A chloromethyl polystyrene grafted silica gel (PS-SG) supported 1-(propyl-3-sulfonate) imidazolium hydrosulfate ([(CH2)3SO3H-HIM]HSO4) Brønsted acidic ionic liquid catalyst ([(CH2)3SO3H-HIM]HSO4/PS-SG) was prepared in this study. After characterization through elemental analysis, BET, SEM and FT-IR, it was found that chloromethyl polystyrene had grafted on the surface of silica gel, and [(CH2)3SO3H-HIM]HSO4 had been immobilized on PS-SG. [(CH2)3SO3H-HIM]HSO4/PS-SG showed high catalytic activity for a series of esterifications and could be recovered easily. After being reused for 9 times in the synthesis of methyl propionate, [(CH2)3SO3H-HIM]HSO4/PS-SG could still give satisfactory catalytic activity.

Vapor–liquid equilibrium (VLE) data for binary systems of 2-methyl-1-butanol with ethylbenzene and xylene isomers are isobarically obtained with a modified Rose still at 101.33 kPa, as well as for the quinary system of 2-methyl-1-butanol + ethylbenzene + xylene isomers. The binary VLE data are considered to be thermodynamically consistent according to the Herington method and the point-to-point test. Taking the nonideality of the vapor phase into consideration, the activity coefficients are calculated. All systems show positive deviation from ideality. The VLE data are correlated using the nonrandom two-liquid (NRTL), universal quasichemical activity coefficient (UNIQUAC), and Wilson models. The calculated vapor-phase compositions and temperature agree well with the experimental values. The obtained model parameters of the binary systems are used to predict the VLE data for the quinary system. The results indicate that these three models allow a good prediction of the phase equilibrium for the quinary system.

•Real-time monitoring of dielectric measurements was performed by DRS.•Dielectric parameters were obtained by fitting Cole–Cole equation to DRS data.•Hanai method was employed to estimate the phase parameters.•Dependences of the obtained parameters on the extractive time were investigated.•Result of dielectric analysis was confirmed reasonable by interfacial electrokinetic model.Real-time monitoring of dielectric behaviors of CMPS-supported imidazolium ionic liquids (ILs) microspheres in model gasoline was performed by dielectric relaxation spectroscopy (DRS) from 40 Hz to 110 MHz. One dielectric relaxation in MHz frequency range is obviously observed for all systems and determined to be closely related to the interfacial polarization. The interfacial polarization is attributed from the different conductivities between dispersed microspheres and model gasoline since imidazolium-based ionic liquids have been immobilized on the surfaces of dispersed microspheres in the form of optimized spatial configurations. Meanwhile, dielectric parameters (ɛl, κl, ɛh, κh and f0) for all the systems are obtained by fitting Cole–Cole equation to the dielectric data. From the dielectric parameters, Hanai equations are employed to calculate phase parameters (ϕ, κm, ɛp and κp), which is used to characterize the electrical and structural properties of constituent phases of suspensions of conducting particles in non-conducting medium. The time-dependences of dielectric parameters and phase parameters are investigated in detail, and interfacial electrokinetic model for suspension of dense particles has been employed for interpreting these time-dependences. Here, we found that possible π–complexation bond and π–π interaction between imidazole rings of ILs and thiophene are responsible for time-dependences of all parameters. Furthermore, the time-dependences of parameters indicate that the electron density (polarization strength) on surfaces of dispersed microspheres decreases with the increment of extraction time.Dependences of (a) permittivity ɛ′(ω) and (b) dielectric loss ɛ″(ω) spectra of suspension of CuCl/CMPS-Im(Cl) microspheres in model gasoline on extractive time.

A series of polymer-supported metal chlorides imidazolium ionic liquid (IL) moieties, M/CMPS-Im(Cl) (M = CuCl, ZnCl2 and FeCl3), were synthesized by grafted method using chloromethylated polystyrene (CMPS) resin as support. Meanwhile, the structures of synthesized ILs were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The results showed that the surface of CMPS resin was covered with a thin layer of extraction activity components. Then, the synthesized CMPS-supported imidazolium-based ILs were investigated to extract thiophene and its derivatives from model gasoline (n-octane/thiophene) under certain conditions. For a given imidazolium-based IL: first, the order of extraction capacity of extractant was CuCl/CMPS-Im(Cl) > ZnCl2/CMPS-Im(Cl) > FeCl3/CMPS-Im(Cl); the reason for this was that the π-complexation capability between Cu+ and thiophene was stronger than those of Fe3+ and Zn2+. Second, the sulfur removal selectivity of sulfur compound followed the order of TS < BT < DBT under the same conditions; it indicated that the extraction was favored for those aromatic heterocyclic sulfur compounds with higher density aromatic π-electrons density. Meanwhile, the effect of mass ratio of model gasoline to M/CMPS-Im(Cl) ILs, different initial sulfur concentrations, and extraction time on desulfurization rates of M/CMPS-Im (Cl) ILs was performed, respectively. Finally, regeneration of M/CMPS-Im(Cl) ILs was investigated.

