KR790001938B1 - Process for preparing heteropoly-acids - Google Patents

Abstract

An aq. slurry of Mc, V, and P oxides or oxyacids, in the approx. ratio desired in product, was heated at 60-250OC and l atm-30kg/cm2 ; a heteropolyacid was crystd. out. The heteropolyacids are useful as dehydrogenation catalysts, e.g., in prepg. methacrylic acid from isobutyric acid. Thus, powd. MoO3 360, V2O5 63.8 and H3PO4 28.8g in 2l H2O were refluxed with air injection for 20 days, filtered, concd. to 300ml, to obtain red crystals of H5M10V2PO40.

Description

Preparation of Heteropoly Acid

The present invention relates to a process for the preparation of heteropolyacids. More specifically, the present invention relates to a free heteropolyphosphoric acid containing molybdenum and vanadium, and optionally tungsten as a coordinating element, and a method for producing a heteropolyacid catalyst by carrying it on a carrier.

Heteropolyphosphoric acid is generally a water-soluble substance, and has a structure in which coordination elements, such as molybdenum, vanadium, and tungsten, have condensed with regularity around the central element phosphorus.

Heteropolyphosphoric acid containing molybdenum and vanadium as the isotope, i.e., molybdobanadophosphoric acid, is useful as a catalyst for oxidation reactions, but the synthesis involves problems. Conventionally, the following method is known as a method for synthesizing molybdobanadophosphoric acid.

(1) A method of preparing an aqueous slurry from alkali vanadate, phosphoric acid, and molybdate acid, heating it, adding hydrochloric acid, and then performing ether extraction [Zh. obshch. Khim. 24 966 (1954).

(2) adding sulfuric acid to an aqueous solution of alkali vanadate, alkali phosphate and alkali molybdate, followed by ether extraction [Inorg. Chem., 7, 437 (1968)].

The above methods (1) to (2) are effective for shortening the reaction time, but it is necessary to use alkali vanadate as the vanadium source or to uniformly dissolve vanadium oxide in alkali prior to the condensation reaction, It is necessary to use excess vanadium. In addition, in order to remove said alkali, it is not industrially advantageous since the process of the acid treatment which adds excess photo acid, makes it strong acidic, and extracts it with organic solvents, such as an ether, is needed.

One of the inventors of the present invention first proposed an extraction method in which a homogeneous mixture of molybdenum, vanadium and phosphorus compounds was calcined at high temperature in an oxidizing atmosphere and then extracted with water (Japanese Patent Laid-Open No. 49-). 133, 298), the solution of slow water extraction rate was not sufficiently solved in this method.

On the other hand, a method of obtaining an alkali metal salt of molybdovanadophosphoric acid by heating an aqueous slurry containing alkali vanadate, alkali phosphate and molybdenum oxide, adding alkali hydroxide to dissolve, and then adding a photoacid is proposed ( Permanent Patent Nos. 1, 376, 432).

However, this method was unable to obtain free molybdenum banadophosphoric acid effective as an oxidation catalyst.

It is an object of the present invention to provide a method for producing a heteropolyacid catalyst in which the disadvantages of these conventional methods are improved and economically advantageous, together with free molybdovanadoic acid, supported on a carrier.

(1) an aqueous slurry containing oxides and / or oxyacids of molybdenum, vanadium and phosphorus and further containing oxides and / or oxyacids of rungsten, by hydrothermal reaction to form molybdenum and vanadium as coordinating elements, again A process for the preparation of heteropolyacids, characterized in that a part of the molybdenum produces an aqueous solution of heterpolyphosphoric acid that can be substituted with tungsten, and

(2) an aqueous slurry containing oxides of molybdenum, tungsten and phosphorus and / or oxyacids, and which may also contain oxides of tungsten and / or oxyacids to hydrothermally react to learn molybdenum and vanadium as elements; In addition, a part of the molybdenum is to produce an aqueous solution of heteropolyphosphoric acid that can be substituted coordination with tungsten, and the method for producing a heteropolyacid catalyst characterized in that the heteropolyphosphoric acid is supported on the carrier by immersing the carrier.

