Dimethyl Carbonate Selectivity Research Articles

Supported Copper Catalysts for Direct Vapor-Phase Oxycarbonylation of Methanol

The supported copper catalysts were prepared by the incipient wetness impregnation method and used for direct vapor-phase oxycarbonylation of methanol to dimethyl carbonate (DMC). The effects of impregnation solvents, supports, promoters, and Cu loading on the catalytic activity were investigated. The results showed that the activated carbon (AC)-supported copper catalyst prepared using CuCl as the starting material and ammonia as the impregnation solvent had high catalytic activity for methanol oxycarbonylation. Under the specified conditions, methanol conversion and DMC selectivity reached 27.7% and 95%, respectively. Compared with the AC support, the zeolite-supported copper catalyst gave methanol conversion of less than 1% and DMC selectivity as high as 100%. The catalytic activity increased with increasing copper loading. However, the DMC selectivity decreased when the copper loading exceeded a certain amount. The addition of palladium compounds or potassium hydroxide enhanced the activity of the catalyst prepared using CuCl2 as the starting material; however, the side reactions were promoted simultaneously. During the reaction for 60 h, the DMC selectivity remained stable, whereas methanol conversion decreased because of the loss of active components.

High Efficient Electrochemical Carbonylation of Methanol to Dimethyl Carbonate by Br2 ∕ Br − Mediator System over Pd ∕ C Anode

Electrochemical carbonylation of methanol to dimethyl carbonate (DMC) was studied over anode with XBr electrolyte (, , ). The formation rate, the current efficiency, and the selectivity of DMC with LiBr electrolyte were considerably higher than that with other supporting electrolyte, , , LiCl, , LiI, and . A turnover number of Pd electrocatalyst for DMC formation was over . Current efficiency of 80% and selectivity based on and CO of 95% were observed. Data of kinetic experiments and stoichiometric experiments strongly suggested that electrochemically produced works as an oxidant for the oxidative carbonylation of methanol to DMC catalyzed by on carbon. A very active and selective carbonylation of methanol to DMC was performed by indirect electrolysis with redox mediator.

Direct synthesis of dimethyl carbonate on H 3PO 4 modified V 2O 5

The catalytic properties of modified V 2O 5 catalysts for the dimethyl carbonate (DMC) synthesis from CO 2 and CH 3OH were investigated. Experimental results showed that the modified V 2O 5 catalysts were effective for the direct and selective synthesis of DMC from carbon dioxide and methanol. The characterization of modified V 2O 5 catalysts was performed by means of X-ray diffraction (XRD), thermogravimetric (TG) and diffuse reflectance FTIR (DRIFT) spectra. XRD patterns showed that the crystal phase changed from orthorhombic to orthorhombic-tetragonal double phase. TG results showed that the weaker acid sites increased when V 2O 5 was treated with varying H 3PO 4 contents. DRIFT spectra of the CO 2 and CH 3OH absorbed on catalysts indicated that both CO 2 and CH 3OH were effectively activated on the catalysts. Finally, the experiment results demonstrated that the crystal phase of the catalyst influenced greatly on the reaction yield and selectivity of DMC.

Oxidative Carbonylation of Methanol to Dimethyl Carbonate in Ionic Liquid 1‐Butyl‐3‐methylimidazolium Hexafluorophosphate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Oxidative Carbonylation of Methanol to Dimethyl Carbonate in Ionic Liquid 1-Butyl-3-Methylimidazolium Hexafluorophosphate

The synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol with PdCl2 as a catalyst was investigated in the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]). The products were recovered in situ using supercritical carbon dioxide. Enhanced selectivity of DMC over this catalyst was observed in the synthesis in [bmim][PF6] compared with the situation without the ionic liquid (IL). The mixture of catalyst and [bmim][PF6] could be recycled.

Transesterification of ethylene carbonate with methanol in supercritical carbon dioxide

Supercritical carbon dioxide was used as the reaction medium for the transesterification of ethylene carbonate (EC) with methanol to produce dimethyl carbonate (DMC) with K 2CO 3 as the catalyst under pressure up to 30 MPa. The effects of the presence of supercritical CO 2 and the pressure on the conversion of EC and the selectivity of DMC were investigated. From the experimental results, it was found that the selectivity of DMC could be enhanced when the reaction was pressurized with supercritical CO 2, although the conversion of EC decreased.

