DE2007795A1 - Bismuth phosphorus molybdate supported catalysts - Google Patents

Description

ERD Ö 1 e HEMIE
Limited liability company

JKöln-Wojrringen

WlsmutphosphoTOolybdate Support Catalysts

The invention relates to a method for increasing ' the effectiveness of bismuth, molybdenum and possibly Supported catalysts containing phosphorus,

Such catalysts are known to be used in the production of (Lr% ß-unsaturated aliphatic nitriles by reacting olefins with ammonia and a salt at elevated temperatures and at normal or elevated pressures in a fixed or fluidized bed (cf. German Patent 1,127 35.1). In particular, this process is used with the use of bismuth-phosphomolybdate supported catalysts for the industrial production of acrylonitrile (cf.; •, Petroleum Refiner, Ho. 11, Nov. 1962, Vol. 41 »p. 188 and 42, No. 11, Nov. 1963, p. 139; Chemical Week, ν, 28,1,6 / i., [P. 39 * Technical Week ν. 8/16/68, p. 28). J

; In this process, the nitrile yield drops, as is often the case with catalytic manufacturing process, with increasing running! time due to gradual catalytic converter exhaustion. In general For the catalyst exhaustion and the resulting decrease in yield, the decrease in the specific surface area of the catalytic converter blamed ...

In order to avoid a drop in the yield of acrylonitrile, it is also necessary, the reaction temperature required for the conversion of propylene, oxygen and ammonia in a proportionate manner keep tight limits constant. It is generally 455 ° bia 475 ° C and even if possible must not be exceeded (see Z. vses. Chim. Obscf. U, (1969), No. 3, pp. 274-280). Even a brief temperature increase to, for example, 490 ° to 500 ° C can cause a clear and irreversible decrease in the acrylonitrile yield. Of course, every decrease is the Catalyst effectiveness an extremely undesirable process, which in particular impairs the economic viability of the process. There is consequently a great deal of interest in the effectiveness, i.e. the activity and selectivity, of Bismuth Phosphomolybdate Catalysts for Acrylonitrile Synthesis to increase or, if a certain catalyst fatigue has already occurred with a decrease in the yield due to longer running times or excessive reaction temperatures, again to manufacture.

It has now been found that the effectiveness of bismuth, molybdenum and optionally phosphorus-containing carrier catalysts can increase if the catalysts are heated to temperatures between 580 ° and 750 ° C.

The inventive method is applicable to both fresh, in a known manner and unused as well as used catalysts, their effectiveness has already declined due to their use in amoxidation processes such as acrylonitrile synthesis.

The active ingredient concentration on the support of the catalysts to be treated according to the invention can vary within wide limits will. Generally the bismuth content is between

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about 10 and about 30 percent by weight, the Holybden content between about 6 and about 18 weight percent and, the phosphorus content between about 0 and 1 percent by weight. For example, the method according to the invention is called a catalyst applied, the 24-25 weight percent ¥ ismut, 13 »5 - 14i5 Contains percent by weight molybdenum and 0.2-0.4 percent by weight phosphorus. Pure these proportions are definitely stronger Swan blades, - "especially with regard to the ratio of JWisniut to molybdenum, permissible, but this is not possible, if the catalyst does not comply with the process of the invention is subjected. In this case, adjustments of the Catalyst composition mentioned to reduce activity and thus to reductions in exploitation.

The temperature range from 580 to 750 ° C. is most suitable for achieving the activation according to the invention; particularly preferred are temperatures of 620 ° to 67o C. At temperatures above 75O ^{0 0} G, for example at 800 ° C, can also be achieved yet an activation? However, a very short treatment time must then be chosen, po that the technical implementation is more difficult.

In general, the treatment time at the temperatures according to the invention is 0.5 to 20 hours, a lower temperature requiring a longer heating time within the stated temperature range of 580 ° to 750 ° C. and a shorter treatment time being required at higher temperatures. Preferably, the catalyst is heated for 3-5 hours at 620 ° to 670 ⁰ C.

