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The room-temperature ionic liquids (RTILs) have potential in realizing the ethylene (C(2)H(4)) and acetylene (C(2)H(2)) separation and avoiding solvent loss and environmental pollution compared with traditional solvents. The interaction mechanisms between gases and RTILs are important for the exploration of new RTILs for gas separation; thus, they were studied by quantum chemical calculation and molecular dynamics simulation in this work. The optimized geometries were obtained for the complexes of C(2)H(4)/C(2)H(2) with anions (Tf(2)N(-), BF(4)(-), and OAc(-)), cation (bmim(+)), and their ion pairs, and the analysis for geometry, interaction energy, natural bond orbital (NBO), and atoms in molecules (AIM) was performed. The quantum chemical calculation results show that the hydrogen-bonding interaction between the gas molecule and anion is the dominant factor in determining the solubility of C(2)H(2) in RTILs. However, the hydrogen-bonding interaction, the p-π interaction in C(2)H(4)-anion, and the π-π interaction in C(2)H(4)-cation are weak and comparable, which all affect the solubility of C(2)H(4) in RTILs with comparable contribution. The calculated results for the distance of H(gas)···X (X = O or F in anions), the BSSE-corrected interaction energy, the electron density of H(gas)···X at the bond critical point (ρ(BCP)), and the relative second-order perturbation stabilization energy (E(2)) are consistent with the experimental data that C(2)H(2) is more soluble than C(2)H(4) in the same RTILs and the solubility of C(2)H(4) in RTILs has the following order: [bmim][Tf(2)N] > [bmim][OAc] > [bmim][BF(4)]. The calculated results also agree with the order of C(2)H(2) solubility in different RTILs that [bmim][OAc] > [bmim][BF(4)] > [bmim][Tf(2)N]. Furthermore, the calculation results indicate that there is strong C(2)H(2)-RTIL interaction, which cannot be negligible compared to the RTIL-RTIL interaction; thus, the regular solution theory is probably not suitable to correlate C(2)H(2) solubility in RTILs. The molecular dynamics simulation results show that the hydrogen bond between the H in C2 of the imidazolium cation and the anion will weaken the hydrogen-bonding interaction of the gas molecule and anion in a realistic solution condition, especially in the C(2)H(4)-RTIL system.

Characteristics of carbonyl compounds (carbonyls) emissions from biodiesel-ethanol-diesel (BE-diesel) were investigated in a Commins-4B diesel engine and compared with those from fossil diesel. Acetaldehyde was the most abundant carbonyls in the exhaust, followed by formaldehyde, acetone, propionaldehyde and benzaldehyde. Apliphatic carbonyls emitted from BE-diesel were higher than those from diesel fuel, while formaldehyde and aromatic carbonyls were less than those from diesel fuel. Total carbonyls emissions from BE-diesel were 1-12% higher than those from diesel fuel depending on engine operating conditions. The effects of engine speed and load level were also investigated carefully. It was found that total carbonyls emission was in positive correlation with the engine speed. During the constant speed/ varying load tests, minimum total carbonyls emission was found at 50% load. Compared with fossil diesel, the BE-diesel was observed to significantly reduce PM emission and increase slightly NO x emission. r

This paper presents an extensive study on the feasibility of ionic liquids (ILs) for the extractive separation of a 1hexene/n-hexane mixture. Seventeen ILs were tested at 313 K. The extraction selectivities of 1-hexene to n-hexane were in the range 1.5−3.0. The chemical structures of anion and cation in ILs greatly affected the extraction, and the functional groups, such as carbon−carbon double bond, nitrile, ester, and amide, in the ILs led to higher selectivities. The increase of alkyl chain length in cation led to the increase of extraction capacity of 1-hexene. To increase the distribution of 1-hexene in IL phase, silver salt was added to the ILs. It was found that ILs containing silver salt had a high distribution of 1-hexene, as well as high selectivity of 1hexene against n-hexane. The extraction efficiency increased with the concentration of silver salt in ILs. When the initial feed concentration of 1-hexene was smaller, the selectivity of 1-hexene to n-hexane was higher. A simple mathematical model has been developed to describe the total 1-hexene content in the reaction media under study, on the basis of the formation of complexes between silver and 1-hexene with different stoichiometry. This work proves that the ILs can act as effective extractants in 1hexene/n-hexane separation.

As green and designable solvents, ionic liquids (ILs), have great potential in the separation of olefins and paraffins. The introduction of functional groups into ILs enhances its separation selectivity for olefin to paraffin; however, the absorption capacities of such functionalized ILs obviously decrease due to the strong polarity of the functional group. In this work, we designed a symmetrical dual nitrile-functionalized IL 1,3-dibutyronitrile-imidazolium bis((trifluoromethyl)sulfonyl)imide ([(CP)2im][NTf2]) and determined the solubility of ethylene and ethane at 303.15 K in three ILs: nonfunctionalized 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][NTf2]), single-functionalized 1-butyronitrile-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([CPmim][NTf2]), and dual-functionalized [(CP)2im][NTf2]. The experimental results showed that enhanced separation selectivity for ethylene/ethane could be achieved in the symmetrical dual-functionalized [(CP)2im][NTf2] with only a slight reduction of absorption capacity. A COSMO-RS calculation was carried out to understand the underlying dissolution mechanism of ethylene and ethane in ILs and showed that the polarity of the IL and its misfit interaction with gases were the major factors in determining the solubilities of ethylene and ethane in it. In addition, a silver-containing IL was also tested because of its higher absorption capacity for olefins. It was found that the silver-containing IL was superior to any of the common ILs in the separation of ethylene/ethane, particularly [Bmim][NTf2]. A simple equilibrium model was used to describe the absorption of ethylene in the silver-containing IL.

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