US3530060A

US3530060A - Gasoline manufacture

Info

Publication number: US3530060A
Application number: US787442A
Authority: US
Inventors: Robert D Offenhauer
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1968-12-30
Filing date: 1968-12-30
Publication date: 1970-09-22
Anticipated expiration: 1987-09-22

Description

United States Patent 3,530,060 GASOLINE MANUFACTURE Robert D. Difeuhauer, Pennington, N..l., assignor to Mobil Oil Corporation, a corporation of New York Filed Dec. 30, 1968, Ser. No. 787,442 Int. Cl. Cg 13/00 US. Cl. 208-60 10 Claims ABSTRACT OF THE DISCLOSURE The production of high octane gasoline from a hydrocarbon charge stock is maximized by fractionating the same to obtain a gasoline fraction (a), a catalytic cracking charge stock (b), and hydrocracking charge stock (c). Stock (c) is hydrocracked to form gasoline fraction (d) and isobutane which is dehydrogenated selectively to form a mixture of isobutene and isobutane suitable as an alkylation charge. The mixture is alkylated to high octane gasoline components and recovered isobutane is recycled for selective dehydrogenation.

This invention has to do with the manufacture of gasoline and, more particularly, with maximizing the production of high octane gasoline from a hydrocarbon charge stock.

In recent years, considerable attention has been focused upon pollution of air by a variety of chemicals. Among the chemicals singled out for attention are lead compounds alleged to be expelled into the atmosphere from automobile, bus and truck exhausts. Legislation has been prepared with lower tetraethyllead (TEL) and tetramethyllead (TML) contents of gasolines, and with even an absence of such compounds, with a view toward reducing the possibility of lead compounds passing from vehicle, internal combustion engines into the atmosphere. Since lead alkyls, and particularly TEL increase the octane number of fuels, it follows that any reduction in lead alkyl content will have to be remedied by including other high octane components in gasolines. Thus, a demand is created for alkylate and reformate components.

Another attack has been directed at volatile components in gasolines. Legislation in preparation calls for reducing gasoline volatility. One result is that normal butane and isobutane would be omitted or the quantities now in use would be decreased markedly. The normal butane so made available could be isomerized to isobutane. As a consequence, a substantial quantity of isobutane would be available.

Apart from such developments in the petroleum field,

the use of hydrocracking has increased substantially in recent years. One of the products obtained by hydrocracking of a variety of hydrocarbon stocks is isobutane. Thus, here again, a large quantity of isobutane has become available and, for economic refinery operation, it is obvious that some satisfactory use should be made of this hydrocarbon.

It is an object of the present invention, therefore, to provide a process for efficient utilization of isobutane and to maximize the production of high octane gasoline from a hydrocarbon charge stock.

ice

As contemplated herein, high octane gasolines are those having an octane rating of at least about (unleaded).

In accordance with the present invention, there is provided a process for producing high octane gasoline, which comprises:

1) Contacting a hydrocarbon charge consisting essentially of isobutane with a dehydrogenating catalyst at a temperature from about 700 F. to a higher temperature at which substantially no cracking occurs, whereby a portion of the isobutane is dehydrogenated to isobutene, and

'(2) Contacting the reaction product obtained in 1) with an alkylation catalyst under alkylating conditions to form said gasoline.

Another embodiment of the present invention is a process for producing high octane gasoline, which comprises:

(1) Contacting a gas oil with a hydrocracking catalyst under hydrocracking conditions whereby a reaction product containing isobutane and a gasoline fraction is formed;

(2) Separating said isobutane from the reaction product formed in (l);

(3) Contacting said isobutane with a dehydrogenating catalyst at a temperature from about 700 F. to a higher temperature at which substantially no cracking occurs, whereby a portion of the isobutane is dehydrogenated to isobutene, and

(4) Contacting the reaction product obtained in (3) with an alkylation catalyst under alkylation conditions to form said high octane gasoline.

