AU2006201072A1 - Process for the production of olefins - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: BP CHEMICALS LIMITED Invention Title: PROCESS FOR THE PRODUCTION OF OLEFINS The following statement is a full description of this invention, including the best method of performing it known to me/us: 2

ID

o The present application is a divisional of parent 0application no. 2001274338.

The parent and present inventions relate to processes for the production of olefins. Olefins such as ethylene and propylene may be produced by the catalytic dehydrogenation or cracking of a hydrocarbon feed. In this specification the term "cracking" will be used to embrace c both of these chemical reactions.

o The cracking of hydrocarbons is an endothermic process. Accordingly, heat has to be consumed for the Ci reaction to occur. In a process known as auto-thermal o cracking, the heat required for cracking is generated by ocombusting a portion of the original feed stock. This is ci achieved by passing a mixture of a hydrocarbon feed and an oxygen-containing gas over catalyst capable of supporting combustion beyond the fuel rich limit of flammability. The hydrocarbon feed is partially combusted, and the heat produced by the combustion reaction is used to drive the cracking of the remainder of the feed. An example of an auto-thermal cracking process is described in EP-A- 0332289.

Generally, in known auto-thermal cracking processes, a reactant stream of a hydrocarbon and an oxygen-containing gas are passed over a single catalyst bed to produce product olefin. Typically, the catalyst bed comprises at least one platinum group metal, for example, platinum, supported on a catalyst support. Recently, research has been conducted on how to improve the selectivity of these catalysts to olefin product. One method is to modify the catalysts with a metal promoter from Groups IIIA, IVA, VA of the Periodic Table and/or from the transition metals. For example, WO 97/26987 discloses that the selectivity of platinum catalysts may be enhanced by incorporating tin or copper onto the supported platinum catalyst.

In WO 97/26987, the promoted platinum catalysts are prepared by impregnating a catalyst support in a platinum-containing solution, and thereafter into a solution I:\I sabelH\Speci\60143.doc 9/93/1j6 3 o containing the tin or copper promoter. As a result the platinum and copper or tin c'i promoter are distributed uniformly throughout the support. After prolonged use, however, the concentration of promoter on the support may decrease through evaporation, leading to a loss of activity.

5 According to Journal of Catalysis 191, 62-74 (2000), the problem of loss of promoter may be addressed by adding the tin to the catalyst by an on-line addition ctechnique. More specifically, an aqueous solution of SnC1 2 may be added to the hot ooperating catalyst support to deposit a thin coating of metal on to the front surface of the osupport. This compensates for the loss of tin due to evaporation, and restores the 10 catalyst's initial performance. This in-situ regeneration technique is also described in oCatalysis Letters 63 (1999), 113 120.

The catalytic behaviour of a supported Cr 2

O

3 catalyst is studied in detail in Applied Catalysis A (1999), 187(1), 13 24. This reference proposes the theory that the Cr 2

O

3 catalyst exhibits a distinctive boundary between the oxidising environment at the front of the catalyst and the reducing environment at the rear of the catalyst In the oxidising environment near the front face of the catalyst, the catalyst acts as an oxidative dehydrogenation catalyst. Once the majority of the oxygen has been consumed at the front end of the catalyst, however, Cr20 3 acts as a dehydrogenation catalyst, using the heat generated by oxidation reactions at the front of the catalyst to crack the hydrocarbon feed. To support this premise, a Pt-coated monolith was placed in front of a series of Cr2O3 monoliths. At high C 2 HJ0 2 ratios, the arrangement showed higher C 2 1H 4 selectivities than the Pt-monolith alone, confirming that Cr 2 O3 can utilise heat generated by the exothermic oxidative reactions occurring over the Pt-monolith to crack any unreacted hydrocarbon in the feed.

The teaching of Applied Catalysis A (1999), 187(1), 13 24, however, is very specific to Cr2O3. There is nothing in the reference to suggest that other catalyst beds could be employed to increase olefin selectivity in a corresponding manner.

We have now found that the selectivity of a catalyst zone comprising a catalyst bed (a first catalyst bed) can be enhanced by positioning a second catalyst bed comprising at least one metal selected from the group consisting of Mo, W, and Group .IB, IB, IVB, VB, VIIB and VIII of the Periodic Table downstream of the first catalyst bed.

