Tài liệu Chất lỏng ion - Ionic Liquids: tổng quan, tổng hợp và ứng dụng

BACK KHOA UNIVERSITY FALCUTY OF CHEMICAL ENGINEERING SCIENTIFIC REPORT ADVANCEMENTS IN GREEN CHEMISTRY Topic: IONIC LIQUIDS (ILs) Performer: Nguyễn Văn Tú Nguyễn Phước Tấn - PhD Student (51305919) - PhD Student Supervisor: PGS.TS Phan Thanh Sơn Nam TPHCM, tháng 4 năm 2017 CONTENTS An overview about Ils in Green Chemistry Synthesis methods of ILs Applications of ILs 2 GENERALITY OF ILs 1. What are Ionic liquids (ILs)? 2. Why consider of ILs? 3. The characteristic properties of ILs GENERALITY OF ILs History      1888 Gabriel and Weiner found ethanolammonium nitrate (m.p. 52–55◦C) 1914 The “first” RTIL ethylammonium nitrate [EtNH3][NO3] with melting point 12◦C 1948 Development of IL with chloroaluminate ions by Hurley and Wier at the Rice Institute in Texas 1982 reported by Wilkes , A new class of RTILs that consist of dialkylimidazolium chloroaluminate 1992 Development of air- and water-stable imidazolium based ILs by Wilkes et al. GENERALITY OF ILs Development 2003 Year 2001 1999 1997 1995 0 200 400 600 800 Number of publications 1000 GENERALITY OF ILs What are ionic liquids? Definition: - Simply, they are liquids that are composed entirely of ions. - In the broad sense, this term includes all the molten salts, for instance, sodium chlorine at temperatures higher than 800oC. GENERALITY OF ILs What are ionic liquids? - Ionic liquids are salts that are liquid at low temperature (<100oC) which represent a new class of solvents with nonmolecular, ionic character. GENERALITY OF ILs What are ionic liquids? Traditional salts like sodium chloride are able to efficiently pack to form a crystal lattice With ionic liquids, the cations are asymmetrically substituted with different length groups to prevent the packing of the cations/anions into a crystal lattice GENERALITY OF ILs Room temperature Ionic liquids • Room temperature ionic liquids (RTIL) are salts which are already liquid below room temperature. • Variations in cations and anions can produce literally millions of ionic liquids, including chiral, fluorinated, and antibacterial IL. • Large number of possibilities allows for fine-tuning the ionic liquid properties for specific applications. GENERALITY OF ILs The driving forces The problems in the chemical industry with the volatile organic compounds (VOCs) : • toxic and/or hazardous • serious environmental issues, such as atmospheric emissions and contamination of aqueous effluents The driving force in the quest for novel reaction media: • greener processes • recycling homogeneous catalysts GENERALITY OF ILs What is “green chemistry”? - Recently ionic liquids have often been discussed as promising solvents for “clean processes” and “green chemistry”. - These two catchwords means to reduce drastically the amounts of side and coupling products and the solvent processes. and catalyst consumption in chemical GENERALITY OF ILs Why consider Ionic liquids ? • ILs are environmentally-friendly alternatives to organic solvents for liquid/liquid extractions. Catalysis, separations, and electrochemistry. • ILs will reduce or eliminate the related costs, disposal requirements, and hazards associated with volatile organic compounds (VOCs). • The ability to fine-tune the properties of the IL medium will allow selection of IL to replace specific solvents in a variety of different processes. GENERALITY OF ILs Important IL Properties • High ionic conductivity • Non-flammable • Non-volatile • High thermal stability • Wide temperature range for liquid phase (- 40 to + 200°C) • Highly solvating, yet non-coordinating • Good solvents for many organic and inorganic materials GENERALITY OF ILs Great promise • Designability: By combining different anions with cations, it is possible to generate a huge number of different ionic liquids, each with their own specific solvent properties. Some ionic liquids are water soluble, others are not. Some dissolve typical organic solvents, other are not. • They can be functionalized to act as acids, bases or ligands and have the potential to catalyze certain reactions in certain systems. GENERALITY OF ILs Great promise • Ionic liquids are non-volatile, hence they may be used in high vacuum systems and high temperature reactions without the requirement of a pressure vessel to contain the vapors. • They are good solvents for a wide range of both inorganic, organic and polymeric materials and unusual combinations of reagents can be brought into same phase. However they do not dissolve glass, polyethylene, or Teflon. High solubility usually implies small reactor volumes in the final process. GENERALITY OF ILs Great promise • They are immiscible with a number of organic solvents and provide a non-aqueous, polar alternative for two phase systems, this has been used to effect total catalyst recovery in a number of transition metal catalyzed reactions. Hydrophobic ionic liquids can also be used as immiscible polar phase with water. • They are often composed of poorly coordinating ions, so they have the potential to be highly polar non-coordinating solvents, this is particularly important when using transition-metal based catalysts. GENERALITY OF ILs Characteristics of RTIL • Choice of cation and anion determine physical properties (e.g. melting point, viscosity, density, water solubility, etc.) • Cations are typically big, bulky, and asymmetric accounting for the low melting points • The anion contributes more to the overall characteristics of the IL and determines the air and water stability • Melting point can be easily changed by structural variation of one of the ions or combining different ions GENERALITY OF ILs Typical RTIL Cations • Room temperature ionic liquids consist of bulky and asymmetric organic cations such as : Imidazolium ion Pyridium ion Ammonium ion Phosphonium ion Scheme 1. Important types of cation GENERALITY OF ILs Anions for RTIL •A wide range of anions is employed, from simple halides which inflect high melting points, to inorganic anions such as: Anions: GENERALITY OF ILs Comparison of organic solvents with ionic liquids