DE1618744C3 - Use of an oxide catalyst for the production of acrylic acid from acrolein - Google Patents

Description

The invention relates to the use of an oxide catalyst for the production of acrylic acid by Oxidation of acrolein with molecular oxygen in the gas phase at elevated temperature in the presence of water vapor.

The terms "conversion", "selectivity" and "yield per pass" used in the following correspond to the following definitions:

Conversion C%) = 100 * converted moles of acrolein
added moles of acrolein

Selectivity (%) = 100 ■ obtained moles of acrylic acid
converted moles of acrolein

Yield per pass (%) = moles of acrylic acid obtained
added moles of acrolein

The yield per pass thus corresponds to the product of conversion and selectivity.

Processes for the production of acrylic acid by oxidation of acrolein are already known, which use oxide catalysts containing molybdenum and vanadium.

From British patent specification 1 007 353 a method is already known in which one by Immersing substances containing antimony oxide and iron oxide in an aqueous solution of ammonium paramolybdate and ammonium metavanadate and subsequent calcination used catalyst. The highest described for this procedure The yield per pass is 82.7%, based on the acrolein used. The yield at Acrylic acid is good, but the process for preparing the catalyst is very complicated and can be not easily reproduce. In addition, the finished catalyst has insufficient mechanical properties Strength.

In Japanese Patent Publication 41-1775, a molybdenum oxide catalyst free from these defects is disclosed and vanadium oxide on silica gel, which, however, has the highest reported yield Acrylic acid per pass, based on the acrolein used, is only 76%.

Finally, in Japanese patent specification 41-6262, a catalyst made of molybdenum oxide, vanadium oxide and phosphoric acid on aluminum sponge, but with the highest reported yield of acrylic acid per pass 62.5%, based on the acrolein used.

It has now been found that catalysts made from molybdenum oxide, vanadium oxide and tungsten oxide on silica gel can achieve yields of up to 89% acrylic acid per pass or at considerably lower Reaction temperatures can work, which affects the life of catalysts containing molybdenum oxide extended considerably, especially in the presence of steam.

Accordingly, the invention relates to the use of an optionally applied to a carrier, calcined oxide catalyst of the formula

Mo ₁₂ V _0i5 _ ₁₂ W _Oil _ ₆ O ₃₇ _ ₈₄

for the production of acrylic acid by oxidation of acrolein with molecular oxygen in the gas phase at elevated temperature in the presence of water vapor.
According to a preferred embodiment, oxidation catalysts of the type used according to the invention are used with a silica support. The catalysts used according to the invention are easy to prepare, are preferably used on 35 to 70% of a silica gel support, have excellent mechanical strength and give excellent yields of acrylic acid.

The catalyst used in the present invention is usually prepared by mixing aqueous solutions water-soluble salts of molybdenum, vanadium and tungsten, for example ammonium paramolybdate, Ammonium metavanadate and ammonium paratungstate are produced. The solution obtained becomes appropriate added with silica sol or silica gel and the resulting slurry subsequently for removal of the water is heated and the solid cake formed is dried, pulverized, granulated and one Subjected to heat treatment at high temperature in the presence of air.

The catalysts used according to the invention are mixtures and / or compounds of the oxides of molybdenum, vanadium and tungsten, the exact structure of the catalyst not being known for sure is. However, the composition of the catalyst corresponds regardless of the actual Structure of the formula listed above.

The catalysts used according to the invention can also be used without a support material but give higher yields of acrylic acid per pass when a carrier is used, see above that they are preferred in this form. Among the inert ones customary for the preparation of catalysts Support materials such as silicon carbide, alumina, and silica, the latter gives the best results. Catalysts with a silica content of 35 to 70 percent by weight give the highest Yield of acrylic acid per pass based on the acrolein used, excellent mechanical Strength as well as no falling off of the catalyst from the support material and can be easily granulated and with Success can be used in technical processes. The catalysts used according to the invention can used equally in fixed or fluidized bed reactors or reactors with moving beds will.

The oxidation reaction is advantageously carried out at temperatures between 200 and 350 ^° C. and pressures between 1.5 and 11 atm. The contact time of the mixture of acrolein, air and steam with the catalyst is usually from 0.5 to 10 seconds. The gaseous starting mixture can preferably contain 0.5 to 4 moles of oxygen and 1 to 20 moles of steam per mole of acrolein.

In the process according to the invention, in general Air is used as a source of molecular oxygen, however, molecular oxygen can also be used as a such or as a mixture with inert gases, such as nitrogen, carbon dioxide, etc., are used.

In the following, preferred embodiments of the invention are further illustrated by examples explained.

example 1

There were 42.4 g of ammonium paramolybdate, 4.7 g of ammonium metavanadate and 2.7 g of ammonium paratungstate separately dissolved in distilled water, the resulting solutions mixed and the mixture with 23.6 g of silica in the form of silica sol were added. The resulting slurry was dried, the solid cake is pulverized in a ball mill, the powder obtained is granulated and the catalyst granulate Annealed at 400 ° C for 5 hours. The composition of the catalyst obtained corresponded to that formula

M ₁₂ V ₂ W _{0, 5} O _{42nd 5}

A stainless steel tube immersed in a bath of molten potassium nitrate with a internal diameter of 20 mm was charged with 30 ml of the obtained catalyst. Then became over the catalyst at a temperature of 220 ° C with a contact time of 2 seconds a gaseous Mixture with a content of 10 moles of air and 6 moles of water vapor per mole of acrolein passed. Under Under these conditions, acrolein conversion of 97.8%, a selectivity to acrylic acid of 89.0% and achieved a yield of acrylic acid per pass of 87.0%.

