RU2710016C1 - Method of preparing a catalyst in dehydrogenation of paraffin hydrocarbons c3-c5 and device for its implementation - Google Patents

Abstract

FIELD: petroleum chemistry.

SUBSTANCE: invention relates to petrochemistry, in particular to plants for dehydrogenation of paraffin hydrocarbons C₃-C₅ into corresponding olefin hydrocarbons used to obtain basic monomers for synthetic rubber, as well as in the production of polypropylene, methyl tert-butyl ether, etc. Disclosed is a method for reduction-desorption preparation of an aluminum chromium catalyst in dehydrogenation of paraffin hydrocarbons C₃-C₅ with fluidized bed at successive cycles of dehydrogenation, regeneration and preparation of catalyst, circulating in system containing reactor, regenerator 1 with heating of the catalyst in the upper part of the fluidized bed by burning coke on the spent catalyst from the reactor and supplied fuel gas with subsequent oxidation of the catalyst and desorption of oxidation products by the supplied oxygen-containing gas in the lower part of the fluidized bed of regenerator 1, as well as a device for preparing a regenerated catalyst before feeding it into a reactor, carried out by successive reduction of the catalyst with a reducing gas and desorption of the reduction products with an inert gas, in which regenerated catalyst from regenerator 1 fluidized bed lower part is supplied to device, divided into three sections 11, 13, 15 using partitions 5, 6, wherein first for preliminary desorption to the top of the first fluidized bed of section 11, which is blown with inert gas is counterflow to the downward catalyst flow, then, to reduction to the bottom of the second fluidized bed of section 13, which is blown with reducing gas by direct flow with upward flow of catalyst and then for final desorption to the top of the third fluidized bed of section 15, which is blown with inert gas, is counterflow to the downward catalyst flow.

EFFECT: technical result consists in increase in efficiency of reduction-desorption preparation of aluminum chromium catalysts with increase in their activity in dehydrogenation of paraffin hydrocarbons C₃-C₅ at more compact and technological scheme of preparation unit.

10 cl, 1 dwg

Description

The invention relates to the field of petrochemistry, in particular to installations for the dehydrogenation of C ₃ -C ₅ paraffin hydrocarbons into the corresponding olefinic hydrocarbons used to produce basic monomers for synthetic rubber, as well as in the production of polypropylene, methyl tertiary butyl ether, etc.

The technological design of the processes of dehydrogenation of C ₃ -C ₅ paraffin hydrocarbons in a fluidized bed of chromium-chromium catalysts provides for sequential cycles of dehydrogenation, regeneration and recovery-desorption preparation of the regenerated catalyst before it is fed to the reactor by reducing the catalyst with a reducing gas and desorbing the products of reduction with an inert gas, respectively, in the reactor, regenerator and reducing glass with the circulation of the catalyst between them (Tyurye IJ "Physical and chemical bases of reception of butadiene from butane and butylene," Leningrad, "Chemistry", 1966, p. 159).

A feature of oxide alumina-chromium catalysts is the very significant effect of water on the catalytic properties of the surface, leading to poisoning of these catalysts (Minachev H.M. et al., Neftekhimiya journal, 1969, v. 27, No. 5, p. 677, I. Tyuryaev. I., “The theoretical basis for the production of butadiene and isoprene by dehydrogenation methods”, Kiev, “Naukova Dumka”, 1973, p. 153).

Under production conditions, water can enter the catalyst with raw materials and air, as a result of the reactions of combustion of fuel gas and burning of coke in the regenerator and during the interaction of fuel gas (natural gas, gas) and components of the reaction mixture with oxygen on the catalyst surface, respectively, in the device (apparatus) catalyst preparation and in the reactor. The course of combustion reactions in the reactor is confirmed by the constant presence in the contact gas of the dehydrogenation of H ₂ O, CO and CO ₂ (up to 3% by weight). Most water is formed during combustion in a fuel gas regenerator. But since this process takes place both on the surface of the catalyst and in the volume, only a certain, but significant part of the water formed during the combustion of fuel gas is adsorbed by the catalyst. In other cases, during the combustion of hydrocarbons and burning of coke, occurring on the surface of the catalyst, the resulting water is almost completely adsorbed. The water adsorbed by the catalyst in the regenerator during the combustion of fuel and coke is removed to some extent by purging with oxygen-containing gas (air) in the lower part of the regenerator, where the catalyst is simultaneously oxidized. Catalyst deactivation with water is reversible (I. Tyuryaev, “Physicochemical Basics of Divinyl Production from Butane and Butylene”, M.-L., “Chemistry”, 1966, p. 159).

The presence of hexavalent chromium oxide (CrO ₃ ) on the catalyst surface initiates deep oxidation reactions with the formation of water. The stages of reduction of hexavalent chromium oxides of the catalyst surface to trivalent chromium oxides (Cr ₂ O ₃ ) proceed quickly, but the speed of the total process is determined by the rate of slow desorption of water, which limits the process (I. Tyuryaev, “Journal of Applied Chemistry”, 1961, v. 34 , No. 3, p. 703; O. Sterligov, journal "Petrochemistry", 1969, v.15, No. 1, p. 35).

