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Selectivity and kinetics of methyl crotonate hydrogenation over Pt/Al2O3

Chaoquan Hu (Institutionen för kemi och kemiteknik, Kemisk reaktionsteknik ; Kompetenscentrum katalys (KCK)) ; Derek Creaser (Institutionen för kemi och kemiteknik, Kemisk reaktionsteknik ; Kompetenscentrum katalys (KCK)) ; Henrik Grönbeck (Institutionen för teknisk fysik, Kemisk fysik ; Kompetenscentrum katalys (KCK)) ; Houman Ojagh (Institutionen för kemi och kemiteknik, Kemisk reaktionsteknik ; Kompetenscentrum katalys (KCK)) ; Magnus Skoglundh (Institutionen för kemi och kemiteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK))
Catalysis Science & Technology (2044-4753). Vol. 5 (2015), 3, p. 1716-1730.
[Artikel, refereegranskad vetenskaplig]

The hydrogenation of gas-phase methyl crotonate (MC) over Pt/Al2O3 was investigated with the aim to understand C=C hydrogenation in unsaturated methyl esters. Three Pt/Al2O3 catalysts with different Pt dispersions were prepared by varying calcination temperature and evaluated for MC hydrogenation. The main products were found to be methyl butyrate (MB) and methyl 3-butenoate (M3B), resulting from hydrogenation and shift of the C=C bond in MC, respectively. The measured activity for both hydrogenation and shift of the C=C in MC was found to depend on the Pt dispersion where higher Pt dispersion favors the C=C hydrogenation reaction. The effect of reactant concentrations on the activity and selectivity for MC hydrogenation over the Pt/Al2O3 catalyst was examined in detail. Under the investigated conditions, the C=C hydrogenation was found to have a negative reaction order with respect to MC concentration but a positive H2 order. Further understanding of the MC hydrogenation was provided from H2 chemisorption experiments over the catalyst with and without pre-adsorbed MC and from transient experiments using alternating MC and H2 feeds. Based on the present experimental results, a reaction pathway was proposed to describe gas-phase MC hydrogenation over Pt/Al2O3. In order to gain more insight into the reaction, a kinetic analysis of MC hydrogenation was performed by fitting a power-law model to the kinetic data, moreover, dissociative H2 adsorption on the catalyst was found to be the rate-determining step by comparing the power-law model with the overall rate expressions derived from mechanistic considerations.



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Denna post skapades 2014-12-14. Senast ändrad 2015-06-01.
CPL Pubid: 208080

 

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