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Research Paper | Chemical Engineering | Saudi Arabia | Volume 4 Issue 10, October 2015

The Effect of Different Coverages of Bismuth on a 5% Pt/G Supported Catalysts on Enantiomeric Excess (ee) and Reaction Rate of Ethyl Pyruvate Hydrogenation Rate in Dichloromethane

Salem El Khaseh | Mohammed M. Bukhari | Salah Eldeen F. Hegazi

Abstract: The primary objective of this study was to investigate the effect of reaction conditions, solvents, thermal annealing, the presence of CD-derivative and CN-derivative and sintering on the enantioselective hydrogenation of ethyl pyruvate, both distilled and non-distilled. In this work an autoclave reactor was used to carry out the reactions. The effect of pre-heating the Pt/graphite in 5 % H2/Ar at 700K was also investigated Also, the effect of bismuth adsorption on the catalyst for title reaction, in particular, the selective blocking of steps and chiral sites by (Bi) by G. A. Attardet al (1999), and its effect on enantioselectivity was to be investigated in order to augment previous work by Albdulrahmanet al (2005). Cyclic voltammetry (CV) is a widely used technique and can give much information concerning the coverage and structure of a metal electrode, in particular has allowed for detailed scrutiny of catalyst adsorption sites giving rise to enantioselectivity and therefore, new insights into structure-selectivity relationships. It has been used to investigate metal deposition and to characterise the morphology of catalysts under investigation, and also to assess the effects of catalyst modification by ad-atom adsorption and thermal annealing. In addition, investigate (i) the surface morphology of Pt particles of the terraces, steps and kinks present in as-received and conditioned catalysts and (ii) the adsorption of bismuth at Pt surfaces. By the selective blocking of Pt adsorption sites using bismuth ad atoms it is shown that the modifiers hydroquinine 4-chlorobenzoate (CD-der) and hydroquinidine 4-chlorobenzoate (CN-der) give rise to novel catalytic behaviour in relation to the enantioselective hydrogenation of ethyl pyruvate. It is reported that hydrogenation of ethyl pyruvate affords an enantiomeric excess (ee) to R- (S-) ethyl lactate in DCM if CD-der (CN-der) is adsorbed at step/defect sites whereas an excess of S- (R-) ethyl lactate results from adsorption of CD-der (CN-der) at Pt{111} terrace sites. Modified Pt catalysts supported on graphite (C) was investigated in order to determine the part played by the support in the reaction mechanism and then analyse enantioselectivities by using gas chiral chromatography (GC).

Keywords: Enantioselective, heterogeneous, enantioselective, ethyl pyruvate

Edition: Volume 4 Issue 10, October 2015,

Pages: 1632 - 1641

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