| Sec-butanol(SBA) is an important organic chemical material, which can mix with petrol at specific ratio for using as vehicle fuel instead of the petrol. Also, it is one of most essential chemical intermediates, which are widely used in the preparation of various chemicals. And the production of methyl ethyl ketone (2-butanone, MEK) is its main application. Currently there are three commercial routes to produce SBA:the direct hydration of n-butene, the indirect hydration of n-butene, the transesterification of sec-butyl acetate (SBAC). However, some drawback that still existed in those process. Such as complex technics flow, severe equipment corrosion, serious waste pollution, more consumption of energy; high purity for the n-butene, short life of catalyst and suffering from low conversion per pass of n-butene (<10%); easier deactivation and precipitation, difficult regeneration of catalyst. Reported new method were still largely confined to the laboratory, and there are still some problems existed in the industrialized application. Therefore, this paper proposed a benign preparation method of SBA via transesterification from SBAC and methanol using the ionic liquids (ILs) as catalysts, which was based on the drawback of traditional synthetic method. The research focused on the following aspect:(1) Firstly, the five acidic Imidazolium ionic liquids were synthesized by the two-step method, Which included [BMIM]HSO4, [HSO3-BMIM]HSO4, [HSO3-PMEvI]HSO4, [HSO3-PMIM]p-TSA, [HSO3-PMMICH3SO3. The structure of those ILs were characterized by using FT-IR、1H NMR、13C NMR; The acidity of those ILs was determined by using the UV-visible spectroscopic and Harnrnett theoretical model. The catalytic activity of those ILs were tested by the transesterification model of SBAC and methanol. The result shown that the structure of ILs what we prepared were coincided with the theoretical structure, and the purity of ILs was very high. Furthermore, there is a positive relationship between the acidity and catalytic activity of acidic Imidazolium ILs. Among them, [HSO3-PMIM]HSO4 is more active than the other ILs in the transesterification.(2) In the high-pressure reactor, the reaction kinetics of the transesterification of SBAC and methanol were studied in the presence of [HSO3-PMIM]HSO4 as catalyst. The influences of temperature, molar ratio of methanol to SBAC, catalyst dosage on the transesterification were investigated. According to the reaction mechanism of transesterification and Br(?)nsted 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 model can characterize the reaction process well.(3) In the high-pressure reactive distillation column, SBA was synthesized from SBAC and methanol by reaction distillation were studied in the presence of [HSO3-PMIM]HSO4 as catalyst. The influences of column pressure, evaporation, catalyst concentration, reflux ratio, molar ratio of methanol SBAC, space velocity on the reactive distillation process were investigated. The applicable operating condition was obtained after reactive distillation experiments:column pressure 0.50 MPa, evaporation 315.67 m3/(m2·h), catalyst concentration 1.50%, reflux ratio 3, molar ratio of methanol SBAC 3.7:1, space velocity 0.75 m3/(m3·h), the conversion of SBAC was 93.80%.(4) In order to evaluate the catalyst stability, the catalyst [HSO3-PMIM]HSO4 was repeatedly used for several times in the reactive column under the optimum conditions. The result shown that catalyst [HSO3-PMIM]HSO4 possessed excellent reusability, The conversion of SBAC can be maintained at over 93.10% with no significant change after the catalyst was repeatedly used for the fifth time. The structure of the used [HSO3-PMIM]HSO4 catalysts still remained unchanged after the characterization by using FT-IR,1H NMR and 13C NMR spectroscopy. |
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