U.S. patent application number 10/168480 was filed with the patent office on 2003-05-15 for process for the production of olefins.
Invention is credited to Couves, John William, Griffiths, David Charles, Messenger, Brian Edward, Reid, Ian Allan Beattie.
Application Number | 20030092953 10/168480 |
Document ID | / |
Family ID | 26243888 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030092953 |
Kind Code |
A1 |
Couves, John William ; et
al. |
May 15, 2003 |
Process for the production of olefins
Abstract
A process for the production of an olefin from a hydrocarbon,
which process comprises: partially combusting the hydrocarbon and
an oxygen-containing gas in the presence of a catalyst,
characterised in that the catalyst comprises palladium and at least
one further metal, said further metal being a Group IIA, Group IVA,
VA or a transition metal.
Inventors: |
Couves, John William;
(Buckinghamshire, GB) ; Griffiths, David Charles;
(Esher, GB) ; Messenger, Brian Edward; (Englefield
Green, GB) ; Reid, Ian Allan Beattie; (Southfields,
GB) |
Correspondence
Address: |
Nixon & Vanderhye
8th Floor
1100 North Glebe Road
Arlington
VA
22201-4714
US
|
Family ID: |
26243888 |
Appl. No.: |
10/168480 |
Filed: |
September 19, 2002 |
PCT Filed: |
December 14, 2000 |
PCT NO: |
PCT/GB00/04813 |
Current U.S.
Class: |
585/652 ;
502/325; 502/333; 585/651; 585/653 |
Current CPC
Class: |
C07C 2523/44 20130101;
B01J 23/62 20130101; C07C 5/48 20130101; C07C 2523/08 20130101;
B01J 23/56 20130101; C07C 2523/14 20130101; C07C 2523/18 20130101;
B01J 23/626 20130101; C07C 11/02 20130101; C07C 2521/02 20130101;
C07C 5/48 20130101 |
Class at
Publication: |
585/652 ;
585/651; 585/653; 502/325; 502/333 |
International
Class: |
C07C 004/06; B01J
023/44 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 1999 |
GB |
9930597.1 |
Mar 16, 2000 |
GB |
0006387.5 |
Claims
1. A process for the production of an olefin from a hydrocarbon,
which process comprises: partially combusting the hydrocarbon and
an oxygen-containing gas in the presence of a catalyst,
characterised in that the catalyst comprises palladium and at least
one further metal, said further metal being a Group IIIA, Group
IVA, VA or a transition metal.
2. A process as claimed in claim 1, wherein the stoichiometric
ratio of hydrocarbon to oxygen is 5 to 13.5 times the
stoichiometric ratio of hydrocarbon to oxygen required for complete
combustion of the hydrocarbon to carbon dioxide and water.
3. A process as claimed in claim 1 or claim 2, wherein said partial
combustion of hydrogen and oxygen-containing gas is carried out in
the presence of hydrogen.
4. A process as claimed in any preceding claim, wherein said
catalyst comprises at least one further metal which is a Group IIIA
metal.
5. A process as claimed in claim 4, wherein said Group IIIA metal
is Al, Ga, In and/or Tl.
6. A process as claimed in any preceding claim, wherein said
catalyst comprises at least one further metal which is a Group IVA
metal.
7. A process as claimed in claim 6, wherein said Group IVA metal is
Ge, Sn and/or Pb.
8. A process as claimed in any preceding claim, wherein said
catalyst comprises at least one further metal which is a Group VA
metal.
9. A process as claimed in claim 9, wherein said Group VA metal is
Sb and/or Bi.
10. A process as claimed in any preceding claim, wherein said
catalyst comprises at least one further metal which is a transition
metal.
11. A process as claimed in claim 10, wherein said transition metal
is selected from the group consisting of Cr, Mo, W, Fe, Ru, Os, Co,
Rh, Ir, Ni, Pt, Cu, Ag, Au, Zn, Cd and Hg.
12. A process as claimed in any preceding claim, wherein said
catalyst comprises only one further metal selected from Group IIIA,
Group IVA, VA and the transition metal series.
13. A process as claimed in any one of claims 1 to 11, wherein said
catalyst comprises at least two further metals selected from Group
IIIA, Group IVA, VA and the transition metal series.
14. A process as claimed in claim 13, wherein the catalyst
comprises one metal selected from Groups IIIA, IVA and VA, and one
metal selected from the transition metal series.
15. A process as claimed in claim 14, wherein said metal selected
from the transition metal series is Pt.
16. A process as claimed in claim 14 or 15, wherein said one metal
selected from Groups IIIA, IVA and VA is Sn.
17. A process as claimed in claim 13, wherein said catalyst
comprises two metals selected from the transition metal series.
18. A process as claimed in claim 17, wherein said catalyst
comprises Pd, Pt and Cu.
19. A process as claimed in any preceding claim, wherein said
catalyst further comprises alkali metal ions.
20. A process as claimed in any preceding claim, wherein said
hydrocarbon comprises at least one hydrocarbon selected from the
group consisting of ethane, propane and butane.
21. A catalyst comprising a) palladium, b) a further transition
metal and c) a metal from Group IIIA, IVA and/or VA.
Description
[0001] The present invention relates to a process for the
production of olefins.
[0002] Olefins such as ethylene and propylene may be produced by a
variety of processes, including the steam cracking of hydrocarbons
or by the dehydrogenation of paraffinic feedstocks. More recently,
olefins have been produced by a process known as auto-thermal
cracking. In such a process, a hydrocarbon feed is mixed with an
oxygen-containing gas and contacted with a catalyst. The
hydrocarbon feed is partially combusted, and the heat produced is
used to drive the dehydrogenation reaction.
[0003] An example of an auto-thermal cracking process is described
in EP 0 332 289. The patent describes platinum group metals as
being capable of supporting combustion beyond the fuel rich limit
of flammability. Preferred catalysts are supported platinum
catalysts such as platinum/gamma alumina spheres, and
platinum/monoliths such as platinum/cordierite or mullite
monoliths.
[0004] In WO 97/26987, such platinum catalysts are modified with Sn
or Cu, in the substantial absence of palladium. According to page
4, lines 32 to 34 of the patent, palladium causes the catalyst to
coke up and deactivate very quickly.
[0005] We have now found that, contrary to prior art suggestions,
compositions comprising palladium are effective as catalysts for
auto-thermal cracking processes.
[0006] Accordingly, the present invention provides a process for
the production of an olefin from a hydrocarbon, which process
comprises:
[0007] partially combusting the hydrocarbon and an
oxygen-containing gas in the presence of a catalyst, characterised
in that the catalyst comprises palladium and at least one further
metal, said further metal being a Group IIIA, Group IVA, VA, a
transition metal or a lanthanide.
[0008] It should be understood that unless otherwise specified, the
term "(further metal" covers all elements of Group IIIA, IVA, VA,
transition metal and lanthanide series of the Periodic Table.
[0009] For the avoidance of doubt, the platinum and at least one
further metal in the catalyst may be present in any form, for
example, as a metal, or in the form of a metal compound, such as an
oxide.
[0010] The partial combustion reaction is carried out by contacting
a feed comprising the hydrocarbon and a molecular oxygen containing
gas with the catalyst. Any suitable oxygen-containing gas may be
employed; air being an example.
[0011] The preferred stoichiometric ratio of hydrocarbon to oxygen
is 5 to 16, preferably, 5 to 13.5 times, more preferably, 6 to 10
times the stoichiometric ratio of hydrocarbon to oxygen required
for complete combustion of the hydrocarbon to carbon dioxide and
water.
[0012] Preferably, hydrogen is co-fed into the reaction. It is
believed that in the presence of the catalyst, hydrogen combusts
preferentially relative to the hydrocarbon, thereby increasing the
olefin selectivity of the overall process.
[0013] Additional feed components such as nitrogen, carbon monoxide
and steam may also be fed into the reaction.
[0014] Suitable Group IIIA metals include Al, Ga, In and Tl. Of
these, Ga and In are preferred.
[0015] Suitable Group IVA metals include Ge, Sn and Pb. Of these,
Ge and Sn are preferred.
[0016] Suitable Group VA metals include Sb and Bi. Of these, Bi is
preferred.
[0017] Suitable metals in the transition metal series are any metal
from Group IB to VIIIB of the Periodic Table. In particular,
transition metals selected from Groups IB, IIB, VIB, VIIB and VIIIB
of the Periodic Table are preferred. Examples of such metals
include Cr, Mo, W, Fe, Ru, Os, Co, Rh, Ir, Ni, Pt, Cu, Ag, Au, Zn,
Cd and Hg. Preferred transition metals are Mo, Rh, Ru, Ir, Pt, Cu
and Zn.
[0018] Suitable lanthanides include lanthanum and cerium.
[0019] In one embodiment of the present invention, the catalyst
comprises only one metal selected from Group IIIA, Group IVA, VA,
the transition metal and lanthanide series. For example, the
catalyst may comprise palladium and one metal selected from the
group consisting of Ga, In, Sn, Ge, Sb, Bi, Cu, Ce and La.
Palladium may nominally form between 0.01 and 5.0 wt %, preferably,
between 0.01 and 2.0 wt %, and more preferably, between 0.05 and
1.0 wt % of the total weight of the catalyst. It should be noted,
however, that not all the metal employed during the preparation of
the catalyst necessarily becomes incorporated in the catalyst
composition. Thus, the actual loading of metal may differ from the
nominal loading. To ensure that the desired actual metal
concentrations are achieved, the nominal metal concentrations may
have to be varied accordingly.
[0020] The actual loading of palladium may be between 10 and up to
100% of the nominal value. Preferably, the actual loadings are
above 40%, more preferably, above 70% (e.g. 90 to 99%) of the
nominal values. In a preferred embodiment, the actual loading of
palladium is between 0.01 and 5.0 wt %, preferably, between 0.01
and 2.0 wt %, and more preferably, between 0.05 and 1.0 wt % of the
total weight of the catalyst.
[0021] The atomic ratio of palladium to the Group IIIA, IVA, VA,
transition or lanthanide metal may be 1:0.1-50.0, preferably,
1:0.1-12.0, more preferably, 1:0.2-3.0, and even more preferably,
1:0.5-1.5.
[0022] Where the metal is a Group IIIA metal, Ga and In are
preferred. Atomic ratios of Pd to Ga or In may be 1:0.1 to 50,
preferably, 1:0.1-12.0, and more preferably, 1:0.5-8.0. For
example, where the Group IIIA metal is In, the Pd to In ratio may
be 1:0.7-2, for example, 1:1.
[0023] Where the metal is a Group IVA metal, Sn and Ge are
preferred. Sn is most preferred. Atomic ratios of Pd to Sn or Ge
may be 1:0.1 to 50, preferably, 1:0.1-12.0, and more preferably,
1:0.5-8.0. For example, the Pd:Ge ratio may be 1:0.1 to 8,
preferably, 1:0.5 to 6, for example, 1:5.8; 1:1 and 1:0.5. The
Pd:Sn ratio may be 1:0.5 to 17. In one embodiment, the atomic ratio
of Pd:Sn is 1:13 to 17, for example 1:15. In another embodiment the
atomic ratio of Pd:Sn is 1:0.5 to 4.5, for example 1:2.5.
[0024] Where the metal is a Group VA metal, Sb and Bi are
preferred. Atomic ratios of Pd to Sb or Bi may be 1:0.1 to 50,
preferably, 1:0.1-12.0, and more preferably, 1:0.5-8.0.
[0025] Where the metal is a transition metal, the metal is
preferably Mo, Rh, Ru, Ir, Zn, and more preferably, Cu. Preferred
atomic ratios of Pd:Cu are 1:0.1-3.0, preferably, 1: 0.2-2.0, and
more preferably, 1:0.5-1.5, for example, 1:0.8.
[0026] Where the metal is a lanthanide, the metal is preferably La
or Ce.
[0027] In another embodiment, the catalyst comprises at least two
metals selected from Group IIIA, Group IVA, VA, the transition
metal and lanthanide series. For example, the catalyst may comprise
Pd, Pt and Cu, or Pd, Pt and Sn. Palladium may nominally form
between 0.01 and 5 wt %, preferably, between 0.01 and 2.0 wt %, and
more preferably, 0.05-1.0 wt % of the total weight of the catalyst.
As described above, the actual loading of metal may differ from the
nominal loading. Thus, the actual loading of palladium may be
between 10 and up to 100% of the nominal value. Preferably, the
actual loadings are above 40%, more preferably, above 70% (eg 90 to
99%) of the nominal values. In a preferred embodiment, the actual
loading of palladium is between 0.01 and 5 wt %, preferably,
between 0.01 and 2.0 wt %, and more preferably, 0.05-1.0 wt % of
the total weight of the catalyst.
[0028] Where the catalyst comprises at least two metals selected
from Group IIA, Group IVA, VA, the transition metal and lanthanide
series, the catalyst preferably comprises a) palladium, b) a
further transition metal and c) a Group IIIA or IVA metal. The
transition metal (b) is preferably platinum. The metal c) is,
preferably, a Group IVA metal, more preferably, Sn or Ge, and most
preferably, Sn. The atomic ratio of palladium to metal (b) (e.g.
platinum) may be 1:0.1-10.0, preferably, 1:0.5-8.0, and more
preferably, 1:1.0-5.0. The atomic ratio of palladium to metal c)
may be 1:0.1-60, preferably, 1; 0.1:50. Thus, where metal c) is Sn,
the atomic Pd:Sn ratio may be 1:0.1-60, preferably, 1:0.1-50.0.
Atomic Pd: metal c) ratios of 1:0.1-12.0 may also be suitable. For
example, where metal c) is Cu, the atomic Pd:Cu ratio is preferably
1:0.1-3.0, more preferably, 1:0.2-2.0, and most preferably,
1:0.5-1.5.
[0029] The catalyst may be unsupported. For example, the catalyst
may be in the form of a metal gauze. Preferably, however, the
catalyst employed in the present process is a supported catalyst.
The catalyst may be supported on any suitable support. Ceramic
supports are generally preferred, although metal supports may also
be employed.
[0030] Where ceramic supports are used, the composition of the
ceramic support may be any oxide or combination of oxides that is
stable at high temperatures of, for example, between 600.degree. C.
and 1200.degree. C. The support material preferably has a low
thermal expansion co-efficient, and is resistant to phase
separation at high temperatures.
[0031] Suitable ceramic supports include lithium aluminium silicate
(LAS), alumina (.alpha.-Al.sub.2O.sub.3), yttria stabilised
zirconia, alumina titanate, niascon, and calcium zirconyl
phosphate. The supports may be wash-coated, for example, with
.gamma.-Al.sub.2O.sub.3.
[0032] The structure of the support material is important, as this
may affect flow patterns through the catalyst. Such flow patterns
may influence the transport of reactants and products to and from
the catalyst surface, thereby affecting the catalyst's activity.
Preferably, the substrate is a continuous multi-channel ceramic
structure, such as a foam, a regular channelled monolith or a
fibrous pad. The pores of foam monolith structures tend to provide
tortuous paths for reactants and products. Such supports may have
20 to 80, preferably, 30 to 50 pores per inch. Channel monoliths
generally have straighter, channel-like pores. These pores are
generally smaller, and there may be 80 or more pores per linear
inch of catalyst. The support may be in the form of spheres or
other granular shapes, or may be present as a thin layer or wash
coat on another substrate.
[0033] The catalyst employed in the present invention may comprise
further elements, such as alkali metals. Suitable alkali metals
include lithium, sodium, potassium and caesium.
[0034] The catalyst employed in the present invention may be
prepared by any method known in the art. For example, gel methods
and wet-impregnation techniques may be employed. Typically, the
support is impregnated with one or more solutions comprising the
metals, dried and then calcined in air. The support may be
impregnated in one or more steps. Preferably, multiple impregnation
steps are employed. The support is preferably dried and calcined
between each impregnation, and then subjected to a final
calcination, preferably, in air. The calcined support may then be
reduced, for example, by heat treatment in a hydrogen
atmosphere.
[0035] In the case of a catalyst comprising palladium, platinum and
tin, the support material is preferably impregnated in a
palladium/platinum solution, and then in a solution comprising tin.
Once impregnated, the catalyst is dried at eg 50 to 200.degree. C.,
and calcined at eg 100 to 700.degree. C., e.g. 300 to 700 between
each impregnation. The support is then subjected to a final
calcination step at eg 400 to 1500.degree. C. in air. The catalyst
may then be reduced in, for example, a hydrogen atmosphere. This
reduction treatment may be carried out at temperatures of up to
1000.degree. C., for example, 100 to 750.degree. C.
[0036] The catalyst may be in the form of a fluidised or fixed bed.
Preferably, a fixed bed catalyst is employed.
[0037] The partial combustion reaction may be suitably carried out
at a catalyst exit temperature of between 600.degree. C. and
1200.degree. C., preferably between 850.degree. C. and 1050.degree.
C. and most preferably, between 900.degree. C. and 1000.degree.
C.
[0038] The reaction may be carried out at atmospheric or elevated
pressure. Suitable pressures range from 0 to 2 bara, preferably 1.5
to 2 bara, for example 1.8 bara. Elevated pressures of for example,
2 to 50 bara, may also be suitable.
[0039] The hydrocarbon may comprise any suitable hydrocarbon.
Preferably, gaseous hydrocarbons are employed. Suitable gaseous
hydrocarbons include ethane, propane, butane and mixtures
thereof
[0040] The hydrocarbon is passed over the catalyst at a gas hourly
space velocity of greater than 10,000 h.sup.-1, preferably above
20,000 h.sup.-1 and most preferably, greater than 100,000 h.sup.-1.
It will be understood, however, that the optimum gas hourly space
time velocity will depend upon the pressure and nature of the feed
composition.
[0041] Advantageously, heat may also be supplied by pre-heating the
hydrocarbon. The temperature to which the hydrocarbon,
oxygen-containing gas and (optionally) hydrogen mixture may be
preheated, however, is limited by the autoignition properties (eg
temperature) of the feed.
[0042] Where the cracking reaction is carried out at elevated
pressure, the reaction products may be quenched as they emerge from
the reaction chamber to avoid further reactions taking place.
[0043] Any coke produced in the process of the present invention
may be removed by mechanical means, or using one of the decoking
methods described in EP 0 709 446.
[0044] According to a second aspect of the present invention, there
is provided a catalyst comprising a) palladium, b) a further
transition metal and c) a metal from Group IIIA, IVA and/or VA.
[0045] These and other aspects of the present invention will now be
described, by way of example, with reference to FIG. 1 of the
drawings, which is a schematic view of an apparatus suitable for
carrying out an embodiment of the present invention.
[0046] FIG. 1 depicts an apparatus 10 comprising a reactor 12
surrounded by a furnace 14. The reactor 12 may be formed of quartz
or metal. Where a metal reactor 12 is employed, the inside of the
reactor is lined with quartz (not shown). Typically, metal reactors
are more susceptible to heat loss than quartz reactors.
[0047] The reactor 12 is coupled to an oxygen supply 16 and a
hydrocarbon feed supply 18. The hydrocarbon feed comprises ethane,
and small amounts of hydrogen and nitrogen. A catalyst 20 is
located within the reactor 12. The catalyst 20 is placed between a
pair of LAS heat shields 22, 24.
[0048] The furnace is set to minimise heat losses, and the
reactants 16, 18, are introduced into the reactor via line 26. As
the reactants contact the catalyst 20, some of the ethane in the
hydrocarbon feed 18 combusts to produce water and carbon oxides.
The hydrogen co-feed also combusts to produce water. Both these
combustion reactions are exothermic, and the heat produced is used
to drive the dehydrogenation of ethane to ethylene.
EXAMPLES
Example 1
[0049] Preparation of Pd/Pt/Sn Catalyst
[0050] The catalyst was prepared by multiple impregnation of a
lithium aluminium silicate support having a high purity alumina
(HPA) wash-coat. The support was impregnated in 1) a
platinum/palladium solution ((NH.sub.3).sub.4Pt.sup.IICl.sub.2,
(NH.sub.3).sub.4Pd.sup.IICl.sub.2), and 2) an SnCl.sub.2/HCl
solution. Between each impregnation, the support was dried at
120.degree. C., and calcined at 450.degree. C. The catalyst was
then calcined in air at 600.degree. C. for 6 hours, and then
reduced in an atmosphere of hydrogen (1.0 nl/min), and nitrogen
(1.5 n/min) for 1 hour (at 700.degree. C.).
[0051] The catalyst was analysed and found to have 0.36 wt % Pt,
0.04 wt % Pd and 1.85 wt % Sn.
Comparative Example A
[0052] 1 wt % Pt
[0053] A catalyst having a nominal loading of 1 wt % Pt was
prepared by impregnating a lithium aluminium silicate support
having an HPA wash-coat in a solution of
(NH.sub.3).sub.4Pt.sup.IICl.sub.2. The impregnated support was
dried at 120.degree. C., and calcined at 450.degree. C. The
catalyst was then calcined in air at 1200.degree. C. for 6 hours.
The catalyst was analysed and found to have 0.86 wt % Pt.
Comparative Example B
[0054] Pt/Sn
[0055] A catalyst comprising Pt and Sn was prepared by impregnating
a lithium aluminium silicate support having an HPA wash-coat in a
solution of 1) (NH.sub.3).sub.4Pt.sup.IICl.sub.2, and 2)
SnCl.sub.2/HCl. The impregnated support was dried, calcined and
reduced as described in connection with Example 1 above. The
catalyst was analysed and found to have 0.48 wt % Pt, and 2.80 wt %
Sn.
Example 2
[0056] The catalysts of Example 1, Comparative Example A and
Comparative Example B above were each tested as catalysts for the
oxidative dehydrogenation of ethane. Each catalyst was mounted in
the apparatus of FIG. 1, and an oxidative dehydrogenation reaction
was carried out under the conditions summarised in Table 1 below.
For the tests below, a metal reactor 12 was employed.
1 TABLE 1 1 (Pd/Pt/Sn) A (Pt only) B (Pt/Sn) GHSV @ stp/h 120863
119759 120268 ethane flow (g/min) 18.07 17.28 18.07 hydrogen flow
(g/min) 1.18 1.21 1.18 Oxygen flow (g/min) 9.39 9.68 9.39 nitrogen
flow (g/min) 4.95 4.52 4.72
[0057] As shown in Table 2 below, the selectivity of the catalyst
of Example 1 towards ethylene is greater than those of Comparative
Examples A and B, respectively.
2 TABLE 2 1 (Pd/Pt/Sn) A (Pt only) B (Pt/Sn) ethane conversion (%)
74.70 75.69 73.03 selectivity 73.93 67.54 69.7 (g ethylene per 100
g ethane converted)
Example 3
[0058] Preparation of 0.2 wt %Pd/4.0 wt %Sn Catalyst
[0059] The catalyst was prepared by multiple impregnation of a
lithium aluminium silicate support having an HPA wash-coat. The
support was impregnated in 1) a palladium solution
((NH.sub.3).sub.4Pd.sup.IICl.sub.2- ), and 2) an SnCl.sub.2/HCl
solution. Between each impregnation, the support was dried at
120.degree. C., and calcined at 450.degree. C. The catalyst was
then calcined in air at 600.degree. C. for 6 hours, and then
reduced in an atmosphere of hydrogen (1.0 nl/min), and nitrogen
(1.5 nl/min) for 1 hour at 750.degree. C.
[0060] The nominal loadings of the resulting catalyst were: 0.2 wt
% palladium and 4.0 wt % tin. The catalyst was analysed and found
to have 0.19 wt % Pd and 3.18 wt % Sn.
Example 4
Preparation of 1 wt %Pd/4.0 wt %Sn Catalyst
[0061] The process of Example 3 was repeated but the concentration
of the palladium solution employed was increased such that the
nominal loadings of the resulting catalyst were 1 wt % palladium
and 4 wt % tin. The catalyst was analysed and found to have 0.98 wt
% Pd and 2.70 wt % Sn.
Comparative Example C
[0062] A catalyst having the same composition as Comparative
Example B was prepared by impregnating a lithium aluminium silicate
support having an HPA wash-coat in a solution of 1)
(NH.sub.3).sub.4Pt.sup.IICl.sub.2, and 2) SnCl.sub.2/HCl. The
impregnated support was dried, calcined and reduced as described in
connection with Example 1 above. However, instead of being reduced
at 700.degree. C., the catalyst of Comparative Example C was
reduced at 750.degree. C.
Example 5
[0063] The catalysts of Examples 3, 4, and Comparative Examples A
and C were each tested as catalysts for the dehydrogenation of
ethane. Each catalyst was mounted in the apparatus of FIG. 1, and a
dehydrogenation reaction was carried out under the conditions
summarised in Table 3 below. For the tests below, a quartz reactor
12 was employed. The quartz reactor employed is less susceptible to
heat loss than the metal reactor employed, for example, in Example
2. For this reason, the ethylene selectivities obtained using a
quartz reactor tend to be higher than those obtained using a metal
reactor.
3 TABLE 3 3 4 A C (0.2 wt % Pd/ (1 wt % Pd/ (1 wt % (1 wt % Pt/ 4
wt % Sn) 4 wt % Sn) Pt only) 4 wt % Sn) GHSV @ stp/h 120864 121073
121073 120864 ethane flow 18.94 18.94 18.94 18.94 (g/min) hydrogen
flow 1.14 1.14 1.14 1.14 (g/min) Oxygen flow 9.09 9.09 9.09 9.09
(g/min) nitrogen flow 4.95 5.03 5.00 4.95 (g/min)
[0064] As shown in Table 4 below, Examples 3 and 4 are more
selective towards ethylene than Comparative Example A. Examples 3
and 4 show a similar selectivity to ethylene as Comparative Example
C, but at a higher rate of ethylene conversion.
4 TABLE 4 3 4 (0.2 wt % Pd/ (1 wt % Pd/ A C 4 wt % Sn) 4 wt % Sn)
(Pt only) (Pt/Sn) ethane conversion 77.75 77.05 73.55 75.67 (%)
selectivity (g 73.21 73.93 70.65 73.50 ethylene per 100 g ethane
converted)
Example 6
[0065] Preparation of Pd/Cu catalyst
[0066] The catalyst was prepared by multiple impregnation of a
lithium aluminium silicate support having an HPA wash-coat. The
support was calcined in air to 1200.degree. C. for 6 hours prior to
impregnation. The support was impregnated in (1) an aqueous
palladium solution (NH.sub.3).sub.4Pd.sup.IICl.sub.2 and (2) an
aqueous copper solution Cu(NO.sub.3).sub.2. Between each
impregnation the support was dried at 120.degree. C. and calcined
at 450.degree. C. The catalyst was then calcined at 600.degree. C.
for 6 hours then reduced in an atmosphere of hydrogen (1.0 nl/min)
and nitrogen 91.5 nl/min) at 750.degree. C. for 1 hour prior to
testing.
[0067] The target/nominal loadings of the resulting catalyst were
0.2 wt % palladium and 0.5 wt % copper.
Example 7
[0068] The catalyst of Example 6 was tested as a catalyst for the
dehydrogenation of ethane using the apparatus of FIG. 1. A quartz
reactor 12 was employed. The performance of this catalyst was
compared to that of three other catalysts: one having Pd, as the
only metal component, a second comprising only Pt, and a third
catalyst comprising Pt and Cu. The reaction conditions are
summarised in Table 5. The ethane conversions and selectivities
obtained are summarised in Table 6.
5 TABLE 5 1 wt % Pd/ 0.5 wt % Cu Pd only Pt only Pt/Cu GHSV @ stp
(/h) 120864 120482 121073 119948 ethane flow (g/min) 18.94 18.07
18.94 18.07 hdrogen flow (g/min) 1.14 1.18 1.14 1.18 Oxygen flow
(g/min) 9.09 9.39 9.09 9.39 nitrogen flow (g/min) 4.95 4.80 5.00
4.60
[0069]
6 TABLE 6 1 wt % Pd/ 0.5 wt % Cu Pd only Pt only Pt/Cu target
(nominal) --/1.0/0.5 --/0.2/-- 1.0/--/-- 1.0/--/0.5 loadings
Pt/Pd/Cu (wt %) ethane conversion (%) 78.17 76.29 73.55 78.00
ethylene selectivity 72.01 69.70 71.44 71.47 (g per 100 g ethane
converted)
Example 8
[0070] Preparation of Pd/Ge Catalysts
[0071] In this example, Pd/Ge catalysts having the following Pd:Ge
atomic ratios were prepared: 1:5.8, 1:1 and 2:1. The nominal Pd:Ge
weight % ratios of these catalysts were 1:4, 1:0.74 and 1:0.37,
respectively.
[0072] The catalysts were prepared by sequential impregnation of 30
ppi ceramic foam blocks (lithium aluminium silicate with alumina
washcoat, pre-calcined in air to 1200.degree. C.,) with aqueous
tetramminepalladium(II) chloride and germanium tetrachloride in
ethanol. The foam blocks employed were 15 mm in diameter and 30 mm
in depth. Between impregnations, the blocks were dried in air at
120-140.degree. C. for ca. 30 minutes, calcined in air at
450.degree. C. for 30 minutes, and then cooled to room temperature.
Once all the impregnation solution had been absorbed onto the foam
the blocks were calcined in air at 600.degree. C. for 6 hours.
[0073] Prior to ATC testing the catalysts were given an in situ
reduction at 750.degree. C. under flowing hydrogen (ca. 1.0 nl/min)
and nitrogen (ca. 1.5 nl/min) for 1 hour.
Example 9
[0074] The catalysts of Example 8, and Comparative Example A were
tested as catalysts for the oxidative dehydrogenation of ethane.
Each catalyst was mounted in the apparatus of FIG. 1, and an
oxidative dehydrogenation reaction was carried out under the
conditions summarised in Table 7 below.
7 TABLE 7 Pd/Ge Pd/Ge Pd/Ge (atomic ratio (atomic ratio (atomic
ratio A Pd:Ge = 1:5.8) Pd:Ge = 1:1) Pd:Ge = 2:1) (Pt only) GHSV @
stp/h 250972 250734 250719 250510 ethane flow 8.07 8.07 8.07 8.07
(g/min) hydrogen flow 7.87 7.87 7.87 7.87 (g/min) Oxygen flow 3.94
3.94 3.94 3.94 (g/min) nitrogen flow 2.30 2.27 2.27 2.25
(g/min)
[0075] As shown in Table 8 below, the ethylene selectivities of the
catalysts of Example 8 were greater than that of Comparative
Example A.
8 TABLE 6 Pd/Ge Pd/Ge Pd/Ge (atomic ratio (atomic ratio (atomic
ratio A Pd:Ge = 1:5.8) Pd:Ge = Pd:Ge = 2:1) (Pt only) ethane 76.35
76.74 78.83 78.27 conversion (%) selectivity 70.05 70.10 69.25
68.57 (g ethylene per 100 g ethane converted)
Example 10
[0076] Preparation of Pd/In catalysts
[0077] In this Example, a Pd/In catalyst having a Pd:In atomic
ratio of 1:1 was prepared.
[0078] Foam blocks (lithium aluminium silicate (LAS) with an
alumina wash-coat (28 mm diameter by 30 mm deep, 30 pores per inch)
were pre-calcined in air at 1200.degree. C. to remove
porosity/surface area associated with the wash-coat. The blocks
were then repeatedly impregnated from an aqueous solution of
tetra-amine palladium(II) chloride nitrate and indium(III) nitrate
with sufficient salt to give a nominal loading of 2 wt % palladium
and 2.16 wt % indium, assuming 100% absorption of the salt onto the
foam. (Corresponding to an atomic palladium:indium ratio of 1:1).
Impregnation was carried out alternately from the Pd and In
solutions Between impregnations excess solution was removed from
the foam blocks and the blocks were dried in air at 120-140.degree.
C. then calcined in air at 450.degree. C. for ca. 30 minutes.
[0079] Once all the solutions had been absorbed onto the foams the
blocks were dried and given a final air calcination at 600.degree.
C. for 6 hours.
Example 11
[0080] The catalyst of Example 10 was loaded into the quartz
reactor then given an in-situ hydrogen reduction at 750.degree. C.
for 1 hour.
[0081] The catalyst was then tested as a catalyst for the oxidative
dehydrogenation of ethane. The catalyst was mounted in the
apparatus of FIG. 1, and an auto-thermal cracking reaction was
carried out under the conditions summarized in Table 9 below.
9 TABLE 9 GHSV @ stp/h 119845 Ethane flow (g/min) 18.07 Hydrogen
flow (g/min) 1.18 Oxygen flow (g/min) 9.39 Nitrogen flow (g/min)
4.56
[0082] Table 10 below shows the ethane conversion and ethylene
selectivity of the reaction.
10 TABLE 10 Ethane conversion (%) 80.01 Ethylene selectivity (g
ethylene 71.37 per 100 g ethane converted)
* * * * *