Catalytic pyrolysis of lignin for the production of aromatic hydrocarbons: Effect of magnesium oxide catalyst

A base catalyst is expected to suppress coke formation of the catalyst, leading to less catalyst deactivation and more efficient production of bio-oil. To examine the feasibility of a solid-base catalyst as a lignin pyrolysis catalyst, MgO loaded on supports with different textural, acid, and base properties (i.e. carbon, Al₂O₃, and ZrO₂) was applied. In addition, because the co-processing of biomass with plastic significantly improves the quality of bio-oil in the catalytic pyrolysis process, co-pyrolysis of lignin with linear low-density polyethylene was performed, and the effects of the MgO catalysts were analyzed. Thermogravimetric analysis and a tandem micro-reactor–gas chromatography/mass spectrometry system were used to evaluate the performance of the MgO catalysts in terms of thermal decomposition behavior and yield of monoaromatic hydrocarbons. Overall, MgO supported on carbon (MgO/C) showed the highest yield of aromatic hydrocarbons during the pyrolysis of lignin, due to its well-balanced acid/base sites and high surface area. Also, MgO/C exhibited the strongest positive synergy toward the production of aromatic hydrocarbons during co-pyrolysis, which suggests that a metal oxide with base properties supported on high-surface-area carbon could be an efficient catalyst for producing bio-oil with high energy density fuel additives from the lignin.