Method for producing organic acid

Abstract

A novel method is provided whereby a free organic acid can be produced particularly from an ammonium salt of an organic acid having a high melting point obtainable by bioconversion of a carbon source in the presence of a neutralizing agent, efficiently at a low cost, and the used material for reaction and a byproduct can be recycled for reuse without being disposed. An ammonium salt of organic acid A such as a dicarboxylic acid, a tricarboxylic acid or an amino acid is subjected to reactive crystallization by means of acid B such as a monocarboxylic acid satisfying the following formula (1), to separate free organic acid A in solid form: pKa(A)≦pKa(B)  (1) where pKa(A) and pKa(B) represent ionization indices of organic acid A and acid B, respectively, provided that when they have plural values, they represent the minimum pKa among them. The crystallization mother liquor after precipitating and separating organic acid A is, after separating acid B and then an ammonium salt of acid B, recycled for use in the reactive crystallization step. The ammonium salt of acid B is decomposed into acid B and ammonia, which are recycled for use in the reactive crystallization step and as a neutralizing agent in the bioconversion step, respectively.

1 - 24 . (canceled)  
   
   
       25 . In a process for separating and recovering acid B and ammonia by decomposing an ammonium salt of acid B to acid B and ammonia, a method for decomposing the ammonium salt of acid B, which comprises a heating step of heating a liquid comprising the ammonium salt of acid B, an alkali metal and/or alkaline earth metal salt of acid B, and water, and withdrawing a gas of a basic aqueous solution, and a step of subjecting the basic aqueous solution withdrawn from the heating step, directly or after condensation, to gas/liquid separation, gas/solid separation or gas/liquid/solid separation at a temperature of not higher than the melting point of the ammonium salt of acid B.  
   
   
       26 . The method according to  claim 25 , wherein the alkali metal and/or alkaline earth metal constituting the alkali metal and/or alkaline earth metal salt of acid B, is at least one member selected from the group consisting of Na, K, Ca and Mg.  
   
   
       27 . The method according to  claim 25 , wherein acid B is at least one member selected from the group consisting of formic acid, acetic acid, propionic acid and butyric acid.  
   
   
       28 . The method according to  claim 25 , which comprises a step of recovering acid B, wherein the liquid after withdrawing the gas of a basic aqueous solution in the heating step, is subjected to a separation step which is carried out under reduced pressure or atmospheric pressure at a temperature of at least 125° C., to separate and recover acid B.  
   
   
       29 . The method according to  claim 25 , wherein the residual liquid after the separation step is mixed with a system containing water to hydrolyze an amide compound formed as a byproduct in the heating step and the separation step and then recycled to the heating step.  
   
   
       30 . In a process for separating and recovering acid B and ammonia by decomposing an ammonium salt of acid B to acid B and ammonia, a method for decomposing the ammonium salt of acid B, which comprises a heating step of supplying a liquid comprising the ammonium salt of acid B, an alkali metal and/or alkaline earth metal salt of acid B, and water, to a site of a distillation column having at least two plates as the real number of plates, where the temperature is not higher than the melting point of the ammonium salt of acid B, and withdrawing a gas of a basic aqueous solution from the top of the distillation column.  
   
   
       31 . The method according to  claim 30 , wherein the alkali metal and/or alkaline earth metal constituting the alkali metal and/or alkaline earth metal salt of acid B, is at least one member selected from the group consisting of Na, K, Ca and Mg.  
   
   
       32 . The method according to  claim 30 , wherein acid B is at least one member selected from the group consisting of formic acid, acetic acid, propionic acid and butyric acid.  
   
   
       33 . The method according to  claim 30 , which comprises a step of recovering acid B, wherein the liquid after withdrawing the gas of a basic aqueous solution in the heating step, is subjected to a separation step which is carried out under reduced pressure or atmospheric pressure at a temperature of at least 125° C., to separate and recover acid B.  
   
   
       34 . The method according to  claim 30 , wherein the residual liquid after the separation step is mixed with a system containing water to hydrolyze an amide compound formed as a byproduct in the heating step and the separation step and then recycled to the heating step.  
   
   
       35 . Organic acid A produced by a method comprising subjecting an ammonium salt of organic acid A to reactive crystallization by means of acid B satisfying the following formula (1), to separate organic acid A in solid form:  
       pKa(A)≦pKa(B)  (1)  where pKa(A) and pKa(B) represent ionization indices of organic acid A and acid B, respectively, provided that when they have plural values, they represent the minimum pKa among them.    
   
   
       36 . A polymer prepared by using, as a material, organic acid A produced by a method comprising subjecting an ammonium salt of organic acid A to reactive crystallization by means of acid B satisfying the following formula (1), to separate organic acid A in solid form:  
       pKa(A)≦pKa(B)  (1)  where pKa(A) and pKa(B) represent ionization indices of organic acid A and acid B, respectively, provided that when they have plural values, they represent the minimum pKa among them.