US2458980A

US2458980A - Production of gasoline

Info

Publication number: US2458980A
Application number: US633814A
Authority: US
Inventors: Robert M Cole
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1945-12-08
Filing date: 1945-12-08
Publication date: 1949-01-11
Anticipated expiration: 1966-01-11

Description

Jan. 11, 1949. COLE 2,458,980

PRODUCTION OF GASOLINE Filed Dec. 8, 1945 Per Cen? Saruranon v o w E \nvenror loberf MCole 59 his Afl'orneg 4% Patented Jan. 11, 1949 .PRODUCTION oricliso RobertMiGolamakland, catfzgs sigttrtashat g, Development Company, gSan Francisco, acahfi, acorporation of Delaware 7 Application Deceniber 8, 1-945, Serial Nos633t8I4 :cf catalytic methodsthe most important means 2 Glaims. (all es-+30) "This "invention relates to the production of hi'gh-octane leaded :gasolines from .thermal gasoline stocks.

of producing high-=octane gasolinesis by thermal methods; that is, by the thermal cracking of higher boiling oils (Dubbs, De Florez, Cross, "Holmes Manley,'T. V.-P.1processe's) andyor the thermal reforming of low octanegasoline stocks.

These processes give highly olefinic gasolines having"octane numbers generally between about 65 and 74. "These octane'ratings are not sufiiciently 'high to produce" the maximum quantities of finished "gasoline meeting the present requirements.

(The octane number' requirements for most automobile motors has graduallydncreased and is now ber couldbeproduced by these thermal. methods.

numbers of these stocks. Consequently,.it is the practice to=- obtain the required octane rating of these stocks by the addition of tetra ethyl lead (T. E. L.). In general," the desired octane numabout '75.) Thermal stocks of. higher octane num- :ber itl-islusual l-y rec mm-nded to efiectrthe hydrogenation at a relatively high temperatureto .obtaina certain :amount of catalytic reforming simultaneously with the .hydrogenation. However, hydrogenation lat reforming temperatures is! coupled with-shortlcatalyst life; and :greater eX- pens-e-and.- is not entirely satisfactory.

.Ithasbeen fOH'IIdJ-thatiiH the refining of thermal gasoline-stocks (i. .e.-:olefinic,;gasoline stocks produced tby thermal methods. :such in particular as rthermal. cracking and thermal reforming) by. hydrogenationthe octane=number=of the product goesthr.ough- -a maximumras theipercentage of saturation (it e. then-percent 1 decrease in bromine :number due to hydrogenation) is-increased and then declines eat razrrelatively rapid rate. This point of maximumoctane number occurs atla relaitivelylowsperceritage of saturation. The hydrogenation can .be married tout to this point of .120 .maximurrr octane number *and ;the octane number of vthe--refined; product increased to the desired leveltby the additionof T.:E.'L. It has now :been 1 found, Yhowever, that this :method of operationais not.the-most-advantageous. It has been as tfoundnthattthe optimum saturation to be effected ber of the leaded product is appreciably above the 'octane'ratin'g or the marketed'ga'solinein'order to compensate for a certainamouritdfblended low-octane components, such .insparticular as straight-run gasoline. The amount and quality of the. low-octane components -to be blended .thereforeilargely control the octane number-re- .quired of the leaded thermal gasoline in order .tmmeet the prevailing octane numberspecifications.

These thermal gasoline stocks are quite highly unsaturated and require considerable refining be- .fore they can be leaded. and blended. They may be refined by any one of a number of refining treatments such'as the'conventional treatments .withsulfuric acid .or clay, .but these treatments A:-preferred method a for refining: such thermahstocksis byt'hydrogenaincur." large refining losses.

tion. A hydrogenation treatment destroys the small amounts of diolefins and other gum-forming constituents with substantially no treating losses. While very mild treatment has been quite successful in some cases it has been frequently reported that refining by hydrogenation results in an excessive depreciation of the octane number of the stock. This has been postulated to be due to the hydrogenation of olefins. In order to counteract this depreciation of the octane numby: the :hydrogenation ttreatm'ent is a function of the desired octane number of the finished product and does nottcorrespond 1 to this maximum octane-number. .v i

Accordingkito theaprocess'of thepresentinvention. thermalrgasolin'ewstocks from petroleum are ,hydrogenated.toranzoptimurm saturation which is @afunction .ofi'and lidependent upon the desired .octane.'numbertof'theeleaded product. Stated in another way, the-hydrogenationisLcarried out to a specific degree of saturation which allows a refined product of any given -desired octane number "to :be 1 obtained with "the minimum amount :o'f TfiEJL. Therelationship between the optipercentagewf saturation'oS) and the desired octane 'number is given approximately by r wherein 'Sis thejpercent saturation as hereinbenumber of the thermal stock treated, and i5 is a small allowable variation to allow for slight differences between difierent feed stocks.