A further embodiment of the invention involves a process for maximizin the production of a high octane gasoline from a hydrocarbon charge stock, which comprises:

(1) Fractionating said charge stock whereby a gasoline fraction (a), a catalytic cracking charge stock (b), and hydrocracking charge stock (c) are obtained,

(2) Contacting said stock (c) with a hydrocracking catalyst under hydrocracking conditions to form a gasoline fraction (d) and isobutane,

(3) Contacting said isobutane with a dehydrogenating catalyst at a temperature from about 700 F. to a higher temperature at which substantially no cracking occurs, whereby a portion of the isobutane is dehydrogenated to isobutane,

(4) Contacting the reaction producted obtained in 3) with an alkylation catalyst under alkylation conditions to form a high octane gasoline (e),

(5) Separating unreacted isobutane from the alkylation product obtained in (4) and recycling the unreacted isobutane to 3 (6) Combining said gasoline fractions (a) and (d) and contacting the combined fractions with a reforming catalyst under reforming conditions to form a reformate gasoline, and

(7) Combining the reformate gasoline obtained in (6) and said high octane gasoline (e).

In order to facilitate description of the process contemplated herein, reference is now made to the accompanying drawing, which shows a typical flow diagram of a preferred arrangement for practicing the invention. The

flow diagram serves to illustrate the invention and, in no sense, to limit it.

In the flow diagram, a hydrocarbon charge stock is passed through line to fractionator 1 1. A gaseous stream containing isobutane is removed from fractionator 11 through line 12, a gasoline fraction is removed through line 13, a gas oil suitable as cracking stock is removed through line 14, and a heavier gas oil suitable as hydrocracking stock is removed through line 15.

The heavier gas oil in line 15 is passed into a hydrocracking unit 16 together with hydrogen from line 17, wherein it is in contact with a suitable hydrocracking catalyst. Products obtained in unit 16 include an isobutane-rich fraction which is removed through line 18 and a gasoline fraction which is removed through line 19.

The isobutane-rich fraction is passed through line 18 into fractionator 20 such that isobutane is removed therefrom as an overhead stream, which is passed through line 21 to dehydrogenator 22. Normal butane present in the isobutane-rich fraction is removed from fractionator 20 through line 23 and is passed, for example, to an isomerization zone (not shown) for the production of additional isobutane.

In dehydrogenator 22, isobutane is in contact with a suitable dehydrogenation catalyst under conditions selected to provide a relatively minor proportion of isobutene and to avoid any substantial cracking of the isobutane charge. The dehydrogenator product is passed from dehydrogenator 22 through line 23 into flash tower or fractionator 24 in order to remove hydrogen from the product. The hydrogen is removed through line 25 and can be employed as described below.

Dehydrogenator product free of hydrogen is cooled in tower 24 and further cooling can be accomplished, as desired, by passing this product through line 26 and cooler 27. The cooled product is passed from tower 24 through line 28 into alkylator 29, wehrein it is in contact with a suitable alkylation catalyst. An alkylation product containing a substantial proportion of isooctane is formed in alkylator 29. The alkylation product is passed from 29 through line 30 to fractionator 31.

Isobutane in the alkylation product is removed therefrom in fractionator 31 and is recycled through line 32 to line 21 and dehydrogenator 22.

Purge line 33 is provided in conjunction with line 32 should it be necessary to remove contaiminants.

Alkylate predominating in isooctane is removed from fractionator 31 through line 34. As explained below, the alkylate is blended or combined with one or more gasoline fractions.

The cracking stock in line 14 is charged to cracking unit 35 wherein it is in contact with a suitable cracking catalyst. One product formed in unit 35 is a gasoline fraction which is removed therefrom through line 36. As shown, this gasoline fraction can be combined with the alkylate in line 34 and additional products as described below.

The straight run gasoline fraction in line 13 is combined with the hydrocracked gasoline in line 19 and is passed into reforming zone 37 wherein the combined gasoline fractions are in contact with a suitable reforming catalyst, preferably in the presence of hydrogen charged from line 38. Hydrogen in line 25 can be routed from fractionator 26 to line 38 to supply part of the hydrogen requirements of reformer 37. The reformate gasoline formed in zone 37 is removed thereform and is passed through line 39 to be combined with the gasoline in line 36, and with the alkylate in line 34. The combined products are removed through line 40.

