Enantioselectivity of tartaric acid-modified Ni-Al2O3 catalysts

Nitta, Yuriko; Kawabe, Masayuki; Imanaka, Toshinobu

doi:10.1016/s0166-9834(00)81018-0

Cited by 19 publications

(6 citation statements)

References 18 publications

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“…It must be stressed that the investigations carried out by Nitta et al did not address the corrosive effects of TA adsorption and the ovtical vield in each instance was related to the nature of the metal phase in the premodified catalyst. The divergence in the data generated in this study with that reported by Nitta and co-workers (20,21,37,38) highlights the difficulty in attempting to compare different enantioselective systems where the possible permutations of experimental variables involved in the catalyst preparation, activation, modification, and reaction steps mitigates against anything but a tentative qualitative comparison.…”

Section: Resultscontrasting

confidence: 55%

“…With regard to the published studies (20,21,37,38) which have ascribed structure sensitivity to the asymmetric conversion of MAA, the quoted enantioselectivities were related, in each case, to the dimensions of the metal particles supported on the premodified catalyst. A s shown in an earlier report (4), the composition of the modified catalyst differs considerably from the freshly reduced catalyst.…”

Section: Resultsmentioning

confidence: 99%

“…Nitta et al (20,21,37,38) have attributed observed differences in enantioselectivities to variations in the morphology of the supported nickel metal and to differences in the strength of nickel-support interactions. They concluded that optical yield was enhanced by surfaces where weak precursor-carrier interactions generated larger (more selective) nickel crystallites.…”

Section: Resultsmentioning

confidence: 99%

“…Although the modification and reaction steps have received considerable attention, the role of catalyst precursor preparation and activation has largely been ignored. The dependence (20,21,37,38) or independence (30) of enantioselectivity on metal particle dimensions remains open to question. With regard to the published reports of MAA hydrogenation on nickel catalysts, reaction rates have either been omitted or included as addenda to the enantioselectivity data.…”

Section: Introductionmentioning

confidence: 99%

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The role of catalyst activation in the enantioselective hydrogenation of methyl acetoacetate over silica-supported nickel catalysts

Keane¹

1994

Can. J. Chem.

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A range of Ni-Si02 catalysts have been prepared by homogeneous precipitation-deposition and impregnation techniques and modified with aqueous solutions of R-(+)-tartaric acid (TA) to induce enantioselectivity in the asymmetric hydrogenation of a prochiral P-ketoester (methyl acetoacetate) to a P-hydroxyester ((R)-(-)-methyl3-hydroxybutyrate). The effects of catalyst precursor preparation, nickel loading, and precalcination on the reduction of the precursor were examined and the nature of the resultant nickel particle size distribution is described. The influence of metal-support interactions on the uptake of TA was investigated and data on the corrosive metal leaching and the consequent changes in metal dispersion are presented. Modification of the catalysts with TA not only induced enantioselectivity, but also increased the turnover frequency by up to 15 times that observed for the unmodified surface. The amount of TA adsorbed and the fractional surface coverage by TA is related to the degree of enantiodifferentiation. The effects of variations in supported nickel metal particle sizes (in the overall range of 1.4-13.6 nm) on the reaction rate and enantioselectivity were examined; while the selectivity was independent of metal particle size, the rate of hydrogenation was found to be structure sensitive and a correlation between reaction rate sensitivity and particle size is presented.MARK A. KEANE. Can. J. Chem. 72,372 (1994). On a prCparC une sene de catalyseurs Ni-Si02 par des techniques de prCcipitation-dCp6t et d'imprkgnation homogbnes et on les a modifiCs avec des solutions aqueuses d'acide R-(+)-tartrique (AT) dans le but d'induire de I'CnantiosClectivitC dans l'hydrogCnation asymCtrique d'un ester P-cCtonique prochiral (acetoacetate de mCthyle) en ester P-hydroxylC, (R)-(-)-3-hydroxybutyrate de mCthyle. On a CvaluC les effets de la prCparation des prCcurseurs des catalyseurs, de la quantitC de nickel et de la prCcalcination sur la reduction du prCcurseur et on dCcrit la nature de la distribution des grosseurs des particules de nickel qui en rCsulte. On a CtudiC l'influence des interactions mCtal-support sur la quantitC d'AT adsorb6 et on prCsente des donnCes concernant le lixiviation par des mCtaux corrosifs et sur les changements qui en rCsultent sur la dispersion du mCtal. La modification des catalyseurs par I'AT n'induit pas seulement de l'CnantiosClectivitC, le frCquence dlCchange est 15 fois plus rapide que sur une surface non modifiCe. La quantitC d'AT adsorbke et la fraction de la surface qui est couverte sont relikes au degrC d'Cnantiodiffkrentiation. On a examink les effets des variations dans les grosseurs des particules du nickel support6 (grosseurs allant de 1,4 B 13,6 nm) sur la vitesse de rCaction et sur llCnantiosClectiviC; alors que l'on a trouvC que la sClectivitC est indCpendante de la grosseur des particules mktalliques, la vitesse d'hydrogknation est sensible ? I la structure et on prCsente une corrClation entre la sensibilitC de la vitesse rkactionnelle et la grosseur des particules.[...

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Section: Resultscontrasting

confidence: 55%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The role of catalyst activation in the enantioselective hydrogenation of methyl acetoacetate over silica-supported nickel catalysts

Keane¹

1994

Can. J. Chem.

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“…This catalyst hydrogenates ␤-ketoesters and 2-alkanones in high optical yields [1][2][3][4][5][6][7]. Easy recovery and reuse are the important characteristics for solid catalysts, especially for practical applications.…”

Section: Introductionmentioning

confidence: 99%