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One-pot synthesis of Mg containing MCM-41 (Mg-MCM-41) materials was respectively carried out by a room temperature (RT) method and a hydrothermal (HT) method for aldol condensation of 4-nitrobenzaldehyde and acetone and self-condensation of acetone. The RT method can prepare MCM-41 materials containing large amounts of Mg while maintaining the structural characteristics of MCM-41 even at very low Si/Mg ratios (large Mg loadings), but the HT method cannot. The RT method can also give more active catalysts than the HT method, because the catalysts prepared by the RT method are more basic than those prepared by the HT one. The characterization indicates that Mg atoms in the Mg-MCM-41 prepared by the RT method exist as MgO disperses well on the wall surface of pores, while those in Mg-MCM-41 prepared by the HT method are included in the bulk with a smectite-like structure. [ABSTRACT FROM AUTHOR]

The desired product of primary amines can selectively be produced in hydrogenation of nitriles using a multiphase reaction medium including both CO2and H2O.

A series of magnesium containing mesoporous smectites has been prepared with and without incorporation of alkali hydroxide (NaOH, KOH or LiOH) and employed for the reaction of CO2with aminobenzonitrile to produce quinazoline-2,4(1H,3H)-dione. The effects of the quantity and kind of the incorporated alkali atoms on the catalytic properties of the smectites were investigated. Characterization of the smectites has shown that the incorporation of alkali atoms reduces their surface area and total pore volume but enhances the amount and strength of their basic sites. The product yield increases with the amount of alkali atoms incorporated. The incorporation of Li was less effective than that of Na and K for the enhancement of the yield. It has been suggested that weak and/or moderate base sites are responsible for the reaction. The active sites should be alkali hydroxide particles existing between the smectite layers for the alkali incorporated smectites, while for the un-incorporated smectite, the active sites should be the Mg atoms and/or the neighboring O atoms. The Na incorporated smectite was deactivated by repeated catalyst recycling, while such deactivation was not observed with the un-incorporated smectite. The reason for the deactivation was discussed in connection with the structures of the active sites and the actions of the reaction intermediate.

Hydrogenation of nitrostyrene (NS) was studied with a Pt/TiO2catalyst in CO2-dissolved ethanol and toluene phases at 323 K. The effects of CO2pressure and organic solvents on the total conversion and the product distribution were examined. The conversion simply decreases with CO2pressure in the both expanded solvents. The pressurization with CO2varies the product selectivity in the nonpolar solvent but not in the polar solvent. The interactions among the substrate, solvent, and CO2molecules were measured by in situ high-pressure FTIR methods in transmittance and attenuated total reflection modes. The reactivity of the nitro group of NS is lowered by interactions with CO2, which is responsible for the change in the product distribution. The local structures of an NS molecule in the expanded solvents are discussed from the results of FTIR and molecular dynamics simulations. The change in the product distribution is explained by the change of the local composition around the substrate molecule depending on CO2pressure. The local composition is likely to change in the toluene but not in the ethanol, in accordance with the changes in the product selectivity in these two solvents. The substrate−CO2interactions are important in toluene while those between the substrate and the solvent are predominant in ethanol even at high CO2pressures.

Under control: The synthesis of a MFI‐zeolite was effectively controlled and the zeolite length was minimized to 20 nm by adding alkyltriethoxysilane to the conventional hydrothermal synthesis. Owing to intracrystal mesopores and a large external surface area, the zeolite materials (see figure for examples) exhibited a remarkably enhanced catalytic activity for reactions involving large organic molecules, as compared to conventional MFI‐zeolites.

Supported liquid phase catalyst (SLPC) is one of effectively heterogenized homogeneous catalysts using organometallic complexes as active components, which are dissolved in a small quantity of liquid phase dispersed in the form of isle or film on the surface of supports. The SLPC has successfully been applied for several chemical transformations and this article will review recent results with respect to the preparation and catalytic performance, the applicability to continuous flow operations, and the capability of multifunctional catalysis.

MgO-clay nanocomposites were prepared from a synthetic smectite-type clay, TS, using three different non-ionic surfactants (Igepal CA-720, Brij 30 and Brij 56) and the resulting clay nanocomposites were impregnated with Ni for the methane reforming reaction with carbon dioxide to synthesis gas. A Ni/TS catalyst was also prepared for comparison. The prepared supports and catalysts were characterized by X-ray diffraction, X-ray fluorescence, thermogravimetric analysis and N2adsorption/desorption isotherms. The thermal stability, pore structure and the surface area strongly influence the catalytic behavior of the catalysts. The methane conversions (at 700°C for 4 h) were 91, 95 and 97% for Ni/TSIGE, Ni/TSBR30 and Ni/TSBR56, respectively, indicating that the surface properties and the catalytic performance of the resulting solids slightly improved as the polyethylene oxide number of the surfactant increased. A reduced conversion (10%) and a rapid deactivation was observed in the Ni/TS catalyst, attributed to its Na content and low thermal stability, which led to sintering and coke deposition.

