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Abstract: This paper presents the results of catalytic endo- to exo-isomerization of tetrahydrodicyclopentadiene. Several zeolites were tested and influences of calcinations temperatures, Si/Al ratio and cations of the zeolites on the reaction were investigated. The results showed that HY zeolites were more active than other zeolites and Y zeolites with other cations, because of its large pore size and relative strong acidity. In all HY zeolites with different Si/Al, H-USY is best. On one hand, H-USY has more moderate acids than others. On the other hand, the high thermal stability of H-USY makes it suitable choice for recycling catalysts. In all the zeolites tested, H-USY calcined at 450°C was favorable. Regeneration of H-USY showed no decrease of exo-yield while had better exo-selectivity. [Copyright &y& Elsevier]

Abstract: The production of epichlorohydrin with hydrogen peroxide is an environmentally benign process, but the relatively high cost of hydrogen peroxide prevents it from being commercialized. In the present work, the production of epichlorohydrin by epoxidation of allyl chloride with molecular oxygen in the presence of 2-ethyl anthrahydroquinone using TS-1 as the catalyst was studied. The catalysts after reaction were characterized with FT-IR and TGA. The reaction results showed that the heterogeneous reaction could be carried out under mild conditions, and the addition of methanol solvent could increase the yield of the product. It was found that the concentration of 2-ethylanthrahydroquinone in the working solution should not be too high, otherwise, it would decrease the yield of the product. The product and unreacted reactants could be separated simply by distillation. [Copyright &y& Elsevier]

Abstract: The phase-transfer catalytic epoxidation of hydroxyl-terminated polybutadiene (HTPB) by hydrogen peroxide was investigated by using quaternary ammonium salts, ammonium tungstate hydrate and phosphoric acid as the phase-transfer catalyst and cocatalysts, respectively. The influences of quaternary ammonium salts, the amount of Aliquat 336 and hydrogen peroxide, the molar ratio of phosphoric acid to ammonium tungstate hydrate (PO4 3−/WO4 2−), pH value and organic solvents on the conversion of double bonds in HTPB polymer were studied in detail. The kinetic of epoxidation of HTPB was also discussed and the apparent activated energy for epoxidation of HTPB was estimated to be 21.04kJ/mol. [Copyright &y& Elsevier]

Abstract: Zn-doped and La/Zn co-doped TiO2 nanoparticles were prepared by sol–gel method and utilized as the photocatalysts for the isomerization of norbornadiene to quadricyclane that has significant potential for solar energy storage and high-energy fuel synthesis. For Zn-doped samples, Zn ions do not enter the TiO2 lattice, but distribute on the particle surface in the form of ZnO crystallites. These crystallites inhibit the agglomeration, growth and anatase-to-rutile phase transformation of TiO2. The prepared particles contain considerable amount of surface-bound OHs, especially for 1%Zn/TiO2. A red shift in the optical absorption is observed due to the electron transfer between TiO2 and ZnO. In the photocatalytic isomerization reaction, Zn-doped TiO2 exhibits higher activity than homogenous sensitizer like Ethyl Michler''s Keton, and 1%Zn/TiO2 produces the highest yield of quadricyclane. To further enhance the activity, 1%Zn/TiO2 was co-doped with La. La2O3 crystallites also distribute on the surface of TiO2, similar to the case of ZnO. The particle size is reduced to <7nm but the surface-bound OHs are decreased to some degree. There is a significant blue shift in the optical absorption with a sharply increased absorbance in the UV region due to the quantum-size effect. 5%La–1%Zn/TiO2 and 3%La–1%Zn/TiO2 exhibit higher activity compared with 1%Zn/TiO2, but higher or lower content of La is detrimental to the reaction. It is concluded that doping Zn can significantly increase the surface-bound OHs, whereas doping La reduces the particle to quantum-size at the expense of surface-bound OHs. A good compromise between the two factors eventually provides a high activity. The isomerization reaction over semiconductors is proposed to proceed through an exciplex (charge-transfer) intermediate. [Copyright &y& Elsevier]

Abstract: Continuous epoxidation of propylene with 30-wt% hydrogen peroxide in isopropyl alcohol solvent over titanium silicalite (TS-1) zeolite was carried out and the good selectivity to propylene oxide and stability of TS-1 were obtained. After the reaction of 263h, the deactivation of the TS-1 catalyst occurred. The spent catalysts were regenerated by calcinations at 550°C for 5h, washing with isopropyl alcohol solvent or washing with dilute hydrogen peroxide, and the activity evaluation of the regenerated catalysts were studied. The deactivated and regenerated catalysts were characterized by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, 29Si magic angle spinning nuclear magnetic resonance, thermogravimetric analysis and Brunauer–Emmett–Teller method. The compositions deposited on the surface of the catalysts were collected by solvent extraction and were analyzed by gas chromatography–mass spectrometry (GC–MS). The results showed that calcination and washing with dilute hydrogen peroxide were highly effective regeneration methods and the catalytic activity of TS-1 catalysts can be mostly recovered after these treatments. Washing with isopropyl alcohol had a subtle effect in recovering the catalytic activity of the TS-1 catalyst. The major cause of the deactivation of the TS-1 catalyst for epoxidation is blocking micropores induced by bulky organic by-products formed by consecutive reactions of target reaction, such as dimerization or oligomerization of propylene oxide, etherification of propylene oxide with isopropyl alcohol. In addition, leaching of framework titanium also contributes to the deactivation of the catalyst. [Copyright &y& Elsevier]

Abstract: Pd-B/γ-Al2O3 amorphous catalysts were prepared through impregnation and KBH4 reduction for the hydrogenation of tricyclopentadiene. The effects of reduction conditions, pre-calcination and thermal annealing on the hydrogenation activity were studied. It is found that the reduction should be conducted in ice water batch with KBH4 solution added by dropping to avoid the crystallization of amorphous metals. Pre-calcination of the catalyst before reduction can increase the amount of Pd on the prepared catalyst. With pre-calcination at 200°C, the highest hydrogenation turnover frequency is obtained. The amorphous catalyst is thermally stable at temperature below 150°C. When annealed at higher temperature, the amorphous metals are gradually crystallized and the particle size is increased. After annealing at 600°C, the catalyst is uniformly crystallized. It is noticed that the size of amorphous Pd calculated from H2-adsorption is much smaller than the actual size observed by transmission electron microscope (TEM). This indicates that amorphous metal has stronger H2-adsorption ability than crystal metals with comparative particle sizes. The hydrogenation activity decreases with the increase of annealing temperature. Moreover, the hydrogenation activity is solely dependent on the amount of H2-adsorption, suggesting that the excellent performance of amorphous catalyst should be attributed to their better H2-adsorption ability. [Copyright &y& Elsevier]