CN221789223U - Isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene - Google Patents

Abstract

The utility model belongs to the field of chemical technology, and specifically relates to an isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene, comprising: a multi-stage isothermal fixed bed, which has a feed port, a multi-stage catalyst bed layer and a discharge port in sequence; a dual-channel nozzle for inter-stage feeding, which is arranged between two adjacent catalyst beds, one channel of the dual-channel nozzle is an inter-stage liquid phase water feeding channel for spraying atomized water droplets, and the other channel is an inter-stage butene feeding channel; an air distributor for inter-stage feeding, which is arranged between two adjacent catalyst beds and located in the space below the dual-channel nozzle. The utility model sprays the inter-stage feeding liquid phase water from the nozzle in an atomized form to form micron-sized water droplets, thereby achieving full mixing of the inter-stage materials, avoiding local overcooling of the materials, and solving the problem of carbon deposition at the inlet of the inter-stage isothermal fixed bed, which affects the long-term operation of the device.

Description

Isothermal reaction system for oxidative dehydrogenation of butene to butadiene

Technical Field

The utility model belongs to the technical field of chemical engineering, and specifically relates to an isothermal reaction system for preparing butadiene through oxidative dehydrogenation of butene.

Background Art

In recent years, butadiene production has undergone great changes. The traditional naphtha raw material steam cracking production of ethylene and propylene and by-product butadiene units have gradually turned to low-priced light hydrocarbon raw materials such as ethane, propane and butane due to the high price of naphtha raw materials. The lightness of cracking raw materials has led to a significant reduction in the butadiene production of cracking units; in recent years, the technology of methanol to olefins and propane dehydrogenation units has matured and achieved large-scale industrial application, which has also replaced part of the production capacity of steam cracking units, further reducing the expected butadiene production capacity; on the other hand, the downstream rubber industry of butadiene has developed rapidly, and the emerging ABS industry and the rapidly developing adiponitrile industry have made it difficult for butadiene production to meet market demand in the future. Therefore, opening up new sources of butadiene has received much attention, especially the development and industrialization of butene oxidative dehydrogenation technology to produce butadiene.

The industrialized catalyst for the oxidative dehydrogenation of butene to butadiene adopts a two-stage or three-stage adiabatic fixed bed. Carbon deposition between the adiabatic fixed beds is relatively serious, resulting in a rapid increase in the pressure drop of the reaction system during the operation of the device, which seriously restricts the long-term stable operation of the device. On the other hand, in the currently industrialized two-stage or three-stage adiabatic fixed bed, the total water vapor and n-butene molar ratio of the reaction feed is 10-13, and the water-to-olefin ratio is relatively high. It is necessary to further reduce the amount of water vapor used in the reaction process to improve the economy of the device.

In recent years, reducing the water vapor consumption during the oxidative dehydrogenation of butene, inhibiting carbon deposition at the inlet of the fixed bed, and achieving stable operation of the reaction unit have always been the top priorities of development in this technical field. The use of an isothermal fixed bed has attracted great attention in the field of oxidative dehydrogenation due to the potential low water vapor consumption of the reaction system.

Chinese patent CN102442874 proposes a tubular constant temperature fixed bed for oxidative dehydrogenation of butene to butadiene using an iron catalyst. The patent adopts a constant temperature fixed bed process and a temperature control medium to indirectly transfer heat, which can reduce the amount of water vapor used in the reaction process, and the reaction process does not require water spraying for cooling, but the operating time of the device provided by the patent is only 200 hours; Chinese patents CN103553864 and CN103073382 provide a method of using an isothermal bed for oxidative dehydrogenation of butene, and point out that in order to avoid local supercooling and carbon deposition at the reactor inlet, the patent uses an inter-stage heat exchanger to transfer heat to reduce the feed temperature of the next stage of material, and does not use an inter-stage liquid water feed reduction method.

Liquid water has a large latent heat of vaporization and a better cooling effect than water vapor. Feeding liquid water between stages can achieve rapid cooling of the feed material. Feeding liquid water between stages can also increase the water-olefin ratio of the next isothermal fixed bed, increase the water vapor partial pressure of the reaction, reduce the hot spot temperature of the catalyst bed, and extend the operating life of the catalyst. However, feeding liquid water will cause carbon deposition from the feed inlet of the fixed bed to the upper inert ceramic balls loaded with the catalyst, which will lead to a rapid increase in the bed pressure drop of the fixed bed. The problem of significantly shortening the catalyst reaction operation time has not been solved.

Utility Model Content

The utility model aims at the technical problem that, in the process of butene oxidative dehydrogenation to butadiene, although the use of interstage liquid phase water feeding can achieve the advantages of rapid cooling of the feed material and increasing the water-to-olefin ratio of the next isothermal fixed bed, it will cause carbon deposition in the section from the fixed bed feed port to the upper inert ceramic balls loaded with catalysts. The utility model aims to provide an isothermal reaction system for butene oxidative dehydrogenation to butadiene.

In order to solve the above technical problems, the first aspect of the utility model provides an isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene, wherein the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene adopts a multi-stage isothermal fixed bed and liquid phase water is fed between stages. By using a dual-channel nozzle to break up the water into the form of atomized water droplets, not only the water-olefin ratio of the next stage of the isothermal fixed bed and the rapid cooling of the feed material are increased, but also the carbon formation phenomenon in front of the next stage of the catalyst bed can be prevented. The isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene comprises:

A multi-stage isothermal fixed bed, wherein the multi-stage isothermal fixed bed has a feed inlet, a multi-stage catalyst bed layer and a discharge outlet in sequence;

A dual-channel nozzle for inter-stage feeding, wherein the dual-channel nozzle is arranged between two adjacent catalyst beds, wherein one channel of the dual-channel nozzle is an inter-stage liquid phase water feeding channel for spraying atomized water droplets, and the other channel is an inter-stage butene feeding channel;

An air distributor for inter-stage feeding is arranged between two adjacent catalyst beds and in the space below the dual-channel nozzle.

