US3838042A - Demetallization process using ironcontaining catalysts - Google Patents

Abstract

A PROCESS FOR THE DEMETALLIZATION OF HYDROCARBONS BY CONTACTING WITH AN IRON-CONTAINING CATALYST UNDER HYDROGENATION CONDITIONS.

Description

United States Patent US. 'Cl. 208-451 H 3 Claims ABSTRACT on THE nrscLosUiiE A process for the demetallization of hydrocarbons by contacting with an iron-containing catalyst under hydrogenation conditions.

Our invention relates to a process for the demetallization of hydrocarbon stocks containing undesirable quantities of metalliferous contaminants. More particularly, our invention relates to the removal of metals such as nickel and vanadium from hydrocarbon stocks by contacting the stock with an iron-containing catalyst and hydrogen under hydrogenating conditions.

A Wide variety of liquid hydrocarbon stocks such as crude petroleum oil, shale oil and synthetic crudes derived from coal or tar sands, are known to contain trace amounts of metals. Usually, these metals are part of the heavier, higher boiling, more complex, molecules present in the hydrocarbon stocks and while, at times, small amounts can be tolerated in a feed stock, the presence of any significant quantity of metals can result in an undesirable high metals content in products and/or can pre sent a problem in the catalytic processing of stocks containing the heavier molecules. What actually constitutes a significant quantity of metals can, of course, vary depending upon the processing to which the stock is to be subjected. Thus, for example, in the hydrodesulfurization of residual containing stocks or synethic crudes, a comparatively high metals level can be tolerated relative to the requirements of many other processes; however, it is still desirable to reduce the metals content of such stocks, usually greater than about 50 p.p.m., to a level of less than about 50 p.p.m., e.g. less than about 35 p.p.m. and

preferably less than about 25 p.p.m. On the other hand,

the presence of comparatively small concentrations of metals, e.g. p.p.m., in a stock to be subjected to eatalytic cracking is undesired and the metals content of such stock should be reduced to less than about 1 p.p.m.

In connection with the catalytic processing of stocks comprising heavier components containing metalliferous contaminants, the usual result is that the metals deposit on the surface of the catalyst resulting in deactivation of the catalyst. While it is known in the art to remove carbonaceous deposits from catalysts by an oxidative burnoff technique, such procedure is apparently ineffective for the removal of metals deposited from the feed stock and, accordingly, metals poisoned catalysts generally are not regenerable employing simple, art-recognized techniques. Thus, for example, in a fluidized bed operation, such as, fluidized catalytic cracking, wherein a portion of the catalyst is continuously withdrawn, subjected to an oxidative burn-otf, and then returned to the reactor, the life of the catalyst, in the absence of metals poisoning, is theoretically indefinite and practically quite extensive. When treating a hydrocarbon stock containing metalliferous contaminants, however, such operation, While removing carbon, does not remove any of the metals deposited on the catalyst surface and the metals poisoning is irreversible and cumulative thus providing an extremely short life for the catalyst.

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Another problem is presented by the hydrocarbon stock having an extremely high metals content, for example, greater than about or 100 p.p.m. nickel plus vanadium, but having a comparatively low yet still undesirably high sulfur content, for example, about 1.5 to 2% by weight sulfur. In the treatment of such stocks by traditional techniques for the removal of sulfur, a lesser overall reduction of sulfur or a lesser percentage of sulfur removal is practiced resulting in a reduction in the quantity of metals removed thereby producing a product still containing a high concentration of metals. Such desulfurized material is generally not a desirable feed stock to another catalytic process or suitable as an end product per se.

It will be seen, therefore, that a need still exists in the art for a convenient means of reducing the metals content of hydrocarbons prior to various catalytic treatments and to avoid producing high metals content products. This is particularly so in dealing with high metals content and comparatively low sulfur content stocks wherein a high proportion of demetallization is required together with only a moderate degree of desulfurization.

In recent years, the problem confronting the art has been the reduction of comparatively high sulfur content (e.g. about 4%) and comparatively low metals content stocks (e.g. less than about or p.p.m.) to products containing about 1% by weight sulfur or less. To accomplish this desirable goal, it has been found that some traditional desulfurization catalysts, when employed under specific conditions, were effective to reduce the sulfur content of the high sulfur feed stocks without an undesirably high degree of metals removal. More recently, improved catalysts and improved processes have been developed whereby increased desulfurization could be effected with decreased metals removal thereby extending catalyst life in such situations. The process of our invention is not directed to such an operation, but rather is directed to the reverse situation of removing substantial quantities of metals without removing substantial quantities of sulfur.

