Note: Descriptions are shown in the official language in which they were submitted.
CA 02388881 2002-04-24
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METHOD FaR -PA~D'UC~~TG AN AI~Ct3H~ AN AI~KENE
The present invention relates to a process for preparing an alcohol from an
alkene
by hydration of the alkene by means of a zeolitic catalyst having an MCM-22,
MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or more of
these structures. The present invention also relates to an integrated process
for
preparing an alcohol in which unreacted starting material is recycled to the
process.
It is known from the prior art that alkenes can be hydrated to alcohols using
acid
catalysts. Examples of such catalysts are described, for example, in Tanabe et
al.,
Stud. Surf. Sci. Catal. 51 (19$9), pp. 247-254. There, Si02-A1203, inter alia,
is
disclosed as catalyst for the hydration of ethene to ethanol. However, low
selectivity and therefore the formation of undesirable by-products are
mentioned as
disadvantages of this catalyst. This publication likewise discloses cation-
exchange
zeolites of type A and Y as catalysts far the preparation of ethanol, with
type A,
which comprises Mg, Ca, Cd, Zn, etc., allowing no by-product formation while,
on
the other hand, type Y makes it possible for by-products to be formed.
Specifically for the liquid-phase hydration of cyclohexene to cyclohexanol,
Ishida,
2 0 Catalysis Surveys of Japan 1 (1997), pp. 241-246, makes a closer
examination of
zeolites of the type ZSM-5, ZSM-11, ZSM-12, ZSM-35, mordenite and Y, with
ZSM-5 and ZSM-11 being mentioned as those catalysts which display acceptable
by-product formation.
DE-A 34 41 072 discloses a process for preparing cyclic alcohols by catalytic
hydration of cyclic olefins, in which the catalyst used is a zeolite having a
population ratio of acid sites on the outer surface to the total number of
acid sites
of 0.07 or more. Examples disclosed are, inter alia, zeolites, and examples of
zeolites disclosed are in turn mordenite, faujasite, clinoptilolite, zeolite
L, zeolites
of the ZSM type, chabazite and erionite.
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However, a disadvantage of these processes is that satisfactory conversions
are
achieved only when using extremely finely particulate zeolites which are
difficult
to remove from the reaction mixture. A pertinent improvement is described in
EP-
B 0 634 361. This patent discloses a specific agglomeration of pentasil
zeolite
particles which combines the advantages of high catalytic activity with ready
reparability. However, the method of producing these agglomerates requires an
outlay in terms of apparatus which may be undesirable.
It is an object of the present mention to provide a process for-preparing an
alcohol
from an alkene which does not have the abovementioned disadvantages.
We have found that this object is achieved by hydrating alkenes using a
zeolite
having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture
of two or more of these structures as heterogeneous catalyst.
A zeolite of the structure MCM-22 is described, fvr example, in Kennedy et
al., J.
Am. Chem. Soc. 116 (1994), pp. 10000-10003, or in Leonowicz et al., Science
264
( 1994), pp. 1910-1913.
The present invention accordingly provides a process for preparing at least
one
alcohol, in which
(i) at least one alkene is hydrated in the presence of water by the bringing
into
2 5 contact with at least one catalyst to form an alcohol or alcohols,
wherein the heterogeneous catalyst or catalysts comprises/comprise a zeolitic
catalyst having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a
mixture of two or more of these structures.
Zeolites are, as is known, crystalline aluminosilicates having ordered channel
and
cage structures which have micropores. The term "micropores" as used for the
purposes of the present invention corresponds to the definition in Pure Appl.
Chem. 57 (1985), pp. 603-619, and refers to pores having a pore diameter of
less
3 5 than 2 nm. The network of such zeolites is built up of Si04 and A104
tetrahedra
which are cormected via joint oxygen bridges. An overview of these structures
may
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be found, for example, in W.M. Meier, D.H. Olson and Ch. Baerlocher in Atlas
of
Zeolite Structure Types, Elsevier, 4th edition, London 1996.
The zeolitic catalyst used according to the present invention which has an MCM-
22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or more of
these structures can here be prepared by all suitable methods of the prior
art. For
example, it can be prepared by a method described, for example, in US
4,954,325
or US 5,354,718.
In particular, the catalysts according to the present invention have an Si:AI
ratio in
the range from 10 to 1000, particularly preferably in the range from 10 to 100
and
more preferably in the range from 10 to 50.
The specific surface area. of the zeolites used according to the present
invention,
determined by the Langmuir method, is preferably in the range from 400 to
1000 m2/g, more preferably in the range from 450 to 850 m2/g and particularly
preferably in the range from 500 to 750 m2/g.
One of the advantages offered by, for example, the type MCM-22 used according
to the present invention is that zeolites of this type are, owing to their
2 0 crystallization form, obtained as agglomerates of thin platelets and
accordingly
have a high activity per unit mass.
It is also conceivable for the zeolite used according to the present invention
to
comprise further elements. For example, it preferably comprises at least one
2 5 element of transition groups I, II and VIII. The present invention
therefore also
provides a process as described above in which the zeolitic catalyst or
catalysts
comprises/comprise at least one element of transition group I, II or VIII of
the
Periodic Table. As elements of these transition groups, particular mention may
be
made of: Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Zn, Ag, Cd, Au, Hg.
