CA1089391A - Method for presulfiding hydrodesulfurization catalysts - Google Patents

Abstract

METHOD FOR PRESULFIDING HYDRODESULFURIZATION CATALYSTS

ABSTRACT OF THE DISCLOSURE

An improved method for presulfiding a hydrodesulfur-ization catalyst which comprises continuously contacting the catalyst with a sulfur-containing hydrocarbon in an inert hydrogen-free atmosphere at relatively low pressure.

Description

BACKGROUND OE THE INVENTION
The hydrodesulfurization of hydrocarbon stocks with catalysts comprising supported hydrogenating components selected from the Group VI-B and Group VIII metals in a form capable of promoting hydrogenation reactions is conventional in the art.
Especially effective catalysts for the purpose of such-~ydro-desulfurization reactions are those comprising molybdenum and two members of the iron group metals. Preferred catalysts of this class are those containing nickel, cobalt and molybdenum but other effective combinations of iron group metals and molybdenum comprise iron-molybdenum-cobalt, nickel-molybdenum-iron, as well as combina-tions of nickel and molybdenum, cobalt and molybdenum, nickel and tungsten. The hydrogenating or desulfurizing components of such catalysts are employed in the sulfided form.
Although the hydrogenating components indicated above may be employed in any proportions with each other, especially effective catalysts are those in which the hydrogenating components consist of (a) a combination of 2 to 25~, preferably 4 to 16% by weight molybdenum and at least two iron group metals where the iron group metals are present in such proportions that the atomic ratio ' ,' :

1(~893~1 of each iron group metal with respect to molybdenum is less than about 0.6 and (b) a combination of about 5 to 40~, preferably lO
to 25~ of nickel and tungsten where the atomic ratio of tungsten to nickel is about 1:0.1 to 5, preferably 1:0.3 to 4.
In the preparation of the hydrodesulfurization catalysts, the hydrogenating components are composited with a porous refrac-tory oxide support, preferably alumina. Molybdenum, for example, can be deposited on the support from an aqueous solution of salts such as ammonium molybdate, ammonium paramolybdate, molybdenum pentachloride, or molybdenum oxalate. After drying the impregnated support can be calcined to convert molybdenum into the oxide form.
The molybdenum containing carrier, which is normally shaped in the form of extrudates, granules, pellets or balls, can then be treated with an aqueous solution of the Group VIII metal salt followed by oven drying and calcining. If a second Group VIII metal is employed, it can be deposited in a like manner or simultaneously with the first Group VIII metal. Nitrates or acetates of the Group VIII
; metals are normally utilized although any water soluble salt which leaves no harmful residue can be employed. If desired, the Group VIII metals and molybdenum can be deposited simultaneously, but are preferably deposited in sequence with intervening oven drying which is normally conducted at a temperature in the range of 220 to 350F.
(104 to 177C.) for a period of 1 to 24 hours.
In addition to the hydrogenating components of Group VI-B and Group VIII, the desulfurization catalyst can also contain a Group IV-B metal as a promoter. Under such circumstances, the Group IV-B metal, preferably titanium or zirconium, is present in the catalyst in an amount in the range of l.0 to lO.0 weight .~

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.. . .. . - ., - ~ -.: . . . , .. . . . .... . -: . .

