MXPA00002331A - Improved process and installation for the production of aromatics on a fixed bed - Google Patents

Abstract

The aromatization process involves a synergism between several techniques for the production of aromatics resulting in an increase in capacity of the installation for similar yields of reformate and an increase in length of cycle of the catalyst. The hydrocarbon charge passes successively through at least two fixed catalyst beds containing Pt and Re, the catalyst, A, of the first bed(s) having a wt. ratio Re/Pt greater than the wt. ratio Re/Pt of the catalyst, B, in the last bed(s).The beds are disposed in at least one reactor and the incoming charge is subjected to a thermal exchange with the effluent from the last fixed bed. The exchange is effected with a charge loss lower than 1 bar and a heat difference (temperature difference between hot effluent and reheated charge) no more than 70 deg C.

Description

IMPROVED PROCEDURE AND INSTALLATION FOR THE PRODUCTION OF AROMATICS IN FIXED BED FIELD OF THE INVENTION The invention relates to a process and an installation for the production of aromatic compounds, which operate in a fixed catalyst bed.

BACKGROUND OF THE INVENTION The invention is applied, for example, to aromatization reactions, ie production of aromatic hydrocarbons (benzene, toluene, xylenes), or to the reforming reactions. The catalysts generally used include at least one noble metal, generally platinum, deposited in alumina, as well as at least one promoter metal which is generally rhenium. These catalysts have been widely described in the literature. Thus, the patent FR-2,373,602 describes a catalyst that includes a support of alumina, 0.05 to 0.6% by weight of platinum, 0.02 to 2% by weight of rhenium, 0.05 to 3% Ref .: 32892 by weight of thallium or of indium and 0.1 to 10% by weight of a halogen (generally chlorine). The patent US-4,772,780 shows a reforming process in which the load passes successively on 2 types of fixed beds of 2 different catalysts. Each catalyst contains platinum and rhenium and eventually an additional metal chosen from tin, germanium, lead, indium, thallium, titanium. The catalyst A of the first type of bed (traversed by the load) has a weight ratio Re / Pt higher than the weight ratio Re / Pt of the catalyst B of the second type of bed, and the catalyst B contains at least 0.08% by weight of rhenium (in relation to support). In this type of bond it is possible to use a catalyst according to the patent FR-2,373,602 mainly in the second type of bed. Other catalysts are also suitable, which contain 0.01 to 3% of additional metal, as indicated by US-4, 722, 780. Therefore, the industrial use of such procedures is expensive, systems have been developed to increase the volumes and charged catalyst masses, for the same reactor. Thus, US Pat. No. 5,202,097 proposes a device which is placed on top of the accessories of the catalyst. The device comprises a layer of fabric of a suitable material that substantially covers the accessories. In this fabric layer, the inert balls are deposited to ensure the maintenance of the fabric layer. As this document shows, this device avoids the upper dead zones of the reactor and allows increasing the amount of catalyst in the reactor. In the same object of catalytic mass performance, a so-called dense load technique described in patent FR-2, 646, 399 has been developed, which allows to increase the amount of solid introduced in a certain volume. Likewise, means have been developed to optimize the installation energetically, for example, heat exchangers are used on the fluids, on the outside of the reactors. The exchangers marketed by the Packinox company and which are generally used in this field will be cited. Each of these techniques, used up to the present separately, has been able to bring improvements. It has now been discovered, and quite surprisingly, that the combination of these techniques used in an aromatics production process allows to obtain a synergy whose effects go beyond those expected. It follows that the installation capacity can be increased to more than 10% by maintaining the reforming performance and its quality without increasing the wear of the catalyst, and also in a preferred case, the cycle time of the catalyst is increased.

