US2472494A - Safety fuel ingredients and their preparation - Google Patents

Description

Patented June 7,1949

SAFETY FUEL INGREDIENTS ANDTHEIR/ PREPARATION Ober C. Slotterbeck, Rahway, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application January 26, 1946, Serial No. 643,757

1 Claim.

This invention relates to antiknock motor fuel ingredients particularly useful in aviation safety fuel blends. It is concerned primarily with enhancing yields of safety fuel ingredients in an acid polymerization of butylenes and treatment of their polymer products.

In the past, most attention was first given to the synthesis of di-isobutylene in polymerizing isobutylene to derive low flash point antiknock motor fuel ingredients. More recently, requirements of safety fuel ingredients focused attention on the production of isobutylene trimers or triisobutylene in polymerizing isobutylene.

In the interest of supplying aviation safety fuel, methods were developed for obtaining maximum yields of tri-isobutylene with certain control of acid strength, polymerization conditions, and contact time. These methods were considered best suited for a feed of pure isobutylene or were controlled to restrict absorption of normal butylenes in order to avoid extensive formation of copolymers. However, it is now found that in btaining the optimum yields of tri-isobutylene by these methods losses are sustained. These losses arose from failure to utilize the normal butylenes more fully owing to lack of information on how the copolymers, both lighter and heavier than triisobutylene, can be converted into hydrogenated derivatives which are satisfactory safety fuel ingredients of high antiknock quality.

A primary object of this invention is to provide a method for obtaining increased yields of hydrocarbon products suitable for use in high antiknock safety fuels from both normal and isobutylenes. A further object is to provide an efficient method of treating low boiling copolymers of butylenes to obtain safety fuel ingredients. Additional objects will become apparent in the following description.

Suitable feed stocks for the process of the present invention are hydrocarbon mixtures comprising ,chiefly C4 hydrocarbons, such as C4 refinery cuts commonly obtained in distilling and stabilizing cracked petroleum. These cuts generally contain about to 20% of isobutylene with a similar or higher proportion of normal butylenes and substantial quantities of butanes.

To attain the objects of this invention, a refinery C4 cut feed, in the first step, is treated with sulfuric acid of adequate strength and at a suitable temperature to give a high yield of triisobutylene with substantial amounts of copolymers that are lower and higher boiling than triisobutylene, which boils in the range of 170 to 180 C. After fractionation of the resulting polymer product from the first step to separate a copolymer fraction of codimers lower boiling than a tri-isobutylene fraction, this lower boiling fraction is further treated with sulfuric acid of adequate strength and under suitable conditions to obtain optimum yields of polymers boiling within the limited range of 200 C. at 760 mm. mercury pressure absolute and 120 C. at 10 mm. mercury pressure absolute. The latter polymers hydrogenated alone or with the trimers and higher boiling butylene polymers from the first step yield high antiknock blending value ingredients for safety fuels.

For the preferred method of operation, a C4 refinery out in the first step is treated with sulfuric acid of about to strength at a temperature in the range of 0 C. to C. for a period which may vary from a fraction of a minute to about 60 minutes or longer. The time of contact is difiicult to'fix on account of other factors, such as the extent of mixing and dilution of the reactive olefins. Accordingly, the extent of contact is determined by the final polymer distribution in the reaction mixture. 7

It is desirable that the extent of contact be adjusted in the first step so that a major weight proportion of thetotal polymer product boils in the range of 145 C. to 200 C., the lighter copolymer fraction boiling from about C. to 145 C. constituting about 15 to 30 weight per cent of the total polymer product and the heavier fraction boiling above 200 C. not exceeding about 20 weight per cent of the total polymer product. More particularly, it'is preferred that the first step polymerization be ended when no appreciable amount of isobutylene dimer (di-isobutyl) remains in the polymer product and when the polymer fraction boiling above 200 C. is about 5 to 20 weight per cent of the total polymer product. At this stage of the first step, a good cleanup of normal butylenes is obtained and the formation of heavier bottoms, which are not useful for safety fuels, is not excessive at the expense of useful lower boiling polymers.

In the second step, the light fraction substan tially composed of codimer boiling in the range of 105 C. to 145 C. is contacted with sulfuric acid of between 70% and 90% strength, more preferably 80% to 90% strength, and preferably at a temperature in the range 0 C. to 60 C., until the codimer polymers are converted mainly into polymers (cotetramers) boiling above 200 C. and in major proportion boiling from 200 C. at 760 mm. mercury pressure absolute to C. at 10 mm. mercury pressure absolute.

By a combination of the two steps a high composite yield of C12 to C16 polymers for hydrogenation to safety fuel ingredients is obtained.

The C12 to C16 polymers obtained by the twostep process may be selectively hydrogenated by conventional methods wtihout undesirable decomposition to gaseous olefins. They may be hydrogenated with an active metallic catalyst, such as nickel, or active metal oxide catalyst, such as chromium oxide or molybdenum oxide, at temperatures ranging from about 150 C. to 350 C. under moderate pressures of hydrogen. The resulting hydrogenated polymers boiling in the safety fuel boiling range, i. e., mainly between 149 C. and 204 C. (300 F. to 400 F.) have arrexpectedly high antiknocl; blending value, especially when blended with a safety fuel alkylate, such as obtained by alkylating isobutane with butylenes and recovering from the alkylation a bottoms fraction which boils in the range of 149 C. to 204 C.

The following example. which is not intended to limit the invention, is presented to illustrate the procedure.