l(~B9391 percent based upon the total weight of the catalyst. The Group IV-B metal can be added to the catalyst composite by the technique of impregnating the calcined support with an aqueous solution of -the ~letal salt, such as titanium tetrachloride. The Group IV-B
metal can be deposited on the support following impregnation of the support with the Group VI and Group VIII metals or simultane-ously with the deposition of the Group VI and/or Group VIII metals.
The carrier or support employed in the preparation of the hydrodesulfurization catalyst can be any refractory oxide having a surface area in excess of 3 square meters per gram such as pure alumina, a silica stabilized alumina containing up to about 5 percent by weight based upon the carrier of silica, silica gels, acid leached boro-silicate glass and spinels, e.g. magnesium aluminate. Preferably, however, the carrier is an alumina which is silica-free.
Conventionally hydrodesulfurization catalysts as described above can be presulfided after calcination, or after calcination and reduction by contacting the catalyst with a hydrogen sulfide and hydrogen gaseous mixture at a temperature in the range of 500 to 20 700F. (261 to 372C.) and at an elevated pressure. Gaseous mixtures containing low or high concentrations of hydrogen sulfide have been used, with gaseous mixtures containing low concentration of hydrogen sulfide being preferably employed for economic reasons. Conven-tional presulfiding methods employing hydrogen sulfide or other sulfiding agents are directed to adding to the catalyst composite at least the stoichiometric amount of sulfur required to completely sulfide the hydrogenation metals of the catalyst composite.

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1(~89391 To insure completeness of the sulfiding reaction, the presulfiding process is normally conducted until the concentration of the sulfur contained in the total effluent withdrawn from the presulfiding zone is substantially equivalent to the concentration of the sulfur in the feed to the presulfiding zone. Normally, the presulfiding step is conducted for a period of from 16 to 24 hours to insure complete conversion of the hydrogenation metals to the most stable sulfide forms.
According to the present invention there is provided a process which consists essentially of initially contacting a catalyst comprising Group VI-B and Group VIII hydrogenation components on a refractory oxide support with a sulfur-containing liquid hydrocarbon in an inert substantially oxygen-free and hydrogen-free atmosphere and at a pressure in the range of atmospheric to 400 psig and at a temperature in the range of 200 to 700F, maintaining the contact between said catalyst and said sulfur-containing liquid hydrocarbon until the total amount of sulfur in said hydrocarbon brought into contact with said catalyst is in the range of 200 to 1400 weight percent of the amount of sulfur required to completely sulfide the metals at the contact temperature and pressure, and thereafter contacting said catalyst with a sulfur-containing hydrocarbon feed under hydrodesulfurization conditions.
The drawing illustrates a specific embodiment of the novel presulfiding procedure when compared with the conventional method for presulfiding hydrodesulfurization catalyst.
The invention is directed to the presulfiding of the previously described hydrodesulfurization catalysts. The catalysts containing Group VI-B and Group VIII hydrogenating .' . . ' - ~ ' .' :
,: . ~ .. : . .

1~89391 components are contacted with a sulfur-containing hydrocarbon at a temperature in the range of 200 to 700F. (93 to 371C) and at a nitrogen pressure in the range of atmospheric to 400 psig ~1.05 to 28 kg/cm ).

- 4a --, 1(3~9391 The sulfur-containing hydrocarbon employed in the presulfiding procedure is a liquid at the contacting conditions and preferably comprises a gas oil or furnace oil boiling sub-~tantially above 400F. (204C.). The liquid hydrocarbon can comprise the feed to the hydrodesulfurization process or another hydrocarbon boiling substantially above 400F. (204C.). Prefer-ably, the liquid hydrocarbon employed in the presulfiding step will contain at least 1.0 weight percent sulfur, thereby reducing the length of time required for the presulfiding step.
The contacting between the presulfiding hydrocarbon and the catalyst is conducted in a substantially oxygen-free, hydrogen-free, inert atmosphere. If a gas is employed in the presulfiding ~tep, the gas must be inert under the presulfiding conditions and can be suitably selected from the group consisting of argon, helium, carbon dioxide, and nitrogen with nitrogen being a preferred gas.
Preferably, the inert gas-pressure employed in the presulfiding step is in the range of 200 psig tl4 kg/cm2) to 400 psig t28 kg/cm2).
Presulfiding of the catalyst is conducted until the total amount of the sulfur in the hydrocarbon brought into contact with the catalyst is in the range from 200 to 1400 weight percent of the amount of sulfur required to sulfide the metals on the catalyst to their completely sulfided forms. Normally, when employing a pre-sulfiding hydrocarbon as described above, contact between the catalyst and the hydrocarbon can be conducted at a sulfur weight hourly space velocity (weight of sulfur in the sulfiding agent per weight of catalyst per hour) of less than 0.03 and under such conditions that the time for conducting the presulfiding process will be in the range of from 12 to 24 hours.

