Brønsted Acidic Ionic Liquids Mediated Metallic Salts Catalytic System for the Chemical Fixation of Carbon Dioxide to Form Cyclic Carbonates

Abstract  

The catalysts of COOH- and SO₃H-functionalized ionic liquids mediated metallic salts had been developed for the coupling of carbon dioxide and epoxides to form cyclic carbonates under mild reaction conditions without using additional organic solvents. The effects of different ionic liquids, metallic salts, varying the molar ratio of ionic liquid to metallic salt and reaction conditions were examined. The excellent yield of cyclic carbonates and the high turnover frequencies (TOF) were obtained at the optimum reaction conditions. In addition, the catalytic system offered high stability and reusability.     

Novel SO<Subscript>3</Subscript>H-Functionalized Ionic Liquids Based on Benzimidazolium Cation: Efficient and Recyclable Catalysts for One-Pot Synthesis of Biscoumarin Derivatives

Abstract  

In this article, a new group of SO₃H-functionalized ionic liquids based on benzimidazolium cation was synthesized and used as environmentally benign catalysts for the one-pot synthesis of biscoumarin derivatives. The ionic liquids showed high catalytic activities and reusabilities with good to excellent yields of the desired products. H ₀ (Hammett function) values and the minimum-energy geometries of SO₃H-functionalized ionic liquids were determined and the results revealed that the acidities and catalytic activities of ionic liquids in the synthesis of biscoumarin derivatives were related to their structures.     

Diels–Alder Reaction of Cyclopentadiene and Alkyl Acrylates in the Presence of Pyrrolidinium Ionic Liquids with Various Anions

Abstract  

The conversion and stereoselectivity of transformation to endo and exo norbornene derivatives was determined in the Diels–Alder reaction of cyclopentadiene with alkyl acrylates. The reactions were carried out in the pyrrolidinium ionic liquids in the presence of metal chlorides and trifluoromethanesulfonates as the catalysts. Shorter reaction times and higher conversions of dienophile were observed in a comparison with analogous cycloadditions carried out in the presence of conventional organic solvents. A higher stereoselectivity to the endo isomer was found in the majority of cases. The ionic liquids composed of 1-butyl-1-methylpyrrolidinium cation (Pyrr_1.4) and various anions were used. The influence of ionic liquid anion and several metal chlorides and metal triflates used as the catalysts on the conversion was determined.     

Incorporation of Metal Ions into Silica-Grafted Imidazolium-Based Ionic Liquids to Efficiently Catalyze Cycloaddition Reactions of CO<Subscript>2</Subscript> and Epoxides

Abstract  

A variety of imidazolium-based ionic liquids (ILs) have been widely developed to effectively catalyze the cycloaddition reactions of CO₂ and epoxides. To further improve the catalytic performance of those IL catalysts, we incorporated various metal chlorides (CoCl₂, NiCl₂, CuCl₂, ZnCl₂, and MnCl₂) into silica-grafted 1-methyl-3-[(triethoxysilyl)propyl] imidazolium chloride to produce a series of heterogeneous catalysts. Catalytic reaction tests demonstrated that the incorporation of such metal ions can significantly enhance the catalytic reactivity of the silica-grafted ILs towards cycloaddition reactions of CO₂ and epoxides that produce cyclic carbonates in solvent-free conditions. In addition, the effects on the catalytic reactivity of reaction parameters including reaction time, reaction temperature and CO₂ pressure were investigated.     

Catalytic performance of pyridinium salt ionic liquid in the synthesis of cyclic carbonate from carbon dioxide and butyl glycidyl ether

The catalytic performance of pyridinium salt ionic liquids in the reaction of butyl glycidyl ether and carbon dioxide was investigated in this study. The catalytic activity was studied in a batch reactor with different 1-alkylpyridinium salt ionic liquids at 60–140°C. The conversion of butyl glycidyl ether was affected by the structure of the ionic liquid; the one with the cation of bulkier alkyl chain length showed better reactivity. The effect of carbon dioxide pressure, reaction temperature and zinc bromide co-catalyst on this reaction was also discussed.     

Quaternary Ammonium Ionic Liquids as Bi-functional Catalysts for One-step Synthesis of Dimethyl Carbonate from Ethylene Oxide,Carbon Dioxide and Methanol

Abstract  

One kind of novel ionic liquids (ILs) with a tertiary amino moiety and a quaternary ammonium group were synthesized and identified by FT-IR, ¹H and ¹³C NMR. The elemental chemical state and basicity of ILs were determined by XPS and Hammett indicator method, respectively. Then the catalytic performance of these bi-functional catalysts was investigated in one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol. The best catalytic performance with 99% EO conversion and a maximum of 74% DMC selectivity was obtained using [N_111,6N11]I as catalyst under optimized reaction conditions. And the catalyst could be reused for several times. Normally, stronger basicity could be obtained by altering the anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly. A mechanism that both the ring opening of epoxide through nucleophilic attacks and the transesterification play an important role in the reaction was proposed based on experimental results.     

