Integrated process for the preparation of polybenzimidazole precursors

An integrated process for preparing a complex of 2,3,5,6-tetraaminotoluene and an aromatic diacid, wherein the complex is generally described by Formula I

• wherein Ar is a divalent group containing one or two aromatic rings wherein said one or two aromatic rings may contain one or more substituents in addition to the —COOH groups shown, wherein said one or more substituents are selected from the group consisting of OH, SH, methyl, ethyl, F, Cl, and Br;
• comprising the sequential steps under exclusion of oxygen:
• a) nitrating 2,6-dihalotoluene (II)
• wherein each Z is independently Cl or Br, in a reaction mixture comprising oleum or SO3, nitric acid, and H2SO4
• wherein
• (iv) the concentration of nitric acid is about 2.0 to about 2.3 moles per mole of 2,6-dihalotoluene;
• (v) the concentration of SO3 is about 1 to about 3 moles per mole of 2,6-dihalotoluene;
• (vi) the concentration of 2,6-dihalotoluene in the reaction mixture is between about 12 and about 24 weight percent;
• and
• wherein the temperature of the reaction mixture does not exceed 120° C.;
• thereby producing 2,6-dihalo-3,5-dinitrotoluene;
• b) directly separating the 2,6-dihalo-3,5-dinitrotoluene from the reaction mixture by filtration, while recycling the sulfuric acid mother liquor;
• c) washing the 2,6-dihalo-3,5-dinitrotoluene with water or acid then water, then with NH4OH, and then mixing it with glycol as a suspension;
• d) aminating the 2,6-dihalo-3,5-dinitrotoluene by heating the suspension formed in step (c) to a temperature in the range of about 100° C. to about 160° C. and contacting it with NH3(g), thereby converting the 2,6-dihalo-3,5-dinitrotoluene to 2,6-diamino-3,5-dinitrotoluene;
• e) directly separating the 2,6-diamino-3,5-dinitrotoluene from the reaction mixture by filtration, washing with glycol, then washing with water,
• f) forming a slurry of the 2,6-diamino-3,5-dinitrotoluene with water and transferring the slurry to a hydrogenation reactor containing a hydrogenation catalyst to form a reaction mixture;
• g) hydrogenating the 2,6-diamino-3,5-dinitrotoluene by contacting the reaction mixture formed in step (f) with hydrogen at a pressure in the range of about 0.31 to about 3.45 MPa and a temperature in the range of about 20° C. to about 100° C. for sufficient time to hydrogenate the 2,6-diamino-3,5-dinitrotoluene, thereby producing 2,3,5,6-tetraaminotoluene;
• h) contacting the 2,3,5,6-tetraaminotoluene produced in (g) with an aqueous solution comprising 1 to 6 equivalents of acid per mol of 2,3,5,6-tetraaminotoluene, and optionally a co-solvent;
• optionally heating the solution, thereby dissolving the 2,3,5,6-tetraaminotoluene;
• i) filtering the reaction mixture, thereby removing the spent hydrogenation catalyst;
• j) adding base to the filtered reaction mixture, thereby precipitating 2,3,5,6-tetraaminotoluene;
• k) dissolving the 2,3,5,6-tetraaminotoluene in alcohol, thereby forming a solution;
• l) contacting the solution with a solution of an aromatic dicarboxylic acid generally described by Formula III in a solvent, wherein the aromatic dicarboxylic acid is insoluble in water;
• wherein the solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and mixtures thereof;
• and wherein the molar ratio of aromatic dicarboxylic acid to the 2,3,5,6-tetraaminotoluene salt is from 1:1 to 1.1:1;
• thereby producing and precipitating the complex generally described by Formula I;
• and
• m) cooling, filtering, and washing the precipitated complex.