The zeolite used according to the present invention can likewise contain
elements
Ga and B.
As regards the form in which the catalyst is used in the process of the
present
3 5 invention, all suitable geometries are generally possible. Thus, for
instance, the
above-described platelet agglomerates themselves can be used. It is also
possible to
process the zeolite by a suitable method to give a shaped body.
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To produce the shaped bodies, the zeolite can, for example, be mixed with a
binder, an organic viscosity-increasing substance and a liquid for forming a
paste
and be compounded in a kneader or-pan mill. The mass obtained can subsequently
also be shaped by means of a ram extruder or screw extruder. The shaped bodies
obtained are subsequently dried and, if appropriate, calcined.
To produce shaped bodies which are also suitable for preparing very reactive
products, it is necessary to use chemically inert binders which prevent
further
reaction of these products.
A series of metal oxides are suitable as binders. Mention may be made, for
example, of oxides of silicon, of aluminum, of titanium or of zirconium.
Silicon
dioxide as binder is disclosed, for example, in the patents US 5,500,199 and
US
4,859,785.
In such binders, it may be necessary, for example, for the content of alkali
metal or
alkaline earth metal ions to be very low, making it necessary to use binder
sources
which are low in or free of alkali metals or alkaline earth metals.
As starting material for preparing the abovementioned metal oxide binders, it
is
possible to use corresponding metal oxide sots. In the preparation of, for
example,
the abovementioned silicon dioxide binder which is low in or free of alkali
metals
and alkaline earth metals, silica sol which is low in or free of alkali metals
or
2 5 alkaline earth metals accordingly serves as binder source.
Such shaped bodies can be obtained, inter alia, by, in one step of the
process,
mixing the zeolite with metal oxide sol and/or metal oxide, where the metal
oxide
sol and the metal oxide in each case have a low content of alkali metal and
alkaline
3 0 earth metal ions. Accordingly, the present invention also describes a
process in
which a shaped body comprising at least one zeolite having an MCM-22, MCM-
36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or more of these
structures and at least one metal oxide, where
(I) the zeolite or zeolites is/are mixed with at least one metal oxide sol
which
3 5 has a low content of alkali metal and alkaline earth metal ions and/or at
least one metal oxide which has a low content of alkali metal and alkaline
earth metal ions.
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In a preferred embadiment of the process of the present invention, the metal
oxide
sol is prepared by hydrolysis of at least one metallic ester.
The metallic esters employed for the hydrolysis can be purified prior to the
hydrolysis. All suitable methods are conceivable for this purpose. The
metallic
esters are preferably subjected to distillation prior to the hydrolysis.
As regards the hydrolysis of the metallic ester, it is in principle possible
to use all
suitable methods. However, in the process of the present invention, the
hydrolysis
is preferably carried out in an aqueous medium.
The hydrolysis can be catalyzed by addition of basic or acidic substances.
Preference is given to basic or acidic substances which can be removed without
leaving a residue by calcination. In particular, use is made of substances
selected
from the group consisting of ammonia, alkylamines, alkanolamines, arylamines,
carboxylic acids, nitric acid and hydrochloric acid. Particular preference is
given to
using ammonia, alkylamines, alkanolamines and carboxylic acids.
2 0 Preferred metallic esters for the purposes of the process of the present
invention
are, inter alia, orthosilicic esters.
In the process of the present invention, the hydrolysis of the metallic esters
is
carned out at from 20 to 100°C, preferably from 60 to 95°C, and
at a pH of from 4
2 5 to 10, preferably from 5 to 9, particularly preferably from 7 to 9.
In the process of the present invention, the hydrolysis gives metal oxide
sots,
preferably silica sols, which have, for example, a content of alkali metal and
alkaline earth metal ions of less than 800 ppm, preferably less than 600 ppm,
more
3 0 preferably less than 400 ppm, more preferably less than 200 ppm, more
preferably
less than 100 ppm, particularly preferably less than 50 ppm, more particularly
preferably less than 10 ppm, in particular less than 5 ppm.
The metal oxide content of the metal oxide sol prepared according to the
present
3 5 invention is generally up to 50% by weight, preferably from 10 to 40% by
weight.
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'The alcohol formed in the hydrolysis is generally distilled off in the
process of the
present invention. However, small amounts of alcohol can remain in the metal
oxide sol as long as they do not interfere in further steps of the process of
the
present invention.
An advantage for the industrial use of the metal oxide sots prepared according
to
the present invention is the fact that they display no tendency to form a gel.
Specific precautions for preventing gel formation are thus superfluous. The
metal
oxide sots prepared according to the present invention can be stored for a
number
of weeks, making timewise coordination with further steps unproblematical.
In the process of the present invention, a mixture comprising the zeolite or
zeolites
having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture
of two or more of these structures and at least one metal oxide is prepared
using a
metal oxide sol prepared as described above as metal oxide source.
In principle, there are no restrictions as regards the method of preparing the
mixture. However, in the process of the present invention preference is given
to
spraying a suspension comprising the zeolite or zeolites having an MCM-22,
MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or more of
2 0 these structures and a metal oxide sol.
As regards the zeolite content of the suspension, there are no restrictions as
long as
the processability of the suspension during preparation and spraying is
ensured.
The weight ratio of zeolite to metal oxide of the metal oxide sol is
preferably
2 5 chosen so as to be in the range from 10 to 0.1; particularly preferably in
the range
from 8 to 1.
