U.S. patent application number 10/726185 was filed with the patent office on 2005-02-17 for combinatorial preparation and testing of heterogeneous catalysts.
Invention is credited to Demuth, Dirk, Hibst, Hartmut, Schunk, Stephan Andreas.
Application Number | 20050037426 10/726185 |
Document ID | / |
Family ID | 7932417 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050037426 |
Kind Code |
A1 |
Schunk, Stephan Andreas ; et
al. |
February 17, 2005 |
Combinatorial preparation and testing of heterogeneous
catalysts
Abstract
A process for preparing arrays of heterogeneous catalysts and/or
their precursors, made up of a body which has, preferably parallel,
through-channels and in which at least n channels comprise n
different heterogeneous catalysts and/or their precursors, where n
is 2, preferably 10, particularly preferably 100, comprises the
following steps: a1) preparing solutions, emulsions and/or
dispersions of elements and/or element compounds of the chemical
elements present in the catalyst and/or catalyst precursor and, if
appropriate preparing dispersions of inorganic support materials,
a2) if appropriate introducing adhesion promoters, binders,
viscosity regulators, pH regulators and/or solid inorganic supports
into the solutions, emulsions and/or dispersions, a3)
simultaneously or successively coating the channels of the body
with the solutions, emulsions and/or dispersions, a predetermined
amount of the solutions, emulsions and/or dispersions being
introduced into each channel to obtain a predetermined composition,
a4) treating and reacting with one or more reactive gases the
freshly impregnated moist channels obtained after the coating, and
a5) if appropriate heating the coated body in the presence or
absence of inert gases or reactive gases to a temperature in the
range from 20 to 1500.degree. C. to dry, with or without sintering
or calcining, the catalysts and/or catalyst precursors.
Inventors: |
Schunk, Stephan Andreas;
(Heidelberg, DE) ; Demuth, Dirk; (Nussloch,
DE) ; Hibst, Hartmut; (Schriesheim, DE) |
Correspondence
Address: |
KEIL & WEINKAUF
1350 CONNECTICUT AVENUE, N.W.
WASHINGTON
DC
20036
US
|
Family ID: |
7932417 |
Appl. No.: |
10/726185 |
Filed: |
December 3, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10726185 |
Dec 3, 2003 |
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09734018 |
Dec 12, 2000 |
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6720171 |
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Current U.S.
Class: |
435/7.1 ;
436/518 |
Current CPC
Class: |
B01J 37/02 20130101;
B01J 2219/00585 20130101; C40B 30/08 20130101; Y10T 436/175383
20150115; B01J 2219/00704 20130101; B01J 2219/0052 20130101; B01J
19/0046 20130101; Y10T 436/25875 20150115; B01J 2219/00659
20130101; B01J 35/04 20130101; B01J 2219/00747 20130101; B01J
2219/00603 20130101; Y10T 436/18 20150115; Y10T 436/20 20150115;
B01J 2219/00745 20130101; Y10T 436/205831 20150115; C40B 40/18
20130101 |
Class at
Publication: |
435/007.1 ;
436/518 |
International
Class: |
G01N 033/53; G01N
033/543 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 1999 |
DE |
19959973.4 |
Claims
1. (canceled)
2. A process for preparing arrays of heterogeneous catalysts,
heterogeneous catalyst precursors, or combinations thereof,
comprising of a body having through-channels and in which at least
n through-channels comprise n different heterogeneous catalysts,
heterogeneous catalyst precursors, or combinations thereof, where n
is 2 or more, comprising the following steps: b1) preparing
solutions, emulsions or dispersions of elements or element
compounds of the elements present in the catalysts, catalyst
precursors, or combinations thereof and, optionally, preparing
dispersions of inorganic support materials, b2) optionally,
introducing adhesion promoters, binders, viscosity regulators pH
regulators or solid inorganic supports into the solutions,
emulsions or dispersions, b3) simultaneously or successively
coating catalyst supports present in the channels of the body with
the solutions, emulsions or dispersions, a predetermined amount of
the solutions, emulsions or dispersions being introduced into each
channel to obtain a predetermined composition on the catalyst
supports, to produce freshly impregnated moist channels, b4)
treating and reacting with one or more reactive gases the freshly
impregnated moist channels obtained after the coating, and b5)
optionally, heating the body comprising the coated catalyst
supports in the channels in the presence or absence of inert gases
or reactive gases to a temperature in the range from 20 to
1500.degree. C. to dry, optionally with or sintering or calcining,
the catalysts, catalyst precursors, or combinations thereof.
3. A process for preparing arrays of heterogeneous catalysts and/or
their precursors made up of a body which has, preferably parallel,
through-channels and in which at least n channels comprise n
different heterogeneous catalysts and/or their precursors, where n
is 2, preferably 10, particularly preferably 100, comprising the
following steps: c1) preparing solutions, emulsions and/or
dispersions of elements and/or element compounds of the chemical
elements present in the catalyst and/or catalyst precursor and, if
appropriate preparing dispersions of inorganic support materials,
c2) mixing predetermined amounts of the solutions, emulsions and/or
dispersions with or without precipitation aids in one or more
reaction vessels run in parallel, c3) if appropriate introducing
adhesion promoters, binders, viscosity regulators pH regulators
and/or solid inorganic supports into the resultant mixture(s), c4)
coating one or more predetermined channels of the body with the
mixture or a plurality of mixtures, c5) repeating steps c2) to c4)
for other channels of the body until the channels containing the
respective predetermined catalyst and/or catalyst precursor
compositions are coated, c6) treating and reacting with one or more
reactive gases the freshly impregnated moist channels obtained
after the coating, and c7) if appropriate heating the coated body
in the presence or absence of inert gases or reactive gases to a
temperature in the range from 20 to 1500.degree. C. to dry, with or
without sintering or calcining, the catalysts and/or catalyst
precursors.
4. A process for preparing arrays of heterogeneous catalysts and/or
their precursors made up of a body which has, preferably parallel,
through-channels and in which at least n channels comprise n
different heterogeneous catalysts and/or their precursors, where n
is 2, preferably 10, particularly preferably 100, comprising the
following steps: d1) preparing solutions, emulsions and/or
dispersions of elements and/or element compounds of the chemical
elements present in the catalyst and/or catalyst precursor and, if
appropriate preparing dispersions of inorganic support materials,
d2) mixing predetermined amounts of the solutions, emulsions and/or
dispersions with or without precipitation aids in one or more
reaction vessels run in parallel, d3) if appropriate introducing
adhesion promoters, binders, viscosity regulators, pH regulators
and/or solid inorganic supports into resultant mixture(s), d4)
coating catalyst supports present in one or more predetermined
channels of the body with the mixture or one or more of the
mixtures, d5) repeating steps d2) to d4) for other channels of the
body until the catalyst supports present in the channels of the
body are coated with the respective predetermined catalyst
compositions and/or catalyst precursor compositions, d6) treating
and reacting with one or more reactive gases the freshly
impregnated moist channels obtained after the coating, and d7) if
appropriate heating the body comprising the coated catalyst
supports in the channels in the presence or absence of inert gases
or reactive gases to a temperature in the range from 20 to
1500.degree. C. to dry, with or without sintering or calcining, the
catalysts and/or catalyst precursors.
