Imidazolium Hydrogen Sulfate Research Articles

Ionic liquid on the acidic organic-inorganic hybrid mesoporous material with good acid-water resistance for biodiesel production

Different amounts of acidic ionic liquid sulfonic acid functionalized imidazolium hydrogen sulfate ([Ps-im]HSO4) were immobilized on the acidic organic-inorganic hybrid mesoporous material SO42−/ZrO2-SiO2(Et) by the chemical grafting. The structure of the catalyst was characterized by FT-IR, XRD, N2 absorption–desorption measurement, XPS and TG. The results showed that the ethane-bridge organosilica moieties were incorporated into the framework of SO42−/ZrO2, enhancing the acidity of SO42−/ZrO2-SiO2(Et) with respect to SO42−/ZrO2. Meanwhile, the ionic liquid was successfully immobilized onto the acidic mesoporous materials SO42−/ZrO2-SiO2(Et) and with the increase of ionic liquid loading, the BET surface areas and the pore volumes decreased and the average pore diameters increased. SO42−/ZrO2-SiO2(Et)-IL-i were very efficient in the transesterification of soybean oil with methanol and gave an approximate 99% biodiesel yield when the reaction was carried out at 150 °C with a 5 wt% catalyst amount at 18:1 methanol/oil molar ratio for 3.0 h. And they not only own the abilities of water and acid resistance, but also maintain satisfactory catalytic activity after five runs.

Direct Production of Furfural in One-pot Fashion from Raw Biomass Using Br\xf8nsted Acidic Ionic Liquids

The conversion of raw biomass into C5-sugars and furfural was demonstrated with the one-pot method using Brønsted acidic ionic liquids (BAILs) without any mineral acids or metal halides. Various BAILs were synthesized and characterized using NMR, FT-IR, TGA, and CHNS microanalysis and were used as the catalyst for raw biomass conversion. The remarkably high yield (i.e. 88%) of C5 sugars from bagasse can be obtained using 1-methyl-3(3-sulfopropyl)-imidazolium hydrogen sulfate ([C3SO3HMIM][HSO4]) BAIL catalyst in a water medium. Similarly, the [C3SO3HMIM][HSO4] BAIL also converts the bagasse into furfural with very high yield (73%) in one-pot method using a water/toluene biphasic solvent system.

Synthesis of Tetrahydrotriazoloacridines: A Synergistic Effect of Microwave Irradiation and Brönsted Acidic Ionic Liquids

3‐Methyl‐1‐sulfonic acid imidazolium hydrogen sulfate ([MSIm][HSO4]) catalyzed the condensation of 5‐aminobenzotriazole and 5,5‐dimethyl‐cyclohexane‐1,3‐dione (dimedone) with aromatic aldehydes under microwave irradiation. This method is efficient to synthesize 11‐aryl‐8,8‐dimethyl‐6,7,9,11‐tetrahydro[1,2,3]triazolo[4,5‐a]acridine‐10(1H)‐one derivatives as a series of tetrahydroacridines in good to excellent yields, while the catalyst can be recovered and reused up to six times without significant loss of activity. This one‐pot three‐component reaction provided an efficient method for the synthesis of aromatic heterocycles.

Acidic ionic liquid polymers: poly(bis-imidazolium-p-phenylenesulfonic acid) and applications as catalysts in the preparation of 1-amidoalkyl-2-naphthols

A new class of polymeric acidic ionic liquids with imidazolium hydrogen sulfate and p-phenylene sulfonic acid units built into the main polymer chain were prepared by a simple two step method in 87–89% yield. These new polymers were characterized by elemental analysis, 1H, 13C NMR, FT-IR, TGA and GPC. The catalytic activity of sulfonic acid group functionalized ionic liquid polymers was demonstrated through the synthesis of 1-amidoalkyl-2-naphthols in 78–90% yield by condensation of 2-naphthol, benzaldehyde and amides without a solvent at 100 °C.

