JPH0764763B2 - Method for producing methylstyrene - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing methylstyrene, and more specifically, to a method for producing a heat-resistant resin comprising oxidative dehydrogenation of ethyltoluene in the presence of molecular oxygen. The present invention relates to a method for producing methylstyrene, which is useful as a raw material or a raw material for agricultural chemicals.

[Prior Art] Methylstyrene is conventionally produced by a conventional dehydrogenation method, that is, a method of dehydrogenating ethyltoluene at a high temperature of about 600 ° C. using a large amount of superheated steam. However, this method has the drawbacks of high energy cost and restricted reaction conditions.

Therefore, as a method for solving such a drawback of the conventional method, for example, JP-A-61-37745 discloses that ethyltoluene is oxidized by using an oxygen carrier such as lead oxide in the absence of a molecular oxygen-containing gas. A method of dehydrogenating is disclosed. However, this method has a drawback that the oxygen carrier needs to be frequently regenerated due to the nature of the oxygen carrier.

Further, JP-A-61-158940 discloses a method of oxidatively dehydrogenating ethyltoluene in the presence of oxygen and hydrogen sulfide using magnesium oxide as a catalyst. High conversion and selectivity are obtained with this method. However, the method requires hydrogen sulfide, and since it requires a high temperature equivalent to the conventional dehydrogenation reaction using heated steam,
It was not an industrially advantageous method.

Furthermore, a method for producing styrene by oxidative dehydrogenation of ethylbenzene in the presence of molecular oxygen is already known. However, since ethyltoluene is more reactive than ethylbenzene, the oxidative dehydrogenation catalyst for styrene production could not be directly applied to the production of methylstyrene.

[Problems to be solved by the invention]

Therefore, an object of the present invention is to provide a method which can be carried out at a relatively low temperature and can produce methylstyrene from ethyltoluene with a high selectivity without requiring a highly dangerous substance such as hydrogen sulfide. is there.

[Means for solving problems]

The present invention is characterized in that a catalyst comprising an oxide of phosphorus, an oxide of tin and an oxide of silicon is brought into gas phase contact with a reaction feed mixture containing ethyltoluene and oxygen to oxidatively dehydrogenate ethyltoluene. To a method for producing methylstyrene.

The present invention will be described below.

In the present invention, a catalyst composed of phosphorus oxide, tin oxide and silicon oxide is used. The catalyst may include a complex oxide of phosphorus, tin and silicon.

The catalyst composed of a phosphorus oxide, a tin oxide and a silicon oxide used in the present invention is a silica gel on which tin and phosphorus oxides are, for example, uniformly and supported as small particles.

The above catalyst is preferably adjusted to an atomic ratio of tin: silicon of 0.5 to 20: 100, preferably 2 to 15: 100 from the viewpoint of producing methylstyrene with high selectivity. Further, the above catalyst preferably has an atomic ratio of phosphorus: tin in the range of 0.1 to 2: 1 from the viewpoint of producing methylstyrene with a high selectivity and a high conversion rate.

The catalyst composed of a phosphorus oxide, a tin oxide and a silicon oxide used as a catalyst in the present invention is a tin oxide and a silicon oxide by known methods such as vapor deposition, impregnation and coprecipitation. It can be prepared by preparing a catalyst (precursor) consisting of and then supporting a phosphorus oxide on the catalyst.

First, a catalyst composed of tin oxide and silicon oxide can be prepared as follows.

For example, in the case of the impregnation method, the silica gel is immersed in a tin compound dissolved in a suitable solvent, the solvent is evaporated and removed, for example, under heating conditions and atmospheric pressure or reduced pressure conditions. Dry overnight at 110 ° C.
Here, if necessary, the catalyst precursor used in the present invention can be prepared by washing with ammonia water, further washing with water, and then calcination in air at 500 to 900 ° C. for 2 to 20 hours.

Examples of the tin compound used in the above impregnation method include solvent-soluble tin compounds, for example, stannous chloride, stannic chloride, stannous acetate, tetraethoxytin, stannous bromide, stannous iodide. , Stannous sulfate, stannic sulfate, and the like. Examples of the solvent include water, methanol, ethanol, hexane and the like.

Silica gel is not particularly limited, but specific surface area
It is preferably 100 to 500 m ² / g and an average pore size of 30 to 500Å.

