Patent GB-757790-A (GB)
Title: Improvements in or relating to the interaction of carbon disulphide and primary aromatic amines
Inventor: MILNER DAVID WILLIAM
IPC: C10G29/20
Filed: 1953-02-05
Abstract: Hydrocarbon materials, particularly coal tar hydrocarbon fractions, containing carbon disulphide, are purified by treating them with a primary aromatic amine to convert the carbon disulphide, wholly or in part, to the corresponding substituted thiourea (according to the reaction RNH2+R1NH2+CS2=RNHCSNHR1 +H2S, where R and R1 are the same or different aromatic residues), and segregating the purified hydrocarbon materials from the substituted thiourea and hydrogen sulphide. Examples of hydrocarbon materials which may be purified by the process are crude coal tar benzene fractions and the low-boiling fore-runnings resulting from the fractionation of crude coal tar benzole.  The primary aromatic amine may be added in the form of a basic coal tar fraction which may contain such primary aromatic amines as aniline, toluidines and xylidines, together with heterocyclic nitrogen bases such as pyridine, picolines, lutidines, quinoline, isoquinoline and their homologues.  The reaction between the carbon disulphide and the primary aromatic amine is slow at 10 DEG  C., takes place more readily at 18-20 DEG  C., and proceeds rapidly at temperatures up to the boiling point of the mixture. However, the reaction is catalysed by the presence of sulphur and the use of elevated temperatures is then not essential.  After the reaction, the purified hydrocarbon material may be removed by distillation and washed with aqueous alkali to remove hydrogen sulphide.  In the examples, a crude coal tar benzene fraction containing carbon disulphide is mixed with toluidine coal tar fraction and either left for 24 days at 18-23 DEG  C., or left for 9 days at 22 DEG  C. in the presence of dissolved sulphur.  The benzene is then distilled off and washed with aqueous caustic soda.  The reaction between carbon disulphide and a primary aromatic amine may also be used in the purification of a heterocyclic nitrogen base material containing such an amine. Thus, heterocyclic nitrogen base materials, particularly basic coal tar fractions, containing one or more primary aromatic amines, are purified by treating them with carbon disulphide to convert the primary amine or amines to the corresponding substituted thiourea or thioureas, and segregating the purified heterocyclic nitrogen base materials from the substituted thiourea or thioureas and hydrogen sulphide.  The process is applicable to the conjoint purification of a carbon disulphide-containing coal tar hydrocarbon fraction and a basic coal tar fraction.  Distillation of the reaction mixture may yield the purified hydrocarbon material, the purified heterocyclic nitrogen base material and the substituted thioureas as separate fractions. The substituted thioureas may be decomposed by boiling with aqueous mineral acid, such as hydrochloric acid, to form a mixture of aryl isothiocyanate and the acid salt of the primary aromatic amine or amines.  The aryl isothiocyanate may then be isolated by steam distillation or solvent extraction, and the primary aromatic amine then liberated by the action of alkali on the acid salt.  In examples (a) a basic coal tar fraction containing primary aromatic amines is refluxed with sulphur and carbon disulphide, the product is refluxed with aqueous hydrochloric acid and the aqueous phase is then made alklinae to release a material enriched in the primary aromatic amines and (b) a basic coal tar fraction containing primary aromatic amines is heated with benzole forerunnings containing carbon disulphide, the product is washed with aqueous caustic soda to remove hydrogen sulphide and phenols and then steam distilled, the bases in the distillate are washed out with dilute acid and distilled and the residue from the steam distillation is refluxed with aqueous hydrochloric acid, whereupon it separates into an oily layer of aryl isothiocyanates and an aqueous layer containing hydrochlorides of primary aromatic amines.ALSO:Hydrocarbon materials, particularly coal tar hydrocarbon fractions, containing carbon disulphide, are purified by treating them with a primary aromatic amine to convert the carbon disulphide, wholly or in part, to the corresponding substituted thiourea (according to the reaction RNH2 + R1NH2 + CS2 = RNHCSNHR1 + H2S, where R and R1 are the same or different aromatic residues), and segregating the purified hydrocarbon materials from the substituted thiourea and hydrogen sulphide.  Examples of hydrocarbon materials which may be purified by the process are crude coal tar benzene fractions and the low-boiling fore-runnings resulting from the fractionation of crude coal tar benzole.  The primary aromatic amine may be added in the form of a basic coal tar fraction which may contain such primary aromatic amines as aniline, toluidines and xylidines together with heterocyclic nitrogen bases such as pyridine, picolines, lutidines, quinoline, isoquinoline and their homologues. The reaction between the carbon disulphide and the primary aromatic amine is slow at 10 DEG C., takes place more readily at 18 DEG -20 DEG C. and proceeds rapidly at temperatures up to the boiling point of the mixture.  However, the reaction is catalyzed by the presence of sulphur and the use of elevated temperatures is then not essential.  After, the reaction, the purified hydrocarbon material may be removed by distillation and washed with aqueous alkali to remove hydrogen sulphide.  In the examples, a crude coal tar benzene fraction containing carbon disulphide is mixed with a toluidine coal tar fraction and either left for 24 days at 18-23 DEG C., or left for 9 days at 22 DEG C., in the presence of dissolved sulphur.  The benzene is then distilled off and washed with aqueous caustic soda.