KR790000805B1 - Process for producing acrylic acid - Google Patents

Abstract

Acrylic acid was prepd. by vapor-phase contact oxidn. of CH2:CH:CHO at 200-350≰C under 0.5-10 atms. in the presence of catalyst comprising (1) Mo oxide 10, (2)Nb oxide 0.001-70, (3)Si oxide 2.5-500, and(4) Cu, Zn, Ti, Mn, W, Fe, Co, Ni, Cd, Ga, Hg, Th, or B oxide 0.01-60. Thus, paramolybdenic acid ammonium was mixed with niobium oxide, ferrous oxalic acid, and silica sol. The product was impregnated into the porous α-alumina carrier and sintered in an electric furnace to give the catalysts.

Description

Preparation of Acrylic Acid

Triangular diagram showing the ratio (Gram atom percent) of Mo-Nb-V tricomponent of the catalyst of the present invention.

The present invention relates to a process for producing acrylic acid by vapor phase oxidation of acrolein in the presence of a catalyst composed mainly of molybdenum and niobium.

Conventionally, various catalysts have been proposed for the purpose of oxidizing acrolein to produce acrylic acid. Among them, a catalyst composed of a combination of molybdenum and vanadium has relatively good performance, and many examples of such catalysts are known. However, these catalysts have difficulty in catalyst life, difficulty in production, reaction activity, and selectivity, and have not been satisfactory catalysts. Accordingly, although a catalyst composed of molybdenum and niobium has been proposed as a catalyst that is thermally durable and relatively easy to manufacture, compared to a molybdenum-vanadium-based catalyst, it is considered to have insufficient reaction activity and selectivity and is not satisfactory as a practical catalyst.

Therefore, the present inventors have studied a catalyst used to produce acrylic acid by oxidizing acrolein, and thus, a new catalyst having excellent activity and selectivity, which is solved the above-mentioned problems, is easy to use industrially, and has no problems in preparing a catalyst. Was found. That is, a catalyst containing at least one component of an oxide of molybdenum, niobium, silicon, and an oxide composed of copper, zinc, titanium manganese, tungsten, iron, cobalt, nickel, cadmium, gallium, mercury, thorium, and boron is active and selective. I found this extremely excellent. The present invention has been completed based on this.

Therefore, when preparing acrylic acid by vapor-phase catalytic oxidation of acrolein in the method for producing acrylic acid according to the present invention, a catalyst comprising the following components is used.

1) oxide of molybdenum

2) silicon oxide

3) niobium oxide

4) Oxides of elements selected from copper, zinc, titanium, manganese, tungsten, iron, cobalt, nickel, cadmium, gallium, mercury, thorium and boron.

The catalyst used in the present invention is extremely good in performance. For example, the atomic ratio is 28.4% of a composition containing molybdenum 10, niobium 7, iron 1, copper 1, and 12.5 parts of silicon on a porous α-alumina carrier (manufactured by Fujimi Kenmaza K. K.). By oxidizing acrolein with air at a reaction temperature of 250 ° C. using a catalyst, acrylic acid can be obtained in a high yield of 96.6% of acrolein and 93.8% of acrylic acid.

As such, catalysts containing oxides of elements consisting of copper, zinc, titanium, manganese, tungsten, iron, cobalt, nickel, cadmium, gallium, mercury, thorium, and boron have phenomenal performance over catalysts composed of molybdenum and niobium. Although the reason for the indication is not known, it is presumed that a new polyvalent oxide is formed which is different from that produced in the molybdenum and niobium components.

The catalyst of the present invention has a high performance as described above and the production of the catalyst is extremely easy. Since the catalyst of the present invention has sufficient strength even in tablet molding, but its activity is large, sufficient performance can be obtained even when a small amount thereof is supported on a porous carrier, and catalyst strength and cost are preferable.

The catalyst used in the present invention can generally be prepared by conventional methods for producing a plurality of metal oxide catalysts. That is, compounds of molybdenum and niobium such as ammonium paramolybdate, niobium chloride, niobium oxalate, and niobium hydroxide, nitrates such as copper, zinc, titanium, manganese, tungsten, iron, cobalt, nickel, cadmium, potassium, mercury, thorium, Compounds such as organic acid salts, halides and hydroxides are mixed and preferably dissolved to form a uniform solution, whereby silica sol or silica gel is uniformly mixed and dispersed therein. Elements of the group consisting of copper, zinc, titanium, manganese, tungsten, iron, cobalt, nickel, cadmium, gallium, mercury, thorium and boron are preferably added with one or more of them, especially boron and other metals. It can be added in the form of borate. The mixture containing a predetermined amount of each element obtained above is evaporated and solid, and the resulting mass is pulverized, tablet-formed and calcined at 300 to 500 ° C. or thermally decomposed at a temperature of 300 to 500 ° C. as it is. The powder obtained by thermal decomposition is compressed into tablets, or a predetermined amount is added to distilled water, and then sufficiently mixed. The powder is then supported on a porous carrier such as α-alumina or silicon carbide and soaked at a temperature of 300 to 600 ° C. for use as a catalyst. . Furthermore, these components can be introduced step by step through impregnation, drying or pyrolysis.

