Pervaperation Separation Of Trace Water From Crude N-Butyl Caetate And Organic Compounds From Waste Water During N-Butyl Aceate Production

N-butyl acetate, a kind of aromatic compound, is an important chemical material used in painting, coating, pharmaceutical as well as perfume industries. Moreover due to low toxicity of n-butyl acetate, it is gradually replacing some high toxicity solvents. Therefore its application is increasingly recognized. Up to now, the better method to produce n-butyl acetate in industry is the esterification via catalysis distillation-reaction. In the esterification process, n-butyl acetate is withdrawn from the bottom of the distillation tower, meanwhile water from the top. A demixer is used to separate water and organics in the top. But in the water phase, there are still a little organics remaining, including to n-butyl acetate as well as n-butanol and acetic acid unreacted. Although these organics only keep in lower content (around 1.3 %), removal of organics is necessary to avoid environment pollution andwaste. In addition, the crude product from the bottom still includes a small quantity of water (around 0.2 %) that will affect on the stability of the crude n-butyl acetate if not to remove it. The traditional technique to remove water from the crude product is distillation. This is uneconomical. So pervaporation separation to be applied two separation aims mentioned is appropriate. In this study, hydrophobic polyether-block-amide (PEBA) membrane is used to remove organics from aqueous solution and hydrophilic polymer-vinyl-alcohol (PVA) membrane is used to the removal of water from the crude n-butyl acetate via pervaporation separation.Membrane separation is an emerging technology now. Pervaporation is one of the most active areas in membrane research to be used in the separation of liquid mixtures, especially to remove a small quantity of water from organic solution or volatile organic compounds from aqueous solutions. It has to save energy and operate conveniently comparing with traditional separation technique.In this study, PEBA membrane was firstly used in removal of n-butyl acetate, n-butanol or acetic acid from organics/water binary mixtures by pervaporation separation. The effects of some technique parameter, for example feed concentration and operation temperature on the separation properties were studied. The results showed that the membrane preferentially permeates the organic compounds over water, and itsperm-selectivity follows the order of n-butyl acetate >n-butanol > acetic acid, moreover such membrane was especially selective to n-butyl acetate permeation. With an increase in feed VOCs content, the permeation fluxes and separation factors of VOCs were increased too, while an increase in temperature resulted in an increase in their permeation fluxes also as well as a reduction in separation factors of n-butanol/water and acetic acid/water mixtures, respectively. In addition, the activation energy was evaluated in n-butyl acetate/water and n-butanol/water binary system basing on the correlation between the permeation flux and operation temperature. The membrane was further tested for recovery of n-butyl acetate, n-butanol and acetic acid from dilute aqueous solutions that are relevant to n-butyl acetate production by esterification via reactive distillation. It was shown that the membrane was especially selective and high permeation flux to n-butyl acetate permeation similar to in binary system; under the experimental conditions tested, the separation factor is between 98.7-193, the membrane perm-selectivity follows the order of n-butyl acetate >n-butanol > acetic acid too. The concentration of n-butyl acetate in the permeation was sufficiently high that the permeation separated into two phases. This is of particular interest from an industrial application point of view because the organic phase can be recycled to the distillation column for reprocessing, while the aqueous phase can be recycled to the pervaporation unit for further treatment.In the final study, PVA membrane is used to remove water from organics/water mixtures. The effect of pervaporation time, temperature and feed concentration on per...