Process for carbon monoxide hydrogenation

Details Process for carbon monoxide hydrogenation Process for carbon monoxide hydrogenation

2003-02-28

2004-07-20

Johnson, Edward M. (Department: 1754)

Chemistry: fischer-tropsch processes; or purification or recover

Group viii metal containing catalyst utilized for the...

Iron containing catalyst

C518S719000

Reexamination Certificate

active

06765026

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a process for the preparation of novel, highly active catalysts for conducting carbon monoxide hydrogenation reactions, especially Fischer-Tropsch reactions. It also relates to the catalyst, to the process utilizing the catalyst, and to the product of such process; particularly to the production of waxy paraffins of high quality from synthesis gas.
BACKGROUND
Reactions involving the hydrogenation of CO, e.g., Fischer-Tropsch (F-T) synthesis to produce hydrocarbons, are complex and produce many stages. As a consequence, this necessitates the use of multicomponent, polyfunctional catalysts; catalysts constituted of a supported catalytic metal, or metals, component, e.g., an Iron Group metal such as cobalt, which may be modified or promoted with an additional metal, or metals, e.g., rhenium. (Periodic Table of the Elements, Sargent-Welch Scientific Company; Skokie, Ill. Copyright 1979). Reaction occurs between the feed components, on contact with the catalytic metal, or metals, component and its oxide, reduction of the oxide (which may be reduced only with difficulty), and support component. Knowledge of these reactions is largely empirical, requiring the accumulation and correlation of large amounts of experimental data covering various parameters including not only the composition of the catalyst but also its method of preparation. Trial-and-error methods outstrip theory in the development of catalysts; and these methods are based on more than one hundred years of process developments utilizing catalysts.
Early F-T catalysts were formed by compositing Group VIII or Iron Group metals with kieselguhr, e.g., (100 wt. parts Co per 100 wt. parts kieselguhr), and additionally 20 wt. parts of an oxide of a Group VIIB metal, e.g., Mn, to improve the activity and yield of higher molecular weight hydrocarbons at higher reaction temperature. Further improvements in the development of F-T catalysts resulted in the use of ThO
2
(optimum 18 wt. parts per 100 parts Co) instead of MnO
2
, and then to the replacement of part of the ThO
2
by a Group IIA metal oxide, MgO, while doubling the kieselguhr content to produce a commercial form of the catalyst (100:5:8:200).
Typically, in preparing catalysts for conducting F-T synthesis reactions, a Group VIII metal, preferably with an additional metal, e.g., a Group VIIB or VIII metal, or metals, to modify or promote the activity of the catalyst is composited with a particulate refractory inorganic oxide solids component by impregnation techniques. For example, cobalt may be first impregnated onto an alumina, silica, or titania support from a solution in which a soluble compound or salt of cobalt has been dissolved, and then a promoter metal, e.g., platinum, similarly added; or, cobalt and platinum can be coimpregnated onto a support from a single solution containing soluble compounds or salts of both cobalt and platinum. The metals impregnated support is then shaped, dried, calcined, and the metals component then reduced to activate and complete formation of the catalyst. These catalysts have considerably less activity than desired, and very low selectivity in producing hydrocarbon wax. Gas production is higher than is desirable. Consequently, there is need of a process for producing catalysts of these compositions but which have higher activity and improved selectivity.
THE INVENTION
This need and others is achieved in accordance with the present invention which embodies, in preparation of the catalyst, compositing with a refractory inorganic oxide solid, or solids, preferably silica, a catalytic metal of the Iron Group, preferably cobalt, and a Group VIII noble metal, preferably platinum. Preferably, the composite is formed by impregnation of the refractory inorganic oxide solid, or solids, with a solution of (a) a soluble compound, or salt, of the catalytic metal of the Iron Group, and a solution of (b) a soluble compound, or salt, of the Group VIII noble metal; the solid, or solids, being contacted with the solutions separately or in admixture, in a single or in multiple steps, and in any combination or sequence; and drying, calcining and washing the impregnated solid with an organo- or hydrocarbyl ammonium hydroxide, or ammonium hydroxide solution after the impregnation of the Group VIII noble metal salt or compound. The finished catalyst is produced, preferably by shaping the precursor, and then reducing at least a portion of the metals in the precursor to the metallic state. A catalyst produced by this process, quite surprisingly, is more active and selective in conducting a carbon monoxide hydrogenation reaction to produce hydrocarbon waxes, with lower gas make, than a catalyst of corresponding composition similarly prepared except that the catalyst was prepared from a catalyst precursor which was not washed with an organo- or hydrocarbyl ammonium hydroxide, or an ammonium hydroxide solution.
In preparation of the catalyst of this invention, the particulate solids support is contacted with a solution, or solutions, containing the solubilized metals in the desired stoichiometric amounts. For example, as is conventional, cobalt and platinum can be impregnated onto a particulate silica support by serial contact of the support, with, initially, a solution of a cobalt salt, e.g., cobalt nitrate and, preferably after drying and calcining the cobalt-impregnated solids, by contact of the cobalt impregnated support with a solution of a platinum salt, or compound, e.g., chloroplatinic acid or platinum acetylacetonate. Conversely, the order of the metals impregnation of the solids may be reversed, i.e., impregnation of the solids with the platinum may be conducted first; this being followed, after drying and calcination, by impregnation of the solids with cobalt. Alternatively, cobalt and platinum can be simultaneously impregnated onto the support by contact of the solids with a single solution containing both metals, and thereafter the catalyst may be dried, and calcined. In either event, after compositing the Group VIII noble metal, e.g., platinum, upon the support the noble metal, or platinum-impregnated solids is washed with a solution, or solutions, of the organoammonium, hydrocarbyl ammonium, or ammonium hydroxide. Preferably the wash step, or steps, is conducted immediately after impregnation of the noble metal onto the particulate support, after the noble metal-impregnated support has been first dried and calcined, whether or not the support was previously impregnated by the Iron Group metal. If increased concentrations of the catalytic metal, or metals, is desired, the cycle of impregnation steps can be repeated; or a partial cycle may be employed if it is desirable to increase the concentration of one metal on the support, without increasing the concentration of the other metal already impregnated onto the support. In either case, the catalyst precursor is washed with the organoammonium, hydrocarbyl ammonium, or ammonium hydroxide after application of the Group VIII noble metal.
The organoammonium, hydrocarbyl ammonium, or ammonium hydroxide compound used for washing the particulate Group VIII noble metal-containing solids is characterized generally by the formula
wherein R
1
, R
2
, R
3
and R
4
are the same or different, and identified as hydrogen, or an organo or hydrocarbyl substituent group, particularly an alkenyl, alkynyl or alkyl group, especially the latter. The chain length or an organo, or hydrocarbyl substituent can range from 1 to about 6, preferably 1 to about 3, sufficient that the organo, or hydrocarbyl ammonium compound is readily solubilized in the wash solution, preferably water. Exemplary of such hydrocarbyl groups are methyl, ethyl, vinyl, 1-propenyl, isobutyl, sec butyl, tert butyl, n-amyl, n-hexyl and the like. The preferred compound is one wherein at least 2, and preferably all of R
1
, R
2
, R
3
and R
4
are hydrogen, i.e., an organoammonium hydroxide, or ammonium hydroxide, directly or indirectly added to the solvent; e.g., by the addition of ammonia to water or ot

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