Mineral oils: processes and products – Chemical conversion of hydrocarbons – Plural serial stages of chemical conversion
Reexamination Certificate
2002-05-23
2004-08-03
Parsa, J. (Department: 1621)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Plural serial stages of chemical conversion
C208S108000, C518S700000, C585S324000
Reexamination Certificate
active
06770191
ABSTRACT:
The present invention relates to a process for the preparation of linear olefins and to a process to prepare linear alcohols from an olefin-containing feed, which is at least partly based on these linear olefins.
BACKGROUND OF THE INVENTION
There are various methods known in the art to prepare linear olefins.
Such process is disclosed in U.S. Pat. No. 4,579,986. This U.S. patent discloses a process for the preparation of linear C
10
-C
20
olefins, which process comprises preparing a mixture of hydrocarbons substantially consisting of linear paraffins by:
(a) contacting a mixture of carbon monoxide and hydrogen at elevated temperature and pressure with a cobalt-containing catalyst,
(b) separating from the paraffin mixture thus prepared a heavy fraction which consists substantially of C
20
+ paraffins, and
(c) converting at least this heavy fraction (a “wax”) by mild thermal cracking into a mixture of hydrocarbons which consists substantially of linear olefins and contains the desired C
10
-C
20
olefins.
Although the wax cracking method according to U.S. Pat. No. 4,579,986 performs satisfactorily, there is still room for improvement. Particularly if the starting point is to produce an olefin-containing feed which can be used as (part of) the feedstock for a hydroformylation reaction stage to produce linear detergent and plasticizer alcohols, the method according to U.S. Pat. No. 4,579,986 can be improved. Namely, linear plasticizer alcohols typically contain from 7 to 11 carbon atoms, while linear detergent alcohols typically contain 12 to 15 carbon atoms. Accordingly, any hydrocarbon fraction produced to serve at least partly as the source of hydroformylation feedstocks should contain a significant portion of C
6
to C
14
olefins, at least 80% by weight, but preferably at least 85% by weight, of which consists of the corresponding linear &agr;-olefins. It was found that by hydrogenating the wax feed prior to subjecting it to the mild thermal cracking treatment very high quality C
6
to C
10
and C
11
to C
14
linear &agr;-olefins are produced: the C
6
to C
14
olefins produced (contained in a mixture of C
5
+ olefins) consist for more than 80% by weight of C
6
to C
14
linear &agr;-olefins.
SUMMARY OF THE INVENTION
A process for the preparation of a mixture comprising C
5
+ linear olefins, which process comprises the steps of
(a) reacting carbon monoxide and hydrogen in the presence of a Fischer-Tropsch catalyst under Fischer-Tropsch reaction conditions thereby producing a hydrocarbon mixture;
(b) separating, from the hydrocarbon mixture, at least one hydrocarbon fraction, of which at least 95% by weight consists of hydrocarbons containing 15 carbon atoms or more;
(c) contacting the thus-separated hydrocarbon fraction with hydrogen in the presence of a hydrogenation catalyst under hydrogenation conditions thereby producing a hydrogenated hydrocarbon fraction;
(d) subjecting said hydrogenated hydrocarbon fraction to a mild thermal cracking treatment thereby producing a cracked product; and
(e) separating, from the cracked product, a mixture comprising C
5
+ linear olefins.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to the preparation of linear olefins by a process which also involves a Fischer-Tropsch hydrocarbon synthesis reaction.
Accordingly, in a first aspect the present invention relates to a process for the preparation of a mixture comprising C
5
+ linear olefins, which process comprises the steps of
(a) reacting carbon monoxide and hydrogen in the presence of an effective amount of Fischer-Tropsch catalyst under Fischer-Tropsch reaction conditions;
(b) separating from the hydrocarbon mixture thus prepared at least one hydrocarbon fraction, of which at least 95% by weight consists of hydrocarbons containing 15 carbon atoms or more;
(c) contacting this hydrocarbon fraction with hydrogen in the presence of an effective amount of hydrogenation catalyst under hydrogenation conditions;
(d) subjecting the hydrogenated hydrocarbon fraction thus obtained to a mild thermal cracking treatment; and
(e) separating from the cracked product thus prepared the mixture comprising C
5
+ linear olefins.
