The Research On The Chemical Basis Of Coking Benzene Purification Method By Used The Halogenated Reaction

In this paper, the chemical basis of a novel purification method for the coking benzene was studied. The halogenated method for coking benzene purification was base on the characteristics of the thiophene can easily occurs the electrophilic substitution reaction with halogen, and after the halogenated reaction the thiophene will conversion to a high boiling point compound that easily removed by distillation. At the same time, the compounds of unsaturated hydrocarbons in the coking benzene will be oxidized by the acidic potassium permanganate solution, so that, used the purification method presented in this paper, can realize the both removal of the thiophene and the olefins by one process.In this study, a coking benzene sample from the coking plant was used as the raw material. A gas chromatography with the FPD detector and a gas chromatography mass spectrometer were used to analyze the components in the coking benzene sample. The qualitative calculation of the mass percents for each groups were used the GCMS analysis results by area normalization method. After that, a small experimental device was used to carried out on the studies of raw benzene chlorinated, brominated and potassium permanganate oxidation experiments. Then the coking benzene samples will be washed with 20% sodium hydroxide solution. Finally, the coking benzene sample will be analysis by qualitative and quantitative again to find the changes in the sample before and after experimentals. The detailed discussions will be done in terms of the unsaturated compounds, saturated hydrocarbons, sulfide, benzene group hydrocarbons, indene and naphthalene components. After that, the kinetic study of thiophene bromination reaction was investigated.The experimental results from the raw benzene chlorinated, brominated and potassium permanganate oxidations show that:1, The removal of unsaturated hydrocarbons by potassium permanganate oxidation reaction are efficient, especially for the compounds that the boiling point less than the toluene, and the removal of styrene and indene are also obvious effect.2, The potassium permanganate oxidation of coking benzene on the removal of thiophene and carbon disulfide are little effect.3, The effect of potassium permanganate oxidation of coking benzene in the saturated hydrocarbon removal was not obvious.4, Carried out the halogenated reaction in the acidic potassium permanganate solution can remove all the unsaturated, which is part of the unsaturated compound be removed by oxidation, as well as some are react with halogen conversion to Halogenated hydrocarbons.5, The thiophene in the coking benzene can be completely converted into thiophene derivatives during the halogenated process, but the removal of carbon disulfide in the coking benzene are little effect.6, During the chlorinated, benzene compounds can also occur the electrophilic substitution reaction with chlorine. The experiment relusts shows:about 0.6% of benzene have conversion into the chlorobenzene, and the proportion of toluene transform into the chlorotoluene is 10%, while the xylene and mesitylene will have a higher proportion of conversion into the chlorinated benzene.7, In contrast, the brominated process for the purification of coking benzene with a litter proportion of conversion of benzene transform into the chlorinated benzene, under the experimental conditions carried out in the paper, the brominated benzene can hardly find in the GCMS analysis.8, In short, the method for purification of coking benzene by used the halogenation reaction is a novel one can removal the both the unsaturated hydrocarbon and the thiophene by one process.The kinetics of thiophene bromination was studied by used the thiophene and bromine solutions. Before the experimental, the thiophene and bromine were pre-prepared in the reagent benzene solution with a certain concentrations, and then the reaction rate of thiophene and bromine under the equimolar ratio was measured at the same concentration of different temperatures and the same temperature of different concentrations. A GC with the FPD detector was used the determination of the concentration of thiophene and its derivatives in the solution. The concentration of bromine was measured by the method of chemical titration (iodometric method). According to the concentration of thiophene and bromine solutions, two reactants will be mixed in the molar ratio at 1:1, after that the reactants will be sampling regular and diluted immediately used to measure the relationship of the conversion thiophene versus reaction times. Later, the GC-MS was used to qualitative analysis of reaction products. Base on the GC and GC-MS analysis results, they are revealed that the 2-bromothiophene is the mainly product for the equimolar reaction of thiophene and bromine, and acooding the kinetic equations, the kinetic parameters were calculated as the following results, the activation energy of the equimolar reaction of thiophene and bromine is 22.92kJ/moL, the order of reaction is 3.37, the pre-exponential factor is 273758.