JP3994164B2 - Propylene oxide production method - Google Patents

Description

  The present invention relates to a method for producing propylene oxide by vapor phase direct oxidation of propylene.

  Currently, propylene oxide has become a major basic chemical and is widely used mainly as a raw material for polyethers, polyols and propylene glycol. As industrial production methods for propylene oxide, the chlorohydrin method and the peroxide method are mainly used. However, the chlorohydrin method produces a large amount of calcium chloride and harmful organic chlorine compounds as by-products, and the peroxide. The law points out that the economy varies depending on the amount of alcohol produced as a by-product.

An ideal reaction for producing propylene oxide is a direct epoxidation method using propylene and molecular oxygen represented by a reaction formula of C ₃ H ₆ + 1 / 2O ₂ → C ₃ H ₆ O as raw materials. This reaction is different from the method of synthesizing ethylene oxide from ethylene and oxygen. Propylene oxide is obtained with high selectivity because allylic hydrogen abstraction tends to occur preferentially by nucleophilic attack by oxygen anions. This is known to be extremely difficult.

Conventionally, known catalysts used in a method for producing propylene oxide by direct epoxidation reaction of propylene are roughly classified into three types: silver-based, nitrate molten salt-based, and titanium-based. As typical examples of the silver-based catalyst, the following documents (see Non-patent Documents 1 to 3 and Patent Document 1) can be cited. 5, Patent Document 2). Furthermore, after the silicate containing alkali metal / heavy metal is ion-exchanged with an aqueous solution of ammonium nitrate and / or ammonia, the silicate carrier obtained by firing is supported with nitrate and / or nitrite, and then fired in a hydrogen gas stream There are proposed catalysts prepared (see Patent Document 4), catalysts obtained by microwave irradiation (see Patent Document 5), and the like.
Further, as titanium-based catalysts, the following documents (see Non-Patent Documents 6 and 7, Patent Document 3) are known, and among them, epoxidation of propylene using a heterogeneous catalyst such as silica-supported titania. A method (see Patent Document 3) has been proposed.

US Pat. No. 4,992,567 JP-A-7-97378 Japanese translation of PCT publication No. 2002-508779 Japanese Patent Laid-Open No. 10-316669 Japanese Patent Laid-Open No. 10-314594 Catal. Lett. 58, p67-70, 1999 Applied Catalysis A: General 237, p11-19, 2002 Journal of Catalysis 207, p331-340, 2002 Appl. Catal. A: General 196, p217-224, 2000 Catal. Today 71, p169-176, 2001 Chemical Communications 15, p 1356-1357, 2001. Fourth Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT4) 2002, Program / Abstracts, p128

  However, the above silver catalyst has disadvantages such as expensive silver must be used, and coprecipitation method and the like need to use a preparation method for discharging alkaline waste liquid and cleaning liquid. Further, in the molten salt method, it is necessary to use a large amount of nitrate which may explode, the contact efficiency with the raw material gas is low, and a relatively high pressure of 25 atm is required to achieve a high conversion rate, etc. There are disadvantages.

  Furthermore, the method using a titanium-based catalyst has disadvantages such as a large amount of hydrocarbons generated and the need to use an expensive carrier such as high silica zeolite. Because it is a liquid phase method, it is necessary to liquefy propylene and react under high pressure, and an organic solvent is used, and it is preferable to use expensive activities such as hydrogen peroxide and organic hydroperoxide as an oxidizing agent. Since it is an oxygen species, there are problems such as high cost and poor workability.

  The present invention has been made to solve the above-described problems of the prior art. That is, the object of the present invention is to suppress the generation of environmental pollutants when producing propylene oxide by the gas phase oxidation reaction of propylene, maintain good catalytic activity, and have a relatively high selectivity at a safe and low cost. And providing a method for producing propylene oxide in high yield.

  As a result of intensive investigations on the development of a method for obtaining propylene oxide by direct epoxidation of propylene with molecular oxygen, the present inventors have used a catalyst combined with a specific inexpensive metal compound, and at the same time, in the raw material gas By mixing specific gas components, it has been found that the selectivity of the reaction is relatively high and that propylene oxide is obtained in a high yield and that the catalytic activity is maintained for a long time, and the present invention has been completed. It was.

