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Lattice strained Ni-Co alloy as high-performance catalyst for catalytic dry-reforming of methane Zhaoxuan Wu, Bing Yang, Shu Miao, Wei Liu, Jinglin Xie, Sungsik Lee, Michael J Pellin, Dequan Xiao, Dangsheng Su, and Ding Ma ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b02821 • Publication Date (Web): 04 Jan 2019 Downloaded from http://pubs.acs.org on January 5, 2019
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ACS Catalysis
Lattice strained Ni-Co alloy as high-performance catalyst for catalytic dry-reforming of methane Zhaoxuan Wu1,2, Bing Yang2,3, Shu Miao2, Wei Liu2, Jinglin Xie1, Sungsik Lee4, Michael J. Pellin3, Dequan Xiao5, Dangsheng Su2,*and Ding Ma1,* 1
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering and
College of Engineering, and BIC-ESAT, Peking University, Beijing 100871, P. R. China 2
Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, China
3 Material
Science Division and 4 X-ray Science Division, Argonne National Laboratory, 9700 S. Cass Ave.
Lemont, IL 60439, USA 5 Center
for Integrative Materials Discovery, Department of Chemistry and Chemical Engineering,
University of New Haven, 300 Boston Post Road, West Haven, Connecticut 06516, United States Corresponding Author Emails:
[email protected] (D. M.);
[email protected] (D. Su.)
ABSTRACT Dry reforming of methane (DRM) is an effective route to convert methane and carbon dioxide to syngas. Herein, we report an efficient nickel-cobalt bimetallic catalyst with activity of 4.97 molCH4 molNi-1 s-1 at 800 °C. It is active at low temperature as well and near-thermodynamic equilibrium conversion was achieved as low as 350 °C, with a high yield of H2 implying inhibition of side reaction, i.e., reverse water gas shift (RWGS). The formation of Ni-Co alloy during the reaction was observed, and its lattice contraction was revealed by HAADF-STEM and EXAFS experiments. The lattice-strained Ni-Co alloy has good CO2 1
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dissociation ability, responsible for its superior catalytic performance. Its weak chemisorption with H2 results in inhibition of side-RWGS reactions. This work is helpful to design and develop other metal alloy materials with novel structure and/or electronic configurations for catalytic applications. .
KEYWORDS Methane, dry reforming, activity, Ni-Co alloy, lattice contraction
1 Introduction Dry reforming of methane (DRM) is industrially profitable and environmentally friendly catalytic process to transform methane and carbon dioxide to syngas whose ratio (H2/CO=1) is suitable for the synthesis of oxygenated chemicals1, 2 and hydrocarbons3, 4 via Fischer-Tropsch synthesis processes. Carbon dioxide is the major industrial exhaust gas and well-known greenhouse gas with its atmospheric concentration exceeding 400 ppm5. Many methods were developed for the effective utilization of CO26, 7. However, most of these processes need to use large amount of hydrogen which limit their economic efficiency and industrial feasibility. Although recently photo-chemical or electrochemical approaches using hydrogen in water to convert CO28-10 have been designed and demonstrated to be chemically achievable, the approaches normally suffer from low productivity, especially in terms of space-time-yield of the designated products. Another important carbon source, methane, which possesses four hydrogens in each molecule, is an ideal candidate to be converted with CO2 to syngas and then to high-value chemicals. Theoretically, DRM is believed to be an effective process with 100% utilization for both carbon and hydrogen species. However, this non-oxidative process, on the other hand, requests high temperature (>700 C) to obtain good reaction performance, as the catalyst needs to be active for methane activation and CO2 activation. High temperatures (>700 C) normally results in the sintering of the catalyst and serious carbon deposition11. Many efforts have been devoted to investigate DRM reactions at relatively low temperatures using Ni-based catalysts. However, most of the work still required high temperatures (>600 C) to achieve high yields due to 2
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unfavorable low-temperature activities and endothermic nature of the reactions. Fierro and co-workers prepared high-dispersed Ni catalysts supported on Mg-Al oxides with high catalytic performance at 650 C.12 Luisetto et al.13 reported near 50% of CH4 conversion and good stability over Co-Ni-Ce catalysts at 600 C. More recently, DRM reactions at moderate temperature (400-600 C) have attracted growing interests because of the economy, coke-resistance and catalyst durability. Rodemerck et al.14 for the first time carried out this reaction at 400 C over La2O3-ZrO2 supported Ni catalysts with near-equilibrium yields of CO and H2. The intrinsic Ni/SiO2 performances were found to be independent of nickel particle size in DRM at 500 C.15 Recent years, cobalt has been added to Ni-based catalyst to form bimetallic catalyst because of their similar electronic configuration. Chen et al.16 reported that the promotion effect of Co could greatly enhance the RWGS activity of Mo2C catalysts at low temperatures. Aika et al. reported Ni-Co bimetallic catalyst prepared by co-impregnation methods provided high catalytic stability, suggesting the alloy formation of two metals.17 In case of low-temperature DRM (
