US2337601A - Treatment of natural gasoline - Google Patents

Description

Dec. 28, 1943. H. L. HAYS TREATMENT OF NATURAL GASOLINE Filed June 9. 1941 GAS - CATALYTIC ISOMERIZATION FURNACE BUTANE BOTTOM PRODUCT 9' INVENTOR HARRISON LOWE HAYS BY ATI'ORN Z a MOTOR FUEL Patented Dec. 28, 1943 TREATMENT OF NATURAL GASOLINE Harrison L. Hays, Bartlcsville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Application June 9, 1941, Serial No. seizes Claims. (01. 196-50) The present invention relates to the manufacture oi high octane aviation gasoline and high octane number motor fuel by the treatment of natural gasoline in such a manner that substan- I tially all hydrocarbons lying within this range are utilized and converted into highly valuable products.

High octane number hydrocarbons are known for their efllciency and improved performance as fuels for internal combustion engines. It is also known that such high octane fuels reduce the detonation property and allow much higher compression ratio and consequently greater power and the higher speeds demanded of modem airplane engines. Likewise it has been demonstrated that olefin hydrocarbons are of higher octane number and consequently have higher anti-detonation qualities than corresponding straight chain hydrocarbons. The various individual hydrocarbons of the same molecular weight also difier widely among themselves as to detonation or combustion properties, which may be exempliged by the detonation characteristics of normal hexane as compared to 2,2-dimethyl butane (neohexane). The normal hexane, a straight chain hydrocarbon, exhibits an octane number rating of 59, whereas the isomer 2,2-dimethyl butane or neohexane having a highly branched molecu lar structure demonstrates an octane number rating of 95.

A number of methods have been proposed for the manufacture of higher octane number hydrocarbons from those of lower octane number, such as alkylation, polymerization, and various other-methods which have been widely used for the treatment or various hydrocarbon mixtures.

An example of such a process is the production of iso-octane from isobutane and other saturated or unsaturated hydrocarbons by various thermal and catalytic means. A principal advantage mssessed by the present process over other methods proposed for the improvement oi'hydrocarbon octane number is that through the use of catalysts and suitable selected conditions of temperature and pressure a feed stock which contains any combination of hydrocarbons in the natural gasoline range may be converted by a combination of integrated and mutually dependent and flexible treatments to other hydrocarbons of higher oc tane number which are suitable for use in aviatlon and/or motor fuels of premium grade in any desired proportion, thereby obtaining maximum octane number efficiency from charge stock of varying constitution.

The principal object or this invention isi to produce higher octane number normally liquid hydrocarbons from lower octane number normally liquid hydrocarbons in the natural gasoline range. It is specifically an object of this invention to provide a treatment for natural gasoline hydrocarbons to enable production of aviation gasoline and motor fuel of high octane number. It is thus possible to attain a high percentage recovery of hydrocarbons in the natural gasoline range of maximum efiiciency for use in internal combustion engines. The process is of such flexibility that aviation gasoline and motor fuel may be recovered in any desired percentage limited only by the character of the charge stock.

Further objects and advantages of the invention will become apparent as the following description and disclosure proceed. In accordance with this invention certain conditions of temperatureiand pressure are applied to hydrocarbon charge stock, particularly natural gasoline, which result-in the separation of a fraction comprising a material having characteristics desired for reformation into highly branched-chain aviation gasoline hydrocarbons. A second heavier fraction composed principally of higher molecular weight straight-chain hydrocarbons is separated and catalytically dehydrogenatedi according to the present invention.

The light reformation stock is catalytically isomerized under controlled conditions for the recovery of a highly valuable aviation gasoline. A relatively high-boiling fraction of the isomerization eilluent comprises essentially straight-chain hydrocarbons composed of unconverted hydrocarbons and a substantial percentage of higher molecular weight straight-chain hydrocarbons produced as the result of reforming reactions in the isomerization process. This fraction separated irom the isomerization eflluent combined with the high-boiling fraction separated from the initial iractionof natural gasoline feed stock ESS- overhead fraction boiling from approximately 100 to 150 F. at a pressure of about 10 to 170 pounds per square inch is separated which includes a range of hydrocarbons in the natural gasoline range especially suited for improvement by the catalytic isomerization treatment hereinafter described. These materials advantageously comprise hydrocarbons containing from four to seven carbon atoms to the molecule, and include butanes, pentanes, hexanes, heptanes, and simi-v lar materials which on reformation will meet high octane requirements for aviation gasoline. A heavier fraction separated in this step comprises the raw feed stock to the dehydrogenation proc- The lighter hydrocarbon fraction so separated is subjected in the presence of a suitable catalyst such as one of the metallic halides, particularly aluminum chloride carried on a satisfactory supporting material, and in the presence of hydrogen chloride, to pressure and temperature conditions of the order of from to 500 or more pounds per square inch and 0 to 1000 F.,