Although the structure of the catalyst used in the present invention is not clear in structure, it contains various kinds of metals, and in terms of atomic ratio, molybdenum is 10, niobium 0.5 to 60, copper, zinc, titanium, manganese, tungsten, iron, cobalt, It has been found to have extremely good performance when one or more of the elements consisting of nickel, cadmium, gallium, mercury, thorium and boron are contained in the range of 0.1 to 10 (total amount). Since silicon is mainly used as a diluent, the content of silicon is not particularly limited, but is preferably in the range of 2.5 to 60 when molded using a carrier and 2.5 to 500 when molded into tablets.

The catalytic oxidation reaction of the present invention is carried out at a temperature of about 200 to 350 캜 and a pressure of 0.5 to 10 atmospheres. The contact time for the catalyst of the mixture with acrolein, molecular oxygen (air) and diluent (eg water vapor) is suitably about 0.5 to 10 seconds.

The composition of the gas mixture passing through the catalyst bed is 0.5 to 4 moles of molecular oxygen and about 1 to 20 moles of water vapor per mole of acrolein. As an oxygen source, air is generally used, but a mixed gas diluted with pure oxygen or inert gas such as carbon dioxide or nitrogen may be used. In addition, as long as it does not depart from the scope of the present invention, a conventional vapor phase catalytic oxidation method of acrolein can be used.

EXAMPLE

The present invention will be described in detail by the following examples.

Example 1

35.3 g of ammonium paramolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O] was dissolved in 240 ml of distilled water, followed by niobium hydroxide [containing 82.8 wt% of Nb (OH) _no Nb ₂ O ₅ ] 22.5 g, oxalate 1 3.6 g of iron [FeC ₂ O ₄ 2H ₂ O] and 1.98 g of cuprous chloride [CuCl] were added thereto, and 75 g of silica sol [trade name: 20 wt% of Snowdex N SiO ₂ content] was added thereto. The powder obtained by evaporation to dryness with stirring the mixture is thermally decomposed at 350 ° C. for 1 hour. Take 25 g of this powder, add 25 ml of distilled water, mix well in a grinding machine, and then spherical porous α-alumina carrier having an outer diameter of 5 mm [Fujimi Kenzamai K. K. 4] It is supported by 50g. It is dried and baked in an electric furnace at 380 degreeC for 5 hours.

The catalyst thus obtained has an atomic ratio of each component of Mo = 10, Nb = 7, Fe = 1, Cu = 1, and Si = 12.5, which is 28.4 weight of the total catalyst.

20 ml of this catalyst was filled in a stainless steel reaction tube with an inner diameter of 15 mm, and a mixed gas of acrolein 3.6%, air 46%, water vapor 41%, and nitrogen 9.4% (capacity) was subjected to normal pressure under a reaction temperature of 250 ° C and a catalyst time of 4.3 seconds Reaction in NTP conversion) is as follows.

Acrolein conversion rate 96.6%

93.8% selectivity of acrylic acid

One-time yield of acrylic acid 90.6%

In addition, acetaldehyde, acetic acid, carbon monoxide and carbon dioxide were produced as by-products.

Comparative Example 1

In the same manner as in Example 1, a catalyst having a composition of Mo-Nb-Si (10: 7: 12.5) was prepared and reacted under the same reaction conditions as in Example 1, as follows. (However, the reaction temperature is 27 ℃).

Acrolein conversion rate 95.7%

Acrylic acid selectivity 72.4%

Yield 69.2% per one pass of acrylic acid

In addition, acetaldehyde, acetic acid, carbon monoxide and carbon dioxide were produced as by-products.

Comparative Example 2

The same catalyst and catalyst firing temperature as in Comparative Example 1 were reacted at 450 ° C. to obtain the following results. (However, the reaction temperature is 250 ℃)

Acrolein conversion rate 84.8%

Acrylic acid selectivity 80.2%

Yield 68.1% with one pass of acrylic acid

In addition, acetaldehyde, acetic acid, carbon monoxide and carbon dioxide were produced as by-products.

Example 2-29

In the same manner as in Example 1, a catalyst was prepared in which the type, amount and calcining temperature of the component (4) were different and reacted under the same reaction conditions as in Example 1. The catalyst is represented by Mo-Nb-Si-X and the atomic ratio of Mo: Nb: Si is 10: 7: 12.5.

TABLE 1

As described above, the effect of the X component was clearly shown in comparison with Comparative Examples 1 and 2, and it was clearly revealed that the X component was effective in improving heat resistance as compared with the case of firing at 450 ° C.

[Examples 30-31 and Comparative Examples 3-5]

Even when the composition of Mo-Nb-Si is changed, the effect of component (4) is apparent as shown in Table 2 below.

TABLE 2

Claims (1)

At least one elemental oxide selected from the group consisting of volleybdenum oxide 10, copper, zinc, titanium, manganese, tungsten, iron, cobalt, nickel, cadmium, gallium, mercury, thorium and boron 0.001 to 60, niobium oxide 0.001 to 70 In the presence of an oxidation catalyst composed of 2.5 to 500 silicon oxide, acrolein is catalytically vapor-phase oxidized by oxygen molecules at a temperature of 200 ° C to 350 ° C and a pressure of 0.5 to 10 atm.

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