TRANSPORT PROPERTIES FOR 1-ETHYL-3-METHYLIMIDAZOLIUM n-ALKYL SULFATES: POSSIBLE EVIDENCE OF GROTTHUSS MECHANISM

The objective of this work was to study the effect of the temperature and the lengthening of the linear alkyl chain of the anion in the transport physical properties of the pure ionic liquids 1-ethyl-3-methyl imidazolium n-alkyl sulphate (being n=0, 1, 2, 4, 6 and 8). Density, viscosity and electrical conductivities were measured at atmospheric pressure in a wide temperature range. In the bibliography, data existed for these magnitudes for all ionic liquids studied but none of these had information about the electrical conductivity of 1-ethyl-3-methyl imidazolium n-alkyl sulfate whith n=0, 4, 6 and 8. The experimental results show clearly 1-ethyl-3-methyl imidazolium hydrogen sulphate cannot be considered part of the 1-ethyl-3-methyl imidazolium n-alkyl sulphate family because of its hydrogen bonding ability. Results of density and viscosity behave as expected. However, in the case of the electrical conductivity due to the lack of alkyl chain in the hydrogen sulfate we expected to get extreme values but in practise, we obtained intermediate values between 1-ethyl-3-methyl imidazolium butyl sulphate and 1-ethyl-3-methyl imidazolium hexyl sulphate. This suggests that a Grotthus mechanism exists as result of a protonic current in addition to ionic conductivity, being Waldeńs plot consistent with this idea.

Enzymatic and catalytic hybrid method for levulinic acid synthesis from biomass sugars

In this study, an enzymatic and catalytic integrated approach is presented for high yield levulinic acid (LA) production from saccharified biomass hydrolysate prepared from acid pretreatment of corn stover. In order to convert glucose from a biomass hydrolysate solution to fructose the simultaneous isomerization and reactive extraction (SIRE) and back-extraction (BE) method was implemented. The SIRE-BE process successfully overcomes unfavorable glucose to fructose equilibrium and produce fructose at 88% yield. Besides, fructose was transferred to an acidic ionic liquid (IL) and aqueous mixture reaction medium by this pathway. It was noticed that the aqueous mixture of the task specific IL, 1-(4-sulfobutyl)-3-methyl imidazolium hydrogen sulfate ([BMIM-SO3H]HSO4), provides a uniquely suitable reaction medium. The mixtures are not only very effective in back-extracting ketose from the organic phase (following SIRE), but also able to effect the conversion of fructose to LA without the extra need for an acid catalyst in the medium. This highlights a significant advantage of the process since the issues with the extraneous acid catalyst recovery are eliminated. Besides, in the acidic [BMIM-SO3H]HSO4 aqueous mixture, high LA yield of 70% was achieved at 95 °C for 1 h from 2.5 wt% fructose loading.

Sulfonated imidazolium ionic liquid-catalyzed transesterification for biodiesel synthesis

Four kinds of imidazolium ionic liquids (ILs) were employed to catalyze the transesterification reaction of rapeseed oil. The effects of molar ratio of methanol to rapeseed oil, catalyst dosage, reaction temperature, and reaction time, and the deactivation of water on catalytic activity were explored. The results showed that imidazolium ILs with long alkyl chains and sulfonated groups exhibited the best catalytic activities due to their strong Brønsted acidity. The catalytic activity was depend on the SO3H group in the cation, not the anion HSO4−. Water molecules competed with the anion to bind with the protons of the imidazolium cation. This results in the disruption of the structure of ILs, leading to deactivation; increasing the reaction temperature could alleviate this negative effect of water. The yield of fatty acid methyl ester (FAME) remained constant (∼85%) at 130°C, when the water content increased from 1wt% to 5wt%. The highest yield of FAME for the catalyst 1-butylsulfonate-3-methyl imidazolium hydrogen sulfate ([BSO3HMIM][HSO4]) could reach 100% under optimum conditions.

