固体碱在二氧化碳-甲醇法合成碳酸二甲酯反应中的作用

本文探讨了固体碱的制备和预处理等因素对于ＣＯ_２~－甲醇法合成碳酸二甲酯（ＤＭＣ）的影响,发现微波法所制碱性沸石等多孔材料的反应活性高于浸渍法所制样品。本文首次报道了微波辐射低压合成ＤＭＣ的新方法,该法能极大地缩短反应时间并提高产物选择性。研究表明： ＣＯ_２和甲醇生成 ＤＭＣ的反应在热力学上是几乎不能进行的,加入固体碱的实质是提供了一条耦合的途径。     

二氧化碳和甲醇直接合成碳酸二甲酯的研究进展

碳酸二甲酯是一种重要的绿色化工原料,二氧化碳和甲醇直接合成碳酸二甲酯是一种绿色合成方法.本文介绍了近年来此方法的催化剂及其催化机理研究的进展,讨论了不同催化体系设计的理论基础和催化剂的作用机理,并对助催化剂和吸水剂以及反应条件对催化剂活性和选择性的影响进行了评述.     

甲醇直接气相氧化羰基化合成碳酸二甲酯

碳酸二甲酯(DMC)是一种重要的绿色有机合成中间体.合成DMC有多种方法,甲醇直接气相氧化羰基化法对设备腐蚀小,产物易分离,原料易得,有着诱人的工业化前景.本文综述了甲醇直接气相氧化羰基化合成DMC的研究进展,包括反应条件的影响,催化剂的选择,反应机理及动力学的研究.针对反应副产物水会造成催化剂快速失活、设备腐蚀等问题,提出将二甲醚引入反应体系,通过耦合二甲醚水解反应消除水引起的负面效应,改善催化剂的稳定性.     

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。     

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。     

镁掺杂氧化铈整体式催化剂催化CO2和CH3OH直接合成碳酸二甲酯

采用共沉淀法成功地合成了不同Mg掺杂量的Ce_1-xMg_xO₂(x=0.05、0.10、0.15、0.20)固溶体催化材料,并运用透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸附-脱附测试、拉曼光谱、X射线光电子能谱(XPS)、CO₂程序升温脱附(CO₂-TPD)等技术对这些材料进行了表征。结果发现,通过调控CeO₂晶格中Mg的含量,可以调控所制备的Ce_1-xMg_xO₂催化材料的粒径、比表面积、表面缺陷等。其中Ce_0.90Mg_0.10O₂展现了最佳的表面性质,具有最小的平均粒径(约5.8 nm),最大的比表面积(约136 m2·g^-1)以及最高的表面氧含量(31.98%)。将Ce_1-xMg_xO₂催化材料涂覆在堇青石蜂窝陶瓷上制成整体催化剂,考察其对CO₂和CH₃OH直接合成碳酸二甲酯的催化性能。在140℃、2.4 MPa、反应2 h的条件下,Ce_0.90Mg_0.10O₂整体催化剂上碳酸二甲酯的收率高达20.21%,催化效果明显优于CeO₂和其余的Ce_1-xMg_xO₂(x=0.05、0.15、0.20)催化材料。     

CO2和CH3OH直接合成碳酸二甲酯Cu-Ni/V2O5-SiO2催化剂

采用表面反应改性法制备了V2O5 SiO2(VSiO)表面复合物 ,用等体积浸渍法制备了VSiO担载的Cu Ni双金属催化剂 ,用IR、TPD、TPSR和微反技术研究了CO2 和CH3OH在催化剂表面上的化学吸附与反应性能.结果表明,在Cu Ni/VSiO催化剂上存在着金属位Cu Ni合金、Lewis酸位Vn 和Lewis碱位V=O三类活性中心 ;CO2 在金属位和Lewis酸位协同作用下可生成CO2卧式吸附态M -(CO) -O→Vn ,此吸附态在138℃左右可解离成M -CO和V=O ;CH3OH在Lewis酸位和Lewis碱位协同作用下可形成解离吸附态V -OCH3和V -OH ;CO2 和CH3OH在Cu Ni/VSiO催化剂表面上的反应产物主要为碳酸二甲酯(DMC)、CH2O、CO和H2O ,其生成DMC的选择性在85%以上.     

