BE615232A - - Google Patents

Description

       

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 EMI1.1
 



  'Improvements in the isomerization of paraffinic hydrocarbons.
 EMI1.2
 



  The present invention relates to the ltinomerination of hydrochloride. paraffinic C4 or higher., boiling in the range of gasoline; that is to say up to 204 C, and this at temperatures ranging: up to 204C, and more particularly to the i80mérioation "of pentanes and / or hexane. The term wisomerisa-
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 tions encompasses both the conversion of normal paraffins to
 EMI1.4
 iso-paraffins and the conversion of iso-paraffins to iso-paraffins

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 having a higher degree of branching.



   The isomerization of normal paraffins is becoming increasingly important in the development of high octane engine fuels. Heretofore, the desired increase in octane number has been achieved primarily through catalytic reforming processes which increase the aromatic / gasoline content, however, an increase in engine compression ratio. Modern technologies make other means of increasing the octane number of fuels desirable.

   It is known that the feedstock of naphtha to the catalytic reforming process contains appreciable amounts of normal lower boiling paraffins and it is evident that a considerable increase in the octane number would be. obtained by converting these normal paraffins into iso-paraffins.



   The present invention relates to an isomerization process using a particular catalyst and, according to the present invention, a process for the isomerization of paraffinic hydrocarbons C4 and higher, boiling in the boiling range of gasoline, comprises contacting paraffinic hydrocarbons in the presence of hydrogen at a temperature below 204 ° C. with a catalyst prepared by contacting alumina with a compound of the general formula:
 EMI2.1
 in which X and Y are the same or different and chosen from H, Cl, Br, F or SC1, or else X and Y together form oxygen or sulfur, under non-reducing conditions and at a temperature such that chlorine is fixed by the alumina without the production of free aluminum chloride.



   The alumina preferably contains a proportion of a metal or a metal compound having hydrogenating activity and selected from groups Via or VIII of the Periodic Table.



  The preferred metal is a metal of the platinum group which can be

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 present in an amount of 0.01 to 5% by weight, preferably 0.1 to 2% by weight. The preferred platinum group metals are platinum and palladium, which have equivalent effectiveness in low temperature isomerization catalysts.



   The feed for the process is preferably a feed containing a major proportion of pentanes, hexanes or a mixture of these paraffins. A feedstock containing a major proportion of hexanes is especially preferred. If it is desired to isomerize only normal paraffins, the feedstock can first be treated to separate normal paraffins from other hydrocarbons, and the normal paraffins are contacted with the isomerization catalyst. Such a separation can conveniently be achieved by so-called molecular sieves.



   The product of the isomerization reaction can be treated in a similar fashion to recover unconverted normal paraffins, which can be recycled to the isomerization reaction zone. Such a separation can also be carried out in a suitable manner by means of ular mol sieves.



   The isomerization can be carried out under the following conditions, in liquid or vapor phases.



   Temperature 50 to 400 F, preferably 150 to 3500
Atmospheric pressure - 2000 l.p.p.c., preferably 225 to 1000
Space speed 0.05 to 10 vol./vol./Hre, preferably
0.2 to 5.



   Hydrogen molar ratio / 0.01 to 20/1, preferably 1.5 to 15/1 hydrocarbons
The feedstock is advantageously free of sulfur, water and aromatic hydrocarbons. It also advantageously has a low content of naphthenic hydrocarbons.



  Suitable feed pretreatment processes for an isomerization process using a catalyst of an aluminum halide and a hydrogenating metal, on an oxide support

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 refractory, are described and claimed in other patents of the applicant. The processes in question can also be used with the isomerization process of the present invention.



   The process for preparing catalysts for use in the isomerization process of the present invention is described and claimed in still other patents of the Applicant.



   A particular feature of the preparation of the catalyst is the use of the particular compounds of the general formula indicated, these compounds providing a particular form of chlorination which produces isomerization catalysts active at low temperature.

   The following examples of compounds giving active catalysts and inactive catalysts illustrate the particular nature of the compounds employed. u compounds yielding compounds yielding active catalysts inactive catalysts
Carbon tetrachloride (C314) Hydrogen chloride gas (HC1)
Chloroform (CHC13) Chlorine (C12 to
Methylene chloride (CH2C12) Methyl chloride (CH3C1)
Uichlorodifluoromethane (CC12F2) Acetyl chloride (CH3COC1)
Trichlorobromomethane CC13Br) Dichloroethane (CH2C1-Ch2C1) Thiocarbonyl tetrachloride (CC13SC1) Tetra chloroethane CHClgèCHGLg) 3 Tetrachloroethane (CHC12 @@ HC12)
Tetrachlorethylene (CC12-CC12)
In the case of compounds containing elements other than chlorine, carbon and hydrogen,

   processing can add other elements to the catalyst in addition to chlorine. For example, treatment with dichlorodifluoromethane results in the attachment of both chlorine and fluorine to the catalyst. It has been found, however, that catalysts thus prepared are still active for low temperature isomerization, and they may further have other properties resulting from the addition of the other elements.

