In-situ catalytic upgrading of bio-oil derived from fast pyrolysis of sunflower stalk to aromatic hydrocarbons over bifunctional Cu-loaded HZSM-5

Abstract Commercial HZSM-5 zeolite (Si/Al = 24) was modified with Cu species using the wet impregnation method, and applied in the in-situ upgrading of bio-oil from the fast sunflower stalk pyrolysis with a catalyst to biomass ratio of 1:1 at 500 °C. The main objective was to study the Cu doping effect on the HZSM-5 catalytic performance in terms of the selectivity to aromatic hydrocarbons (especially the specific aromatic hydrocarbons including benzene, toluene and xylene) yield. It was found that Cu/HZSM-5 with low Cu loading amounts preserved HZSM-5 crystalline structure as well as its acid sites. The HZSM-5 with 0.5 wt.% Cu loading amount exhibited the best catalytic performance with a high relative amount of aromatic hydrocarbons of 73.2% and a yield of specific aromatic hydrocarbons as high as 56.5 mg/g-biomass (d.a.f), which were much higher than those based on the parent HZSM-5 (55.0% and 26.0 mg/ g-biomass (d.a.f)). It should be mainly attributed to its suitable acidity and best textural properties for the deoxygenation of the bio-oil thanks to the optimum Cu loading amount. In addition, the 0.5 wt.% Cu loaded HZSM-5 catalyst also showed excellent catalytic reusability and regeneration property, and the spent catalyst was easily recovered by a simple calcination in air for a short time.