JP2005097212A - Method for producing propylene oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing propylene oxide, by which propylene oxide is efficiently produced. <P>SOLUTION: The method for producing propylene oxide, by which the concentration of ethylbenzene contained in a solution containing cumene recycled to an oxidation process is ≤10 wt.%, comprises the oxidation process for oxidizing cumene to give cumene hydroperoxide, an epoxidation process for reacting cumene hydroperoxide obtained by the oxidation process with propylene to give propylene oxide and cumyl alcohol, a dehydration process for dehydrating cumyl alcohol obtained by the epoxidation process in the presence of a solid catalyst to give α-methylstyrene and a hydrogenation process for hydrogenating α-methylstyrene in the presence of a solid catalyst to give cumene and recycling the cumene as a raw material for the oxidation process into the oxidation process. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing propylene oxide. More specifically, the present invention can use cumene hydroperoxide obtained from cumene as an oxygen carrier to convert propylene to propylene oxide, and to repeatedly use the cumene, and to effectively increase the reaction volume in each step. The present invention relates to a method for producing propylene oxide, which has an excellent feature that it can be utilized and an epoxidation reaction can be efficiently performed, and thus propylene oxide can be efficiently produced.

  A process in which propylene is oxidized using ethylbenzene hydroperoxide as an oxygen carrier to obtain propylene oxide and styrene is known as the Halcon method. According to this method, styrene is inevitably produced as a byproduct with propylene oxide, which is unsatisfactory from the viewpoint of selectively obtaining only propylene oxide.

  In addition, the concept of a process of converting propylene to propylene oxide using cumene hydroperoxide obtained from cumene as an oxygen carrier and repeatedly using the cumene is described in Patent Document 1, Patent Document 2, and the like. The method described in the patent publication is a process including an oxidation step, an epoxidation step, and a hydrocracking step, and is basically different from the configuration of the present application. When cumyl alcohol obtained in the epoxidation step is cumene only by hydrogenolysis as in the patent publication, the life of the catalyst is shortened and the yield is also low, which is sufficient for industrial realization. It is hard to say.

Czechoslovak Patent CS140743 JP 2001-270872 A

  Under such circumstances, the problem to be solved by the present invention is that cumene hydroperoxide obtained from cumene can be used as an oxygen carrier to convert propylene to propylene oxide, and the cumene can be repeatedly used. The present invention is to provide a method for producing propylene oxide having an excellent characteristic that the reaction volume of the catalyst can be effectively utilized, the epoxidation reaction can be efficiently performed, and thus the propylene oxide can be efficiently produced. Is.

That is, the present invention relates to a method for producing propylene oxide including the following steps, wherein the concentration of ethylbenzene in the solution containing cumene recycled to the oxidation step is 10% by weight or less. It is.
Oxidation step: Step of obtaining cumene hydroperoxide by oxidizing cumene Epoxidation step: Step of obtaining propylene oxide and cumyl alcohol by reacting cumene hydroperoxide obtained in oxidation step with propylene Dehydration step: Solid Step of obtaining α-methylstyrene by dehydrating cumyl alcohol obtained in the epoxidation step in the presence of a catalyst Hydrogenation step: Oxidation step of hydrogenating α-methylstyrene to form cumene in the presence of a solid catalyst Recycling process to oxidation process as raw material

  According to the present invention, cumene hydroperoxide obtained from cumene can be used as an oxygen carrier to convert propylene to propylene oxide, and the cumene can be repeatedly used, and the reaction volume of each step can be effectively utilized. Thus, it was possible to provide a method for producing propylene oxide having an excellent feature that the epoxidation reaction can be efficiently performed, and thus propylene oxide can be efficiently produced.

The oxidation step of the present invention is a step of obtaining cumene hydroperoxide by oxidizing cumene. Cumene is usually oxidized by auto-oxidation with an oxygen-containing gas such as air or oxygen-enriched air. This oxidation reaction may be carried out without using an additive, or an additive such as an alkali may be used. The normal reaction temperature is 50 to 200 ° C., and the reaction pressure is between atmospheric pressure and 5 MPa. In the case of the oxidation method using an additive, alkaline reagents include alkali metal compounds such as NaOH and KOH, alkaline earth metal compounds or alkali metal carbonates such as Na ₂ CO ₃ and NaHCO ₃ , ammonia, and ( NH ₄ ) ₂ CO ₃ , alkali metal ammonium carbonate and the like are used.