respectively. These conditions are so maintained about 200 to 700 F. and pressures of the order of 50 to 300 pounds per square inch.

Isomerization is accompanied by the formation of substantial amounts of higher molecular weight straight-chainhydrocarbons in addition to highly branched-chain structures. This is 11- lustrated in the isomerization of butane to isobutane in which substantial quantities of butane are alkylated to pentane and materials of higher molecular weight.

Following the isomerization treatment, suit-' able means such as a fractionating tower are employed to separate the highly-branched-chain aviation hydrocarbons from heavier material, ordinarily predominately straight-chain hydrocarbons, formed during the isomerization reaction, and the latter material is subjected to catalytic dehydro enation in admixture with relatively high-boiling material from original raw feed stock asheretofore. described. This combined feed with insumciently reacted recycle stock from a later stage in the process is subjected in the presence of a suitable catalyst such as chromic oxidegel, chromlc oxide carried on a suitable support, or bauxite, to reaction pressure and temperature conditions of the order of 0 to 100 or more pounds per square inch and 600 to 1200 F., respectively. These conditions are carefully maintained so that not more than 30% of the total feed stock is converted per pass through the scale, and illustrates one means by which the process may be practiced.

By reference to the drawing, a natural gasoline feed stock as heretofore described is introduced through conduit I and compressed to a suitable pressure by means of pump 2 for entry into separation element 4 'by Way of conduit 8. The hydrocarbons in the aviation fuel range pass through conduit 5, condenser and cooler 6, and into accumulator 8 via conduit 1. A portion of the condensate is taken from accumulator 8 through conduit 9 and compressed by means of pump In to a pressure sufficiently high to introduce it through conduit I l as a reflux or cooling medium near the top of 4. A quantity in excess of that required for this purpose is continuously removed from 8 through conduit l2. This material together with recycle stock which enters through conduit 62 is compressed to a suitable isomerization reaction pressure by means of pump l3. This pressure is between 0 and 500 or more pounds per square inch. The total feed then passes through conduit l4 and thence through heat exchanger I5 where a satisfactory isomerization reaction temperature is obtained by heat interchange with hot dehydrogenation catalyst chamber efiiuent products which are passing through conduit 80. Conduit l8 and valve ll comprise the elements of a by-pass around I5 through which a portion of the isomerization feed is passed for the purpose of controlling the temperature of the feed. The preheated feed stock then passes into a suitable catalyst case M through conduit I 8, together with light hydrocarbon vapors and hydrogen chloride which join this stream through conduit 55. In the catalyst case the natural gasoline hydrocarbons are subjected to the influence of a suitable catalyst such as one of the metallic halides. The reaction temperature is such that the decomposition of the hydrocarbons so treated will be less than 5 per cent by weight for reaction periods which may vary from about 5 to about 30 minutes, the most suitable exact conditions being determined by trial. Conditions may-be maintained to vary the composition of the equilibrium mixture of reaction products in accordance with the type of product desired.