H:\IsabeI\Specli\60142.doc 9/03/,6 4 Va o The present invention provides a process a 0 process for the production of an olefin, the process ci comprising passing a mixture of a hydrocarbon and an oxygen-containing gas through a catalyst zone which is capable of supporting combustion beyond the fuel rich limit of flammability to produce the olefin, the catalyst zone comprising at least a first catalyst bed and a second Ci catalyst bed, wherein the first catalyst bed comprises a 1 Group VIII metal catalyst which is a mixture of at least 1 I0 two of rhodium, platinum and palladium and/or is a Ci promoted Group VIII metal catalyst, and wherein the second Va o catalyst bed is located downstream of the first catalyst O bed, is of a different composition to the first catalyst ci bed and comprises a Group VIII metal.

The first catalyst bed comprises a catalyst which is capable of supporting combustion beyond the fuel rich limit of flammability. Suitably, the first catalyst bed may comprise a Group VIII metal catalyst which is a mixture of at least two of platinum, palladium and rhodium. Typical Group VIII metal loadings range from 0.01 to 100 wt%, preferably, from 0.01 to 20 wt%, and more preferably, from 0.01 to 10 wt%, for example 1-5 wt%, such as 3-5 wt%.

Additionally or alternatively, the first catalyst bed may comprise a promoted Group VIII metal catalyst. The promoter may be selected from the elements of Groups IIIA, IVA and VA of the Periodic Table and mixtures thereof.

Alternatively, the promoter may be a transition metal; the transition metal being a different metal to the metal(s), such as the Group VIII metal(s) employed as the catalyst component.

Preferred Group IIIA metals include Al, Ga, In and Tl. Of these, Ga and In are preferred. Preferred Group IVA metals include Ge, Sn and Pb. Of these, Ge and Sn are preferred, especially Sn. The preferred Group VA metal is Sb. The atomic ratio of H \IsabelHSpec1\60143-doc 14/03/06 5 IND Group VIII metal to the Group VIA, IVA or VA metal may be 1 :0.1 50.0, preferably, 0 S1:0.1 12.0, such as 1 0.3-5.

ci .Suitable transition metal promoters may be selected from any one or more of Groups JIB to VIII of the Periodic Table. In particular, transition metals selected from Groups IB, HB, VIB, VIIB and VIII of the Periodic Table are preferred. Examples of Ssuch transition metal promoters include Cr, Mo, W, Fe, Ru, Os, Co, Rh, Ir, Ni, Pt, Cu, Ag, Au, Zn, Cd and Hg. Preferred transition metal promoters are Mo, Rh, Ru, Ir, Pt, Cu C<1 and Zn, especially Cu. The atomic ratio of the Group VIII metal to the transition metal promoter may be 1:0.1 50.0, preferably, 1:0.1 12.0.

C Specific examples of promoted Group VIII catalysts for use as the first catalyst 0 bed include Pt/Ga, Pt/In, Pt/Sn, Pt/Ge. Pt/Cu, Pd/Sn, Pd/Ge, Pd/Cu and Rh/Sn. Where s the Group VIm metal is Rhb, Pt or Pd, the Rh, Pt or Pd may comprise 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. The atomic ratio of Rh, Pt or Pd to the Group MlIA, IVA, VA or transition metal promoter may be 1:0.1 50.0, preferably, 1: 0.1 12.0. For example, atomic ratios ofRh, Pt orPd to Snmay be 1: 0.1 to preferably, 1:0.1 12.0, more preferably, 1: 02 3.0 and most preferably, 1:0.5 Atomic ratios ofPt or Pd to Ge may be 1:0.1 to 50, preferably, 1:0.1 12.0, and more preferably, 1: 0.5 8.0. Atomic ratios of Pt or Pd to Cu may be 1:0.1 3.0, preferably, 1:0.2 2.0, and more preferably, 1:0.5 The second catalyst bed comprises a Group VIII metal as catalyst and is of a different composition to the first catalyst bed. Suitable Group VIII metals include platinum, palladium, ruthenium, rhodium, osmium, iridium, cobalt. and nickel. Preferably, the Group VIII metal is selected from rhodium, platinum, palladium or mixtures thereof. Particularly preferred are platinum, palladium or mixtures thereof, especially platinum. Typical Group VIII metal loadings range from 0.01 to 100 wt%, preferably, from 0.01 to 20 wt%, and more preferably, from 0.01 to wt%, for example 1-5 wt%, such as 3-5 wt%.

H:\IsabelH\SpeCi\6OL43.doc S/t'3/JE 6 o Prekbrably, the second catalyst bed compises a promoted catalyst such as a 0. promoted Group VIII metal catalyst. The promoter may be selected from the elements of Groups ILA, IVA and VA of the Periodic Table and nibcuxc thereof Alternatively, the promoter may be a transition metal; said transition metal being a different metal to the Group VIII metal(s) employed as the catalytic component.

