Novel Brønsted acidic ionic liquid as efficient and reusable catalyst system for esterification

Synthesis and Characterization of Phosphoric Silica Catalyst from Bamboo Leaves for Production of Triacetin

In this research, the bamboo leaf shows promise as an alternative raw material for silica production. This study investigated the performance of heterogeneous catalyst prepared from silica derived bamboo leaf ash after that impregnated with phosphoric acid at ratio various. The catalyst was characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Brunauer Emmet Teller (BET) and Barrett, Joyner and Halenda (BJH) method and triacetin product analyzed by GC-MS. The optimum condition phosphoric silica catalyst was obtained at phosphoric silica molar ratio of 1:2 and employed in the acetylation of glycerol, respectively. As result, 24 % selectivity for triacetin was obtained in the presence of catalytic amount 5%, molar ratio 1:9 at 100 °C for 4 hours. Bamboo leaf derived phosphoric silica calcined showed high potential to be used as an easy to prepare and high-performance solid catalyst for industrial scale.

Homogeneous Catalysis and Heterogeneous Recycling: A Simple Zn(II) Catalyst for Green Fatty Acid Esterification

This work describes the use of simple zinc(II) salts (ZnCl₂, ZnCO₃, Zn(OAc)₂, ZnO, Zn(ClO₄)₂, Zn(TfO)₂, and Zn(BF₄)₂) as effective catalysts for the esterification of fatty acids with long-chain alcohols and simple polyols through a homogeneous system that allows the gradual and selective removal of water. The results show that the catalytic activity depends on the nature of the counterion: the most effective are the salts with poorly coordinating anions (perchlorate and triflate) or containing basic Brønsted anions (oxide, acetate, and carbonate). However, only with the latter is it possible to fully recover the catalyst at the end of each run, which is easily filtered in the form of zinc carboxylate, given its insolubility in the ester produced. In this way, it is possible to recycle the catalyst numerous times, without any loss of activity. This beneficial prerogative couples the efficiency of the homogeneous catalysis with the advantage of the heterogeneous catalysis. The process is, therefore, truly sustainable, given its high efficiency, low energy consumption, ease of purification, and the absence of auxiliary substances and byproducts.

Determination of physicochemical properties of ionic liquids by gas chromatography

Over the years room temperature ionic liquids have gained attention as solvents with favorable environmental and technical features. Both chromatographic and conventional methods afford suitable tools for the study of their physicochemical properties. Use of gas chromatography compared to conventional methods for the measurement of physicochemical properties of ionic liquids have several advantages; very low sample concentrations, high accuracy, faster measurements, use of wider temperature range and the possibility to determine physicochemical properties of impure samples. Also, general purpose gas chromatography instruments are widely available in most laboratories thus alleviating the need to purchase more specific instruments for less common physiochemical measurements. Some of the main types of physicochemical properties of ionic liquids accessible using gas chromatography include gas-liquid partition constants, infinite dilution activity coefficients, partial molar quantities, solubility parameters, system constants of the solvation parameter model, thermal stability, transport properties, and catalytic and other surface properties.

Synthesis of alkyl polyglycosides using SO3H-functionalized ionic liquids as catalysts

An effective process for synthesis of alkyl polyglycosides (APG) was developed using SO₃H-functionalized ionic liquids (SFILs) as catalysts. Four SFILs, [PSmim][HSO₄], [PSmim][pTSA], [PSPy][HSO₄] and [PSPy][pTSA], were designed and synthesized for APG synthesis. The results indicated that [PSmim][HSO₄] shows the best catalytic performance among these four SFILs, which has a great agreement with the order of their acidities. When the [PSmim][HSO₄] was used as catalyst, the reaction time could be decreased from 24 h to 8 h, and molar ration of n-octanol to glucose could be decreased from 5 : 1 to 3 : 1 under the optimization reaction conditions. In addition, the [PSmim][HSO₄] could be easily regenerated and recycled at least 5 times with slight decrease in catalytic activity. Moreover, the catalytic mechanism of [PSmim][HSO₄] was further investigated by molecular simulation. The high catalytic activity of [PSmim][HSO₄] is attributed to hydrogen bonds between [PSmim][HSO₄] and glucose and n-octanol, which could accelerate the protonation of glucose and removal of hydrogen ions from the hydroxyl in n-octanol.