That is, the present invention is a method for producing propylene oxide by vapor phase oxidation of propylene, wherein a gas containing propylene and oxygen is brought into contact with a catalyst in which an alkali metal compound and an alkaline earth metal compound are supported on an inorganic carrier. In addition, the propylene oxide production method is characterized in that the gas containing propylene and oxygen further contains nitrogen monoxide and / or nitrogen dioxide in an amount of 0.1% or more based on 100 % of the entire raw material gas. The catalyst is preferably prepared using an alkali metal nitrate as the alkali metal compound and an alkaline earth metal nitrate as the alkaline earth metal compound. As the catalyst, a catalyst in which a potassium compound and a calcium compound are supported on silicon dioxide is preferable.

  According to the present invention, when producing propylene oxide by vapor phase oxidation of propylene, it is possible to suppress the discharge of environmental pollutants and secondary components of valuable components, and to extend the catalyst life, and to be relatively safe and low cost. Propylene oxide can be obtained with high selectivity and high yield.

  The present invention relates to a method for producing propylene oxide by directly epoxidizing propylene by a gas phase oxidation reaction of propylene, and introducing nitrogen monoxide and / or nitrogen dioxide into a raw material gas, and an alkali metal compound as a catalyst. A material in which an alkaline earth metal compound is supported on an inorganic carrier is used. Presence of nitrogen monoxide and / or nitrogen dioxide, an alkali metal compound and an alkaline earth metal compound in this reaction system is presumed to function effectively for the direct epoxidation of propylene.

  The catalyst used in the present invention is one in which an alkali metal compound and an alkaline earth metal compound are supported on an inorganic carrier. Examples of the alkali metal contained in the alkali metal compound used as the catalyst component include lithium, sodium, potassium, rubidium, and cesium. Examples of the alkali metal compound include oxides, chlorides, fluorides, bromides, iodides, sulfides, nitrides, nitrates, sulfates, carbonates, phosphates, and silicates. Of these, nitrate is preferable.

  Examples of the alkaline earth metal contained in the alkaline earth metal compound used as a catalyst component simultaneously with the alkali metal compound include magnesium, calcium, strontium, and barium. Examples of the alkaline earth metal compounds include oxides, chlorides, fluorides, bromides, iodides, sulfides, nitrides, nitrates, sulfates, carbonates, phosphates, and silicates. Of these, nitrates are preferred.

  As described above, the catalyst used in the present invention is a catalyst containing both an alkali metal compound and an alkaline earth metal compound as essential components. However, the alkali metal compound and alkaline earth metal compound used as the catalyst component are not necessarily It is not necessary to use one type at a time, and any one of plural types may be used in combination, or both types may be used in combination. Specific examples of such combinations include a four-component supported catalyst in which a total of four components of sodium nitrate and potassium chloride, which are alkali metal compounds, and calcium sulfate and barium carbonate, which are alkaline earth metal compounds, are supported on an inorganic carrier, alkali metal Examples thereof include a two-component supported catalyst in which potassium nitrate is used as a compound and calcium nitrate is supported on an inorganic carrier as an alkaline earth metal compound. However, these are shown as examples and are not limited thereto. In addition, good catalytic performance cannot be obtained with an alkali metal compound alone or an alkaline earth metal compound alone.

  In addition, the inorganic carrier for supporting these catalyst components can be used as long as it is known as a catalyst carrier, and examples thereof include metal compounds, carbon materials, silicon compounds, and zeolite compounds. It is not limited to these. Examples of the metal compound include magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zirconium (Zr), aluminum (Al), niobium (Nb), zinc ( Zn, cerium (Ce), lanthanum (La), and gallium (Ga) oxides are exemplified as preferred examples, but are not limited thereto.