  The epoxidation step of the present invention is a step of obtaining propylene oxide and cumyl alcohol by reacting cumene hydroperoxide obtained in the oxidation step with propylene. The epoxidation step is preferably carried out in the presence of a catalyst comprising a titanium-containing silicon oxide from the viewpoint of obtaining the target product with high yield and high selectivity. These catalysts are preferably so-called Ti-silica catalysts containing Ti chemically bonded to silicon oxide. For example, a Ti compound supported on a silica carrier, a compound compounded with silicon oxide by a coprecipitation method or a sol-gel method, or a zeolite compound containing Ti can be used.

  In the present invention, cumene hydroperoxide used as a raw material in the epoxidation step may be a diluted or concentrated purified product or non-purified product.

  The epoxidation reaction is performed by bringing propylene and cumene hydroperoxide into contact with a catalyst. The reaction can be carried out in a 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 hydroperoxide solution used. For example, when cumene hydroperoxide is a mixture comprising cumene as a raw material, it can be used as a substitute for a solvent without 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 between 100 and 10000 kPa.

  The epoxidation reaction can be advantageously carried out using a catalyst in the form of a slurry or fixed bed. For large scale industrial operations, it is preferred to use a fixed bed. Moreover, it can implement by a batch method, a semi-continuous method, a continuous method, etc. When the liquid containing the reaction raw material is passed through the fixed bed, the liquid mixture discharged from the reaction zone contains no or substantially no catalyst.

  The dehydration step of the present invention is a step in which cumyl alcohol obtained by the epoxidation reaction is used as a dehydration catalyst to obtain α-methylstyrene and water. Propylene oxide obtained in the epoxidation step is preferably separated from cumyl alcohol before the dehydration step from the viewpoint of obtaining a high propylene oxide yield. Distillation can be used as a method for separation.

  Examples of the catalyst used in the dehydration step include acids such as sulfuric acid, phosphoric acid, and p-toluenesulfonic acid, and metal oxides such as activated alumina, titania, zirconia, silica alumina, and zeolite. Activated alumina is preferred from the viewpoints of separation, catalyst life, selectivity and the like.

  The dehydration reaction is usually carried out by bringing cumyl alcohol into contact with the catalyst, but in the present invention, hydrogen may be fed to the catalyst in order to carry out a hydrogenation reaction following the dehydration reaction. The reaction can be carried out in a liquid phase using a solvent. The solvent must be substantially inert to the reactants and products. The solvent may consist of substances present in the cumyl alcohol solution used. For example, when cumyl alcohol is a mixture composed of cumene, which is a product, it can be used as a substitute for a solvent without particularly adding a solvent. The dehydration reaction temperature is generally 50 to 450 ° C, but a temperature of 150 to 300 ° C is preferable. In general, the pressure is advantageously between 10 and 10000 kPa. The dehydration reaction can be advantageously carried out using a catalyst in the form of a slurry or fixed bed.

  In the hydrogenation step of the present invention, α-methylstyrene obtained by the dehydration reaction and water are supplied to a hydrogenation catalyst, α-methylstyrene is hydrogenated and converted to cumene, and cumene is used as a raw material for the oxidation step to the oxidation step. It is a process to recycle.

  Examples of the hydrogenation catalyst include catalysts containing metals from Group 10 or Group 11 of the Periodic Table, and specific examples include nickel, palladium, platinum, and copper. Palladium or copper is preferable from the viewpoints of suppressing the production and high yield. Examples of the copper-based catalyst include copper, Raney copper, copper / chromium, copper / zinc, copper / chromium / zinc, copper / silica, copper / alumina, and the like. Examples of the palladium catalyst include palladium / alumina, palladium / silica, palladium / carbon, and the like. These catalysts can be used alone or in combination.