The purpose of the operation of oxidation of the catalyst in the regenerator is to provide the desired depth of oxygen diffusion deep into the crystal lattice of the active component and thereby restore the activity of the catalyst from cycle to cycle under conditions of its unsteady activity. The content on the surface of the regenerated catalyst of higher chromium oxides (CrO ₃ ) is an indicator of the quality of the regeneration of aluminum-chromium catalysts (B. Balzhinimaev and others in the book: Second All-Union Conference on the kinetics of catalytic reactions "Kinetics-2", Volume 3, Novosibirsk, Institute catalysis of the Siberian Branch of the Academy of Sciences of the USSR, 1975, p. 85, I. Fridshtein and others in the book: “Scientific Foundations of the Selection and Production of Catalysts”, Novosibirsk, RIO SB of the USSR Academy of Sciences, 1964, p. 267).

The solution to the problem of preparing the regenerated catalyst before entering the reactor under industrial conditions is to remove water, weakly bound oxygen and reactive oxygen adsorbed during the regeneration in the form of hexavalent chromium oxides, the presence of which causes the occurrence of deep oxidation reactions. To this end, preliminary catalyst reduction is carried out with hydrocarbons, H ₂ or CO, followed by desorption of the resulting water with an inert gas (reduction-desorption method). It was shown that the quality of the preparation improves with an increase in its duration, the molecular weight of the reducing gas and its space velocity, temperature. It is indicated that desorption of the catalyst with an inert gas (nitrogen) improves the process. Gases in descending order of their reducing ability can be arranged in a row: С _n Н _{2n + 2} , C _n-1 H _{2 (n-1) +2} , СH ₄ Н ₂ + СН ₄ . (A.S. USSR 134693, IPC С07С 11/02, published on July 21, 1959; Eng. Patent 734089, 1958; Novak S., Viewig N., Chem. Techn., 1970, Bd. 22. No. 2, p. .94; Mikhailov PK et al., “Production of isobutylene by isobutane dehydrogenation”, M., TsNIITENeftekhim, 1968, p. 18; journal “Synthetic rubber industry”, 1969, No. 4, p. 3; 1970 No. 2, p. 1 ; Journal of Chemical Industry, 1970, No. 1, p. 3).

A known industrial method of carrying out the processes of dehydrogenation of n-butane to n-butylene and dehydrogenation of isopentane to isoamylene in a fluidized bed of an aluminum-chromium catalyst circulating in a reactor-regenerator-device for preparing a catalyst (I. Kirpichnikov et al., “Album of technological schemes of basic productions of the synthetic rubber industry ”,“ Chemistry ”, Leningrad, 1986, pp. 8-14 and pp. 56-58). In this method, the spent catalyst from the reactor is transported by air through a transport line to the upper part of the fluidized bed of the regenerator. The fluidized bed of the regenerator, partitioned by gratings, is divided in height into two zones: the heating zone of the catalyst in its upper part by burning coke on the spent catalyst and the supplied fuel gas to replenish the heat expended in the reactor during the endothermic dehydrogenation reaction, and the catalyst oxidation and desorption zone oxidation products supplied to the regenerator by air. The catalyst is regenerated in countercurrent mode of the catalyst and air at a temperature of 600-650 ° C and a pressure of 0.118 MPa. Next, the regenerated catalyst from the oxidation zone is fed into a reducing glass installed in the lower part of the regenerator. At the bottom of the reducing glass, methane-containing natural gas or hydrogen-containing production gas is fed to reduce hexavalent chromium oxides of the catalyst surface to trivalent chromium oxides. The reduction gases from the reducing cup enter the bottom of the catalyst oxidation zone, and the regenerated, reduced and heated catalyst from the bottom of the cup is transported by nitrogen to the reactor. The main disadvantages of this method include:

- a low degree of catalyst recovery when combining the processes of recovery and desorption of water by reduction products in a fluidized bed of a reducing glass;

- inefficient desorption of water from the surface of the catalyst coming from the oxidation zone of the regenerator, reduction products containing reaction water;

- the release of exhaust gases from the reduction cup containing reaction water and unreacted excess of the reducing gas to the bottom of the regenerator oxidation zone, which significantly reduces the degree of catalyst oxidation and water desorption in the specified zone;

- low heat and mass transfer in a free (unorganized) fluidized bed of a reducing glass.

There is a known reduction-desorption method for preparing an aluminum-chromium catalyst (WO 2017/105283, IPC B01J 38/30; С07С 11/06; С07С 11/08; С07С 11/10; С07С 5/333, publ. 06/22/2017). In the given analogs, the preparation of the catalyst before it enters the reactor is carried out in a beaker integrated in the lower part of the regenerator body for the recovery-desorption preparation of the catalyst (beaker-reducer) with a fluidized bed organized by sectional gratings, having a pipe for introducing a reducing gas for reducing the catalyst in the lower part and slightly below it, a pipe for introducing inert gas to desorption of reduction products, as well as a gas pipe for venting recovery gases in the zone of combustion of coke and fuel gas of the regenerator and a pipe in the bottom of the glass to output the prepared catalyst into the reactor.

