CA1064846A - Hydrocarbon conversion using a sputtered catalyst comprising a metal of group viii of the periodic table - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Hydrocarbon reforming and/or hydroisomerisation in the presence of hydrogen with a sputtered catalyst com-prising a Group VIII metal on a support.

Description

H.27636 i~64~

THE PRESENT INVENTION relates to processes for converting hydroearbons in the presence of hydrogen. '~
', Hydrocarbon conversion processes employing hydrogen are well-known and widely used. Examples '~
of such processes are the reforming of hydrocarbon ~, '' feestocks to increase their content o~ aromatic ~-hydrocarbons, isomerisation processes, cracking '~, and hydrogenation processes. Many of these ,' :: . ` -- ` 10 ,processes employ catalysts which may comprise one or more metals or metal compounds either on a '`' support or unsupported.
Among the ~actors influencing the economic J; .
',~, - and commercial success of hydrocarbon conversion ~, , 15 processes the choice of catalyst is particularly ,~
important. me catalyst influences not only the- I '~
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~ rate of conversion but also the range and relative , ,.
amounts of the various products obtained from any ', particular ~eedstock. In cases where it is desired to maximise the yield of one desired product with ,'~
as little by-product formation as possible, a , .: .
suitable catalyst would be one which combined high ~, activity in converting the feedstock with hlgh :~i selectivity to t~e ;desired product~ At the same ,'' ' ,' ;~ 25 time, another catalyst may have high selectivity '~
but this may be coupled with relatively low~'' '`, activity. Various proposals have been made to ~- improve catalysts ~or hydrocarbon conversion

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processes. These proposals include, for example, the use of specific metals or metal compounds for particular con~ersions and the use of two or more metals on a ca-talyst support.
We have now found that certain catalysts, when manufactured in a particular manner, are specially useful for hydrocarbon conversions and ~:
provide certain advantages over catalysts proposed hitherto.
-~ 10 Accordingly, one form of the present inv-ention is a process for converting a hydrocarbon ; feedstock which comprises a reforming and/or isom-erisation process wherein the hydrocarbon feedstock .
is contacted at hydrocarbon conversion conditions with hydrogen and with a sputtered catalyst compris-ing a metal of Group VIII of the Periodic Table on a support. Thus the sputtered catalyst comprises a ;
metal selected from iron, cobalt, nickel7 ruthenium, rhodium, palladium, osmium, iridium and platinum.
Optionally, the catalyst may comprise one or more ~; additional metals, preferabl~ one or more metals seIected from Groups Ib, IVb, VIa, VIIa and V~II of .:
I the Periodic Table. Thus the additional metal may - comprise a metal selected from copper, silver, goldl ~;
germanium~ tinj lead, chromium,molvbdenum, ~ungsten manganese, rhenium, technetium, iron7 cobalt7 nickel~
ruthen~umr rhodium 5 palladium osmium, ixidium, and platinum~

_..... , H,27636 ~0648~a~D
, ' The catalys-t usled in the process of this - invention is one which has been prepared by sput~
tering the metal component or components, pref-~-~ erably in the form of atoms~ monatomic or diat-omic ions onto a support. Sputtering usually involves driving an atomic or ionic dispersion of the catalytic material at a support surface so ;`
as to attach onto the support surface a major proportion of the atoms of the catalytic material which impinge on the surface. The aim is to ob-tain a catalytically active surface. One of the ways in whi`ch this may be achieved is by deposition of ~ .
isolated particles on the surface. Another way~
which might lead to improved activity because of ~ ~-the greater accessibility of the active phase on the surface of the support, is to ~orm islands of active material on the surface. If the catalys-t system involves two or more components then they may be sputtered on to the support either together or successively. For example, a layer of one - component may be sputtered onto the support followed ~`
by a layer of the other component and these steps ;
repeated until a catalytic layer of the requir~ed thickness is buiIt up. Alternatively, an alloy of the desired components may be sputtered on to the ,~l surface. Additional componen~sl ~ay also be ad,~ed to ' the support by conventional:m~ans, for example by `
- impregnation, either before or after sputtering.

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H.27636 ~ 64~ 6 Sputtering of the catalytic material may be achieved by bombarding a source of the material in the neighbourhood of the support wi-th energetic ions or electrons. The ions may be provided by an ion beam from an accelerator, ion separator or ion gun. Electrons may be provided by an electribal discharge to a cathode of the metal which it is desired to deposit. The conditions of atmosphere and celec-tivity of ions or electrons permitted to bombard the catalytic material are chosen so tha-t the metal atoms reach the support, if desired without -~undue agglomeration, and so that the co-deposition -~ -of unwanted material on the support is avoided. ;
Another technique which may be suitable in .. . -certain cases is the evaporation of a metal from a heated usllrface, for example from a filament either -coated with or consisting of the metal.
Ion and electron bombardment methods have .
the advantage that the metal source remains relatively cool during the sputtering process; therefore there is less danger of con-tamination, for example by evapor-ating the mechanic~l holder of the ~etal sample. ;
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; Furthermore, it is recognised that ion and electron bornbardment permits control, for example of the energy, of the ejected (sputtered) atom and suchcontrol may be useful since in sorne cases the~energy of the sputtered a-tom may be importan-t in determining the structure of the catalytic ma-terial.