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated in detail.

Heteropolyacids produced by the process of the invention are phosphorus as the center element and molybdenum and vanadium and optionally tungsten as the coordinating element. Typically, such heteropolyacids are represented by the following general formula (A).

_{H 3 + X M 12-XY} W Y V X PO 40 · nH 2 O (A)

Wherein X and Y are each an integer, X = 1 to 4, Y = 0 to 3, and X + Y = 1 to 4, n represents the number of crystals, and a value of about 16 to 32 is usually determined in the crystal state. Have

In the present invention, oxides of molybdenum, vanadium, phosphorus and tungsten and / or oxyacids are used as raw materials. Specific examples of these raw material compounds include molybdenum trioxide, molybdate acid, vanadium pentoxide, metavanadinic acid, phosphoric acid, phosphorus pentoxide, tungsten trioxide and tungstic acid.

In preparing the aqueous slurry containing these starting compounds, the amount ratio of each starting compound is preferably set to a ratio (maximum about 20% excess) that is almost equal to the ratio calculated from the stoichiometric ratio, that is, the composition of the desired heteropolyacid.

It is preferable that a raw material compound is in a fine powder state as much as possible. For this purpose, for example, molybdenum trioxide, vanadium pentoxide and the like are preferably micronized using a bowl mill and other mills. More advantageously, for example, in the case of molybdenum trioxide, it is a finely divided substance obtained by sublimation purification from a molybdenum oxide preparation obtained by air roasting molybdenum sulfide ore, and in the case of vanadium pentoxide, fine powder obtained by air roasting ammonium metavanadate Raw materials such as phase oxides are used. The smaller the particle size of the powder, the more advantageous in terms of reaction rate. If it is very fine and inconvenient for transportation or handling, it is better to add an appropriate amount of water.

The hydrothermal reaction of the aqueous slurry can be carried out according to a conventional method. The reaction is usually carried out in an oxidizing atmosphere using air, oxygen or the like. Slurry concentration can be selected in a wide range, but at extreme low concentrations, a large amount of energy is consumed when the reaction liquid is concentrated, and on the contrary, at extreme high concentrations, it may cause agitation and slow down the hydrothermal reaction rate. have. Therefore, the weight ratio of raw material oxide / water is preferably adjusted to about 60/40 to 1/99. Temperature and pressure are typically in the range of 60 ° to 250 ° C., atmospheric pressure to 30 kg / cm 2, especially 60 to 220 ° C., and atmospheric pressure to 18 kg / cm 2. The reaction continues until most of the solids in the slurry are dissolved. The rate of dissolution varies greatly depending on the temperature and pressure, and also depending on the size of the particles of the starting compound, so that the reaction time cannot be defined uniformly, but is usually 1 hour to 20 days. In order to improve the reaction rate, the aqueous slurry is preferably stirred sufficiently. At the end of the reaction, insoluble matters are almost lost, and the reaction solution exhibits a characteristic bright red color. After completion of the reaction, the insoluble residue is filtered off to obtain an aqueous solution of the desired heteropolyphosphoric acid. The resulting aqueous solution of heteropolyphosphoric acid is used as it is, or diluted or concentrated to an appropriate concentration and used for various applications. In the case of isolating free heteropolyphosphoric acid, heteropolyphosphoric acid can be obtained as crystals by concentrating an aqueous solution and then ice-cooling.

The free heteropolyacid obtained by the above method is also useful as various catalysts, but the heteropolyphosphoric acid catalyst attached to the carrier can be easily obtained by immersing the catalyst carrier in the above-mentioned aqueous solution of heteropolyphosphoric acid to support heteropolyphosphoric acid. As the catalyst carrier, a conventional catalyst carrier which can be used industrially can be used, and particularly, a high siliceous compound such as silica, silica sol, diatomaceous earth, or the like is preferable. Since diatomaceous earth is normally fine powder, it is good to add a suitable well-known shaping | molding adjuvant and to use it as a molded object with a large mechanical strength. Furthermore, in order to increase the catalytic activity, an appropriate element can be added as the second component as necessary. For this purpose, the target catalyst can be obtained by carrying out drying on the polypolyacid, the compound of the said element, and a support simultaneously or sequentially, and baking in air if necessary.

Periodic table of the second component in the case of using it as an oxidation catalyst. It is a compound of Group I to Group VIII elements, and specifically, it is a compound as shown in a 1st table | surface.

[Table 1]

The addition amount of these 2nd components is normally added in the range of 10 times mole or less of a 2nd component element with respect to heteropolyphosphoric acid.

The heteropolyphosphoric acid catalysts obtained according to the present invention are mainly used for oxidation reactions, and have a high solid acidity compared to catalysts composed of the same kind of elements, and therefore many organic chemical reactions known as acid catalyst reactions, such as hydration and esterification of olefins. It can also be advantageously used for isomerization reaction. In addition, the aforementioned oxidation reaction broadly refers to an organic chemical reaction in which oxygen addition and / or oxidative dehydrogenation is generated in the reaction substrate by reaction of the reaction substrate with molecular oxygen. Production of methacrylic acid from butyric acid, production of methacrylic acid esters from isobutyric acid esters, production of methacrolein and methacrylic acid from isobutyric aldehydes Production, production of maleic anhydride from butene, production of methyl isopropynyl ketone from methyl isopropyl ketone, and the like.

As specifically described above, according to the present invention, heteropolyphosphates, which are based on the stoichiometrically calculated proportions of molybdenum, vanadium, phosphorus and tungsten, as a raw material, are easily and economically advantageous in high yields. Phosphoric acid can be obtained.

The specific aspects of the present invention will be described in more detail with reference to the following Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1

360 g of molybdenum trioxide (industrial purity product obtained by sublimation refining, fine powder), 63.8 g of vanadium pentoxide (fine powder) and 28.8 g of phosphoric acid (85%, special reagent) were weighed out, and 2 liters of water were added to obtain a yellow orange slurry. (Raw atomic ratio Mo / V / P = 10 / 2.4 / 1). This was placed in a flask equipped with a reflux condenser, and heated water was blown and heated on a mantle heater while stirring to reach a boiling state after about 2 hours (liquid was 104 ° C). After 20 days of boiling water in this state, the liquid turned to a clear red color and most of the solid was dissolved. This liquid was filtered using a filter paper for quantification (Japanese Oriental Filter Paper No. 5B), and the insoluble residue was filtered to obtain an aqueous solution of heteropolyphosphoric acid. The aqueous solution was concentrated to 300 ml using a rotary evaporator and left at room temperature to grow dark red large crystals. This crystal was confirmed by X-ray diffraction to be a crystal of free 10-molybdo-2-banadorinic acid. In addition, the crystals were recrystallized in an aqueous solution and subjected to elemental analysis. As a result, the atomic ratio was Mo / V / P = 10 / 2.0 / 1.0, which was consistent with the theoretical formula (H ₅ M ₁₀ V ₂ PO ₄₀ ). A quantitative analysis of the insoluble residue was carried out according to a conventional method, and the total amount was 11.26 g, and more than 98% of the insoluble residue was V ₂ O ₅ . Therefore, the insoluble residue of hydrothermal reaction can be used as a vanadium raw material at the next heteropoly acid synthesis | combination time.

