Abstract
Catalytic hydrogenation is commcercially used to reduce the aromatics content from petroleum derivatives such as medium distillates, kerosene and paraffinic solvents. Due to the stringent environmental regulations, supported group VIII metals based catalysts are required to reach high rates of reaction at mild operating conditions. These catalysts are more active than the conventional hydrotreating one, although they are highly sensitive to the sulfur compounds present in the industrial feed-stocks. For these reasons, the liquid-phase hydrogenation of p-xylene (arenes) was studied over Ru and Rh dispersed on mesoporous support (MCM-41, SBA-15,…). The main goal of this work is to compare the behavior of silica supported Ru and Rh catalysts in the p-xylene hydrogenation and examine the effects of CO2-expanded liquid on the reaction performance. It is commonlly thought that rate-enhancement in catalytic hydrogenation involving CO2-expanded media is associated with an increase in the solubility of H2 in the liquid phase. Another explanation that has been proposed for the rate enhancement is that CO2 modifies the reactivity of the substrate via intermolecular interactions with its functional groups. There is also the possibility that CO2 influences the catalytic activity of small supported metal particles.