DE2147838C3 - Catalysts with a shellite crystal structure and process for the catalytic oxidation of olefins - Google Patents

Description

The invention relates to new catalysts with a scheelite crystal structure and processes for catalytic purposes Oxidation of olefins.

The catalytic oxidation of olefins is present of great technical importance, e.g. B. the conversion of propylene to acrolein. The implementation this reaction in the presence of ammonia with the formation of acrylonitrile is even greater technical importance. The oxidative dehydrogenation of olefins to diolefins, e.g. B. of butene- (l) too Butadiene- (1,3) is of great industrial importance. These reactions are currently being used on an industrial scale Scale carried out with catalysts containing bismuth molybdate and bismuth phosphorus molybdate. Such catalysts are described, for example, in US Pat. Nos. 4,1007 and 3,415,886.

In AT-PS 2,47,304 and 2,48,410 it is stated as important to keep the ratio of bismuth to molybdenum in such catalysts above 2: 3 and preferably above 3: 4 in order to sublimate the molybdenum and thus reduce the decomposition of the Avoid catalysts, and it is proposed that improved catalysts can be obtained by using molybdates of lead or of calcium and / or strontium in admixture with wisdom molybdate. However, the patents do not contain any general · ¹ re teaching on combinations of ions other than

valuable oxidation catalysts.

In GB-PS 11 57 821 are ternary molybdenum-bismuth-vanadium compounds in which the crystal lattice structure typical of monoclinic bismuth vanadate is distorted by the introduction of molybdenum atoms instead of vanadium atoms and the Molar ratios are within certain limits; however, it does not become a more general teaching discloses catalysts made from combinations of elements other than that in this patent to produce specified ternary bismuth-molybdenum-vanadium combination.

The US-PS 33 87 038 relates to a catalyst, the molybdenum oxide in combination with an oxide of Magnesium, Calcium, Strontium or Barium and also preferably contains a catalytic promoter, compounds of Phosphorus, silicon and 16 other compounds including bismuth compounds can be used can.

The teachings of the prior art, of which the above examples are typical, have generally held out Focused on empirical observations on certain catalysts that are reported to be that they have unique, unexplained properties. It was now using a group of catalysts found a certain crystal structure, which is characterized by the common property of a good catalytic Distinguish activity in the above oxidation reactions.

The invention relates to catalysts of the general formula ABO4 with the crystal structure of scheelite with 0.1 to 15% unoccupied A-ion sites, with regard to the B-ions, the Α-ions at least partly consist of trivalent bismuth ions and the other Α- Ions lead, calcium, strontium, barium, mercury, cadmium, silver, lithium, sodium, potassium, zirconium, hafnium, yttrium, lanthanides (atomic number 57 to 71), uranium , Represent thallium and / or thorium ions and the B ions are vanadium, molybdenum, tungsten, iron, germanium, zinc, arsenic, rhenium, gallium, aluminum, niobium and / or chromium ions , with the proviso that compounds consisting only of bismuth, molybdenum and vanadium oxide are excluded, and that compounds in which some of the Α ions consist of lead, calcium or strontium and none of the B ions consist of vanadium, have no more than 7.5% unoccupied A-cation sites, produced by one or multiple calcination of a mixture of the oxides or oxide-forming salts or hydroxides of the metals A and B at temperatures of 40ObIsIlOO ⁰ C.

The invention also relates to methods of catalytic vision Oxidation of olefins, especially to unsaturated aldehydes and for the catalytic oxidation of Olefins in the presence of ammonia to form unsaturated nitriles and for oxidative dehydrogenation to diolefins, in which the new catalysts can be used.

Surprisingly, it has been shown that. as will be shown in the later following comparative experiments, with Help the catalysts according to the invention in comparison to very similar ones, but not in every respect Catalysts which satisfy the conditions according to the invention have surprisingly advantageous results (such as suddenly increased degrees of conversion and yields in the oxidation of propylene) can be achieved.

