Oxidative Carbonylation Of Methanol Research Articles

The effect of Si/Al ratios on the catalytic activity of CuY zeolites for DMC synthesis by oxidative carbonylation of methanol: a theoretical study

Cu-exchanged Y zeolites with different Si/Al ratios have been investigated using a density functional theory method in order to determine the effect of Si/Al ratios on the catalytic activity for producing DMC by the oxidative carbonylation of methanol. The stable structures and catalytic activity of the CuY zeolites with different Si/Al ratios are identified. In addition, CO adsorption and the effect of CH3O on CO adsorption, including the changes in the adsorption energy and stretching vibrational frequency for the adsorbed CO, are obtained. Our results indicate that the CuY zeolite with a Si/Al ratio = 6.5 has the highest catalytic activity for producing DMC by oxidative carbonylation of methanol among all the Si/Al ratios considered in this work, which is supported by the experimental facts. Finally, our results suggest that theoretical calculations can be used as a useful tool and provide good theoretical guidance for the experimental design of CuY zeolites.

The influence of support in the synthesis of dimethyl carbonate by Cu-based catalysts

The effects of various anions containing copper based catalysts were studied in regard to the preparation of dimethyl carbonate (DMC) through oxidative carbonylation of methanol under a liquid phase system. A copper compound providing the strong withdrawing power of halides as anion yielded excellent results with respect to the conversion of methanol and selectivity to DMC.However, copper homogenous catalysts suffer from separation of the catalyst after reaction. Thus, the development of a new reaction system using various supports including Y-zeolite was attempted. The conversion of methanol and selectivity to DMC were affected by the properties of the supports. In particular, Y-zeolite showed the best yield among various supports.The influence of various promoters was examined with the aim of increasing the yield of DMC from methanol. The yield of DMC was increased with the addition of alkali metal in the order Li+<Na+<K+, but with selectivity in the order of Li+>Na+>K+, respectively.Various analyses were conducted in order to elucidate these results. From a XRD analysis, the existence of crystal forms of copper chloride hydroxide of Cu/Na/Y-zeolite (dry) was observed. We confirmed the presence of peaks of CuO in Cu/Na/Y-zeolite (550°C). The CO-TPD analysis revealed that CO desorption is an important step to determine the formation of DMC. The addition of NaOH as a co-catalyst resulted in a lower desorption temperature of carbon monoxide in Cu catalyst. Also, XPS analysis results showed that Cu+ on the calcined Cu/Na/Y-zeolite catalyst was formed by the reduction of Cu2+. XANES results provided the difference of reactivity according to the state of the copper catalyst. Activity of this reaction in terms of DMC yields, obtained in the order of CuCl2>Cu/Na/Y-zeolite (dry)>Cu/Na/Y-zeolite (550°C)>Cu(OH)2 was in accordance with the maximum peak of the low photon energy position.

Chloride-free Cu-modified SAPO-37 catalyst for the oxidative carbonylation of methanol in the gas phase

The substitution of harmful phosgene or chloride-containing catalysts in the synthesis of dimethyl carbonate (DMC) and its use as “green solvent” or polycarbonate building block direct its manufacture towards environmental benign syntheses. Thus, copper was introduced into silicoaluminophosphate structure SAPO-37 (belonging to the same FAU structure family like aluminosilicate zeolites Y and X) by solid state ion exchange (SSIE) using Cu(II) acetyl acetonate. This strategy circumvented structural breakdown being observed when using aqueous copper solutions for impregnation or ion exchange. The SSIE efficiently ran when the organic template is widely extracted from the synthesis form of SAPO-37, e.g. through treatment with methanolic HCl. The parent SAPO-37, template-free SAPO-37 and Cu-SAPO-37 materials were characterized by XRD, TG, temperature programmed reduction (TPR), temperature programmed desorption of ammonia (TPDA) and FTIR spectroscopy of adsorbed pyridine and CO. The Cu-SAPO-37 catalyst pre-treated in inert gas exhibits a high selectivity for DMC and dimethoxymethane (DMM) in the oxidative carbonylation of methanol (OCM). The catalytic behavior of Cu-SAPO-37 is shown to be comparable with those of a Cu-containing Y zeolite catalyst that is so far regarded as one of the best chloride-free catalyst for the OCM reaction in the gas phase.

