Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Reexamination Certificate
2002-01-03
2004-04-13
Koslow, C. Melissa (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
C502S182000, C502S185000, C518S715000, C518S717000
Reexamination Certificate
active
06720283
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to activated carbon supported cobalt based catalysts and their use in the process for the conversion of synthesis gas to diesel fuels with nil sulfur, nil nitrogen or nil aromatics.
BACKGROUND OF THE INVENTION
The search for processes to provide alternate feedstocks for fuels, and particularly high quality diesel fuels, has been prompted by the potential shortage of traditional petroleum reserves, and increasing instability of international hydrocarbon resources.
One approach to the problem has been the utilization of the Fischer-Tropsch synthesis in producing paraffins having selective product distribution as well as containing a few olefins, in varying paraffin/olefin ratios, depending on the catalyst composition, pretreatment procedures, and reaction conditions. Catalysts having various combinations of elements have been tested in the past, and the chief constituent element of the catalyst has been nickel, cobalt, iron and ruthenium.
U.S. Pat. No. 4,478,954 discloses a catalyst for the production of C
2
~C
4
olefins from carbon monoxide and hydrogen consisting of 5-50 wt % iron metal and 20-90 wt % an activated carbon support, promoted by magnesium and chromium metals.
U.S. Pat. No. 4,542,122 states that a cobalt catalyst, especially a thoria promoted cobalt catalyst, formed by dispersing the cobalt, or cobalt and thoria, upon a titania or titania-containing support wherein the titania support is one having a rutile:anatase ratio of at least about 2:3. By passing methanol, or a mixture of carbon monoxide and hydrogen over the catalyst at reaction conditions, a distillate fuel consisted principally of a mixture of linear paraffin and olefins; particularly a C
10
+
distillate can be formed. The distillate can be further refined and upgraded to high quality fuels, and other products such as diesel fuel, jet fuel, lubes and specialty solvents, particularly premium middle distillate fuels of carbon numbers ranging from about C
10
to about C
20
.
U.S. Pat. No. 4,579,986 discloses that synthesis gas is subjected to Fischer-Tropsch synthesis over a Co/Zr/SiO
2
catalyst and the C
20
+
fraction of the synthesized product is converted into linear C
10
~C
20
olefins by mild thermal cracking.
More recently, U.S. Pat. No. 6,274,029 discloses diesel fuels or blending stocks having excellent lubricity, oxidative stability and high cetane number are; produced from non-shifting Fischer-Tropsch processes by separating the Fischer-Tropsch product into a lighter and heavier fractions, e.g., at about 370° C., subjecting the 370° C.
+
fraction to hydro-treating, and combining the 370° C.
+
portion of the hydrotreated product with the lighter fraction that has not been hydrotreated.
Venter and Vannice (J. Catal., 1987, 103:450; Catal. Lett., 1990, 7:219; J. Phys. Chem., 1992, 96:9944) disclose that the higher activity and C
2
-C
4
olefins selectivities were observed over an activated carbon supported iron based catalyst promoted by manganese and potassium promoters.
The synthesis of hydrocarbons from carbon monoxide and hydrogen in liquid phase slurry containing a catalyst has been performed in the past. Although it permits very good control of the reaction temperatures, the use of slurry of catalyst in a liquid phase for this reaction generally has necessitated an additional step for the separation of the product from the catalyst and the use of modest space velocities.
Thus far, no one has disclosed a metal-containing activated carbon catalyst for use in a liquid phase system which affords improved yields of diesel fuels from the reaction between carbon monoxide and hydrogen, which minimizes the need for an additional step for the separation of product from the catalyst and which permits the use of high space velocities.
