Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Removing and recycling removed material from an ongoing...
Reexamination Certificate
1999-06-24
2001-07-24
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Removing and recycling removed material from an ongoing...
C526S090000, C526S095000, C526S104000, C526S901000, C526S069000, C034S367000, C034S430000
Reexamination Certificate
active
06265501
ABSTRACT:
This invention relates to a process for treatment of
metathesis catalysts (regeneration, activation, reactivation). Patent FR 2.608.595 of the French Petroleum Institute describes a process for continuous regeneration of metathesis catalysts with a rhenium base. This patent describes a process in which the catalyst flows out under the action of gravity from top to bottom of a column that is called a regenerator by successively passing through zones where stages of stripping, combustion, calcination and cooling are carried out. This requires conveying the catalyst from the bottom of the metathesis reactor through which the feedstock passes toward the top of the regenerator, then in bringing the catalyst back from the bottom of the regenerator toward the top of the reactor. This conveying of catalysts that is carried out by, for example, liquid or gaseous lifts, is able to gradually deteriorate the catalyst, for example by generating fines and powders or by breaking catalyst particles.
The applicant now sought to improve the regeneration of the metathesis catalyst.
This invention relates to a process for treatment of metathesis catalysts for olefins, polyolefins or acetylenic compounds that consists in conveying the catalyst particles into at least one vibratory helicoidal conveyor that contains at least one vibratory helicoidal coil, in subjecting them over at least a portion of their path and preferably over a major portion of their path to a temperature profile, and in bringing them into contact with at least one fluid over at least a portion of their path.
The transit of the catalyst particles in the vibratory helicoidal conveyor can be carried out according to an ascending mode or descending mode.
The treatment of said catalyst can be carried out continuously or by batch, preferably it is carried out continuously.
In this description, the means that comprises at least one vibratory helicoidal coil in which the catalyst particles transit is called “vibratory helicoidal conveyor,” and when the process operates in ascending mode, said vibratory helicoidal conveyor is called “vibratory helicoidal lifting device”; in contrast, the term “olefins” more generally covers olefins, polyolefins and acetylenic compounds.
The metathesis process of the olefins consists in causing one or more olefins to react on themselves or among themselves, which gives rise to a redistribution of the alkylidene groups of the olefins of the feedstock and thus produces new olefins. This reaction offers great practical significance, for example for the rebalancing between them of the light olefins that are obtained from the steam cracking, such as ethylene, propylene and butenes. These olefins are used below for the production of polymers and/or copolymers.
The process for metathesis of olefins uses catalysts that are integral with metal or metal oxide bases, such as molybdenum, tungsten, rhenium, titanium, niobium, tantalum, ruthenium, alone or in a mixture, supported on refractory oxides such as alumina, silica, silica-alumina, zeolites, titanium oxide, zirconia, magnesia thorine, tin oxide , used alone or mixed. These catalysts can also be doped by the addition of components that increase or reduce their acidity, for example salts of fluoride, chloride, sulfate or phosphate anions, salts of alkaline or alkaline-earth metals, such as potassium, cesium, barium, salts or complexes of boron, aluminum or gallium, for example boron trifluoride, aluminum trichloride or aluminum complexes that comprise alkyl, alkoxy or aryloxy groups.
Over time, these catalysts are deactivated. In the case of catalysts that operate at relatively high temperature (200 to 400° C.), as is the case of catalysts with a molybdenum or tungsten base, the deactivation is attributed to the gradual deposition of complex-structure polyaromatic hydrocarbons that bear the common name of coke. In the case of catalysts that operate at low temperature (less than 150° C.), as is the case of catalysts with a rhenium base, the deactivation is attributed at least in part to the accumulation of impurities that are contained in the feedstocks that are to be treated and to the formation of polymers that clog the porous network of the catalyst.
The deposition of coke, polymers, or more generally impurities makes it necessary to regenerate the catalyst at the end of an operating cycle of from one or several days to several weeks. In the continuous regeneration units of the catalyst, it is not necessary to stop the units to initiate the regeneration of the catalyst. The catalyst is conveyed from the reactor (or reactors) to a regenerator that carries out the rejuvenation of the catalyst by a suitable process, and the conveying is carried out by means of a mechanical or pneumatic nature, then the regenerated catalyst is brought back toward the reactor (or reactors) by the same means.
To implement the process according to the invention, the regenerator can also be used off-site, for example the catalyst can be conveyed to a company that is specialized in the treatment of catalysts where it will be regenerated.
The regeneration of the metathesis catalysts can comprise a single stage, and this stage is then combustion that is provided in an oxidizing medium. The purpose of this stage is the elimination of the coke, accumulated impurities and polymers that are deposited on the catalyst. This stage generally consists in passing over said catalyst a gas that contains between 0.1 and 5% of molecular oxygen at a temperature of between 350° C. and 800° C., whereby the duration of this stage is longer than 10 minutes and preferably between 1 and 12 hours. Most often, the metathesis catalyst is dried before being used in the reaction zone.
In a preferred manner, the regeneration of the metathesis catalysts comprises a combustion stage that is provided following a calcination stage that is intended to improve the attachment of the active phase, to dry the catalyst and adjust its acidity to the value that is required for optimum catalytic performance levels.
The combustion stage that is provided consists in treating the catalyst between 350° C. and 800° C. by a gas that contains 0.1 to 5% of molecular oxygen for a period that is more than 10 minutes and preferably between 1 and 12 hours. The calcination stage consists in treating the catalyst for a duration that is longer than 10 minutes and preferably between 1 and 12 hours, at a temperature that is between 400° C. and 800° C.—whereby this temperature is generally higher than the temperature of the combustion zone that is provided —by a gas that contains 5 to 40%, and preferably 15 to 25% molecular oxygen, and this gas can be, for example, air.
These two stages that are carried out successively—in separate combustion and calcination zones that are arranged one on top of the other in the vibratory helicoidal conveyor in the direction of flow of the catalyst—or simultaneously—in combined combustion and calcination zones—can also be preceded by a stage of stripping hydrocarbons that are trapped in the pores of the catalyst under a stream of inert gas, for example under nitrogen, and can be followed by a stage of cooling of the catalyst under a dry gas, whereby this gas can be air or nitrogen.
These stages are, for example, used in the meta-4 process of the French Petroleum Institute (French Patent FR 2,608,595), which is a continuous regeneration process of metathesis catalysts with a rhenium base.
The process according to this invention is used with a helicoidal conveyor that is driven in vibrations whose force resultant that is applied to the catalyst particles is calculated to make possible either the rise or the fall of these catalyst particles.
The helicoidal conveyor—or optionally the helicoidal conveyors—comprises at least one coil and is wound around a hollow drum in which is placed a system that is intended to produce the vibrations that are necessary for the catalyst particles to rise or fall. The vibrations can be produced by at least one system that is placed at any suitable level, for example at the bottom
Commereuc Dominique
Olivier Helene
Saussine Lucien
Cheung William K
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
Wu David W.
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