DE2019996C3 - Catalyst for the production of acrylonitrile - Google Patents

Description

characterized in that the temperature ranges are produced by known methods. Coaming hdl bi 580 bi 00 bki d d d

Treatment at 580 to 800 ^J C takes place until a specific surface area between 5 and 30 m ² / g is reached.

2. A method for producing a catalyst according to claim J, softer 6 to 26 percent by weight Bismuth, 2 to 20 percent by weight molybdenum, 0.5 to 10 percent by weight iron and 0.1 to Contains 1.0 percent by weight of phosphorus on silicon dioxide as a support material, the amount of

then he can be used in a fixed bed reaction it is advisable to precipitate the individual components together, to grind the catalyst mass and deform into pills or balls. You can also use the preformed support with the aqueous solution of the Soak active ingredients. If the catalyst is to be used in a fluidized or fluidized bed, then that is Production by spray drying a solution or a gel of the active ingredients and the carrier is advantageous.

Support material 50 to 87 percent by weight of the 25 But fluidized bed catalysts can also be made through the entire catalyst, by jointly soaking the beads with the active ingredient solution, precipitating the individual components or being made. In all cases, the deformed ones are made by impregnating the preformed support with the
aqueous solution of the active ingredients, drying and

and dried catalysts to achieve the surface according to the invention a final subsequent temperature treatment, thereby subjected to temperature treatment,
indicates that the temperature treatment is used as a carrier for the catalytically active substances

Occurs 580-800 ⁰ C until a specific upper Turning preferably silicon dioxide, it may area 5-30 m ² / g is reached. however, silicon carbide can also be used.

3. Use of the catalyst according to claim 1, for example, you can use a spray dryer herzu r production of acrylonitrile by reaction 35 provided Kicselgel with a specific surface area of propylene with ammonia and molecular of z. B. 350 m ² / g with a solution of the metal salts

Oxygen or air.

soak, then dry and calcine. But it can also be the solutions of the metal salts mixed with 30-40% silica sol. This sol is then granulated in a spray dryer and then calcined. Soaking preformed silica gel particles with solutions of metal salts can be advantageous compared to the spray granulation of the silica sol-metal salt mixture, because it only does

are needed

and no active ingredient encapsulated by silica gel and thus inaccessible to the catalytic reaction will.

The content of the catalytically active metals and

The invention relates to a catalyst for production of acrylonitrile from propylene, ammonia and

Oxygen or air, as well as a method for producing low concentrations of active ingredients
position of the catalyst.

It is already known to combine propylene with ammonia and oxygen or air in the presence of bismuth,

Molybdenum and phosphorus (see German patent specification _

11 27 351) or of iron, bismuth, molybdenum and optionally phosphorus in the supported catalyst Phosphorus (cf. German patent specification 12 43 175) can fluctuate within the stated limits, The total content of the active ingredients can be from 13-50 laws, be weight percent of the total catalyst.

The active substance contents in the catalyst which are suitable for the process according to the invention and which are preferably used for the process according to the invention are IL 27 351 and 12 43 175, but in the catalysts they have the disadvantage that the following table is given,
in order to achieve the stated conversions and yields, the presence of steam as a table I
thinning agent is required in the starting gas and
Yield and resilience for the economical 60
Implementation of the large-scale process not
is satisfactory.

The catalysts known from DT-OS 18 11 063 are for Jen use in large-scale Process unsuitable because their mechanical properties (abrasion resistance) meet the requirements not sufficient in modern processes.

An improved catalyst has now been found

Active ingredient Bi 7th Fc I> Mon Weight percent 14th 7th 23 2 0.3 16 14th 4th 0.5 13th 1 0.5 18th 7th 0.5

O 19 996

In order to achieve a specific surface area of the catalyst of 5-30, preferably 8-20 m- / g, the catalysts are 0.5-20, preferably 3-5 hours, at temperatures from about 580 to about 800 ° C, preferably 650-750 ° C.

The catalysts of the invention can be used in a particularly advantageous manner for the preparation of Acrylonitrile by reacting propylene with ammonia and molecular oxygen or air linden.

A particular advantage of using the catalysts according to the invention is that the Process in the absence of steam as a diluent in the starting mixture and in compliance an oxygen content in the reaction gas of less than 1 vol .- ",,, preferably 0.1-0.4 VcI .-" ,,, can be carried out and so far using molybdenum, bismuth, iron and phosphorus containing Catalysts not achieved acrylonitrile yields of up to 74%, based on the amount used Propylene.