When the isothermal reaction system of the utility model is in use, mixed butene, air and water vapor enter the first stage catalyst bed through the feed port of the multi-stage isothermal fixed bed for catalytic reaction; liquid phase water fed between stages is sprayed out from the liquid phase water feed channel of the double-channel nozzle in an atomized form to enter between stages, and butene is sprayed out from the other channel of the double-channel nozzle to enter between stages; air enters between stages through the air distributor below the double-channel nozzle; the atomized water droplets sprayed out from the double-channel nozzle and butene are mixed and contacted with the discharge of the upper stage isothermal fixed bed, so that the atomized water droplets of micron size are rapidly vaporized and fully mixed with the discharge, and then mixed with the air fed by the air distributor arranged in the lower space of the double-channel nozzle, and the temperature of the reaction feed material of the next stage isothermal fixed bed is controlled by the amount of liquid phase water, and the mixed reaction feed material of the next stage enters the next stage catalyst bed for catalytic conversion. The material temperature of the next stage reaction feed is usually controlled at 80°C to 200°C, preferably at 115°C to 160°C. The material temperature is controlled by the amount of liquid water fed between stages. The lower the material temperature, the more liquid water is fed, which is more beneficial to the improvement of the catalyst reaction performance. However, the liquid water feed amount should ensure that the mixed material is in a gas phase when entering the next isothermal fixed bed.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the size of the atomized water droplets sprayed from the inter-stage liquid phase water feed channel is 1 micron to 500 microns, preferably 5 microns to 200 microns.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, there are a plurality of dual-channel nozzles, and the plurality of dual-channel nozzles are evenly arranged on a plane perpendicular to the axial direction of the isothermal fixed bed.

The utility model arranges a plurality of double-channel nozzles in a certain manner to better promote uniform distribution of materials.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the number of the dual-channel nozzles arranged is 0.2 to 10 per square meter, preferably 1 to 4 per square meter.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the air distributor is a ring tube with a plurality of air nozzles, or any other form that is conducive to uniform distribution of materials.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the multiple-stage isothermal fixed bed is a single isothermal fixed bed having multiple-stage catalyst beds;

Alternatively, the multi-stage isothermal fixed bed is a series connection of multiple isothermal fixed beds with a single-stage catalyst bed layer disposed therein.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the number of layers of the catalyst bed is preferably 2 to 3 layers.

The multi-stage isothermal fixed bed of the utility model can be set as a single multi-stage catalyst bed, or can be set as a series of multiple single-stage catalyst beds. The water vapor of the isothermal reaction system enters only from the first stage isothermal fixed bed, and butene and air are fed from the first stage isothermal fixed bed and the inter-stage. In this way, the more catalyst beds there are, the lower the molar ratio of the total water vapor and n-butene in the isothermal reaction system, and the lower the water vapor consumed by the isothermal reaction system. However, an increase in the number of catalyst beds will also cause problems such as difficulty in manufacturing the reactor, large area of equipment, increased investment, and complex operation and difficulty in controlling stability of the equipment. Considering factors such as energy consumption, investment and stable operation, the multi-stage isothermal fixed bed is preferably a single multi-stage isothermal fixed bed, and the number of catalyst beds is preferably set to 2 or 3.

Optionally, in the isothermal reaction system for the oxidative dehydrogenation of butene to produce butadiene as described above, the isothermal fixed bed is a shell-and-tube fixed bed, which includes a closed container, the feed port is provided above the closed container, the discharge port is provided below the closed container, at least one section of the catalyst bed is provided inside the closed container, and the catalyst bed includes a plurality of shells and tubes arranged in parallel.

The isothermal fixed bed of the utility model adopts a tube-in-tube fixed bed, which refers to a reactor form in which a plurality of tubes are arranged in parallel in the same container and packaged together. The number of tubes depends on the production scale and the output of a single tube-in-tube.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the tubes of the tube array are respectively filled with an upper inert filler, a catalyst and a lower inert filler from top to bottom, and a support frame for supporting the catalyst and the inert filler in the tube array is provided at the bottom of the tube array;

The catalyst bed also includes a liquid molten salt feed port and a liquid molten salt discharge port connected to the inside and outside of the closed container. The shell side of several of the tubes is filled with liquid molten salt. The present invention removes the reaction heat through the shell side of the tubes, and controls the temperature of the catalyst bed through the temperature difference of the liquid molten salt entering and leaving the closed container.

Optionally, in the isothermal reaction system for oxidative dehydrogenation of butene to butadiene as described above, the upper part of the tube side of the tube array is filled with an inert filler with a height of 50mm to 400mm, preferably 100mm to 300mm, and the filling height of the catalyst is 500mm to 3000mm, preferably 800mm to 2000mm.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the inner diameter of the tube array is 20 to 50 mm, preferably 22 to 40 mm.

Optionally, in the isothermal reaction system for oxidative dehydrogenation of butene to butadiene as described above, the general chemical formula of the catalyst is Mo _a Bi _b Fe _c Mg _d O _e ; a=5-10; b=0.8-1.0; c=0.5-1.2; d=0.1-1.0, and e is a number satisfying the sum of the valence states of each atom in the general chemical formula of the catalyst to be 0;

Alternatively, the catalyst has a general chemical formula of [Mg _x Zn _y ]Fe ₂ O ₄ , wherein 0≤x≤1.0, 0≤y≤1.0, and x+y is 1.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the catalyst is in a granular form, and the particle morphology of the catalyst is one or more of cylindrical, Raschig ring and spherical particles;

Among them, the outer diameter of the cylindrical particles is 2mm to 8mm, the height is 1.5mm to 6mm, preferably the outer diameter is 3mm to 6mm, and the height is 2mm to 3mm;

The Raschig ring particles have an outer diameter of 4 mm to 8 mm, an inner diameter of the inner cavity of 1.5 mm to 3 mm, and a height of 1.5 mm to 6 mm, preferably an outer diameter of 4 mm to 6 mm, preferably an inner diameter of the inner cavity of 1.5 mm to 2.5 mm, and preferably a height of 2 mm to 4 mm;

The diameter of the spherical particles is 2 mm to 6 mm, preferably 2 mm to 3 mm.