In the case of the vapor deposition method, a suitable tin compound having a vapor pressure, for example, stannic chloride is transferred under reduced pressure or under atmospheric pressure onto silica gel using a carrier such as nitrogen or helium,
It can be supported by reacting with silanol groups on silica gel. This is hydrolyzed by steam treatment,
After removing chlorine as hydrogen chloride, 500-900 ℃ in air
The catalyst precursor used in the present invention can be prepared by calcining at 2 to 20 hours.

In the case of the coprecipitation method, ethyl orthosilicate is added to a tin compound solution dissolved in an appropriate solvent, stirred thoroughly, and then hydrolyzed with excess ammonia water,
For example, evaporate off the solution on a water bath to dry the precipitate,
The catalyst precursor used in the present invention can be prepared by calcination in air at 500 to 900 ° C. for 2 to 20 hours.

Examples of the tin compound used in the air-precipitation method include solvent-soluble tin compounds such as stannous chloride, stannic chloride, stannous acetate, tetraethoxytin, stannous bromide, and stannous iodide. Examples thereof include stannous tin, stannous sulfate, and stannous sulfate. Further, as an example of the above solvent, water,
Examples thereof include methanol, ethanol, hexane and the like.

Although several examples have been shown above, the catalyst (precursor) composed of tin oxide and silicon oxide can be prepared by other methods.

Then, the oxide of phosphorus is supported on the catalyst (precursor) composed of the oxide of tin and the oxide of silicon.

The phosphorus oxide is supported by immersing the catalyst composed of the tin oxide and the silicon oxide in a phosphorus compound solution dissolved in an appropriate solvent, and, for example, after removing the solvent by evaporation on a hot water bath. Furthermore, it can be carried out by firing in air at a temperature of 500 to 900 ° C. for 2 to 20 hours.

At this time, the atomic ratio of phosphorus and tin can be set within the above-mentioned effective range by repeating loading from a rare phosphorus compound, or by using a concentrated phosphorus compound solution to excessively add the phosphorus component. It is also possible to remove excess phosphorus oxide by immersing it in water or a dilute aqueous nitric acid solution after supporting and firing it.

As an example of the phosphorus compound, a compound that is soluble in a solvent and does not leave any component other than an oxide of phosphorus after firing can be used, and examples thereof include orthophosphoric acid, diphosphorus pentoxide, ammonium phosphate, and ammonium hydrogenphosphate. You can The solvent is not limited as long as it dissolves the phosphorus compound such as water, ethanol and ether.

The catalyst used in the present invention can also be prepared by simultaneously supporting tin oxide and phosphorus oxide on silicon oxide.

The catalyst used in the present invention is, for example, extruded using a binder such as silica sol or alumina sol in order to use the catalyst in an industrially advantageous manner, and can be freely formed by using a molding means such as tablet molding. It can be molded.

When carrying out the method of the present invention, oxygen or air can be used as the oxygen source. The oxygen / ethyltoluene molar ratio in the reaction feed mixture is 0.1 to 1, preferably 0.2.
~ 0.5. When the oxygen / ethyltoluene molar ratio is less than 0.1, the conversion of ethyltoluene tends to be low, and when it is more than 1, the selectivity of methylstyrene tends to decrease.

In addition to the ethyltoluene and oxygen, an inert gas such as nitrogen or water vapor can be used as a diluent in the reaction feed mixture in order to prevent local overheating of the catalyst layer or to prevent explosion of the reaction product.

The gas phase contact temperature between the catalyst and the reaction feed mixture, that is, the reaction temperature, is suitably 350 to 500 ° C, preferably 400 to 450 ° C. When the reaction temperature is lower than 350 ° C, the ethyltoluene conversion tends to be low, and when it is higher than 500 ° C, the methylstyrene selectivity tends to be low.

The amount of the catalyst to the reaction feed mixture per hour is 1.0 to 20.0 g · mol ⁻¹ · hour, preferably 5.0 to 10.0 g ·
It is appropriate that the range is mol- ¹ · hour.

The method for producing methylstyrene according to the present invention can be carried out under any of reduced pressure, normal pressure and increased pressure, but it is usually advantageous to carry out under normal pressure. As the reaction system, either a fixed bed or a fluidized bed can be used.

〔The invention's effect〕

According to the method of the present invention, ethyltoluene can be oxidatively dehydrogenated at a relatively low reaction temperature to highly selectively produce methylstyrene at a high conversion rate.