Example 2

Take 228 g of commercially available molybdenum trioxide (Kishitaga Chemical Co., Ltd., advanced crystallized product) and 43.6 g of vanadium pentoxide (copper phase), add 80 ml of water, and grind and mix in a bowl grinder for 1 hour, and add 560 ml of water and 85% phosphoric acid. 23.0 g was added to obtain a yellow orange slurry (raw material atomic ratio Mo / V / P = 10 / 2.4 / 1). This was heated in a flask attached with a reflux condenser on an oil bath, and most of the bar solids which had been refluxed for 20 days dissolved. The solution was concentrated to 200 ml, filtered using a quantitative filter paper (Japanese Oriental Filter Paper No. 5C), and the insoluble residues were separated. Then, ice-cold, or deep red, large crystals were grown. It was confirmed by X-ray diffraction that it was-molybdo-2- vanadic acid. The yield of the crystals was quantitative. The insoluble residue was quantitatively analyzed by a conventional method, that is, the total amount was 7.2 g, and 99% of it was vanadium pentoxide. Therefore, the insoluble residue in hydrothermal reaction can be used directly as a vanadium raw material at the next heteropoly acid synthesis time.

Example 3

The same operation as in Example 1 was repeated, and the aqueous solution obtained by filtering out the insoluble residue was concentrated to 600 ml to obtain an aqueous solution of heteropolyphosphoric acid. This was used for preparation of the catalyst in the following example.

Example 4

10 ml of the aqueous solution of heteropolyphosphoric acid obtained in Example 3 was taken, and the carrier was immersed and supported by 3 g of molded diatom, and then dried to prepare Catalyst 1.

Example 5

35.4 mg of ammonium paramolybdate was dissolved in 2 ml of water, and 2 g of the molded diatomaceous earth carrier screened with 24 to 40 mesh was immersed in this aqueous solution. This was dried and calcined for 2 hours in air at 400 ° C. The calcined product contains molybdenum trioxide, the second component, as the molybdenum atom per gram of molded diatomaceous earth carrier. Subsequently, the calcined product was immersed in 2 ml of a heteropolyphosphoric acid aqueous solution prepared in Example 3 and dried to prepare Catalyst 2.

Example 6

1 ml of water was added to 1 ml of 0.05 M vanadium hydroxide aqueous solution, and 2 g of shaped diatomaceous earth carrier was immersed and dried-fired as in Example 5. This contains 0.05 mmol of vanadium as the second component as vanadium atoms per gram of shaped diatomaceous earth support. Subsequently, the calcined product was immersed in 2 ml of the aqueous heteropolyphosphoric acid solution obtained in Example 3 and dried to prepare Catalyst 3.

Example 7

A heteropolyphosphoric acid catalyst containing various second components as shown in the second table was prepared according to the method of Example 5.

[Table 2]

1 소성하지 않았음)(

1 not fired)

Example 8

18.0 g of molybdenum trioxide (the same as used in Example 1) in a 200-liter titanium-lined oatgleb, 3.19 g of vanadium pentoxide, 1.44 g of saline (85%, special reagent), and 100 g of water were heated to 200 ° C. , 15.4kg / cm 2, and the reaction was carried out for 11 hours with vigorous stirring (700rpm). The obtained solution was filtered and the filtrate was concentrated to give dark red crystals. The pattern of X-ray diffraction of this crystal is a pattern cubic system of H ₃ Mo ₁₂ PO ₄₀ .3OH ₂ O of the same structure, pd 3m, a = ± 23.15 kPa (JL Hoard. Z. Krist., 84 , 217 (1933), which was substantially the same as the quantity of crystals.

Example 9

Molybdenum trioxide (the same as used in Example 1) 14.40 g, vanadium pentoxide (Nichiagagaku Co., Ltd., industrial purity product powder, average particle diameter 1.5μ) 1.819 g, phosphoric acid (85% express) 1.140 g and 320 ml of water were mixed to prepare a brass colored slurry (raw material ratio Mo / V / P = 10/2/1). This was placed in a 500 ml flask equipped with a reflux condenser, a stirrer, and a thermometer, heated to 90 ° C. for 20 hours, and a small amount of remaining insoluble matter (about 20 mg) was filtered off. The filtrate was concentrated to give crystals of dark red free H ₅ MO ₁₀ V ₂ PO ₄₀ .

