Molybdenum based oxidation catalysts

Details Molybdenum based oxidation catalysts Molybdenum based oxidation catalysts

1999-03-22

2001-08-07

Wood, Elizabeth D. (Department: 1755)

Catalyst, solid sorbent, or support therefor: product or process

Catalyst or precursor therefor

Metal, metal oxide or metal hydroxide

C502S303000, C502S306000, C502S311000

Reexamination Certificate

active

06271169

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to compounds comprising molybdenum, oxygen and certain cations, and the use of these compounds as catalysts in C
4
oxidation processes, especially butane oxidation processes.
TECHNICAL BACKGROUND
Oxidative organic processes are widely used in industrial operations. One commercially valuable process involves the oxidation of butane to maleic anhydride. Maleic anhydride is used as a raw material for products ranging from agricultural chemicals, paints, paper sizing and food additives to synthetic resins. To fill the high demand for this valuable chemical, a variety of commercial processes have been developed.
One important route to maleic anhydride involves the vapor phase oxidation of n-butane over a vanadium/phosphorus oxide (VPO) catalyst. The reaction step involves oxidation of n-butane with air (oxygen) to form maleic anhydride, carbon oxides, water and smaller amounts of partially oxidized by-products. Typically, the process is carried out in fixed-bed reactors, fluid-bed reactors, or more recently in recirculating solids reactors having two reaction zones in which two separate reactions take place with a catalyst (the solid) circulating between the two reaction zones and taking part in reactions in both zones.
A number of non-VPO catalysts have been reported in the literature. Zazhigalov, V. A. et al., in an article entitled “Oxidation of n-butane on Vanadium Molybdenum-Oxide Catalysts”, Inst. Fiz. Khim. im. Pisarzhevskogo, Kiev USSR Neftekhimiya (1977), 17 (2), 268-73 describe the activity of V
2
O
5
-MoO
3
catalysts in butane oxidation as passing through a maximum at 25% MoO
3
, and that a certain catalytic structure consisting of, V
4+
, V
5+
and Mo
6+
ions correspond to their preferred catalyst composition. These results obtained at 500-600° C. indicate low catalyst activity at normal operating temperatures.
Mazzochia, C. R. et al., in “Selective Oxidation of Butane in the Presence of NiO—MoO
3
catalysts”; An. Quim. Ser. A 79, no. 1 108-113(1983) disclose nickel molybdate catalysts prepared by coprecipitation that exhibit low hydrocarbon conversions. At 475° C., 19% conversion of n-butane was noted with low selectivities to maleic anhydride.
Umit Ozkan and G. L. Schrader, in “Synthesis, Characterization and catalytic behaviour of cobalt molybdates for 1-butene oxidation to maleic anhydride”, Applied Catalysis, 23 (1986) 327-338 disclose the use of cobalt molybdate for the oxidation of 1-butene.
In spite of the progress in catalyst and process development over the years, a need still remains for improved non-VPO catalysts useful in the oxidation of C4 hydrocarbons, particularly n-butane, to maleic anhydride and especially catalysts which are active at lower temperatures and have shorter contact times; and it is to that end that the present invention is directed.
SUMMARY OF THE INVENTION
The present invention provides a catalyst. comprising a molybdenum compound of formula I, II, III, IV or V:
V
q
MoA
y
O
z
  I
NiMo
x
B
y
O
z
′  II
VNi
w
Mo
x
C
y
′O
z
″  III
CoNi
w
Mo
x
D
y
O
z
′″  IV
VNi
w
Co
r
Mo
x
E
y
O
z
″″  V
wherein:
q is a number from 0.1 to 10;
r is a number from 0.1 to 10;
w is a number from 0.1 to 10;
x is a number from 0.1 to 10;
y is a number from 0.1 to 10;
y is a number from 0 to 10,
A is at least one cation selected from the group consisting of cations of: Cr, Sb, Co, Ce and Pb;
B is at least one cation selected from the group consisting of cations of: Sb, Al and W;
C is at least one cation selected from the group consisting of cations of: Fe, Zn, Al, Sb, Bi, W, Li, Ba, Nb and Sn;
D is at least one cation selected from the group consisting of cations of: Ba, Mn, Al, Sb, Sn, and W;
