High‐Temperature‐Stable and Regenerable Catalysts: Platinum Nanoparticles in Aligned Mesoporous Silica Wells

Abstract

We report the synthesis, structural characterization, thermal stability study, and regeneration of nanostructured catalysts made of 2.9 nm Pt nanoparticles sandwiched between a 180 nm SiO2 core and a mesoporous SiO2 shell. The SiO2 shell consists of 2.5 nm channels that are aligned perpendicular to the surface of the SiO2 core. The nanostructure mimics Pt nanoparticles that sit in mesoporous SiO2 wells (Pt@MSWs). By using synchrotron-based small-angle X-ray scattering, we were able to prove the ordered structure of the aligned mesoporous shell. By using high-temperature cyclohexane dehydrogenation as a model reaction, we found that the Pt@MSWs of different well depths showed stable activity at 500 °C after the induction period. Conversely, a control catalyst, SiO2 -sphere-supported Pt nanoparticles without a mesoporous SiO2 shell (Pt/SiO2 ), was deactivated. We deliberately deactivated the Pt@MSWs catalyst with a 50 nm deep well by using carbon deposition induced by a low H2 /cyclohexane ratio. The deactivated Pt@MSWs catalyst was regenerated by calcination at 500 °C with 20 % O2 balanced with He. After the regeneration treatments, the activity of the Pt@MSWs catalyst was fully restored. Our results suggest that the nanostructured catalysts-Pt nanoparticles confined inside mesoporous SiO2 wells-are stable and regenerable for treatments and reactions that require high temperatures.

Explaining the Size Dependence in Platinum‐Nanoparticle‐Catalyzed Hydrogenation Reactions

“…However, substantial challenges still remain when these nanoparticles are used as the catalyst for many organic syntheses. These challenges include that the systematic relationship between the properties of metal nanoparticles and their catalytic performance is yet to be fully established, and that the stabilization and precise size engineering of these catalysts are difficult, especially of ultrasmall one . In a more specific scenario, supported Pt nanoparticles (PtNPs) are promising candidates for various hydrogenation reactions.…”

Explaining the Size Dependence in Platinum‐Nanoparticle‐Catalyzed Hydrogenation Reactions

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] However,substantial challenges still remain when these nanoparticles are used as the catalyst for many organic syntheses.T hese challenges include that the systematic relationship between the proper-ties of metal nanoparticles and their catalytic performance is yet to be fully established, and that the stabilization and precise size engineering of these catalysts are difficult, especially of ultrasmall one. [15][16][17][18][19] In am ore specific scenario, supported Pt nanoparticles (PtNPs) are promising candidates for various hydrogenation reactions.H owever,m any synthetic PtNPs show low catalytic activity in hydrogenation of certain functionalities and undesired selectivity when dealing with multifunctional molecules. [20,21] In the regioselective hydrogenation of quinoline with hydrogen, which is important for the synthesis of many biologically active molecules, [22] both homo-and heterogeneous catalytic systems have been developed including transition-metal complexes [23][24][25][26] and nanoparticles.…”

Design of Efficient Noble Metal Free Copper‐Promoted Nickel‐Ceria‐Zirconia Nanocatalyst for Bio‐Fuel Upgrading

“…The decarbonylation of the aldehyde group was promoted at high temperature and some undesired side reactions occurred including demethoxylation and HDO/demethylation by catalyst deactivation . It was reported hat elevated temperature accelerated the reaction and deactivated the catalyst, due to the sintering or coalescence of metal NPs, producing undesired products . We also conducted vanillin HDO over Cu−Ni/CZ‐ B with various solvents including isopropanol, water, and isopropanol/water mixture (Figure S1, SI).…”