DESCRIPTION OF THE INVENTION More precisely, the invention relates to a process for the production of aromatics, in which the charge passes through at least one fixed bed of a catalyst containing at least platinum and at least 0.08% by weight of rhenium ( in relation to the support), a process in which the fixed beds are arranged in at least one reactor, and in which, before being introduced into the first fixed bed of the catalyst, the load to be treated suffers a thermal change with the effluent leaving the last fixed bed of the catalyst, the heat exchange is carried out with a loading part lower than 1 bar and a heat approximation of more than 70 ° C. More particularly, the invention relates to a process for the production of aromatics, in which the charge passes successively through at least 2 fixed beds of catalyst containing at least platinum and rhenium, the catalyst A of the first beds (in the direction of circulation of the load) have a weight ratio of the metals Re / Pt higher than the weight ratio of the metals Re / Pt of the catalyst B contained in the last bed (s), procedure in which the beds fixed are arranged in at least one reactor, and in which, before being introduced into the first fixed bed of catalyst, the load to be treated undergoes a thermal change with the effluent leaving the last fixed bed of the catalyst, the heat exchange is carried out with a load part lower than 1 bar and a heat approximation of more than 70 ° C. Preferably, at least one radial fixed bed located in the upper part of the reactor is covered with a fabric or weft layer. The catalyst is in the form of one or more fixed beds in one or several reactors. According to the invention, a single type of catalyst can be used (catalyst B). It can be preceded by another catalyst which is advantageously the type A catalyst, it can also be followed by another catalyst for this process. When a single fixed bed of catalyst B is used, the load undergoes a thermal change with the effluent exiting from this bed.

If several fixed beds are used (from A, B or any other catalyst), the load, before entering the first bed, has undergone a thermal change with the effluent from the last bed. The description of the invention will be continued from Figure 1. The load (section or oil cup) to be treated is conducted in the process through line 1. It will pass successively in reactors 2, 3, 4 after heating in the reactor. the furnaces 5, 6, 7. Each reactor comprises one or more fixed beds of the catalyst. According to the invention, the first fixed bed 8 containing a catalyst A having a weight ratio (Re / Pt). the last fixed bed 10 contains a catalyst B having a weight ratio (Re / Pt) B which is less than (Re / Pt) A 'and preferably the amount of Re of catalyst B is at least 0.08% by weight (in relation to the support). Preferably, the catalyst A is bimetallic with a Re / Pt ratio greater than 1 and the trimeric catalyst B with a Re / Pt ratio less than or equal to 1. The fixed-bed catalyst 9 can be of type A or of type B or present an intermediate Re / Pt relation between that of A and that of B.

If several beds are arranged in the same reactor, the catalysts between the first bed of the first reactor and the last bed of the last reactor are of type A, B or intermediate. The effluent leaving the last reactor, here 4, through a duct 11 heats the load conducted by the duct 1 through a heat exchanger 12. Any type of heat exchanger is suitable, which has high thermal performances, ie an approximation of heat below 70 ° C, preferably 50 ° C (difference between the temperature of the hot effluent and that of the heated charge exiting through the exchanger duct 13), and a loading part of less than 1 bar. The approximation of the heat is often between 10-70 ° C or 10-50 ° C. Suitable plate exchangers, and particularly those commercialized by the Packinox company for which the load part is less than 0.7 bar and the heat approximation of 20-40 ° C most of the time. The cooled effluent which exits through line 14 passes in an air cooler 15, a water cooler 16 and a flask or separating vessel 17 which separates the reformed (conduit 18) from hydrogen gas (conduit 19). A part of this gas is advantageously recycled by the conduit 20, after the recompression in the compressor 21, to the process in mixture with the charge of the conduit 1. Advantageously the mixture takes place before the thermal change. In a preferred relation, the fixed bed comprises in its upper part a layer of a fabric of appropriate shape, in refractory material, substantially inert and substantially impermeable or having a texture and porosity such that the fabric creates a part of load greater than that generated by the fixed bed of catalyst particles, the tissue cooperating with a substantially inert first layer of pellets or a particular material of granulometry and of appropriate weights resting on the fabric and arranged in the fixed bed of particles so that a substantially total coating of the bed is ensured. By appropriately shaped fabric, a fabric is understood to adhere or adapt substantially to the geometry of the bed section. The fabric layer is preferably placed at the top of the bed above the reactor, that is, at the level of the entrance of the load. Advantageously, each reactor contains a bed provided with this layer of fabric.

