Effect of hierarchical HZSM-5 zeolite on the catalytic depolymerization of organosolv lignin to renewable phenols

In order to intrinsically boost the lignin catalytic depolymerization performance of HZSM-5 (HM5) zeolite catalyst, we investigated the depolymerization of lignin-to-aromatic products over different hierarchical HM5 zeolite catalyst to understand the presence of mesoporosity on the catalytic activity in generating aromatic monomers. Firstly, different hierarchical HM-5 zeolite catalyst (HM5, 0.15HM5, 0.35HM5 and 0.75HM5) were prepared by the physical method. X-ray powder diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) and temperature-programmed desorption of ammonia (NH3-TPD) were used to characterize catalysts. Compared with conventional HM5 zeolite catalyst, the hierarchical HM5 (0.35HM5) catalyst showed a significant strengthening effect on the depolymerization of organosolv lignin. Among them, the 4-unsaturated phenolic monomer product was decreased from 0.52 to 0%, the 4-alkyl phenol product was increased from 1.6 to 4.07%, and the no side chain phenolic monomer product was increased from 3.4 to 9.16%. In addition, we also illustrated that the hierarchical 0.35HM5 zeolite catalyst had high stability, and it could be reused for up to five cycles without loss of catalytic activity. It was worth noting that phenolic monomers products produced by hierarchical 0.35HM5 zeolite catalyst had great potential to be a promising renewable alternative to fossil resources.