AU596661B2 - Catalysts - Google Patents

Description

r

L

COMMONWEALTH OF AUS516 A6 1 L6 Mr B PATENTS ACT 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE 134tA/r) Class Int. .Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: rl document conta h amendments made under Section 49 and is correct for priting.

*0 Oat S Name of Applicant: THE FLINDERS UNIVERSITY OF 4.1 *1 SOUTH AUSTRALIA.

I

Address of Applicant: 0* SActual Inventor(s): Address for Service: Bedford Par':, South Australia, Commonwealth of Australia.

Bruce George BAKER, Neville John CLARK, Hamish McARTHUR and Edward SUMMERVILLE.

DAVIES COLLISON, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

0 t Complete specification for the invention entitled:

"CATALYSTS"

The following statement is a full description of this invention, including the best method of performing it known tous -1- _1_111_ ii _II la

"CATALYSTS"

The present invention relates to the production of hydrocarbons. In particular, the present invention relates to primary and secondary catalysts for use in the Fischer-Tropsch process for synthesising hydrocarbons adapted for gasoline production and to supports for such primary catalysts.

The Fischer-Tropsch process is one of the major processes for producing synthetic hydrocarbons. The process is based on the use of carbon monoxide and hydrogen which can both be readily derived from 10 gasification of coal or char or by steam reforming of natural gas. The process relies on catalytic synthesis and basically comprises passing a gaseous feed stream of carbon monoxide and hydrogen over a 00o." catalyst bed. The catalyst and process operating conditions are selected so that one or other of the 0 following reactions predominates: CO (2n+l)H 2 CnH2n+2 n CO 2 nH 2 CnH2n i' r 2 2n CO H 2 n nCO 2 2n CO nH 2

C

2

H

2 n nCO 2 The Fischer-Tropsch process is subject to a number of limitations. One limitation is that the hydrocarbons produced by the process include a significant proportion of straight chain hydrocarbons of low octane number. Various processes have been proposed to improve the octane number of the hydrocarbons, and thus the suitability for use in gasoline production, by converting the straight chain hydrocarbons into branched hydrocarbons. However, the known processes tend to be expensive and are not adapted to form part of a continuous process with the Fischer-Tropsch process.

15 Another limitation is that it is difficult to control the process reaction to selectively form hydrocarbons having carbon numbers suitable for use in gasoline production. One reason for this particular limitation of the Fischer-Tropsch process is the 20 selection of catalysts for use in the process. Iron is a major component of most existing commercial catalysts, and although it is active as a catalyst, the hydrocarbons produced cover a wide distribution of carbon numbers, many of which are not suitable for *25 gasoline production. For example, depending on the process conditions, the hydrocarbons produced include significant proportions of either low carbon number gaseous products or high carbon number straight chain 3 products which form as waxes. Both products are generally not suitable for use in gasoline production.

According to the present invention there is provided a secondary catalyst for the production of branched chain alkenes from straight chain alkenes, the catalyst comprising an intermediate oxide of tungsten in which the average valence state of the tungsten radical is greather than 4 and less than 6, the surface having been activated at a predetermined oxygen partial pressure to cause skeletal isomerisation of straight chain alkenes to form branched chain alkenes at that predetermined o ,"oxygen partial pressure.

o L o N11 1

L

In a particularly preferred form the average valence state of the tungsten radical is 5.6± 0.2.

It has been found that the secondary catalyst catalyses the following reactions to form branched chain alkenes: 1-alkenes having carbon numbers up to 8 double bond shift to form 2-alkenes and then form branchea chain alkenes, each with at least one methyl group adjacent the double bond.

2-alkenes form branched chain alkenes, each with at lest one methyl group adjacent the double bond.

a 1-alkenes having carbon numbers greater than «ip 8 are cracked to form alkenes having carbon numbers 4 between 4 and 8, the alkenes double bond shift and 15 then carbon bond skeletal isomerise to form branched chain alkenes.

9o S, The invention also provides a method fo. the manufacture of the secondary catalyst, the method comprising oxidising tungsten metal with a gas atmosphere at a predetermined oxygen partial pressure.

The gas atmosphere may comprise a hydrogen/water S. mixture, a carbon monoxide/carbon dioxide mixture or an oxygen buffer in a closed system.

I

t -e s -e- The invention also provides an alternative metiod for the manufacture of the secondary catalyst, the method comprising passing a gas atmosphere at a predetermined oxygen partial pressure over tungsten trioxide. The gas atmosphere may comprise a hydrogen/water mixture, a carbon monoxide/carbon dioxide mixture or an oxygen buffer in a closed system. It is preferred that the gas atmosphere comprise hydrogen/water in a ratio 40:1 arranged to flow over tungsten trioxide heated to 400°C for 16 hours. The temperature may be varied between 200°C and 900 0 C with consequential changes to the ratio of hydrogen and water.

P.o" It is also preferred that the tungsten trioxide first be formed on a suitable support. Preferably the support may comprise alpha-alumina or gamma-alumina.

o The tungsten trioxide may be formed on the support by impregnation of the support with a tungsten salt or with a slurry of tungsten trioxide powder. By way of example tungsten trioxide has been loaded onto *supports in amounts up to 13 weight percent.

0 a* In one preferred method of forming tungsten o trioxide on the support, the suppor:t is impregnated with sodium tungstate, dried, treated with concentrated nitric acid and then washed with dilute nitric acid. The sodium tungstate is converted to S o. tungstic acid and then most of the sodium is eluted as the nitrate. After drying, the catalyst is heated to decompose the tungstic acid to form tungsten trioxide.

1 17 -9- In another preferred method of forming tungsten trioxide, the support is impregnated with ammonium metatungstate, dried, and then heated to decompose the ammonium tungstate to form tungsten trioxide.

The present invention also provides a process for producing branched chain alkenes from straight chain alkenes, the process comprising passing a gaseous stream comprising a carrier gas and straight alkenes over the secondary catalyst. It is preferred that the secondary catalyst be heated to between 100°C and 450°C. The selection of the temperature for the catalyst is dependent on the nature of the alkene and the reaction being performed. In general, branching of alkenes having carbon numbers approaching 8 is ,n 15 preferably carried out with the catalyst at a temperature between 150°C and 200 0 C; branching of :a shorter alkenes having ;arbon numbers towards 4 is o 0 Spreferably carried out with the catalyst heated at a temperature between 300°C and 350 0 C; and cracking of alkenes having carbon numbers greater than 8 is carried out with the catalyst heated to between 200°C and 400 0

C.

The carrier gas may comprise argon, carbon dioxide, nitrogen or a carbon monoxide/carbon dioxide mixture. It is preferred that the carrier gas Scomprise a hydrogen/water mixture at a predetermined oxygen partial pressure. The process may be carried S out at atmospheric pressure although higher pressures may be used.

LC--

i i -1 4-4 The primary-and secondary catalyst described above may be used in a continuous process for producing branched chain alkenes from a Fischer-Tropsch reactor for producing alkenes in a stream of alkenes, carbon monoxide and hydrogen. The product may be used to form the feed stock for the production of high octane fuel by alkylation. The product may also be used in the petro-chemical industry. I-nelation to the primar catalyct i'should h g is I ed that use the r l to catalyse reaction of carbon monoxide a rogen to form a significant proportio the product as 1-alkenes makes thep ary catalyst potentially suitable ,-se in synthesis processes in the p;o-chomic!iszj.

4 4 It should be readily apparent that the secondary catalyst described above may also be used for the a conversion of straight chain alkenes produced by S" processes other than the Fischer-Tropsch process.

Having outlined the invention in broad terms, t ofurther details will be provided by way of specific examples which are provided herein for purposes of Sillustration only and are not intended to be limiting to the invention.

4 44 i 0 1 1 EXAMPLE 1 A sample of the primary catalyst was prepared and tested in the Fischer-Tropsch process. The sample of the primary catalyst comprised 2% iron (as Fe) and 3% praseodymium (as Pr 6 011) impregnated as an alumina support and was tested under the following reaction conditions: Temperature: 280°C Pressure: 1200KPa Gas Hourly Space -1 Velocity (GHSV) 900hr Gas ratio CO/H 2 2 Alumina support: a -alumina heat treated at 1250°C for 10 minutes 0 449 15 It was found that after an initial conditioning .4 Q o period of two hours the reaction products and activity of the sample of the primary catalyst were essentially constant over 600 hours. Gas chromatographic analysis showed that greater than 90% of the hydrocarbon 20 reaction products were alkenes and less than 4% were methane gas. Figure 1 is a graph illustrating the distribution of the carbon members of the hydrocarbons in the reaction product. It is evident from the figure that a significant proportion of the product 25 comprises hydrocarbons having carbon numbers between 2 t *and 8, 4 I- _-1~11 1 It is known that carbon chain growth in the Fischer-Tropsch process commonly follows a Schultz-Flory mechanism which leads to a logarithmic relation between moles of reaction product and the carbon number of the reaction product. Figure 2 is a plot of the product yield versus carbon number for the sample of primary catalyst tested and it is evident that there is a departure from the straight line expected under the Schultz-Flory mechanism for carbon numbers 1'ass than 4. This diminished production of light gaseous product is an important improvement over the results with conventional Fischer-Tropsch catalysts since it is achieved without excessive production of very high carbon number products.

on, \61 15 EXAMPLE 2 Tables 1 to 4 sumarise experimental data in 66o relation to primary catalysts prepared in accordance with the present invention. Before dealing with the 6o experimental results in detail the followihg experimental procedures were followed in order to prepare the data: 1. Preparation of Catalyst Support S6, A catalyst support was prepared by heat treating S" granular Y -alumina in accordance with the following 25 procedure: 1 'o Granular y-alumina (Merck, anhydrous, containing 0.2% Na 0 on analysis) was sieved and the 125-150V fraction %20% of total) retained and dried at 200°C for 3 hr.