  The hydrogenation reaction is usually carried out by bringing α-methylstyrene and hydrogen into contact with a catalyst. However, in the present invention, a hydrogenation reaction is carried out subsequent to the dehydration reaction. You may isolate | separate by isolation | separation etc., You may use for a hydrogenation catalyst with (alpha) -methylstyrene, without isolate | separating. The amount of hydrogen required for the reaction may be equimolar with α-methylstyrene, but usually the raw material also contains other components that consume hydrogen, and an excess of hydrogen is required. Further, since the reaction proceeds more rapidly as the partial pressure of hydrogen is increased, 1 to 10 is usually used as the hydrogen / α-methylstyrene molar ratio. More preferably, it is 1 to 5. The excess hydrogen remaining after the reaction can be recycled after being separated from the reaction solution. The reaction can be carried out in a liquid phase or a gas phase using a solvent. The solvent must be substantially inert to the reactants and products. The solvent may consist of substances present in the α-methylstyrene solution used. For example, when α-methylstyrene is a mixture composed of cumene as a product, it can be used as a substitute for a solvent without particularly adding a solvent. The hydrogenation reaction temperature is generally 0 to 500 ° C, preferably 30 to 400 ° C. In general, the pressure is advantageously between 100 and 10000 kPa.

  The form of the dehydration reaction and hydrogenation reaction can be advantageously carried out by a continuous process using a catalyst in the form of a fixed bed. Separate reactors may be used for the dehydration reaction and the hydrogenation reaction, or a single reactor may be used. The continuous reactor includes an adiabatic reactor and an isothermal reactor. The isothermal reactor is preferably an adiabatic reactor because it requires equipment for heat removal. In the case of a single adiabatic reactor, the dehydration reaction of cumyl alcohol is an endothermic reaction, so the temperature decreases with the progress of the reaction, while the hydrogenation reaction of α-methylstyrene is an exothermic reaction, so the temperature increases with the progress of the reaction. Rises. As a result, since the calorific value is larger, the outlet temperature is higher than the reactor inlet temperature.

  The reaction temperature and pressure are selected so that water contained in the α-methylstyrene solution after the dehydration reaction does not condense. The reaction temperature is preferably 150 to 300 ° C., and the reaction pressure is preferably 100 to 2000 kPa. If the temperature is too low or the pressure is too high, water will condense at the dehydration reaction outlet and the performance of the hydrogenation catalyst will be reduced. If the pressure is too high, it is disadvantageous in the reaction equilibrium of the dehydration reaction. If the temperature is too high or the pressure is too low, a large number of gas phase portions are generated, which is disadvantageous because the catalyst life decreases due to fouling and the like.

  Hydrogen can be fed from either the fixed bed reactor inlet or the hydrogenation catalyst inlet, but it is preferably fed from the fixed bed reactor inlet in view of the activity of the dehydration catalyst. That is, when hydrogen is always present in the dehydration reaction zone, vaporization of water generated by dehydration is promoted, the equilibrium dehydration conversion rate is increased, and a higher conversion rate can be obtained more efficiently than when no hydrogen is present. Although the water generated in the dehydration reaction passes through the hydrogenation catalyst, it can be operated at a low cost without providing a facility for removing water by operating at a level that does not condense as described above. it can. Unreacted hydrogen at the reactor outlet can be recycled and reused after the gas-liquid separation operation. It is also possible to separate the water generated in the dehydration reaction from the reaction liquid during the gas-liquid separation operation. A part of the obtained reaction liquid (mainly cumene) can be recycled at the inlet of the reactor.

  The amount of the dehydration catalyst may be an amount sufficient to convert cumyl alcohol, and the cumyl alcohol conversion rate is preferably 90% or more. The amount of the hydrogenation catalyst may be an amount that sufficiently converts α-methylstyrene, and the α-methylstyrene conversion rate is preferably 98% or more. From the viewpoint of cost, it is preferable that the dehydration catalyst and the hydrogenation catalyst are packed in a single fixed bed reactor without using a multistage reactor. The reactor may or may not be separated into several beds. If they are not separated, the dehydration catalyst and the hydrogenation catalyst may be brought into direct contact with each other, but may be partitioned with an inert filler.

