酸性离子液体催化降解纤维素的研究

以离子液体1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)为溶剂,以咪唑类酸功能离子液体[Cnmim]HSO_4(n=2,3,4,5,6,7)为催化剂,在微波辅助加热条件下降解微晶纤维素(MCC),考察了反应温度、反应时间、催化剂用量、加水量、催化剂的哈米特酸度及种类等反应条件对MCC降解反应的影响。结果表明,酸性离子液体的催化效果与其酸性大小有关,其中[C_6mim]HSO_4的哈米特酸度值最小,酸性最强,作为催化剂时效果最佳,当[C_6mim]HSO_4的加入量为0.1 g,纤维素和催化剂的摩尔比为1∶1,反应温度为110℃,反应时间为40 min,加水量为70μL时,微晶纤维素转化率为100%,可还原糖收率为89.94%,葡萄糖收率高达46.24%。该反应使用常见的微波法,操作简单、方便、快速且无污染,与以往反应相比得到的葡萄糖收率较高,为在工业上应用提供了一种可行的方法。     

酸性离子液体催化降解纤维素的研究

以离子液体1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)为溶剂,以咪唑类酸功能离子液体[Cnmim]HSO_4(n=2,3,4,5,6,7)为催化剂,在微波辅助加热条件下降解微晶纤维素(MCC),考察了反应温度、反应时间、催化剂用量、加水量、催化剂的哈米特酸度及种类等反应条件对MCC降解反应的影响。结果表明,酸性离子液体的催化效果与其酸性大小有关,其中[C_6mim]HSO_4的哈米特酸度值最小,酸性最强,作为催化剂时效果最佳,当[C_6mim]HSO_4的加入量为0.1 g,纤维素和催化剂的摩尔比为1∶1,反应温度为110℃,反应时间为40 min,加水量为70μL时,微晶纤维素转化率为100%,可还原糖收率为89.94%,葡萄糖收率高达46.24%。该反应使用常见的微波法,操作简单、方便、快速且无污染,与以往反应相比得到的葡萄糖收率较高,为在工业上应用提供了一种可行的方法。     

Diphenylmethane synthesis using ionic liquids as lewis acid catalyst

Friedel-Crafts alkylation of benzene with benzyl chloride was studied by using organochloroaluminate ionic liquids as Lewis acid catalyst. The reaction was performed in the temperature range of 40 to 70 oC at benzene/ benzyl chloride=17, where selectivity to diphenylmethane was high. The optimum AlCl3/BMIC ratio of the ionic liquid for the benzylation reaction was 2. Superior performance was obtained with butyl group constituting the cationic species of the ionic liquid. Stirring speed had a major impact on catalytic activity of the BMIC-AlCl3 ionic liquid; benzyl chloride conversion decreased substantially from 98 to 68% as stirring speed was reduced from 900 to 500 rpm, and eventually no reaction took place at 200 rpm. BMIC-AlCl3 ionic liquid was more active than Fe-MCM-41 at the expense of a small drop in selectivity but still higher than 96% selectivity was obtained. The ionic liquid could be easily recovered after phase separation. The performance of BMIC-AlCl₃ ionic liquid was maintained after the second run with 97.4% conversion and 95.6% selectivity, but a sudden drop in activity was observed after the third run with only 26.8% conversion.     

Sugar-derived ionic liquids

Ionic liquids (ILs) are special molten salts with melting points below 100 degrees C that are typically constituted of organic cations (imidazolium, pyridinium, sulfonium, phosphonium, etc.) and inorganic anions. Due to their ionic nature, they are endowed with high chemical and thermal stability, good solvent properties, and non-measurable vapor pressure. Although the recycling of ILs partly compensate their rather high cost, it is important to develop new synthetic approaches to less expensive and environmentally sustainable ILs based on renewable raw materials. In fact, most of these alternative solvents are still prepared starting from fossil feedstocks. Until now, only a limited number of ionic liquids have been prepared from renewable sources (e.g., hydroxy acids, amino acids, terpenes), and even less from naturally occurring carbohydrates. This short review describes the synthesis and applications of chiral and achiral ILs obtained from inexpensive sugars.     

Lewis酸性离子液体催化合成丁二酸二异丙酯

采用两步法制备了9种不同的Lewis酸性离子液体,采用¹H NMR、FT-IR对离子液体的结构进行了表征,并系统地考察了其对丁二酸和异丙醇酯化反应的催化性能。结果表明,离子液体随着卤化物用量增加表现出更强的酸性。其中[Bmim]Br-Fe₂Cl₆催化合成丁二酸二异丙酯效果良好,催化剂用量为丁二酸质量的10.0%,反应温度100℃,反应时间4 h,酸醇摩尔比为1：5,丁二酸二异丙酯收率为88.9%,酯化率达92.7%。离子液体重复使用6次后,产品收率下降1.7%。     

Efficient synthesis of benzophenone derivatives in Lewis acid ionic liquids

Benzophenone and its derivatives were prepared via Friedel–Crafts acylation reactions using ionic liquids (ILs) of BmimCl–FeCl₃, BmimCl–AlCl₃ and BmimCl–ZnCl₂ as dual catalyst–solvent. Among them, BmimCl–FeCl₃ showed much higher catalytic activity than that observed for the other two ILs, and in conventional organic solvents. In these reaction systems, good to excellent yields (up to 97%) of acylation products were obtained in a short reaction time. This method features high yield, a simple product isolation procedure, ILs reusability and reduced waste discharge, thus rendering this catalytic system both efficient and environmentally friendly.     

