Synthesis of dimethyl carbonate (dmc) from co2, ethylene oxide and methanol using heterogeneous anion exchange resins as catalysts

Summary A two-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol using heterogeneous anion exchange resins as catalysts is reported. The first step is the reaction of EO with CO₂ to form ethylene carbonate (EC), and the second one the transesterification of EC with methanol to yield DMC. Effect of various reaction parameters on the activity and selectivity of the catalysts used was investigated. After the first step, the crude mixture containing EC was directly reacted with methanol in the presence of a heterogeneous anion exchange resin catalyst to produce DMC in high yield and selectivity. Our process is highly economic.     

KOH/4A分子筛催化剂对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应的催化性能

 首次开发出对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应具有较高活性和稳定性的KOH/4A分子筛固体催化剂,考察了反应温度和催化剂活性组分KOH的负载量等因素对催化剂性能的影响. 在优化的实验条件下,环氧丙烷可以完全转化,碳酸二甲酯的收率为168%. 从实验结果推测,产物碳酸二甲酯是由环氧丙烷和二氧化碳加成生成碳酸丙烯酯,然后与甲醇发生酯交换反应生成的,甲醇对环氧丙烷和二氧化碳合成碳酸丙烯酯反应具有助催化作用.     

二氧化碳和甲醇合成碳酸二甲酯研究进展

本文综述了以二氧化碳和甲醇为起始原料合成碳酸二甲酯（DMC）的研究状况。提出以CO₂和甲醇直接合成DMC,不仅对合成化学,碳资源利用和环境保护具有重大意义,而且可使生产成本显著降低,它是发展DMC生产的一个具有很大潜力的方面。     

添加剂在碳酸二甲酯直接合成中的作用

二氧化碳;甲醇;添加剂在碳酸二甲酯直接合成中的作用     

Promotion of Ionic Liquid to Dimethyl Carbonate Synthesis from Methanol and Carbcn Dioxide

Promotion of ionic liquid, 1-ethyl-3-methylimidazolium bromide (emimBr), to the synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide in the presence of potassium carbonate and less amount of methyl iodide under mild conditions was investigated. The results showed that the high selectivity and raised yield of DMC was achieved due to the addition of emimBr in the reaction system. And effect of several reaction conditions such as temperature, pressure and amount of emimBr was discussed.     

Promotion of Ionic Liquid to Dimethyl Carbonate Synthesis from Methanol and Carbon Dioxide

Introduction Dimethyl carbonate (DMC) is an important carbon-ylating and methylating agent substituting dimethyl sul-fate and toxic phosgene, and an intermediate for higher carbonates and carbamates.1 In addition, it is also a promising octane enhancer.2 The widely used method of its preparation is the oxidative carbonylation of metha-nol by carbon monoxide with copper(II) or palladium(II) catalysts.3 Recently, the utilization of carbon dioxide as the raw material for DMC synthesis has bee…     

One-pot Synthesis of Dimethyl Carbonate in the Presence of a Two-component Catalyst

The one-pot synthesis of dimethyl carbonate（DMC） with co-production of propy-lene carbonate（PC） and propylene glycol（PG） from propylene oxide（ PO）, carbon dioxide and methanol as the starting materials was investigated. The catalyst adopted here was a mixture of tetrabutyl ammonium bromide and sodium methoxide. It was found that un- der the reaction conditions of t = 150 ℃, p =3-4 MPa and 2 h, the PO conversion could reach 100%, the DMC, PC and the PG selectivities were 49. 7%, 42. 7% and 49. 8%, respectively, and the selectivity of by-products was below 10%.     

Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide Catalyzed by Potassium Hydroxide under Mild Conditions

The synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide using potassium hydroxide as catalyst in the presence of CH3I and the effect of ionic liquid on the reaction were investigated. The results showed that KOH is an effective catalyst; the high selectivity and raised yield of DMC formation under mild conditions were achieved. However, the addition of the ionic liquid, l-ethyl-3-methylimidazolium bromide （emimBr）, can evidently accelerate the conversion of methanol and yield of the product.     

