共查询到20条相似文献,搜索用时 328 毫秒
1.
Synthesis of diethyl carbonate from ethanol through different routes: A thermodynamic and comparative analysis 下载免费PDF全文
In this study, thermodynamic analysis of various possible synthesis routes of diethyl carbonates (DEC), a benign organic carbonate, was carried out and a comparative analysis was performed. Chemical equilibrium constants at standard conditions were calculated using Gibbs free energy of the system. The Benson group contribution method was used to estimate standard heat of formation and standard entropy change of some raw materials/components like dimethyl carbonate. Variation of heat capacity (Cp) with temperature was estimated for different components from the Rozicka‐Domalski model. Variation of chemical equilibrium constants with temperature and pressure was studied for various routes. Synthesis of DEC from ethylene carbonate (EC) was also found to be better considering equilibrium constants at room temperature. The CO2 route was found to be the most unfavourable route for DEC synthesis due to stability of CO2 molecules. Moreover, DEC synthesis through the urea route was found to be best at high temperatures since the equilibrium constants were found to increase exponentially. Experiments were conducted for DEC synthesis using the EC route at two temperatures. Activity coefficients were calculated using the UNIFAC model. Experimentally and theoretically determined chemical equilibrium constant values were found to be similar. PRO/II was also used to minimize Gibbs free energy of the system and estimate the equilibrium constants and the results were comparable with those obtained by the equilibrium constant method and the trend was found to be the same for both the methods. 相似文献
2.
3.
Junwei Jiang 《Electrochimica acta》2004,49(26):4599-4604
Accelerating rate calorimetry (ARC) was used to study the thermal stability of Li0.81C6 in dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), and an EC/DEC mixture as well as in LiPF6- and LiBOB-based electrolytes. ARC results show that linear carbonates like DMC or DEC react strongly with Li0.81C6 and that robust passivating layers do not form. By contrast, the cyclic carbonate, EC, creates a robust passivating film that limits the rate of reaction between Li0.81C6 and EC as the temperature increases. X-ray diffraction shows that the addition of LiPF6 to EC/DEC changes the surface film that forms on Li0.81C6 at elevated temperature to one dominated by LiF instead of lithium-alkyl carbonate or lithium carbonate. This increases the thermal stability of Li0.81C6 in LiPF6 electrolyte compared to pure EC/DEC solvent. By an apparently similar mechanism, the addition of only 0.2 M LiBOB to EC/DEC greatly improves the thermal stability of Li0.81C6. ARC results for Li0.81C6 in pure and mixed salt LiPF6 and LiBOB EC/DEC electrolytes of various molarities shed light on the reasons for the beneficial effect of the salts. 相似文献
4.
Soon-Ki JeongMinoru Inaba Yasutoshi IriyamaTakeshi Abe Zempachi Ogumi 《Electrochimica acta》2002,47(12):1975-1982
In situ AFM observation of the basal plane of highly oriented pyrolytic graphite (HOPG) was performed before and after cyclic voltammetry in 1 mol dm−3 LiClO4 dissolved in ethylene carbonate (EC), EC+diethyl carbonate (DEC), and EC+dimethyl carbonate (DMC) to clarify the effects of co-solvents in EC-based solutions on surface film formation on graphite negative electrodes in lithium-ion cells. In each solution, surface film formation involved the following two different processes: (i) intercalation of solvated lithium ions and their decomposition beneath the surface; and (ii) direct decomposition of solvent molecules on the basal plane to form a precipitate layer. The most remarkable difference among these solvent systems was that solvent co-intercalation took place more extensively in EC+DEC than in EC+DMC or EC. Raman analysis of ion-solvent interactions revealed that a lithium ion is solvated by three EC molecules and one DEC molecule in EC+DEC, whereas it is solvated exclusively by EC in EC+DMC and in EC, which suggested that the presence of linear alkyl carbonates in the solvation shell of lithium ion enhance the degree of solvent co-intercalation that occurs in the initial stage of the surface film formation. 相似文献
5.
6.
通过对不同碳酸二甲酯生产方法的比较,并针对我国目前碳酸二甲酯的发展现状,提出了采用尿素两步醇解法生产工艺。建议将尿素、碳酸丙烯酯和碳酸二甲酯3套生产装置联用,有助于国内碳酸二甲酯生产企业走出亏损的困境。 相似文献
7.
A large-scale dimethyl carbonate (DMC) production process from ethylene oxide (EO), CO2, and methanol was simulated and optimized. Unlike most industrial processes of DMC production, the direct conversion of EO and CO2 to ethylene carbonate (EC) and EC transesterification to DMC were performed in a single reactor. The reaction volume and the reactor operating pressure were selected as decision variables and evaluated. The key performance parameters, e.g., conversion per pass and CO2 intensity, were compared with conventional commercialized routes or novel promising processes in the literature. 相似文献
8.
