GB622999A - Improvements relating to the production of high quality aviation fuels - Google Patents

Abstract

Aviation fuel is obtained by fractionating an alkylate produced by condensing isobutane or isopentane with one or more of the lower olefines, except ethylene, in the presence of an alkylation catalyst, such as concentrated sulphuric acid or hydrofluoric acid, and blending one or more of the fractions boiling within the ranges 45-69 DEG , 95-106 DEG and 106-120 DEG C. with at least one diluent consisting of a hydrocarbon fuel boiling in the aviation fuel range so that the resulting blend contains not more than 30 per cent of diluent and about 10-40 per cent of components boiling below 70 DEG C. Diluents mentioned are (a) paraffinic or naphthenic straight-run gasoline, (b) isoheptane, isohexane or isopentane, (c) catalytically cracked gasoline produced by the Houdry or the fluid catalyst process, (d) hydroformed naphtha, (e) benzene, toluene, mixed xylenes or cumene, (f) alkylate produced by the interaction of isobutane and butenes or pentenes in the presence of a catalyst, (g) alkylate (mainly diisopropyl) produced by the interaction of isobutane and ethylene by thermal or catalytic means, (h) hydrocodimer produced by catalytic dimerisation of butylenes and hydrogenation of the dimer, (i) hot acid iso-octane produced by polymerization of butylenes in the presence of sulphuric acid followed by hydrogenation of the iso-octenes thus formed and (j) neohexane. The blend should not contain more than 25 per cent of isopentane, which may be an alkylate fraction or more than 15 per cent of aromatics which may be added in the form of an aromatic extract obtained by the solvent extraction of a petroleum distillate with a polar solvent. Tetraethyl lead may be added to the aviation fuel. In the examples, aviation fuel is produced by blending (1) the 45-69 DEG , 95-106 DEG and 106-120 DEG C. cuts with (a) cumene, (b) cyclopentane, neohexane, diisopropyl and isopentane, (c) toluene, isopentane and tetraethyl lead, or (d) cyclopentane, neohexane, diisopropyl, xylenes, isopentane and tetraethyl lead; (2) the 106-120 DEG C. cut with triptane and (3) the 95-120 DEG C. cut with (a) toluene, cyclopentane, isohexane, isopentane and tetraethyl lead, (b) toluene, neohexane, isopentane and tetraethyl lead, (c) aromatic extract, cyclopentane, neohexane, diisopropyl, isopentane and tetraethyl lead or (d) aromatic extract, isopentane and tetraethyl lead. The 95-120 DEG C. cut of examples (3) (c) and (3) (d) is obtained from alkylate produced by condensing isobutane with C4 olefins in the presence of sulphuric acid while the 106-120 DEG C. cut of example (2) is obtained from alkylate produced by condensing an impure isobutane containing small amounts of propane and n-butane with an olefin mixture containing propylene, isobutene, normal butenes, butadiene, pentenes, propane, isobutene, normal butane and pentanes in the presence of sulphuric acid. The 45-69 DEG C. cut of the latter alkylate consists of diisopropyl and 2-methyl pentane, the 95-106 DEG cut of 2,2,4-trimethyl pentane and the 106-120 DEG C. cut of 2,3,3-, 2,3,4- and 2,2,3-trimethyl pentanes and some dimethyl hexanes. For comparison purposes, blends of these cuts without the addition of diluents are described. Specification 479,345 is referred to.