Example 10

20.15 g of molybdenum trioxide (the same as that used in Example 1) and 2.57 g of vanadium pentoxide (Kishida Chemical Co., Ltd., high crystallization) were pulverized with a bowl mill for 30 hours with 30 ml of phosphoric acid (85% 1.29 g) and 1,000 ml of water were mixed to prepare a slurry (raw material atomic ratio Mo / V / P = 10/2 / 0.8). This was placed in a 1 L flask equipped with a reflux condenser, a stirrer and a thermometer, heated at 104 ° C. for 3 hours, and then heated at 60 ° C. to 70 ° C. for 40 hours. The reaction mixture was then filtered to remove 5.7 g of insoluble residue. The filtrate was concentrated to give a crystal of heteropolyphosphoric acid in a yield of 94.7% (amount based on phosphoric acid based on theoretical yield).

Usage Example 1 (oxidative dehydrogenation reaction of isobutyric acid)

The oxidative dehydrogenation reaction of isobutyric acid was examined using the catalysts 1-18 prepared in Examples 4-7. In the reaction, a vertical mixed glass-phase flow reaction tube was used, and the product was analyzed by means of acid titration, gas chromatography, or the like. The reaction conditions were as follows.

Source gas: Isobutyric acid / water vapor / oxygen / nitrogen = 2/4/3/91 (mol%)

Space velocity (GHSV): 5,000

Reaction temperature: 310 ℃

The reaction results are summarized in the third table.

[Table 3a]

[Table 3b]

[Use Example 2] (oxidative dehydrogenation reaction of methyl isobutyrate)

A mixed gas of methyl isobutyrate, oxygen and nitrogen was introduced into a reactor filled with 15 ml of catalyst 1. The reaction tube was the same as that used in Example 1, and the reaction conditions were as follows.

Source gas: methyl isobutyrate / oxygen / nitrogen = 3.2 / 2.7 / 94.1 (mol%)

Space velocity (GHSV): 1,000

Reaction temperature: 280 ℃

The reaction results are summarized in the fourth table.

[Table 4]

[Example 3] (oxidative dehydrogenation reaction of isobutyraldehyde)

A mixed gas of isobutyraldehyde, oxygen and nitrogen was introduced into a reactor filled with 15 ml of catalyst 1. The reaction tube was the same as what was used in the use example 1, and reaction conditions were set as follows.

Source gas: isobutyraldehyde / oxygen / nitrogen = 4.7 / 12.7 / 8.2 (mol%)

Space velocity (GHSV): 1,000

Reaction temperature: 290 ℃

The reaction results are summarized in the fifth table.

[Table 5]

[Example 4] (oxidation reaction of methacrolein)

A reaction gas containing 4% by volume of methacrolein, 5% by volume of oxygen, 25% by volume of steam, and 66% by volume of nitrogen was introduced into the reaction tube filled with the catalyst 1 and reacted. The reaction results at the space velocity (GHSV) of 1, 000 and the reaction temperature of 320 ° C are summarized in Table 6.

[Table 6]

[Example 5] (Oxidation dehydrogenation reaction of methyl isopropyl ketone)

A mixed gas of methyl isopropyl ketone, water vapor, oxygen and nitrogen was introduced into a reaction tube filled with 2.0 ml of catalyst 1. The reaction tube was the same as that used in the use example 1, and the feed rate of the raw material was as follows.

Methyl Isopropyl Ketone 10.9m Mole / Hour

H ₂ O 52.8

O ₂ 15.0

N ₂ 234.9

The reaction was carried out at each temperature of 265 ° C and 285 ° C. The results are summarized in the seventh table.

[Table 7]

Claims (1)

In an aqueous slurry, an oxide of molybdenum, vanadium and phosphorus, an oxyacid or a mixture thereof is hydrothermally reacted at a temperature of from 60 ° to 250 ° C. under a pressure of from normal pressure to 30 kg / cm 2 to produce an aqueous solution of heteropolyphosphoric acid containing molybdenum and vanadium as atoms. And wherein the slurry components of molybdenum, vanadium and phosphorus in the slurry are in excess of a stoichiometric amount of up to 20% relative to each component of the desired heteropolyacid.