Multi-metal oxide compounds with a two-phase structure

Details Multi-metal oxide compounds with a two-phase structure Multi-metal oxide compounds with a two-phase structure

2000-10-06

2004-05-18

Richter, Johann (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acids and salts thereof

C502S353000

Reexamination Certificate

active

06737545

ABSTRACT:

SUMMARY OF THE INVENTION
The present invention relates to multimetal oxide materials of the formula I
(A)
p
(B)
q
  (I),
where:
A is Mo
12
V
a
X
1
b
X
2
c
X
3
d
X
4
e
X
5
f
X
6
g
O
x
,
B is X
7
1
Sb
h
H
i
O
y
,
X
1
is W, Nb, Ta, Cr and/or Ce, preferably W, Nb and/or Cr,
X
2
is Cu, Ni, Co, Fe, Mn and/or Zn, preferably Cu, Ni, Co and/or Fe,
X
3
is Sb and/or Bi, preferably Sb,
X
4
is Li, Na, K, Rb, Cs and/or H, preferably Na and/or K,
X
5
is Mg, Ca, Sr and/or Ba, preferably Ca, Sr and/or Ba,
X
6
is Si, Al, Ti and/or Zr, preferably Si, Al and/or Ti,
X
7
is Cu, Zn, Co, Fe, Cd, Mn, Mg, Ca, Sr and/or Ba, preferably Cu, Ni, Zn, Co and/or Fe, particularly preferably Cu and/or Zn, very particularly preferably Cu,
a is from 1 to 8, preferably from 2 to 6,
b is from 0.2 to 5, preferably from 0.5 to 2.5,
c is from 0 to 23, preferably from 0 to 4,
d is from 0 to 50, preferably from 0 to 3,
e is from 0 to 2, preferably from 0 to 0.3,
f is from 0 to 5, preferably from 0 to 2,
g is from 0 to 50, preferably from 0 to 20,
h is from 0.1 to 50, preferably from 0.2 to 20, particularly preferably from 0.2 to 5,
i is from 0 to 50, preferably from 0 to 20, particularly preferably from 0 to 12,
x and y are each numbers which are determined by the valency and frequency of the elements in (I) other than oxygen and
p and q are each numbers which differ from zero and the ratio p/q is from 20:1 to 1:80, preferably from 10:1 to 1:35, particularly preferably from 2:1 to 1:3,
which contain the moiety (A)
p
in the form of three-dimensional regions A of the chemical composition
A: Mo
12
V
a
X
1
b
X
2
c
X
3
d
X
4
e
X
5
f
X
6
g
O
x
and the moiety (B)
q
in the form of three-dimensional regions B of the chemical composition
B: X
7
1
Sb
h
H
i
O
y
where the regions A, B are distributed relative to one another as in a mixture of finely divided A and finely divided B, with the proviso that the multimetal oxide materials (I) are prepared using at least one separately preformed oxometallate B,
X
7
1
Sb
h
H
i
O
y
,
 which is obtainable by preparing a dry blend from suitable sources of the elemental constituents of the oxometallate B which contain at least a part of the antimony in the oxidation state +5 and calcining said dry blend at from 200 to 1200° C., preferably from 200 to 850° C., particularly preferably from 250 to <600° C., frequently ≦550° C.
The present invention also relates to processes for the preparation of multimetal oxide materials (I) and their use as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid.
DESCRIPTION OF THE BACKGROUND
WO 96/27437 relates to multimetal oxide materials which contain the elements Mo, V, Cu and Sb as essential components and whose X-ray diffraction pattern has the line of strongest intensity at a 2&thgr; value of 22.2°. WO 96/27437 recommends these multimetal oxide materials as suitable catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid. Furthermore, WO 96/27437 recommends using Sb
2
O
3
as an antimony source for the preparation of these multimetal oxide materials. Preparation of an antimony-containing component beforehand is not described in WO 96/27437.
EP-B 235760 relates to a process for the preparation of Sb, Mo, V and/or Nb-containing multimetal oxide materials which are suitable as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid. EP-B 235760 recommends using an antimony prepared beforehand as an antimony source for the preparation of these multimetal oxide materials.
The disadvantage of the multimetal oxide materials of the prior art is that their activity and the selectivity of the acrylic acid formation are not completely satisfactory when they are used as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide novel multimetal oxide materials which, when used as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid, have the disadvantages of the catalysts of the prior art to a reduced extent, if at all.