Closest to the proposed invention is a method for producing olefinic hydrocarbons C ₃ -C ₅ (patent RU 2666541, IPC С07С 5/333, С07С 11/08, С07С 11/10, B01J 21/08, B01J 23/04, B01J 23/26 , B01J 35/02, B01J 37/02, published 04.12.2017) carried out in a fluidized bed of finely dispersed alumina-chromium oxide catalyst circulating in the reactor-regenerator system, including coke burning and oxidation of the catalyst with atmospheric oxygen in the regenerator, as well as reduction of the oxidized hydrogen catalyst methane-containing gas, desorption of inert gas reduction products in a reducing glass, replenishment with a fresh catalyst.

The disadvantages of this method of preparing alumina-chromium catalysts include.

High water content on the catalyst entering the preparation unit from the oxidation zone of the regenerator with insufficient desorption of water by air in the regenerator.

The low efficiency of desorption of the catalyst directly with nitrogen due to the short residence time of the catalyst in the desorption zone in the lower part of the reducing glass.

The low degree of catalyst reduction and the ineffectiveness of its desorption by nitrogen and reduction products containing reaction water, when these processes are combined in the reduction zone.

The high height of the reducing glass with the sequential arrangement of the recovery and desorption zones along the height of the glass, which limits the possibilities for the optimal layout of the dehydrogenation unit as a whole and leads to difficulties in meeting the requirements for simultaneously observing the recommended residence time of the catalyst in the glass and the volumetric flow rate of gas flows into the glass , to compromise inefficient design decisions. This is especially evident in dehydrogenation units with a coaxial arrangement of the regenerator above the reactor and a reducing glass between them, in which the layout of the dehydrogenation blocks requires a significant reduction in the volume of the reducing glass, reducing the catalyst residence time in the glass, combining the reduction and desorption operations in one fluidized bed, etc. .d .. Combining the processes of recovery and desorption of the catalyst in one fluidized bed also limits the ability to control these processes.

Use for organizing a fluidized bed of catalyst and increasing the intensity of heat and mass transfer of sectional gratings during countercurrent movement of catalyst and gas in the holes of the gratings, leading to the formation of gas cushions under the gratings, the value of which can reach 20-30% of the volume of the fluidized bed, which significantly reduces the amount of catalyst and, accordingly, the residence time of the catalyst in the reducing glass, and also limits the possibility of increasing the amount of reducing gas supplied to the glass and rtnogo gas due to "choking" gratings with increasing gas velocity up to the discharge nozzle termination and catalyst circulation. The operation of sectional gratings in a fluidized bed of catalyst with countercurrent movement of catalyst and gas in the holes of the gratings is described in detail in patent RU 2625880. The increase in the free cross-section of the gratings, to reduce the size of gas cushions and increase the gas velocity, for example, when using gratings with incomplete overlap on some dehydrogenation units the cross section of the reducing glass (semilattices), reduces the intensity of heat and mass transfer, the formation of stagnant zones in the reducing glass as gas and the catalyst with the creation of a number of additional problems: reducing the working volume of the glass, not using part of the loaded catalyst, sometimes the formation of coke in stagnant zones, problems with regulating the circulation of the catalyst and stabilizing the thermal regime of the reactor, erosion of internal devices.

These disadvantages reduce the effectiveness of the recovery-desorption preparation of the catalysts in the known method, which prevents the achievement of the potential activity of the catalysts in the dehydrogenation processes. This is especially manifested in the transition to the use of new effective catalysts with a high content of hexavalent chromium in the oxidized state, which requires a significant increase in the amount of gas flows supplied to the device for preparing the catalyst.

The objective of the present invention is to increase the efficiency of the recovery-desorption preparation of chromium-chromium catalysts in order to increase their activity in the processes of dehydrogenation of C ₃ -C ₅ paraffinic hydrocarbons with a more compact and technological scheme of the preparation unit.

To solve this problem, a method for the recovery and desorption preparation of the chromium-chromium catalyst in the dehydrogenation of C ₃ -C ₅ paraffin hydrocarbons with a fluidized bed during successive cycles of dehydrogenation, regeneration and preparation of the catalyst circulating in a system containing a reactor, regenerator 1 with catalyst heating in the upper parts of the fluidized bed by burning coke on the spent catalyst coming from the reactor and the supplied fuel gas, followed by oxidation reactor and desorption of oxidation products by the oxygen-containing gas supplied in the lower part of the fluidized bed of the regenerator 1, as well as a device for preparing the regenerated catalyst before feeding it into the reactor, carried out by sequential reduction of the catalyst with a reducing gas and desorption of the reduction products with an inert gas, in which the regenerated catalyst is from the lower part of the fluidized bed of the regenerator 1 is fed into a device divided into three sections 11, 13, 15 using partitions 5, 6, and I started to preliminary desorption to the top of the first fluidized bed of section 11, blown with an inert gas countercurrently to the downward flow of the catalyst, then to the recovery to the bottom of the second fluidized bed of section 13, blown by the reducing gas directly with the upward flow of the catalyst and then to the final desorption to the top of the third boiling layer section 15, purged with an inert gas countercurrent to the downward flow of the catalyst.

Preferably, the portion of the reduced catalyst after the second fluidized bed of section 13 and the final desorption in the third fluidized bed of section 15 is discharged into the reactor, and the part after the second fluidized bed of section 13 is recycled back to the top of the fluidized bed of regenerator 1.