Preferred Group ERA metals include Al, Ga, In and TI. Of these, Ga and In are Ci preferred. Preferred Group IVA metals include Ge, Sn and Pb. Of these, Ge and Sn are o preferred, especially Sn. The preferred Group VA metal is Sb. The atomic ratio of oGroup VIII metal to the Group MA, IVA or VA metal may be 1 0.1 50.0, preferably, IND 1: 0.l 12.0, such as I 0.3 oSuitable transition metal promoters may be selected from any one or more of Groups lB to VIII of the Periodic Table. In particular, transition metals selected from Groups IB, IIB, VIB, VJfIB and VIII of the Periodic Table are preferred. Examples of such transition metal promoters include Cr, Mo, W, Fe, Ru, Os, Co, Rh, Ir, Ni, Pt, Cu, Ag, Au, Zn, Cd and Hg. Preferred transition metal promoters are Mo, Rh, Ru, Ir, Pt, Cu and Zn, especially Cu. The atomic ratio of the Group VIII metal to the transition metal promoter may be 1: 0.1 50.0, preferably, 1:0.1 12.0.

Specific examples of promoted Group VIII catalysts for use as the second catalyst bed include Pt/Ga, Pt/In, Pt/Sn, Pt/Ge, Pt/Cu, Pd/Sn, Pd/Ge, Pd/Cu and Rb/Sn. Where the Group VIII metal is Rh, Pt or Pd, the Rh, Pt or Pd may comprise between 0.01 and 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. The atomic ratio of Rh, Pt or Pd to the Group IRA, VA, VA or transition metal promoter may be I 0.1 50.0, preferably, 1: 0.1 12.0. For example, atomic ratios of Rh, Pt or Pd to Sn may be 1: 0.1 to preferably, 1: 0.1 12.0, more preferably, 1: 0.2 3.0 and most preferably, 1:0.5 Atomic ratios of Pt or Pd to Ge may be 1: 0.1 to 50, preferably, 1: 0.1 12.0, and more preferably, 1: 0.5 8.0. Atomic ratios of Pt or Pd to Cu may be 1: 0.1 3.0, preferably, 1: 0.2 2.0, and more preferably, 1: 0.5 For the avoidance of doubt, the Group VIII metal and promoter in the catalyst beds may be present in any form, for example, as a metal, or in the form of a metal compound, such as an oxide.

H:\Ij3be1H\Spec1\60i43AdoC 14/03/06 7 O In addition to the first and second catalyst beds 0 the catalyst zone may comprise further catalyst beds. For example, the catalyst zone may comprise 3 to preferably, 3 to 5 catalyst beds.

Where the catalyst zone comprises more than two catalyst beds, the catalyst of the additional bed(s) may be the same or different to the catalysts used for either of the first and second catalyst beds. Suitably, the 0catalyst used for the additional bed(s) is the same as that of the second catalyst bed.

ID It should be understood that actual o concentrations of metal in the catalysts tend not to be identical to the nominal concentrations employed in the preparation of the catalyst because not all the metal employed during the preparation of the catalyst actually becomes incorporated in the catalyst composition. Thus, the nominal metal concentrations may have to be varied to ensure that the desired actual metal concentrations are achieved. Generally, however, the catalyst beds are prepared such that the actual concentration of a particular metal is between 80 and 99%, preferably, between 90 and 99% of the nominal value.

Each catalyst employed in the catalyst zone may be unsupported or supported. Suitably, an unsupported catalyst may be in the form of a metal gauze. Preferably, at least one catalyst in the catalyst zone is a supported catalyst. Suitably, each catalyst in the catalyst zone is a supported catalyst. The support used for each catalyst may be the same or different. Although a range of support materials may be used, ceramic supports are generally preferred. However, metal supports may also be used.

H:\IsabelH\Speci\60143,doc 14/03/06 8 o Suitably, the ceramic support may be any oxide or combination of oxides that is o stable at high temperatures of, for example, between 600°C and 1200°C. The ceramic Ssupport material preferably has a low thermal expansion co-efficient, and is resistant to Sphase separation at high temperatures.

tn 5 Suitable ceramic supports include cordierite, lithium aluminium silicate (LAS), alumina (alpha-A 2 0 3 yttria stabilised zironia, aluminium titanate, niascon, and (S calcium zirconyl phosphate, and, in particular, alumina. U'o The ceramic support may be wash-coated, for example, with gamma-Al2Oa.

o The structure of the support material is important, as the structure may affect 0 ,D 10 flow patterns through the catalyst. Such flow patterns may influence the transport of o reactants and products to and from the catalyst surface, thereby affecting the activity of the catalyst Typically, the support material may be in the form of particles, such as spheres or other granular shapes or it may be in the form of a foam or fibre such as a fibrous pad or mat Suitably, the particulate support material may be alumina spheres.

