Dimethyl Carbonate Production Research Articles

Techno-economic evaluation of different CO2-based processes for dimethyl carbonate production

In this work, several chemical processes for production of dimethyl carbonate (DMC) based on CO2 utilization are evaluated. Four CO2-based processes for production of DMC are considered: (1) direct synthesis from CO2 and methanol; (2) synthesis from urea; (3) synthesis from propylene carbonate; and (4) synthesis from ethylene carbonate. The processes avoid the use of toxic chemicals such as phosgene, CO and NO that are required in conventional DMC production processes. From preliminary thermodynamic analysis, the yields of DMC are found to have the following order (higher to lower): ethylene carbonate route>urea route>propylene carbonate route>direct synthesis from CO2. Therefore, only the urea and ethylene carbonate routes are further investigated by comparing their performances with the commercial BAYER process on the basis of kg of DMC produced at a specific purity. The ethylene carbonate route is found to give the best performance in terms of energy consumption (11.4% improvement), net CO2 emission (13.4% improvement), in global warming potential (58.6% improvement) and in human toxicity-carcinogenic (99.9% improvement) compared to the BAYER process. Also, the ethylene carbonate option produces ethylene glycol as a valuable by-product. Based on the above and other performance criteria, the ethylene carbonate route is found to be a highly promising green process for DMC production.

Selective oxidation of 1,2-propanediol to lactic acid catalyzed by nanosized Mg(OH)2-supported bimetallic Au–Pd catalysts

1,2-Propanediol co-produced in the dimethyl carbonate production is oversupplied in market. 1,2-Propanediol can also be facilely produced starting from glycerol, which is oversupplied in the biodiesel production. Catalytic conversion of low-valued 1,2-propanediol to high-valued and environmental benign lactic acid was investigated under mild reaction conditions over Au–Pd/Mg(OH)2 catalysts in our present work. The Au–Pd/Mg(OH)2 catalysts were prepared by the sol-immobilization method and characterized by XRD, SEM, HRTEM, UV–vis DRS, and O2-TPD techniques. Small-sized Au and Pd nanoparticles were coalesced together to form secondary nanoparticles, which were well dispersed on the surfaces of Mg(OH)2 nanoslices. The Au and Pd nanoparticles synergistically catalyzed the oxidation of 1,2-propanediol with O2 to lactic acid in an alkaline solution. When the catalytic oxidation of 1,2-propanediol was carried out over Au0.75Pd0.25/Mg(OH)2 catalyst at 60°C for 240min, the lactic acid selectivity of 88% was obtained at the 1,2-propanediol conversion of 97.5%. A power-function type reaction kinetic model well fitted the experimental data, r=−dCP/dt=kCP0.8PO21.4Wcat1.0. The reaction activation energy was 64kJmol−1.

Process analysis and economic optimization of intensified process alternatives for simultaneous industrial scale production of dimethyl carbonate and propylene glycol

Several processes in the chemical and petrochemical industries are limited by chemical and phase equilibria. Therefore, these processes require several steps to produce the desired products with the required purity. These complex steps lead to high production costs due to the high capital investment required. Moreover, the vast utility demand required by most chemical processes contributes to high operating and production costs. Promising alternatives are intensified processes such as hybrid or integrated reactive separation processes, which can reduce the number of apparatuses as well as the utility demand, thereby increasing process sustainability. However, the identification of the final configuration and dimensions of these apparatuses and an optimal operating point is a challenging task. This task usually involves solving a mixed-integer nonlinear programming problem to identify optimal values for the degrees of freedom. This work presents a memetic optimization algorithm and validates its ability to handle such problems by optimizing a benchmark function. This optimization algorithm was applied to economically optimize several intensified process alternatives allowing to compare their capabilities to a base-case process. The transesterification of propylene carbonate with methanol served as a case study with high potential for process intensification and production of dimethyl carbonate in the framework of “green chemistry”. Validated rate-based models were used to model four intensified process alternatives consisting of different combinations of reactive distillation, reactive dividing wall columns, pressure-swing distillation and vapor permeation. This study has shown that alternatives using reactive dividing wall columns can improve process economics up to 35% over the base-case process.