One-Pot Synthesis of Dimethyl Carbonate Using Ethylene Oxide, Methanol, and Carbon Dioxide under Supercritical Conditions

The synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), methanol, and carbon dioxide was investigated. In the proposed one-pot synthesis of DMC, the reaction of EO with CO2 was coupled simultaneously with the reaction of ethylene carbonate with methanol under reaction conditions at which carbon dioxide was in supercritical state. The catalysts were experimentally screened at temperatures from 80 to 140 °C and pressures from 5.0 to 15.0 MPa. The mixture of KI and K2CO3 showed the highest catalytic activity for the one-pot DMC synthesis. The preferential weight ratio of KI to K2CO3 in the mixed catalyst ranges from 1:3 to 5:3. The effects of the reaction conditions, such as catalyst concentration, temperature, pressure, reaction time, and reactant compositions, were experimentally studied. High temperature favors the formation of the desired products, DMC and ethylene carbonate. The effect of pressure on the DMC yield is not significant. A high EO content in the feed is beneficial to increasing the selectivity of the desired products. Using the mixture of KI and K2CO3 (weight ratio of KI/K2CO3 = 1:1) as the catalyst with a molar ratio of catalyst to EO of 0.05, the DMC selectivity can reach above 73.0% at 100.0% EO conversion with less than 4.0% selectivity of the byproduct 2-methoxyethanol at the appropriate reaction conditions.

Effect of base strength and basicity on catalytic behavior of solid bases for synthesis of dimethyl carbonate from propylene carbonate and methanol

MgO and CaO prepared from the dissociation of basic magnesium carbonate and calcium carbonate at elevated temperature were used to investigate the effect of base strength and basicity on the synthesis of dimethyl carbonate (DMC) from propylene carbonate (PC) and methanol (MeOH). It was found that the rise of base strength could reduce the temperature needed for this reaction remarkably. On the other hand, with the increase of the amount of base site, the reaction rate rises but DMC selectivity decreases.

Synthesis of dimethyl carbonate by vapor phase oxidative carbonylation of methanol over Cu-based catalysts

Dimethyl carbonate (DMC) synthesis reaction by oxidative carbonylation of methanol has been studied using vapor phase flow reaction system in the presence of Cu-based catalysts. A series of Cu-based catalysts were prepared by the conventional impregnation method using activated carbon (AC) as support. The effect of various promoters and reaction conditions on the catalytic reactivities were intensively evaluated in terms of methanol conversion and DMC selectivity. The morphological analysis by X-ray diffraction and SEM was also conducted in order to characterize the emloyed catalysts. Regardless of catalyst compositions, the optimal reaction temperature for oxidative carbonylation of methanol was found to be around 120–130°C. The reaction rate was too slow below 100°C, while too much by-products was produced above 150°C. Among the various catalysts employed, CuCl2/NaOH/AC catalyst with the molar ratio of OH/Cu=0.5–1.0, has shown the best catalytic performance, which appears to have a strong relationship with the formation of intermediate species, Cu2(OH)3Cl.

The effects of catalyst composition on the catalytic production of dimethyl carbonate

The synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of MeOH has been studied in the presence of various catalyst systems. The effect of catalyst composition on the catalytic activity and product composition is investigated. A three-component catalyst system composed of PdCl 2(PPh 3) 2, Cu(OMe) 2 and Me 4NCl shows synergy effects in terms of the MeOH conversion (26%) and DMC selectivity (95%). The reaction performed in the presence of a single-component catalyst PdCl 2(PPh 3) 2 produces dimethoxy methane (DMM) as a major product with selectivity over 90%, while the addition of Me 4NCl or Cu(OMe) 2 to PdCl 2(PPh 3) 2 results in the increase of DMC selectivity from 2% to 60%.

A new type of support `bipyridine containing aromatic polyamide' to CuCl 2 for synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol

A new type of heterogeneous catalyst, `bipyridine containing aromatic polyamide' (poly( N, N′-bisphenylene-2,2′-bipyridine-4,4′-dicarboxylic amide, Bpya)–CuCl 2, for dimethyl carbonate (DMC) synthesis by oxidative carbonylation of methanol in the liquid-phase reaction was investigated. This catalyst showed good performance (high DMC yield and DMC selectivity), as in the case of poly(vinylpyridine) (PVP)–CuCl 2. Bpya shows higher heat resistance than PVP, and thus Bpya–CuCl 2 is considered to be more stable than PVP–CuCl 2 under the reaction condition. Bpya–CuCl 2 could be easily recycled after filtration, and actually similar activity was found after three repetitions. During the reaction, 20∼30% of total CuCl 2 was eliminated from the immobilized catalyst. Although the elimination of CuCl 2 occurred considerably in the initial step, it became slight during the reaction. The characteristics of corrosion resistance of Bpya–CuCl 2 was studied, and it became obvious that corrosion is closely related to the trend of CuCl 2 elimination. From these results, we proposed two types of reaction mechanism for the reaction system.

