US2982716A - Upgrading cracked gasoline - Google Patents

Description

May 2, 1961 R. A. FINDLAY UPGRADING cRAcKED GAsoLINE 2 Sheets-Sheet 1 Filed Oct. 2, 1958 2 Sheets-Sheet 2 Filed OOt. 2, 1958 sETTLER ACIDJ RECYCLE RAFF|NATE7 lsoBU TAM?J INVENTOR. R A FINQLAY A TTORNEKS i 2,982,716` Y. 'latented May 2,A 1961 n 2,982,116 Y UPGRADING ycreacion) GAsoLINE Robert A. Findlay, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Filed oef. z, 19ss, ser. No. 764,993

' 's Claims. (ci. 20s-7o) This invention relates to a method for upgrading cracked gasoline. In one `aspect the invention involves the processing of heavy cracked gasoline in a series of mutually inter-related steps to obtain a plurality of high quality fuel stocks. In a more specific aspect the invention involves a step in which isobutane is dehydrogenated to isobutene, isobutane is alkylated with isobutene to form synthetic octan, and heavy olens are hydrogenated to form valuable saturated hydrocarbons, all three reactions being elected simultaneously in the presence of an HF alkylation catalyst.

With thetrend of internal combustion engines requiring ever increasing octane number fuels for their operation, it is becoming increasingly apparent that future supergasolines must consist largely of isoparafns and aromatics because of the relatively high octane numbers of these line 5. The extract phase is Withdrawn through line 4 and passed to distillation zoner6 in which the extract hydrocarbons are separated from the solvent, which is recycled through line 17 to line 5. When the extraction solvent is the diethylene glycol monomethyl-ether mentioned, the extraction is usually effected at a temperature in the range from 80120 F., a solvent to feed Weight ratio in the range from :1 to 20:1 and a reflux ratio in the range from 3 to 5. Conditions will, of course, de-

1Q pend upon the particular feed and solvent used.

Other examples of applicable `solvents which can be mentioned are triethylene glycol, acetonitrile, diethylene glycol and sulfur dioxide.

The extract hydrocarbon passes from distillation zone 6 through line 7 and is an aromatic gasoline of high octane number.

components. The present process provides a method for more eciently converting a heavy cracked gasoline to high octane streams and other fuel products of high quality. f

It is an object of the invention to provide a process for converting heavy cracked `gasoline in a more efficient and economical manner to high quality fuel products. Other objects, as well as aspects and advantages, of the invention will become apparent from a study of the accompanying disclosure and drawing.

According to the invention there is provided an integrated process comprising thesteps of subjecting the gasoline to solvent extraction with a polar solvent to form a high octane aromatic gasoline extract stream and a raffinate stream; contacting the said railinate stream with an HF catalyst and isobutane and thereby dehydrogenating a portion of said isobutane to form isobutene and alkylating isobutane with said isobutene while at the same time hydrogenating the olens contained in the ratnate with hydrogen resulting from dehydrogenating of said isobutane, and recovering the products resulting from said contacting.

The invention will be better understood in connection with a description of the drawings, of which Figure 1 is a schematic flow diagram and Figure 2 is a ow diagram in more detail of zone 10 of Figure 1.