A density functional theory investigation on the mechanism and kinetics of dimethyl carbonate formation on Cu2O catalyst

A theoretical analysis about the mechanism and kinetics of dimethyl carbonate (DMC) formation via oxidative carbonylation of methanol on Cu(2)O catalyst is explored using periodic density functional calculations, both in gas phase and in solvent. The effect of solvent is taken into account using the conductor-like screening model. The calculated results show that CO insertion to methoxide species to produce monomethyl carbonate species is the rate-determining step, the corresponding activation barrier is 161.9 kJ mol(-1). Then, monomethyl carbonate species reacts with additional methoxide to form DMC with an activation barrier of 98.8 kJ mol(-1), above reaction pathway mainly contributes to the formation of DMC. CO insertion to dimethoxide species to form DMC is also considered and analyzed, the corresponding activation barrier is 308.5 kJ mol(-1), suggesting that CO insertion to dimethoxide species is not competitive in dynamics in comparison with CO insertion to methoxide species. The solvent effects on CO insertion to methoxide species involving the activation barriers suggest that the rate-determining step can be significantly affected by the solvent, 70.2 kJ mol(-1) in methanol and 63.9 kJ mol(-1) in water, which means that solvent effect can reduce the activation barrier of CO insertion to methoxide species and make the reaction of CO insertion to methoxide in solvents much easier than that in gas phase. Above calculated results can provide good theoretical guidance for the mechanism and kinetics of DMC formation and suggest that solvent effect can well improve the performance of DMC formation on Cu(2)O catalyst in a liquid-phase slurry.

Recent progress in phosgene-free methods for synthesis of dimethyl carbonate

Dimethyl carbonate (DMC) is considered as an environmentally benign chemical due to negligible ecotoxicity, low bioaccumulation, and low persistence. However, the traditional process of DMC synthesis via phosgene and methanol is limited in industry owing to the toxic raw material involved. Thus, environmentally friendly phosgene-free processes for DMC production have been proposed and developed in the past decades. Until now, the alternatives appear to be the oxidative carbonylation of methanol, the transesterification of propylene or ethylene carbonate (PC or EC), the methanolysis of urea, and the direct synthesis of DMC from CO2 with methanol. In this review, we present some recent developments of these phosgene-free approaches and their prospects for industrialization.

Adsorption and dissociation of O 2 on CuCl(1 1 1) surface: A density functional theory study

The adsorption and dissociation of O 2 on CuCl(1 1 1) surface have been systematically studied by the density functional theory (DFT) slab calculations. Different kinds of possible modes of atomic O and molecular O 2 adsorbed on CuCl(1 1 1) surface and possible dissociation pathways are identified, and the optimized geometry, adsorption energy, vibrational frequency and Mulliken charge are obtained. The calculated results show that the favorable adsorption occurs at hollow site for O atom, and molecular O 2 lying flatly on the surface with one O atom binding with top Cu atom is the most stable adsorption configuration. The O–O stretching vibrational frequencies are significantly red-shifted, and the charges transferred from CuCl to oxygen. Upon O 2 adsorption, the oxygen species adsorbed on CuCl(1 1 1) surface mainly shows the characteristic of the superoxo (O 2 −), which primarily contributes to improving the catalytic activity of CuCl, meanwhile, a small quantity of O 2 dissociation into atomic O also occur, which need to overcome very large activation barrier. Our results can provide some microscopic information for the catalytic mechanism of DMC synthesis over CuCl catalyst from oxidative carbonylation of methanol.