  In the present invention, the concentration of ethylbenzene in the solution containing cumene recycled to the oxidation step needs to be 10% by weight or less, and preferably 5% by weight or less. Ethylbenzene is a compound formed as a result of decomposition of cumene hydroperoxide in the oxidation step and epoxidation step to produce acetophenone, and hydrogenation of acetophenone in the hydrogenation step. Ethylbenzene is an accumulative component in the system, and if it is continuously recycled, the concentration increases with time, the reaction effective volume of each process is reduced, and reaction inhibition of the oxidation process and epoxidation process by ethylbenzene-derived by-products is inhibited. And the inconvenience that the by-product can become an impurity in propylene oxide occurs. Considering effective utilization of the reaction volume and suppression of by-products, it is necessary to keep the concentration of ethylbenzene in the solution containing cumene recycled to the oxidation process within the scope of the present invention. As a method for suppressing the concentration of ethylbenzene, the concentration is reduced by distillation, extraction or the like, a method of removing all or part of ethylbenzene from the system comprising the steps of the present invention, a method of converting to another compound by reaction, an adsorbent, etc. Any method such as a method of decreasing may be used. When removing out of the system, the step of removing ethylbenzene (hereinafter sometimes referred to as “ethylbenzene removal step”) is at least in each step of each of the oxidation step, the epoxidation step, the dehydration step and the hydrogenation step or in each step. Usually, distillation, extraction, etc. can be carried out at least at one place connecting the two, but performing the distillation after the hydrogenation step that produces the most difference from the boiling point of the active ingredient reduces the loss of the active ingredient and reduces the distillation. This is preferable from the viewpoint of minimizing the required energy.

Example 1
1. Cumene recycled from the hydrogenation process in the oxidation process (the concentration of ethylbenzene in the solution containing cumene recycled to the oxidation process is 1.5% by weight or less) at a ratio of 1 to 1. The mixture was mixed with a 5 wt% aqueous sodium carbonate solution, and the reaction was carried out for 5 hours by supplying air under conditions of a pressure of 630 kPa and a temperature of 95-110 ° C. The produced oxidizing solution had the following composition.
Oxidizing liquid composition Cumene hydroperoxide 27.3% by weight
Cumyl alcohol 2.5% by weight
Cumene 67.8% by weight
Acetophenone 0.8% by weight
Ethylbenzene 1.0% by weight
In the presence of Ti-containing silicon oxide catalyst, the oxidation solution obtained in the epoxidation step is added to a fixed bed flow reactor together with 8 times mole of propylene per mole of cumene hydroperoxide in the washing oxidation solution. It was continuously passed through the reactor. By adjusting the reactor inlet temperature, the cumene hydroperoxide conversion rate was kept at 99%, and it was stabilized stably. The reaction temperature at this time is 70-135 degreeC. Light-boiling components such as unreacted propylene and propylene oxide were further separated and recovered from the obtained epoxidized liquid. The resulting reaction solution composition was as follows.
Epoxidized liquid composition Cumene hydroperoxide 0% by weight
Cumyl alcohol 25.6% by weight
Cumene 70.7% by weight
Acetophenone 1.2% by weight
Ethylbenzene 1.0% by weight
The reaction liquid obtained in the dehydration / hydrogenation step epoxidation step was passed through a fixed bed reactor packed with an activated alumina catalyst, and then passed through a fixed bed reactor packed with a palladium alumina catalyst. In the reaction solution, 2 moles of hydrogen were continuously passed through the reactor per mole of cumyl alcohol. By adjusting the inlet temperature, cumyl alcohol was almost 100% converted. The reaction temperature at this time was 180-230 degreeC. The composition of the obtained dehydration / hydrogenation reaction solution was as follows.
Dehydration and hydrogenation reaction solution composition Cumene hydroperoxide 0% by weight
Cumyl alcohol 0% by weight
Cumene 96.5% by weight
Acetophenone 0.3% by weight
Ethylbenzene 2.0% by weight
Ethylbenzene removal process Ethylbenzene was removed by distillation from the reaction solution obtained in the dehydration and hydrogenation process . The composition of the obtained oil layer was as follows.
Composition for removing ethylbenzene Cumene hydroperoxide 0% by weight
Cumyl alcohol 0% by weight
Cumene 97.9 wt%
Acetophenone 0.0% by weight
Ethylbenzene 1.5% by weight

Claims (2)

A method for producing propylene oxide comprising the following steps, wherein the concentration of ethylbenzene in the solution containing cumene recycled to the oxidation step is 10% by weight or less.
Oxidation step: Step of obtaining cumene hydroperoxide by oxidizing cumene Epoxidation step: Step of obtaining propylene oxide and cumyl alcohol by reacting cumene hydroperoxide obtained in oxidation step with propylene Dehydration step: Solid Step of obtaining α-methylstyrene by dehydrating cumyl alcohol obtained in the epoxidation step in the presence of a catalyst Hydrogenation step: Oxidation step of hydrogenating α-methylstyrene to form cumene in the presence of a solid catalyst Recycling process to oxidation process as raw material The production method according to claim 1, further comprising a step of removing ethylbenzene from the system at least in one step connecting each step or in each step according to claim 1.