In the process of the invention the feed stock in line 1 is a heavy cracked gasoline which consists, sentially of gasoline boiling in the range from 260 F. to the end point of the gasoline boiling range, usually about 400 F., and which results from the thermal or catalytic cracking of gas oils or reduced crudes. Small amounts of materials boiling below 260.o F., say not more than l or 2 weight percent, can be present in the feed, but'these are not desirable for reasons to be discussed hereafter. According to the present invention, this vfeed stock is subjected to solvent extraction in zone 2. with a polar selective solvent, such as diethylene glycol monomethyl ether containing 5-20 weight percent water, to produce an extract aromatic gasoline stream containing substantially all 65 of the aromatics in the feed stream as extract and a raflnate stream containing most of the olenic hydrocarbons in the feed stream. These Yoleiinic hydrocarbons are mainly straight chain oleins and olens of low branching produced by cracking, with some cyclic olens. The cracked gasoline feed stock is fed through line 1 to extraction zone 2 countercurrent to the solvent entering Since it will contain some diolens it can be clay treated, if desired, for engine cleanliness. /The rallnate stream passes through line 3 to deoleinizeralkylator zone 10. 'Ihe olens in this stream contain 9 or more carbon atoms. It has been mentionedthat the feed stream in line 1 can contain a small percentage of materials boiling lower than 260 F. However, this is undesirable since this can result in lower boiling olens of 8 or fewerxcarbon atoms being present in zone 10. This is not desired because C8 and lower ole'ns alkylate more rapidly than the desired heavier olens, a reaction not desired in zone 10. An HF alkylation catalyst enters zone 10 through line 9, while isobutane is introduced to zone 10 through line 8. In this zone the C9 and heavier olelins promote the dehydrogenation of part of the isobutane to isobutene, acting as hydrogen acceptors, and becoming saturated in the process. Isobutane is then alkylated with the resulting isobutene to produce a high 5 quality alkylate, mainly 2,2,4-methylpentane containing a smaller amount of the other tri-methylpentanes. After the reaction in zone 10 excess isobutane is separated from the reaction products and is recycled from zone 10 to line 8 to be introduced to the reaction zone.

The reaction eluent from zone 10, minus the isobutane, passes rfrom .zone 10 through line 11 to zone 12 where it is fractionated into a plurality of cuts. From line 13 there is passed a cut containing a high proportion of synthetic octanes produced in the alkylation reaction and boiling up to about 250 F. Preferably, the end point of this cut is 240 F. in order to eliminate any small amount of methyl heptanes which can be present due to side reactions or due to a small amount of methyl heptanes in the original feed stock in line 1 should this feed stock not be sharply cut. The next cut is a saturated gasoline cut taken through line 14, with an end point of about 400 F. This cut contains the hydrogenated C9-{ parafnichydrocarbons produced in zone 10. It is an excellent feed to a catalytic reforming operation to produce further high octane gasoline since it is virtually sulfur-free and olefinfree and contains considerable amounts of naphthenes, employing methods and catalyst known to the art. The third cut passes from distillation zone 12 through line 15. This material is highly paraflnic since it vforms in the main by the small extent of unavoidable alkylation ofthe heavier olens, useful'as such as a high grade jet fuel, boiling mainly over 400 F. Alter.- natively, this cut can be processed by thermal reforming to form high octane motor fuel. l

The box 10 or'deolenizer-alkylator zone is shown in more detail in Figure 2. Zone 10 is the portion within the dotted lines, and lines 3, 8 and 11 are as previously described with respect to Figure 1. Rallinate in line3 is charged to reactor 18, while fresh isobutane in line 8 is introduced to reactor 18 together ywith recycle isobutane and some HF in line 19, through 1ine20. Reactor eilluent is withdrawn through line 21 to separator or phase separation z'oneZZ. The heavier acid phase is recycled' to the reactor through line 23, while the lighter hydrocarbon phase containing a small portion of the HF catalyst passes to the deisobutanizer 24 through line 25. y The conditions employed in thel reaction zone 18 are generally in the following ranges: temperatures $0- 1`0OVF.; contact time '3-2'0 minutes, pressure toV maintain liquidphase, liquid volume ratio of HF to hydroearbons :1:1 to 2:1, mol ratio of isobutaner charged to: olens charged 10:1 to 15 :1. The HF alkylation catalyst ideally contains as little water as possible, but amounts. up -to weight percent are operable, although it is preferred to operate using acid containing less than two weight percent water. Y