Optionally, in the isothermal reaction system for oxidative dehydrogenation of butene to butadiene as described above, the catalyst is uniformly diluted with a granular inert material having the same or different diameter as the catalyst.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the upper inert filler and the lower inert filler are the same or different inert fillers.

Optionally, in the isothermal reaction system for oxidative dehydrogenation of butene to produce butadiene as described above, the inert filler is one or more of inert aluminum oxide and silicon carbide, the inert filler is in granular form, and the particle morphology of the inert filler is one or more of cylindrical, Raschig ring and spherical.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, a plurality of baffles are provided on the shell side of the tube array, and the length direction of the baffles is perpendicular to the tube side direction of the tube array.

The utility model avoids the existence of dead zones in the shell-side liquid-phase molten salt, which would otherwise cause uneven temperature of the liquid-phase molten salt, by setting the baffles, and further ensures that the catalyst bed has a lower hot spot temperature and a suitable temperature distribution, so as to give full play to the catalyst reaction performance.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene further comprises:

A steam generator, wherein the steam generated by the steam generator is obtained by indirect heat exchange between a water bag and circulating liquid-phase molten salt.

After the liquid molten salt of the utility model flows out from the shell side of the tubular fixed bed, water vapor is generated by a water vapor generator, and the water vapor can be returned to the isothermal reaction system as the first stage fixed bed feed, thereby reducing energy consumption.

Optionally, in the isothermal reaction system for the oxidative dehydrogenation of butene to produce butadiene as described above, the circulation system formed by the liquid molten salt used in each catalyst bed can be set up as an independent system, so that the operating temperature of the catalyst in each catalyst bed can be better controlled to ensure the catalyst reaction performance.

The utility model removes reaction heat through the shell side of the tube array, and realizes temperature control of the catalyst bed layer in the tube array through the temperature difference of the molten salt entering and leaving the fixed bed.

Optionally, in the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene as described above, the liquid molten salt is a mixture of sodium nitrate, sodium nitrite and potassium nitrate;

The mass composition of the liquid phase molten salt is: 30wt% to 55wt% of sodium nitrite, 5wt% to 10wt% of sodium nitrate, and 40wt% to 65wt% of potassium nitrate, and the total mass composition satisfies 100wt%;

The mass composition of the liquid-phase molten salt is preferably: 35wt% to 45wt% of sodium nitrite, 6wt% to 8wt% of sodium nitrate, and 50wt% to 55wt% of potassium nitrate, and the total mass composition satisfies 100wt%.

The molten salt of the above combination of the utility model has the characteristics of high heat capacity and strong heat buffering ability, and is particularly suitable for heat removal in isothermal fixed bed catalytic reactions at a temperature of 300° C. or above.

The liquid molten salt flowing in the shell side of the tube array of the utility model passes through the tube wall and the inert filler in the upper part of the tube array to intensively mix and evenly distribute the reaction feed material with a temperature of 80°C to 200°C, preferably 115°C to 160°C, entering the isothermal fixed bed, and is superheated to the temperature required for the catalyst reaction, and then enters the catalyst bed layer in the tube array for catalytic conversion. Obviously, the inert filler layer in the upper part of the tube array makes full use of the reaction heat.

In order to solve the above technical problems, the second aspect of the present invention provides an isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene, and the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene comprises:

Initial feed materials of butene, air and water vapor enter the first stage catalyst bed from the feed port of the multi-stage isothermal fixed bed and undergo catalytic reaction in the first stage catalyst bed;

Liquid water enters the interstage in the form of atomization. At the same time, butene enters the interstage, and air enters the interstage below the butene, so that the butene in the interstage is mixed with the atomized water droplets and the discharge formed by the catalytic reaction of the previous catalyst bed, and then mixed with the air entering the interstage to form the reaction feed material of the next stage, which enters the next catalyst bed for catalytic reaction;

Until the last stage of the reaction feed material undergoes catalytic reaction in the last stage of the catalyst bed, it is discharged through the discharge port of the multi-stage isothermal fixed bed.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the initial feed material enters the first-stage catalyst bed layer from the feed port of the multi-stage isothermal fixed bed in the form of gas phase.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the butene fed into the interstage enters the interstage in the form of liquid phase or gas phase, preferably in the form of gas phase.

Gas-phase butene feeding can better promote the mixing and uniform distribution of materials between stages, thereby better promoting the performance of catalyst reaction.

Optionally, in the isothermal reaction method for producing butadiene by oxidative dehydrogenation of butene as described above, the liquid water and the butene fed between stages are fed from a dual-channel nozzle arranged between the catalyst beds of two adjacent stages, and one channel of the dual-channel nozzle sprays atomized water droplets, and the other channel sprays butene. Preferably, the size of the atomized water droplets is 1 micron to 500 microns, and more preferably 5 microns to 200 microns.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the air fed between stages is fed from an air distributor disposed between two adjacent catalyst beds.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the feed temperature of the next stage of reaction feed material when entering the next stage of catalyst bed is controlled by the amount of liquid phase water.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the temperature of the reaction feed material in the next stage is controlled at a temperature condition of 80°C to 200°C, preferably a temperature condition of 115°C to 160°C.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the reaction feed material of the next stage is in a gas phase when entering the catalyst bed of the next stage.

The material temperature is controlled by the amount of liquid water fed between stages. The lower the material temperature, the more liquid water is fed, which is more beneficial to the improvement of catalyst reaction performance. However, the liquid water feed amount should ensure that the mixed material is in the gas phase when entering the next isothermal fixed bed.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the control conditions of the isothermal reaction for preparing butadiene by oxidative dehydrogenation of butene are as follows:

In the initial feed material entering the first stage catalyst bed, the molar ratio of feed water vapor to n-butene is 2-14, preferably 6-13, the molar ratio of feed oxygen to n-butene is 0.5-1.2, preferably 0.6-0.9, and the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 50 cubic meters to 350 cubic meters, preferably 100 cubic meters to 300 cubic meters;

The molar ratio of oxygen and n-butene fed to the catalyst bed in each subsequent stage is 0.6-1.2, preferably 0.7-1.0, and the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 50 cubic meters to 350 cubic meters, preferably 100 cubic meters to 300 cubic meters;

The total amount of feed water to each subsequent catalyst bed is determined by the feed water to the previous catalyst bed, the water produced by the reaction conversion of the previous catalyst bed, and the amount of liquid phase water fed between stages.

