US2431243A - Conversion of hydrocarbon oils - Google Patents

Description

N 1947- B. s. GREENSFELDER ET AL 3 I CONVERSION OF HYDROCARBON OILS Filed Dec. 2, 1946 Cracking Feed Szparafion Zone Separation Zonz Hgdrogcna-i-ion Zonz jam/q Gasolinz; L

137 cai'algi'ic cmc king V Zone Szparafion Zone Exfmcfion Zone 20 v I 1 Fuel Diesel Olefinic Olzflnic Lower Oil Fu z\ Gasoline C705 Ohfins Eng 'Hwe'ar A++orncq: g}ZZ::

Patented Nov. 18, 1947 2,431,243 F ICE Y 2,431,243 CONVERSION or maocannoN-ops Bernard s. Greensfelder, omits, n we n.

Voec, Berkeley, and George M. Good, Albany, Calif., assignors to Shell Development Company, San Francisc Delaware 0, Calii'., a corporation of Application December 2, 1946, Serial No. 713,490

8 Claims.

This invention relates to a new and improved process for the production of anti-knock gasoline and other valuable products from hydrocarbon oils boiling above the gasoline boiling range.

In the past, many methods for the production of gasoline have been suggested in which gasoline of improved anti-knock rating is produced through the agency of catalytic cracking. However, in general, if the production of anti-knock gasoline is improved through the use of catalytic cracking, the production of Diesel fuel suffers both in quality and quantity. Also, if the catalytic cracking is carried out under conditions optimum for the production of quality gasoline, reduced amounts of valuable oleflns are produced. In practice it is usually necessary to strike a compromise between producing smaller amounts of gasoline of excellent anti-knock rating and producing a larger amount of gasoline of lesser antiknock rating. and also upon striking a compromise between producing gasoline at the expense of other valuable products and producing other valuable products at the expense of gasoline.

The process of the present invention allows considerable amounts of valuable products such in particular as olefinic gases, lower olefins and Diesel fuel of high octane number to be produced while at the same time producing excellent yields of gasoline of high anti-knock value. The excellent yields of these quality products are largely made possible through the action of, and at the expense of, relatively high boiling aromatic hydrocarbons. In the hitherto proposed processes, large amounts of highly aromatic gas oils of little value are produced. These are commonly blended with black oil or cracked residues and sold as fuel oil. In the process of the present invention, little of such products is formed.- Also, many of the hitherto proposed processes involving catalytic cracking give substantially saturated gasoline. This results in an unfavorable hydrogen balance. In the process of the present invention, an olefinic gasoline is produced and this allows greater production of other products.

In the broader, more general aspects of the process of the invention, the oil feed boiling above the gasoline boiling range (400 F.) is subjected to a catalytic cracking treatment under relatively severe conditions. The product is separated into a fraction of normally gaseous products, a light gasoline fraction, a heavy gasoline fraction, a reflux condensate heavier than gasoline and a higher boiling residue. This separation is usually done in two steps. The reflux condensate is subjected to a catalytic hydrogenation treatment under conditions to produce a minor amount of destructive hydrogenation. The hydrogenated reflux condensate is then combined with the heavy gasoline fraction, and the mixture is subjected to a second catalytic cracking treatment under less severe cracking conditions. The product from the second catalytic cracking treatment is then separated into a fraction of normally gaseous products, a gasoline fraction, a reflux condensate heavier than gasoline, and a higher boiling residue. The gasoline separated from the reaction product of the second catalytic cracking treatment is blended with an amount of the first-mentioned light gasoline fraction to produce a gasoline of suitable volatility.

The process will be explained in more detail and with certain modifications in connection with the attached fiow sheet.

