JP2006232753A - Method for suppressing increase of pressure loss in solid catalyst layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for suppressing increase of pressure loss in a solid catalyst layer on stream when continuously producing propylene oxide by epoxidation reaction comprising supplying an organic peroxide and propylene to an epoxidation reactor filled with a solid catalyst, wherein the method has excellent effect of avoiding situations such as catalyst destruction due to increase of pressure loss and decrease of production. <P>SOLUTION: The method for suppressing increase of pressure loss in the solid catalyst layer giving physical condition changes to a raw material flow by temporarily changing the heating medium flow rate to the heater of feed raw material propylene or a feed mixture of the raw material propylene and an organic peroxide to an epoxidation reactor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for suppressing an increase in pressure loss of a solid catalyst layer. More specifically, the present invention provides an organic peroxide and propylene to an epoxidation reactor filled with a solid catalyst, and continuously produces propylene oxide by the epoxidation reaction. An increase in pressure loss in a solid catalyst layer, which is a method for suppressing an increase in loss and has an excellent effect of avoiding a situation in which a catalyst is destroyed due to an increase in pressure loss and a reduction in production volume is unavoidable. It is related with the suppression method.

  For example, a method is known in which propylene oxide is continuously produced by supplying an organic peroxide and propylene to an epoxidation reactor filled with a solid catalyst such as titanium-containing silicon oxide (for example, Patent Document 1). reference.).

  However, with continuous operation, the pressure loss of the solid catalyst layer increases, the problem is that the catalyst is destroyed exceeding the crushing strength of the catalyst, and the feed flow rate of the raw material to avoid the destruction of the catalyst There was a problem that the production volume had to be reduced by suppressing the above.

JP-A-2-42072

  In such a situation, the problem to be solved by the present invention is to supply an organic peroxide and propylene to an epoxidation reactor filled with a solid catalyst and continuously produce propylene oxide by epoxidation reaction. Is a method for suppressing an increase in pressure loss of a solid catalyst layer, and has an excellent effect of avoiding a situation in which the destruction of the catalyst due to the increase in pressure loss and the reduction in production amount are unavoidable It is in providing a method for suppressing an increase in the pressure loss of the layer.

  That is, the present invention supplies an organic peroxide and propylene to an epoxidation reactor filled with a solid catalyst and continuously produces propylene oxide by the epoxidation reaction. The flow rate of the heating medium supplied to the heater of the raw material propylene supplied to the epoxidation reactor or the mixed raw material of raw material propylene and organic peroxide is temporarily increased or decreased. The present invention relates to a method for suppressing an increase in pressure loss of a solid catalyst layer that gives a physical state change to a raw material fluid.

  According to the present invention, when an organic peroxide and propylene are supplied to an epoxidation reactor filled with a solid catalyst and propylene oxide is continuously produced by the epoxidation reaction, the pressure loss of the solid catalyst layer during operation is increased. A method for suppressing an increase in pressure loss of a solid catalyst layer, which has an excellent effect of avoiding a situation in which the catalyst is destroyed due to an increase in pressure loss and the production amount is forced to be reduced. Can be provided.

  In the present invention, an organic peroxide and propylene are supplied to an epoxidation reactor filled with a solid catalyst, and propylene oxide is continuously produced by an epoxidation reaction.

  As the solid catalyst, a titanium-containing silicon oxide catalyst is used from the viewpoint of obtaining the target product in a high yield. These catalysts are preferably so-called titanium-silica catalysts containing titanium chemically bonded to silicon oxide. For example, a titanium compound supported on a silica carrier, a compound compounded with silicon oxide by a coprecipitation method or a sol-gel method, a zeolite compound containing titanium, and the like can be given.

  Examples of the organic peroxide include cumene hydroperoxide, ethylbenzene hydroperoxide, tert-butyl hydroperoxide, and the like.

  As a specific example of the present invention, an organic peroxide and propylene are supplied to an epoxidation reactor filled with a titanium-containing silicon oxide catalyst, and a method of continuously producing propylene oxide by an epoxidation reaction can be mentioned. . The reaction is carried out in the liquid phase using a solvent. The solvent must be liquid under the temperature and pressure during the reaction and be substantially inert to the reactants and products. The solvent may consist of substances present in the organic peroxide solution used. For example, when cumene hydroperoxide is a mixture composed of cumene as a raw material, ethylbenzene hydroperoxide is a mixture composed of ethylbenzene as a raw material, or tert-butyl hydroperoxide is a raw material. In the case of a mixture composed of certain isobutane, this can be used as a substitute for the solvent without particularly adding a solvent.