As a means of evaluating or characterizing catalysts, we employ an index or ratio indicating metals removal relative to sulfur removal represented by the expression AM/AS wherein AM is the percent by weight reduction of metals content, i.e. nickel plus vanadium, of the material treated while AS is the percent by weight sulfur reduction. Generally, catalysts suitable for employment in desulfurization, particularly in desulfurization of comparatively high sulfur content stocks, will be found to have an index of AM/AS of less than about 1.15 and preferably less than about 1.10 With certain exceptional catalysts having an index below about 0.75. As distinguished from such prior art catalysts, the materials we employ have an index of AM/AS of at least about 1.20 and preferably greater than about 1.25.

In accordance with our invention, we contact a hydrocarbon stock containing metalliferous contaminants with hydrogen and an iron-containing catalyst under hydrogenating conditions of elevated temperature and pressure. The catalyst employed in our process contains at least about 1% by weight iron based upon the total catalyst.

The feed stocks suitable for employment in our process comprise any hydrocarbon stock containing a significant or undesired quantity of metalliferous contaminants. Usually, such feed stocks will be found to be those containing the heavier higher boiling components, such as the residual components of crude petroleum oil. Thus, generally, our process is suitable, for example, for the treatment of any petroleum stock boiling above about 300 F. and particularly stocks containing residual components.

Illustrative of such materials are full crudes, topped crudes, reduced crudes, atmospheric tower bottoms, vacuum tower bottoms and fractions thereof whether subject to prior treatment or not. More specifically, suitable feed stocks to our process are stocks to be treated for demetallization prior to catalytic processing such as charge stocks to hydrodesulfurization processes (particularly residual stocks) or charge stocks to catalytic cracking processes, including previously desulfurized charge stocks. Also, our process is particularly suitable for the treatment of comparatively high metals content 70 p.p.m.) and low sulfur content 2%) crude oils, such as Venezuelan crudes.

As mentioned above, the catalyst employed in our process contains at least about 1% by weight iron as the metal and can be comprised of up to 100% iron oxide. Advantageously, the catalyst of our process will also contain a metalliferous hydrogenating component, such as, for example, the Group VI and Group VIII metals, their oxides and sulfides either alone or in combination. The hydrogenating component is believed to be effective in the prevention of coke formation on the surface of the catalyst thereby extending its cycle life. Usually, the hydrogenating component is distended on the surface of a carrier such as any of the high surface area materials well known in the art including, for example, the refractory metal oxides. The iron component of the catalyst employed in our process, when employed in conjunction with a hydrogenating component, however, can be present either as a portion of the carrier itself or distended on the surface of a carrier in the same manner as a hydrogenating component. Thus, for example, iron and another Group VIII metal of a Group VI metal can be distended on a carrier such as alumina in order to provide a satisfactory catalyst for our process. Alternatively, the iron component can be present in the carrier for a Group VI or Group VIII metal hydrogenating component. In such case the carrier can be iron oxide, a mixture of iron oxide and a wellknown catalyst support such as silica, a complex metal oxide such as an iron-containing spinel (e.g. iron silicate), or, preferably, an inorganic polymer of iron, silicon and oxygen obtained by cogelling a silica sol and an aqueous solution of an iron salt of the type described in U.S. Pat. No. 3,551,352.

The operating conditions employed in the process of our invention comprise a temperature in the range from about 600 to about 1,000 F., preferably from about 650 to 900 F.; a pressure from about 500 to about 5,000 p.s.i.g., preferably from about 750 to 2,000 p.s.i.g.; a liquid hourly space velocity (LI-ISV) from about 0.1 to about 10 volumes of feed stock per volume of catalyst per hour, perferably from about 0.5 to 5 v./v./hr.; and a hydrogen feed rate in the range from about 500 to about 10,000 standard cubic feet per barrel (s.c.f./b.), preferably from about 2,000 to 8,000 standard cubic feet per barrel.

In order to illustrate our invention in greater detail, reference is made to the following examples.