It will be seen that the processing scheme of the invention is highly advantageous when the ordinary operations necessary according to the prior art to upgrade a feed stream such as that of lines 3 and 8 are considered. Ordinarily, the isohutane would have to be d'ehydrogenated or cracked in order to produce isobutene for alkylation with isobutane. Then a separate Step would be required to alkylate isobutane with isobutene. A further separate step would also be required tohydrogenate the oletinic hydrocarbons in line 3 to produce a saturated hydrocarbon cut suitable for feed to a reforming zone. This would he an expensive step because of the high cost of hydrogen and of operation at high pressures and temperatures for the hydrogenation. Thus, the three steps of the invention, dehydrogenation, alkylation and hydrogenation, are combined in a, novel manner in deolelinizer-alkylator zone 10. By eliminating from zone essentially all olefinic materials of fewer carbon atoms than 9, the alkylation in the zone is almost entirely between isobutane and isohutene, thus avoiding undesired alkylation between isobutane and lower olens such as C5 to C8 olelins which alkylate rnuch more rapidly than C94- oleiins. There is thus avoided consumption of isobutane to form the less valuable and only moderately branched C9 to C12 paratiins which would otherwise be formed if these lower olens were present. On the other hand, the presence of the slowly alkylatable Cg-lolens promotes the dehydrogenation of a portion of the isobutane, thus enabling the isobutene to be formed in situ, and thereby promoting the alkylation of isobutane with isobutene. At the same time the CQ-loleins which are acting as hydrogen acceptors become saturated to form a valuable feed stream for catalytic reforming to produce more high octane gasoline.

Olens in gasoline resulting from cracking Vof a hydrocarbon feed stock are quite stable under the conditions existing in the deolenizer-alkylator zone and do not undergo appreciable scission to form lower oleiins. On the other hand, polymer gasoline or gasoline containing substantial amounts of oleiins resulting from the polymerization of lower oleiins, would be undesirable as feed stocks to the presentrprocess. polymer olens are relatively highly branched and would undergo scission to lower olens, and alkylation ofisobutane with these olens would result in substantial amounts of C5, C5 and C7 isoparatiins appearing in the product from the deolenizer-alkylator'zone.

Elimination of most aromatics from the feed stock to the reaction step of the process has another benecial result in reducing to a practically insigniiicant amount the formation of acid-soluble-oils in the reaction; that is, oils which are soluble in the HF acid phase andl must he eventually eliminated from the catalyst phase, as is well known in the art of HF alkylation. Attempts to treat a cracked gasoline without the preliminary extraction step have resulted in conversion of asr much as percent of the oleflns to acid-soluble-oils. The preextraction not only prevents this but yalso provides a high quality fuel, as previously discussed.

Thev followingtables summarize a speciiic example of This is because liquid -aeaarieA Y 4 the invention according to the process described with respect to Figures 1 and 2. i Feed (line 1): Heavy cnt `(2SC-400 F. boiling range) of catalytically cracked gasoline, lbs/hr. SolventaDiethylene glycol monoethyl ether containing 11 Weight percent Water. l Solvent to feed weight ratio 12.5:1

Reflux to feed weight ratio 3.8:1 Number of extraction stages 15 Rainate from extractor, lbs/hr. 205 Extract from extractor 311 Reaction temperature in 18, F. 90 Contact time in 18, minutes 6 Mol ratioisobutane in 20 to olefins in 3 12:1 Isobutane, fresh, lbst/hr. (linev 8) 126 HF 2% water), volumesper volume of hydrocarhoncharged to reactor 0.7:1 Products:

-Aviation alkylate (line 13), lbs./hr. 8l Hydrogenated ranate (line 14), lbs/hr. 170 Heavy naphtha (linelS), lbs/hr. 8O

Characterization of feed and products from extractor Feed Extract Rainate Gravities, API

ASTM Dern., F.: 39' 2 8 3 47 4 BP- 263 282 248 10%.. 279 293 270 20 286 299 262 30 298 312 283 357 372 342 370 383 354 383 395 368 Ei-:ii: iii i 32 Sulfur, wt. percent- :II-

Gum, mg'lloo m1.: 0. D55 0.090 0.012 Preformed 52 139. 2 0. 9

Octzie Nurlrbrs: 1 88 0. 5

- esearc 3 m TEL 93, 3

Motor +3 m1. TEL sa. e gig Characterization of products from deolenzer-alkylator ZOfle Aviation 1 Bydro- Heavy Alkylate genated N aphtha (line 13) Ranato (line 15) (line 14) Gravity, API ASTM Distn., F.: 6M 4&1 33' 5 IBP 171 5% 195 10 2(1 4 20... 211 30.- 215 40 217 50-- 219 60 221 70 223 80-- 226 90-- 232 95.- 248 EP, 250 SulfuLVWt. percent 0. 003 PONA Analysis, v01, percent:

Paraus Olens--. Naphthenes Arnmatine Octane Numbers:

Research +3 m1. 'PEL n loor -ll-B m1. TEL 7l. 2

o or c ear 94'. 0 Aviation- 91.6 1-0 clear 93. 6 l-C +45 ml. TEL..V 110; 8 Rich Rating, 4.0 ml. TEL.- 139 "1 75-85% trimethylpentanes.