Oxidation desulfurization of fuel using pyridinium-based ionic liquids as phase-transfer catalysts

In this work, several ionic liquids based on pyridinium cations are prepared. The ionic liquids are employed as phase-transfer catalysts (PTCs) for phase-transfer catalytic oxidation of dibenzothiophene (DBT) dissolved in n-octane. The partition coefficients of DBT between ionic liquids and n-octane are investigated. Then H₂O₂-formic acid is used as an oxidant and ionic liquids are used as PTCs. The reaction turns to be heterogeneous and desulfurization rate of DBT increased apparently. When IL ([BPy]HSO₄) is used as PTC, and the condition are: temperature is 60 °C, time is 60 min, H₂O₂/sulfur molar ratio (O/S) is 4, the desulfurization rate reaches the maximum (93.3%), and the desulfurization of the real gasoline is also investigated, 87.7% of sulfur contents are removed under optima reaction conditions. The PTC [BPy]HSO₄ can be recycled for five times without significant decrease in activity.     

Study on Selective Dimerization of α-Methylstyrenes Promoted by Ionic Liquids

The catalytic systems composed of ionic liquids containing BF₄⁻ anion and HBF₄ showed high catalytic activity to produce 4-methyl-2,4-diphenyl-1-pentene (MDP-1) or 1,1,3-trimethyl-3-phenylindan (TPI) under different temperature conditions. Up to 90.8% selectivity to MDP-1 with a 98.7% conversion of α-methylstyrene was obtained at 60 °C in the presence of [HexMIm]BF₄–HBF₄, while exclusive TPI was yielded when the reaction temperature increased to 120 °C. Further studies showed that another ionic liquid, [BMIm]Cl · 2AlCl₃, could act as an excellent catalyst and solvent for the dimerization of α-methylstyrene to produce TPI. The dimerization of α-methylstyrene catalyzed by [HexMIm]BF₄–HBF₄ and [BMIm]Cl · 2AlCl₃ performed the same reaction mechanism and the proton was the active species.     

Preparation of Ni/SiO2 catalyst in ionic liquids for hydrogenation

A series of silica supported nickel catalysts were prepared from nickel nitrate and tetraethyl orthosilicate by the sol-gel method with the imidazolium type ionic liquids as solvents. The catalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Their catalytic performances for the selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde were investigated. The results show that the Ni/SiO₂ catalyst prepared with 1-(2-hydroxyethyl)-3-methylimidazole tetrafluoroborate ionic liquid as solvent exhibits the highest catalytic activity for the reaction. Under the optimal conditions of catalyst dosage (based on the mass of cinnamaldehyde used) 10%, reaction pressure 2 MPa, temperature 373 K and reaction time 2 h, the conversion of cinnamaldehyde and the selectivity to hydrocinnamaldehyde can reach 97.6% and 98.8%, respectively. __________ Translated from Petrochemical Technology, 2007, 36(1): 9–14 [译自:石油化工]     

Cycloaddition of carbon dioxide to butyl glycidyl ether using imidazolium salt ionic liquid as a catalyst

The catalytic performance of imidazolium salt ionic liquids in the cycloaddition of carbon dioxide to butyl glycidyl ether (BGE) was investigated. The catalytic activity was tested with different imidazolium salt ionic liquids at 60–140 °C under 0.62–2.17 MPa of CO₂ pressure. The imidazolium salt ionic liquid with the cation of bulkier alkyl chain length and with more nucleophilic anion showed higher conversion of BGE. High carbon dioxide pressure and high reaction temperature up to 140 °C was favorable for the high reactivity of the catalyst. The presence of zinc bromide co-catalyst enhanced the reactivity of the imidazolium salt ionic liquid. Kinetic studies with a semi-batch reactor revealed that the reaction could be considered as first order with respect to the concentration of BGE, and the activation energy was estimated as 22.6 and 22.8 kJ/mol for 1-ethyl-3-methylimidazolium chloride (EMImCl) and 1-butyl-3-methylimidazolium chloride (BMImCl), respectively.     

