Study On Adsorption Of Water From 2- Methyltetrahydrofuran By Molecular Sieves

2-methyltetrahydrofuran(2-MeTHF)is an important green organic solvent,which can be used to prepare reagents,reagents for organometallic reactions,and lithium reagents.The water contained in 2-MeTHF solution has a negative impact when it's used as an organic solvent.It is required that water content in 2-MeTHF solution is less than 3000 ppm.The coupling process combining distillation and adsorption method has been applied to dehydrate water from 2-MeTHF solution and the obtained solution is less than 1000 ppm.We have not find ant study on removing the water from 2-MeTHF by molecular sieve adsorption method as yet.In this paper,the removal of the water from 2-MeTHF solution was studied using 3A,4A,5A and ZSM-5 molecular sieves as adsorbents.The research contained four parts: preparation and adsorption of ZSM-5 molecular sieve,screening of molecular sieve,adsorption of 5A molecular sieve and adsorption of 3A molecular sieve.The main content is as follows.(1)The nanosized ZSM-5 molecular sieve was prepared at different crystallization time,and the optimal crystallization time was 36 h.The adsorption effect of ZSM-5 and 3A molecular sieve on water in 2-MeTHF solution was compared and studied.The 3A molecular sieve superior than the ZSM-5 molecular sieve performance in adsorbing water from 2-MeTHF solution.So,a several kinds of molecular sieve A were selected for the next experiment.(2)Using 3A,4A and 5A molecular sieves as adsorbent,the process of removing the trace water from 2-MeTHF was studied.The effect of molecular sieve type and dose on the removal of water was studied in detail.The results showed that the water removal efficiency increased with an increase of the dose of adsorbent.5A and 3A molecular sieves were more efficient than 4A molecular sieves in removal of water from 2-MeTHF solution.When the dose of adsorbent at a lower amount,the adsorption effect of 5A molecular sieve is better than that of 3A.When the dose of the two molecular sieves increased to 400 g/L,the water removal efficiency was as high as 99.6% and 99.4%,respectively,and the water in the feed solution decreased to 130 ppm and 200 ppm.(3)The thermodynamics of this process was studied.The isothermal adsorption data were obtained,and fitted by Langmuir,Freundlich and Langmuir-Freundlich adsorption isotherm model.The result showed that Langmuir-Freundlich model fitted best for 5A and 3A,which indicated that the adsorption process takes place on a homogeneous or heterogeneous surface.(4)The dynamics of this process was studied The adsorption data at different time were obtained and fitted by pseudo-first-order and pseudosecond-order kinetic model,respectively.The result showed that pseudofirst-order kinetic model fitted better than pseudo-second-order.This exhibited that adsorption of water on 5A and 3A molecular sieves is physical process,driven by mass transfer.(5)The desorption of 2-MeTHF and water on 5A and 3A molecular sieve was compared.The result showed that the adsorption to water is much stronger than that to 2-MeTHF on both of molecular sieves.(6)Finally,the break-through curves of molecular sieves 5A and 3A were studied by fixed-bed adsorption experiments.The penetration curves of molecular sieves with flow rates of 5 mL/min and 7 mL/min and initial concentrations of 35950 ppm and 41000 ppm were compared,respectively.The adsorption effect of 5A molecular sieve is better than that of 3A.Thomas model and Yoon-Nelson model were used for model fitting,and the fitting parameters of the model were obtained,which provided basic data for industrial amplification.