Abstract
Biomass-derived feedstocks bring significant challenges to the longevity of the catalysts used for their conversion, and alkali metals, for example, K, in the feedstock have been widely ascribed as one of the important factors causing catalyst deactivation. To address this challenge, it is critical to understand the mechanism of catalyst deactivation caused by K accumulation to guide the improvement of catalysts and processes and the development of catalyst regeneration strategies. 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 the ex situ catalytic fast pyrolysis of biomass. We simulated the K-poisoning of Pt/TiO2 catalysts by purposely loading different amounts of K (100–6000 ppm by weight) on the catalysts. A series of characterization approaches, including scanning transmission electron microscopy, Fourier transform infrared spectroscopy, and chemical titration, were combined with a kinetic assessment of multiple probe reactions to elucidate the mechanism of Pt/TiO2 deactivation by K accumulation. At low K loadings (<800 ppm), K preferentially poisons the strong Lewis acid sites, leading to significantly reduced activity for acid-catalyzed alcohol dehydration. However, acetone condensation is less sensitive to the poisoning of strong Lewis acid sites. Reactions that occur on Pt sites or at the metal–support interface, including alkene hydrogenation, m-cresol hydrodeoxygenation (HDO), and CO oxidation, were not impacted. At high K loadings (>800 ppm), K starts to accumulate on the Pt–TiO2 interfacial area, poisoning the interfacial active sites for HDO and CO oxidation reactions. We further found that the poisoning of the Pt/TiO2 catalyst by K is reversible, and water washing can successfully remove the accumulated K and recover the activities for both alcohol dehydration and m-cresol HDO reactions.
Original language | English |
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Pages (from-to) | 465-480 |
Number of pages | 16 |
Journal | ACS Catalysis |
Volume | 12 |
Issue number | 1 |
DOIs | |
State | Published - Jan 7 2022 |
Funding
The authors gratefully acknowledge funding for this research, provided by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), and Bioenergy Technologies Office (BETO). This work was performed in collaboration with the Chemical Catalysis for Bioenergy Consortium (ChemCatBio), a member of the Energy Materials Network, and at the Pacific Northwest National Laboratory (PNNL) under Contract no. DE-AC05-76RL01830, the Oak Ridge National Laboratory (ORNL) under Contract no. DE-AC05-00OR22725, and the National Renewable Energy Laboratory (NREL) under Contract no. DE-AC36-08-GO28308. Microscopy was performed at ORNL through a user project supported by ORNL’s Center for Nanophase Materials Sciences (CNMS), which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Part of the microscopy research was also supported by the Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. The authors thank S.K. Reeves for assistance with TEM sample preparation. Part of this work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). Y. Lu and Y. Wang would acknowledge the financial support by U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences for funding this project (DE-AC05-RL01830) related to the measurement of CO oxidation kinetics. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, expressed, or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. The authors gratefully acknowledge funding for this research, provided by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), and Bioenergy Technologies Office (BETO). This work was performed in collaboration with the Chemical Catalysis for Bioenergy Consortium (ChemCatBio), a member of the Energy Materials Network, and at the Pacific Northwest National Laboratory (PNNL) under Contract no. DE-AC05-76RL01830, the Oak Ridge National Laboratory (ORNL) under Contract no. DE-AC05-00OR22725, and the National Renewable Energy Laboratory (NREL) under Contract no. DE-AC36-08-GO28308. Microscopy was performed at ORNL through a user project supported by ORNL?s Center for Nanophase Materials Sciences (CNMS), which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Part of the microscopy research was also supported by the Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. The authors thank S.K. Reeves for assistance with TEM sample preparation. Part of this work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE?s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). Y. Lu and Y. Wang would acknowledge the financial support by U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences for funding this project (DE-AC05-RL01830) related to the measurement of CO oxidation kinetics. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, expressed, or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.
Keywords
- Lewis acid
- Pt/TiO
- catalyst deactivation
- catalytic fast pyrolysis
- hydrodeoxygenation
- hydrogenation
- potassium