US2965564A - Hydrodesulfurization and hydrogenation with platinum-eta alumina catalyst - Google Patents

Description

United States Patent HYDRODESULFURIZATION AND HYDROGENA- WITH PLATINUM-ETA ALUMINA CATA- i No Drawing. Filed Feb. 1, 1956, Ser. No. 562,660

4 Claims. (creas -217) This invention concerns a novel process for upgrading petroleum fractions boiling in the range of about 300 to 650 F. in a hydrogenation process by the selective hydrogenation of aromatic compounds. The invention is of particular application for processing virgin stocks, but is also applicable and of value in improving catalytically cracked stocks. While this selective hydrogenation of aromatic compounds is valuable for treatment of a number of stocks, this process is of particular value for improving the burning qualities of kerosene, diesel fuel, jet fuel, and fuels for gas turbines.

In accordance with this invention, petroleum fractions containing aromatic hydrocarbons boiling in the range of about 300 to 650 F. are hydrogenated at temperatures of about 500 to 675 F., a pressure of about 100 to 1,000 p.s.i.g., in the presence of about 2000 to 15,000 standard cubic feet of hydrogen per barrel of feed, preferably 5,000 to 8,000 standard cubic feet of hydrogen per barrel of feed, specifically employing a catalyst consisting of platinum supported on eta alumina. The invention resides in use of this particular catalyst at specific hydrogenation conditions with selected feed stocks so as to obtain unique product quality improvements. As indicated, while the invention is of value in the treatment of a variety of feed stocks, it will be described with particular reference to the treating of diesel fuels and kerosenes, including jet fuels and gas turbine fuels.

In the case of diesel fuels and kerosenes, for example, the ignition characteristics and burning characteristics respectively are of particular importance from the viewpoint of product quality. These characteristics are often controlling in refining operations, necessitating specific techniques for improving these properties of these stocks. Burning characteristics of a kerosene may be measured by smoke point tests which can readily be carried out by determining the height of flame obtainable at incipient smoking, With the aim being to obtain kerosenes having the highest values of smoke point. The ignition characteristics of diesel fuels which are pertinent to this inventtion can be determined by cetane number inspections. These properties of the fuels identified are each dependent on the aromatic content of the fuel. Thus, both kerosene and diesel fuels, which are highly aromatic, are normally deficient in the aforementioned characteristics. To a lesser degree, these characteristics are also related to, and affected by, the naphthene content of the fuel. For these reasons, the present invention is particularly aprange of about 300 to 650 F. containing at least and up to about 50% of aromatic hydrocarbons and having a naphthene ring content of less than about 30%. More specifically, the invention is of particular applicaplicable to petroleum fractions boiling within a boiling 2 tion to virgin kerosenes boiling in the range of about 300 to 500 F., and to virgin or cracked diesel fuels boiling in the range of 300 to 625 F. This process, is however, applicable but somewhat less efficiently, to feeds containing less than 10% and more than 50% of aromatic hydrocarbons.

In order to improve the burning properties of these fuels, it is necessary to hydrogenate selectively the aromatic compounds present. It is, of course, preferable to obtain complete conversion of all aromatic hydrocarbons, although conversions above about and particularly above 98% are effective for substantially upgradingthese fuels.

The present invention is based on the provision of a suitable process for the conversion of aromatic hydrocarbons present in such stocks as kerosenes and diesel fuels. covery of a catalyst and conditions for using this catalyst which attains the unique objectives which are involved in this problem. These and other features of the invention will be brought out in the description of the invenion which follows:

In order to establish the nature and advantages of this invention, reference will be made to some of the critcial features involved in upgrading kerosenes and diesel fuels. As a starting point, it must be appreciated that unusual problems are involved in providing a hydrogenation process suitable for hydrogenation of aromatic hydrocarbons while preventing other undesirable results such as hydrocracking. In this connection, in a first step of thestudy on which this invention is based, a wide variety of hydrogenation catalysts which have proved of value in other types of hydrogenation were evaluated for activity in hydrogenating aromatic compounds. In the specific tests referred to, a low sulfur kerosene derived from Sweden crude was employed. Standard hydrogenation conditions were selected for testing each of the catalysts, and theseconditions were a pressure of 800 p.s.i., a temperature of 600 F., and a throughput of 4 v./hr./v.

