Diseño de catalizadores para una obtención limpia de 2-feniletanol

Identificador:  TDX:864

Handle: https://hdl.handle.net/20.500.11797/TDX864

Autors:  Bergadà Miró, Olga

Resum:
2-phenylethanol is the main component of rose oils. This compound is widely used in all chemical perfumes, and cosmetics due to its pleasant smell. The hydrogenation of styrene oxide to obtain selectively 2-phenylethanol by heterogeneous catalysis is an alternative to solve the environmental and economical problems which present the traditional industrial methods used for the obtention of this alcohol.The aim of this Doctoral Thesis is to obtain highly active and selective to 2-phenylethanol catalysts which should be resistant to deactivation in order to develop a sustainable process for industrial applications. The catalytic systems studied in this work are:- Ni and Ni-MgO catalysts- Catalysts based on Ni/Mg/Al Hydrotalcite-like compounds- Ni-Mordenite catalysts with different Ni contents and prepared by different methodsThe bulk Ni catalysts tested present high selectivity to 2-phenylethanol (60-95%) despite their different conversion values. There is some relation between the particles morphology, and the formation of condensation products, which block the active centres, deactivating the catalyst. Catalysts with commercial MgO (4NiMgO and NiMgO) present conversion and selectivity to 2-phenylethanol values that increase when the content of magnesia increases arriving to 100% for the catalyst NiMgO after 6 hours of reaction at room temperature. The TPD-CO2 profile for this catalyst showed the disappearance of the peak corresponding to the weaker basic sites of commercial magnesia. This means that there is some influence between the nickel particles and these basic sites that favour the formation of 2-phenylethanol and minimizes other side reactions.The rest of prepared Ni-MgO catalysts showed higher amounts of basic sites available which are responsible for the formation of condensation products explaining their lower activity.The use of microwaves during aging gives hydrotalcites with higher crystallinity in shorter times. Also, they have some different properties depend on the aging procedure. Thus, the hydrotalcite aged in an autoclave under microwaves at the highest temperature (453 K) and at longest time (120 min) presents higher BET area and higher basicity than the rest of prepared samples. These results could be related to the appearance of a new mesoporosity as a consequence of the dealumination of the hydrotalcite layers due to some local overheating during the microwaves treatment of this sample. The catalysts obtained from the hydrotalcites aged under microwaves had higher metallic areas than the rest of catalysts. All catalysts showed total conversion and 95% of selectivity to 2-phenylethanol after 1h of reaction at room temperature. After reusing them ten times, they maintain high conversion and high selectivity to 2-phenylethanol.Respect to the Ni-mordenite samples prepared by liquid exchange, we obtained 84 % of exchanged Ni2+ when we submitted the mordenite exchanged under microwaves at 333K for 15 minutes to a thermal treatment under microwaves followed by a second exchange process at the same conditions than the first exchange. This value of exchanged Ni2+ is the highest value found in the literature for this kind of samples. We also observed that the use of microwaves allows us to obtain Ni-mordenites with different acidic properties.The catalysts obtained from the samples exchanged by microwaves or by conventional method in the liquid phase did not show metallic areas, explaining their null activity. In contrast, the Ni-Mordenite catalysts prepared in solid state showed the formation of 2-phenylethanol which is detected in higher amounts for the catalysts with higher metallic area. These results allow us to conclude that there is a competition between the acidic and metallic sites in these catalytic systems for this reaction.In this Doctoral Thesis we present an alternative to obtain 2-phenylethanol, alcohol with a great industrial interest, by using a cleaner and more sustainable process.