Following passage through the reaction zone, the hot reaction products pass via conduit 20 into exchanger 2! where they are cooled by suitable means prior to entry into separation element 25 through pump 2 l-A and conduit 24. Conduit 22 and valve 23 constitute a by-pass through which a portion of the reaction products may be passed for temperature control. Hydrocarbons lighter than those desired in aviation fuel together with hydrogen chloride pass through conduit 26, condenser and cooler 21, conduit 28, and into condensate accumulator 29. A portion of the condensate is taken from accumulator 29 through conduit 30 and compressed by means of pump 3| to a pressure sufiiciently high to permit its introduction as a reflux or cooling medium near the top of 25 via 32. One portion of a. quantity in excess of that required for this purpose is continuously removed from the system as a liquid through conduit 33, valve 36, and conduit 35. A second portion of the quantity in excess of that required for this purpose and which contains an appreciable concentration of hydrogen chloride is removed as a vapor near the top of 29 and passes through conduit 53, pump 54, and conduit 55 to its point of juncture with the hot catalyst acted material and some heavier hydrocarbons which were formed in the reaction zone, passes .through conduit 99 into a neutralization contactor 91 where a material such as caustic soda is employed for the purpose of neutralizing or removing a small quantity of hydrogen chloride. Thence the hydrocarbons and neutralizing solution pass through conduit 98 and into a settling tank 39 where the hydrocarbons are separated from the neutralizing solution and pass through conduit 44 into separation element 45. .Condllit 4|, pump 42, and conduit 43 permit recirculation of the partially used neutralizing solution. Fresh solution is'introduced through conduit 49, and spent solution is removed from the system through valve and conduit 4I--A .and 4I'B. 1

The aviation fuel constituent passes through conduit 46, condenser and cooler 41, conduit 49, and into condensate accumulator 49. As in the preceding step, a portion of this material is introduced near the top of 45 by means of conduit 59,

pump 5i, and conduit 52, to act as reflux or cooling medium. The valuable constituent in-excess of the amount required for this purpose is removed from the system through conduit 69, pump GI, conduit 93, valve 94, and conduit 65. A portion of this material, however, is recycled to the system through conduit 69, for the purpose of reaction control. The bottom product which consists of hydrocarbons of higher molecular weight passes through conduit 51, pump 58, and conduit 59 into dehydrogenation feed tank 99 together with dehydrogenation recycle stock ifrom conduit 9. Here these two streams are mixed with raw feed which has entered through conduit 99, pump 91, and conduit 99.

The combined feed to the dehydrogenation ystem passes through conduit I9 into pump II where it is compressed to a suitable reaction pressure. This pressure is between 0 and 199 pounds or more per square inch. The total feed then passes through conduit 12 and thence through heat exchanger I3 where a certain temperature is obtained by heat interchange with hot The pressure and temperature obtained by means of pump 99 and condenser and cooler 98 are such that a satisfactory separation is obtained in 99 between ethane and lighter hydrocarbons containing the hydrogen, and butane and heavier hydrocarbons. These lighter hydrocarbons containing the hydrogen can be continuously removed from the system through conduit 9|, valve 92, and conduit 93. However, it is considered to be essential for proper control of the dehydrogenation reaction to recycle a certain portion of the stream containing hydrogen through conduit I2. This is accomplished by the provision of a juncture of line 9| with line I2. The bottom product from 94 passes through conduit 94 into pump 99 where it is compressed to a pressure sufficient for entry, together with the bottom product from 99 which is passing through conduit 91, into separation element 98 through conduit 96. Hydrocarbons which are essentially butane in composition pass through conduit 99, condenser and cooler Hi9, conduit I9I, and into condensate accumulator I92. A portion of the condensate is introduced near the top of 98 by means of conduit I93, pump I94. and conduit I 95, as a, reflux or cooling medium. The quantity in excess of that required for this purpose is continuously removed from the system through conduit I99. The bottom product passes through conduit I91 into separation element I99 where the motor fuel fraction passes through conduit I99, condenser and cooler H9. conduit Ill, and into condensate accumulator III. A portion of the condensate is catalyst chamber eiiiuent products which are feed then passes through conduit I4 into a heatins coil-15 which is enclosed in a suitable furnace or heating means I9. The preheated hydrocarbons (699 to 1299 F.) then pass via conduit 11 into a suitable catalyst case I8 where the are subjected to the influence of a suitable dehydrogenation catalyst such as one of those heretofore described. The reaction temperature is such that the conversion of the hydrocarbons so treated. will be not more than 39 per cent by weight for reaction periods corresponding to flow rates which may vary from 1% to 3 volumes or liquid feed per volume of catalyst per hour, the most suitable exact conditions being determined by trial.

