离子液体

nullCatalysis with Ionic Liquids: Progress and Prospects Youquan DENG   Centre for Green Chemistry and Catalysis Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou, 730000, China Catalysis with Ionic Liquids: Progress and Prospects Youquan DENG   Centre for Green Chemistry and Catalysis Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou, 730000, China 1. INTRODUCTION:What are ionic liquids1. INTRODUCTION:What are ionic liquids Room temperature ILs contain organic cations and inorganic anions N-alkyl imidazoliumN-alkyl pyridiniumquaternary ammonium quaternary alkylphosphoniumFunctional groups e.g. X=NH2, SO3H, CO2H, etc. incorporated upon the side chain of Imidazolium [CF3COO]- [CF3SO2]- [BF4]- [PF6]- [(CF3SO2)2N]-Air and water stable Decreasing coordinating abilibity Increasing hydrophobicity Second generation ILsTypical cations[AlCl4]-[AuCl4]- [PdCl4]2-Typical anionsReactive to water First generation ILsFunctional ILs Third generation ILsNew !Chloroaluminate 1. INTRODUCTION: Properties of ionic liquids1. INTRODUCTION: Properties of ionic liquids Lower melting point: ＜-90 oCNegligible vapor pressure: Green solventsLarge liquid range ＞200 oCSelective dissolvability: ‘liquid’ zeoliteDesignable: Acidity, Density, Hydrophility Diversity: over a trillion possibleGood electrechemical satbility: E. W. ca 5VHigh thermal stability > 400 oCILs contaning 1-alkyl-3 methylimidazolium cationsStrong coulombic force: Much different from molecular solvents ILs possess some special physical and chemical propertiesreasonably good electrical conductivity (25 mS/cm)1. INTRODUCTION: General situation of ILs research 1. INTRODUCTION: General situation of ILs research ca. 200 papers have appeared on the 226th ACS National Meeting Hundreds patents on ILs have also been issuedCatalysisOrganic synthesisSeparation & analysisFunctional materialslife sciencesThe figure illustrates the growth in publications on ILsAt least another 500 papers will appeared by the end of 2003 There has been much work performed on ILs as reaction media or functional materials Lubricants, sensing & optical materials Stationary phase for GC, treating nuclear wasteElectro chemistryNano technologyClean energyHeack, Beckmann etc Nano-metal particles, filmElectrolytes, Electrodeposition Electrolytes for solar cell, batteryArtificial muscle, drug reservoirs1. INTRODUCTION: General research situation of catalysis with ILs1. INTRODUCTION: General research situation of catalysis with ILs ILs as catalysts or reaction media have been reported to have excellent performances for many catalytic reactionsCatalytic reactions using ILs as reaction mediaCatalytic activity enhanced Selectivity improvedEnzyme catalysisCatalyst stability improvedILs biphasic systemSeparation of desired products from reaction was simplified ILs used as substitute of volatile organic solvents Catalytic reaction may become greener 2. PROGRESS:Catalysis with ILs — Biocatalysis in ILs2. PROGRESS:Catalysis with ILs — Biocatalysis in ILsLipase-Catalyzed Polytransesterification of DVA and BDThe use of ILs to replace organic solvents in biocatalytic processes has recently gained much attention J.Am.Chem.Soc., 2003, by A.J. Russell et alPolyesterThe figure illustrates Lipase possess higher activity and stability in BMIMPF6 IL than that in tetrahydrofuran No reaction occurred in the hydrophilic ILS investigated, eg BMIMNO3DVABDNovozym 435 & porcine pancreatic lipase in tetrahydrofuranNovozym 435 & porcine pancreatic lipase in BMIMPF6At 50 oC in the presence of DVA and BD2. PROGRESS:Catalysis with ILs — Functional ILs 2. PROGRESS:Catalysis with ILs — Functional ILs Recently, functional ILs,eg Bronsted acidic ILs used as solvent-catalyst were developedJ.Am.Chem.Soc., 2002, by J.H. Davis, Jr. et alSulfonic acid group was incorporatedSolid acids, due to non-volatility, are being more widely used, but they have shortcomings as well Such Bronsted acidic IL has negligible vapor pressure, and is some kind of ‘solidlike’ liquid acid Nearly 100％ of ester selectivity achieved Isolation of desired products can be obtained by a simple distillation The IL could be reused Such Bronsted acidic ILs is also an effective catalysts for esterification of alkenes with acetic acid 2. PROGRESS:Catalysis with ILs — Combination with Sc CO22. PROGRESS:Catalysis with ILs — Combination with Sc CO2 Continuous-flow hydromylation in a Sc CO2-IL biphasic system has been successfully established Science, 2003, by D. J. Cole-HamiltonA diagram of