Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-01-27
2001-02-06
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S308000, C502S311000, C502S312000, C502S321000, C502S242000, C502S246000, C502S247000, C502S248000, C423S593100, C423S595000, C423S598000
Reexamination Certificate
active
06184173
ABSTRACT:
The present invention relates to multimetal oxides of the general formula I
Mo
12−a−b−c
V
a
M
b
1
M
c
2
O
x
(I),
where
M
1
is W and/or Nb,
M
2
is Ti, Zr, Hf, Ta, Cr, Si and/or Ge,
a is from 0.1 to 6, preferably from 0.5 to 4.5,
b is from 0 to 6, preferably from 0.1 to 6, particularly preferably from 0.5 to 4,
c is from 0 to 6, frequently from 0.1 to 6 or from 0.5 to 4,
with the proviso that a+b+c is from 0.1 to 6, preferably from 0.5 to 4.5, and
x is a number which is determined by the valency and frequency of the elements in I other than oxygen,
whose
three-dimensional atomic arrangement obtained using CuK&agr; radiation (&lgr;=1.54178 Å) gives an X-ray powder diffraction spectrum (the intensity A of the diffracted X-rays plotted as a function of twice the diffraction angle (2⊖)) which contains, in the 2⊖ range (stated in the unit for angles in a plane: °=degree) from 5 to 50°, at least the following characteristic diffraction lines A
1
, A
3
, A
5
, A
9
and A
10
, but at most the following diffraction lines A
1
to A
10
:
X-ray
diffraction line
2⊖ [°]
A
1
8.3 ± 0.7
A
2
14.4 ± 0.7
A
3
22.3 ± 0.2
A
4
23.5 ± 0.7
A
5
27.2 ± 0.4
A
6
32.0 ± 0.8
A
7
34.8 ± 0.6
A
8
38.7 ± 0.5
A
9
45.4 ± 0.4
A
10
48.8 ± 0.4
The wavelength &lgr; of the X-radiation used for the diffraction and the diffraction angle ⊖ are related to one another by the Bragg relationship:
2 sin⊖=&lgr;/
d,
where d is the interplanar spacing of the three-dimensional atomic arrangement, associated with the respective diffraction line.
Furthermore, the present invention relates to a process for the preparation of multimetal oxides I and their direct use as active material of catalysts for the catalytic gas-phase oxidation of organic compounds.
The present invention also relates to the use of multimetal oxides I as starting compounds for the preparation of multimetal oxide materials which contain Mo and V and in turn are suitable as active material for the catalytic gas-phase oxidation of organic compounds.
The preparation of multimetal oxide materials containing Mo and V and their use as active materials of catalysts for the catalytic gas-phase oxidation of organic compounds (eg. acrolein to acrylic acid) is generally known (eg. EP-A 293 859).
Initially, the preparation of such multimetal oxide materials containing Mo and V was carried out by providing a suitable source (starting compound) of each of their elemental constituents, producing from the total amount of these sources a very thorough, preferably finely divided dry mixture having a composition corresponding to the required stoichiometry of the desired multimetal oxide material and calcining said dry mixture at elevated temperatures for several hours under inert gas or under an oxygen-containing gas (eg. air) (single-vessel process). All that was important with regard to the sources of the elemental constituents of the multimetal oxide materials was that they were either already oxides or compounds convertible into oxides by heating, at least in the presence of oxygen (cf. for example DE-A 4 335 973 and U.S. Pat. No. 4,035,262).
It is now known (cf. for example EP-A 835, DE-C 3 338 380, DE-A 4 220 859, DE-A 4 307 381, DE-A 4 405 085, DE-A 4 405 059, DE-A 4 405 060, DE-A 4 405 514 and DE-A 44 404 891) that it may be advantageous first to preform separately a multimetal oxide comprising only a fraction of the total amount of the elemental constituents of the desired multimetal oxide material and then to use this separately preformed fractional multimetal oxide as a finely divided source for producing the desired multimetal oxide material.
