JPS5935377B2 - Method for producing unsaturated carboxylic acid having 3 to 4 carbon atoms - 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. . Methacrone, which is originally a raw material for methacrylic acid, has a 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, the present invention enables the production of methacrylic acid, which has been delayed in industrialization compared to the conventional production of acrylic acid, to be carried out industrially in high yield over a relatively long period of time by using a new catalyst. In addition, in the case of producing acrylic acid, it also provides a method that is more advantageous than conventional methods.

That is, the present invention combines an unsaturated aldehyde having 3 to 4 carbon atoms and molecular oxygen into a system consisting of molybdenum, phosphorus, thallium, and oxygen, and one element selected from zirconium, niobium, tantalum, and barium, iron, vanadium, and selenium. and a method for producing a corresponding unsaturated carboxylic acid, characterized in that the reaction is carried out in a gas phase in the presence of a catalyst to which an element selected from tin is added.

As is clear from the comparative examples shown later, the method of the present invention
Only by using a catalyst containing a combination of the elements specified above can the desired unsaturated carboxylic acid be advantageously produced over a relatively long period of time and in high yields, satisfying the above conditions. If not, the catalyst performance will deteriorate and satisfactory results will not be 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 especially when molybdenum is set to 12, the following experimental formula is used. Favorable results are obtained when using the catalysts indicated. MOl2PaTlβX,Y6Oδ Here, X is one element selected from zirconium, niobium, tantalum, and barium, Y is one element selected from iron, vanadium, selenium, and tin, α=0.1 to 5, β-0.2-9, γ-0.1-7
, ε-0.2 to 9, particularly preferably α-0.3 to
3, β-0.5~5, γ-0.3~5, ε-0.3~5
It is.

As mentioned above, δ is a number determined by the oxidation state of other elements, and when each element is in a high oxidation state, it is about 36 to
It is 130. Among the catalysts of the present invention, when x is zirconium or niobium and Y is vanadium or selenium, a catalyst particularly excellent in terms of activity and selectivity is provided.

In preparing the above-mentioned catalyst, common methods for preparing this type of oxidation catalyst are employed.

For example, as a raw material, the molybdenum component is (ortho, meta, para) molybdic acid or a salt thereof, phosphomolybdic acid, etc., and the phosphorus component is phosphoric acid or a salt thereof, polymerized phosphoric acid or a salt thereof. . As a common starting material for phosphorus and molybdenum, it is preferable to use phosphomolybdic acid or a salt thereof. In addition, thallium components include thallium nitrate, thallium carbonate, zirconium, niobium, tantalum, iron, vanadium, barium, etc.
As selenium and tin components, raw materials such as their oxides, chlorides, sulfates, or nitrates are used. When preparing a catalyst from these raw material compounds, various methods such as an evaporation to dryness method or a coprecipitation method may be employed, but it is preferably prepared, for example, as follows.

That is, the above raw material compounds of molybdenum, phosphorus, and thallium are uniformly mixed into a slurry using a medium such as water. The slurry liquid is preferably aged at 60 to 90° C. for 3 to 6 hours under acidic conditions, preferably at a pH of 4 or lower, more preferably at a pH of 1 or lower. A raw material compound of zirconium, niobium, tantalum or barium or iron, vanadium, selenium or tin is mixed into such a system. After the above-mentioned ripening, these raw material compounds are mixed and stirred into the above-mentioned slurry liquid, or if these elements are not soluble in water, such as oxides, these compounds are added to the slurry liquid before ripening from the beginning. It may be added to. The slurry liquid after aging is concentrated or dried by evaporating the medium. Thereafter, the concentrated or dried product is dried, preferably at 150 to 500°C, more preferably at 200°C.
Bake at ~450°C for about 1-48 hours. The calcined product is then sized to be 35 to 10
Shattered to 0 mesh. The catalyst of the present invention thus produced preferably has a surface area of 0.01 to 50 cd/7. 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. It is preferable to include thallium salt in terms of catalyst 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 unsaturated carboxylic acids from unsaturated aldehydes according to the invention, the reaction temperature is advantageously between 230 and 450°C, particularly preferably between 250 and 38°C.
It is 0°C. Moreover, the pressure 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. Also, the apparent contact time during the reaction is 0
．． Although the time can be selected from a wide range of 2 to 30 seconds, the range of 1 to 20 seconds is particularly optimal. In the present invention, the molar ratio of oxygen to unsaturated aldehyde in the raw material mixed gas is generally about 10:1 to 2:10, and most preferably 3:1 to 1:3.

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 other raw material mixed gases> Saturated hydrocarbons such as nitrogen, methane, ethane, propane, butane, and other inert gases can coexist in the grass. When carrying out the process of the invention, any convenient 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. Alternatively, it 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 cyanohydrin method. It is something. 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.

Example 1 Thallium nitrate 13.4f7 and ammonium nitrate 2.0 were added to a solution of 587 phosphomolybdic acid dissolved in 50 cc of water.
A solution of 7 dissolved in 50 cc of water was added.

This mixed solution contains 3.0f7 zirconium oxide and 10% iron nitrate.
, 27 was added and heated and stirred to form a slurry. The obtained slurry was dried at 120°C for 12 hours and fired at 420°C for 6 hours, so that the atomic ratio of the metal components was MOl2PlTl2ZrlF.
A catalyst having a composition of el was obtained.

This is crushed into 35 to 100 meshes, and the crushed material has an inner diameter of 8
mmf) was filled into a U-shaped stainless steel reaction tube, the reaction temperature was 340°C, the contact time was 1 second, and the raw material gas (methacrolein:
4%, oxygen: 10%, water: 30%, nitrogen: 56%), and the following results were obtained. Methachlorene conversion rate 74% Methacrylic acid selectivity 76% Acetic acid selectivity 7% Examples 2 to 10 In Example 1, 3.37% of niobium pentoxide was used instead of zirconium oxide, and 3.37% of niobium pentoxide was used instead of iron nitrate. in some cases ammonium metavanadate 3.07;
Using 3.87y of barium oxide, 3.27y of selenite, or 3.8y of tin oxide, a catalyst having the composition ratio of metal components as shown in Table 1 was obtained and reacted under the same reaction conditions as in Example 1. The results shown in Table 1 were obtained.

Examples 11-12 The reaction was carried out in the same manner as in Example 1, except that the catalyst selected from the above examples and shown in Table 2 below was used, acrolein was supplied instead of methacrolein, and the reaction was carried out at 360°C. The results are 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_αTl_βX_γY
_εO_δ (wherein, X is one element selected from zirconium, niobium, tantalum, and barium, Y is iron,
Represents one element selected from vanadium, selenium, and tin, α, β, γ, ε, and δ represent the number of atoms of each element, and when the number of atoms of molybdenum is 12, α=
0.1-5, β=0.2-9, γ=0.1-7, ε=0
．． 2 to 9, and δ is a number determined by the oxidation state of other elements), the reaction is carried out in a gas phase in the presence of a catalyst.