Preferably, the form of the support is a monolith which is a continuous multi-channel ceramic structure. Such monoliths include honeycomb structures, foams, or fibrous pads.

The pores of foam monolith structures tend to provide tortuous paths for reactants and products. Such foam monolith supports may have 20 to 80, preferably, 30 to 50 pores per inch. Channel monoliths generally have straighter, channel-like pores. These pores 0 are generally smaller, and there may be 80 or more pores per linear inch of catalyst Preferred ceramic foams include alumina foams.

Alternatively, the support may be present as a thin layer or wash coat on another substrate.

Where a supported catalyst is employed, the metal components of the catalyst are preferably distributed substantially uniformly throughout the supportL The catalysts employed in the present invention may be prepared by any method known in the art. For example, gel methods and wet-impregnatiodn techniques may be employed. Typically, the support is impregnated with one or more solutions oompfising 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.

-9o The catalyst zone may be achieved in any suitable Cl manner provided that the reactant stream (hydrocarbon and oxygen-containing gas) contacts the first catalyst bed thereby producing an effluent stream (comprising reaction products and unreacted feed) therefrom, and said effluent stream passes from the first catalyst bed to the second catalyst bed. A convenient method of achieving the Scatalyst zone is to use a single reactor with a space 0 being provided between the beds. The space can be provided S 10 by placing substantially inert materials such as alumina, D silica, or other refractory materials between the catalyst Cbeds.

C Alternatively, the space between the catalyst beds is a substantial void.

The space between the catalyst beds is not critical in relation to the beds. Preferably, however, the space will be as small as practical. Most preferably, there is no substantial space between the catalyst beds, that is, the beds are directly adjacent to one another.

Where the catalyst zone comprises more than two beds, the size of the space between the beds may vary.

The size of the catalyst beds can vary one from the other.

The catalyst beds may be arranged either vertically or horizontally.

The hydrocarbon may be any hydrocarbon which can be converted to an olefin, preferably a mono-olefin, under the partial combustion conditions employed.

The process of the present invention may be used to convert both liquid and gaseous hydrocarbons into olefins. Suitable liquid hydrocarbons include naphtha, gas oils, vacuum gas oils and mixtures thereof. Preferably, however, gaseous hydrocarbons such as ethane, propane, butane and mixtures thereof are employed. Suitably, the hydrocarbon is a paraffin-containing feed comprising hydrocarbons having at least two carbon atoms.

H:\IsabeIH\Speci\60143.doc 14/03/06 10 IThe hydrocarbon feed is mixed with any suitable ooxygen-containing gas. Suitably, the oxygen-containing gas ci is molecular oxygen, air, and/or mixtures thereof. The oxygen-containing gas may be mixed with an inert gas such as nitrogen or argon.

Additional feed components may be included, if so desired. Suitably, methane, hydrogen, carbon monoxide, Ci carbon dioxide or steam may be co-fed into the reactant ostream.

Any molar ratio of hydrocarbon to oxygencontaining gas is suitable provided the desired olefin is produced in the process of the present invention. The ci preferred stoichiometric ratio of hydrocarbon to oxygencontaining gas is 5 to 16, preferably, 5 to 13.5 times, preferably, 6 to 10 times the stoichiometric ratio of hydrocarbon to oxygen-containing gas required for complete combustion of the hydrocarbon to carbon dioxide and water.

The hydrocarbon is passed over the catalyst at a gas hourly space velocity of greater than 10,000 h 1 preferably above 20,000 h 1 and most preferably, greater than 100,000 h 3. It will be understood, however, that the optimum gas hourly space velocity will depend upon the pressure and nature of the feed composition.

Prferably, hydrogen is co-fed with the hydrocarbon and oxygen-containing gas into the reaction zone. The molar ratio oflhydrogen to oxygen-containing gas can vary over any operable range provided that the desired olefin product is produced. Suitably, the molar ratio of hydrogen to oxygen-containing gas is in the range 0.2 to 4, preferably, in the range 1 to 3.

Hydrogen co-feeds are advantageous because, in the presence of the catalyst, the hydrogen combusts preferentially relative to the hydrocarbon, thereby increasing the olefin selectivity of the overall process.

Preferably, the reactant mixture of hydrocarbon and oxygen-containing gas (and optionally hydrogen co-feed) is preheated prior to contact with the catalyst. Generally, the reactant mixture is preheated to temperatures below the autoignition tempeaure of the reactant mixture.