The crystal structure of scheelite is described by RWG Wyckoff in "Crystal Structures", Volume 2, 2nd edition, 1965, pages 19-22, Interscience Publishers. These substances can be identified by their characteristic X-ray diffraction spectrum; they generally have a tetragonal symmetry and can be characterized by lattice constants aa between about 4.8 and 6 A and ca of generally about 22o. The Scheelit-Kxistallstruktur includes variants that have little distortion in the angle and edge size compared to the classic tetragonal symmetry, z. B. an orthorhombic distortion that requires a third lattice constant ba , which for the present purposes does not deviate by more than 10% from the value of ao and should be in the same range from 4.8 to 6 A, or a monoclinic distortion, which results from a change in β or γ and, for the purposes of the present invention, should not deviate from the angle of 90 ° by more than 5 °. Such distortions generally split up some of the different diffraction maxima and to this extent change the characteristic X-ray diffraction spectrum of the classic tetragonal crystal structure of scheelite.

The B cations are tetrahedrally coordinated by oxygen, ie they should have a coordination number of 4, and they should also generally have an ionic radius of about 0.3 to 0.5 Å, so that they can be accommodated in the Scheeüt structure. Shannon and Prewitt have published a table of effective ionic radii in "Acta Crystallographic?", B-25 (1969), on pages 925-926, from which it can be seen that the following ions with the specified positive valencies have the coordination number 4 and an ionic radius from 03 to 03 A can have: Re ^{+ 7} , Mo ⁺⁶ , W ⁺⁶ , V ⁺⁵ , Cr ⁺⁵ , As ^{+ S} , Nb * ⁵ , Ge ⁺⁴ , Cr ⁺⁴ , Al ^{+ 3} , Ga ^{+ 3} and Fe ^{+ 3} . Furthermore, zinc can form the desired scheelite crystal structures, although it has a larger ionic radius.

The A cation sites in the scheelite crystal structure connect the BO ₄ tetrahedra and are eight-fold coordinated by oxygen. At least some of the A-cation sites must be occupied by bismuth, while others must be unoccupied. Any remaining A cations should have the coordinate number 8 and generally have an ionic radius in the range from 0.9 to 1.6 A, including the following ions according to the publication by Shannon and Prewitt: Ag ^{+ 1} , Na ^{+ 1} , K ^{+ 1} , Rb * '. Ti ^{+ 1} , Ca * ² , Sr ^{+ 2} , Ba * ² , Pb * ² , Hg ^{+ 2} , Cd * ² , Sn ^{+ 2} , Eu * ² , Bi * ^! , Y * ³ , TI + ³ , the positive trivalent ions of the lanthanides (the rare earth metals) with atomic numbers from 57 up to and including 71.Ce ⁺⁴ , Th * ⁴ . U * ⁴ , Np * ⁴ , Pa * ⁴ and Po * ⁴ . Furthermore, lithium can also form the desired scheelite crystal structures, although it has a smaller ionic radius.

The content of B and Α cations including bismuth ions can be determined by conventional analytical methods. Since according to the formula ABO4 there is only one A and one B position in the scheelite structure. And since the B-cation sites are always completely occupied by B-atoms, the number of unoccupied A-cation sites (which are sometimes also referred to as imperfections and are represented in the formulas below by the symbol D) can be determined by using the Total amount of gram atoms of A ^ ionefi Subtracted from the total amount of gram atoms of B ions. B. a single-phase scheelite has analytically shown the composition Na ⁺¹ O ₁ -H Bi + ³ oi2 Mo + ⁶ O ₄ , the sum of the gram atoms A is 0.96, which means that 0.04 Α-positions are unoccupied, ie the Formula can be written more correctly than Na _o . + T Bi _o , 52 Ö _O , O4 MoO ₄ (and is also written this way below). This connection is electrically neutral because the eight negative charges of oxygen are exactly balanced by the six positive charges of molybdenum, the 1.56 (3x0.52) pcjitive charges of bismuth and the 0.44 positive charges of sodium, as the sum makes up eight positive charges. The number of desired vacancies is 0.1 to 15%, preferably at least 1% and in particular up to 10%, based on the number of B ions. Too many imperfections lead to a different crystal structure than the desired scheelite structure, which contains random voids. The upper limit depends in general on the respective ions in the lattice and on the temperature and is often around 15% at relatively high equilibrium temperatures, although even at lower temperatures in certain systems together with the tetragonal scheelite phase a certain amount of an undesired phase with less vacant positions appears as described in more detail below. Even if the presence of a phase in small amounts does not generally interfere with the catalytic activity of the scheelite phase, which contains both vacant cation sites and bismuth ions, a single-phase scheelite structure is preferable, and large amounts of excess or unreacted components impair the catalytic effectiveness, in particular when these substances accumulate on the surface of the catalytic converter.