Rhodium-catalyzed hydroformylation of 1,5-hexadiene to dialdehydes was investigated in compressed CO2 and in toluene using different fluorinated phosphane compounds as ligands at a temperature of 60 °C. Product yields depend greatly on the ligand used and, of the ligands examined, tris[3,5-bis(trifluoromethyl)phenyl]phosphane is the most effective for the production of dialdehydes both in supercritical CO2 (scCO2) and in toluene. The total yield of the dialdehydes passes through a minimum at about 9 MPa as the CO2 pressure is increased and increases appreciably as the H2 pressure in scCO2 increases. The effect of the syngas (H2/CO) and H2 pressures on the reaction in scCO2 is different from that in toluene. It has been suggested that scCO2 promotes the hydroformylation reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The synthesis of styrene carbonate SC from styrene oxide SO and CO2has been studied with various catalyst systems including metal halides and ionic liquids. The total conversion of SO and the selectivity for SC strongly depend on the catalyst systems used. The highest SC yield of 93 can be achieved at a low temperature of 80 °C for 1 h with a catalyst system of ZnBr2and C4-mimCl at a molar ratio of 1 2. A CO2pressure of 4 MPa is optimal but elevated pressures have no positive effects on this SC synthesis.

Two-step synthesis of dimethyl carbonate DMC from urea has been investigated with various solid catalysts. The first step involves reaction of urea with ethylene glycol EG to form ethylene carbonate EC and the second step transesterification of EC formed with methanol to give DMC and EG. It has been found that ZnO is highly active and selective for the two steps, of which the former should be conducted under reduced pressure. At around ambient pressure, 2-oxazolidone and ethyleneurea are formed in the first step. Similar to EG, other glycols such as 1,2- and 1,3-propanediols can also be transformed to corresponding cyclic carbonates.

This paper reports the effect of various reaction variables on the activity and selectivity performance on a two-step synthesis of dimethyl carbonate (DMC) and glycol from propylene oxide, carbon dioxide and methanol using a heterogeneous Mg containing smectite catalyst. The first step, the reaction of propylene oxide with CO₂ to form propylene carbonate, and the second step, the transesterification reaction of the cyclic carbonate such as ethylene carbonate with methanol to DMC and ethylene glycol, have been studied. The catalyst was found to be effective for one-pot synthesis of DMC, i.e. the sequential reaction of the epoxide, CO₂ and methanol.

Two-step synthesis of dimethyl carbonate (DMC) from urea has been investigated with various solid catalysts. The first step involves reaction of urea with ethylene glycol (EG) to form ethylene carbonate (EC) and the second step transesterification of EC formed with methanol to give DMC and EG. It has been found that ZnO is highly active and selective for the two steps, of which the former should be conducted under reduced pressure. At around ambient pressure, 2-oxazolidone and ethyleneurea are formed in the first step. Similar to EG, other glycols such as 1,2- and 1,3-propanediols can also be transformed to corresponding cyclic carbonates.

Smectites containing magnesium and/or nickel in the lattice were found to be excellent heterogeneous catalysts for the concurrent synthesis of dimethyl carbonate and ethylene glycol by transesterification of ethylene carbonate with methanol. The catalytic activity strongly depends on the elemental composition of the catalysts and is correlated with the number of moderately basic sites present on the catalyst.

Rhodium-catalyzed hydroformylation of 1-hexene was investigated in compressed CO₂ and organic solvents using different fluorinated phosphine compounds as ligands at a temperature of 333 K. The reaction runs were conducted under conditions where the reaction mixtures were homogeneous in order to examine the activity of the rhodium complexes in different media. The effects of phosphine ligand, CO₂ pressure, syngas (H₂/CO) pressure and solvent on the hydroformylation activity were studied, along with FTIR examination of reaction mixtures. Such phosphine compounds as diphenyl(pentafluorophenyl)phosphine (II), bis(pentafluorophenyl)phenylphosphine (III), and tris(p-trifluoromethylphenyl)phosphine (VI) are effective ligands in scCO₂. Compound II is better since with it the undesirable isomerization side reaction is avoided. The n/iso ratio (heptanal/2-methylhexanal) does not change so much with the phosphine ligand used. It is interesting that the aldehyde yield goes through a minimum at about 9 MPa with increasing CO₂ pressure, and it tends to increase with an increase in the syngas pressure. The catalytic activities in scCO₂ are comparable with those in toluene and it is suggested that scCO₂ has some positive effects in promoting the hydroformylation.