A gaseous overhead product from zone 11 contains isobutane and isobutene, which may be present in substantially equal proportions or one or the other may predominate dependent upon the hydrocarbon charge in line 10 and/or upon the operating conditions maintained in fractionator 11. The gaseous product in line 12 is passed with an additional quantity of isobutane recycled from line 32 to line 41 to cooler 42, thence to line 43 and alkylator 44. The alkylation product formed in alkylator 44 is passed through line 45 to fractionator 46. Alkylate is removed from fractionator 46 through line 47 for combination with the gasoline fractions in line 36. Isobutane in the alkylation product in fractionator 46 is passed through overhead line 48 for recycle to line '12. As shown, a combined gasoline of high octane number can be removed from the system through line 40.

Should hydrogen be charged to dehydrogenator 22, it can be passed through line 49.

By way of illustration, 100 gallons of a hydrocarbon charge comprising a Mid-Continent crude is fractionated in fractionator 11 into 40 gallons of straight run gasoline fraction in

line

13, 31 gallons of light gas oil in

line

14, and 28 gallons of heavier gas oil and residuum in line 15. The straight run gasoline fraction has an octane number (unleaded) of about 38. The heavier gas oil is charged with hydrogen to hydrocracker '16, the hydrogen being charged at a molar hydrogen to hydrocarbon charge ratio of about 2:1 to :1. Hydrocracking conditions employed are those conventionally used in the art, for example:

Temperature, F. 400-950 Pressure, p.s.i.g -5000 Liquid hourly space velocity 0.1-10 H /hydrocarbon charge, molar 2-80 Similarly, conventional hydrocracking catalysts can be used, as those typified by cobalt molybdate on alumina, nickel-tungsten sulfide, and chromia on alumina.

Products obtained from the hydrocracking step include about 30 gallons of a gasoline fraction having an octane number (unleaded) of about 76, in line '19 and a quantity in line 18 corresponding to about 5.7 gallons of a C fraction comprising about 4.1 gallons of isobutane and about 1.6 gallons of normal butane.

The C fraction in line 18 is fractionated in fractionator 20, the isobutane recovered therefrom being charged to dehydrogenator 22 wherein it is in contact with a conventional dehydrogenation catalyst such as an oxide or sulfide of any metal of Group VIA of Mendeleefis Periodic Table, or mixture thereof. Typical of such catalysts are chromium sulfide, molybdenum sulfide and tungsten sulfide. Others include oxides and sulfides of Group VHI of said Periodic Table or mixture thereof, as illustrated by: the sulfides or iron, cobalt, nickel, palladium, platinum, rhodium, osmium and iridium. Still other catalysts include mixtures of the above oxides and sulfides of the metals of Group VIA and VIII of said Periodic Table, typified by mixtures of: nickel sulfide and tungsten sulfide; cobalt sulfide and molybdenum sulfide; and nickel sulfide and molybdenum sulfide. These metals can be deposited upon adsorbent carriers such as alumina, silica-alumina and silica-zirconia. The catalyst should have substantially no cracking activity and operating conditions are selected to avoid cracking of the C charge. Generally, less than about 1 percent by volume of the charge is cracked when in contact with such catalysts.

Operating conditions for dehydrogenator 22 are selective such that the product will contain isobutane and isobutene in a molar ratio suitable for an alkylation charge, as from about 3:1 to about 15:1 and preferably 7:1 to 10:1. Expressed in another manner, approximate ratios of 3:1 to 15:1 will correspond to approximate isobutene contents of 5-40 percent by volume, and preferred approximate ratios of 7 :1 to 10:1 will correspond to isobutene contents of 10-25 percent by volume. When hydrogen is not charged to zone 20, the temperature is maintained between about 700 F. and about 970 F. preferably 750- 900 F. When hydrogen is also charged to zone 20, particularly to extend catalyst life, the temperature will range from about 870 F. to about 1050 F., preferably 9201000 F. When hydrogen is charged, it is charged at a molar hydrogen to hydrocarbon charge ratio of about 2:1 to 10:1. Pressure can be atmospheric, subatmospheric or above atmospheric. In general, conversion of i-C to isobutene increases with lower pressures and decreases with higher pressures.

