Note: Descriptions are shown in the official language in which they were submitted.
CA 02302439 2000-02-28
1
USE OF SHAPED BODIES AS A CATALYST FOR THE PRODUCTION OF
CAPROLACTAM
Specification
The present invention relates to the use of shaped articles
essentially comprising a catalytically active oxide as a catalyst
for preparing cyclic lactams by reacting aminocarbonitriles with
water.
OZ.0050/44458 discloses the use of shaped articles having no
soluble consitutents under the reaction conditions as a catalyst
for preparing cyclic lactams by reacting aminocarbonitriles with
water in the liquid phase in a fixed bed reactor. The catalysts,
which can comprise a multiplicity of oxides, selenides,
tellurides and phosphates, are obtainable, for example, by
extruding powders of the corresponding compounds.
It is true that the shaped articles afford cyclic lactams, but
selectivity and yield are not fully satisfactory, especially at
short residence times which make a high space-time yield possible
and so make it possible to make the reactors smaller.
It is an object of the present invention to provide a method of
using shaped articles having no soluble constituents under the
reaction conditions as a catalyst for preparing cyclic lactams by
reacting aminocarbonitriles with water in the liquid phase in a
fixed bed reactor without the above-described disadvantages.
we have found that this object is achieved according to the
present invention by a method of using shaped articles
essentially comprising a catalytically active oxide as a catalyst
which has no soluble constituents under the reaction conditions
for preparing cyclic lactams by reacting aminocarbonitriles with
water in the liquid phase in a fixed bed reactor, said catalyst
consisting of shaped articles obtainable by shaping the oxide
into shaped articles and, before or after said shaping, treating
the oxide with from 0.1 to 30~ by weight, based on the oxide, of
an acid in which the oxide is sparingly soluble.
preferred embodiments of the method of use of the present
invention are revealed in the subclaims.
The starting materials used in the process of the present
invention are aminocarbonitriles, preferably those of the general
formula I
' 0050/48308 CA 02302439 2000-02-28
- 2
20
R1
HzN - C CHz - C = N (I)
5
Rz
n m
where n and m are each 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 and n + m
totals at least 3, preferably at least 4.
R1 and Rz can in principle be substituents of any type. It is
merely necessary to ensure that the desired cyclization reaction
is not affected by the substituents. Preferably, R1 and Rz are
independently C1-C6-alkyl or C5-C~-cycloalkyl or C6-C1z-aryl.
Particularly preferred starting compounds are aminocarbonitriles
of the general formula
H2N-( CH2 ) m-.-~= N
where m is 3, 4, 5 or 6, especially 5. When m = 5, the starting
compound is 6-aminocapronitrile.
In the process of the present invention, the above-described
aminocarbonitriles are reacted with water in the liquid phase
using heterogeneous catalysts to form cyclic lactams. Use of
aminocarbonitriles of the formula I results in the corresponding
cyclic lactams of the formula II
R1
C -(CHz)m
Rz/ n
/C= O
N
H
where n, m, R1 and Rz are each as defined above. Particularly
preferred lactams are those where n is 0 and m is 4, 5 or 6,
especially 5 (caprolactam being obtained in the latter case).
The reaction is carried out in the liquid phase at generally from
140 to 320~C, preferably at from 160 to 280~C; the pressure is
generally within the range from 1 to 250 bar, preferably from 5
to 150 bar, it being necessary to ensure that the reaction
' 0050/48308 CA 02302439 2000-02-28
3
mixture is predominantly liquid under the conditions employed.
The residence times are generally within the range from 1 to 120,
preferably 1 to 90, and especially 1 to 60, min. In some cases,
residence times of from 1 to 10 min have proven to be completely
adequate.
The amount of water used per mole of a~ninocarbonitrile is
generally at least 0.01 mol, preferably within the range from 0.1
to 20 mol, especially within the range from 1 to 5 mol.