5. A process for preparing arrays of heterogeneous catalysts and/or
their precursors made up of a body which has, preferably parallel,
through-channels and in which at least n channels comprise n
different heterogeneous catalysts and/or their precursors, where n
is 2, preferably 10, particularly preferably 100, comprising the
following steps: e1) reacting predetermined dry porous catalyst
supports with one or more reactive gases for preparing
predetermined supported catalysts outside or inside the body, e2)
if appropriate introducing the supported catalysts prepared outside
the body into predetermined channels of the body, and e3) if
appropriate heating the filled body in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts.
6. A process for preparing arrays of heterogeneous catalysts and/or
their precursors made up of a body which has, preferably parallel,
through-channels and in which at least n channels comprise n
different heterogeneous catalysts and/or their precursors, where n
is 2, preferably 10, particularly preferably 100, comprising the
following steps: f1) coating and if appropriate heating
predetermined catalyst supports to prepare predetermined supported
catalysts in the manner defined in claim 2 outside the body, f2)
introducing the supported catalysts into predetermined channels of
the body, f3) if appropriate heating the packed body in the
presence or absence of inert gases or reactive gases to a
temperature in the range from 20 to 1500.degree. C. to dry, with or
without sintering or calcining, the catalysts.
7. A process for preparing arrays of heterogeneous catalysts and/or
their precursors made up of a body which has, preferably parallel,
through-channels and in which at least n channels comprise
different heterogeneous catalysts and/or their precursors, where n
is 2, preferably 10, particularly preferably 100, following steps:
g1) simultaneous or sequential coating of the channels of the body
with gasified chemical elements or their mixtures of the chemical
elements present in the catalysts, and g2) if appropriate heating
the coated body in the presence or absence of inert gases or
reactive gases to a temperature in the range of from 20 to
1500.degree. C. to dry, with or without sintering or calcining, the
catalysts and/or catalyst precursors.
8. A process for preparing arrays of heterogeneous catalysts and/or
their precursors made up of a body which has, preferably parallel,
through-channels and in which at least n channels comprise n
different heterogeneous catalysts and/or their precursors, where n
is 2, preferably 10, particularly preferably 100, comprising the
following steps: h1) simultaneous or sequential coating of the
channels of the body with pulverulent chemical elements or their
mixtures of the chemical elements present in the catalyst, and h2)
if appropriate heating the coated body in the presence or absence
of inert gases or reactive gases to a temperature in the range of
from 20 to 1500.degree. C. to dry, and if appropriate sinter or
calcine, the catalysts and/or catalyst precursors.
9. An array obtainable by a process as claimed in claim 2.
10. A process for determining the activity, selectivity and/or
long-term stability of the catalysts in an array as claimed in
claim 9, comprising the following steps: i1) if appropriate
activating the catalyst in the body, i2) heating or cooling the
body to a desired reaction temperature, i3) passing a fluid
reactant or fluid reaction mixture through channels of the body,
i4) discharge of the reacted fluids from individual or a plurality
of collective channels of the body, i5) analysis of the discharged
reacted fluids, i6) if appropriate comparative evaluation of the
analytical results of a plurality of analyses.
11. The process as claimed in claim 2, wherein n is at least
10.
12. The process as claimed in claim 11, wherein n is at least
100.
13. The process as claimed in claim 2, wherein the through-channels
are parallel relative to each other.
Description
[0001] The invention relates to a process for the combinatorial
preparation and testing of heterogeneous catalysts and catalysts
obtained by this process.
[0002] To prepare and study novel chemical compounds, in addition
to classical chemistry which is directed towards the synthesis and
study of individual substances, combinatorial chemistry has
developed. In this approach, a multiplicity of reactants were
reacted in a one-pot synthesis and analysis was carried out as to
whether the resultant reaction mixture displays the desired
properties, for example a pharmacological activity. If an activity
was found for such a reaction mixture, it was then necessary to
determine in a further step which specific substance in the
reaction mixture was responsible for the activity. In addition to
the high expenditure for determining the actual active compound, it
was difficult with a multiplicity of reactants to exclude to
unwanted side reactions.
[0003] In another combinatorial synthesis approach, a multiplicity
of compounds were synthesized by specific dosage and reaction of a
number of reactants in a multiplicity of different reaction
vessels. In this process, preferably, in each reaction vessel one
reaction product is present, so that in the event of, for example,
a given pharmacological activity of a mixture, the starting
materials used for its preparation are known immediately.
[0004] In addition to the first applications of this more specific
combinatorial synthesis in the search for novel pharmacologically
active substances, very recently the synthesis method has also been
extended to low-molecular-weight organic compounds and to organic
and inorganic catalysts.
[0005] X.-D. Xiang et al., "A Combinatorial Approach for Materials
Discovery", Science 268, (1995), pages 1738 to 1740 describe the
preparation of BiSrCaCuO and YBaCuO superconductivity films on
substrates, a combinatorial array of different metal compositions
being obtained by physical masking processes and vapor deposition
techniques in the deposition of the appropriate metals. After the
calcination, different compositions are present at different
positions of the array and can be studied by microprobes, for their
conductivity for example.
[0006] WO 96/11878 describes, in addition to the preparation of
such superconductivity arrays, the preparation of zeolites, the
amounts required in each case being metered without prior mixing
from a plurality of metal salt solutions using an ink jet onto a
type of spot plate, a precipitation starting on addition of the
last solution. BSCCO superconductors can also be prepared by
separate metering of the individual nitrate solutions of the metals
required by spraying onto a type of spot plate and subsequent
heating.
[0007] Various types of heterogeneous catalysts can be prepared
using the known processes. However, testing the catalysts is
complex and frequently cannot be performed under realistic
conditions, e.g. using the required residence times of the
reactants on the catalyst, since the catalysts are present, for
example, on a relatively large, generally flat support and this
must be charged, for example, with a gas mixture to be reacted.
[0008] It is an object of the present invention to provide a
process for preparing arrays of inorganic heterogeneous catalysts
or their precursors in which the resultant catalysts can be tested
with low expenditure and under conditions which resemble an
industrial process. In addition, the disadvantages of the existing
systems are to be avoided. Corresponding arrays are also to be
provided.
[0009] Therefore, DE-A-198 05 719 proposed arrays of, preferably
inorganic, heterogeneous catalysts and/or their precursors made up
of a body which has, preferably parallel, through-channels in which
at least n channels comprise n different, preferably inorganic,
heterogeneous catalysts and/or their precursors, where n is 2,
preferably 10, particularly preferably 100, in particular 1000,
especially 10,000. The body can be a tube-bundle reactor or heat
exchanger and the channels are tubes, or a block made of a solid
material which has the channels, in the form of boreholes for
example.
[0010] It is an object of the present invention to provide
processes for preparing arrays of heterogeneous catalysts and/or
their precursors which extend the spectrum of arrays accessible via
WO.
[0011] We have found that this object is achieved by the processes
described below for preparing arrays of heterogeneous catalysts
and/or their precursors, made up of a body which has, preferably
parallel through-channels and in which at least n channels comprise
n different heterogeneous catalysts and/or their precursors, where
n is 2, preferably 10, particularly preferably 100, in particular
1000, especially 10 000.