If a single type of cation site is occupied by several cations, an irregular occupation of the site may produce superstructure lines in the characteristic X-ray diffraction spectrum of the scheelite. In such circumstances, the precise identification of unit cell parameters requires that one or more of the unit cell dimensions be multiplied by a small integer to identify the particular distribution of the cations. So z. B. a fault-free scheelite structure from the stoichiometric composition BiFeInMo ^ O ₄ can be generated in which '/ 3 of the B-sites is occupied by Fe ^{+ 3} ions.

However, the arrangement of the? E ^{+ i} and Mo * ⁶ ions is apparently ordered, since weak superstructure lines appear in the X-ray diffraction spectrum, and these require a larger cell unit for indexing. The resulting monoclinic cell with a = 16.16 Å

(corresponding to 3 χ 5.39 A), 6 = 5.25 A, C = 11.65 A and y = 90.97 °, which extends along the a-axis is longer. is, as you can easily see, a mere modification of the order of the monoclinic scheelite variant within the limits given above for Scheelite. On the other hand, the well-known bismuth molybdate, Βΐ2θΐ · 3 MoOj, in the sense of the present Invention not the scheelite structure, what from its clearly different X-ray diffraction spectrum it can be seen

The catalysts can in general most simply by calcining one or more times a mixture of oxides in the for the composition quantities required for the finished catalytic converter *

Conditions are established. In some cases it may be more appropriate to use salts, such as carbonates, nitrates and using oxalates, or hydroxides, and converting them to the corresponding oxides. Soluble Salts, such as the nitrates, can be used in solution, e.g. B. in aqueous solution, or optionally in one organic solvents are mixed with one another, whereupon the solvent is evaporated off before calcining

The BOi tetrahedra are characteristic of the scheelite structure. The oxides involved or the Compounds from which the oxides are formed should be selected so that in their normal oxidation states after calcination, as described below, essentially 4 gram atoms of oxygen for each gram atom of B cations is absent The presence of significantly more or less oxygen in relation to the B cations leads to the dilution of the ABQt catalyst according to the invention with another Phase. The correct proportions of the different oxides or oxide formers that go together should be combined in order to keep a pure scheelite phase with the desired content of vacancy ι, can easily be derived from the above-described requirements for electrical neutrality and determine the filling of the positions. In the simple cases in which a single lon occupies the B positions and the required cation vacancies from a simple permutation of the charge on the A cation result, the following general formulas apply to ternary metal oxides, where ζ equals the number of Spaces is:

+ Ί-Ι3, A + + 'os-15 / A

O ₄

i- ₄ , □,

^{+ 6} O ₄

^{+ 5} O ₄

The required vacant A-cation sites can also come about through permutations of differently charged ions in the B cation sites come as in the system

A ⁺ ^, O, B ⁺ 3, e-, B ⁺⁶ 2/3 _{+ i} rO ₄ .

To z. B. to produce a pure scheelite catalyst in the ternary system B12O3 _{- Fe2O 3} - MOO3 with a content of unoccupied cation sites of 4%, one uses the last-mentioned formula with z = 0.04 and then obtains the preferred molar ratios of the starting materials, namely 0.480 Bi ₂ Oj; 0.146 Fe ₂ Oj; 0.707 MOO3. One can also make further permutations of the A and the B cations in the same compound as in the system

A ' ^? , _: , Bi ", D-Fe" _{,, 2} .B ' ⁶ , _t2. -O ₄

in order to arrive at a very wide range of new catalysts with a prescribed content of Bi * ' (y) and unoccupied positions (z) at the A-cation sites. To z. B. to produce a pure scheelite catalyst in the quaternary system CaO-Bi ₂ Oj-Fe ₂ Oj-MoOj, you can use the last-mentioned formula with 2 = 0.05 and .K = OJO, using the preferred molar ratio of the starting materials, namely 0.25 CaO; 035 Bi ₂ O ₃ ; 0.10 Fe ₂ O ₃ JO ₁ SO MoO ₃

