US2904498A - Process for producing high octane motor fuels - Google Patents

Description

Sept. 15, 1959 R. A. FINDLAY PROCESS FOR PRODUCING HIGH OCTANE MOTOR FUELS Filed July 25, 1955 ATTORNEYS United States Patent C) PROCESS FOR PRODUCING HIGH OCTANE MOTOR FUELS Robert A. Findlay, Bartlesville, Okla., assignor to Philhps Petroleum Company, a corporation of Delaware Application July 25, 1955, Serial No. 524,254 8 Claims. (Cl. 208-49) yThe invention relates to a process for upgrading cracked gasoline to produce high-octane, clean-burning motor fuel.

One of the major sources of motor fuels is from cracked gasoline stocks. Recently developed high compression engines are placing increasingly greater demands on motor fuels in the wayof octane number rating (antiknock characteristics) and clean-burning qualities. It is frequently found necessary to undercut the end point of cracked gasoline in order to promote engine cleanliness and decrease octane requirement increase (ORI) of the engine during use. This method of handling the problem by distillation is non-selective, i.e., it removes hydrocarbons according to molecular Weight rather than according to type. It is preferable to remove from the fuel (cracked gasoline) only those hydrocarbons which tend to cause trouble. While not all of the factors of this phenomenon are fully understood, there is some evidence that high reactive materials including oleins and certain impurities such as sulfur compounds can be the source of trouble. The process of the invention is concerned with the removal of reactive materials from cracked gasoline and purifying and upgrading the same.

The principal object of the invention is to provide a process for converting a maximum amount of cracked gasoline into clean-burning, high-octane motor fuel. Another object is to provide a process for upgrading heavy cracked gasoline. A further object is to provide a process for converting cracked gasoline into high octane motor fuel which is exceptionally clean burning. It is also an object of the invention to provide a flexible process for converting cracked gasoline into high quality motor fuel and burner fuel which permits variation in the proportions of these products. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises subjecting a heavy cracked gasoline fraction to catalytic polymerization under conditions which polymerize the more reactive components and substantially reduce the olefin content of the fraction; fractionating the polymerzate to recover an overhead gasoline fraction having an end point not substantially in excess of about 400 F. and a bottoms fraction including the polymerized material from the polymerization step; and catalytically reforming the overhead gasoline fraction so as to improve its octane rating, thereby upgrading the same. The reformate may then be blended with other high octane gasoline components such as isopentane and butane, light cracked gasoline, and/or a gasoline fraction obtained by alkylating an intermediate cracked gasoline fraction together with a light isoparafhn, with or without the addition of C3 to C5 refinery olens to the feed to the alkylation step. It is generally preferred ICC the polymerized material which isv suitable for burner fuel, and to catalytic reformation, preferably admixed with straight run gasoline and/ or natural gasoline as described above. In accordance with one procedure the light gasoline fraction may be blended with the reformate along with other blending ingredients. In accordance with another procedure the light gasoline fraction is again fractionated into an overhead fraction having an end point in the range of to 195 F. and preferably about 190 F. and a bottoms fraction comprising an intermediate gasoline having an end point of about 300 F. The bottoms fraction comprising intermediate gasoline is admixed with a C4 to C5 isoparaffn, such as isobutane or isopentane with or without the addition of C3 to C5 oleiins, and the admixture is subjected to alkylation to produce high quality alkylate boiling in the gasoline range. The resulting alkylate is fractionated to recover as an overhead fraction the gasoline boiling range material and the higher boiling range materials as a bottoms fraction which is suitable for use as low-odor solvents.

To more fully illustrate the invention, reference is made to the drawing which shows a schematic arrangement of apparatus for effecting the process of the invention in some of its various aspects. A cracked gasoline is fractionated finto three cuts including a light gasoline in line 10, an intermediate gasoline in line 12, and a heavy gasoline in line 14. The heavy gasoline fraction having an end point of about 400 F. is introduced to catalytic polymerization vessel 16 where it is subjected to polymerization under conventional polymerization conditions including a temperature in the range of 425 to 625 F., a pressure in the range of 400 to 600 p.s.i.g., a space velocity in the range of 2.5 to 3.0 volumes of feed per Volume of catalyst per hour (v./v./hr.), and in Contact with a suitable polymerization catalyst, such as synthetic silicaalumina. Any conventional polymerization catalyst may be used in this step. The effluent from the polymerizaa separation is made into an overhead fraction having an end point of about 400 F. and a bottoms fraction ofv higher boiling materials which are suitable for burner fuel. The temperature in the top of fractionator 20 is preferably maintained in the range of about 330 to 350 F., while the bottom temperature is maintained inthe range of about 600 to 650 F. The burner fuel is recovered via line 22 and the 400 end point gasoline fraction is passed via lines 24 and 25 to catalytic reforming vessel 2S. Straight run gasoline and/or natural gasoline, which is preferably deisopentanized, may be introduced via line 30 to reformer 28. In instances where light components make up a sizable proportion of the overhead gasoline from fractionator 20, it is desirable to separate the light ends therefrom, taking overhead a cut boiling up to a temperature in the range of about 175 to F., such as 190 F.