An integrated process for preparing a complex of 2,3,5,6-tetraaminotoluene and an aromatic diacid, wherein the complex is generally described by Formula I

• wherein Ar is a divalent group containing one or two aromatic rings wherein said one or two aromatic rings may contain one or more substituents in addition to the —COOH groups shown, wherein said one or more substituents are selected from the group consisting of OH, SH, methyl, ethyl, F, Cl, and Br;
• comprising the sequential steps under exclusion of oxygen:
• a) nitration of 2,6-dihalotoluene (II)
• wherein each Z is independently Cl or Br, in a reaction mixture comprising oleum or SO3, nitric acid, and H2SO4
• wherein
• (iv) the concentration of nitric acid is about 2.0 to about 2.3 moles per mole of 2,6-dihalotoluene;
• (v) the concentration of SO3 is about 1 to about 3 moles per mole of 2,6-dihalotoluene;
• (vi) the concentration of 2,6-dihalotoluene in the reaction mixture is between about 12 and about 24 weight percent;
• and
• wherein the temperature of the reaction mixture does not exceed 120° C.;
• thereby producing 2,6-dihalo-3,5-dinitrotoluene;
• b) directly separating the 2,6-dihalo-3,5-dinitrotoluene from the reaction mixture by filtration, while recycling the sulfuric acid mother liquor;
• c) washing the 2,6-dihalo-3,5-dinitrotoluene with water or acid then water, then with NH4OH, and then mixing it with glycol as a suspension;
• d) aminating the 2,6-dihalo-3,5-dinitrotoluene by heating the suspension formed in step (c) to a temperature in the range of about 100° C. to about 160° C. and contacting it with NH3(g), thereby converting the 2,6-dihalo-3,5-dinitrotoluene to 2,6-diamino-3,5-dinitrotoluene;
• e) directly separating the 2,6-diamino-3,5-dinitrotoluene from the reaction mixture by filtration, washing with glycol, then washing with water,
• f) forming a slurry of the 2,6-diamino-3,5-dinitrotoluene with water and transferring the slurry to a hydrogenation reactor containing a hydrogenation catalyst to form a reaction mixture;
• hydrogenating the 2,6-diamino-3,5-dinitrotoluene by contacting the reaction mixture formed in step (f) with hydrogen at a pressure in the range of about 0.31 to about 3.45 MPa and a temperature in the range of about 20° C. to about 100° C. for sufficient time to hydrogenate the 2,6-diamino-3,5-dinitrotoluene, thereby producing 2,3,5,6-tetraaminotoluene;
• h) contacting the 2,3,5,6-tetraaminotoluene produced in (g) with an aqueous solution comprising 1 to 6 equivalents of acid per mol of 2,3,5,6-tetraaminotoluene and optionally a co-solvent;
• optionally heating the solution, thereby dissolving the 2,3,5,6-tetraaminotoluene;
• i) filtering the reaction mixture, thereby removing the spent hydrogenation catalyst;
• j) combining the filtered reaction mixture with an acid, thereby precipitating 2,3,5,6-tetraaminotoluene salt;
• k) cooling, filtering, and washing the precipitated 2,3,5,6-tetraaminotoluene salt;
• l) dissolving the washed 2,3,5,6-tetraaminotoluene salt in water;
• m) contacting the 2,3,5,6-tetraaminotoluene salt with base, thereby converting the 2,3,5,6-tetraaminotoluene salt into 2,3,5,6-tetraaminotoluene;
• n) dissolving the 2,3,5,6-tetraaminotoluene in alcohol, thereby forming a solution;
• o) contacting the solution with a solution of an aromatic dicarboxylic acid generally described by Formula III in a solvent,
• wherein the aromatic dicarboxylic acid is insoluble in water;
• wherein the solvent is selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and mixtures thereof;
• and wherein the molar ratio of aromatic dicarboxylic acid to the 2,3,5,6-tetraaminotoluene salt is from 1:1 to 1.1:1, thereby producing and precipitating the complex generally described by Formula I;
• and
• p) cooling, filtering, and washing the precipitated complex.