Experimental Study On The Separation Of N-hexane From Hydrogenated Naphtha By 5A Molecular Sieve

Isohexane is alkane solvent oil widely applied in market for a range of industries with good production value and market foreground,which has the characteristics of low sulfur,low aromatic,narrow distillation range,high purity,tasteless,colorless,non-toxic once processed by hydrogen refining.This research is based on the needs of enterprises designed a pilot process in accordance with the requirements of the industrial production of hexane separation,and solvent oil as raw material,according to the characteristics of molecular sieve shape selective adsorption,combined with pressure swing adsorption(PSA)and temperature swing separation(TSA)and other modern gas separation technology to a preparation of high purity isohexane and n-hexane in the pilot production project.Firstly,selecting the 5A molecular sieve adsorption gas separation method to conduct small scale production in the self-made dynamical apparatus and draw n-hexane breakthrough curve,then completing the inspection of adsorption properties of molecular sieve,selection of adsorbent and determination of the optimum technology condition on the basic of experiment results.The results show that 5A molecular sieve from Sinopharm Chemical Reagent Co.,Ltd.has a strong absorption and greater amount of n-hexane,the biggest breakthrough capacity was obtained at 80? and the velocity of 3 h-1,the content of n-hexane in the solvent oil was significantly reduced and the content in the desorption liquid was more than 99%.Secondly,based on single tower fixed bed dynamical apparatus,establishing program controlled fixed bed twin towers parallel adsorption separation device to automatically control adsorption and desorption process of electromagnetic valve.The pilot device has the benefits of high degree of automation,stable operation,simple operation,good safety performance,which can achieve continuous separation of n-alkanes and isohexane.After the accomplishment of the design specification,large number of drawing work was done in this design as follows:Test equipment,process flow chart,valve timing action table.The process of pressure swing adsorption is established:adsorption,vacuum pumping,gas stripping,vacuum,the adsorption and desorption temperature of 110?,the vacuum pressure is-97 kPaG,the adsorption velocity is 0.33 h-1,the adsorption cycle is 60 min;the final establishment of temperature swing adsorption is adsorption,steam blowing,nitrogen purge,adsorption temperature is 80?,the desorption temperature is 170?,the adsorption velocity is 0.22 h-1,the adsorption cycle is 120 min;the process of temperature and pressure swing adsorption joint is finally established:adsorption,steam cleaning,nitrogen purge,gas cooling,vacuum pumping,breaking vacuum,adsorption temperature is 80?,the desorption temperature is 150?,the vacuum pressure is-97 kPaG,the adsorption velocity is 0.44 h-1,the adsorption cycle is 150 min.Strictly control was needed in the parameters and sanitary condition of the operation steps,rigidly following the standards of the GMP.In this paper,5A zeolite was used as adsorbent to realize the pilot scale separation of n-hexane in solvent oil.These studies lay a solid foundation for large-scale isohexane industrialization,providing a useful reference for the efficient use of n-hexane,also for developing solutions to provide scientific basis for petrochemical industry.