GB577282A - An improved manufacture of aromatic hydrocarbons - Google Patents

Abstract

<PICT:0577282/IV/1> A non-naphthenic hydrocarbon oil boiling between 150 DEG and 550 DEG F. derived from any source, is subjected to a heat treatment above 500 DEG F. in the presence of hydrogen and a dehydrogenation catalyst. The resulting aromatic hydrocarbons, after fractionation to obtain a product boiling in the desired range is purified by extracting with a selective solvent for aromatic hydrocarbons, washing with a highly paraffinic hydrocarbon having a boiling range different from that of the desired aromatic hydrocarbon and recovering the latter from the washed aromatic extract. In the Figure, oil from supply tank 1 and hydrogen from a holder 5 are heated and passed to a reactor 11 containing a dehydrogenation catalyst maintained at 850-1050 DEG F. The products are cooled and passed to a separator 15, the low molecular hydrocarbons such as methane being recycled. The liquid products are fractionated in a still 21 to give a light fraction which is removed by pipe 22, a heavy fraction which is removed by pipe 23 and the desired fraction which, in the case of toluene, boils between 200 DEG and 250 DEG F. and is collected in a tank 25. The toluene &c. enters the bottom of a tower 29 in which it meets a downward stream of solvent, such as liquid sulphur dioxide from a tank 30. In place of liquid sulphur dioxide, phenol, cresylic acid, furfural, nitroaniline, chloraniline and chlorbenzene may be used. The raffinate from tower 29 passes to a still 33, the recovered solvent being returned to the tank 30 and the hydrocarbons to the reactor 11. The extracted aromatic hydrocarbon passes to a second tower 38 in which it is washed with a paraffin diluent from tank 39 either boiling below the aromatic hydrocarbon product, such as pentane or boiling above it such as heavy naphtha or light kerosene. A second raffinate passes to a still 44 to separate the solvent, hydrocarbon and paraffin diluent. The secondary extract containing the aromatic product passes to a still 50 to recover the latter and the solvent. Finally, the toluene &c. is freed from olefines by an acid wash and distilled in a still 57 to give the pure product which is collected in a tank 59. As dehydrogenation catalysts, the following are mentioned: alumina gel, activated alumina, peptised alumina, silicaalumina gels, hydrofluoric and fluosilicic treated alumina mixed with an oxide or sulphide of a metal of Group VI of the Periodic Table, e.g. an oxide of molybdenum, chromium, tungsten, vanadium, cobalt or nickel. The catalyst may be used dispersed in the stream of hydrocarbon.