Abstract
Alcohols (bioalcohols) is a class of chemicals that are used as a feedstock for the manufacturing of a large number of valuable intermediates in industrially important processes. Currently, sustainable technologies for selective conversion of alcohols utilize “green” oxidants, mainly, ambient air or oxygen. Due to the high affinity of oxygen towards silver, the latter serves as an active component of supported heterogeneous catalysts. In this review, we consider Ag-based catalysts that participate in gas- or liquid-phase oxidation of alcohols. Oxidation of methanol, ethanol, ethylene glycol, propylene glycol, glycerol, benzyl and allyl alcohols is mostly considered. A particular attention is paid to selective photooxidation of alcohols over Ag-based catalysts. We discuss the catalyst composition in terms of (1) the state of the active component, (2) the nature of the substrate, (3) support nature, and (4) the strength of the metal–support interactions.
Highlights
Mono- and polyalcohols are important platform molecules for industrial manufacturing of a large number of value-added products, including but not limited to aldehydes, ketones, ethers, molecular hydrogen, etc
Many effective catalytic composites were proposed for selective oxidation of alcohols [1,2,3,4], including those based on individual noble metals (Au [5,6,7], Pd [7], Pt [8], Ru [9], Cu [9], Ir [9], etc.) and bimetallic compositions (e.g., [7])
In our previous work [57] we showed that the impurities of Fe in the Si3N4 support, which was prepared by self-propagating high-temperature synthesis from Fe-Si alloy, influence on the surface redox properties of Ag/Si3N4 and are a part of bifunctional active species in selective oxidation of ethanol
Summary
Mono- and polyalcohols (including such important bioalcohols as ethanol, glycerol, etc.) are important platform molecules for industrial manufacturing of a large number of value-added products, including but not limited to aldehydes, ketones, ethers, molecular hydrogen, etc. The composites were synthesized by a decoration of polymeric colloids with the bimetallic NPs followed by an assembly into a colloidal crystal backfilled with the matrix precursor and a subsequent removal of the polymeric template The performance of these catalysts in selective oxidation of both methanol and ethanol to esters was superior to nanoporous dilute Ag3Au97 alloy catalysts. Recent trends are connected with (1) the transition to the hierarchical porous composite fibrous materials having high hydrodynamic permeability [34], (2) the use of the nanosized Ag particles fixed on the surface of MCFs modified by Nb or Ta [31] In the latter case the effect of methanol interaction with the reduced sites of Nb having their own activity is discussed. The role of Nb lies in the significant changing of the selectivity towards formaldehyde that opens wide prospects for further development of such materials
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