The catalysts according to the invention can be used in a fluidized bed or a fixed bed. In general, it is preferred to carry out the reaction in a fluidized bed. The catalyst is used in a particle size of about 10 to about 120 μ. In the process, be brought ammonia and oxygen or air with the catalyst carrier in a conventional manner at temperatures between 400 and 500 ¹ C, preferably 440 and 490C, and at pressures of 1-3 ata contacting propylene, however, the starting gases In deviation from the usual procedure, no steam or any other diluent other than nitrogen is added in the event that air is used as the oxygen-containing gas. Particularly preferred reaction temperatures of 450-470 ⁰ C and pressures between 1.5 and 2.5 are ata. The residence times are 5-15, preferably 8-12, seconds. The oxygen content of the reaction gas is constantly checked with the aid of a suitable analyzer and kept at a concentration of a maximum of 1% by volume, preferably 0.1-0.4% by volume, by regulating the amount of oxygen or air used.

In general, a molar ratio of air to propylene to ammonia in the starting gas mixture is such as 9.5-10: 1: 1-1.1 suitable for the purposes of the invention To achieve concentration of oxygen in the reaction gas. The acrylonitrile yield is up to 74%, based on the propylene used. Because of this so far with molybdenum, bismuth, iron and Phosphorus-containing catalyst yields of acrylonitrile not achieved are those according to the invention Catalysts of considerable economic importance, especially for large-scale implementation the acrylonitrile synthesis. In addition to the increased acrylonitrile yield, another advantage is that that in the reaction the need for oxygen or Air is less and the reactor can be more heavily loaded.

The advantages of the catalysts according to the invention can be summarized as follows:

a) From the comparative experiments it can be seen that by applying the eriindungsgemcn Catalytic converters are achieved, which represent a significant technical advance.

b) The catalysts of the invention are moderate; i.e., they are selective. An uneconomical one Admixture of steam, as described in the examples of DT-PS 12 43 175 is not necessary or harmful.

c) The catalysts of the invention can be operated with longer residence times.

ίο This is not applicable when using the invention In contrast to the process known from DT-PS 1243175, the need for catalysts operate the catalyst near the point at which the gas mixture is discharged from the reactor. You can use the catalysts in their physical properties, e.g. B. in the grain distribution, lose within wide limits, which facilitates their use in existing large reactors, b2w. partly made possible in the first place.

Example la)

280 g Fe (NO _{: i} ) ₃ '9 H ₂ O are dissolved in a nitric acid solution, consisting of 330 g Bi (NOj) ₃ · 5 H ₂ O, 120 ml H ₂ O and 84 g HNO, (65%) solved. At 25 ° C., 50 ml of H ₂ O ₂ (30 percent by weight) are stirred in with cooling. 340 g (NH _{4) e} "MO ₇ O ₂₄ · 4 H ₂ O and 18 (S g NH ₄ HPO ₄ are also under cooling dissolved in 250 ml H ₂ O ₂ (30gewichtsprozentig). Then, the molybdenum-containing solution is in the iron and bismuth-containing solution at 25 ° C stirred with cooling. the clear red-brown solution is then charged with 500 g of SiO ₂ carrier of mixed grain size 0.01 to 0.1 mm, and the resulting slurry at 12O ⁰ C dried and then 6 Hours at 700 ^° C. The catalyst then has a specific surface area of 10-15 m / g; it contains 49-50 percent by weight of active ingredients in the form of oxides. The bulk density is 0.6 g / ml.

Example 1 b)

720 ml of this catalyst are placed in a fluidized bed reactor with a diameter of 40 mm. 1: at 456-460 ⁰ C by passing a mixture of air, propylene and ammonia in a molar ratio of air to propylene to ammonia as 9.5-10 1-1.1 and holds a reactor head pressure of 0.4 atmospheres gauge constant. The reaction gases are passed through a cold 0.1 HCl, whereby all reaction products are absorbed and can be determined in this solution by gas chromatography. The oxygen content of the reaction gases should be 0.1-0.3% by volume and is constantly checked by gas chromatography. Deviations from the desired oxygen value are corrected by changing the amount used. Depending on the load, the following results are achieved:

Catalyst- carbon Acrylonitrile 60 volumes in action yield (ml) gas (%, based (g / hour) on turned put it Propylene) ⁶ 5 720 15th 72 720 20th 73 720 25th 70

Example 2

According to Example 1, catalysts with different contents of bismuth and molybdenum are used. iron and phosphorus and, as described in Example 1, tested. The results are as follows receive:

Catalyst composition
(Wt .- "ο)

Carbon in

Feed gas

(g / hour)

Acrylonitrile

yield

(%, based on

inserted

Propylene)

7 °, ', molybdenum
7% bismuth
2% iron
0.3% phosphorus

13% molybdenum
23% bismuth

2% iron

0.5% phosphorus

16 °;, molybdenum
14% bismuth
4% iron

Example 3

68.7

69

finally calcined for 4 hours at 700.degree. The bulk density of the catalyst obtained in this way is 0.91 g / ml, the surface area 14 m ² / g. The testing of the catalyst in the acrylonitrile synthesis was carried out according to Example 1 b) and gave a yield of 70.7% acrylonitrile.