The main constituents of the suspension are generally zeolite, metal oxide sol
and
water. The suspension can also contain residual traces of organic compounds.
3 0 These can originate, for example, from the preparation of the zeolite. It
is likewise
conceivable for alcohols formed in the hydrolysis of metallic esters or
substances
which are added as described above for promoting the hydrolysis of metallic
esters
to be present.
3 5 Depending on the moisture content which the mixture is to have for further
processing, drying can follow. Here, all conceivable methods can be employed.
Drying of the mixture is preferably corned out simultaneously with spraying in
a
CA 02388881 2002-04-24
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spray-drying procedure. The spray dryers are preferably operated using inert
gases,
particularly preferably nitrogen or argon.
In a likewise preferred embodiment of the process of the present invention,
the
zeolite having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a
mixture of two or more of these structures is mixed in (I) with at least one
metal
oxide which has a low content of alkali metal and alkaline earth metal ions.
If the zeolite is mixed with two or more metal oxides, it is conceivable for
the
zeolite to be mixed firstly with the one metal oxide and the resulting mixture
to be
mixed with a further-metal oxide. If desired, the mixture obtained here can in
turn
be mixed with a further-metal oxide. It is likewise possible to mix the
zeolite with a
mixture of two ormore metal oxides.
The alkali metal and alkaline earth metal content of this metal oxide or the
mixture
of two or more metal oxides is generally less than 800 ppm, preferably less
than
600 ppm, particularly preferably less than 500 ppm and more particularly
preferably less than 200 ppm.
2 0 Examples of such metal oxides having a low content of alkali metal and
alkaline
earth metal ions are pyrogenic metal oxides, for example pyrogenic silica.
In the process of the present invention, it is naturally also possible for the
mixture
resulting from the mixing of the zeolite with the metal oxide to be mixed with
at
least one metal oxide sol which has, if appropriate, a low content of alkali
metal
2 5 and alkaline earth metal ions. With regard to the preparation of this
mixture, there
are in principle no restrictions, as in the preparation of the mixture of
zeolite and
metal oxide sol described above. However, preference is given to spraying a
suspension comprising the mixture of the zeolite or zeolites and the metal
oxide or
oxides and the metal oxide sol or sols. There are no restricions in respect of
the
3 0 zeolite content of this suspension, as long as, as described above, the
processability
of the suspension is ensured.
Furthermore, in the process of the present invention it is naturally also
possible for
a mixture resulting from the mixing of at least one zeolite having an MCM-22,
3 5 MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or more of
these structures with at least one metal oxide sol to be mixed with at least
one
metal oxide which has, if appropriate, a low content of alkali metal and
alkaline
CA 02388881 2002-04-24
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earth metal ions. Here, mixing with the metal oxide or oxides can directly
follow
the preparation of the mixture of the zeolite or zeolites having an MCM-22,
MCM-
36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or more of these
structures and the metal oxide sol or sols. Should, as described above, drying
be
necessary after the preparation of the mixture of the zeolite or zeolites
having an
MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or
more of these structures and the metal oxide sol or sols, it is also possible
to mix
the metal oxide with the dried mixture after drying.
It is likewise possible in the process of the present invention to mix the
zeolite or
zeolites having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a
mixture of two or -more of these structures simultaneously with at least one
metal
oxide sol and at least one metal oxide.
The mixture obtained according to one of the above-described embodiments of
the
invention is compounded in a further step of the process of the present
invention.
In this compounding or shaping step, fiwther metal oxide can be introduced if
desired, using a metal oxide sol prepared as described above as metal oxide
source.
This processing step can be carried out in all apparatuses known for this
purpose,
2 0 but preference is given to kneaders, pan mills or extruders. A pan mill is
particularly preferred for industrial implementation of the process of the
present
invention.
If, according to one of the above-described embodiments, a mixture of the
zeolite
2 5 having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture
of two or more of these structures and at least one metal oxide is prepared
first, this
mixture is compounded and a metal oxide sol having a low content of alkali
metal
and alkaline earth metal ions is additionally added in the compounding step,
then,
in a preferred embodiment of the present invention, use is made of from 20 to
80%
3 0 by weight of zeolite, from 10 to 60% by weight of metal oxide and from 5
to 30%
by weight of metal oxide sol. Particular preference is given to using from 40
to
70% by weight of zeolite, from 15 to 30% by weight of metal oxide and from 10
to
25% by weight of metal oxide sol. These percentages are in each case based on
the
final shaped body produced, as described below.
In a further embodiment of the process of the present invention, the mixing of
the
zeolite or zeolites having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2
CA 02388881 2002-04-24
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structure or a mixture of two or mare of these structures with the metal oxide
or
oxides which, if appropriate, has/have a low content of alkali metal and
alkaline
earth metal ions is carried out during the compounding step. It is likewise
possible
to mix the zeolite or zeolites having an MCM-22, MCM-36, MCM-49, PSH-3 or
ITQ-2 structure or a mixture of two ormore of these structures, the metal
oxide or
oxides and additionally at least one-metal oxide sol in the compounding step.
