Preparation Of Acid Ionic Liquids And Its Applicatipn In The Synthesis Of Isopropanol

Acidic ionic liquids,a kind of novel environmentally friendly solvent and catalyst,have attracted significant attention of scholars from various fields owing to its adjustable physical-chemical properties,high catalytic activity,and excellent recyclability.Isopropanol(IPOH)is an excellent organic raw material and industrial solvents,which is widely used in industry.At present,the major method to synthesis of IPOH is the reaction of propylene with water at home and abroad.However,there are many drawbacks of this method,such as complex technics flow,serious corrosion to equipment,high energy requirement and difficult regeneration of catalyst.Therefore,this paper proposed a benign preparation method of IPOH via transesterification from isopropyl acetate(IPAc)and methanol(MeOH)using the ionic liquids(ILs)as catalysts.The major research contents are as follows:(1)The thermodynamic properties(?RHI,T0,?RSI,T0,?RGI,T0,Keq)of the transeterification for product of IPOH from 303 K to 403 K was calculated.The results indicate that the transesterification is an weak exothermic reaction and the reaction equilibrium constant is low.(2)The five acidic ionic liquids with diffirent cations were synthesized by the two-step method.The structures of the five acidic ILs were investigated using 1H NMR,13C NMR and FT-IR spectroscopy.The acidity of those ILs was determined by the UV-visible spectroscopic and Harnrnett theoretical model.The catalytic activity of those ILs was tested by the transesterification of IPAc and methanol for the product of IPOH in a small stainless steel reactor.The results shown that the structure of the ILs we prepared were coincided with the theoretical structure,and the purity of ILs was very high(>98%).Furthermore,there is a positive relationship between the acidity and catalytic activity of acidic ILs.Among them,1-propylsulfonate-3-methyl iminazole hydrogensulfate([Ps-mim]HSO4)is more active than the other ILs in the transesterification.(3)In the high-pressure reactor,the reaction kinetics of the transesterification of IPAc and methanol were studied with[Ps-mim]HSO4 as catalyst.The influences of temperature,molar ratio of methanol to IPAc,catalyst dosage on ·the transesterification were investigated.According to the reaction mechanism of transesterification and Bronsted theory,a homogeneous kinetics was established,and were used to correlate the experiment data.The comparison of the model values and the experiment values indicated that the kinetic model can describe the kinetic behavior of the system reliably.(4)In the high-pressure reactive distillation column,IPOH synthesized from IPAc and methanol by batch reaction distillation were studied with[Ps-mim]HSO4as catalyst.The influences of column pressure,catalyst concentration,molar ratio of methanol to IPAc and reaction time on the reactive distillation process were investigated.From the experimental study done in this work,the optimum batch reactive distillation operation conditions can be concluded as follows:reaction pressure,0.3 MPa;catalyst dosage,1.0 wt%;initial mole ratio of MeOH to IPAc,4:1;and reaction time,3.0 h.Under the optimum conditions,the conversion of IPAc is above 99.4%.(5)In order to evaluate the potential reusability of catalyst in the transesterification of IPAc with MeOH,a series of recycle experiments were conducted in stainless steel column under the optimum conditions.The results indicate that the conversion of IPAc was still above 99.0%after the catalyst was repeatedly used for four times.Furthermore,the characterization of recycled ILs verify that no obvious changes in the structure.It also shows that the[Ps-mim]HSO4 as the catalyst for the transesterification of IPAc with MeOH is recyclable and stable.