Preparation of Chlorine-Free Cu/AC Catalyst and Its Catalytic Properties for Vapor Phase Oxidative Carbonylation of Methanol

Preparation of Chlorine-Free Cu/AC Catalyst and Its Catalytic Properties for Vapor Phase Oxidative Carbonylation of Methanol

Structure of CuCl/SiO&lt;SUB&gt;2&lt;/SUB&gt;-TiO&lt;SUB&gt;2&lt;/SUB&gt; Catalyst and Its Catalytic Properties for Oxidative Carbonylation of Methanol

Structure of CuCl/SiO&lt;SUB&gt;2&lt;/SUB&gt;-TiO&lt;SUB&gt;2&lt;/SUB&gt; Catalyst and Its Catalytic Properties for Oxidative Carbonylation of Methanol

Oxidative carbonylation of methanol over copper ion-containing ionic liquids immobilized on SBA-15

A new catalyst of copper ion-containing ionic liquids immobilized on SBA-15 was prepared and characterized by XRD, HRTEM, N 2 physical adsorption, FTIR, elemental analysis, TGA, AA, and XPS. The CuBr 2–PyIL/SBA-15 catalyst was found to be more active and selective than CuBr 2 and CuBr 2/SBA-15 prepared by the conventional impregnation method in the synthesis of dimethyl carbonate by oxidative carbonylation of methanol. Although the CuBr 2–PyIL/SBA-15 catalyst deactivated rapidly during the initial three runs, it still maintained a comparable activity with the fresh CuBr 2/SBA-15 catalyst after three recycling.

The influence of halogen anions and N‐ligands in CuXn/N‐ligands on the catalytic performance in oxidative carbonylation of methanol

AbstractThe catalytic properties of CuXn/N‐ligands (X = Cl, Br and I; n = 1 or 2) in oxidative carbonylation of methanol were investigated. It was found that the interaction of halogen anions, N‐ligands and Cu (I) affected the catalytic performance of copper complex catalyst in the reaction, especially iodide anion and 1,10‐phenanthroline (Phen). When CuI/Phen was used as a catalyst, the conversion of methanol was 42.6%, the selectivity to dimethyl carbonate was 99.2% and the TOF was 13.1 h−1 at an optimized conditions: CuI/Phen 0.2 mol l−1, 120 °C, 2 h, 2.4 MPa, PCO/PO2 = 2:1. Compared with the plain CuI catalyst, the catalytic activity of CuI/Phen increased about 36 times. When CuI/Phen catalyst was immobilized on polystyrene (PS), the heterogenized catalyst, CuI/Phen–NH–PS, also exhibited very high catalytic activity in oxidative carbonylation. The CuI/Phen—NH—PS catalyst remained its high catalytic activity even after seven recycles. The average weight loss of CuI/Phen—NH—PS after reaction was less than 1.0%, and the leaching of copper was only about 0.15% in each recycling test. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Synthesis of Dimethyl Carbonate by Oxidative Carbonylation Using an Efficient and Recyclable Catalyst Co−Schiff Base/Zeolite

Dimethyl carbonate (DMC) has been synthesized by oxidative carbonylation of methanol over the Co−Schiff base complexes, which have been encapsulated in situ in zeolite Y by a “ship-in-the-bottle” approach. These hybrid materials Co−Schiff base/zeolite Y have been characterized by FT-IR, UV−vis, XRD, BET, and TG/DTA techniques. Analysis of the hybrid materials indicates the formation of complexes in the cavity without affecting the zeolite framework structure. The catalytic activities and corrosion behavior of the encapsulated complexes and their homogeneous analogues were examined. Zeolite-encapsulated Co complexes were found to be more active and stable than the neat Co complexes. When the reaction was carried out using 1.0 g of encapsulated catalyst, 40 mmol of methanol, CO/O2 ratio of 2:1, and at 3.0 MPa and 120 °C for 4 h, zeolite-encapsulated Co−salophen shows the highest activity; and the conversion of methanol and selectivity to DMC were 25.4 and 99.5%, respectively. It was also demonstrated that zeolite-encapsulated Co−salophen catalyst can be reused five times without loss of activity. Both neat and encapsulated Co−salophen exhibit noncorrosive behavior to the reactor made by stainless steel.