The reforming step in vessel 28 is conducted underL F. This heavy gasoline fraction is subconditions well known in the art including contacting the feed With a platinum-containing reforming catalyst in admixture with hydrogen at a temperature in the range of 850 to 950 F. and at a pressure in the range of 200 to 900 p.s.i.g. The preferred catalyst is a platinum-containing catalyst comprising platinum deposited on a cracking catalyst such as silica-alumina or alumina and containing combined halogen, particularly, fluorine. Other catalysts which may be utilized in this reaction include platinum deposited on at least one metal oxide of the group alumina, silica, thoria, and zirconia containing chemically combined alkali metal (sodium); metal oxides or sulfides oflgroups IV, V, VI and VIII, such as molybdena on a support of silica, alumina, and magnesia, alone, or in admixture; and platinum or palladium on a silica-alumina cracking catalyst. It has been found that removal of olefins from the feed to the reforming zone has materially increased catalyst life. The reformate is passed via line 32fto blendingzone 34 for blending with othergasoline components hereinafter described.

The intermediate gasoline fraction, together with a light isoparafn, such as isobutane, is introduced via line 12` into alkylator 36. It is feasible and highly desirable where an abundance of light isoparafins and olefins are available to introduce C3 to C5 olefns to alkylator 36 such as via line 38. The alkylation step is eiected in the presence of and in contact with a suitable alkylation catalyst, preferably HF, of 85 to 95 percent concentration. Other alkylation catalysts, such as sulfuric acid, metal halides, etc., may also be used. The temperature in the alkylator is maintained in the range of 50 to 120 F. with sufcient pressure to maintain liquid phase, such as approximately 140 p.s.i.g. Reaction time is controlled in the range of 2 to 20 minutes, preferably, about 10 minutes. The isoparain to olefin ratio is preferably at least 6:1' but may be maintained in the range of 3:1 to 10:1 on a volume basis.

Reactions taking place in alkylator 36 are complex. By hydrogen exchange a portion of the oleiins is saturated to the corresponding parafns or naphthenes. 'I'his reaction produces isobutylene as a byproduct from supplying hydrogen which promptly alkylates more isobutane resulting in highly branched octanes of high octane number. Another portion of the oleiins alkylates isobutane to produce highly branched nonanes, decanes, undecaues, and dodecanes which are also of high octane number. In this manner high octane blending stock is made indirectly from isobutane Without having to separately crack or dehydrogenate it, the isobutane dehydrogenation taking place in the alkylator.

The alkylate from alkylator 36, after removal of isoparans, HF (or other catalyst) and fluorides in conventional manner, is passed via line 40 to fractionator 42 for separation of the alkylate into a deolelinized gasoline fraction taken overhead and having an end point not substantially above 400 F. The bottoms fraction comprising higher boiling hydrocarbons suitable as W-odor solvents is recoveredvia line 44. The gasoline fraction from fractionator 42 taken overhead is passed via line 46` to blender 34.

Isopeutane and n-butane are introduced to blender 34 as desired via line 48 and in the same manner light gasoline is introduced to this blending zone Via line 10. The resulting motor fuel is recovered from blender 34 via line 50.

To illustrate the invention, data are presented in Table I'beloW which are obtained from fractionating a cracked gasoline stock and polymerizing the heavy gasoline fraction (about 400 F. end point) to cause the more reactive materials, principally olefins, to be polymerized to a good' quality burner fuel. Operating conditions include a synthetic 90% silica-10%v alumina (by weight) catalyst, a space velocity of 2.5 to 3.0 v./v./hr., a pressure in the range of 400 to 600 p.s.i.g., and a temperature in the range of 425 to 625 F.r v

Y 4 TABLE r Original distillation of cracked gasoline and catalytic polymerization treatment Distillatiou Poly-treating heavy cracked gasoline Feed to Light Heavy Light Treated Burner dist. cracked cracked ends heavy oil gasoline gasoline cracked Yield, volume per- 132 272 106 306` 465 202 323 164 319 504 238 341 267 344 597 265 373 301 374 675 300 403 332v 407 Reid vapor press'. 3; 6 2. 7 0. 7 6. 6- 0. 2V Grav., 'API, at

