Oxidative Carbonylation Of Methanol Research Articles

Green Routes to Dimethyl Carbonate: A Green and Versatile Methylating Reactant

Abstract: This mini-review reports the current routes used for the production of dimethyl carbonate (DMC), a green and versatile methylating reactant widely used in organic synthesis. The use of DMC in methylation processes is also discussed. The main routes of DMC production, encompassing the reaction between phosgene and methanol and the oxidative carbonylation of methanol with CO and urea methanolysis, are summarised. However, none of them can be considered entirely green, and the drawbacks in terms of green chemistry principles are addressed. The present commercial route to DMC, which involves the initial reaction of CO2 with ethylene oxide to produce ethylene carbonate that further reacts with excess methanol, is also explored regarding the green chemistry principles. Moreover, this review focuses on the direct DMC production from the reaction of methanol and CO2, discussing catalysts and strategies to shift equilibrium. An emphasis is given to heterogeneous catalysts, especially those based on CeO2. A final remark on the production of DMC through the capture of CO2 using chitosan-derived adsorbents and renewable methanol is addressed.

DFT Investigations of the Reaction Mechanism of Dimethyl Carbonate Synthesis from Methanol and CO on Various Cu Species in Y Zeolites

In this study, a density functional theory method is employed to investigate the reaction mechanisms of dimethyl carbonate (DMC) formation, through oxidative carbonylation of methanol, on four types of Y zeolites doped with Cu+, Cu2+, Cu2O and CuO, respectively. A common chemical route is found for these zeolites and identified as, first, the adsorbed CH3OH is oxidized to CH3O species; subsequently, CO inserts into CH3O to CH3OCO, which reacts with CH3O to form DMC rapidly; and finally, the adsorbed DMC is released into the gas phase. The rate-limiting step on Cu2+Y zeolite is identified as oxidation of CH3OH to CH3O with activation barrier of 66.73 kJ·mol−1. While for Cu+Y, Cu2O-Y and CuO-Y zeolites, the rate-limiting step is insertion of CO into CH3O, and the corresponding activation barriers are 63.73, 60.01 and 104.64 kJ·mol−1, respectively. For Cu+Y, Cu2+Y and Cu2O-Y zeolites, adsorbed CH3OH is oxidized to CH3O with the presence of oxygen, whereas oxidation of CH3OH on CuO-Y is caused by the lattice oxygen of CuO. The order of catalytic activities of these four types of zeolites with different Cu states follows Cu+Y ≈ Cu2O-Y > Cu2+Y > CuO-Y zeolite. Therefore, CuY catalysts with Cu+ and Cu2O as dominated Cu species are beneficial to the formation of DMC.

An Intensified Green Process for the Coproduction of DMC and DMO by the Oxidative Carbonylation of Methanol

Dimethyl carbonate (DMC) is an eco-friendly and sustainable compound with widespread industrial applications. Various extensive routes have been exploited in the chemical industry to produce DMC. However, these routes have several environmental and energy drawbacks. In this study, a promising novel industrial scheme for the synthesis of DMC via the oxidative carbonylation of vaporized methanol with dimethyl oxalate (DMO) as a byproduct is investigated. A methanol conversion of 81.86% and a DMC selectivity of 83.47% were achieved using an isothermal fixed-bed reactor at 130 °C. The DMC is withdrawn at a purity of >99 mol% via pressure-swing azeotropic distillations. Heat integration was performed to optimize energy consumption, reducing the energy requirements by 28%. An economic evaluation was performed for estimating the profitability via cash-flow diagrams, predicting a payback period of 3.7 years. The proposed green process exhibits several benefits, including high profitability and being environmentally friendly. It also eliminates the use or production of hazardous materials, and it enhances safety characteristics.

New Strategies on Green Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol over Oxide Composites.

Dimethyl carbonate is a generally used chemical substance which is environmentally sustainable in nature and used in a range of industrial applications as intermediate. Although various methods, including methanol phosgenation, transesterification and oxidative carbonylation of methanol, have been developed for large-scale industrial production of DMC, they are expensive, unsafe and use noxious raw materials. Green production of DMC from CO2 and methanol is the most appropriate and eco-friendly method. Numerous catalysts were studied and tested in this regard. The issues of low yield and difficulty in tests have not been resolved fundamentally, which is caused by the inherent problems of the synthetic pathway and limitations imposed by thermodynamics. Electron-assisted activation of CO2 and membrane reactors which can separate products in real-time giving a maximum yield of DMC are also being used in the quest to find more effective production method. In this review paper, we deeply addressed green production methods of DMC using Zr/Ce/Cu-based nanocomposites as catalysts. Moreover, the relationship between the structure and activity of catalysts, catalytic mechanisms, molecular activation and active sites identification of catalysts are also discussed.