The mechanism of dimethyl carbonate synthesis on Cu-exchanged zeolite Y

The mechanism of dimethyl carbonate (DMC) synthesis from oxidative carbonylation of methanol over Cu-exchanged Y zeolite has been investigated using in situ infrared spectroscopy and mass spectrometry under transient-response conditions. The formation of DMC is initiated by reaction of molecularly adsorbed methanol with oxygen to form either mono- or di-methoxide species bound to Cu + cations. Reaction of the mono-methoxide species with CO produces monomethyl carbonate (MMC) species. DMC is formed via two distinct reaction pathways—CO addition to di-methoxide species or by reaction of methanol with MMC. The rate-limiting step in DMC synthesis is found to be the reaction of CO with mono-methoxide or di-methoxide species. The first of these reactions produces MMC, which then reacts rapidly with methanol to produce DMC, whereas the second of these reactions produces DMC directly. Formaldehyde was identified as an intermediate in the formation of dimethoxy methane (DMM) and methyl formate (MF). Both byproducts are thought to form via a hemiacetal intermediate produced by the reaction of methanol with adsorbed formaldehyde at a Cu + site.

A Theoretical Investigation of Dimethyl Carbonate Synthesis on Cu−Y Zeolite

A theoretical analysis of the mechanism of dimethyl carbonate (DMC) synthesis via oxidative carbonylation of methanol on Cu-exchanged Y zeolite, Cu−Y, was explored using density functional theory. These calculations show that methanol adsorbs in the presence of oxygen to form coadsorbed methoxide and hydroxide species and dimethoxide species on extraframework Cu+ cations. DMC can form by CO addition to the former species to produce monomethyl carbonate species, which then react with additional methanol or by CO addition to dimethoxide species to form DMC directly. The turnover frequency for DMC synthesis is estimated to be 1.2 × 10-5 s-1 for the reaction conditions used in the experimental work of Zhang and Bell (J. Catal., in press). This value compares very closely with that observed, 5 × 10-5 s-1. The calculated value of the apparent activation energy is 15.0 kcal/mol, in good agreement with that measured experimentally, 14.8 kcal/mol. The effects of methanol and oxygen on the adsorption of CO have als...

Ionic liquid as an efficient promoting medium for synthesis of dimethyl carbonate by oxidative carbonylation of methanol

Abstract The synthesis of dimethyl carbonate by oxidative carbonylation of methanol using Cu salt catalysts in the presence of various room temperature ionic liquids (RTILs) was reported. Among the ionic liquids used, N -butylpyridinium tetrafluoroborate was the most effective promoter in terms of the conversion of methanol and the selectivity to dimethyl carbonate (DMC). The influences of reaction temperature, pressure, time, molar ratio of CO/O 2 , and amount of the ionic liquid on the oxidative carbonylation of methanol were investigated. The results indicated that under the reaction conditions of 120 °C and 2.4 MPa of a 2:1 mixture of CO and O 2 , 17.2% conversion of methanol, 97.8% selectivity of DMC and a DMC productivity of 4.6 g g −1 cat h −1 were achieved. The N -butylpyridinium tetrafluoroborate-meditated CuCl catalyst system could be reused at least five recycles with the same selectivity and a slight loss of catalytic activity due to loss of the catalyst during handling and transferring the reaction mixture.

