Process for the production of hydroaromatic hydrocarbons from coal tar and coal tar fractions and products therefrom

摘要

Coal tar, coal tar fractions and aromatic hydrocarbons derived from coal tar are hydrogenated in two stages, the first using a sulphur-resistant catalyst at 350-450 DEG C. and a hydrogen partial pressure of 0.5-70 atmospheres to destructively hydrogenate sulphur compounds and hydrogenate part of the aromatic hydrocarbons, the second being a non-destructive, complete hydrogenation of the product entirely in the vapour phase at 200-500 DEG C. and 20-100 atmospheres hydrogen partial pressure using a catalyst consisting of one or more Group 8 metals. The coal tar fractions used may comprise mixtures of aromatic hydrocarbons with partially hydrogenated derivatives, paraffins, olefins, and naphthenes. The first stage may be effected in liquid, vapour or mixed phase, continuously or batchwise. Catalysts include molybdates and thiomolybdates, supported or not, especially cobalt molybdate on alumina. The hydrogen partial pressure used increases with the complexity of the sulphur compounds present. The exit gas may be re-used after removal of H2S. The products are treated, if necessary, to remove H2S and completely hydrogenated in the second stage as in Specification 761,755. Excess hydrogen from each stage may be recycled. In examples: (1) sublimed naphthalene is desulphurized by hydrogenation at 375 DEG C. and 32 atmospheres using cobalt molybdate, and the product vaporized in hydrogen at 300 DEG C. and 32 atmospheres in the presence of nickel on kieselguhr to yield decahydronaphthalene; (2) a 200-280 DEG C. coal tar fraction freed of tar acids and bases is similarly desulphurized but at 410 DEG C., and then hydrogenated, after a caustic soda wash, to yield naphthenes; (3) a 300-380 DEG C. fraction is similarly treated, first at 410 DEG C. and 42 atmospheres, and then at 300-330 DEG C. and 32 atmospheres, the product then being recycled to the second stage at 360-370 DEG C. and 55 atmospheres; (4) a 120-200 DEG C. fraction is treated first at 410 DEG C. and 20 atmospheres, then at 270-280 DEG C. and 30 atmospheres.