The concentration of catalyst in the first and third fluidized bed can withstand in the range from 600 to 1100 kg / m ³ and in the second in the range from 200 to 850 kg / m ³ , with a catalyst concentration in the first and third fluidized bed more than in the second . The reduction and final desorption gases, respectively, after the second and third fluidized bed can be directed to the upper part of the fluidized bed of the regenerator together with part of the reduced catalyst.

A device is also proposed for the recovery and desorption preparation of a C ₃ -C ₅ paraffin hydrocarbon dehydrogenation catalyst with a fluidized bed, consisting of a cup body 2 of cylindrical shape mounted coaxially to the cylindrical shell of the body of the regenerator 1 and connected to the bottom end 3 of the body of the regenerator 1, and the bottom butt end 4 of the cup 2, having means 16 for supplying the regenerated catalyst, bubblers-distributors 12 for supplying a reducing gas, bubblers-distributors 10 for supplying an inert gas, a pipe 9 for discharging gaseous products of catalyst preparation, a pipe 17 for discharging the prepared catalyst into a reactor, in which the device further comprises a first partition 5 mounted on the bottom 4 of the cup 2 coaxially with its body, the upper end of which is located at or above the upper end of the cup body 2, and between the cup body 2 and the first partition 5 coaxially mounted on the bottom 4 of the cup 2, the second partition 6, having in the lower part of the hole 7 for the flow of catalyst, and installing at its upper end located above the upper end of the first partition 5, the chamber 8 for collecting exhaust gases of the recovery-desorption preparation of the catalyst in the form of a truncated cone with a large base connected to the upper end of the second partition 6, and with a smaller base located below the partition gratings 19 of the regenerator 1, directed upward and connected to the pipe 9 for removal of the exhaust gases of the preparation of the catalyst in the upper part of the fluidized bed of the regenerator 1 in the coke and fuel supply zone aza, while between the cup body 2 and the second partition 6 below the holes 7 for the catalyst overflow, bubbler distributors 10 are installed for supplying inert gas to the first fluidized bed section 11, which has means 16 for supplying the regenerated catalyst from the bottom of the regenerator 1 to the upper part of the specified layer in the form of an open annular space located under or above the distributor 18 for supplying oxygen-containing gas to the regenerator 1 between the second partition 6 and the upper end of the cup body 2, and between the first a town 5 and a second partition 6 below the opening 7 for the catalyst overflow there is a bubbler distributor 12 for supplying a reducing gas to the section 13 of the second fluidized bed, and a bubbler distributor is installed in the lower central part of the fluidized bed bounded by the first partition 5 above the bottom 4 of the cup 2 14 for supplying an inert gas to the section 15 of the third fluidized bed, which has a pipe 17 for discharging the prepared catalyst from the lower part of the specified section installed in the bottom 4 of the glass 2.

In addition, one or two sectional gratings may be installed above the input level at the top of the fluidized bed of the regenerator of catalyst preparation products and below the level of the fluidized bed of the regenerator.

The height of the first and / or third and / or second fluidized bed sections 11, 13, 15 can be located sectional gratings.

In the first and / or third and / or second fluidized bed may be located a small nozzle.

Vertical partitions 5, 6 may have a given shape.

Vertical partitions 5, 6 may have a flat, cylindrical shape.

To implement the proposed method for the recovery and desorption preparation of the chromium-chromium catalyst, devices of various structural designs and, for example, combined with a regenerator or made as separate apparatuses included in the sequential conduct of cycles of dehydrogenation, regeneration and preparation of the catalyst, can be proposed.

In accordance with the proposed method of preparation of the catalyst, there may be other schemes of devices for preparation. For example, the implementation of the preparation of the catalyst can be organized in a system of three separate apparatus with a fluidized bed with a flow of catalyst between them.

As dehydrogenation feedstocks, C ₃ -C ₅ paraffin hydrocarbons, such as, for example, isobutane, n-butane, isopentane, propane with a paraffin content in the feed, preferably 95-99 wt. %, as well as mixtures of these paraffin hydrocarbons.

When implementing the proposed method for the preparation of the catalyst in the reactor-regenerator system, an aluminum-chromium catalyst containing Cr ₂ O ₃ - 13.0-25.0 wt. %, K ₂ O - 1.0-3.0 wt. %, SiO ₂ - 1.0-10.0 wt. %, Al ₂ O ₃ - the rest, when the content in the oxidized state of CrO ₃ - 0.25-3.5 wt. %, for example, an industrial catalyst of the type AOK-73-24.

Spent catalyst means a catalyst that was used in a dehydrogenation reactor, was desorbed, for example, using nitrogen to remove hydrocarbons from the catalyst, and sent to the regenerator when it was cooled during the endothermic dehydrogenation reaction, coked and reduced.

