Hongshuai Gao

In situ magnetic separation and immobilization of dibenzothiophene-desulfurizing bacteria

In situ cell separation and immobilization of bacterial cells for biodesulfurization were developed by using superparamagnetic Fe(3)O(4) nanoparticles (NPs). The Fe(3)O(4) NPs were synthesized by coprecipitation followed by modification with ammonium oleate. The surface-modified NPs were monodispersed and the particle size was about 13 nm with 50.8 emu/g saturation magnetization. After adding the magnetic fluids to the culture broth, Rhodococcus erythropolis LSSE8-1 cells were immobilized by adsorption and then separated with an externally magnetic field. The maximum amount of cell mass adsorbed was about 530 g dry cell weight/g particles to LSSE8-1 cells. Analysis showed that the nanoparticles were strongly absorbed to the surface and coated the cells. Compared to free cells, the coated cells not only had the same desulfurizing activity but could also be easily separated from fermentation broth by magnetic force. Based on the adsorption isotherms and Zeta potential analysis, it was believed that oleate-modified Fe(3)O(4) NPs adsorbed bacterial cells mainly because of the nano-size effect and hydrophobic interaction.

Desulfurization of Diesel Fuel by Extraction with Lewis-Acidic Ionic Liquid

Abstract Ionic liquids were found to be highly selective for the extractive removal of aromatic sulfur compounds from fuels at room temperature. The efficiency of ionic liquids for the removal of aromatic sulfur compounds is dependent on the properties and structure of the ionic liquids. In this work, the Lewis-acidic ionic liquid 1-butyl-3-methylimidazolium tetrahalogenoferrate(III) ([BMIM] [FeCl4]) was synthesized and demonstrated to be more effective for the removal of aromatic sulfur compounds from diesel over ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM] [BF4]) because of its Lewis-acidic property. The ionic liquids favorably extracted organic compounds with a higher density of aromatic π-electrons. [BMIM][FeCl4] ionic liquid can be regenerated through reextraction by hexane, and could be used in multiple steps for the removal of sulfur compounds from diesel.

Improving SO2 capture by tuning functional groups on the cation of pyridinium-based ionic liquids

In this work, three kinds of novel functionalized ionic liquids (ILs) [NEt2C2Py][SCN], [C4OPy][SCN] and [C4CNPy][SCN] were developed by introducing a tertiary amino group, ether group and nitrile group on the pyridinium cation to improve SO2 absorption performances. Among the investigated ILs, [NEt2C2Py][SCN] showed the highest absorption capacity of 1.06 gSO2 gIL−1 under ambient conditions due to a combination of chemical and physical absorption. By contrast, the enhancement in SO2 capacity by [C4CNPy][SCN] and [C4OPy][SCN] is mainly ascribed to the stronger physical interaction between ILs and SO2 than the conventional IL [C4Py][SCN]. Meanwhile, higher SO2/CO2 selectivity was also obtained using these functionalized ILs, which was increased up to 41% comparing with that of [C4Py][SCN]. Moreover, the effect of water on SO2 capacity and the absorption mechanism were studied. The results indicated that the presence of water caused a slight decrease in SO2 capacity of [C4CNPy][SCN] and [C4OPy][SCN] because of physical absorption, whereas a slight increase in SO2 capacity by [NEt2C2Py][SCN] due to the formation of hydrogen sulfite salts through chemical absorption. In addition, three kinds of cation-functionalized ILs could remain the stable absorption performance after five cycles of absorption and desorption, implying these ILs show great potentials for SO2 capture.

Extractive desulfurization of fuel using N-butylpyridinium-based ionic liquids

Sulfur compounds in fuels have become one of the sources of serious environmental problems. The extractive desulfurization using ionic liquids (ILs) has attracted great attention in recent years. In this work, the pyridinium-based ionic liquids (ILs) N-butylpyridinium thiocyanate ([C4Py][SCN]), N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([C4Py][NTf2]), and N-butylpyridinium dicyanamide ([C4Py][N(CN)2]) were used as extractants for desulfurization of model fuels. The results demonstrate that the structure of the anion influences the extractive performance of ILs, following the order of [NTf2] benzothiophene (BT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). Moreover, the [C4Py][N(CN)2] can be recycled at least 4 times with little decrease in the desulfurization activity.