The feed entering by line I is any hydrocarbon oil boiling above the gasoline boiling range. Petroleum gas oil is, for example, an excellent feed. However, other feeds such as vacuum flashed distillate or deasphaltized reduced crude may also be used. Although hydrocarbons in the gasoline boiling range are not desired in this feed, the presence of a small amount of hydrocarbons in this range can be tolerated. The process is particularly advantageous when the feed is from a naphthenic petroleum; also it is particularly advantageous when the petroleum contains large amounts of nitrogen bases and/or sulfur com pounds. Thus the process isparticularly advantageous for use with California and West Texas petroleum stocks.

The feed is passed to a catalytic cracking zone 2 where it is catalytically cracked under severe conditions. In general, catalytic cracking is carried out at temperatures between 750 F. and 950 F. at relatively low space velocities. In the process of the present invention, the catalytic cracking is preferably carried out at a temperature of at least 900 F. and preferably above 950 F., for example 1000 F. or even higher. When operating at temperatures above 1000 F., the method described in U. S. Patent No. 2,398,739 may be advantageously used. Otherwise any of the conventional cracking techniques or processes may be applied. The space velocity is also maintained lower than usual so as to produce a depth of cracking of at least 40% and preferably between 50% and (depth of cracking is defined as minus the percent of recovered oil boiling above 400 F). In this primary catalytic cracking step, any of the conventional cracking catalysts 'may be used.

7 While any of .the clay type catalysts (see U. S.

Patent No. 2,400,431) will give fair, to excellent results, it is to be pointed out that hardly any two of these cracking catalysts are equivalent. In catalytic cracking many reactions take place. It has been found that the various catalysts differ widely in their ability or tendency to catalyze one or more of these reactions in preference to others. A preferred catalyst is a silica-magnesia cracking catalyst (see, for example, U. 8. Patent No. 2,343,- 295). Another preferred catalyst is boric oxide supported on alumina (see U. S. Patent No. 2,407,- 918).

The cracking is carried out in the absence of added hydrogen, and preferably in the presence of steam at slightly elevated pressure, for example 1.1- atmospheres. Under these conditions, and especially when using a feed stock havinga nitrogen content of 0.2% or over, a large amount of valuable olefins, particularly butylenes and amylenes. is produced. The gasoline, although having a high anti-knock rating, is not of the best quality. However it is particularly amenable to the subsequent treatments of the process.

The total product from the catalytic cracking is passed by line 3 to a separation zone. This zone comprises a fractionation system. Here the product is separated into a fraction con. sisting of gasoline and gas, a reflux condensate boiling above the gasoline boiling range and a higher boiling residue. The higher boiling residue is withdrawn by line 6. The reflux condensate boiling from about 400 F. up to about 600 F. or 700 F. is withdrawn by line 5. The

gasoline and gas are passed by line 6 to a second separation zone I wherein they are separated into a gas which is withdrawn by line 8, a light gasoline fraction having a final boiling point between 200 F. and 300 F. which is withdrawn by line 9, and a heavy gasoline fraction having an initial boiling point between 200 F. and 300 F. and a final boiling point of about 400 F. which is withdrawn by line E0.

The reflux condensate is passed to a hydrogenation zone ll wherein it is treated with hydrogen in the presence of a sulf-active hydrogenation catalyst under'conditions to produce a minor amount of destructive hydrogenation. The destructive hydrogenation should be carried out to such an extent that about 25% or somewhat less of the feed is converted into hydrocarbons of the gasoline boiling range. The hydrogenation is otherwise carried out with the conventional catalysts under the conventional conditions.

The product from the hydrogenation treatment is commingled with the described heavy gasoline fraction from line In and the mixture is passed to a second catalytic cracking zone l3. The cracking conditions in catalytic cracking zone I3 are conventional and preferably less severe than in catalytic cracking zone 2. Thus, the temperature is preferably in the common catalytic cracking range ('750-950 F). Here again any of the clay type cracking catalysts may be used. However, due to the diiIerence in the catalytic behaviors of the various catalysts, it is advantageous to utilize a different catalyst in the two zones. While the use of any two difierent catalysts will give some advantage, some combinations of catalysts are better than others. Particularly suitable combinations are, for example, silica-magnesia and acid-treated clay (F'lltrol), borlc oxide-alumina and acidtreated clay (Filtrol), boric oxide-alumina and silica-alumina, boric oxide-alumina and silicamagnesia, acid-treated clay (Filtrol) and activated carbon, activated carbon and silicaalumina, silica-magnesia and activated carbon, boric oxide-alumina and activated carbon. With these combinations there is little tendency for refractory hydrocarbon types to accumulate in the system.

