Water → 3-Hydroxy-2-naphthoic acid

Participants

Reaction Steps

A 30-liter reactor was charged continuously with 75 kg/hr of β-naphthol, 30 kg/hr of diisopropyltoluene (isomer mixture) and 23.5 kg/hr of 50% aqueous sodium hydroxide solution while it was held at 100° C. in a nitrogen atmosphere. The liquid mixture was fed to a fractionating column while water was withdrawn as an overhead distillate. During fractionation, the reboiler was kept between 230° and 240° C. The residence time in the column was about 20 minutes and the distillate withdrawal rate was 51.1 kg/hr. The residue from the column was supplied continuously to an autoclave with a metering pump under pressure at a rate of 111.46 kg/hr for reaction with carbon dioxide. The reaction conditions were as follows: a temperature of 260° C., a total pressure of 7.0 kg/cm2G, and a residence time of 1.0 hr. The reaction mass was recovered from the reactor at a rate of 117.0 kg/hr and supplied to a water addition tank where it was mixed with 250 kg/hr of water and the pH of the mixture was adjusted to 6.0 with 70% sulfuric acid at a controlled temperature of 90° C. The mixture was supplied to a separation tank where it was separated into the organic layer and the aqueous layer. The aqueous layer was fed to an extraction tank where β-naphthol in the aqueous layer was extracted with 85 kg/hr of xylene. The extraction conditions were as follows: an extraction temperature of 80° to 85° C., an agitation period of 10 minutes, a standing period of 10 minutes, and a pH of 6.0 (adjusted with dilute sulfuric acid). The mixture was then supplied to a separation tank where it was separated into the organic layer and the aqueous layer. The aqueous layer was sent to a precipitation tank where it was adjusted to a pH of 2.0 with 70% sulfuric acid at 80° C. The precipitate was filtered at 80° C. to give 24 kg/hr of 2-hydroxynaphthalene-3-carboxylic acid (99% purity and β-naphthol content of 0.05%). The yield of 2-hydroxynaphthalene-3-carboxylic acid was 43.5% based on the sodium β-naphtholate and was 86% based on β-naphthol consumed. The recovery rate of β-naphthol was 54 kg/hr.

Provenance & Evidence