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H.27636 For some hydrocarbon conversion processes it may be more convenient to modify preparation of the sputtered catalyst by sput-tering the support ~ indirectly. For examp:Le, the sputtered material ;~ 5 may first be t~apped by a matrix, for example an ~ organic compound, and only later brought ~nto contact : with the support.
Another modification in sputtering technique involves agglomeration of already sputtered small ~
- - 10 particles, either alone or mixed with other suitable ,~ -materials, for example ceramic oxides, which may themselves be catalytically active or carry a ca-tal~
ytically active component. One method o~ forming a - catalytically useful aggregate is to coat small sputtered particles on to a preformed support, ~or example a fibrous "wool", a metallic honeycomb matrix ~ ;
or a granular ceramic material.
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It is t-o~'be understood that the process of ~- this lnvention is not limitéd to use of a sputtered catalyst prepared by one of the,l methods hereinbefore ~-mentioned but that sputtered catalysts prepared by other methods are also suitable for use in the process.
The amount o~ me-tal used in the catalyst - preferably lies in the range 0.002 to 20% by weight .. . - . ...
25 of the total catalyst, more preferably in the ~ange 0.01 to 2.0% by weight.
The primary support can be in any convenient ~ -' ~ mechanical shape, for example, discrete particles, ~
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especially rounded granules or cylindrical pellets - or fibres or honeycombs or as a coating on any of such forms or on a metal substra-te such as a wire, vessel wall or perforated structure or mesh. The ;, 5 primary support may be made of refractory non-metallic material, especially oxidic material and suitably comprises an oxide such as magnesia, alumina,;~
silica, etc. etc. and mixtures or compounds of these with each o-ther or with other refractory oxides.
They may be in highly refractory forms such as ` fused magnesia, highly calcined alumiha~ spinels, and hydroxylic cement. If desired, -the refractory metal oxide may be fibrous in nature. The primary ~- support which is used may be one having relatively - 15 high porosity but preferably the support is one of :
low porosity. Preferably the pore volume lies in the range 0 to 1.0 cm3/g, more preferably in the ., ;
, ~ range 0.05 to 0.5 cm3/g. The particle size of the ~
o support preferably lies in the range lOOA to 10 mm., `;- ;
more preferably in the range 100~ to 5 mm.
, :! : : , , For certain hydrocarbon conversions, for example reforming or hydroisomerisation, it is desirable to increase the acidity of the catalyst in order to promote its activity. The increased acidity may be obtained either by a suitable modi~ication to the sputtering method, by deliverately adding an acldic material to the sputtered catalyst or by choosing a sui-tably acidic support to receive ths i :.

H.27~,36 ::~06~ 6 "
sputtered metal. The addition or incorporation of halides, especially chlorid~es, is the preferred means of increasing the acidity of an alumina-supported catalyst. A suitable amount of halide lies in the range 0.1 to 3% by weight based on the total weight of the catalyst.
; The halide may be incorporated onto the catalyst carrier at any suitable stage of catalyst manufacture, for example prior to, or following, 1~ sputtering. The halide may be incorporated by cont-acting suitable halide-containing compounds either in the gaseous form or in a water-soluble form with the support material, either before or after sputtering. Alternatively, halide-containing ~; ~
particles may be mixed intimately with particles ~ -containing sputtered metal and if desired the mixture may be agglomerated, for example in ~ pellets.
If desired, the acidity of the catalyst may .-be maintained during hydrocarbon conversion by the addition of a halide material to the process stream during the conversion.
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Removal of carbonaceous deposits by regen-eration of the catalyst may be effected in known manner, for example by~burning off in a stream of oxygen-containing gas.