The product from the second catalytic cracking 4 treatment is passed by line [4 to a separation zone I 5 wherein it is separated by conventional methods into a gas fraction which is withdrawn by line IS, a gasoline fraction which is withdrawn y line an intermediate oil fraction (reflux condensate) withdrawn by line l8, and a heavy higher boiling residue which is withdrawn by line I9. The gaseous fractions from lines 8 and i6 may be combined. This gas may be utilized to produce high octane fuel components by polymerization or alkylation or may be employed for chemical synthesis such as the production oi butadiene, alcohol, etc. 9 is blended with the gasoline in line i! to produce an oleflnic gasoline of suitable volatility. Any excess of the light gasoline fraction beyond that required to produce the required volatility may be withdrawn by line 20; this material constitutes an excellent source of valuable oleflns for chemical synthesis, for example, the production of alcohols by the 0x0 process. The heavy residues of lines 4 and [9 may be combined. This .product is a superior quality fuel oil. It may be used as such or may be blended with inferior or under-grade material to make a salable fuel oil.

The character of the intermediate fraction (reflux condensate) withdrawn by line l8 may vary considerably. In some cases it may be very aromatic in nature. In such cases it is most advantageously combined with the first reflux condensate by lines 24 and 12. In other cases it may contain sizable amounts of parafllnic hydrocarbons. In such cases it may be advantageously passed to an extraction zone 22. Here the fraction, or a portion of it, is separated into two fractions, namely a hydrogen-rich fraction (raffinate) and a hydrogen-poor fraction (extract) by solvent extraction. The hydrogen-poor fraction is preferably withdrawn by line l2 and combined with the first reflux condensate. The raflinate fraction may be advantageously cycled to the first cracking step by lines 25 and 2|. However, this raffinate fraction is an excellent Diesel iuel and may in most cases be more advantageously withdrawn by line 23. In still other cases the reflux condensate withdrawn by line l8 may contain sizable amounts of naphthenic hydrocarbons. In such cases it is usually more advantageous to combine it directly with the feed to the first cracking step by lines 26 and 2| or, if desired, to subject it to the described extraction step, in which case the railinate only is cycled to the first cracking step and the extract again sent by line l2 to the hydrogenation zone. .The character of this reflux condensate from the second cracking step depends primarily upon the conditions, and especially the catalysts, employedin the two cracking treatments.

A typical application of the process is as follows:

The feed stock is a vacuum flashed distillate (from a California petroleum) having the following inspection:

Gravity, A. P. I 25.2 Viscosity, S. S. U. at 100 F Sulfur, w 1.0

Nitrogen, w 0.25

The gasoline from line Catalyst: 60% synthetic silica-alumina. and 40% Super Filtrol.

The product is separated into fractions as follows:

Percent weight Gas frac 25.3 Light gasoline 14.5 Heavy gasoline 18,7 Reflux condensate 17.6 Bottoms 14.9 Coke 9.0

The inspections of these fractions are as follows:

Gas fraction Percent weight HzS 1.7

H2 0.6 CH4 13.0

CzH4 6.6 CzHe 12.7 CaHs 22.5 C3Hs. 10.0 iC4Hs 9.3

n-Cd-Is 13.3 i--C4H1o 7.2 n-C4Hl0 3.1

Heavy gasoline fraction Gravity, A. P. I 35.5 Sulfur, wt 0.50 Bromine No., g./ 100 g 63 Blending octane No., F-Z 84 A. S. T. M. distn., F.:

