FR2760386A1 - REGENERATION OF CATALYSTS FOR REFORMING OR ISOMERIZATION OR DEHYDROGENATION OF PARAFFINS IN A VIBRANT HELICOIDAL SPIRE - Google Patents

Abstract

The invention concerns the application of a method for regenerating catalysts or adsorbents, consisting in causing the catalyst particles to rise in a vibrating helical elevator (12), said particles being subjected to a temperature profile and being contacted with one or several fluids over part of their travel in said spire, regenerating paraffin reforming, isomerization or dehydrogenation catalysts. The helical elevator can be maintained at the appropriate temperature by circulating gas at the required temperature outside and in contact with the helical elevator, The regenerator comprises at least a combustion zone (14) and at least an oxychlorination (15) or more generally a chlorination zone, which can be merged. A pre-heating zone (13), a hydrocarbon stripping zone, a calcining zone (16) and a cooling zone for the catalyst can also be included in the device.

Description

 Thus, the present invention relates in particular to the application to processes of catalytic reforming, of dehydrogenation of paraffins with preferably continuous regeneration of the catalyst, of a process described in the prior art, consisting in raising the particles of catalysts in the at least one vibrating helical turn, subjecting them over at least part of their path and preferably over the major part of their path to a temperature profile and bringing them into contact with at least one fluid over at least part of their path.

 One possible application is therefore catalytic reforming which is a process consisting in increasing the octane number of gasolines by promoting the reactions of dehydrogenation of naphthenes, of isomerization of alkylnaphthenes and paraffins, and of dehydrocyclization of paraffins. The paraffin dehydrogenation process makes it possible to obtain olefins having the same number of carbon atoms as the starting paraffins.

These olefins can be used later for the production of bases for super fuels (ethers, alkylates) or biodegradable detergents. The paraffin reforming and dehydrogenation processes use solid catalysts based on precious metals such as platinum or rhenium or oxides such as molybdenum oxide or chromium oxide, supported on a refractory oxide such as alumina.

 Over time, these catalysts deactivate due to the progressive deposition of polyaromatic hydrocarbons of complex structure bearing the usual name of coke. The deposition of coke makes it necessary to regenerate the catalyst at the end of an operating cycle ranging from a few days to more than a year. In units with continuous catalyst regeneration, it is not necessary to stop the units in order to regenerate the catalyst. The catalyst is transported from one reactor to another by an adequate process, of a mechanical or pneumatic nature, then it is transported to a regeneration column operating the rejuvenation of the catalyst, finally the regenerated catalyst is transported to the head of the first reactor and and so on.

 The regeneration of the reforming, isomerization or dehydrogenation catalysts for paraffins can comprise several stages, for example in the case of the reforming of a stage of combustion of coke intended to remove the hydrocarbon deposit by combustion managed in an oxidizing medium, a stage chlorination (and in particular oxychlorination) intended to improve the dispersion of the metallic active phase (in the case of platinum-based catalysts) and a calcination step intended to improve the fixation of the active phase, dry the catalyst and fix its chlorine content at the value required for optimal catalytic performance. A step of cooling the catalyst in air or under nitrogen can also follow the calcination step.

 All these steps are implemented successively in existing processes for the continuous regeneration of reforming catalysts.

In these processes, for example the Octafining process of the French Institute of
Oil or the CCR Platforming process from UOP, the catalyst flows by gravity from top to bottom of a column called regenerator, for example the Hi-Q-Regenerator from IFP or the CycleMax from UOP, successively crossing zones where the combustion, oxychlorination, calcination and cooling steps described above are carried out. This requires transporting the catalyst from the bottom of the last reforming reactor crossed by the charge to the top of the regenerator, then transporting the catalyst from the bottom of the regenerator to the top of the first reforming reactor crossed by the charge or the reducing agent (zone of reduction of the catalyst at the inlet of the reforming reactor ltr). These transportations of catalysts operated, for example by gaseous lifts, are liable to gradually deteriorate the catalyst, for example by generating fines and dust or by breaking up particles of catalyst.

 The implementation of a process derived from a process known from the prior art makes it possible to avoid the implementation of a process for transporting catalyst upwards from the regenerator and from the bottom of the regenerator.

The apparatus for implementing the process is in fact a regenerator supplied by the catalyst in its lower part, the regenerated catalyst leaving at the top of the regenerator. So, at the same time as the catalyst is regenerated, its recovery is simultaneously carried out at the top of the reforming reaction zone. These reaction zones are generally placed side by side or superimposed, the charge and the catalyst generally circulating successively from top to bottom through each reaction zone.

This same type of arrangement can also be used for dehydrognenation or isomerization of paraffins. This device is a vibrating elevator comprising a helical ramp of substantially tubular shape. The device can be used in a catalytic reforming process in a circulating bed, or during the off-site regeneration of reforming catalyst. The catalyst particles rising within the coil are subjected to a temperature profile over part of their path, as described in French patent 943,865. This temperature profile can be obtained by indirect contact with a heat transfer fluid bathing the steps of the coil, as described in French patent application 2,634,187. In this patent application, the turns of the helical ramp are connected to each other by two helical bands, fixed to the ramp on two opposite sides thereof to form a helical channel, between the turns of the helical ramp, in which a heat transfer fluid can circulate. More generally, as described in French patent application No. 943,865, the entire tube-coil device may be placed in an enclosure, where the products transported will be subjected to a heat treatment, for example a insulated enclosure in which circulates a heat transfer fluid bathing the steps of the turn. It follows from the same patent application that the heat transfer fluid can cross the turn itself. This gas can circulate in co- or counter-current. coil can also be obtained by effect
Joule, by directly heating the metal mass of the tube as described in the French European patent application EP-A-612561.