We have found that this object is achieved by the multimetal oxide materials (I) defined at the outset.
Very particularly preferred materials (I) are those whose regions A have a composition of the following formula (II)
Mo
12
V
a
,X
1
b
,X
2
c
,X
5
f
,X
6
g
,O
x
,  (II),
where
X
1
is W and/or Nb,
X
2
is Cu and/or Ni,
X
5
is Ca and/or Sr,
X
6
is Si and/or Al,
a′ is 2 to 6,
b′ is 0.5 to 2.5,
c′ is 0 to 4,
f′ is 0 to 2,
g′ is 0 to 2 and
x′ is a number which is determined by the valency and frequency of the elements in (II) other than oxygen.
DETAILED DESCRIPTION OF THE INVENTION
It is also advantageous if at least one of the moieties (A)
p
, (B)
q
of the novel multimetal oxide materials (I) is contained in the latter in the form of three-dimensional regions having the chemical composition A or B, whose maximum diameters d
A
and d
B
(longest connecting line between two points present on the surface (interface) of the region and passing through the center of gravity of the region), respectively, are from >0 to 300 &mgr;m, preferably from 0.01 to 100 &mgr;m, particularly preferably from 0.05 to 50 &mgr;m, very particularly preferably from 0.05 to 20 &mgr;m.
However, the maximum diameters can of course also be from 0.05 to 1.0 &mgr;m or from 75 to 125 &mgr;m (the experimental determination of the maximum diameter is permitted, for example, by a microstructure analysis by means of a scanning electron microscope (SEM)).
As a rule, the moiety (B)
q
is present in the novel multimetal oxide materials essentially in crystalline form, i.e. as a rule the regions B essentially comprise small crystallites whose maximum dimension is typically from 0.05 to 20 &mgr;m. However, the moiety (B)
q
can of course also be amorphous and/or crystalline.
Particularly preferred novel multimetal oxide materials are those whose regions B essentially comprise crystallites which have the trirutile structure type of &agr;- and/or &bgr;-copper antimony CuSb
2
O
6
. &agr;-CuSb
2
O
6
crystallizes in a tetragonal trirutile structure (E.-O. Giere et al., J. Solid State Chem. 131 (1997), 263-274), whereas &bgr;-CuSb
2
O
6
has a monoclinically distorted trirutile structure (A. Nakua et al., J. Solid State Chem. 91 (1991), 105-112, or reference diffraction pattern in index card 17-284 in the JCPDS-ICDD index 1989). In addition, regions B which have the pyrochlore structure of the mineral partzite, a copper antimony oxide hydroxide with the variable composition Cu
y
Sb
2-x
(O, OH, H
2
O)
6-7
(y≦2.0≦x≦1), are preferred (B. Mason et al., Mineral. Mag. 30 (1953), 100-112, or reference pattern in index card 7-303 of the JCPDS-ICDD index 1996).
Furthermore, the regions B may consist of crystallites which have the structure of copper antimony Cu
9
Sb
4
O
19
(S. Shimada et al., Chem. Lett. (1983) 1875-1876 or S. Shimada et al., Thermochim. Acta 133 (1988), 73-77 or reference pattern in index card 45-54 of the JCPDS-ICDD index) and/or the structure of Cu
4
SbO
4.5
(S. Shimada et al., Thermochim. Acta 56 (1982), 73-82 or S. Shimada et al., Thermochim. Acta 133 (1988), 73-77, or reference pattern in index card 36-1106 of the JCPDS-ICDD index).
Of course, the regions B may also consist of crystallites which constitute a mixture of the abovementioned structures.
The novel materials (I) are obtainable in a simple manner, for example by first separately preforming oxometallates B,
X
7
1
Sb
h
H
i
O
y
,
in finely divided form as starting material 1. The oxometallates B can be prepared by preparing a preferably intimate, advantageously finely divided dry blend from suitable sources or their elemental constituents and calcining said dry blend at from 200 to 1200° C., preferably from 200 to 850° C., particularly preferably from 250 to <600° C., frequently ≦550° C. (as a rule for from 10 min to several hours). All that is essential to the invention is that at least a part of the oxometallates B of the starting material 1 (re

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