The pressure drop of each catalyst bed is controlled at 5kPa to 50kPa, preferably 5kPa to 30kPa, and the discharge pressure of the last catalyst bed is controlled at 50kPa to 75kPa;

The temperature of each catalyst bed is controlled at 300°C to 480°C, preferably 340°C to 480°C.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the butene refers to an oxidative dehydrogenation hydrocarbon raw material, including n-butene, a mixture of other hydrocarbons and oxygen-containing compounds, the n-butene is preferably at least one of cis-trans-butene-2 and butene-1, the other hydrocarbons are n-butane, isobutane, isobutene and C5 and hydrocarbons with more than five carbon atoms, and the oxygen-containing compound is a mixture of methanol, ethanol and dimethyl ether; in order to fully improve the reaction efficiency, the total mass of other hydrocarbons and oxygen-containing compounds contained in the oxidative dehydrogenation hydrocarbon raw material is not higher than 10%, of which the mass fraction of isobutene is less than 2.0%, and the mass fraction of C5 and hydrocarbons with more than five carbon atoms is less than 1.0%.

Optionally, in the isothermal reaction method for producing butadiene by oxidative dehydrogenation of butene as described above, the reaction feed material in the last stage is subjected to catalytic reaction in the last stage catalyst bed layer, and then discharged through the discharge port of the multi-stage isothermal fixed bed. The butadiene formed by heat exchange, water washing, compression and separation enters the butadiene extraction unit to finally obtain a butadiene product.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, in the butadiene extraction unit, the solvent used for extraction is acetonitrile, N,N-diformamide (also known as DMF) or N-methylpyrrolidone (also known as NMP), and the optimal solvent is NMP.

Optionally, in the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene as described above, the isothermal reaction method for preparing butadiene by oxidative dehydrogenation of butene is implemented by using an isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene provided by the first aspect of the utility model.

The positive progress of the utility model is that the utility model sets a double-channel nozzle between the isothermal fixed bed sections, sprays the liquid phase water between the sections in the form of atomization from one of the channels on the double-channel nozzle, forms micron-level atomized water droplets, achieves full mixing of the materials between the sections, avoids local overcooling of the materials, and solves the problem of carbon deposition at the inlet of the isothermal fixed bed between the sections, which affects the long-term operation of the device. The utility model adopts an isothermal fixed bed, which also reduces the total water vapor/n-butene ratio of the feed, and the energy consumption of the reaction system is greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure of the present invention will become more apparent with reference to the accompanying drawings. It should be understood that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings:

FIG1 is a schematic diagram of the structure of a single isothermal fixed bed with a two-stage catalyst bed layer in the utility model;

FIG2 is a schematic diagram of a structure of the utility model using two isothermal fixed beds in series with a single-stage catalyst bed;

FIG3 is a schematic diagram of the structure of a single isothermal fixed bed with three-stage catalyst beds in the utility model.

DETAILED DESCRIPTION

The following is an explanation of the implementation of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

Embodiment 1:

1 , the isothermal reaction system for oxidative dehydrogenation of butene to butadiene in this embodiment adopts a multi-stage isothermal fixed bed and inter-stage feeding. The isothermal reaction system specifically includes a multi-stage isothermal fixed bed, a dual-channel nozzle and an air distributor.

Among them, the multi-stage isothermal fixed bed adopts a single isothermal fixed bed with a two-stage catalyst bed layer.

A two-stage catalyst bed is arranged in a closed container 2, and a single tube array in a first-stage catalyst bed is filled with an inert filler 3 for the upper part of a first-stage tube side, a catalyst 4 for a first-stage tube side, and an inert filler 5 for the lower part of a first-stage tube side. A first-stage shell-side liquid-phase molten salt feed port 6 and a first-stage shell-side liquid-phase molten salt discharge port 8 are arranged on the closed container 2. The first-stage shell side is filled with a first-stage shell-side liquid-phase molten salt 7. A double-pass feed port for feeding between the first and second stages is arranged between the first-stage catalyst bed and the second-stage catalyst bed. The single tube array in the second stage catalyst bed is filled with the second stage tube side upper inert filler 12, the second stage tube side catalyst 13 and the second stage tube side lower inert filler 14. The closed container 2 is provided with the second stage shell side liquid phase molten salt feed port 15 and the second stage shell side liquid phase molten salt discharge port 17. The second stage shell side is filled with the second stage shell side liquid phase molten salt 16. The second stage reaction discharge 18 is discharged from the discharge port of the single isothermal fixed bed.

Water vapor, butene and air as initial feed materials 1 enter the first stage catalyst bed through the feed port of the isothermal fixed bed. Between the first stage catalyst bed and the second stage catalyst bed, liquid phase water and butene are fed through a double-channel nozzle 9 for feeding between the first and second stages, and air is fed through an air distributor 10 for feeding between the first and second stages.

The diameter of the sealed container 2 is 7000 mm, and the inner diameter of each tube is 25.6 mm; the tubes are filled with Mo _6.0 Bi _0.8 Fe _1.2 Mg _1.0 O with a height of 800 mm. _22.0 catalyst (first tube-side catalyst 4 and second tube-side catalyst 13), the catalyst particles are cylindrical particles with an outer diameter of 5mm and a height of 3mm, and are diluted with equal-diameter silicon carbide particles. Silicon carbide has been tested to have no conversion effect on the reaction raw materials; the upper part of the catalyst is filled with 100mm high equal-diameter silicon carbide (inert filler 3 at the upper part of the first tube-side and inert filler 12 at the upper part of the second tube-side), and the shell-side liquid molten salt (first shell-side liquid molten salt 7 and second shell-side liquid molten salt 16) passes through silicon carbide respectively, and the initial feed material 1 and the second-stage feed material are superheated to the temperature required for the catalyst reaction, and then enter the catalyst for conversion respectively; the lower part of the tubular catalyst is filled with equal-diameter silicon carbide particles (inert filler 5 at the lower part of the first tube-side and inert filler 14 at the lower part of the second tube-side), and the catalyst and filler in the tube are supported by a support frame.