A preferred form of -the present invention lS a process for reforming a hydrocarbon charge fraction boiling in the gasoline boiling range ~hich ~-~:;

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H.27636 ~06~ 6 comprises contacting a stream of the hydrocarbon charge fraction together wi-th hydrogen in a reaction zone at reforming conditions in the presence of a sputtered catalyst comprising a metal, or compound of a metal, selected from platinum, iridium, palladium, rUthenium, osmium, rhodium, iron, nickel and cobalt - on a support.
It is preferred to use a noble metal, especially platinum, as the catalyst but other noble - 10 metals, for example palladium, rhodium, ruthenium, osmium and iridium, may also be used. The performance of the noble metal catalyst may be improved by using one or more additional metal components. Suitable ~
additional metals include iridiun, rhenium, tin, lead, -copper, gold, manganese and germanium. The amount of additional metal component used may vary depending on the particular me~al but will generally lie in the - range 0.001% to 5.0% by weight of metal based on the total weight of catalyst. It is preferred also to use in the reforming process a catalyst of increased acidity as hereinbefore described. Other components, if any, of the catalyst may be incorpora-ted in known ways, for example by impregnation ~f a solution containing a suitable soluble precursor such as a metallic halide complex, or for example during the sputtering procedure either concurrently with or consecutively to the preferred metal.
- The reforming conditions used will depend on _ g _ , .

~ 4~ H.27~-the hydrocarbon feedstock used. The eedstock is preferably a light hydrocarbon oil, for example a naphtha fraction. The temperature in the reforming process will generally be in the rang~ 300 to 600 C.
The pressure in the reaction zone may be a-tmospheric or superatmospheric, preferably lying in the range 25 to 500 p.s.i.g. The particular relationship of - temperature and pressure, together with the liquid hourly space velocity, is chosen depending on the nature of the reforming reaction required. In general, however, the liquid hourly space velocity will lie in the range 0.1 to 10, more preferably in the range 0.1 to 5. A

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:, , suitable molar ratio of hydrogen to hydroc~rbon ~eed lies in the range 0.5 to 20 : 1, prefer~bly in the range 3 to 8 ~
A further pre~erred ~orm of th0 present invention is a process ~or hydroisomerising an alkyl-benzene hydrocarbon or a mixture o~ alkylbenzenes which comprise~ contacting the alkyl ben~ene or mixture of alkylbsnzenes together with hydrogen under isomerisation conditions with a sputtered catalyst com-prising a metal ox a compo~nd of a metal selected rrOmplatinum, palladium, rhenium, molybdenum, tun~sten, chromium, copper and silver on a support.
Suitable isomerisation conditio~s include a ... :
temperature in the range 200 to 550C, atmospheric ~ --15 or superatmospheric pressure, preferably in the range 15 to 500 p.s.i.g. and a weight hourly space velocity ~-in the range 0.1 to 20. A suitable mole ratio of hydrogen to hydrocarbon lies in the range 1 to 30 ~
The process of the invention is illustrated by the ~ollowing Examples.

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E~hMPLES
100 g. of commercially available 1/16" spheres o~ gamma-alumina were steeped ove~night at ambient tem-perature in 200 ml. o~ 2N aqueous nitric acid, then washed twice with 200 ml. distilled water and finally dried ror 16 hours at 120 ~ 10 C. The dry solid was calcined ~or 6 hours at 550 C, a~ter which it had a surface area o~ 235 ~ 30 m /g (measured by B.E.T. N2 ' ` ~

'' . . _ H.2'763~

isotherm method), a pore volume of 0.95 ~ 0.10 ml/g.
and a sodium content of 250 + 200 p.p.m. Se~eral batches of solid m~de in this way were mixed together.

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Portions of about 100 g. of the solid were loaded with platinum in an evacuated chamber containing a platinum cathode sustaining a discharge. T~ assist even deposition of platinum on to the alumina spheres, the container holding the spheres was agitated during j - - the discharge period. A~ter the loading! the solid - 10 was found to contain 0.05 to 0.07%.platlnwm by weight.
When broken, the platinised alumina spheres prepared in this way were found to carry d~posited -::
- metal only peripherally. As the total platinu~ content . . -~
was too low for examination by con~en*ional means, ~ -the peripheral parts of the spheres were removed and colleoted by ultrasonic agitation of the particles immersed in acetone. It was ~ound that most o~ the platlnum had been removed when a thick~ess of about 1.8~b of the~spheres had been eroded. X-ray diffraotion . .
of the eroded mat~rial showed (1) poorly defined gam~a~

alumina, and (2) platin-um metal of mean crystallits :` O .
-- size of 190 ~ 70A.
- Part of the bulk of the platinised alu~ina spheres was chlorided to form a naphtha refo~ling ~-catalyst as rollows. A sample was 1oaded intQ a tubular reactor and heated in a stream of nitrogen to 51V
~! 5 C. The nltrogen stream was then replaced by air (31.6 l~ r.) and 2.3 ml ~ ~. of 1.83M aqueous hydro-'' ~.27636 ~L~6~8~6 chloric acid was fed to the roactor ~ia a vaporiser.
AP$er 1 to 4 hours ~dep~nding on the level of chloride required), the hydrochloric acid feed was stopped. The catalyst was held in an air stream at 510 C for 30 minutes and then Por a ~urther 30 minutes at 400 C
before being allowed to cool.

