Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Silicon containing or process of making
Reexamination Certificate
2000-06-20
2002-11-19
Hendrickson, Stuart L. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Silicon containing or process of making
C502S302000, C502S303000, C502S304000, C502S325000, C502S326000, C502S327000, C502S328000, C502S329000, C502S331000, C502S332000, C502S333000, C502S334000
Reexamination Certificate
active
06482766
ABSTRACT:
The present invention concerns a catalytic formulation, its preparation and its use in a process for synthesising hydrocarbons from a CO—(CO
2
)—H
2
mixture, i.e., a CO—H
2
mixture which may contain CO
2
, known as synthesis gas, more particularly the use thereof to convert synthesis gas to a mixture of linear and saturated hydrocarbons essentially constituted by C
5
+
hydrocarbons (i.e., containing at least 5 carbon atoms per molecule), or more precisely to a mixture of essentially linear and saturated hydrocarbons containing at least 25% by weight of C
5
+
hydrocarbons with respect to the total of the hydrocarbons formed.
Synthesis gas is known to be converted to hydrocarbons in the presence of catalysts containing transition metals. This conversion, operated at high temperatures and under pressure, is known as the Fischer-Tropsch synthesis. Metals from group VIII of the periodic classification of the elements such as iron, ruthenium, cobalt and nickel catalyse the transformation of CO—(CO
2
)—H
2
mixtures to liquid and/or gaseous hydrocarbons.
The products prepared by the Fischer-Tropsch process in the presence of catalysts comprising group VIII metals have a very wide molecular weight distribution. Thus only a small proportion of the products obtained are situated in the range of middle distillates constituted by kerosine and gas oil fractions, the kerosine fraction(s) being constituted by a mixture of hydrocarbons with boiling points which are in the range 140° C. to 300° C., and the gas oil fractions being constituted by a mixture of hydrocarbons with boiling points which are in the range 180° C. to 370° C. during atmospheric distillation as would be carried out by the skilled person on crude oil.
Since 1973, great efforts have been made to improve the yield of middle distillates from processes based on synthesis gas conversion. Thus the catalyst described in U.S. Pat. No. 5,302,622, comprising cobalt, copper and ruthenium and prepared by gelation, produces a mixture of essentially linear and saturated hydrocarbons containing at least 80% by weight of C
5
+
hydrocarbons with respect to the total amount of hydrocarbons formed.
These formulations can synthesise essentially paraffinic, linear hydrocarbons. However, a substantial proportion of these hydrocarbons is constituted by paraffins with high boiling points, i.e., with boiling points which are above that of middle distillates.
Such high boiling point hydrocarbons are thus advantageously treated in a hydrocracking process which is normally used for treating heavy cuts from a crude oil, in order to improve the yield of middle distillates.
In some cases, however, it is advantageous to synthesise a mixture of essentially linear saturated hydrocarbons generally containing less than 80% of C
5
+
hydrocarbons, and preferably 25% to 70% by weight of C
5
+
hydrocarbons. Such a mixture contains a high proportion of hydrocarbons which are liquid at ambient temperature and at atmospheric pressure.
After simple fractionation (for example atmospheric distillation), such an essentially liquid product constitutes a synthetic crude which can readily be transported and/or mixed with a crude oil then processed separately or as a mixture in conventional refinery units.
U.S. Pat. No. 4,522,939 describes a process for the preparation of a Fischer-Tropsch catalyst based on cobalt and containing a second metal selected from zirconium, titanium or chromium and supported on silica, alumina or silica-alumina. That catalyst is prepared by impregnation or mixing and the second metal is introduced before, after or simultaneously with introduction of the cobalt. Preferably, the catalyst is calcined after each introduction. Reduction after the various impregnation or mixing steps leading to the production of the catalyst is not anticipated, a single reduction step being carried out after preparation of the catalyst and before the catalytic test. Such catalysts deactivate to a greater or lesser extent over time.
U.S. Pat. Nos. 4,794,099 and 4,960,801 describe catalysts based on cobalt and optionally rhenium deposited on supports based on titanium oxide. In U.S. Pat. No. 4,794,099, a silicon based precursor is added to the titanium oxide before or after deposition of cobalt and rhenium, to improve the activity of the catalyst. In U.S. Pat. No. 4,960,801, an aluminum, zirconium, or silicon based binder is added to the titanium oxide based support to increase the porosity of the support. Similarly, a single reduction step is provided after calcining the catalyst containing all of the elements and before the catalytic test.
The present invention describes the preparation of a Fischer-Tropsch catalyst with performances which are particularly stable, and which after reduction in hydrogen leads to the conversion of synthesis gas to a mixture of essentially linear and saturated hydrocarbons containing at least 25% by weight of C
5
+
hydrocarbons with respect to the total amount of hydrocarbons formed.
The present invention provides a process for the preparation of a catalyst comprising a support selected from the group formed by at least one oxide of an element selected from the group formed by the following elements Si, Al, Ti, Zr, Sn, Zn, Mg or Ln (where Ln is a rare earth, i.e., an element with an atomic number which is between 57 and 71 inclusive), preferably selected from the group formed by silica, alumina, zirconia and titanium oxide, cobalt, titanium, at least one additional element A selected from the group formed by copper, ruthenium, platinum, palladium, scandium and yttrium, the process being characterized in that the catalyst preparation comprises at least the following successive steps.
(1) forming a precursor comprising at least cobalt, element A and the support,
(2) at least partial reduction of said precursor in the presence of at least one reducing compound, and
(3) depositing titanium on the reduced precursor.
The catalyst prepared in accordance with the invention generally comprises, in % by weight of the element with respect to the weight of the support in the catalyst, between 1% and 60%, preferably between 2% and 50%, of cobalt, between 0.01% and 20%, preferably between 0.05% and 10%, of additional element A and between 0.01% and 15%, preferably between 0.05% and 5%, of titanium.
The invention also concerns the catalyst obtained by the preparation process of the invention, also the use of the catalyst in a process for the synthesis of essentially linear and saturated hydrocarbons containing at least 25% by weight of C
5
+
hydrocarbons with respect to the total amount of hydrocarbons formed, from a feed comprising carbon monoxide CO, hydrogen and optionally, carbon dioxide CO
2
, said feed being known as synthesis gas. The catalyst of the invention has improved stability over prior art catalysts.
Any titanium based compound can be used in the present invention, for example titanium can be incorporated in the form of a halide, oxalate, sulphate, or an alkoxide such as ethyl orthotitanate or isopropyl orthotitanate.
The cobalt and additional element A present in the precursor can be introduced in step (1) using any method which is known to the skilled person, such as ion exchange, dry impregnation, co-precipitation, gelation, ion mixing or grafting of organometallic complexes.
Of these methods, impregnation, co-precipitation, gelation or mixing are preferred for the preparation of said precursor in step (1), as they allow intimate contact between the cobalt and the optional additional element A.
The use of impregnation, co-precipitation, gelation or mixing of cobalt, element A and the support element can generally produce a precursor for a catalyst for the conversion of synthesis gas to hydrocarbons which is active and can lead to the formation of at least 25% by weight of C
5
+
hydrocarbons with respect to the total amount of hydrocarbons formed.
A preferred method for the preparation of the catalyst precursor used in accordance with the invention consists, for example, of impregnating
Azib Hedi
Chaumette Patrick
Clause Olivier
Hendrickson Stuart L.
Instuit Francais du Petrole
Millen White Zelano & Branigan P.C.
LandOfFree
Process for catalyst preparation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for catalyst preparation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for catalyst preparation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2935831