TY - JOUR
T1 - Increasing the catalytic stability by optimizing the formation of zeolite-supported Mo carbide species ex situ for methane dehydroaromatization
AU - Rahman, Mustafizur
AU - Infantes-Molina, Antonia
AU - Sridhar, Apoorva
AU - Khatib, Sheima
AU - Boubnov, Alexey
AU - Bare, Simon R.
AU - Stavitski, Eli
N1 - Funding Information:
This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award DE-SC0019074. AIM thanks the Ramon y Cajal Program RyC-2015-17870 (Spanish Ministry of Economy and Competitiveness, Spain), RTI2018-099668-B-C22 Project (Spanish Ministry of Science, Innovation and Universities) and Central Research Support Services at the University of Malaga (SCAI-UMA) for XPS and TEM measurements. The authors would like to thank Dr. Daniel Unruh from the Department of Chemistry and Biochemistry for his help in acquiring the XRD patterns. This research used beamline 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The authors would like to thank Dr. Klaus Attenkofer for his help in acquiring XAS data at NSLS-II, Brookhaven National Laboratory. Co-ACCESS, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences under Contract DE-AC02-76SF00515. The authors would like to thank Dr. Adam Hoffman (from SLAC National Accelerator Laboratory) for his involvement in discussions regarding the XAS data.
Funding Information:
This research was supported by the U.S. Department of Energy , Office of Science, Office of Basic Energy Sciences, under Award DE-SC0019074. AIM thanks the Ramon y Cajal Program RyC-2015-17870 ( Spanish Ministry of Economy and Competitiveness , Spain), RTI2018-099668-B-C22 Project ( Spanish Ministry of Science, Innovation and Universities ) and Central Research Support Services at the University of Malaga (SCAI-UMA) for XPS and TEM measurements. The authors would like to thank Dr. Daniel Unruh from the Department of Chemistry and Biochemistry for his help in acquiring the XRD patterns. This research used beamline 8-ID (ISS) of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The authors would like to thank Dr. Klaus Attenkofer for his help in acquiring XAS data at NSLS-II, Brookhaven National Laboratory. Co-ACCESS, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences under Contract DE-AC02-76SF00515. The authors would like to thank Dr. Adam Hoffman (from SLAC National Accelerator Laboratory) for his involvement in discussions regarding the XAS data.
Publisher Copyright:
© 2019 Elsevier Inc.
PY - 2019/7
Y1 - 2019/7
N2 - The synthesis of zeolite-supported Mo carbide species was studied by testing different reduction/carburization conditions applied to a zeolite-supported Mo oxide catalyst, with the aim to find the optimized treatment conditions necessary to form stable supported Mo carbide catalysts ex situ for application in methane dehydroaromatization reaction. Four types of treatment were performed and studied using temperature-programmed reduction and carburization profiles: (1) heating the catalyst in a reducing gas, H2, up to reaction temperature and switching to CH4; (2) heating the catalyst in a reducing gas, H2, mixed with dilute CH4; (3) heating the catalyst in CH4 up to reaction temperature; and (4) heating the catalyst in an inert gas (commonly He) up to reaction temperature and then switching to CH4 or to H2 followed by CH4 or to H2/CH4 mixture. Each of these processes were stopped at intermediate points to analyze the phases that were present in order to identify the structural evolution of the supported Mo carbides that originate from the supported Mo oxides. Once the supported carbides were formed, they were quenched under the same gas mixture, and then they were each tested in methane dehydroaromatization via previous heating to reaction temperature in He flow. Despite all of them showing only presence of Mo2C species on HZSM-5, the catalytic properties were dramatically different. Catalysts treated in H2 or CH4/H2 showed remarkably higher stability. These catalysts exhibited a higher Mo dispersion and thus exposure on the active surface.
AB - The synthesis of zeolite-supported Mo carbide species was studied by testing different reduction/carburization conditions applied to a zeolite-supported Mo oxide catalyst, with the aim to find the optimized treatment conditions necessary to form stable supported Mo carbide catalysts ex situ for application in methane dehydroaromatization reaction. Four types of treatment were performed and studied using temperature-programmed reduction and carburization profiles: (1) heating the catalyst in a reducing gas, H2, up to reaction temperature and switching to CH4; (2) heating the catalyst in a reducing gas, H2, mixed with dilute CH4; (3) heating the catalyst in CH4 up to reaction temperature; and (4) heating the catalyst in an inert gas (commonly He) up to reaction temperature and then switching to CH4 or to H2 followed by CH4 or to H2/CH4 mixture. Each of these processes were stopped at intermediate points to analyze the phases that were present in order to identify the structural evolution of the supported Mo carbides that originate from the supported Mo oxides. Once the supported carbides were formed, they were quenched under the same gas mixture, and then they were each tested in methane dehydroaromatization via previous heating to reaction temperature in He flow. Despite all of them showing only presence of Mo2C species on HZSM-5, the catalytic properties were dramatically different. Catalysts treated in H2 or CH4/H2 showed remarkably higher stability. These catalysts exhibited a higher Mo dispersion and thus exposure on the active surface.
KW - Methane dehydroaromatization
KW - MoC
KW - MoO
KW - Supported molybdenum carbide
KW - Temperature programmed reduction and carburization
UR - http://www.scopus.com/inward/record.url?scp=85067899680&partnerID=8YFLogxK
U2 - 10.1016/j.jcat.2019.06.002
DO - 10.1016/j.jcat.2019.06.002
M3 - Article
VL - 375
SP - 314
EP - 328
JO - Journal of Catalysis
JF - Journal of Catalysis
ER -