 As it rises in the turn, the catalyst successively crosses an area where it is preheated, so that its temperature reaches a level where the subsequent combustion of the coke takes place under optimal conditions, a coke combustion area, where a air or oxygen flow is introduced in a staggered fashion at several successive turns, so as to limit the oxygen concentration and not to risk degrading the catalysts by local overheating, a chlorination zone where a chlorinating agent such perchlorethylene is introduced with air and a calcination zone where the catalyst is swept by a stream of nitrogen or dry air containing less than 50 ppm of water. It is possible to combine the combustion and chlorination zones in a single zone, by introducing the chlorinating agent at the bottom of the combustion zone. It is also possible to modulate the injections of air or oxygen into the coke combustion zone, by introducing, for example, increasing amounts of air from the bottom to the top of the helical elevator. The temperatures of the gases entering the combustion zone can be between 350 and 5500C, preferably between 420 and 5200C.

 The turn or turns if there are several, has at least 2 steps and is wound around a hollow shaft in which is arranged a system intended to produce vibrations, for example an unbalance motor as described in the request. French Patent 943,865. The turns can be contiguous or non-contiguous. The gases or fluids intended for the regeneration of isomerization or dehydrogenation reforming catalysts can be introduced by one or more pipes so that said gases or fluids circulate against the current in one or more steps of the turn. The pressure within the coil can be between 0.1 and 20 bars, preferably between 1 and 7 bars. The gases or fluids can be introduced into the coil laterally, from above or from below the coil by passing through a fine-mesh grid or any suitable device intended to prevent the ingress of particles of catalyst in the inlet pipes. gases. The same applies to the gas withdrawal line (s).

 The example and the figure described below illustrate the invention without limiting its scope.

 Figure 1 illustrates the example described below. The coil is arranged on a vibrating table (1) and two unbalanced motors (2) generate the vibrations necessary for the rise of the catalyst. This catalyst is in the form of spherical balls with a diameter of 1.8 mm. The entry of solid particles takes place via line (3) and the exit of particles through line (4).

The barrel-turn assembly is contained in a thermally insulated enclosure secured to the vibrating table (5). A nitrogen flow rate of 500 Nm3 / h is introduced at the top of the device through line (6), at a pressure of 5 bars. This gas is preheated to 480 "C by means of an oven external to the device described in the example. Said gas bathes the steps of the turn then is introduced in (7) laterally at the bottom of the turn, in the turn, and crosses the coil co-current with the catalyst. Air is introduced by means of twelve pipes (8) each delivering a flow of 8
Nm3 / h of air preheated to 480 "C. The catalyst enters the coil at a temperature of 350" C at a flow rate of 500 kg / h. Its carbon content (coke) is 6.0% by weight.

Example
The catalyst is in a metallic platinum phase dispersed on alumina, the platinum content being 0.30% by weight. The metal surface exposed before regeneration is 81%. The specific surface of the catalyst is 200 m2 / g. The catalyst passes through the coke burn zone. The first air inlet pipe is positioned laterally at the level of the second pitch of the turn, the first step, bathed in nitrogen introduced by the pipe (7), is used for preheating (zone 13) of the catalyst. The residence time of the catalyst in the combustion zone (zone 14) is 30 min, ie a tube length of 60 m. The catalyst then enters the oxychlorination zone (zone 15), the pipe (9) introducing a flow rate of 500 Nm3 / h of air containing perchlorethylene. The pipes (8), (9) and (11) are supplied by pipes and a device located inside the central barrel. The residence time of the catalyst in the oxychlorination zone is 30 min, ie a tube length of 60 m. The effluent from the combustion and oxychlorination zones leaves the coil via the pipe (10). The catalyst then enters the calcination zone (zone 16). The residence time of the catalyst in the calcination zone is 15 min, ie a tube length of 30 m.

The catalyst is swept against the current by a stream of dry air at 500 Nm3 / h introduced at the top of the coil through the pipe (11). The calcining effluent leaves the coil via the pipe (10) together with the combustion and oxychlorination effluent.

 The characteristics of the catalyst at the exit of the turn are as follows specific surface, 195 m2 / g; dispersion of the metallic phase, 95%; carbon content, 0.1%. The mechanical characteristics of the catalyst balls (resistance to attrition, crushing grain to grain) are unchanged. The chlorine content is 1.2% by weight. The device described in the example therefore allows complete regeneration of the reforming catalyst.

Claims (6)

1. Process for the treatment of a catalyst or a powdery adsorbent  comprising at least one step carried out in at least one zone and consisting  causing the particles of catalyst or adsorbent to rise in at least one  vibrating helical coil in which the said zone is arranged, process in  which further said particles are subjected to a temperature profile  on at least part of their journey during which they are put in  contact with at least one fluid. 2. Method according to claim 1 comprising at least two steps. 3. Method according to one of claims 1 and 2 applied to the regeneration or  activation or reactivation of catalysts. 4. Method according to claim 3 applied to regeneration or activation or  continuous reactivation of catalysts. 5. Method according to claim 4 comprising at least one step of  combustion and a chlorination step, each carried out in zones  distinct superimposed in the vibrating helical coil. 6. Catalytic process for reforming or isomerizing paraffins or  paraffin dehydrogenation carried out in several reaction zones  in series, superimposed or side by side, the charge and the circulating catalyst  successively through each reaction zone from top to bottom, the  catalyst withdrawn in bar from the last reaction zone crossed by the  filler then being treated according to the method of claim 1, then being  withdrawn from the top of said coil and sent to the top of the first zone  reaction crossed by said charge.