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Abstract: Acidity adjustment of MCM-22 was carried out by hydrothermal treatment of parent MCM-22 with flowing pure steam at high temperature. XRD, SEM and N2 adsorption/desorption results indicated that the crystallinity and pore properties of MCM-22 were affected slightly by hydrothermal treatment at different temperatures. NH3-TPD and FT-IR with pyridine adsorption showed only a slight decrease in Brønsted acid sites, compared with parent MCM-22, with hydrothermal treatment temperature in the range 773–873K. The strength of Brønsted acid sites was reduced severely at hydrothermal treatment temperatures of 973 and 1073K. The Lewis acid sites were only slightly affected by hydrothermal treatment. A substantial improvement in ethylbenzene selectivity along with a slight decrease in benzene conversion was achieved in catalytic synthesis of ethylbenzene by alkylation of benzene with diethyl carbonate over MCM-22 hydrothermally treated at 873K. A sharp decrease in benzene conversion was detected over MCM-22 hydrothermally treated at 973K. The results indicate that alkylation of benzene with diethyl carbonate occurred mainly on Brønsted acid sites, and the effect of Lewis acid sites on the alkylation process is negligible. Reduction of Brønsted acid sites of the catalyst can suppress side reactions and improve selectivity for ethylbenzene. It was found that a particular acid strength of catalyst was required to maintain high benzene conversion and ethylbenzene selectivity. [Copyright &y& Elsevier]

A diastereoselective catalytic asymmetric hydrophosphination reaction was performed using a palladacycle catalyst to produce chiral PCP phosphine ligand with high dr (95:5) and excellent enantioselectivity (>99% ee). Subsequent facile metalation of the chiral ligand with Pt and Pd metal salts yielded the desired pincer complexes. The protonated form of these pincer complexes was also synthesised, and their structures were confirmed through the use of X-ray crystal diffraction and NMR spectroscopy analyses. [ABSTRACT FROM AUTHOR]

A series of B 2 O 3 /HZSM-5 catalysts were prepared by impregnation of HZSM-5 zeolites with triethyl borate, trimethyl borate and boric acid. The selective synthesis of para -diethylbenzene by alkylation of ethylbenzene with diethyl carbonate was carried out over the B 2 O 3 /HZSM-5 catalysts. The physicochemical properties of the catalysts were characterized by X-ray diffraction, N 2 adsorption–desorption, Fourier-transform infrared spectroscopy with pyridine adsorption and NH 3 temperature programmed desorption. The characterization results indicated that the 15% B 2 O 3 /HZSM-5 catalyst prepared by using triethyl borate as the precursor exhibited an outstanding shape-selectivity along with a high catalytic activity in alkylation of ethylbenzene with diethyl carbonate. This might be ascribed to the large molecular size of triethyl borate, which would lead to the formation of B 2 O 3 on the external surface of HZSM-5 zeolite and preserve the acid sites in the micropores of HZSM-5 zeolite. By contrast, the B 2 O 3 /HZSM-5 catalysts prepared by using trimethyl borate or boric acid led to the severe reduction in catalytic activity, which was attributed to the decrease in the amount of the total acid sites caused by the blockage of the partial pores of HZSM-5 zeolite. [ABSTRACT FROM AUTHOR]

Abstract: An organopalladium complex containing orthometalated (R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used to promote the asymmetric hydroalkoxylation reactions between weak nucleophile methanol and 1,1-bis(diphenylphosphino)ethylene or 1,1-bis(diphenylphosphino)ethylene monoxide in good regio- and stereo-selectivities in the presence of an external base. The major addition product obtained from methanol and 1,1-bis(diphenylphosphino)ethylene monoxide was subsequently isolated in a quantitative yield in its configurationally pure form and characterized by means of two-dimensional rotating-frame nuclear Overhauser enhancement (ROESY) NMR spectroscopy as well as single crystal X-ray diffraction analysis. The enantiomerically pure bis-phosphine monoxide ligand was subsequently liberated in high yield. [ABSTRACT FROM AUTHOR]

Abstract: A promising electrochemical sensor for sensitive determination of nitrite was fabricated by construction of Au nanoparticles on the surface of choline chloride (Ch) modified glassy carbon electrode (GCE). Field emission scanning electron microscope, powder X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical techniques were used for the surface characterization of the modified electrode. It was demonstrated that Ch was covalently immobilized onto the GCE surface forming a planted Ch monolayer, which could provide a suitable supporting material for the construction of Au nanoparticles. As a result, the Au nanoparticles with average size of about 110nm were assembled to form a flowerlike structure on the surface of Ch monolayer. Moreover, the uniform nano-Au/Ch film exhibited remarkable electrocatalytic activity towards the oxidation of nitrite with obvious reduction of overpotential. Under the optimum conditions, the linear range for the detection of nitrite was 4.0×10−7 to 7.5×10−4 M with a high sensitivity of 0.354μAμM−1, and a low detection limit of 1.0×10−7 M. The proposed method was successfully applied in the detection of nitrite in water samples and sausage samples, and the results were consistent with those obtained by ion chromatography and UV–visible spectrophotometric methods. [Copyright &y& Elsevier]