Mineral oils: processes and products – Chemical conversion of hydrocarbons
Reexamination Certificate
2000-06-01
2002-02-19
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
C208S137000, C208S138000, C208S139000, C208S140000
Reexamination Certificate
active
06348144
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to hydrocarbon conversion catalyst regeneration that employs a halogen-containing compound.
BACKGROUND OF THE INVENTION
Although catalysts for the conversion of hydrocarbons have a tendency to deactivate, usually a catalyst's activity may be restored by one of a number of processes that are known generally as regeneration processes. Regeneration processes are extensively used. What specific steps comprise a regeneration process depend in part on the reason for the deactivation. For example, if the catalyst deactivated because coke deposits accumulated on the catalyst, regeneration usually includes removing the coke by burning. If the catalyst deactivated because a catalytic metal such as platinum became agglomerated, regeneration usually includes redispersing the metal by contacting the catalyst with oxygen and chlorine. If the catalyst deactivated because a catalytic promoter such as chloride became depleted, regeneration usually includes replenishing the promoter by contacting the catalyst with a chlorine-containing species. Operating conditions and methods for these regeneration processes are well known. Regeneration processes can be carried out in situ, or the catalyst may be withdrawn from the vessel in which the hydrocarbon conversion takes place and transported to a separates regeneration zone for reactivation. Arrangements for continuously or semicontinuously withdrawing catalyst particles from a reaction zone and for reactivation in a regeneration zone are well known.
Many of these regeneration processes share the common feature of introducing one or more chlorine-containing compounds into the regeneration zone in order to restore the activity of the catalyst for use in the reaction zone. Although chlorine is sometimes introduced into the regeneration zone, it is much more common that one of several chlorine-containing compounds, such as 1,1 dichloroethane, 1,2 dichloroethane, 1,1 dichloropropane, and 1,2 dichloropropane, is introduced into the regeneration zone. The most commonly used compounds thus contain not only chlorine but also carbon and/or hydrogen. Many regeneration zones into which these compounds are introduced typically contain molecular oxygen and operate at conditions that have been carefully optimized with a view towards combusting coke deposits on the catalyst or towards oxidizing or dispersing a catalytic metal on the catalyst. When a chlorine-containing compound is introduced into such a regeneration zone, it also is generally combusted or oxidized, and by-products of combustion, such as carbon dioxide, water, hydrogen chloride, and chlorine, are formed. As the chlorine-containing compound combusts, regions of intense burning can arise in the regeneration zone, either in portions of the catalyst and/or near to mechanical internals within the regeneration zone.
Two problems associated with localized regions of intense combustion of the chlorine-containing compound within the regeneration zone are catalyst deactivation and mechanical failure. As to catalyst deactivation, the combination of temperature, water vapor, and exposure time determine the useful life of the catalyst. Exposure of high surface area catalyst to high temperatures for prolonged periods of time will transform the catalyst into a more amorphous material that has a decreased surface area. Decreased surface area in turn can lower the activity of the catalyst to a level at which the catalyst is considered deactivated. This type of catalyst deactivation is permanent and can eventually render the catalyst unusable. Similarly, with respect to mechanical failure, the exposure of the internal mechanical parts of the regeneration zone to high temperatures for extended periods of time will change the physical properties of the parts and degrade or weaken their structural integrity. Consequently, the internal parts can break or crack, thereby necessitating costly repairs and downtime.
SUMMARY OF THE INVENTION
This invention is a method of introducing a halogen-containing compound that contains hydrogen or carbon into a catalyst regeneration zone. The method of this invention precombusts at least a portion of the hydrogen or carbon of the halogen-containing compound prior to using the halogen for catalyst regeneration. This invention is useful even though the catalyst regeneration zone operates at conditions that are sufficient to combust at least a portion of the hydrogen or carbon of the halogen-containing compound. By precombusting some or preferably all of the hydrogen or carbon of the halogen-containing compound in a precombustion zone, rather than in the regeneration zone, the possibility of localized regions of intense combustion of the halogen-containing compound in the regeneration zone is minimized or eliminated. Thus, this invention decreases the exposure of the catalyst to high temperatures, decreases the risk of permanent catalyst deactivation because of surface area decline, and prolongs the activity of the catalyst even after many regenerations. This invention also decreases the exposure of the internals of the regeneration zone to high temperatures, decreases the risk of weakening the internals of the regeneration tower, and prolongs the useful life of the mechanical equipment employed for regeneration.
Accordingly, in one embodiment, this invention is a method for regenerating a hydrocarbon conversion catalyst. At least a portion of the hydrogen or the carbon of a halogen-containing compound comprising hydrogen or carbon is precombusted in a precombustion zone. The hydrocarbon conversion catalyst is at least partially regenerated in the presence of the halogen in a regeneration zone at regeneration conditions comprising a regeneration temperature.
In a more specific embodiment, this invention is a hydrocarbon conversion process. A hydrocarbon feedstock is passed to a reaction zone where the feedstock is contacted with catalyst particles containing platinum. A hydrocarbon product is recovered from the reaction zone. Catalyst particles are withdrawn from the reaction zone and passed to a regeneration zone. Oxygen and perchloroethylene are passed to a precombustion zone, where at least 95% of the perchloroethylene that is passed to the precombustion zone is precombusted, thereby generating heat of the precombustion in the precombustion zone. A precombustion effluent stream comprising oxygen and molecular chlorine is withdrawn from the precombustion zone and passed to a cooling zone where the precombustion effluent stream is cooled. A cooled precombustion effluent stream comprising oxygen and molecular chlorine and having a precombustion effluent temperature of less than a regeneration temperature is withdrawn from the cooling zone. The precombustion effluent stream is passed to a regeneration zone that contains catalyst particles. In the regeneration zone, catalyst particles are contacted with the precombustion effluent stream and at least a portion of the platinum on the catalyst particles in the regeneration zone are redispersed at regeneration conditions. The regeneration conditions comprise a regeneration temperature of less than 1100° F. Catalyst particles are withdrawn from the regeneration zone, and catalyst particles are passed to the reaction zone.
INFORMATION DISCLOSURE
U.S. Pat. No. 3,652,231 (Greenwood et al.) describes a process and apparatus for continuous catalyst regeneration which are used in conjunction with catalytic reforming of hydrocarbons. U.S. Pat. No. 3,647,680 (Greenwood et al.) and U.S. Pat. No. 3,692,496 (Greenwood et al.) also deal with regeneration of reforming catalyst. The teachings of U.S. Pat. Nos. 3,652,231, 3,647,680, and 3,692,496 are hereby incorporated in full into this patent application.
U.S. Pat. No. 4,687,637 (Greenwood) describes a process for continuous catalyst regeneration in which a halogenation agent, such as an organic chloride, is injected into an air stream, which is then heated and introduced into a halogenation section of a regeneration tower. The teachings of U.S. Pa
Griffin Walter D.
Moore Michael A.
Spears, Jr. John F.
Tolomei John G.
UOP LLC
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