  Examples of the carbon material include activated carbon, graphite, fullerene, carbon nanotube, carbon nanohorn, and diamond. Examples of the silicon compound include silicon dioxide, silica gel, silicon nitride, silicon carbide, silica alumina, and silicalite, and the zeolite compound is Y-type as aluminosilicate (structure code defined by the International Zeolite Society: FAU structure). , Mordenite (MOR), beta type (BEA), ZSM-5 (MFI), ZSM-11 (MEL) are exemplified as typical examples, and AlPO-n (n is an integer of 1 to 60) as an aluminophosphate system. ), SAPO-n (n is an integer of 1 to 60) and the like. The silica / alumina ratio and silicon content are not particularly limited. Of these, silicon dioxide is preferred.

Silicon dioxide suitable as an inorganic carrier will be described in more detail. Silicon dioxide is a compound represented by the chemical formula SiO ₂ and is called silica, silica gel or the like. Examples of the silicon dioxide carrier used in the present invention include commercially available ones and those prepared by various known preparation methods reported in the literature. The purity is preferably a high purity, but may contain a trace amount of impurities or a trace component mixed during production as long as it does not adversely affect the catalyst activity. As elements of the trace components, alkali metals represented by sodium and potassium, magnesium and alkaline earth metals represented by calcium, aluminum, phosphorus, iron, titanium, zinc, gallium, germanium, vanadium, chromium, Manganese, cobalt, nickel, copper and the like are exemplified, and the preferred concentration is in the range of about 1 ppb to 1% by weight, but is not limited to this range. The structure is not particularly limited, but typical examples include amorphous (amorphous), mesoporous type, and zeolite type. As examples of amorphous, the carrier sect series (Q-3, Q-6, Q-10, Q-15, Q-30, Q-50) manufactured by Fuji Silysia Chemical, Sunsphere series (H- 31, 51, 121, 201, 32, 52, 122), reference catalysts (JRC-SIO4, JRC-SIO5, JRC-SIO6, JRC-SIO7, JRC-SIO8) provided by the Catalysis Society of Japan are exemplified. . In addition, various products are commercially available or provided and can be easily obtained and used. Examples of the mesoporous type include MCM-41, SBA-15, FSM-16 and the like, but other methods for preparing silicon dioxide having various mesoporous structures are known and can be used. Further, the zeolite type is exemplified by silicalite-1 and silicalite-2, but other methods for preparing silicon dioxide having various zeolite-like crystal structures have been reported. These can also be used as the catalyst carrier of the present invention.

  The content of the alkali metal compound and the alkaline earth metal compound as the catalyst component with respect to the catalyst carrier is not particularly limited. However, if the range of the preferred content is exemplified, alkali metal and alkaline earth metal are contained in 1 g of the inorganic carrier. The sum of the number of atoms is 0.01 to 100 mmol. The ratio of alkali metal to alkaline earth metal is preferably such that the ratio of alkali metal is 0.1 to 99.9%, more preferably 1 to 99, where the sum of the number of atoms is 100%. %.

  Next, the method for preparing the catalyst will be described in detail. The catalyst is prepared by supporting an alkali metal compound and an alkaline earth metal compound on an inorganic carrier. As a supporting method, a known method such as an impregnation method, a vapor deposition method, a liquid phase adsorption method, or a sol-gel method can be used as appropriate. Among them, the impregnation method is preferably used.

Hereinafter, as an example of a catalyst preparation method, a case where potassium nitrate and calcium nitrate are used as a catalyst component and silicon dioxide is used as an inorganic carrier will be specifically described. This can be done in the same manner when other alkali metal compounds, alkaline earth metal compounds, inorganic carriers and preparation methods are used.
First, a uniform solution in which potassium nitrate and calcium nitrate are dissolved in a solvent is obtained. Examples of the solvent at this time include water and alcohol. Disperse silicon dioxide powder or pellets in this solution and stir well. After becoming a uniform slurry or suspension and fully incorporating silicon dioxide into the solution, the solvent is removed by drying under reduced pressure, heating, electromagnetic wave irradiation, and the like. In order to facilitate handling, it is desirable to perform sufficient drying. At this time, if too much energy is applied due to reduced pressure, heating, or electromagnetic waves, the supported compound may be decomposed, so it is desirable to appropriately adjust the temperature, pressure and output. The heating and vacuum drying conditions are preferably a temperature range of 0 to 200 ° C. and a pressure range of 0 to 760 mmHg, but are not limited thereto.