F:\taabeiH\Speci\COI43.doc 14/03/0E 11

ID

SAdvantageously, a heat exchanger may be employed to preheat the reactant mixture prior to contact with the catalyst. The use of a heat exchanger may allow the reactant mixture to be heated to high preheat temperatures such as temperatures at or above the autoignition temperature of the reactant mixture. The use of high pre-heat temperatures is beneficial in that less oxygen reactant is required which leads to Ci economic savings. Additionally, the use of high preheat temperatres can result in 0 improved selectivity to olefin product It has also be found that the use of high preheat 0 temperatures enhances the stability of the reaction within the catalyst thereby leading to higher sustainable superficial feed velocities.

0 It should be understood that the autoignition temperature of a reactant mixture is dependent on pressure as well as the feed composition: it is not an absolute value.

Typically, in auto-thermal crackldng processes, where the hydrocarbon is ethane at a pressure of 2 atmospheres, a preheat temperature of up to 4500 C may be used.

The process of the present invention may suitably be carried out at a catalyst exit temperature in the range 600°C to 1200°C, preferably, in the range 850°C to 1050°C and, most preferably, in the range 9000°C to 1000°C.

The process of the present invention may be carried out at atmospheric or elevated pressure. Suitably, the pressure may be in the range from 0 to 2 bara, preferably 1.5 to 2 bara, for example 1.8 bara. Elevated pressures of, for example, 2 to bara, may also be suitable.

Where the process of the present invention is carried out at elevated pressure, the reaction products inay be quenched as they emerge from the reaction chamber to avoid further reactions taking place.

Any coke produced in the process of the present invention may be removed by mechanical means, or by using one of the decoking methods such as that described in EP-A- 0 70944A thecontents 2 f which are hereby incorporated by reference.

H:\IsabelH\Speci\60143.doc 14/03/06 12

IND

o The present invention will now be illustrated by way of example only and with reference to Fig. 1 and to the following examples.

Fig. 1 represents, in schematic form, an apparatus 10 suitable for use in the process of the present invention. The apparatus 10 comprises a quartz reactor 12 surrounded by an electrically-heated furnace c-I 14. The reactor 12 is coupled to an oxygen-containing gas o supply 16 and a hydrocarbon feed supply 18. Optionally, the hydrocarbon feed may comprise a co-feed such as Clhydrogen and a diluent such as nitrogen. In use, the IN reactor 12 is provided with a catalyst zone 20 which is ocapable of supporting combustion beyond the fuel rich limit of flammability and comprises between one to three catalyst beds, 22, 24 and 26. The catalyst beds 22, 24 and 26 are positioned between LAS heat shields 28, In use, the furnace 14 is set so as to minimise heat losses, and the reactants are introduced into the reactor via line 32. As the reactants contact the catalyst beds 22, 24 and 26, some of the hydrocarbon feed combusts to produce water and carbon oxides. The optional hydrogen co-feed also combusts to produce water. Both of these combustion reactions are exothermic, and the heat produced therefrom is used to drive the cracking of the hydrocarbon to produce olef in.

Preparation of catalysts Catalyst A: 3wt% platinum on alumina spheres.

Alumina spheres (100g) ex Condea (1.8mm diameter, surface area 2 10M2/g) were impregnated with a solution containing 5.42g of tetrazmuineplatinum(II) chloride (ex Johnson Matthey) in de-ionised water.

Preparation was via incipient wetness technique.

After immersion in the Pt(II) solution for minutes, excess solution was removed from the spheres and the spheres were dried in air at 120'C then calcined at 450 0 C for ca. 30 minutes.

i: \IsabelH\Spect\C01lltdoc Z4103/Qc 13 Va o After cooling to room temperature the spheres were re-immersed in the remaining Pt-solution and the t drying and calcination process was repeated.

iThe spheres then received a final calcination in S 5 air at 1200°C for 6 hours.

After calcination the diameter of the spheres had reduced CA from ca. 1.8mm to ca. 1.2mm.

o Catalyst B: 3wt% platinum/0.2-0.5wt% palladium on alumina o spheres.

S 10 The procedure for Catalyst A was repeated using a Cl solution that contained 5.42g of tetrammineplatinum(II) chloride (ex Johnson Matthey) in de-ionised water and tetramminepalladium(II)chloride in an amount required to give between 0.2 and 0.5 wt% palladium (for example, 0.49g of tetramminepalladium(II)chloride gives 0.2wt% palladium).

Experimental The apparatus of Figure 1 was used.