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, ~ , The presulfided catalyst can be employed in the hydro-desu]furization of sulfur-containing hydrocarbon stocks. Generally, the operating conditions employed in the hydrodesulfurization pro-cess comprises a temperature in the range from about 500 to about lOOO"F. (260 to about 538C.), preferably in the range from about 600 to about 800F. (316 to about 427C.) and more preferably in the range from about 650 to about 780F. (343 to 416C.). The space velocity can be in the range from about 0.10 to about 10.0 volumes of charge stock per volume of catalyst per hour. The hydrogen feed rate employed normally ranges from about 500 to about 10,000 standard cubic feet per barrel of feed stock (8.9 to about 178 SCM/lOOL). The pressure employed in the process can be in the range from about 100 to about 5,000 psig (7 to about 350 kg/cm2).
The feed stocks which can be hydrodesulfurized employing the pre-sulfided catalysts of this invention include all naphtha and heavier hydrocarbons. The feed stocks particularly suitable are those containing a substantial quantity of components, i.e.
greater than 50 percent by volume, boiling above about 400F.
(204C.) and preferably above about 500F. (260C.). Such materials can be synthetic crude oils such as those derived from shale oil, tar sands and coal or full petroleum crudes or any individual frac-tion thereof. Thus, for example, the feed stock to the hydrode-sulfurization process can be an atmospheric topped crude or it can be a vacuum residual fraction boiling substantially above 950F.
(510C.). Similarly, it can be a naphtha or any of the intermediate distillate fractions, such as, a furnace oil boiling above about 450 to about 650F. (232 to about 343C.) or a gas oil boiling from above about 650 to 950F. (343 to 510~C.).

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- 1~'89391 The following examples are presented to illustrate ~-objects and advantages of the invention. It is not intended, howeve!r, that the invention should be limited to the specific embodiments presented therein.

BXAMPLE I

In this example a catalyst composition comprising 0.5 weight percent nickel, 1.0 weight percent cobalt, and 8.0 weight percent molybdenum on alumina was presulfided employing sulfur-containing hydrocarbons in the absence of hydrogen and oxygen in four runs. The hydrocarbon employed in each of the pre-sulfiding steps is identified and characterized in the following Table I.

TABLE I

Run No. 1 Run No. 4 (Vacuum GasRuns 2 ~ 3(Atmospheric Tower Oil)(Furnace Oil)Bottoms) Gravity, API 20.3 37.8 16.8 Sulfur, wt. %1.99 1.11 3.79 -Nitrogen, wt. % 0.13 .04 .21 Carbon, wt. %86.01 86.60 84.74 20 Hydrogen, wt. % 11.87 12.25 11.36 Asphaltenes~ wt. % -- -- 2.6 Distillation, F.
Over Point 750 409 600 End Point 1050 639 --10~ 795 443 667 50% 886 518 929 90% 984 609 --In each of the runs, the pre-sulfiding conditions included a space velocity of 1.0 LHSV, a pressure of 200 psia (14 kg/cm ) and a pre-sulfiding time of 24 hours. The temperature employed in each of the pre-sulfiding runs was as shown below in Table II.

1(~89;391 TABLE II

Temperature, F.
Run No. 1 650(343C) Run No. 2 500(260C) Run No. 3 400(204C) Run No. 4 650(343C) The prepared pre-sulfided catalysts were thereafter employed in the hydrodesulfurization of a hydrocarbon feed charac-terized as shown below in Table III.