[0012] The term "array of inorganic heterogeneous catalysts or
their precursors" describes here an arrangement of different
inorganic heterogeneous catalysts or their precursors on
predetermined areas of a body which are spatially separate from one
another, preferably a body having parallel through-channels,
preferably a tube-bundle reactor or heat exchanger. The geometric
arrangement of the individual areas to one another can be chosen
freely in this case. For example, the areas can be arranged in the
manner of a row (quasi one-dimensional) or a chessboard pattern
(quasi two-dimensional). In a body having parallel
through-channels, preferably a tube-bundle reactor or heat
exchanger having a multiplicity of tubes parallel to one another,
the arrangement becomes clear when a cross-sectional area
perpendicular to the longitudinal axis of the tubes is considered:
an area results, in which the individual tube cross sections
reproduce the different areas separated from one another. The areas
or tubes can, for example for tubes having a circular cross
section, also be present in a dense packing, so that different rows
are arranged from areas staggered to one another.
[0013] The term "body" describes a three-dimensional object which
has a multiplicity (at least n) of through-channels. The channels
thus connect two surface areas of the body and run through the
body. Preferably, the channels are essentially, preferably
completely, parallel to one another. In this case, the body can be
made up of one or more materials and can be solid or hollow. It can
have any suitable geometric shape. Preferably it has two surfaces
parallel to one another in which in each case one orifice of the
channels is situated. The channels preferably run perpendicularly
to these surfaces. An example of a body of this type is a
parallelepiped or cylinder in which the channels run between two
parallel surfaces. However, a multiplicity of similar geometries is
also conceivable.
[0014] The term "channel" describes a connection running through
the body between two orifices situated on the body surface which,
for example, permits the passage of a fluid through the body. The
channel here can have any desired geometry. It can have a
cross-sectional area changing over the length of the channel or,
preferably, can have a constant channel cross-sectional area. The
channel cross section can have, for example, an oval, round or
polygonal outline with straight or rounded connections between the
corners of the polygon. Preference is given to a round or
equilateral polygonal cross section. Preferably, all channels in
the body have the same geometry (cross section and length) and run
parallel to one another.
[0015] The terms "tube-bundle reactor" and "heat exchanger"
describe collective parallel arrangements of a multiplicity of
channels in the form of tubes, where the tubes can have any desired
cross section. The tubes are arranged in a fixed spatial
relationship to one another, are preferably present spatially
separated from one another and are preferably surrounded by a shell
which encloses all of the tubes. By this means, for example, a
heating or cooling medium can be conducted through the shell, so
that all of the tubes can be heated or cooled uniformly.
[0016] The term "block of a solid material" describes a body of a
solid material (which in turn can be made up of one or more
starting materials) which has the channels, for example in the form
of boreholes. The geometry of the channels (boreholes) can here be
chosen freely as described above for the channels generally. The
channels (boreholes) need not be installed by boring, but can be
left open, for example even when forming the solid body/block, for
instance by extruding an organic and/or inorganic molding
composition (for example by an appropriate die geometry during
extrusion). In contrast to the tube-bundle reactors or heat
exchangers, the space in the body between the channels in the block
is always filled by the solid material. Preferably, the block is
made up of one or more metals.
[0017] The term "predetermined" means that, for example, a number
of different catalysts or catalyst precursors is introduced into a
tube-bundle reactor or heat exchanger in such a manner that the
assignation of the different catalysts or catalyst precursors to
the individual tubes is recorded and can later be retrieved, for
example, when determining the activity, selectivity and/or
long-term stability of the individual catalysts, in order to make
possible an unambiguous assignation of defined measured values to
defined catalyst compositions. Preferably, the catalysts or their
precursors are prepared and distributed to the different tubes of
the tube-bundle reactor under computer control the respective
composition of a catalyst and the position of the tube in the
tube-bundle reactor into which the catalyst or catalyst precursor
is introduced is stored in the computer and can later be retrieved.
The term "predetermined" thus serves to differentiate from a chance
or random distribution of the generally different catalysts or
catalyst precursors to the tubes of a tube-bundle reactor.
[0018] The arrays according to the invention of, preferably
inorganic, heterogeneous catalysts and/or their precursors can be
prepared according to the invention by a variety of processes:
[0019] Process a comprises the following steps:
[0020] a1) preparing solutions, emulsions and/or dispersions of
elements and/or element compounds of the chemical elements present
in the catalyst and/or catalyst precursor and, if appropriate
preparing dispersions of inorganic support materials,
[0021] a2) if appropriate introducing adhesion promoters, binders,
viscosity regulators, pH regulators and/or solid inorganic supports
into the solutions, emulsions and/or dispersions,
[0022] a3) simultaneously or successively coating the channels of
the body with the solutions, emulsions and/or dispersions, a
predetermined amount of the solutions, emulsions and/or dispersions
being introduced into each channel to obtain a predetermined
composition,
[0023] a4) treating and reacting with one or more reactive gases
the freshly impregnated moist channels obtained after the coating,
and
[0024] a5) if appropriate heating the coated body in the presence
or absence of inert gases or reactive gases to a temperature in the
range from 20 to 1500.degree. C. to dry, with or without sintering
or calcining, the catalysts and/or catalyst precursors.
[0025] The process b comprises the following steps:
[0026] b1) preparing solutions, emulsions and/or dispersions of
elements and/or element compounds of the elements present in the
catalyst and/or catalyst precursor and, if appropriate preparing
dispersions of inorganic support materials,
[0027] b2) if appropriate introducing adhesion promoters, binders,
viscosity regulators, pH regulators and/or solid inorganic supports
into the solutions, emulsions and/or dispersions,
[0028] b3) simultaneously or successively coating catalyst supports
present in the channels of the body with the solutions, emulsions
and/or dispersions, a predetermined amount of the solutions,
emulsions and/or dispersions being introduced into each channel to
obtain a predetermined composition on the catalyst supports,
[0029] b4) treating and reacting with one or more reactive gases
the freshly impregnated moist channels obtained after the coating,
and
[0030] b5) if appropriate heating the body comprising the coated
catalyst supports in the channels in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts and/or catalyst precursors.
[0031] Process c) comprises the following steps:
[0032] c1) preparing solutions, emulsions and/or dispersions of
elements and/or element compounds of the chemical elements present
in the catalyst and/or catalyst precursor and, if appropriate
preparing dispersions of inorganic support materials,
[0033] c2) mixing predetermined amounts of the solutions, emulsions
and/or dispersions with or without precipitation aids in one or
more reaction vessels run in parallel,
[0034] c3) if appropriate introducing adhesion promoters, binders,
viscosity regulators, pH regulators and/or solid inorganic supports
into the resultant mixture(s),
[0035] c4) coating one or more predetermined channels of the body
with the mixture or a plurality of mixtures.
[0036] c5) repeating steps c2) to c4) for other channels of the
body until the channels containing the respective predetermined
catalyst and/or catalyst precursor compositions are coated,
[0037] c6) treating and reacting with one or more reactive gases
the freshly impregnated moist channels obtained after the coating,
and
[0038] c7) if appropriate heating the coated body in the presence
or absence of inert gases or reactive gases to a temperature in the
range from 20 to 1500.degree. C. to dry, with or without sintering
or calcining the catalysts and/or catalyst precursors.
