Production of upgraded bio-oils by biomass catalytic pyrolysis in an auger reactor using low cost materials

Abstract

Production of upgraded bio-oils by catalytic pyrolysis of wood biomass was studied in an auger reactor using low cost materials as catalysts. These materials included several clay minerals (sepiolite, bentonite and attapulgite) and an industrial waste from alumina production, known as red mud. The influence of temperature (400–500 °C) and the effect of catalyst to biomass ratio (3:1–1:6, in weight) were also analysed. A temperature of 450 °C and the lowest catalyst proportion (1:6, in weight) were selected as the most appropriate to aim the pyrolysis for bio-oil production. Catalyst to biomass ratio resulted critical since an excess on catalyst addition seemed to reduce liquid production while char yield increased. Under the selected conditions, the catalysts tested improved the characteristics of the obtained bio-oil as fuel (viscosity, acidity, oxygen content and calorific value). For every catalyst, the viscosity of the organic liquid fraction decreased (up to 34% in case of bentonite) while lower heating value increased (up to 20% in red mud tests). Concerning acidity, sepiolite and red mud produced a decrease in the total acid number (around 29% and 23%, respectively). The stability of the organic fraction after aging test (equivalent to long time storage) was also improved by each catalyst.