I.B.P 250 10% 272 50% 316 90% 381 F. B, P 418 Light gasoline fraction Gravit, A. P. I 74.4 Sulfur, w 0.08 Bromine No. g./100 g. olefins about 181 Blending octane No.,F-2 84 A. S. T. M. distn., F.:

I. B. P 96 10% 111 50% 1 133 182 F. B. P 209 Reflux condensate Gravity, A. P. I 22.1 Viscosity, S. S. U. at F 36 Sulfur, w 0.80 A. S. T. M. distn., F.:

1. B. P 413 10% 450 50% 515 90% 596 F. B. P 662 The reflux condensateis subjected to hydrogenation under the ioll owing conditions:

Catalyst: Tungsten-"nickel ulfide. Temperature: 720 F. Pressure: 1000 p. s. i. g..

Throughput: 2.0 L. H. S. V. hydrogen to oil mol ratio: 10.

About 10% of the charge is converted into hydrocarbons boil-ing in the gasoline boiling range.

The product from the hydrogenation treatment is blended with the above-mentioned heavy gasoline and the mixture is subjected to catalytic cracking under the following conditions:

Reactor temperature, "F 850 Weight hourly space velocity 1.0 Catalyst/oil weight ratio 15 Reactor pressure, top, p. s. i. g 10 Catalyst Synthetic silica-alumina The product is separated into fractions as follows:

This gasoline is blended with the above-mentioned light gasoline to produce a gasoline having suitable volatility characteristics. Excess light gasoline may be used as a source of lower olefins.

The yield of gasoline may be increased by combining the second reflux condensate with the flashed distillate feed to the first catalytic cracking step. This reflux condensate is of a different character than the first reflux condensate and is amenable to catalytic cracking.

Also the yield of gasoline may be increased and Diesel fuel of good quality may be produced by extracting this second reflux condensate and returning the extract to the hydrogenation zone.

It may alternately be advantageous to extract only a portion of the reflux condensate (preferably a portion having the boiling range of the desired Diesel oil) and to cycle the remainder to the first catalytic cracking step, which simplifies the extraction treatment. If a catalyst which is more or less selective for the cracking of paraflin hydrocarbons (as for example boric oxide-alumina catalyst or activated carbon) were applied in the second catalytic cracking step, it would be more advantageous to either cycle the raffinate to the first cracking step or to cycle the reflux condensate without extraction to the first cracking step. On the other hand, if the conditions and catalyst in the second cracking step were such as to produce a reflux condensate of highly aromatic character, the reflux condensate would advantageously be combined with the first reflux condensate.

Most of theprocesses involving two or more catalytic treatments which have been heretofore proposed are designed to produce a gasoline containing little or no olefins which is suited for use in aviation gasoline. The gasoline produced in the present process is an olefinic gasoline usually having a bromine number of at least 80. It is eminently suited as so-called motor gasoline.

The invention claimed is:

1. Process for the conversion of hydrocarbon oils boiling. above the gasoline boiling range into anti-knock gasoline and other valuable products which comprises subjecting said oil to catalytic cracking with a clay type cracking catalyst at a temperature above 950 F. for a time to effect 7 a depth of cracking between 50% and 75%, separating the resulting reaction mixture into a fraction of normally gaseous products, a light gasoline fraction having an end point between 200 F. and 300 F., a heavy gasoline fraction having second catalytic cracking treatment with a clay type cracking catalyst at a temperature between 750 F. and 950 F., separating the resulting product from said second catalytic cracking treatment into a fraction of normally gaseous products, a gasoline fraction and a reflux condensate heavier than gasoline, and combining said latter gasoline fraction with such an amount 01 the above-mentioned light gasoline fraction to produce an olefinic gasoline of suitable volatility.