A large furnace set at 1250°C was fitted with a rotatable alumina tube with the closed end positioned in the hot zone. A 20 g batch of the dried granular alumina was pre-heated to 750 0 C in a silica tube in a separate furnace. The large furnace was tilted up to receive the 750 0 C alumina sample, returned to the horizontal position with the thermocouple for the furnace controller inserted into the sample. The alumina tube was rotated during the heating stage within the furnace with the sample occasionally being r, a .a S stirred by the thermocouple. The temperature of the alumina sample rose from 750°C to 1250°C over a period of three to four minutes and then remained constant.

S. Ten minutes after the alumina was placed in the 1250°C 4 furnace, the furnace was tilted down and the alumina S0o discharged from the alumina tube into a platinum dish.

Tests carried out on alumina samples heat treated in ,accordance with the above procedure indicate that: 1. The heat treated alumina has a surface area S2 -1 Sof 8 to 10 m g when formed from y-alumina 2 -1.

having an initial surface area of 70m g Thi£s compares with known surface area of a-alumina which is generally less than 2 -1 a, Im g 2. The heat treated alumina gives an intense ,t w y i L~:9iP 1: pink colour with phenolphthalein indicator which indicates that the surface of the heat treated alumina exhibits basic properties.

The initial Y -Al O The initial 2 3 and excessively heated alumina does not give this result.

3. X-ray diffraction analysis indicates that the crystallographic structure of the heat treated alumina predominantly comprises a -alumina.

2. Preparation of Modifier Component for Primary Catalyst Praseodymium Nitrate Solution Praseodymium oxide, Pr60 11 (1.55g) was weighed into a silica crucible, concentrated nitric acid 15 2 .5ml) added and heated on a hot plate until the oxide had dissolved and the acid evaporated (u2 hr). The crucible and contents were heated overnight in an oven at 100 0 C. The praseodymium nitrate was dissolved in water, transferred to a 20 volumetric flask (25 ml) and made up to volume.

Note: 1) 0.65 ml of the solution/g Al 2 0 3 forms a 3% loading of praseodymium oxide,Pr 6 0 11 2) pH of the solution is 0 oo 0 a e a o o o o op 0 9 o 4, a, Technical Ceria Solution a" "i

A

Technical ceria, Ce0 2 (AJAX) (4.0 g) was digested with concentrated nitric acid (30 mls) for about three hours. A very small amount of undissolved solid remaining was ignored. The solution was made up to 50 ml.

Note: 1) 0.65 ml of the solution/g A1 2 0 3 forms a 5% loading of rare earth oxides.

2) AJAX Technical Ceria contains approximately equal amounts of lanthanum sesquioxide, La 2 0 3 and cerium dioxide, CeO 2 with approximately 2% neodymium sesquioxide, Nd 2 0 3 and 15 praseodymium oxide, Pr 6 11 3. Preparation of Active Component for Primary Catalyst o* Ferric Nitrate Solution .o Ferric nitrate, Fe(NO ).9H 0 (11.0 g) was 20 dissolved in water and mar- up to 50 ml.

Note: 1) 0.65 ml of the solution/g A1 2 0 3 forms a 2% loading of iron.

2) pH of the solution is I 4. Preparation of Primary Catalyst 25 Fe/5% AJAX Technical Ceria/A 2 0 3 Alumina oxide (10 g) peteated in accodance Alumina oxide (10 g) pretreated in accordance e -S L3 with the procedure described under the heading "Preparation of Catalyst Support" was weighed into a silica crucible, the ceria solution mis) added and mixed well with the aid of an ultrasonic bath. [When stirred with a spatula in an ultrasonic bath the mixture becomes very fluid. After the ultrasonic bath is switched off, continued stirring causes the alumina to reabsorb the free liquid]. Most of the alumina was transferred to a petrie dish, spread 2 mm thick and, with the crucible, dried 20 hours in a vacuum dessicator. The alumina was returned to the crucible, dried 1 hour at 90°C and fired for 1 hours at 5006C. The ceria/alumina was impregnated with ferric nitrate solution mis), mixed as above, dried under vacuum hours) dried at 901C (1 hour) and fired at 450°C (2 hours).

rvro.