Comparative tests:

In the following table the following ίο catalysts were compared:

a) Catalyst prepared according to DT-OS 20 19 996 with a specific surface area of 6-8 ni ² / g

b) Catalyst according to Example 1 of DT-PS 12 43 175

c) Catalyst according to Example 1 of DT-OS 18 11 063

The catalysts were tested according to Example 1 b) of DT-OS 20 19 996, the feed gas being as follows Composition had:

1000 g of a catalyst used for about 14,000 operating hours in an acrylonitrile plant with a content of 22.5 percent by weight bismuth, 13.5 percent by weight molybdenum and 0.3 percent by weight phosphorus on SiO ₂ as a carrier, which has a specific surface area of 41 m ² / g of an acrylonitrile yield of 57% is obtained with a solution of 72.3 g of Fe (NO ₃ ), 9 H ₂ O, 20 g of HNO ₁ , (65%) and 15 ml of H ₂ O ₂ (30% by weight) soaked in 400 ml of water, ^{dried at 120 °} C. and ^{heated at 700 °} C. for 4 hours. The surface is then 8 to ^{12 m 2} / g with a bulk density of 0.96-1.0 g / ml. The catalyst obtained in this way is used according to Example 1 b) for converting air, propylene and ammonia to acrylonitrile, the loading of 20 g of carbon per hour per 720 ml of catalyst, the temperature 460 ° C., the reactor head pressure 0.4 atm and the molar ratio from air to propylene to ammonia was 9.5: 1: 1.1. The yield of acrylonitrile is 69.1%.

Example 4

An active ingredient solution as described in example la) is made with as much 40 weight percent silicon dioxide sol mixed that the proportion of metal and phosphorus oxides in the finished, calcined catalyst 45 percent by weight of the total mass. This mixture is granulated in the spray dryer and

CH. ( According to the invention > pez 12.5 NH f catalyst Over- 12.5 air r Without water vapor smile c 120.0 Addition of 50 N ltr / h Tl ² / g Yield to Steam Acrylonitrile Catalyst according to DT-PS with a C-loading 12 43 175, example 1 burden of Without water vapor 20 g / 720 ml Addition of 50 N ltr / h 6-8 Contact a) Steam Catalyst according to DT-OS 72.3% 18 11 063, example I ¹ ) Without water vapor 68.2% Addition of 50 N ltr / h 46.8 b) Steam Modified ¹ ) ² ) 50.1%, Without water vapor Addition of 50 N ltr / h 55.3% Steam 1.1 c) 38.2%, 1.3 40.1% c) 60 8 "- ' 55 9 ° / ^J -M ⁷ / θ

The catalyst was unsuitable for a long-term test because of the mechanical disintegration of the catalyst grains. ^:) Catalyst was crushed to the following grain size:

5% 88-105 µ
70% 44-88 µ
25% --- 44IX.

Claims (1)

Patent claims: 1. Catalyst consisting of 6 to 26 percent by weight bismuth, 2 to 20 percent by weight molybdenum, 0.5 to 10 weight percent iron and 0.1 to 1.0 weight percent phosphorus on silica as a carrier material, the amount of the carrier material being 50 to 87 percent by weight of the total consisting of 6 to 26 percent by weight bismuth, 2 to 20 weight percent molybdenum, 0.5 to 10 weight percent iron and 0.1 to 1.0 weight percent phosphorus on silicon dioxide as the carrier material, the amount of the carrier material being 50 to 87 percent by weight of the entire catalyst, produced by the common precipitation of the individual components or by soaking the preformed carrier with the aqueous solution of the active ingredients, drying and Catalyst is produced by "jointly subsequent temperature treatment, thereby ge same precipitation of the individual components or by impregnating the preformed carrier with the aqueous solution of the active ingredients, drying and subsequent temperature treatment, thereby kih indicates that the temperature treatment at 580 takes place up to 800C, until a specific surface between 5 and 30 m- / g is reached. The catalyst according to the invention can after number pg,