Removal And Utilization Of Thiophene In Benzene By F-C Acylation

Pure benzene is an important chemical material.Its materials mainly originate from petrobenzene generated in petroleum refining and coking crude benzene generated in coal coking.The sulfide in coking crude benzene mainly exists in the form of thiophene which would lead to poisoning of catalyst,corrosion of equipment and influence of pure benzene quality.?-thiophene and?-thiophene derivatives produced from thiophene as raw materials play an important role in the fields of synthetic pharmaceuticals,pesticides,dyes and macromolecule auxiliaries.Therefore,it is of great significance and practical value to find a method in which thiophene can not be only removed thiophene from coking crude benzene efficiently,but also be fully utilized.In this thesis,N,N-dimethyl-2-thiophene formamide was synthesized by F-C acylation between and thiophene in simulated coking crude benzene with dimethylcarbamyl chloride as acylation reagent.Firstly,A method for the determination of thiophene content in simulated coking crude benzene by HPLC was established.The optimal detection wavelength was determined by ultraviolet spectrophotometer,and the selection of mobile phase and elution gradient were optimized.Meanwhile,the target products obtained via column separation were elucidated by MS and NMR.Then,the effects of ZnCl₂ catalyst,the amount of dimethylcarbamyl chloride,reaction temperature and reaction time on the thiophene removal rate were investigated by controlling variable method.Furthermore,the conversion,selectivity and yield under the optimum experimental conditions were obtained.Finally,the reaction kinetics was studied and the kinetic model was established.The apparent kinetics series of the reaction was obtained by trial method,and the apparent reaction rate constants at different temperatures were gained by linear fitting method.Then the apparent activation energy and pre-exponential factor of the reaction were acquired by Arrhenius equation.The experimental results are shown as follows:?1?Thiophene,benzene,toluene and xylene have maximum absorption peaks at 230,240,240 and 240 nm,respectively.Acetonitrile is chosen as the mobile phase with smaller absorption wavelength and higher separation efficiency than methanol.The best experimental elution gradient is acetonitrile-water 70:30?0.0 min??90:10?9.0 min??90:10?10.0 min?.The target product was confirmed as N,N-dimethyl-2-thiophene formamide by MS and NMR.?2?Under certain reaction time,the removal rate of thiophene increases with the enlargement of dimethylcarbamyl chloride,catalyst addition and reaction temperature.The removal rate of thiophene was 98.14% after 2 h reaction and thiophene was almost completely removed as well as the conversion,selectivity and yield of the reaction are respectively 100%,98.54% and 99.13%after 3 h under the reaction conditions of the molar ratio of thiophene/dimethylcarbamyl chloride/ZnCl2=1:12:10,300 r/min,318 K.?3?The acylation of thiophene with dimethylcarbamyl chloride approximately accorded with the first order kinetic equation at 303?323 K.The activation energy was 53.9850 k J/mol and the pre-exponential factor was 1.4521×10⁹h^-1.