US3520798A - Hydrocracking process with controlled addition of sulfur - Google Patents

Description

United States Patent U.S. Cl. 20889 5 Claims ABSTRACT OF THE DISCLOSURE A hydrocracking process for the conversion of nitrogenfree heavier feed stocks to lower boiling materials utilizing a catalyst comprising a Group VIII noble metal on an acidic support and adding to the hydrocracking Zone a controlled amount of at least one sulfur compound which is soluble in said feed stock. Hydrorefining may precede the hydrocracking step.

This application is a continuation of U.S. application Ser. No. 132,550, filed Aug. 21, 1961 and now abandoned.

This invention relates to a process for hydrocracking of fractions of petroleum in the presence of a catalyst comprising a metal of the platinum and palladium series distended on a suitable acidic support. This series, in addition to these two metals, consists of ruthenium, rhodiums, osmium and iridium.

The objective of a hydrocracking operation using such a catalyst of the platinum and palladium series is to convert the charged oil to a lighter product (i.e., a product having a lower average molecular Weight) and especially to a product in which the gasoline fraction contains a substantial amount of branched chain hydrocarbons.

One problem that arises in carrying out the hydrocracking process results from the fact that most, if not all, petroleum charge stocks for this process contain nitrogen compounds which reduce the activity of the hydrocracking catalyst. Accordingly, it has been proposed to treat the charge stock to reduce its nitrogen content. This can be effectively accomplished by hydrogenating the charge stock in the presence of a hydrogenation catalyst and under conditions adapted to reduce the nitrogen content of the charge to less than 5 parts per million (p.p.m.) and preferably to less than one p.p.m.

While the hydrocracking stock is improved by the denitrogenation treatment, We have found the results obtained in the following hydrocracking step using a catalyst of the platinum and palladium series are not entirely satisfactory because the relative yields of branched chain hydrocarbons in the gasoline fraction are not as good as had been expected.

We have discovered in accordance with the invention that a high ratio of branched chain hydrocarbons to straight chain hydrocarbons in the gasoline fraction of a product resulting from hydrocracking a denitrogenated charge stock in the presence of a catalyst of the platinum and palladium series can be obtained by adding sulfur to the denitrogenated charge stock. We have also discovered that the addition of sulfur to the charge stock results in a naphtha fraction (boiling range210 to 350 F.),

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which has a greater content of cyclic hydrocarbons than when the sulfur is not added to the denitrogenated stock.

The sulfur may be incorporated in the charge stock in the form of a compound or compounds comprising this element. It has been found that treatment of the charge stock to remove nitrogen also removes sulfur compounds. The presence of sulfur in the reaction system is apparently necessary if a high ratio of branched chain hydrocarbons to straight chain hydrocarbons shall appear in the gasoline fraction of the product of the hydrocracking process and a higher yield of cyclic hydrocarbons in the naphtha fraction is obtained.

Accordingly, the process of the invention comprises denitrogenating a petroleum hydrocracking charge stock under conditions to reduce the nitrogen content of the change stock to less than 5 p.p.m., or better, to less than one p.p.m., thereafter incorporating sulfur in the charge stock and hydrocracking the sulfur-containing product.

In order that the invention may be understood more fully, there will be described an application of the process to a South Louisiana No. 2 fuel oil. This oil contained 28 p.p.m. of nitrogen which was reduced to 0.5 p.p.m. by hydrodenitrogenation. The catalyst employed in this operation comprised nickel and tungsten supported on an alumina base. The nickel and tungsten, as the metals, constituted 24 percent of the weight of the catalyst.

The following Table 1 sets out the process conditions of the denitrogenation of the fuel oil.

