DD160769A3 - METHOD AND DEVICE FOR PREPARING ACRYLNITRILE - Google Patents

Abstract

The invention relates to a method and a device for Ammoxydationsumwandlungen in the fluidized bed using feinkoernigen metal oxide oxidation catalysts. In particular, the selectivity and the activity of the catalyst should be increased. It has been found that with a continuous catalyst regeneration outside the synthesis reactor in a regeneration cycle and the reduction of the oxygen content of 0.01-1.0 vol .-% in the synthesis reactor exhaust gas, the reaction course of the ACN system can be significantly improved in several parameters. By a hot air supply at a temperature range of 750 to 1000 K in the fluidized bed regenerator and a linear velocity of 5-30m / s in the regeneration line, the regeneration of the catalyst is ensured in its long service life. The increase in yield by 5-8% of acrylonitrile at a much lower burden on the purification stages and a low expenditure on equipment in the realization of the device make the process much more economical.

Description

Method and device for the production of

acrylonitrile

IPK CO7C 121-32

Field of application of the invention;

The present invention relates to a method and a device consisting of parallel operated synthesis reactor and fluidized bed Regenera tor for the ammoxidation of olefins in the fluidized bed · The method and apparatus are suitable for Ammoxydationsumwandlungen in the fluidized bed using fine-grained metal oxide oxidation catalysts ·

Characteristic of the known technical solutions;

The production of nitriles can be carried out heterogeneously catalytically from olefins, ammonia and air in the fluidized bed. In this case, the fluidized bed is usually generated in upright cylindrical reactors by turbulence of the fine-grained catalyst with the reactant gas · distributor plate or gas distribution devices ensure a uniform distribution of the reactant gas over the reactor cross-section. To improve the heat and mass transfer soils or other suitable internals can be used in the synthesis reactor, but often lead to more reductive damage to the catalyst »About cooling systems, the heat released in the synthesis in the reactor heat dissipated.

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In the upper region of the reactor, the removal of the entrained catalyst from the reaction gas takes place by suitable devices, such as cyclones, before the reaction products are fed to the workup.

In the synthesis of nitriles by this method show highly active catalysts with increasing Betriebsaeit a more or less significant decrease in nitrile yield or the selectivity of Olefinumwandlunge Since this change in the catalyst affects the economics of large-scale nitrile synthesis, were methods with synthesis reactors with internal regeneration by downcomers or Autoregeneration zones, z. For example, in US Patent 3472892 and DE-OS 2119061 suggested Palis in this regeneration zone does not complete regeneration or such a zone is not present, the regeneration, z. B. with air from time to time in the fluidized bed reactor itself, the air is fed as a regeneration gas through the existing gas distributor to the reactor. Or it must be taken for regeneration from the reactor catalyst and refilled outside regenerated catalyst in the reactor werder _β

These methods and devices have among others the following wax parts:

- A regeneration zone in the synthesis reactor reduces the reactor space available for the synthesis and is very ineffective, since an exact separation between synthesis gas and regeneration gas through intensive backmixing in a fluidized bed reactor is not possible.

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The reactions of synthesis and regeneration taking place in one and the same reactor are negatively influenced by the parameters of the reaction and the reactants. An optimal design of the synthesis as well as the regeneration in a common apparatus, including adaptation to the changing during the operating time catalyst properties is difficult to get »zormrt z. Sine lowering the oxygen content in the Reoktantengasmischung reduces by-product formation and thus increases the yield of target product, The required for maintaining the catalyst activity higher oxygen content in the reaction gas with еіязг significant by-product formation and a corresponding decrease linked to the selectivity for the target product *

The temporary regeneration in the fluidized-bed reactor always leads to interruption; Synthesis processes and is also bound to the reaction reactor which can be set in the synthesis reactor and is not freely selectable. "Discontinuous regeneration processes do not ensure a uniform, high level of Ni / Rila yield and selectivity during the entire operating time.

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Aim of the invention;

According to the invention, a process and an apparatus for the production of acrylonitrile are to be developed with an increase in the catalytic selectivity and activity of the chemical synthesis.

Presentation of the essence of the invention ;

It has been found that in a continuous catalyst regeneration outside of the synthesis reactor in a regeneration cycle and the Absenkimg the oxygen content in the synthesis reactor, the reaction course of the acrylonitrile synthesis over known methods in several parameters can be significantly improved »According to the invention, a fluidized bed regenerator is used, the 0, 1 - 0.8 times the diameter of the synthesis reactor »The fluidized bed regenerator is equipped in the lower part with an air-ammonia feed, in the upper part with a cyclone for separating the catalyst particles from the fluid bed regenerator leaving the gas phase. The continuous supply of damaged catalyst from the synthesis reactor in the fluidized bed regenerator is carried out by pneumatic conveying with an injector nozzle via зіпе regeneration line, which opens tangentially into the fluidized bed regenerator. At the fluidized bed regenerator bottom, the discharge line for the reactivated catalyst is attached. The fluid bed regenerator is provided with internals to improve the mass and heat exchange.

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These internals should have 20-90 % free cross-section The gas flow velocity in the fluidized bed regenerator should reach at least ten times the minimum fluidization rate of the catalyst. For feeding the catalyst and the gas into the synthesis reactor, devices having a distributing effect over the synthesis reactor cross section should be used.