Efficient absorption of ammonia with hydroxyl-functionalized ionic liquids

Ammonia (NH3) emitted from the ammonia synthesis process is a kind of waste chemical resource and a major environmental pollutant. The traditional water scrubbing method suffers from high energy consumption due to the concentrated NH3 from aqueous ammonia. Therefore, it is desirable to develop novel absorbents for the efficient, reversible and environmentally-friendly recovery of NH3. In this paper, a series of hydroxyl-functionalized imidazolium ILs ([EtOHmim]X, X = [NTf2], [PF6], [BF4], [DCA], [SCN] and [NO3]) were designed and prepared. Their physical properties and NH3 absorption capacities under different temperatures and pressures were systematically investigated. The effects of hydroxyl cation, anionic structures, pressure and temperature on absorption performance were sufficiently studied. In addition, the absorption mechanism was investigated in detail by spectral analysis and quantum chemistry calculations. Compared with conventional IL [Emim]X, a higher absorption capacity was achieved by introducing the hydroxyl group on the imidazolium cation. The mechanism results showed the fascinating absorption performance of the task-specific ILs was attributed to the stronger hydrogen bonding interaction between NH3 and the H atom of the hydroxyl group. Considering the excellent absorption performance, high thermal stability, and super reversibility, this type of IL provides great improvement over conventional IL and shows their enormous potential in NH3 recovery.

Deep Desulfurization of Diesel Oil with Extraction Using Pyridinium-Based Ionic Liquids

The pyridinium-based ionic liquids (ILs) 1-butyl-3,5-dimethylpyridinium tetrafluoroborate , 1-hexyl-3,5-dimethylpyridinium tetrafluoroborate and, 1-octyl-3,5-dimethylpyridinium tetrafluoroborate were found to be effective for the selective removal of aromatic heterocyclic sulfur compounds from diesel. The results suggested that the structure and size of the cation greatly affect the extractive performance of ILs. For each sulfur compound studied here (4,6-Dimethyldibenzothiophene (4,6-DMDBT), dibenzothiophene (DBT), benzothiophene (BT), and thiophene (TS)), the extractive performance using pyridinium-based ILs followed the order of [C4Py][BF4] < [C6Py][BF4] < [C8Py][BF4] < < < < < < . In addition, the pyridinium-based ILs would not contaminate the diesel due to their insolubility. On the other hand, diesel has a certain solubility in pyridinium-based ILs, varying from 0.49 wt% for [C4Py][BF4] to 19.6 wt% for . Considering these results, ILs studied in this work are more competitive and feasible for extractive desulfurization applications. Moreover, the extractive desulfurization using pyridinium-based ILs could be used at least as a complementary process to hydrodesulfurization (HDS).

Protic ionic liquid [Bim][NTf2] with strong hydrogen bond donating ability for highly efficient ammonia absorption

Cost-efficient and environmentally benign treatment of NH3-containing exhaust gas has been a challenge. Ionic liquids (ILs) due to their unique structures and properties are recognized as potential solvents to absorb NH3. In this study, three types of ILs, including [Bmim][NTf2], [Bim][NTf2], [HOOC(CH2)3mim][NTf2], were designed and synthesized with various hydrogen bond donating abilities and characterized based on their thermodynamic dissociation constants (pKa). The results showed that protic ionic liquid (PIL) [Bim][NTf2] with a moderate pKa value had the highest NH3 absorption capacity (up to 2.69 mol NH3 per mol IL, 313 K, 100 kPa). Experimental characterization and theoretical calculations verified that such extremely high NH3 absorption capacity for [Bim][NTf2] resulted from the interactions between H-3 on the imidazole ring and the NH3 molecule and NH3 molecules sintering themselves. Furthermore, stable absorption performance was recorded for [Bim][NTf2] over four cycles, implying potential applications in the industry for NH3 recycling.

