Supported vanadia catalyst for nitrile production and process for preparing the catalyst

Vanadia supported on a silica-alumina or gamma-alumina support in an amount to provide a vanadia to support weight ratio ranging from about 0.3:1 to about 3:1 substantially entirely within the pores of the support, the vanadia having been placed in molten form substantially within the pores of a support having a surface area greater than about 50m.sup.2 gram, a porosity greater than about 0.4 cc/gram which further includes an alkali metal, with the vanadium metal to alkali metal mole ratio being from 2:1 to 30:1. At least a portion of the alkali metal is preferably in the form of alkali metal vanadate. The catalyst is used for the production of nitriles from a compound containing at least one alkyl group.

This invention relates to a supported vanadia catalyst and the use thereof 
for the production of nitriles. 
U.S. Pat. No. 3,963,645 discloses a supported vanadia catalyst wherein the 
vanadia is supported on a silica-alumina or gamma-alumina support in an 
amount to provide a metal oxide to support weight ratio ranging from about 
0.3:1 to about 3:1 substantially entirely within the pores of the support, 
with the vanadia having been placed in molten form within the pores of the 
support which has a surface area greater than about 50m.sup.2 /gram and a 
porosity greater than about 0.4 cc/gram. The supported vanadia catalyst is 
particularly suitable for the production of nitriles by oxidative 
ammonolysis (ammoxidation). The present invention is directed to an 
improvement in the supported vanadia catalyst of the aforesaid patent, and 
the use of such an improved catalyst for the production of nitriles. 
In accordance with the present invention, there is provided a catalyst of 
vanadia supported on a porous support in an amount to provide a vanadia to 
support weight ratio ranging from about 0.3:1 to about 3:1 substantially 
entirely within the pores of the support, with the vanadia having been 
placed in molten form substantially within the pores of a support having a 
surface area greater than about 50m.sup.2 /gram, a porosity greater than 
about 0.4 cc/gram, with the catalyst further containing an alkali metal in 
an amount to increase the catalytic effect of the catalyst. 
More particularly, the catalyst includes an alkali metal which is either 
lithium, sodium, potassium, rubidium or cesium, in an amount to provide a 
vanadium metal to alkali metal mole ratio of from about 2:1 to 30:1, and 
preferably from about 8:1 to 20:1. The alkali metal is preferably sodium. 
The support on which the vanadium pentoxide is to be supported has a 
surface area of greater than about 50m.sup.2 /gram and a porosity greater 
than about 0.4 cc/gram. In general, the surface area of the support is no 
greater than about 600m.sup.2 /gram and the porosity is no greater than 
about 1.2 cc/gram. Supports having a surface area of about 200m.sup.2 
/gram have been found to provide particularly good results. As 
representative examples of preferred supports having such properties there 
may be mentioned: silica-alumina, zeolites, alumina, including 
microcrystalline and .gamma., .delta., .eta., .kappa. and .chi. 
modifications of alumina. The silica-alumina and gamma-alumina supports 
are particularly preferred. 
The fused supported vanadia catalyst which is promoted with an alkali metal 
may be conveniently prepared by mixing the support with an aqueous 
solution of the alkali metal hydroxide to provide the desired amount of 
alkali metal in the support. The support containing the alkali metal is 
then mixed with vanadia and heated to above the fusion point of the 
vanadia to draw the vanadia into the pores of the alkali metal treated 
support. 
As an alternative, the supported vanadia catalyst may be prepared by a 
fusion technique without initial treatment of the support with an alkali 
metal, followed by impregnation of the supported vanadia catalyst with an 
aqueous solution of the alkali metal hydroxide to provide the required 
amount of alkali metal, and heating to above the fusion point of vanadia. 
As another alternative, the vanadia and an alkali metal compound such as 
the hydroxide or oxide, may be preblended in the appropriate amounts by 
procedures known in the art and the resulting blend supported on the 
support by the fusion technique. 
The general technique for supporting the vanadium pentoxide within the 
pores of a porous support is described in U.S. Pat. No. 3,963,645. 