EXAMPLE In the first step of the preparation, a refinery C4 cut containing 16% isobutylene and about the same percentage of normal butylenes was contacted with 75% H2304 and the absorbed olefins were polymerized in the acid by heating through a temperature range of C. to 100 C. in a 60-minute period. The resulting polymer product was obtained in about 20.3 weight per cent yield, based on the total C4 cut, or 12'? weight per cent based on the i-C4Ha in the feed, indicating a considerable amount of copolymert In t e second ste the. 105- 45 C. co imer fraction (amounting to about 22.1 weight per cent of the total polymer) was contacted with 85% H2804 at 35 C. to 40 C. for about 60 minutes. The total amount of trimer and heavier polymer was increased 21.5 weight per cent by this operation. The total yield of composite polymer, including trimer, cotrimer, tetramer, and cotetramer, suitable for hydrogenation with the use of a contact catalyst was 18 weight per cent on the total C4 out or about 1 weight per cent based on the i-CiHt in the feed. The composite polymer fractions (B. P. 145 C./760 mm.- 120 C./ mm.) was hydrogenated over Raney nickel catalyst at 150 C. under a pressure of about 1500 pounds per square inch.

Pertinent data on the polymer preparation steps and the blending value of the hydrogenated polymer composite are given in the following tables.

TWO-STEP Tamrmnnr or Rummy C4 CUT F t s ep Run 1 Run 2 Charge:

75% H2304, g 3,910 3, 910 5, 270 5. 270 Total Olefin Content in 04 Cut 1, 690 1, 690 Lsobutylene in 04 Cut, g 845 845 Polymerization 'Iemp., C 0100 0-100 Contact Time, Minutes 00 60 Wt. of Spent 04, g-. 4. 105 4,120 Isobutylenc Content of Spent, Ci, g..... 12. 3 20 Recovery:

Acid, g 3, 910 a, 915 Polymer, g ,160 1, 140 Wt. of Polymer after Purification, g... 1,085 1. 055 Wt. Per Cent Yield of P lymer, o

04 Cut... 20. 6 20. 0 i-C4Ha--- 128 125 Product Work-Up (First Step):

Wt. Per Cent F-l Fraction boiling from l0 5 145 C 21.9 22.4 Wt. Per Cent F-2 Fraction boiling -f m 1457 6 4.-.--- 7.2 66.0 Wt Per Cent F-3 Fraction bo g above ------Maw-m 7 Product Work-Up of F43 and F-C:

Wt. per cent boiling from 200 C./700 mm. to 120 C./ 4

10 mm Wt. per cent boiling above 120 C./10 mm 25 5 Total Wt. Per Cent Polymer (145 C./760 rum-120 C./

10 mm.) For Safety Fuel:

Based on Total C4 Cut Charged 18 Based on Isobutylene Charged 111 TABLE II INSPECTION or SAFETY FUEL ALKYLATE AND or A 40% BLEND OF SAME ALKYLATE WITH HYDRO- cnrm'rnn Cozvrrosrrn or POLYMER (145 C./'760 MM.120 C./10 MM.)

I Alkylntc 40% Blend Gravity, A. P. I. 57.1 55. t. Aniline Point, F. 182 187 Doctor Pass Pass Acid Heat, ASTM, F- 3 4 Flash Tag, "F 104 103 Octane N0. +3 cc. TEL, ASTM-CFR 95. 4 09. 9 Initial Boiling Point, F 314 316 F 350 401 It will be appreciated that the present invention makes possible a recovery of larger yields of polymers suitable for deriving safety fuel ingredients. The hydrogenated C12 to C16 butene polymers including substantial amounts of hydrogenated cotetramers are shown to have high blending values with safety fuel alkylate.

It is to be understood that hydrogenated polymer derivatives or fractions thereof may be employed in various motor fuel blends and with various types of fuel additives although they have been shown to be exceptionally useful in safety fuel blends with safety alkylate. The unsaturated polymer products may be used in the blends also, if desired, or may be subjected to other types of treatment.

I claim:

The method of preparing a hydrocarbon prodnot suitable for use in a safety fuel, which comprises contacting a C4 refinery cut containing isoand normal butylenes with about 75% sulfuric acid at a temperature in the range of 0 C. to C. until a final total polymer product formed from the butylenes contains substantially no di-isobutylene, about 15 to 30 weight per cent of a codimer fraction boiling in the range C. to 0., about 50 to 80 weight per cent of a polymer fraction boiling in the range of 145 C. to 200 C. and about 5 to 20 weight per cent of a polymer fraction boiling above 200 C., separating the codimer fraction boiling in the range 105 C. to 145 C., contacting the codimer fraction with about 85% strength sulfuric acid at a temperature in the range 0 C. to 60 C. until above 80% by weight of the polymers in said codimer fraction are converted to polymers boiling above 200 C.

OBER C. SLOTTERBECK.

(References on following page) 0 2,472,494 5 6 REFERENCES CITED Number Name Date The following references are of record in the 2342974 Deanesly et 1944 2,396,753 Rosen et a1 Mar. 19, 1946 file thls patent 2,409,727 Bailey Oct. 22, 1946' UNITED STATES PATENTS 5 FOREIGN PATENTS Number Name Date 2,174,247 McAllister Sept. 26, 1939 gg g gg g 2,215,876 Herold et a1. Sept. 24, 1940 2,270,052 Hattox Ja,n,13, 1942 OTHER REFERENCES 2,300,817 Sweeney at a] 1942 w Whitmore et aL: Jour. Am. Chem. Soc., vol. 63,

2,321, 80 Brown June 8, 1943 75647 (1941)