Steam, butene and air are used as initial feed materials 1 to enter a catalyst bed layer, and the feed temperature is 140°C. The initial feed material 1 passes through an inert filler 3 at the upper part of a tube side of the tubular catalyst, is superheated by a shell side liquid molten salt 7 composed of 41wt% sodium nitrite, 6.0wt% sodium nitrate and 53.0wt% potassium nitrate, and then enters a tube side catalyst 4 for reaction conversion. The catalyst reaction conditions are: the volume of normal butene fed per cubic meter of catalyst per hour under standard conditions is 120 cubic meters, and the feed steam: oxygen: normal butene = 9.0: 0.70: 1.0 (in moles). The temperature of the catalyst bed layer is controlled at 340°C to 440°C through the temperature difference between a shell side liquid molten salt feed port 6 and a shell side liquid molten salt discharge port 8 and the temperature control of the shell side liquid molten salt 7.

Between the two catalyst beds, multiple first-stage and second-stage inter-stage feed dual-channel nozzles 9 are arranged. The dual-channel nozzles 9 are produced by Spray Systems (Shanghai) Co., Ltd., and the nozzle model is SUE175B. The dual-channel nozzles 9 are evenly distributed on a plane perpendicular to the axis of the fixed bed reactor, and the number of nozzles arranged is 4 per square meter. An air distributor 10 for first-stage and second-stage inter-stage feed is arranged at the bottom of the nozzle. Liquid water is sprayed out in atomized form through one channel of the dual-channel nozzle 9, and the size of the atomized water droplets is 5 microns to 200 microns. Butene is sprayed out from the other channel of the dual-channel nozzle 9, and then mixed with the atomized water droplets and the high-temperature discharge formed by the reaction of the first-stage catalyst bed, and then mixed with the feed air of the air distributor 10 to form the second-stage feed material. The temperature of the second-stage feed material before entering the second-stage catalyst bed is controlled at 150°C by the amount of liquid water. The second-stage feed material first passes through the second-stage tube upper inert filler 12 on the upper part of the second-stage tube catalyst, and is composed of 41wt% sodium nitrite and 6. The second shell-side liquid molten salt 16 containing 0wt% and 53.0wt% potassium nitrate is overheated and then enters the second tube-side catalyst 13 for reaction conversion. The catalyst reaction conditions are controlled as follows: the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 80 cubic meters, feed oxygen/n-butene = 0.90 (mol/mol), and the temperature difference between the second shell-side liquid molten salt feed port 15 and the second shell-side liquid molten salt discharge port 17 and the temperature of the second shell-side liquid molten salt 16 are used to control the temperature of the second catalyst bed at 360°C to 450°C, and the outlet pressure of the second catalyst bed is controlled to 60kPa.

During the operation of the isothermal reaction system, the total water vapor/n-butene molar ratio of the reaction feed can be well controlled at 5.4. The pressure drop changes of the two-stage catalyst beds are shown in Table 1. During the 20 months of operation, the total pressure drop only increased by 2.4 kPa, which is a very small increase.

Comparative Example 1:

As in Example 1, liquid water, butene and air were used as feed materials between stages, but liquid water and butene were not fed through nozzles. The feed temperature of the second stage was controlled at 300°C. The other reaction conditions were the same as in Example 1. During the operation of the device, it was found that the pressure drop of the fixed bed increased significantly. After 2 months, the device was shut down for carbon burning.

Table 1: Changes in pressure drop during operation of the reaction apparatus of Example 1 and Comparative Example 1

Pressure drop unit: kPa

Embodiment 2:

2 , the isothermal reaction system for oxidative dehydrogenation of butene to butadiene in this embodiment adopts a multi-stage isothermal fixed bed and inter-stage feeding. The isothermal reaction system specifically includes a multi-stage isothermal fixed bed, a dual-channel nozzle and an air distributor.

The following are the differences from Example 1, and the rest are the same as Example 1:

The multi-stage isothermal fixed bed adopts the form of two isothermal fixed beds with a single-stage catalyst bed layer connected in series. The double-channel nozzle 9 for feeding between the first and second stages and the air distributor 10 for feeding between the first and second stages are arranged at the reaction outlet of the first catalyst bed layer and form an integrated closed container with the first isothermal fixed bed. The two isothermal fixed beds are connected by a pipeline. The first-stage reaction discharge 11 flowing out of the discharge port of the first isothermal fixed bed enters the feed port of the second isothermal fixed bed through the pipeline, and the second-stage reaction discharge 18 is discharged from the discharge port of the second isothermal fixed bed.

The diameter of the sealed container 2 is 8000 mm, and the inner diameter of each tube is 40 mm; the tubes are filled with 2000 mm high [Mg _0.8 Zn _0.2 ]Fe ₂ O ₄ catalysts (first tube-side catalyst 4 and second tube-side catalyst 13), the catalyst particles are Raschig rings with an outer diameter of 5mm, a height of 5mm, and a cavity of 1.5mm, and are diluted with equal-diameter inert alumina balls, the upper part of the catalyst is filled with equal-diameter alumina balls with a height of 300mm (inert filler 3 at the upper part of the first tube-side and inert filler 12 at the upper part of the second tube-side), and the alumina balls have no conversion on the reaction raw materials after testing; the shell-side composition is 45wt% of sodium nitrite, 8wt% of sodium nitrate and 47wt% of potassium nitrate. Liquid molten salt (first shell-side liquid molten salt 7 and second shell-side liquid molten salt 16) passes through the alumina balls, and the initial feed material 1 and the second-stage feed material (first reaction discharge 11) are superheated to the required temperature of the catalyst reaction, and then enter the catalyst conversion; the lower part of the tubular catalyst is filled with equal-diameter alumina balls (inert filler 5 at the lower part of the first tube-side and inert filler 14 at the lower part of the second tube-side), and the catalyst and filler in the tubular are supported by a support frame.