Following passage through the reaction zone,

the hot reaction products exchange heat in turn duit 99, pump 99, conduit 9I,condenser and cooler 99, and conduit 99 into separation element 99.

taken from the accumulator H2 through conduit H9 and compressed by means of pump I I4 to a pressure suiilciently high to introduce it as a refluxor cooling medium near the top of I99 via conduit I IS. The motorfuel fraction in excess of that required for this purpose is removed from the system through-conduit IIB, pump 1, valve 9, and conduit I 29. However. it is considered to be desirable to recycle a portion or this material to the system for control. Provision for this recycling operation has been made through the juncture of conduit H9 with conduit 59. A hydrocarbon fraction boiling above the motor fuel range is removed from separation element or vi'ractionator, I 98 as a bottom product through conduit Hi.

The motor fuel fraction which results from the foregoing procedure constitutes a highly valuable product of greatly improved octane number. The economies of the process are evidenced in the fact that this highly improved fuel includes hydrocarbons not amenable to the isomerization treatment as well as those of higher molecular weight formed thereby which are thus sufliciently improved in octane number to meet premium motor fuel requirements.

I claim:

1. A process of producing high octane number hydrocarbons from relatively low octane number -hydrocarbons in the natural gasoline range which comprises separating from natural gasoline feed stock a relatively low-boiling fraction boiling from about 109 to F. at a pressure ofabout 10 to 179 pounds per square inch, separating a relatively higher-boiling fraction from said feed stock, catalytically isomerizing said low-boiling fraction ata temperature of about 299 to 799 F. and recovering from the isomerization efliuent a fraction consisting essentially of high octane number branched-chain hydrocar-- and a further fraction substantially composed of straight-chain hydrocarbons, combining said last mentioned fraction with said relatively higherboiling fraction from said naturalgasoline feed stock, catalytically dehydrogenating. said combined fractions, and recovering high octane number motor fuel from the dehydrogenation eflluent.

2. A process of producing high octane number hydrocarbons from relatively low octane number hydrocarbons in the natural gasoline range which comprises separating from natural gasoline feed stock a relatively low-boiling fraction boiling from about 100 to 150 F. at a pressure of about to 170 pounds per square inch, separating a relatively higher-boiling fraction from said feed stock, catalytically isomerizing said low-boiling fraction by contacting same with a metallic halide in the presence of hydrochloric acid and at a temperature of about 200 to 700 F. and recovering from the isomerization eiliuent a fraction consisting essentially of high octane number branched-chain hydrocarbons suitable as aviation gasoline components and a further fraction substantially composed of straight-chain hydrocarbons, combining said last mentioned fraction with said relatively higher-boiling fraction from said natural gasoline feed stock, catalytically dehydrogenating said combined fractions, and recovering high octane number motor fuel from the dehydrogenation efiiuent.

3. A process of producing high octane number hydrocarbons from relatively low octane number hydrocarbons in the natural gasoline range which comprises separating from natural gasoline feed stock a relatively low-boiling fraction boiling from about 100 to 150 F. at a pressure of about 10 to 170 pounds per-square inch, separating a relatively higher-boiling fraction from said feed fraction substantially composed of straight-chain hydrocarbons, combining said last-named fraction with said relatively higher-boiling fraction from said natural gasoline feed stock, catalytical- I ly dehydrogenating said combined fractions, and

10 pounds per square inch, separating a relative higher-boiling fraction from said feed stock, catalytically isomerlzing said first mentioned fraction under such conditions that less than 10% of the charge stock undergoes splitting reaction,

separating from the isomerization effiuent a fraction consisting essentially of high octane branched-chain hydrocarbons suitable as aviation gasoline components and a further fraction consisting substantially of straight-chain hydrocarbons, combining said last-named fraction with said higher-boiling fraction from said natural gasoline feed stock, and subjecting said combined fractions to catalytic dehydrogenation.

5. A process of treating natural gasoline which comprises fractionating a natural gasoline feed stock, isolating a fraction boiling from 100 to 150 F. at a pressure of from 10 to 170 pounds per square inch, separating a relatively higher-boiling fraction from said feed stock, catalytically isomerizing said first fraction under such conditions that less than 10% of the charge stock undergoes splitting reactions, separating from the isomerization efiluent a fraction consisting essentially of high octane branched-chain hydrocarbons suitable as aviation gasoline components and a further fraction consisting substantially of straight-chain hydrocarbons, combining said last-named fraction with said higher-boiling fraction from said natural gasoline feed stock,

so and subjecting said combined fractions to catalytic dehydrogenation under such conditions that not more than 30% of the total feed is converted per pass through the reaction zone.

HARRISON L. HAYS.

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