The dehydrogenation product obtained in dehydrogenator 22 contains a balance of isobutane and isobutene, as explained above, and is suitable for alkylation without modification. It is removed from dehydrogenator 22 through line 23 and is passed to fractionator 24 for removal of hydrogen therefrom via line 25. The hydrogenfree dehydrogenation product in line 26 is cooled in cooler 27 and is passed through line 28 into alkylator 29. The cooled product is in contact in alkylator 29 with a conventional alkylation catalyst such as hydrogen fluoride, sulfuric acid and aluminum chloride. Conventional alkylation conditions are employed such as those for HF alkylation, namely: 150 F.; pressures at least sufliciently high to keep the C hydrocarbons and HF in the liquid phase; HF :hydrocarbon of at least 1:1 reaction time, 1-60 minutes; and HF titratable acidity of 7090 percent by weight.

The alkylation product is passed from alkylator 29 through line 30 to fractionator 31. Approximately 1.2 gallons of alkylate, predominately isooctane, are recovered through line 34 and approximately 2.9 gallons of isobutane are removed from fractionator 31 through line 32. The isobutane in line 32 is recycled to line 21 to extinction in dehydrogenator 22 thereby providing about 4 gallons of alkylate. A portion of the isobutane in line 32 can also be passed through line 41 to alkylator 44 to provide a part of the isobutane required therein.

Returning to fractionator 11, the quantity (31 gallons) of light gas oil in line 14 is passed to cracking unit 35 wherein it is cracked in the presence of a conventional cracking catalyst under customary cracking conditions. Fixed bed (e.g. Houdry), TCC and fluid processes are typical of those which can be employed. Since the catalysts and operating conditions are well-known in the art, reference is made to the literature and patents which are available. As shown in the flow diagram, a gasoline fraction comprising about 16 gallons and having an octane number (unleaded) of about 89.3, is removed from unit 35 through line 36 and is combined with the reformate in line 39.

The reformate in line 39 is obtained by combining the 40 gallons of straight run gasoline fraction (octane number, 38) in line 13 with the 30 gallons of hydrocracked gasolin (octane number, 76) in line 19, and charging the combined gasolines to reformer 37. In 37, they are in contact with a typical reforming catalyst under customary reforming conditions. Suitable catalysts are platinum group metals with or without a halogen, particularly chlorine. Reforming conditions are typified by and include: 500-1200 p.s.i.g., 900980 F., and liquid hourly space velocity of 0.5-3. As shown, hydrogen can be charged from line 38 to reformer 37. The reformate product comprises about 55 gallons and has an octane number of about 89.7. It is removed from reformer 37 through line 39 for combination with gasoline in line 36 and alkylate in line 34.

In accordance with this illustration, there is obtained aproximately 75 gallons of combined gasoline product in line 40 from the original gallons of hydrocarbon charge from line 10. The gasoline product in line 40 has an octane rating of about 90.2, in contrast to an octane rating of about 89.6 for the 71 gallons of gasolines combined from only lines 36 and 39.

It is to be understood that hydrocarbon charge stocks passed from line 10 to fractionator 11 can be crudes of parafiinic, naphthenic and other character, and can be topped or desalted crudes.