〔Example〕

Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1 18.8 g of stannous chloride dihydrate (SnCl ₂ · 2H ₂ O) was added to ethanol.
It was dissolved in 200 ml. The resulting solution is silica gel (Fuji Davidson microbead silica 5D, 30-60 mesh,
After immersing 50.0 g of a specific surface area of 213 m ² / g) and removing the solvent on a hot water bath, the mixture was left in a dryer at 110 ° C. overnight. The obtained silica gel supporting the tin compound was washed 4 times with 300 ml of 4N ammonia water, and further washed with pure water until the washing liquid became neutral. After that, it is dried overnight at 110 ℃ and then at 500 ℃ in air for 2
It was calcined for a time to obtain a catalyst A. Composition analysis of this catalyst A with a fluorescent X-ray analyzer showed that the atomic ratio of tin: silicon was 10.7: 1.
It was 00.

20 g of catalyst A was immersed in 200 ml of a 12 wt% phosphoric acid aqueous solution for 10 hours, filtered on filter paper, dried at 110 for 2 hours, and then calcined at 700 ° C. for 2 hours to obtain catalyst B. When the composition of the catalyst B was analyzed by a fluorescent X-ray analyzer, the atomic ratio of tin: silicon was 10.7: 100 and the atomic ratio of phosphorus: tin was 0.2: 1.

Next, 1.5 g of this catalyst was filled in a glass reaction tube, and this reaction tube was placed in a sand fluidized tank equipped with a temperature controller to carry out an oxidative dehydrogenation reaction of ethyltoluene. The reaction conditions were such that the molar ratio of ethyltoluene / oxygen / nitrogen / water in the reaction feed mixture was 1 / 0.5 / 2.6 / 3.1, and the feed rate of the reaction feed mixture was 2
It was 00 mmol / hour. The reaction temperature was 450 ° C.

The results are shown in Table 1.

Comparative Example 1 Using catalyst A (catalyst containing no phosphorus component) obtained in Example 1, oxidative dehydrogenation reaction of ethyltoluene was performed under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Examples 2 and 3 In the same manner as in Example 1, the atomic ratio of tin: silicon was set to 0: 100.
(Comparative Example 2) and the catalyst set to 100: 0 (Comparative Example 3) were prepared, and the oxidative dehydrogenation reaction was carried out using these catalysts under the same conditions as in Example 1. The results are shown in Table 1.

Example 2 10 g of each catalyst A was immersed in a solution prepared by diluting 1.01 g of an 85% phosphoric acid aqueous solution with 50 ml of water and evaporating the water content in a drier.
The catalyst C was obtained by calcination for 2 hours. The phosphorus: tin atomic ratio of catalyst C was 0.4: 1. The oxidative dehydrogenation reaction was carried out using the catalyst C under the same conditions as in Example 1. The results are shown in Table 1.

Example 3 A catalyst D was obtained in the same manner as in Example 2 except that 1.87 g of an 85% phosphoric acid aqueous solution was used. The phosphorus: tin atomic ratio of catalyst D is 1: 1.
Met. The oxidative dehydrogenation reaction was carried out using the catalyst D under the same conditions as in Example 1. The results are shown in Table 1.

Claims (6)

[Claims] 1. A reaction feed mixture containing ethyltoluene and oxygen is brought into gas phase contact with a catalyst comprising a phosphorus oxide, a tin oxide and a silicon oxide to oxidatively dehydrogenate ethyltoluene. A method for producing methylstyrene. 2. The method according to claim 1, wherein the catalyst composed of oxides of phosphorus, oxides of tin and oxides of silicon contains a complex oxide of phosphorus, tin and silicon. 3. A catalyst comprising a phosphorus oxide, a tin oxide and a silicon oxide in which a tin oxide and a phosphorus oxide are supported on a silicon oxide. The method described in 1). 4. A catalyst comprising a phosphorus oxide, a tin oxide and a silicon oxide having a tin: silicon atomic ratio of 0.1.
The method according to claim (1), which is 5 to 20: 100. 5. A catalyst comprising a phosphorus oxide, a tin oxide and a silicon oxide, wherein the atomic ratio of phosphorus: tin is 0.1.
The method according to claim (1), wherein the method is 1 to 2: 1. 6. A process according to claim 1, wherein the molar ratio of oxygen: ethyltoluene in the reaction feed mixture is 0.1 to 1: 1.