[0039] Preferably, it comprises the following steps:
[0040] c1) preparing solutions of element compounds of the chemical
elements present in the catalyst except for oxygen, and if
appropriate preparing dispersions of inorganic support
materials
[0041] c2) mixing predetermined amounts of the solutions or
dispersions with or without precipitation aids in one or more
reaction vessels run in parallel with precipitation of the chemical
elements present in the catalyst,
[0042] c3) if appropriate introducing adhesion promoters, binders,
viscosity regulators, pH regulators and/or solid inorganic supports
into the resultant suspension,
[0043] c4) coating with the suspension one or more predetermined
tubes of the tube-bundle reactor or heat exchanger,
[0044] c5) repeating steps c2) to c4) for different tubes of the
tube-bundle reactor or heat exchanger until the tubes containing
the respective predetermined catalyst compositions are coated,
[0045] c6) treating and reacting with one or more reactive gases
the freshly impregnated moist channels obtained after the coating,
and
[0046] c7) heating the coated tube-bundle reactor or heat exchanger
in the presence or absence of inert gases or reactive gases to a
temperature in the range from 20 to 1500.degree. C. to dry, with or
without sintering or calcining, the catalysts.
[0047] Process d) comprises the following steps:
[0048] d1) preparing solutions, emulsions and/or dispersions of
elements and/or element compounds of the chemical elements present
in the catalyst and/or catalyst precursor and, if appropriate
preparing dispersions of inorganic support materials,
[0049] d2) mixing predetermined amounts of the solutions, emulsions
and/or dispersions with or without precipitation aids in one or
more reaction vessels run in parallel,
[0050] d3) if appropriate introducing adhesion promoters, binders,
viscosity regulators, pH regulators and/or solid inorganic supports
into the resultant mixture(s),
[0051] d4) coating catalyst supports present in one or more
predetermined channels of the body with the mixture or one or more
of the mixtures,
[0052] d5) repeating steps d2) to d4) for other (that is generally
the as yet uncoated) catalyst supports in the channels of the body
until (preferably all) the catalyst supports present in the
channels of the body are coated with the respective predetermined
(generally differing from one another) catalyst compositions and/or
catalyst precursor compositions,
[0053] d6) treating and reacting with one or more reactive gases
the freshly impregnated moist channels obtained after the coating,
and
[0054] d7) if appropriate heating the body comprising the coated
catalyst supports in the channels in the presence or absence of
inert gases or reactive gases to a temperature in the range from 20
to 1500.degree. C. to dry, with or without sintering or calcining,
the catalysts and/or catalyst precursors.
[0055] In this process, the adhesiveness of the channels (e.g. of
the inner surface of the tubes) of the body or of the catalyst
supports can be increased prior to the coating by chemical,
physical or mechanical pretreatment of the inner walls of the
channels (e.g. inner tubes) or the catalyst supports or by applying
an adhesive layer. This applies in particular to the processes a)
and c) and to b) and d) respectively.
[0056] Process e comprises the following steps:
[0057] e1) reacting predetermined dry porous catalyst supports with
one or more reactive gases for preparing predetermined supported
catalysts outside or inside the body,
[0058] e2) if appropriate introducing the supported catalysts
prepared outside the body into predetermined channels of the body,
and
[0059] e3) if appropriate heating the filled body in the presence
or absence of inert gases or reactive gases to a temperature in the
range from 20 to 1500.degree. C. to dry, with or without sintering
or calcining, the catalysts.
[0060] Process f) comprises the following steps:
[0061] f1) coating and if appropriate heating predetermined
catalyst supports to prepare predetermined supported catalysts in
the manner defined above in processes b) and d) outside the
body,
[0062] f2) introducing the supported catalysts into predetermined
channels of the body,
[0063] f3) if appropriate heating the packed body in the presence
or absence of inert gases or reactive gases to a temperature in the
range from 20 to 1500.degree. C. to dry, with or without sintering
or calcining, the catalysts.
[0064] Preferably, the external shape of the supported catalysts
corresponds here to the shape of the channel interior in the body
at least essentially, preferably approximately or completely.
[0065] Process g) comprises the following steps.
[0066] g1) simultaneous or sequential coating of the channels of
the body with gasified chemical elements or their mixtures of the
chemical elements present in the catalyst, and
[0067] g2) if appropriate heating the coated body in the presence
or absence of inert gases or reactive gases to a temperature in the
range of from 20 to 1500.degree. C. to dry, with or without
sintering or calcining, the catalysts and/or catalyst
precursors.
[0068] Process h) comprises the following steps:
[0069] h1) simultaneous or sequential coating of the channels of
the body with pulverulent chemical elements or their mixtures of
the chemical elements present in the catalyst, and
[0070] h2) if appropriate heating the coated body in the presence
or absence of inert gases or reactive gases to a temperature in the
range of from 20 to 1 500.degree. C. to dry, and if appropriate
sinter or calcine, the catalysts and/or catalyst precursors.
[0071] The invention also relates to inorganic heterogeneous
catalyst arrays which are obtainable by one of the abovementioned
processes. The arrays can also be prepared by any combination of
the abovementioned processes.
[0072] The processes are suitable for preparing a multiplicity of
catalyst systems, as are described, for example, in G. Ertl, H.
Knozinger, J. Weitkamp, editors, "Handbook of Heterogeneous
Catalysis", Wiley--VCH, Weinheim, 1997.
[0073] In addition, the invention relates to a process i) for
determining catalytic properties, in particular the activity,
selectivity and/or long-term stability of the catalysts described
above and below in an array described, which comprises the
following steps:
[0074] i1) if appropriate activating the catalysts in the body,
[0075] i2) heating or cooling the body to a desired reaction
temperature,
[0076] i3) passing a fluid reactant or a fluid reaction mixture
through (one, a plurality or all of the channels of the body,
[0077] i4) (preferably separate) discharge of the reacted fluids
from individual or a plurality of collective channels of the
body,
[0078] i5) (preferably separate) analysis of the discharged reacted
fluids,
[0079] i6) if appropriate comparative evaluation of the analytical
results of a plurality of analyses.
[0080] In a preferred process variant, after heating or cooling the
body to a first reaction temperature in step i2), steps i3) to i6)
are carried out successively for a plurality of different fluid
reactants or fluid reaction mixtures, where in each case a purge
step with a purge as can be introduced, and then the body can be
heated or cooled to a second reaction temperature and the
abovementioned reactions can be repeated at this temperature.
[0081] At the start of the analysis, the collected gas stream of
the entire array can be analyzed to detect whether there has been
any reaction at all.
[0082] Thereafter, if a reaction is present, the discharges of the
individual tubes or a plurality of tubes can be analyzed to
determine an optimum catalyst using a minimum number of analytical
processes.
[0083] Flow can pass through individual tubes or a plurality or all
of the tubes collectively.
[0084] Preferably, the fluid reactant or fluid reaction mixture is
a gas or gas mixture.
[0085] The invention permits the automated preparation and
catalytic testing for the purpose of mass screening of
heterogeneous catalysts for chemical reactions, in particular for
reactions in the gas phase, very particularly for partial
oxidations of hydrocarbons in the gas phase by molecular oxygen
(gas-phase oxidations).
[0086] Suitable reactions for investigation are described in G.
Ertl, H. Knozinger, J. Weitkamp, editors, "Handbook of
Heterogeneous Catalysis", Wiley--VCH, Weinheim, 1997. Examples of
suitable reactions are principally listed in this reference in
Volumes 4 and 5 under numbers 1, 2, 3 and 4.