For use with catalysts prepared on alumina spheres the quartz liner had an inner diameter of diameter and an overall catalyst bed length of 60mm was used.

Reactant gases were fed to the reactor using Bronkhorst Hi-Tec thermal mass flow controllers. Gaseous effluent was analysed by gas chromatography, with residual oxygen being measured using a trace oxygen analyzer (Teledyne Analytical Instruments).

For each experiment, the required catalysts were loaded into the reactor and the reactor heated to 200°C under nitrogen at the required pressure.

Ethane, hydrogen and oxygen were then introduced to the reactor at a gas hourly space velocity of 500,000 H:\Issbe]eH\SpeCi\60143.doc 14/1,0/ 14 h 1 and at target values to achieve ethane conversions in the range 60-70%. The volumetric hydrogen oxygen feed ratios were either 1:1 or 0.5:1.

For each experiment, carbon monoxide was then introduced to the reaction. The amount of carbon monoxide was increased gradually to the desired amount (except where reaction could not be maintained on addition of carbon monoxide as described).

Table 1: Results at 10 barg TABLE 1: Ethane Carbon Monoxide Co-feed Tests at ethane 02 H2 N2 CO co max max max g/min gfmin g/min g/min gtmin vol% in fuel 1 3wt% platinum extinguished 100 51 3 11 2.5 1.81 2 3wt% platinum reaction stable 100 55 3.19 11 4 2.82 3 3wt% platinum extinguished 100 53.8 3.19 11 4 2.82 4 3wt% platinum extinguished 80 32 2 11 2 1.91 3wt% platinum extinguished 80 35 1,09 11 3 3.23 6 3wt% platinum reaction stable 80 35 2.19 11 8 7.06 7 3wt% platinum extinguished 80 35 2.19 11 1 0,94 8 3wt% platinum extinguished 70 31 2.19 11 1.75 1.79 9 3w1% platinum 0.2-0,5% palladium reaction stable 100 55 3.44 11 5.34 3,64 3wt% platinum 0.2-0.5% palladium reaction stable 100 55 1.72 11 6 4.86 11 3wt% platinum 0.2-0.5% palladium reaction stable 100 55 3.44 11 12 7.82 12 3wt% platinum 0.2-0.5% palladium reaction stable 80 35 1.08 11 20 18.22 13 3wt% platinum 0.2-0.5% palladium reaction stable 80 35 2.18 11 20 15.98 14 sequential bed: 3%PtO.2%Pd reaction stable 75 32.5 2.62 11 15.11 12.,41 followed by 3%Pt sequential bed: 3%PtO.2%Pd reaction stable 75 32.36 3.65 11 11,09 8.39 followed by 3%Pt 16 sequenlial bed: 3%PtO.2%Pd reaction stable 80 35.17 2,19 11 29.6 21.94 followed by 3%Pt 17 sequential bed: 3%PtO.2%Pd reaction stable 80 35,11 1.1 11 31 25.61 followed by 3%Pt I I Eight experiments were performed over a bed of platinum catalyst (catalyst A) at 10 barg.

single Of these, 6 experiments extinguished before the required carbon monoxide levels were obtained. Although reactions 2 and 6 achieved reaction at 2.8 and 7 vol% CO in fuel respectively, these experiments could not be repeated 1: \1sabelH\5peci\6143.d-c 14/03/6 15 consistently (see experiments 3 and 7 where essentially similar reactions extinguished at lower carbon monoxide levels).

In contrast, in 5 experiments over a single bed of platinum/palladium catalyst (catalyst B) and 4 experiments over a sequential bed at 10 barg no extinguishment was observed, even at much higher carbon monoxide levels.

