Novel porous and hydrophobic POSS-ionic liquid polymeric hybrid as highly efficient solid acid catalyst for synthesis of oleate

A novel porous and hydrophobic Brønsted acidic solid catalyst (POSS-[VMPS][H₂SO₄]) was successfully synthesized by copolymerization of polyhedral oligomeric vinylsilsesquioxanes (POSSs) and sulfonic acid-functionalized imidazole ionic liquids. Catalytic tests for the esterification of oleic acid with methanol have shown that this newly obtained polymeric hybrid exhibits very high catalytic activity and selectivity, which was more active or comparable to those of the common solid acid Amberlite-732 and liquid acid H₂SO₄. Moreover, the catalyst has a good recyclability without significant loss in the activity.     

Effect of cocatalyst and carbon dioxide pressure on the synthesis of polycarbonate from phenyl glycidyl ether and carbon dioxide

The copolymerization of phenyl glycidyl ether (PGE) and carbon dioxide was performed in the presence of ionic liquid catalyst. 1-Butyl-3-methyl imidazolium chloride, tetrabutylamouim chloride and 1-n-butylpyridinium chloride were used as catalyst for this reaction carried out in a batch reactor. All the ionic liquid catalysts showed good catalytic activity for the synthesis of polycarbonates with very low polydispersity, close to 1. The carbonate content, turnover number (TON), and average molecular weight of the copolymer were affected by the structure of the ionic liquid. High carbon dioxide pressure enhanced TON and carbonate content because of the increase of carbon dioxide absorption in PGE solution. ZnBr₂ and a Zn-Co cyanide complex were also tested as a catalyst and/or cocatalyst for this reaction to compare their catalytic performance with the imidazolium salt ionic liquids.     

Prominent Roles of Impurities in Ionic Liquid for Catalytic Conversion of Carbohydrates

Impurities present in commercially available ionic liquids display prominent catalytic functions toward carbohydrate conversion. Little conversion was observed at 180?°C with high purity [EMIM]Cl ionic liquid whereas significant conversion was observed for ionic liquids of lower purity levels. Addition of metal halides to high purity [EMIM]Cl catalyze cellulose conversion with drastically different product selectivities dependent on the metal ions. CuCl₂ is an active catalyst for hydrolyzing cellulose and further degrading the products. CrCl₂ is an active and a selective catalyst for the formation of 5-hydroxymethylfurfural (5-HMF). CrCl₂ also helps stabilize the 5-HMF product. FeCl₂ does not show catalytic activity. Metal impurities in ionic liquid correlate to the activities observed when similar metals were added to high purity ionic liquids.     

Synthesis of poly(lactic acid)–poly(ethylene glycol) copolymers using multi-SO3H-functionalized ionic liquid as the efficient and reusable catalyst

Poly(lactic acid)–poly(ethylene glycol) copolymers were synthesized under the catalysis of multi-SO₃H-functionalized ionic liquid. Compared to the ordinary ionic liquids and the traditional Lewis acid catalysts, the ionic liquids with multi-sulfonic acid groups were more catalytically active, and the reaction conversion rate reached up to 97.8 %. The molecular weight of the resulting copolymer was 5.69 × 10⁴ g mol^?1 and the degree of crystallinity was 42.9 %. The copolymers were also of higher hydrophilicity and better mechanical properties. The reaction kinetics of copolymerization was analyzed. The intrinsically high catalytic activity of multi-SO₃H groups originated from the lower activation energy and the higher free acidity. The recovering catalytic activity of the multi-SO₃H ionic liquid catalyst was higher, suggesting that it is a recyclable, environmentally friendly catalyst.     

Deep removal of sulfur from real diesel by catalytic oxidation with halogen-free ionic liquid

A halogen-free task-specific ionic liquid (TSIL) of 1-(2-carboxylic acid) ethyl-3-methylimidazolium bisulfate ([(CH₂)₂COOHmim] [HSO₄]) is applied for deep oxidative desulfurization of real diesel as a catalyst and reaction media. The sulfur level of real diesel can be reduced from 200 to 20.5 μg/g at room temperature with small amount of ionic liquid using H₂O₂ as an oxidant. The used ionic liquid can be easily recycled and no obvious decrease in catalytic activity can be found after recycling five times.     

