Patent GB-686166-A (GB)
Title: Purification of crystallisable aromatic to compounds in tar distillates
IPC: C07C7/14
Filed: 1949-04-25
Abstract: Purified crystalline compounds such as naphthalene, anthracene, phenanthrene, and carbazole, are obtained from tar distillates by cooling the distillate to effect crystallization, draining away the supernatant oil by gravity, washing the crystals with a solvent (e.g. methanol or industrial methylated spirits) in which the crystals are relatively insoluble but in which the oil is relatively soluble, draining away by gravity the solvent containing the impurities, and separating adhering solvent from the crystals, e.g. by heating.  The invention obviates the necessity of centrifuging and hot pressing. In an example, a coal tar distillate (1000 lbs.) having a boiling range of 200-240 DEG  C. was charged to a vertical column and allowed to cool slowly.  When the temperature had fallen to 25 DEG  C., a valve at the base of the column was opened and the liquid was allowed to drain from the crystals, which remained in the column in the form of a honeycomb.  Methanol (45 gallons) which had been used previously and contained 10 per cent of oil, was then added to the column; and after standing for 2 hours, it was drained away again and passed to a still for recovery of methanol.  Fresh methanol (45 gallons) was then added, and upon draining, the oil content was found to be 9 per cent; this material was stored to be used as initial wash for a succeeding batch.  The naphthalene crystals remaining were melted by means of a steam-coil in the vessel, and the methanol which remained adhering to the crystals, was distilled off and recovered, before subjecting the purified naphthalene to sublimation.  The yield of sublimed naphthalene (M.P. 79.8 DEG  C.) was 3 cwts.  Specification 630,397 is referred to.ALSO:Purified crystalline compounds such as naphthalene, anthracene, phenanthrene, and carbazole, are obtained from tar distillates by cooling the distillate to effect crystallization, draining away the supernatant oil by gravity, washing the crystals with a solvent (e.g. methanol or industrial methylated spirits) in which the crystals are relatively insoluble but in which the oil is relatively soluble, draining away by gravity the solvent containing the impurities, and separating adhering solvent from the crystals, e.g. by heating.  The invention obviates the necessity of centrifuging and hot pressing.  In an example a coal tar distillate (1000 lbs.) having a boiling range of 200 DEG -240 DEG C was charged to a vertical column and allowed to cool slowly.  When the temperature had fallen to 25 DEG C, a valve at the base of the column was opened and the liquid was allowed to drain from the crystals, which remained in the column in the form of a honeycomb. Methanol (45 gallons) which had been used previously and contained 10 per cent of oil, was then added to the column; and after standing for 2 hours, it was drained away again and passed to a still for recovery of methanol.  Fresh methanol (45 gallons) was then added, and upon draining, the oil content was found to be 9 per cent; this material was stored to be used as initial wash for a succeeding batch.  The naphthalene crystals remaining were melted by means of a steam-coil in the vessel, and the methanol which remained adhering to the crystals, was distilled off and recovered, before subjecting the purified naphthalene to sublimation.  The yield of sublimed naphthalene (M.P. 79.8 DEG C) was 3 cwts.  Specification 630,397 is referred to.