The temperature and duration of the calcination depend on the constituents, but are generally in the range from 400 to 1100 ^° C. or 16 to 48 hours, longer periods of time, for example up to 100 hours, being required at lower temperatures in this range. For compositions rich in bismuth, lead and molybdenum, lower temperatures are generally preferred, while higher temperatures are generally preferred for calcining oxides of tungsten. However, the calcination temperature should not be so high that a liquid phase is formed. In general, ej is advantageously calcined in several stages, with

ίο to the mass again grinding the mixture may be 2 to 16 hours at 600 to 800 ⁰ C calcine, then ground the ground again and then calcined for a further 16 to 32 hours in the same temperature range for example between the stages. Suitable containers in which the mass can be calcined should be inert, e.g. B. made of gold or other precious metals, aluminum oxide or other ceramic materials. The calcination can expediently take place in the muffle furnace in the air, avoiding a reduced atmosphere. The calcined masses should preferably be cooled quickly so that as little νοτ, the scheelite phase converts into another phase and dws particularly applies to catalysts that are rich are divalent ions.

The progress of the calcining process can be followed by actually making X-ray diffraction diagrams and comparing them with the diagram for the expected scheelite structure. The lattice dimensions vary considerably as the composition changes; z. B. rises in equilibrated at 600 ⁰ C system

Lio5-13 / BtOj ₊ 05 / □ / MoO ₄

the cell length approx. regularly from 11.469 to 11.627 Å to the extent that the number ζ of unoccupied cation sites increases from 0 to 0.15 so that 15% of scheelite this type oberhai ι 600 ⁰ C, relationship ^ ^ ng seems to represent independently of the Tempei a practical upper limit, even when the lithium ions by other a * '- ions, a part of the bismuth ions by other A ^{+ 1} ions and / or the molybdenum a H replaced other B * ⁶ ions. In the system balanced ^{at 800 c C}

Pb, i, Bi ₂ / a, MoO ₄

Ca regularly decreases from 12,109 to 12,047 A. when the vacant cation sites increase from 0 to 7.5%; however, a further increase in the vacant cation sites has no effect on the

^C 5 double dimensions. but eventually additional lines of monoclinic phase appear. Similar systems containing divalent ions A * contain ^2, tolerate relatively few unoccupied Kalior, enstellen before a monoclinic phase occurs at calcination temperatures below 550 ⁰ C and above 800 ° C. The practical limit of calcination temperatures can be determined empirically for any system! Eight by examining the X-ray diffraction diagrams.

The catalysts can be used for various processes known per se for the oxidation of olefins, ζ. Β. at temperatures from 350 to 550 ⁰ C, preferably from 400 to 500 ⁰ C (the actual surface temperature

the catalyst particle is considerably higher), and bet Atmospheric pressure or lower pressure, e.g. B. at 0.5 at, or at overpressure, e.g. at 10 at, in Ruheschütturtg or ifi of the fluidized bed with or without Carriers are used. As shown in the examples below, one obtains with the catalysts excellent conversion rates and selectivity, and the catalysts keep theirs initial high activity without frequent regeneration. As with many known ones Catalysts, the presence of water is also when the catalysts according to the invention are used not mandatory.

In general, the catalysts are advantageously used on supports; it must, however, n shall ensure that the vacant cation sites of the scheelite not, for the carrier material. B. with a carrier with a very high specific surface area oc he with a reactive carrier, re 'ye, since this reduces the efficiency of the catalysis. In particular, intimate mixtures of the catalyst and a reactive form of silica should not be heated too high. The gas feed need not contain water, as is the case with some known analyzers; however, the presence of water is harmless.

The compositions of the catalysts can be anything from the compositions given above differ, especially in the course of catalytic reactions, as many of those in the catalytic converters Metals used have several valencies and in the catalysts in more than one valence may exist.

In the examples below, parts and percentages relate to unless otherwise specified. on the weight.

Examples

The catalyst samples given in Table I - »o are made according to the following processes:

Samples A to G are shared through

Vcrmah'.cr. ve "V; r ^u: ~ ^J ™ ^J * ''

Components and calcining in air at the temperatures given in Table I. The calcining is carried out in two stages, first 16 hours at the first given temperature, and after regrinding a further 16 hours at the second given temperature. Sample G, on the other hand, which contains sodium and yttrium as well as bismuth and molybdenum, is calcined in five successive stages and re-ground in two successive stages; in the first two stages it is 16 hours at 625 ^° C., in the next

Table I (continued)

two stages 64 hours or 16 hours at 75 (i ° C, and in the final stage for 16 hours at 800 ° C calcinisrt Sample E is initially 16 hours 800 ⁰ C and then after the regrinding 6; S hours at 80C ° C heated sample C is heated in three steps, 2 hours or 2 days at 8oC ⁰ C and in the last stage 16 hours 900 ° C, wherein .jas material between each two steps is ground again in the first two stages. the Samples H and 1 are heated for 60 hours and 10 hours, respectively, to 800 ^° C. In all cases, the B component is molybdenum, with the exception of sample F, in which the B component is tungsten, and sample E, in which the B Component is an equimolecular mixture of molybdenum and tungsten oxide, and sample 1, in which the B component is a mixture of 9 mol of molybdenum oxide and 1 mol of vanadium oxide.

The samples W to Z are by mixing together the specified salts in solution, evaporating the Solution and subsequent similar grinding and Calcine prepared as described above. In addition to the specified salts, the lowest possible Amount of water to dissolve the salts and nitric acid added to dissolve the To facilitate bismuth and cadmium in sample Z; for sample Y 114.95 parts are bismuth dissolved in nitric acid and for the sample Z wenlen 78.68 part? Cadmium dissolved in nitric acid Calcining is carried out for sample W in 10 hours, for the Sample X in two stages of 16 hours each, for sample Y in two stages, each overnight, and for the sample Z carried out in two stages of 2 hours and 16 hours respectively.

Table I.

Sample catalyst
formula

HI

WXYZ Sr _o .s-Pbn.8s
Pb _{n ss}
Pb _n 01

YlI. '40
Pb _n q _S <

Pb _0. *,

Well _n .:
Ago. ·. *
Cd ₀ ^ ₇

Am.*}
ΒίηΛ »
B ions'

Βίο OSO

Binni
Bi,,,-.

Bi _n oq;
Am*",

Bio.os7

Dow
Oo.os

Oo 045 □, 104 U ₀ 04
O _n ,,;

OfI (K, *

Oooo *
Doo -.-

Oo on-
Do.;

O ₀₁ O

Oo.04J

MoO ₄
MoO ₄
MoO ₄
MoO ₄

woT

MoO ₄
MoO ₄

MoO ₄
MoO ₄
MoO ₄

sample Part B A. 12.116 B. 12482 C. 13.98 D. 1,864 F. 3,728

Other Parts A component Na ₂ COj 2,332 Li ₂ CO ₃ 1.404 SrCO-, 8848 PbO 19.642 PbO 39.281

Parts of MoO; Calcination temp.
C.

Lattice constants, Ä

14.395

14.395

99.32

14,395

I4J94

23,185 WO ₅ 625-625
625-600
800-900
600-800
800-800

5J276

5.232

5.3894

5.424

5,436

11,595

11,530

11.9967

12,072

12.0436

continuation

ίο

Sample parts BI

Other parts

Λ component

Parts MOO3 calcination temp. Lattice Conslants, A

«Fo

0.9785 PbO

[PbO

2.796 j Na ₂ CO ₃

IYjO ₃

0.5 i 04 PbO

9.16 PbO

Bi (NO ₁ ), -5H ₂ O
136.61

f 136.1

Fe (NO,),
• 9 H ₃ O

271.66 NaNO,

[114.95 Bi] AgNOj
33,957 cd

14.2172

14.230
1.510
4.065

48.365

40.07

27.20
59.46
78.68

16.2295 WO ₃
21,592

800-800
625-800

31,667 800

29.44 800

2.0668 V ₂ O,

• 4 H ₂ O

JJ, / U

176.56
176.56
142.134

OUU

600-625
500-600
600-600

5.45
5.319

12,030
11.753

5.276
5.284
5.169

• monocline

11,640
11.678
11.243

The catalyst samples show a single phase tetragonal scheelite structure with those given in Table I. Lattice constants, with the exception of sample W, which is a monoclinic variant of the scheelite crystal structure set up. As described below, the Samples catalytic activity.

