Note: Descriptions are shown in the official language in which they were submitted.
~ 7~
This invention relates to a supported vanadia catalyst
and the use thereof for the production of nitriles.
United States Patent 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 ratio
of metal oxide to support by weight ranging from about 0.3:1
to abou-t 3 1 substantially enti.rely wi-thin the pcres of the
support. The vanadia is placed in molten form within the pores
of the support which has a surace area greater than about SOm2/
gram and a porosity greater than about 0.4 cc/gram.
The present invention i.s directed to an improvement in
the suppor-ted 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 pro-
vided a catalyst of vanadia supported on a porous support in
an amount to provide a ratio vanadia to support by weight
from about 0.3:1 to about 3:1 substantially entirely within
the pores of the support, with ~.he vanadia having been placed
. 20 in molten form substantially within the pores oE a support
having a surface area greater than 50m2/gram and a porosity greater
- than about 0.4 cc/gram, 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 mole ratio of vanadium metal to alkali
metal from about 2:1 to 30:1~ and preferably from~about 8::L
to 20:1. The alkali metal is preferabl.y sodium.
The support on which the vanadium pentoxide is to ~e supported
has a surface area grea-ter than about 50m2/gram and a porosity
greater than about 0.4 cc/gram. In general, the surface area of
76
is no greater than about 1.2 cc/gram. Supports having a surface
area of about 200m2/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 and alumina, including microcrystalline and the ~ ;
and X modifications of alumina. The silica-alumlna
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 solutlon of the alkali metal hydroxide to provide
the desired amount of alkali metal in the support. The support
containing the alkali metal i9 then mixed with vanadia and heated
to above the fusiorl point of the vanadia to draw the vanadia
into the pores of the support treated wi~h the alkali metal.
Another method for preparing the supported vanadia catalyst
is by a fuslon 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 o vanadia.
Still another method :Eor preparing the supported vanadia '
catalyst is to pre-blend the vanadia and an alkali metal compound,
such as the hydroxide or oxide, in the appropriate amouDts and
to support the resulting blend on the support by fusion.
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 hydro~ide 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
supported mlxture is heated to the vanadia fusion temperature at an
76
average rate oE less than 20F/minute, preferably less than 15F/
minute, with a particularly preferred heating rate being 10F/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,
5 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 withln the pores of the support. In
10 general, the supported mixture is maintained at a temperature
of from 1300F to 1450~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
15 alkali metal is present in the final catalyst as -the alkali metal
vanadate; preferably sodium vanadate. If the hea-tirlg 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
20 an improvement over the fused catalyst without the alkali metal.
Thus, in accordance with -the particularly preferred embodiment,
the catalyst includes bo-th vanadia and alkali metal vanadate,
preferably sodium vanadate. Preferably at least 106 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
ammoxldation is a co~lpound including at least one alkyl group;
namely, aromatic, aliphatic, alicyclic and heterocyclic compounds
having at least one alkyl group.
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q6
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
5 groups in which case the resulting product is a polynitrile.
The alkyl group generally con-tains 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;
10 ethyl benzene, trimethyl benzenes, methyl-naphthalenes, 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
15 acrylonitrile and methacrylonitrile, respectively.
As representative examples of suitable alicyclic compounds,
there may be mentioned: methylcyclopentane, methylcyclohexane,
the alkyl substituted decalins, and the like.
Th~ heterocyclic compounds useful as starting materials
20 for producing nitriles by ammoxidation in accordance with ;the
present invention include alkyl substituted furans, pyrroles,
indoles, thiophenes, pyrazoles r imidazoles, thiazoles, oxazoles,
pyrans, pyridines, quinolines, isoquinolines, pyrimidines,
pyridazines, pyrazines and the llke. The preferred heterocyclic
25 compounds are the alkyl, preferably lower alkyl, substltuted
pyridines, with pyridines having an alkyl group in a beta-
positlon with respect to the heterocycllc nitrogen atom belng
partlcularly preferred ln that such pyrldines can be converted
to nicotinonitrile; in particular, 3-picoline, 2, 3-and 2,5-
30 dimethylpyridlne, 2-methyl-5-ethylpyridlne and 3-ethylpyrldlne.
-- 5
The starting material, con~aining 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 invent:ion, either in the absence
or presence of a gas containing free oxygen, preferably in the
absence of a gas con~aining free oxygen. The contacting is
generally effected at a temperature from about 300C to about
500C, preferably from about 375C to about 475C, 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 of ammonia to starting material generally ranges from
about 2:1 to about 16:1, preferably from about 3:1 to about
8:1. If a gas containing free oxygen 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 ou~side 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 and contacted therein with a gas con-
.
taining free oxygen to effect regeneration of the catalyst,
generally at a time period from about 2 to about 20 minutes.
In general,the supported vanadia catalyst is not maintained on
stream ~or a period greater than about 30 minutes, preferably
from about 2 to about 10 minutes. The supported vanadia catalyst
is then recycled to a nitrile productlon zone. It is believed
-that the supported vanadia catalyst is reduced during the nitrile 30 production step and, consequently, periodic oxidation thereof
is required to maintain the supported vanadia catalyst in the
oxidized form necessary for the nitrile produc~lorl.
