Synthesis and characterization of catalysts based on ligand‐stabilized clusters incorporated in mesoporous oxides

Abstract

MCM 41 was loaded with ligand-stabilized palladium clusters in the size range of 3-4 nm via different pathways. A mixture of seven- and eight-shell clusters (Pd7/8(phen)) was directly introduced into the mesoporous structure during the synthesis of MCM 41 as well by incipient wetness impregnation. The Samples were characterized by X-ray diffraction, N²-sorption, DTA and TEM. The clusters show different thermal stability depending on the synthesis pathway used. In situ incorporation leads to a decomposition of the Pd clusters after calcination at 873 K. However, the clusters that were introduced by incipient wetness impregnation are thermally stable up to 513 K in air. As a first catalytic test the oxidation of CO with synthetic air was used. Compared to catalysts prepared by conventional methods with appropriate palladium salts, the impregnated samples show high activity in the CO oxidation

Inclusion Chemistry in Periodic Mesoporous Hosts

“…The catalytic activity of small palladium clusters supported on MCM materials was tested in several reactions. Schüth et al used a novel method to support monodispersed, preformed Pt clusters on MCM-41. The clusters were synthesized by reduction of Pd(II) acetate in the presence of stabilizing phenantroline ligands, and the clusters with seven and eight-shells of Pd, Pd7/8(phen), were isolated.…”

Host−Guest Chemistry Using an Oriented Mesoporous Host: Alignment and Isolation of a Semiconducting Polymer in the Nanopores of an Ordered Silica Matrix

“…Recent attempts have thus been made to use surfactant templated porous silicas as hosts for new nanostructured composite materials. Efforts have been made to incorporate catalytic clusters, − confine graphitic carbon, and synthesize semiconductor filaments and polymers − within the pores of ordered silica matrixes. Potential applications for such composites range from size selective catalysts and chemical sensors to nanoscale electronics.…”

A new palladium nanoparticle catalyst on mesoporous silica prepared from a molecular cluster precursor

“…Trimethylphosphine, bis(dibenzylidene acetone) palladium, tetraamine palladium(II) chloride, palladium acetate, palladium acetylacetonate, disodium tetrachloropalladate, hexadecyltrimethylammonium chloride solution (CTACl, 25% in water), tetradecyltrimethylammonium bromide (TTABr), sodium aluminate, and crotonic acid (trans-2-butenoic acid) were purchased from Sigma-Aldrich. Sodium water glass (SiO 2 25.5-28.5% in water) was purchased from Merck. Aerosil 380 was obtained from Degussa.…”

“…Metal loading of MCM-41 was performed, e.g., by conventional ionexchange methods 22 or vapor deposition of volatile palladium complexes 23 generating active catalysts for the hydrogenation of acetylenics or Heck reactions. Platinum particles which were directly synthesized on a MCM-41 support 24 as well as preformed, phenanthroline-stabilized palladium particles which were combined with MCM-41 25 were shown to represent active catalysts for low temperature oxidation of carbon monoxide. Moreover, the high concentration of silanol groups per unit weight has led to the exploitation of M41S materials as support for anchored catalysts, derived from organometallic complexes 26-30 and defined cluster molecules.…”