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This work deals with the dealumination of zeolite beta under different conditions to optimize its catalytic performance. The dealumination was carried out either using oxalic or tartaric acid solution of different pH values or steaming up to 500 °C. The dealuminated zeolite samples were characterized using X-ray diffraction, N2-physisorption, ICP, 27Al NMR and NH3-TPD. Their catalytic activities were studied for acylation reaction of 2-methoxy naphthalene or naphthalene with acetic anhydride and esterification of benzyl alcohol with hexanoic acid. Among the dealuminated samples examined, those treated with oxalic acid or tartaric acid at pH 2 showed high activity. The high activity can be correlated with the relative increase in the amount of strong acid sites and with the enhanced accessibility of the reactants to the active sites, which are caused by removal of extra-framework Al species on the acid treatments. [ABSTRACT FROM AUTHOR]

Abstract: The recyclability of water-soluble ruthenium–phosphine complex catalysts was investigated in water–toluene and in water–pressurized carbon dioxide systems for selective hydrogenation of trans-cinnamaldehyde (CAL). For the first hydrogenation run, the selectivity for cinnamyl alcohol (COL) is high for both toluene and dense CO2, because of interfacial catalysis in which the reaction mainly occurs at the interface between the aqueous phase and the other toluene or dense CO2 phase. The total CAL conversion and the COL selectivity decrease on the second run, more significantly with dense CO2 than toluene. On the subsequent runs, however, less significant changes were observed. During the first run, the active metal complexes should change to much less active ones such as Ru(H)2L n (TPPTS) m (L=COL) by accumulation of the main product of COL. This structural change may occur more easily in multiphase hydrogenation with dense CO2 than that with toluene, probably because the solubility in the dense CO2 gas phase is even smaller than that in toluene. For homogeneous reaction of COL in aqueous phase, Ru(H)2L n (TPPTS) m catalyzes the isomerization to HCAL compared with the hydrogenation to hydrocinnamyl alcohol. With those complexes, however, the selectivity for COL is still comparable to that for HCAL for multiphase hydrogenation reactions because the hydrogenation of an ampholytic substrate of CAL occurs mainly at interface between water and toluene or dense CO2 gas phase. Interactions of CO2 molecules with CAL would also increase the reactivity of carbonyl group of the substrate. [Copyright &y& Elsevier]

Abstract: The selective hydrogenation of trans-cinnamaldehyde (CAL) has been investigated with several types of multiphase reaction systems using Ru–phosphine complex catalysts in the presence of high-pressure CO2. The selective formation of an unsaturated alcohol, cinnamyl alcohol (COL), can be achieved in an organic solvent free two-phase system, which includes the liquid (CAL, Ru complex) and gas (H2, CO2) phases. Both total conversion and COL selectivity are enhanced with increasing CO2 pressure. This enhancement is due to the dissolution of CO2 molecules into the CAL phase, which promotes the dissolution of H2 and activates the reactivity of the carbonyl group of CAL molecules, and a high concentration of CAL in the reaction medium. The high COL selectivity can also be obtained in three- and two-phase reaction systems, which include a gas (H2, CO2) phase, a liquid (water-dissolving Ru complex) phase, and/or another liquid phase (CAL). The COL selectivity is high irrespective of CO2 pressure because of a water–CAL interface or a water–CO2 interface as a main reaction locus, but the total conversion is not enhanced by pressurization with CO2, and it decreases at elevated CO2 pressure under the two-phase conditions because of a simple dilution effect. In contrast, the highly selective formation of COL is not possible in a homogeneous dense CO2 gas phase or in a two-phase system that includes a gas (H2) phase and a liquid (DMF, CAL, Ru complex) phase. Pressurization with CO2 is not effective in improving the conversion and COL selectivity for these systems. [Copyright &y& Elsevier]

Abstract: A catalyst system of ZnBr2/n-Bu4NI is reported for the first time as a highly efficient binary catalyst for the synthesis of styrene carbonate (SC) from styrene oxide and carbon dioxide under supercritical conditions. In a very short reaction time (30min) and even at a mild reaction temperature (80°C), 100% selectivity and nearly 100% yield of SC have been obtained; the TOF value obtained is 46 times larger than those so far reported under similar conditions. The effects of the ZnBr2/n-Bu4NI ratio, types of cation and anion, and other reaction conditions on the reaction were investigated. On the basis of the results, a reaction mechanism has been proposed. [Copyright &y& Elsevier]

The application of multiphase catalytic systems for palladium catalyzed Heck reactions brings several benefits such as easy catalyst–product separation and catalyst recycling. The effective multiphase Heck systems can be prepared by using different types of catalyst phases, including biphasic catalysis and supported liquid phase catalysts, and a new generation solvent of supercritical carbon dioxide. [Copyright &y& Elsevier]

Using the form of supported liquid-phase catalysts, two or more homogeneous catalysts can simultaneously be used with retaining their own activities and taking the advantage of catalyst–product separation and catalyst recycling. [Copyright &y& Elsevier]

Abstract: Several heterogeneous basic metal oxide catalysts were screened for the synthesis of 2-oxazolidinones and 2-imidiazolidinones via transesterification of ethylene carbonate with different β-aminoalcohols or 1,2-diamines. Among the several catalysts screened, MgO was found to be the best catalyst, as it has excellent recyclability. Various reaction parameters were studied in detail. Excellent yields of the products were obtained using MgO as catalysts at 80°C within 6h in ethanol. Basic properties of the metal oxide catalysts were compared using temperature programmed desorption (TPD) studies with CO2. The relationship between the catalyst performance and the basic property of each catalyst has been discussed. [Copyright &y& Elsevier]