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Dioxygen Activation on Cu-MOR Zeolite: Theoretical Insights into the Formation of Cu2O and Cu3O3 Active Species
Mahyuddin M.H.a,b, Tanaka T.a, Staykov A.a, Shiota Y.a, Yoshizawa K.a
a Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University, Fukuoka, 819-0395, Japan
b Engineering Physics Research Group, Bandung Institute of Technology, Bandung, 40132, Indonesia
[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]Copyright © 2018 American Chemical Society.The utilization of low-cost and abundant oxygen (O2) as an oxidant in the activation of copper-exchanged zeolites is highly important for the direct, selective oxidation of methane to methanol at low temperatures. While two motifs of active sites, i.e., the [Cu2(μ-O)]2+ and [Cu3(μ-O)3]2+, have been experimentally observed in mordenite (MOR) zeolite, the mechanisms of their formation from the reaction of Cu-MOR with O2 are still unclear. In this study, we performed density functional theory (DFT) calculations for O2 activation over 2[Cu2]2+-MOR and [Cu3O]2+-MOR zeolites. For the reaction on the dicopper species, we found two possible reaction routes: O-O bond cleavage leading to (1) formation of a [Cu2(μ-O)]2+ active species and a trans-μ-1,2-peroxo-Si2 species and (2) simultaneous formation of two [Cu2(μ-O)]2+ active species neighboring to each other. These routes are both exothermic but require completely different O-O bond activation energies. For the reaction on the tricopper species, we suggest a peroxo-Cu3O species as the intermediate structure with two transition states (TSs) involved in the reaction. The first TS where a significant rearrangement of the tricopper site occurs is found to be rate-determining, while the second TS where the peroxo bond is cleaved results in a smaller activation barrier. This reaction, in contrast to the dicopper case, is slightly endothermic. The present study provides theoretical insights that may help design of better Cu-exchanged zeolite catalysts for methane hydroxylation to methanol.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Author keywords” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Indexed keywords” size=”size-sm” text_align=”text-left”][vc_column_text][/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Funding details” size=”size-sm” text_align=”text-left”][vc_column_text]This work was supported by KAKENHI Grant nos. JP24109014 and JP15K13710 from Japan Society for the Promotion of Science (JSPS) and the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), the MEXT Projects of “World Premier International Research Center Initiative (WPI)”, “Integrated Research Consortium on Chemical Sciences”, and “Elements Strategy Initiative to Form Core Research Center”, the Cooperative Research Program of “Network Joint Research Center for Materials and Devices”, and the JST-CREST JPMJCR15P5.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”DOI” size=”size-sm” text_align=”text-left”][vc_column_text]https://doi.org/10.1021/acs.inorgchem.8b01329[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]