Deoxygenation upgrading of pine pyrolysis oil over H-X zeolite/carbon composite catalysts derived from coal gasification fine slag

Abstract

Integrating biomass energy development with solid waste utilization supports sustainable development. Against this backdrop, low-cost and efficient Na-X zeolite/carbon composite catalysts were developed from coal gasification fine slag(CGFS) through acid leaching, alkali-fusion activation, and hydrothermal crystallization for the deoxygenation upgrading of biomass pyrolysis oil. The effect of hydrothermal synthesis temperature on the crystal structure of the catalysts was first investigated, and the support prepared at the optimal temperature was subsequently subjected to NH4Cl ion exchange followed by calcination, during which exchangeable Na ions were ultimately replaced by H + , converting the zeolite into the H-form and generating acidic sites. The results showed that the sample synthesized at 110 °C exhibited distinct characteristic peaks of Na-X zeolite and relatively high crystallinity, making it suitable as the base support for subsequent modification. Characterization results indicated that the modified composite catalysts retained the X-type zeolite framework and the zeolite/porous carbon structure, while featuring an increased number of acid sites. In the catalytic upgrading of bio-oil, the catalyst prepared with 1 mol/L NH 4 Cl (1HX) showed the best performance, with the relative content of hydrocarbons in bio-oil reaching 47.70% and that of phenols decreasing to 36.52% during the first use. Cycling experiments showed that the catalytic activity of 1HX decreased after five uses, whereas the hydrocarbon content recovered to 46.63% after regeneration, indicating that its deactivation was mainly caused by reversible coke deposition. This study provides a reference for the preparation of coal gasification fine slag-derived composite catalysts and their application in bio-oil upgrading.