In accordance with a preferred embodiment of the present invention, a 
particularly active form of the catalyst is produced by providing a 
mixture of alkali metal hydroxide and vanadia on the support and heating 
the supported mixture to the fusion temperature of the vanadia at a 
controlled heating rate. More particularly, the average rate of less than 
20.degree. F/minute, preferably less than 15.degree. F/minute, with a 
particularly preferred heating rate being 10.degree. F/minute or less. 
Thus, in general, the supported mixture is heated up to the fusion 
temperature over a time period of at least 1 hour, with particularly good 
results being achieved over a period of 2 hours or more. 
The supported mixture is maintained at or above the fusion temperature for 
a time sufficient to place the vanadia substantially entirely within the 
pores of the support. In general, the supported mixture is maintained at a 
temperature of from 1300.degree. F to 1450.degree. F for a time period of 
from 1 to 10 hours. 
In preparing the catalyst in accordance with the preferred procedure, i.e., 
controlled heating of vanadia and alkali metal hydroxide on the support, 
at least a portion of the alkali metal is present in the final catalyst as 
the alkali metal vanadate; preferably sodium vanadate. If the heating to 
fusion temperature is effected at a more rapid rate, alkali metal vanadate 
is not formed and such a catalyst has been found to be less selective for 
the production of nitriles, even though it is an improvement over the 
fused catalyst without the alkali metal. Thus, in accordance with the 
particularly preferred embodiment, the catalyst includes both vanadia and 
alkali metal vanadate, preferably sodium vanadate. In general, at least 
10% by weight of the alkali metal is present as the vanadate. 
The supported vanadia catalyst of the present invention is particularly 
suitable for the production of nitriles by oxidative ammonolysis 
(ammoxidation). The organic reactant employed as a starting material for 
the production of nitriles by ammoxidation is a compound including at 
least one alkyl group; namely aromatic, aliphatic, alicyclic and 
heterocyclic compounds having at least one alkyl group. 
As representative examples of alkyl substituted aromatic hydrocarbons which 
are suitable as starting materials, there may be mentioned the alkyl 
substituted benzenes and naphthalenes, and in particular, benzene which 
may contain two or more alkyl groups in which case the resulting product 
is a polynitrile. The alkyl group generally contains no more than 4 carbon 
atoms, preferably no more than 2 carbon atoms. As particular examples of 
suitable alkyl substituted aromatic hydrocarbons, there is: toluene; 
various xylenes to produce the various phthalonitriles; ethyl benzene, 
trimethyl benzenes, methylnaphthalenes, durene and the like. 
As representative examples of suitable aliphatic compounds, there may be 
mentioned: olefinic hydrocarbons having at least one alkyl group, such as 
propylene and isobutylene to produce acrylonitrile and methacrylonitrile, 
respectively. 
As representative examples of suitable alicyclic compounds, there may be 
mentioned: methylcyclopentane, methylcyclohexane, the alkyl substituted 
decalins, and the like. 
The heterocyclic compounds useful as starting materials for producing 
nitriles by ammoxidation in accordance with the present invention include 
alkyl substituted furans, pyrroles, indoles, thiophenes, pyrazoles, 
imidazoles, thiazoles, oxazoles, pyrans, pyridines, quinolines, 
isoquinolines, pyrimidines, pyridazines, pyrazines and the like. The 
preferred heterocyclic compounds are the alkyl, preferably lower alkyl, 
substituted pyridines, with pyridines having an alkyl group in a 
beta-position with respect to the heterocyclic nitrogen atom being 
particularly preferred in that such pyridines can be converted to 
nicotinonitrile; in particular, 3-picoline, 2,3-and 2,5-dimethylpyridine, 
2-methyl-5-ethylpyridine and 3-ethylpyridine. 