As the oxidizing gas for supplying to the regenerator, a gas containing an oxidizing agent, preferably oxygen, can be used. The preferred oxygen-containing gas may contain air, oxygen-enriched air (air and oxygen mixture), nitrogen-oxygen mixtures of various origins, obtained, for example, in the production of high-purity nitrogen in air separation plants, etc. The concentration of oxygen in oxygen-containing gases supplied for regeneration the catalyst is limited by the conditions of compliance with the safety of the process at a preferred range of from 23 to 50 wt. %

As the reducing gas can be used natural gas, preferably containing methane up to 98 wt. % abhaz dehydrogenation processes containing up to 25 wt. % hydrogen, paraffin hydrocarbons, etc.

As an inert gas for desorption of the catalyst, a feed of nitrogen or reusable combustion gases is preferred.

As fuel gas for combustion in the catalyst heating zone in the regenerator, it is preferable to use natural methane-containing gas, exhaust gases of dehydrogenation processes.

Dehydrogenation can be carried out at a temperature of 530-610 ° C and a volumetric feed rate of feed vapor 120-250 h ^-1 . The regeneration of the catalyst, including burning coke, heating the catalyst and its oxidation can be carried out at a temperature of 630-690 ° C and a volumetric rate of supply of oxygen-containing gas of 100-500 h ^-1 . The preparation of the catalyst after its oxidation in the regenerator before being fed into the reactor can be carried out at a temperature of 635-700 ° С, with a preliminary desorption time of nitrogen for 1-3 minutes, with a recovery time of the catalyst depending on the amount and composition of the reducing gas 0.5-3 min., and with a time of final desorption by nitrogen of 1-3 minutes, as well as with a volumetric rate of nitrogen supply for preliminary desorption of the catalyst 40-100 h ^-1 , reducing gas for reduction of the catalyst 20-150 h ^-1 and nitrogen for final desorption cat recuperators 40-100 h ^-1. To increase the degree of reduction of the catalyst, it is preferable to supply the reducing gas with an excess compared to that necessary for the complete reduction of the catalyst in accordance with the stoichiometry of the reduction reactions. When using the proposed method for preparing the catalyst, the supply of the reducing gas can be increased until the excess coefficient is equal to 1.1-2.0, which ensures the maximum efficiency of the recovery process when the residual reducing gas is taken to be burned to the coke burning zone in the regenerator bypassing the catalyst oxidation zone and, accordingly, the high activity of the catalyst in the dehydrogenation system. (Mikhailov R.K., “Research and development of hardware and technological design of industrial methods for the dehydrogenation of isopentane and isobutane”, Dissertation, Abstract, Yaroslavl, 1970, pp. 10-11; patent RU 2666541, IPC S07C 5/333, S07C 11 / 08, C07C 11/10, B01J 23/04, B01J 23/26, B01J 35/02, B01J 37/02, publ. 09/11/2018).

Sectional gratings for the organization of the fluidized bed is preferably used slotted design. Lattices can be made of individual plates, angles, pipes, etc. To organize a fluidized bed in the catalyst preparation device, a spring wire nozzle can be used as a low-volume nozzle. The preferred volume occupied by the nozzle in the working volume may be 6-8%. The location of the nozzle in the layer is arbitrary. The preparation of the catalyst can be performed in a free fluidized bed (without the use of mass transfer devices - gratings, nozzles), preferably at increased gas flow rates and the ratio of the height of the fluidized bed to its effective diameter, preferably in the range from 3.0 to 9.0. The preferred ratio of the cross-sectional area of the sections of preliminary desorption, recovery and final desorption may be respectively (0.5-2.0): 1.0: (0.5-2.0). The surface velocity of the gas in the reduction section is usually higher than 0.2 m / s, preferably 0.2-2.5 m / s. The surface velocity of the gas in the desorption sections is less than 0.5 m / s, preferably in the range of 0.01 to 0.4 m / s. The speed of the reducing gas in the second fluidized bed may be greater than the speed of the inert gas in the first and third fluidized bed.

Possibilities for achieving the claimed catalyst concentrations in sections of the catalyst preparation device under the indicated conditions and under the operating conditions of the process (temperature, pressure, hydrodynamic characteristics of the catalyst, the amount of catalyst loading into the system, fluidized bed sizes, etc.), including also the distribution of the catalyst concentration over the height fluidized bed illustrated in S.M. Komarov et al., “Model of expansion of a fluidized bed”, (journal “Theoretical Foundations of Chemical Technology”, 1983, Volume XVII, No. 6, pp. 808-812).

The possibility of organizing the circulation of the catalyst in the reactor-regenerator system through the proposed device for preparing the catalyst with vertical baffles in the fluidized bed, organizing directional internal circulation in the system of the preparation-regenerator, ensuring the required catalyst circulation through the overflow holes in the partitions, sectional gratings and a small volume nozzle in a fluidized bed with a direct flow and countercurrent catalyst and gas, regulation of the amount of circulation, the calculation of the size of the metering holes are presented in the work of S.M. Komarov et al., “Investigation of the directed circulation of a catalyst in fluidized bed reactors”, (Journal of Theoretical Foundations of Chemical Technology, 1982, Volume XVI, No. 5, pp. 702-706). The overflow openings in the partitions should be small enough to prevent mass leakage of the reducing gas from the recovery section to the preliminary desorption section. On the other hand, these openings should be large enough to allow a free flow of catalyst particles from the desorption section to the recovery section. The total area of the holes depends on the size of the required catalyst circulation through the transfer openings in the partitions, taking into account the circulation of the catalyst in the reactor-regenerator system and the additional internal directional catalyst circulation in the preparation-regenerator system. The overflow openings should preferably be evenly spaced around the perimeter of the lower part of the partition, in a horizontal section.

The main differences of the proposed method and devices for its implementation in comparison with the prototype are.

The organization of an additional operation of preliminary desorption of the oxidized catalyst leaving the regenerator and entering the preparation in the first fluidized bed, purged with an inert gas countercurrent to the downward flow of the circulating catalyst at a concentration of the latter from 600 to 1100 kg / m ³ .

The separation of the recovery and desorption of recovery products with the operation of the recovery of the catalyst in the second fluidized bed, purged with a reducing gas directly with the upward flow of the circulating catalyst at a concentration of the latter from 300 to 800 kg / m ³ and the operation of the final desorption in the third fluidized bed, blown inert gas countercurrent to the downward flow of the circulating catalyst at a concentration of the latter from 600 to 1100 kg / m ³ .

The use of a compact three-section catalyst preparation system, including sequentially performing preliminary desorption, reduction, and final desorption operations of the circulating catalyst in three parallel fluidized-bed sections with independent modes of performing catalyst preparation operations in them, which reduces the height of the catalyst preparation unit (device) , solve the problems of optimal layout of dehydrogenation units of various configurations, get more a flow chart of a catalyst preparation device with the ability to control the process in each section by changing the gas flow rate in these sections, significantly increase the catalyst residence time in the desorption sections, which limits the catalyst preparation process, due to the opening possibility of increasing the volume of the corresponding sections of the preparation unit.

The increase in heat and mass transfer and the reduction of stagnant zones in the fluidized bed of the preparation unit sections due to the possibility of increasing gas flow rates and using mass transfer devices (sectioning gratings, low-volume nozzles) that are effective at these speeds. This is especially manifested in the once-through motion of the catalyst and gas in the fluidized bed of the catalyst recovery section. The structure of the fluidized bed is characterized by an increased mass transfer surface with a decrease in the size of gas bubbles, which is characteristic of the direct flow of phases. When using sectional gratings, the gas cushions in the sublattice spaces of the recovery section also practically disappear during the forward flow.

Recycling of part of the reduced catalyst through the regenerator and then through the fluidized bed of the preliminary desorption section of the catalyst of the proposed device allows you to return part of the additional heat received during catalyst recovery (adiabatic heating of the catalyst passing through the reduction zone reaches 5-20 ° C - depending on the content of hexavalent chromium oxide on used catalyst) in the initial stages of catalyst regeneration, improving the heat balance of the regenerator, and glublyaet regeneration processes and catalyst preparation. When recirculating through the regenerator, the required temperature to ensure a sufficient degree of coke combustion on the surface of the catalyst particles and further heating of the catalyst in the upper part of the fluidized bed of the regenerator is achieved by mixing spent and cooled catalyst from the reactor with part of the recovered and heated catalyst from the recovery section of the catalyst preparation device with a corresponding decrease the amount of fuel gas supplied to the combustion in the heating zone of the regenerator. Recycling a portion of the catalyst through the pre-desorption zone of the catalyst preparation apparatus increases the efficiency of catalyst preparation. When recirculating a portion of the reduced catalyst through the oxidation zone of the regenerator, the oxidation processes of the catalyst deepen, which is also preferable to increase the activity of the catalyst from cycle to cycle under conditions of its non-stationary activity.

In FIG. 1 shows a diagram of the proposed device for the preparation of the catalyst. The fluidized bed of the device is divided using vertically mounted cylindrical partitions 5 and 6 into sections 11 for preliminary desorption of the oxidized catalyst exiting the regenerator, section 13 for the reduction of the catalyst and section 15 for the final desorption of the circulating catalyst. The partition 6 separates the section for preliminary desorption and the section for the recovery of the catalyst and contains transfer openings 7. In the lower part of the indicated sections there are annular tubular bubblers-distributors: 10 for supplying inert gas for preliminary desorption of the catalyst, 12 for supplying the reducing gas to reduction of the catalyst and 14 for supplying an inert gas to the final desorption of the circulating catalyst. The device has means 16 for supplying the regenerated catalyst, a pipe 17 for discharging the prepared catalyst into the reactor, a pipe 9 for discharging gaseous products of catalyst preparation to the upper part of the fluidized bed of the regenerator 1 into the coke burning zone and the fuel gas supplied to the burners (these zones and burners in FIG. . 1 not shown). The regenerator has a distributor 18 for supplying oxygen-containing gas for catalyst regeneration to the lower part of the fluidized bed of the regenerator, sectional grilles 19 in the fluidized bed of the regenerator, a transport pipe for supplying spent catalyst from the reactor to the regenerator with a catalyst distributor (not shown in Fig. 1). The fluidized bed of catalyst in the recovery section 13 is organized by sectional gratings 20.

Consideration of the proposed device for the preparation of the catalyst, it is advisable to conduct together with the regenerator of the installation of dehydrogenation of paraffin hydrocarbons With ₃ -C ₅ . Spent catalyst from the reactor in a coked, reduced and cooled form during the endothermic dehydrogenation reaction in a mixture with transporting air is fed through a transport pipe through a distributor (not shown in Fig. 1) to the upper part of the fluidized bed of the regenerator. Under the fluidized bed for regeneration of the catalyst through the distributor 18, air is supplied. Air passes through a fluidized bed of a regenerator, partitioned by horizontal gratings 19, countercurrently to a downstream circulating catalyst. To heat the circulating catalyst and provide heat for the endothermic dehydrogenation reaction in the reactor, natural gas is supplied to the upper part of the fluidized bed of the regenerator through a burner located in the catalyst heating zone (not shown in Fig. 1), while burning in the flow of air supplied to the regenerator while burning coke on the catalyst. The catalyst sequentially passes through the heating zone and the oxidation zone below, with simultaneous desorption of the catalyst by the supplied air and gaseous oxidation products. Next, the oxidized catalyst containing a significant amount of adsorbed oxygen, hexavalent chromium oxide and residual adsorbed water enters the beaker 2 for preparing the catalyst through the means 16 for supplying the regenerated catalyst to the first catalyst desorption section 11 from the adsorbed water supplied with nitrogen through a tubular bubbler distributor 10. Having passed the indicated section in the downward flow to nitrogen supply mode, the catalyst stripped from water from the bottom of the section through the metering transfer openings 7 enters the bottom of the catalyst recovery section 13, in which the adsorbed oxygen is removed and CrO _{3 is} reduced to Cr ₂ O ₃ supplied through a bubbler natural methane-containing gas distributor 12. Section 15 of the final desorption of the catalyst from the reaction water adsorbed in the recovery section operates in a downward flow mode of the circulating catalyst to nitrogen supplied to the desorption through the bubbler distributor 14. The flow of nitrogen and pre-desorption products comes from section 11 of the preparation device to the regenerator. After the catalyst is restored in the upward flow mode with natural gas supplied, a part of the recovered catalyst from the top of the recovery section 13 is discharged through the final desorption section 15 and the pipe 17 for discharging the prepared catalyst into the reactor, and the part is returned to the upper part of the fluidized bed of the regenerator in the coke burning zone and supplied fuel gas through the collection chamber 8 and the pipe 9 together with the exhaust gases from sections 13 and 15 of the recovery-desorption preparation of the catalyst. This situation becomes possible in connection with the organization of the directed internal circulation of a portion of the reduced catalyst in the "catalyst recovery section-regenerator" system. The internal circulation of the catalyst part in the proposed catalyst preparation device according to the circuit shown in FIG. 1, is implemented by creating a circulation circuit with a lifting part of the circuit, including a fluidized bed of the recovery section 13, a collection chamber for collecting exhaust gases 8 and a pipe 9 for removing exhaust catalyst preparation gases together with the specified part of the circulating catalyst to the top of the fluidized bed of the regenerator in the coke burning zone and the supplied fuel gas, and with the pressure part of the circuit, including the fluidized bed section 11 of the preliminary desorption of the preparation device and the fluidized bed of the regenerator to the level of the upper end of the pipe s 9 at the top of the fluidized bed regenerator (FIG. 1, not shown). The sections of the circuit included in the pressure part of the internal circulation circuit preferably operate at lower linear gas flow rates and, accordingly, at higher catalyst concentrations than the sections included in the lifting part of the circuit, which creates the conditions for convective directional internal circulation of the reduced catalyst in the system "Catalyst recovery section-regenerator." The difference in hydrostatic heads of the lifting and pressure parts of the circulation circuit is the driving force of the internal directional circulation of the catalyst. It is possible to control the amount of directed internal circulation of the catalyst, for example, by changing the flow of flows into the preparation device or by using auxiliary blowing of small amounts of nitrogen into the pipe 9. In this case, a situation may occur with a decrease in internal circulation until it stops, which can lead to the release of the preparation through pipe 9 only gaseous products of preparation. During the implementation of exothermic reduction reactions along the fluidized bed of section 13, adiabatic heating of the circulating catalyst occurs with a rise in the temperature of the catalyst towards the end of the section depending on the content of hexavalent chromium oxide in the oxidized alumina-chromium catalyst, for example, to 20 ° C with a CrO content _of 1.0 wt% . Thus, part of the recovered and heated catalyst is recycled to the regenerator for heat use, and the prepared catalyst from the lower part of the final catalyst desorption section 15 is transported through the pipe 17 to the reactor. The resulting regeneration gases, including the gases of recovery and desorption preparation of the catalyst after burning the combustible part in the regenerator heating zone, fall into the superlayer space of the regenerator and, after trapping small fractions of the catalyst carried away from the fluidized bed in cyclones (not shown in Fig. 1), leave the regenerator . The small fractions of the catalyst trapped in the cyclones are returned to the upper part of the fluidized bed of the regenerator through the dust risers, and the regeneration gases are supplied for cooling, sanitary cleaning of the catalyst dust and then discharged through the chimney into the atmosphere.

Thus, the technical result of the claimed invention is to increase the efficiency of the reduction-desorption preparation of chromium-chromium catalysts with an increase in their activity in the processes of dehydrogenation of C ₃ -C ₅ paraffin hydrocarbons with a more compact and technological scheme of the preparation unit. The proposed device for the preparation of catalysts can be used to design new and modernize existing industries.