Alkyl polyglycosides (APG), produced from glucose and fatty alcohols, are one kind of renewable green non-ionic surfactants. It is of great significance to develop a green catalyst reaction system for synthesis of alkyl polyglycosides.

The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids

[AAE]X composed of amino acid ester cations is a sort of typically “bio-based” protic ionic liquids (PILs). They possess potential Brønsted acidity due to the active hydrogens on their cations. The Brønsted acidity of [AAE]X PILs in green solvents (water and ethanol) at room temperature was systematically studied. Various frameworks of amino acid ester cations and four anions were investigated in this work from the viewpoint of structure–property relationship. Four different ways were used to study the acidity. Acid dissociation constants (pK_a) of [AAE]X determined by the OIM (overlapping indicator method) were from 7.10 to 7.73 in water and from 8.54 to 9.05 in ethanol. The pK_a values determined by the PTM (potential titration method) were from 7.12 to 7.82 in water. Their Hammett acidity function (H₀) values (0.05 mol·L⁻¹) were about 4.6 in water. In addition, the pK_a values obtained by the DFT (proton-transfer reactions) were from 7.11 to 7.83 in water and from 8.54 to 9.34 in ethanol, respectively. The data revealed that the cationic structures of [AAE]X had little effect and the anions had no effect on the acidity of [AAE]X. At the same time, the OIM, PTM, Hammett method and DFT method were reliable for determining the acidic strength of [AAE]X in this study.

Towards understanding corrosion inhibition of sulfonate/carboxylate functionalized ionic liquids: An experimental and theoretical study

The inhibition performance of ionic liquids, abbreviated as [(CH₂)COOHMIm][HSO₄], [(CH₂)₂COOHMIm][HSO₄], and [(CH₂)₃SO₃HMIm][HSO₄] was investigated for carbon steel in 0.5 M HCl solution. Results indicated that these ionic liquids could act as effective inhibitors by adsorption onto the steel surface, and the inhibition efficiency increases with cation alkyl chain length and concentration up to a limit. The inhibition efficiency of a sulfonate-type ionic liquid with a longer alkyl chain is higher than those of the carboxylate-type ionic liquids. Besides, the order of inhibition efficiency was verified by both computational calculation and electrochemical experimental observations.

Spectroscopic Studies of a Phosphonium Ionic Liquid in Supercritical CO2

Fluorescence spectroscopy was used to study a solution comprised of coumarin 153 (C153)+ trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P6,6,6,14]+ [Tf2N]−)+ supercritical CO2 (scCO2). We compare the spectroscopy of C153 in neat scCO2 to that of C153/scCO2 with the addition of ionic liquid (IL). Excitation and emission peak frequencies of C153 in scCO2 and in IL/scCO2 diverged at reduced densities (ρr = ρ/ρc) below the CO2 critical density. At low fluid density, spectral changes in the IL/scCO2 solutions showed evidence that C153 experiences a very different microenvironment—one that is unlike neat scCO2. The data show that the presence of IL clearly influences the C153 excitation and emission profiles. Excitation was broadened and red shifted by >2000 cm−1 and the presence of an additional low-energy emission component that was red shifted by ~3000 cm−1 was clearly visible and not observed in neat scCO2. The solution heterogeneity was controlled by changing the scCO2 density and at high fluid density, both the excitation and emission spectra were more similar to those in neat scCO2. Steady-state anisotropy also showed that at low fluid density, the C153 emission was significantly polarized. Aggregation of C153 has been reported in the literature and this led us to hypothesize the possibility that C153 dimer (aggregation) formation may be occurring in scCO2. Another possible explanation is that dye–IL aggregates may dissolve into the scCO2 phase due to C153 acting as a “co-solvent” for the IL. Time-resolved intensity decay measurements yielded only slightly non-exponential decays with accompanying time constants of ~3–4 ns that were significantly shorter than the 5–6 ns time constants in neat scCO2, which are suggestive of C153–IL interactions. However, these data did not conclusively support dimer formation. Pre-exponential factors of the time constants showed that almost all of the emission was due to monomeric C153.