2. Process according to claim 1 in which the hydrocarbon oil has a nitrogen content of at least 0.2%.

3. Process for the conversion of hydrocarbon oils boiling above the gasoline boiling range into anti-knock gasoline and other valuable products which comprises subjecting said oil to catalytic cracking with a clay type cracking catalyst at a temperature above 950 F. for a time to eflect a depth of cracking between 50% and 75%, separating the resulting reaction mixture into a fraction of normally gaseous products, a light gasoline traction having an end point between 200 F. and 300 F., a heavy gasoline fraction having an initial boiling point between 200 F. and 300 F., a first reflux condensate heavier than gasoline, and a higher boiling residue, combining said reflux condensate with an aromatic extract produced as hereinafter specified and subjecting the mixture to catalytic hydrogenation with a sulfactive hydrogenation catalyst under conditions to aflord a minor amount less than 25% 01! destructive hydrogenation, combining the hydrogenated reflux condensate with said heavy gasoline IIEC? I tion and subjecting the mixture to a second catalytic cracking treatment with a clay type cracking catalyst at a temperature between 750 F. and 950 F., separating the resulting product from said second catalytic cracking treatment into a fraction of normally gaseous products, a gasoline fraction and a second reflux condensate heavier than gasoline, separating from said second reflux condensate an aromatic extract. combining said aromatic extract with said first reflux condensate, and combining said latter gasoline fraction with such an amount or the above-mentioned light gasoline fraction to produce an oleflnic gasoline of suitable volatility.

4. Process for the the conversion of hydrocarbon oils boiling-above the gasoline boiling range into anti-knock gasoline and other valuable products which comprises subjecting said oil in admixture with reflux condensate rafllnate produced as hereinafter specified to catalytic cracking with a first clay type cracking catalyst at a temperature above 950 F. for a time to eflect a depth of cracking between and 75%, separating the resulting reaction mixture into a fraction of normally gaseous products, a light gasoline fraction having an end point between 200 F. and 300 F., a heavy gasoline traction having an initial boiling point between 200 F. and 300 F., a first reflux condensate heavier than gasoline, and a higher boiling residue, combining said reflux condensate with an aromatic extract produced as hereinafter specified and subjecting the 'mixture to catalytic hydrogenation with a sulf-active hydrogenation catalyst under conditions to afford a minor amount less than 25% of destructive hydrogenation, combining the hydrogenated reflux condensate with said heavy gasoline fraction and subjecting the mixture to a second catalytic cracking treatment with a second clay type cracking catalyst difierent than the first at a temperature between 750 and 950 F., separating the resulting product from said second catalytic cracking treatment into a fraction of normally gaseous products, a gasoline fraction and a second reflux condensate heavier than gasoline, separating from said second reflux condensate an aromatic extract, cornbining said aromatic extract with said first reflux condensate, subjecting the raflinate fraction of the second reflux condensate to catalytic cracking as above specified, and combining said latter gasoline fraction with such an amount of the above-mentioned light gasoline fraction to produce an oleflnic gasoline of suitable volatility.

5. Process for the conversion of hydrocarbon oils boiling above the gasoline boiling range into anti-knock gasoline and other valuable products which comprises subjecting said oil to catalytic cracking with a clay type cracking catalyst at a temperature above 950 F. for a time to effect a depth of cracking between 50% and 75%, separating the resulting reaction mixture into a frac tion of normally gaseous products, a light gasoof destructive hydrogenation, combining the hydrogenated reflux condensate with said heavy gasoline fraction and subjecting the mixture to a second catalytic cracking treatment with an activated carbon cracking catalyst at a temperature between 750 F. and 950 F., separating the resulting product from said second catalytic cracking treatment into a fraction of normally gaseous products, a gasoline fraction and a reflux condensate heavier than gasoline, and combining said latter gasoline fraction with such an amount of the above-mentioned light gasoline fraction to produce an oleflnic'gasoline of suitable volatility.