Synthesis of dimethyl carbonate from methanol and supercritical carbon dioxide

The synthesis of dimethyl carbonate (DMC) from methanol and supercritical carbon dioxide over various base catalysts has been studied. Compounds of group-I elements (Li, Na and K) were used as base catalysts. The promoter and the dehydrating agent were also used to enhance the yield of DMC. The effects of the catalysts, promoter and dehydrating agent on the yield of DMC were investigated. By-products such as dimethyl ether (DME) and C₁–C₂ hydrocarbons were formed with the DMC as a main product. The yield of DMC with different alkali metal catalysts ranked in the following order: K > Na > Li. The catalysts of the metal-CO₃ compounds were more effective than the metal-OH compounds in DMC synthesis. The maximum DMC yield reached up to about 12 mol% in the presence of K₂CO₃ (catalyst), CH₃I (promoter) and 2,2-dimethoxypropane (dehydrating agent) at 130–140°C and 200 bar. The reaction mechanism of DMC synthesis from methanol and supercritical carbon dioxide was proposed.     

碘甲烷在碳酸二甲酯直接合成中的作用

Dimethyl carbonate (DMC) is an environmentally friendly compound and a substitutive intermediate for highly toxic phosgene or dimethyl sulfate in carbonylation and methylation reactions as well as a promising octane booster. The common methods for its preparation are the oxidative carbonylation of methanol catalyzed by a variety of transition metal ions and the transesterification of ethylene carbonate or propene carbonate with methanol[1]. The direct synthesis of DMC from carbon dioxide and methanol is a challenging route in which the most abundant carbon resources and a main greenhouse gas is used as feedstock. A new method for the direct synthesis of DMC catalyzed by the methoxide of main group metal has attracted more and more attention since it was reported[2～6] . However the lower conversion of the reaction has become the main obstacle for its application. In this letter, an efficient promoter for the direct synthesis of DMC is reported.     

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).     

Direct synthesis of dimethyl carbonate from methanol and carbon dioxide using heteropolyoxometalates: the effects of cation and addenda atoms

The direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide over a series of Keggin-type heteropolyoxometalates has been investigated. The effects of the cations and the addenda atoms of the heteropolyoxometalate on the conversion and the product selectivities were investigated. The results showed that Co_1.5PW₁₂O₄₀ was the best catalyst of the series. The effect of reaction temperature and CO₂ pressure on the direct synthesis of DMC demonstrated that lower temperatures and higher pressures are favorable for the synthesis of DMC. Higher temperatures favor the formation of dimethoxymethane (DMM) and methyl formate (MF).     

低压下碱金属碳酸盐催化一步法合成碳酸二甲酯

报道了低压下碱金属碳酸盐催化环氧化物、CO2和甲醇一步合成碳酸二甲酯(DMC)的方法,系统考察了反应条件对一步合成DMC的影响规律.在最优反应条件下(初始压力0.5 MPa,反应温度120°C,碳酸钠7.5 mol%),以环氧乙烷为起始剂的DMC收率达到63.5%.提出了碱金属碳酸盐催化一步法合成DMC的可能反应机理.     

从超临界二氧化碳和甲醇直接合成碳酸二甲酯

Dimethyl carbonate (DMC), an environmentally benign intermediate for organic synthesis, has been mainly synthesized through non-phosgene route of oxidative carbonylation[1]. Direct synthesis of DMC from carbon dioxide and methanol is of more significance due to atom economy. Organometallic compounds of formulae R2M(OR)2, M(OR)2 or M(OR)4[2,3] were employed as catalysts in direct synthesis of DMC, where an activation mechanism of CO2 insertion into metal-oxygen bond was supposed. Unfortunately, the yield of DMC was low even in the presence of chemical dehydrants because mainly of thermodynamic limit.     

Synthesis of dimethyl carbonate and propylene glycol from transesterification of propylene carbonate and methanol using quaternary ammonium salt catalysts

Summary The synthesis of dimethyl carbonate (DMC) was investigated through the transesterification of propylene carbonate (PC) with methanol using quaternary ammonium salt catalysts. The reaction was carried out in an autoclave at 120-140 oC under carbon dioxide pressure of 250-400 psig. The main by-product was propylene glycol. The quaternary salts of larger alkyl group and more nucleophilic counter anion exhibited higher catalytic activity. Kinetic studies were also performed to better understand the reaction mechanism. Quaternary ammonium chlorides immobilized on polystyrene supports were also tested for their possible uses as heterogeneous catalysts.     

From CO2 to dimethyl carbonate with dialkyldimethoxystannanes: the key role of monomeric species

The formation of dimethyl carbonate (DMC) from CO(2) and methanol with the dimer [n-Bu(2)Sn(OCH(3))(2)](2) was investigated by experimental kinetics in support of DFT calculations. Under the reaction conditions (357-423 K, 10-20 MPa), identical initial rates are observed with three different reacting mixtures, CO(2)/toluene, supercritical CO(2), and CO(2)/methanol, and are consistent with the formation of monomeric di-n-butyltin(iv) species. An intramolecular mechanism is, therefore, proposed with an Arrhenius activation energy amounting to 104 ± 10 kJ mol(-1) for DMC synthesis. DFT calculations on the [(CH(3))(2)Sn(OCH(3))(2)](2)/CO(2) system show that the exothermic insertion of CO(2) into the Sn-OCH(3) bond occurs by a concerted Lewis acid-base interaction involving the tin center and the oxygen atom of the methoxy ligand. The Gibbs energy diagrams highlight that, under the reaction conditions, the dimer-monomer equilibrium is significantly shifted towards monomeric species, in agreement with the experimental kinetics. Importantly, the two Sn-OCH(3) bonds are prompt to insert CO(2). These results provide new insight into the reaction mechanism and catalyst design to enhance the turnover numbers.     

甲烷氧化细菌催化二氧化碳生物合成甲醇的研究

甲烷氧化细菌中包含的甲烷单加氧酶(MMO)、甲醇脱氢酶(ADH)、甲醛脱氢酶(FaldDH)、甲酸脱氢酶(FateDH)经过一系列反应能够把甲烷深度氧化生成二氧化碳，并生成一定的能量物质．把二氧化碳还原为甲醇是一个需要能量的过程，目前还没有已知的有机体在温和条件下完成这一反应．研究发现，甲基弯菌Methylosi-nus trichosporium IMV 3011可以催化二氧化碳生物转化生成甲醇．在休眠的悬浮细胞中充人二氧化碳后，反应一段时间在反应液中检测到了甲醇．二氧化碳转化成甲醇是一个需要能量推动的反应，为了补充反应所消耗的能量．反应一段时间后需要用甲烷进行再生，以恢复细胞中的还原当量NADH．我们进行了反应再生的交替连续批式反应，甲醇积累量能够维持在一个比较稳定的水平．理论上，反应不会增加温室效应，这是一个有效的、环境友好的、可恢复的反应过程．     

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.     

铁锆复合氧化物催化甲醇与CO2直接合成 DMC反应性能

采用溶胶-凝胶法制备的铁锆复合氧化物催化甲醇与CO2直接合成碳酸二甲酯（DMC）反应,其催化活性远高于氧化铁和氧化锆,当铁锆摩尔比为5：1时,其催化活性是氧化锆的2倍。利用XRD、XPS、IR、TPD和N2物理吸附-脱附等技术对催化剂进行了表征。结果表明,氧化铁主要以六方晶相的α-Fe2O3形式存在,氧化锆主要以四方晶相存在,铁锆之间发生了相互作用,使铁锆复合氧化物表面L酸增强和少量B酸产生。L酸的增强和B酸的产生是催化剂催化活性增加的主要原因,并对催化剂的催化作用机理进行了探讨。     

铜系催化剂上甲醇蒸气转化制氢过程的原位红外研究

 用原位红外光谱法跟踪研究了不同条件下铜系催化剂上甲醇蒸气转化制氢反应的初始开车过程．结果表明，反应过程中二氧化碳不是在一氧化碳之后产生的．可以推断，铜系催化剂上的甲醇蒸气转化制氢过程不是先进行甲醇分解为一氧化碳和氢气，然后一氧化碳和水蒸气发生变换反应生成二氧化碳和氢气．甲醇蒸气转化反应的主要过程是甲醇和水直接生成二氧化碳和氢气．