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Adsorbed HCAL molecules control the adsorption of CAL and enhance the selective hydrogenation to COL over PdZn catalyst. [Display omitted] • The catalytic function of PdZn alloy for cinnamaldehyde (CAL) hydrogenation is largely different from metallic Pd. • PdZn ally more selectively produces cinnamyl alcohol than Pd. • The product of hydrocinnamaldehyde is suggested to promote the hydrogenation of aldehyde group of CAL. Liquid phase selective hydrogenation of cinnamaldehyde (CAL) was investigated over ZnO-supported Pd and PdZn catalysts different in the Pd loading. The former monometallic catalyst was less selective to the formation of cinnamyl alcohol (COL) irrespective of the Pd loading (5 and 30 wt.-% Pd). When the Pd loading was small (5 wt.-%), PdZn catalyst (PdZn-5) indicated similar catalytic actions. However, PdZn catalyst containing Pd in a larger content of 30 wt.-% (PdZn-30) showed different results: the COL selectivity was about 20% at low conversion but it increased with CAL conversion, reaching to >50% at a conversion of 60%. The COL selectivity was likely to change depending on the concentration of a product of hydrocinnamaldehyde (HCAL). The coadsorption of HCAL should control the orientation of CAL molecules adsorbed on the PdZn-30 catalyst. This may assist the adsorption of CAL via its aldehyde group on the surface of catalyst, resulting in an increase in the COL selectivity. Unique catalysis of PdZn-30 may result from structural features of the surface of its large PdZn particles, which are different from those of PdZn-5 having smaller PdZn particles. [ABSTRACT FROM AUTHOR]

Abstract: Several basic metal oxide catalysts were tested for the synthesis of 1,3-disubstituted urea from ethylene carbonate (EC) and amine. Among the catalysts used, CaO has been found to be an excellent recyclable catalyst for the reaction. It has been suggested that strongly basic property of CaO results in its high activity. Disubstituted ureas are obtained from propylamine and butylamine with high yields at 100°C. Slightly higher reaction temperatures are necessary for obtaining good yields from amines having larger molecular weights and urea is not produced from dibutylamine as a secondary amine. Propylene carbonate can be used instead of EC for the reaction. A reaction mechanism was proposed, which involves reaction between EC and amine giving a carbamate followed by catalytic reaction between the carbamate and amine, yielding 1,3-disubstituted urea. It is suggested that the latter reaction is the rate-determining step. On the basis of this reaction mechanism, the synthesis of unsymmetric urea was also examined. 2-Hydroxyethyl butylcarbamate is selectively produced from EC with butylamine in the absence of the catalyst at a low temperature and reacts with benzylamine producing 1-butyl-3-benzylurea along with symmetric dialkyl ureas. [Copyright &y& Elsevier]

Abstract: This paper reports a direct route for the preparation of cyclic styrene carbonate from styrene, which avoids the preliminary synthesis and isolation of styrene oxide. A catalyst system consisting of Au/SiO2, zinc bromide, and tetrabutylammonium bromide (Bu4NBr) has been applied to the one-pot synthesis of styrene carbonate from styrene, organic peroxide, and CO2. Au/SiO2 is active for the epoxidation of styrene, and zinc bromide and Bu4NBr cooperatively catalyze the subsequent CO2 cycloaddition to epoxide. The influence of various reaction parameters, such as CO2 pressure, reaction temperature, reaction time, catalyst amount, ratio of oxidant to styrene, and oxidant type, has been investigated in detail. [Copyright &y& Elsevier]

