JPS59210043A - Preparation of unsaturated carboxylic acid - Google Patents

Abstract

PURPOSE:To obtain the titled compound in high selectivity in high yield, by oxidizing acrolein or methacrolein with O2 at high temperature in a gaseous phase by the use of a catalyst having high selectivity, life, and utility prepared by adding K, Cu, Fe, etc. to a system consisting of P-Mo-V. CONSTITUTION:In preparing acrylic acid or methacrylic acid by oxidizing catalytically acrolein or methacrolein with O2 at high temperature in a gaseous phase, a catalyst (e.g., catalyst shown by the formula II, etc.) shown by the formula (X is one or more selected from K, Rb, Cs, and Tl; Y is one or more selected from Cu, Si and Sb; Z is one or more selected from Ni, Mn, and U; a=0.5-6; b=12, c=0.2-6; d=0.01-6; e=0.01-6; f=0.01-6) is used. EFFECT:Highly catalytic activity can be maintained for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing the corresponding unsaturated carboxylic acids by oxidizing unsaturated aldehydes with air or molecular oxygen at high temperature in the vapor phase.

Conventionally, a number of methods have been proposed for producing unsaturated carboxylic acids by vapor phase catalytic oxidation of unsaturated aldehydes. These mainly focus on the method of producing acrylic acid from acrolein, and the catalyst proposed therein is used to produce methacrylic acid.
If so, the selectivity would be low due to severe side reactions, and the lifespan would be short (not practical).

On the other hand, many catalysts have been proposed for the production of methacrylic acid from methacrolein, but all of them have poor reaction results, a slow decline in catalyst activity over time, or too high reaction temperature. It has drawbacks and is not necessarily sufficient as an industrial catalyst.

The present inventors conducted extensive research on catalysts used to produce methacrylic acid from methacrolein, and found a catalyst that improved the above-mentioned drawbacks and was highly practical in terms of activity, selectivity, and lifespan. It was discovered that the method could also be applied to a method for producing acrylic acid, and
The present invention has now been completed.

The present invention provides acrylic acid or methacrylic acid by catalytic oxidation of acrolei/or methacrolei/ with molecular oxygen, and the general formula is -Pa MobXc VdYe
ZfOg, where P is phosphorus, Mo is molybdenum/, ■ is vanadium, 0 is oxygen, X is one or more selected from the group consisting of potassium, rubidium, cesium and thallium, Y is copper, One or two selected from the group consisting of silicon and acetate; 2 is iron, nickel,
One or more selected from the group consisting of manganese and uranium, a + b + (! +
d + e * f represents the atomic ratio of each component, a = 0.5 ~ 61 b-12, C = 0
．． 2-6. d=0.01~6, e~0.01~6
．． f = 0.01-6. g+X is a value determined by the oxidation state of the catalyst.

This is a method for producing an unsaturated carboxylic acid, which is characterized by using a catalyst formed by:

According to the method of the present invention, it is possible to obtain the corresponding unsaturated carboxylic acid from an unsaturated aldehyde in high yield and high selectivity, and in particular, high catalytic activity is maintained over a long period of time, so the industrial value is high. Extremely dog-like.

It is well known that a catalyst system containing phosphorus and molybdenum is effective for gas phase catalytic oxidation of acrolein complex or methacrolein. However, when using the previously proposed catalyst systems containing phosphorus and molybdenum for gas phase oxidation, the activity and selectivity decrease over time in the reaction temperature range normally used. This has caused problems as an industrial catalyst.

In contrast, the catalyst of the present invention has extremely high thermal stability (
, high performance can be maintained even after heat treatment at 600°C.

The catalyst of the present invention has the property of forming extremely stable salts with additive metals other than phosphorus and molybdenum, and molybdenum.
This seems to contribute to maintaining activity and selectivity.

The chemical state of existence of each component element of the catalyst used in the present invention is extremely complex and is not strictly clear, but it is likely (
None of the components exist as individual oxides, but appear to be tightly bound together.

There is no need to limit the method for preparing the catalyst to a special method, and as long as it does not involve significant uneven distribution of components, conventional methods (such as known evaporation to dryness method, precipitation method, oxide mixing method, etc.) may be used. You can use this method.