In this shaping step, it is possible to additionally add one or more viscosity-
increasing substances as pasting agents which serve, inter olio, to increase
the
stability of the uncalcined shaped body, as described below. All suitable
substances
known from the prior art can be used for this purpose. In the process of the
present
invention, water or mixtures of water-with one or more organic substances
which
are miscible with water are used as pasting agent. The pasting agent can be
removed again during the later-calcination of the shaped body.
Preference is given to using organic, in particular hydrophilic organic
polymers
such as cellulose, cellulose derivatives, e.g. methylcellulose, ethylcellulose
or
hexylcellulose, polyvinylpyrrolidone, ammonium (meth)acrylates, Tylose or
mixtures of two or more thereof. Particular preference is given to using
2 0 methylcellulose.
Further additives which can be added are ammonia, amines or amine-like
compounds, e.g. tetraalkylammonium compounds or aminoalkoxides. Such further
additives are described in EP-A 0 389 041, EP-A 0 200 260 and WO 95/ 19222,
2 5 the full disclosure of which in this respect is hereby incorporated by
reference into
the present application.
Instead of basic additives, it is also possible to use acidic additives.
Preference is
given to acidic organic compounds which can be burnt out by calcination after
the
3 0 shaping step. Particular-preference is given to carboxylic acids.
The amount of these auxiliaries is preferably from 1 to 10% by weight,
particularly
preferably from 2 to 7% by weight, in each case based on the final shaped body
produced, as described below.
To influence the properties of the shaped body, e.g. transport pore volume,
transport pore diameter and transport pore distribution, it is possible to add
further
CA 02388881 2002-04-24
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substances, preferably organic compounds, in particular organic polymers, as
further additives which can also influence the shapeability of the
composition.
Such additives include alginates, polyvinylpyrrolidones, starch, cellulose,
polyethers, polyesters, polyamides, polyamines, polyimines, polyalkenes,
polystyrene, styrene copolymers, polyacrylates, polymethacrylates, fatty acids
such
as stearic acid, high molecular weight polyalkylene glycols such as
polyethylene
glycol, polypropylene glycol or polybutylene glycol and mixtures of two or
more
thereof. The total amount of these substances, based on the final shaped body
produced, as described below, is preferably from 0.5 to 10% by weight,
particularly preferably from 1 to 6% by weight.
In a preferred embodiment, shaped bodies which are essentially microporous but
can additionally have mesopores and/or macropores are produced in the process
of
the present invention.
The order of addition of the above-described additives to the mixture obtained
according to one of the above-described methods is not critical. It is
possible either
to introduce firstly further metal oxide via metal oxide sol, followed by the
viscosity-increasing substances and then the substances which influence the
2 0 transport properties and/or the shapeability of the compounded
composition, or to
use any other order of addition.
If desired, the generally still pulverulent mixture can be homogenized for
from 10
to 180 minutes in the kneader or extruder prior to compounding. This is
generally
2 5 carried out in a temperature range from about 10°C to the boiling
point of the
pasting agent and under atmospheric pressure or slightly superatmospheric
pressure. The mixture is kneaded until an extrudable composition has been
formed.
The composition which has been compounded and is ready far shaping has, in the
3 0 process of the present invention, a metal oxide content of at least 10% by
weight,
preferably at least 15% by weight, particularly preferably at least 20% by
weight,
in particular at least 30% by weight, based on the total composition.
In principle, kneading and shaping can be carried out using all conventional
3 5 kneading and shaping apparatuses and methods which are known in large
numbers
from the prior art and are suitable for the production of, for example, shaped
catalyst bodies.
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Preference is given to using methods in which shaping is carried out by
extrusion
in customary extruders, for example to give extrudates having a diameter of
usually from about 1 to about 10 mm, in particular from about 1.5 to about 5
mm.
Such extrusion apparatuses are described, for example, in "Ullmanns
Enzyklopadie
der Technischen Chemie", 4th edition, Volume 2 (1972), pp. 95 ff. Apart from
the
use of a screw extruder, preference is likewise given to using a ram extruder.
For
industrial use of the process, purticular-preference is given to screw
extruders.
The extrudates are either rods or honeycombs. The honeycombs can have any
shape. They can be, for example, round extrudates, hollow extrudates or star-
shaped extrudates. T'he honeycombs can also have any diameter. The external
shape and the diameter are generally decided by process engineering
requirements
for the process in which the shaped body is to be used.
After completion of extrusion, the shaped bodies obtained are dried at
generally
from 50 to 250°C, preferably from 80 to 250°C, at pressures of
generally from 0.01
to 5 bar, preferably from 0.05 to 1.5 bar, for from about 1 to 20 hours.
2 0 Subsequent calcination is carried out at from 250 to 800°C,
preferably from 350 to
600°C, particularly preferably from 400 to 500°C. The pressure
range is similar to
that for drying. Calcination is generally carried out in an oxygen-containing
atmosphere having an oxygen content of from 0.1 to 90% by volume, preferably
from 0.2 to 22% by volume, particularly preferably from 0.2 to 10% by volume.
The present invention thus also describes a process for producing shaped
bodies as
described above, in which
(I) the zeolite or zeolites having an MCM-22, MCM-36, MCM-49, PSH-3 or
ITQ-2 structure or a mixture of two or more of these structures is mixed
3 0 with at least ane metal oxide sol having, if appropriate, a low content of
alkali metal and alkaline earth metal ions and/or at least one metal oxide
having a low content of alkali metal and alkaline earth metal ions;
(II) the mixture from (I), with or without addition of metal oxide sol, is
3 5 compounded;
(III)the composition from (II) is shaped to give a shaped body;
CA 02388881 2002-04-24
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(IV) the shaped body from (III) is dried and
(V) the dried shaped body from (IV) is calcined.
