DE1269100B - Process for the preparation of catalysts for the production of acrylonitrile - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

German class:

Number:
File number:
Registration date:
Display day:

BOIj

C07c

12 g-11/32
12O-21

1 269 100
P 12 69 100.8-41
August 28, 1961
May 30, 1968

The present invention is a process for the preparation of catalysts which Contains molybdenum, bismuth and silicon, but does not contain phosphorus. These catalysts are found at the Synthesis of acrylonitrile from propylene, ammonia and oxygen application and possess opposite the previously known catalysts containing these or similar components have the advantage that in the reactions to be catalyzed with it, an increase in yield can be achieved and that ίο the reaction also becomes more manageable.

It has been known for a long time that in the manufacture of catalysts using molybdenum, Containing bismuth and silica, catalysts can be obtained by the wet route, which for oxidation reactions, especially for the synthesis of acrylonitrile from propylene, ammonia and oxygen, are usable. Usually the procedure is so that a slurry of solid Molybdic acid in a solution of bismuth nitrate, nitric acid and phosphoric acid mixed with silica sol and the mixture is then dried and calcined (Method A). The one with that The resulting catalyst conversions are, for example, in the acrylonitrile synthesis Fluidized bed maximum 50%, based on the propylene used. It has also already been suggested to prepare such catalysts in the absence of phosphoric acid by adding ammonium molybdate in one very large volume of a silica gel suspension dissolved with bismuth nitrate and then with diluted Nitric acid is added and the resulting precipitate is filtered off, dried and calcined becomes (method B). However, the conversions achieved with such phosphorus-free catalysts were essential worse and amounted to only 22.9% in the acrylonitrile synthesis, based on the propylene used. In general, it has been the view that catalysts based on bismuth phosphorus molybdate on silica carriers give the best results, but neither do the raw material sources nor the method of preparation of the catalyst affect the yields achievable with this.

In contrast, it has now been found that the yield in the recovery of acrylonitrile with the help of molybdenum-bismuth catalysts can be significantly improved if the catalyst mass used in this process is completely homogeneous and thus the highest atomic ratio of the for the particular case Molybdenum to bismuth of 4: 3, also in the molecular size range is realized. This requirement process for the production of catalysts
for the production of acrylonitrile

Applicant:

Lentia limited liability company
Chem. And pharm. Products-industrial supplies,
8000 Munich 15, Schwanthalerstr. 39

Named as inventor:

Dr. Heinz König, Linz (Austria)

however, neither the catalyst obtained by process A nor the catalyst obtained by process B are sufficient. at Method A only partially uses the solid molybdic acid used as the starting material as phosphomolybdic acid in solution, and the undissolved molybdic acid remains unevenly distributed in the catalyst mass. In method B are the conditions are even more unfavorable, since silica gel is assumed here and both that Bismuth, through hydrolysis, as well as the molybdenum through the action of acids in the course of the Catalyst production fail and naturally do not form a homogeneous mass. The one with the Yields obtained after the catalyst obtained from B are accordingly also significantly lower.

It has also already been proposed in the production of oxidation catalysts based Bismuth — molybdenum from dissolved phosphomolybdic acid go out and this by mixing with bismuth salts, silica sol and nitric acid in a transfer homogeneous solution, from which a largely homogeneous catalyst mass by drying can be obtained (method C). This catalyst can be used as a test reaction Acrylonitrile synthesis used from propylene conversions of 60% can be obtained. This method however, has the disadvantage that the starting substance is phosphomolybdic acid in a separate complex process must be produced and thereby the process for production of the catalytic converter becomes complicated and therefore costly.

Surprisingly, it has now been found that it is possible in the absence of phosphoric acid and / or phosphates to produce a catalyst based on bismuth, molybdenum and silica, the acrylonitrile used as the test reaction

809 557/478

3 4

Synthesis sales of over 60% can be achieved if exposure or electrolyte addition, for example by

the catalyst components can be accelerated using the addition of ammonium nitrate. That

of silica in sol form, into a homogeneous, acidic gel thus obtained is then dried and

Solution transferred and ensures that even while calcined and can in the usual way, for example

the drying, demixing processes, such as, for example, 5 by breaking or grinding and then subsequent

wise formation of precipitation should be avoided. Tableting or granulation, preferably under

The subject of the present invention is therefore the exclusion of dissolving liquids in

according to a process for the production of catalysts in the form required for use in the reactor

which are used for the production of acrylonitrile by Um-.

