Application Of 3A Molecular Sieve In Isopropanol Dehydration

Isopropanol is a kind of important chemical and organic solvent,which is widely used in chemical and pharmaceutical industries.A large amount of isopropanol and water mixtures are produced in the industrial process.So removal of water from isopropanol is important.The industrial production process needs the high-purity isopropanol.But under the atmospheric pressure isopropanol and water form an azeotropic mixture at 80.4℃.Using the ordinary distillation methods is unable to obtain isopropanol with enough purity.In this paper,the traditional methods for the purification of isopropanol were introduced,which include azeotropic distillation,extractive distillation, pervaporation,extractive azeotropic distillation with the addition of salts.All this methods need the addition of another solvent.In addition,they all have a complex process,higher investment cost as well as higher energy consumption. The idea of purification of isopropanol with the adsorption of 3A molecular sieve was put forward in this paper.The regeneration conditions of 3A molecular seive were determined via experimental method.That are:P = -0.095MPa,t = 250℃,t = 3h.According to the regeneration conditions,a setup was designed,in which adsorption and regeneration of the molecular seive can be realized in situ.Regeneration was carried out using n-octanol as heating medium at a pressure of 0.095Mpa.Experiments have been performed using 3A molecular seive as an adsorbent for the removal of water in isopropanol in liquid and gas phase.The water adsorption rate and the isopropanol adsorption rate were determined to be 10%and 20%respectively for the adsorption of liquid mixture of isopropanol and water as well as for the adsorption of liquid mixture of isopropanol and water followed by the adsorption of gas mixture of isopropanol and water.The relative adsorption ratio of water to isopropanol is only 0.5.At 80℃,the water adsorption rate and the isopropanol adsorption rate were determined to be 10%and 8%respectively for the adsorption of gas mixture of isopropanol and water.The relative adsorption ratio of water to isopropanol reached 1.2.This means that a better effect for the removal of water from isopropanol can be obtained when the adsorption was carried out in gas phase.Finally,a process was designed for the removal of water from isopropanol using 3A molecular seive based on the experimental results. Calculations for the operation cost demonstrated that using the high temperature heating medium in one column where the molecular seive has been regenerated to preheat another column which will be regenerated can save 27%energy.