The reaction of propylene oxide and carbon dioxide to propylene carbonate was carried out using Mg-, Ni- and Mg-Ni-containing smectite catalysts which contain different amounts of alkali atoms such as sodium, potassium and lithium. These catalysts are highly active and selective for this reaction. The catalytic activity strongly depends on the elemental composition of the catalyst used. Particularly the amount of alkali atoms incorporated in the catalyst is the most important factor governing the catalytic performance. The most active catalyst among those prepared in the present study shows a turnover number of 105 mmol/g for the propylene carbonate formation, which is the highest turnover number compared with those reported so far (10 mmol/g) for the title reaction.

The synthesis of dimethyl carbonate (DMC) from methanol and CO₂ was studied in the presence of methyl iodide and various base catalysts. Among the catalysts used, potassium carbonate was found to be most active. Dimethyl ether (DME) is formed as a byproduct. When the reaction was carried out at various pressure of CO₂, two maxima in DMC formation were observed at 4.5 and 8 MPa, while DME formation decreased monotonically with increasing the CO₂ pressure. The effects of the amounts of methyl iodide and potassium carbonate on the DMC and DME formation were also investigated. Mechanistic studies suggest that DMC and DME are produced in parallel pathways and methyl iodide is involved in the formation of both DMC and DME. Other alcohols show less reactivity than methanol.

For characterization of the surface structure of metallic copper formed on the support, temperature programmed oxidation (TPO) with N2O was carried out over various Cu/ZnO catalysts. Four peaks of the N2 formation (a, ß, ? and d) were observed at 223, 400, 545 and 600 K in the TPO runs. The average copper crystallite size estimated from the sum of the amount of a- and ß-peaks agreed fairly with those determined by X-ray diffraction and transmission electron microscopy. It was concluded that a- and ß-peaks resulted from the oxidation of metallic copper atoms on the steps, corners and/ or defect sites, and on the flat sites of the surface of copper crystallites, respectively, while ?- and d-peaks resulted from the bulk oxidation of copper.

Precursors of Cu/ZnO catalysts with various Cu/Zn molar ratios were prepared by a coprecipitation method. It was found that amorphous copper hydroxycarbonate and sodium zinc carbonate were intermediates for the formation of various precursors such as hydrozincite, malachite and aurichalcite. Aurichalcite having a high Cu/Zn ratio was prepared from a mechanical mixture of these intermediates.

Temperature programmed desorption (TPD), IR spectroscopy and chemical trapping of the surface species with H2O revealed that the TPD peak of CO frequently assigned to zinc formate species, which were formed in the course of the methanol synthesis from CO-H2, arose from zinc methoxide species.

Temperature programmed desorption, FT-IR spectra and hydrolysis of adsorbed oxygen species revealed that a considerable amount of adsorbed peroxide species were formed on CaO by decomposition of N2O, whereas no adsorbed species were formed by molecular oxygen.

Methanol synthesis from CO2 and H2 was carried out over a Cu/ZnO catalyst (Cu/Zn = 3/7) at atmospheric pressure, and the surface species formed were analyzed by diffuse reflectance FT-IR spectroscopy and temperature programmed desorption method. Two types of formate species and zinc methoxide were formed in the course of the reaction. Zinc methoxide was readily hydrolyzed to methanol. H2O formed through the reverse water gas shift reaction was suggested to be involved in the hydrolysis of zinc methoxide.

In CO methanation, the hydrogenation of surface carbon species are inhibited by reversibly adsorbed CO. The extent of inhibition is markedly different on the methals used.

Clean synthesis to cyclic urea and cyclic urethane compounds using direct reaction of urea with diamine, amino alcohol or amino phenol has been achieved at 150 °C without any catalyst.

Clean synthesis to cyclic urea and cyclic urethane compounds using direct reaction of urea with diamine, amino alcohol or amino phenol has been achieved at 150 °C without any catalyst.

Clean synthesis to imidazolidone and oxazolidone compounds using direct reaction of carbon dioxide with diamine or amino alcohols can be achieved at 6 MPa CO2and 150 °C without use of any catalyst.

Clean synthesis to imidazolidone and oxazolidone compounds using direct reaction of carbon dioxide with diamine or amino alcohols can be achieved at 6 MPa CO₂ and 150 °C without use of any catalyst.

Methanol Synthesis from CO2–H2was carried out over a ZnO catalyst. Pretreatments with a CO–H2mixture caused a transient increase of the methanol formation as Bowker et al. found. It was shown that methoxide species was formed in the course of the pretreatments, being readily hydrolyzed to methanol by water formed via the reverse water gas shift reaction.

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.

The chemoselective, Ni‐catalyzed hydrogenation of water‐insoluble aromatic nitro compounds in a water‐compressed CO2system is reported.

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