S• 2% Fe/3% PrO /Al20 catalyst.

o 20 A similar procedure to was followed.

5. Experimental Results Tables 1 to 4 present the results of experimental work carried out on catalysts prepared in accordance with the procedures described in the foregoing, together with the results of experimental work carried S out on conventional catalysts. The reaction S. conditions for experimental work are indicated in the Nw

'^QSU

-I

4

J

tables and the details of the experimental reactor and precondition procedure are as follows: Reac tur The samples of catalyst tested were placed in a stainless steel (type 316) tube 4 cm long with an internal diameter of 0.476 cm The reactor had a volume of 1.07 ml and typically held about 1.1 g of alumina supported catalyst. A stainless steel frit (type 316) with a pore size of 10 1 was positioned at each end of the reactor. Carbon monoxide and hydrogen were flowed into the reactor from separate flow controllers upward through the catalyst bed to a stainless steel pressure control valve. All connecting tubing was made of copper.

Q a q 15 Preconditioning Prior to introduction into the reactor the catalyst samples were exposed to a stream of hydrogen at 400 0 C, atmospheric pressure and gas hourly space velocity of 1000 hr for 16 hours.

a a a* t a a a •a a« aa,

*W

Table 1 illustrates the effect of heat treatment of the alumina support and the inclusion of praseodymium oxide on the properties of the catalyst.

The experimental results shown in Table 1 were prepared by positioning samples of the catalysts in the reactor and maintaining the following reaction conditions: Temperature: 2800C Pressure: 800 kPa

CO/H

2 2 Gas hourly space velocity (GHSV) 900hr- 1 The table indicates that: 1. An improvement in catalyst properties can be realised by impregnating the active component on 15 a Y-alumina support heat treated in accordance a4 a with the procedure outlined under the heading '°ao "Preparation of Catalyst Support". For exanple a catalyst comprising Fe impregnated on a heat treated Y-alumina support exhibits higher 20 activity and better selectivity than a catalyst ~comprising 1.6wt% Fe impregnated on a conventional Y-alumina support. In this regard it should be noted that the activity increases from 0,3 to 10.4% CO converted to hydrocarbons in the first pass. Furthermore, it should be noted that the catalyst including the heat treated J i x Al /6 TABLE 1 A ="Merck" Y-alumina B ="Alfa" alumina 999* 049: 9090 94 99 0 9 9 9* o 0 O* 9.

9, 9*0 o *9 0e 0 99 0* 9 9 0 9 04 9s t Fe wt.% 6.0 6.0 1.6 1.6 1.6 2.0 Pr 6

O

1 i wt.% 1.0 2.0 Support Catalyst type A A A A A A B composition Heat treatment 800/ 1250/ 1250/ 0 C/miLn 120 10 CO converted to I %14.0 2.4 0.3 0.3 10.4 14.7 12.3 hydrocarbon at at 300c 300C' C1 30.4 22.6 21.9 25.8 14.1 7.0 26.1 C 2 14.0 17.5 13.4 7.4 7.8 16.7 7.4 C 3 17.6 22.9 18.4 15.9 17.1 25.6 17.7 C 4 8.5 12.5 12.2 11.7 12.9 20.7 14.4 Alkenes C 5 2.6 6.9 6.0 3.3 118 6.0 9.3 C 6 1.3 2.7 2.7 1.8 8.4 3.9 5.7 WegtC 7+ 1.3 L3 2.7 1.8 13.6 7.1 7.61 Percent C 2 13.9 8.5 16.4 24.8 3.7 5.6 7.6 C 3 5.9 2.3 2.8 3.4 2.5 1.5 3.4 C 4 2.8 1,,0 1.9 2,,5 2.0 1.2 3.4 AknsC 5 0.9 0.5 0.9 0.7 2.1 1.4 2.8 Alae C 6 0.4 0.2 0.4 0.4 1.4 1.2 2.3 C 7+ 0.4 0.2 0-4 0. "if 17 Y-alumina support results in a substantial reduction in undesirable methane formed in the product and a significant increase in preferred alkenes having carbon numbers between C 2 and C 8 2. A further improvement in properties is obtained by impregnating the heat treated Y -alumina with both the active component and a modifier component such as praseodymium oxide.

For example a catalyst comprising 2% Fe, 2% Pr 6

O

11 impregnated on heat treated Y -alumina exhibits higher activity and better selectivity than catalysts which do not include praseodymium oxide.

Table 2 illustrates the effect of a modifier component in catalysts comprising 2% Fe impregnated on a heat treated Y -alumina support on the product 4 ct distributior resulting from tests carried out under conditions described in relation to Table i.