Liangnian He Ya Du Chengxia Miao Jinquan Wang Xiaoyong Dou Ying Wu 《Frontiers of Chemical Engineering in China》2009,3(2):224-228
The reactions of CO2 with oxirane to produce cyclic carbonate, and with aziridine to afford oxazolidine have been of interest as a useful method
for its fixation by a chemical process. Highly efficient processes employing recyclable CO2-phlilic homogeneous catalyst were devised for environmentally benign synthesis of cyclic carbonates and oxazolidinones under
supercritical CO2 without any organic solvent. These processes represent pathways for greener chemical fixations of CO2 to afford industrial useful materials such as organic carbonates and oxazolidinones with great potential applications. 相似文献
9.
Shung-Ik Lee Un-Ho Jung Yun-Sung Kim Myung-Hwan Kim Dong-June Ahn Hai-Soo Chun 《Korean Journal of Chemical Engineering》2002,19(4):638-644
Limiting current densities equivalent to the transport-controlling step of lithium ions in organic electrolytes were measured
by using a rotating disk electrode (RDE). The diffusion coefficients of lithium ion in the electrolyte of PC/LiClO4, EC : DEC/LiPF6 and EC : DMC/LiPF6 were determined by the limiting current density data according to the Levich equation. The diffusion coefficients increased
in the order of PC/LiClO4<EC : DEC/LiPF6<EC : DMC/ LiPF6 with respect to molar concentration of lithium salt. The maximum value of diffusivity was 1.39x10-5cm2/s for 1M LiPF6 in EC : DMC=1 : 1. Exchange current densities and transfer coefficients of each electrolyte were determined according to
the Butler-Volmer equation. 相似文献
10.
11.
12.
Two different separator materials (polyethylene fleece – Freudenberg 2190 and porous glass fiber – Whatman® GF/D) and two different lithium-ion battery electrolytes have been investigated regarding their behavior in an autoclave extraction with supercritical helium head pressure carbon dioxide (sc HHPCO2). Mixtures of dimethyl carbonate (DMC)/ethylene carbonate (EC) and ethylmethyl carbonate (EMC)/EC, each with 1 mol/L LiPF6 were used.In addition to these proof of principle experiments, the developed extraction method was further applied to real battery samples. Commercial 18650 cells (after formation and aging) were opened and the jelly roll was extracted with sc HHPCO2. Extracts were analyzed with gas and ion chromatography (GC, IC). Recovery rates and extract compositions strongly depend on the material of which the electrolyte is extracted. Further structure determination of electrolyte aging products was performed with different ionization modes in GC–mass spectrometry (GC–MS) experiments. Diethyl carbonate (DEC), dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC), ethylmethyl-2,5-dioxahexane dicarboxylate (EMDOHC) and diethyl-2,5-dioxahexane dicarboxylate (DEDOHC) are aging products of electrolyte degradation which were successfully extracted and identified. Their concentrations correlate with solid electrolyte interphase (SEI) growth on the negative electrode which was investigated with scanning electron microscopy (SEM). 相似文献
13.
14.
The interfacial phenomena between Cu electrode and solution of lithium perchlorate in ethylene carbonate (EC)-dimethyl carbonate (DMC) have been investigated using in situ reflection absorption Fourier transform infrared (FTIR) spectroscopy and single reflection ATR-FTIR spectroscopy. The ATR spectra confirmed the bands due to free EC and DMC and the molecules solvated to lithium ions in the solution. The bands due to the result of the interaction between ClO4− and DMC in the mixture solution also appeared in the ATR spectra. In the FTIR spectra, the potential dependence on the concentration of EC and DMC in the vicinity of the Cu electrode was observed. It was understood that the reversible changes in the concentration of free EC and DMC and solvated EC and DMC in the diffuse double layer take place with changing in potential. As the potential decreased, the free EC and DMC concentrations increased, while the concentration of the EC and DMC solvated to lithium ions decreased. Thus, it can be concluded that the equilibrium shifts from Li+(EC)2(DMC)2 to Li+(EC)2(DMC) + DMC or Li+(EC)(DMC)2 + EC as the potential decreases. The bands due to (CH2OCO2Li)2 and CH3OCO2Li were observed for an irreversible reaction. 相似文献
15.