continuous-flow hydromylation in a Sc CO2-IL biphasic systemHigher aldehyde selectivity Higher ratio of the linear : the branched Hydroformylation of hexene catalysed by Rh catalystPROGRESS:Catalysis with ILs — Dimerization of alkenesPROGRESS:Catalysis with ILs — Dimerization of alkenes The Institut Francais du Pétrole, IFP launched the first commercial process based on ILs, known as the Difasol process Typical Difasol process: butenes dimerization to octenes based on nickel(II) salt in ionic liquid.IFP claim that the Difasol process was much better than other dimerisation processes and without any other solventA continuous run has been carried out over a period of 5500 h, and butene conversion and selectivity were stablePhase separatorDifasol reaction sectionSeparation of IL and product occurs rapidly and completely due to insolubilityIonic Liquids in synthesis, 2002, by P. Wasserscheid et al2. PROGRESS：Catalysis with Ionic liquids on large scale 2. PROGRESS：Catalysis with Ionic liquids on large scale BASF'S SMART IL: the first commercial use of the ILs in an organic process Intelligent IL separates as lower phase from productdeprotonation & recycling+++Using N-methylimidazole to scavenge acid that is formed in the process. N-methylimidazole is also a catalyst HmIm-Cl IL, formed during reaction, separate as a clear liquid phase from the product HmIm-Cl, after deprotonation, it can be distilled like any other organic solvent and can be recycled Such process is on a multiton scale in batch reactor without producing solidsManufacturing Process of alkoxyphenlphosphines C&E News, 2003, by M. Freemantle2. PROGRESS：Catalysis with Ionic liquids in China2. PROGRESS：Catalysis with Ionic liquids in China Ionic liquid-catalystH2O-H2O21. Water / IL biphasic reaction for benzene oxidation to phenolAqueous phase H2O-H2O2IL + cat + benzeneCat＋IL＋benzeneH2O2phenolH2O-phenolIL＋catalystA schematic show of the aqueous / IL biphasic reaction system1. OMImPF6 (O=n-Octyl), Fe(O3SC12H25)3 and benzene: insoluble in water 2. Oxidation of benzene occurred at interface between IL and H2O, phenol was in the water 3. H2O+phenol phase was separated from IL phase by simple decantation phenolreusedResults of selective oxidation of benzene to phenolaAlmost 100% selectivity for phenol was achieved The water / IL system could be reusedGreen Chem, 2003, by Y. Deng et al.Step1 ChargingStep2 ReactionStep3 Separationa. At 50℃ for 6.0 h , C6H6/H2O2 =1, 2. ILs + Pd complex for carbonylation of aniline to afford carbamate 2. ILs + Pd complex for carbonylation of aniline to afford carbamate intermediates for isocyanates by non-phosgene routes 2. PROGRESS：Catalysis with Ionic liquids in ChinaBMIm BF4 + Pd (1,10-phenanthroline)2+ complex catalyst Aim: To demonstrate that the diversity of ILs may form an optimal homogeneous catalyst system with a specific organometallic complexlts solubility in ILs can be adjusted through tuning the ILs. Pd(phen)2Cl2 is insoluble in most of organic solvents. FTRaman analysis: some interaction between Pd(phen)2Cl2 and the ILO2MeOHResults of Carbonylation of aniline to afford carbamateTOF reached to ca. 6100 mol·mol-1·h-1, which is much higher than that reported in previous literature.J. Catal., 2003, by Y. Deng et al2. PROGRESS：Catalysis with Ionic liquids in China 2. PROGRESS：Catalysis with Ionic liquids in China 3. Electrochemical activation of CO2 for the synthesis of cyclic carbonates through cycloaddition of CO2 to epoxides in ILsA schematic show of the reaction systemMg anodeCu cathodeIL+ substratePumpCO2 gas tankResults of synthesis of cyclic carbonates in BMImBF4Chem. Commun. 2002, By Y Deng et alGood to excellent results were obtained. The reaction was conducted under room temperature and atmospheric pressure without additional supporting electrolyte and co-catalyst 2. PROGRESS：Catalysis with Ionic liquids in China 2. PROGRESS：Catalysis with Ionic liquids in China 4. Effective catalytic synthesis of disubstituted ureas in IL with CO2 & aminesproductWater+ IL+baseAfter reactionAfter adding waterSymmetric ureas synthesis with CO2 and amines in IL(BMImCl) + CsOHa: the catalyst was reused at the third timeEffective catalytic synthesis of disubstituted ureas from amines and CO2 without addition of dehydration agent The catalytic system could be reused after distillation of waterAngew.Chem.In. Edi., 2003, Chinese Patent CN1424310A, by Y. Deng et alAddition of H2O into the mixture, IL and base would transfer into H2O layer, the desired