Setting of propylene with ammonia and oxygen io Gelation can also be achieved in this way in the presence of steam are and will be that the acidic, homogeneous solution in the same Containing molybdenum, bismuth and silicon, added from moderate drops in a heated oil Mixtures of ammonium molybdate, bismuth salts, will. The resulting gel balls can Silicic acid and a mineral acid, which thereby likewise dried and calcined in the usual way is characterized by being made of ammonium molybdenum and are based on their uniformity dat, bismuth salts, silica sol and one to form especially suitable for fluidized bed processes. Preventing the hydrolysis of the bismuth salts from - It is of course also possible to use the homogeneous, sufficient amount of nitric acid, optionally in acidic solution by spraying in or on a Presence of phosphate-free compounds to dry the preheated medium. This can entBerylliums, Calcium, strontium, barium, zinc, 20 neither by injecting into a hot gas stream Cadmium, lithium, sodium and / or or by spraying onto a heated solid Silver prepares a homogeneous acidic solution, this body, for example a wall, happens, dries while avoiding segregation and According to a preferred embodiment of the then to temperatures of 350 to 500 ° C, the present invention becomes the homogeneous acidic heated. 25 Solution by spraying as a layer on preheated For the success of the process according to the invention, crystalline, compact cores made of aluminum silicate, rens it is immaterial in which order the corundum, quartz, feldspar or granite from 1 to individual components ammonium molybdate, bismuth salt, 8 mm grain size and a porosity of less than Silica sol and nitric acid are mixed. 10 percent by volume applied. With this application temporary Any precipitates that occur are quickly removed. The acidic catalyst solution dries immediately back in solution. The nitric acid is so on, and the coated cores obtained in this way can dimensioned so that no hydrolysis of the bismuth salt is then post-dried in the usual way and more can occur. This is usually then calcined. The catalysts thus obtained, reached when the acid concentration in the catalytic converter consists of an inactive core and a catalytic one lysatorlösungf consist of at least about 2 acid equivalents 35 active coating, namely have next per liter. Essential for the success of the complete homogeneity of the active substance layer, which is not in accordance with the invention The process is that in the reac the advantage that with the help of such a catalyst solution Phosphoric acid or phosphate ions do not cause oxidation reactions, especially are present, as these with the ammonium molybdate, when it is a fixed bed process, with the formation of precipitates to the sparingly soluble Am- 40 can be controlled much better than monophosphorus molybdate react. One of a kind that uses full contacts A catalyst obtained from a similar mixture then lacks and sudden general or local, unnatural the necessary homogeneity and delivers desired temperature increases that occur with accordingly only very poor yields. the acrylonitrile synthesis from olefins the total cons Catalyst components such as phosphate-free 45 promote combustion and considerable yield compounds of the metals beryllium, calcium, and electricity lead to losses. Furthermore, such Katatium have Barium, zinc, cadmium, lithium, sodium lysers also have the advantage of better yields and / or silver, which surprisingly provides a further per kilogram of catalyst mass and better space increase of conversion, yields can be achieved at a time as the reaction takes any Place of production of the acidic, homo- 5 ° conditions such as reaction temperature and dwell conditions Solution according to the present invention can be better adapted to the reaction at the time, be set. The atomic ratio of these metals in this preferred embodiment of the invention Molybdenum can be up to 30: 100. As a proper method is the nature of the Compounds are especially important for the nitrates trains, but acetates, oxides or the quality of the catalyst obtained with them can also be used. Kom-hydroxides only be used. compact crystalline cores are suitable for this purpose, and it is also essential that the drying of a porosity of 10 volumetric acids is exceeded homogeneous solution while avoiding any percentage already a significant decrease in yield Licher segregation processes such as Nie brings with it. Under conditions where you can the impact formation is carried out. This conveyor 60 with a catalyst containing a corundum is not in a conventional evaporation process or a quartz core with less than 10 percent by volume fulfilled, because the salts in the solution obtained for porosity, excellent conversions Reason of the solubility differences to different one with catalysts, whose active mass over Points in time begin to drop out. No low or partially sintered tablets or granules On the other hand, impact formation occurs if, according to 65, the same material, but with a porosity of In the present invention, the solution is first layered to gel 10 to 25 percent by volume, only 80 to leaves. This can be done simply by letting it stand, 90% of the changes that can be achieved with compact cores can be achieved through additional measures such as heat settlement. If you coat aluminum oxide or

Aluminum silicate carrier of 40 to 50 volume percent porosity with the catalytically active material, so the degree of implementation falls to half of the maximum values. However, not only the porosity, but also the crystallinity is essential for the good properties of the catalysts, one can see from the fact that catalysts, which by coating pore-free, but of course not crystalline glass spheres are produced, cause a degree of conversion of only 60% of the maximum values.

As a low-pore, crystalline material which is used for the production of the catalysts according to the invention is suitable, can be named, for example: densely fired, predominantly crystalline aluminum silicate, Corundum, quartz, spinel, feldspar and granite. Of course, any other inert material is also possible suitable, which is predominantly crystalline, meets the requirements regarding porosity and below is resistant to the manufacturing conditions of the catalyst. The grain size of the kernels can be between 1 and 8 mm, grain sizes of 2 to 5 mm are preferably used.

example 1

63.5 g of ammonium molybdate are dissolved in 200 ml of distilled water and combined with 142 ml of 5.9 molar silica sol. This solution is slowly stirred into 180 ml of half-concentrated nitric acid. 131 g of bismuth nitrate of the formula Bi (NO ₃ ) ₃ · 5 H ₂ O are still dissolved in the mixture obtained in this way.