As raw material compounds used for preparing the catalyst, salts and oxides of each element such as nitrates, ammonium salts, and halides, or heteropolyacids such as phosphomolybdic acid or salts thereof may not be used in combination. For example, am/monium metavanadate heptamate is dissolved in an aqueous solution of am/monium molybdate, an aqueous solution of phosphoric acid is added thereto, an aqueous thallium nitrate solution and an aqueous iron nitrate solution are added, and an appropriate carrier material is added to the resulting slurry. Add and evaporate to dryness.

The temperature of heat treatment is 300-650°C, preferably 350-650°C
Although the heat treatment time varies depending on the temperature within the range of 600° C., it is suitable for one hour to several tens of hours.

The catalyst used in the method of the present invention can be supported on an inert carrier such as silica, alumina, silica-alumina, silicon carbide, etc., or can be diluted with these.

The catalyst of the invention can be used in fixed beds, fluidized beds or moving beds.

Although the concentration of unsaturated aldehyde in the raw material gas can be varied over a wide range, it is suitably between 1 and 20% by volume, and preferably between 3 and 15%.

The raw material unsaturated aldehyde may contain small amounts of impurities such as water and lower saturated aldehydes (these impurities v!lJ
has no substantial effect on the reaction.

It is economical to use air as the oxygen source, but air enriched with pure oxygen can also be used if necessary. The oxygen concentration in the raw material gas is defined by the molar ratio to the unsaturated aldehyde, and this value is preferably 0.3 to 4 and 0.4 to 2.5.

The raw material gas may be diluted by adding an inert gas such as nitrogen, water vapor, or carbon dioxide gas. The reaction pressure is preferably from normal pressure to several atmospheres. The reaction temperature can be selected within the range of 240 to 450°C, but preferably 270 to 400°C.

The method of the present invention will be explained in more detail below with reference to Examples and Comparative Examples. Hereinafter, "Kg" means parts by weight.
The unsaturated carboxylic acid/acid selectivity represents the percentage of the number of moles of unsaturated carboxylic acid produced relative to the number of moles of reacted unsaturated aldehyde.

Example 1 Ammonium rosemolybdate was dissolved in pure water at about 60°C. Add 85% phosphoric acid to this.

Next, a solution of cesium nitrate, ammonium metavanazine branch, copper nitrate, and iron nitrate dissolved in pure water is added. The mixture was evaporated to dryness while heating and stirring.

The resulting cake was dried at 130° C. for 16 hours, compression molded, and calcined at 450° C. for 2 hours to be used as a catalyst.

The composition of the catalyst is Mo, 2p, C52vo, 3C in atomic ratio.
uo, IP'e (1,5. This catalyst was packed into a reactor and 75% methachloride, 10% oxygen, 30% water vapor,
A mixed gas containing 55% nitrogen (volume %) was reacted at a reaction temperature of 330°C.
One contact time was 3.6 seconds. When the product was analyzed by gas chromatography, the methacrolein reaction rate was 80.
．． 9%, and the methacrylic acid selectivity was 82.2%.

In addition, acetic acid, carbon dioxide gas, -carbon oxide, etc. were generated.

Examples 2 to 6 The following catalysts were prepared in the same manner as in Example 1, and reacted under the same conditions as in Example 1 to obtain the results shown in Table 1.

Table 1 225

Claims (1)

[Claims] When acrylic acid or methacrylic acid is obtained by catalytically oxidizing acrolein or methacrylic acid in a high-temperature gas phase with molecular oxygen, the following general formula % is used, where P is phosphorus and Mo is Molybdenum, ■ vanadium,
0 represents oxygen and X is selected from the group consisting of potassium, rubidium, cesium and thallium]) 1. l
Ji or 2 or more, Y is 1 or 1 (or 2) selected from the group consisting of copper, silicon and anti-mono, Z is iron,
Nickel or manganese? 1 or 2 selected from the group consisting of J:ilE or more'? : b> Vv, a, b, (!, a, e, f and g are the atomic ratios of each component, a =
0.5-6, b = 12, c = 0.
2-6, d ~0.0 1-6. e =
O, Ol~6. f ~0.0 1~6°g is a value that is sufficient depending on the oxidation state of the catalyst. A method for producing an unsaturated carboxylic acid, characterized by using a catalyst formed by: