JP2003231681A - Method for producing propylene oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing propylene oxide from an organic peroxide and propylene in the presence of a fixed catalytic bed by which production can economically and stably be carried out in high yield. <P>SOLUTION: The method is to produce the propylene oxide from the organic peroxide and propylene in the presence of the fixed catalytic bed. A catalyst having a higher activity than that in use is added without removing the catalyst during use and without changing the position of the catalyst in use when the catalytic activity is lowered to an unacceptable level. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing propylene oxide. More specifically, the present invention is a method for producing propylene oxide from an organic peroxide and propylene in the presence of a fixed catalyst layer, which can be economically and stably carried out in a high yield. The present invention relates to a method for producing propylene oxide having the excellent feature of

[0002]

2. Description of the Related Art A technique for producing propylene oxide from an organic peroxide and propylene in the presence of a fixed catalyst layer is known. For example, Japanese Patent Application Laid-Open No. 2000-117101 describes that an epoxidation reaction is carried out using a titanium-containing silicon oxide catalyst. It is also disclosed that the reaction is carried out in the presence of a fixed catalyst layer. For example, European Patent No. 0232663 discloses a reaction method of epoxidizing propylene in the presence of a fixed catalyst.
However, when propylene is epoxidized in the presence of a fixed bed catalyst to produce propylene oxide, there is a problem that the operation for maintaining the yield becomes difficult due to a decrease in catalyst activity over time, and in some cases, stable operation cannot be performed. . For example, in WO01 / 12617, when a propylene oxide is obtained from ethylbenzene hydroperoxide and propylene in the presence of a fixed catalyst, a catalyst having a reduced activity in a reactor containing a fixed bed catalyst continuously connected to two or more catalysts. It discloses a method of recovering the catalyst by transferring a reactor containing the above-mentioned to a reactor at a subsequent stage, contacting it with a reaction liquid at a temperature higher by 5 ° C. or more than the reaction temperature before transferring. However, since the reactor is moved to the latter stage, the change of the piping system and the operation of the valve are complicated, and when the catalyst with low activity is moved to the latter stage and treated at a high reaction temperature, the produced propylene oxide is sequentially reacted. And cause a decrease in the yield of propylene oxide. Also, US Pat. No. 5,849,937 comprises at least two or more continuous fixed bed reactors, one of which is removed from the system when the activity drops to an undesired level, resulting in higher activity. A method of replacing the catalytic reactor is disclosed. However, in this method, it is necessary to frequently stop the operation when replacing the catalytic reactor, and there is a concern that the production efficiency is low. Further, there is a problem that the valve operation becomes complicated even when the valve operation is continuously switched. Furthermore, since the new catalyst has a high activity, there is a concern that a rapid progress of reaction may cause exothermic runaway depending on the insertion location.

[0003]

Under the present circumstances,
The problem to be solved by the present invention is a method for producing propylene oxide from an organic peroxide and propylene in the presence of a fixed catalyst layer, which is economically and stably carried out in a high yield. The present invention is to provide a method for producing propylene oxide having an excellent feature that

[0004]

That is, the present invention is a method for producing propylene oxide from an organic peroxide and propylene in the presence of a fixed catalyst layer, when the catalytic activity is lowered to an unacceptable level. In addition, the present invention relates to a method for producing propylene oxide, which comprises adding a catalyst having an activity higher than that of the catalyst in use without removing the catalyst in use and changing the position of the catalyst in use. Is.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The catalyst of the present invention may be a solid catalyst having sufficient catalytic activity. A titanium-containing silicon oxide catalyst is preferable from the viewpoint that a high yield and a high selectivity can be achieved. Examples of the titanium-containing silicon oxide catalyst include, for example, EP-A-0345856.
JP-A-2000-117101, JP-A-20
No. 00-107605 and Japanese Patent Laid-Open No. 2000-1076.
The catalyst etc. which are indicated by the 04th publication are mentioned.

When propylene oxide is produced by reacting an organic peroxide with propylene in the presence of a fixed catalyst layer, the catalytic activity decreases with the lapse of time in continuous operation for a certain period of time. Deteriorates to an industrially unacceptable level. During this period, the reaction temperature must be increased in order to maintain the conversion rate of the organic peroxide, but not only the yield of propylene oxide with respect to propylene decreases as the reaction temperature increases,
Impurities derived from organic peroxides, for example, when the organic peroxide is cumene hydroperoxide, it is feared that formic acid, acetic acid, aldehydes, and alcohols will be generated, and that the distillation step as a subsequent step will be affected. When the catalytic activity reached an industrially unacceptable level, the yield was maintained by removing the previously used catalyst and replacing it with a new catalyst or a more active catalyst. In order to solve such a problem, as a result of intensive studies by the present inventors, as shown in FIG. 1, the catalyst used in the present reaction system has a low catalyst deterioration rate and shows almost no activity after a certain period of time. Focusing on the fact that there is no decrease, the used catalyst is not removed from the catalyst layer, but by adding a new catalyst with higher activity and using it together, the deterioration rate of the catalyst is not accelerated and deteriorated It was found to be stable and have higher durability compared to the case where only one is used. In addition, usually, in order to maintain the catalytic activity for a certain period of time,
It is industrially practiced to fill the catalyst with a margin, but in this case, the cause of the decrease in catalyst activity is the product generated by the reaction, so the catalyst that is hardly reacted and is not used in the initial stage of the actual operation. Will also be poisoned by the product. Therefore, compared with the reaction using only the new catalyst, the combination of the used catalyst and the additional catalyst enables continuous operation for a long period of time, and the total catalyst use efficiency is improved. In the present invention, since the catalyst layer that has been used further is used as it is, the reaction time can be increased and the temperature of the entire catalyst layer can be lowered, so that the yield of propylene oxide can be kept high. In addition, after the catalyst is added, the temperature setting can be changed without largely changing the temperature setting, so that the operation time until the adjustment can be shortened.

The organic peroxide referred to in the present invention is t-
Examples thereof include butylbenzene hydroperoxide, ethylbenzene hydroperoxide, cumene hydroperoxide and the like.

In the present invention, it is preferable to use cumene hydroperoxide as the organic peroxide. The use of cumene hydroperoxide minimizes the thermal decomposition of water found in other organic peroxides, such as peroxides such as ethylbenzene hydroperoxide, resulting in the formation of propylene oxide. It is possible to suppress the sequential reaction due to the reaction between propylene and water, and to maintain a high propylene yield.

The reaction in the present invention is an exothermic reaction, and in order to remove the heat of the reaction, an external slow heating system using a multi-tube reactor can be adopted, but from the economical viewpoint, an adiabatic reactor is preferable. In this case, in order to remove the heat of reaction, it is preferable to provide a heat exchanger between the catalyst layers for cooling.

In a specific embodiment of the present invention, the number of catalyst layers is preferably at least two. In this case, one or more empty catalyst layers are provided at the start of the operation, and when the activity decreases after the operation for a certain period of time, the empty catalyst layer can be additionally filled with the catalyst. The greater the number of catalyst layers, the easier it becomes to control the reaction amount in each catalyst layer, so stable operation is possible.However, if too many, negative factors such as system complexity and maintenance cost increase. , Preferably 20 or less. The catalyst is added at a time when the activity is reduced to an industrially unacceptable level, but it is preferable to add a new catalyst when the rate of conversion of propylene oxide to reacted propylene is lower than 99%. preferable.
When adding a new catalyst, there is no limit to the place or number of filling. A portion of the reactant flowing out from the outlet of the catalyst layer is the same or / and
And may be recycled to the inlet of a different catalyst layer. This is effective in preventing a temperature rise due to the reaction heat of the catalyst layer.

Further, as in the present invention, the catalyst layer is divided,
Since the temperature rise due to the reaction heat can be controlled by adjusting the feed amount to each catalyst layer, the catalyst activity decreases and the yield deteriorates due to the rapid temperature rise of the catalyst layer, and the runaway reaction due to the reaction temperature rise. Can be suppressed in advance, and more stable operation becomes possible.

The epoxidation reaction temperature is generally 0 to 200 ° C.
However, a temperature of 25 to 200 ° C. is preferable. Pressure is
Sufficient pressure may be sufficient to keep the reaction mixture in the liquid state.
Generally, it is advantageous that the pressure is 100 to 10,000 kPa. The amount of olefin fed is 1 to the total number of moles of organic peroxide fed to the catalyst layer.
100 times, preferably 3 to 50 times, more preferably
It is fed 5 to 20 times. Usually, the unreacted olefin is separated and purified and then recycled to be used as an epoxidation reaction raw material.

The reaction can be carried out in the liquid phase using a solvent. The solvent must be liquid under the temperature and pressure of the reaction and substantially inert to the reactants and products. The solvent may consist of the substances present in the cumene hydroperoxide solution used, usually the cumene hydroperoxide concentration is from 5 to 50% by weight, preferably from 10 to 40% by weight. For example, in the case of a mixture consisting of the starting material, cumene, it is possible to use this as a substitute for the solvent without adding any solvent. Other useful solvents include aromatic monocyclic compounds (eg, benzene, toluene, chlorobenzene, orthodichlorobenzene), alkanes (eg, octane, decane, dodecane) and the like. When a titanium-containing silicon oxide catalyst is used as the catalyst, the reaction pressure is 1 to 10 MPa and the reaction temperature is 50.
Propylene oxide can be obtained by feeding propylene in an amount of 1 to 20 times the molar amount of fresh isopropylbenzene hydroperoxide fed to propylene at 150 ° C. Unreacted propylene is recycled to the epoxidation reaction step and reused after purification and separation.