EXAMPLE 1 In this example, three separate runs were conducted employing a 50% reduced Kuwait crude containing nominally 4% by weight sulfur as the feed stock. The operating conditions employed in all runs were a temperature of 700 F., a pressure of 1,000 p.s.i.g., an LHSV of 1 and a hydrogen feed rate of 5,000 s.c.f./b. In the first run, a commercially available catalyst containing 0.5% by weight nickel, 1% by weight cobalt and 8% by weight molybenum supported on an alumina carrier was employed. In the second run, the catalyst contained the same hydrogenating metals in the same proportions but the carrier employed was an experimental support comprised of an intimate mixture of two different aluminas obtained by calcining a mixture of an alumina trihydrate and an alumina hydrate containing from 1.2 to 2.6

4 L rnols of water of hydration per mol of A1 0 The third run was conducted employing a catalyst containing the same hydrogenating metals in the same proportions as in the other two runs but employing a carrier comprising an inorganic polymer of iron, silicon and oxygen obtained by cogelling a silica solution and an aqueous solution of ferric chloride and then calcining the gel. This carrier contained about 17% by weight iron.based upon the carrier or about 15% by Weight based upon the total catalyst.

The feed stock and product inspections for the three runs of this example are shown in Table I below. The results shown were obtained between 40 and 48 hours for the commercial and experimental aluminas and between 32 and 40 hours for the polymer carrier.

From the above data it will be seen that the process of our invention was effective to remove a substantial quantity of metals from the feed stock. Further, it will be noted that the index, AM/AS, indicates that such metals removal was accomplished with a comparatively low sulfur removal. Thus, the catalyst support on the commercial alurnina had an index of 1.03 and the catalyst support in the experimental alumina (a catalyst specifically designed for high sulfur removal with low metals removal) had an index of only 0.57, while the catalyst required by our invention had the extremely high index of 1.48. Further, it will be noted that these varying results were obtained under identical operating conditions with catalysts having identical hydrogenating components.

EXAMPLE 2 In this example three separate runs were also conducted employing a 50% reduced Kuwait crude containing nominally 4% by weight sulfur as the feed stock. Again, the operating conditions employed in all runs were a temperature of 700 F., a pressure of 1,000 p.s.i.g., an LHSV of 1 and a hydrogen feed rate of 5,000 s.cf./b. In all of the runs of this example the catalyst carrier was the same commercial alumina employed in Example 1 and there were deposited on the carriers three metallic components. In all of the catalysts two of the components were 8% by weight molybdenum and 5% by weight titanium. The three catalysts differed, however, in that each one contained 3% by weight of a different iron group metal (i.e. iron, cobalt and nickel).

The feed stock and product inspections for the three runs of this example are shown in Table II below. The results shown were obtained between 40 and 48 hours on stream.

From the above data it will be seen that the catalyst required by our invention provides a comparatively high dernetallization for the amount of sulfur removed as shown by the index of 1.67 compared with the indices of 1.09 and 0.96 obtained with the other catalysts. Furthermore, it will be noted that the operating conditions in all runs were identical and that the catalysts differed, one

from the other, only in the presence of the different iron group metals, thereby demonstrating that the characteristic of demetallization is possessed only by iron and not by the other iron group metals.

We claim:

1. A process for the demetallization of hydrocarbon stocks which comprises contacting the stock containing metals with hydrogen and a catalyst at a temperature in the range of from about 600 to about 1000 F. and a pressure in the range from about 500 to about 5000 p.s.i.g., said catalyst comprising at least one hydrogenating metal selected from the Group VI and Group VIII metals composited with a support containing iron, the concentration of iron being at least 1.0% by weight of said catalyst.

2. The process of Claim 1 wherein said hydrogenating metals comprise nickel, cobalt and molybdenum.

3. A process for the demetallization of hydrocarbon stocks containing sulfur which comprises contacting a stock containing metals and sulfur with hydrogen and a catalyst at a temperature in the range of from about 600 References Cited UNITED STATES PATENTS 3,271,302 9/1966 Gleim 208264 3,496,099 2/1970 Bridge 208251 H 3,573,201 3/1971 Annesser et al. 208253 3,551,352 12/1970 Carr et al. 252439 DELBERT E. GANTZ, Primary Examiner J. M. NELSON, Assistant Examiner US. Cl. X.R. 208253