[0087] Examples of suitable reactions are the decomposition of
nitrogen oxides, the synthesis of ammonia, the oxidation of
ammonia, oxidation of hydrogen sulfide to sulfur, oxidation of
sulfur dioxide, direct synthesis of methylchlorosilanes, oil
refining oxidative coupling of methane, methanol synthesis,
hydrogenation of carbon monoxide and carbon dioxide, conversion of
methanol to hydrocarbons, catalytic reforming, catalytic cracking
and hydrocracking, coal gasification and liquefaction, fuel cells,
heterogeneous photocatalysis, synthesis of MTBE and TAME,
isomerizations, alkylations, aromatizations, dehydrogenations,
hydrogenations, hydroformylations, selective or partial oxidations,
aminations, halogenations, nucleophilic aromatic substitutions,
addition and elimination reactions, oligomerizations and
metathesis, polymerizations, enantioselective catalysis and
biocatalytic reactions.
[0088] The invention is described in more detail below with
reference to preferred embodiments.
[0089] Preparation of the Inorganic Heterogeneous Catalyst
Array
[0090] Firstly, two or more, preferably 10 or more, very
particularly preferably 100 or more, in particular 1000 or more,
especially 10,000 or more, liquid starting mixtures (termed
mixtures below) which comprise selected chemical elements of the
Periodic Table of the Elements are prepared in the form of
solutions, emulsions and/or preferably suspensions (dispersions),
the mixtures prepared generally differing, in their chemical
composition or concentration. To test the reproducibility, a
plurality of mixtures of the same composition can also be used.
[0091] The liquid mixtures generally comprise a liquid chemical
component which is used as solvent, emulsifying aid or dispersant
for the other components of the mixture. As solvent or dispersant,
use is made of organic solvents, emulsifying aids and/or water,
preferably water.
[0092] Apart from the chemical elements of the solvent or
dispersant, the liquid mixtures comprise one or more, preferably 2
or more, particularly preferably 3 or more, chemical elements,
generally, however, no more than 50 different chemical elements
being present in an amount of in each case greater than 1% by
weight. Preferably, the chemical elements are present in the
mixtures very intimately mixed, e.g. in the form of a mixture of
various miscible solutions, intimate emulsions having a small
droplet size and/or preferably as a suspension (dispersion) which
comprises the chemical elements in question generally in the form
of a finely divided precipitate, e.g. in the form of a chemical
mixed precipitate. The use of brines and gels has proved
particularly useful, in particular of those which comprise the
chemical elements in question in a substantially homogeneous
distribution, and preferably those which show an adhesion and flow
behavior expedient for the coating. Suitable starting compounds for
the chemical elements selected are in principle the elements
themselves, preferably in finely divided form, furthermore all
compounds which contain the chosen chemical elements in a suitable
manner, such as oxides, hydroxides, hydroxideoxides, inorganic
salts, preferably nitrates, carbonates, acetates and oxalates,
organometallic compounds, alkoxides etc. The respective starting
compounds can be used in solid form, in the form of solutions,
emulsions and/or in the form of suspensions.
[0093] Preferred element compounds, in particular catalytically
active metals, are water-soluble oxides, hydroxides or salts of
organic or inorganic acids. Active metals are preferably located in
the subgroups of the Periodic Table of the Elements, for example in
subgroups 5 and 6 for oxidation catalysts and in the platinum group
for hydrogenation catalysts. The process according to the invention
also permits the screening of (atypical) elements which were not
previously considered to be catalytically active, in particular
metals or metal oxides.
[0094] In addition, the liquid mixture can comprise other compounds
which affect the adhesion properties and the flow behavior of the
liquid mixture on the channel interior or tube interior to be
coated or catalyst supports and thus affect the coating properties
of the liquid mixture. Organic compounds which may be mentioned
here are, for example, ethylene glycol or glycerol, as described in
DE-A 4 442 346, or, for example, maleic acid copolymers, and
inorganic compounds which may be mentioned are, for example,
SiO.sub.2, organosilicone compounds or siloxanes.
[0095] In addition, the mixtures can comprise known inorganic
support materials, such as Al.sub.2O.sub.3, ZrO.sub.2, SiO.sub.2,
Y.sub.2O.sub.3, TiO.sub.2, activated carbon, MgO, SiC or
Si.sub.3N.sub.4, which generally increase the surface area
accessible to the catalysis of the catalytically active chemical
elements present in the mixture and in addition can affect the
catalytic properties of the active composition present and which
likewise can affect the adhesion and flow properties of the
resultant mixture. Generally, coatings are obtained in this case
which comprise, in addition to the actual catalytic material, the
preferred oxide, nitride or carbide support material. However, when
the components are being mixed or during the subsequent heating of
the coating, said support material can also react with the chemical
elements used above it to form a novel solid material.
[0096] Furthermore, the mixtures used can additionally comprise an
inorganic and/or organic binder or a binder system which stabilizes
the mixture used. Binders suitable for this are, for example,
binders or binder systems which comprise metal salts, metal oxides,
metal hydroxide oxides, metal hydroxide oxide phosphates and/or
eutectic compounds melting at the service temperature of the
catalyst.
[0097] The mixture can in addition be set to a defined pH range by
adding acids and/or bases. In many cases, pH neutral suspensions
are used. For this purpose, the mixture can advantageously be set
to a pH between 5 and 9, preferably between 6 and 8. Special
results may be obtained by the process according to the invention
if the mixture has a high solids content of up to 95% by weight,
preferably from 50 to 80% by weight at low viscosity. If
precipitation is insufficient, precipitation aids, such as ammonia,
can be added.
[0098] In a preferred embodiment of the invention, the mixture is
stirred after, and generally also during, the preparation and its
flowability is measured continuously, but at least at the end of
the preparation. This can be done, for example, by measuring the
power consumption of the agitator unit. Using this measurement, the
viscosity of the suspension can be set, for example by adding
further solvents or thickeners, so as to result in optimum
adhesion, layer thickness and layer thickness uniformity on the
tube inner wall to be coated or on the auxiliary support (catalyst
support) to be coated.
[0099] In principle, the invention is not restricted to certain
catalyst materials and catalyst compositions. The preparation of
the mixture can be performed in parallel or successively and is
generally performed in automated form, e.g. using an automated
pipette or automated pipetting system or else an ink-jet process,
as described, for example, in U.S. Pat. No. 5,449,754.
[0100] To coat the tubes of the tube-bundle reactor or heat
exchanger by process variant a), solutions, emulsions or
suspensions of individual elements or element compounds can be
introduced into the tubes simultaneously or successively separated
from one another. Simultaneous introduction can be performed, for
example, using a modified ink-jet printer head which comprises
separate feed lines for the individual solutions, emulsions or
suspensions and permits the simultaneous atomization Compared with
this process variant a, the process variant b is preferred, which
is carried out in particular as follows:
[0101] To prepare the catalysts or their precursors, solutions,
emulsions and/or suspensions of the required elements are firstly
prepared in separate vessels. These are frequently metal salt
solutions, for example nitrates. The amounts of the separate
solutions required to prepare a catalyst or catalyst precursor are
transferred in the desired ratio into a small separate reaction
vessel in which the components are intensively mixed. They can be
metered, for example, using automated pipettes or an ink-jet unit.
When the components are mixed, a reaction or precipitation of the
components can occur. Using precipitants such as ammonia,
precipitation is induced or completed if necessary, so that a
suspension of the mixed catalyst precursor material is frequently
present.