0 The table illustrates that catalysts prepared with modifier components 1 to 4 of the invention 1 exhibit better activity and selectivity properties 0 04 *than a catalyst prepared with a conventional modifier *o component 5 comprising l.8wt% K 2 0. In particular, it should be noted that the catalysts which include modifier components of the invention catalyst the formation of product distributions which have significantly lower amounts of methane and alkanes TABLE 2 0 4 t 44 a 0* 11 2) 4) Catalyst 3% Ceria 3% Tech. 3% 1.8% Modif ier Pr6O, 1 CTech.Grade) Ceria La203 CO converted to hydrocarbon M% 5.4 2.6 3.9 2.5 0.6 C 1 .875 5.1 6.0 27.6

JC

2 13.8 16.2 9 .4 12.2 11.8 3 19.5 22.2 16.7 17.8 17.4

K

4 17.8 1 1912 13.8 16.3 t Alkenes C 5 14.1 13.3 13.0 16.0 6.6

C

6 10.2 1 8.5 I 8.6 10.0 5.1

C

7 17.6 12.9 14.4 11.5 6.4 Weight P r e tC 2 0.6 0 24.7 4.1 5.9 C 3 0.a. 3.0 2.3 1.2 C 0.r 0.3 3.2 1.2 3.1 C 5 f 0.1 3.0 1.1 2.8 AknsC 6 0.1 0.1 2.0 0.7 2.3 C 7+ 3.3 0.8 .4 .4 4 *44 4* 4 4 4 44 4* 4 *44

I

It TABLE 3 so 0 4a 0 so* '44 .446 1 Temperature 260 260 26.0 280 280 300 320 (hrV 1 1800 1800 900 900 900 900 900 Pressure (KP a) 1240 800 800 800 800 800 800 CO/H 2 2.0 2.0 2.0 2.0 2.0 2.0 CO converted to 2.9 2.5 5.2 16.8 12.5 22.6 37.2 hydrocarbon(%

C

1 7.3 8.6 7.3 8.0 5.0 6.0 8.6 C 2 7.8 9.2 7.7 7.0 15.0 14.8 16.0 C 3 13.1 15.3 14.5 15.4 23.8 23.8 24.4 C 4 12.0 13.2 13.2 13.9 17.5 16.1 15.2 Alkenes C 5 11.1 10.8 12.4 12.1 :12.0 11.3 10.0 C 6 7. 7.5 8.0 5.7 8.0 7.1 C 7 26.7 22.5 22.1 15.3 14.8 15.1 11.7 Weight Percent C 2 3.4 4.0 3.1 2.9 0.9 0.6 1.3 C 3 2.1 2.3 2.2 1.8 1.0 1.4 C4 2.0 2.2 2.0 1.9 0.7 1.0 1.2 C 5 1.6 1.1 2.2 2.3 0.6 0.8 0.9 kaeC 6 1.1 0.8 1.4 1.1 0.5 0.7 7 +3.8 2.5 4.0 2.8 0.9 1.4 TABLE 4 0 .3 0[t 04 4 Temperature 250 280 240' 260 260 260 -HV1 900 900 9.00 900 900 900 (hr Pressure (KP a 800 800 800 800 800 800 ,d0/82 2 2 0.5 0.5 2 CO converted to 51 1. 28 36 1.

hydrocarbon ()51 1. 28 36 1.

C1 6.9 7.4 10.2 13.0 6.6 15.6 C 2 9. 6.9 8.0 6.1 9.8 4.9 C3 15.0 15.3 14.3 16.7 14-.9 16.6 C 4 13.1 13.7 -11.4 12.4 13.5 12.3 Alkenes C5 12.7 13.5 11.8 -11.7 14.2 10.1 C 6 8.8 9.9 7.4 7.2 11.6 C7 +24.0 19.6 -17.2 9.2 21.9 11.1 Weight Percent C 2 2,8 2.3 4.0 8.0 3.0 7.1 C 3 1.9 1.8 3.0 3.5 -1.7 C 4 1.5 2.1 2.6 3.4 1.1 3.3 AkesC 5 1.1 22 3.1 3.5 0.5 3.1 Ine C 6 0.8 1.7 2.1 2.4 0.3 2.2 C 7 2.3 3.3 4.9 3.0 0.9 3.7 Mole ratio C0 2 /H 2 0 2.83 1.27 I- S 'ft than is the case with a catalyst which includes a conventional modifier component.

Table 3 illustrates the effect of reaction conditions on product distribution for catalysts comprising 1.6wt% Fe and 1.0wt% Pr6011 impregnated on a heat treated y -alumina support (1 4) and catalysts comprising 1.6wt% Fe and 2.0wt% Pr60 11 impregnated on a heat treated Y-alumina support (5 In particular, the table indicates that as the reaction temperature increases there is a significant increase in activity with only a marginal deterioration in selectivity. (cf sample 5 and 7).