Synthesis of Trimethylolpropane Esters of Oleic Acid Using a Multi-SO<Subscript>3</Subscript>H-Functionalized Ionic Liquid as an Efficient Catalyst

Biodegradable trimethylolpropane triesters of oleic acid were synthesized by esterification of trimethylolpropane and oleic acid over a multi-SO₃H-functionalized strong Brønsted acidic ionic liquid as the catalyst. The results showed that the esterification can proceed satisfactorily over the catalyst at an ambient pressure even without simultaneous removal of water. Under the optimal reaction conditions (temperature: 100 °C, reaction time: 3 h, reactant molar ratio: 3.6:1, and catalyst amount, high conversion rate of trimethylolpropane (99.0%) and selectivity of trimethylolpropane triester (92.1%) were obtained. The ionic liquid was reused six times after the removal of water and no obvious change in catalytic activity was detected. Operational simplicity, high yields along with good reusability makes the multi-SO₃H-functionalized ionic liquid a promising catalyst for the esterification of trimethylolpropane with oleic acid.     

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.     

Molybdovanadophosphoric anion ionic liquid as a reusable catalyst for solvent-free benzene oxidation to phenol by H2O2

Molybdovanadophosphoric anion (H₂PMo₁₁VO₄₀^2 −) room temperature ionic liquid was prepared and characterized by the methods of FT-IR and TG. Then, this ionic liquid was employed as catalyst for the oxidation of benzene to phenol by H₂O₂ without using solvent. The homogeneous emulsion formed by the catalyst and substrates during the reaction facilitated the catalytic process. After reaction, the catalyst could self-precipitate from the reaction media and proved to be recyclable.     

Rhodium Acetate Dimer Immobilized in 1‐Butyl‐3‐methylimidazolium Hexafluorophosphate Ionic Liquid: a Novel and Recyclable Catalytic System for the Cyclopropanation of Alkenes

Alkenes undergo smooth cyclopropanation with ethyl diazoacetate using a catalytic amount of rhodium acetate dimer, Rh₂(OAc)₄, immobilized in the air‐ and moisture‐stable 1‐butyl‐3‐methylimidazolium hexafluorophosphate ionic liquid, [bmim]PF₆, to afford cyclopropanecarboxylates in excellent yields with high trans‐selectivity. The recovery of the catalyst is facilitated by the hydrophobic nature of [bmim]PF₆. The recovered ionic liquid containing Rh₂(OAc)₄ can be reused for three to five subsequent runs with only a gradual decrease in activity.     

Oxidative Desulfurization of Model Diesel Using a Fenton‐Like Catalyst in the Ionic Liquid [Dmim]BF4

A Fenton‐like catalyst prepared from tetrabutylammonium chloride and ferric trichloride was characterized by Fourier transform infrared, UV‐vis and Raman spectroscopy. The catalyst (C₄H₉)₄NFeCl₄ (TBAFeCl₄) in an extraction and catalytic oxidative desulfurization (ECODS) system containing H₂O₂ and the ionic liquid (IL) 1‐decyl‐3‐methylimidazolium tetrafluoroborate ([Dmim]BF₄) exhibited high catalytic activity for the removal of dibenzothiophene (DBT) in model diesel. Desulfurization with the Fenton‐like catalyst TBAFeCl₄ in ECODS involves the structural distortion of DBT via polarization of the IL and its subsequent oxidation. The catalytic system could be recycled multiple times without significant decrease in desulfurization activity due to the high stability of the system.     

Preparation of well-defined dendrimer encapsulated ruthenium nanoparticles and their application as catalyst and enhancement of activity when utilised as SCILL catalysts in the hydrogenation of citral

Silica supported dendrimer encapsulated ruthenium nanoparticles were prepared and evaluated as catalysts in the hydrogenation of citral. The dendrimer encapsulated nanoparticles were prepared using the generation 4 (G4), generation 5 (G5) and generation 6 (G6) hydroxyl-terminated poly(amidoamine) (PAMAM-OH) dendrimers as templating agents with different Ru metal:dendrimer ratios. The effects of ionic liquids as catalyst coatings on the catalytic activity were investigated for the ionic liquids [BMIM][NTf₂], [OMIM][NTf₂], [BMIM][BF₄], [BMIM][PF₆], [EMIM][OcS] and [EMIM][EtS]. An enhancement in catalytic activity was observed when utilising [BMIM][NTf₂] as an ionic liquid coating with selectivity towards citronellal.     

Ionic liquid supported on magnetic nanoparticles as highly efficient and recyclable catalyst for the synthesis of β-keto enol ethers

A magnetically ionic liquid supported on γ-Fe₂O₃ nanocatalyst (Al_xCl_y-IL-SiO₂@γ-Fe₂O₃) was synthesized and evaluated as a recoverable catalyst for the synthesis of β-keto enol ethers. The immobilized catalyst proved to be effective and provided the products in high to excellent yield at room temperature. Moreover, the catalyst could be easily recovered by magnetic separation and recycled for six times without significant loss of its catalytic activity.     

