Patent GB-586161-A (GB)
Title: Improvements in or relating to the production of aviation fuels
IPC: C10L1/00
Filed: 1944-04-24
Abstract: An aviation spirit blending stock comprises an aromatic fraction separated from cracked naphtha and an ethylene-isobutane alkylate containing 2, 3- dimethylbutane.  Alkylates from isobutane and C5-4 olefins, and from benzene and propylene, as well as an isomerized C5-6 fraction of the original naphtha, and isopentane and isoheptane fractions may also be included.  A typical stock contains in volume per cent.: 40 C5-8, mostly C7-8, branched hydrocarbons, 34 2, 3- dimethylbutane, and 26 benzene, toluene, and xylenes, the benzene being not more than 5 per cent. of the total blend.ALSO:An aviation gasoline blending stock is produced by thermally cracking at 1200-1400 DEG  C. a heavy naphtha of boiling range 200-410 DEG  F. to convert paraffins and naphthenes to aromatics, including benzene, toluene and xylene, olefins containing a large amount of ethylene, and some diolefins, separating an aromatic fraction of aviation gasoline boiling range, and ethylene, alkylating said ethylene with isobutane, which may be separated from the heavy naphtha, to give a fraction containing 2,3-dimethylbutane, and blending at least part of the aromatic fraction with the alkylate fraction.  C3 and C4 olefins may be separated from the cracked products and alkylated or C5 and C6 fractions separated from the heavy naphtha and isomerized to give blending material.  Part of the benzene may also be alkylated to cumene.  The heavy naphtha is cracked, using a short contact time and, preferably, a diluent gas, for example 80 mol. per cent of superheated steam.  The products are rapidly quenched to 600-1000 DEG F. and fractionated in stages to separate ethylene, propylene, C4, optionally C5, and aromatic fractions.  Th aromatics are treated with concentrated sulphuric acid to remove olefins, and fractionated to separate aromatics boiling up to about 350 DEG  F. for aviation gasoline or, if desired, further treated to recover benzene and toluene.  The ethylene is alkylated with isobutane, obtained by isomerizing butane, using aluminium chloride, an organic complex thereof or boron fluoride-water at 100-130 DEG  F. and 350 p.s.i. The products are fractionated to recover C5-6, containing 2,3-dimethyl butane, and C7-8 fractions for blending in the aviation gasoline. The propylene, together with the C4 fraction, from which butadiene is first recovered by solvent extraction, is alkylated with isobutane, for example using sulphuric or hydrofluoric acid at 100 DEG  F. and 200 p.s.i. Alternatively, ethylene and propylene may be alkylated in a single zone or C2, C3 and C4 olefins separately alkylated.  The alkylation products are fractionated to recover C5-8, and C9-12 fractions which are blended in the aviation gasoline.  Part of the propylene may be alkylated with benzene from the aromatic fraction to form cumene which is also introduced into the gasoline.  Using a motor gasoline feedstock, this is fractionated in stages to separate C4, C5, C6 and C7 fractions, the remainder being cracked and worked up as described.  The C4 fraction, together with C4 hydrocarbons from the isomerization stage referred to below, is fractioned to recover isobutane for use in the alkylations, the n-butane with extraneous butane being isomerized, for example using aluminium chloride at 200-325 DEG  F. The C4 fraction is treated to separate isopentane for blending with the gasoline, the n-pentane, together with the C6 fraction, being isomerized in presence of hydrogen to give isoparaffins for blending, the lighter degradation products being treated to separate n- and isobutane.  The C7 fraction which is mainly isoheptane may also be used for blending or fed to the cracking zone.  To produce butadiene, isoprene and piperylene for rubber synthesis, cracking is effected in two stages, for example at 1300-1375 DEG  F. for 0.3 secs. followed, after recovery of diolefins, by higher temperatures for 1 sec.  A typical gasoline blending stock of the process contains by volume, 40 per cent branched chain C5-8, mostly C7-8, hydrocarbons, 34 per cent 2,3-dimethyl butane and 26 per cent benzene, toluene and xylenes, the benzene being not more than 5 per cent of the total blend.