Rh nanoparticles grafted on mesoporous silica support as a high-efficiency catalyst for Anthracene hydrogenation

Abstract

An active, efficient and easy-to-recycle rhodium catalyst was developed, characterized and applied in the hydrogenation of polyaromatic hydrocarbons (PAHs) under mild reaction conditions (40°C, H2 pressure = 4bar, t < 10min). Rhodium nanoparticles were in situ produced by the reduction of Rh3+ ions and deposited onto a previous prepared mesoporous silica support. Rh3+ reduction was carried out using molecular hydrogen (4bar) and temperature (75°C). XPS analysis reveals that the rhodium nanoparticles are present as oxidized species (Rh+1 and Rh3+) and they are reduced to the active species (Rh°) in the presence of H2 gas. After the reaction was completed the catalyst could be rapidly isolated magnetically using a Nd magnet placed on the reactor wall. Recycling studies showed that a single portion of the catalyst could be used for six successive times with no apparent loss of activity. Important features such as the reduction of the catalyst active species using H2 instead of unfriendly environmental chemicals, mild reaction temperature and pressure employed, and the possibility of multiple runs using a single portion of the catalyst are in good agreement with important green chemistry principles such as atom economy and design for energy efficiency.