Examples 2 to 6

Following the procedure of Example 1, further catalysts were prepared and under the im Example 1 used conditions for converting acrolein to acrylic acid. The one used to manufacture the starting materials used for the catalysts and the results of these experiments are in Table 1 compiled.

table

Starting materials for the catalyst Ammo
nium
meta-
vanadate Ammo
nium
para-
wolframate SiO ₂ (as
pebble
acid sol) composition
of the catalyst bath
temperature sales volume
of
Acroleins selectivity
to
Acrylic acid yield example Ammo
nium
para-
molybdate (G) (G) (G) ( ⁰ C) (%) (%) on
Acrylic acid
Per
Passage (G) 3.5 2.7 20th Mo ₁₂ V ₁₁₅ W ₀₁₅ O ₄₁ 235 95.5 87.8 (%) 2 42.4 7.0 5.4 30th Mo ₁₂ V ₃ W ₁ O ₄₆ 239 95.8 89.0 83.8 3 42.4 9.3 10.8 40 Mo ₁₂ V ₄ W ₂ O ₅₂ 242 95.8 86.9 85.3 4th 42.4 11.6 10.8 40 Mo ₁₂ V ₅ W ₂ O _54-5 246 95.6 86.9 83.2 5 42.4 7.0 6.1 30th Mo ₁₂ V ₃ W ₁₁₂ O ₄₇₄ 240 98.0 90.8 83.1 6th 42.4 89.0

Examples 7 to

Five catalyst products with the same composition as in Example 1 were prepared according to the process described in Example 1 with the exception that the catalysts ^{were calcined at 350, 370, 390, 410 and 430 °} C., respectively.

The reaction conditions were the same as given in Example 1, with only the bath temperatures were varied. The results of these tests are shown in Table 2.

Table 2

Glow bath Around
change selectivity yield at temperature temperature from
Acrolein to
Acrylic acid on
Acrylic acid game at a
malignant CQ CQ (%) (%) Passage 350 280 95.0 87.0 (%) 7th 370 230 95.6 90.2 82.7 8th 390 220 95.5 90.6 86.2 9 410 220 95.5 90.2 86.5 10 430 240 95.8 86.0 86.1 11th 82.4

!O

Examples 12-14 There were catalysts of the empirical formulas

Mo ₁₂ V ₉ W ₄ O ₇₀ ,,, Mo ₁₂ V ₂ W ₅ O ₅₆ and

Mo ₁₂ V ₁₀ W ₁ O ₆₄
prepared according to the preceding examples.

a) The catalyst of the formula Mo ₁₂ V ₉ W ₄ O _70-5 was made from 88.6 g (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O, 44.9 g (NH ₄ J ₆ W ₇ O ₂₄ - 6H ₂ O, 43.9 g _NH4 voj and 221.8 g of an ammonia stabilized 40% aqueous silica sol prepared. The catalyst was heated slowly over a period of 3 hours from room temperature to 400 ° C and then 3 hours at 400 ⁰ C annealed.

b) The catalyst of the formula Mo ₁₂ V ₂ W ₅ O ₅₆ was made from 88.6 g (NHJ ₆ Mo ₇ O ₂₄ · H ₂ O, 56.2 g (NH ₄ ) ₆ W ₇ O ₂₄ · 6H ₂ O, 9.75 g of NH ₄ VO ₃ and 196 g of an ammonia-stabilized 40% silica sol were prepared The catalyst was treated as described above.

c) The catalyst of the formula Mo ₁₂ V ₁₀ W ₁ O ₆₄ was made from 88.6 g of (NH ₄ I ₆ Mo ₇ O ₂₄ · 4H ₂ O, ll,? g (NH ₄ I ₆ W ₇ O ₂₄ · 6H ₂ 0.48.7 g of NH ₄ VO ₃ and 183.5 g of an ammonia-stabilized 40% silica sol were produced The catalyst was treated further as described above.

All catalysts contained 62% active catalyst product and 38% silica support.

The catalysts were ground and sieved to a particle size of 0.59 χ 0.84 mm and in given the reactor of Example 1. Acrolein, air and water vapor were given to the reactor in proportion 1:10: 6 with a contact time of 2 seconds.

The reaction product containing acrylic acid was counter-titrated with alkali and thereby the total amount determined by the acid present in the product. The product was then subjected to gas phase chromatography analyzed to determine the amount of acrylic acid present. The reaction temperatures used and the results obtained are shown in Table 3.

table

composition
of the catalyst Bath temperature conversion selectivity yield CQ of acrolein to acrylic acid of acrylic acid example Mo ₁₂ V ₉ W ₄ O ₇₀₁₅ 246 (%) (%) at one-time
Passage Mo ₁₂ V ₂ W ₅ O ₅₆ 260 100 79 (%) 12th Mo ₁₂ V ₁₀ W ₁ O ₆₄ 246 98.7 82.1 79 13th 98.8 78.6 81.1 14th 77.7

Claims (1)

1, 2 Claim: Use of a calcined oxide catalyst optionally applied to a support formula Mo ₁₂ V _{0 5} _ ₁₂ W _Oi i_ ₆ O ₃₇ _ ₈₄ for the production of acrylic acid by the oxidation of acrolein with molecular oxygen in the Gas phase at elevated temperature in the presence of water vapor.