固体碱在二氧化碳-甲醇法合成碳酸二甲酯反应中的作用

本文探讨了固体碱的制备和预处理等因素对于CO₂-甲醇法合成碳酸二甲酯(DMC)的影响,发现微波法所制碱性沸石等多孔材料的反应活性高于浸渍法所制样品。本文首次报道了微波辐射低压合成DMC的新方法,该法能极大地缩短反应时间并提高产物选择性。研究表明:CO₂和甲醇生成DMC的反应在热力学上是几乎不能进行的,加入固体碱的实质是提供了一条耦合的途径。     

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…     

Dimethyl Carbonate Synthesis from CO2 over CeO2 with Electron-Enriched Lattice Oxygen Species

Direct synthesis of dimethyl carbonate (DMC) from CO₂ plays an important role in carbon neutrality, but its efficiency is still far from the practical application, due to the limited understanding of the reaction mechanism and rational design of efficient catalyst. Herein, abundant electron-enriched lattice oxygen species were introduced into CeO₂ catalyst by constructing the point defects and crystal-terminated phases in the crystal reconstruction process. Benefitting from the acid-base properties modulated by the electron-enriched lattice oxygen, the optimized CeO₂ catalyst exhibited a much higher DMC yield of 22.2 mmol g^-1 than the reported metal-oxide-based catalysts at the similar conditions. Mechanistic investigations illustrated that the electron-enriched lattice oxygen can provide abundant sites for CO₂ adsorption and activation, and was advantageous of the formation of the weakly adsorbed active methoxy species. These were facilitating to the coupling of methoxy and CO₂ for the key *CH₃OCOO intermediate formation. More importantly, the weakened adsorption of *CH₃OCOO on the electron-enriched lattice oxygen can switch the rate-determining-step (RDS) of DMC synthesis from *CH₃OCOO formation to *CH₃OCOO dissociation, and lower the corresponding activation barriers, thus giving rise to a high performance. This work provides insights into the underlying reaction mechanism for DMC synthesis from CO₂ and methanol and the design of highly efficient catalysts.     

Study On Dimethyl Carbonate Synthesis from Methyl Nitrite And CO1

Recently, dimethyl carbonate (DMC) has attracted much attention as a less toxic reagent in relation to environmental problem. DMC is a novel reagent for methylation and carbonylation in place of toxic dimethyl sulfate and phosgene, respectively. DMC is also a promising fuel additive because it can improve octane number.     

Kinetics of Dimethyl Carbonate Synthesis From Ethylene Carbonate and Methanol Using Alkali-Metal Compounds as Catalysts

Dimethyl carbonate (DMC) was synthesized by the ester exchange reaction of ethylene carbonate and methanol. K₂ CO₃ , KOH, LiOH and NaOH were used as catalysts for DMC synthesis and their catalytic abilities were compared in terms of kinetics. LiOH showed the best reaction rate among the catalysts. The rate constant was estimated to be 0.02538 (dm 3 /mol) 0.21 /min at 298 K.     

CO_2和丙三醇直接合成碳酸甘油酯的新方法

报道了一种以CO_2和丙三醇为原料,Cs_2CO_3为碱,DMF为溶剂,bmimBF_4为增溶剂,直接合成碳酸甘油酯(GC)的新方法。在最优反应条件[丙三醇5 mmol,Cs_2CO_310 mmol,CH_2Cl_25 m L,bmimBF_41 m L,DMF 5 m L,P(CO_2)1 MPa,于100℃反应24 h]下,GC收率76%,其结构经1H NMR和ESI-MS确证。在最优条件下进行50倍放大实验,GC收率72%。     

A New Process for Synthesis of Dimethyl Carbonate from Ethylene Carbonate and Methanol without any Catalyst under Supercritical Conditions

Dimethyl carbonate was synthesized by transesterification reaction between ethylene carbonate and methanol under supercritical conditions without any catalyst. Experimental results showed that the residence time and the molar ratio of methanol to ethylene carbonate all can affect the conversion of ethylene carbonate. When the molar ratio of methanol to ethylene carbonate was 8:1, 81.2% conversion can be achieved at 9.0 MPa and 250℃ after 8 h.     