Steam, butene and air are used as initial feed materials 1 to enter a catalyst bed layer, and the feed temperature is 160°C. The initial feed material 1 passes through the alumina balls on the upper part of the tubular catalyst (the inert filler 3 on the upper part of the first tube side), is superheated through a shell side liquid molten salt 7, and then enters a tube side catalyst 4 for reaction conversion. The catalyst reaction conditions are: the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 300 cubic meters, and the feed steam: oxygen: n-butene = 12: 0.70: 1.0 (in moles). The catalyst temperature is controlled at 340°C to 440°C through a shell side liquid molten salt 7.

In the closed container of the first isothermal fixed bed, a plurality of dual-channel nozzles 9 for feeding between the first and second stages are arranged at the bottom. The dual-channel nozzles 9 are produced by Spray Systems (Shanghai) Co., Ltd., and the nozzle model is SUE175B. The dual-channel nozzles 9 are evenly distributed on a plane perpendicular to the axis of the fixed bed reactor, and the number of nozzles arranged is 3 per square meter. An air distributor 10 for feeding between the first and second stages is arranged at the lower part of the nozzle. Liquid water is sprayed out in an atomized form through one channel in the dual-channel nozzle 9, and the size of the atomized water droplets is 5 microns to 200 microns. The gaseous butene is sprayed out from the other channel of the dual-channel nozzle 9, and then mixed with the high-temperature discharge formed by the reaction and conversion of the first catalyst bed layer, and then mixed with the feed air of the air distributor 10 to form a first-stage reaction discharge 11. The discharge temperature is controlled to be 140°C by the amount of liquid water. The first-stage reaction discharge 11 is first passed through The inert filler 12 at the upper part of the second-stage catalyst bed tube-side catalyst is superheated by the second-stage shell-side liquid-phase molten salt 16, and then enters the second-stage tube-side catalyst 13 for reaction conversion. The catalyst reaction conditions are controlled as follows: the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 280 cubic meters, feed oxygen/n-butene=0.95 (mol/mol), the catalyst bed is controlled at 360°C to 460°C by the second-stage shell-side liquid-phase molten salt 16 composed of 45wt% sodium nitrite, 8wt% sodium nitrate and 47wt% potassium nitrate, and the outlet pressure of the second-stage catalyst bed is controlled to 75kPa.

During the operation of the isothermal reaction system, the total water vapor/n-butene molar ratio of the two-stage reaction feed can be well controlled at 5.4. The pressure drop changes of the two-stage catalyst beds are shown in Table 2. During the 20-month operation of the isothermal reaction system, the total pressure drop of the multi-stage isothermal fixed bed only increased by 2.1 kPa, and the increase was negligible, indicating that the carbon deposition problem was effectively solved.

Comparative Example 2: As in Example 2, liquid water, butene and air were used as feed between stages, but liquid water and butene were not fed through nozzles. The feed temperature of the second stage was controlled at 300°C, and the other reaction conditions were the same as in Example 2. The device was in operation for 3 months, and it was found that the pressure drop of the catalyst bed increased significantly, and the device needed to be shut down to treat the carbon deposits.

Table 2: Changes in pressure drop during operation of the reaction apparatus of Example 2 and Comparative Example 2

Pressure drop unit: kPa

Embodiment 3:

3 , the isothermal reaction system for oxidative dehydrogenation of butene to butadiene in this embodiment adopts a multi-stage isothermal fixed bed and inter-stage feeding. The isothermal reaction system specifically includes a multi-stage isothermal fixed bed, a dual-channel nozzle and an air distributor.

The following are the differences from Example 1, and the rest are the same as Example 1:

Among them, the multi-stage isothermal fixed bed adopts a single isothermal fixed bed with three-stage catalyst beds, and multiple dual-channel nozzles and air distributors are arranged between two adjacent catalyst beds to feed liquid water, butene and air. That is, compared with Example 1, this embodiment is also provided with a dual-channel nozzle 19 for feeding between the second and third stages and an air distributor 20 for feeding between the second and third stages between the second and third stages of the catalyst bed, and a single tube array in the three-stage catalyst bed is filled with an upper inert filler 21 of the three-stage tube side, a catalyst 22 of the three-stage tube side and a lower inert filler 23 of the three-stage tube side, a three-stage shell side liquid phase molten salt feed port 24 and a three-stage shell side liquid phase molten salt discharge port 26 are arranged on the closed container 2, and the three-stage shell side is filled with a three-stage shell side liquid phase molten salt 25, and the three-stage reaction discharge 27 is discharged from the discharge port of the single isothermal fixed bed.

The diameter of the closed container 2 is 9000 mm, and the inner diameter of each tube is 22 mm; each tube of the first stage catalyst bed is filled with a first tube-side catalyst 4 of [Mg _0.8 Zn _0.2 ]Fe ₂ O ₄ with a height of 1500 mm, and the first tube-side catalyst 4 is a cylindrical particle with an outer diameter of 4 mm and a height of 3 mm, and is diluted with alumina balls with a size of 3 mm; each tube of the second stage catalyst bed is filled with a second tube-side catalyst 13 of [Mg _0.1 Zn _0.9 ]Fe ₂ O ₄ with a height of 1600 mm, and the second tube-side catalyst 13 has a specification size of Raschig ring cylindrical particles with an outer diameter of 5 mm, a height of 2 mm, and a cavity size of 2.5 mm, and is diluted with alumina balls with a size of 3 mm; each tube of the third stage catalyst bed is filled with a first tube-side catalyst 4 of [Mg _0.8 Zn _0.2 ]Fe ₂ O 4 with a height of 1500 mm, and the first tube-side catalyst 4 is a cylindrical particle with an outer diameter of 4 mm and a height of 3 mm, and is diluted with alumina balls with a size of 3 mm. ₄ The three-stage tube-pass catalyst 22 has a specification size of 3mm balls and is diluted with alumina balls with a size of 3mm.