The carrier for the catalysts to be treated is used in general silica. The amount of carrier is usually less than 85 weight percent of the catalyst mass.

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The catalyst ka: in after numerous l.oLe.nnton procedures getting produced. Should it be used in Fe3tl; ettrcaktior. (: N then it is useful - the individual components geineincara to fill up the Kakalysatoruz-ifiGe do grind and · shape into pills or balls. Γ; πη can also the preformed carrier with the more flavorful. Slogan of Soak active ingredients. If the catalyst is to be used in a fluidized or fluidized bed, then its manufacture by spray drying a solution or a gel of the active ingredients and the wearer advantageous. But "also · fluidized bed catalysts can be produced by soaking the pellets with the active ingredient solution. In all cases will be the molded and dried catalysts of a final Subjected to temperature treatment. A method by which such catalysts can be obtained is described in German Patent 1,127,351, in particular Example 1.

A pretreatment of the catalyst before carrying out the process according to the invention is not necessary. If an unused catalyst is subjected to the process according to the invention. so it can be treated 580 ° to 75O ⁰ C in connection with the required in a known manner for the production of the activating heating calcination are subjected bsi or directly without prior calcination. If a catalyst that has already been used is to be reactivated, the heating according to the invention is carried out directly.

It must be described as extremely surprising that

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an increase in the catalyst efficiency is achieved by the process according to the invention ". If, namely, a bismuth phosphomolybdate catalyst with about 24.5 percent by weight bismuth, 14 percent by weight molybdenum and 0.3 percent by weight phosphorus, as it is" for example for the purpose "of the acrylonitrile synthesis according to the example. 1 of German Patent 1,127,351 is available, is used in this process for a longer period of time, the decrease in the catalytic activity, which leads to a gradual decrease in yield, with increasing running time, simultaneously leads to a decrease in the specific surface area of the catalyst. This process is illustrated in Table I below . A decrease in the acrylonitrile yield after 6 or 12 months of running time is accompanied by a decrease in the specific surface area of the catalyst »

Table I.

catalyst fresh 64 , 5 6 months
running time S. 12 months
running time - 47 , 6 apezifisöhe upper *
area / m / gy 58 - 25th 52 - 53 , 3 46 6-24 , 2 % Bi 24 - - H 23.8 »24 23 , 2 - 14 Mon 13.5 65 13.3-14 13th - 57 icrylonitrile
prey . fltj 63 - 59-61 55

The inventive treatment of the catalyst at temperatures between 580 ° and 750 C. but also leads to a. Decrease in the specific catalyst surface, so that a Damage to the catalyst activity and a decrease in the acrylonitrile yield were to be expected. That the inventive Temperature treatment, however, an increase "or.

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The fact that I / amncphoaphormolybdate catalysts were only recently discovered was by no means foreseeable. This result was not to be expected, also inasmuch as it was ascertained that the V / iamutphoaphormolybdate catalyst was found Reaktionθtemperatüren is severely damaged above required for the Acrylni trilsynUieae Tempez'atur and below the lower ?! ilrsn ^ o ^r IEA erfiiv'mg'igemäiien Tenperacurbereicha in its activity.

Ea had to be erwartet- accordingly, that a heating at 580 ° -temperatures anernalb am utva river 75O ^U C, dae a weUf;: · Abiiüliiae d - r npe zi.Z • ..Z -.- hi-... ^:: -: n KacalyBRCoroterfjache to Foi ^ e Lit. ii-j ¥ ^ ir JDMK. . .- ·. * ^ Atalyaaccii-J «ticer vfii.ii;.; Im: -τη ^ tirde. Γ · .ί.ί · au ^; ·: «..-. The measure according to the invention was found ^ fi-Uo ^ [- g-lriii ^ ο; .Γ ^; 'λ4 ₍ ■ · - ·.: .- ;..? .. ^. Ι ⁺ in h ^ .- j ^;?. - ^ - roohenern W! .. i0i'3 ,,: - i; ^ \ ,: ■!? L.>:. ^ I- r.ä. '.; a: -. A ί "-:.;. Is bachteei: a; d results.