In a rotary drum 1 kg fused alumina grain size is 3 to 4 mm with a porosity of 5 volume percent, heated to about 15O ⁰ C and sprayed with the catalyst solution. The coated corundum is then slowly brought to a temperature of 350 ° C. and held at this temperature for 4 hours. Finally, it is heated to 500 ° C for a further 16 hours.

For comparison purposes, the catalyst according to Methods A and B were also determined according to the following detailed regulation:

Method A (corresponding to U.S. Patent 2904580, Example 1)

A solution or suspension containing 9.3 cc of 85 ° / _o by weight phosphoric acid, 272 grams of molybdic acid (85% MoO _3), 40 cc of nitric acid and 582 g of Bi (NO _{3) 3} · 5H ₂ O was about 750 g Silica sol (30% SiO ₂ ) was added. The mixture was then evaporated to dryness and heated for 16 hours 54O ⁰ C. The product was crushed and sieved to a grain size of 3 to 4 mm.

Method B (corresponding to French patent specification 1 247 785, example 9)

170 g of ammonium molybdate, dissolved in 100 ecm of water, were added to 13 l of an aqueous suspension of silica gel containing 30 g of SiO ₂ per liter. Then 364 g of Bi (NO ₃ ) ₃ · 5H ₂ O were dissolved in 200 ecm of water and 40 ecm of nitric acid and added. The catalyst was filtered off, washed, dried for 16 hours at 110 ° C and heated for 16 hours 54O ⁰ C. The product was crushed and sieved to a grain size of 3 to 4 mm.

The catalyst according to the invention prepared according to the above procedure and that of the prior art counting catalysts were tested as follows:

Propylene, ammonia and air were reacted in the presence of steam in a fixed bed, a volume ratio of the starting materials of 1: 1: 7.5: 1 being selected. The contact bed length was 160 cm, the gas velocity 39 normal liters per hour and the maximum temperature 465 ^° C. (with the exception of the catalyst according to process A, in which the temperature rose slightly higher at times due to the difficult controllability, but always remained below 500 ^° C.). The conversions to acrylonitrile, based on propylene, obtained under these conditions are given in the table below:

catalyst Sales too
Acrylonitrile Remarks Oxidation catalyst according to the invention
Catalyst according to method A
Catalyst according to process B 62%
50%
25% Catalyst heavy in the fixed bed
manageable
Catalyst very brittle

Example 2

A catalyst solution prepared according to Example 1 is also added 4.6 g of sodium nitrate and dissolved. The finished solution is sprayed onto 730 g of preheated granite with a grain size of 3 to 4 mm and subjected to the thermal treatment described in Example 1. 64% of the amount used was used Propylene converted to acrylonitrile.

Example 3

131 g of bismuth nitrate of the formula Bi (NO ₃ ) ₃ · 5H ₂ O are dissolved in a mixture of 70 ml of water and 70 ml of concentrated nitric acid and poured into a solution of 63.5 g of ammonium molybdate in 200 ml of distilled water while stirring. The temporary precipitate that forms quickly dissolves again. 142 ml of 5.9 molar silica sol are then added. The finished solution is 650 g of light colored Tonklinker 3-4 mm grain size, which is preheated to 15O ⁰ C, and sprayed on the thermal treatment described in Example 1 subjected. 62% of the propylene used was converted to acrylonitrile.

Claims (2)

Patent claims: 1. Process for the preparation of catalysts used for the production of acrylonitrile by Reaction of propylene with ammonia and oxygen in the presence of steam is suitable and containing molybdenum, bismuth and silicon, from mixtures of ammonium molybdate, Bismuth salts, silicic acid and a mineral acid, characterized in that from Ammonium molybdate, bismuth salts, silica sol and one to prevent hydrolysis of the Bismuth salts sufficient amount of nitric acid, if necessary in the presence of phosphate-free Compounds of beryllium, calcium, strontium, barium, zinc, cadmium, lithium, Sodium and / or silver, a homogeneous acidic solution prepares this while avoiding Segregation dries and then heated to temperatures of 350 to 500 ° C. 2. The method according to claim 1, characterized in that that the homogeneous acidic solution is preheated, dense crystalline cores made of dense, crystalline aluminum silicate, corundum, Quartz, feldspar or granite with a grain size of 1 to 8 mm and a porosity below 10 percent by volume dries up as a layer. Considered publications:
U.S. Patent No. 2,904,580;
French patent specification No. 1 247 785. 809 557/478 5.68 © Bundesdruckerei Berlin