Preparation of CuCl/1,10-phenanthroline immobilized on polystyrene and catalytic performance in oxidative carbonylation of methanol

The heterogenization of homogeneous catalysts combines the advantages of both heterogeneous and homogeneous catalysis systems. In oxidative carbonylation of methanol to dimethyl carbonate (DMC), a novel heterogenization of a homogeneous catalyst system, CuCl/1,10-phenanthroline immobilized on polystyrene, was investigated. Characterizations with FTIR, XPS, EA, TGA and AA revealed that CuCl was successfully immobilized on polystyrene modified 1,10-phenanthroline (Phen-PS) through chelating between the N–N bidentate ligand and Cu. The catalytic performance of the CuCl/Phen-PS catalyst tested proved that it is an efficient heterogenized catalyst for the oxidative carbonylation of methanol. The conversion of methanol, the selectivity to DMC and the yield of DMC based on O2 were 15.5%, 96.4% and 78.2%, respectively, at 120 °C, 5 h, 3.0 MPa, and PCO:PO2=9:1. The CuCl/Phen-PS catalyst retains its catalytic activity after seven recycles. The average weight loss of CuCl/Phen-PS was about 2.2%, and the leaching of copper was about 0.68% in each recycle.

Erratum to “The role of copper chloride hydroxides in the oxidative carbonylation of methanol for dimethyl carbonate synthesis” [J. Mol. Catal A 203 (2003) 137–143

Erratum to “The role of copper chloride hydroxides in the oxidative carbonylation of methanol for dimethyl carbonate synthesis” [J. Mol. Catal A 203 (2003) 137–143

Separation of dimethyl carbonate/methanol/water mixtures by pervaporation using crosslinked chitosan membranes

This study deals with the separation of dimethyl carbonate (DMC) by pervaporation using crosslinked chitosan membranes. DMC, an environmentally benign chemical, is commercially produced by oxidative carbonylation of methanol, and the separation and purification of DMC is critical to DMC manufacture due to azeotropic nature of the reaction mixtures. In this study, chitosan membranes crosslinked by dilute sulfuric acid were prepared for DMC separation by pervaporation. The membranes were tested for separation of binary DMC/water, DMC/methanol and methanol/water mixtures and ternary DMC/methanol/water mixtures in a temperature range of 25–55 °C. The experimental results showed that the membrane could be used effectively to break the DMC/methanol azeotrope and to remove a small amount of water from DMC. It was also shown that coupling effect was important in pervaporation separation of multi-component mixtures due to interactions among the permeating species.

EFFECT OF Cu CATALYST PREPARATION ON THE OXIDATIVE CARBONYLATION OF METHANOL TO DIMETHYL CARBONATE

In this paper, the effect of catalyst preparation on the activity of supported Cu catalyst for oxidative carbonylation of methanol to dimethyl carbonate was investigated. The results showed that after addING metal hydroxide, the supported Cu catalyst enhanced the conversion of methanol and the selectivity TO of DMC and the suitable mole ratio of OH/Cu is 1.0. The optimum Cu content lies in 6-10 wt.% and varies with reaction temperature. The suitable calcination temperature range is 200-300oC considering both factors of methanol conversion and DMC selectivity. The effect of particle size of the catalysts on the activity is negligible.

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.

Poly(pyridine-2,5-diyl)–CuCl 2 catalyst for synthesis of dimethyl carbonate by oxidative carbonylation of methanol: catalytic activity and corrosion influence

A π-conjugated polymer, poly(pyridine-2,5-diyl) (PPy) was investigated as a support for CuCl2 in the synthesis of dimethyl carbonate by oxidative carbonylation of methanol. The PPy–CuCl2 adduct had high catalytic activity which was comparable to that of the homogeneous CuCl2 catalyst. The adduct caused corrosion of stainless-steel vessels only to minor extent, compared with the homogeneous CuCl2 catalyst. This PPy–CuCl2 catalyst was easily recycled by filtration and showed a similar catalytic activity in the third time use. The presence of the π-conjugated system in PPy, through which electrons can move, may bring about the high catalytic activity for the oxidative carbonylation of methanol, which involves Cu(II)/Cu(I) redox processes.