Brönsted acidic ionic liquid based ultrasound-microwave synergistic extraction of pectin from pomelo peels

3-Methyl-1-(4-sulfonylbutyl) imidazolium hydrogensulfate, [HO3S(CH2)4mim]HSO4, was applied as an extractant in an ultrasound-microwave synergistic extraction approach to substitute conventional solvent for the extraction of pectin from the albedo part of pomelo peels. The analysis of variance (ANOVA) test and response surface method were employed for the optimization of the extraction conditions. A pectin yield of 328.64±4.19mg/g was achieved using the obtained optimal conditions, which was significantly higher than yields of conventional methods with reference solvents. Pectin samples extracted with [HO3S(CH2)4mim]HSO4 and hydrochloric acid solutions were tested by ANOVA and showed no significant differences in total carbohydrate content and degree of esterification; while galacturonic acid content was significantly different for the pectin from each extraction solvents. The differences revealed from images of atomic force microscopy and scanning electron microscope, Fourier transform infrared spectroscopy, and thermogravimetric analysis suggested the physiochemical properties of pectin could be affected by the extraction solvent. The [HO3S(CH2)4mim]HSO4 proved to be a promising alternative to conventional solvents and the proposed method is efficient for the extraction of pectin from the albedo of pomelo peels.

An efficient one-pot synthesis of thiochromeno[3,4-d]pyrimidines derivatives: Inducing ROS dependent antibacterial and anti-biofilm activities

An efficient synthesis of thiochromeno[3,4-d]pyrimidine derivatives has been achieved successfully via a one-pot three-component reaction of thiochrome-4-one, aromatic aldehyde and thiourea in the presence of 1-butyl-3-methyl imidazolium hydrogen sulphate [Bmim]HSO4. This new protocol has the advantages of environmental friendliness, high yields, short reaction times, and convenient operation. Furthermore, among all the tested derivatives, compounds 4b and 4c exhibited promising antibacterial, minimum bactericidal concentration and anti-biofilm activities against Staphylococcus aureus MTCC 96, Staphylococcus aureus MLS16 MTCC 2940 and Bacillus subtilis MTCC 121. The compound 4c also showed promising intracellular ROS accumulation in Staphylococcus aureus MLS16 MTCC 2940 comparable to that of ciprofloxacin resulting in apoptotic cell death of the bacterium.

Novel approach for preparation of poly (ionic liquid) catalyst with macroporous structure for biodiesel production

An efficient poly (ionic liquid) catalyst for biodiesel production was synthesized from Brønsted acidic ionic liquid 1-vinyl-3-(3-sulfopropyl) imidazolium hydrogen sulfate [VSIM][HSO4] through free radical polymerization from a novel approach, where Fe3O4 particles acted as hard template. The template could be easily removed in short time and macrospores formed after the removal of Fe3O4. The structure of the polymer was characterized by different techniques and the results demonstrated that the macroporous polymeric network was multi-layered and exhibited repeating units of SO3H and HSO4 with fine separation efficiency, as a novel heterogeneous acidic catalyst. The catalytic performance of the macroporous polymer was assessed in the esterification reaction of oleic acid for biodiesel production and the Box-Behnken response surface methodology (RSM) was applied for maximizing the biodiesel yield by optimizing process variables at 80°C. Under the optimum conditions (reaction time was 4.5h, catalyst amount was 8.5wt%, and alcohol/acid molar ratio was 12:1), a high biodiesel yield of 92.6% was obtained. The polymeric catalyst also showed favorable reusability after six runs. The combination of macrospores with poly (ionic liquid) would significantly reduce the limitation of mass transfer in biodiesel production compared with other porous solid acidic catalysts.

MCM-36 zeolites tailored with acidic ionic liquid to regulate adsorption properties of isobutane and 1-butene

Adsorption properties of an adsorbent or a catalyst towards adsorbates are crucial in the process of adsorption separation or catalytic reaction. Surface morphology and structure of adsorbents have a significant impact on the adsorption properties. In this study, a novel acidic ionic liquid, 1-butyl-3-(triethoxysilylpropyl)imidazolium hydrogen sulfate (i.e., [BTPIm][HSO4]), was synthesized and subsequently grafted onto the MCM-36 zeolite for the regulation of its adsorption properties towards isobutane and 1-butene. The resultant [BTPIm][HSO4]-immobilized MCM-36 (i.e., MCM-36-IL) was characterized by FT-IR, XPS, XRD, SEM, TG/DTG and N2 adsorption–desorption measurement. It was found that the specific surface area, micropore volume and mesopore volume of the MCM-36 support underwent a reduction upon the immobilization of ionic liquid, while the surface density of acid increased from 0.0014 to 0.0035mmol·m−2. The adsorption capacity of isobutane and 1-butene on the MCM-36-IL was determined by a static volumetric method. Results demonstrated that the interaction between isobutane and MCM-36-IL was enhanced and the interaction between 1-butene and MCM-36-IL was reduced. As a result, a tunable adsorption ratio of isobutane/1-butene on MCM-36 was achieved. With the increase in surface density of acid and the tunable adsorption ratio of isobutane and 1-butene on the functionalized MCM-36, the acidic ionic liquid-immobilized zeolites are beneficial to obtain an improved reaction yield and a prolonged catalyst life in the reactions catalyzed by solid acid.