季铵盐型离子液体催化合成乙酸正丁酯

一步法制备了4种季铵盐型离子液体,并用FT-IR和¹H NMR表征结构。结果表明所合成的离子液体符合其理论结构;以它们为催化剂进行了乙酸正丁酯的合成研究,在相同条件下乙酸正丁酯的产率顺序为［Et₂NH₂］［HSO₄］>［Et₃NH］［HSO₄］>［n-Pro₃NH］［HSO₄］>［n-But₃NH］［HSO₄］,并且［Et₂NH₂］［HSO₄］和［Et₃NH］［HSO₄］与产物不互溶,而［n-Pro₃NH］［HSO₄］和［n-But₃NH］［HSO₄］与产物互溶,表明季铵盐离子液体的催化活性和极性都随阳离子链长度的增加而降低。以三乙胺硫酸为催化剂考察了反应时间、反应温度、醇酸摩尔比和离子液体用量对乙酸正丁酯产率的影响规律,结果表明：在n(正丁醇)∶n(乙酸)∶n(离子液体)=1∶2∶0. 25,反应时间8 h,反应温度 90℃的条件下乙酸正丁酯的产率达到81. 94%。采用减压蒸馏,除去离子液体相中的水、乙酸正丁酯和未反应的原料,将离子液体进行循环使用4次,结果表明乙酸正丁酯的产率没有明显下降,说明离子液体的稳定性和循环使用性较好。     

Brönsted Acidic Ionic Liquids as Efficient and Recyclable Catalysts for the Carbonylation of Formaldehyde

Abstract  

Methyl glycolate (MG), as a precursor to ethylene glycol (EG), was synthesized by an efficient and eco-friendly procedure of one-pot, two-step, sequential reaction, including carbonylation and esterification from HCHO with Br?nsted acidic ionic liquids (BAILs) as catalysts. MG was obtained in high yield under mild conditions. In addition, the catalyst could be recycled eight times after separating the unreacted materials and products from the reaction system by distillation under vacuum and no significant decrease in catalytic activity was observed.     

磺酸功能化离子液体催化制生物柴油的性能

通过1-烯丙基咪唑与1,4-丁基磺酸内酯反应制备的两性离子分别与硫酸、三氟甲基磺酸、磷钨酸、磷钼酸和硅钨酸直接反应制备了5种磺酸功能化离子液体。采用¹H NMR、FTIR、TG/DTA等技术手段对其结构及热稳定性进行了表征。最后通过催化油酸与甲醇酯化反应制生物柴油过程对催化剂的催化活性和重复使用性进行了评价。结果表明,5种离子液体均具有高催化活性（高于浓硫酸）,并且重复使用4次后,催化活性基本保持不变。3种杂多酸离子液体不溶于产物,以固态形式与产物混合,为其回收和重复利用提供了有利条件。     

Synthesis of thermally stable polyamides with pendant 1,3,4-oxadiazole units via direct polycondensation in ionic liquids

The synthesis of high molecular weight polyamides by using 1-methyl-3-alkyl imidazolium bromides (alkyl = C₃–C₈) as reaction media has been reported. Polymers were prepared from the reaction of 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine, POBD, and aromatic/aliphatic dicarboxylic acids in ionic liquids in the presence of triphenyl phosphite as a condensing agent without requiring any extra components such as CaCl₂ or pyridine. The number average molecular weight of the polymers was measured by vapor pressure osmometry. The effects of various reaction parameters such as alkyl chain length of ionic liquids, reaction temperature, and reaction time on the molecular weight were investigated. No regular relationship between inherent viscosity or molecular weight with the alkyl chain length in the ionic liquid was observed; however, the highest molecular weight was observed in 1-butyl-3-methyl imidazolium bromide. The thermal properties of the prepared polymers were also studied with DSC and TGA methods. Removal of Co²⁺ from aqueous solutions was performed using polymer (7).     

Dynamic Behavior of Pd Species in an LaFe<Subscript>0.95</Subscript>Pd<Subscript>0.05</Subscript>O<Subscript>3</Subscript> Perovskite

Abstract  

LaFe_0.95Pd_0.05O₃ prepared by a sol–gel process was stable under reducing atmospheres up to 1,073 K. Under reducing atmospheres metallic palladium left the LaFeO₃ lattice and ionic palladium was reversibly incorporated into the perovskite framework in oxidizing environments. The catalytic activity of LaFe_0.95Pd_0.05O₃ was higher than that of LaFeO₃.     