The aminocarbonitrile is advantageously used in the form of a
from 1 to 50% strength by weight, especially from 5 to 50%
strength by weight, particularly preferably from 5 to 30%
strength by weight, solution in water (in which case the solvent
is also reactant) or in water/solvent mixtures. Examples of
usable solvents are alkanols such as methanol, ethanol, n- and
i-propanol, n-, i- and t-butanol and polyols such as diethylene
glycol and tetraethylene glycol, hydrocarbons such as petroleum
ether, benzene, toluene, xylene, lactams such as pyrrolidone or
caprolactam, or alkyl-substituted lactams such as N-methyl-
pyrrolidone, N-methylcaprolactam or N-ethylcaprolactam, and also
carboxylic esters, preferably of carboxylic acids having from 1
to 8 carbon atoms. Ammonia can also be present in the reaction.
Mixtures of organic solvents can also be used. Mixtures of water
and alkanols in a water/alkanol weight ratio of 1-75/25-99,
preferably 1-50/50-99, have been found to be particularly
advantageous in some cases.
It is in principle equally possible to use the aminocarbonitriles
as solvent as well as reactant.
The catalytically active oxides used can be, for example, acidic,
amphoteric or basic oxides, preferably aluminum oxide, such as
alpha- or gamma-alumina, tin oxide, zinc oxide, cerium oxide,
especially titanium dioxide, amorphous, as anatase or rutile, and
also their mixtures and mixed phases.
The aforementioned compounds can be doped with, or comprise,
compounds of main groups 1 to 7, especially 2, 3 or 4, of the
periodic table, of transition groups 1 to 7 of the periodic
table, of the elements of the iron group or of the lanthanides or
actinides and also mixtures thereof.
If desired, these catalysts may comprise up to 50% by weight in
each case of copper, tin, zinc, manganese, iron, cobalt, nickel,
ruthenium, palladium, platinum, silver or rhodium.
005048308 CA 02302439 2000-02-28
4
These catalytically active oxides are preparable in a
conventional manner, for example by hydrolysis of the
corresponding organics, alkoxides, salts with organic or
inorganic acids and subsequent heating or calcining and also
advantageously, especially in the case of titanium dioxide,
pyrogenically and are generally commercially available.
According to the invention, the oxides are treated with an acid
before or after shaping. Suitable acids include organic acids
such as acetic acid, oxalic acid, propionic acid, butyric acid,
malefic acid or inorganic acids such as isopolyacids,
heteropolyacids, sulfuric acid or hydrochloric acid. Particularly
suitable catalysts are obtainable by treatment with acetic acid,
formic acid, nitric acid, especially phosphoric acid or
polyphosphoric acid.
It is also possible to use mixtures of acids.
The treatment can be carried out continuously or batchwise in one
or more stages. The individual stages can be carried out with the
same acid, different acids or identical or different mixtures of
acids.
Similarly, the oxides can be treated with an acid in the form
mentioned before and after shaping.
Preferably, the oxides are treated with an acid before shaping.
The amount of acid used according to the invention is from 0.1 to
30%, preferably from 0.1 to 10%, especially from 0.1 to 5%, by
weight, reckoned as pure acid, based on pyrogenic titanium
dioxide. The acid can be mixed with a liquid diluent, such as
~,rater.
The catalysts can be prepared from the oxides without additives.
It is similarly possible to add additives such as binders, for
example titanium dioxide sols, salts of the oxides used, soluble
titanium salt compounds, hydrolyzable titanium compounds such as
titanium alkoxides or aluminum salts, such as pore-formers, for
example methylcellulose, carbon fibers, fibers of organic
polymers, melamine, starch powder, preferably before shaping.
The shaped articles can be present in various forms, for example
as ball, tablet, cylinder, hollow cylinder, pellet, granule or
strand. Such shaped articles are preparable in a conventional
manner using appropriate shaping machines such as tableting
005048308 CA 02302439 2000-02-28
machines, extruders, rotary granulators, pelletizers or
combinations thereof.
