Platinum incorporated into the SBA-15 mesostructure via deposition-precipitation method: Pt nanoparticle size estimation and catalytic testing

We report the use of the deposition precipitation (DP) method for the functionalization of mesoporous silica SBA-15 with Pt. [Pt(NH3)(4)](OH)(2) was used as a platinum precursor. Experiments were performed at 90 degrees C, and urea was used to control the pH during precipitation. From the obtained pH profiles, an interaction between the support and the precipitating species is suggested. A general formula of the species is proposed to be [Pt-II(OH)(n)](s)(II-n). By Transmission electron microscopy (TEM) it is shown that the majority of Pt nanoparticles on SBA-15 reside in the range between 2 and 4 nm. However, particles in the range of 15 nm were also detected, which indicates that the precipitation does not occur exclusively within the channels of the SBA-15. The obtained material is compared to a reference catalyst, Pt/SBA-15, prepared by a conventional wet impregnation method. Here, larger Pt nanoparticles (4-6 nm) were detected. The catalysts were found to exhibit comparable activity in toluene hydrogenation in terms of turnover frequency based on CO chemisorption.