In order that the invention may be better understood, reference is had to the attached drawing wherein there is shown by means of a graph the change in ASTM octane number of a 400 end point cracked gasoline from Dubbs cracking rises relatively sharply to a maximum and then drops sharply with increasing saturation so that at complete saturation the octane number has fallen over 18 points. Similar curves can be determined for leaded gasolines produced from such cracked gasoline stocks. However, the maximum points of the curves for various particular maximum octane numbers, corresponding to minimum T. E. L. requirements, shift to the right with increasing octane number requirements. The path of this shift is expressed by the above-given formula. a

The process of the invention is generally applicable for the production'of leaded gasoline from thermal gasoline stocks such as described above. Such stocks have bromine numbers of at least 50. The hydrogenation of the thermal gasoline stocks may be carried out with any of the hydrogenation catalysts commonly used for the hydrogenation of petroleum fractions. Particularly suitable catalysts are tungsten sulfide, nickel sulfide, molybdenum sulfide, tungsten sulfide promoted with a sulfide of iron, cobalt or nickel, and cobalt molybdate. Various other suitable catalysts are discussed in U. S. Paten No. 1,890,434 and British Patent 335,511.

The hydrogenation may be carried out with the gasoline stock in the vapor: phase,in the liquid phase, or in mixed phase, and under various'conditions of temperature, pressure and space velocity commonly used for hydrogenation of gasoline stocks. The temperature, for example, may be advantageously between 400 and 850 F. and the pressure may be advantageously between 100 and 1000 p. s. i. may be controlled-by control of any one or combination of the operating variables such as the catalyst activity, space velocity, temperature and pressure. A preferred variable for control is the liquid hourly space velocity either alone or in combination with hydrogen pressure. The conditions, in any case, are so controlled for the individual catalyst,-feed stock and desired octane number that the bromine number is decreased by an amount satisfying the above equation.

Example I A California pressure distillate fraction boiling essentially between 110 F. and 210 F. and having a bromine number of 92 was hydrogenated with a nickel sulfide-tungsten sulfide catalyst in which the nickel sulfide was the predominant constituent. The temperature was 700 F.; the pressure was 700 p. s. i., and the molal ratio of recycled gas (largely hydrogen) to hydrocarbon 60 feed was about 7:1. The liquid hourly space velocity was varied between 10 and 55 to obtain The degree of saturation the desired percent saturation. The original ASTM octane number was 73.8. The maximum clear ASTM octane number occurred when the saturation was carried to about 8%. However, for a gasoline of ASTM octane number of 77 the optimum saturation was found to be about 7%. For a gasoline of ASTM octane number of 75 the optimum saturation was found to be about 14%.

Example II A thermally cracked gasoline boiling essentially between 200 F. and 300 F. and having a bromine number of 87.2 and an ASTM octane number of 70.4 washydrogenated at temperatures between 700 and 800 F., pressure between 426 and 625 p. s. i., molal ratio of recycled gas (largely hydrogen) to hydrocarbon feed of about 7:1 and liquid hourly space velocities between 2.0 and 27.4 to control the percent saturation. It was found that the maximum clear ASTM octane number occurred 1 at about 9% saturation. However,

when a gasoline of 75 ASTM octane number was desired it was found that the optimum saturation was about 32%. When a gasoline of 73 ASTM octane number was desired the optimum saturation was found to be about 21%.

I claim as my invention:

.1. Ina process for the production of a leaded gasoline having an improved ASTM octane number from a thermal gasoline stock having an ASTM octane number N by hydrogenation of said thermal gasoline stock and addition of tetraethyl-lead, the improvement which comprises ,carry ing'out the hydrogenation of the thermal asoline stock under conditions to effect such a percentage saturation of the stock S that S='11+4.7(N'-N) :5 wherein N is the desired ASTM octane number of the hydrogenated and leaded product.

2. Process according to claim 1 in which the hydro enation is carried out at a temperature between about 400 F. and 850 F. and the percentage saturation is controlled by varying the space velocity.

ROBERT M. COLE.

file of this patent:

UNITED STATES PATENTS Number Name Date 2,202,401 ROSBIl n; May 28, 194:0 2,367,527 Ridgway Jan. 16, 1945 "2,371,355 ROSS 6t a1. Mar. 13, 1945 2,382,910 Pinkston Aug. 14, 1945 I FOREIGN PATENTS Number Country Date 423,001 Great Blitaill Jan. 23, 1935 OTHER REFERENCES ll me 'Congr. mond. Petrole, vol. 2, pages 271-275 (1937) (article by Kudo et al., 0n the Hydrogenation of Cracked Gasoline").