1. School of Chemistry and Chemical EngineeringShanxi University Taiyuan 030006 Shanxi P. R. China
2. On leave to Institution of Process Engineering
3. Beijing Key Laboratory of Ionic Liquids Clean Process Key Laboratory of Green Process and Engineering State Key Laboratory of Multiphase Complex Systems Institution of Process EngineeringChinese Academy of Sciences Beijing 100190 P. R. China
4. College of Chemistry and Chemical EngineeringUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China