Os(VIII)/Ru(III) Catalysed Oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-Valine by Ag(III) Periodate Complex in Aqueous Alkaline Medium: A Comparative Kinetic Study

Abstract  

The kinetics of osmium(VIII) (Os(VIII)) and ruthenium(III) (Ru(III)) catalysed oxidation of l-valine (l-val) by diperiodatoargentate(III) (DPA) in aqueous alkaline medium at 25 °C and a constant ionic strength of 0.006 mol dm⁻³ was studied spectrophotometrically. The stoichiometry is the same in both the catalysed reactions, i.e., [l-val]:[DPA] = 1:1. The reaction is of first order in [Os(VIII)], [Ru(III)], and [DPA] and has less than unit order in [l-val] and negative fractional order in [OH⁻]. Added periodate had no effect on rate of reaction. The products were identified by spot test and characterized by spectral studies. The catalytic constant (K _C) was also calculated for both catalysed reactions at different temperatures. The activation parameters with respect to slow step of the mechanisms were computed and discussed and thermodynamic quantities were also determined. It has been observed that the catalytic efficiency for the present reaction is in the order of Os(VIII) > Ru(III). The probable active species of catalyst and oxidant have been identified.     

Effects of Reaction Variables on Fischer–Tropsch Synthesis with Co-Precipitated K/FeCuAlO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Catalysts

Abstract  

The effects of reduction temperature and reaction temperature, pressure and space velocity on iron-based K/FeCuAlO _x Fischer–Tropsch catalysts prepared by co-precipitation were investigated. The catalyst reduced at 150 °C deactivated quickly due to an abundance of unreduced iron species. With increasing reduction temperature, the iron oxide’s phase transformed from hematite (α-Fe₂O₃) to magnetite (Fe₃O₄) and finally to metallic iron (α-Fe). The induction period to reach steady-state catalytic activity was reduced at increased reduction temperatures due to in situ reduction by syngas during reaction. CO conversion increased with increasing reaction temperature, and selectivity to C₅+ decreased with increasing reaction pressure and space velocity. At reaction temperatures up to of 300 °C, CO₂ formation by the water–gas shift reaction was linearly correlated with the extent of CO conversion, and CO₂ formation was slightly suppressed at ≥350 °C by a reverse water–gas shift reaction.     

Ionic liquid as an efficient promoting medium for synthesis of dimethyl carbonate by oxidative carbonylation of methanol

The synthesis of dimethyl carbonate by oxidative carbonylation of methanol using Cu salt catalysts in the presence of various room temperature ionic liquids (RTILs) was reported. Among the ionic liquids used, N-butylpyridinium tetrafluoroborate was the most effective promoter in terms of the conversion of methanol and the selectivity to dimethyl carbonate (DMC). The influences of reaction temperature, pressure, time, molar ratio of CO/O₂, and amount of the ionic liquid on the oxidative carbonylation of methanol were investigated. The results indicated that under the reaction conditions of 120 °C and 2.4 MPa of a 2:1 mixture of CO and O₂, 17.2% conversion of methanol, 97.8% selectivity of DMC and a DMC productivity of 4.6 g g⁻¹ cat h⁻¹ were achieved. The N-butylpyridinium tetrafluoroborate-meditated CuCl catalyst system could be reused at least five recycles with the same selectivity and a slight loss of catalytic activity due to loss of the catalyst during handling and transferring the reaction mixture.     

PdCl2(P(OPh)3)2 Catalyzed Coupling and Carbonylative Coupling of Phenylacetylenes with Aryl Iodides in Organic Solvents and in Ionic Liquids

Efficient cross-coupling and carbonylative coupling of terminal alkynes with aryl iodides catalyzed by PdCl₂(P(OPh)₃)₂ in the presence of NEt₃ in toluene and in ionic liquids is described. In imidazolium ionic liquids, [bmim]PF₆ or [mokt]PF₆ (bmim = 1-butyl-3-methyl imidazolium cation, mokt = 1-methyl-3-octyl imidazolium cation) catalyst was recycled and used in four concecutive catalytic cycles with high activity. In the absence of aryl iodide the same catalytic system catalyzed head-to-tail dimerization of phenylacetylene to the 1,3-diphenyl enyne, trans-PhC ≡ C–C(Ph)=CH₂, with a yield of 85%.     

Ionic Liquid Catalyzed 4,6-Disubstituted-3-Cyano-2-Pyridone Synthesis Under Solvent-Free Conditions

Abstract  

A green protocol for the synthesis of 4,6-disubstituted-3-cyano-2-pyridones from cyanoacetamides and 1,3-dicarbonyl compounds or chalcones using guanidine based ionic liquid as catalyst has been developed. In solvent-free conditions at 30 °C, [TMG][Lac] (1,1,3,3-tetramethylguanidine lactate) was found to have the highest catalytic activity among the ionic liquids including [TMG][Ac] (1,1,3,3-tetramethylguanidine acetate), [TMG][Pr] (1,1,3,3-tetramethylguanidine propionate), [TMG][n-Bu] (1,1,3,3-tetramethylguanidine n-butyrate) and [TMG][TFA] (1,1,3,3-tetramethylguanidine trifluoroacetate). The catalyst was recovered and recycled several times without significant loss of catalytic activity.