Liquid-phase hydrogenation of acetophenone over silica-supported Ni, Co and Cu catalysts: Influence of metal and solvent
In this work, we studied the influence of solvent and metal nature on the liquid-phase hydrogenation of acetophenone (AP) over Ni/SiO2, Co/SiO2 and Cu/SiO2. Catalysts were prepared by wetness impregnation method with metal loads of about 7¨C8 wt%. Catalytic tests were performed in a batch reactor, a...
| Autores: | , , , |
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| Formato: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2014 |
| País: | Argentina |
| Recursos: | Consejo Nacional de Investigaciones Científicas y Técnicas |
| Repositorio: | CONICET Digital (CONICET) |
| Idioma: | inglés |
| OAI Identifier: | oai:ri.conicet.gov.ar:11336/31732 |
| Acesso em linha: | http://hdl.handle.net/11336/31732 |
| Access Level: | acceso abierto |
| Palavra-chave: | Hydrogenation 1-Phenylethanol Acetophenone Solvent Effect Metal-Based Catalysts https://purl.org/becyt/ford/2.4 https://purl.org/becyt/ford/2 |
| Resumo: | In this work, we studied the influence of solvent and metal nature on the liquid-phase hydrogenation of acetophenone (AP) over Ni/SiO2, Co/SiO2 and Cu/SiO2. Catalysts were prepared by wetness impregnation method with metal loads of about 7¨C8 wt%. Catalytic tests were performed in a batch reactor, at 363 K and 10 bar (H2), using 2-propanol (IPA), cyclohexane (CHX), toluene (TOL) and benzene (BEN) as solvents. Considering the three catalysts, the general pattern for the initial hydrogenation rate was: Ni/SiO2 > Co/SiO2 > Cu/SiO2, whereas the trend for selectivity to 1-phenylethanol (PHE) was just the oppo-site. AP can interact with nickel metal surface through both -C=O group and aromatic ring and thus the aromatic alcohol and saturated compounds were obtained. Instead, cobalt and copper metal surfaces interact preferentially with the -C=O group leading to selective hydrogenation of AP into PHE. In addition, an important interaction between ¨CC¨COH group of PHE and Co/SiO2 surface takes place, leading to rapid alcohol hydrogenolysis into ethylbenzene. The general activity pattern with the four solvents was: IPA > CHX >= TOL >= BEN. The magnitude of solvent influence on the catalytic performance strongly depended on the metal nature. The most significant solvent effect took place with Ni/SiO2, whereas the less noticeable influence was observed in the case of Cu/SiO2. From pseudo-homogenous kinetic modeling and temperature-programmed desorption, the following noteworthy observations arose: (1) IPA has a positive contribution by hydrogen transfer and/or AP activation by polarization; (2) the magnitude of the positive IPA influence on AP hydrogenation rate follows the trend: Ni/SiO2 > Co/SiO2 > Cu/SiO2; (3) CHX has a neutral contribution because of its weak adsorption on the metal phase and low interaction with reactant and products; (4) the effect of TOL and BEN is clearly negative for Ni/SiO2 due to block-age of active sites by strong adsorption of solvent on the metallic surface; (5) the effect due to strong adsorption of TOL and BEN is much less noticeable on Co/SiO2 and Cu/SiO2, as a consequence, the pattern for AP hydrogenation rates in BEN and TOL is Cu/SiO2 > Co/SiO2 > Ni/SiO2. Selectivity to PHE was less influenced by solvent nature. However, in the case of Ni/SiO2 and Co/SiO2, maximum PHE yields and selectivities increased with the solvent¨Cmetal interactions, mainly due to inhibition of the PHE hydrogenolysis. Cu/SiO2 was always 100% selective to PHE in all of the solvents. These results are clearly indicating that the magnitude of the solvent effect on catalytic performance strongly depends on the metal nature. |
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