Table 4 illustrates the effect of the CO2/H 2 .o ratio on activity and product distribution. The 15 catalyst tested comprised 1.6%wt%Fe and 1.0wt% Pr 6 0 11 impregnated on heat treated Y -alumina. The 0 significant point evident from the table is that an excess of hydogen still results in the formation of alkenes as the major product.

20 EXAMPLE 3 SECONDARY CATALYST 0 0 S. Samples of the secondary catalyst comprising an intermediate oxide of tungsten were prepared and tested to investigate the effect of the catalyst on 0.00 specific 1-alkenes. The intermediate oxide comprised o 25 WO where x 2.8 ±0.15.

I

7- Both supported and unsupported samples of the secondary catalyst were prepared.

The supported samples were prepared by impregnating alumina supports with sodium tungstate in accordance with the following procedures: Sodium Tungstate Solution Sodium tungstate, Na 2

WO

4 .2H 2 0(6.56g) was dissolved in water and made up to Note: 0.65ml of the solution/g of A 203 formed a 6% loading of tungsten trioxide, WO 3 Preparation of 6% Tungsten Trioxide on Alumina Alumina (10g, thermally treated as previously I described) was weighed into a 250ml beaker, sodium tungstate solution (6.5ml) added and the 15 mixture stirred with the aid of ultrasonic agitation. The sample was dried in a vacuum dessicator "4 hour) and in air at 90°C (1 hour). Concentrated nitric acid (10ml) was added and the beaker warmed on a hot plate for 20 minutes and the solid was then washed with "1 M nitric acid by decantation. To remove sodium nitrate, 1 M nitric acid (250mls) was added, the s 4* catalyst digested for 1 hour on a hot plate and the nitric acid decanted. This washing was repeated three times and the catalyst dried at 3 150-160 0

C.

i N 9 ev/g I 7 The WO 3 was reduced to WO 2.9 by reduction with wet hydrogen. The catalyst was placed on a glass frit in a pyrex tube and heated to about 400 0

C.

Hydrogen was bubbled through water at room temperature and then up through the heated catalyst at a flow rate of 200ml/min. The catalyst was reduced for 4 hours at 400°C; it was then blue and was cooled and stored.

Preconditioning The catalyst in the reactor was heated for 1 hour in a stream of wet hydrogen (obtained by bubbling hydrogen through water at room temperature) under the following conditions: 4 9 *r Temperature Pressure Gas hourly space velocity 400°C 100kPa 900 hr 1

I

r 9.

9 4 0* 9 94.

The specific 1-alkenes tested comprised but-1-ene; pent-1-ene and hex-1-ene. The alkenes were separately introduced into a gaseous hydrogen/water 20 mixture and passed over the samples of secondary catalyst heated to 300 0 C at a flow rate of 10cm3min and at a pressure of The alkenes were introduced into the hydrogen stream by inserting a bubbler containing the alkene, upstream from the bubbler containing water. The bubblsr containing the alkene was cooled in a solid/liquid bath at an appropriate temperature to set 4"A K~ ,JI 3 -r b 1 -w the alkene vapor pressure at 10mm Hg. Chlorobenzene was found to be an appropriate bath for 1-pentene and chloroform was found to be suitable for 1-hexene. (An alternative method which is less quantitative involves collection of vapour from a solution of alkene in a low vapor pressure paraffin oil). The hydrogen stream thus picked up the alkene, was then saturated with water and flowed over the catalyst under the conditions described above.

A summary of an analysis of the reaction products for each of the 1-alkenes is shown in Table

I

t oo 9 9 «*t 99 4 949k 9 99* 99 9 i 94 9 9g Table 9,.

9* 4 999.

9 4 4, 9* 4~ 4

I

940 '4 9 09t 9 99 49 9 p 94 4* 94 9 .9 9 t 4<'

I

REACTANT PRODUCTS% But-1--ene But-1"-ene 9) But-2-ene 43) 57 Butane 2 Methyl propene 38) 2 Methyl propane 5) 43 Pent-1-ene Pent-1-ene 1) Pent-2 -ene, 32) 34 Pentane 1 2 Methyl but-2-ene 58) 2 Methyl but-1-ene 1 66 2 Methyl butane 2) 2 Methyl propane Hex-1-ene Hex-l-ene 6) Hex-2-ene 15) 26 Hexane 3 Methyl pent-2-ene 59) 2 Methyl pent-l-ene 2) 74 2,3 Dimethyl but-2-ene 6) 3 Methyl pentane 7) U 7 i The table indicates that conversions from the 1-alkene to branched alkenes increased with increasing carbon number of the 1-alkene. For example, 38% of the product formed from but-1-ene comprised 2-methyl propene whereas 58% of the product formed from pent-1-ene comprised 2 methyl but-2-ene.