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) has been investigated with supported liquid-phase catalysts (SLPC), which contain Ru–TPPTS complexes in water film supported on a porous silica gel, in organic solvent (toluene). It was shown that COL can be mainly produced with small quantities of hydrocinnamaldehyde (HCAL) and hydrocinnamyl alcohol (HCOL). The influence of various reaction and catalyst preparation parameters on the overall rate of reaction and the product selectivity have been examined. In addition, liquid-phase adsorption of CAL on water-loaded silica samples has also been measured. It is believed that the hydrogenation of CAL to COL occurs at the interface between the water film and the organic solvent while that to HCAL at the interface between silica, water, and toluene. The hydrophilic nature of the C&z.dbnd;O bond of CAL is significant for the selective formation of COL at the water/toluene interface, to which polar C&z.dbnd;O bonds of CAL molecules are pointing. The product, COL, also has a polar OH group, and so it is difficult for COL to be hydrogenated to HCOL at this interface. At the other silica/water/toluene interface, CAL molecules may be adsorbed with their C&z.dbnd;C bonds as well, which enables the hydrogenation to HCAL. On recycling of SLPC, its activity and COL selectivity decrease. Both oxygen dissolved in toluene and change of active Ru complexes in the water film are responsible for the decrease of catalytic activity, and the change of the state of dispersion of the water film is significant for the decrease of COL selectivity. [Copyright &y& Elsevier]

Rhodium-catalyzed hydroformylation of 1,5-hexadiene and 1,7-octadiene to corresponding dialdehydes was investigated in compressed CO2 and in toluene using different fluorinated phosphine compounds as ligands. A rhodium complex using tris(3,5-bis(trifluoromethyl)phenyl)phosphine is highly effective in compressed CO2 for double hydroformylation of 1,5-hexadiene, whose TOF value is much larger than those reported so far. It has been shown that this ligand is effective also for the hydroformylation of 1,7-octadiene and scCO2 is a better solvent than a conventional organic solvent of toluene for the title reaction. [Copyright &y& Elsevier]

Calcium oxide has been proved to be an excellent solid catalyst for the synthesis of N,N'-disubstituted ureas from ethylene carbonate and primary amines under mild conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] The doping of NiO x can improve the photocatalytic activity of TiO2. [•] NiO x /TiO2 is active for photocatalytic H2 production from aqueous glycerol. [•] The catalytic performance of NiO x /TiO2 depends on calcination temperature. [ABSTRACT FROM AUTHOR]

The selective hydrogenation of nitrobenzene (NB) over Ni/γ-Al2O3 catalysts was investigated using different media of dense phase CO2, ethanol, and n-hexane. In dense phase CO2, the total rate of NB hydrogenation was larger than that in organic solvents under similar reaction conditions; the selectivity to the desired product, aniline, was almost 100% over the whole conversion range of 0–100%. The phase behavior of the reactant mixture in/under dense phase CO2 was examined at reaction conditions. In situ high-pressure Fourier transform infrared measurements were made to study the molecular interactions of CO2 with the following reactant and reaction intermediates: NB, nitrosobenzene (NSB), and N-phenylhydroxylamine (PHA). Dense phase CO2 strongly interacts with NB, NSB, and PHA, modifying the reactivity of each species and contributing to positive effects on the reaction rate and the selectivity to aniline. A possible reaction pathway for the hydrogenation of NB in/under dense phase CO2 over Ni/γ-Al2O3 is also proposed. [Copyright &y& Elsevier]

Abstract: Liquid-phase semihydrogenation of phenylacetylene under mild conditions has been investigated on a series of solvothermal-derived nano-TiO2 supported Pd catalysts with various TiO2 crystallite sizes in the range of 9–23 nm. As revealed by CO chemisorption and transmission electron microscopy, all the catalysts exhibited strong metal–support interaction (SMSI) when reduced at 500 °C. The catalysts with SMSI show remarkably high catalytic performance in terms of both hydrogenation activities (turnover frequencies (TOFs) 9.1–21.4 s−1) and moderate-high selectivities to styrene (86–90%) at complete conversion of phenylacetylene. Without SMSI effect (the catalysts reduced at 40 °C), styrene selectivity and catalytic activity depended largely on the Pd particle size in which small Pd particles (formed on small crystallite size TiO2 supports) exhibited lower phenylacetylene conversion and poor styrene selectivity. Moreover, the TOF values of the non-SMSI catalysts were similar to those reported in the literature for other supported Pd catalysts in liquid-phase semihydrogenation of phenylacetylene under mild conditions (TOFs 1.3–2.8 s−1). [Copyright &y& Elsevier]