Direct Coupling of Cs2CO3and Alcohols for the Synthesis of Dimethyl, Diethyl, and Various Dialkyl Carbonates

Dimethyl carbonate (DMC) has been used in synthetic organic chemistry as a low-toxicity and versatile methylating and carbonylating agent. In industrial processes, DMC is widely used as a fuel additive, electrolyte for lithium ion batteries, and monomer for polycarbonate and polyurethane synthesis. Therefore, an efficient and high-yield synthesis for DMC has been actively investigated. Reaction conditions typically involve either carbon monoxide (CO) or derivatives (e.g., phosgene), or carbon dioxide (CO2) or derivatives (e.g., inorganic carbonates or organic cyclic carbonates). Due to the toxicity and flammability of CO and phosgene, the more environmentally benign and sustainable carbon sources CO2 and derivatives have been actively employed for production of DMC and related acyclic carbonates. The DMC and acyclic carbonate syntheses that have been reported include: 1) transesterification of cyclic carbonates derived from oxirane and CO2; 2) dehydrative condensation of alcohols with CO2; 3) reactions between alkyl halide and metal carbonates; 4) reactions between alcohol, alkyl halide, and CO2; and 5) reactions between alcohol and CO2 in the presence of condensing agents. Other than transesterification of cyclic carbonates, DMC is generated from alcohols or alkyl halide. In terms of chemical cost, use of an alcohol without an extra step for alkyl halide preparation appears more desirable; however, direct coupling of alcohols with CO2 or metal carbonates is challenging. In dehydrative condensation of alcohols with CO2, very efficient dehydrating reagents and metal catalysts are necessary to drive the reaction equilibrium to the product. In direct coupling of alcohols with CO2, alcohol-activation reagents such as the Mitsunobu reagent are required. According to Saito et al., dichloromethane, a common organic solvent, has been used as an alcohol-activating reagent for synthesis of various aliphatic carbonates in the presence of CO2 and Cs2CO3 (base), although synthesis of DMC has not been reported using dichloromethane. In the present study, we used dibromomethane (CH2Br2) as an alcohol-activating reagent and solvent. Using CH2Br2 and an ionic liquid, direct coupling of alcohols with Cs2CO3 in the absence of CO2 was achieved. Using Cs2CO3-mediated conditions, various aliphatic carbonates, including DMC and diethyl carbonate (DEC), were prepared with good yields. Optimization of the synthesis of carbonate 1 is summarized in Table 1. Reaction of cinnamyl alcohol and Cs2CO3 in a mixture of dichloromethane (CH2Cl2) and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) was carried out at 70 C. Even in the absence of CO2, carbonate 1 was formed with 71% yield (entry 1). In this reaction, Cs2CO3

Synthesis of dimethyl carbonate and propylene glycol in a membrane-assisted reactive distillation process: Pilot-scale experiments, modeling and process analysis

The simultaneous production of dimethyl carbonate and propylene glycol by transesterification of propylene carbonate with methanol is limited by several thermodynamic restrictions. The reactant conversion is limited by the chemical equilibrium, whereas the purification of dimethyl carbonate is hindered by the formation of an azeotrope with methanol thus necessitating an energy-intensive reference process to produce both products. Process intensification is a promising tool to increase the sustainability of chemical processes by using novel apparatuses and techniques. Therefore, an intensified, membrane-assisted reactive distillation process was investigated in this study allowing to overcome both limitations. Reactive distillation was used to overcome the chemical equilibrium, whereas vapor permeation was used to overcome the azeotrope. However, detailed experimental studies remain necessary to reduce the general industrial skepticism towards these processes and thus increase their use. Hence, a detailed pilot-scale experimental study was performed to quantify synergistic effects between both unit operations. The experimental results were applied to validate a process model that was used to analyze the process. In the future, the insights of the process analysis can be used to define the operating range of the process. This step is necessary to initialize the economic optimization of this process concept in industrial scale.

Production of DMC from CO2 via Indirect Route: Technical–Economical–Environmental Assessment and Analysis

Interest in dimethyl carbonate (DMC), a saleable chemical destination of CO2, has grown significantly. DMC is an oxygenated octane-booster and a safer and nontoxic substitute of well-established methylating-carbonylating hazardous chemicals like dimethyl sulfate and phosgene. Considering the CO2 routes to DMC, the one commercially promising converts CO2 with ethylene oxide (EO) to ethylene carbonate (EC), which then reacts with excess methanol (MeOH) to DMC and ethylene glycol (EG). This indirect route (IR) apparently exhibits green chemistry attributes. It converts greenhouse gases (GHG) to valuables, such as EG, EC, and DMC. Apparently, it is not energy intensive; it has 100% atom economy without wastes. However, there is a massive energetic obstacle occluded in the separation of the azeotropic pair DMC–MeOH yet to be considered. This work assesses the technical, economical, and environmental IR flowsheet for CO2 conversion to DMC. Assessment of entrainers for extractive distillation of DMC–MeOH was acc...