I claim:

1. In a process for producing high octane gasoline components wherein isobutane is dehydrogenated catalytically to form isobutene and the isobutene and isobutane are alkylated catalytically to form said gasoline components, the improvement which comprises:

(1) contacting a hydrocarbon charge consisting essentially of isobutane with a dehydrogenating catalyst at a temperature from about 700 F. to a higher temperature at which substantially no cracking occurs, whereby a portion of the isobutane is dehydrogenated to isobutene and the resulting iso-C dehydrogenation reaction product contains isobutane and isobutene in a molar ratio of from about 3:1 to about 15:1 of isobutane to isobutene, and

(2) contacting substantially all of the i-C reaction product obtained in 1) consisting essentially of isobutane and isobutene with an alkylation catalyst under alkylating conditions to form said gasoline components.

2. Process of claim 1 wherein unreacted isobutane is recovered from the alkylation product of (2) and is recycled to (1).

3. Process as defined by claim 1, wherein the temperature in (1) is from about 750 F. to about 900 F.

4. Process as defined by claim 1, wherein the isobutane is so contacted in (1) in the presence of hydrogen at a temperature of from about 870 F. to about 1050 F.

5. Process as defined by claim 4, wherein the temperature is from about 920 F. to about 1000 F.

6. In a process for producing high octane gasoline wherein a gas oil is contacted with a hydrocracking catalyst under hydrocracking conditions whereby a reaction product containing isobutane and a gasoline fraction is formed, wherein said isobutane is separated from said reaction product, and wherein said isobutane is dehydrogenated catalytically to form isobutane and the isobutene and isobutane are alkylated to form high octane gasoline components, the improvement which comprises:

(1) contacting said isobutane with a dehydrogenating catalyst at a temperature from about 700 F. to a higher temperature at which substantially no cracking occurs, whereby a portion of the isobutane is dehydrogenated to isobutene and the resulting iso- C dehydrogenation reaction product contains isobutane and isobutene in a molar ratio of from about 3:1 to about 15 :1 of isobutane to isobutene, and

(2) contacting substantially all of the i-C reaction product obtained in (1) consisting essentially of isobutane and isobutene with an alkylation catalyst under alkylation conditions to form high octane gasoline components.

7. Process of claim 6 wherein unreacted isobutane is recovered from the alkylation product of (2) and is recycled to 1).

8. Process of claim 6 wherein said gasoline fraction is recovered and is contacted with a reforming catalyst under reforming conditions to form a reformate gasoline.

9. Process of claim 8 wherein said reformate and said high octane gasoline are combined.

10. In a process for maximizing the production of high octane gasoline from a hydrocarbon charge stock, wherein said charge stock is fractionated to provide a gasoline fraction (a), a catalytic cracking charge stock (b) and hydrocracking charge stock (c), wherein stock (0) is contacted with a hydrocracking catalyst under hydrocracking conditions to form a gasoline fraction (d) and isobutane, and wherein said isobutane is dehydrogenated catalytically to form isobutane and the isobutene and isobutane are alkylated to form high octane gasoline components, the improvement which comprises:

(1) contacting said isobutane with a hydrogenating catalyst at a temperature from about 700 F. to a higher temperature at which substantially no cracking occurs, whereby a portion of the isobutane is dehydrogenated to isobutene and the resulting iso-C dehydrogenation reaction product contains isobutane and isobutene in a molar ratio of from about 3:1 to about 15:1 of isobutane to isobutene,

(2) contacting substantially all of the i-C reaction product obtained in (1) consisting essentially of isobutane and isobutene with an alkylation catalyst under alkylation conditions to form high octane gasoline components (e),

(3) separating unreacted. isobutane from the alkylation product obtained in (2) and recycling the unreacted isobutane to (1),

-(4) combining said gasoline fractions (a) and (d) and contacting the combined fractions with a reforming catalyst under reforming conditions to form a reformate gasoline, and

(5 combining the reformate gasoline obtained in (4) and said high octane gasoline components (e).

References Cited UNITED STATES PATENTS DELBERT E. GANTZ, Primary Examiner A. RIMENS, Assistant Examiner U.S. C1. X.R.

Patent No. 3,53 ,060

UNITED STATES PATENT OFFICE Dated September 97 Inventor(s) ROBERT D. OFFENHAUER It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

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