PURPOSE: To increase purity by distilling an isopropylation product of naphthalene or isopropylnaphthalene, providing a diisopropylnaphthalene fraction, cooling the resultant fraction, depositing crystals of the 2,6-isomer and charging the deposited crystals into a continuous crystallizer.
CONSTITUTION: Naphthalene or isopropylnaphthalene is isopropylated with propylene, etc., to provide a product, which is then distilled to provide a diisopropylnaphthalene fraction. The resultant fraction is subsequently cooled to about -20°C to deposit crystals of the 2,6-isomer. The deposited crystals are then charged to a continuous crystallizer, crystallized and purified to afford the 2,6-isomer of ≥99wt.% purity. The aforementioned crystallizer has a raw material feed port at a suitable position of a vertical column, a cooling means above the feed port, a heating means below the feed port, a mother liquor taking out port in the upper part and an objective substance taking out port at the bottom. A cooling crystallizing part, a purifying part for countercurrent contact of the crystals with a liquid and a crystal melting part are constructed from the upper part of the column.
WATANABE TAKEHIKO
OKA TOSHIMITSU