Quantum-chemical study of thermodynamics of ethylene carbonate reactions with methanol

Thermodynamic parameters of the major and side reactions in the course of dimethyl carbonate formation from ethylene carbonate and methanol have been determined by means of the B3LYP/6-311++G(df,p) quantum-chemical method. Enthalpy and entropy of the reactions have increased with enhanced association of the alcohols. Temperature dependences of the equilibrium constants have been determined. Technological conditions of dimethyl carbonate production via ethylene carbonate methanolysis have been elaborated.

Synthesis of dimethyl carbonate and propylene glycol in a pilot-scale reactive distillation column: Experimental investigation, modeling and process analysis

The transesterification of propylene carbonate with methanol to produce the two valuable products dimethyl carbonate and propylene glycol is associated with an unfavorable chemical equilibrium and complex thermodynamic behavior. This results in a challenging and cost-intensive process currently used for their production. The application of reactive distillation, which integrates chemical reaction and distillation into one single column is considered as potential candidate to improve efficiencies and product yields within chemical-equilibrium-limited systems. However, the design of such a column for industrial-scale applications is challenging as it needs the integration of model-based approaches with reliable experimental data. This paper presents an experimental and theoretical investigation of the simultaneous production of dimethyl carbonate and propylene glycol in a pilot-scale reactive distillation column. Experiments varying decisive operating parameters were successfully performed showing the feasibility of simultaneously producing dimethyl carbonate and propylene glycol in a reactive distillation column. The experimental results were used to select and validate a modeling approach for the simulation of the reactive distillation process. The successfully validated non-equilibrium stage model was applied to perform a process analysis pointing out the trends of both the reactant conversions and the product purities. The simulation results showed the option of achieving high propylene carbonate conversions while recovering an azeotropic mixture of dimethyl carbonate and methanol in the distillate. These results define the operating range for the economic optimization and establishment of an industrial-scale reactive distillation process for this chemical system.

Mesostructured graphitic carbon nitride as a new base catalyst for the efficient synthesis of dimethyl carbonate by transesterification

Mesostructured graphitic carbon nitride (CN-MCF) material has been prepared using carbon tetrachloride and ethylenediamine as precursors and mesocellular silica foam as a hard template, and characterized by XRD, N2 adsorption–desorption, TEM, FT-IR, and XPS techniques. The material was employed as a catalyst for the production of dimethyl carbonate (DMC) via transesterification of ethylene carbonate (EC) with methanol (MeOH). The influences of reaction conditions, including time, temperature, and the molar ratios of MeOH to EC, on the catalytic performance have been investigated in detail. Catalytic results revealed that CN-MCF could catalyze the transesterification reaction with high efficiency, affording a high DMC yield of 78% and stable catalytic activity for several running cycles. Furthermore, a possible reaction mechanism for the g-CN-catalyzing transesterification of EC with MeOH has been proposed.

One-Pot Synthesis of Dimethyl Carbonate over Basic Zeolite Catalysts

One-pot synthesis of dimethyl carbonate (DMC) from methanol, propylene oxide (PO) and carbon dioxide has been investigated using the basic zeolites as catalysts. Among the zeolites studied, Beta showed the best catalytic performance for DMC production. That the desilication of zeolite structure resulted in a hierarchical porosity of Beta, leading to more amount of KOH can be loaded on the surface of zeolite and therefore enhancing the base strength of the catalyst was proposed to be the reason for improved catalytic performance.

Investigation of metal cyclam complexes as potential catalysts for the production of dimethyl carbonate

While Zn cyclam complexes are known to readily react with CO2 and methanol to provide carbonato complexes, we were interested in trying to extend this chemistry into a possible catalytic cycle for the production of dimethyl carbonate. This route would require a cleavage of the Zn-carbonato complex with methanol. Towards this goal we modified the cyclam ligands by attaching various Lewis basic donors as pendant groups on the cyclam that could potentially act as hemilabile arms. The crystal structures of 1-(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane 2, 1-(3-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane 3, and 1-propionitrile-1,4,8,11-tetraazacyclotetradecane 4 are presented. Ligand 2 was reacted with M[ClO4]2 (M=Zn, Cd) and the resulting complexes were structurally and spectroscopically characterized. Despite the modifications, again these complexes did not perform as catalysts for the formation of dimethyl carbonate. Ligand 4 was found to react with methanol in the presence of Zn[ClO4]2·6H2O to convert the nitrile group into a methyl propionimidate, forming the methyl propionimidate (1,4,8,11-tetraazacyclotetradecane) zinc perchlorate. It is likely that the donor arms used bind too strongly to Zn or Cd to allow complexation of CO2 or methanol.

