Catalytic upgrading of biomass pyrolysis oil over tailored hierarchical MFI zeolite: Effect of porosity enhancement and porosity-acidity interaction on deoxygenation reactions

Abstract The catalytic upgrading of beech wood pyrolysis oil has been carried out over microporous and hierarchical MFI zeolites to produce a blendable stream with FCC unit feedstock. Mesoporosity was introduced within the zeolite structure through the desilication process by alkaline NaOH solution with various concentrations aiming at investigating the effect of porosity improvement on catalytic upgrading parameters. The zeolite catalysts were characterized using XRD, SEM, EDS, BET and NH3-TPD analyses and the results showed that the desilication improved textural properties of the zeolites preserving crystallinity. In addition, the effect of mesoporosity, catalyst to biomass ratio, and their interactions on the bio-oil upgrading parameters such as upgrading factor, degree of deoxygenation, effective hydrogen index, relative content of various compounds and coke yield have also been analyzed. The results revealed a significant effect of the parameters on the deoxygenation activity, coke formation potential, and selectivity towards desired products. Indeed, the improved accessibility of weak and strong acid sites, as well as controlled acidity caused to the enhanced conversion of large, oxygenates to smaller ones. The larger coke yield for the optimum hierarchical catalyst (synthesized by 0.5 M solution) was associated with a lower oxidation temperature, which is suited for cost-effective catalyst regeneration.