60 F 53. 3 56. 9 40. 9 56.8 41.5 17. 6 Bromine number 48 43 26 2 22 Oxygen stability,

minutes 720 690y 840 Sulfur, weight percen 0.150 0.218 0.054 ASTM octane numbers:

Clear 66.9 70.6 60. 9 +1 ml. TEL 72.0 78. 4 67. 4 +3 m1. TEL-. 75. 9 84. 7 71. 2 Research octanev numbers:

Clear- 71.9 66.0 +1 ml. TEL 80. 2 72. 3 +3 n1l. TEL.-. 83.8 78.8

The treatment removes olens and sulfur compounds..

Extent of removal can be controlled by varying severity of treating conditions. Some loss of octane number re,- sults but this is rectified by catalytic reforming of the product which is now low in olefin content. Also a small amount of catalytic cracking takes place during the polymerization treatment, producing the light ends shown.

Octane numbers of the light ends were not determined'` but they should be high.

This method of operation can also be used to sonrieA `extent to fly-Wheel seasonal demand. In Winter when gasoline demand is low (storage may be for a longer period) and extra burner fuel is needed, a wider-boiling, range (i.e., more gasoline) can be charged to the polymerization process, increasing gasoline stability to allow. for slower movement, decreasing amount of gasoline, and increasing burner fuel production.

The heavy, deolefinized, cracked gasoline is catalytically reformed along with straight run and naturalusingV conventional platinum-type catalyst and hydrogen at 2,00 to 900 p,s.i.g., and 850 to 950 F., to produce a highf. octane product.

The light cracked gasoline formed in thefractionation step can be further fractionated Where necessary to produce a material which will lead to octane number with 3 ml. TEL. This `was not done in the example because the gasoline was somewhat deficient in light ends.l Choice of end point depends on composition of the cracked gasoline available. Normally, hydrocarbons boiling up to 175V to 195 F. may be included. In many cases 190 F. is a good cut point. Amount depends largelyon the normal-hexane content of the gasoline. The more nhexane, the lower the cut point must be.

Intermediate cracked'gasoline contains olensmainly in the heptene and octene rangewith some nonenes. These may be fed to the alkylation unit with regular renery olens, such as propylene and butylenes, giving good yields of gasoline boiling-range materials. Materials boiling above. 400 F. produced from this alkylationstepmay; be used in .manufacture of low-odorsolvents or may go to highquality jet fuel.

Processing-may be balanced to make the total refineryI gasoline high octane number. For example, if 100 octane` gasoline may be polymerization treated and catalytica'lly reformed (along with straight run) to give 97 to 98 octane number (Res.) with 3 ml. TEL. The alkylation unit is operated at high isobutane to olefin ratio to produce material having 102 to 105 octane (Res.) with 3 ml. TEL. The gasoline produced in this manner is also very clean burning, consisting mainly of light olefns, heavier aromatics, and isoparains.

Certain modications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A process for producing high octane motor fuel which comprises fractionating a cracked gasoline into a light, an intermediate, and a heavy gasoline fraction; subjecting said heavy fraction to catalytic polymerization at a temperature in the range of 425 to 625 F., a pressure in the range of 400 to 600 p.s.i.g., and a space velocity in the range of 2.5 to 3.0 v./v./hr., so as to polymerize the major portion of the olens present; fractionating the eluent from said polymerization to recover an overhead gasoline fraction having an end point of about 400 F. and a bottoms fraction comprising heavy polymerized materials; catalytically reforming said overhead gasoline fraction in contact with a platinum-containing reforming catalyst and in admixture with hydrogen at a temperature in the range of 850 to 950 F. anda pressure in the range of 200 to 900 p.s.i.g. so as to produce a high octane reformate; subjecting said intermediate gasoline fraction in admixture with C3-C4 isoparans and added C3-C5 olefins to HF alkylation at a temperature in the range of 50 to 120 F., a pressure sufficient to maintain liquid phase, and a reaction time in the range of 2 to 20 minutes; fractionating the resulting alkylate to recover an overhead gasoline fraction having an end point not substantially above 400 F.; and blending the alkylate overhead fraction with said reformate to produce a high octane blend motor fuel.

2. The process of claim 1 including the step of blending said light gasoline fraction with said alkylate overhead and said reformate.

3. The process of claim 1 wherein straight run and deisopentanized natural gasoline `are incorporated in the feed in the reforming step.