A specific embodiment of the invention comprises adding the metal oxide sol to
the above-described suspension, drying the resulting suspension, preferably by
spray drying, and calcining the resulting powder. The dried and calcined
product
can then be furrherprocesssed as described in (III).
Of course, the extrudates obtained can be converted into a finished form. All
methods of comminution are conceivable here, for example by crushing or
breaking the shaped bodies; further chemical treatments, for example as
described
above, are likewise possible. If comminution takes place, granules or
chippings
having a particle diameter of from 0.1 to 5 mm, in particular from 0.5 to 2
mm, are
preferably produced.
These granules or chippings and also shaped bodies produced in another way
contain virtually no material having a particle diameter of less than about
0.1 mm.
As support material for the catalytically active component, namely the zeolite
having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture
of two or more of these structures, it is also possible to use all other
suitable
materials. Examples which may be mentioned are shaped bodies or packing made
2 5 of metal, ceramic or plastics, for instance distillation packing, static
mixers, mesh
packing or resin beads. The zeolite having an MCM-22, MCM-36, MCM-49, PSH-
3 or ITQ-2 structure or a mixture of two or more of these structures can be
deposited and immobilized on these materials by all conceivable and suitable
methods. Such methods are disclosed, for example, in DE-C 42 16 846.5 and DE-
3 0 A 196 07 577.7, the full disclosure of which on this subject is hereby
incorporated
by reference into the present application.
The alkene which is hydrated as described in (i) can in principle come from
any
suitable source, for example can be prepared by any suitable process. It is
possible
3 5 to hydrate, inter alia, alkenes having from 2 to 20 carbon atoms. It is
likewise
conceivable for the alkenes to be hydrated to have not only at least one C-C
double
bond but also further functional groups which may also be able to undergo
CA 02388881 2002-04-24
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hydration. Furthermore, alkenes which are substituted in a suitable fashion
can be
used. Examples of suitable alkenes are:
ethane, propane, 1-butane, 2-butane, isobutene, butadiene, pentanes,
piperylene,
hexenes, hexadienes, heptenes, octenes, diisobutene, trimethylpentene,
nonenes,
dodecene, tridecene, tetradecenes to eicosenes, tripropene and tetrapropene,
polybutadienes, polyisobutenes, isoprene, terpenes, geraniol, linalool,
linalyl
acetate, methylenecyclopropane, cyclopentene, cyclohexene, norbornene,
cycloheptene, vinylcyclohexane, vinyloxirane, vinylcyclohexene, styrene,
cyclooctene, cyclooctadiene, vinylnorbornene, indene, tetrahydroindene,
methylstyrene, dicyclopentadiene, divinylbenzene, cyclododecene,
cyclododecatriene, stilbene, diphenylbutadiene, vitamin A, beta-carotene,
vinylidene fluoride, allyl halides, crotyl chloride, methallyl chloride,
dichlorobutene, allyl alcohol, methallyl alcohol, butenols, butenediols,
cyclopentenediols, pentenols, octadienols, tridecenols, unsaturated steroids,
ethoxyethene, isoeugenol, anethole, unsaturated carboxylic acids such as
acrylic
acid, methacrylic acid, crotonic acid, malefic acid, vinylacetic acid,
unsaturated
fatty acids such as oleic acid, linoleic acid, palmitic acid, naturally
occurring fats
and oils.
Particular preference is given to preparing the alkene itself in the process
of the
present invention from suitable starting materials, with the alkene preferably
being
prepared from at least one starting material by hydrogenation of this starting
material. Preference is given to preparing alkenes having from 2 to 6 carbon
atoms
2 5 from at least one starting material, with these alkenes also being able to
have more
than one C-C double bond. The present invention therefore also provides a
process
as described above in which
(ii) the alkene or alkenes is/are prepared by hydrogenation of at least one
3 0 starting material.
It is possible, inter alia, for the alkene to be prepared by selective
hydrogenation of
a compound having at least one C-C triple bond. It is likewise possible,
starting
from a starting material having at least two C-C double bonds, to prepare the
3 5 alkene by selectively hydrogenating at least one C-C double bond of the
starting
material and leaving at least one C-C double bond in the hydrogenated starting
material. Of course, it is also conceivable for starting materials having, for
CA 02388881 2002-04-24
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example, at least one C-C double bond and at least ane further functional
group
capable of hydrogenation to be selectively hydrogenated in such a way that the
hydrogenated starting-material has at least one C-C double bond.
Other functional groups capable of hydration other than C-C double bonds can
of
course also be hydrated in the process of the present invention. Examples
which
may be mentioned are cyano groups, carboxylic ester groups or carbvxamide
groups. As mentioned above, one or-mvre of these functional groups can be
present
in the compound to be hydrated in addition to at least one C-C double bond.