Ionic liquid functionalized cellulose as an efficient heterogeneous catalyst for the facile and green synthesis of benzoxazine, pyrazine and quinoxaline derivatives in aqueous media

Immobilization of acidic ionic liquid, 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate on cellulose (Cell-[pmim]HSO4) as an efficient heterogenous catalyst for the simple and environmentally benign synthesis of benzoxazine, pyrazine and quinoxaline derivatives in aqueous media at room temperature is described. The catalyst was characterized by FTIR spectroscopy and X-ray diffraction pattern. This method provides several advantages such as mild reaction conditions, environmentally friendly catalyst, good to excellent yields and simple work-up procedure.

Solubility of Mixtures Containing Soybean Oil, Ionic Liquid and Methanol

This paper presents data on mutual solubility of the binary (soybean oil + ionic liquid) and ternary (soybean oil + methanol + ionic liquid) systems, where ionic liquid stands for 1-butyl-3-methylimidazolium thiocyanate [C4MIM][SCN] or 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide [C4MIM][NTf2] or 1-butyl-3-methylimidazolium dicyanamide [C4MIM][DCA] or 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM][PF6] or 1-butyl-3-methyl imida zolium hydrogensulfate [C4MIM] [HSO4] or 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C10MIM][NTf2] or methyltrioctylammonium bis(trifluoromethylsulfonyl)imide [ALIQUAT][NTf2] or methyltrioctylammonium chloride [ALIQUAT][Cl]. Solubilities were determined by the cloud point titration method in the temperature range of 298 K to 343 K. Obtained results suggest that imidazolium based ionic liquids exhibit lower solubility in soybean oil than ionic liquids with the aliquat cation. Thus, aliquat based ionic liquids are good candidate to be used as co-solvents for biphasic (methanol + soybean oil) mixture.

Magnetic Nanoparticles Supported Acidic Ionic Liquid as a Highly Active and Reusable Catalyst for Esterification

A magnetic nanoparticles supported dual acidic ionic liquid catalyst was prepared via anchoring 3-sulfobutyl-1-(3-propyltriethoxysilane) imidazolium hydrogen sulfate onto the surface of silica-coated Fe3O4 nanoparticles. And this novel supported acidic ionic liquid catalyst showed good catalytic performance in esterification. More importantly, the catalyst could be easily recovered by an external magnet and reused six times without significant loss of catalytic activity.

Silica-Gel-Supported Dual Acidic Ionic Liquids as Efficient Catalysts for the Synthesis of Polyoxymethylene Dimethyl Ethers

The supported ionic liquids were prepared by anchoring 3-sulfobutyl-1-(3-propyltriethoxysilane) imidazolium hydrogen sulfate onto silica gel of different types. The properties of the catalysts were characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), thermogravimetry/differential scanning calorimetry (TG/DSC), and X-ray photoelectron spectroscopy (XPS). The catalytic activities of both the immobilized ionic liquids and the free one (1-butylsulfonate-3-methylimidazolium bisulfate, [MIM-BS][HSO4–]) were investigated by the synthesis of polyoxymethylene dimethyl ethers (DMMn) from methylal (DMM) and trioxane (TOX), which suggested that all covalently anchored ionic liquids have better catalytic effects than [MIM-BS][HSO4–]. The optimization experiment of catalyst dosage demonstrated that the acid amount of ionic liquid is a major factor for the catalytic activity.

