous, agricultural, and algae biomasses. Generally, both catalysts decreased the yield and increased the quality at the same time, and more acidic catalysts decreased the yield further. Thus, zeolites usually decreased the yield more than metal oxides. Although the quality was increased, the oxygen content and calorific value were both increased, which favored further applications. Wood biomass had a lower ash content and nitrogen content than herbaceous, agricultural, and algae biomasses, simultaneously resulting in better yield and quality. This review helps understand the current status of bio-oil investigations and can help find new research directions in the future.