TABLE 1 Feed Pretreatment for Nitrogen Removal Charge Stock, South Louisiana No. 2 Fuel Oil Operating Conditions:

Temperature, F., 700

Pressure, p.s.i.g., 1,000 Space velocity, vol./hr./vol., 2.0 Hydrogen rate, s.c.f./bbl., 3,800 Hydrogen consumption, s.c.f./bbl., 215

Inspections Charge Product Gravity, API 36. 6 38. 5 Nitrogen, p.p.m 28. 0. Sulfur, p.p.m 800 10-12 Hydrocarbon Type, percent by vol Aromatics 21. 5 14. 2 Olefins 1.1 1.0 saturates 77. 4 84. 8 Mass Spectrometer Analysis:

lkanes 35. 2 Naphthenes 53. 6 Cycloparaifins 31. 5 Bicycloparaifin 22. 1 Aromatics 11.2 Distillation:

Overpoint, F 356 347 End Point, F 620 622 10% 42A 414 50% 500 494 588 588 Denitrogenatiou, percent by Weight of N in charge 98. 2 Desuifurization, percent by weight of S in charge 98. 7 Aromatics Saturation, percent by vol. of aromatics in charge 34. 0

fuel oil upon the products of a hydrocracking process. The hydrodenitrogenated stock was hydrocracked employing a palladium catalystin whilch the palladium was supported on a silica alumina catalyst containing 25 percent alumina and 75 percent silica by weight. The silica alumina support was made into inch tablets by conventional techniques. The tablets were then broken into -20 mesh size and calcined by heating in air in an electric mufile to 1000 F. in 6 hours and holding at this temperature for about 20 hours to 'burn out the lubricant and binder which had been added in forming the tablets. Palladium was deposited upon the carrier by dissolving palladium chloride in a solution of hydrochloric acid. The resulting solution contained the equivalent of 1.08 percent palladium by weight and 1.68 percent chlorine by weight. The silica alumina base was placed in a vessel, and the palladium solution was added to the vessel while stirring. The resulting wet material was dried at about 250 F. for 24 hours and calcined by heating in air in an electric muflle to 1000 F. in 6 hours and holding at this temperature for about 10 hours. The analysis of the finished catalyst was, palladium 0.99 percent by weight, chlorine 0.00 percent, and compacted bulk density 0.6 gram per cc.

The hydrocracking process was carried out as shown by the following Table 2. The sulfur added to the charge was added in the form of butyl mercaptan. There was a net consumption of hydrogen during the reaction.

The conditions for the hydrocracking step of the process are generally conventional and comprise temperatures in the range of 450 to 800 F. and preferably 550 to 750 F.; pressures of 500 to 2000 p.s.i.g. and preferably 700 to 1500 p.s.i.g.; space velocities of 0.1 to 10 and preferably 0.5 to 3; hydrogen circulation of 2000 to 20,000 cubic feet per barrel of charge and preferably 6000 to 10,000 cubic feet per barrel.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A hydrocracking process for converting a substantially nitrogen-free hydrocarbon feedstock containing aromatic hydrocarbons and boiling above the gasoline range to high-octane gasoline, which comprises subjecting said feedstock plus added hydrogen to catalytic hydrocracking at a pressure between about 500 and 2000 p.s.i.g., and a temperture between about 500 and 750 F. in contact with a Group VIII noble metal-containing hydrocracking catalyst, and maintaining during said contacting a concentration of hydrogen sulfide greater than about 0.01 millimole per mole of hydrogen.

2. A process as defined in claim 1 wherein said Group VIII noble metal is palladium.

TABLE 2.EFFECT OF SULFUR IN HYDROCRACKING Charge, Pretreated South Louisiana No. 2 Fuel Oil (N 1 p.p.m.) Conditions, 750 p.s.i.g., 625 F., 1 LHSV, 10,000 s.c.f. He/bbl.

Yield of naphtha:

Total butanes,

sulfur Millimoles Naphtha fraction 400 F.

present in of H28 Ratio of iso/n-parafiins (210350 F.) percent by Amount of sulfur added charge, per mole of naphthenes: vol. of to charge, p.p.m. p.p.m. hydrogen isO-Ca/n-Cr iso-C5/n-C iSOCE/H-CB percent by vol. charge From consideration of the data in Table 2, it is apparent that the addition of sulfur to the denitrogenated hydrocracking charge stock substantially increases the ratio of branched chain hydrocarbons to normal hydrocarbons in the gasoline fraction of the product of hydrocracking. Further, the naphthene content of the naphtha fraction is increased.

