Critical temperatures and pressures of reacting mixture in synthesis of dimethyl carbonate with methanol and carbon dioxide

Critical temperatures and pressures of nominal reacting mixture in synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide （quaternary mixture of carbon dioxide ＋ methanol ＋ water ＋ DMC） were measured using a high-pressure view cell. The results suggested that the critical properties of the reacting mixture depended on the reaction extent as well as its initial composition （initial ratio of carbon dioxide to methanol）. Such information is essential for determining the reaction conditions when one intends to carry out the synthesis of DMC with CO2 and methanol under supercritical conditions.     

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.     

Effects of Mo promoters on the Cu-Fe bimetal catalysts for the DMC formation from CO2 and methanol

The Mo-promoted Cu-Fe bimetal catalysts were prepared and used for the formation of dimethyl carbonate（DMC） from CO₂ and methanol.The catalysts were characterized by X-ray diffraction（XRD）, temperature programmed reduction（TPR）,laser Raman spectra（LRS）,energy dispersive spectroscopy （EDS） and temperature programmed desorption（TPD） techniques.The experimental results demonstrated that the Mo promoters can decrease the reducibility and increase the dispersion of Cu-Fe clusters.The concentration balance of base-acid sites can be readily adjusted by changing the Mo content.The moderate concentration balance of acid and base sites was in favor of the DMC formation. Under optimal experimental conditions,the highest methanol conversion of 6.99%with a DMC selectivity of 87.7%can be obtained when 2.5 wt%of Mo was loaded.     

New device for controlling the amount of methanol in carbon dioxide mobile phase for supercritical fluid chromatography

A new device to accurately deliver a small amount of methanol into supercritical carbon dioxide fluid is described. Carbon dioxide, the most widely used mobile phase in supercritical fluid chromatography, is a relatively non-polar fluid, and hence the addition of a small amount of methanol could change the solvent strength of the mobile phase. In this work, supercritical CO₂ and methanol are delivered from the pump to a 100-μl mixing chamber in which a small magnetic bar is rotating. After passing through the mixing chamber, supercritical CO₂ is changed to a new mobile phase with different polarity. The modified mobile phase was successfully used for the separations of polar compounds and polyaromatic hydrocarbons (PAHs).     

The solubility of water in mixtures of dimethyl ether and carbon dioxide

This paper reports measurements of the solubility of water in liquid and supercritical fluid mixtures of dimethyl ether and carbon dioxide. The measurements were made by extracting water under saturation conditions using premixed liquid dimethyl ether–carbon dioxide mixtures. Results are reported for temperatures of 313.8 K and 333.3 K at 9.0 MPa and 15.0 MPa. Results are fitted to the Peng–Robinson cubic equation of state with mixing rules according to Wong and Sandler, using binary interaction parameters fitted to the literature data for the respective binary systems: dimethyl ether–water; dimethyl ether–carbon dioxide; and carbon dioxide–water. Liquid densities for dimethyl ether–carbon dioxide mixtures, measured using a coriolis flow instrument, are also reported.     

超临界条件下负载型配合物催化剂Cu2(μ-OEt)2/SiO2合成碳酸二甲酯的反应性能

采用表面改性和离子交换相结合的方法制备了负载型配合物Cu2(μ-OEt)2／SiO2催化剂，用化学分析、IR、TPD和超临界反应技术考察了催化剂的表面构造、CO2和甲醇在催化剂上的化学吸附及超临界条件下的反应性能，结果表明：双核配合物Cu2(μ-OEt)2中金属离子Cu^2 与载体SiO2表面O^2-以双齿配位键合，配体以桥基形式连接双金属离子形成双核物种Cu2(μ-OEt)2；CO2在催化剂表面存在桥式和乙氧碳酸酯基两种吸附态，其中乙氧碳酸酯基吸附态是生成DMC的关键物种；CH3OH在催化剂上只有一种分子吸附态．催化剂用量、反应压力、反应温度和反应时间对甲醇的转化率都有不同程度的影响，在超临界条件下，DMC的选择性为100％，甲醇的转化率超过4％．     

二氧化碳的间接利用:碳酸乙烯酯应用研究进展

以二氧化碳(CO2)为主的温室气体排放所导致的全球气候和生态系统变异问题正得到普遍重视,全球CO2年排放量已达数百亿吨[1].控制CO2排放量,对其回收、固定、利用及再资源化,已成为世界各国严重关切的问题.同时,从资源化角度出发,CO2是世界上最为丰富和廉价的碳一(C1)资源[2,3],因此,大力发展二氧化碳的绿色化利用技术,开发绿色高新精细化工产业链,提高产品的附加值,具有重要的意义.     