Green Synthesis of Dimethyl Carbonate from CO2 and Methanol: New Strategies and Industrial Perspective

AbstractDimethyl carbonate (DMC) is a commonly used and environmentally sustainable chemical compound and intermediate in a variety of industrial applications. To date, several large‐scale industrial DMC synthesis routes have been developed, including methanol phosgenation, transesterification, and oxidative carbonylation of methanol. However, these manufacturing routes have several disadvantages, such as the use of hypertoxic phosgene as raw material, costly processing, and explosion risks. The most encouraging and ecofriendly path is the green production of DMC from CO2 and methanol. Various catalytic materials have been examined concerning their suitability for DMC synthesis. The issues of low yield and difficulty in tests have not been resolved fundamentally, which is caused by the inherent problems of the synthetic pathway and limitations imposed by thermodynamics. The search for more efficient production routes has driven the activation of CO2 via electro‐assisted synthesis as well as membrane reactors, which can isolate products in real‐time to maximize DMC yield. The green synthesis of dimethyl carbonate catalyzed by different catalysts including Zr/Ce/Cu‐based nanocomposites, organometallic compounds, heteropoly acid, ionic liquid, metal‐organic frameworks, etc, is discussed in detail. Further, the structure–activity relationships and insights into molecular activation and catalytic mechanisms, as well as the identification of active sites on catalysts are addressed.

The Influence of Iron Group Promoters on the Synthesis of Dimethyl Carbonate over CuY Catalysts Prepared via Modified Vapor Impregnation Method

CuY and CuMY (M = Fe, Co, Ni) catalysts were prepared by modified vapor impregnation using cupric acetylacetonate as copper source and M acetylacetonate as promoter. The catalysts were evaluated in heterogeneous catalytic vapor phase oxidative carbonylation of methanol to dimethyl carbonate (DMC). The catalyst samples were analyzed by XRD, H2-TPR, XPS, CO-TPD, and NH3‑TPD, and their catalytic performance was assessed in a fixed-bed reactor. The experimental results indicate that all introduced species were well dispersed on zeolite Y, and the addition of iron group promoters have effect on the Cu+ contents, acidity and CO adsorption-desorption performance. Finally the influence of various promoters was examined with the aim of increasing space-time yield of DMC from methanol. Space-time yield of DMC was increased with the addition of iron group promoters in the order Fe < Co < Ni, but the selectivity follows the order of Fe < Ni < Co, respectively.

Hierarchical Porous Carbon-Supported Copper Nanoparticles as an Efficient Catalyst for the Dimethyl Carbonate Synthesis

A series of three-dimensional (3D)-interconnected hierarchical porous carbons (HPCs) were prepared through a “leavening” strategy. α-Cellulose and NaHCO3 were used as a raw material and foaming agent, respectively, to support copper catalysts (Cu/HPC) for dimethyl carbonate (DMC) synthesis by the oxidative carbonylation of methanol. The calcination temperature had a significant influence on the textural properties of the HPC and the catalytic performance of the Cu/HPC. The catalyst calcined at 900 °C exhibited the highest catalytic activity with a DMC space–time yield of 2018 mg/(g h). The characterization results indicated that the outstanding catalytic activity was related to the highest dispersion of copper species and to a high content of surface Cu0 species, which can be attributed mainly to the enhanced anchoring effect of abundant micro- and mesopores of a 3D-interconnected network. In addition, the well-developed 3D-interconnected hierarchical porous structure provided a rapid and efficient channel for reactant and product transport and migration, which enhanced the catalytic performance. This work expands the potential application range of HPC materials and presents a novel procedure to prepare catalysts for DMC synthesis.

Oxycarbonylation of methanol over modified CuY: Enhanced activity by improving accessibility of active sites

CuY zeolite is a promising catalyst in the field of manufacturing dimethyl carbonate (DMC) through oxidative carbonylation of methanol. Cu+ exchanged with Brønsted acid sites are supposed to be active for this reaction. However, the location of Cu+ in small cages can not interact with reactants because of steric hindrance, which lead to a waste of Cu species. In this work, NH4F solution was used to modify the pore structure of zeolite Y by etching the framework T atoms. Physical and chemical adsorption of probe molecules with different size are used to determine the changes of porosity as well as the accessibility of Cu+ sites. At an optimized etching time, the small cages were opened with maintained zeolitic framework. As a result, more Cu+ species located in small cages become accessible to reactants, which contributes to the enhanced activity in this reaction.

