JPS5936969B2 - Production method of unsaturated carboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves the oxidation of unsaturated aldehydes having 3 to 4 carbon atoms, particularly methacrolein, with molecular oxygen in the presence of a novel catalyst to obtain the corresponding aldehydes in good yield. It relates to a new method for producing saturated carboxylic acids, especially methacrylic acid.

Conventionally, various catalysts have been proposed for use in producing a corresponding unsaturated carboxylic acid by oxidizing an unsaturated aldehyde having 3 to 4 carbon atoms with molecular oxygen.

Among them, there are some very good catalysts used for producing acrylic acid from acrolein, and the production of acrylic acid is now being carried out on a large scale industrially. On the other hand, although various catalysts have been proposed for use in producing methacrylic acid from methacrolein, production of methacrylic acid by this method has not yet been carried out industrially. It is clear that a major reason for this is that in the case of producing methacrylic acid, the yield of the target product is quite small, unlike in the case of producing acrylic acid, or that it is not possible to maintain a large amount for a relatively long period of time. . Methacrolein, which is originally a raw material for methacrylic acid, has higher activity than acrolein, and under the above oxidation conditions, complete oxidation (combustible products such as Co and CO2 are generated) is more likely to occur than partial oxidation that yields the target product. Therefore, the yield of the target product is low, and the development of catalysts is said to be difficult. Thus, to date, no catalyst is known that exhibits such excellent performance that it can be used in an industrial process for producing methacrylic acid. As mentioned above, compared to the conventional production of acrylic acid, the present invention enables the production of methacrylic acid, whose industrialization has been delayed, to be carried out industrially in high yield over a relatively long period of time by using a new catalyst. The present invention provides a method that can be carried out in a practical manner, and also provides a method that is more advantageous than conventional methods in the production of acrylic acid.

That is, the present invention provides a catalyst in which an unsaturated aldehyde having 3 to 4 carbon atoms is added to a system consisting of molybdenum, phosphorus, cesium, tin, and oxygen and one element selected from cobalt, iron, niobium, selenium, and tungsten. The present invention relates to the production of an unsaturated carboxylic acid characterized by oxidizing it with molecular oxygen in the presence of.

As will be made clear from the comparative examples shown later, the method of the present invention adds one element among molybdenum, phosphorus, cesium, tin, and oxygen defined above, as well as cobalt, iron, niobium, selenium, and tungsten. The target unsaturated carboxylic acid can be more advantageously produced in high yield over a relatively long period of time only by using a catalyst that has been modified.If the above conditions are not met, the catalyst performance will deteriorate. , no satisfactory results are obtained.

On the other hand, the catalyst of the present invention gives good results at any composition ratio as long as it contains each element specified above, but in particular, when molybdenum is fixed at 12,
Favorable results are obtained when using a catalyst represented by the following empirical formula. Here, X is one element selected from cobalt, iron, niobium, selenium and tungsten, α=0.1-5, β=0.2-9, γ-0
．． 1 to 7, ε60.1 to 10, particularly preferably α
=0.5~3, β=0.5~5, γ=0.3~5, ε=
It is 0.3-5.

δ is approximately 36 to 130 when in the oxidation state of other elements.
It is. In preparing the above-mentioned catalysts, this type of method for preparing oxidation catalysts is generally used.

For example, the molybdenum component as a raw material is (ortho, meta, para)-molybdic acid or its salt, phosphomolybdic acid, molybdenum oxide, etc., and the phosphorus component is preferably phosphoric acid or its salt, polymerized phosphoric acid or its salt, etc. used for. Molybdic acid is preferred as a common starting material for phosphorus and molybdenum. Further, as the cesium component, cesium nitrate, cesium carbonate, cesium chloride, and as the tin component, stannous chloride, stannic chloride, tin oxide, etc. are advantageously used. Further, tungsten components include tungsten trioxide, tungstic acid or its salts, niobium components include niobium oxide, niobium hydroxide, niobium oxalate, etc., and selenium components include selenic acid, niobium oxalate, etc.
Advantageously, selenite, selenium oxide, etc. are used as the iron component, iron nitrate, iron oxide, iron chloride, etc. as the iron component, and cobalt nitrate, cobalt oxide, etc. as the cobalt component.
When preparing a catalyst from raw material compounds of each of the above elements,
Although various methods such as evaporation to dryness or coprecipitation may be employed, it is preferably adjusted as follows. That is, the raw material compounds of molybdenum, phosphorus, and cesium are uniformly mixed into a slurry using a medium such as water. The slurry liquid preferably has a pH of 4 or less, more preferably a pH of 4 or less, and more preferably a pH of 4 or less.
3 to 6 at 60 to 110°C under acidic conditions below Fll
Preferably, it is aged for a period of time. A tin compound or each of the above-mentioned raw material compounds of cobalt, iron, niobium, selenium, or tungsten is mixed into such a system.
Each of these raw material compounds is mixed and stirred into the slurry liquid after the above-mentioned ripening, or if these elements are not soluble in water, such as oxides, the starting compounds are added to the slurry liquid before ripening. It may be added. The slurry liquid after aging is concentrated or dried by evaporating the medium. After that, the concentrated or dried product is dried, preferably at 150%
~500℃, more preferably about 1 at 200~450℃
Bake for ~48 hours. The calcined product is then ground into 35-100 meshes, a size suitable for use as a catalyst. The catalyst of the present invention produced in this way preferably has a surface area of 0.01 to 50/9.
In the catalyst of the present invention prepared in this way, one or more of the catalyst components has a structure of a compound or a mixture bonded with oxygen, and in particular, phosphomolybdic acid is included in the structure. Preferably, the catalyst is prepared to contain a cesium salt in terms of catalytic performance. The catalyst of the present invention preferably uses a carrier in order to reduce cost and provide favorable physical properties to the catalyst.