An in situ infrared study of dimethyl carbonate synthesis from carbon dioxide and methanol over well-shaped CeO2

The mechanism of dimethyl carbonate(DMC) formation from CO_2 and methanol is investigated using three well-shaped CeO_2 catalysts, nanorod, nanocube and octahedron, which are packed with different crystal planes. In situ Fourier Transform Infrared Spectroscopy(FTIR) is employed to probe each reaction step in the DMC synthesis. The number of –OH groups and the species of CO_2 adsorptions on ceria surface have significant influence on the activity of ceria with different morphologies. Rod-ceria has favorable catalytic activity because of the large amount of –OH groups and the formation of bidentate carbonate species.     

超临界CO2/离子液体体系

超临界CO2和离子液体是两种具有优异性能的绿色化学试剂,本文介绍了将两者结合反应,分离体系的物化性质和多种绿色化学过程。利用超临界CO2可以广泛地萃取离子液体中的不挥发性化合物而不导致离子液体及其中催化剂的流失,在加氢、醛化、甲酰化等反应,分离过程中的应用表明,过程具有很好的反应分离特性和环境友好性,应用前景广阔。     

High resolution synchrotron X-ray investigation of carbon dioxide evolution in operating direct methanol fuel cells

The carbon dioxide evolution and bubble formation in an operating fuel has been studied by means of synchrotron X-ray radiography. Two different observation directions have been chosen: a through-plane insight has been employed to track the formation of bubbles starting at the corner of the lands of the flow field; a depth profile of the carbon dioxide evolution has been derived from cross sectional studies describing an affected area of up to 100 μm. The dynamics of the bubble formation and detachment of the bubbles from the position of formation is strongly correlated with the current density. Cracks and breaks in the catalyst layer which result from the preparation process are visible under operating conditions and a possible swelling of the catalyst layer does not reach a complete vanishing of the cracks.     

Ni(OCH3)2/SiO2催化剂的制备及其合成碳酸二甲酯的反应性能

采用表面改性和离子交换相结合的方法，制备了负载型单核金属甲氧基配合物Ni(OCH3)2/SiO2催化剂。利用IR、TPD、TPSR和微反技术，考察了催化剂的表面结构以及CO2、CH3OH在催化剂表面上的化学吸附和反应性能。结果表明，负载型单核金属甲氧基配合物Ni(OCH3)2/SiO2中，Ni^2 与载体SiO2表面的O^2-以双齿形式配位；在催化剂表面存在CO2的桥式吸附态和甲氧碳酸酯基物种两种吸附态，CH3OH则只有一种分子吸附态。在373-473K条件下，CO2和CH3OH在催化剂上的反应物主要是DMC、H2O以及少量的CO、CH4和CH2O，催化剂的活性由表面甲氧碳酸酯基物种与分子吸附态甲醇的反应决定的。讨论了催化剂上CO2和CH3OH的活化过程及吸附态的形成机理。     

Electrochemical carboxylation with carbon dioxide

Studies carried out in the past two years on electrochemical fixation of carbon dioxide with carbon-carbon bond formation, so-called electrochemical carboxylation or electrocarboxylation, are reviewed. Among about twenty papers on electrochemical carboxylation published from 2014 to the present, recent advances in electrochemical carboxylation regarding asymmetric carboxylation, sacrificial anode-free carboxylation, and carboxylation following aryl radical cyclization are focused on and discussed.     

Highly effective direct synthesis of DMC from CH_3OH and CO_2 using novel Cu-Ni/C bimetallic composite catalysts

Novel Cu-Ni/C has been prepared and utilized as an efficient catalyst system in direct synthesis of DMC from CH3OH and CO2.     

Polyacrylate liquid crystalline stationary phases in supercritical fluid chromatography with carbon dioxide mobile phase

Summary New polyacrylate liquid crystalline compounds were coated onto glass or fused-silica capillary columns as stationary phases and applied to supercritical fluid chromatography. These stationary phases, were very stable: no bleeding was observed at 200°C and up to 200kg/cm² pressures of carbon dioxide mobile phase. The wide working range of the capillary column was extended below the g-n transition temperature. Isomeric compounds such as - and -methoxynaphthalene, anthracene and phenanthrene and several phenolic compounds were separated.     

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.     

Important electromigration effects of carbon dioxide in capillary electrophoresis at high pH

This paper deals with unwanted effects of carbonate in capillary zone electrophoretic analyses of anions in alkaline BGEs with indirect UV absorption and conductivity detection. Computer simulations and experimental study of selected model systems have shown that carbon dioxide absorbed from air into BGEs and samples induce important electrophoretic effects like formation of new additional zones and/or boundaries that may further induce strong and pronounced temporary changes in the migration of analytes. Examples are reduction of the pH of alkaline BGEs around pH 11 by up to 1 unit or formation of a pronounced detectable carbon dioxide peak comparable with peaks of analytes at 1 mM level. The higher the pH of the BGE, the stronger these effects and the broader their spectrum, involving (i) changes of effective mobilities and selectivity due to changes in pH of the BGE, (ii) occurrence of additional system zones appearing in form of peaks, dips or more complex disturbances in the detection signal, (iii) temporary interactions with the sample components and subsequent modification of the separation process and of its result. This paper reveals all these effects and brings the knowledge necessary to prevent problems with qualitative and quantitative evaluation of the analysis results.     

Catalytic utilization of carbon dioxide to polymer blends via cyclic carbonate

In the present study, the synthesis of bis(cyclic carbonate) from carbon dioxide and bisphenol A (or bisphenol S)-diglycidyl ether was investigated using quaternary ammonium salts as catalyst. Among the salts tested, the one having a larger alkyl group and more nucleophilic counter anion exhibited a better catalytic activity. Poly(hydroxyurethane)s were prepared by the polyaddition reaction of bis(cyclic carbonate) and diamine. The poly(hydroxyurethane) has shown higher thermal stability than conventional polyurethane, and is expected as novel reactive polyurethane. The miscibility of blends containing poly(hydroxyurethena) and poly(styrene-co-acrylonitrile)(SAN) has been also studied by the optical clarity method and DSC.     

Metal-organic frameworks MOF-808-X as highly efficient catalysts for direct synthesis of dimethyl carbonate from CO2 and methanol

A series of metal-organic frameworks MOF-808-X (6-connected) were synthesized by regulating the ZrOCl₂·8H₂O/1,3,5-benzenetricarboxylic acid (BTC) molar ratio (X) and tested for the direct synthesis of dimethyl carbonate (DMC) from CO₂ and CH₃OH with 1,1,1-trimethoxymethane (TMM) as a dehydrating agent. The effect of the ZrOCl₂·8H₂O/BTC molar ratio on the physicochemical properties and catalytic performance of MOF-808-X was investigated. Results showed that a proper ZrOCl₂·8H₂O/BTC molar ratio during MOF-808-X synthesis was fairly important to reduce the redundant BTC or zirconium clusters trapped in the micropores of MOF-808-X. MOF-808-4, with almost no redundant BTC or zirconium clusters trapped in the micropores, exhibited the largest surface area, micropore size, and the number of acidic-basic sites, and consequently showed the best activity among all MOF-808-X, with the highest DMC yield of 21.5% under the optimal reaction conditions. Moreover, benefiting from the larger micropore size, MOF-808-4 outperformed our previously reported UiO-66-24 (12-connected), which had even more acidic-basic sites and larger surface area than MOF-808-4, mainly because the larger micropore size of MOF-808-4 provided higher accessibility for the reactant to the active sites located in the micropores. Furthermore, a possible reaction mechanism over MOF-808-4 was proposed based on the in situ FT-IR results. The effects of different reaction parameters on DMC formation and the reusability of MOF-808-X were also studied.     

Heck reactions with various types of palladium complex catalysts: application of multiphase catalysis and supercritical carbon dioxide

The application of multiphase catalytic systems for palladium catalyzed Heck reactions brings several benefits such as easy catalyst-product separation and catalyst recycling. The effective multiphase Heck systems can be prepared by using different types of catalyst phases, including biphasic catalysis and supported liquid phase catalysts, and a new generation solvent of supercritical carbon dioxide.