EXAMPLE 4 Samples of the secondary catalyst prepared in Example 3 were tested to investigate the effect of the catalyst on a feed stream of 1-octene. Reaction conditions were as follows: Loading of the intermediate oxide of tungsten: 6% by weight on alumina support Temperature: 300 0

C

Pressure: 100kPa Flow rate: 100cc/min H 2

/H

2 0/1-octene 0O* A summary of an analysis of the reaction products is shown in Table 6.

4 a. -1- <I a) Wt. Table 6 Products from the cracking and isomerization of 1-octene over a 6% tungsten catalyst. 300-C, 1 atmo~sphere, 100 cc m~in H,/H,0/1-octene.

Reactant PrQducts* OCT-l-ENE Cl C2 C3 4.1 C4 39.8 C5 C6 3.6 C7 2.9 C8 41.6 C9 95% products branched, 999t 9* 99* *9 4R 9 9 99 9 9 *9* '9 9 4 99 49 9 D4 4$ a Ii 9 k EXAMPLE Samples of the secondary catalyst prepared in Example 3 were tested to investigate the effect of the secondary catalyst on higher carbon number hydrocarbons, specifically 1-dodecene (C 1 2 The 1-dodecene was included in a gaseous hydrogen/water mixture and passed over samples of the supported secondary catalyst, under the following experimental conditions: Catalyst weight: approx Ig Loading of the intermediate oxide of tungsten: 13% by weight on alumina support S* 1Ratio H 20: 40:1 Pressure: 100kPa S 15 Gas space velocity: 600hr 1 l Alkene loading 0.03 0.01 g/g of catalyst/hour a The result of an analysis of the reaction products is shown in Figure 3 which is a plot of the weight percent of products versus product carbon number. Figure 3 illustrates that the secondary catalyst cracked the 1-dodecene and caused reactions to form branched alkenes having carbon numbers predominantly in the range 4 to 8.

It was also found in further experiments that similar results were obtained for higher loadings of alkene although at lower temperatures the conversion 7 I to branched alkenes falls as the alkene content in the hydrogen/water carrier increases. The results indicate that high conversions can be obtained with the alkene loading in excess of .5g alkene/gram of catalyst/hour.

It was found that the life of the secondary catalyst is limited to a few hours when cracking is occurring. This is believed to be caused by the deposition of coke on the surface of the secondary catalyst. Regeneration of the surface may be performed quickly by raising the temperature of the catalyst to 45 0 °C or above while flowing a stream of air or other oxidizing gas over the secondary catalyst. Under experimental conditions it was found E 15 that regeneration could be completed after four ,minutes of flowing a stream of air at 450 0

C.

*I*a EXAMPLE 6 Samples of the secondary catalyst desqribed in Example 3 were tested to investigate the effect of the Alo 20 catalyst on a Fischer-Tropsch product stream. In this regard, synthesis gas was passed over the primary Al Fischer-Tropsch catalyst which was operated at 800kPa.

S. The products from this catalyst passed through a pressure control valve (downstream from the catalyst) through a coil of copper tubing (1 metre) at room U temperature and over the tungsten oxide catalyst operated at atmospheric pressure. The product stream was subsequently analysed and the results are shown in -43- Figure 4, which is a plot of weight percent of product versus product carbon number. For comparative purposes the figure also includes the results of the analysis for the product stream directly leaving the Fischer-Tropsch process and prior to being directed over th. secondary catalyst.

It is evident from Figure 4 that the secondary catalyst caused significant production of branched chain alkenes having carbon numbers between 4 to 8.

In addition there was an increase in the product between carbon numbers 4 and 6 due to cracking of the higher alkenes.

Note: Any products greater than C9 were trapped in the coil, limiting the extent of poisoning of the tungsten oxide catalyst by cracking. Operation life under these conditions was 3 hours (after which the catalyst should be regenerated). The tungsten oxide 4 catalyst was regenerated by heating it to 450 0 C (or -1 a space velocity of 10,000hr Heating to this temperature and cooling to operating temperature were Sperformed as quickly as possible. As soon as the

P

catalyst had cooled the Fischer-Tropsch stream was re-connected and isomerisation recommenced immediately.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those bw hge a oe n rdcsgeae hnC9wr rpe t s a a. *a a 4,.

0 4.4..

4* 4* a 4 44 p a 'a 9 a p a a~ .4 4 04 a a*~ a o a a 4' specifically described. It is to be understood that the invention includes all such variations and modifications within its spirit and scope.

I

A.