In the process according to the invention, which are based on an increase in the selectivity of the olefin conversion to the desired nitrile, in addition to the parallel to the synthesis reactor operated continuous catalyst regeneration cycle, in which the required oxidation and regeneration of the catalyst takes place, the Säuerst off reduction of 1 - 0.01 VoI, -% residual oxygen content in the synthesis reactor exhaust gas, the molar ratio of reactants for the synthesis reactor feed propene, ammonia and air of 1: 1: 8.5 - 9.2 and the hot air feed into the fluidized bed regenerator in a temperature range of 750 - 1000 K, the most important parameters for the Process · The regeneration temperature above the temperature of the synthesis reaction is inventively achieved by the catalytic reaction of a corresponding amount of ammonia with regeneration air outside the synthesis reactor and the oxidation of the catalyst * The Katalysatorregenerationskrei slauf outside the synthesis reactor is operated at a temperature range of 750 - 1000 K, which is set by the air ammonia feed into the preheater and fluidized bed regenerator, and a pressure range of 0.1-1 MPa »

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For molybdenum oxide containing catalysts, the temperature should not exceed 900 K. The regeneration in the catalyst circuit is carried out with an air-ammonia mixture having a molar ratio of 15-25: 1 or other suitable oxygen-containing gas mixture in said temperature range at a linear velocity of 5-30 m / s in the regeneration line and C, 1 - 1 m / s in the fluid bed regenerator. The fluid bed regenerator is designed to allow a mean residence time of the catalyst of 0.5-3 hours. The achieved improvement in the selectivity of the synthesis reaction leads to the reduction of the effort for the removal of carbonaceous pesticides from the downstream parts of the system, to increase the reliability and reduce the cost of wastewater treatment and allows Er-, increase the capacity of the entire system up to 8 %.

Exemplary embodiments Example 1

The regeneration temperature of 844 ^е К above the temperature of the synthesis reaction is achieved by catalytically converting a corresponding amount of ammonia to the regeneration air in the preheater (3), the regeneration line (4) and the fluidized bed regenerator (5) ) and the associated mixture with the regeneration gas mixture at a linear speed of 12 m / s in the regeneration line (4) takes place with an injector which is arranged in the preheater (3) *

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The regeneration line (4) opens tangentially into the fluid bed regenerator (5), which allows a residence time of the catalyst up to two hours. The withdrawal of the reactivated catalyst from the fluidized bed regenerator through the line (6) or, through the regeneration exhaust gas line (7) allows a targeted influencing of the particle size distribution of the catalyst "In order to improve the regeneration effect internals (8) are arranged in the fluidized bed regenerator (5) have a free cross-section of 65% «

Example 2

A fluid bed regenerator (5) according to the figure was operated in parallel with an acrylonitrile synthesis reactor. The diameter of the fluidized bed regenerator (5) was 0.6 m, the reaction temperature was 85 ° ^C. , and the average residence time of the catalyst particles was 1 h. The catalyst was prepared according to DD-WP 126181 * The removal of the deactivated catalyst was carried out via the Reaktantengasverteiler the S \> nthesereaktors «The exhaust gas of the fluidized bed regenerator was passed into the synthesis reactor. Compared to the synthesis without parallel, high-level reactivation of the catalyst, the molar ratio of the propene, ammonia and air reactants was lowered from 1: 10 to an average of 1: 1: 9.2, and the reactor had a residual oxygen content of 0 in the synthesis reactor effluent , 5 VoI · -% are driven «

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The synthesis could be operated with a significant reduction of the carbon compounds in the process water and an increase in the yield of acrylonitrile of 3.7 % permanently without selectivity and activity drop. The change in the molar ratio of the reactants for the synthesis reactor was in addition to increasing the throughput of propene and ammonia at unchanged. Exploit total reactant volume. This corresponded to an additional capacity increase of the synthesis reactor and acrylonitrile production recovery of 6.5 % ·

Claims (2)

209 invention claim 1. A process for the preparation of acrylonitrile with continuous catalyst regeneration, characterized in that the reactants propene, ammonia and air are fed in the molar ratio 1: 1: 8.5-9.2 in the synthesis reactor, the residual oxygen content of the synthesis reactor exhaust gas at 0.01 - 1.0 vol .- # is maintained and the regeneration at a temperature in the preheater (3) of 750 - 1000 ⁰ K with an air-ammonia molar ratio of 15-25: 1 and a residence time of the catalyst in the fluidized bed regenerator (5) of 0.5-3 hours, wherein the pressure in the regeneration cycle 0.1-1.0 MPa, the linear velocity in the regeneration line (4) 5-30 m / s and in fluidized bed regenerator (5) 0.1-1.0 m / s is. 2. Apparatus for carrying out the method according to item 1, characterized in that a regeneration circuit outside of the synthesis reactor, consisting of 'a preheater and an injector nozzle P) a regeneration line (h) and a fluidized bed regenerator (5) is operated, wherein a 209 Air (9) and an air, Ammoniakeinepeisung (10), (12) and a tangential integration of the regeneration line (4-) is used in the regenerator and the fluidized bed regenerator with internals (8) having a free cross section of 20-90 % , and with an air-ammonia regeneration gas distributor (1) and a line (6) for the reactivated catalyst and in the upper part with a päer several cyclone (s) (2) with regeneration exhaust gas line (7) is provided and the 0, 1 to 0.8 times the diameter of the synthesis reactor. For this 1 page drawings