Biomass derived feedstocks bring new challenges to the longevity of the catalysts used for their conversion and alkaline metal, i.e. K, in the biomass feedstock have been widely ascribed as one of the important factors causing biomass conversion catalyst deactivation. To address this challenge, it is critical to understand the mechanism of catalyst deactivation caused by K accumulation to guide catalyst and process improvement and catalyst regeneration development. In this work, we report a deep understanding of the impact of K on a bifunctional Pt/TiO2 catalyst, which is an efficient catalyst for ex-situ catalyst fast pyrolysis (CFP). We simulated the K-poisoning of Pt/TiO2 catalysts by purposely loading different amount of K (100-6000 ppm by weight) on the catalysts. A series of characterization approaches (XRD, ICP, BET, FTIR, chemical titration, TEM) were combined with kinetic assessment of multiple probe reactions to elucidate the mechanism of Pt/TiO2 deactivation by K accumulation. With low K loading (&lt;800 ppm), K preferentially poisons the strong Lewis acid sites, decreasing most of the activity for the acid-catalyzed alcohol dehydration. However, the acetone condensation is less sensitive to the poisoning of strong Lewis acid sites. The Pt catalyzed reactions, including alkene hydrogenation, m-cresol hydrodeoxygenation (HDO), and CO oxidation are not impacted. With high K loading, K starts to accumulate on the Pt-TiO2 interfacial area and poison the active sites for HDO and CO oxidation reactions. The poisoning of Pt/TiO2 catalyst by potassium is reversible. Water washing successfully removes the accumulated K and recovered both the activities of alcohol dehydration and m-cresol HDO reactions.

Deactivation by potassium accumulation of Pt/TiO2 bifunctional catalyst for biomass catalytic fast pyrolysis

ACS Spring Meeting 2021

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