4. The process of claim 1 wherein said light gasoline fraction has an end point of about 190 F., said intermediate fraction has a boiling range of about 190 to about 300 F., and said heavy fraction has a boiling range of about 300 to about 400 F.

5. A process for producing high octane motor fuel which comprises subjecting a heavy cracked gasoline fraction to catalytic polymerization at a temperature in the range of 425 to 625 F., a pressure in the range of 400 to 600 p.s.i.g., and a space velocity in the range of 2.5 to 3.0 v./v./hr., so as to polymerize the more reactive components of said fraction to fuel suitable for burner fuel; fractionating the etlluent from said polymerization to recover an overhead gasoline fraction having an end point of about 400 F. and a bottoms fraction comprising polymer-ized material from the polymerization step; cata lytically reforming said overhead gasoline fraction in admixture with at least one gasoline of the group con sisting of straight run and natural so as to` improve the octane rating thereof; catalytically alkylating an alkylatable mixture comprising C4-C5 isoparains and C3-C5 olens; fractionating the resulting alkylate to recover a gasoline fraction of high octane number; and blending last said fraction with at least a portion of the reformed gaso line to produce a high octane motor fuel.

6. A process for producing high octane motor fuel which comprises fractionating `a cracked gasoline and recovering a light overhead fraction having an end point in the range of about 275 to about 310 F. and a bottoms fraction; catalytically polymerizing said bottoms.` fraction to substantially free same of olens; catalytically reforming the effluent from said polymerizing together with at least one gasoline of the group straight run and natural; fractionating said light overhead fraction into an overhead light gasoline fraction having an end point in the range of 175 to 195 F. and an intermediate ga-soline bottoms fraction; catalytically alkylating said intermediate gasoline fraction with a C4-C5 isoparaflin; fractionating the resulting alkylate to recover an overhead gasoline fraction having an end point not substantially above 400 F.; and blending at least a portion of said light gasoline fraction and at least a portion of said overhead gasoline fraction with at least a portion of said reformate.

7. The process of claim 5 wherein n-butane and isopentane are blended with the reformate.

8. The process of claim 6 including the step of blending isopentane and n-butane with said fuel.

References Cited in the le of this patent UNITED STATES PATENTS 2,090,333 Osterstrom Aug. 17, 1937 2,371,355 Ross et al. Mar. 13, 1945 2,401,859 Clarke June 11, 1946 2,404,483 Frey July 23, 1946 2,700,013 Oblad Jan. 18, 1955 OTHER REFERENCES Sachanen: Chemical Constituents of Petroleum (1945), Reinhold Publishing Corporation, New York, page 253.

Claims (1)

1. A PROCESS FOR PRODUCING HIGH OCTANE MOTOR FUEL WHICH COMPRISES FRACTIONATING A CRAKED GASOLINE INTO A LIGHT , AND INTERMEDIATE,AND A HEAVY GASOLINE FRACTION; SUB JECTING SAID HEAVY FRACTION TO CATALYTIC POLYMERIZATION AT A TEMPERATURE IN THE RANGE OF 425 TO 625* F., A PRESSURE IN THE RANGE OF 400 TO 600 P.S.I.G., AND A SPACE VELOCITY IN THE RANGE OF 2.5 TO 3.0 V./V./HR., SO AS TO POLYMERIZE THE MAJOR PORTION OF THEOLEFINS PRESENT; FRACTIONATING THE EFFLUENT FROM SAID POLYMERIZATION TO RECOVER AN OVERHEAD GASOLINE FRACTION HAVING AN END POINT OF ABOUT 400* F. AND A BOTTOMS FRACTION COMPRISING HEAVY POLYMERIZED MATERIALS; CATALYTICALLY REFORMING SAID OVERHEAD GASOLINE FRACTION IN CONTACT WITH A PLATINUM-CONTAINING REFORMING CATALYST AND IN ADMIXTURE WITH HYDROGEN AT A TEMPERATURE IN THE RANGE OF 850 TO 950* F. AND A PRESSURE IN THE RANGE OF 200 TO 900 P.S.I.G. SO AS TO PRODUCE A HIGH OCTANE REFORMATE; SUBJECTING SAID INTERMEDIATE GASOLINE FRACTION IN ADMIXTURE WITH C3-C4 ISOPARAFFINS AND ADDED C3-C5 OLEFINS TO HF ALKYLATION AT A TEMPERATURE IN THE RANGE OF 50 TO 120 *F., A PRESSURE SUFFICIENT TO MAINTAIN LIQUID PHASE,

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