The shaped material, if desired after an acid treatment, is
5 advantageously dried, especially at from 20 to 120~C, preferably
in an inert gas atmosphere or in the air, and then calcined,
especially at 400-700~C, preferably in an inert gas atmosphere or
in the air.
The heterogeneous catalysts are arranged in a fixed bed. The
reaction can take place in a conventional manner, for example in
a downflow or preferably upflow mode, especially continuously, by
bringing the reaction mixture into contact with the catalyst bed.
The advantage of the process of the present invention is the
possibility to operate the cyclization continuously in a simple
manner with very high throughputs and high yields and
selectivities and short residence times. Since the catalysts used
have a long lifetime from observations to date, the result is an
extremely low catalyst consumption.
Example 1: Preparation of pyrogenic titanium dioxide extrudates
(formic acid)
8350 g of pyrogenic titanium dioxide powder having a
rutile/anatase ratio of 80/20 were kneaded for 3 hours with 47 g
of 85% strength formic acid and 3750 g of water and thereafter
molded into 4 mm extrudates under a molding pressure of 70 bar.
The extrudates were dried at 120~C for 16 hours and then calcined
at 500~C for 3 hours.
Analysis of extrudates:
Density 989 g/1
Water regain 0.31 ml/g
Cutting hardness 25 N
Surface area 37 m2/g
Example 2: Preparation of pyrogenic titanium dioxide extrudates
(phosphoric acid)
1950 g of precipitated titanium dioxide powder (anatase) were
kneaded for 3 hours with 60 g of concentrated phosphoric acid and
900 g of water and then molded into 1.5 mm extrudates under a
molding pressure of 70 bar. The extrudates were dried at 120~C for
6 hours and then calcined at 350~C for 5 hours.
0050/48308 CA 02302439 2000-02-28
6
Analysis of extrudates:
Density 722 g/1
Water regain 0.46 ml/g
Surface area 204 m2/g
Example 3: Preparation of gyrogenic titanium dioxide extrudates
(nitric acid)
11,000 g of precipitated titanium dioxide powder (anatase) were
kneaded for 2 hours with 420 g of concentrated phosphoric acid
and 3650 g of water and then molded into 3 mm extrudates under a
molding pressure of 70 bar. The extrudates were dried at 120~C for
6 hours and then calcined at 320~C for 2 hours and at a 350~C for
a further 3 hours.
Analysis of extrudates:
Density 919 g/1
Water regain 0.32 ml/g
Cutting hardness 25 N
Surface area 105 m2/g
Examples 4 to 16: Conversion of 6-aminocapronitrile into
caprolactam
A solution of 6-aminocapronitrile (ACN) in water and ethanol in
the weight ratios reported in the table was passed into a 25 ml
capacity heated tubular reactor (diameter 6 mm; length 800 mm)
packed with catalysts 1 to 4 recited in the table, in the form of
granules. The product stream leaving the reactor was analyzed by
gas chromatography. The results are recited in the table as
examples.
As well as caprolactam, the product stream comprises essentially
ethyl g-aminocaprylate and ~-aminocaprylamide. Both can likewise
be cyclized to form caprolactam. In addition, the stream includes
from 5 to 8~ of caprolactam oligomer which can be cracked to form
caprolactam monomer.
45
0050/48308
CA 02302439 2000-02-28
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0050/48308 CA 02302439 2000-02-28
8
Catalysts 1 to 4 were prepared similarly to catalyst examples 1
to 3:
Catalyst 1: Precipitated titanium dioxide extruded with 3%
of phosphoric acid as 3 mm extrudates and then
ground to granules Z.0-1.5 mm in size
Catalyst 2: Precipitated titanium dioxide extruded with 3%
of phosphoric acid as 3 mm extrudates
Catalyst 3: Pyrogenic titanium dioxide extruded with 3% of
phosphoric acid as 4 mm extrudates and then
ground to granules 1.6-2.0 mm in size
Catalyst 4: Pyrogenic titanium dioxide extruded with 0.5% of
formic acid as 4 mm extrudates and then ground
to granules 1.6-2.0 mm in size
25
35
45
