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[en] Dehydrogenation of propane (DHP) was studied over a series of Cr2O3-Al2O3 and Cr2O3-SiO2 catalysts, prepared by incipient wetness impregnation and sol gel (SG) method, respectively, to gain a better understanding of the nature and distribution of chromium (Cr) species and their catalytic function. To this end, the catalysts were characterized by N2-physisorption and X-ray diffraction (XRD). N2-physisorption analysis of Cr2O3-SiO2 showed the relatively higher surface area of 391.1 m2/g, compared with Cr2O3-Al2O3 of 224.3 m2/g. The combination method of sol gel and sonothermal also produced smaller particles size of catalyst with higher microporosity of 23.5 % and smaller pores size of 6 nm. The good surface properties of Cr2O3-SiO2 enabled the high conversion of propane of 55 % at 550 degree Celsius. At higher temperature of 600 degree Celsius, the Cr species might be reduced into lower oxidation state and inhibit the catalytic behavior to produce hydrogen. (author)
[en] Hydrogen storage system development is a key enabling technology for the widespread introduction of hydrogen fuel cells. We have developed novel liquid-phase materials that undergo catalytic hydrogenation at the hydrogen production location, and are readily de-hydrogenated at the point of use. This material-based hydrogen storage approach provides a liquid fuel paradigm where the consumer and other participants within the supply chain never come into contact with gaseous or liquid hydrogen. In addition to removing hydrogen from the supply chain, this approach provides the opportunity to build on the current liquid fuel infrastructure for a smooth fuel transition. Technical details of the approach, additional advantages over other hydrogen storage technologies, and remaining challenges will be covered. (authors)
[en] The dehydrogenation of cycloalkanes can be effected under mild conditions in the presence of a group VIII C-H bond activation catalyst and an uranium hydrogen sponge. The reaction between a cyclohexane substrate and active uranium, U*, in the presence of the group VIII catalyst quantitatively yields UH3 and the corresponding aromatic hydrocarbon. The uranium hydride UH3 is subsequently heated to evolve hydrogen gas and regenerate U*. The physical separation of the catalyst from the uranium sponge prevents the sintering of the uranium metallic particles. The addition of titanium hydride, as a diluent, to the uranium also aids in maintaining the uranium in a highly dispersed state
[en] Cyclohexanone is important intermediate for the manufacture of caprolactam which is monomer of nylron. Cyclohexanone is generally produced by dehydrogenation reaction of cyclohexanol. In this study, highly mesoporous metal oxides such as meso-WO3, meso-TiO2, meso-Fe2O3, meso-CuO, meso-SnO2 and meso-NiO were synthesized using mesoporous silica KIT-6 as a hard template via nano-replication method for dehydrogenation of cyclohexanol. The overall conversion of cyclohexanol followed a general order: meso-WO3 >> meso-Fe2O3 > meso-SnO2 > meso-TiO2 > meso-NiO > meso-CuO. In particular, meso-WO3 significantly showed higher activity than the other mesoporous metal oxides. Therefore, the meso-WO3 has wide range of application possibilities for dehydrogenation of cyclohexanol
[en] We present here, anaesthesia management of a patient having glucose-6-phosphate dehydrogenase (G6PD) deficiency who underwent thyroidectomy. The main concern is to avoid any precipitating factor which could lead to oxidative stress in these patients. There is very limited data available on anaesthesia management of thyroid surgery in such patients. (author)
[en] Conversion of cyclohexanol has been used to investigate the deactivation modes of the HZSM-5, AIPO4-5 and MnAPSO-5. Conversion of cyclohexanol as a test reaction was used to evaluate the activity of these catalysts
[en] The development of novel and practical synthetic methods with a minimum number of operations for the construction of bioactive structurally complex compounds is a major challenge in synthetic organic chemistry. Recently, we reported an efficient method for the stereoselective synthesis of 2,3-disubstituted indoline derivatives; cis-2,3-disubstituted indolines were obtained by the aza-alkylation/Michael cascade reaction of 2-(tosylamino)phenyl α,β-unsaturated ketones with α-bromoacetophenones in good yields and with excellent diastereoselectivities (Scheme 2, Eq. (1)). Among the available synthetic strategies, domino or cascade reactions have received wide acceptance as highly efficient and powerful methods for the synthesis of molecules with a high structural complexity. An efficient synthesis of 2,3-disubstituted indoles was developed by the domino aza-alkylation/intramolecular Michael reaction of 2-(tosylamino)phenyl α,β-unsaturated ketones with α-bromoacetophenones, followed by desulfonative dehydrogenation with DBU. The reaction afforded structurally diverse and highly functionalized 2,3-disubstituted indoles in moderate to excellent yields (up to 99%). The synthesis of 2,3-disubstituted indoles without desulfonation through DDQ-induced oxidative dehydrogenation was also achieved.
[en] Koser’s reagent is found to be effective in the oxidative double dehydrogenation of various carbocyclic β-dicarbonyl compounds, which constitutes the first example on dehydrogenation reactivity of hypervalent iodine(III) reagents for carbocyclic carbonyl compounds. DFT calculations reveal that the rate-determining step is the electrophilic addition of PhI+OH onto enolate of monodehydrogenated product.
[en] The possibilities of hydrogen storage using borohydrides are presented and discussed specially in regard of the recoverable hydrogen amount and related to the recovering conditions. A rapid analysis of storage possibilities is proposed taking in account the two main ways for hydrogen evolution: the dehydrogenation obtained through thermal decomposition or the hydrolysis of solids or solutions. The recoverable hydrogen is related to the dehydrogenation conditions and the real hydrogen useful percentage is determined for each case of use. The high temperature required for dehydrogenation even when using catalyzed compounds lead to poor outlooks for this storage way. The hydrolysis conditions direct the chemical yield of the water consuming, and this must be related to the experimental conditions which rule the storage capacity of the 'fuel' derived from the borohydride. (authors)