In the process of the present invention, particular-preference is given to
hydrating
cyclic alkenes. In principle, the cyclic alkenes which are preferably used can
come
from all conceivable sources; they are particularly preferably, as described
above,
prepared from all suitable starting materials by hydrogenation. In a very
particularly preferred embodiment, the present invention provides a process as
described above wherein the alkene or alkenes is/are cycloalkene and is/are
prepared by selective hydrogenation of benzene as starting material. The
selective
hydrogenation of benzene can, for example, be corned out by a process
described
in EP-A 0 220 525.
In a preferred embodiment, the hydrogenation of at least one suitable starting
material and the hydration of the alkene or alkenes prepared in this way are
carried
out in a single step. The term "single step" means, for the purposes of the
present
application, that the suitable starting material or materials is/are
hydrogenated in at
2 5 least one suitable reactor and the alkene prepared in this way is hydrated
in the
same reactor. The present invention therefore also provides a process as
described
above in which the preparation of the alkene as described in (ii) and the
hydration
of the alkene as described in (i) are carried out in a single step.
3 0 It is conceivable that, for example, the catalyst or catalysts required
for the
hydrogenation and the catalyst or catalysts required for the hydration are
used in
different ways. Here, it is conceivable that, for example, the hydrogenation
catalyst
or catalysts is/are used as a fixed bed and the hydration catalyst or
catalysts is/are
used in suspension or the hydrogenation catalyst or catalysts is/are used in
3 5 suspension and the hydration catalyst or catalysts is/are used as a fixed
bed or the
hydrogenation catalyst or catalysts and the hydration catalyst or catalysts
are both
used in suspension or as a fixed bed.
CA 02388881 2002-04-24
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In a further embodiment, the process of the present invention is carried out
as a
reactive distillation. Here, it is conceivable, for example, to use at least
one
hydrogenation catalyst in, for example, suspension or a fixed bed, while at
least
one hydrogenation catalyst is applied, for example as a thin layer, to the
distillation
packing or packings used to separate the organic phase from the aqueous phase.
Likewise, it is of course conceivable for both at least one hydrogenation
catalyst
and at least one hydration catalyst to be applied as, for example, a thin
layer to the
distillation packing or packings used for the separation. It is of course also
conceivable to use both hydrogenation and hydration catalysts in either
suspension
or a fixed bed and at the same time to load the distillation packing or
packings used
with at least one hydration catalyst or both at least one hydration catalyst
and at
least one hydrogenation catalyst.
It is likewise conceivable for, for example, interior-walls of pipes and/or
the reactor
which are in contact with compounds to be hydrogenated and/or to be hydrated
to
be loaded, for example coated, with the appropriate catalyst.
In a preferred embodiment of the process of the present invention, the
2 0 hydrogenation catalyst or catalysts and the hydration catalyst or
catalysts are used
as a single catalyst system. The present invention therefore also provides a
process
as described above in which the zeolite having an MCM-22, MCM-36, MCM-49,
PSH-3 or TTQ-2 structure or a mixture of two or more of these structures is
used as
support for at least one catalytically active component used for preparing the
2 5 alkene by hydrogenation of at least one starting material.
Here, it is conceivable, for example, to apply at least one hydrogenation-
active
component by any suitable method of the prior art to the zeolite having an
MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a mixture of two or
3 0 more of these structures. The resulting compound can then, for example, be
used as
such either in a fixed bed or in suspension. It is likewise conceivable to
apply the
resulting compound, as described above, to the distillation packing or
packings
used for separating the organic phase from the aqueous phase in the reactive
distillation. It is likewise possible to apply the resulting compound to
interior walls
3 5 of, for example, the reactor ar pipes, for example in the form of a thin
layer. As
regards the application of the hydrogenation-active component to the zeolite
and
the presence of the hydrogenation-active component on the zeolite, reference
may
CA 02388881 2002-04-24
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be made to DE-A 44 25 672, the full disclosure of which on this subject is
hereby
incorporated by reference into the present application.
It is likewise conceivable to produce a shaped body in a way described in
detail
above, in which case at least one hydrogenation-active component is
incorporated
in addition to the zeolite having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-
2 structure or a mixture of two or more of these structures. Thus, for
example,
zeolite and hydrogenation-active component can firstly be mixed and
subsequently
shaped together with metal oxide sol and/or metal oxide by any suitable
methods.
It is possible, for example, to subject the mixture of zeolite and
hydrogenation-
active component together with metal oxide sol to at least one spray-drying
step
and subsequently, with or without addition of pasting agents, to shape the
spray-
dried product, with kneaders or pan mills, for example, being able to be used
for
shaping. It is also conceivable to produce a shaped body as described above
from
at least zevlite and binder and to apply at least one hydrogenation-active
component to the shaped body. These shaped bodies can subsequently be used,
for
example, in suspension or as a fixed bed in the process of the present
invention.
These shaped bodies can also be used, for example, as coatings on distillation
2 0 packing for reactive distillation or on interior walls of the reactor
and/or pipes, as
described above.
In a further preferred embodiment, the process of the present invention is
carried
out by carrying out hydrogenation and hydration in at least two different
steps. The
2 5 present invention therefore also provides a process as described above in
which the
preparation of the alkene as described in (i) and the hydration of the alkene
as
described in (ii) are carried out in at least two different steps.
The alkene or alkenes can be prepared a~s described in (ii) using all
conceivable
3 0 processes of the prior art, in particular by hydrogenation of at least one
suitable
starting material using arty conceivable process. There are generally no
restrictions
in respect of the hydrogenation catalyst or catalysts preferably used here.