Table 2: Results at 20 barg TABLE 2: Ethane Carbon Monoxide Co-feed Tests at ethane 02 max H2 max N2 CO CO max g/min g/min glmin g/min glmin vol% in fuel 18 3wt% platinum extinguished 200 97 5.31 11 2.5 0.95 19 3wt% platinum Stable 200 68 2.19 11 3.4 1.54 3wt% platinum extinguished 200 90 2.81 11 4.38 1.90 21 3wt% platinum Stable 160 61 1.9 11 10 5.38 22 3wt% platinum Stable 160 60 3.8 11 10 4.71 23 3wt% platinum extinguished 160 67 4.19 11 2 0.95 24 3wt% platinum extinguished 160 67 4.18 11 3 1.42 3wt% platinum extinguished 160 67.35 4.12 11 5 2.36 26 3wt% platinum 0.2-0.5% palladium Stable 160- 69 2.09 '11 5.18 2.82 27 3wt% platinum 0.2-0-5% palladium Stable 160 67 4.18 11 12.01 5.46 28 3wt% platinum 0.2-0.5% palladium Stable 160 73.5 2.3 11 8.1 4.27 29 3wt% platinum 0.2-0.5% palladium Stable 160 61 1.9 11 6.65 3.64 3wt% platinum 0.2-0.5% palladium Stable 160 54.37 3.39 11 11.9 5.70 31 3wt% platinum 0.2-0.5% palladium Stable 160 67 0.88 11 6 3.58 32 3wt% platinum 0.2-0.5% palladium Stable 160 67 4.18 11 5 2.35 33 3wt% platinum 0.2-0.5% palladium Stable 160 67 2.09 11 20 10.07 34 3wt% platinum 0.2-0.5% palladium Stable 160 67 4.18 11 20 8.78 sequential bed; 3%PtO.2%Pd Stable 160 68.2 3.37 11 30 13.24 followed by 3%Pt__ 36 sequential bed: 3%PtO.2%Pd Stable 160 66 1.68 11 30 14.79 __followed by Eight experiments were performed over a single bed of platinum catalyst (catalyst A) at 20 barg. Of these, 5 experiments extinguished before the required carbon monoxide levels were obtained.

In contrast, in 9 experiments over a single bed of platinum/palladium catalyst (catalyst B) and 2 experiments over a sequential bed at 20 barg no R:\Is&beIH\Speci\60143.dOc 141/3/06 16 ID extinguishment was observed, even at much higher carbon O monoxide levels.

tThe above results show that platinum only catalysts have an intolerance to carbon monoxide in the feed resulting in unstable reaction. In contrast, the use of platinum/palladium as a first catalyst bed provides C tolerance to carbon monoxide in the feed that is not 0present in a platinum catalyst alone, improving catalyst 0 stability and hence selectivity with time.

ci N 10 Comparison of the results from the experiments 0 using platinum/palladium as a first catalyst bed is shown in Tables 1 and 2. The results are from use of single beds of depth 60mm comprising 3wt% platinum/0.2wt% palladium on alumina spheres and of sequential beds with a first bed of depth 10mm comprising 3wt% platinum/0.2wt% palladium on alumina spheres followed by second bed of depth comprising 3wt% platinum on alumina spheres at reaction pressures of 25 barg are shown in Tables 3 and 4 below.

These Tables show that the use of a sequential bed catalyst comprising platinum and palladium in the first catalyst bed (which leads to improved tolerance of the presence of carbon monoxide in the feed compared to a single bed of platinum) also provides an improved catalyst zone compared to a single bed of platinum and palladium.

In particular, the Tables show that, the sequential bed shows higher ethylene selectivity and generally lower methane selectivities (It should be noted that, ideally, data should be compared at equivalent ethane conversion, whereas in Table 4, for example, the sequential bed data is reported at a higher ethane conversion than the single bed data.

However, increasing ethane conversion generally results in H: \1sabelH\Speci\6014.doc 14/03/06 17 o decreasing ethylene selectivity, whereas Table 4 shows 0 that even at increased ethane conversion over the Ssequential bed compared to the single bed a generally higher ethylene selectivity is observed.) ci

V'

0 0 ci H:\IsabelH\Speci\(('143.docc L4/ij3/0 2006201072 15 Mar 2006 18 Table 3: Ethane ATC in the presence of CO at 25barg with hydrogen co-feed feed C2 Selectivity feed feed feed feed feed H2:02 CO:C2 conv C2H4 CH4 (g/100g C2 Pressure C2H6 H2 CO 02 N2 v/v v/v conv.) Barg g/min g/min g/min g/min g/min Pt-Pd 25.58 160.87 2.09 1.53 67.02 10.98 0.50 0.010 63.20 51.34 14.53 Pt-Pd 25.96 159.30 2.09 3.26 66.99 11.05 0.50 0.020 64.46 50.85 15.05 Pt-Pd 26.95 160.25 2.09 5.18 66.98 11.01 0.50 0.032 64.85 49.87 15.28 PtPd IPt 24.75 159.75 2.00 10.03 66.06 9.56 0.48 0.063 64.44 52.71 14.24 PtPdHlPt 25.11 161.22 1.85 15.02 66.09 9.48 0.45 0.093 64.10 52.48 13.74 PtPd IPt 25.54 161.27 1.76 20.02 66.14 9.89 0.43 0.124 64.88 52.46 14.05 PtPd IPt 26.16 160.45 1.77 25.03 65.93 9.91 0.43 0.156 63.99 53.28 14.03 PtPd IPt 26.85 -159.32 1.68 30.01 66.01 9.57 0.41 0.188 64.77 52.53 14.09 H:\IsabelH\Specl\60143.doc 14/03/06 2006201072 19 Table 4: Ethane ATC in the presence of CO at 25barg with hydrogen co-feed 15 Mar 2006 feed feed feed feed feed selectivity C2 pressure C2H6 H2 CO 02 N2 H2:02 CO:C2 conv C2H6 CH4 C2 barg g/min g/min g/min g/min g/min v/v v/v conv PtPd 26.24 159.850 4.180 3.090 66.980 11.230 1.00 0.019 63.23 50.52 16.43 PtPd 26.35 160.100 4.180 6.520 67.000 11.240 1.00 0.041 63.94 49.74 16.29 PtPd 26.08 160.450 4.180 10.360 67.010 11.210 1.00 0.065 63.74 50.76 16.35 PtPd 25.63 160.850 4.180 12.010 66.990 11.150 1.00 0.075 62.06 52.71 16.14 PtPdi iPt 24.30 159.820 4.316 1.020 70.070 10.180 0.99 0.006 68.66 51.23 16.30 PtPdI IPt 24.76 159.620 4.475 2.030 69.920 9.570 1.02 0.013 67.23 52.26 16.49 PtPdl IPt 24.65 159.670 4.185 5.030 68.060 9.660 0.98 0.032 66.40 52.28 15.75 PtPd IPt 25.06 160.670 4.170 10.030 68.030 10.270 0.98 0.062 65.62 53.32 15.58 PtPdI IPt 24.99 159.420 4.225 15.000 68.060 10.270 0.99 0.094 65.12 53.46 14.84 H:\Isabe1l\SpecL\60143.doc 14/03/06 20 I It is to be clearly understood that although prior art publication(s) are referred to herein, this reference does not constitute an admission that any of these documents forms part of the common general knowledge in the art in Australia or in any other country.

In the claims which follow and in the preceding C- description of the invention, except where the context orequires otherwise due to express language or necessary oimplication, the word "comprise" or variations such as IN 10 "comprises" or "comprising" is used in an inclusive sense, 0ie. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

H:\IsablH\Speci\61-43 .doc 14/03/K6

Claims (9)

1. 2. A process as claimed in claim 1 wherein the first catalyst bed comprises platinum.
2. 3. A process as claimed in claim 1 or claim 2 wherein the first catalyst bed comprises platinum and palladium.
3. 4. A process as claimed in any one of the preceding claims wherein the Group VIII metal of the second catalyst bed is selected from rhodium, platinum, palladium or mixtures thereof. A process as claimed in any one of the preceding claims wherein the first catalyst bed and/or the second catalyst bed is supported.
4. 6. A process as claimed in claim 5 wherein the support is a ceramic support. H: \sabelH\Speci\O0143.doc 14/03/ 6 22 ID o 7. A process as claimed in any one of the C- preceding claims wherein the catalyst zone further comprises additional catalyst beds. In 5 8. A process as claimed in claim 7 wherein the catalyst zone comprises 3 to 10 catalyst beds.
5. 9. A process as claimed in any one of the Spreceding claims wherein the first and second catalyst o 10 beds are directly adjacent to one another. q0 A process as claimed in any one of claims 1 to 8 wherein a space is provided between the first and second catalyst beds.
6. 11. A process as claimed in any one of the preceding claims wherein the hydrocarbon is a paraffin- containing hydrocarbon feed having at least two carbon atoms.
7. 12. A process as claimed in claim 11 wherein the hydrocarbon is selected from the group consisting of ethane, propane, butane, naphtha, gas oil, vacuum gas oil and mixtures thereof.
8. 13. A process as claimed in any one of the preceding claims wherein the molar ratio of hydrocarbon to the oxygen-containing gas is 5 to 16 times the stoichiometric ratio of hydrocarbon to oxygen-containing gas required for complete combustion to carbon dioxide and water.
9. 14. A process as claimed in any one of the preceding claims in which hydrogen is a co-feed. H:\IsabeFI\Specl\\60143,doc 14103106 23 O o 15. A process as claimed in claim 14 in which 0 C- the molar ratio of hydrogen to oxygen-containing gas is in the range 0.2 to 4. 5 16. A process as claimed in any one of the preceding claims wherein the process is conducted at a gas hourly space velocity of greater than 10,000 /h. ci 010 o VD Dated this 15 th day of March 2006 o BP Chemicals Limited By its Patent Attorneys GRIFFITH HACK H:'1sabelH\Speci\6C143.doc i4/03/06