TABLE III
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Gravity, API 22.5 Sulfur, wt. % 1.01 Nitrogen, wt. % .17 Carbon, wt. % 86.61 Hydrogen, wt. % 12.21 Distillation, F.
Over Point 500 End Point --10% 596 50% 868 90% ~~

The hydrodesulfurization conditions employed in each of the runs included a space velocity of 0.5 LHSV, a hydrogen partial pressure of 1,980 psia (138.60 kg/cm ) and a hydrogen circulation rate of 4,235 standard cubic feet per barrel of charge (754 m2/m2). The temperature was adjusted during each run to maintain a concentra-tion of sulfur in the product of 0.32 weight percent. After 200 hours of operation, the average reactor temperature for each of the runs was as shown below in Table IV.

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TABLE IV
Temperature, F.
Run No. 1 697 (369C) Run No. 2 702 (372C) Run No. 3 691 (366C) Run No. 4 699 (371C) EXAMPLE II
In this example the performance of a catalyst prepared ~
10 by the novel pre-sulfiding procedure is compared with the perform- -.
ance of a catalyst which had been pre-sulfided by a conventional process. The hydrodesulfurization catalyst of Example I was sub-jected to a conventional pre-sulfiding procedure which comprised contacting the catalyst for a period of 12 hours with the vacuum gas oil of Table I in the presence of a hydrogen pressure of 2,000 psig (140 kg/cm2) with the hydrogen being circulated through the catalyst at the rate of 5,000 standard cubic feet per barrel (89.0 SCM/lOOL). The vacuum gas oil was passed through the catalyst at the space velocity of 1.0 LHSV and at a temperature of 650F.
20 (343C.).
Thereafter, the conventionally pre-sulfided catalyst was employed in a hydrodesulfurization run utilizing the feed and hydrodesulfurization conditions of Example I. The drawing is illustrative of the temperature required to maintain a desulfurized ; hydrocarbon product having 0.32 weight percent sulfur during the ` run (Run No. 5).

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The results of the hydrodesulfurization of Run No. 3 of Exa!mple I are also plotted in the drawing. A comparison of Runs 3 and 5 demonstrates that the novel pre-sulfiding process results in an improvement in the hydrodesulfurization process.
At a catalyst age of 200 hours, for example, the catalyst pre-pared by the novel pre-sulfiding technique shows a temperature advantage of 8F. This temperature advantage, as indicated in the drawing, increases as the catalyst age increases. At 280 hours the temperature differential is 14F.
Although the invention has been described with reference to specific embodiments, references, and details, various modifica-tions and changes will be apparent to one skilled in the art and are contemplated to be embraced in this invention.

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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process which consists essentially of initially contacting a catalyst comprising Group VI-B and Group VIII
hydrogenation components on a refractory oxide support with a sulfur-containing liquid hydrocarbon in an inert substantially oxygen-free and hydrogen-free atmosphere and at a pressure in the range of atmospheric to 400 psig and at a temperature in the range of 200 to 700°F, maintaining the contact between said catalyst and said sulfur-containing liquid hydrocarbon until the total amount of sulfur in said hydrocarbon brought into contact with said catalyst is in the range of 200 to 1400 weight percent of the amount of sulfur required to completely sulfide the metals at the contact temperature and pressure, and thereafter contacting said catalyst with a sulfur-containing hydrocarbon feed under hydrodesulfurization conditions.

2. The process of Claim 1 wherein said sulfur-containing hydrocarbon comprises a gas oil or furnace oil.

3. The process of Claim 1 wherein the initial contacting is conducted in a nitrogen atmosphere.

4. The process of Claim 1 wherein said sulfur-containing liquid hydrocarbon contains at least 1.0 weight percent sulfur.

5. The process of Claim 1 wherein said catalyst also contains a Group IV hydrogenation component.

6. The process of Claim 1 wherein said catalyst comprises nickel, cobalt and molybdenum on alumina.