6. Process for the conversion f hydrocarbon oils boiling above the gasoline boiling range into anti-knock gasoline and other valuable products which comprises subjecting said oil to catalytic cracking with a first clay type cracking catalyst at a temperature above 950 F. for a time to efiect a depth of cracking between 50% and 75%, separating the resulting reaction mixture into a fraction of normally gaseous products, a light gasoline fraction having an end point between 200 F. and 300 F., a heavy gasoline fraction having an initial boiling point between 200 F, and 300 F., a reflux condensate heavier than gasoline, and a, higher boiling residue, subjecting said reflux condensate to catalytic hydrogenation with a sulf-active hydrogenation catalyst under conditions to afford a minor amount less than 25% of destructive hydrogenation, combining the 9 hydrogenated reflux condensate with said heavy gasoline fraction and subjecting the mixture to a second catalytic cracking treatment with a second clay type cracking catalyst different than the first at a temperature between 750 F. and 950 F., separating the resulting product from said second catalytic cracking treatment into a fraction of normally gaseous products, a gasoline fraction and a reflux condensate heavier than gasoline and combining said latter gasoline fraction with such an amount of the above-mentioned light gasoline fraction to produce an oleflnic gasoline of suitable volatility.

'7. Process for the conversion of hydrocarbon oils boiling above the gasoline boiling range into anti-knock gasoline and other valuable products hich comprises subjecting said oil in admixture with reflux condensate produced as hereinafter specified to catalytic cracking with a clay type cracking catalyst at a temperature above 950 F. for a time to efiect a depth of cracking between 50% and 75%, separating the resulting reaction mixture into a fraction of normally gaseous products, a light gasoline fraction having an end point between 200 F. and 300 F., a heavy gasoline fraction having an initial boiling point between 200 F. and 300 F., a reflux condensate heavier than gasoline, and a, higher boiling residue, subjecting said reflux condensate to eatalytic hydrogenation with. a sulf-active hydrogenation catalyst under conditions to afiord a minor amount less than 25% of destructive hydrogenation, combining the hydrogenated reflux condensate with said heavy gasoline fraction and subjecting the mixture to a second catalytic cracking treatment with a clay type cracking oatalyst at a temperature between 750 F. and 950 F., separating the resulting product from said second catalytic cracking treatment into a fraction of normally gaseous products, a gasoline fraction and a second reflux condensate heavier than gasoline, subjecting said second reflux condensate to catalytic cracking as above specified and combining said latter gasoline fraction with such an amount of the above-mentioned light gasoline fraction to produce an oleflnic gasoline of suitable volatility.

8. Process for the conversion of hydrocarbon oils boiling above the gasoline boiling range into anti-knock gasoline and other valuable products which comprises subjecting said oil to catalytic cracking with a clay type cracking catalyst at a temperature above 950 F. for a time to eflect a depth of cracking between 50% and 75%, separating the resulting product into a fraction of normally gaseous products, a light gasoline fraction having an end point between 200 F. and 300 F., a heavy gasoline fraction having an initial boiling point between 200 F. and 300 F., a reflux condensate heavier than gasoline, and a higher boiling residue, subjecting said reflux condensate in admixture with a second reflux condensate obtained as hereinafter specified to eatalytic hydrogenation with a sulf-active hydrogenation catalyst under conditions to afford a minor amount less than 25% of destructive hydrogenation, combining the hydrogenated product with the above-said heavy gasoline fraction and subjecting the mixture to a second catalytic cracking treatm with a clay type cracking catalyst at a temperature between 750 F. and 950 F., separating the resulting product from said second catalytic cracking treatment into a fraction of normally gaseous products, a gasoline fraction and a second reflux condensate heavier than gasoline, combining said second reflux condensate with said first reflux condensate, and

combining said latter gasoline fraction with such an amount of the above-mentioned light gasoline fraction to produce an oleflnic gasoline of suitable volatility.

BERNARD S. GREENSFELDER.

HERVEY H. VOGE.

GEORGE M. GOOD.

REFERENCES crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,342,983 Thomas Feb. 29, 1944 2,358,888 Thomas Sept. 26, 1944 2,398,846 Munday Apr. 23, 1946

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