Catalytic Pyrolysis of Guaiacol over Ni/La–Modified Hierarchical HZSM‐5

Abstract

AbstractCatalytic pyrolysis of guaiacol as a model compound of lignin was conducted to explore the lignin pyrolysis mechanism in this study. The effects of catalyst and temperature on product distribution were studied. Five catalysts were tested including HZSM‐5, hierarchical HZSM‐5, metal‐modified hierarchical HZSM‐5 catalysts. And the Ni/La bimetallic hierarchical HZSM‐5 (NiLa/HZ‐SH) contributes to the achievement of high conversion and selectivity in catalytic pyrolysis of guaiacol. we obtained the yields of monocyclic aromatic hydrocarbons over NiLa/HZ‐SH (550°C): Phenol (23.01%), Benzofuran (6.68%), Salicylaldehyde (1.54%), 2‐Methylphenol (31.48%), 4‐Methylphenol (6.54%), 2‐Ethylphenol (14.89%), 4‐Vinylphenol (1.45%) and Catechol (8.67%), and the maximal yields of these monocyclic aromatic hydrocarbons is 94.26%. Moreover, the yield of polycyclic aromatic hydrocarbons (PAH) as the non‐target product reached a minimum of 1.46% over NiLa/HZ‐SH, while it was 16.88% without catalyst. In addition, catalyst stability was investigated, the reason that led to the decrease of target products could be the acidity and surface area of catalysts decreased as the coke blocked the pore channels, spent catalyst can be successfully regenerated through calcination treatment. Finally, based on the experiment results in this work and other published studies, a guaiacol pyrolysis mechanism was summarized and proposed aiming to understand the lignin pyrolysis process.