After
preparation of the alkene, it can be separated by all conceivable and suitable
methods from the reaction mixture resulting from (ii) and passed to the
hydration
3 5 as described in (i). It goes without saying that the hydrogenation can in
principle be
carried out in a plurality of stages.
CA 02388881 2002-04-24
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In a further preferred embodiment of the process of the present invention, the
reaction mixture formed in the hydrogenation described in (i) is passed
without
further work-up to the hydration as described in (i).
In a further particularly preferred embodiment of the process, unreacted
starting
material still present in the reaction product from (ii) is, after the
hydration step or
steps (i), separated from the reaction product from (i) and is recycled to the
hydrogenation as described in (ii). The present invention therefore also
provides an
integrated process for-preparing at least one alcohol, in which
(a) at least one alkene is prepared by hydrogenation of at least one starting
material,
(b) the reaction product from (a) comprising the alkene or alkenes and
unreacted starting material is passed to a further step (c),
(c) the alkene or alkenes is/are hydrated in the presence of water by bringing
into contact with at least one heterogeneous catalyst, and
2 0 (d) the unreacted starting material from (a) is separated from the
reaction
product from (c) and is recycled to (a),
wherein the heterogeneous catalyst or catalysts comprises/cvmprise a zeolitic
catalyst having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a
2 5 mixture of two or more of these structures.
In step (a), particular preference is given to preparing cyclic alkenes,
especially
cyclohexene by selective hydrogenation of benzene. The present invention
therefore also provides an integrated process as described above in which the
3 0 alcohol is cyclohexanol, the alkene is cyclohexene and the unreacted
starting
material which is recycled to (a) is benzene.
In the process of the present invention, it is of course quite generally
conceivable
for a plurality of alkenes to be prepared in (ii) either simultaneously or in
a
3 5 plurality of steps which can also be carried out in different ways. It is
likewise
conceivable for a plurality of alkenes to be prepared either simultaneously or
in a
CA 02388881 2002-04-24
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plurality of steps, which may also be carned out in different ways, by
hydrogenation of suitable starting materials.
It is also possible to use two or more alkenes in (i), where at least one of
these
alkenes is com~erted into one alcohol or, depending on the number of C-C
double
bonds capable of hydrogenation, a plurality of alcohols.
If the preparation of the alkene or alkenes to be hydrated and the hydration
itself
are carned out in separate steps, each step can be carned out, depending on
the
starting materials, in the liquid phase, in the gas phase or in the
supercritical phase.
It is likewise conceivable for each step to be carried out either continuously
or
batchwise.
The hydration is preferably carried out in the liquid phase. In addition to
the alkene
or the alkene and unreacted starting material from (i) or quite generally the
reaction
mixture from the preparation of the alkene or alkenes, water and the catalyst
or
catalysts having an MCM-22, MCM-36, MCM-49, PSH-3 or ITQ-2 structure or a
mixture of two or more of these structures, further suitable components can be
fed
into the reactor or reactors used for the hydration. For example solvents
suitable
2 0 for hydration can be fed into the~hydration reactor or reactors.
The hydration is preferably carried out at from 50 to 250°C and at
residence times
of the reaction mixture in the reactor-in the range from 0.5 to 8 hours.
2 5 Should the activity of the catalyst having an MCM-22, MCM-36, MCM-49, PSH-
3
or ITQ-2 structure or a mixture of two or more of these structures decrease
during
the course of the reaction, the present invention provides for it to be
regenerated if
desired. Thus, for example, it is possible to wash it with a suitable solvent
at, if
appropriate, elevated temperature or superatmaspheric pressure or at
3 0 superatmospheric pressure and elevated temperature.
In a liquid-phase reaction, possible washing media are, inter alia, oxidizing
agents
such as oxidizing acids or peroxide solutions, e.g. hydrogen peroxide. In the
supercritical phase, it is also possible to use, for example, carbon dioxide
as
3 5 washing medium. Likewise, the catalyst to be regenerated can be treated at
increased temperature and/or increased pressure with a suitable gas mixture
which
is able to increase the activity of the deactivated catalyst. Here, preference
is given
CA 02388881 2002-04-24
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to using, for example, oxygen-contairring gases or gases which can liberate
oxygen
under the regeneration conditions chosen. Examples which may be mentioned are
nitrogen oxides, preferably N20.
All the abovementioned regeneration procedures can be carried out while the
catalyst is installed in the reactor or else outside the reactor after the
catalyst has
been taken out. It is of course also possible to regenerate the catalyst a
number of
times. The present invention therefore also provides a process or an
integrated
process as described above wherein the zeolitic catalyst or catalysts is/are
regenerated at least once and is/are reused in the process.
For the regeneration of the catalyst used according to the present invention,
it is in
principle preferable to use all methods known from the prior art for the
regeneration of silicate-containing catalysts, in particular zeolite
catalysts. The
deactivated catalyst is generally treated at from 20 to 700°C in the
presence or
absence of oxygen or oxygen-releasing substances so that the activity of the
regenerated catalyst is higher than that of the deactivated catalyst.