Imidazole-functionalized magnetic Fe3O4 nanoparticles: an efficient, green, recyclable catalyst for one-pot Friedländer quinoline synthesis

An efficient and cost-effective procedure for preparation of Fe3O4 nanoparticles and supported Bronsted acidic ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl)imidazolium hydrogen sulfate (Fe3O4-IL-HSO4) as a Bronsted acidic ionic liquid and efficient magnetic catalyst is described, together with its use for one-pot synthesis of polysubstituted quinolines through Friedlander condensation of 2-aminoaryl ketones with 1,3-dicarbonyl compounds under solvent-free conditions. The most noteworthy aspects of this methodology are its environmental friendliness, simplicity of operation, excellent yield within short reaction time, easy product isolation, and excellent reusability potential of the catalyst.

ChemInform Abstract: Nanosilica‐Supported Dual Acidic Ionic Liquid as a Heterogeneous and Reusable Catalyst for the Synthesis of Flavanones under Solvent‐Free Conditions.

AbstractVarious flavones are obtained by cyclization of the corresponding hydroxychalcones using the nanosilica‐supported dual acidic ionic liquid based on 1‐methyl‐3‐(4‐sulfobutyl)imidazolium hydrogen sulfate as efficient, green, stable, and reusable catalyst.

Backbone Phosphonamide-Functionalized Imidazol-2-ylidene Complexes

The synthesis of M(CO)5 complexes bearing 4-phosphonamide and 4,5-bis(phosphonamide)-imidazol-2-ylidene ligands (NHCP = phosphonamide-based N-heterocyclic carbene) is reported. Deprotonation of respective imidazolium hydrogensulfate salts with potassium tert-butoxide (KOtBu) in the presence of [M(CO)5(CH3CN)] afforded complexes with the formula [M(CO)5(NHCP)]. In a similar fashion, reaction of in situ generated NHCP with [Rh(cod)Cl]2 (cod = 1,5-cyclooctadiene) afforded a complex with the formula [Rh(cod)Cl(NHCP)]. Low-temperature deprotonation of the imidazolium NHCP·H2SO4 with potassium hexamethyldisilazide (KHMDS) in the presence of [AuCl(SMe2)] furnished the corresponding AuI NHC complex. All complexes were characterized by various spectroscopic and spectrometric methods. In addition, further structural confirmation is provided by key single-crystal X-ray structure determinations for three of the new complexes.

Functionalized ionic liquids supported on silica as mild and effective heterogeneous catalysts for dehydration of biomass to furan derivatives

A series of functional ionic liquid supported silica nanoparticles with different acidity (ILs/SiO2) have been prepared by covalent bonds using novel, non-toxic ethanol as solvent. Compared with using toluene or acetonitrile as solvent in traditional prepared method, the process represents a green, environmental friendly route to synthesize supported functional ionic liquid catalysts (SFILCs). These SFILCs, with the benefits of ionic liquid and the advantages of immobilization, were first systematically utilized in biomass dehydration reactions and proved to be efficient heterogeneous catalysts for the preparation of furan derivatives from various carbohydrates. However, the supported dual acidic functional ionic liquid catalyst (3-sulfobutyl-1-(3-propyltriethoxysilane) imidazolium hydrogen sulfate) was found to be more active and selective than other ILs/SiO2 and the conversion of fructose, glucose, xylose, sucrose, cellobiose was up to 99, 96, 94, 76 and 99%. Moreover, the reducing sugar (TRS) yield of microcrystalline cellulose dehydration was up to 77%.

Efficient conversion of chitosan into 5-hydroxymethylfurfural via hydrothermal synthesis in ionic liquids aqueous solution

A new process for the efficient conversion of chitosan into 5-hydroxymethylfurfural (5-HMF) has been developed. Chitosan was hydrolyzed in the presence of acidic ionic liquids (ILs), with N-methyl imidazolium hydrogen sulfate ([MIM]HSO4) giving the best results. The effects of reaction time, temperature and quantity of water and IL were investigated in detail. The optimal reaction conditions were found to be 4wt % IL ([MIM]HSO4) aqueous solution under hydrothermal condition, 180 °C and a reaction time of 5 h. A yield of 29.5 mol% 5-HMF was obtained from 100 mg chitosan. Furthermore, chitosan with different molecular weight could be directly converted into 5-HMF in good yields under these conditions. More importantly, [MIM]HSO4 could be recovered by simple post-processing and exhibited constant activity over 5 cycles.