Methods for preparing 1,3 butylene glycol
1,3 butylene glycol, prepared through an intermediate aldol condensation reaction of acetaldehyde, is produced at increased yield efficiencies. The efficiencies are achieved by utilizing an acetaldehyde having low carboxylic concentrations. The aldol condensation takes place in the presence of an alkali agent at a concentration of about 2 ppm to about 10 ppm to produce a 3-hydroxybutanal intermediate product that is hydrogenated in the presence of a Raney nickel catalyst to yield 1,3 butylene glycol at efficiency yields of greater than about 75%.
1 . A process for the preparation of 1,3-butylene glycol comprising:
(a) aldol condensation of acetaldehyde comprising a carboxylic acid concentration less than or equal to about 0.04 wt. % in the presence of an alkali agent to obtain a reaction mixture comprising 3-hydroxy butanal; and
(b) hydrogenating at least a portion of the 3-hydroxy butanal prepared in step (a) to obtain 1,3-butylene glycol.
2 . The process of claim 1 wherein the process is continuous.
3 . The process of claim 2 wherein the aldol condensation of the acetaldehyde takes place at a temperature of about 20° C. to about 30° C.
4 . The process of claim 1 wherein the alkali agent is present at a concentration of about 2 ppm to about 10 ppm based upon the weight of the acetaldehyde.
5 . The process of claim 1 wherein the carboxylic acid concentration of less than or equal to about 0.04 wt. % is the concentration of acetic acid.
6 . The process of claim 5 wherein the 1,3 butylene glycol is produced at an efficiency yield of greater than about 75%.
7 . The process of claim 4 wherein the alkali agent is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and mixtures thereof.
8 . The process of claim 5 wherein the carboxylic acid concentration of the acetaldehyde is less than or equal to about 0.02 wt. %.
9 . The process of claim 7 wherein the alkali agent is present at a concentration of about 3 ppm to about 5 ppm based upon the weight of the acetaldehyde.
10 . The process of claim 9 wherein the alkali agent is sodium hydroxide present at a concentration of about 3 ppm to about 4 ppm.
11 . The process of claim 10 wherein the 1,3 butylene glycol is produce at an efficiency yield of greater than about 80%.
12 . The process of claim 8 wherein the carboxylic acid concentration of the acetaldehyde is less than or equal to about 0.01 wt. %.
13 . The process of claim 2 wherein 1,3 butylene glycol is produced at rate of at least 0.35 liter of crude 1,3 butylene glycol product per hour per liter of reaction mixture.