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BATH ORIGINAL

example 1 f

A bismuth phosphorus molybdate catalyst with 24.5 percent by weight bismuth, 14 percent by weight molybdenum and 0.3 percent by weight phosphorus, obtained according to Example 1 of German Patent 1,127,351, was used in a large-scale reactor in the customary manner for the synthesis of acrylonitrile. The acrylonitrile yield at the start of the experiment was 64 56, the catalyst having a specific surface area of 58 m 2 / g (Table II, column a). After 18 months of running, the acrylonitrile yield was $ 55; the catalyst surface area had dropped to 44 m 2 / g (Table II, column b). The catalyst was heated under this term of 18 months in each case for 5 hours at 55O ⁰ C, 600 ⁰ G, 650 ⁰ C and 700 ⁰ C, and the information needed to assess its activity values for the specific surface area and the acrylonitrile (column c - f Table II) determined by the following method:

Using 720 g of catalyst (obtained according to Example 1 of German Patent 1,127,351) with a particle size of 10-100 μis, a mixture of 108 NL / h air and 19 g / h propylene (93% ) is produced in a fluidized bed reactor with a diameter of 50 mm #ig), 7.4 g / h ammonia and 7.8 g / h water. The reaction temperature is 46O ⁰ C, the pressure in the reactor head is 0.2 0.3 atm. The reaction gases are passed through a cold 0.1 η HCl, the reaction products are absorbed there and analyzed by gas chromatography. The values for surface area and acrylonitrile yield of the catalyst in states c, d, e and are shown in Table II below:

Table II

State of the
Catalyst ' ^a b C. d e f Surface m / g
Acrylonitrile
yield 56 58
64 44
55 40
50 32
62 29
64 24
63

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From! 'Beauty II is seen that the temperature treatment at 55O ⁰ C (b catalyst after 18 months duration, column) a further reduction of the acrylonitrile yield of 55% at 50 has i "(column c) result. In contrast, the catalyst at 500 °, 650 ° and 700 ⁰ C by further heating (column d, e, and f) reaches the original yield of acrylonitrile (column a) again, although the specific surface area of the d in the columns in accordance with, e and f values in comparison to the original catalyst surface (column a) falls further.

The catalyst with the properties specified in column e of Table II shows at a further running time of 700 Hours in the acrylonitrile synthesis no decrease in its activity.

Example 2

The catalyst described in Example 1 with the specific

see surface 58 m / g, which gives an acrylonitrile yield of 64 i> (cf. also column a of Table II), is in the fresh state, that is, without subjecting it to a running time that already causes a decrease in yield and surface area, to 64O ^{0 for 5 hours} C and its activity determined as described in Example 1. While the specific surface area of the catalyst after the temperature treatment is 32 m 2 / g, when the temperature-treated catalyst is used in the acrylonitrile synthesis, an acrylonitrile yield of 67 % of theory is obtained.

Example 5

The catalyst with the properties shown in column a of Table II of Example 1 is, as in the Table III shown below, at 750 °, 800 ° and 850 ° c heated, used in the acrylonitrile synthesis and according to

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Example 1 subjected to the determination of the yield:

Table III

temperature 75O ⁰ C 5 h 800 ° C 1 30 min 850 ° C 30 min Time of treatment 30 min $ 58-60 10 min $ 58 10 min $ 51 Acrylonitrile yield
after 10 hours
operation $ 64 $ 58-59 $ 62 $ 56 $ 57 $ 50 Acrylonitrile yield
after 100 hours
operation $ 64 60 $ $ 54

Example 4

According to the process described in German Patent 1,127,351, catalysts with those listed in Table IV are used Prepared drug concentrations and treated at 500 ° and 650 C each for 5 hours and then, as in Example 1 described, tested to determine the acrylonitrile yield.