In addition to propylene and oxygen, nitrogen monoxide and / or nitrogen dioxide-containing gas is used as the raw material gas in the present invention. As this oxygen, in addition to pure oxygen, oxygen diluted with an inert gas such as air is used. In addition, since nitric oxide (NO) and nitrogen dioxide (NO ₂ ) are in an equilibrium state in the presence of oxygen and easily oxidize or decompose each other, there is little need to distinguish them. The content rate of nitrogen monoxide and / or nitrogen dioxide is 0.1% or more with 100% of the entire raw material gas. Examples of the nitrogen monoxide and / or nitrogen dioxide-containing gas include not only nitrogen monoxide and / or nitrogen dioxide, but also inert gases such as helium, argon, and nitrogen that do not adversely affect the reaction, carbon dioxide, carbon monoxide, What contains water vapor | steam etc. is used.

  The propylene content in the raw material gas is 0.1 to 99.9%, preferably 10 to 90%, and the oxygen content is 0.1 to 99.9%, preferably Is 10 to 90%. The composition ratio of propylene and oxygen is such that the ratio of propylene is 0.1 to 99.9%, preferably 10 to 90%, where the total content of propylene and oxygen is 100%. As a reactor for the gas phase oxidation of propylene, a known type of reactor such as a fixed bed, a fluidized bed, a circulation type, a batch type or a semibatch type can be used as appropriate.

  The reaction temperature is in the range of 30 to 500 ° C, preferably 100 to 350 ° C. If it is too low, the reaction does not proceed sufficiently. On the other hand, if it is too high, undesirable phenomena such as progress of side reactions, deactivation due to decomposition of active ingredients, and explosion due to reaction of propylene and oxygen in the raw material may occur. Moreover, although reaction pressure can be performed in all the pressure ranges including a normal pressure, a preferable pressure is 1-50 atmospheres. The flow rate of the raw material gas is in the range of 0.1 to 10,000 mL per minute with respect to 1 g of the catalyst, but preferably 1 to 100 mL per minute.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, this invention is not limited at all by these Examples.

(Production Example 1)
1.5 g (0.015 mol) of potassium nitrate as a catalyst component and 3.6 g (0.015 mol) of calcium nitrate tetrahydrate were completely dissolved in 50 mL of distilled water. 5.0 g of silicon dioxide (Caractect Q-30, manufactured by Fuji Silysia Chemical Co., Ltd., surface area 100 m / g, pore volume 1 mL / g) is introduced and dispersed in the solution, and the dispersion is magnetic for 30 minutes. Stir with a stirrer. Then, white catalyst powder was obtained by drying under reduced pressure at 80 degreeC.

(Reference example)
1.0 g of the catalyst powder prepared in Production Example 1 and 3.0 g of quartz sand (manufactured by Nacalai Tesque) were thoroughly mixed in a mortar, and 4 g of the mixed powder was placed in a quartz inner tube (inner diameter 1.2 cm, length 50 cm). Filled into a stainless steel flow reactor.
Next, while supplying a mixed gas consisting of 10 mL / min of helium containing 5 mL / min of oxygen, 10 mL / min of propylene and 0.2% of nitric oxide as a source gas from one port of the reactor, Propylene oxide (PO) was obtained by reaction at 0.5 atm. The proportion of nitric oxide in the total raw material gas was 0.08% (calculated value). After 25 minutes from the start of the reaction, it was confirmed that the reaction temperature and the pressure in the system were stable, and then the product was analyzed using an online gas chromatograph having TCD and FID detectors.

The detector, column, and column temperature used in the analysis are as follows. (1) FID detector, TC-FFAP capillary column, 30 m, 40 ° C. (2) TCD detector, Polapack Q, 2 m, 40 ° C.
(3) FID detector, gas chromatography pack 54, 2 m, 90 ° C.
(4) TCD detector, molecular sieve 5A, 2 m, 90 ° C.
Thereafter, the reaction was continued under the same conditions, and the propylene conversion rate and PO selectivity for 330 minutes were measured. The results are shown in Table 1.