Synthesis of Dimethyl Carbonate(DMC) by Oxidative Carbonylation of Methanol Using Polymer-supported CuCl2 Catalyst.

Polymer, including 2, 2'-bipyridine, poly(4-methyl-4'-vinyl-2, 2'-bipyridine)(Pvbpy), was investigated for the synthesis of dimethyl carbonate (DMC) as a support for CuCl2, by oxidative carbonylation of methanol in the liquid-phase. The CuCl2 complex (Pvbpy-CuCl2) was insoluble in methanol, and the reaction system was heterogeneous. The Pvbpy-CuCl2 catalyst showed considerable catalytic activity (DMC yield: 44.4% and DMC selectivity: 92.6%, at methanol conversion: 1.79%), which is comparable to the previously reported data of poly (vinylpyridine)(PVP)-CuCl2 catalyst; the Pvbpy-CuCl2 catalyst could be recycled after filtration and washing thrice, provided, not having lost activity. The corrosion originating from Cl- was greatly improved by immobilizing the CuCl2 by Pvbpy. Elimination of CuCl2 from the Pvbpy support was observed during the reaction. In the first reaction, about 38% of the initially supported Cl was released, and in the second and the third reactions, most of the Cl was retained. The rate of corrosion of stainless steels in the first use of the catalyst (0.6m gh-1 for HC276) was greater than that in the rate of the second and the third uses (<0.1mg h-1). These results are closely related to the amount of Cl- released from the Pvbpy support, which demonstrates that the main cause of corrosion in the catalytic system is Cl- released from the Pvbpy-CuCl2 catalyst. From XPS study of the catalyst, it became obvious that Cu(II) was gradually reduced to Cu(I) during the reaction.

Novel type of heterogenized CuCl2 catalytic systems for oxidative carbonylation of methanol

A novel type of heterogenized CuCl2 catalysts was designed for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) taking account of the plausible reaction mechanism and intermediates. To prevent severe corrosion of the reaction equipment materials due to Cl− while keeping the catalytic activity of the homogeneous CuCl2 catalyst, we adopted, as supports (or ligands) of CuCl2, four polymers, bearing a 2,2′-bipyridine (bpy) or pyridine (py) unit, namely, poly(2,2′-bipyridine-5,5′-diyl) (Pbpy), poly(pyridine-2,5-diyl) (Ppy), poly(N,N′-bisphenylene-2,2′-bipyridine-4,4′-dicarboxylic amide) (Bpya), and poly(4-methyl-4′-vinyl-2,2′-bipyridine) (Pvbpy), together with one chelate compound, 8-quinolinol. The catalytic activity, stability of heterogenized CuCl2 and their corrosivities to stainless steels were examined in the liquid-phase reaction of the oxidative carbonylation of methanol. These polymer-supported catalysts showed considerable catalytic activity and stability for the DMC synthesis. In particular, the Pbpy-CuCl2 and Ppy-CuCl2 catalysts exhibited high DMC yields and selectivity comparable to those of the homogeneous CuCl2 catalyst. This high activity appears to be associated with the presence of the π-conjugated system in the polymers, which affect the redox reactions of Cu involved in the catalytic reaction. All of the polymer-supported CuCl2 catalysts could be easily recycled after filtration, and the initial catalytic activity was maintained after three times of use. The corrosive characters of the catalysts were closely related to CuCl2 leaching from the supports, which reflects the ability of supports to coordinate Cu. These experimental results suggest that both the electronic structure and the coordination ability of the polymer supports are key factors for the development of an effective catalytic system.

Novel effective poly(2,2′-bipyridine-5,5′-diyl)-CuCl 2 catalyst for synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol

A novel type of polymer-supported CuCl 2 catalyst for dimethyl carbonate (DMC) synthesis has been obtained by choosing π-conjugated poly(2,2′-bipyridine-5,5′-diyl) (PBpy) as the supporting ligand; its catalytic activity for oxidative carbonylation of methanol in the liquid phase reaction has been investigated. The catalyst gives higher DMC yield and DMC selectivity than similar heterogeneous poly(vinylpyridine) (PVP)-CuCl 2 catalyst. The high catalytic activity is associated with the π-conjugated conductive properties of the supporting ligand, PBpy. Both the PBpy-CuCl 2 and PVP-CuCl 2 catalysts can be easily recycled after filtration, and the catalytic activity is maintained after three times use. The PBpy-CuCl 2 catalyst is much less corrosive toward stainless steels compared with the PVP-CuCl 2 and ligand-free CuCl 2 catalyst.