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

Abstract

eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. 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 C-O cleavage of the cinnamyl alcohol reactant to trans--methylstyrene, and of cinnamaldehyde decarbonylation to styrene. Highlights: An ultrathin alumina coating has been grafted onto a SBA-15 mesoporous silica architecture. Pd impregnated Al-SBA-15 materials are superior catalysts for the aerobic selox of allylic alcohols to aldehydes compared to pure silica or alumina supports.  Operando XAS confirms cinnamyl alcohol selox occurs over a PdO active species, which is prone to on-stream reduction and associated catalyst deactivation under static oxygen. [20,21] have highlighted PdO reduction to metallic palladium as a potential deactivation pathway, and hence the importance of generating highly dispersed nanoparticles which favour an oxide phase [20,[22][23][24]. KeywordsTemperature-programmed desorption and XPS of crotyl alcohol (but-2-en-1-ol) and crotonaldehyde (but-2-en-1-al) over Pd(111) and palladium-rich Au/Pd surface alloys suggest deactivation arises from crotonaldehyde decarbonylation and subsequent site-blocking by strongly adsorbed propylidyne and CO [20,21]. Computational modelling predicts Pd(111) can also drive propanoic acid decarbonylation [25]. Vapour phase studies of crotyl alcohol oxidation show that such in-situ palladium reduction is reversible under oxidising environments [17,19], enabling selox to be maintained, however the ability of dissolved oxygen to preserve palladium as PdO during liquid phase selox is unknown. Experimental Catalyst synthesisThe parent SBA-15 silica framework was synthesised following the method of Zhao et al [30]. Pluronic P123 (10 g) was dissolved in water (75.5 ...

Liquid phase oxidation of cinnamyl alcohol to cinnamaldehyde using multiwall carbon nanotubes decorated with zinc-manganese oxide nanoparticles

“…Parlett et al observed productivity of 56 mmol.g -1 .h -1 with PdO-meso alumina and 42.5 mmol.g -1 .h -1 with Pd-gamma alumina catalysts [2]. The values reported in blue solvents were slightly higher but comparable with the results obtained in this study.…”

“…The aldehydes have been usually synthesized with a stoichiometric amount of oxidizing agents such as dichromate, hypochlorite, permanganates, and others [1][2][3]. These oxidant were harmful and environmental malignant, expensive, and yield a large amount of byproducts [4,5].…”

Tunable Silver-Functionalized Porous Frameworks for Antibacterial Applications

“…The expected hexagonally close-packed channels of the SBA-15 mesopore network were observed in all cases, with surface areas and mesopore diameters decreasing with successive TiO 2 grafting cycle (Figure 2 and Figure S1), reflecting pore narrowing and partial blockage of micropores in the silica framework [31]. Uniform mesopores of 6.3 nm diameter were in accordance with previous reports [29].…”

Mechanism of Catalytic Ozonation in Fe2O3/Al2O3@SBA-15 Aqueous Suspension for Destruction of Ibuprofen

“…20 The results indicated that these samples retained a highly ordered structure of SBA- 15 23 whereas the Si 2p XPS spectra also exhibited two BEs, 103.4 and 102.3 eV, assigned to Si−O−Si and Al−O−Si, respectively (Figure 1). 23 The same results also were observed in the XPS spectra of Al 2 O 3 @SBA-15 (not data shown). In addition, FTIR spectra also show that the surface Si−OH groups of SBA-15 at 966 cm −1 disappeared with the loading of aluminum oxide (SI Figure S5).…”