Upgrading of bio-oil from biomass pyrolysis over Cu-modified β-zeolite catalyst with high selectivity and stability

• Catalytic upgrading of bio-oil over Cu-modified β-zeolite is investigated in details.
• The loading of Cu on β-zeolite with a small amount can improve selectivity to hydrocarbons.
• Low concentration Cu-modified β-zeolite shows high coking resistance during bio-oil upgrading.
• 0.5 wt% Cu-modified β-zeolite shows excellent selectivity and stability for bio-oil upgrading.
• The synergetic effect between the doped metal sites and the protonic sites on the zeolite structure is important.

Upgrading of bio-oil from biomass pyrolysis over Cu-modified β-zeolite catalyst in a down-draft fixed-bed reactor, in which the pyrolysis and upgrading processes are integrated, is investigated in details. It is found that high silica β-zeolite has high selectivity to the hydrocarbon during the upgrading process. When it is modified by a small amount of Cu, the selectivity can be obviously promoted. Especially, when 0.50 wt% of Cu is loaded on it, almost only hydrocarbons can be detected in the light oil of upgraded bio-oil and its activity can be remained for several reuses even without regeneration treatment. However, if more Cu is loaded, the selectivity decreases to some extent. Interestingly, low Cu loading on β-zeolite results in the increase of surface area as well as the formation of more micropores. The surface area reaches the maximum in the case of 0.50 wt% of Cu doping. Based on XRD analysis, when the loading amount is over 1.00 wt%, Cu species aggregate on the surface of zeolite, resulting the blockage of zeolite pores and the decrease of surface area. Doping of Cu decreases the coke deposit on spent catalyst but overloading of Cu results in the increase of coking and the decrease of activity and selectivity. These results indicate that the synergetic effect between the doped metal sites and the protonic sites on the zeolite structure should be benefit for the promising catalytic performance and thus, a proper loading amount is very important for this kind of catalyst.

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