TY - JOUR
T1 - Synthesis Gas Conversion over Rh-Mn-WxC/SiO2 Catalysts Prepared by Atomic Layer Deposition
AU - Liu, Yifei
AU - Zhang, Lifeng
AU - Göltl, Florian
AU - Ball, Madelyn R.
AU - Hermans, Ive
AU - Kuech, Thomas F.
AU - Mavrikakis, Manos
AU - Dumesic, James A.
N1 - Funding Information:
The authors acknowledge support of this research by the U.S. Department of Energy-Basic Energy Sciences (DOE-BES), Division of Chemical Sciences, Grant DE-FG02-05ER15731 and the Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE), under Award Number DE- EE0006878. We acknowledge support of this research by the National Science Foundation through the University of Wisconsin Materials Research Science and Engineering Center (DMR-1121288). The computational work was performed, in part, using supercomputing resources at the following institutions: the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility at Pacific Northwest National Laboratory (PNNL); the Center for Nanoscale Materials (CNM) at Argonne National Laboratory; the Center for High Throughput Computing (CHTC) at UW Madison; and the National Energy Research Scientific Computing Center (NERSC). EMSL is sponsored by the Department of Energy’s Office of Biological and Environmental Research located at PNNL. CNM and NERSC are supported by the U.S. Department of Energy, Office of Science, under Contracts DE-AC02-06CH11357 and DE-AC02-05CH11231, respectively. CHTC is supported by UW-Madison, the Advanced Computing Initiative, the Wisconsin Alumni Research Foundation, the Wisconsin Institutes for Discovery, and the National Science Foundation, and is an active member of the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy’s Office of Science.
Funding Information:
The authors acknowledge support of this research by the U.S. Department of Energy-Basic Energy Sciences (DOE-BES), Division of Chemical Sciences, Grant DE-FG02-05ER15731 and the Department of Energy Office of Energy Efficiency and Renewable Energy (EERE), under Award Number DE-EE0006878. We acknowledge support of this research by the National Science Foundation through the University of Wisconsin Materials Research Science and Engineering Center (DMR-1121288). The computational work was performed, in part, using supercomputing resources at the following institutions: the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility at Pacific Northwest National Laboratory (PNNL); the Center for Nanoscale Materials (CNM) at Argonne National Laboratory; the Center for High Throughput Computing (CHTC) at UW Madison; and the National Energy Research Scientific Computing Center (NERSC). EMSL is sponsored by the Department of Energy's Office of Biological and Environmental Research located at PNNL. CNM and NERSC are supported by the U.S. Department of Energy, Office of Science, under Contracts DE-AC02-06CH11357 and DE-AC02-05CH11231 respectively. CHTC is supported by UW-Madison, the Advanced Computing Initiative, the Wisconsin Alumni Research Foundation, the Wisconsin Institutes for Discovery, and the National Science Foundation, and is an active member of the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy's Office of Science.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/11/2
Y1 - 2018/11/2
N2 - The catalytic conversion of synthesis gas to value-added oxygenates and light hydrocarbons was studied on Rh and Rh-Mn clusters on tungsten carbide-overcoated silica (WxC/SiO2) at 523 K, 580 psi, and CO/H2 = 1/1. The WxC-modified SiO2 support was prepared by the overcoating of WOx on SiO2 using atomic layer deposition (ALD) followed by carburization. The reactivities of Rh/WxC/SiO2 catalysts with varying number of ALD cycles (number of cycles = 2, 5, 10, 20, and 30) were measured and showed that 5 ALD cycles of WxC suppressed the formation of methane. All WxC-modified catalysts showed enhancement in selectivity toward methanol and ethanol through CO hydrogenation and acetaldehyde hydrogenation, respectively. These catalysts also improved the overall turnover frequency (TOF). The addition of Mn species further promoted the activity and the selectivity toward ethanol and C2+ hydrocarbons, especially light alkenes. The best performing Rh-2Mn/5cycle-WxC/SiO2 catalyst (Rh:Mn molar ratio = 1:2) achieved 84.7% selectivity toward valuable oxygenates and C2+ hydrocarbons with a ratio of alkenes to alkanes equal to 1.7, compared to Rh/SiO2 which exhibited 80.4% selectivity toward the products aforementioned with a ratio of 0.5. The overall TOF was 20 times higher than that over Rh/SiO2 (i.e., 5.6 × 10-2 s-1 vs 2.9 × 10-3 s-1). X-ray diffraction revealed that the existence of W2C, which was the dominant phase in Rh/5cycle-WxC/SiO2, favored the suppression of methane and enhanced the production of alcohols and C2+ hydrocarbons compared to the WC support. Density functional theory calculations for Rh19, Rh31, and Rh37 clusters on various WC surfaces suggested that the shape of Rh clusters is condition dependent and subject to H2 pressure. The C- and O- binding energies on various sites for the clusters were used with scaling relations to probe their catalytic activity. With the use of this approach, the increase in the O binding energy when moving from the SiO2-supported Rh37 cluster to the WC-supported cluster leads to an increase in the activity of Rh/WxC/SiO2 at the expense of the reduction in the number of sites that are selective toward C2 oxygenates.
AB - The catalytic conversion of synthesis gas to value-added oxygenates and light hydrocarbons was studied on Rh and Rh-Mn clusters on tungsten carbide-overcoated silica (WxC/SiO2) at 523 K, 580 psi, and CO/H2 = 1/1. The WxC-modified SiO2 support was prepared by the overcoating of WOx on SiO2 using atomic layer deposition (ALD) followed by carburization. The reactivities of Rh/WxC/SiO2 catalysts with varying number of ALD cycles (number of cycles = 2, 5, 10, 20, and 30) were measured and showed that 5 ALD cycles of WxC suppressed the formation of methane. All WxC-modified catalysts showed enhancement in selectivity toward methanol and ethanol through CO hydrogenation and acetaldehyde hydrogenation, respectively. These catalysts also improved the overall turnover frequency (TOF). The addition of Mn species further promoted the activity and the selectivity toward ethanol and C2+ hydrocarbons, especially light alkenes. The best performing Rh-2Mn/5cycle-WxC/SiO2 catalyst (Rh:Mn molar ratio = 1:2) achieved 84.7% selectivity toward valuable oxygenates and C2+ hydrocarbons with a ratio of alkenes to alkanes equal to 1.7, compared to Rh/SiO2 which exhibited 80.4% selectivity toward the products aforementioned with a ratio of 0.5. The overall TOF was 20 times higher than that over Rh/SiO2 (i.e., 5.6 × 10-2 s-1 vs 2.9 × 10-3 s-1). X-ray diffraction revealed that the existence of W2C, which was the dominant phase in Rh/5cycle-WxC/SiO2, favored the suppression of methane and enhanced the production of alcohols and C2+ hydrocarbons compared to the WC support. Density functional theory calculations for Rh19, Rh31, and Rh37 clusters on various WC surfaces suggested that the shape of Rh clusters is condition dependent and subject to H2 pressure. The C- and O- binding energies on various sites for the clusters were used with scaling relations to probe their catalytic activity. With the use of this approach, the increase in the O binding energy when moving from the SiO2-supported Rh37 cluster to the WC-supported cluster leads to an increase in the activity of Rh/WxC/SiO2 at the expense of the reduction in the number of sites that are selective toward C2 oxygenates.
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U2 - 10.1021/acscatal.8b02461
DO - 10.1021/acscatal.8b02461
M3 - Article
AN - SCOPUS:85055546227
VL - 8
SP - 10707
EP - 10720
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 11
ER -