A carbon-based solid acid catalyst was prepared by incomplete carbonization of H3PO4-impregnated pulp fibers followed by sulfonation. XRD, FT-IR, BET, TGA, and acid density test were employed to characterize the structure and performance of the catalyst. Results showed that the catalyst was amorphous carbon composed of aromatic carbon sheets with –COOH, –OH and –SO3H groups. Previous impregnation with H3PO4 could promote porosity formation of the catalyst. The optimized carbonization temperature and time for the catalyst were 250 °C and 1.5 h. The –SO3H density and specific surface area for the catalyst prepared under the optimized conditions were 1.1 mmol g−1 and 118 m2 g−1, respectively. Compared to HZSM-5, Amberlyst-15 and previous reported carbon catalysts, the catalyst showed higher catalytic activity for transesterification of methyl acetate with n-butanol as hydrophobic reaction. The catalyst had good thermal stability, which could bear 200 °C without decomposition. The catalyst retained satisfactory catalytic activity for transesterification of methyl acetate after 8 reaction cycles.

Isobaric vapor–liquid equilibrium (VLE) data are reported for binary mixtures of methyl formate + o-xylene, methyl formate + m-xylene, methyl formate + p-xylene, and methyl formate + ethylbenzene at 101.33 kPa. The data are obtained using a vapor recirculating type (modified Othmer's) equilibrium still. All of the binary systems show positive deviation from ideality. None of the systems form an azeotrope. The VLE data for these binary systems are checked to meet rigorous thermodynamic consistency by the Herington method and the point-to-point test of the Fredenslund method. The experimental VLE data are well-correlated by the nonrandom two-liquid (NRTL), universal quasichemical activity coefficient (UNIQUAC), and Wilson equations.

Isobaric binary vapor–liquid equilibrium (VLE) data for 1-butanol + ethylbenzene, or o-, or m-, or p-xylene and isobaric quinary VLE data for 1-butanol + ethylbenzene + o-xylene + m-xylene + p-xylene are measured at 101.33 kPa using a modified Rose cell with circulation of both phases. The four binary systems of 1-butanol + ethylbenzene, or o-, or m-, or p-xylene exhibit minimum boiling azeotropes, and the composition of the azeotropes are reported. The VLE data for the four binary systems are checked to meet rigorous thermodynamic consistency by Herington method and the point-to-point test of the Fredenslund method. The nonideality in vapor phase of the measured binary systems is analyzed through calculating fugacity coefficients. Combined with the Hayden–O'Connell (HOC) equation, the VLE data for 1-butanol + ethylbenzene, or o-, or m-, or p-xylene are well-correlated by the nonrandom two-liquid (NRTL), universal quasichemical activity coefficient (UNIQUAC), and Wilson equations. The NRTL model parameters obtained from correlation are used to predict the VLE data of the quinary system. According to the average absolute deviation values, the obtained quinary predicted values are in good agreement with the experimental values.

Imidazolium-silica heterogeneous catalyst (SG-[(CH2)3SO3H-HIM]HSO4) was prepared by immobilization of acidic ionic liquid 1-(propyl-3-sulfonate) imidazolium hydrosulfate ([(CH2)3SO3H-HIM]HSO4) on silica–gel using tetraethoxysilane (TEOS) as silica source in this study. The properties of the samples were characterized by FT-IR, SEM and TG/DSC. The results suggested that [(CH2)3SO3H-HIM]HSO4 had been successfully immobilized on the surface of silica–gel and the immobilized ionic liquid catalyst SG-[(CH2)3SO3H-HIM]HSO4 had good thermal stability. The original smooth surface of silica–gel was covered with [(CH2)3SO3H-HIM]HSO4 and a rough surface of SG-[(CH2)3SO3H-HIM]HSO4 was formed, but the size of particles had no obvious change. Moreover, SG-[(CH2)3SO3H-HIM]HSO4 exhibited high catalytic activity for a series of acetalization and could be recovered easily. After reused for 10 times in the synthesis of benzaldehyde ethanediol acetal, the catalyst could still give satisfactory catalytic activity.Graphical abstractThe original smooth surface of silica–gel was covered with [(CH2)3SO3H-HIM]HSO4 resulting in a rough surface of SG-[(CH2)3SO3H-HIM]HSO4, but the size of particles had no obvious change. The whole and magnified SEM images of silica–gel (A and B), and SG-[(CH2)3SO3H-HIM]HSO4 (C and D).Highlights► Immobilized [(CH2)3SO3H-HIM]HSO4 prepared by using TEOS as silica source was prepared. ► SG-[(CH2)3SO3H-HIM]HSO4 exhibited high catalytic activity for acetalization. ► SG-[(CH2)3SO3H-HIM]HSO4 could be recycled easily and exhibited excellent reusability.

