The PPh3 ligand modified Rh/SiO2 catalyst for hydroformylation of olefins

A novel family of hybrid catalyst with high turnover frequency (TOF) and high selectivity towards aldehydes for hydroformylation of olefins could be successfully approached through direct coordination with the PPh3 ligand to the highly dispersed Rh metal particle precursors. A further advantage is that the catalyst is easily prepared and recyclable. The results revealed that hydroformylation of olefins to aldehydes dominantly took place on the surface of PPh3 ligand modified Rh metal particles of the hybrid catalyst. It was found that the formation of chemical coordination bond between the Rh metal particles and the lone-pair electron of PPh3 was evident through the TG and P-31 NMR measurement. Moreover, the addition of PPh3 onto the Rh/SiO2 exert a significant influence on the adsorption state of reactant CO, H-2 and C2H4 on the PPh3-Rh/SiO2 sample, which probably lead to good catalytic performances for hydroformylation of olefins. (C) 2004 Elsevier B.V. All rights reserved.

Recyclable heterogeneous Rh/SiO2 catalyst enhanced by organic PPh3 ligand

Heterogeneous PPh3-Rh/SiO2 catalysts for hydroformylation of olefins, prepared by direct doping of phosphine onto the heterogeneous Rh/SiO2 precursor, exhibited high activity and selectivity towards aldehydes, which originated from chemical coordination bond between the phosphine and Rh metal nantoparticles on the SiO2 support.

Preparation and characterization of microencapsulated hexadecane used for thermal energy storage

Polyurea microcapsules about 2.5 mum in diameter containing phase change material for thermal energy storage application were synthesized and characterized by interfacial polycondensation method with toluene-2,4-diisocyanate and ethylenediamine as monomers in an emulsion system. Hexadecane was used as a phase change material and OP, which is nonionic surfactant, and used as an emulsifier. The chemical structure and thermal behavior of the microcapsules were investigated by FTIR and thermal analysis respectively. The results show encapsulated hexadecane has a good potential as a solar energy storage material.

Effect of acid strength distribution on conversion of FCC gasoline over a ZSM-5 zeolite catalyst

Acid strength distribution and the distribution of aromatics formed in the FCC gasoline conversion reaction on a ZSM-5 zeolite with different Na contents have been studied. With increasing Na content in the ZSM-5 zeolite, the acid sites determined by NH3-TPD technique, especially the strong acid sites, clearly decrease. When used as catalyst for the aromatization reaction, the transformation of olefins in the FCC gasoline into aromatics is governed directly by the strong acid sites on the ZSM-5 catalyst. Only under the conditions that a ZSM-5 catalyst possesses suitable strong acid sites is reaction temperature favorable for the aromatics formed.

Performance improvement in direct methanol fuel cell cathode using high mesoporous area catalyst support

Black Pearls 2000 (designated as BP- 2000) and Vulcan XC-72 (designated as XC-72) carbon blacks were chosen as supports to prepare 40 wt % (the targeted value) Pt/C catalysts by a modified polyol process. The carbon blacks were characterized by N-2 adsorption and Fourier tranform infrared spectroscopy. The prepared catalysts were characterized by inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, scanning electron microscopy (SEM), in situ cyclic voltammetry, and current-voltage curves. On BP- 2000, Pt nanoparticles were larger in size and more unevenly distributed than on XC-72. It was observed by SEM that the corresponding catalyst layer on BP- 2000 was thicker than that of XC-72 based catalyst at almost the identical catalyst loading. And the BP- 2000 supported catalyst gave a better single cell performance at high current densities. These results suggest that the performance improvement is due to the enhanced oxygen diffusion and water removal capability when BP- 2000 is used as cathode catalyst support. (C) 2004 The Electrochemical Society.

Preparation of stir bars for sorptive extraction using sol-gel technology

A sol-gel coating method for the preparation of extractive phase on bars used in sorptive microextraction is described. The extraction phase of poly(dimethylsiloxane) is partially crosslinked with the sol-gel network, and the most part is physically incorporated in the network. Three aging steps at different temperatures are applied to complete the crosslinking process. Thirty-micrometer-thick coating layer is obtained by one coating process. The improved coating shows good thermal stability up to 300degreesC. Spiked aqueous samples containing n-alkanes, polycyclic aromatic hydrocarbons and organophosphorus pesticides were analyzed by using the sorptive bars and GC. The results demonstrate that it is suitable for both aploar and polar analytes. The detection limit for chrysene is 7.44 ng/L, 0.74 ng/L for C-19 and 0.9 ng/L for phorate. The extraction equilibration can be reached in less than 15 min by supersonic extraction with the bars of 30 mum coating layer. (C) 2004 Elsevier B.V. All rights reserved.

Preparation and characterization of long methacrylate monolithic column for capillary liquid chromatography

Long methacrylate monolithic columns (100 cm x 320 mum i.d.) were prepared from silanized fused-silica capillaries of 320 mum i.d. by in situ copolymerization of butyl methacrylate (BMA) with ethylene dimethacrylate (EDMA) in the presence of a suitable porogen. The separation performance and selectivity of the column were evaluated and compared with a 25 cm x 320 mum i.d. column prepared in the same way by capillary high-performance liquid chromatography (mu-HPLC) The results showed that the 1 m long monolithic column can generate 33 x 10(3) plate number and exhibited good permeability, higher sample loadability, and separation capability. (C) 2004 Elsevier B.V. All rights reserved.

Preparation of A-type zeolite membranes on nonporous metal supports by using electrophoretic technique

A-type zeolite membranes were prepared on the nonporous metal supports by using electrophoretic technique. The as-synthesized membranes were characterized by XRD and SEM. The effect of the applied potential on the formation of the A-type zeolite membrane was investigated, and the formation mechanism of zeolite membrane in the electric field was discussed. The results showed that the negative charged zeolite particles could migrate to the anode metal surface homogenously and rapidly under the action of the applied electric field, consequently formed uniform and dense membranes in short time. The applied potential had great effect on the membrane formation, and more uniform and denser zeolite membranes were prepared on the nonporous metal supports with 1 V potential.