7699-00-5Relevant articles and documents
A Novel Aminoalcohol Modifier for the Enantioselective Hydrogenation of Ethyl Pyruvate on Pt/Alumina
Minder, B.,Mallat, T.,Baiker, A.,Wang, G.,Heinz, T.,Pfaltz, A.
, p. 371 - 378 (1995)
A novel chiral modifier, (R)-2-(1-pyrrolidinyl)-1-(1-naphthyl) ethanol (PNE), has been synthesised and tested in the enantioselective hydrogenation of ethyl pyruvate over Pt/alumina.An enantiomeric excess in (R)-ethyl lactate of up to 75percent was achieved.The influence of solvent, pressure, temperature, and concentrations of the components (reactant, modifier, catalyst) on the reaction rate and enantiodifferentiation was investigated.Among various polar and nonpolar solvents, acetic acid was found to be most suitable for reaching good enentioselectivity.Favorable reaction conditions are 1-10 bar hydrogen pressure, 0-25 deg C, and a catalyst loading 15 g liter-1.The efficiency of PNE is demonstrated by the very low modifier : reactant molar ratio (1 : 30,000) which is required to obtain maximum enantioselectivity.The performance and stability of the aminoalcohol-type modifier are compared to those of cinchona alkaloids.At low hydrogen pressure, the enantiodifferentiation of PNE is comparable to that of 10,11-dihydrocinchonidine.
Platinum nanoparticles supported on mesocellular silica foams as highly efficient catalysts for enantioselective hydrogenation
Kim, Jeongmyeong,Song, Byeongju,Hwang, Gyohyun,Bang, Yongju,Yun, Yongju
, p. 306 - 313 (2019)
Mesocellular silica foams (MCFs) with different pore size were synthesized and used as supports for Pt catalysts for enantioselective hydrogenation of ethyl pyruvate. The influences of the pore size of MCFs, the amount of Pt loading and H2 pressure on catalytic performance of cinchonidine-modified Pt/MCFs were investigated. Both activity and enantioselectivity of the Pt/MCF catalyst increased with the increase in the pore size. These results were attributed to the fact that the larger mesopores facilitate intraparticle diffusion of bulky chiral modifier molecules and generate more chirally modified Pt sites. The performances of Pt/MCFs were compared to those of Pt supported on non-porous silica (Pt/SiO2) and commercial Pt/Al2O3 catalysts. The 1 wt% Pt/MCFs showed superior performance than the 1 wt% Pt/SiO2 and the commercial 1 wt% Pt/Al2O3 catalysts. Furthermore, the 0.6 wt% Pt/MCF exhibited higher activity and enantioselectivity than the commercial 5 wt% Pt/Al2O3, one of the most efficient heterogeneous catalysts for this reaction, in spite of a considerably less Pt loading. At optimized reaction conditions, the Pt/MCF catalyst gave enantiomeric excess of 96% at 100% conversion. They also maintained high enantioselectivity during 10 successive reaction cycles, exhibiting high reusability.
Enhancing Effect of Residual Capping Agents in Heterogeneous Enantioselective Hydrogenation of α-keto Esters over Polymer-Capped Pt/Al2O3
Chung, Iljun,Song, Byeongju,Kim, Jeongmyeong,Yun, Yongju
, p. 31 - 42 (2021/01/11)
Heterogeneous enantioselective catalysis is considered a promising strategy for the large-scale production of enantiopure chemicals. In this work, polymer-capped Pt nanocatalysts having a uniform size were synthesized using poly(vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) and supported on γ-Al2O3. After a facile heat treatment process, their catalytic performance for enantioselective hydrogenation of α-keto esters, a structure-sensitive reaction, was investigated. The presence of residual capping agents on the Pt surface often perturbs the adsorption of reacting species and reduces performance in structure-sensitive reactions. However, the 1 wt % PVP-Pt/Al2O3 catalyst exhibited an enhancement in both activity and enantioselectivity compared to a reference Pt/Al2O3 catalyst prepared by wet impregnation. Under optimized reaction conditions, the cinchonidine-modified PVP-Pt/Al2O3 gave an enantiomeric excess of 95% for the enantioselective hydrogenation of methyl pyruvate despite the low Pt loading. We demonstrate that depending on the type of polymers, the residual capping agents can lead to site-selective blockage of the Pt surface, that is, defects or terraces. Quantitative and qualitative analyses also show that the noticeable improvement in enantioselectivity is attributed to the stable adsorption of chiral modifiers on selectively exposed Pt terrace sites. The findings of this work provide a promising strategy to prepare metal nanoparticles having selectively exposed sites and offer insights into the enhancing effect of residual capping agents on the catalytic properties in structure-sensitive reactions.
Mesoporous silica-supported Pt catalysts in enantioselective hydrogenation of ethyl pyruvate
Chung, Iljun,Kim, Jeongmyeong,Song, Byeongju,Yun, Yongju
, (2020/06/28)
Catalytic properties of Pt catalysts supported on mesoporous silica (Pt/m-SiO2) have been studied in enantioselective hydrogenation of ethyl pyruvate. The influences of pore structure of mesoporous silica (m-SiO2), type of chiral modifier, and H2 pressure on the catalytic performance have been investigated by using various m-SiO2 supports and cinchona alkaloids and by varying H2 pressure. The use of MCM-41, SBA-15, KIT-6, and MCF reveals that characteristic pore structure and size of m-SiO2 supports significantly affect both activity and enantioselectivity. A facile diffusion of chiral modifier through large mesopores of MCF support enables Pt/MCF to exhibit excellent performance. A comparison of the efficiency of cinchona alkaloids-modified Pt catalysts shows that QN and QD lead to higher performance than CD and CN at ambient H2 pressure. The influence of cinchona alkaloids on enantioselectivity noticeably depends on H2 pressure. Cinchona alkaloid-modified Pt/m-SiO2 exhibit superior enantioselectivity to the corresponding Pt/Al2O3 under various H2 pressures. These results imply that m-SiO2 is a promising support and that fine control of pore structure can further improve catalytic performance of Pt/m-SiO2 in heterogeneous enantioselective hydrogenation.