Clean diesel fuels that contain no or nil sulfur, nitrogen, or aromatics, are, or will likely be in great demand as diesel fuel or in blending diesel fuel. Clean diesel fuels having relatively high cetane number are particularly valuable. Typical petroleum derived distillates are not clean, in that they typically contain significant amounts of sulfur, nitrogen, and aromatics, and they have relatively low cetane numbers. Clean diesel fuels can be produced from petroleum based distillates through severe hydrotreating at great expense. The production of clean, high cetane number distillates from Fischer-Tropsch waxes has been discussed in the open literature, but few literatures that reported the catalyst which can directly convert synthesis gas to diesel distillates with high quality have appeared.
This invention will first show that the diesel distillates with sulfur-free, nitrogen-free or aromatics-free can be synthesized from synthesis gas over an activated carbon supported cobalt based catalyst that cut off the heavier end of the Schultz-Flory distribution.
SUMMARY OF THE INVENTION
An activated carbon supported cobalt based catalysts containing a Group IVB metal promoter, e.g., Ti, Zr, or Group IIIB metal promoter e.g., La, Ce, or Group VIII metal promter, e.g., Ru, Rh, Pt, wherein the weight ratio of Co: Activated carbon component is 0.05 to 0.4, exhibit enhanced activity and selectivity toward diesel fuels during Fischer-Tropsch synthesis. These catalysts also maintain high C
10
~C
20
hydrocarbons selectivity under slurry reaction conditions.
In accordance with this invention, a clean distillate being useful as a diesel fuel or as a diesel fuel blend stock and having a cetane number of at least about 60, preferably at least about 70, is produced, preferably direct from synthesis gas through Fischer-Tropsch process over an activated carbon supported cobalt based catalyst. In particular, there is provided a process for preparing directly diesel distillates from synthesis gas over modified Fischer-Tropsch catalysts.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The active catalyst is prepared from an activated carbon supported cobalt containing metal phase, wherein the Co:Activated Carbon weight ratio is about 0.05 to 0.4, promoted by zirconium- or cerium-containing oxide phase or promoted by ruthenium-containing metal phase. Catalysts derived from nitrate salts wherein the total Co:Activated Carbon weight ratio is in the specified range are expected to give acceptable performance, although it is preferred to operate with a single phase catalyst precursor so as to preclude any irregular behavior in subsequent activation procedures.
A preferred activated carbon carrier has a surface area in the range of about 200-2000 m
2
/g, preferably 800-1500 m
2
/g, and pore volume of 0.3 to 2.0 ml/g, preferably 0.35 to 0.75 ml/g, distribution of pore diameter of 4 to 1000 Å, preferably 5 to 500 Å, bulk density of about 0.1 to 1.0 g/ml, preferably 0.3 to 0.6 g/ml, and side crushing strength of about 0.08 to 3.0 kg/mm.
The preferred catalysts comprise a Group VIII non-noble metal, e.g. cobalt, iron and nickel, in conjunction with a Group IVB metal promoter, e.g., zirconium, titanium, and a Group IIIB metal promoter, e.g., cerium, lanthanum, or Group VIII metal promoter, e.g., ruthenium, platinum, rhodium, supported on a porous support. The support is preferably an activated carbon, which is made from almond core, cocoanut shell, palm tree wood, or coal.
Group IVB metal promoter, e.g., Zr, or Group IIIB metal promoter e.g., Ce, or Group VIII metal promoter, e.g., Ru, may be added to the activated carbon carrier before impregnating cobalt component or by co-impregnating with cobalt component, the cobalt preferably being doped as a solution of the nitrate salt, while the zirconium or cerium preferably being added as a solution of the nitrate salt although their other compounds such as sulfates may be used, and the ruthenium metal preferably being added as a solution of the chloride.
The catalyst is prepared by co-impregnating or stepwise-impregnating the metals from solutions onto the support, drying at room temperature for several days, then at 80 to 90° C. for 8 hours, and finally at 110 to 120° C. for 10 hours.
Ding Yunjie
Lin Liwu
Ma Wenping
Burdett James R.
Dalian Institute of Chemical Physics
Hailey Patricia L.
Koslow C. Melissa
Venable LLP
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