The detailed description of the fabric layer and its arrangement in the reactor will not be repeated here, but it will be reported in the teaching of the patent US Pat. No. 5,202,097 which is taken up integrally in the present description. The placement of this layer of tissue requires the use of the radial or transverse fluid circulation reactor, the fluid enters the upper part of the reactor, is distributed in the space delimited between the side wall of the reactor and the fixed bed. A reactor shown in Figure 1 (reactors 2, 3, 4) is reproduced in more detail in Figure 2 (fabric of US Pat. No. 5,202,097). The load to be treated is introduced through the inlet opening 22 located above the reactor 2, it is distributed to the annular space 23 delimited by the wall of the reactor and the wall 24 which maintains the fixed bed 8 of the catalyst. The wall 24 is perforated with openings and the load is thus distributed substantially radially in the compartment of the fixed bed 8. After having passed through the catalytic bed in a substantially radial manner, the effluent is recovered by a central collector 25 of cylindrical shape here. , and which is in general a perforated tube advantageously covered with a grid and the effluent leaves through an opening 26. The effluent (reformed) leaving the process generally has a temperature of 350-600 ° C, and more particularly 350 -500 ° C, or better yet 400-500 ° C. The fabric layer 27 is disposed above the bed and is held in place by a layer 28 of inert material for example. Figure 2 has been taken up here partly for the understanding of the invention, but all the other non-continuous elements can also be used (layer that replaces the lower grid 29 on which the catalyst bed rests, for example). It is pointed out that if the tissue layer is not used, spherical axial reactors can be used. To show the synergy between the different elements of the invention, it will be reported in the following tables. The yield of hydrogen, C5 + (compounds of at least 5 carbon atoms), LPG (light gases) has been reported to obtain the same quality of gasoline (identical octane number sought) obtained from the same load. , refurbished and the number of days of operation at full capacity. The installation considered operates with a molar ratio H2 / hydrocarbons of 5 and a P.P.H. of 1.75 in the 2 reactors, each containing a fixed catalyst bed. The first catalyst bed has a weight ratio Re / Pt >; 1 and the second of 1, the amount in Re of the second bed is 0.3% by weight. The first catalyst is bimetal, the second trimetalic. The pressure in the separating flask is 12 bar. The heat exchanger is a plate heat exchanger whose approximation of heat is 33 ° C sold by the company Packinox. The Texicap® brand fabric layer is marketed by IFP. Table 1 shows for a given load efficiency of 20,000 barrels / day (already approximately 3 200 m3 / day) the yields driven by each element taken separately. Table 2 shows that the best yields are obtained from table 1 (in terms of yield H2, C5 +, reformed, RON) but with an increased capacity of 10% for the same duration of the catalyst. This represents a huge benefit for the refiner. Table 2 also shows that the heat exchanger taken only at this higher capacity (22,000 barrels / day, or 3,500 m3 / day) does not provide such a benefit. It is also shown that the use in addition to the fabric layer allows to increase the time of use of the unit maintaining the high level of performance.

The refiner may also prefer, at a constant capacity, to increase the recirculation rate of the gas, which has the effect of prolonging the cycle time of the catalyst. In order to further improve the operations, dense loading of the catalyst can be carried out as described, for example, in patent FR-2, 646, 399.

Table 1 Table 2 It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property

Claims (7)

1. A process for the production of aromatics characterized in that the charge passes through at least one fixed bed of a catalyst containing at least platinum and at least 0.08% by weight of rhenium, a process in which the fixed beds are placed in at least a reactor, and in which, before being introduced into the first fixed catalyst bed, the load to be treated undergoes a thermal change with the effluent leaving the last fixed bed of the catalyst, the heat exchange has been carried out with a load part less than 1 bar and a heat approximation of more than 70 ° C.

2. The process according to claim 1, characterized in that the charge passes successively through at least 2 fixed beds of catalyst containing at least platinum and rhenium, the catalyst A of the first bed (in the direction of circulation of the load) has a weight ratio of the metals Re / Pt higher than the weight ratio of the metals Re / Pt of the catalyst B contained in the last bed (s).

3. The method according to one of the preceding claims, characterized in that the heat approximation is 10-70 ° C.

4. The method according to one of the preceding claims, characterized in that at least one radial fixed bed located in the upper part of the reactor is covered with a layer of fabric.

5. The process according to one of the preceding claims, characterized in that the catalyst B is a tritretic catalyst with a Re / Pt ratio less than or equal to 1.

6. The process according to one of the preceding claims, characterized in that the catalyst A is bimetallic with a Re / Pt ratio greater than 1 and the trimeric catalyst B with a Re / Pt ratio less than or equal to 1.

7. The process according to one of the preceding claims, characterized in that the catalyst has been densely charged.