E is at least one cation selected from the group consisting of cations of: Fe, Ca, Mn, Sr, Eu, La, Zr, Ga, Sn and Pb; and
z, z′, z″, z′″, and z″″ are determined using the amounts and oxidation states of all cations present in each formula according to the following equations:
z=((q times oxidation state of V)+(1 times oxidation state of Mo)+(y times oxidation state of A)) divided by 2 (oxidation state of oxygen);
z′=((1 times oxidation state of Ni)+(x times oxidation state of Mo)+(y times oxidation state of B)) divided by 2 (oxidation state of oxygen);
z″=((1 times oxidation state of V)+(w times the oxidation state of Ni)+(x times oxidation state of Mo)+(y′ times oxidation state of C)) divided by 2 (oxidation state of oxygen);
z′″=((1 times oxidation state of Co)+(w times the oxidation state of Ni)+(x times oxidation state of Mo)+(y′ times oxidation state of D)) divided by 2 (oxidation state of oxygen); and
z″″=((1 times oxidation state of V)+(w times the oxidation state of Ni)+(r times the oxidation state of Co)+(x times oxidation state of Mo)+(y times oxidation state of E)) divided by 2 (oxidation state of oxygen).
The present invention also provides a process for the oxidation of a C4 hydrocarbon to maleic anhydride, comprising: contacting the C4 hydrocarbon with a source of oxygen in the presence of a catalytic amount of a molybdenum catalyst comprising a compound of formula I, II, III or V, as defined above, to yield maleic anhydride.
The present invention further provides a process for the oxidation of n-butane to maleic anhydride, comprising contacting n-butane with a source of oxygen in the presence of a catalytic amount of a molybdenum catalyst comprising a compound of formula IV, as defined above, wherein the molybdenum catalyst is in a bulk state, to yield maleic anhydride.
The present invention also provides a process for the oxidation of n-butane to maleic anhydride, comprising: contacting n-butane with a source of oxygen in the presence of a catalytic amount of a catalyst comprising a molybdenum compound of formula VI or VII in a crystalline, active phase
V
9
Mo
6
O
40
  VI
V
2
MoO
8
  VII
to yield maleic anhydride.
The present invention also provides a process for the preparation of a molybdenum compound comprising a crystalline oxide of formula I, II, IlI, IV or V, as described above, comprising the steps of: contacting at least one compound having a cation of the molybdenum compound with at least one cation containing compound for each of the other cations of the molybdenum compound in a solution comprising water to form a resultant solution or colloid; freezing the resultant solution or colloid to form a frozen material, freeze drying the frozen material; and heating the dried frozen material to yield the molybdenum compound of formula I, II, III, IV, V, VI or VII.
DETAILED DESCRIPTION OF THE INVENTION
Multicomponent catalyst systems have been identified herein wherein the presence of molybdenum in combination with other particular cations show a significant beneficial effect on catalyst performances compared with many non-VPO catalysts reported in the literature for n-butane oxidation. These new multicomponent catalysts of the present invention comprise a molybdenum compound of formula I, II, III, IV or V:
V
q
MoA
y
O
z
  I
NiMo
x
B
y
O
z
′  II
VNi
w
Mo
x
C
y
′O
z
″  III
CoNi
w
Mo
x
D
y
O
z
′″  IV
VNi
w
Co
r
Mo
x
E
y
O
z
″″  V
wherein: q is a number from 0.1 to 10; r is a number from 0.1 to 10; w is a number from 0.1 to 10; x is a number from 0.1 to 10; y is a number from 0.1 to 10; and y′ is a number from 0 to 10.
A is at least one cation selected from the group consisting of cations of: Cr, Sb, Co, Ce and Pb. A is preferably Sb, and a preferred compound of formula I is V
1
Mo
1
Sb
1
O
z
. B is at least one cation selected from the group consisting of cations of: Sb, Al and W. B is preferably Sb, and a preferred compound of formula II is Ni
1
Mo
2.3
Sb
1
O
z
′. C is at least one cation selected f

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