As a rule, this results in multimetal oxide materials which have a multiphase composition and some of which are more advantageous for the catalytic gas-phase oxidation of organic compounds than the multimetal oxide materials prepared by the single-vessel processes known per se.
It is an object of the present invention to provide novel fractional metal oxides of multimetal oxide materials containing Mo and V, which multimetal oxide material can be used as starting compounds for the preparation of multiphase multimetal oxide materials which contain Mo and V and are particularly suitable as active material for the gas-phase catalytic oxidation of acrolein to acrylic acid.
We have found that this object is achieved by the multimetal oxides I defined at the outset. Advantageous multimetal oxides I include those in which x is from 15 to 50. x is preferably from 25 to 40, particularly preferably from 30 to 40. Other suitable multimetal oxides I include those in which c is 0. Where c is 0 and M
1
is exclusively W, suitable multimetal oxides I are those in which ≧25 or ≧50 or ≧75 or ≧95 or ≧99% of the vanadium is present as V
4+
.
Typical of the novel multimetal oxides I is that their X-ray powder diffraction spectrum obtained using CuK&agr; radiation in the 2⊖ range from 5° to 50° as a characteristic fingerprint contains at least the diffraction lines A
1
, A
3
, A
5
, A
9
and A
10
but on no account more than the diffraction lines A
1
, A
2
, A
3
, A
4
, A
5
, A
6
, A
7
, A
8
, A
9
and A
10
.
It is noteworthy that some of the diffraction lines are those which have a relatively large half-width FWHM (the width of the diffraction line (the intensity plotted as a function of 2⊖) at half the height of their maximum amplitude, stated in the unit for angles in a plane), reflecting an unusual pattern of short-range and long-range order in the novel multimetal oxides I (cf. Examples). In the author's opinion, this particular pattern of short-range and long-range order is responsible, inter alia, for the particular catalytic properties of the novel multimetal oxides I.
Owing to the particular half-width conditions, the X-ray powder diffraction spectrum of the novel multimetal oxides I does not contain the diffraction lines A
i
in completely resolved form. However, the presence of the multiplicity of diffraction lines A
i
(after subtraction of the linear background) is directly visually evident as a relative maximum in the envelope of the X-ray powder diffraction spectrum of the novel multimetal oxides I, the position of these relative maxima defining, in this publication, the position of the diffraction lines A
i
according to the claims.
After subtraction of the linear background (the connecting line between A(2
⊖
=5°) and A(2
⊖
=65°)), the following relative line intensities (I
A
rel
=(I/Io)×100%), based on the most intense of the diffraction lines A
1
to A
10
, can be furthermore assigned to these diffraction lines A
1
to A
10
, the amplitude, measured from the base line to the relative maximum, being used as a measure of the intensity:
X-ray
diffraction line
I
A
rel
[%]
A
1
7 ± 5
A
2
5 ± 5
A
3
100
A
4
40 ± 40
A
5
70 ± 40
A
6
25 ± 25
A
7
20 ± 20
A
8
10 ± 10
A
9
25 ± 15
A
10
35 ± 20
With regard to this line intensity data, it should be noted that, in contrast to the position of the lines, the relative line intensities are markedly influenced in a manner known per se to a person skilled in the art by the individual crystal orientations obtained in various powder preparations and based on the anisotropy of the crystal form and are therefore of little significance for identification of the novel multimetal oxides.
In this connection, it should be stated that observation has shown that a further characteristic of the CuK&agr; X-ray powder diffraction spectrum of the novel multimetal oxides I appears to be the fact that it generally contains no diffraction lines whose FWHM<0.25°.
In all embodiments, the X-ray powder diffraction spectrum was recorded by means of a Siemens D-5000 diffractometer using CuK&agr; radiation (40 kV, 30 mA, &lgr;=1.54178 Å). The diffractometer was equippe
Hibst Hartmut
Marosi Laszlo
Tenten Andreas
BASF - Aktiengesellschaft
Bell Mark L.
Hailey Patricia L.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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