product was precipitated H2O3. Prospects: Catalysis with Ionic liquids 3. Prospects: Catalysis with Ionic liquids The research of catalysis in/with ILs is still in its early stage. There is still large research space for catalysis with ILs. The need of green catalysis and curiosity of chemists to these ‘unorthodox’ liquids may strongly drive the development of the research of ILs and catalysis with ILs Directions for potential future research of catalysis with ILs:3. Prospects: Molecular design, syntheses and characterization of catalytic task-specific ILs3. Prospects: Molecular design, syntheses and characterization of catalytic task-specific ILs Computer simulation, and specific and in situ characterization methods for the study of the ILs physicochemical properties - catalytic performance are highly desired Functional groups can be incorporated upon side chain of imidazolium cation, or other quaternary ammonium cationsChiral ILsThe picture shows that the arrangement of both the chloride anions and imidazolium cations3. Prospects: Homogeneous catalysis using ILs as reaction media 3. Prospects: Homogeneous catalysis using ILs as reaction media Homogeneous catalysis offer a number of important advantages in which reaction media play an important role. Using ILs as reaction media may open up new possibilities for Homogeneous catalysis For a specific homogeneous catalytic reaction, ILs may offer a number of advantages:ILs may function as ‘soft’ support to immobilize either metal complex or nano-metal particle to form ‘solidlike’ liquid catalyst system Nano Pt particles in BMIMPF6 IL DiversitySimple separationSelective dissolvabilityGreener reaction mediumNegligible vapor pressureoptimal homogeneous catalyst systemInorganic Chemistry 2003, by J. Dupout et al3. Prospects: Development of Immobilized ILs Catalysts3. Prospects: Development of Immobilized ILs CatalystsPrepared sample The chemical industry still prefers heterogeneous catalysts, it is desirable to minimize the amount of ILs needed for a practical processPreparation of surface anchored IL Chemical bonding of imidazolium cation to solid surface may change properties of the ILs.J.Am.Chem.Soc, 2002 by J.P Mehnert et al IL physically confined into nanopores of silica gel as immobilized ILs catalystAdding Metal complex or notIonic liquidsSi(OEt)4 HCl/EtOH-H2OILs confined act as catalyst or media; silica gel with desired sizes of pores and channels are used as nano-reactor with inlet and outlet . Size of nanopores is big enough to contain ILs; size of channel is small enough to prevent ILs from leaching, but big enough for R and P transport One-pot assembly of ILs, silicate ester via a sol-gel process The key concept of designing such catalyst system involves: 3. Prospects: Developmeny of Immobilized ILs catalysts — Physical confinement of IL into nanopores of silica gel 3. Prospects: Developmeny of Immobilized ILs catalysts — Physical confinement of IL into nanopores of silica gel Pure DMImBF4+ DMImBF4 /silica gelFTRaman spectra of ILs confined in silica gel were markedly different with bulk ILs Oxidative carbonylation of aniline to carbamateRh(PPh3)3Cl The amount of IL used was greatly reduced Catalytic activity and efficiency were greatly enhancedO2MeOHSuch unusual enhancement in catalytic activity may be derived from the formation of nano and aberrant ILs due to the confinement? 3. Prospects: Integration of ionic liquids with other techniques 3. Prospects: Integration of ionic liquids with other techniques Integration of ILs with Sc-CO2 When ILs are used as reaction media with nonvolatile products, product isolation can be achieved by Sc-CO2 Integration of ILs with electrochemical techniques The good electrical conductivity and wide E.W. of ILs, in combination with their good dissolvability to transition metal catalysts,open up new possibilities for electocatalysis IL phase changes with increasing carbon dioxide pressureEquipment for combinatorial electrocatalysis with ILs 3. Prospects: Development of catalytic reaction engineering based on ionic liquids3. Prospects: Development of catalytic reaction engineering based on ionic liquids For a large-scale catalytic process in involved with ILs Flow phenomena, mass and heating transfer, and reaction kinetics are required An optimum reactor design must be developedSummary: Although it has been generally recognized that ILs may well contribute to the development of catalysis, it is unlikely that ILs will provide all the answers