Catalytic upgrading of beech wood pyrolysis oil over iron- and zinc-promoted hierarchical MFI zeolites

Abstract

The catalytic upgrading of beech wood pyrolysis oil has been carried out over iron- and zinc-promoted hierarchical Mordenite Framework Inverted (MFI) zeolites to produce a blendable stream with fluid catalytic cracking (FCC) feed. The iron and zinc were introduced to the zeolite structure in different loadings through the impregnation technique using metal nitrate solutions with various concentrations. The aim was to investigate the effect of zeolite acidity control along with mesoporosity of HZSM-5 zeolite on catalytic upgrading parameters. The results showed that the metal doping reduced textural properties through coverage of the catalyst surface by metal species. The existence of metals also altered acid site distribution of the hierarchical zeolite retaining crystallinity. The results of bio-oil upgrading experiments revealed a rather significant effect of extra framework metal species, particularly in 2 wt% loading, on the deoxygenation activity, coke formation potential, and selectivity towards desired products. Indeed, the improved accessibility of original and new weak and strong acid sites, as well as controlled acidity by incorporation of metals caused the enhanced conversion of large oxygenates to desired products. Zn-modified hierarchical HZSM-5 showed high selectivity towards desired oxygenates such as ketones via the promotion of carboxylic acids ketonization and reduced the formation of polycyclic aromatics. The analysis of coke also indicated that the coke yield and oxidation temperature decreased by 15% and 10%, respectively, over Zn-promoted catalyst compared with hierarchical sample showing desirable characteristics for cost-effective catalyst regeneration.