Chemical fixation of CO2 into useful organic compounds has been attracting much attention from the viewpoint of CO2 emission reduction and energy structure reformation. A useful and widely investigated chemical utilization of CO2 is the cycloaddition of CO2 to epoxides for the synthesis of cyclic carbonates. Efforts have been paid to the design and preparation of various catalyst systems that are active and selective to the production of the desired products under mild conditions and in green processes. This article is to review the current state of the catalyst development and the experimental and theoretical analysis of reaction mechanism for the cyclic carbonate synthesis from epoxides, one of currently important reactions involving CO2 as a reactant with 100% atom economy. Particular attention is given to the catalysis of multifunctional catalyst systems such as metal- and hydrogen-bond donor (HBD)-based catalysts. 相似文献
16.
An in situ Raman study of dimethyl carbonate synthesis from carbon dioxide and methanol over zirconia 总被引:3,自引:0,他引:3
In situ Raman spectroscopy has been used to investigate the mechanism of dimethyl carbonate (DMC) synthesis via the reaction of methanol with carbon dioxide over zirconia. Methanol adsorption leads to the appearance of adsorbed methoxide groups, whereas CO2 adsorption leads to the formation of carbonate species. Monomethyl carbonate species, (CH3O)COO(Zr)2, are formed by the reaction of methoxide and monodentate carbonate species and DMC is formed via the further reaction of monomethyl carbonate species with methanol. This sequence is supported by evidence that DMC decomposition on zirconia proceeds via the reverse of the proposed mechanism. 相似文献
17.
尿素直接醇解法合成碳酸二甲酯催化剂研究进展 总被引:5,自引:0,他引:5
综述了甲醇与尿素醇解法催化合成碳酸二甲酯所用催化剂的研究进展,尿素醇解法合成碳酸二甲酯具有原料价廉易得、工艺简单、操作条件温和、反应过程无水生成和反应产生的氨气可以回收利用等优点,具有工业化前景。 相似文献
18.
A novel catalytic application of titanosilicate molecular sieves (TS-1 and TiMCM-41), in the synthesis of polycarbonate precursors like cyclic carbonates and dimethyl and diphenyl carbonates, avoiding toxic chemicals like phosgene or CO, is reported. Cyclic carbonates were prepared, over TS-1 and TiMCM-41, in high yields, by cycloaddition of CO2 to epoxides, like epichlorohydrin, propylene oxide and styrene oxide, at low temperatures and pressures. Further, transesterification of the cyclic carbonates with methanol and phenol, over TiMCM-41, yielded other polycarbonate precursors like dimethyl carbonate (DMC) and diphenyl carbonate (DPC). The cyclic carbonates could also be synthesized from the olefins in the same reactor by reacting the olefins, in the presence of TiMCM-41, with a mixture of an epoxidizing agent (like H2O2 or tert-butyl hydroperoxide) and CO2. 相似文献
19.
Efficient synthesis of organic carbonates and poly(1,4‐butylene carbonate‐co‐terephthalate)s 下载免费PDF全文
Jin Gu Kim Jong Yeob Jeon Jiseul Chun Chung Sol Kim Pyung Cheon Lee Bun Yeoul Lee 《应用聚合物科学杂志》2017,134(24)
Dimethyl carbonate (DMC) is an environmentally benign chemical currently produced using CO2. Using the conventional Dean–Stark apparatus, a method was developed for the effective and selective removal of the methanol generated in the transesterification of DMC with alcohol. Using this device, various diols (HO‐A‐OH; A = (CH2)4, (CH2)2O(CH2)2, CH2C6H10CH2, and CH2C6H4CH2) were converted to mixtures of the corresponding MeOC(O)[O‐A‐OC(O)]OMe and MeOC(O)[O‐A‐OC(O)]2OMe. Dialkyl carbonates such as dibutyl carbonate, dibenzyl carbonate, and diallyl carbonate were also efficiently prepared from the corresponding alcohols using this device. The compound prepared from 1,4‐butanediol, MeOC(O)[O(CH2)4OC(O)]1.5OMe, was subjected to polycondensation with HO(CH2)4[O2CC6H4CO2(CH2)4]1.5OH or HO(CH2)4[O2CC6H4CO2(CH2)4]1.8OH, which directly was prepared from terephthalic acid and 1,4‐butanediol. The polycondensation afforded high‐molecular‐weight poly(1,4‐butylene carbonate‐co‐terephthalate)s (PBCTs) with Mw of 80–270 kDa and 0.40–0.46 terephthalate mole fractions. PBCTs are attractive materials with potential biodegradability and LDPE‐like thermal properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44951. 相似文献
20.
Cuihong Yan Bin Lu Xiaoguang Wang Jingxiang Zhao Qinghai Cai 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(11):1413-1417
BACKGROUND: 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 相似文献