CO2和CH3OH直接合成碳酸二甲酯Cu-Ni/V2O5-SiO2催化剂

采用表面反应改性法制备了Ｖ２Ｏ５－ＳｉＯ２（ＶＳｉＯ）表面复合物,用等体积浸渍法制备了ＶＳｉＯ担载的Ｃｕ－Ｎｉ双金属催化剂,用ＩＲ,ＴＰＤ,ＴＰＳＲ和微反技术研究了ＣＯ２和ＣＨ３ＯＨ在催化剂表面上的化学吸附与反应性能。结果表明,在Ｃｕ－Ｎｉ／ＶＳｉＯ催化剂上存在着金属位Ｃｕ－Ｎｉ合金,Ｌｅｗｉｓ酸位Ｖ＾ｎ＋和Ｌｅｗｉｓ碱位Ｖ＝Ｏ三类活性中心;ＣＯ２在金属位和Ｌｅｗｉｓ酸位协同作用下可生成ＣＯ２卧式     

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.     

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.     

同位素示踪研究K2CO3/CH3I促进的碳酸二甲酯直接合成反应

 采用同位素示踪技术,系统地研究了K2CO3/CH3I促进的CO2插入甲醇直接合成碳酸二甲酯(DMC)的反应机理. 结果表明,固体碱碳酸钾催化剂直接参与了DMC的合成过程, DMC分子中的羰基由CO2插入甲醇后形成,两个甲基分别来源于甲醇和碘甲烷. 本文将以往文献中提出的DMC生成机理和二甲醚生成机理结合起来,并对其进行适当补充后,可以很好地解释实验结果.     

KIT-6负载CeO2催化CO2和甲醇合成碳酸二甲酯

采用不同老化温度(80、100、120和150℃)合成了一系列KIT-6载体,并通过浸渍法制备了相应的CeO_2/KIT-6催化剂。结合X射线衍射、N_2物理吸附、NH_3程序升温脱附、CO_2程序升温脱附、透射电子显微镜、傅里叶变换红外光谱和X射线光电子能谱等表征结果,详细考察了老化温度对KIT-6结构以及CeO_2/KIT-6催化剂直接催化CO_2和甲醇合成碳酸二甲酯(DMC)反应活性的影响。结果表明,不同老化温度下制备的KIT-6均保持其独特的三维孔道结构。随着老化温度升高,KIT-6比表面积先增大后减小,当老化温度为100℃时,KIT-6比表面积达到最大(683 m~2·g~(-1))。KIT-6较高的比表面积有利于提高CeO_2分散度,进而提高暴露的活性位点数量,催化活性随催化剂表面中等碱/酸性吸附位数量和Ce~(3+)含量的增加而逐渐提高。其中,CeO_2/100-KIT-6催化剂中CeO_2颗粒尺寸最小(5.9 nm),暴露的活性位数量最高,催化活性最佳。随后,考察了反应温度和压力对CeO_2/100-KIT-6催化活性的影响。随着反应温度提高,催化活性先升高后降低,当反应温度为140℃时,催化活性最高;且催化活性随反应压力的提高而逐渐增加。在反应温度为140℃、压力为6.8 MPa条件下,催化剂经6次循环后,DMC收率由15 mmol·g_(CeO_2)~(-1)逐渐降低至2.8 mmol·g_(CeO_2)~(-1),原因归结为反应过程中CeO_2纳米颗粒发生团聚,使暴露出的活性位数量减少。     

Microwave-Assisted Synthesis of Dimethyl Carbonate

Microwave assisted synthesis of dimethyl carbonate directly from CO₂ and methanol can be completed in a relative short time, at lower temperature and fewer by-products compared with conventional heating mode. This revised version was published online in June 2006 with corrections to the Cover Date.