CuY Zeolite Catalyzed Oxidative Carbonylation of Methanol to Dimethyl Carbonate: Comparative Investigation of Reduction Method

CuY zeolite is a promising catalyst for oxidative carbonylation of methanol to dimethyl carbonate (DMC). In this work, auto-reduction at high temperature and vapor-induced reduction were comparatively investigated to activate the CuY precursors. XPS, XRD as well as CO adsorption demonstrated that methanol as reduction agent can achieve a high proportion of Cu(I) and avoid the formation of Cu(0) as far as possible, which is responsible for the enhanced DMC yield.

Corrigendum to “Influence of dehydrating agents on the oxidative carbonylation of methanol for dimethyl carbonate synthesis over a Cu/Y-zeolite catalyst” [Chin. J. Chem. Eng. 26(2018)1059-1063

Corrigendum to “Influence of dehydrating agents on the oxidative carbonylation of methanol for dimethyl carbonate synthesis over a Cu/Y-zeolite catalyst” [Chin. J. Chem. Eng. 26(2018)1059-1063

Influence of dehydrating agents on the oxidative carbonylation of methanol for dimethyl carbonate synthesis over a Cu/Y-zeolite catalyst

Abstract The influence of the dehydration by metal oxides on the synthesis of dimethyl carbonate (DMC) via oxidative carbonylation of methanol was studied. A Cu/Y-zeolite catalyst was prepared by the ion exchange method from CuCl 2 ·2H 2 O and the commercial NH 4 -form of the Y type zeolite. The catalyst was characterized by X-ray fluorescence (XRF), N 2 adsorption (BET method), X-ray diffraction (XRD), and temperature-programmed desorption of ammonia (NH 3 -TPD) to evaluate its Cu and Cl content, surface area, structure, and acidity. Reaction tests were carried out using an autoclave (batch reactor) for 18 h at 403 K and 5.5 MPa (2CH 3 OH + 1/2O 2 + CO ⇌ (CH 3 O) 2 CO + H 2 O). The influence of various dehydrating agents (ZnO, MgO, and CaO) was examined with the aim of increasing the methanol conversion ( X MeOH , MeOH conversion). The MeOH conversion increased upon addition of metal oxides in the order CaO >> MgO > ZnO, with the DMC selectivity ( S DMC ) following the order MgO > CaO > ZnO. The catalysts and dehydrating agents were characterized before and after the oxidative carbonylation of methanol by thermogravimetric and differential thermogravimetric (TG/DTG), and XRD to confirm that the dehydration reaction occurred via the metal oxide (MO + H 2 O → M(OH) 2 ). The MeOH conversion increased from 8.7% to 14.6% and DMC selectivity increased from 39.0% to 53.1%, when using the dehydrating agent CaO.

Nitrogen-doped graphene supported copper catalysts for methanol oxidative carbonylation: Enhancement of catalytic activity and stability by nitrogen species

Nitrogen-doped graphene (NG) has recently attracted much interest because of its ability to fix the metal nanoparticles (NPs). In this study, NG materials with a nitrogen content of 4.5–7.6 wt% were prepared by hydrothermal method and then used to support Cu catalysts for dimethyl carbonate (DMC) synthesis via the oxidative carbonylation of methanol. The Cu/NG catalysts showed significantly enhanced catalytic activity and stability as compared with copper/reduced graphene oxide (rGO) catalyst. The characterization results show that the enhancing effect of nitrogen doping can be attributed to the decrease in size of Cu NPs and the increase in density of carrier for efficient charge transfer. Density functional theory calculations gave further evidence that the energy barrier for the rate-limiting step for DMC formation (CO insertion) is 89.6 to 67.5 kJ/mol, and that the energies of binding between Cu and the substrate on Cu/rGO and Cu/NG catalysts are 723.1 and 922.7 kJ/mol, respectively.

Environmental Assessment of Dimethyl Carbonate Production: Comparison of a Novel Electrosynthesis Route Utilizing CO2with a Commercial Oxidative Carbonylation Process

Life cycle assessment (LCA) has been used at an early design stage to evaluate the environmental sustainability of a novel process for synthesizing dimethyl carbonate (DMC) from waste CO2. The process involves an electrochemical reaction of CO2 and methanol in the presence of potassium methoxide and the ionic liquid 1-butyl-3-methylimidazolium bromide to produce DMC. Experimental data and process simulation have been combined to estimate the environmental impacts and compare them to the conventional commercial “Eni” process based on oxidative carbonylation of methanol. Eleven environmental impact categories have been assessed from “cradle to gate”, including global warming potential (GWP), toxicity potentials, and resource depletion. For example, GWP of DMC produced in the electrochemical process ranges from 63.3 to 94.5 kg CO2 eq./kg DMC, depending on a process configuration. This is around 25 times higher than GWP of the commercial process estimated in this study at 3.2 kg CO2 eq./kg DMC. This is becaus...