Sample X is mixed with an equal amount by weight of silicon carbide powder and the mixture is shaped into 3 mm pills to increase the catalytic activity of the quiescent bed in a reactor with an internal diameter of 12.5 mm when a gas composed of 5.0 mol percent propylene is supplied. To investigate 47.9 mol percent air and 47.1 mol percent nitrogen with a residence time of 2 seconds and a temperature of 485 ° C. Under these conditions 83.5% of the propylene is consumed and 61% of the initial propylene is converted to acrolein. When the gas feed is 4.0% propylene, 4.9% ammonia, 48.7% air and 42.4% nitrogen on a mole basis , 88.4% of the propylene is consumed and 64.6% of the initial propylene is converted to acrylonitrile while only 1.8% is converted to acrolein. Assuming a gas feed made up of 5% butene- (I), 26% air and 69% nitrogen on a mole basis ^; exists, then 450 ⁰ C and a residence time of 3 seconds 97.0% of Butens- (l) are at atmospheric pressure, consumed for the formation of butadiene (13) at a degree of conversion of 67.4%

Comparative experiments

To the efficiency of the catalyst sample X for the conversion of propylene into acrolein and Acrylonitrile in comparison to other catalysts tu show becomes a comparative catalyst composition Nao ^ oBio5oMo04 (a pure tetragonal Scheelite phase with the lattice constant 20 = 5.276 Å and Cb = I 1.582 Å, but without cation vacancies) produced under the same conditions investigated Γη in this case, due to the absence of unoccupied cation sites, only 5.2 resp. 2.7% of the supplied propylene is used for the formation of acrolein or acrylonitrile.

But if you look at the comparative catalyst (27.595

Parts) in the ball mill with 14.964 parts single phase

monoclinic B12O3 · 3 M0O3 mixed and the mixture in two stages depending on the air calcined for 16 hours at 640 ⁰ C, which is ground again between the two stages, to obtain a pure tetragenalen scheelite catalyst of formula

Naoj3 Bio. " D 0.11 ΜΟΟ4

Other samples are tested using a similar procedure. Sample B gives a degree of conversion of propylene to acrolein of 65.1 mol percent, while a Yergycnskaiaiysator of the composition Lio, sBio3Mo04 (without unoccupied cation sites) under the same conditions only gives a degree of conversion of 23.7%. Sample Y gives a degree of conversion of at least 53%, regardless of whether the gas feed used is a mixture of air and propylene in a ratio of 10: 1, undiluted or diluted with nitrogen or with nitrogen and hydrogen; if the feed contains ammonia, a 55 percent conversion to acrylonitrile is achieved; In contrast, a comparative catalyst of the composition AgnsBio ^ MoOi (without unoccupied cation sites) provides a degree of conversion to acrolein of less than 4% under the same process conditions. Sample I gives a 40 percent conversion of propylene into acrylonitrile, while a comparative catalyst with the composition Pboi5Bioi5Moot5Vo ₁ 504 (without unoccupied cation sites) only gives a degree of conversion of 1.6% 57%. The degrees of conversion to acrylic acid nitride obtained with samples E, F and G at 460.480 and 500 ° C. are 75.5, 563 and 54.1%, respectively.

Table II

Catalyst sample

Comparative sample 2

Comparative sample 3

R.
S.
T
U

Comparative sample 4

Composition of the catalyst Oitterkonstariten, A

"o Co

PbMoO ₄

Pb _n ., 7Bio.o2Öo.oiMo0 ₄
Pb _0. "Bi ₀ . ₀₆ D ₀ .o ₃ Mo0 ₄

-Mo0 ₄ Thu.o2i

5.435

5.431

5.422 5.433 5.426 5.412 5.418

5.4i4 12.109

12.088

I AU 53

Mole percent
consumed

3.6

9.4

ζο, υ

converted to acrylonitrile

4.8

12,068 95.4 66.5 12,100 61.5 40.1 12,082 96.7 61.2 12,046 97.2 63.4 12.051 86.2 63.9

A further comparison of the efficiencies of the catalysts according to the invention for the conversion of propylene into acrylonitrile with the efficiencies of control samples that are not composed according to the invention can be found in Table II Invention correspond to. All catalysts are prepared by grinding the constituents together, calcining for ² hours at 800 ° C., regrinding, calcining again at 800 ° C. over the course of 34 to 58 hours and rapid cooling in the air is described above for sample X, and used in the same reactor, with the difference that the temperature is kept at 460 ⁰ C, the residence time is 6 to 8 seconds and the gas feed from a mixture of propylene, air and ammonia in the molar ratio 1: 12: 1.2. diluted with 40 to 45 moiprozeni of nitrogen. All catalysts have a single-phase scheelite structure, the tetragonal lattice constants of which are given in the table. The samples according to the invention contain both unoccupied cation sites and bismuth, while comparative samples 2 and 3 have no bismuth and comparative samples 2 and 4 have no unoccupied cation sites, which distinguishes them from the catalysts according to the invention.

