Patent GB-587269-A (GB)
Title: Improvements in or relating to the dehydration of acetic acid or mixtures of acetic acid and acetic anhydride
IPC: C07C51/46
Filed: 1940-02-07
Abstract: <PICT:0587269/III/1> In the dehydration of aqueous solutions of acetic acid or of acetic acid and anhydride by distilling in the presence of an entrainer consisting of an acetic ester, and supplementary entrainer, which is insoluble in water and forms with water or water and the acetic ester an azeotropic mixture boiling at a lower temperature than the azeotropic mixture formed by the ester and water, a charge of the entrainers is placed in the still and remains without replenishment while it dehydrates a continuous supply of the aqeuous solution fed into the still, whereby distinct zones of operation of the supplementary, and principal entrainer respectively are formed.  Ethyl acetate is the p  preferred entrainer while hydrocarbons, particularly a petroleum distillate boiling, for example, at 84-85 DEG C., are preferred supplementary entrainers. The entrainers are placed in column A, and the aqueous acid solution supplied continuously from pipe 1. The vapours condense in B, the liquid separates in decanter C, an aqueous layer being withdrawn by pipe 3, and an entrainer layer totally refluxed by pipe 4.  A pipe 41 permits direct refluxing of part of the condensate.  The dehydrated product leaves through pipe 5.  Two distinct zones a and b form when the still is in operation where the ester entrainer and supplementary entrainer operate respectively.  Generally about 10 plates suffice for ester-water binary mixture, and 5 for the hydrocarbon-water mixture.  When cyclohexane is used as supplementary entrainer, a ternary azeotrope is formed with ester and water in zone b.  The column may be divided into several parts suitably connected.ALSO:<PICT:0587269/IV/1> In the dehydration of aqueous solutions of acetic acid or of acetic acid and anhydride by distilling in the presence of an entrainer consisting of an acetic ester, and a supplementary entrainer, which is insoluble in water and forms with water or water and the acetic ester an azeotropic mixture boiling at a lower temperature than the azeotropic mixture formed by the ester and water, a charge of the entrainers is placed in the still and remains without replenishment while it dehydrates a continuous supply of the aqueous solution fed into the still, whereby distinct zones of operation of the supplementary and principal entrainer respectively are formed.  Ethyl acetate is the preferred entrainer, while hydrocarbons, particularly a petroleum distillate boiling, for example, at 84-85 DEG  C., are preferred supplementary entrainers.  The entrainers are placed in column A, and the aqueous acid solution supplied continuously from pipe 1.  The vapours condense in B, the liquid separates in decanter C, an aqueous layer being withdrawn by pipe 3, and an entrainer layer totally refluxed by pipe 4.  A pipe 41 permits direct refluxing of part of the condensate.  The dehydrated product leaves through pipe 5.  Two distinct zones a and b form when the still is in operation where the ester entrainer and supplementary entrainer operate respectively. Generally about 10 plates suffice for the ester-water binary mixture, and 5 for the hydrocarbon-water mixture.  When cyclohexane is used as supplementary entrainer, a ternary azeotrope is formed with ester and water in zone b.  The column may be divided into several parts suitably connected.