Brønsted acidic ionic liquids (ILs), N-methylimidazole hydrogen sulfate ([HMIm]HSO4) and N-methylpyrrolidone hydrogen sulfate ([HNMP]HSO4), are synthesized and employed as extractants to extract thiophene from model gasoline (thiophene dissolved in n-octane). The effect of extraction temperature, extraction time and volume ratio of ILs to model gasoline on desulfurization rates is investigated. Then, the optimal desulfurization conditions are obtained: the ratio of ILs to model gasoline is 1.... 1, extraction temperature is 50°C for [HMIm]HSO4 and 60°C for [HNMP]HSO4, extraction time is 60 min. Meanwhile, the desulfurization rate of [HNMP] HSO4 for model gasoline is 62.8%, which is higher than that of [HMIm]HSO4 (55.5%) under optimal conditions. The reason is discussed on the basis of the interaction energy between thiophene and ILs at the B3LYP/6-311 ++ G(d,p) level. Furthermore, the total desulfurization rate of [HNMP]HSO4 and [HMIm]HSO4 reaches 96.4% and 94.4%, respectively, by multistage extraction. Finally, the used ILs can be reused by vacuum drying, and their desulfurization rates are not significantly decreased after recycling 7 times in single-stage desulfurization.

A carbon-based solid acid catalyst is prepared by incomplete carbonization of sulfonated naphthalene and used for the hydrolysis of carboxylic acid esters. XRD, FT-IR, TGA and acid density test are employed to characterize the structure and performance of the catalysts. The results show that the catalysts prepared under different synthesis temperature and time are amorphous carbon composed of small aromatic carbon sheets with –SO3H groups. The catalytic activities of catalysts for methyl acetate hydrolysis are closely related with their acid densities. The appropriate synthesis temperature and time for the catalyst are 230 °C and 12 h and the acid density of catalyst under the optimized conditions can reach 4.49 mmol g−1. The carbon-based solid acid shows higher catalytic activity than Amberlyst-15 resin as a popular hydrolysis catalyst for a series of carboxylic acid esters hydrolysis. The catalyst has good thermal stability, which can bear 250 °C without decomposition. It also remains satisfactory catalytic activity for methyl acetate hydrolysis after six times recycling.

The melting points of ionic liquids (ILs) of imidazolium bromides and imidazolium chlorides have been investigated by means of quantitative structure–activity relationship (QSAR) approach in order to develop prediction models for predicting the melting points of ionic liquid salts. The cationic structures of these ILs were optimized by means of Hyperchem software and MOPAC program. QSAR module of Materials Studio software and Genetic Algorithm (GA) programs were employed to calculate and select the structure descriptors of ILs, then prediction models correlating the selected structure descriptors and melting points of ionic liquids were set up by using the multiple linear regressions (MLR) method and the back-propagation artificial neural network (BP ANN) method, separately. Finally, the obtained QSAR models, including MLR model and BP ANN model, were validated by external test sets. In this work, three data sets, which were 30 imidazolium bromides, 20 imidazolium chlorides and the merging of above two data sets, respectively, were used to investigate the QSAR correlation of the melting points of ILs. The results demonstrated that the prediction mean absolute errors (MAEs) of MLR models for test sets of those three data sets were in the order of 20.52 K, 13.59 K and 21.95 K, and the prediction MAEs of BP ANN models were 8.77 K, 4.98 K and 9.31 K, respectively. It indicated that the predictions of two models for all melting points of ILs were reliable, and the prediction precision of BP ANN model was higher than that of MLR model.

Polystyrene (PS)-supported 1-(propyl-3-sulfonate) imidazolium hydrosulfate acidic ionic liquid (PS-CH2-[SO3H-pIM][HSO4]) catalyst was prepared by supporting the ionic liquid onto highly cross-linked chloromethylated polystyrene (PS-CH2Cl). FT-IR, SEM and TG-DSC were employed to characterize the structure and property of the catalyst. Results suggested that acidic ionic liquid was supported onto the surface of PS-CH2Cl by covalent bond. The original rough surface of PS-CH2Cl was covered with acidic ionic liquid, forming a compact and thin surface layer, and its size had no obvious change. Moreover, the PS-CH2-[SO3H-pIM][HSO4] catalyst showed a better thermal stability than that of PS-CH2Cl support. It also exhibited high catalytic activity for a series of esterifications. After the catalyst was reused for 13 times in the synthesis of n-butyl acetate, the yield only decreased 7.3%. A reaction mechanism of esterification over this new catalyst was proposed as well.Graphical abstractThe original rough surface of highly cross-linked chloromethylated polystyrene (PS-CH2Cl) was covered with acidic ionic liquid, forming a compact and thin surface layer, and its size had no obvious change.Research highlights▶ Polystyrene (PS)-supported 1-(propyl-3-sulfonate) imidazolium hydrosulfate acidic ionic liquid (PS-CH2-[SO3H-pIM][HSO4]) catalyst was prepared. ▶ The prepared PS-CH2-[SO3H-pIM][HSO4] catalyst was used for esterifications with high yields. ▶ The PS-CH2-[SO3H-pIM][HSO4] catalyst could be recovered by simple filtration, and the yield only decreased 7.3% for the synthesis of n-butyl acetate after reusing for 13 times.