Claims (10)

1. The method of reduction-desorption preparation of an aluminum-chromium catalyst in a dehydrogenation process of C ₃ -C ₅ paraffin hydrocarbons with a fluidized bed during successive cycles of dehydrogenation, regeneration and preparation of the catalyst circulating in a system containing a reactor, a regenerator (1) with heating of the catalyst in the upper part fluidized bed by burning coke on the spent catalyst coming from the reactor and supplied fuel gas, followed by oxidation of the catalyst and desorption of oxide products supplying oxygen-containing gas in the lower part of the fluidized bed of the regenerator (1), as well as a device for preparing the regenerated catalyst before feeding it into the reactor, carried out by sequential reduction of the catalyst with a reducing gas and desorption of the reduction products with an inert gas, characterized in that the regenerated catalyst from the lower parts of the fluidized bed of the regenerator (1) are fed into a device divided into three sections (11), (13), (15) using partitions (5), (6), and first to backward desorption to the top of the first fluidized bed of section (11), blown with an inert gas countercurrently to the catalyst downward flow, then to reduction to the bottom of the second fluidized bed of section (13), purged by the reducing gas directly with the catalyst upward flow and then to the final desorption to the top the third fluidized bed section (15), purged with an inert gas countercurrent to the downward flow of the catalyst. 2. The method according to p. 1, characterized in that part of the recovered catalyst after the second fluidized bed of section (13) and final desorption in the third fluidized bed of section (15) is discharged into the reactor, and part after the second fluidized bed of section (13) is recycled for regeneration to the top of the fluidized bed of the regenerator 1. 3. The method according to p. 1, characterized in that the concentration of the catalyst in the first and third fluidized bed is maintained in the range from 600 to 1100 kg / m ³ and in the second in the range from 200 to 850 kg / m ³ , the concentration more catalyst in the first and third fluidized bed than in the second. 4. The method according to p. 1, characterized in that the recovery and final desorption gases, respectively, after the second and third fluidized bed are sent to the upper part of the fluidized bed of the regenerator together with part of the recovered catalyst. 5. A device for the recovery and desorption preparation of an aluminum-chromium catalyst for the dehydrogenation of C ₃ -C ₅ paraffin hydrocarbons with a fluidized bed, consisting of a barrel body (2) of a cylindrical shape mounted coaxially to the cylindrical shell of the regenerator body (1) and connected to the bottom with a bottom (3) the regenerator housing (1), and the bottom end (4) of the cup (2) having means (16) for supplying the regenerated catalyst, bubblers-distributors (12) for supplying a reducing gas, bubblers-distributors (10) for inert gas, a pipe (9) for discharging gaseous products of catalyst preparation, a pipe (17) for discharging the prepared catalyst into the reactor, characterized in that the device further comprises a first baffle mounted on the bottom (4) of the glass (2) coaxially with its body ( 5), the upper end of which is located at or above the upper end of the cup body (2), and between the cup body (2) and the first partition (5), a second partition (6) is coaxially mounted on the bottom (4) of the cup (2), having at the bottom of the hole (7) for the flow of catalysis ora, and installed on its upper end, located above the upper end of the first partition (5), a chamber (8) for collecting exhaust gases from the recovery-desorption preparation of the catalyst in the form of a truncated cone with a large base connected to the upper end of the second partition (6), and with a smaller base, located below the sectional grilles (19) of the regenerator (1), directed upwards and connected to the pipe (9) for exhausting the catalyst preparation exhaust gases to the upper part of the fluidized bed of the regenerator (1) in the coke burning zone and supplied fuel gas, while between the housing of the glass (2) and the second partition (6) below the holes (7) for the catalyst flow, bubbler distributors (10) are installed to supply inert gas to the first fluidized bed section (11), which has means ( 16) for supplying the regenerated catalyst from the bottom of the regenerator (1) to the upper part of the specified layer in the form of an open annular space located under or above the distributor (18) for supplying oxygen-containing gas to the regenerator (1) between the second partition (6) and the upper end to cup housing (2), and between the first partition (5) and the second partition (6) below the hole (7) for the catalyst flow, a bubbler distributor (12) is installed to supply the reducing gas to the second fluidized bed section (13), and the lower central part of the fluidized bed, limited by the first partition (5) above the bottom (4) of the glass (2) has a bubbler distributor (14) for supplying inert gas to the section (15) of the third fluidized bed, which has a pipe (17) for the release of prepared catalyst from the bottom of the specified section installed in bottom (4) cups (2). 6. The device according to claim 5, characterized in that one or two sectional gratings are installed above the input level into the upper part of the fluidized bed of the regenerator of catalyst preparation products and below the level of the fluidized bed of the regenerator. 7. The device according to claim 5, characterized in that sectional gratings are arranged along the height of the first and / or third and / or second fluidized bed of sections (11), (13), (15). 8. The device according to p. 5, characterized in that in the first and / or third and / or second fluidized bed is a low-volume nozzle. 9. The device according to p. 5, characterized in that the vertical partitions (5), (6) have a given shape. 10. The device according to p. 5, characterized in that the vertical partitions (5), (6) have a flat, cylindrical shape.

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