The starting material, containing at least one alkyl group is converted to 
a nitrile by contacting the starting material with ammonia, in the vapor 
phase, in the presence of the supported vanadia catalyst of the present 
invention, either in the absence or presence of a free oxygen containing 
gas, preferably in the absence of a free oxygen containing gas. The 
contacting is generally effected at a temperature from about 300.degree. C 
to about 500.degree. C, preferably from about 375.degree. C to about 
475.degree. C, with the contact time generally ranging from about 0.5 to 
about 15 seconds, preferably from about 2 to about 8 seconds. Reaction 
pressures generally range from about 1 to about 5 atmospheres. The mole 
ratio ammonia to starting material generally ranges from about 2:1 to 
about 16:1, preferably from about 3:1 to about 8:1. If an 
oxygen-containing gas is employed in the feed, the gas is employed in an 
amount such that the quantity of oxygen and starting material in the feed 
is outside of the explosive range. 
In accordance with the preferred embodiment of the invention, the starting 
material and ammonia are contacted with the supported vanadia catalyst of 
the present invention in the absence of oxygen, with the supported vanadia 
catalyst being periodically passed to another reactor (in general the 
supported vanadia catalyst is not maintained on stream for a period 
greater than about 30 minutes, preferably from about 2 to about 10 
minutes), and contacted therein with a free oxygen containing gas to 
effect regeneration of the catalyst, generally at a time period from about 
2 to about 20 minutes. The supported vanadia catalyst is then recycled to 
a nitrile production zone. It is believed that the supported vanadia 
catalyst is reduced during the nitrile production step and, consequently, 
periodic oxidation thereof is required to maintain the supported vanadia 
catalyst in the oxidized form necessary for the nitrile production. 
The invention will be further described with respect to the following 
examples; however, it is to be understood that the scope of the invention 
is not to be limited thereby.

EXAMPLE I 
Catalyst A (Present Invention) 
3000 g. of silica-alumina fluid bed catalyst support (Grace 135) was 
slurried in 4500g. of 1wt.% NaOH and agitated for 30 minutes. After 
settling, the supernatent liquid was decanted and replaced with 4500g. of 
water, and the mixture agitated for another 30 minutes. The mixture was 
again separated by decantation. After drying at 110.degree. C, the treated 
support contained 0.9 wt.% Na. This support was then blended with 2000g. 
of powdered vanadia and heated at 1400.degree. F for 5 hours in a slowly 
rotating cylindrical kiln. After cooling, the catalyst was removed from 
the kiln and screened through a 40 mesh screen. 
Catalyst B 
3000 g. of a silica-alumina fluid bed catalyst support (Grace 135) was 
blended with 2000g. of powdered vanadia and heated at 1400.degree. F for 5 
hours in a slowly rotating cylindrical kiln. After cooling, the catalyst 
was removed from the kiln and screened through a 40 mesh screen. 
Catalyst A and B were then employed for the production of isophthalonitrile 
under the following conditions. The ammoxidation was effected in the 
absence of molecular oxygen with catalysts A and B being regenerated in a 
separate regenerator by contact with oxygen. 
TABLE I 
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Catalyst Type B A 
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Reactor Pressure, PSIG 
10 10 
Reactor Temp., .degree. F 
800 800 
Regenerator Temp., .degree. F 
910-930 910-930 -Catalyst circulation, 
gms/min. 56 53 
Organic Feed Rate/cc/min. 
3.3 3.4 
Feed Composition 
m-xylene, wt.% 69 69 
M-toluonitrile, wt.% 
31 31 
NH.sub.3 in feed 
mol/mol. organic feed 
9.1 8.8 
Inert gas in feed 
mol/mol. organic feed 
9.4 8.9 
Conversion, mol % 52.5 41.5 
Ultimate Yield of Isophthalonitrile 
Basis m-xylene, mol% 
80.7 86.6 
Basis ammonia, mol% 27 49 
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Improved results are obtained by using the catalyst of the present 
invention (Catalyst A) as evidenced by increased ammonia and hydrocarbon 
yield. 
EXAMPLE II 
Catalyst A (Present Invention) 
3000 g. of a silica-alumina fluid bed catalyst support (Grace 135) was 
slurried in 4500g. of 1wt.% NaOH and agitated for 30 minutes. After 
settling, the supernatent liquid was decanted and replaced with 4500 g. of 
water, and the mixture agitated for another 30 minutes. The mixture was 
again separated by decantation. After drying at 110.degree. C, the treated 
support contained 0.9 wt.% Na. This support was then blended with 2000 g. 
of powdered vanadia and heated at a rate of 10.degree. F/minute in a 
slowly rotating cylindrical kiln to a temperature of 1400.degree. F and 
maintained at such temperature for 5 hours. After cooling, the catalyst 
was removed from the kiln and screened through a 40 mesh screen. 
Catalyst B 
In Runs A & B, the catalyst is employed for production of 
terephthalonitrile from p-xylene, and nicotinonitrile from beta-picoline, 
respectively. The ammoxidation was effected in the absence of molecular 
oxygen, with catalysts being regenerated in a separate regenerator by 
contact with oxygen. 
TABLE II 
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A B 
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Reactor Pressure, PSIG 
25.0 15.0 
Reactor Temp., .degree. F 
800 775 
Regenerator Temp., .degree. F 
935-955 935-955 
Catalyst circulation, gms/min. 
112.8 73.8 
Organic Feed Rate, cc/min. 
6.7 8.0 
NH.sub.3 in feed 
mol/mol. organic feed 
7.8 5.0 
Inert gas in feed 
mol/mol. organic feed 
0.7 0.6 
Conversion, mol% 50.67 30.05 
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In Run A the following selectivities and yields are achieved: 
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Selectivity mole % 
Terephthalonitrile 
93.53 
p-tolunitrile 0.00 
benzonitrile 0.04 
carbon oxides 6.43 
Yields, mole % 
Ultimate Organic 
93.53 
Ammonia 65.71 
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In Run B, the following selectivities and yields are achieved: 
______________________________________ 
Selectivity, mole % 
Nicotionitrile 89.66 
Pyridine 0.74 
Carbon Oxides 9.60 
Yields, mole % 
Ultimate Organic 
89.66 
Ammonia 66.70 
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EXAMPLE III 
Two catalysts are prepared as described with reference to Example II, (40% 
vanadia and 1% sodium) except that one catalyst was heated at the rate of 
10.degree. F/min. and the second at a rate of greater than 20.degree. 
F/min. 
In Runs A and B of Table III the catalysts are employed for producing 
isophthalonitrile from m-xylene. The ammoxidation is effected in the 
absence of molecular oxygen, and regeneration of the catalyst is effected 
on a cyclic basis rather than by continuous circulation of the catalyst, 
as in the previous examples. 
TABLE III 
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Run A B 
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Heating Rate for catalyst, .degree. F/min. 
&gt;20 10 
Temperature, .degree. F 
800 800 
Catalyst Charge, g 400 400 
Cat/Oil, g/cc 20.8 20 
Pressure, psig 5 5 
GHSV (STP), h.sup.-1 1040 1242 
NH.sub.3 /Organic, mol/mol 
5.4 6 
Selectivities, mol % 
IPN 56.5 64.9 
m-TN 33.9 22.3 
BN -- 1.7 
CO.sub.x 9.5 11.1 
Conversion, % 37.2 47.4 
Ultimate Yield, % 85.4 83.8 
Space-Time Yield, g/gh 0.15 0.20 
______________________________________ 
The catalyst produced by slow heating provides improved selectivity in 
terms of conversion of methyl group to nitrile. 
The present invention is an improvement over the catalyst of U.S. Pat. No. 
3,963,645 in that the catalyst of the present invention, when employed for 
the production of nitriles, provides improved hydrocarbon selectivity and 
ammonia yield. Although Applicant does not intend to be limited by 
theoretical reasoning, it is believed that the improved catalytic effect 
results from a modification of the vanadia by reaction with the alkali 
metal at the fusion temperature. 
Numerous modifications and variations of the present invention are possible 
in light of the above teachings and, therefore, within the scope of the 
appended claims, the invention may be practiced otherwise than as 
particularly described.