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The catalyst prepared as described eontained o . o6 ~ o . ol % platinum, 1.1 ~ O.2% Cl on gamma-alumina.
-- 10 44.7 g. catalyst was loaded iuto a reactor to test ~ its naphtha re~orming activity. ;; ~-; The catalyst was reduced in a ~low of -~
hydrogen (500 l/hr,) at 350C and then a naphtha feed~-tock oP C6 to Cg hydrocarbons was fed to the reac*or containi~g the catalyst. The ~eedstock con-tained (parts by weight) 54% para~Pins, 37% naphthenes, 9% aromatics and less than 1 p.p.m. sulphur. The Peedstock was reformed under the Pollowin~ conditionsO
temperature 480C; pres~ure 340 p.s.i o g~; liquld hourly space velocity (LHSV) 2.2; and molar ratio of hydrogen ~ to hydrocarbon of 8 ; The liquid product ~C5 and C5~) contained `~
28~ by weight oP aromatics. I~e yield of liquid product was 87% by weight.
A~ter the reforming reaction, the outer `~

portion of the catalyst particles was removed ~s herein-before described. ~he platinum crystallite si~e was found to be 230 + 70A.
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-H. 27636 ~6f~

E~AMPLE_2 -Example 1 was repeated except that the reforming conditions were: temperature 500C; pressure ~;
340 p.s.i.g.; LHSV 1.7; mole ratio of hydro~e~ to hydrocarbon 5 : 1.
The yield of liquid product ~as 77~ by weight and it contained 36% br wei~ht o~ aromatics.
These Examples illustrate the increased activity o~ metals in sputtered catalysts when compared with metals in catalysts prepared by conventional ~ ~.
methods. The loading of catalyst metal r~quired on the support ln a sputtered catalyst is appr~ciably lower than ln the conventional catalysts in order to ~ -- achieve similar conversions of feedstocks and yields of products. We believe that this impro~e~ent in catalyst performance is due, at least in part, to the ~;~
fact that in sputtered catalysts much o~ the catalytic material is readily available on or ve~y close to the 3ur~ace of the support, whereas in conven-tional catalysts, appreciable quantities of c~talytic material pene-trate to the interior o~ the support ~nd are thereby unavailable for catalysis.

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Claims (10)

WHAT WE CLAIM IS:

1 A process for converting a hydrocarbon feed-stock which comprises a reforming and/or isomerisation process wherein the hydrocarbon feedstock is contacted at hydrocarbon conversion conditions with hydrogen and with a sputtered catalyst comprising a metal of Group VIII of the Periodic Table on a support.

2. A process as claimed in Claim 1 in which the sputtered catalyst comprises a metal of Group VIII of the Periodic Table and one or more additional metals on the support, the additional metals being selected from copper, silver, gold, germanium, tin, lead, chromium, molybdenum, tungsten, manganese, rhenium, technetium, iron, cobalt, nickel, ruthenium, rhodium, palladium;
osmium, iridium and platinum.

3. A process as claimed in Claim 1 in which the catalyst has been prepared by sputtering the metal component or components in the form of atoms, monatomic or diatomic ions onto a support.

4. A process as claimed in Claim 2 in which the catalyst comprises at least two metal components and in which the catalyst has been prepared by sputtering the metal components on to the support either together or successively.

5. A process as claimed in Claim 1 in which the sputtered catalyst has been prepared by bombarding a source of the catalytic component in the neighbourhood of the support with energetic ions or electrons

6. A process as claimed in Claim 1 in which the catalyst has been prepared by evaporation of a metal component from a heated surface.

7. A process as claimed in Claim 1 in which the sputtered catalyst has been prepared by sputtering the support indirectly.

8. A process as claimed in Claim 1 in which the catalyst has been prepared by agglomerating already sputtered small particles.

9. A process as claimed in Claim 8 in which the catalyst has been prepared by coating small sputtered particles on to a pre-formed support.

10. A process as claimed in Claim 1 for reforming a hydrocarbon charge fraction boiling in the gasoline boiling range which comprises contacting a stream of the hydrocarbon charge together with hydrocarbon in a reaction zone at reforming conditions which include a temperature in the range 300 to 600°C, a pressure in the reaction zone in the range 25 to 500 p.s.i.g., a liquid hourly space velocity in the range 0.1 to 10, and a molar ratio of hydrogen to hydrocarbon feed in the range 0.5:1 to 20:1, in the presence of a sputtered catalyst comprising a metal, or a compound of a metal, in an amount (calculated as metal) of 0.002 to 20% by weight of the total catalyst, selected from platinum, iridium, palladium, ruthenium, osmium, rhodium, iron, nickel and cobalt on a support.