Transformation of Levulinic Acid to Valeric Biofuels: A Review on Heterogeneous Bifunctional Catalytic Systems

Valerate esters (VAEs) commonly derived from levulinic acid (LA), which is deemed as one of the most promising biomass platform molecules, have been hailed as "valeric biofuels" in recent years. The cascade transformation of LA to VAEs consists of a series of acid- and metal-catalyzed processes alternately, in which heterogeneous bifunctional catalysts are required for better catalytic performance. The transformation pathway from LA to VAEs is presented, and bifunctional catalytic systems for the cascade transformation of LA into valeric acid (VA) and its esters, as well as one-pot conversion processes, are reviewed. Additionally, effects of metal and acid sites on the catalytic performance are discussed in detail. Impacts of and improvements to coke deposition, which is determined to be the primary reason for the reduction in catalytic activity, are also analyzed. Finally, feasible suggestions are proposed for enhanced catalytic performance and a reduction in overall costs.

Clean Synthesis of Adipic Acid by Direct Oxidation of Cyclohexene with H2O2 catalysed by Na2WO4.2H2O and Acidic Ionic Liquids

Without any other organic solvents or halide present, direct catalytic oxidation of cyclohexene to adipic acid with hydrogen peroxide catalysed by Na2WO4.2H2O and acidic ionic liquids has been performed with excellent yields and selectivities, and the catalyst system could be easily reused.

Control of phase separation behaviour of ionic liquid catalysts with reactants/products toward synthesis of long-chain wax esters at moderate temperatures

Phase separation of products from ionic liquid catalysts promotes the equilibrium reaction to prepare long-chain wax esters at moderate temperatures.

Ionic liquid-assisted catalysis for glycosidation of two triterpenoid sapogenins

In order to study the universality of ionic liquids-assisted glycosidation and explore their catalytic behaviors together with potential, oleanolic acid and ursolic acid were selected to establish catalytic system as typical triterpene sapogenins.

Hydrothermal conversion of glucose to levulinic acid using multifunctional ionic liquids: effects of metal ion co-catalysts on the product yield

An efficient catalytic system comprising Bronsted acidic ionic liquids and Lewis acidic metal salts for hydrothermal glucose conversion to platform chemicals.

DABCO-based ionic liquids: introduction of two metal-free catalysts for one-pot synthesis of 1,2,4-triazolo[4,3-a]pyrimidines and pyrido[2,3-d]pyrimidines

In this study, structurally functionalized 1,2,4-triazolo[4,3-a]pyrimidines and pyrido[2,3-d]pyrimidines were synthesized by two non-metal DABCO-based ionic liquids which were compared in catalytic activity in both reactions.

Green Brönsted acid ionic liquids as novel corrosion inhibitors for carbon steel in acidic medium

New ionic liquids with multiple Brönsted acid sites were synthesized in ≥98% yield, and their inhibiting properties for the corrosion of carbon steel in 0.5 M HCl solution had been evaluated using electrochemical impedance spectroscopy, potentiodynamic polarization and weight loss method, finally the possible inhibiting mechanism was proposed according to UV–visible spectroscopic measurements and surface analysis including SEM and XPS techniques. The designed cation structure of Brönsted acid ionic liquids (BAILs), with one phenyl and two imidazolium rings, makes them good mixed-type inhibitors via the adsorption of BAILs on the steel surface to suppress both anodic and cathodic processes, obeying Langmuir adsorption isotherm. As potential acid catalysts, BAILs show nice corrosion inhibiting performance in acidic medium regardless of their Brönsted acidity, which is of great significance to enlarge the industry applications of BAILs.

Efficient esterification of n-butanol with acetic acid catalyzed by the Brönsted acidic ionic liquids: influence of acidity

BAILs having different structures and their related acidities have been investigated for their role in the esterification of n-butanol with acetic acid, and it was found that IL-5 containing double –SO₃H groups exhibits excellent catalytic activity.

Ir/C and Brφnsted acid functionalized ionic liquids: an efficient catalytic system for hydrogenation of nitrobenzene to p-aminophenol

Hydrogenation of nitrobenzene to p-aminophenol using Ir/C and Brφnsted acid functionalized ionic liquids as catalysts.

Catalytic activity comparison of Zr–SBA-15 immobilized by a Brønsted–Lewis acidic ionic liquid in different esterifications

Zirconium-incorporated SBA-15 mesoporous molecular sieves (Zr–SBA-15) with different Si/Zr molar ratios were one-pot synthesized and characterized by XRD, TEM and N₂ physical adsorption.