'p

I

Claims (2)

1. 32. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A secondary catalyst for the production of branched chain alkenes from straight chain alkenes, the catalyst comprising an intermediate oxide of tungsten in which the average valence state of the tungsten radical is greater than 4 and less than 6, the surface having been activated in a gas atmosphere at a predetermined oxygen partial pressure to cause skeletal isomerisation of straight chain alkenes to form branched chain alkenes at that predetermined oxygen partial pressure, being substantially equivalent to that achieved in a stream c.n of hydrogen saturated with water vapour at ambient temperature. o*0 2. A secondary catalyst as claimed in claim 1, *o Owherein the average valence state of the tungsten radical in the intermediate oxide is 5.6 0.2. 3. A secondary catalyst as claimed in claim 1, wherein the intermediate oxide comprises WOx, where 0o4 0 X 2.8 0.15. 4. A method for the manufacture of a secondary catalyst as defined in any one of claims 1 to 3, comprising oxidising tungsten metal with a gas atmosphere 4 I t at a predetermined oxygen partial pressure, said t t "j predetermined oxygen partial pressure being substantially equivalent to that achieved in a stream of hydrogen saturated with water vapour at ambient temperature. A method as claimed in claim 4, wherein the gas atmosphere comprises a hydrogen/water mixture, a carbon monoxide/dioxide mixture or an oxygen buffer in a closed system. -4V\ 0.41, S i I
2. 36- 6. A method for the manufature of a secondary catalyst as defined in any one of claims 1 to 3, comprising passing a gas atmosphere at a predetermined oxygen partial pressure over tungsten trioxide, said predetermined oxygen partial pressure being substantially equivalent to that achieved in a stream of hydrogen saturated with water vapour at ambient temperature. 7. A method as claimed in. claim 6, wherein the gas atmosphere comprises a hydrogen/water mixture, a carbon monoxide/carbon dioxide mixture or an oxygen buffer in a closed system. 8. A method as claimed in claim 7, wherein the gas atmosphere comprises hydrogen/water and the reactor temperature lies betwe'en 200°C and 500 0 C. 9. A method as claimed in claim 8, wherein the tv gas atmosphere comprises hydrogen/water in a ratio 40:1, and said atmosphere is arranged to flow for 16 hours over tungsten trioxide heated to 400 0 C. o 10. A method as claimed in claim 6, wherein the 0 tungsten trioxide is first formed on a support. al 11. A method as claimed in claim 10, wherein the 0 0 support comprises a-alumina or y-alumina. 12. A method as claimed in claim 11, wherein the Ssupport comprises a heat treated alumina material having a crystallographic structure predominantly indicative of ct-alumina, and a surface area intermediate y-alumina and a-alumina, said material exhibiting basic properties at the surface thereof. Z 13. A method as claimed in claim 10, claim 11 or claim 12, wherein the tungsten trioxide is formed on the support by impregnation of the support with a tungsten salt followed by treatment to convert the salt to tungsten trioxide, or by impregnation with a slurry of tungsten trioxide powder. 14. A method as claimed in claim 13, wherein tungsten trioxide is loaded onto the support in amounts up to 13 weight percent. A method as claimed in claim 10, claim 11 or claim 12, wherein the support is impregnated with sodium tungstate, dried, treated with concentrated nitric acid and then washed with dilute nitric acid so that the sodium tungstate is converted to tungstic acid and ,ti most of the sodium being eluted as the nitrate, and subsequently drying and heating the support to decompose Sthe tungstic acid to form tungsten trioxide. 16. A method as claimed in claim 10, claim 11 :a or claim 12, wherein the support is impregnated with ammonium metatungstate, dried and then heated to decompose the ammonium tungstate to form tungsten trioxide. oa4 ,4 17. A process for producing branched chain alkenes from straight chain alkenes, the process comprising s0 passing a gaseous stream comprising a carrier gas and straight chain alkenes over the secondary catalyst as defined in any one of claims 1 to 3. *4 I S 18. A process as claimed in claim 17, wherein the secondary catalyst is heated between 100°C and 450 0 C. 19. A process as claimed in claim 17 or claim 18, wherein the carrier gas is non-oxidising with respect to the catalyst in the active state. L A A process as claimed in claim 19, wherein the carrier gas comprises argon, carbon dioxide, nitrogen or a carbon monoxide/carbon dioxide mixture. 21. A process as claimed in claim 17, wherein the carrier gas comprises a hydrogen/water mixture at a predetermined oxygen partial pressure. 22. A catalyst as claimed .in claim 1, a method as claimed in claim 4 or claim 6, or a process as claimed in claim 17, substantially as herein described with reference to -he Examples S to Dated this 26th day of May, 1987. THE FLINDERS UNIVERSITY OF SOUTH AUSTRALIA, a, By its Patent Attorneys, VS 4 0 DAVIES COLLISON. a 0 t a 9Q I I 14tr