Comparative study between gas phase and liquid phase for the production of DMC from methanol and CO2

Direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide over Co1.5PW12O40 in liquid and in gas phase is investigated. The synthesized catalyst has been characterized by means of FTIR and XRD. Liquid phase experiment results showed that high pressures are favorable for the synthesis of DMC. However, DMC formation is limited by the reaction with co-produced water. DMC selectivity is more strongly dependent on the temperature than on the pressure of CO2. As for the reactions in gas phase, it has been found that both CH3OH conversion and DMC selectivity decreased with increasing temperature, owing to the decomposition of DMC at high temperatures. High temperatures and more amount of Co1.5PW12O40 catalyst favor the formation of dimethoxymethane (DMM) and methyl formate (MF).

Synthesis of dimethyl carbonate over waste eggshell catalyst

Dimethyl carbonate is an important methylating and carbonylating agent. Eggshell catalysts, prepared from eggshell waste, were tested in the synthesis of dimethyl carbonate from propylene carbonate and methanol. The eggshell-derived catalyst was characterized by using techniques of nitrogen physisorption, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and energy dispersive X-ray spectroscopy (EDS). The effects of calcination temperature on structure and activity of eggshell catalysts were investigated. The reusability of eggshell catalysts was also examined. It was found that highly active, reusable solid catalyst was obtained by just calcining eggshell. Dimethyl carbonate yield of 75% can be achieved at 25°C and 1atm pressure. Utilization of eggshell as a catalyst for dimethyl carbonate production not only provides a cost-effective and environmental friendly way of recycling this solid eggshell waste, but also makes the process of dimethyl carbonate production economic and fully ecologically friendly.

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.

Electrochemical synthesis of dimethyl carbonate from methanol, CO2 and propylene oxide in an ionic liquid

AbstractBACKGROUND: Dimethyl carbonate (DMC) can be used effectively as an environmentally benign substitute for highly toxic phosgene and dimethyl sulfate in carbonylation and methylation, as well as a promising octane booster owing to its high oxygen content. Two‐step transesterification from epoxide, methanol, and CO2 is widely used in the bulk production of DMC. However, major disadvantages of this process are high energy consumption, and high investment and production costs. A one pot synthesis of DMC from carbon dioxide, methanol, and epoxide was, therefore, developed. But the yields of DMC are below 70% due to the thermodynamic limitation.RESULTS: Electrochemical synthesis of DMC was conducted with platinum electrodes from methanol, CO2 and propylene oxide in an ionic liquid was conducted. The bmimBr (1‐butyl‐3‐methylimidazolium bromide)‐methanol‐propylene oxide system with CO2 bubbling allows DMC to be effectively synthesized and a high yield (75.5%) was achieved.CONCLUSION: In this electrolysis, redox reactions of substrates, CO2, methanol, and propylene oxide, on Pt electrodes were carried out, producing the activated particles, CH3O−, CH3OH+, CO2− and PO−, resulting in the effective synthesis of DMC with a 75.5% yield in an ionic liquid (bmimBr). Finally, a mechanism for this synthesis reaction was proposed, which is very different from those reported in the literature. Copyright © 2011 Society of Chemical Industry

Production of dimethyl carbonate from ethylene carbonate and methanol using immobilized ionic liquids on MCM-41

Ionic liquids on ordered mesoporous silica were prepared and their catalytic performance in the synthesis of dimethyl carbonate (DMC) was investigated. The ionic liquids were immobilized on chloropropyl-functionalized MCM-41 (CP-MS41) through the quaternization of trialkylamines. The supported ionic liquids were proven to be an effective heterogeneous catalyst for the synthesis of DMC from transesterification of ethylene carbonate (EC) with methanol. The immobilized quaternary ammonium salt (QCl-MS41) catalysts with longer alkyl chains showed higher EC conversion and turnover number (TON). Higher temperatures and longer reaction times were favorable for the reactivity of QCl-MS41. However, carbon dioxide pressure showed a maximum for catalytic activity. The catalyst can be reused for reactions in up to three consecutive runs with only a slight decrease in catalytic activity.