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Table IV

temperature
treatment 5 hours at 500 ^° C b
20.0
11.5
0.3 C.
10.0
6.0
0.2 d
20.0
14.0
0.3 e
30.0
14.0
0.3 5 hours at 65O ⁰ C G
20.0
11.5
0.3 H
10.0
6yO
0.2 i
20.0
Λ4.0
0.3 k
30.0
14.0
0.3 Weight pro
cent bismuth
Weight pro
cent molybdenum
Weight pro
cent Phosphoi a
24.5
14.0
0.3 58 49 60 59 f
24.5
14.0
0.3 7 65 62-6 3 65 65 Acrylonitrile?
yield (%) 64 66-6

The values shown in Table IV show that the ratio is only in the case of the temperature treatment according to the invention in the drug concentrations, especially the ratio the proportion of bismuth to molybdenum can be varied within wide limits. The acrylonitrile yields obtained with the inventive Catalysts obtained (columns g, h, i and k of Table IV) are only slightly reduced compared to that listed in column f of Table IV. Yield, while the yields for catalysts that have not been heated by the process of the invention (acrylonitrile yields of columns b, c, d and e of Table IV) are in some cases considerably lower than the free standard composition The acrylonitrile yield obtained from the catalyst is shown in column a of Table IV. In addition, Table IV shows that a catalyst of the standard composition 24.5 percent by weight bismuth, 14.0 percent by weight molybdenum and 0.3 Weight percent phosphorus provides higher acrylonitrile yields (column f compared to column a of Table IV) when it is already is heated to a temperature of the range according to the invention during manufacture.

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Example 5

According to the German patent specification 1 127 351 »
Example 1, procedures described are solutions of
Bismuth nitrate, ammonium molybdate and phosphoric acid prepares and

then applied to silica gel granules with a ^ surface area of 160 m / g and a grain size of 10-J, 2 ^^ mu. The catalysts are dried, every 5 hours, treated as in Example 4 beschrjL & beiif ^ at 500 ° C or 65O ⁰ and, as shown in

Case 1 was described with regard to the acrylonitrile yield and the specific surface area checked.

Table V

Temperature-
treatment 5 hours at 500 ^° C 10.0
6.0
0.2 5 hours at 650 ^° C 10.0
6.0
0.2 io bismuth
# Molybdenum
i » Phosphorus 24.5
14.0 69 24.5
14.0
0.3 36 S pe ζ. surface
according to temperature
treatment / ~ m / g_ / 55 42 28 62 Acrylonitrile
yield C ^ J 47 64

Example 6

The same catalysts as described in Example 5 are used, produced, but without the addition of phosphorus, the acrylonitrile compounds available with these types of catalysts

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They are those shown in Table V of Example 5 comparable.

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Claims (1)

Claims 1. A method for increasing the effectiveness of bismuth, molybdenum and optionally phosphorus-containing supported catalysts, characterized in that the catalysts are heated to temperatures between. 580 and 750 ⁰ C heated. 2. The method according to claim 1, characterized in that the catalysts are heated for 0.5-20 hours. 3. The method according to claim 1 and 2, characterized in that heating the catalysts 3-5 hours at 620 ° to 670 ⁰ C. 4. The method according to claim 1-4, characterized in that the catalysts 10-30 weight percent bismuth, Contain 6-18 percent by weight of molybdenum and optionally up to 1 percent by weight of phosphorus. 5. The method according to claim 1-4, characterized in that the catalysts 24-25 percent by weight bismuth, 13.5 14.5 Contains percent by weight molybdenum and 0.2-0.4 percent by weight phosphorus. 6. The process according to claim 1- 5 »characterized in that the catalysts are prepared by depositing bismuth, molybdenum and optionally phosphorus-containing solutions on silica and then heated to 580 ° to 75O ⁰ C. 7. The method according to claim 1-6, characterized in that catalysts are heated, .The effectiveness of their Use in amoxidation processes has already subsided. 8. The method according to claim 1-7, characterized in that one heated catalysts for the conversion of propylene EC 47-13-109836/1521 have been used with ammonia and oxygen to make acrylonitrile. 14 - 1 09836/152 1