US2890995A

US2890995A - Process for producing high octane motor fuels

Info

Publication number: US2890995A
Application number: US514867A
Authority: US
Inventors: Robert A Findlay
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1955-06-13
Filing date: 1955-06-13
Publication date: 1959-06-16
Anticipated expiration: 1976-06-16

Description

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Filed June 13, 1955 mio mjmaJow Q 9] INVENTR.

R'A. FINDLAY Hymn/,YM

PROCESS FOR PRODUCHNG HIGH OCTANE MOTOR FUELS IRobert A. Findlay, Bartlesville, Okla., Iassignor to Phillips Petroleum Company, a corporation of Delaware Application .lune 13, 1955, Serial No. 514,867

8 Claims. (Cl. 208-65) This invention relates to a process for upgrading light cracked gasoline stock to produce high octane motor fuels,

The need for conserving hydrocarbons normally boiling in the gasoline range and heavier cracking stocks from which gasoline is produced is becoming increasingly important in the petroleum industry. The increasing demand for high octane gasoline and the inching up of octane requirements in motor fuels is placing increasingly greater demands on our reserves of petroleum. One method of conserving the valuable heavier hydrocarbons from which gasoline is made comprises utilizing as large an amount of more abundant light hydrocarbons, such as butanes and natural gasoline, as it is possible to use in blending and incorporation in motor fuels. Obviously the high volatility of these llight hydrocarbons ordinarily places a rather low limit on the amount 'which may be incorporated in motor fuels. The present invention is concerned With a process which conserves the heavier hydrocarbons from which gasoline is formed and utilizes a greater proportion of light hydrocarbons in high octane motor fuel than has previously been used.

An object of the invention is to provide a process for increasing the yield off high octane gasoline from a feedstock comprising cracked gasoline. Another object is to provide a process for producing motor fuel Which utilizes increased amounts of such light hydrocarbons as n-butane, iso-butane, and natural gasoline and which conserves gasoline-boiling-range hydrocarbon stocks. Another object is to provide a process which provides extra heavy synthetic gasoline which permits blending with extra large amounts of natural gasoline and/or butane to produce high octane motor fuel. A further object is to provide a process for increasing the octane number of a gasoline stock. It is also an object of the invention to provide a process for utilizing deolefinized light cracked gasoline in high octane motor fuel. Other objects of the invention will become apparent upon consideration of the accompany-ing disclosure.

A broad aspect of the invention comprises fractionating a cracked gasoline stock into a light fraction comprising principally olens and a heavier bottoms fraction; mixing the light olelin fraction with at least one isoparaftin of the group isobutane and isopentane Iand catalytically alkylating `the same to produce a heavy alkylate comprising principally C9-C12 isoparaflins; separating the resulting alkylate into a substantially deolelinized light fraction and a heavier fraction containing the major portion of the C9C12 isoparains; and recovering the C9-C12 fraction as a blending stock which can be blended with relatively large amounts of lighter hydrocarbons, such as butane and natural gasoline. lnanother embodiment of the in vention the deolenized light gasoline fraction obtained from the alkylate is ,admixed with straight-run gasoline and/ or natural gasoline and Vthe resulting mixture is catalytically reformed by conventional methods to produce a reformate whichris then blended ywith the synthetic heavy gasoline fraction comprisingfCg-Cm isoparaffins to produce a premium grade motor fuel. In accordance with the invention, it is also feasible to blend the heavier bottoms fraction from the fractionation step used in sepai 2,890,995 Y Patented June 16, 1959 rating the cracked gasoline stock into a light olen fraction and a heavier fraction with the aforementioned components of Vtheblended fuel to produce a regular grade motor fuel.

More complete understanding of the invention may be had by reference to the accompanying drawing which is a schematic illustration of an arrangement of apparatus for effecting a preferred embodiment of the invention. A cracked gasoline stock from a conventional cracking process is introduced via line 10 to fractionator 12 for separation into two or more fractions, preferably an overhead fraction ranging from initial boiling point to about 250 F., more particularly, having an end point `-`in the range of 20D-250 F. and, preferably, about 210 F., and a bottoms fraction having a boiling range of 210- 400 F. This fractionator is operated at approximately atmospheric pressure with an overhead temperature in the range of 15S-175 F., preferably about 162 F., and a bottom temperature in the range `of 280-320 F., preferably about 305 F.

The overhead fraction, Which is high in oleins, is passed via line 14 to an alkylation reactor 16 Where it is mixed with a `large excess of isobutane to suppress alkylation of the aromatics and/ or cycloparaflins present in the olefin fraction. (lsopentane or a mixture of same with isobutane may be used.) The isobutane to olefin ratio is preferably at least 6:1 but may be in the range of 3:1 to 10:1 on a volume basis. The isobutane is supplied to alkylator 16 through line l from any suitable source such as from the isomerization of n-butane supplied to isomerization reactor 20 from 4line 22 by means of line 24, the isomerizate passing into line 18 via line 25. Isomerization reactor 2lb is operated in conventional manner well known in the art. The alkylation step effected in alkylator 16 utilizes a temperature in the range of 50- F., a pressure suflicient to maintain liquid phase, such as approximately p.s.i.g., a time in the range of 2-20 minutes, preferably about 10 minutes, and a catalyst comprising, preferably, HF of 85-95% concentration. Other alkylation catalysts, such as sulfuric acid, metal halides, etc., may be used. Acid soluble oils and acid are Withdrawn from alkylator 16 via line 26 for recovery and recycling of the acid or any other treatment or disposal which is desired.