Synthesis and Properties of Novel Chiral Ionic Liquids from L-Proline

A novel class of chiral ionic liquids with chiral cations directly derived from natural l-proline has been synthesized and their physical properties such as melting point, thermal degradation, and specific rotation have been characterized. Further, their potential use in chiral recognition was demonstrated by studying interactions with racemic Mosher’s acid salt.

Deep Desulfurization of Gasoline Fuel using FeCl3-Containing Lewis-Acidic Ionic Liquids

The FeCl3-containing Lewis-acidic ionic liquids (ILs) [C6mim]Cl/FeCl3(1:1.5), [C6mim]Cl/FeCl3(1:2), [C8mim]Cl/FeCl3(1:1.5), and [C8mim]Cl/FeCl3(1:2) were used as extractants for desulfurization of model fuel and gasoline fuel, respectively. The results demonstrate that these ILs are effective for the removal of sulfur compounds from model fuel under different mass ratio of IL to model fuel (1:1, 1:3, 1:5, 1:10) at 25°C. The extractive performance of ILs increased as the molar ratio of FeCl3 to [Cnmim]Cl(n = 6, 8) varied from 1:1 to 1:2. The selectivity of sulfur compounds by extraction process followed the order of dibenzothiophene (DBT)>benzothiophene (BT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). The sulfur removal of gasoline fuel containing sulfur content of 440.3 ppmw could be up to 85.8%; that is to say that the sulfur content of gasoline fuel varied from 440.3 ppmw to 62.4 ppmw after one extraction stage. Moreover, the [C6mim]Cl/FeCl3(1:2) can be recycled for at least 4 times with a little decrease in the desulfurization activity.

Pebax-based composite membranes with high gas transport properties enhanced by ionic liquids for CO2 separation

Membrane-based separation technology has been reported as one of the possible methods to efficiently and economically separate carbon dioxide (CO2). To provide synergistic enhancements in the gas separation performance, organic polymer (Pebax 1657), zeolite imidazolate framework-8 (ZIF-8) nanoparticles, and ionic liquid (IL) have been integrated to develop three-component composite membranes. To achieve high separation performance of three-component membranes, the effects of IL anions and ZIF-8 content on gas permeability and selectivity were investigated first. The ILs were 1-butyl-3-methyl imidazolium ([Bmim]) cation based on different anions of bis(trifluoromethylsulfonyl)imide ([NTf2]), dicyanamide ([DCA]), and tetrafluoroborate ([BF4]). Gas transport properties of all the prepared membranes were investigated at 23 °C and 1 bar. The results showed that the anion of IL is a key factor to determine the CO2 permeability of the membranes, which is similar to the principle of CO2 solubility in pure ILs. In addition, ZIF-8 could increase both CO2 diffusivity and solubility coefficients of the Pebax/ZIF-8 membranes, resulting in a two-fold increase in the CO2 permeability. For the Pebax/ZIF-8(15%)/[Bmim][NTf2] membranes, it has been revealed that [Bmim][NTf2] acts as a low molecular weight additive, leading to a more amorphous structure and a higher FFV (fractional free volume) of the membranes, which are beneficial for gas diffusion. The addition of IL can improve the compatibility between the inorganic particles and the polymer matrix; thus, the non-selective voids decrease, which leads to a higher CO2/N2 selectivity. The CO2 permeability of the Pebax/ZIF-8(15%)/IL(80%) membrane was 4.3 times that of the pure Pebax membrane without sacrificing the CO2/N2 selectivity. Therefore, the high gas transport properties of the Pebax/ZIF-8/IL membranes make them promising candidates for CO2-effective separation materials.