A commercially available cobalt molybdate alumina catalyst of the nature now used in commercial hydrofining operations was first tested. While this catalyst has excellent activity for conversion of sulfuf compounds, and for saturation of olefinic compounds, this catalyst was found to have no activity for the conversion of aromatic hydrocarbons under the conditions of this test. Other catalysts such as a commercially available platinum on alumina catalyst, a commercially available rhodium on alumina catalyst, and other experimental catalysts were found to have substantially no activity for the hydrogenation of aromatic nuclei. One catalyst found to have good activity for this purpose was a commercially available nickel catalyst supported on kieselguhr. However, this nickel catalyst exhibited rapid and serious deactivation in use.

As a result of such studies, it has been found that platinum supported on eta alumina exhibits unique properties for the hydrogenation of armoatics. The catalyst constitutes about 0.001 to 5% of platinum supported on the particular form of alumina known as eta alumina. As now known to the art, eta alumina may be produced by heating alumina beta trihydrate at temperatures of about 500 to 1400 F. In accordance with'this invention, this particular catalyst is used for treating petroleum fractions containing aromatic hydrocarbons.

A particular feature of the invention is the dis- The catalyst used in this invention may be prepared in the following manner.

One method of preparing eta alumina is to hydrolyze aluminum alcoholate with an aqueous solution containing ammonium hydroxide. The aluminum alcoholate may be prepared in any suitable manner. One method of preparation of aluminum alcoholate is given in Kiberlin U.S. Patent No. 2,636,865. ,Aluminum alcoholate is hydrolyzed with good agitation with from about 1 to 10 volumes of ammonium hydroxide per volume of aluminum alcoholate, preferably two to three volumes of ammonium hydroxide per volume of aluminum alcoholate, the concentration of NH being in the range of about 1.8 to 3.4 weight percent. The temperature of hydrolysis is preferably kept within a range of about 35 to 100 F. Upon hydrolysis, an alumina slurry is obtained and this slurry is aged for a period of one to 15 hours, preferably 3 to 8 hours at room temperature. The aging is preferably carried out in the range of about 35 to 80 F.

The alumina slurry contains alumina in the beta trihydrate form and the slurry is first dried at a temperature of about 200 to 400 F. to remove the ammonia and water to recover dry alumina. Crystalline eta alumina is formed by further dehydrating the beta alumina trihydrate and it has been found that the conversion to the eta form is essentially quantitative when the activating temperature is in the range of about 450 to 1100 F. The activation is generally in the presence of air but can be done in the presence of inert gases.

The eta alumina is used as a support for platinum and is impregnated with an aqueous solution of water soluble inorganic platinum containing compounds such as chloroplatinic acid, platinum sulfide, etc. The term Water soluble also includes platinum-containing compounds which form colloidal solutions.

A preferred solution is one containing 15 grams of H PtCI JcH O (40% Pt) per liter. This strength of solution can be employed to yield catalysts containing about 0.6% platinum but the strength of the solution may be varied to obtain a catalyst containing about 0.001 to 5% platinum by weight. The alumina support is impregnated with the platinum solution, is then heated to dryness, con veniently at temperatures of about 100 to 600 F., preferably about 250 F., at atmospheric pressure and this results in removal of a substantial portion of the water. Thereafter the catalyst is calcined at a temperature between about 800 and 1250 F., preferably about 1100 F. The calcining step is preferably carried out for about 1 to 24 hours.

Before impregnating the eta alumina base with the platinum compound, it is also within the contemplation of this invention to calcine the eta alumina and this can be done at a temperature between about 800 and 1600 F., preferably about 1100 to 1500 F., for 1 to 24 hours. In some cases it is also desirable to treat the platinum catalyst or the eta alumina base either before or after calcination with an aqueous dilute mixed acid solution such as one containing nitric acid, perchloric acid, or hypochlorous acid, together with a hydrogen halide such as HCl, HF, HI and HBr The mixture containing nitric acid and hydrochloric acid is preferred. An amount of nitric acid based on the total catalyst of about 0.1 to 8 weight percent on the total catalyst is preferred. The HCl is employed in an amount of about 1 to 30 weight percent based on the total catalyst. The nitric and hydrochloric acids are contained in about 50 to 500 Weight percent of water on the total catalyst.

In acid treating the catalyst, the catalyst is mixed with the acid solution, heated on a steam bath at about 150 to-180 F. for at least one hour, the acid solution is then drained off and the catalyst is Washed thoroughly with distilled water. The washed catalyst is then dried at about 250 F. and recalcined for about 1 to,4 hours at between about 800 and 1250 F., preferably about 1100 F.

In a specific example, the alumina support for a catalyst was obtained by hydrolysis of aluminum alcoholate solution by the method discussed above. The alumina after drying at about 250 F. was pulverized to pass through a 20 mesh screen and was then heated and activated at about 1100 F. for about 4 hours. To each 100 grams of activated alumina was added a solution made by dissolving 1.5 grams of H PtCl (40% platinum) in about cc. of distilled water. The composition Was well mixed and dried overnight at room temperature. The catalyst was then dried at 250 F., screened and pilled. The pilled catalyst was calcined for 1 hour at about 1100 F.

The pilled and calcined catalyst was then treated with a solution containing 7 weight percent on catalyst of concentrated HCl and 4 weight percent on catalyst of concentrated HNO and 200 weight percent on catalyst of distilled water. The catalyst pills were'slurried in the acid solution on a steam bath-for about one hour. The temperature of the solution was about 150 to 190 F. The acid solution was then drained ofi and the catalyst washed with distilled water. The washed catalyst was dried at 250 F. and calcined at 900 to 1100 F. for one hour.

In a first experiment conducted, a platinum on eta alumina catalyst not acid treated, was employed in the hydrogenation of a xylene fraction constituting mixed xylenes, although predominating in meta xylene. A temperature of 615 F., a pressure of 400 p.s.i.g., a feed rate of 1 v./v./hr. and 7000 cubic feet of hydrogen per barrel of feed were employed. obtained showed a 96% conversion of the mixed xylenes to dimethyl-cyclo hexanes and tri-methyl cyclo pentanes. Other experiments conducted with substantially pure aromatic hydrocarbons boiling in the range of about 430 to 650 F., supported these results in showing the practicality of hydrogenating aromatic hydrocarbons with this specific catalyst.

Other tests which were conducted to demonstrate the process of this invention employed a commercial kerosene having the inspections shown in Table I.

TABLE I Kerosene inspections Gravity, API 42. 6 ASTM Distillation S ecific Gravit 60 50 0.813 Percent Tern p y I O.H. Aniline Point, F 148 TB? 319 Smoke Point, mm 21. 5 10 382 FIA, vol. percent 20 400 Aromatics... 17 805.9) 30 414 Ole 51 S 5. 3 40 425 Satu "ates 76. 9 50 435 Sulfur. Wt. perce 0.023 60 445 Bro "nine 310., cg. Brz.'gu1.. 1.77 456 Refractiverlndor, 20 C./D 1. 4490 469 Viscosity at 30 F., cs. 11.2 484 Freezing Point, F. -42 498 Flash Point, F 134 FBP 516 A variety of tests for the hydrogenation of this kerosene and additional tests for the hydrogenation of xylene, are summarized in Table II. These tests were conducted in a continuous hydrogenation operation at a pressure of 400 p.s.i.g., and 0.8 to 1.0 v./hr./v., employing aplatinum on eta alumina catalyst containing 0.6% of platinum which was diluted with an equal amount of tabular alumina. Temperatures of 500, 600 and 675 F. were studied and hydrogen dilutions ranging between It was found that the product 6,000 to 7,500 standard cubic feet per barrel were employed. Table II summarizes the results of these tests:

