A study of guaiacol, cellulose, and Hinoki wood pyrolysis with silica, ZrO2&TiO2 and ZSM-5 catalysts

- Guaiacol, cellulose, and wood were pyrolyzed with silica, ZrO2&TiO2 and ZSM-5 with different SiO2-to-Al2O3 ratios (SAR).
- High SAR ratio ZSM-5 catalyst increased oxygenated aromatics.
- However, only low SAR ratio ZSM-5 catalyst converted the oxygenated aromatics to aromatic hydrocarbons.
- The oxide layer on silica had strong interactions with hydroxyl groups on levoglucosan during pyrolysis.
- ZrO2&TiO2 increased cyclopentanones with Hinoki wood pyrolysis.

Catalytic pyrolysis of biomass is often used to improve bio-oil quality and energy content. In order to better understand the interactions between various catalysts and biomass components, individual components of biomass were isolated and pyrolyzed with different catalysts. Understanding the interactions between pyrolysis vapors and catalysts is important to create catalysts that can improve bio-oil quality and energy content in the future. In this study, cellulose, guaiacol (as a model for lignin), and Hinoki wood were pyrolyzed and catalyzed with silica, ZrO2&TiO2, and ZSM-5 with an SiO2-to-Al2O3 (SAR) ratio of 40 and 1500. GC-MS analysis was used to measure the effects of the different catalysts on the pyrolysis vapors. It was found that silica had a strong interaction with the hydroxyl groups of levoglucosan and significantly decreased sugars in both cellulose and Hinoki wood pyrolysis. ZrO2&TiO2 increased the amount of cyclopentanones and aromatics with Hinoki wood pyrolysis. The ZSM-5 catalysts also increased aromatic hydrocarbons and oxygenated hydrocarbons with Hinoki wood pyrolysis. Based on these results, specific reactions of the catalysts were proposed. Additionally, ZSM-5 with a SAR ratio of 1500 has very few acidic sites, so the steric effects of ZSM-5 could be isolated. These results are discussed and contrasted with ZSM-5 with a SAR ratio of 40. These results show that microporous catalysts and moderate acidity are optimal for improving bio-oil quality.