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Exploitation of synergy in oxidation catalysis with bimetallic aluminophosphate catalysts

Exploitation of synergy in oxidation catalysis with bimetallic aluminophosphate catalysts
Exploitation of synergy in oxidation catalysis with bimetallic aluminophosphate catalysts
A series of novel bimetallic aluminophosphate catalysts were prepared with the simultaneous isomorphous substitution of cobalt (III) and manganese (III) for aluminium (III) and titanium (IV) replacing phosphorus (V). By substituting simultaneously for both Al (III) and P (V) in the ordered microporous aluminophosphate AlPO-5, the potential for catalytic application as either a solidacid or redox catalyst is produced. The bimetallic hydrothermal synthesis produced a phase pure and highly crystalline microporous catalyst which displayed properties not seen in monometallic AlPO-5 materials. These catalysts were fully characterized by physical, diffraction, spectroscopic and electrochemical techniques including powder X-ray diffraction, diffuse reflectance UV/Visible spectroscopy, cyclic voltammetry, extended X-ray absorption fine structure, X-ray absorption near edge spectra, scanning electron microscopy and surface/elemental (BET and ICP) methods. A significant change was observed when two metals were combined in the same structural framework, leading to an enhancement in the catalyst performance over the monometallic analogues. EXAFS indicated a change in the relative bond lengths, thought to be as a result of compensation in the structural distortion, similarly UV/Visible spectroscopy highlighted a change in the tetrahedral environment around the titanium centre when in combination with a redox metal. These catalysts were tested for the ammoximation of cyclohexanone using benign reagents to produce cyclohexanone oxime, a vital precursor in the production of nylon-6. Currently produced through hazardous processes, the ammoximation of cyclohexanone with metal substituted catalysts provides a more environmentally favourable solution. The use of a redox metal such as cobalt (III) in combination with titanium (IV) was shown to facilitate higher catalytic conversions compared with the monometallic AlPO-5 analogues while maintaining the high oxime selectivity. Similarly the epoxidation of cyclohexene with the solid oxidant acetylperoxyborate (APB) indicated a significantly higher conversion with the CoIIITiIVAlPO-5 catalyst. The substitution of two metals to replace both aluminium and phosphorus sites clearly influences and modifies the nature of the active site and provides an enhanced catalytic performance for ammoximation and epoxidation reactions. This synergy exerted through bimetallic substitution provides an important alternative approach to academic and industrial application of metal substitution within heterogeneous catalysis
Paterson, A. James
1d034012-e93a-4bb8-bcc0-ca561e9597ad
Paterson, A. James
1d034012-e93a-4bb8-bcc0-ca561e9597ad
Raja, Robert
74faf442-38a6-4ac1-84f9-b3c039cb392b

Paterson, A. James (2011) Exploitation of synergy in oxidation catalysis with bimetallic aluminophosphate catalysts. University of Southampton, Chemistry, Doctoral Thesis, 304pp.

Record type: Thesis (Doctoral)

Abstract

A series of novel bimetallic aluminophosphate catalysts were prepared with the simultaneous isomorphous substitution of cobalt (III) and manganese (III) for aluminium (III) and titanium (IV) replacing phosphorus (V). By substituting simultaneously for both Al (III) and P (V) in the ordered microporous aluminophosphate AlPO-5, the potential for catalytic application as either a solidacid or redox catalyst is produced. The bimetallic hydrothermal synthesis produced a phase pure and highly crystalline microporous catalyst which displayed properties not seen in monometallic AlPO-5 materials. These catalysts were fully characterized by physical, diffraction, spectroscopic and electrochemical techniques including powder X-ray diffraction, diffuse reflectance UV/Visible spectroscopy, cyclic voltammetry, extended X-ray absorption fine structure, X-ray absorption near edge spectra, scanning electron microscopy and surface/elemental (BET and ICP) methods. A significant change was observed when two metals were combined in the same structural framework, leading to an enhancement in the catalyst performance over the monometallic analogues. EXAFS indicated a change in the relative bond lengths, thought to be as a result of compensation in the structural distortion, similarly UV/Visible spectroscopy highlighted a change in the tetrahedral environment around the titanium centre when in combination with a redox metal. These catalysts were tested for the ammoximation of cyclohexanone using benign reagents to produce cyclohexanone oxime, a vital precursor in the production of nylon-6. Currently produced through hazardous processes, the ammoximation of cyclohexanone with metal substituted catalysts provides a more environmentally favourable solution. The use of a redox metal such as cobalt (III) in combination with titanium (IV) was shown to facilitate higher catalytic conversions compared with the monometallic AlPO-5 analogues while maintaining the high oxime selectivity. Similarly the epoxidation of cyclohexene with the solid oxidant acetylperoxyborate (APB) indicated a significantly higher conversion with the CoIIITiIVAlPO-5 catalyst. The substitution of two metals to replace both aluminium and phosphorus sites clearly influences and modifies the nature of the active site and provides an enhanced catalytic performance for ammoximation and epoxidation reactions. This synergy exerted through bimetallic substitution provides an important alternative approach to academic and industrial application of metal substitution within heterogeneous catalysis

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Published date: 25 June 2011
Organisations: University of Southampton

Identifiers

Local EPrints ID: 192867
URI: http://eprints.soton.ac.uk/id/eprint/192867
PURE UUID: f7e2b06f-fc21-488c-bb18-b2074c096902
ORCID for Robert Raja: ORCID iD orcid.org/0000-0002-4161-7053

Catalogue record

Date deposited: 08 Jul 2011 14:01
Last modified: 15 Mar 2024 03:26

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Contributors

Author: A. James Paterson
Thesis advisor: Robert Raja ORCID iD

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