Shin-ichiro Fujita

Synthesis of dimethyl carbonate and glycols from carbon dioxide, epoxides, and methanol using heterogeneous basic metal oxide catalysts with high activity and selectivity

Abstract This paper gives a comprehensive report on a two-step synthesis of dimethyl carbonate (DMC) from epoxides, carbon dioxide and methanol using various basic metal oxide catalysts. The first step is the reaction of ethylene oxide or propylene oxide with CO 2 to form the corresponding cyclic carbonates, and the second step is the transesterification reaction of the cyclic carbonates with methanol to DMC and glycols. Among the catalysts examined, MgO is the most active and selective for both these reactions. Other alcohols can be used for the second step, but the activity decreases as the carbon number of the alcohol increases. Although a one-pot synthesis of DMC, i.e. the sequential reaction of the epoxide, CO 2 and methanol, is also possible with MgO, the selectivity is low because of the alcoholysis of the epoxide. In contrast with the reactions of ethylene oxide and propylene oxide, when styrene oxide is used for the first reaction and for the one-pot synthesis, mandelic acid is produced. Basic properties of the metal oxide catalysts were measured by temperature programmed desorption of CO 2 . The relationship between the catalytic performance and the basic property is discussed.

Synthesis of styrene carbonate from styrene oxide and carbon dioxide in the presence of zinc bromide and ionic liquid under mild conditions

The synthesis of styrene carbonate (SC) from styrene oxide (SO) and CO2 has 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 ZnBr2 and [C4-mim]Cl at a molar ratio of 1 ∶ 2. A CO2 pressure of 4 MPa is optimal but elevated pressures have no positive effects on this SC synthesis.

Synthesis of dimethyl carbonate and glycols from carbon dioxide, epoxides and methanol using heterogeneous Mg containing smectite catalysts: effect of reaction variables on activity and selectivity performance

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.

Transesterification of urea and ethylene glycol to ethylene carbonate as an important step for urea based dimethyl carbonate 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.

Mechanism of the reverse water gas shift reaction over Cu/ZnO catalyst

The reverse water gas shift reaction (RWGS) and the reaction with CO{sub 2} alone were carried out over a Cu/ZnO catalyst. The surface of the catalyst was characterized by N{sub 2}O titration, XPS, and FT-IR spectroscopy. CO{sub 2}dissociated to give CO and the surface oxygen species. Surface Cu(I) oxide was formed by the reaction with CO{sub 2}. The oxygen species were hydrogenated to H{sub 2}O and the surface Cu(I) oxide was reduced to metallic Cu. It is suggested that the RWGS reaction proceeds through surface oxidation and reduction with CO{sub 2} and H{sub 2}, and the dissociation of CO{sub 2} is the rate determining step.

Synthesis of cyclic ureas and urethanes from alkylene diamines and amino alcohols with pressurized carbon dioxide in the absence of catalysts

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.

Chemical fixation of carbon dioxide to propylene carbonate using smectite catalysts with high activity and selectivity

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.

Difference in the selectivity of CO and CO2 methanation reactions

CO and CO2 methanation at steady states and under transient states was conducted over Ni, Ni/Al2O3, Ni/SiO2 and Ru/SiO2. The CO2 methanation proceeded highly selectively as compared with the CO methanation. In the CO methanation, weakly adsorbed CO retarded the hydrogenation of surface carbon species. In the CO2 methanation, the retardation was absent. The selectivity for the CO2 methanation was estimated from the selectivity for the CO methanation, the extent of the retardation and the ratio of the steady state rates of these reactions. The selectivity estimated was in fair agreement with that experimentally obtained.

Mechanisms of methanation of carbon dioxide and carbon monoxide over nickel/alumina catalysts

Abstract By the use of diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) and the temperature-programmed reaction (TPRx) method, it was shown that two types of adsorbed CO in bridged structures (referred to as weakly adsorbed bridged CO(a) and strongly adsorbed bridged CO (a) species) were predominantly present along with formate species in the methanation of CO 2 on Ni/Al 2 O 3 . The amount of carbidic carbon species (referred to as C (a) species) and adsorbed CO in linear structures (referred to as linear CO (a) species) were practically negligible. In the methanation of CO, a considerable amount of linear CO(a), weakly and strongly adsorbed bridged CO(a) and C(a) species was present along with formate, methozide and surface hydrocarbon species. C (a) species were produced by dissociation of strongly adsorbed bridged CO (a) species, being hydrogenated to methane. On the basis of the reactions under transient states and those of C (a) species with H 2 , CO 2 /H 2 and CO/H 2 , it was suggested that one of the steps involved in the hydrogenation of C (a ) species to methane was markedly retarded in the presence of linear CO (a) species.

Steam reforming of methanol on binary CuZnO catalysts: Effects of preparation condition upon precursors, surface structure and catalytic activity

Precursors for CuZnO catalysts, with CuZn molar ratios in the range from 1000 to 0100, were prepared by two coprecipitation methods. These methods differ by the addition rate of a mixed Cu(NO3)2Zn(NO3)2 solution to a NaHCO3 solution. Characterisation by powder X-ray diffraction (PXRD), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), FT-IR and UV/VIS spectroscopies indicated that the structure of precursors with CuZn ratios in the range of 3070 to 7030 depends greatly upon the addition rate of the mixed solution. Amorphous copper hydroxycarbonate and sodium zinc carbonate were formed prior to the various precursors such as malachite, aurichalcite and hydrozincite. The uZnO catalysts subsequently formed from the precursors showed the activity for steam reforming of methanol to vary with its composition. Based on the results of temperature programmed oxidation (TPO) with N2O and an infrared spectra of CO chemisorption, the TOF of the reaction is proposed to be associated with the surface of metallic Cu.