Table ΙΠ

Catalyst - catalyst support
sample

Consumes conversion%

Degree, %

J none 98.5 K 50% SiO ₂ (cal- 97.7 ciniert at 900 ⁰ Q L. 50% ZrO ₂ 98.4 M. 50% Nb ₂ O ₅ 99.5 N 50% TiO ₂ (anatase) 98.4

75.7
63.7

67.4
60.3

Catalyst - catalyst support
pfobe

Consumes conversion%

Degree, %

30 ρ

35

25% PbMoO ₄ 98.5 69.7

50% mullite 94.4 64.8

50% Al ₂ O ₃ (α; 96.1 60.8
Grain size <37 μ)

Table III explains the use of various catalyst supports together with sample D according to FIG Table I. The catalyst samples are first taken separately and then together with that in the table Grind the specified carrier in the ball mill and finally with a little polyvinyl alcohol as a binder deformed into 3 mm pills, whereupon the binder is removed by slowly heating in air to about 500 ° C

rr II U. The silica support used for sample K is prepared separately from the catalyst in order to avoid a reaction with the silicon dioxide. If a similar catalyst with a solution of colloidal silica treated and is then heated by evaporation to dryness at 500 ⁰ C, suffers from its catalytic activity by the degree of conversion of propylene to acrylonitrile then amounts to only about 30%.
The catalysts of the compositions given in Table IV are obtained by methods similar to those given above.

60

65

Table IV

Li _0-2 T ₅

La _0-50

Tl ₀ J ₄

Tho, i5

Th _0-80

BJ047S □ o.l5 Mon O ₄ O ₄ Dl0.02 Co 04 W. O ₄ O ₄ Dl _0-02 D ₀ 04 re O ₄ O ₄ Bi ₀ so Thu.os As O ₄ O ₄ Bi ₀ IO Thu io Ge _0-5 As _0-5 Bi _0-99 Ga _0-323 Mo _0- Sr? Binos Dn _-02 Mon _0-51 Βϊο.96 Πθ.04 Mon _0-78

continuation

Pb _0-997 Bio.002

S Tq, 16 Bl _0-79

B'o.os
Bi _0-4 O

Bjo. 173

Bio. 54

Bjo.27

Bio.4o

Ca _0-55
Pb _0-79

ΖΓο.55

Ago. ι η Sr ₀ τ «

Bio. "
Bio.sn
Bi _0- W
Bio.so

Πο.οι

Oo.oci

Thu.os

Πθ.037
Thu.O7

do.05
Πο.οι
□ ο.κ
do. ι η

Fe _O- 323

Mon

Alo. 23

Nb _0-5
As _0-10

Mo "

Fe _0-20

As _0-50

W _0-5

Mon _0-90

Mon ₀ J ₀

Mo _0-677 O ₄ O ₄

Mo _r , _-77 O ₄ Ue _0-5 O ₄ Mo _0-90 O ₄ Mo _0-90 O ₄ Mo _0-90
O ₄

V _0-80
O ₄
V ₀ «o
V0.5 Vo.10

Vo.7O

As can be seen from the above description, there are the following preferred groups of catalysts:

A. Those in which the A-cationites are occupied (i.e. all except four vacant Places) all by trivalent bismuth, or some of them by bismuth and others by others Α ions than those of the divalent group, namely by one or more ions of silver, Sodium, lithium, potassium, zirconium, hafnium, yttrium, the lanthanides (the elements with atomic numbers from 57 to 71), uranium, thallium and thorium, especially Sodium, lithium, silver and yttrium, and in which the B ion is different from the vanadium ion, namely one or more of the ions of molybdenum, tungsten, iron, germanium, zinc, arsenic, rhenium, Gallium, aluminum, niobium and chromium, especially molybdenum and iron. Examples of such catalysts are Samples A, B, W. X and Y of Table I and the first nine compositions of Table IV.

