Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By alkyl transfer – e.g. – disproportionation – etc.
Reexamination Certificate
1999-07-30
2001-09-04
Knode, Marian C. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By alkyl transfer, e.g., disproportionation, etc.
C585S645000, C585S646000, C585S647000, C585S921000
Reexamination Certificate
active
06284939
ABSTRACT:
The invention pertains to a catalytic process that uses a down-flowing catalyst in the form of a moving bed in at least one reaction zone and a regenerator. The catalyst that comes from the reaction zone and, in general, from the last reaction zone is at least partially deactivated by the presence of organic matter.
Said organic matter includes coke, gums, and the adsorbed organic matter, which are adsorbed hydrocarbons in the case of a process that treats petroleum fractions.
The coke and gums are formed from the adsorbed organic matter and turn into deposits on the catalyst. Gums and coke shall be excluded from the meaning of the term “adsorbed organic matter.”
In order to reactivate the catalyst, it is necessary to transfer it into the regenerator, which comprises at least one regeneration zone in which, in a first stage, the organic matter is eliminated from the catalyst, whereby the catalyst may undergo other types of treatment.
The elimination of the organic matter is generally done with combustion, in one or more zones.
It has been found that, in certain processes such as metathesis that operate in the liquid phase, the catalyst is very sensitive to the adsorbed organic matter, which is hydrocarbons in the case of metathesis.
When the organic-matter contents are high, they can even exceed 50% of the weight of the catalyst, for example 70%.
Such quantities cannot, however, be burned in installations that generally can handle up to 8-10% organic matter to be burned, which is essentially coke.
The applicant has found that the adsorbed organic matter, for example, in the metathesis process essentially includes relatively light hydrocarbons. As a matter of fact, the preferred olefins that are likely to react under conditions of metathesis are olefins that have 2-40 carbon atoms and generally 2 to 10 carbon atoms. The existing processes operate essentially on fractions C4, C5, C6 or even fractions that contain C18-C30 olefins.
Patent FR 2.608.595 describes a process for metathesis of olefins in a moving bed, in which the catalyst is transferred by a lift from the reaction zone to the regenerator, whereby the regenerated catalyst is brought back up to the reaction zone by a lift with a liquified gas. It was thus necessary to add an additional stage for the elimination of a large portion of the adsorbed matter prior to regeneration or to provide for more combustion zones in the regenerator.
One solution would involve desorbing a portion of the organic matter by heat exchange between the solid and a high-temperature gas, followed by drainage-depressurization phases.
The applicant has found, however, that this technique was attended by major drawbacks: poor heat exchange between the gas and catalyst particles, elevated gas temperature, the need for high gas flow rates and a technology that is difficult to implement owing, in particular, to the presence of an exchanger which has difficulty tolerating the necessary gas pressurization-depressurization cycles.
Moreover, in these liquid-phase processes such as metathesis wherein the catalyst is quickly deactivated, regeneration has to be done continuously, and the presence of such an exchanger would further impede this circulation.
The reaction-regeneration operations are well-known, for example in connection with reforming that operates in the gas phase (EP-439,388 or U.S. Pat. No. 3,839,197). The catalyst that emerges from the last reaction zone is picked up in a lift pot that also receives a gas (hydrogen, nitrogen, . . . ) which brings the catalyst in the lift to the receptacle located at the top of the regenerator. The catalyst that emerges from the regenerator is carried by lift gas up to the top of the first reaction zone.
Surprisingly enough, the applicant found that it was possible to eliminate a significant portion of the adsorbed organic matter without an additional stage and without additional combustion zones by stripping the adsorbed organic matter in the lift itself that brings the catalyst from the reaction zone to the regenerator.
What was particularly surprising was that it was found that the stripper-lift could be effective even at fairly low temperatures, at ambient temperature, for example, for certain processes that use light hydrocarbons.
The invention is applicable to any catalytic process that operates at least partly in the liquid phase with a feedstock that contains carbon-containing substances, especially hydrocarbons.
The invention thus pertains to a continuous catalytic process that uses a catalyst circulating in a moving bed in at least one reaction zone that operates in the liquid phase and in a regenerator, with a lift to transfer the deactivated catalyst emerging from the reaction zone to the regenerator, whereby said process is characterized by the fact that the transfer is accomplished by a gas that does not react with the catalyst and with the stripping off of at least a portion of the organic matter that is adsorbed on the deactivated catalyst.
More particularly, the invention pertains to a metathesis process and, preferably, to a process for metathesis of olefins having 2-40 carbon atoms, preferably 2-30 carbon atoms, or advantageously 2-10 carbon atoms, and more specifically the C4, C5, C6 olefins or heavier olefins (C18-C30), between them (the same or different olefins) or ethylene or propylene.
The catalyst circulates in a descending moving bed, continuously or in batch mode.
The deactivated (i.e., at least partly deactivated) catalyst that contains adsorbed organic matter (hydrocarbons, for example) is transferred to the regenerator by a stripper-lift.
The transfer is accomplished under the action of at least one gas that does not react with the catalyst under the conditions of the process; this may be nitrogen, methane, or ethane, for example. The gas that is used is also intended to strip off at least a portion of the adsorbed organic matter, such that a catalyst that contains no more than 10% by weight of total organic matter (gums+coke+adsorbed material) arrives at the regenerator. However, before the catalyst is subjected to the action of said gas, the catalyst contains at least 10% by weight of total organic matter. The organic matter is mainly adsorbed organic matter; there may or may not be coke, and in all cases less than 10% coke by weight, and more generally less than 8% coke by weight.
In metathesis, there are only adsorbed hydrocarbons; coke is not formed. The invention thus applies especially well to the catalytic processes that operate at temperatures below the point at which coke forms on the catalyst.
It has been found that in the process according to the invention the ratio of adsorbed organic matter to catalyst at the inlet to the stripper-lift is 0.50% (by weight) or else 1-50% or 2-50%, and more particularly 5-20% (by weight), and at the outlet it is 0-10% (by weight) and preferably 1-6% (by weight).
The speed of the solid in the stripper-lift is generally 1-10 m/sec, and preferably 2-5 m/sec. The ratio of catalyst to gas (in kg/cm
3
) is generally between 1 and 20, and advantageously between 5 and 12. The temperature of the gas is variable: 0-400° C., but more generally 10-150° C., for metathesis for example. The pressure of the gas can be up to 5.0 MPa, and more particularly 0.02-0.7 MPa for metathesis.
BRIEF DESCRIPTION OF THE DRAWING
The attached is a schematic flowsheet of an embodiment of the invention wherein metathesis is conducted.
REFERENCES:
patent: 2465255 (1949-03-01), Moorman
patent: 2709673 (1955-05-01), Berg
patent: 3365513 (1968-01-01), Heckelsberg
patent: 3978150 (1976-08-01), McWilliams, Jr.
patent: 4615792 (1986-10-01), Greenwood
patent: 4981575 (1991-01-01), Bonneville
patent: 2 608 595 (1988-06-01), None
Commereuc Dominique
Hoffmann Frederic
Mege Philippe
Dang Thuan D.
Institut Francais du Pe'trole
Knode Marian C.
Millen White Zelano & Branigan P.C.
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