The product mixture comprising C
5
+ linear olefins preferably is a mixture comprising C
5
to C
m
linear olefins with m being an integer of from 10 to 20, preferably 12 to 18, more preferably 12 to 15. A very useful mixture is a mixture comprising C
5
to C
14
linear olefins. Such mixture suitably comprises at least 20% by weight, and more preferably from 25 to 50% by weight, of C
11
to C
14
linear &agr;-olefins. The C
5
to C
10
linear &agr;-olefins typically constitute up to 75% by weight of the stream, suitably from 40 to 75% by weight. The balance up to 100% by weight, which forms a relatively small proportion of the stream, consists of hydrocarbons other than the olefins mentioned, such as C
4
hydrocarbons and the corresponding C
5
+ linear alkanes, iso-alkanes, iso-olefins, internal olefins and dienes. Typically this small proportion of other hydrocarbons will not exceed 20% by weight and suitably is less than 10% by weight.
In step (a) of the present process hydrocarbons are formed by reacting carbon monoxide and hydrogen under suitable conditions. In general, the preparation of hydrocarbons from a mixture of carbon monoxide and hydrogen at elevated temperature and pressure in the presence of an effective amount of a suitable catalyst is known as the Fischer-Tropsch hydrocarbon synthesis. Catalysts used in this hydrocarbon synthesis are normally referred to as Fischer-Tropsch catalysts and usually comprise one or more metals from Groups 8, 9 and 10 of the Periodic Table of Elements, optionally together with one or more promoters, and a carrier material. In particular, iron, nickel, cobalt and ruthenium are well known catalytically active metals for such catalyst. The Fischer-Tropsch catalyst to be used in step (a) of the present process suitably comprises a porous carrier, in particular a refractory oxide carrier. Examples of suitable refractory oxide carriers include alumina, silica, titania, zirconia or mixtures thereof, such as silica-alumina or physical mixtures such as silica and titania. Very suitable carriers are those comprising titania, zirconia or mixtures thereof. Titania carriers are preferred, in particular titania which has been prepared in the absence of sulphur-containing compounds. This carrier may further comprise up to 50% by weight of another refractory oxide, typically silica or alumina. More preferably, the additional refractory oxide, if present, comprises up to 20% by weight, even more preferably up to 10% by weight, of the carrier.
The preferred catalytically active metal is cobalt, although nickel, iron and ruthenium could also be used. The amount of catalytically active metal present in the catalyst may vary widely. Typically, the catalyst comprises 1-100 parts by weight of such metal per 100 parts by weight of carrier, preferably, 3-60 parts by weight, more preferably, 5-40 parts by weight. The above amounts of catalytically active metal refer to the total amount of metal in element form and can be determined by known elemental analysis techniques. For the sake of convenience cobalt is referred to hereinafter as the catalytically active metal, but it is emphasized that instead of or in addition to cobalt other catalytically active metals as mentioned hereinbefore may also be used.
In addition to cobalt the catalyst may comprise one or more promoters known to those skilled in the art. Suitable promoters include manganese, zirconium, titanium, ruthenium, platinum, vanadium, palladium and/or rhenium. The amount of promoter, if present, is typically between 0.1 and 150 parts by weight, for example between 1 and 50 parts by weight, per 100 parts by weight of carrier.
Typically, the Fischer-Tropsch catalyst does not contain alkali or alkaline earth metals, apart from possible impurities introduced with starting materials in the preparation process of the catalysts of the present inventi
Ali Abdul Razak Mohamad
Ansorge Joachim
Dirkzwager Hendrik
Fenouil Laurent Alain Michel
Geijsel Joannes Ignatius
Parsa J.
Shell Oil Company
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