Reactions taking place in alkylator 16 are complex. By hydrogen exchange a portion of the olelins` are saturated to the corresponding paraliins or naphthenes. This 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 olefins alkylates isobutane yto produce highly branched nonanes, decanes, undecanes, 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 16, after removal of isobutane, HF, and fluorides in conventional manner, is passed via line 2.8 to 'fractionator 30 for separation of the alkylate into a deolenized light gasoline fraction taken overhead and having a boiling range from the initial boiling point of the feed to about 205 F. The bottoms fraction comprises principally C9-C12 isoparaiiins and is a true synthetic gasoline fraction. Fractionator 30 is operated with a top temperature in the `range of Mtl-160 P. and preferably about 153 F. The bottom temperature is maintained in the range of about 27d-360 F. and, preferably, at about 285 F. This column is operated at approximately atmospheric pressure.

The overhead fraction from fractionator 30, compris- Table Feed to Deolen- Synthetic AJkylized Light Material ator 16 Product inline 46 in line 32 ASTM Dist. F):

IBP 147 100 220 156 132 251 162 153 285 174 178 312 EP-- 211 195 397 ASTM Octane No. Clear. 60. 4 91. 8

Parafns percent.. 8. 6 Naphthenes do-- 13. 2

s 73.0 0.07 0. 24 V5.2 i..-

ing a deolenized gasoline containing only paraiiins, naphthenes, and aromatics, is well suited for catalytic reforming and is passed via line 32 to a catalytic reforming reactor 34 which is provided with a suitable reforming catalyst, preferably, 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 reactor include platinum deposited on at least one metal oxide of the group alumina, magnesia, thoria, and zirconia containing chemically combined alkali metal (sodium); metal oxides or sulfdes of groups 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. The reaction conditions maintained in reforming reactor 34 include a temperature in the range of 880- 970 F. and a pressure in the range of 200-900 p.s.i.g. It has been found that removal of olens from the feed to the reforming zone has materially helped catalyst life.

The deolenized light gasoline fraction admitted through line 32 to reactor 34 is admixed with straightrun gasoline introduced via line 36 and it is also feasible to introduce natural gasoline to this reforming step via lines 38 and 39. The mixture of deolenized light cracked gasoline, straight run, and natural is catalytically reformed to produce a material which leads to 90-98 octane (depending on the naphthene and aromatic content). The synthetic gasoline from the alkylation step is normally 85-95 clear octane number and leads to the range of 105 to 113 octane with 3 ml. TEL. It thus provides an excellent blending stock for making high octane motor fuel of 100 octane or higher. The catalytic reformed gasoline leads to 90-98 octane With 3 m1. TEL depending on the naphthene-aromatic content of the straight run, natural, and of the deolefinized cracked gasoline and therefore can be used in 100 plus octane motor fuel. The heavier catalytically cracked fraction from fractionator 12 is of lower quality and can be blended with reformed, natural, and/ or straight-run gasoline, together with the synthetic gasoline recovered from the bottoms from fractionator 30 to produce regular gasoline of relatively high octane number.

The bottoms from fractionator 30 is passed via line 40 to a fractionator 42 where heavy ends are removed via line 44 as a bottoms fraction which can be utilized as burner fuel. The overhead fraction comprising principally C9-C12 isoparaflins is passed via line 46 to blending zone 48 where it is blended with one or more fractions from

lines

50, 38, 22, and 52, as desired, to produce premium motor fuel which is recovered via line 54 or regular motor fuel recovered via line 56,

In performing one phase of the invention the light fraction of a catalytically cracked gasoline obtained from line 14 was alkylated under the preferred conditions set forth for operating alkylation zone 16 and the alkylate was separated in column 30 as described. The data obtained from this operation are set forth in the table below.

It is significant that the light deoleiinized product from line 32 had an octane number of 60.4 and that the synthetic gasoline from line 46 had an octane No. of 91.8 (both clear). It can be seen, also, that the olefin concentration in line 14 is reduced from 73 to 0.07 in the deoleiinized stream and 0.24 in the synthetic product stream.

The process described has a number of important advantages as follows:

(l) It conserves natural resources by utilizing butane in motor fuel directly, both by dehydrogenating and then alkylating it and by alkylating it with C5, C6, and C1 oleiins.

(2) It conserves natural resources by making extra heavy synthetic gasoline of 200-400 F. boiling range which permits blending of extra large amounts of natural gasoline and/ or butane into motor fuels. .i

(3) It increases octane number by producing heavy synthetic isoparaffins in the 85-95 octane number (clear) range.

