Patent GB-470338-A (GB)
Title: Improvements in the recovery of polynuclear compounds
IPC: C10G1/00
Filed: 1936-02-07
Abstract: The liquid or pulpy residue ("sludge") from the destructive hydrogenation of coal, comprising solid constituents and oils of high boiling point, is distilled after removal of a part of its oil by mechanical means, and the distillate is treated for the recovery of polynuclear compounds therefrom by the methods described in Specification 435,254 or by the methods ordinarily used in recovering polynuclear compounds from coal-tar fractions. The removal of a part of the oil from the sludge may be effected by filtration or centrifuging, if desired, after dilution with a mobile hydrocarbon oil.  The distillation of the residue is preferably effected under conditions which promote decomposition and to a temperature at which all the constituents capable of being distilled are removed.  If the distillation is effected by bringing the material to the necessary temperature in bulk and relatively slowly, the distillate may contain paraffin wax, which is preferably removed before the further treatment, suitably by mixing the distillate with a selective solvent, e.g. methyl formate, a chlorinated hydrocarbon, or a liquefied, normally gaseous paraffin hydrocarbon, and cooling the mixture. Preferably, however, the distillation is effected rapidly by passing the material to be distilled into a vessel heated to at least about 500 DEG  C., whereby the paraffin wax is cracked and a dehydrogenation of hydrogenated compounds in the material may be effected.  The crude distillate may then be subjected to fractional distillation, preferably in vacuo, and the fractions treated for the recovery of polynuclear compounds.  An oxidizing gas or steam is preferably supplied to the material during the fractional distillation, particularly at temperatures above the boiling point of pyrene.  In the examples: (1) sludge from the destructive hydrogenation of coal is centrifuged to remove a part of the oil, and the residue is introduced continuously into a rotary furnace heated to 500--550 DEG  C.; the vapours from the furnace are condensed, and the condensate is fractionally distilled at 10 mm. pressure into fractions having a boiling range of 2--3 DEG  C., and from successive fractions polynuclear compounds such as carbazole, hydropyrenes, pyrene, methylpyrenes, dimethylpyrenes, 1 : 12-benzoperylene and coronene (hexabenzobenzene) are obtained; the methylpyrenes may be purified by washing with xylene and alcohol, or benzene and alcohol; 1 : 12-benzoperylene and coronene may be separated from one another by fractional crystallization from xylene; the picrates of the two latter compounds are described; (2) the process is effected as in example 1 up to the stage in the fractional distillation when pyrene and its homologues have been removed; the residue is then fractionally distilled with introduction of air into the still, whereby a 1 : 12-benzoperylene fraction and a coronene fraction are obtained, the coronene being recovered in this case as a sublimate. Other products stated to be obtainable are anthracene, picene, chrysene and fluorene.  The second Provisional Specification states that an oxidizing gas or steam may be supplied during the preliminary distillation of the partly oil-freed sludge.ALSO:The liquid or pulpy residue from the destructive hydrogenation of coal is distilled after removing a part of its oil by mechanical means, and the distillate is treated for the removal of paraffin wax, suitably by mixing it with a selective solvent, e.g. methyl formate, a chlorinated hydrocarbon, or a liquefied, normally gaseous paraffin hydrocarbon, and cooling the mixture.