The upper part of each tube-by-tube catalyst (the first tube-side catalyst 4, the second tube-side catalyst 13 and the third tube-side catalyst 22) is filled with 3mm alumina balls with a height of 250mm (the inert filler 3 on the upper part of the first tube-side, the inert filler 12 on the upper part of the second tube-side and the inert filler 21 on the upper part of the third tube-side), and the shell-side liquid molten salt (the first shell-side liquid molten salt 7, the second shell-side liquid molten salt 16 and the third shell-side liquid molten salt 25) composed of 35wt% sodium nitrite, 7wt% sodium nitrate and 58wt% potassium nitrate is respectively passed through the alumina balls to indirectly superheat the initial feed material 1, the second stage feed material and the third stage feed material to the temperature required for the catalyst reaction, and then enter the catalyst conversion respectively; the lower part of the tube-by-tube catalyst is filled with 3mm alumina balls (the inert filler 5 on the lower part of the first tube-side, the inert filler 14 on the lower part of the second tube-side and the inert filler 23 on the lower part of the third tube-side), and the catalyst and filler in the tube are supported by a support frame.

Steam, butene and air are used as initial feed materials 1 for a catalyst bed, and the feed temperature is 130°C. The initial feed material 1 passes through an inert filler 3 on the upper part of a tube side of the tubular catalyst, is superheated through a shell side liquid molten salt 7, and then enters a tube side catalyst 4 for reaction conversion. The catalyst reaction conditions are: the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 50 cubic meters, and the feed steam: oxygen: n-butene = 2.0: 0.50: 1.0 (in moles). The catalyst bed is controlled at 300°C to 360°C through a shell side liquid molten salt 7.

Between the first stage catalyst bed and the second stage catalyst bed, there are multiple dual-channel nozzles 9 for feeding between the first stage and the second stage. The dual-channel nozzles 9 are produced by Spray Systems (Shanghai) Co., Ltd., and the nozzle model is SUE175B. The dual-channel nozzles 9 are evenly distributed on a plane perpendicular to the axis of the fixed bed reactor, and the number of nozzles arranged is 1/square meter. An air distributor 10 for feeding between the first stage and the second stage is arranged at the bottom of the nozzle. Liquid water is sprayed out in an atomized form through one channel in the dual-channel nozzle 9, and the size of the atomized water droplets is 5 microns to 200 microns. The gaseous butene is sprayed out from the other channel of the dual-channel nozzle 9, and then mixed with the high-temperature discharge formed by the reaction and conversion of the first stage catalyst bed, and then mixed with the feed air of the air distributor 10 to form the second stage feed material. The amount of liquid water fed by the dual-channel nozzle 9 is controlled to adjust the second stage feed material before it enters the second stage catalyst bed. The temperature is controlled at 150°C, the second-stage feed material first passes through the second-stage tube-side upper inert filler 12 on the upper part of the second-stage tube-side catalyst, is indirectly superheated by the second-stage shell-side liquid-phase molten salt 16 composed of 41wt% sodium nitrite, 6.0wt% sodium nitrate and 53.0wt% potassium nitrate, and then enters the second-stage tube-side catalyst 13 for reaction conversion. The catalyst reaction conditions are controlled as follows: the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 80 cubic meters, feed oxygen/n-butene=0.65 (mol/mol), and the catalyst temperature is controlled at 340°C to 420°C by the second-stage shell-side liquid-phase molten salt 16.

Between the second-stage catalyst bed and the third-stage catalyst bed, a plurality of dual-channel nozzles 19 for feeding between the second and third stages are arranged. The dual-channel nozzles 19 are manufactured by Spray Systems (Shanghai) Co., Ltd., and the nozzle model is SUE175B. The dual-channel nozzles 19 are evenly distributed on a plane perpendicular to the axis of the fixed bed reactor, and the number of nozzles arranged is 2 per square meter. An air distributor 20 for feeding between the second and third stages is arranged at the bottom of the nozzle. Liquid water is sprayed out in an atomized form through one channel in the dual-channel nozzle 19, and the size of the atomized water droplets is 5 microns to 200 microns. Gas-phase butene is sprayed out from the other channel of the dual-channel nozzle 19, and then mixed with the high-temperature discharge formed by the reaction and conversion of the second-stage catalyst bed, and then mixed with the feed air of the air distributor 20 to form the third-stage feed material. The amount of liquid water in the dual-channel nozzle 19 is controlled, and the temperature of the third-stage feed material before entering the third-stage catalyst bed is controlled at 140 ℃, and then the three-stage feed material first passes through the three-stage tube-side upper inert filler 21 on the upper part of the three-stage tube-side catalyst, is indirectly overheated by the three-stage shell-side liquid-phase molten salt 25 composed of 35wt% sodium nitrite, 7wt% sodium nitrate and 58wt% potassium nitrate, and then enters the three-stage tube-side catalyst 22 for reaction conversion. The catalyst reaction conditions are controlled as follows: the volume of n-butene fed per cubic meter of catalyst per hour under standard conditions is 100 cubic meters, feed oxygen/n-butene=0.94 (mol/mol), the catalyst bed temperature is controlled at 380℃～480℃ by the three-stage shell-side liquid-phase molten salt 25, and the three-stage catalyst bed outlet pressure is controlled to 50kPa.

During the 18-month operation of the isothermal reaction system, the total water-to-olefin molar ratio of the three-stage reaction can be well controlled at 1.5. The pressure drop changes of each catalyst bed during the operation are shown in Table 3. It can be seen that the pressure drop changes of the three-stage catalyst bed are relatively low, and the total inlet and outlet pressure drop only increases by 2.1 kPa. The pressure drop changes during the reaction process are very low.

