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H2 Pressure (h2 + pressure)
Selected AbstractsAllyl-Functionalised Ionic Liquids: Synthesis, Characterisation, and ReactivityHELVETICA CHIMICA ACTA, Issue 3 2005Dongbin Zhao The two known Me- and allyl-substituted 1H -imidazol-3-ium bromides 1 and 2, respectively, were converted to the corresponding BF and BPh salts 3,6 (Scheme,1). Compounds 3 and 4 were liquids at ambient temperature. Reaction of 1 or 2 with [PdCl2] afforded the corresponding 2,:,1 imidazolium/metal complexes 7 and 8. The latter complex, melting at 58°, can be regarded as a ,true' ionic liquid. Attempts to polymerise 7 by radical promotion (AIBN) were unsuccessful, but resulted in the centrosymmetric 2,:,1 complex 9. The allyl group of 1 could be arylated (giving rise to 10) or hydrogenated (at 100,bar H2 pressure). The solid-state structures of compounds 5,7 and 9 were solved by means of single-crystal X-ray analyses (Figs.,1,4). [source] Combustion-type hydrogenation of nanostructured Mg-based composites for hydrogen storageINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2009M. V. Lototsky Abstract In this study Reactive Ball Milling in hydrogen gas was used to synthesize nanostructured hydrogenated composites of Mg and V-based alloy. After hydrogen desorption, the nanocomposites exhibited a dramatic facilitation of the rate of H absorption by Mg and reduction of the temperature of onset of hydrogenation. These favourable changes were caused by a synergy of catalytic effect of the V-based alloy on hydrogen absorption by Mg and heat release caused by exothermic hydrogen absorption by the V-based alloy. When the initial interaction temperature exceeded a threshold, rather low, value of 20,125°C, depending on the H2 pressure, composition of the sample and its total amount, a combustion-type hydrogenation took place. With optimal interaction parameters applied, H absorption was completed in just 5,70,s and was accompanied by a significant heat release. The observed features can be utilized to reach fast recharge of the Mg-based H stores and to develop efficient heat management systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Production of bio-crude from forestry waste by hydro-liquefaction in sub-/super-critical methanolAICHE JOURNAL, Issue 3 2009Yun Yang Abstract Hydro-liquefaction of a woody biomass (birch powder) in sub-/super-critical methanol without and with catalysts was investigated with an autoclave reactor at temperatures of 473,673 K and an initial pressure of hydrogen varying from 2.0 to 10.0 MPa. The liquid products were separated into water soluble oil and heavy oil (as bio-crude) by extraction with water and acetone. Without catalyst, the yields of heavy oil and water soluble oil were in the ranges of 2.4,25.5 wt % and 1.2,17.0 wt %, respectively, depending strongly on reaction temperature, reaction time, and initial pressure of hydrogen. The optimum temperature for the production of heavy oil and water soluble oil was found to be at around 623 K, whereas a longer residence time and a lower initial H2 pressure were found to be favorite conditions for the oil production. Addition of a basic catalyst, such as NaOH, K2CO3, and Rb2CO3, could significantly promote biomass conversion and increase yields of oily products in the treatments at temperatures less than 573 K. The yield of heavy oil attained about 30 wt % for the liquefaction operation in the presence of 5 wt % Rb2CO3 at 573 K and 2 MPa of H2 for 60 min. The obtained heavy oil products consisted of a high concentration of phenol derivatives, esters, and benzene derivatives, and they also contained a higher concentration of carbon, a much lower concentration of oxygen, and a significantly increased heating value (>30 MJ/kg) when compared with the raw woody biomass. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Aqueous phase carbon dioxide and bicarbonate hydrogenation catalyzed by cyclopentadienyl ruthenium complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2007Sylvain S. Bosquain Abstract The water-soluble ruthenium(II) complexes [Cp,RuX(PTA)2]Y and [CpRuCl(PPh3)(mPTA)]OTf (Cp, = Cp, Cp*, X = Cl and Y = nil; or X = MeCN and Y = PF6; PTA = 1,3,5-triaza-7-phosphaadamantane; mPTA = 1-methyl-1,3,5-triaza-7-phosphaadamantane) were used as catalyst precursors for the hydrogenation of CO2 and bicarbonate in aqueous solutions, in the absence of amines or other additives, under relatively mild conditions (100 bar H2, 30,80 °C), with moderate activities. Kinetic studies showed that the hydrogenation of HCO3, proceeds without an induction period, and that the rate strongly depends on the pH of the reaction medium. High-pressure multinuclear NMR spectroscopy revealed that the ruthenium(II) chloride precursors are quantitatively converted into the corresponding hydrides under H2 pressure. Copyright © 2007 John Wiley & Sons, Ltd. [source] Carbohydrate-Derived 1,3-Diphosphite Ligands as Chiral Nanoparticle Stabilizers: Promising Catalytic Systems for Asymmetric HydrogenationCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 8 2009Aitor Gual Dr. Abstract Metallic Ru, Rh, and Ir nanoparticles were prepared by the decomposition of organometallic precursors under H2 pressure in the presence of 1,3-diphosphite ligands, derived from carbohydrates, as stabilizing agents. Structural modifications to the diphosphite backbone were found to influence the nanoparticles, size, dispersion, and catalytic activity. In the hydrogenation of o - and m -methylanisole, the Rh nanoparticles showed higher catalytic activity than the corresponding Ru nanoparticles. The Ir nanoparticles presented the lowest catalytic activity of the series. In all cases, the hydrogenation of o -methylanisole gave total selectivity for the cis -product, however, the ee of the product was always less than 6,%. A maximum of 81,% cis -selectivity was obtained for the hydrogenation of m -methylanisole, however, no asymmetric induction was observed. These results show that the catalytic activity is affected by a combination of influences from the substrate, the diphosphite ligands, and the metallic nanoparticles. [source] Synthesis of ethylene/propylene elastomers containing a terminal reactive group: The combination of metallocene catalysis and control chain transfer reactionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2005U. Kandil Abstract This article discusses a chemical route to prepare new ethylene/propylene copolymers (EP) containing a terminal reactive group, such as ,-CH3 and OH. The chemistry involves metallocene-mediated ethylene/propylene copolymerization in the presence of a consecutive chain transfer agent,a mixture of hydrogen and styrene derivatives carrying a CH3 (p -MS) or a silane-protected OH (St-OSi). The major challenge is to find suitable reaction conditions that can simultaneously carry out effective ethylene/propylene copolymerization and incorporation of the styrenic molecule (St-f) at the polymer chain end, in other words, altering the St-f incorporation mode from copolymerization to chain transfer. A systematic study was conducted to examine several metallocene catalyst systems and reaction conditions. Both [(C5Me4)SiMe2N(t -Bu)]TiCl2 and rac-Et(Ind)2ZrCl2, under certain H2 pressures, were found to be suitable catalyst systems to perform the combined task. A broad range of St-f terminated EP copolymers (EP- t -p-MS and EP- t -St-OH), with various compositions and molecular weights, have been prepared with polymer molecular weight inversely proportional to the molar ratio of [St-f]/[monomer]. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1858,1872, 2005 [source] | ||||||||||