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Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation

Paper ID Volume ID Publish Year Pages File Format Full-Text
54110 46997 2014 10 PDF Available
Title
Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation
Abstract

•An ultrathin alumina coating has been grafted onto an SBA-15 mesoporous silica architecture.•Al-SBA-15 outperforms silica or alumina as a support for the Pd-catalysed aerobic selox of allylic alcohols to aldehydes.•Operando XAS identifies PdO as the active species, which is prone to on-stream reduction and deactivation under static O2.

Ultrathin alumina monolayers grafted onto an ordered mesoporous SBA-15 silica framework afford a composite catalyst support with unique structural properties and surface chemistry. Palladium nanoparticles deposited onto Al-SBA-15 via wet impregnation exhibit the high dispersion and surface oxidation characteristic of pure aluminas, in conjunction with the high active site densities characteristic of thermally stable, high-area mesoporous silicas. This combination confers significant rate enhancements in the aerobic selective oxidation (selox) of cinnamyl alcohol over Pd/Al-SBA-15 compared to mesoporous alumina or silica supports. Operando, liquid-phase XAS highlights the interplay between dissolved oxygen and the oxidation state of palladium nanoparticles dispersed over Al-SBA-15 towards on-stream reduction: ambient pressures of flowing oxygen are sufficient to hinder palladium oxide reduction to metal, enabling a high selox activity to be maintained, whereas rapid PdO reduction and concomitant catalyst deactivation occurs under static oxygen. Selectivity to the desired cinnamaldehyde product mirrors these trends in activity, with flowing oxygen minimising CO cleavage of the cinnamyl alcohol reactant to trans-β-methylstyrene, and of cinnamaldehyde decarbonylation to styrene.

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Keywords
Palladium; Selective oxidation; Operando; XAS; Alumina; SBA-15.
First Page Preview
Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation
Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 229, 15 June 2014, Pages 46–55
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis