U.S. patent application number 14/944697 was filed with the patent office on 2016-07-14 for process for preparing catalysts.
This patent application is currently assigned to Johnson Matthey PLC. The applicant listed for this patent is Johnson Matthey PLC. Invention is credited to Fiona Mary Campbell, Graeme Douglas Campbell, Gordon James Kelly, Brian Peter Williams.
Application Number | 20160199818 14/944697 |
Document ID | / |
Family ID | 37508021 |
Filed Date | 2016-07-14 |
United States Patent
Application |
20160199818 |
Kind Code |
A1 |
Campbell; Graeme Douglas ;
et al. |
July 14, 2016 |
PROCESS FOR PREPARING CATALYSTS
Abstract
A process for manufacturing a catalyst composition comprises the
steps of (i) precipitating one or more metal compounds from
solution using an alkaline precipitant, preferably comprising an
alkaline carbonate, optionally in the presence of a
thermostabilising material, ii) ageing the precipitated
composition, and (iii) recovering and drying the aged composition,
wherein the ageing step is performed using a pulse-flow
reactor.
Inventors: |
Campbell; Graeme Douglas;
(Lancashire, GB) ; Kelly; Gordon James; (County
Durham, GB) ; Campbell; Fiona Mary; (Cleveland,
GB) ; Williams; Brian Peter; (Lancashire,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Johnson Matthey PLC |
London |
|
GB |
|
|
Assignee: |
Johnson Matthey PLC
London
GB
|
Family ID: |
37508021 |
Appl. No.: |
14/944697 |
Filed: |
November 18, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12446108 |
Oct 12, 2010 |
9221034 |
|
|
PCT/GB2007/050643 |
Oct 18, 2007 |
|
|
|
14944697 |
|
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Current U.S.
Class: |
502/329 |
Current CPC
Class: |
B01J 37/14 20130101;
B01J 2523/00 20130101; B01J 8/40 20130101; B01J 19/006 20130101;
B01J 37/16 20130101; B01F 11/0071 20130101; B01F 3/12 20130101;
B01J 37/0009 20130101; B01J 2219/00777 20130101; B01J 23/002
20130101; B01J 19/243 20130101; B01J 2523/31 20130101; B01J 2523/27
20130101; B01J 2523/17 20130101; B01J 2523/22 20130101; B01J
2523/12 20130101; B01J 2523/842 20130101; B01J 2523/27 20130101;
B01J 2523/22 20130101; B01J 2523/31 20130101; B01J 2523/17
20130101; B01J 2523/00 20130101; B01J 37/031 20130101; B01J 35/0053
20130101; B01J 2523/00 20130101; B01J 37/08 20130101; B01J 23/80
20130101; B01J 35/023 20130101 |
International
Class: |
B01J 23/80 20060101
B01J023/80; B01J 37/03 20060101 B01J037/03; B01J 37/08 20060101
B01J037/08; B01J 23/00 20060101 B01J023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2006 |
GB |
0620793.0 |
Claims
1. A process for manufacturing a catalyst composition comprising
the steps of (i) precipitating a composition comprising one or more
metal compounds from solution using an alkaline carbonate
precipitant, (ii) ageing the precipitated composition with
evolution of carbon dioxide, and (iii) recovering and drying the
aged composition, wherein the ageing step is performed using a
pulse-flow reactor having one or more inlets for introducing a
slurry of the precipitated composition, one or more outlets for
removing the aged composition, and one or more outlets for removing
carbon dioxide.
2. A process according to claim 1 wherein the one or more metal
compounds comprise one or more metals selected from the group
consisting of Ca, Mg, Ti, V, Cr, Mn, Fe, Cr, Co, Ni, Cu, Zn, or
Pb.
3. A process according to claim 1 wherein the one or more metal
compounds comprise one or more metals selected from the group
consisting of Co, Ni, Cu or Fe.
4. A process according to claim 1 wherein the one or more metal
compounds comprise one or more metals selected from the group
consisting of Cu, Zn and Mg.