Comparative Example 3: As in Example 3, liquid water, butene and air were used as feed between stages, but liquid water and butene were not fed through nozzles. The feed temperature of the second stage was controlled at 320°C, and the other reaction conditions were the same as in Example 3. The reaction was run for 4 months, and it was found that the total pressure drop of the fixed bed had increased significantly, and the device needed to be shut down to treat carbon deposition.

Table 3: Changes in pressure drop during operation of the reaction apparatus of Example 3 and Comparative Example 3

Pressure drop unit: kPa

The utility model is described in detail above in conjunction with the embodiments of the drawings. A person skilled in the art can make various variations of the utility model according to the above description. Therefore, some details in the embodiments should not constitute a limitation of the utility model, and the utility model shall be protected within the scope defined by the attached claims.

Claims (18)

1. An isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene, the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene comprising: A multi-stage isothermal fixed bed, wherein the multi-stage isothermal fixed bed sequentially comprises a feed inlet, a multi-stage catalyst bed layer and a discharge outlet; A dual-channel nozzle for inter-stage feeding, wherein the dual-channel nozzle is arranged between two adjacent catalyst beds, characterized in that one channel of the dual-channel nozzle is an inter-stage liquid phase water feeding channel for spraying atomized water droplets, and the other channel is an inter-stage butene feeding channel; An air distributor for inter-stage feeding is arranged between two adjacent stages of the catalyst bed and located in the space below the dual-channel nozzle. 2. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as claimed in claim 1, characterized in that the size of the atomized water droplets sprayed from the inter-stage liquid phase water feed channel is 1 micron to 500 microns. 3. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as claimed in claim 2, characterized in that the size of the atomized water droplets sprayed from the inter-stage liquid phase water feed channel is 5 microns to 200 microns. 4. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene according to claim 1, 2 or 3, characterized in that there are a plurality of dual-channel nozzles, and the plurality of dual-channel nozzles are evenly arranged on a plane perpendicular to the axial direction of the isothermal fixed bed; And/or, the number of the dual-channel nozzles arranged is 0.2/m2 to 10/m2. 5. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as claimed in claim 4, characterized in that the number of the dual-channel nozzles arranged is 1/square meter to 4/square meter. 6. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as described in claim 1, 2 or 3, characterized in that the air distributor is a ring tube with a plurality of air nozzles. 7. The isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene according to claim 1, 2 or 3, characterized in that the multiple-stage isothermal fixed bed is a single isothermal fixed bed with multiple-stage catalyst beds; Alternatively, the multiple-stage isothermal fixed beds are multiple isothermal fixed beds with a single-stage catalyst bed layer arranged in series. 8. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as claimed in claim 7, characterized in that the number of layers of the catalyst bed is 2 to 3 layers. 9. The isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene according to claim 7, characterized in that the isothermal fixed bed is a tube-in-tube fixed bed, the isothermal fixed bed comprises a closed container, the feed inlet is arranged above the closed container, the discharge port is arranged below the closed container, at least one section of the catalyst bed is arranged inside the closed container, and the catalyst bed comprises a plurality of tubes arranged in parallel; The tubes of the tube array are filled with upper inert fillers, catalysts and lower inert fillers from top to bottom, respectively, and a support frame for supporting the catalysts and inert fillers in the tube array is provided at the bottom of the tube array; The catalyst bed also includes a liquid molten salt feed port and a liquid molten salt discharge port connected to the inside and outside of the closed container. The shell side of several of the tubes is filled with liquid molten salt. The temperature of the catalyst bed is controlled by the temperature difference of the liquid molten salt entering and leaving the closed container. 10. The isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene according to claim 9, characterized in that the upper part of the tube side of the tube array is filled with an inert filler with a height of 50 mm to 400 mm, and the filling height of the catalyst is 500 mm to 3000 mm; And/or, the inner diameter of the tube is 20-50 mm; And/or, the catalyst is in granular form, and the particle morphology of the catalyst is one or more of cylindrical, Raschig ring and spherical particles; wherein the cylindrical particles have an outer diameter of 2mm~8mm and a height of 1.5mm~6mm; the Raschig ring particles have an outer diameter of 4mm~8mm, an inner cavity diameter of 1.5mm~3mm, and a height of 1.5mm~6mm; and the spherical particles have a diameter of 2mm~6mm. 11. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene according to claim 10, characterized in that the upper part of the tube side of the tube array is filled with an inert filler with a height of 100 mm to 300 mm, and the filling height of the catalyst is 800 mm to 2000 mm. 12. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene according to claim 10, characterized in that the inner diameter of the tube array is 22-40 mm. 13. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as claimed in claim 10, characterized in that the outer diameter of the cylindrical particles is 3 mm to 6 mm and the height is 2 mm to 3 mm. 14. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene according to claim 10, characterized in that the Raschig ring particles have an outer diameter of 4 mm to 6 mm, an inner cavity diameter of 1.5 mm to 2.5 mm, and a height of 2 mm to 4 mm. 15. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as claimed in claim 10, characterized in that the diameter of the spherical particles is 2 mm to 3 mm. 16. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene according to claim 9, characterized in that the catalyst is uniformly diluted with a granular inert material having the same or different diameter as the catalyst; And/or, the inert filler is in a granular form, and the particle morphology of the inert filler is one or more of a cylindrical shape, a Raschig ring shape and a spherical shape; The upper inert filler and the lower inert filler may be the same or different inert fillers. 17. The isothermal reaction system for oxidative dehydrogenation of butene to butadiene as claimed in claim 9, characterized in that a plurality of baffles are provided on the shell side of the tube array, and the length direction of the baffles is perpendicular to the tube side direction of the tube array. 18. The isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene according to claim 6, characterized in that the isothermal reaction system for preparing butadiene by oxidative dehydrogenation of butene further comprises: A steam generator, wherein the steam generated by the steam generator is obtained by indirect heat exchange between a water bag and a circulating liquid-phase molten salt; And/or, the circulation system formed by the liquid-phase molten salt used in each catalyst bed layer is arranged in the form of an independent system.