CO2: from waste to resource for methanol-based processes

This paper reports on research aiming at developing sustainable processes for the production of methanol (CH3OH) and dimethyl carbonate (DMC, (CH3)2CO3) using carbon dioxide (CO2) as a raw material. Using carbon dioxide as a raw material has several advantages; it is non-toxic, in abundant supply, and promises innovative routes to the production of commodity chemicals. Methanol and dimethyl carbonate are important products and feedstocks of the chemical industry. Methanol is produced commercially from synthesis gas, but it is also possible to use carbon dioxide as a feedstock. Conventional production of dimethyl carbonate involves the use of toxic phosgene or carbon monoxide, while the methanol-based route using carbon dioxide offers better atom economy and safer production. The alternative production processes using carbon dioxide thus transform a secondary resource from an anthropogenic source to high-volume and high-value intermediates while reducing environmental impacts. However, to evaluate fully the sustainability of these intermediates, all the feedstocks of the novel process have to be taken into account and potential applications need to be analysed. This paper also contemplates the issue of what waste actually is, and when carbon dioxide is considered waste and when it ceases to be waste.

Pareto optimization of an industrial ecosystem: sustainability maximization

This work investigates a procedure to design an Industrial Ecosystem for sequestrating CO2 and consuming glycerol in a Chemical Complex with 15 integrated processes. The Complex is responsible for the production of methanol, ethylene oxide, ammonia, urea, dimethyl carbonate, ethylene glycol, glycerol carbonate, β-carotene, 1,2-propanediol and olefins, and is simulated using UNISIM Design (Honeywell). The process environmental impact (EI) is calculated using the Waste Reduction Algorithm, while Profit (P) is estimated using classic cost correlations. MATLAB (The Mathworks Inc) is connected to UNISIM to enable optimization. The objective is granting maximum process sustainability, which involves finding a compromise between high profitability and low environmental impact. Sustainability maximization is therefore understood as a multi-criteria optimization problem, addressed by means of the Pareto optimization methodology for trading off P vs. EI.

Significant influence of microwave dielectric heating on ionic liquid catalyzed transesterification of ethylene carbonate with methanol

This paper reports an energy efficient route for the transesterification of ethylene carbonate (EC) with methanol using ionic liquid (IL) as catalyst through microwave heating. The influence of the reaction parameters such as the microwave irradiation time, power, EC/methanol ratio, and the cation and anion of both 1-alkyl-3-methyl imidazolium and tetraalkyl ammonium salts, was examined under these conditions. Also the heating characteristics of this reaction mixture were examined at various intervals. The coproduction of an equimolar amount of dimethyl carbonate (DMC) and ethylene glycol (EG) were obtained in high yield and better selectivity. Comparative studies were carried out under different reaction conditions with classical heating modes. An induction period observed during conventional reaction can be avoided by microwave dielectric heating. Overall, this study highlights an environmentally benign technology for the production of DMC, a “green reagent”, through microwave irradiation.

Sustainability metrics for eco-technologies assessment, part I: preliminary screening

This work presents a preliminary screening of eco-technologies for dimethyl carbonate (DMC) production. Through sustainability metrics, the assessment of six different chemical routes allows comparisons according to economical and environmental criteria, to determine the most sustainable route. CO2 sequestration potential is also considered. The alternatives are scored according to the adopted metrics, leading to the decision of a suitable route based on economic and environmental grounds, prioritizing pollution-preventing technologies herein referred to as eco-technologies. Casting of technologies was based on alternatives available in the literature: Route 1 production of DMC from methanol and phosgene [Ono in Pure Appl Chem 68(2):367–375, 1996]; Route 2 production of DMC from methyl nitrite and CO [Ono in Pure Appl Chem 68(2):367–375, 1996]; Route 3 production of DMC from CO and methanol [Ono in Pure Appl Chem 68(2):367–375, 1996]; Route 4 production of DMC from urea and methanol (Wang et al. in Ind Eng Chem Res 46:8972–8979, 2007); Route 5 production of DMC from ethylene oxide and CO2 [Ono in Pure Appl Chem 68(2):367–375, 1996]; Route 6 production of DMC from CO2 and methanol (Choi et al. in Green Chem 4:230–234, 2002). The analysis shows that Routes 4 and 5 combine intermediate values of the total (sustainability) score, CO2 sequestration potential and industrial feasibility, therefore entitled as eco-technologies, based on the adopted metrics. Although the two technologies are potentially ecological, they are recommended for a more rigorous analysis on the grounds of process simulation and life cycle analysis.