B. Those where the B ions are the same as in the previous paragraph, especially Molybdenum and tungsten, and some of the A-cation sites occupied by trivalent bismuth, others on the other hand by one or more divalent ions from the group of ions of lead, calcium, strontium, Barium, cadmium and mercury, especially lead, are occupied, while still others may be occupied by the other Α-cations mentioned above, namely one or more of the cations of silver, sodium, lithium, potassium, zirconium, hafnium, yttrium, the Lanthanides (the elements with atomic numbers from 57 to 71), uranium, thallium and thorium are occupied, wöbe ', only up to 7.5% and preferably 0.5 to 5% vacant cation sites are present. Examples of such Catalysts are the remaining samples in Table I with the exception of sample I, i.e. samples C to H and W, also the samples of Table II (R to V) and Table III (K to Q) and the middle seven Compositions of Tables IV.

C. Those in which the vanadium is at least

ίο forms part of the B ions which, if applicable, et,; «·«; or several other of the ions from the above-mentioned groups (A and B) may contain, and in which only some of the occupied A-cation sites are occupied by trivalent bismuth, while the others are occupied by one or more of the abovementioned Α-ions (A and / or B) are occupied, in particular by lead. Examples of such catalysts are the sample of Table I and the last six compositions of the Table IV.

ΡΓΟ ^πυ | ρη is d & S technically wirhtjffstp OIpfin _# and Hpr most of the details of the description are therefore primarily devoted to the oxidation of propylene; however, other olefins, especially those containing up to 8 carbon atoms, can also be used in

similarly oxidize, e.g. butene- (l), butene (2), isobutylene, pentene- (l), pentene- (2), 3-methylbutene- (l). 2-methylbutene (2), hexene (l), hexene (2), 4-methylpentene (l), 33-dimethylbutene (l), 4-methylpentene (2), octene (l), Cyclopentene, cyclohexene, 3-methylcyclohexene and mixtures of the same and / or similar compounds by straight-chain, alicyclic or heterocyclic Radicals are substituted. Preferred conversion processes are those from propylene to Acrolein, from isobutylene to methacrolein, from butene- (l) or butene- (2) to methyl vinyl ketone, from pentene- (l)

or pentene- (2) to ethyl vinyl ketone and / or pentene- (3) -one- (2), from 2-methylbutene- (2) to methylisopropenyl-

ketone and from cyclopentene to cyclopentenone- (2).

The present application for protection covers the known catalyst compositions or processes, i.e. those of AT-PS 2 47 304 and 2 48 411, in which catalysts are described, the oxides of bismuth and molybdenum and oxides of ts.ei oaer of calcium and / or contain strontium which, however, are not scheelites with occupied cation sites of only 7 % , or d. --nigen of GB-PS 11 57 821, in which catalysts are described which contain only bismuth, vanadium and molybdenum oxide, excluded.

Claims (3)

Patent claims: 1. Catalyst of the general formula ABO4 with the crystal structure of scheelite with O ₁ I to 15% unoccupied A ions with respect to the B ions, the Α-ions at least partly consist of trivalent bismuth ions and the other Α-ions that may be present lead -, calcium, strontium, barium, mercury, cadmium, silver, lithium, sodium, potassium, zirconium, hafnium, yttrium, lanthanides (atomic number 57 to 71), uranium, Represent thallium and / or thorium ions and the B ions are vanadium, molybdenum, tungsten, iron, germanium, zinc, arsenic, rhenium, gallium, aluminum, niobium and / or chromium ions, with the proviso that compounds consisting only of bismuth, molybdenum and vanadium oxide are excluded and that compounds in which some of the A-ioners. made of lead. Calcium or strontium and none of the B-ions consists of vanadium, do not have more than 7.5% unoccupied A-cation sites, produced by calcining a mixture of the oxides or oxide-forming salts or hydroxides of the metals A and B at temperatures one or more times from 400 to 1100 ⁰ C Z catalyst according to claim 1, characterized in that not more than 7.5% of the A-ion sites are unoccupied and that at least some of the Α ions (except bismuth ions) lead, calcium, Are strontium, barium and / or mercury ions. 3. A method for the catalytic oxidation of olefins, characterized in that it is in The presence of a catalyst according to claim 1 or 2 carries out