酸性功能化离子液体催化合成马来酸二乙酯

在离子液体［TEA-PS］HSO₄的催化下,由马来酸酐和无水乙醇合成马来酸二乙酯,并研究了其优化条件和催化剂的循环使用性能。当马来酸酐与无水乙醇物质的量比为1∶4以及催化剂用量为马来酸酐质量的20%时,于115 ℃环己烷回流带水条件下反应4 h,酯化率达到99%以上。     

室温离子液体室

介绍了主要由烷基咪唑盐阳离子及氟阴离子组成的室温离子液体的制备、物理性质、化学性质及其在常温条件下的应用.     

Air-drying with ionic liquids

Ionic liquids (ILs) are employed for air-drying for the first time. The experimental gas–liquid equilibrium (EQ) of N₂/O₂ + [EMIM][BF₄] and N₂/O₂ + [EMIM][BF₄] + H₂O systems under a broad temperature range are measured. The new modified UNIFAC-Lei model is successfully extended to predict the N₂/O₂-IL-H₂O system based on extensive phase EQ data. The air-drying experiment using [EMIM][BF₄] as an absorbent is conducted, confirming that this new technology is effective and efficient. © 2018 American Institute of Chemical Engineers AIChE J, 65: 479–482, 2019     

离子液体催化聚乳酸丁醇醇解反应

以离子液体[Bmim][OAc]为反应介质和催化剂, 对聚乳酸 (PLA)丁醇醇解反应进行了研究。考察了反应温度、反应时间、离子液体用量、丁醇(n-butanol)用量对反应结果的影响。得到较佳工艺条件为:反应温度为150℃、反应时间为3 h、m([Bmim][OAc]):m(PLA)=0.2:1、n(n-butanol):n(PLA)=5:1。在上述条件下, PLA醇解反应转化率≥81%, 乳酸正丁酯收率≥70%。采用FT-IR技术对产品的结构进行了表征。 离子液体的回用性能结果表明:[Bmim][OAc]重复利用6次后, PLA转化率和乳酸正丁酯收率无明显变化。     

在离子液体中锡催化多糖分解合成乳酸

淀粉和纤维素能够被四氯化锡催化转化为乳酸甲酯和乳酸,使用离子液体是实现多糖转化的关键。在实验中考察了催化剂、离子液体、反应时间和反应温度对于总乳酸收率的影响。实验结果显示,在1,3-二甲基咪唑硫酸甲酯盐中的淀粉在140℃条件下反应2 h可获得54%总乳酸收率,纤维素的收率为15.1%。果糖在同样的反应条件下收率为95%,葡萄糖为64%,这意味着反应机理可能为纤维素和淀粉首先降解为葡萄糖,然后异构为果糖,最终果糖分解为乳酸。     

Corrosion inhibition of mild steel by alkylimidazolium ionic liquids in hydrochloric acid

The acid corrosion inhibition process of mild steel in 1 M HCl by 1-butyl-3-methylimidazolium chlorides (BMIC) and 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM]HSO₄) has been investigated using electrochemical impedance, potentiodynamic polarization and weight loss measurements. Potentiodynamic polarization studies indicate the studied inhibitors are mixed type inhibitors. For both inhibitors, the inhibition efficiency increased with increase in the concentration of the inhibitor and the effectiveness of the two inhibitors are in the order [BMIM]HSO₄ > BMIC. The adsorption of the inhibitors on mild steel surface obeyed the Langmuir's adsorption isotherm. The effect of temperature on the corrosion behavior in the presence of 5 × 10⁻³ M of inhibitors was studied in the temperature range of 303-333 K. The associated activation energy of corrosion and other thermodynamic parameters such as enthalpy of activation (ΔH), entropy of activation (ΔS), adsorption equilibrium constant (K_ads) and standard free energy of adsorption (ΔG_ads) were calculated to elaborate the mechanism of corrosion inhibition.     