5. A process according to claim 1 wherein a metal oxide
thermostabilising material is present during the precipitation of
the composition.
6. A process according to claim 1 wherein an alumina sol is present
during the precipitation of the composition.
7. A process according to claim 1 wherein the alkaline carbonate
precipitant is selected from the group consisting of sodium
carbonate and potassium carbonate.
8. A process according to claim 1 wherein the pulse flow reactor
comprises an elongate vessel and means for imposing on the slurry a
pulsatile oscillatory motion in a direction substantially parallel
to the direction of fluid flow in the elongate vessel, wherein (i)
the one or more inlets for introducing the slurry of the
precipitated composition is located at a first end or at any other
point along the length of the elongate vessel, (ii) the one or more
outlets for removing the aged composition and carbon dioxide are
located at a second end opposite to the first end or at any point
along the length of the elongate vessel, and (iii) a plurality of
stationary baffles are mounted substantially traversely to the
direction of fluid flow within the elongate vessel.
9. A process according to claim 1 wherein the pulse-flow reactor
comprises a single straight section or a plurality of straight
sections joined by U-bends.
10. A process according to claim 1 wherein the pulse-flow reactor
is in a horizontal orientation or a vertical orientation.
11. A process according to claim 8 wherein the Internal
cross-sectional area of the pulse-flow reactor taken up by each
baffle is the same or different along the length of the reactor and
is 20-80% of the total area.
12. A process according to claim 8 wherein when pulse-flow reactor
is of circular cross-section, the baffles are discs having one
central orifice through which the slurry may pass or comprise
several orifices, or the discs are imperforate and have a smaller
diameter than the internal diameter of the vessel thus leaving an
annular space around their periphery.
13. A process according to claim 8 wherein 5 or more baffles are
present in the pulse-flow reactor.
14. A process according to claim 8 wherein the pulsatile
oscillatory motion is provided by continuously pumping the slurry
along the elongate vessel using a centrifugal, diaphragm or gear
pump and superimposing reciprocating oscillations by using a
mechanism selected from the group consisting of a pump, valve, and
a piston located so as to constitute an end wall of the pulse-flow
reactor, or in hydraulic communication with an end of the
reactor.
15. A process according to claim 8 wherein the pulsatile
oscillatory motion has an oscillation frequency in the range 0.1-10
Hz.
16. A process according to claim 8 wherein the pulsatile
oscillatory motion has an amplitude in the range 0.05-0.5 times the
diameter of the reactor.
17. A process according to claim 1 wherein the ageing step is
performed at a temperature in the range 0 to 100.degree. C.
18. A process according to claim 1 further comprising a step of
calcining the aged composition.
19. A process according to claim 3 further comprising a step of
reducing the one or more metal compounds.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 12/446,108, filed Oct. 12, 2010, which is a U.S. National Phase
application of PCT International Application No. PCT/GB2007/050643,
filed Oct. 18, 2007, and claims priority of British Patent
Application No. 0620793.0, filed Oct. 20, 2006, all of which are
incorporated herein by reference in their entireties.
FIELD OF THE INVENTION
[0002] This invention relates to a process for preparing
precipitated catalyst compositions and in particular in to the
ageing of precipitated catalyst slurries prior to drying and
further processing.
BACKGROUND OF THE INVENTION
[0003] Manufacturing processes whereby catalyst compositions are
precipitated using an alkaline precipitant are known and typically
include the steps of forming an aqueous, often an acidic solution
of metal compounds, combining the solution with an alkaline
precipitant, generally an aqueous solution of one or more of an
alkali metal carbonate, alkali metal bicarbonate, alkali metal
hydroxide, ammonium carbonate or ammonium hydroxide, to effect
precipitation of insoluble metal compounds. The insoluble compounds
may be aged for a period in the slurry phase. The aged slurry is
then filtered to recover the catalyst composition and dried.
Calcination, whereby the dried catalyst composition is heated to
elevated temperature to effect a physiochemical change may also be
performed. Furthermore, for certain reducible catalyst
compositions, for example those comprising Ni, Cu, Co or Fe, the
dried or calcined materials may subsequently be exposed to a
reducing gas such as hydrogen or carbon monoxide to convert the
metal into its elemental or zero-valent state. Subsequent
passivation of the reduced catalyst composition may also be
performed.
[0004] Precipitation is a very rapid process and a subsequent
ageing step allows the initially formed precipitate to transform
into desired phases and/or morphologies, e.g. a desired crystallite
size. Ageing is typically carried out in a batch or semi-continuous
procedure whereby the aqueous slurry of precipitated metal
compounds is held at elevated temperatures in one or more stirred
vessels for selected periods of time. Continuous processes
typically employ a number of stirred tanks in series. Such
procedures have been used although they can be difficult to control
and are therefore prone to give undesirable product variation.
Despite this, the development of a suitable single stage continuous
process has not been heretofore successful.
SUMMARY OF THE INVENTION
[0005] We have found that the use of a pulse-flow reactor in
catalyst ageing overcomes the problems associated with prior art
processes and offers process intensification by reducing the
overall equipment size.
[0006] Accordingly the invention provides a process for
manufacturing a catalyst composition comprising the steps of [0007]
(i) precipitating one or more metal compounds from solution using
an alkaline precipitant, optionally in the presence of a
thermostabilising material, [0008] (ii) ageing the precipitated
composition, and [0009] (iii) recovering and drying the aged
composition, [0010] wherein the ageing step is performed using a
pulse-flow reactor.
BRIEF DESCRIPTION OF THE DRAWING
[0011] The invention is further illustrated by reference to the
following drawing in which FIG. 1 is a diagrammatic cross-section
of a pulse-flow reactor that may be used to age precipitated
catalyst precursors.
DETAILED DESCRIPTION OF THE INVENTION
[0012] We have found that using a pulse-flow reactor, the ageing
step may be performed in a single stage continuous unit.
[0013] Pulse-flow reactors (PFR) are known and generally comprise a
elongate, e.g. tubular, vessel having an inlet for reactants at one
end, an outlet for products the other end, spaced transverse,
sharp-edged baffles or plates arranged along the length of the
vessel, or in a helical arrangement, and means to induce a
pulsatile motion to material passing through the vessel.
[0014] EP 0229139 describes PFR apparatus for mixing a fluid
material comprises an elongated vessel to contain the material,
means to impose oscillatory motion upon the material in a
lengthwise direction, and a plurality of stationary obstacles
mounted on the inner wall of the vessel and arranged in sequence
lengthwise. The obstacles present sharp ridge-form tips, each ridge
pointing in a direction at right angles to that of the oscillating
motion. Each adjacent pair of obstacles and the length of vessel
wall between them define a zone in which the oscillating motion
forms vortices and then ejects those vortices vigorously into the
remainder of the fluid outside the trough, so promoting the
agitation of that fluid. Hence, the oscillating fluid interacts
with each obstacle to form vortices and the resulting motion gives
effective and uniform mixing in the zone. As a plurality of these
well-mixed zones exist within the vessel, the result is excellent
local and global mixing; approaching a plug-flow residence time
distribution.
[0015] EP 0631809 describes the operation of a PFR for mixing
heterogeneous or multiphase systems comprising a continuous phase
and at least a solid dispersed phase wherein mixing is carried out
by actuating means for pulsing the continuous phase. The PFR was
described as being useful for gas phase fluidised bed reactions and
gas slurry reactions such as the production of polyethylene from
ethylene or solid catalysed reactions such as carbonylation
reactions.
[0016] These disclosures do not disclose or suggest that such
reactors may be useful in catalyst manufacture, let alone that they
may be useful in ageing precipitated metal compounds.
[0017] In the present invention, one or more insoluble metal
compounds are precipitated by combining an aqueous solution of one
or more soluble metal compounds, such as a metal nitrate, sulphate,
acetate, chloride or the like, and an aqueous solution of an
alkaline precipitant. The solutions of metal compound and alkaline
precipitant may be combined in any manner known to those skilled in
the art of catalyst manufacture. Upon combining the metal solution
and precipitant solution, the alkaline precipitant reacts with the
soluble metal compound to precipitate insoluble metal compounds
such as the metal hydroxide, metal carbonate and metal
hydroxycarbonate. The precipitation may be performed at
temperatures in the range 0-100.degree. C., preferably
10-90.degree. C. The pH of the combined solution is preferably
6-12, more preferably 8-11.
[0018] The precipitated metal compounds are desirably compounds
suitable for the preparation of catalysts or catalyst precursors.
Hence, the precipitated metal compounds may comprise metal
carbonates, metal hydroxycarbonates and metal hydroxides of any of
the catalytically active metals found in catalyst or catalyst
precursors, including alkali-earth metals, transition metals and
non-transition metals. Preferably the precipitated metal compounds
comprise compounds of metals selected from Ca, Mg, Ti, V, Ce, Zr,
Al, La, Y, Co, Mn, Fe, Cr, Ni, Cu, Zn, or Pb. Mixtures of metal
compounds may be present. More preferably the precipitated metal
compounds comprise compounds of metals selected from Co, Ni, Cu or
Fe, especially Cu and Zn.
[0019] It may be desirable, in order to enhance the properties of
the catalyst or catalyst precursor, to include with the
precipitated metal compound other insoluble components in the
catalyst composition and therefore a metal oxide thermostabilising
material such as a metal oxide powder, gel or sol may be included
or formed during the precipitation of the insoluble metal
compounds. Alumina, silica, titania, zirconia and other insoluble
metal oxide compounds and/or the corresponding metal hydroxides or
hydrated oxides may be present. Metal oxide sols of these oxides
are especially useful and a preferred thermostabilising material is
an alumina sol. Alumina sol-containing catalyst compositions are
described for example in U.S. Pat. No. 4,535,071.
[0020] In addition to the catalytic metal compounds and the
thermostabilising material the catalyst or catalyst precursor may
contain one or more promoters such as an alkali metal compounds,
alkali-earth metal compounds, transition metal compounds, rare
earth compounds and precious metals such as Ru, Pt or Pd. Preferred
promoters in Cu-containing catalyst compositions are compounds of
Mg, Cr, Ce, La, Pd, Zr and Mn.
[0021] The catalyst or catalyst precursor may contain one or more
spinel oxides.
[0022] A preferred catalyst precursor composition comprises, prior
to calcination or reduction, a solid containing mixed metal
hydroxycarbonates, of Cu and Zn, with alumina dispersed therein and
optionally containing one or more Mg, Cr, Ce, La, Pd, Zr or Mn
compounds as a promoter. The ratio of Cu:Zn atomic ratio is
preferably in the range 2:1 to 3.8:1 by weight. The catalyst
precursor preferably comprises 30-70% copper (expressed as oxide),
20-90% zinc (expressed as oxide), 5-40% weight alumina and 0.01 to
2.00% by weight of promoter metal. Particularly suitable catalyst
and catalyst precursor compositions are described in U.S. Pat. No.
4,788,175.
[0023] The alkaline precipitant may be any known precipitant such
as alkaline hydroxides, carbonates or hydrogen carbonates,
including ammonium hydroxide and ammonium carbonate. Mixtures of
alkaline precipitants may be used, for example a mixture of an
alkaline carbonate and an alkaline hydroxide. Suitable organic
bases may also be used. Preferably the alkaline precipitant
comprises an alkaline carbonate. By the term "alkaline carbonate
precipitant" we include bicarbonate or metal hydrogen carbonate.
The alkaline carbonate precipitant is preferably a carbonate of an
alkali metal such as sodium or potassium. Non-carbonate
precipitants such as alkali metal hydroxides, e.g. sodium hydroxide
or potassium hydroxide, or ammonium hydroxide may be combined with
the alkaline carbonate. The concentration of metal carbonate in the
precipitant solution may be >25% wt, preferably >30% wt.
[0024] Once the metal solution and precipitant solutions are
combined and precipitation of insoluble metal compounds has begun,
the resulting slurry may be aged. Ageing allows changes in the
particle size and morphology to occur and these changes can be
desirable in terms of the resulting catalyst physical properties
and performance. Carbon dioxide may be evolved from precipitated
metal carbonate materials during the ageing process. If desired
metal oxide thermostabilising material may be added during the
ageing step.
[0025] In the present invention, the ageing step is performed in a
pulse-flow reactor. While precipitation and ageing may be combined
in the pulse-flow reactor it is preferred to have separate
precipitation and ageing reactors.
[0026] The pulse flow reactor may be an elongate vessel, preferably
of circular cross section. A slurry of the freshly precipitated
composition and water may be introduced into the vessel from one or
more inlets which may be located at either end or at any other
point along the length of the reaction vessel, although preferably
they are located at one end, e.g. at the bottom (where the reactor
is disposed vertically). Correspondingly the vessel is provided
with one or more outlets for removing the aged composition, and any
evolved carbon dioxide, which may again be located at the opposite
end or at any point along the length of the vessel but are
preferably at the other end from the inlet, i.e. where the reactor
is disposed vertically, at the top end. The vessel is provided with
means for imposing on the slurry (i.e. the precipitated composition
and water) a pulsatile oscillatory motion in a pre-determined
direction, preferably a direction substantially parallel to the
direction of fluid flow, and a plurality of stationary baffles
mounted substantially traversely to the direction of fluid flow. By
imposing an oscillating motion to the material contained in the
vessel, the reactants are caused to cross and re-cross the
stationary baffles thereby providing vigorous mixing. Such an
apparatus is described for example in the aforesaid EP 0229139 and
EP 0631809.
[0027] The PFR may comprise a single straight section or may
comprise a plurality of straight sections joined by U-bends so that
the reactor occupies a smaller space. The PFR can be used in a
horizontal orientation or a vertical orientation. In either
orientation, the reactants enter one end of the reactor, flow along
the length of the reactor and emerge at the other end. Carbon
dioxide may be recovered through one or multiple outlets disposed
on the uppermost surface of the vessel wall. In a horizontal
orientation, the baffles in the reactor are suitably spaced from
the lowermost inner wall of the reactor to prevent accumulation of
solids. Preferably however, the PFR is operated in a vertical
orientation as this allows substantially vertical movement of the
reactants through the vessel and simplifies carbon dioxide recovery
from the vessel.
[0028] The internal cross-sectional area of the reactor taken up by
each baffle may be the same or different along the length of the
reactor but is preferably 20-80%, more preferably 40-60% of the
total area. Where the PFR is of circular cross-section, the baffles
preferably are perforate discs which may contact the inside wall of
the reactor or may be in a spaced relationship with the inside wall
of the reactor. Such discs may have one central orifice through
which the slurry may pass or may comprise several orifices.
Alternatively, the discs may be imperforate and have a smaller
diameter than the internal diameter of the vessel thus leaving an
annular space around their periphery.
[0029] The number of baffles is dictated by the dimensions of the
reactor, the desired residence time distribution and the degree of
mixing required. Preferably >5 baffles are present in the
PFR
[0030] Un-baffled regions may be provided within the PFR if desired
to facilitate addition/removal of material to/from the reactor or
to facilitate disengagement of any carbon dioxide from the slurry.
In particular in a vertical arrangement a disengagement portion is
desirable adjacent the one or more outlets of the reactor,
especially where the outlets are at the top of the reactor.
[0031] The pulsatile flow may be provided by continuously pumping
the slurry along the vessel using a centrifugal, diaphragm or gear
pump and superimposing reciprocating oscillations by using suitable
pumps, valves or other mechanisms such as a piston located so as to
constitute an end wall of the reactor, or in hydraulic
communication with and end of the reactor. Other mechanical
reciprocating devices such as double piston pump may be used.
Alternatively a pulsed air leg or other hydraulic means may be
used.
[0032] The scale of the PFR may suitably be chosen according to the
end use. For example, the reactor may have an internal diameter in
the range 15 to 4000 mm, preferably 25-1000 mm and a length in the
range 0.5 to 5 metres and annular baffles spaced apart by 30-600
mm. Furthermore, the cross-sectional width, e.g. Internal diameter,
of the PFR may be the same or different along the length of the
reactor.
[0033] The pulsing or oscillation frequency will depend upon the
reactants, the density of each component therein and the viscosity
of the system, as well as the degree of mass and heat transfer and
mixing required. The pulsing frequency may be 0.1-10 Hz, preferably
1-5 Hz with an amplitude >2 mm, preferably >5 mm. Preferably
the amplitude of the oscillation is in the range 0.05-0.5 times the
diameter of the PFR.
[0034] The mean flow of the PFR will depend upon the scale of
operation as well as particle size of the solid reactants and the
slurry concentration. For example the mean flowrate may be in the
range 5-50 m.sup.3/hr.
[0035] The ageing step within the PFR may be performed at
temperatures in the range 0-100.degree. C. and at ambient or
elevated pressure within the boiling limits of the liquid phase in
the slurry. Hence where the liquid phase comprises water, at
atmospheric pressure, the reactants may suitably be heated to
between 20 and 95.degree. C., preferably 40 and 90.degree. C. using
external heating means such as a steam or hot-water jacket. Higher
temperatures may be used where the reactants are pressurised.
[0036] During ageing some carbon dioxide may be evolved. If
desired, this carbon dioxide may be recovered from the ageing step
and used to prepare a metal carbonate precipitant.
[0037] Once precipitation and ageing steps are completed, the
precipitated compositions comprising the insoluble metal compounds
may be recovered by filtration, centrifuge or decanting using known
methods.
[0038] It is preferable to wash the recovered precipitated
composition to remove soluble compounds such as soluble metal
salts, e.g. Na- or K-nitrates. Washing may be performed using
water, preferably de-mineralised water, at ambient, or preferably,
elevated temperature. The recovered solids are then further
processed into catalyst or catalyst precursor materials.
[0039] The further processing of the insoluble metal compounds into
a catalyst or catalyst precursor will often include a step of
drying the insoluble metal compounds. This may be achieved by
heating the damp precipitated material in air or an inert gas to
temperatures in the range 25-120.degree. C. in an oven or vacuum
oven. The washed catalyst composition may be spray dried using
known methods. For example, suitable spray drying methods are
described in U.S. Pat. No. 4,522,938.
[0040] In one embodiment, the precipitated catalyst compositions
comprising the Insoluble metal compounds may be further processed
by calcining, i.e. by heating them in a calciner to temperatures in
the range 200-600.degree. C., preferably 250-400.degree. C. for a
period up to 24 hours, preferably up to 8 hours to effect a
physiochemical change whereby the precipitated metal compounds are
converted into their corresponding oxides.
[0041] Where the precipitated compositions include one or more
metals selected from Cu, Ni, Co or Fe, they may be further
processed by reduction with a reducing gas such as hydrogen or
carbon monoxide, or gas mixtures containing these in a reducer. The
insoluble compounds may be reduced directly or may be calcined and
then reduced. Direct reduction methods are described in U.S. Pat.
No. 4,863,894.
[0042] Where the catalyst composition comprises Cu, Ni, Fe or Co in
reduced form, the high reactivity of the reduced metal with oxygen
in air may pose a handling problem due to the pyrophoric nature of
the catalysts. It is therefore preferred that such reduced catalyst
compositions are passivated. Passivation may be achieved by using
inert gas/air mixtures, such as nitrogen/air mixtures, whereby the
air concentration is slowly increased over a period in order to
generate a thin metal oxide later on the catalyst surface.
Alternatively, reduced catalyst compositions comprising one or more
of Cu, Fe, Ni or Cu may be passivated using a gas mixture
comprising carbon dioxide and oxygen with a CO.sub.2O.sub.2 ratio
>2:1 in order to form a thin layer of a metal carbonate, e.g. a
metal hydroxycarbonate, on the surface. Suitable passivation
procedures are described in U.S. Pat. No. 5,928,985.
[0043] Preferably the catalyst or catalyst precursor is formed into
shaped units such as tablets, pellets, granules or extrudates using
known methods. Where the catalyst composition comprises Cu, Ni, Fe
or Co, the shaping may be performed before or after any reduction
step.
[0044] In FIG. 1, a pulse-flow-reactor (PFR) suitable for ageing
precipitated catalysts is depicted. The PFR comprises an elongate
tubular body 10 in a vertical arrangement, having a slurry inlet 12
adjacent the bottom of the reactor and a slurry outlet 14 adjacent
the top of the reactor. A CO.sub.2 vent 16 is provided at the top
of the reactor. Stationary baffles 18 are disposed evenly within
the body 10 along the length of the reactor. Thirteen baffles are
depicted, but the reactor may comprise more or fewer baffles as
dictated by its size. The baffles 18 are each in the form of a disc
having a diameter equal to the internal diameter of the body 10 and
supported by support rods (not shown) running the length of the
reactor. The baffles 18 have a single central orifice of cross
sectional area between 80% and 20% of the internal cross-sectional
area of the body 10. At the bottom of the body 10 the end of the
reactor comprises a flexible impermeable membrane 20 that imparts
oscillatory motion to the slurry passing through the body 10. The
body membrane 20 is moved upwards and downwards by a hydraulic
fluid 22, which is in turn moved by a flexible pump membrane 24
driven by a piston 26 and motor (not shown). In this embodiment,
the pump membrane 24 and body membrane 20 are at right angles, but
it will be understood that other configurations are possible. The
body 10 of the vessel has an external heating jacket 28 heated by
hot water.
[0045] In use, the slurry of the catalyst precursor composition,
e.g. composition comprising Cu, Zn, Mg and Al according to U.S.
Pat. No. 4,788,175, is fed continuously by a pump (not shown)
through inlet 12 to the inside of the body 10. The slurry is
maintained at elevated temperature by means of the heating jacket
28. By action of the pump, the slurry is passed vertically up
through the reactor and leaves the body 10 through outlet 14. As it
passes through the body 10, the slurry is subjected to oscillatory
motion caused by oscillating membrane 20 and repeatedly contacts
the edges of each of the baffles 18. The oscillatory motion is
controlled in terms of frequency and amplitude by the piston 26
acting upon the hydraulic fluid 22 and membrane 20. Carbon dioxide
is able to disengage from the slurry at the top of the reactor and
is vented through CO.sub.2 vent 16.
[0046] Whereas only single vessel is depicted in FIG. 1, it will be
understood that more than one PFR may be used depending upon the
scale of catalyst manufacture.
Examples
[0047] The invention is further illustrated by reference to the
following Examples using a PFR as depicted in FIG. 1 having a
length of 1514 mm, an Internal diameter of 50 mm, 21 baffles in the
form of discs, spaced apart by 72 mm and having a diameter of about
50 mm and a single central orifice of 29 mm diameter. Four
parameters (flowrate, slurry temperature, oscillation frequency and
oscillation amplitude) were varied as follows;
TABLE-US-00001 Flowrate Temp Freq. Amplitude Experiment litres/hr
.degree. C. Hz mm 1 15 65 3.5 10 2 15 65 1 5 3 15 45 3.5 5 4 15 45
1 10 5 5 65 3.5 5 6 5 65 1 10 7 5 45 3.5 10 8 5 45 1 5
[0048] Each flow condition (in terms of net flow and oscillatory
flow) can be described by 3 dimensionless groups: net Reynolds
number, Re.sub.n; oscillatory Reynolds number, Re.sub.0; and
Strouhal number, Sf. These dimensionless groups take the form:
Re n = .rho. ( UD ) .mu. ##EQU00001## Re .upsilon. = x .omega. ( D
.rho. ) .mu. ##EQU00001.2## St = D 4 .pi. x ##EQU00001.3##
[0049] The values of each dimensionless group for the 8 experiments
are given below.