Direct and generalized synthesis of carbon-based yolk–shell nanocomposites from metal-oleate precursor

This contribution describes the facile preparation of functional yolk–shell nanoparticles (YSNs) made up of different compositions confined within a hollow porous carbon shell (M@Carbon, M=multiple Cu, NiO nanoparticles or ZnO nanowires). These new yolk–shell hybrid materials have been successfully synthesized using metal-oleate complex and phenolic resin monomers as raw materials through a one-step co-pyrolysis method. A relevant characteristic of these yolk–shell composites is the excellent thermal stability. The Cu@Carbon nanospheres with diameters ranging from 330 to 390nm and cavity size ranging from 190 to 220nm can be controlled by varying synthetic parameters. Comprehensive characterizations reveal that Cu-oleate complex, benefiting from the oleate bilayer, serves as an organometallic precursor while simultaneously acting as a soft template for the formation process. The resultant Cu@Carbon nanocomposite exhibits a promising catalytic properties toward DMC synthesis via oxidative carbonylation of methanol. Taking such complex as precursor, a single-step synthetic fashion is expected to simplify the preparation of yolk–carbon shell nanostructure.

A DFT study of DMC formation on Rh‐doped Cu/AC surfaces

The activity and selectivity of heterogeneous catalysts can be significantly improved by dispersion of another active component in the metal substrate. The impact of Rh promoter on the formation of dimethyl carbonate (DMC) via oxidative carbonylation of methanol on Cu–Rh/AC (activated carbon) catalyst was investigated by density functional theory calculations. The most stable configurations of reacting species (CO, OH, CH3O, monomethyl carbonate, and DMC) adsorbed on the Cu0(zero‐valent copper)/AC and Cu–Rh/AC surfaces were determined on the basis of the calculated results. The reaction energy and activation energy of the rate‐limiting steps on the Cu–Rh/AC and Cu0/AC surfaces were compared. The activation energies of the rate‐limiting step of CO insertion into dimethoxide are 206.3 and 304.8 kJ mol−1 on the Cu–Rh/AC and Cu0/AC surfaces, respectively. The activation energies of the rate‐limiting step of CO insertion into methoxide are 78.5 and 92.7 kJ/mol on the Cu–Rh/AC and Cu0/AC surfaces, respectively. The calculated results indicate that the addition of Rh atom has a significant effect on decreasing the active energy the main pathway for DMC formation. © 2015 Wiley Periodicals, Inc.

Mechanism of microwave-induced carbothermic reduction and catalytic performance of Cu/activated carbon catalysts in the oxidative carbonylation of methanol

Activated carbon–supported copper catalysts (Cu/AC) were prepared by impregnation of AC support with aqueous copper (II) nitrate solutions and subsequent microwave carbothermic reduction under different irradiation conditions. This was done to investigate the effect of the valence of copper on the vapor-phase oxidative carbonylation of methanol to dimethyl carbonate (DMC). Thermogravimetric analysis–mass spectrometry were carried out to explore the mechanism of carbothermic reduction in catalyst preparation. X-ray diffractometry, hydrogen temperature-programmed reduction, X-ray photoelectron spectroscopy, and scanning electron microscopy were employed to examine the bulk and surface properties of the Cu/AC catalysts. Microwave irradiation of the catalyst precursors rapidly induced a series of successive reactions, namely decomposition of Cu2(OH)3NO3 into CuO, reduction in CuO to Cu2O, and carbothermic reduction in Cu2O to Cu0. These reactions resulted in mixed-valence copper species, CuO, Cu2O, and Cu0, in the Cu/AC catalysts. CuO, Cu2O, and Cu0 were active in DMC synthesis, but the catalytic performance of Cu/AC was highly dependent on the Cu0 concentration. High irradiation temperatures resulted in higher Cu0 concentrations because of enhanced carbothermic reduction, and fast heating rates improved the degree of dispersion of Cu2O and Cu0. The catalyst irradiated at 540 °C at a heating rate of 48 °C min−1 showed the highest catalytic activity in the oxidative carbonylation of methanol.

