Improving activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis

Abstract

This work aimed to further enhance the activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis. To this end, various treatment approaches including acidification with H2SO4 and H3PO4 and metal (Ni) loading were performed on the ZSM-5 zeolite. Catalytic fast pyrolysis (CFP) of hydrolysis lignin (HL) was conducted at 450 ᵒC using ZSM-5 zeolites with various strengths of acidity (ZSM-5 and Ni-ZSM-5 with moderate Lewis and Bronsted sites, H2SO4-ZSM-5 and H3PO4-ZSM-5 with more Bronsted sites). The results show that the yield of monomeric aromatic compounds increased considerably by increasing the Bronsted acid site and total acidity of the catalyst. With the best catalyst, H2SO4-ZSM-5, the total monomeric aromatics/phenolics yield increased to 151 mg/g-HL, compared to 68 mg/g-HL without catalyst, 84 mg/g-HL with ZSM-5, 96 mg/g-HL with H3PO4-ZSM-5, and 85 mg/g-HL with Ni-ZSM-5. The H2SO4-ZSM-5 demonstrated to be thermally stable and has superb resistance to carbon/coke deposition, owing to its microporous structure, relative large BET surface area and presence of strong Bronsted acid sites.