Phosphorus as a promoter of a nickel catalyst to obtain 1-phenylethanol from chemoselective hydrogenation of acetophenone

Abstract

Two catalysts were prepared using monodisperse pre-synthetized nanoparticles of metallic nickel and nickel phosphides with the same average diameter. Both nanoparticles species were deposited on the same support: mesoporous silica nano-spheres of MCM-41. This support is suitable to inhibit agglomeration and sintering processes during preparation steps. Therefore, two supported and activated catalysts with the same average nanoparticles diameter were obtained. They differ only in the nature of the active species: metallic nickel and nickel phosphides. The effect of the presence of a second element (phosphorus), more electronegative than nickel, on the activity and selectivity in the chemoselective hydrogenation of acetophenone was studied. The reaction conditions were: H 2 pressure of 1 MPa, 80 °C using n-heptane as solvent. With the aim to understand the catalytic results, nanoparticles, support and catalysts were carefully characterized by X-ray diffraction, diffuse light scattering, transmission electron microcopy, high resolution transmission electron microcopy, selected area electron diffraction, scanning electron microcopy, Fourier transformer infrared spectroscopy, N 2 adsorption at -196 °C, atomic absorption, H 2 and CO chemisorption and volumetric oxidation. Considering these results and geometric and electronic characteristics of the surface of both active species, a change in the adsorption intermediate state of acetophenone in presence of phosphorus is proposed to explain the hydrogenation chemoselectivity of nickel phospides.

Catalyst characterization Ni-Sn nanoparticles supported in Al2O3and MgO: Acetophenone hydrogenation

“…However, the process presents a low selectivity, obtaining secondary products such as acetylcyclohexane and 1-cyclohexylethanol. A better selectivity has been reported by Costa et al 42 using nickel-based catalysts at 145 psi and 80°C to favor the hydrogenation reaction at the C=O bond more than the C=C, however, they have only reached a 30% conversion rate. In the series of catalysts tested in this work, the best conversion of acetophenone to 1-phenylethanol occurs with Ni5% Sn0.5%/MgO catalysts, since they showed higher metal surface area in the hydrogen chemisorption measurements.…”

Influence of Physicochemical Properties of Ni/Clinoptilolite Catalysts in the Hydrogenation of Acetophenone

“…A minimal amount of ethylbenzene (EB) has been detected, the formation of which can be explained by hydrogenolysis of the C–O bond of the intermediate alcohols or by initial hydrogenation of the CO bond followed by dehydration, with the formation of C = C bond, and subsequent addition of hydrogen to this new bond formed. − As can be observed in Table , all the catalysts studied show different conversion values. In order to explain this result, we must evaluate and correlate the relationship between the chemical, textural, acidity, redox, and hygroscopic properties with selectivity and conversion percentage.…”