Patent GB-581336-A (GB)
Title: Production of aviation gasoline
IPC: C10L1/04
Filed: 1943-10-29
Abstract: An aviation gasoline base stock is produced from a cracked hydrocarbon fraction boiling within the limits of 125 and 500 DEG F. and including a portion at least boiling within the limits of 180 and 250 DEG F., said fraction being of low olefin content, generally not above 10 per cent., and concentrated in naphthenes and aromatics, by subjecting at least part of the fraction, including that portion boiling from 180-250 DEG F., to the action of a siliceous cracking catalyst having an activity of over 35 per cent. gasoline, as determined by a standardized laboratory test which is described, under severe cracking conditions of at least 820 DEG F. and 25 p.s.i. excess pressure with a feed rate of not more than 1 vol. of liquid per vol. of catalyst per hour.  The initial boiling point of the cracked fraction may be above 125, e.g., 140 or 180 DEG F., as necessary to exclude the olefins which predominate in the C5 and C6 cuts.  The initial cracked motor fuel may be divided into two or more cuts.  For two cuts, the separation is around the C6 cut which can go either way so that the heavier fraction has an I.B.P. of about 125-225 DEG F.  Highest grade stock is produced from a fraction of 180 or sometimes 140 to 500 DEG F. Cracking is effected at 820-950 DEG F., 25-150 p.s.i. or more excess pressure and feed rates of .4 to 1 : 1.  A low boiling cut of about 85-200 DEG F. containing C5 and C6 may treated under mild cracking conditions of 750-825 DEG F., up to 50 p.s.i., and feed rates of 1-3; 1 to produce isopentane and convert the olefins.  Four cuts may be taken, viz., up to 180, 180-250, 250-325 and 325-500 DEG F.  The first two may not require further treatment if the initial cracking stock is a naphtha or gas oil.  For heavier stocks, the first cut and sometimes the third, requires treating to remove olefins.  The fourth cut should be recracked, and may be combined with the second for treatment under the severe conditions.  The olefin removal may be effected with sulphuric acid, by liquid phase polymerization as disclosed in Specification 503,913, [Group IV], or vapour phase catalytic treatment under mild conditions.  The cracking catalysts are preferably synthetic silica-alumina of low alkali metal content produced as described in Specification 519,808 although highly active silica-zirconia, silica-alumina-zirconia, and silica-alumina-beryllia may be used. For cracking the initial crude, when a gas oil or naphtha, conditions are generally 750-850 DEG F. up to 75 p.s.i. gauge, feed rate .75-2.1, with a catalyst of activity 38-46; for heavy stocks, 800-900 DEG F., up to 35 p.s.i. feed rate .75-1.5 : 1, with a catalyst of activity 30-40 and up to 20 per cent. steam or other vaporizing fluid.  In Examples: (1) a depentanized cracked gasoline of B.R., 125-400 DEG F. is treated with silica-alumina, activity 39, at 850 DEG F., 50 p.s.i., and feed rate 0.75 : 1, and isopentane added to the products of aviation gasoline boiling range; (2) a debutanized cracked gasoline is divided into cuts of up to 200, and 200-450 DEG F. which are treated separately with silica-alumina at 790 and 850 DEG F. 40 and 50 p.s.i., and feed rates 1.25 : 1 and .75 : 1 respectively; (3) gas oil is cracked over silica-alumina, 45 activity, at 800 DEG F., 10 p.s.i. gauge pressure, and 1 : 1 feed rate, and the products divided into four cuts.  The second cut, 180-250 DEG F., alone or with the fourth, 325-500 DEG F., is treated under severe conditions, and the product added to the first and third cuts or first only; (4) a 440-970 DEG F. crude is cracked and divided into four cuts, the second and fourth being severely cracked with recycling, and the gasoline product combined with the third cut and the first cut after treatment. Specifications 470,588 and 543,970 also are referred to.ALSO:An aviation gasoline base stack is produced from a cracked hydrocarbon fraction boiling within the limits of 125 DEG  and 500 DEG  F. and including a portion at least boiling within the limits of 180 DEG  and 250 DEG  F., said fraction being of low olefin content, generally not above 10 per cent, and concentrated in naphthenes and aromatics, by subjecting at least part of the fraction, including that portion boiling from 180-250 DEG  F., to the action of a siliceous cracking catalyst having an activity of over 35 per cent gasoline, as determined by a standardized laboratory test, which is described, under severe cracking conditions of at least 820 DEG  F. and 25 p.s.i. excess pressure with a feed rate of not more than 1 vol. of liquid per vol. of catalyst per hour.  The initial boiling point of the cracked fraction may be above 125 DEG , e.g. 140 DEG  or 180 DEG  F., as necessary to exclude the olefins which predominate in the C5 and C6 cuts.  The initial cracked motor fuel may be divided into two or more cuts.  For two cuts, the separation is around the C6 cut which can go either way so that the heavier fraction has a 1 B.P. of about 125-225 DEG  F. Highest grade stock is produced from a fraction of 180 DEG , or sometimes 140 DEG , to 500 DEG  F.  Cracking is effected at 820-950 DEG  F., 25-150 p.s.i. or more excess pressure and feed rates of .4 to 1 : 1.  A low boiling cut of about 85-200 DEG F. containing C5 and C6 may be treated under mild cracking conditions of 750-825 DEG  F., up to 50 p.s.i., and feed rates of 1-3 : 1 to produce isopentane and convert the olefines.  Four cuts may be taken, viz.: up to 180 DEG , 180-250 DEG , 250-325 DEG  and 325-500 DEG  F. The first two may not require further treatment if the initial cracking stock is a naphtha or gas oil.  For heavier stocks, the first cut and sometimes the third, requires treating to remove olefins.  The fourth cut should be recracked, and may be combined with the second for treatment under the severe conditions.  The olefin removal may be effected with sulphuric acid, by liquid phase polymerization as disclosed in Specification 503,913, or vapour phase catalytic treatment under mild conditions.  The cracking catalysts are preferably synthetic silica-alumina of low alkali metal content produced as described in Specification 519,808, [Group III], although highly active silica-zirconia, silica-alumina-zirconia, and silica-alumina-beryllia may be used. For cracking the initial crude, when a gas oil or naphtha, conditions are generally 750-850 DEG  F., up to 75 p.s.i. gauge, feed rate .75-2 : 1, with a catalyst of activity 38-46; for heavy stocks, 800-900 DEG  F., up to 35 p.s.i., feed rate .75-1.5 : 1, with a catalyst of activity 30-40 and up to 20 per cent steam or other vaporizing fluid.  In examples: (1) a depentanized cracked gasoline of B.R. 125-400 DEG  F. is treated with silica-alumina, activity 39, at 850 DEG  F., 50 p.s.i., and feed rate 0.75 : 1, and isopentane added to the products of aviation gasoline boiling range; (2) a debutanized cracked gasoline is divided into cuts of up to 200 DEG  and 200-450 DEG  F. which are treated separately with silica-alumina at 790 DEG  and 850 DEG  F., 40 and 50 p.s.i., and feed rates 1.25 : 1 and .75 : 1 respectively; (3) gas oil is cracked over silica-alumina, 45 activity, at 800 DEG  F., 10 p.s.i. gauge pressure, and 1 : 1 feed rate, and the products divided into four cuts.  The second cut, 180-250 DEG  F., alone or with the fourth, 325-500 DEG  F., is treated under severe conditions and the product added to the first and third cuts or first only; (4) a 440-970 DEG  F. crude is cracked and divided into four cuts, the second and fourth being severely cracked with recycling, and the gasoline product combined with the third cut and the first cut after acid treatment.  Specifications 470,588 and 543,970, [both in Group III], also are referred to.