Specific mention may be made by way of example of the following processes:
2.0
1. a process for regenerating a deactivated (zeolite) catalyst, which
comprises
heating the deactivated catalyst at a temperature of less than 400°C
but
higher than 150°C in the presence of molecular oxygen for a period
which
is sufficient to increase the activity of the deactivated catalyst, as is
2 5 described in EP-A 0 743 094;
2. a process for regenerating a deactivated (zeolite) catalyst, which
comprises
heating the deactivated catalyst at from 150°C to 700°C in the
presence of a
gas stream containing no more than 5% by volume of molecular oxygen for
3 0 a period which is sufficient to improve the activity of the deactivated
catalyst, as is described in EP-A 0 790 075;
3. a process for regenerating (zeolite) catalysts, in which the deactivated
catalyst is heated at from 400 to 500°C in the presence of an oxygen-
3 5 containing gas or is washed with a solvent, preferably at a temperature
which is from 5°C to 150°C higher than the temperature used
during the
reaction, as is described in JP-A 3 11 45 36;
CA 02388881 2002-04-24
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4. a process for regenerating a deactivated (zeolite) catalyst by calcining it
at
550°C in air or by washing with solvents, so that the activity of the
catalyst
is restored, as described in Proc. 7th Intern. Zeolite Conf. 1986 (Tokyo);
5. a process for regenerating a (zeolite) catalyst, which comprises steps (A)
and (B) below:
(A) heating an at least partially deactivated catalyst to a temperature in the
range from 250°C to 600°C in an atmosphere containing less than
2% by volume of oxygen, and
(B) treating the catalyst at a temperature in the range from 250 to
800°C,
preferably from 350 to 600°C, with a gas stream having a content of
an oxygen-releasing substance or oxygen or a mixture of two or
more thereof in the range from 0.1 to 4% by volume,
where the process may also comprise the further steps (C) and (D),
2 0 (C) treating the catalyst at a temperature in the range from 250 to
800°C,
preferably from 350 to 600°C, with a gas stream having a content of
an oxygen-releasing substance or oxygen or a mixture of two or
more thereof in the range from > 4 to 100% by volume,
2 5 (D) cooling the regenerated catalyst obtained in step (C) in an inert gas
stream containing up to 20% by volume of a liquid vapor selected
from the group consisting of water, alcohols, aldehydes, ketones,
ethers, acids, esters, nitrites, hydrocarbons and mixtures of two or
more thereof.
Details of this process may be found in DE-A 197 23 949.8.
Furthermore, it is likewise conceivable for the catalyst to be regenerated by
washing with at least one hydrogen peroxide solution or with one or more
3 5 oxidizing acids. Of course, the above-described methods can be combined
with one
another in a suitable fashion.
CA 02388881 2002-04-24
-21 -
If hydrogenation-active components such as metals are applied to the zeolitic
catalyst, as is described above for a preferred embodiment of the present
invention,
it is possible for these to be detached from the zeolite and reused for a
renewed
catalyst preparation step.
For the purposes of the present invention, it is of course also conceivable
for the
regenerated catalyst to be used in another process.
The invention is illustrated by the following examples.
Ezamples:
Example 1: Preparation of MCM-22
In a stirred apparatus, 8.3 g of sodium aluminate (43.6% of Na20, 56.8% A1203)
and 5.3 g of NaOH flakes were dissolved in 200 g of deionized water. A
sulfuric
acid solution consisting of 1 g of HZS04 (98% by weight) in 50 g of water was
added to the above solution. T'he resulting solution was added while stirring
to a
suspension of 88 g of pyrogenic silica (Aerosil 200) in 850 g of water. 48 g
of
2 0 hexamethyleneimine were subsequently added and the mixture was homogenized
for 30 minutes. The mixture was reacted at 150°C for 288 hours, the
solid was
filtered off and washed three times with 100 ml of water. It was subsequently
dried
at 120°C and calcined at 500°C in air for 5 hours. 'The product
displayed an X-ray
diffraction pattern typical for MCM-22 and, according to wet chemical
analysis,
had the following composition: 38.0% by weight of Si, 1.9% by weight of Al and
1.2% by weight of Na. T'he specific surface area determined by the Langmuir
method using N2 at 77 K was 639 m2/g. The material was converted into the
ammonium form using a 0.1 N ammonium chloride solution, dried and again
calcined at 500°C in air for 5 hours.
The product obtained in this way had a residual sodium content of 0.1% by
weight.
Example 2: Use of MCM-22 for hydration
3 5 In a 50 ml capacity glass pressure autoclave, 3 g of the catalsyt from
Example 1
were reacted with 0.092 mol of benzene (reaction product from the
hydrogenation
of benzene to cyclohexene), 0.022 mol of cyclohexene and 0.2 mol of water at
CA 02388881 2002-04-24
-22-
120°C for 5 hours while stirring. The resulting phase mixture was
homogenized
after the reaction by addition of dimetlrylformarnide/methanol and analyzed by
means of GC.
The yield of cyclohexanol based on cyclohexene used was 9.2 mol%.
Example 3 : Comparative example using [3-zeolite for the hydration
In a 50 ml capacity glass pressure autoclave, 3 g of ~-zeolite in the H form
were
reacted with 0.092 mol of benzene, 0.022 mol of cyclohexene and 0.2 mol of
water
at 120°C for 5 hours while stirring. 'The resulting phase mixture was
homogenized
after the reaction by addition of dimethylformamide/methanol and analyzed by
means of GC. The yield of cyclohexanol based an cyclohexene used was only 7.5
mol%.