The invention wlll be further described with respect to
the following examples:
EXAMPLE I
_
Catalyst A (Present Invention)
3000 g. of silica-alumina fluid bed catalyst suppor~ (Grace
135) was slurried in 4500 g. of 1% by weight of NaO~ and
agitated for 30 minutes. After settling, the supernatant 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 110C, the treated
support contained 0.9 wt. % Na. This support was then blended
with 2000 g. of powdered vanadia and heated at 1500F 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.
_atalyst B
3000 g. of a silica-a:Lumina fluid bed catalyst support (Grace
135) was blended with 2000 g. of powdered vanadia and heated
at 1400F 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.
Catalysts A and B were then employed for the production
of isophthalonitrile under the following conditi.ons. The ammoxi-
dation was effected in the absence of molecular oxygen,
catalysts A and B being regenerated in a separate regenerator
by contact with oxygen.
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7~i
T E I
Catalyst Type B A
Reactor Pressure, PSIG 10 10
Reactor Temp., E` 800 800
Regenerator Temp.,F 910-930 910-930
5 Catalyst circulation, gms/min. 56 53
Organic Feed Rate/cc/min. 3.3 3.4
Feed Composition
m-xylene, wt.% 69 69
M-toluonitrile,w-t.% 31 31
10 NH3 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
15 Ultimate Yield of Isophthalonitrile
Basis m-xylene, mol% 80.7 86.6
Basis ammonia, mol% 27 49
Improved results are obtained by using the catalyst
of the present invention (Catalyst A) as evidenced by increased
20 ammonia and hydrocarbon yielcl.
-- 8 --
EXAMPLE II
3000 g. of a silica-alumina fluid bed catalyst suppor~
(Grace 135) was slurried in 4500 g. of 1% by weight of NaOH
and agitated for 30 minutes. After settling, ~he supernatant
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 110C, the treated
support contained 0.9 wt. % Na. This support was then blended
with 2000 g. of powdered vanadia and heated at the rate of 10F/
minute in a slowly rotating cylindrical kiln to a temperature
of 1400F and maintained at such temperature for 5 hours. After
cooling, the catalyst was removed from the kiln and screened
through a 40 mesh screen.
Tabel II summarizes the results obtained when using this
catalyst for the production of terephthalonitrile from p-xylene
(Run 1) and the production of nicotinonitrile from beta-picoline
(Run 2). The ammoxidation was effected in the absence of
molecular oxygen, with catalysts being regenerated in a separate
regenerator by contact with oxygen.
.
: :
~9_
76
_BLE II
Run 1 Run 2
Reactor Pressure, PSIG 25.0 15.0
Reactor Temp.,F 800 775
Regenerator Temp.,F 935-955 935-955
Catalyst circulation, yms/min. 112.8 73.8
Organic Feed Rate, cc/min. 6.7 8.0
NH3 in feed
mol/mol. organic feed 7.8 5.0
Inert gas in feed
mol/mol. oryanic feed 0.7 0.6
Conversion, mol% 50.67 30.05
-- 10 --
76
In Run 1 the following selectivities and yields were
achieved:
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
In Run 2, the following selectivities and yields were
achieved:
Selectivity, rnole %
Nicotinonitrile 89.66
Pyridine 0.74
Carbon Oxides 9.60
Yields, mole %
Ultimate Organic 89.66
Ammonia 66.70
EXAMPLE III
Two catalysts were prepared as described with reference to
Example II, (40% vanadia and 1% sodium) except that one catalyst
was heated at the rate of :lOF/min. and the second was heated
at a rate of greater than 20Fimin.
Table III summarizes the results obtained when the
catalysts were employed for producing isophthalonitrile from
m-xylene. The amm~oxidatlon was effected in the absence of molecular
oxygen, and the regeneration of the catalyst was effected on
a cyclic basis rather than by continuous circulation of the
catalyst, as in the previous Examples.
TA~LE III
~eating Rate for catalyst, F/min. > 20 10
Temperature, F 800 800
Catalyst Charge, g 400 400
Ca-t/Oil, g/cc 20.8 20 `
5 Pressure, psig 5 5
GHSV (STP),h 1 1040 1242
NH3/Organic, mol/mol 5.4 6
Selectivities, mol%
IPN 56.5 64.9
m-TN 33.9 22.3
BN - 1.7
CO~ 9.5 11.1
Conversion,% 37.2 47.4
Ultimate Yield,% 85.4 83.8
15 Space-Time Yield, g/gh 0.15 0~20
The catalyst produced by slow heating provides an
lmproved selectivity in terms of conversion of methyl group
to ni.trile.
76
The catalyst of the present inventi.on, when employed for
the production of nitriles, provides improved hydrocarbon
selectivity and ammonia yield over the catalyst described in
U.S. Patent 3,963,645. While it is not intended to limit the
scope of the invention, it is believed tha-t the improved
catalytic effect results from a modification of the vanadia
by reaction with the alkali metal at the fusion temperature.
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