Furthermore, in order to investigate the effect on the durability of the catalyst, the catalyst used in the Reference Example was continuously used for the reaction after 330 minutes. As a compulsory deterioration treatment, oxygen treatment is performed by contacting a mixed gas of 10 mL / min of oxygen and 30 mL / min of helium gas containing 0.2% of nitric oxide at 380 ° C. for a total time of 340 to 400 minutes from the start of the reaction. It was. After the forced deterioration treatment with oxygen is completed, the raw material gas is supplied again. After that, after 430 minutes from the start of the reaction, it is confirmed that the temperature and pressure are the same as those before the oxygen treatment. When measured, the conversion of propylene was 0.57% and the selectivity for PO was 2.8%.

(Example)
The reaction is performed in the same manner as in the reference example except that helium containing 0.2% nitric oxide in the source gas used in the reference example is replaced with helium containing 2% nitric oxide. Analysis of the product was performed. The results are shown in Table 2. In this case, for the same forced degradation as in the reference example between 310 and 370 minutes, a mixed gas of 10 mL / min of oxygen and 30 mL / min of helium gas containing 2% nitric oxide was used at 380 ° C. for 60 minutes. Oxidation treatment is performed. The conversion rate of propylene increases or stabilizes over 180 to 300 minutes, and the effect of mixing nitric oxide clearly appears. In addition, it was confirmed that the result after the forced deterioration treatment shown in the measurement value after 390 minutes was less deteriorated and the durability was improved.

(Comparative example)
The catalyst obtained in Production Example 1 was used, and a mixed gas of oxygen 5 mL / min, propylene 10 mL / min and helium 10 mL / min was supplied to the raw material gas. The reaction was carried out at a reaction temperature of 290 ° C. and a reaction pressure of 3.5 atm. After 150 minutes, oxidation treatment for forced deterioration was performed using a mixed gas of oxygen 10 mL / min and helium gas 30 mL / min at 380 ° C. for 1 hour. After 35 minutes, the propylene conversion was 8.8%, and the PO selectivity was 18.8%. After 60 minutes, the propylene conversion was 4.8% and the PO selectivity was 15.9%. After 135 minutes, the propylene conversion was 1.8% and the PO selectivity was 11.9%. Further, after 240 minutes after the oxidation treatment for forced deterioration, the propylene conversion was 0.06% and the PO selectivity was 0%.
From this result, it was confirmed that a higher temperature was required to obtain almost the same initial performance as compared with the case where NO was added, and the PO generation activity became zero after the oxidation treatment for forced deterioration. Therefore, the effectiveness of adding NO to the reaction gas was confirmed.

  The method for producing propylene oxide of the present invention is environmentally friendly, and the catalytic activity is maintained over a long period of time despite the fact that the catalyst used is an inexpensive and readily available metal compound. Since the selectivity of the object can be achieved, it is useful for industrial use.

Claims (5)

In a method for producing propylene oxide by vapor phase oxidation of propylene, a gas containing propylene and oxygen is brought into contact with a catalyst in which an alkali metal compound and an alkaline earth metal compound are supported on an inorganic carrier, and the propylene and oxygen are contained. A method for producing propylene oxide, further comprising adding 0.1% or more of nitrogen monoxide and / or nitrogen dioxide to the gas to be 100 % of the total raw material gas.   2. The method for producing propylene oxide according to claim 1, wherein the catalyst is prepared using an alkali metal nitrate as the alkali metal compound and an alkaline earth metal nitrate as the alkaline earth metal compound.   The method for producing propylene oxide according to claim 1 or 2, wherein the alkali metal is potassium.   The method for producing propylene oxide according to claim 1 or 2, wherein the alkaline earth metal is calcium.   3. The method for producing propylene oxide according to claim 1, wherein the alkali metal compound is a potassium compound, the alkaline earth metal compound is a calcium compound, and the inorganic carrier is a catalyst made of silicon dioxide.