TABLE II Hydrogenation of aromatics over platinum on em alumina catalyst [0.6% Pt. on 41-0,; 400 p.s.i.g.]

Retractive FIA Feed Hour on Feed Temp., VJHrJV. Hg, Index Smoke F. S.C.F./Bbl 20 CJD Pt.,mn1.

Arorn Olefins Sets.

1.4951 100 0 610 1. 3. 0 1. 428s 28.0 5. 4 1.5 93.1 Xylene 1 510 0. 90 7. o 1. 4258 31. 5 2. 4 1. 7 95. 0 675 0. 90 5. 5 1. 4295 24. 0 9. 4 2. 3 ss. 3 1. 4490 21. 5 17.8 5. 3 76.9 500 0.95 5. 0 1. 4407 29. 0 10. 7 5. 5 83.8 500 0. 92 6. 0 1. 4424 25. 5 14. 0 2. 7 s3. 3 600 0. 9s 6. 0 1. 4438 27. 0 13. 4 a. 5 e3. 1 675 0. s9 5. 0 1. 4440 25. 0 15. s a. 0 s1. 2

500 1. 00 5. 0 1. 4412 28.0 11.2 2.1 35. 7 575 0.80 7. 0 1. 4435 25. 5 15. s 2. a s1. 4 575 0. 86 5. 5 1. 4441 24. 0 15.8 3. 5 s0. 5 575 0. 90 6. 5 1. 4440 24. 0 15. 1 2. 6 s1. 3 Kerosene 12 575 "13. 55' 5.5 1.4447 24.0 16.3 3.3 80.4 675 0.86 6.5 1.4450 500 0. 90 6. 5 1. 4417 28. 0 10. 9 3. 9 85.2 500 0. 55 5.5 1.4440 500 0. 91 5. 5 1. 4441 27. 0 14. 5 5. 2 so. 2

1 Malllnclcrodt A. R. Xylene, 0.003% S.

1 Inspections, Table I I Alternate feed H strip min.

4 Alternate feed 10 mln., H, strip 5 min.

H3, 900 F., 3 Hours.

. Referring to the data of Table II, it will be seen that maintained during the hydrotreating process; that is, in every run reported, substantial conversion of aromatic 4 about 200 to 1000 p.s.i. g.

compounds was obtained. However, the data shows that 0 Alternatively, an oxidative regeneration may be conparticularly good results were obtained in hydrofinishing ducted. In this case the catalyst is first purged of hydrokerosene at 600 F., serving to reduce aromatics from carbons employing an inert gas such as nitrogen. There- 17.8% to 8.7% and improving smoke point from 21.5 after air diluted with nitrogen or other inert gas is conrnm. to 30.5 mm. Included in Table II are data showtacted with the catalyst to secure combustion of caring the effect of regenerating the catalyst used in a hy- 45 bonaceous deposits on the catalyst while holding the temdrogen regeneration treatment. It is shown that contact perature below about 1050" F. After an initial period of spent catalyst with hydrogen at 900 F. for three of regeneration with dilute air, the oxygen content may hours is effective for regenerating the catalyst. Also, as be increased to that of undiluted air, preferably including shown by hours 20 to 22, however, intermittent hydroexposure of the catalyst to air at about 950 F. to 1175 gen stripping at 600 F. is also particularly elfective in F. at reaction pressure for an hour or more, preferably maintaining good catalyst activity. four or more hours.