Sustainability Assessment of Chemical Processes: Evaluation of Three Synthesis Routes of DMC

This paper suggested multicriteria based evaluation tool to assess the sustainability of three different reaction routes to dimethyl carbonate: direct synthesis from carbon dioxide and methanol, transesterification of methanol and propylene carbonate, and oxidative carbonylation of methanol. The first two routes are CO2-based and in a research and development phase, whereas the last one is a commercial process. The set of environmental, social, and economic indicators selected were renewability of feedstock, energy intensity, waste generation, CO2balance, yield, feedstock price, process costs, health and safety issues of feedstock, process conditions, and innovation potential. The performance in these indicators was evaluated with the normalized scores from 0 to +1; 0 for detrimental and 1 for favorable impacts. The assessment showed that the transesterification route had the best potential toward sustainability, although there is still much development needed to improve yield. Further, the assessment gave clear understanding of the main benefits of each reaction route, as well as the major challenges to sustainability, which can further aid in orienting development efforts to key issues that need improvement. Finally, it was concluded that a multicriteria analysis such as the one presented in this paper was a viable method to be used in the process design stage.

The Synthesis of Dimethyl Carbonate by the Oxicarbonylation of Methanol Over Cu Supported on Carbon Norit

The catalytic activity of Norit supported Cu, Ni and Cu–Ni catalysts was investigated in the synthesis of dimethyl carbonate (DMC) by the oxidative carbonylation of methanol. Cu/Norit showed the best catalytic activity. The reaction was carried out in a continuous flow system at atmospheric pressure usually at 393 K. The main products were methyl formate, DMC and CO2. The methanol conversion on Cu/Norit achieved in steady state was about 22 % and the DMC yield 13.2 %. Based on the XPS data we can establish that copper reduced to its metallic form during reduction but oxidized in the reaction mixture, and is mostly in the Cu+ state, with some Cu2+. It is possible that the DMC formation rate depends on the surface concentration of oxidized Cu and on the ratio of Cu+ and Cu2+. Based upon the IR measurements adsorbed DMC was found on the surface of the Cu/Norit catalyst during the catalytic reaction.

The direct synthesis of dimethyl carbonate by the oxicarbonylation of methanol over Cu supported on carbon nanotube

The activity of Cu/MWCNT and Cu–Ni/MWCNT catalysts was investigated in the synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol. The catalysts were prepared via conventional incipient wetness impregnation technique. The samples were characterized by X-ray photoelectron spectroscopy (XPS), and DRIFT. The reaction was carried out in a continuous flow system at atmospheric pressure at 393K. The main products were methyl formate (MF), DMC and CO2. The methanol conversion on Cu/MWCNT achieved a steady state value after 2h, but on Cu–Ni/MWCNT the conversion decreased continuously. The DMC selectivity was more than 30% and the yield was 1.2% on Cu/MWCNT. Based on the XPS data we can establish that copper reduced to its metallic form during reduction but oxidized in the reaction mixture, and is mostly in the Cu+ state, with some Cu2+ also present on the surface at the beginning of the reaction though its ratio decreased in time. We assume that the DMC formation rate depends on the surface concentration of oxidized Cu. Based upon the FTIR data adsorbed DMC is present on the surface of the Cu/MWCNT catalyst during the catalytic reaction but on Cu–Ni/MWCNT sample only methyl formate was detected in the gas phase.

A theoretical investigation on the mechanism of dimethyl carbonate formation on Cu/AC catalyst

The formation mechanism of dimethyl carbonate (DMC) via oxidative carbonylation of methanol on Cu0/AC (activated carbon) catalyst was investigated by density functional theory and cluster models. Interactions between Cu0 and AC were considered. The results indicate that Cu0 prefers to adsorb at the unsaturated sites on AC. On the basis of the calculated results of the reaction species (O, OH, CO, CH3O, CH3OH, DMC, etc.) adsorbed on the Cu0/AC surface, the most stable adsorption configuration of these species are given. Researchers proposed that DMC can be formed by two different pathways. In the first pathway, DMC is formed by the direct addition of CO to dimethoxide; however, our calculated results indicate that this pathway is not dominant because of the difficulty of overcoming its activation barrier (330.6kJ/mol). In the second pathway, monomethyl carbonate (MMC) species is produced by the insertion of CO to the methoxide species. The MMC species reacts with methanol to form DMC. The calculated results indicate that the latter is the main pathway for DMC formation. The activation barriers of the two successive reactions involving the formation of MMC and DMC are 87.9 and 77.3kJ/mol, respectively.