[0102] Since the suspension should have a suitable viscosity to be
able to be introduced into a tube of the tube-bundle reactor and
distributed, so as to give a distribution of the catalyst or
catalyst precursor on the tube inner wall as uniform as possible
and substantially adherent, if necessary the suitable suspension
viscosity can be set to the desired value as described above by
further additives. The suspension can be withdrawn from the
reaction vessel in this case, for example, using pipettes, and
distributed in the tube, as described below, by injection or
atomization. The reaction vessel can in this case be completely or
partially emptied. A plurality of reaction vessels can be operated
in parallel, or one reaction vessel, after partial emptying, can be
refilled with other components, to achieve an altered
composition.
[0103] The mixtures prepared are coated, preferably using an
injection process, onto various parts of an, in particular,
metallic tube reactor or heat exchanger, in particular onto the
tube inner walls of (preferably metallic) reaction tubes of a
tube-bundle reactor at a 10-2000 .mu.m thick layer, generally each
tube being coated with a mixture of differing composition (to test
reproducibility, a plurality of mixtures of the same composition
can also be used in a plurality of tubes).
[0104] To test layer thickness effects (such as transport effects),
the same catalyst compositions can also be applied at different
layer thicknesses to different tubes.
[0105] In a further variant of the invention, auxiliary supports
(preferably metallic or ceramic tubes) are used which have been
coated with the liquid mixture after, or preferably before,
insertion into the reaction tubes of a tube-bundle reactor.
[0106] Auxiliary supports which can be used here are tubes having
any desired cross section, preferably circular. The material of the
auxiliary supports can be chosen freely, for example the auxiliary
supports can be made of glass, metal, activated carbon, graphite,
ceramics such as glass ceramics or sintered quartz. The material in
this case can be densely sintered or porous. Porous metals in this
case are, for example, sintered metals, metal gauzes, knitted metal
fabrics, metal felts or wire meshes. From the reaction aspect,
precisely metals offer great advantages with respect to their
properties, for example their thermal conductivity, especially if
it is expected that large amounts of heat must be removed or an
exact temperature control is necessary. In addition, the metallic
supports can already be the active composition. The tubes in this
case can also be segmented in such a manner that a plurality of
channels, preferably in parallel to one another, extend in parallel
to the longitudinal tube axis. The cross section of such tubes can
resemble a spoked wheel, for example. An outer tube and an inner
tube can also be connected by a multiplicity of through-spokes. The
number of the spokes can be chosen freely here.
[0107] As porous materials, the auxiliary supports can also be
solid, provided that they preferably have a high porosity. They can
be made up, for example, from foams of the abovementioned
materials. The solid bodies can have any desired suitable shape.
Suitable shapes are, for example, cylinders, cones, disks, sheets
etc.
[0108] Suitable auxiliary supports are offered, for example, by
ROBU Glasfilter-Gerte GmbH, D-57644 Hattert as sintered filters, by
PoroCer Keramikmembranen GmbH, D-07629 Hermsdorf as tubular
membranes for cross flow filtration, by Tami Deutschland GmbH,
D-07629 Hernsdorf/Thuringen as ceramic tubular membranes for cross
flow filtration and by Hi-Tech Ceramics, a Vesuvius Group Company,
Alfred, N.Y. 14802, USA as RETICEL ceramics. Clearly, products from
other suppliers can also be used.
[0109] The arrays according to the invention are preferably
prepared using auxiliary supports of this type by process f), as
described above. In this process, the auxiliary supports are
preferably coated outside the body and if appropriate heated. After
the supported catalysts prepared in this way have been introduced
into the predetermined channels of the body, the packed body is if
appropriate heated to dry the catalysts, with or without sintering
or calcining. The above described supported catalysts can have here
the auxiliary supports as catalyst supports.
[0110] Coating the bodies or the preferred heat exchanger is
described in more detail below.
[0111] The parts of the, preferably metallic, heat exchanger which
have been coated with the liquid mixture prepared in advance are
preferably the tube inner walls of, preferably, metallic
tube-bundle reactors. The reaction tubes of the tube-bundle reactor
can have any desired cross section, but generally have a round and,
in particular, circular cross section. The inner diameter is
preferably from 0.2 to 70 mm, preferably from 1 to 25 mm,
particularly preferably from 3 to 10 mm. The tube-bundle reactor
can comprise up to 30,000 reaction tubes or more, preferably from
10 to 20,000, particularly preferably from 100 to 10,000 reaction
tubes, which are generally each provided with a coating of
differing composition.
[0112] The coating with liquid mixtures can be applied by sponging,
slurrying, brushing, centrifuging, spraying and/or dipping.
Furthermore, the mixture can be poured into the individual tubes
and centrifuged at rotary speeds from 200 to 1000 rpm, preferably
at rotary speeds from 300 to 800 rpm. In a preferred embodiment,
the coatings on the inner side of the reaction tubes are prepared
by spraying on the abovementioned liquid mixture. The sprayed-on
mixture material is forced in the course of this into the surface
roughnesses of the substrate, air bubbles below the coating being
prevented. The mixture used can then adhere completely to the
sprayed interior. However, in particular in the case of low
adhesion and/or low viscosity of the mixture, some of the mixture
can be discharged again by dripping off. The auxiliary supports to
be coated, e.g. in the form of inner tubes, can be completely or
only partially coated. In this case, in particular the respective
reactor tube inlet and reactor tube outlet can be spared from the
coating by a suitable apparatus, in order to prevent any
later-occurring sealing problems with the feed and discharge
apparatuses to be connected for the fluid.
[0113] However, a treatment of the freshly impregnated porous
support composition with a reactive gas can be of great interest
precisely in the parallelized production of small amounts of
substances by processes a) to d). Thus, for example, by treating
with ammonia gas a porous support composition which has been
freshly impregnated with a metal nitrate solution, metal hydroxides
or oxide hydrates can be precipitated on the support. The advantage
over the described treatment of the porous support composition with
dispersions is the finer distribution of the active component on
the support which is potentially achievable. Other reaction gases,
for example hydrogen sulfide, carbon monoxide or prussic acid are
also conceivable candidates for this preparation process. Those
which are of particular interest for treating the freshly
impregnated support compositions are, for example, the reactive
gases ammonia, hydrogen sulfide, prussic acid and carbon dioxide.
Preferably, by means of the treatment with reactive gases a working
step, that is to say preparing dispersions of the active
components, can be saved, since the salt solutions of the active
components are employed directly.
[0114] To achieve particularly thick layers or particularly
homogeneous coatings, the reaction tubes can be coated repeatedly
successively. In this case, separate drying steps and/or calcining
steps and/or sintering steps can be connected in-between the
individual coatings of a reaction tube. The inner wall, in the case
of spraying, is advantageously coated using one or more atomizer
lances, preferably using one or more movable atomizer lances. In
this case, the atomizer lance is drawn through the tube to be
coated at a defined constant or varying speed during the atomizing
operation, e.g. using an automatic apparatus.
[0115] The thickness of the applied layer after drying, with or
without calcining or sintering, is preferably from 10 to 2000
.mu.m, particularly preferably from 20 to 500 .mu.m.
[0116] In addition before the coating on the inner tube, an
adhesion promoter and subsequently on this adhesion promoter a
covering layer which comprises a catalyst material and is
catalytically active can be applied. The adhesion promoter can
increase the adhesion of the catalytically active covering layer on
the inner tube. Moreover, when an adhesion promoter is used, the
service lives can be increased. Suitable adhesion promoters are
described above.
