Chemistry: fischer-tropsch processes; or purification or recover – Including regeneration of catalyst
Reexamination Certificate
2001-01-09
2002-09-24
Parsa, Jafar (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Including regeneration of catalyst
C518S700000, C518S715000, C208S015000, C208S018000, C208S028000
Reexamination Certificate
active
06455596
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the reactivation, or regeneration of cobalt catalysts deactivated by sulfur; particularly cobalt catalysts as used in hydrogenation of carbon monoxide or Fischer-Tropsch reactions. It also relates to cobalt-titania catalysts, to the process utilizing the catalyst, and the products of such process.
BACKGROUND
Fischer-Tropsch (F-T) reactions, i.e., catalytic reactions for the production of C
5
+ liquid hydrocarbons from mixtures of hydrogen and carbon monoxide, are well known. The F-T process has become the subject of intense study for commercial development. The catalysts used in conducting F-T reactions are typically constituted of an Iron Group metal (Periodic Table of the Elements, Sargent-Welch Scientific Company, Copyright 1979) of Group VIII, e.g., iron, nickel or cobalt, distributed on a particulate refractory inorganic oxide support, e.g., titania. In formation of the catalyst, the catalytic properties of the Iron Group metal may be modified or promoted by an additional metal, or metals, from Group VIIB or VIII, e.g., platinum or rhenium.
In conducting an F-T synthesis reaction, a synthesis gas constituting a mixture of hydrogen and carbon monoxide is reacted over an Iron Group metal catalyst, e.g., Co—Re/TiO
2
, to produce a C
5
+ waxy hydrocarbon product which is separated into various fractions for further processing into transportation fuels, distillates, diesel and jet fuels, solvents and lubricating oils. While the waxy products from the F-T reactor are generally referred to as essentially “non-sulfur” containing compounds, the presence of sulfur in even a few parts, per million parts by weight (wppm) of a product, has been found to cumulatively poison a cobalt-containing catalyst and shorten its life. It thus becomes necessary for the viability of the process to periodically reactivate, or regenerate the sulfur deactivated catalyst.
Where the reaction product mixture in contact with the catalyst contains even a small amount of sulfur, the catalyst is cumulatively poisoned by the deposited sulfur. The result: All too soon the catalyst must be reactivated, or regenerated, by removal of the sulfur. Whereas methods are known for reactivating cobalt catalysts, such techniques often result in the removal of cobalt along with the sulfur. The result: All too soon the catalyst must be reworked, and replaced.
In U.S. Pat. No. 3,661,798, which issued May 9, 1972 to Institut Francais du Petrole, e.g., there is described a method wherein a sulfur-deactivated cobalt/silica catalyst is regenerated by the successive steps of heating the deactivated catalyst with a gas containing molecular oxygen at 300 to 600° C., contacting the cooled catalyst with water at about 0 to 250° C., and then with hydrogen at about 200 to 500° C. The regeneration is not successfully reactivated when the carrier component of the catalyst is alumina. Moreover, it has been found that cobalt is extracted and lost from the catalyst even when the carrier component for the cobalt is silica. Accordingly, there remains a need for better methods, or processes for reactivating, or regenerating cobalt-containing catalysts.
THE INVENTION
This need and others is achieved in accordance with the present invention which embodies, in the preparation of a cobalt catalyst, compositing cobalt with titania sufficient that when the catalyst is sulfided and deactivated by sulfur, or sulfur-bearing compounds, it can be reactivated, or regenerated, without significant loss of cobalt, if any, from the catalyst. The reactivation, or regeneration is accomplished by treating the sulfided cobalt titania catalyst in a series of steps requiring (1) contact, and treatment, with a gaseous stream of molecular oxygen, preferably air, or oxygen-enriched air or nitrogen, at temperature ranging from about 150° C. to about 600° C., preferably from about 300° C. to about 500° C., sufficient to oxidize the sulfur component (and metal component) of the catalyst, and then (2) contacting, treating or washing the sulfur oxidized catalyst, in situ or ex situ of the reaction zone in which Step (1) was conducted, with a liquid, preferably water, at temperature ranging from about 0° C. to about 100° C., preferably from about 20° C. to about 80° C., sufficient to remove the oxide, or oxides of sulfur. The catalyst is then contacted with hydrogen, or other reducing agent, to reduce the metal, or metals, or oxide of the metal, or metals, component to restore the activity of the catalyst, as measured by CO hydrogenation after reduction of the catalyst. It has been found that the activity, and selectivity of a cobalt-titania catalyst, e.g., a cobalt-rhenium-titania catalyst, sulfur deactivated and used in an F-T synthesis reaction, on reactivation, or regeneration in this manner can be restored to that of the fresh catalyst originally used for conducting the similar operation.
The catalysts of this invention can be prepared by techniques known in the art for the preparation of hydrocarbon synthesis, or F-T catalysts. The catalyst can, e.g., be prepared by gelation, or cogelation techniques. Preferably however the cobalt metal, and if desired a promoter metal, or metals, can be deposited on a previously pilled, pelleted, beaded, extruded, or sieved titania support material by the impregnation method. In preparing catalysts, the metals are deposited from solution on the support in preselected amounts to provide the desired absolute amounts, and weight ratio of the metal or metals being deposited. Suitably, the cobalt by itself, or promoter, if a promoter is desired, are composited with the support by serially contacting the support with a solution of a cobalt-containing compound, or salt, and a solution containing the promoter-containing compound, or salt, respectively. Optionally, the cobalt and promoter can be co-impregnated upon the support. The cobalt and promoter compounds used in the impregnation can be any organometallic or inorganic compounds which when reduced in hydrogen forms water or which can be converted to the corresponding oxide, which when reduced in hydrogen forms water, such as a cobalt nitrate, acetate, acetylacetonate, naphthenate, or the like. The nitrate is preferred for cobalt. The amount of impregnation solution used should be sufficient to completely immerse the carrier, usually within the range from about 1 to 20 times of the carrier by volume, depending on the metal, or metals concentration in the impregnation solution. The impregnation treatment can be carried out under a wide range of conditions including ambient or elevated temperatures.
Rhenium, cerium, hafnium, and uranium are preferred promoters, and can be included with cobalt in forming the catalyst. Usually, these materials are present in a weight ratio to cobalt of at least about 0.05:1, preferably at least about 0.1:1, and may range from about 0.1:1 to about 1:1, but the promoter is usually present in an amount less than the cobalt. Rhenium is a particularly preferred promoter and may be deposited onto the support as perrhenic acid. The amount of cobalt employed is at least that which is catalytically effective, e.g., at least about 2 parts, per 100 parts by weight of catalyst (dry basis), i.e., 2 wt. %. However, cobalt concentrations may range from about 2 wt. % to about 70 wt. %, preferably from about 10 wt. % to about 30 wt. %. The carrier, or support component of the catalyst is constituted of at least 30 wt. % titania, and preferably at least about 70 wt. % titania.
When the catalyst comes in contact with sulfur, the activity of the catalyst gradually declines; eventually to such point that it is not economically sound to continue the operation without a new, or reactivated catalyst. The catalyst, at this point, is discharged from the F-T reaction zone and treated (1) to oxidize the sulfur component of the catalyst. Then the oxidized sulfur catalyst is treated by (2) washing with water to remove the oxidized sulfur component from the catalyst. The catalyst is then reduced, and the catalyst th
Daage Michel A.
Erofeev Anatoliy B.
Koveal Russell J.
Krylova Alla Jurievna
Lapidus Albert L'Vovich
Brumlik Charles J.
ExxonMobil Research and Engineering Company
Parsa Jafar
Simon Jay S.
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