Search

Abstract: Organotin compounds of (MeO)2ClSi(CH2)3SnCl3 have been grafted on a series of mesosporous silicas, as proved by XRD, N2 adsorption/desorption experiments and FTIR, diffuse reflectance UV–vis and 13C CP/MAS NMR spectroscopies. A further substitution of Cl− bonded to Sn4+ by CH3O− led to the formation of a series of active heterogeneous catalysts for the direct synthesis of dimethyl carbonate from methanol and CO2. The catalytic properties of these catalysts depended on the structure, crystal size and surface properties of mesoporous silicas. SBA-15 as a host was superior to SBA-16 and large-pore Ia3d. In addition, the methods used for removing surfactants occluded in mesoporous silicas had strong influences on the catalytic performance as a result of significantly affecting the surface areas and the concentrations of surface hydroxyl groups of the mesoporous silicas. The extraction of surfactants by an ethanol–HCl solution should be available. An increase in the reaction time, reaction temperature, methanol amount and CO2 pressure significantly increased the dimethyl carbonate yield before reaching thermodynamic equilibrium. The dimethyl carbonate yield could also be increased by adding dehydration agents to the reaction system. 2,2-Dimethoxypropane gave a much higher dimethyl carbonate yield than 3A molecular sieve and tetramethyl orthorsilicate. The prepared organotin/mesoporous silica catalysts were highly stable, as corroborated by the findings that the dimethyl carbonate yield obtained over the SBA-15-immoilized organotin compound did not decrease within six repeated runs with regeneration under the same reaction conditions and that the tetrahedral coordination state of Sn species was maintained after reaction. [Copyright &y& Elsevier]

Abstract: A series of Ru(III) tetrahydro-Schiff base complexes (denoted as Ru[H4]-Schiff base with Schiff base=salen, salpn and salcn, see ) were encapsulated in the supercages of zeolite Y by flexible ligand method. The prepared catalysts were characterized by X-ray diffraction, diffuse reflectance UV–Vis spectroscopy, Infrared spectroscopy, elemental analysis, as well as N2 adsorption techniques. It was shown that upon encapsulation in zeolite Y, Ru(III) tetrahydro-Schiff base complexes exhibited higher activity for the hydrogenation of benzene than the corresponding Ru(III)-Schiff base complexes. This indicates that hydrogenation of the C the Schiff base ligands led to a modification of the coordination environment of the central Ru(III) cations. The stability of the prepared catalysts has also been confirmed against leaching of the complex molecule from the zeolite cavities, as revealed by the result that no loss of catalytic activity was observed within three successive runs with regeneration. [Copyright &y& Elsevier]

Ir/H-SSZ-13 catalysts were used for methylcyclopentane (MCP) ring-opening (RO) reaction, and exhibit higher yields to RO products than H-ZSM-5, H-USY and Al 2 O 3 supported Ir catalysts. Ir species supported on H-SSZ-13-A (about 200 nm) exhibits higher activity than those on H-SSZ-13-B (about 8 μm) due to its more accessible acid sites. Ir/H-SSZ-13-A gives higher reactivity than Ir/Al 2 O 3 , especially in the case of low Ir loading because of the promotion of the strong acid sites located on the external surface of H-SSZ-13-A. This work demonstrates that SSZ-13 supported metal is a potential catalyst for RO reaction. [Display omitted] • Ir/H-SSZ-13 was used as catalyst for methylcyclopentane (MCP) ring-opening (RO) reaction. • Ir/H-SSZ-13 shows a higher yield to RO products than ZSM-5, USY and Al 2 O 3 supported Ir catalysts. • The acid sites on the external surface of SSZ-13 promote the activity of the supported Ir species. • This work expands the application range of SSZ-13. [ABSTRACT FROM AUTHOR]