  The epoxidation reaction temperature is generally 0 to 200 ° C, but a temperature of 25 to 200 ° C is preferable. The pressure may be sufficient to keep the reaction mixture in a liquid state. In general, the pressure is advantageously from 0.1 to 10 MPa.

  The molar ratio of propylene / organic peroxide fed to the epoxidation reactor is preferably 2/1 to 50/1. If the ratio is too small, the reaction rate is lowered and the efficiency is poor. On the other hand, if the ratio is excessive, it is very difficult to separate and recover from the epoxidation reaction solution in order to recycle an excessive amount of unreacted propylene. Requires energy.

  Unreacted propylene contained in the mixed solution after the epoxidation reaction is separated and recovered and recycled to the epoxidation reactor. Distillation can be used as a method for separating and recovering unreacted propylene. Distillation usually uses conditions where propylene is easily vaporized from the reaction solution. The distillation conditions vary depending on the temperature and composition of the reaction solution supplied to the distillation step, but usually the pressure is 0 to 5 MPa in gauge pressure, preferably 0 to 3 MPa, the top temperature is −50 to 150 ° C., The tower bottom temperature is 50 to 200 ° C, preferably 80 to 200 ° C. Moreover, you may use the method of distilling propylene in steps using a some distillation column.

  The unreacted propylene recovered in this way can be mixed with newly supplied propylene and supplied to the epoxidation reactor.

  The liquid linear velocity of the reaction mixture in the fixed bed continuous method of the present invention varies depending on the composition of the mixture and the particle size of the solid catalyst, but is generally preferably 0.1 to 3 cm / sec.

  The organic peroxide fed to the epoxidation reactor is synthesized by oxidation of the corresponding hydrocarbon compound. The organic acid generated during the oxidation reaction also acts as a catalyst poison for the epoxidation catalyst. Therefore, the organic peroxide supplied to the epoxidation reactor is preferably contacted with an aqueous solution of a compound containing an alkali metal during or after the oxidation reaction from the viewpoint of removing the organic acid contained. . Examples of the compound containing an alkali metal include sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate and the like, and any of these compounds or a mixed aqueous solution thereof can be used. The concentration of alkali metal in the aqueous solution is preferably 0.05 to 10% by weight. If the concentration is too low, the removal effect of the organic acid may be insufficient. On the other hand, if the concentration is too high, the decomposition reaction of the generated organic peroxide may be promoted and the yield may be reduced. . After contact with an aqueous solution of a compound containing an alkali metal, it is usually separated into an oil phase / water phase, contacted with water to remove the compound containing the alkali metal remaining in the oil phase, and further oil / water Separated into phases. This operation is repeated if necessary.

  The oil phase after separation from the aqueous phase often contains a trace amount of water. Since this water lowers the yield of the epoxidation catalyst and also acts as a catalyst poison, it is preferably removed as much as possible. Examples of the method for removing water include a method for removing using a separation membrane such as a coalescer, a method for consuming and removing by a reaction, a method for removing by distillation, etc., but using distillation from an industrial viewpoint. It is preferable to remove. The solution containing the organic peroxide thus obtained is fed to the epoxidation reactor.

  However, when the organic peroxide supplied to the epoxidation reactor is in contact with an aqueous solution of a compound containing an alkali metal, there arises a problem that the pressure loss of the solid catalyst layer of the epoxidation reactor increases. . In addition, when the propylene supplied to the epoxidation reactor contains unreacted propylene after the epoxidation reaction, there is a problem that the pressure loss of the solid catalyst layer of the epoxidation reactor increases. Further, the organic peroxide supplied to the epoxidation reactor is in contact with an aqueous solution of a compound containing an alkali metal, and the propylene supplied to the epoxidation reactor is an unreacted propylene after the epoxidation reaction. When it is contained, there is a problem that the increase in pressure loss of the solid catalyst layer of the epoxidation reactor is particularly remarkable.

  The present invention temporarily increases or decreases the flow rate of the heating medium supplied to the heater of the raw material propylene or the raw material propylene and organic peroxide mixed raw material supplied to the epoxidation reactor, and changes the physical state of the raw material fluid To suppress the increase in pressure loss of the solid catalyst layer.