(4) It deolefinizes the light cracked gasoline so that it can be catalytically reformed to increase its octane number with increased catalyst life.

(5 It provides greater iiexibility whereby various types of light hydrocarbons may be utilized in blending in accordance with their availability.

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

I claim:

1. A process for producing motor fuel which cornprises fractionating a cracked gasoline stock to recover overhead a light fraction rich in oleiins and having an end point in the range of 200 to 250 F.; admixing at least one isoparafrin of the group consisting of isobutane and isopentane with the oleins in said light fraction in a volume ratio of isoparafiin to olens in the range of 3:1

to 10:1; alkylating the resulting mixture in liquid phase in contact with an alkylation catalyst to produce a substantial proportion of C9 to C12 isoparains; fractionating the alkylation efuent into an overhead fraction comprising deoleiinized light gasoline and a bottoms fraction comprising the major portion of said C9 to C12 isoparafns; recovering said C2 to C12 fraction catalytically reforming said overhead fraction comprising deolenized light gasoline; and blending resulting'reformate with said recovered C9 to C12 isoparafn fraction to produce high octane motor fuel.

2. The process of claim l wherein straight run gasoline is included in the feed to the reforming step.

3. The process of claim 2 wherein at least one of the group consisting of natural gasoline and n-butane is included in the blended motor fuel.

4. A process for producing motor fuel which comprises fractionating a cracked gasoline stock into an overhead olefin-rich fraction having an end point in the range of 200 to 250 F. and a bottoms fraction boiling in the range of 210 to 400 F.; catalytically alkylating isobutane with said olefin-rich fraction in liquid phase in an alkylating zone to which the volume ratio of isobutane to said olefin-rich fraction introduced is in the range of 3:1 to 10:1 using HF as a catalyst, a temperature in the range of 50 to 120 F., and a reaction time in the range of 2 to 20 minutes; fractionating the resulting alkylate into a substantially deolefinized overhead fraction containing isoheptanes and lighter hydrocarbons having an end point in the range of about 205 to 210 F., and a bottoms fraction comprising a synthetic gasoline containing the major portion of C9 to C12 isoprains in said alkylate; passing at least a portion of said deolefinized overhead fraction toa catalytic reforming Zone together Iwith straight runV gasoline and there reforming the resulting mixture in Contact with areforming catalyst at a temperature' in the range of 880 to 970 P. and a pressure in the range of 200 to 900 p.s.i.g.; blending resulting reformate with at least a portion of said C9 to C12 bottoms fraction to produce high octane motor fuel.

5. The process of claim 4 including the step of blending at least a portion of said bottoms fraction boiling in the range of 210 to 400 F. with said reformate and said C9 to C12 fraction.

6. The process of claim 5 wherein at least one of the group consisting of natural gasoline and n-butane is blended into the fuel.

7. The process of claim 4 including the step of blending with said fuel a substantial proportion of at least one of the group consisting of natural gasoline and nbutane.

8. The process of claim 4 wherein the alkylation catalyst comprises 85 to 95% HF and the reforming catalyst comprises platinum deposited on a halogen-containing cracking catalyst.

References Cited in the tile of this patent UNITED STATES PATENTS

Claims

4. A PROCESS FOR PRODUCING MOTOR FUEL WHICH COMPRISES FRACTIONATING A CRACKED GASOLINE STOCK INTO AN OVERHEAD OLEFIN-RICH FRACTION HAVING AN END POINT IN THE RANGE OF 200 TO 250*F. AND A BOTTOMS FRACTION BOILING IN THE RANGE OF 210 TO 400*F.; CATALYSTICALLY ALKYLATING ISOBUTANE WITH SAID OLEFIN-RICH FRACTION IN LIQUID PHASE IN AN ALKYLATING ZONE TO WHICH THE VOLUME RATIO OF ISOBUTANE TO SAID OLEFIN-RICH FRACTION INTRODUCED IS IN THE RANGE OF 3:1 TO 10:1 USING HF AS A CATALYST, A TEMPERATURE IN THE RANGE OF 50 TO 120*F., AND A REACTION TIME IN THE RANGE OF 2 TO 20 MINUTES; FRACTIONATING THE RESULTING ALKYLATE INTO A SUBSTANTIALLY DEOLEFINIZED OVERHEAD FRACTION CONTAINING ISOHEPTANES AND LIGHTER HYDROCARBONS HAVING AN END POINT IN THE RANGE OF ABOUT 205 TO 210*F., AND A BOTTOMS FRACTION COMPRISING A SYNTHETIC GASOLINE CONTAINING THE MAJOR PORTION OF C9 TO C12 ISOPRAFFINS IN SAID ALKYLATE; PASSING AT
8. THE PROCESS OF CLAIM 4 WHEREIN THE ALKYLATION CATALYST COMPRISES 85 TO 95% HF AND THE REFORMING CATALYST COMPRISES PLATINUM DEPOSITED ON A HALOGEN-CONTAINING CRACKING CATALYST.