We performed a systematically comparative study of carbonaceous materials as catalyst supports for the asymmetric heterogeneous hydrogenation of (E)-alpha-phenylcinnamic acid to study the influence of the supports on the reaction enantioselectivity. We prepared Pd-based catalysts supported on activated carbon (AC), graphene oxide (GO), or carbon nanotubes (CNTs) by using deposition methods, and subsequently characterized their physicochemical properties. The results attained from the TGA, FT-IR, and TPD-NH3 analyses revealed an abundance of acidic sites present on the Pd/GO catalyst, which reduced significantly the enantioselective hydrogenation of PCA. The influence of the support acidity on the enantioselectivity was attributed to the preferential adsorption mode of the chiral modifier cinchonidine (CD) on the GO surface via electrostatic interactions between the positively protonated amine groups present in the CD molecule and the negatively charged oxygen functional groups present on the GO surface. Further investigations using functionalized CNTs as catalyst supports confirmed that the ee values increased linearly with the decrease of the acidic sites present on the supports.
Journal: TechConnect Briefs
Volume: 2, Materials for Energy, Efficiency and Sustainability: TechConnect Briefs 2015
Published: June 14, 2015
Pages: 115 - 119
Industry sector: Advanced Materials & Manufacturing