Amino acid ionic liquid bound copper Schiff base catalyzed highly efficient three component A3-coupling reaction

Amino acid ionic liquid Schiff base derived from dl-threonine and salicylaldehyde was complexed with copper (II) ions and used as an efficient and reusable catalyst for multicomponent synthesis of propargylamines via A³ coupling of aldehydes, amines, and alkynes. The ionic liquid derived catalyst was readily synthesized, reusable and exhibited superior catalytic activity. The synthesized catalyst showed consistent activity for several runs without any significant loss in activity and importantly, no leaching had occurred during this course.     

Selective oxidation of alcohols with H2O2 catalyzed by long chain multi-SO3H functionalized heteropolyanion-based ionic liquids under solvent-free conditions

Two novel long chain multi-SO₃H functionalized heteropolyanion-based ionic liquids were prepared and characterized. They as homogeneous catalysts showed high catalytic activity in selective oxidation of alcohols with 35% aqueous hydrogen peroxide under solvent-free conditions without adding any phase transfer catalyst. Two ionic liquids can be recovered readily and reused five times without any significant loss in their catalytic activities.     

Solid Catalyst with Ionic Liquid Layer (SCILL) – A New Concept to Improve Selectivity Illustrated by Hydrogenation of Cyclooctadiene

A new concept of a solid catalyst with ionic liquid layer (SCILL) as a novel method to improve the selectivity of heterogeneous catalysts is presented. The sequential hydrogenation of cyclooctadiene (COD) to cyclooctene (COE) and cyclooctane on a commercial Ni catalyst coated with the ionic liquid [BMIM][n‐C₈H₁₇OSO₃] was tested as first model system. Compared to the original catalyst, the coating of the internal surface with the ionic liquid (IL) strongly enhances the maximum intrinsic COE yield from 40 to 70 %. This effect is already achieved for a pore filling degree of only 10 % and cannot be explained by pore diffusion, as shown by experiments with different particle sizes and theoretical considerations. The IL layer is very robust and no leaching into the organic phase was detectable.     

Triethylsulfonium Bistriflimide as the Reaction Medium in Catalyzed and Uncatalyzed Cycloaddition [4 + 2]

Triethylsulfonium bistriflimide, [S_2.2.2][NTf₂], has been tested and compared with other ionic liquids and molecular solvents as a medium in Diels–Alder reaction between cyclopentadiene and dimethyl maleate. Triflates and chlorides of different metals have been combined with [S_2.2.2][NTf₂] and the catalytic activity of the systems formed have been determined. The effect of concentration of the catalysts in sulfonium ionic liquid and reactants on the yield and endo:exo ratio has been established. The representative catalyst—Yb(OTf)₃·xH₂O in [S_2.2.2][NTf₂] has been examined in the reaction of cyclopentadiene with various dienophiles. The use of sulfonium ionic liquids permitted recycling the catalysts. For the best four catalytic systems, the products have been isolated.     

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。     

Acidic ionic liquid [bmim]HSO4: An efficient catalyst for acetalization and thioacetalization of carbonyl compounds and their subsequent deprotection

Acetalization/thioacetalization of carbonyl compounds, under solvent free conditions, has been described using acidic ionic liquid 1-Butyl-3-methylimidazolium hydrogen sulfate ([bmim]HSO₄) at room temperature, in conjunction with microwave energy and ammonium chloride. The catalyst retains its acidity, catalytic activity, and recyclability in ammonoium chloride, whereas its decomposition is observed under microwave irradiation. The same catalyst has also been used for the deprotection of acetals, thioacetals as well as for transthioacetalization under microwave irradiation.     

Synthesis and application of a novel strong and stable supported ionic liquid catalyst with both Lewis and Brønsted acid sites

Poly(4-vinylpyridine)-supported ionic liquid with both Lewis and Brønsted acid sites was easily prepared from its starting materials and used as a novel and highly efficient heterogeneous catalytic system for the synthesis of biscoumarins by two-component one-pot domino Knoevenagel-type condensation/Michael reaction between various aliphatic and aromatic aldehydes with 4-hydroxycoumarin. The Lewis and Brønsted acidic sites loading in [P₄VPy-BuSO₃H]Cl-X(AlCl₃) were found to be 2.15 and 0.9 mmol per gram of catalyst, respectively. The effect of the simultaneous presence of Lewis and Brønsted acid sites was evaluated. The catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), elemental analysis, and atomic absorption technique. The catalyst is stable (as a bench top catalyst) and reusable.