[0117] In addition, the adhesion of the catalytic layer can be
increased by a chemical, physical or mechanical pretreatment of the
inner tube prior to the coating. In the event of a chemical
pretreatment, the inner tubes can be pickled, for example by lyes
or preferably by acids. Furthermore, the inner tube can be
roughened by blasting with a dry blasting medium, in particular
corundum or quartz sand, to reinforce the adhesion. Furthermore,
cleansers which are a suspension of hard particles, e.g. corundum,
in a dispersion fluid, have also proved useful.
[0118] Furthermore, the coating on the preferably metallic inner
tube can comprise the constituents auxiliary support and a covering
layer which comprises a catalyst material and is catalytically
active, as is described, for example, in DE-A-19 600 685. In this
case, the auxiliary support preferably has an external shape which
at least essentially corresponds to the geometry of the surface to
be coated. Suitable auxiliary supports here are, as described
above, for example, metallic or ceramic bodies, e.g. wire braidings
or metal or ceramic tubes. In this case, at least the auxiliary
support, and preferably only the auxiliary support, is coated with
the catalytically active covering layer and the coated auxiliary
support is arranged in the entire reaction inner tube, or
preferably in a part of the reaction inner tube. In this
tube-in-tube arrangement, the outer tube can have, for example, a
tapering at one end, in order to prevent the inner tube from
falling out, and at the other end the projecting inner tube can be
pushed into the outer tube, for example, by springs or a springy
material.
[0119] The treatment of the dry porous support substances with
reactive gases in accordance with process e) can also lead to
materials of catalytic interest. Thus, for example, by simple
treatment of sintered metals with hydrogen or carbon monoxide,
oxidic surfaces can be removed and thus potential active
compositions can be generated. Or, thin coatings of salts may be
prepared from metallic supports using gases such as H.sub.2S, HCl
or SO.sub.2, which salts are also active components of potential
interest.
[0120] Gases of interest for such methods of preparation are, for
example, CO, NH.sub.3, N.sub.2, H.sub.2S, H.sub.2, HCl, H.sub.2S,
O.sub.2, Cl.sub.2, SO.sub.2, SO.sub.3, prussic acid, vapors of
organic solvents, etc.
[0121] The particular feature of the process according to the
invention is that each auxiliary support in the tube-bundle reactor
used generally has a different composition or a different layer
thickness of the catalytic coating. Furthermore, the coated
auxiliary supports can readily be exchanged for other auxiliary
supports having different coatings. For example, by means of a
suitable reactor construction (provision of shut-off valves etc.)
changing individual auxiliary supports during the reactor operation
can be possible.
[0122] Processes g) and h) describe procedures in which the use of
a solvent for application onto the porous support is completely
dispensed with. Processes g) of interest, which can also be carried
out in an uncomplicated manner, are those in which the active
component is applied to the support via the gas phase. Thus
sputtering or CVD processes can be used. Multicomponent mixtures of
active substances could be generated by sequential preparation
steps, by suitable mixing of the gaseous reactants or, for
instance, by sputtering with multicomponent targets.
[0123] Also of interest for the application of active compositions
is the direct application of a solid substance which is a precursor
of the active composition, see process h).
[0124] In this case processes can be used utilizing electrostatic
charging, similar to the situation as in customary coating methods
(powder coating: CD Rompp Chemie Lexikon [Rompp's chemistry
lexicon]--Version 1.0, Stuttgart/New York: Georg Thieme Verlag
1995; Powder Coating (Electrostatic Spraying) Ullmann's
Encyclopedia of Industrial Chemistry, Sixth Edition, 1998,
Electronic Release, 1998, Wiley-VCH, D 69451 Weinheim, Germany). By
subsequent treatment (for example thermal, using reaction gases),
the contact between the solid porous support composition and the
solid precursor substance can be generated. A high degree of
automation makes this technique appear particularly attractive.
[0125] When the coated tube-bundle reactor is heated under vacuum
or a defined gas atmosphere to temperatures of from 20 to
1500.degree. C., preferably from 60 to 1000.degree. C. particularly
preferably from 200 to 600.degree. C., very particularly preferably
from 250 to 500.degree. C., the coating applied in advance is freed
from solvent, if present, by drying. At an elevated temperature,
furthermore, sintering or calcining of the particles forming the
coating can occur. In this process, the actual catalytically active
coating is generally obtained.
[0126] To regulate the temperature, the reaction tubes are
preferably surrounded by a heat-carrier medium, for example by a
salt melt or liquid metal such as Ga or Na. In this case, the
liquid heat-carrier medium is fed and removed, preferably at
opposite points of the tube-bundle reactor, e.g. using a pump, in
order to lead it then through a (e.g. air-cooled) heat exchanger to
remove or deliver heat. The heat-carrier medium ensures, firstly,
that the temperature for the drying, for any following sintering of
the coating and subsequent fluid-phase test reaction, is set in the
reaction tubes. Secondly, the heat-carrier medium removes the heat
produced in the following test reaction and thus suppresses the
formation of hot spots along the catalyst coating, in which,
locally, a higher temperature prevails than in the remaining
catalyst coating.
[0127] This type of reaction procedure ensures that the heat
produced in the reaction is removed outstandingly well, so that
virtually no hot spots occur any longer.
[0128] In a further embodiment of the invention, the space between
the reaction tubes is filled with a solid material, preferably a
metal or a solid metal alloy. In this case, the tube-bundle reactor
transforms into a material block as described above, in particular
a metal block having channels or boreholes. The inner diameter of
the boreholes corresponds to the inner diameter of the reaction
tubes of the tube-bundle reactor here.
[0129] It is also possible to prepare differing heterogeneous
catalysts having a predetermined composition in the form of
unsupported catalysts or supported catalysts by known, for example
combinatorial, processes and to charge in each case one or more
predetermined tubes of the tube-bundle reactor or heat exchanger
with each of these preprepared heterogeneous catalysts. In this
case, the known types of shaped bodies can be used. For each
individual tube, it is possible to vary the bed height or the inert
content of a bed or to establish other bed parameters.
[0130] The catalysts are tested by reacting fluid reactants or
reaction mixtures which are generally present in the liquid, or
preferably gaseous, state. Preferably, oxidation catalysts are
tested by supplying, in parallel or in succession, individual, a
plurality or all tubes of the coated tube-bundle reactor with a gas
mixture of one or more saturated, unsaturated or polyunsaturated
organic staring materials (e.g. hydrocarbons, alcohols, aldehydes
etc.), oxygen-containing gas (e.g. air, O.sub.2, N.sub.2O, NO,
NO.sub.2, O.sub.3) and/or, for example H2, with or without an inert
gas, e.g. nitrogen or a noble gas, at temperatures of from 20 to
1200.degree. C., preferably at from 50 to 800.degree. C.,
particularly preferably at from 80 to 600.degree. C., the separate
removal of the respective gas streams, performed in parallel or in
succession, from the individual, plurality or all reaction tubes of
the tube-bundle reactor being ensured by a suitable apparatus.
[0131] A gas mixture, consisting of, for example, an
oxygen-containing gas (e.g. air, O.sub.2, N.sub.2O, NO, NO.sub.2,
O.sub.3) and/or H.sub.2 and the organic starting material to be
reacted (for example propene or o-xylene) is, for example, passed
through the generally differently coated reaction tubes of the
tube-bundle reactor. In addition to said gaseous substances, other
gaseous substances, such as Cl- or P-containing substances, can
also be present. The gas mixture can be passed here in succession
through the individual reactor tubes. In the preferred embodiment,
the gas mixture is passed through the reaction tubes in such a
manner that the gas mixture flows through all tubes simultaneously.
