Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By alkyl transfer – e.g. – disproportionation – etc.
Reexamination Certificate
1998-12-10
2001-08-28
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By alkyl transfer, e.g., disproportionation, etc.
C585S643000, C585S646000, C585S647000
Reexamination Certificate
active
06281402
ABSTRACT:
The invention relates to the production of olefins from at least one olefin containing a different number of carbon atoms to that of the desired olefin(s). Processes which can effect this reaction include oligomerisation processes and olefin metathesis or disproportionation reactions. More particularly, the invention relates to metathesis or disproportionation of olefins.
Metathesis or disproportionation of olefins, or a reaction which redistributes alkylidene groups, is of great practical importance, for example for re-equilibration of light olefins from steam cracking or from fluidised bed catalytic cracking (FCC), such as ethylene, propylene and butenes.
Olefin metathesis processes have already been described, in particular in U.S. Pat. 4,795,734, French patent FR-A-2 608 595, U.S. Pat. No. 5,449,852 and FR-A-2 740 056. In FR-A-2 608 595, the reaction is carried out in a moving catalyst bed reactor, and a catalyst regeneration treatment is provided, carried out as follows: a portion of the catalyst is continuously or periodically extracted, the catalyst is sent to an accumulator drum then to a catalyst regeneration apparatus. The regenerated catalyst is returned to the head of the reaction zone.
The present invention provides a process for continuous metathesis or disproportionation of olefins, comprising at least two phases, a reaction phase a) carried out in a zone comprising at least one reactor containing at least one fixed bed of catalyst and a regeneration phase b) carried out in a zone comprising at least one reactor containing at least one fixed bed of catalyst, characterized in that at least one reactor passes from one phase to the other in alternation.
The invention also provides an apparatus for carrying out the process, comprising a reaction zone comprising at least one reactor containing at least one fixed bed of catalyst and a regeneration zone containing at least one reactor containing at least one fixed bed of catalyst.
The apparatus usually comprises 2 to 10 reactors, preferably 2 to 6 reactors and more preferably 4 reactors; when the reaction zone comprises at least 2 reactors, they are mounted in series. The regeneration zone preferably comprises a single reactor. In the reaction phase, the reactors operate in riser mode, but they can also operate in dropper mode or in mixed mode, i.e., a portion of the reactors operate in riser mode, the other reactors operate in dropper mode. Riser mode is preferred, however. In the process, each reactor is alternately in operative mode then in catalyst regeneration mode. Passage from the operative phase of one reactor to its catalyst regeneration phase is carried out as follows: the reactor is isolated from the remainder of the apparatus, the hydrocarbons contained in the reactor are then evacuated and the reactor is purged. The reactor is then connected to a regeneration loop and undergoes catalyst regeneration; at the end of this regeneration phase, the reactor and the regeneration loop are purged by at least one purge treatment, for example using an inert gas or vacuum or successively by at least one purge using an inert gas then vacuum. One or more of the purges can be accomplished by vacuum. After catalyst regeneration, the reactor is replaced in the series of operating reactors, preferably at the end of the series.
The operating reactors can be arranged in series in any order. Preferably, the reactor containing the oldest catalyst is placed at the head (in contact with fresh feed), and the reactor containing freshly regenerated catalyst is placed at the end of the series. This arrangement produces the best performances for feed transformation.
In a preferred implementation of the process of the invention, the reactor to be regenerated is isolated from the operating circuit then the hydrocarbons contained in the reactor to be regenerated are emptied into a receptacle before inserting it into the regeneration loop.
This receptacle can be a surge drum provided for that purpose. After the catalyst regeneration phase, the hydrocarbons contained in this surge drum are sent to the reactor with the regenerated catalyst.
This receptacle can also be a further reactor, in which case the procedure is as follows: the reactor the catalyst of which is to be regenerated is isolated from the operating circuit then the hydrocarbons contained in the reactor are emptied into the reactor which has just been regenerated. The reactor for which the catalyst has just been regenerated is replaced in the operating circuit, preferably at the end of the reactor series, and the emptied reactor is connected to the to regeneration circuit.
Preferably, the hydrocarbons contained in the reactor to be regenerated are recovered in a surge drum.
Advantages of the process of the invention include using a plurality of reactors which are alternately removed from the operating circuit to regenerate the catalyst. Thus if the total catalytic mass (all of the catalysts) is considered, the use of a plurality of reactors enables the unused catalytic mass to be reduced, or more precisely the catalytic mass being regenerated. This operation brings with it a large economic gain, more so since certain of the catalysts used—such as catalysts containing rhenium—are particularly expensive. The use of a plurality of reactors renders the use of catalysts with different compositions and masses possible and also enables elements (furnaces, chillers, pumps, effluent composition monitoring means . . . ) to be inserted depending on the specific requirements of the reaction.
Different types of catalysts are known for use in olefin metathesis or disproportionation which enable either homogeneous type reactors, when the constituent elements are all soluble in the reaction medium, to be used, or heterogeneous type reactions, when at least one of the elements is insoluble in that medium, to be used. The catalysts used in carrying out the process of the invention are solid catalysts preferably containing at least rhenium on a porous support preferably containing alumina. United States patents US-A-4 795 734, French patent FR-A-2 608 595, U.S. Pat. No. 5,449,852 and FR-A-2 740 056 describe catalysts of that type.
Olefins which can react in metathesis or disproportionation catalysed by that type of supported rhenium based catalyst can be linear or branched olefins, preferably linear, with general formula: R
1
R
2
C=CR
3
R
4
, where R
1
, R
2
, R
3
, R
4
, which may be identical or different, are hydrogen or a hydrocarbyl radical containing 1 to 20 carbon atoms. The olefins may also be cyclic in structure, the cycle containing 3 to 20 carbon atoms. An olefin may be reacted with itself or with a mixture of a plurality of olefins. The reactions which are of interest to us are preferably metathesis of ethylene and a C
4
cut containing 2-butene which produces propylene, and metathesis of ethylene and a C
5
cut containing 2-pentene which produces propylene and butenes. The reactions are as follows:
2-butene+ethylene←→propylene
2-pentene+ethylene←→propylene+2-butene+1-butene
The apparatus of the invention uses 2 to 10 reactors, preferably 2 to 6 reactors and more preferably 4 reactors. The process of the invention continuously converts olefins; regeneration of the catalyst or catalysts of one reactor normally takes 25 to 35 hours.
The olefin-containing feed to be treated is introduced into the first reactor where the olefins undergo a first metathesis or disproportionation step; the used catalyst can also capture impurities which may be contained in the feed. In embodiments where at least two reactors are operating, the effluent leaving the first reactor is introduced into the second reactor where it undergoes a second metathesis or disproportionation step. The effluent thus traverses all of the reactors which are in operation, the olefins undergo metathesis or disproportionation in each reactor, then the effluent is evacuated from the reactor zone.
In each reactor, the reaction conditions are as follows: a temperature of about 0° C. to
Boucot Pierre
Commereuc Dominique
Coupard Vincent
Fischer Beatrice
Forestiere Alain
Griffin Walter D.
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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