As will be evident to those skilled in the art, various y modications of this invention can be made or followed in the light of the foregoing disclosure and discussion without departing from the spirit and scope of the disclosure or from the scope ofthe claims.

I claim:

1. An integrated process for producing a plurality of high quality fuel products which comprises the steps of subjecting a gasoline resulting from cracking of a hydrocarbon stock and boiling in the range above about 260 F. to solvent extraction with a polar solvent to form a high octane aromatic gasoline extract containing substantially all of the aromatics in the feed and a rafiinate containing most of the oleiinic hydrocarbons in the feed; contacting the said rainate with an HF catalyst and isobutane at a temperature in the range from 80 to 100 F., a contacting time from 3-20 minutes, and using `a liquid volume ratio of HF to hydrocarbons in the range from 0.1:1 to 2:1 and a mole ratio of isobutane charged to oleiins charged in the range from :1 to 15:1, and thereby in said contacting step dehydrogenating a portion of said isobutane to form isobutene and alkylating isobutane with said isobutene While at the same time hydrogenating the olens contained in the ratlnate with hydrogen resulting from dehydrogenating of said isobutane in said contacting step, and recovering the products resulting from said contacting.

2. Process of claim 1 wherein the products are recovered and separated by removing unreacted isobutane and catalyst from the effluent from said contacting step and then separating the remaining eiuent into a first gasoline boiling range cutboiling up to about 250 F., a second cut boiling in the range from about 250 F. to about 400 F., and a thirdcut higher boiling than said second cut.`

3. Process of claim 1 wherein the products are recovered and separated by removing unreacted isobutane and catalyst from the ei-liuent from said contacting step and then separating the remaining eiuent into a irst gasoline boiling range out boiling up to about 240 F., a second cut boiling in the range from about 240 F. to about 400 F., and a third cut higher boiling than said second cut.

References Cited in the le of this patent

Claims (1)

1. AN INTEGRATED PROCESS FOR PRODUCING A PLURALITY OF HIGH QUALITY FUEL PRODUCTS WHICH COMPRISES THE STEPS OF SUBJECTING A GASOLINE RESULTING FROM CRACKING OF A HYDROCARBON STOCK AND BOILING IN THE RANGE ABOVE ABOUT 260* F. TO SOLVENT EXTRACTION WITH A POLAR SOLVENT TO FORM A HIGH OCTANE AROMATIC GASOLINE EXTRACT CONTAINING SUBSTANTIALLY ALL OF THE AROMATICS IN THE FEED AND A RAFFINATE CONTAINING MOST OF THE OLEFINIC HYDROCARBONS IN THE FEED; CONTACTING THE SAID RAFFINATE WITH AN HF CATALYST AND ISOBUTANE AT A TEMPERATURE IN THE RANGE FROM 80 TO 100* F., A CONTACTING TIME FROM 3-20 MINUTES, AND USING A LIQUID VOLUME RATIO OF HF TO HYDROCARBONS IN THE RANGE FROM 0.1:1 TO 2:1 AND A MOLE RATIO OF ISOBUTANE CHARGED TO OLEFINS CHARGED IN THE RANGE FROM 10:1 TO 15:1, AND THEREBY IN SAID CONTACTING STEP DEHYDROGENATING A PORTION OF SAID ISOBUTANE TO FORM ISOBUTENE AND ALKYLATING ISOBUTANE WITH SAID ISOBUTENE WHILE AT THE SAME TIME HYDROGENATING THE OLEFINS CONTAINED IN THE RAFFINATE WITH HYDROGEN RESULTING FROM DEHYDROGENATING OF SAID ISOBUTANE IN SAID CONTACTING STEP, AND RECOVERING THE PRODUCTS RESULTING FROM SAID CONTACTING.

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