- Protic ionic liquid-promoted synthesis of dimethyl carbonate from ethylene carbonate and methanol
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In this work, the protic ionic liquid [DBUH][Im] (1,8-diazabicyclo[5.4.0]-7-undeceniumimidazolide) was developed as an efficient catalyst for the transesterification of ethylene carbonate with methanol to produce dimethyl carbonate. At 70 °C, up to 97% conversion of ethylene carbonate and 91% yield of dimethyl carbonate were obtained with 1 mol% [DBUH][Im] (relative to ethylene carbonate) as catalyst in 2 h. Even at room temperature, the conversion of ethylene carbonate can reach 94% and the yield of dimethyl carbonate can approach 81% for 6 h. Catalytic mechanism investigation showed the high catalytic efficiency of this ionic liquid results from the synergistic activation effect, wherein the cation can activate ethylene carbonate and the anion can activate methanol through hydrogen bond formation. Although the reusability of the ionic liquid need to be further improved, high efficiency and commercial availability of [DBUH][Im] render it a promising catalyst for the preparation of dimethyl carbonate.
- Song, Yu,He, Xing,Yu, Bing,Li, Hong-Ru,He, Liang-Nian
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supporting information
p. 667 - 672
(2019/08/16)
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- Inclusion complexes of organic salts with β-cyclodextrin as organocatalysts for CO2 cycloaddition with epoxides
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The inclusion complexes between β-cyclodextrin (β-CD) and the organic bases 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU)-based phenolates have been prepared by a simple method and also characterized by FT-IR, 1H NMR, 19F NMR, TGA etc. Among these inclusion complexes, DBU-based 2,3,4,5,6-pentafluorophenolate as a guest compound bound by β-CD ([DBUH][PFPhO]/β-CD) has been employed as an easily-separable organocatalyst for the cycloaddition of CO2 into cyclic carbonate and exhibited the best catalytic performance. High conversion of epoxides and excellent selectivity to carbonates could be achieved at 130 °C and under the 3.0 MPa CO2 without additional organic solvents or additives. Additionally, the organocatalyst [DBUH][PFPhO]/β-CD exhibited the better recycability in consecutive catalytic recycles, as compared with that of corresponding DBU-based phenolates. The β-CD played a crucial role in immobilizing catalytically active species and thus improving the recyclability of the present organocatalysts. The detailed characterization indicated that phenolate anions had been bound inside the cavity of β-CD, while the [DBUH]+ cation was located outside of β-CD. More interestingly, it was observed that phenolate anions could dissociate from the β-CD cavity under the reaction temperature, but the inclusion compound could form on cooling the reaction mixture after reaction, which was extremely attractive for separation and recycling of the supramolecular organocatalysts. Finally, on the basis of the characterization above, a reaction mechanism for the present organocatalysts has been proposed.
- Li, Kun,Wu, Xiaohui,Gu, Qingwen,Zhao, Xiuge,Yuan, Mingming,Ma, Wenbao,Ni, Wenxiu,Hou, Zhenshan
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p. 14721 - 14732
(2017/03/16)
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- METHODS OF DEPOLYMERIZING TEREPHTHALATE POLYESTERS
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A method comprises forming a reaction mixture comprising a terephthalate polyester, a glycol comprising 2 to 5 carbons, and an amidine organocatalyst; and heating the reaction mixture at a temperature of about 120° C. or more to depolymerize the terephthalate polyester, thereby forming a terephthalate reaction product comprising a monomeric dihydroxy terephthalate diester; wherein the terephthalate reaction product contains terephthalate oligomers in an amount less than the amount of terephthalate oligomers that would result from i) substituting the amidine organocatalyst with an equimolar amount of a guanidine catalyst and ii) depolymerizing the terephthalate polyester under otherwise identical reaction conditions.
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Page/Page column 7-8
(2012/09/11)
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