Dispersion and hydrogenation activity of surfactant-stabilized Rh(0) nanoparticles prepared on different mesoporous supports

Supported Rh(0) colloidal particles were prepared by the reduction of Rh(III) ions by sodium borohydride in the presence of N-N-dimethyl-N-cetyl-N-(2-hydroxyethyl) ammonium chloride (HEA16Cl), usually used as a stabilizing agent in solution. Tested supports were Na–Al–SBA-15, SBA-15 and CMK-3. In each case, the influence of HEA16Cl was studied by comparison with blank samples. Surfactant and rhodium uptake were evaluated by means of elemental analysis and eventually thermogravimetry. Obtained materials were also characterized by XRD, N2 sorption and TEM. Given the results, it appears that HEA16Cl promotes rhodium uptake in all cases. Most significant effects on the size and dispersion of particles were observed for the system combining HEA16Cl and Na–Al–SBA-15. All the solids prepared in this study were tested in the room temperature hydrogenation of styrene as well as that of a more demanding substrate, diphenylmethane, at 0.1 MPa of H2. All of them were generally more active than their commercial analogue (5 wt.% Rh0/C). Best catalysts, i.e., those prepared from Na–Al–SBA-15 in the presence of HEA16Cl as well as CMK-3 without HEA16Cl, allowed almost 100% yield of dicyclohexylmethane within 6 h (molar substrate/Rh = 100).

Figure optionsDownload high-quality image (260 K)Download as PowerPoint slideResearch highlights▶ Rh loading is improved after contacting supports with a stabilizing agent, HEA16Cl. ▶ HEA16Cl is needed to get well-dispersed Rh(0) particles over Al–SBA-15 and SBA-15. ▶ There is no need to use HEA16Cl in the case of CMK-3 support. ▶ Best catalysts are Rh0–Na–AlSBA (w HEA16Cl) and Rh0–CMK–NH3 (B) (w/o HEA16Cl). ▶ They are more active than commercial catalysts in the hydrogenation of aromatics.