Production of dimethyl esters
AssigneeEl Paso Products Company
InventorNorbert F. Cywinski
Life of this patent
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Abstract
This invention provides an improved process for the separation and recovery of byproducts associated with the isolation of C.sub.4 -C.sub.6 dicarboxylic acids contained in a waste byproduct stream derived from an adipic acid manufacturing operation involving nitric acid oxidation of a cyclohexanone/cyclohexanol feedstream. The main byproducts which are recovered are high purity dimethyl succinate, dimethyl glutarate and dimethyl adipate.
Claims12
In a process for producing methyl esters of C.sub.4 -C.sub.6 carboxylic acid components contained in an aqueous filtrate, which filtrate is a waste byproduct stream derived from the production of adipic acid by nitric acid oxidation of cyclohexanone/cyclohexanol, the improvement which comprises the steps of (1) concentrating the volume of the aqueous filtrate medium by the partial removal of water and the volatile components which co-distill with water to provide a concentrate solution;
- (2) admixing the concentrate solution with methanol, and heating the solution at a temperature between about 60.degree. C.-90.degree. C. to form methyl esters of the C.sub.4 -C.sub.6 carboxylic acid components;
- (3) extracting the methyl ester components by contacting the esterification medium with a water-immiscible organic solvent at a temperature between about 40.degree. C.-90.degree. C.;
- and (4) separating the immiscible organic solvent phase and aqueous phase.
In a method for producing dimethyl esters of C.sub.4 -C.sub.6 carboxylic acid components contained in an aqueous filtrate, which filtrate is a waste byproduct stream derived from a process for producing adipic acid by nitric acid oxidation of cyclohexanone/cyclohexanol, the improvement which comprises the steps of (1) concentrating the volume of the aqueous filtrate medium by the removal of water and the volatile components which co-distill with water to provide a concentrate solution which has a water content between about 5-30 weight percent and a nitric acid content between about 1-6 weight percent, based on total solution weight;
- (2) admixing the concentrate solution with between about 20-60 weight percent methanol, based on total solution weight, and heating the solution at a temperature between about 60.degree. C.-90.degree. C. to form methyl esters of the C.sub.4 -C.sub.6 carboxylic acid components;
- (3) extracting the methyl ester components by contacting the esterification medium with a water-immiscible organic solvent at a temperature between about 40.degree. C.-90.degree. C.;
- (4) separating the organic solvent phase and washing the said phase with water to reduce the content of methanol and residual nitric acid;
- and (5) recovering the solvent phase which contains dimethyl succinate, dimethyl glutarate and dimethyl adipate components.
In a method for producing dimethyl esters of C.sub.4 -C.sub.6 carboxylic acid components contained in an aqueous filtrate, which filtrate is a waste byproduct stream derived from a process for producing adipic acid by nitric acid oxidation of cyclohexanone/cyclohexanol, the improvement which comprises the steps of (1) concentrating the volume of the aqueous filtrate medium by the removal of water and the volatile components which co-distill with water to provide a concentrate solution which has a water content between about 5-30 weight percent and a nitric acid content between about 1-6 weight percent, based on total solution weight;
- (2) admixing the concentrate solution with between about 20-60 weight percent methanol, based on total solution weight, and heating the solution at a temperature between about 60.degree. C.-90.degree. C. to form methyl esters of the C.sub.4 -C.sub.6 carboxylic acid components;
- (3) extracting the methyl ester components by contacting the esterification medium with a water-immiscible organic solvent at a temperature between about 40.degree. C.-90.degree. C.;
- (4) separating the immiscible organic solvent phase and aqueous phase;
- (5) fractionally distilling the organic solvent phase to recover a refined mixed dimethyl ester fraction;
- and (6) concentrating the aqueous phase by distillation to provide a residual aqueous solution containing nitric acid and metal catalyst values.
Dependencies are inferred from the claim text.