  As the heater, a multi-tube heat exchanger or the like can be used.

  As the heating medium, water vapor or a process fluid having a heat quantity that can be heated can be used.

  To temporarily increase or decrease the flow rate of the heating medium supplied to the heater specifically refers to the next operation. When increasing the degree of opening of the valve installed in the heating medium input path to the heater, or vice versa, or once increasing and then continuing to decrease, or repeatedly increasing and decreasing It is an operation.

  In the present invention, it is preferable to increase or decrease the flow rate of the heating medium between 0 to 200% of the normal time.

  In the case of increasing, the rate of increase and the time to keep increasing depend on the system, and therefore, an optimal value for each system may be determined by some trial and error. Usually, there are many operations in which the flow rate of the heating medium is increased to 100 to 200% of the normal value, then decreased to 0%, and returned to 100%.

  The flow rate of the heating medium is temporarily increased or decreased to change the physical state of the raw material fluid. Here, “physical state change” refers to a change in state such as temperature, pressure, and flow rate of the raw material fluid supplied to the reactor. In addition, the occurrence of a physical state change in the raw material fluid is measured and determined by monitoring an instruction change of a meter installed in the raw material supply path and in the reactor itself.

Example 1
The flow shown in FIG. 1 was used.
Cumene hydroperoxide and propylene were supplied to an epoxidation reactor filled with a titanium-containing silicon oxide catalyst, and propylene oxide was continuously produced by an epoxidation reaction. Cumene was used as the solvent. The epoxidation reaction temperature was about 70 ° C., and the pressure was about 6.5 MPa. The molar ratio of propylene / organic peroxide fed to the epoxidation reactor was 8/1.
Unreacted propylene contained in the mixed solution after the epoxidation reaction was separated and recovered and recycled to the epoxidation reactor. The recovered unreacted propylene was mixed with newly supplied propylene and supplied to the epoxidation reactor.
The liquid linear velocity of the reaction mixture was 1.0 cm / sec.

In accordance with the present invention, the flow rate of the heating medium supplied to the heater for the raw material propylene supplied to the epoxidation reactor is temporarily increased or decreased to give a physical state change to the raw material fluid, thereby reducing the pressure loss of the solid catalyst layer. The rise was suppressed. A multi-tube heat exchanger was used as the heater. Water vapor was used as the heating medium. The flow rate of the heating medium supplied to the heater was temporarily increased or decreased by increasing or decreasing the opening degree of the control valve installed in the heating medium charging path to the heater.
The opening degree of the control valve installed in the heating medium supply path was quickly increased and held for several minutes, and then the opening degree was quickly reduced to zero and then returned to the original opening state. By this operation, the temperature, pressure, and flow rate of the feed mixed raw material to the reactor were changed, and as a result, the pressure loss reduction effect of the reactor catalyst layer of 40 to 50 KPa was obtained.
The change in the physical state of the raw material fluid was measured and judged by monitoring the change in the directions of the meters installed in the raw material supply path and in the reactor itself.
The results are shown in FIG.

Comparative Example 1
FIG. 3 shows the result when the suppression operation for increasing the pressure loss was not performed. A significant increase in pressure loss is observed.

Example 2
Subsequent to Comparative Example 1, an operation for suppressing an increase in pressure loss was performed. As a result, an increase in pressure loss was suppressed. The result. This is shown in FIG.

FIG. 3 is a diagram showing an outline of a flow of Example 1. It is a figure which shows the result of Example 1. It is a figure which shows the result of the comparative example 1. It is a figure which shows the result of Example 2.

Claims (2)

When an organic peroxide and propylene are supplied to an epoxidation reactor filled with a solid catalyst and propylene oxide is continuously produced by the epoxidation reaction, an increase in the pressure loss of the solid catalyst layer that has increased with the production is increased. This is a method of suppressing the flow rate of the heating medium supplied to the heater of the raw material propylene or the raw material propylene and organic peroxide mixed raw material supplied to the epoxidation reactor, and physically increasing the flow rate of the raw material fluid. For suppressing an increase in pressure loss of a solid catalyst layer which gives a state change. The method according to claim 1, wherein the flow rate of the heating medium is increased or decreased between 0 to 200% of the normal time.

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