[0014]

Example 1 As shown in FIG. 1, catalyst bed numbers 10, 12, and 1 were added to a fixed bed flow reactor composed of 10 independent catalyst beds.
4, 16 and 18 were filled with 5 g each of a silicon oxide catalyst containing Ti, and a solution containing 30 wt% of cumene hydroperoxide was added to the catalyst layers of Nos. 10 and 12 at 50 g /
Feed for each hr. On the other hand, propylene is number 10
90 g / hr is fed to the catalyst layer of. The inlet pressure of the catalyst layer 10 is adjusted to 5.0 MPa, and the inlet temperature of each catalyst layer is adjusted so that the conversion rate of the cumene hydroperoxide supplied is 99%. Next, 1000 hours after the start of operation, the propylene oxide yield relative to propylene was 97%, and catalyst layer number 1
1,3,15,17,19 add 5g each catalyst,
The inlet temperature is adjusted so that the conversion rate of the cumene hydroperoxide to be fed is 99%. 1 in Table 1
The propylene oxide yield with respect to propylene after 000 hours and 2000 hours progress is shown.

Example 2 As shown in FIG. 2, in a fixed bed flow reactor composed of six independent catalyst layers, catalyst layer numbers 20, 21 and 22 were filled with 8 g each of a Ti-containing silicon oxide catalyst. 30% by weight
Solution containing cumene hydroperoxide of No. 2
100 g / hr is fed to each catalyst layer of No. 0. On the other hand, propylene feeds the catalyst layer of No. 20 at 90 g / hr. Adjust the pressure of each catalyst layer to 5.0 MPa,
The inlet temperature of each catalyst layer is adjusted so that the conversion rate of the cumene hydroperoxide fed is 99%. Next, 1000 hours after the start of the operation, the yield of propylene oxide with respect to propylene was 98%, 8 g of the catalyst was added to each of catalyst layer numbers 23, 24 and 25, and the conversion rate of the cumene hydroperoxide fed was 99. Adjust the inlet temperature to be%. Table 2 shows the propylene oxide yield relative to propylene after 1000 hours and 2000 hours.

Comparative Example 1 In FIG. 1, reference numerals 10, 11, 12, 13, 14, 1
The conditions are the same as in Example 1 except that the catalyst layers of 5, 16, 17, 18, and 19 are filled with the same catalyst by 5 g each.
At this time, the reaction results after 1000 hours and 2000 hours are shown in Table 1. The propylene oxide yield relative to propylene after 2000 hours is worse than in Example 1.

Comparative Example 2 In FIG. 2, reference numerals 20, 21, 22, 23, 24, 2
5 except that the catalyst layer of 5 was packed with 8 g of the same catalyst.
The conditions are the same as in Example 1. At this time, 1000 hours,
The reaction results after 2000 hours are shown in Table 2. The propylene oxide yield relative to propylene after 2000 hours is worse than in Example 1.

[0018]

[Table 1]

[0019]

[Table 2]

[Explanation of Tables] C3 ′ yield: [Propylene oxide produced (mol)]
/ Reacted C3 '(mol)] x 100 (%)

[0021]

As described above, according to the present invention, there is provided a method for producing propylene oxide from an organic peroxide and propylene in the presence of a fixed catalyst layer, which is economical and stable and has a high yield. It was possible to provide a method for producing propylene oxide having an excellent feature that it can be carried out.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an embodiment of the present invention.

FIG. 3 is a diagram showing an example of an embodiment of the present invention.

Claims (4)

[Claims] 1. A method for producing propylene oxide from an organic peroxide and propylene in the presence of a fixed catalyst layer, wherein the catalyst in use is not removed when the catalytic activity decreases to an unacceptable level. And a method for producing propylene oxide, which comprises adding a catalyst having a higher activity than the catalyst activity during use without changing the position of the catalyst during use. 2. The manufacturing method according to claim 1, wherein the number of catalyst layers is at least two or more. 3. The method according to claim 1, wherein the catalyst is a titanium-containing silicon oxide catalyst. 4. The method according to claim 1, wherein the organic peroxide is cumene hydroperoxide.