In this case, during the start-up of the reaction, i.e. during the
time that the catalytic coatings are activated, the composition of
the feed, the temperature of the heat-exchange medium or the
reaction tube, the residence time of the feed and/or the pressure
of the total gas in the tube-bundle reactor can be changed. The
product gases leaving the respective reaction tube, which gases are
produced by reaction of the reaction gases used, are generally
removed separately, but may also be removed collectively, and are
analyzed by diverse probes or analytical methods, e.g. with respect
to their composition.
[0132] The coated tube-bundle reactor can also be supplied with
said gas mixture directly after the suspension coating (omitting
the drying and sintering or calcining), in this case the drying
process and following sintering process taking place under said gas
mixture. In this case, the composition of the inner tube coating
can change. In particular, oxidic coatings, under highly reducing
conditions, can partially or completely release their oxygen or,
under highly oxidizing conditions, can take up oxygen into their
structure.
[0133] A constant gas mixture can be fed to the individual
differently coated reaction tubes of the tube-bundle reactor, for
example via a gas supply hood which can be mounted essentially
gas-tightly onto the tube-bundle reactor.
[0134] The gases used can be mixed prior to the feed into the gas
supply hood, or not until this, e.g. using a static mixer.
[0135] The individual reaction gases can be removed via an
apparatus mounted essentially gas-tightly on the tube-bundle
reactor, the individual reaction gases of the individual, plurality
of, or all reaction tubes being removed separately and then
analyzed separately via a valve switching.
[0136] Another way of removing separately the individual exhaust
gases of the respective generally differently coated reaction tubes
is a, for example, computer-controlled mechanically moved "sniffing
apparatus" having a sniffing line for the gas to be taken off,
which line is positioned essentially automatically on, in, or over
the exit of the respective reaction tube and then takes off a
reaction gas sample. The positioning and takeoff of the respective
reaction gas is preferably carried out here in such a manner that
only the actual reaction gas to be analyzed later, and no
additional external gas from outside, passes into the sniffing
line. If the sniffing apparatus is positioned on the reaction tube
end, an essentially gas-tight application of the sniffing line to
the reaction tube end, e.g. by pressing the sniffing apparatus onto
the end face of the tube reactor, is advantageous. If the sniffing
apparatus is positioned in or above the exit of the respective
reaction tube, it is advantageous to suck the reaction gases into
the sniffing apparatuses via a reduced pressure set in the sniffing
line in such a manner that the amount of the sucked-in reaction
gases is limited, so that no additional external gases are drawn
into the sniffing line. In the event that the sniffing line is
positioned in the exit of the respective reaction tube, it has
proved particularly advantageous if the end of the sniffing line is
tapered in such a manner that inserting the sniffing line into the
end of the respective reaction tube ensures that the reaction gases
exiting from the reaction tube in question are essentially sealed
gas-tightly from the exterior. After reaction gas has been taken
off from the reaction tube in question of the tube-bundle reactor,
the sniffing apparatus is, preferably automatically, positioned on,
in or over another reaction tube, generally the next exit of a
further reaction tube, in order to effect the next gas takeoff. In
this manner, all exhaust cases of the reaction tubes can be
delivered separately for a sample and then analyzed. It is not only
possible for the positioning to move on, in or over the reaction
tube exit, and the tube-bundle reactor to remain fixed, but the
sniffing line can remain fixed during the positioning and for the
tube-bundle reactor to be moved correspondingly. During the
positioning, both the sniffing apparatus and the tube-bundle
reactor can also move. In a preferred process variant, the
tube-bundle reactor remains unchanged and only the sniffing
apparatus is moved during the positioning, above or onto the
respective reaction tube ends. In another preferred process
variant, the tube-bundle reactor, during the positioning,
experiences a rotary movement around its axis, while the sniffing
line, during a positioning over the respective reaction tube ends,
carries out a linear motion in the direction toward the axis of
rotation of the tube-bundle reactor, while, when it is positioned
onto the respective reaction tube ends, the sniffing apparatus
carries out an additional motion parallel to the reactor axis. A
plurality of sniffing apparatuses can also be used simultaneously
for sampling the various reaction gases. In addition, a plurality
of combined tubes can also be sampled.
[0137] In a similar manner to the removal of gas via what are
termed sniffing lines, as an alternative to the gas supply hood,
the gas can be fed via such a principle, the individual tubes being
tested sequentially. Obviously, the exhaust gas sniffing line must
then be positioned synchronously with the feed line for fresh
gas.
[0138] The catalytic performance of the individual catalytic
coatings of the individual reaction tubes can be screened by
chemical analysis of the respective gas streams using suitable
methods known per se. The gas streams removed individually from the
individual reaction tubes of the tube-bundle reactor are in this
case analyzed individually for their composition, e.g. using
suitable apparatuses, e.g. via gas chromatography using flame
ionization detection and/or thermal conductivity detection, or, for
example using mass spectrometry. The gas composition obtained is
analyzed here in particular with respect to its relative content of
desired product, or of various desired products, and the resultant
concentrations related to the reacted starting material, values for
the respective conversion rates (activity) and product
selectivities being produced. In many cases it is useful here to
measure the product selectivities of the individual catalysts over
a relatively long time period of generally hours to a number of
weeks. In the selection of the catalyst coating most suitable for
the respective reaction, in order to limit the number of gas
analyses, it can be useful to make repeat measurements only on gas
compositions of selected reactor tubes which exceed a desired
limiting concentration or limiting selectivity of certain
products.
[0139] After the catalytic test, the catalytic inner coatings
applied can be removed, so that the remaining tube-bundle reactor
is again accessible to a renewed catalytic coating.
[0140] The catalyst coatings can be renewed by at least essentially
clearing off the old catalytically active covering layer of the
coating and applying a new catalytically active coating by
sponging, brushing, centrifuging, spraying and/or dipping.
Expediently, a choice is made of the same coating process which was
used to apply the catalytic coating previously removed. The old
catalytically active covering layer of the coating can be cleared
off in a simple manner in particular by blasting with a blasting
medium, e.g. corundum, silicon carbide, fine sand or the like.
Alternatively, treatment with steam or the use of chemical clearing
methods has also proved useful.
[0141] An efficient method of removing the inner coatings, for
example after the catalyst testing, is the use of brushing devices,
e.g. similarly to a bottle brush, in general in combination with
the described cleansers. Preference is given to the removal of the
inner coatings by an at least substantially automated route.
[0142] The process according to the invention can readily be
carried out in automated form by automated systems. Coating tubes
with the catalyst ensures an optimal flow of the fluid, causes only
a low pressure drop and prevents blockages in the individual
reaction tubes of the tube-bundle reactor.
[0143] The spatial separation and clear assignation of the tested
coatings offer the advantage of being able to test simultaneously,
using one apparatus (tube bundle), a number of materials, generally
corresponding to the number of tubes, in parallel with reduced cost
and time consumption.
[0144] Furthermore, in comparison with other systems, e.g.
perforated plates, CVD arrays, etc., the tube-bundle reactor offers
the advantage of testing in a manner as close as possible to an
industrial process (scale-up capacity is retained). An industrially
relevant optimization can be carried out very rapidly and
cost-effectively, in particular also, because a multiplicity of
catalysts can be tested in parallel/simultaneously under the same
conditions.
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