Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-12-14
2001-06-26
Geist, Gary (Department: 1623)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
Reexamination Certificate
active
06251821
ABSTRACT:
The present invention relates to the manufacture of acrolein from propylene by oxidation according to a redox reaction. The invention also relates to the use of a solid mixed oxide composition as redox system in the said reaction.
At the present time acrolein is industrially produced by vapour phase catalytic oxidation of propylene. All the attempts to improve this process have hitherto been concerned with the development of catalysts which give the highest possible conversion of propylene and the highest possible selectivity for the desired acrolein.
Thus, French Patent No. 2 093 773 describes the manufacture of acrolein by vapour phase catalytic oxidation of propylene with molecular oxygen in the presence of an oxide catalyst in which the composition of the catalytic elements, expressed as atomic ratio, is the following:
Co
2.0-20.0
Fe
0.1-10.0
Bi
0.1-10.0
W
0.5-10.0
Mo
2.0-11.5
Si
0.5-15.0
Z
0.005-1.0
with W+Mo=12.0 and Z denoting an alkali metal. This catalyst can be prepared by mixing aqueous solutions of ammonium molybdate and of ammonium paratungstate, adding solutions of cobalt nitrate, of iron nitrate and of bismuth nitrate to the aqueous mixture and then adding an aqueous solution of an alkali metal hydroxide or carbonate and then colloidal silica as a source of silicon, by moulding the substance obtained and by calcining it at 350-600° C. in a stream of air.
U.S. Pat. No. 3,855,308 describes the preparation of acrolein by vapour phase catalytic oxidation of propylene with molecular oxygen in the presence of an oxide catalyst in which the composition of the catalytic elements, expressed as atomic ratio, is the following:
Co
2.0-20.0
Fe
0.1-10.0
Bi
0.1-10.0
W
0.5-10.0
Mo
2.0-11.5
Si
0.5-15.0
Tl
0.005-3.0
Z
0-3.0
with W+Mo=12.0 and Z denoting an alkali metal or alkaline-earth metal.
The raw materials employed for forming the catalyst may be the oxides of the various metals, but also, depending on circumstances, the nitrates, carbonates or hydroxides. In the case of Mo and W, the salts of acids, such as ammonium molybdate and ammonium tungstate, are recommended. Thus, according to this U.S. patent a catalyst is prepared by mixing aqueous solutions of ammonium molybdate and of ammonium paratungstate respectively, by adding solutions of cobalt nitrate, of iron nitrate and of bismuth nitrate respectively, and then an aqueous solution of alkali metal hydroxide or carbonate and then colloidal silica as a source of silicon, by concentrating the system by evaporation, by adding a support if necessary and by following with an evaporation, a mixing of the resulting substance and a calcination at 350-600° C.
Japanese Patent Showa 45-125 359 describes a vapour phase process for the manufacture of acrolein by catalytic oxidation of propylene with air or oxygen in the presence of a catalyst of formula:
Ni
a
Co
b
Fe
c
Bi
d
Me
e
H
h
Mo
f
O
g
in which:
a=0-20, b=0-20 with a+b between 0.5 and 20, c=0.5-8, d=0.1-7, 0<e≦2, h=0-0.3, f=12, g=36-90;
Me is one out of Sn, Zn, W, Cr, Mn and Ti; and
H is at least one out of K, Rb and Cs.
To prepare this catalyst, aqueous solutions of Ni, Co, Fe, K (and/or Rb, Cs), Bi and Me compounds may be added to an aqueous solution of a molybdenum compound (ammonium molybdate, molybdic acid or molybdenum oxide), then a support such as alumina, silicon carbide and silica (silica sol or silica gel) may be added and then the resulting mixture is heated to dryness, is calcined at approximately 500° C. and is converted into pastilles.
The Applicant Company has now discovered that acrolein can be manufactured by gas phase oxidation of propylene in the absence of molecular oxygen by passing propylene over a particular solid mixed oxide composition which acts as a redox system and supplies the oxygen necessary for the reaction.