These and other tests which were conducted establish As described, the process of this invention concerns that platinum on eta alumina catalyst may be used in the the hydrofinishing of petroleum fractions for product process of this invention at temperatures in the range quality improvement by the conversion of aromatic hyof 500 to 675 F., with about 600 F. being a preferred drocarbons. The invention has been described with temperature for operation. Non-regenerative operations particular reference to the treatment of diesel fuel in may be conducted at temperatures in the upper portion kerosene, but is also of application in the treating of of this range, particularly when employing intermittent jet fuels and gas oils. In the latter connection, for exhydrogen stripping which may be conducted by periodiample, the hydrotreating process of this invention can cally cutting off hydrocarbon feed at intervals of about 5 desirably be used for the upgrading of catalytic cracking to 180 minutes. Hydrogen stripping will be carried out feed and. cycle stocks by conversion of the aromatic hyat about 500 to 800 F., preferably for about 5 to 60 drocarbons present in such stocks. minutes. However, somewhat lower temperatures better While the invention has been described with particufavor aromatic conversion, although necessitating regenlar reference to fixed bed operation, it is apparant that eration of the catalyst. Pressures to be employed in this the fluidized technique or moving bed principles may be invention are selected from the broad range of 100 to employed. Again, while the invention has been described 1000 P- although pressures of about 200 to 400 as a single stage treatment with platinum on. eta alumina, p.s.i.g. are preferred. Use of higher pressures in the staged operations or combinations with other treating range stated are favorable for aromatics conversion. processes may be used. For example, in the case of high As stated, the present invention may be conducted as sulfur content feed stocks, it may be desirable to emeither a non-regenerative process, or a regenerative ploy a desulfurization step prior to the use of the process. Conventional techniques for catalyst regeneraprocess of this invention. Hydrodesulfurization using a tion may be employed. The preferred procedure, howcatalyst such as cobalt molybdate can desirably be used i5 to p y g temperature y g regenera' for this purpose. These and other variations and modifition entailing hydrogen contact with the catalyst at a cations of the invention may be employed.

- swwsa i 7 What is claimed is: g 1. A process for upgradingetroleum "fractions containing aromatic and sulfur compounds boiling in the range of about 300 to 650 R, which consists of hydrogenating said fractions to obtain substantial hydrogenation of aromatics and removal of sulfur at a"temp'erature of about 500 to 675 F., at a pressure of about 100 to 1000 p.s.i.g., in the presence of about 5,000 to 8,000 standard cubic feet o'fhydrogen"perbarreloffeed in contact with a catalyst comprising platinum supported on eta alumina.

2. The process'defined by cla-im 1 in which the said petroleum fraction is selected "from the group consisting of kerosene, diesel fuel, gas oil, and jetfuel.

3. The process defined'by claim 1 in which the-said catalyst contains-0.001 to-5.0% ofplatinum.

"'4. The proces 'defin'd byblai mdin wfliehthe saiii catalysfcontains 0.05'to 1.0%"platir'1'um.

"References Cited in the file of this patent UNITED STATES PATENTS v. 1 rank

Claims (1)

1. A PROCESS FOR UPGRADING PETROLEUM FRACTIONS CONTAINING AROMATIC AND SULFUR COMPOUNDS BOILING IN THE RANGE OF ABOUT 300* TO 650*F., WHICH CONSISTS OF HYDROGENATING SAID FRACTIONS TO OBTAIN SUBSTANTIAL HYDROGENATION OF AROMATICS AND REMOVAL OF SULFUR AT A TEMPERATURE OF ABOUT 500* TO 675*F., AT A PRESSURE OF ABOUT 100 TO 1000 P.S.I.G., IN THE PRESENCE OF ABOUT 5,000 TO 8,000 STANDARD CUBIC FEET OF HYDROGEN PER BARREL OF FEED IN CONTACT WITH A CATALYST COMPRISING PLATINUM SUPPORTED ON ETA ALUMINA.