Chemistry: fischer-tropsch processes; or purification or recover – Including regeneration of catalyst
Reexamination Certificate
1999-10-08
2001-12-18
Padmanabhan, Sreeni (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Including regeneration of catalyst
C518S700000, C502S020000, C585S734000
Reexamination Certificate
active
06331574
ABSTRACT:
1. 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 transportation fuels and lubricating oils derived from synthesis gas.
2. BACKGROUND
The improvement of Fischer-Tropsch (F-T) catalysts, i.e., catalysts useful for the production of petrochemicals and liquid transportation fuels by hydrogenation of carbon monoxide, has been the subject of ongoing research for some years; and this work continues. Early commercial work with the F-T process began in Germany in the 1920's, and was continued, resulting in the SASOL plants of South Africa. F-T synthesis is well documented in the technical and patent literature. The Group VIII metals, e.g., ruthenium and the Iron Group Metals such as iron and cobalt, have been used extensively as catalytic metals in the production of F-T catalysts, and these metals have been promoted or modified with various other metals, and supported on various substrates in formation of the catalysts.
Cobalt catalysts, particularly the promoted cobalt catalysts, e.g., those constituted of cobalt and rhenium, or cobalt, thoria and rhenium, supported on titania, or other titania-containing support have been found to exhibit high selectivity in the conversion of methanol to hydrocarbon liquids, or synthesis of hydrocarbon liquids from hydrogen and carbon monoxide as disclosed, e.g., in U.S. Pat. No. 4,568,663. The catalysts can be prepared by gellation or cogellation techniques, but typically they are prepared by deposition of the metal, or metals, on the previously pilled, pelleted, beaded, extruded, or sieved support material, or a powder by the impregnation method. In preparing the composite catalysts, the metals are deposited from solution on the support in preselected amounts to provide the desired absolute amounts and weight ratio of the respective metals, e.g., cobalt and rhenium. Suitably, e.g., the cobalt and rhenium are composited with the support by contacting the support with a solution of a cobalt-containing compound, or salt, or a rhenium-containing compound, or salt, e.g., a nitrate, carbonate or the like. Optionally, cobalt and rhenium can be co-impregnated upon the support. The cobalt and rhenium compounds used in the impregnation can be any organometallic or inorganic compounds which decompose to give cobalt and rhenium oxides upon calcination, such as a cobalt, or rhenium nitrate, acetate, acetylacetonate, naphthenate, carbonyl, or the like. The amount of impregnation solution used should be sufficient to impregnate the catalyst via the incipient wetness technique, or sufficient to completely immerse the carrier, usually a volume of liquid ranging 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. The catalyst, after impregnation, is dried, and calcined; suitably by contact with oxygen, air or other oxygen-containing gas at temperature sufficient to oxidize the metal, or metals; e.g., to convert cobalt to Co
3
O
4
. The catalyst, or catalyst precursor, is then reduced and activated by contact of the oxidized metal, or metals, with hydrogen, or hydrogen-containing gas.
The reduced catalysts, e.g., cobalt catalyst, and cobalt catalyst promoted with other metals, have been found to provide relatively high selectivity, activity and activity maintenance in methanol conversion, and in the conversion of hydrogen and carbon monoxide to distillate fuels; predominantly C
5
+ linear paraffins and olefins, with low concentrations of oxygenates. Nonetheless, there remains a pressing need for F-T catalysts of yet higher activity; particularly more active catalysts capable of producing transportation fuels and lubricants of high quality at good selectivity and high levels of productivity.
3. THE INVENTION
This need and others are achieved in accordance with the present invention which embodies the activation, or reactivation of a deactivated catalyst, or the preparation and activation of a fresh catalyst. The process requires, in the preparation of the catalyst, contacting a powder or preformed particulate solids support, suitably a refractory inorganic oxide support, preferably a crystalline aluminosilicate zeolite, natural or synthetic, alumina, silica, silica-alumina or titania in one or a series of two or more steps with a liquid, or solution, suitably an aqueous solution containing a compound, or salt of a catalytic metal, or metals, preferably a Group VIIB or Group VIII metal, or metals, of the Periodic Table of the Elements (Sargent-Welch Scientific Company; Copyright 1968) to impregnate and deposit the metal, or metals, upon the powder or support. The impregnated powder or support is then calcined. Generally, two to four or more metal impregnations, with intermediate calcination of the metal, or metals, impregnated support is preferred, and is sufficient to deposit from about 5 percent to about 70 percent, preferably from about 10 percent to about 30 percent metallic metal, or metals, upon the support or powder, based upon the total weight (wt. %) of the calcined catalyst.
An inactive or deactivated catalyst, or the calcined catalyst, or catalyst precursor, is then contacted, and treated with a solution of a chelating compound, preferably a poly- or multidentate chelating compound, sufficient to complex with, extract and remove some of the metal atoms present in the oxides, or reduced metal particles, and increase the activity or C
5
+ selectivity, or both the activity and C
5
+ selectivity of the catalyst in its use, after reduction, in the hydrogenation of carbon monoxide, or conduct of Fischer-Tropsch synthesis reactions. The extraction, and removal of some of the catalytic metal from the catalyst, or calcined catalyst precursor, in this manner to increase the activity of the catalyst is indeed a surprising effect since past experience has shown that the activity of a catalyst constituted of a given metal, e.g., cobalt, is directly related to the amount of metallic metal, e.g., metallic cobalt, contained on the catalyst; the greater the amount of metallic cobalt contained on the catalyst, after reduction, the greater the activity of the catalyst in conducting carbon monoxide hydrogenation reactions, especially in converting synthesis gas, or mixtures of hydrogen and carbon monoxide, to C
5
+ hydrocarbons. However, it is found that treatment of a deactivated, or calcined metal, or metals, loaded catalyst or catalyst precursor, with the chelating compound sufficient to extract, or remove the metal, or metals, to leave from about 1 percent to about 80 percent, preferably from about 25 percent to about 75 percent, of the metal, or metals present before the extraction, measured as metallic metal, will increase the activity of the catalyst, after reduction, as much as about 10 percent, and higher, and often as much as 25 percent; activity values considerably in excess of those which can be achieved by reducing the deactivated or calcined catalysts without first treating the deactivated, or calcined catalysts with the chelating compound. Moreover, the C
5
+ selectivity of the catalyst is increased, resulting in as much as a four-fold increase in productivity.
In impregnating the support to form a catalyst, it is believed that the metal, e.g., cobalt, initially deposits within the pores of the support, and is then laid down along the peripheral surface between the pores, bridging over and covering some of the previously open pores, or pore mouths. On calcination the cobalt is converted to Co
3
O
4
. Reduction of the cobalt oxide component e.g., with hydrogen, as in conventional practice produces a catalyst active for the hydrogenation of carbon monoxide, or
Daage Michel A.
Fiato Rocco A.
Koveal Russell J.
Krylova Alla Jurievna
Lapidus Albert L'Vovoch
Brumlik Charles J.
ExxonMobil Research and Engineering Company
Padmanabhan Sreeni
Parsa J.
Simon Jay
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