It will be understood that in carrying out the process of the invention it will be advisable to make tests to determine the optimum amount of sulfur to be added to the denitrogenated charge stock at hand. Our experiments have indicated that at least 30 p.p.m. of sulfur should be added to the hydrocracking charge stock. We have found, however, that best results are obtained when to 2500 p.p.m. of sulfur are added, and 5000 p.p.m. of sulfur are effective.

Although the hydrocracking charge stock employed in the example was a furnace oil, it will be apparent to those skilled in the art that other nitrogen-containing petroleum oils can be improved as charge stocks for hydrocracking processes by removing nitrogen and thereafter adding sulfur to the denitrogenated product. By way of example, suitable hydrocracking charge stocks include oils which are employed as charge to a conventional catalytic cracking unit, light and heavy distillate oils, and residual oils.

In carrying out the hydrodenitrogenation step of our process, it will be understood that the process conditions can be varied depending upon the charge stock. However, in general the conditions should comprise temperatures within the range of 550 to 750 F. and preferably within the range of 600 to 700 F.; pressures of 200 to 5000 p.s.i.g.; space velocities (LHSV) vol./hr./vol. in the range of about 0.5 to 1.0, and hydrogen circulation of 1000 to 20,000 cubic feet per barrel of charge.

3. The process of catalytically hydrocracking a feed stock selected from a member of the group consisting of No. 2 fuel oil and heavier petroleum fractions which contain nitrogen and sulfur, in the presence of a hydrocracking catalyst composited with a member of the group consisting of platinum and palladium, wherein the nitrogen tends to deactivate the hydrocracking catalyst, which process comprises subjecting said feed stock to an hydrogenation pretreatment to reduce the nitrogen content of said feed stock while concomitantly removing sulfur from said feed stock, thereafter adding in an amount between about 30 and 250 p.p.m. to said feed stock which is substantially free of nitrogen, at least one sulfur compound soluble in said feed stock, and hydrocracking said feed stock containing the added sulfur compound in the presence of said hydrocracking catalyst at a temperature of between about 450 and 800 F. and at a pressure between about 700 and 1500 p.s.i.g., the conditions of the reaction being selected to result in extensive hydrocracking and substantial consumption of hydrogen.

4. The process in accordance with claim 3 characterized in that the catalyst is palladium hydrocracking catalyst.

5. The process of catalytically hydrocracking a feed stock selected from a member of the group consisting of No. 2 fuel oil and heavier petroleum fractions which contain nitrogen and sulfur, in the presence of a hydrocracking catalyst comprising essentially a silica-alumina cracking catalyst composited with palladium wherein the nitrogen tends to deactivate the hydrocracking catalyst, which process comprises catalytically hydrogenating said feed stock under conditions to reduce the nitrogen content thereof to less than about 5 p.p.m. while con- References Cited comitantly removing sulfur from said feed stock, there- UNITED STATES PATENTS after adding in an amount between about 30 and 2500 2944 006 7/1960 Scott 9 p.p.m. to said pretreated feed stock, at least one sulfur 2911352 11/1959 zg zi 208 89 compound soluble in said feed stock, and hydrocracking 5 3099617 7/1963 Tuneners 2()8 11() said feed stock containing the added sulfur o p in 5:g 10 1963 Engel 208 89 the presence of said hydrocracking catalyst at a tempera- 3,169,106 2/1965 Le Francois et al. 208111 ture of between about 450 and 800 F. and at a pressure between about 700 and 1500 p.s.i.g., the conditions of reac- THOMAS YOUNG Prlmary Examlner tion being selected to result in extensive hydrocracking and 10 US, Cl, X R substantial consumption of hydrogen. 208-111 mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,520, 798 Dated July 14, 1970 e fl Jonas Dedinas and William C. Starnes It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 49, "hydrocracking stock" should be -hydrocracking charge stock-.

Column 3 line 3, "in whilch" should be --in which-.

Column 4, line 54, claim 3 "30 to 250 p.p.m. should be pIpI I l an; (12.41am

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