The advantages of this new process are the following:
the limitation of the overoxidation of the products formed, which takes place in the presence of molecular oxygen; according to the present invention, since the operation is carried out in the absence of molecular oxygen, the formation of CO
x
(carbon monoxide and carbon dioxide), degradation products, is reduced, and this allows the selectivity for acrolein to be increased, as shown hereinafter by the Comparative Examples 4, 8, 12 and 16;
the selectivity for acrolein remains good when the degree of reduction of the solid composition increases;
once it has undergone a reduction and a gradual loss of its activity, the solid composition can be easily regenerated by heating in the presence of oxygen or of an oxygen-containing gas after a certain period of use; after the regeneration the solid recovers its initial activity and can be employed in a new reaction cycle;
the separation of the stages of reduction of the solid composition and of its regeneration makes it possible:
to increase the selectivity for acrolein; and
to increase the partial pressure of propylene, such a partial pressure of propylene feed no longer being limited by the existence of an explosive region of the propylene+oxygen mixture.
The subject-matter of the present invention is therefore firstly the use of a solid mixed oxide composition of formula (I):
Mo
12
W
a
Bi
b
Fe
c
Co
d
Ni
e
Si
f
K
g
Sn
h
O
x
(I)
in which:
a is between 0 and 5, limits included,
b is between 0.5 and 5, limits included,
c is between 0.1 and 10, limits included,
d is between 0.5 and 10, limits included,
e is between 0 and 10, limits included,
f is between 0 and 15, limits included,
g is between 0 and 1, limits included,
h is between 0 and 2, limits included, and
x is the quantity of oxygen bonded to the other elements and depends on their oxidation states, in the manufacture of acrolein by propylene oxidation, the said solid composition reacting with the propylene according to the redox reaction (1):
solid
oxidiszd
+propylene→solid
reduced
+acrolein (1).
The oxides of the various metals forming part of the composition of the mixed oxide of formula (I) can be employed as raw materials in the preparation of this composition, but the raw materials are not restricted to the oxides; other raw materials which may be mentioned are:
in the case of molybdenum, ammonium molybdate and molybdic acid and, in the case of tungsten, ammonium tungstate and tungstic acid,
in the case of cobalt, bismuth, nickel and iron, the nitrates, carbonates and hydroxides, such as cobalt nitrate, bismuth nitrate, nickel nitrate and ferric nitrate,
in the case of tin, tin chloride and tin hydroxide, and
in the case of potassium, potassium hydroxide, carbonate or nitrate,
and, in general, any compounds capable of forming an oxide by calcination, namely metal salts of organic acids, metal salts of inorganic acids, metal complex compounds, organometallic compounds and the like.
The source of silicon generally consists of colloidal silica.
The subject-matter of the present invention is a process for the manufacture of acrolein from propylene, according to which process gaseous propylene is passed over a solid composition of formula (I) as defined above, to conduct the redox reaction (1) as indicated above, while operating at a temperature of 200 to 600° C., especially from 250 to 450° C., at a pressure of 1.01×10
4
to 1.01×10
6
Pa (0.1 to 10 atmospheres), especially of 5.05×10
4
to 5.05×10
5
Pa (0.5-5 atmospheres), and with a residence time of 0.01 second to 90 seconds, especially of 0.1 second to 30 seconds, in the absence of molecular oxygen.
In accordance with particular embodiments of the present invention the gaseous propylene may be introduced as a mixture with an inert gas such as nitrogen and/or with water (water vapour).
During the redox reaction (1) the solid composition undergoes a reduction and a progressive loss of its activity. This is why, once the solid composition has changed to the reduced state, regeneration of the said solid composition is conducted according to reaction (2):
solid
reduced
+O
2
→solid
o
Descat Gilles
Etienne Eric
Hecquet Gerard
Schirmann Jean-Pierre
Simon Michel
Deemie Robert W.
Geist Gary
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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