Search

The effect of reaction conditions for direct oxidation of methane to methanol over Fe-MFI zeolite with H2O2 has been investigated. Sulfolane has been proved to be an efficient solvent for liquid-phase methane oxidation. A sulfolane/water mixture with an appropriate proportion led to an extremely high methanol production with a high selectivity. [ABSTRACT FROM AUTHOR]

A novel strategy for the synthesis of microporous crystalline titanosilicate catalyst (TS-1) was developed based on the combination of liquid-phase and solid-phase transformation mechanisms. The core concept of this strategy was to crystallize the mixed precursors composed of both liquid-phase and solid-phase precursors. The anionic polyelectrolyte poly(acrylic acid) was used as a unique gelating agent to prepare the solid/liquid mixture, which can partly convert the liquid-phase precursor to the solid-phase precursor. Active framework Ti was formed by in situ conversion of the Ti species from the solid-phase precursor during the crystallization stage, as well as by the transfer of Ti species from the liquid-phase precursor to the solid crystal after the crystallization. In this way, the content of active Ti in TS-1 was significantly increased. The obtained product displayed high activity for the oxidation reaction of n-hexane and 1-hexene. [ABSTRACT FROM AUTHOR]

Cr/silicalite-1 and Cr/H[B]MFI catalysts were prepared by the impregnation method, and Cr/H[B]MFI were further treated by steaming. The catalysts were employed for the oxidative dehydrogenation of propane to propylene with CO as the oxidant. Cr/H[B]MFI showed significantly higher catalytic activity than Cr/silicalite-1, and steamed Cr/H[B]MFI was superior in the reaction stability to Cr/H[B]MFI. The nature of the supported chromium species have been characterized by a number of physicochemical techniques, such as Raman, UV-vis and NMR. It is concluded that the steaming led to the auto-reduction of some Cr to Cr, and resultant Cr species might be located near the boron center in the borosilicate framework to counterbalance the negative charge of the framework. The transformation of Cr species to Cr species, facilitated by the steaming process and the presence of boron in the catalyst, is responsible for the enhanced stability of oxidative dehydrogenation of propane to propylene with carbon dioxide as the oxidant. Graphical Abstract: Steaming treatment of Cr/H[B]MFI resulted in enhanced catalytic stability in the dehydrogenation of propane to propylene with CO as oxidant, probably due to the transformation of some Cr species to Cr ones. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Fe, V, or Cu oxide was mixed in mesoporous Nb[sub2]O[sub5], at a few atom percent, and their extremely high dispersion was confirmed by elemental analysis in about 5-nm spots using TEMEDS. These mesoporous Nb[sub2]O[sub5] showed characteristic selectivity for cyclohexene oxidation depending on the kind of the doped metal oxide. [ABSTRACT FROM AUTHOR]

Abstract: The conventional IR method was improved for the in situ observation of oxidation of alkenes with an aqueous solution of H2O2 over heterogeneous catalysts. The reactions of 1-hexene and cyclohexene with H2O2 over TS-1 were successfully observed. In the case of 1-hexene, gradual formation of 1,2-epoxyhexane was observed. On the other hand, 1,2-epoxycyclohexane was not detected but production of 1,2-cyclohexanediol was observed in the case of cyclohexene. This is due to the rapid hydrolysis of 1,2-epoxycyclohexane, which conflicts with the highest selectivity for 1,2-epoxycyclohexane in the liquid phase reaction over TS-1. The controversy is discussed in the text. In addition, the rate of the hydrolysis of 1,2-epoxyhexane with H2O was far lower than that with H2O2, indicating that protons, which are formed by the reaction of H2O2 on Ti sites of TS-1, are responsible for the hydrolysis of epoxides. [ABSTRACT FROM AUTHOR]

Sn-containing mesoporous silica nanospheres (Sn-MSNSs) with uniform crater-like mesopores were successfully synthesized by a direct synthetic method. The effects of Sn content and calcination temperature on the structural properties of Sn-MSNSs were investigated. Moreover, the catalytic performance of Sn-MSNSs in the Baeyer–Villiger (BV) oxidation of bulky cyclic ketone with hydrogen peroxide (H 2 O 2 ) was studied. Compared with Sn-MCM-41, which possessed long mesopores, Sn-MSNSs with high hydrophobicity provided by high-temperature calcination exhibited much higher activity in the BV oxidation of bulky cyclic ketone, 2-adamantanone. [ABSTRACT FROM AUTHOR]

A Co/TiO2 catalyst shows high activity in the dehydrogenation of various secondary alcohols (I) and (III) to afford the corresponding ketones. [ABSTRACT FROM AUTHOR]