Water → 3-Hydroxy-2-naphthoic acid

Participants

Reaction Steps

A reactor was charged continuously with 50 kg/hr of β-naphthol, 20 kg/hr of diisopropyltoluene (isomer mixture) and 13.9 kg/hr of 50% aqueous sodium hydroxide solution while it was held at 100° C. in a nitrogen atmosphere. The mixture was fed to a fractionating column at a rate of 83.9 kg/hr while water was withdrawn as an overhead distillate at a rate of 10.1 kg/hr. During the fractionation, the reboiler was held at 230° C. The residue from the column was supplied continuously to an autoclave with a metering pump under pressure at a rate of 73.8 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 1.5 hr. The reaction mass was recovered from the autoclave at a rate of 77.1 kg/hr and supplied to a water addition tank where it was mixed with 165 kg/hr of water, and the mixture was treated with sulfuric acid to adjust its pH to 6.0 at a controlled temperature between 85° and 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 was extracted with 60 kg/hr of toluene. The extraction temperature was between 80° and 85° C. 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 an acid precipitation tank where it was adjusted to a pH of 2.0 with sulfuric acid at 80° C. The precipitate was filtered to give 14.4 kg/hr of 2-hydroxynaphthalene-3-carboxylic acid (99% purity and β-naphthol content less than 0.1%). The yield of 2-hydroxynaphthalene-3-carboxylic acid was 44% on the basis of the sodium β-naphtholate and was 85% on the basis of β-naphthol consumed.

Provenance & Evidence