TABLE-US-00002 Experiment Re.sub.n Re.sub.o SI 1 149 23500 0.786 2
149 3260 1.572 3 149 11700 1.572 4 149 6510 0.786 5 75 11700 1.572
6 75 6510 0.786 7 75 23500 0.786 8 75 3260 1.572
[0050] A slurry of a catalyst precursor composition comprising Cu,
Zn, Mg and Al was prepared according to U.S. Pat. No. 4,788,175.
The slurry comprising metal carbonates, including
hydroxycarbonates, was passed directly to the PFR, which operated
according to the above conditions. Material leaving the PFR was
filtered on a vacuum filter pot and washed 3 times with twice its
own volume of hot demineralised water. The filtered and washed
material was oven dried at 110.degree. C. for 16 hours. Samples of
the dried material were characterised by particle size, XRD, ICP,
TGA/DSC and copper surface area (CuSA).
[0051] The particle size (in .mu.m) of each sample was measured
using a Malvern Instruments Mastersizer 2000 laser diffraction
unit. The dried sample was re-slurried in demineralised water and
then finely dispersed by ultrasonic agitation. The results for each
experiment are given below.
TABLE-US-00003 Experiment d.sub.10 d.sub.50 d.sub.90 1 2.544 19.704
56.600 2 3.205 17.817 41.122 3 3.083 21.942 75.446 4 2.371 15.082
39.061 5 7.646 21.473 40.062 6 3.602 17.987 43.317 7 2.443 18.958
52.913 8 2.055 18.505 63.729
[0052] The crystal structure of each sample was determined by XRD
technique using a Siemens D5000 diffractometer. All the samples
contained malachite [Cu.sub.2(CO.sub.3)(OH).sub.2] and smithsonite
[ZnCO.sub.3] phases.
[0053] The chemical composition of the samples (in terms of weight
percent CuO, ZnO, MgO, Al.sub.2O.sub.3, Fe.sub.2O and Na.sub.2O)
was determined using ICP-Atomic Emission Spectroscopy on a loss
free basis. The residual alkali composition was recorded to
evaluate the ease by which the sodium ions could be washed from the
filter cake taken from the PFR. The chemical composition of the
samples (% wt) is given below.
TABLE-US-00004 Experiment CuO ZnO MgO Al.sub.2O.sub.3
Fe.sub.2O.sub.3 Na.sub.2O 1 68.4 24.7 1.4 5.2 0.014 0.044 2 63.9
24.6 2.2 9.0 0.014 0.120 3 64.0 24.6 2.2 8.3 0.014 0.680 4 58.9
24.5 3.0 12.9 0.018 0.400 5 65.3 25.0 1.9 7.5 0.020 0.077 6 55.0
25.7 3.8 15.2 0.040 0.067 7 54.1 24.9 3.6 15.1 0.023 1.200 8 64.2
25.0 2.0 7.7 0.013 0.840
[0054] The samples were pelletized by passing the dried filter cake
through a 1.7 mm sieve and then calcining at 300.degree. C. for 6
hours, or until the weight loss on ignition was 14-18%. The
calcined powder was then mixed with 2% w/w graphite and
pre-compacted and passed through a 1.4 mm sieve, before being
pelleted to a density of 2 g/cm.sup.3.
[0055] Copper surface areas were determined on the pellets by first
grinding them 0.6-1.0 mm, reducing the crushed pellets in a stream
of hydrogen and analysing them according the method described in
EP202824.
[0056] The results were as follows;
TABLE-US-00005 Copper surface area (m.sup.2/g) Experiment
Discharged Discharged weight ratio 1 69.22 1.69 2 58.77 1.46 3
51.24 1.27 4.sup.a 60.45 1.47 5.sup.a 60.45 1.47 6.sup.b -- -- 7
49.72 1.21 8 52.34 1.30 standard.sup.c 45.00 1.10 .sup.aThe samples
for Experiments 4 and 5 were combined together. .sup.bNo result
obtained. .sup.cStirred tank ageing at 50-80.degree. C.
[0057] The results demonstrate that the PFR ageing is possible and
that continuous PFR ageing can provide catalysts with high copper
surface areas.
[0058] The references discussed herein are hereby incorporated by
reference.
* * * * *