Using Reduced Catalysts for Oxidation Reactions: Mechanistic Studies of the "Periana-Catalytica" System for CH_4 Oxidation
Abstract
Designing oxidation catalysts based on CH activation with reduced, low oxidation state species is a seeming dilemma given the proclivity for catalyst deactivation by overoxidation. This dilemma has been recognized in the Shilov system where reduced Pt^(II) is used to catalyze methane functionalization. Thus, it is generally accepted that key to replacing Pt^(IV) in that system with more practical oxidants is ensuring that the oxidant does not over-oxidize the reduced Pt^(II) species. The "Periana-Catalytica" system, which utilizes (bpym)Pt^(II)Cl_2 in concentrated sulfuric acid solvent at 200 °C, is a highly stable catalyst for the selective, high yield oxy-functionalization of methane. In lieu of the over-oxidation dilemma, the high stability and observed rapid oxidation of (bpym)Pt^(II)Cl_2 to Pt^(IV) in the absence of methane would seem to contradict the originally proposed mechanism involving CH activation by a reduced Pt^(II) species. Mechanistic studies show that the originally proposed mechanism is incomplete and that while CH activation does proceed with Pt^(II) there is a solution to the over-oxidation dilemma. Importantly, contrary to the accepted view to minimize Pt^(II) overoxidation, these studies also show that increasing that rate could increase the rate of catalysis and catalyst stability. The mechanistic basis for this counterintuitive prediction could help to guide the design of new catalysts for alkane oxidation that operate by CH activation.
Additional Information
© 2013 American Chemical Society. Received: May 22, 2013. Published: August 8, 2013. The authors acknowledge the Center for Catalytic Hydrocarbon Functionalization, a DOE Energy Frontier Research Center (DOE DE-SC000-1298), for funding S.M.B., M.M.K., and B.G.H. Chevron Technology Corporation provided partial funding for O.A.M., V.R.Z., W.A.G., M.A., and R.A.P. The authors declare no competing financial interest.Attached Files
Supplemental Material - ja404895z_si_001.pdf
Supplemental Material - ja404895z_si_002.cif
Supplemental Material - ja404895z_si_003.cif
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Additional details
- Eprint ID
- 42862
- DOI
- 10.1021/ja404895z
- Resolver ID
- CaltechAUTHORS:20131205-135636346
- Center for Catalytic Hydrocarbon Functionalization
- DE-SC000-1298
- Department of Energy (DOE) Energy Frontier Research Center
- Chevron Technology Corporation
- Created
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2013-12-05Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field