Effects of torrefaction pretreatment and Mg-Al modified HZSM-5 catalysts on components distribution in bio-oils from camphorwood pyrolysis

Abstract

Torrefaction pretreatment conducted at a low temperature is an important technique for refining the bio-oil and improving the production of some chemicals in the bio-oil (e.g. aromatic hydrocarbons). In this work, the effects of torrefaction temperature and catalysts on the yields of pyrolysis products and components distribution in the bio-oils were analyzed. The weak acid sites shifted to higher temperature as the HZSM-5 was modified by Mg2+ or Al3+. The catalytic pyrolysis from camphorwood was done at pyrolysis of 450 °C and torrefaction temperature of 200 °C. The catalysts remarkably influenced the yields of bio-oil and components distribution. The catalysts increased the production of phenols. The content of phenols in the resulting bio-oil exhibited the following trend: HZSM-5 < MgO-modified HZSM-5 < Al2O3-modified HZSM-5. In addition, the content of 2,6-dimethoxyphenol was the highest among all phenol components (5.58%). The production of aldehydes was remarkably improved by the Al2O3-modified HZSM-5, resulting in a maximum content of 8.21%. Thus the torrefaction temperature and catalysts would refine the bio-oil (such as the acid value decreased) and significantly improve the contents of components (such as D-allose, 2,6-dimethoxy-4-(2-propeny)-phenol, 1,2,4-trimethoxybenzene, and 2,6-dimethoxyphenol). The results provide a theoretical basis for the resource recovery of biomass.