Densities and surface tensions of ionic liquids/sulfuric acid binary mixtures

The densities and surface tensions of [Bmim][TFO]/H_2SO_4, [Hmim][TFO]/H_2SO_4 and [Omim][TFO]/H_2SO_4 binary mixtures were measured by pycnometer and Wilhelmy plate method respectively. The results show that densities and surface tensions of the mixtures decreased monotonously with increasing temperatures and increasing ionic liquid(IL) molar fraction. IL with longer alkyl side-chain length brings a lower density and a smaller surface tension to the ILs/H_2SO_4 binary mixtures. The densities and surface tensions of the mixtures are fitted well by Jouyban–Acree(JAM) model and LWW model respectively. Redlich-Kister(R–K) equation and modified Redlich-Kister(R–K) equation describe the excess molar volumes and excess surface tensions of the mixtures well respectively. Adding a small amount of ILs(xILb 0.1) into sulfuric acid brings an obvious decrease to the density and the surface tension. The results imply that the densities and surface tensions of ILs/H_2SO_4 binary mixtures can be modulated by changing the IL dosage or tailoring the IL structure.     

Alkylation of anthracene to 2-isopropylanthracene catalyzed by Lewis acid ionic liquids

Alkylation of anthracene with 2-chloropropane to 2-isopropylanthracene catalyzed by various Lewis acidic ionic liquids (ILs), such as [Emim]Cl-AlCl₃, [Emim]Cl-FeCl₃, [Emim]Cl-ZnCl₂, [Bmim]Cl-AlCl₃, and [Omim]Cl-AlCl₃ ([Emim]⁺=1-ethyl-3-methylimidazolium cation, [Bmim]⁺=1-butyl-3-methylimidazolium cation, [Omim]⁺=1-octyl-3-methylimidazolium cation,), was investigated. [Emim]C1-A1C1₃ ionic liquid was found to be the most active catalyst in the alkylation. The yield of 2-isopropylanthracene was up to 74.5% and the selectivity of 2-isopropylanthracene was up to 82.9%. The [Emim]C1-A1C1₃ ionic liquid catalyst showed good catalytic activity after running for 6 times. Ease of product separation and the recycling performance of the ionic liquid catalyst is expected to contribute to the development of clean and environmentally friendly strategy for the synthesis of 2-isopropylanthracene.     

Promoting the sulfuric acid catalyzed isobutane alkylation by quaternary ammonium ionic liquids

Seven typical quaternary ammonium ionic liquids, amino acid ionic liquids, and imidazolium ionic liquids were synthesized, characterized, and investigated as co-catalyst for the sulfuric acid catalyzed isobutane alkylation. The results show that the introduction of [OPSIm][HSO₄] or [Pr₃NPS][HSO₄] both leads to a better catalytic performance and higher quality of alkylate products. The molecular dynamic simulation indicates that the [OPSIm][HSO₄] can promote the dissolution of isobutane molecules at interface, further improving the ratio of isobutane to olefin from 1.02 to 1.18. Differently, the [Pr₃NPS][HSO₄] can significantly increase the interface width from 0.66 to 0.97 nm and reduce the interface tension from 28.49 to 14.62 mN/m, thereby enhancing the reaction area and improving the ion transfer. The [Pro][HSO₄] and [Gly][HSO₄] result in a worse quality of alkylate products due to no positive effect on the interfacial properties such as interfacial solubility of isobutane.     

“绿色”溶剂离子液的研究进展

近年来，离子液由于其独特的优点, 在生物催化及化学合成领域越来越受到青睐。由于缺乏蒸气压，离子液作为绿色溶剂有很大潜能。此外，离子液不像极性有机溶剂那样会使酶失活，因而简化了类似含有糖类这样极性底物的反应。在离子液中，生物催化反应表现出较高的选择性、较快的反应速率和较高的酶稳定性。但这些溶剂还存在着离子液的纯化、控制水活性和pH、高粘度以及产品分离等问题。     

Gas drying with ionic liquids

The gas drying technology with ionic liquids (ILs) was systematically studied ranging from the molecular level to industrial scale. The COSMO‐RS model was first used to screen the suitable IL and provide theoretical insights at the molecular level. Toward CO₂ gas dehydration, we measured the CO₂ solubility in single [EMIM][Tf₂N] and in the [EMIM][Tf₂N] + H₂O mixture, as well as the vapor‐liquid equilibrium (VLE) of [EMIM][Tf₂N] + H₂O system, to justify the applicability of UNIFAC model. Based on the thermodynamic study, the rigorous equilibrium (EQ) stage mathematical model was established for process simulation. The gas drying experiment with IL was also performed and the water content in gas product can be reduced to 375 ppm. It was confirmed that a less flow rate of absorbent, a higher CO₂ recovery ratio and a much lower energy consumption can be achieved with IL than with the conventional triethylene glycol (TEG). © 2017 American Institute of Chemical Engineers AIChE J, 64: 606–619, 2018     

离子液体的应用进展

离子液体由于具有独特的物理化学性质而成为一种新型的绿色介质,近年来成为国际上研究的前沿和热点。它为开发新型绿色工艺,实现将传统重污染、高能耗工业过程的升级换代提供了新机遇。对离子液体应用的研究进展进行了综述,详细介绍了离子液体在催化科学、电化学、材料科学、环境科学和分离技术等领域的应用,并对其发展方向进行了展望。