When using a carrier, any of a variety of carriers can be used, such as silica, titania, alumina, or silicon carbide, but carriers with relatively large pore sizes are particularly preferred. The amount of the carrier to be used is preferably adjusted so that it is contained in the catalyst in an amount of 30 to 97 (wt%). As a method for supporting the catalyst, conventional means such as impregnation method and kneading method can be generally employed. When producing an unsaturated carboxylic acid from an unsaturated aldehyde according to the present invention, the reaction temperature is 23
Advantageously, the temperature is from 0 to 450°C, particularly preferably from 250 to 380°C. The pressure employed is 0.5 to 40 atm, preferably 1 to 10 atm. When the pressure is high, a somewhat lower reaction temperature among those specified above can be used. Further, the apparent contact time during the reaction can be selected from a wide range of 0.2 to 30 seconds, but a range of 1 to 20 seconds is particularly optimal. The molar ratio of oxygen to unsaturated aldehyde in the raw material mixed gas in the present invention is generally about 10:1 to 2:10.
gives preferable results, with -3:1 to 1:3 being the most preferable.

Further, as the oxygen here, any oxygen can be used as long as it provides molecular oxygen during the reaction, and air as the cheapest oxygen source can also be used. When steam is present in the raw material mixed gas in addition to the above-mentioned raw materials, it is significantly advantageous in terms of the yield of the target unsaturated carboxylic acid. In this case, the coexisting amount of water vapor in the raw material gas is preferably 2 to 80%, and more preferably 5 to 50%. In addition, saturated hydrocarbons such as nitrogen, methane, ethane, propane, and butane, and other inert gases may coexist in the raw material mixed gas. When carrying out the process of the invention, any type of apparatus suitable for carrying out gas phase oxidation reactions can be used, such as fixed bed type or fluidized bed type, and their operation can also be continuous or continuous. can be performed intermittently.

Thus, according to the present invention, methacrylic acid can be produced particularly advantageously from methacrolein, which has conventionally been difficult to industrialize due to its low yield.

This fact makes it possible, for example, to advantageously produce methacrylic acid esters (MMA, etc.), which are a major use of methacrylic acid, without employing processes that pose problems in terms of pollution or production, such as the conventional cyanohydride method. be. Examples are given below to concretely illustrate the present invention, but the present invention is not limited to these Examples in any way.

For example, other elements may be added as long as they do not impede the purpose of the present invention. In the present invention, the unsaturated aldehyde conversion rate, the unsaturated carboxylic acid selectivity, and the acetic acid selectivity are defined as follows.

Conversion rate of unsaturated aldehyde (maximum) Comparative example Example 1 is the same except that cesium nitrate, tin chloride, or cobalt nitrate is not used, and the atomic ratios of the metal components are MOL2plsn,, MOL2P, and C, respectively.
A catalyst of Sl was obtained.

When these catalysts were pulverized into 35 to 100 meshes and reacted in the same manner as in Example 1, the following results were obtained. Example 1 Cesium nitrate 9.89 and ammonium nitrate 2.09 were each dissolved in 50 cc of water and mixed, and this mixed solution was added to a solution in which phosphomolybdic acid 589 was dissolved in 50 cc of water with stirring.

Furthermore, add 5.69 stannous chloride to 20 cc of concentrated hydrochloric acid, 40 ml of water.
It was dissolved in a mixed solution of cc and added. In this, cobalt nitrate 7
．． A solution obtained by dissolving 8 g in 50 cc of water was added, and the mixture was heated and stirred to form a slurry. The resulting slurry was dried at 120° C. for 12 hours and then calcined at 420° C. to obtain a catalyst having the following composition: MO, 2plcs2snlcOl. This catalyst was pulverized into 35 to 100 meshes and filled into a U-shaped stainless steel reaction tube with an inner diameter of 8110 mm. Methacrolein: 4%, oxygen 10%, water 30%
, a raw material gas consisting of 56% nitrogen is supplied, and the reaction temperature is 34%.
When the reaction was carried out under conditions of 0°C and a contact time of 1 second, the following results were obtained. Examples 2 to 8 In Example 1, selenite was used instead of nickel nitrate,
Add tungsten oxide, iron nitrate, or niobium pentoxide to obtain a catalyst having the following composition (ratio of metal components),
The reaction was carried out under the same reaction conditions as in Example 1, and the following results were obtained.

Examples 9 to 11 The results of the reaction were carried out in the same manner as in Example 1, except that the catalyst shown in the previous example was used, acrolein was supplied instead of methacrolein, and the reaction was carried out at 380°C. It is shown in Table 2.

Claims (1)

[Claims] 1 An unsaturated aldehyde having 3 to 4 carbon atoms and molecular oxygen are formed by the following general composition formula Mo_1_2P_αCs_βSn_γ
X_εO_δ (wherein, X is cobalt, iron, niobium,
Represents one element selected from selenium and tungsten, α, β, γ, ε, and δ represent the number of atoms of each,
When the number of molybdenum atoms is fixed at 12, α=0.1
~5, β=0.2~9, γ=0.1~7, ε=0.1~
10, and δ is a number determined by the oxidation state of other elements).