   It has also been found that small amounts of halogens (especially chlorine) which may be present in alumina prior to the chlorination treatment of the present invention.

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 tion do not affect the activity of the catalysts for low temperature isomerization, although such halogen does not contribute in any way to the isomerization activity. Thus, the alumina used may already contain up to 1% by weight of chlorine and / or fluorine, as when, for example; the metallic material which is chlorinated by the process of the present invention is a catalyst normally used for the reforming of gasoline boiling range hydrocarbons.

   Preferred compounds providing active catalysts are carbon tetrachloride, chloroform and methylene chloride.



   The compounds covered by the general formula, in which X and Y together form oxygen or sulfur, are phosgene and thiophosgene.



   Any suitable form of alumina can be used, as long as it contains hydrogen. This is a characteristic of activated aluminas which, although consisting mainly of alunina, also contain a small amount of hydrogen, usually less than 1% by weight. This hydrogen is generally considered to be in the form of surface hydroxyl groups and it is believed that the chlorine compound reacts with the surface hydroxyl groups to form the active catalytic zones. Water is in fact a product of the reaction, but the hydrogen is not removed at all and the treated catalyst still contains a measurable amount of hydrogen.

   The amount of chlorine added to the catalyst is preferably of the order of 1 to 15% by weight, the precise amount depending on the surface area, as measured by absorption of nitrogen at low temperature.



  It has been found that the maximum amount of chlorine that can be added without formation of free aluminum chloride is proportional to and the surface area / is about 3-3t5 x 10-4 gr / m2. Maximum chlorination is preferred, but lower amounts of chlorine will still give active catalysts and a suitable range is, therefore, 2 x 10-4 to 3.5 x 10-4 gr / m2.

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   Any of the forms of alumina suitable as a base for reforming catalysts can be used, but a particularly preferred form is that derived from an alumina hydrate precursor in which the trihydrate predominates. A form containing a major proportion of -alumina trihydrate is particularly suitable. A suitable process for the preparation of alumina comprises the hydrolysis of an aluminum alkoxide, eg aluminum isopropoxide, in an inert hydrocarbon solvent, eg benzene.

   Under equal conditions, the higher the quantity of chlorine fixed by the alumina, the greater the activity of the catalyst and since, as already mentioned, the maximum quantity of chlorine that can be added is proportional. - related to the surface area, it is desirable that the alumina has a high surface area, for example of more than 250 m2 per gr., preferably of more than 300 m2 / gr.



   If desired, a small proportion of one or more other refractory oxides selected from Groups II to V of the Periodic Table can be mixed with the alumina. Thus, the alumina can contain up to 50% by weight, for example, of silica, titanium oxide, beryllium oxide, zirconia or magnesia.



   The hydrogenated metal is advantageously incorporated into the lumina before the treatment with chlorine. When using a metal from the platinum group, it is also desirable that it should be finely dispersed as small crystallites on the alumina, the suitable criteria for the size of the crystallites being that these are not detectable. by X-ray diffraction and that upon treatment of the alumina-platinum group metal compound with benzene at 25 C, they have a measurable chemisorption, preferably not less than 0.1 molecules of benzene absorbed per atom of platinum and not less than 0.03 molecule of benzene absorbed per atom of palladium.

   Details of the chemisorption technique of benzene have been published in the Acts of

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 Second International Congress of Catalysis', Paris 1960, Vol. 2, page 1851.



   A suitable method of obtaining the platinum group metal in the required state of subdivision is by adding a solution of a platinum group metal compound to an alumina hydrogel and precipitating the platinum group metal. in the form of sulf.ide, for example by treatment with hydrogen sulfide. The treatment of the alumina compound and a platinum group metal with the chlorine compound is preferably carried out with the platinum group metal in a reduced state, and this can be conveniently carried out by pretreating the compound with. hydrogen.

   When a compound of alumina and a platinum group metal is treated with a chlorine compound according to the present invention, it is believed that a portion of the fixed chlorine is associated with the group metal. platinum as an active complex.



   In some cases, the presence of active complexes in the catalysts can be demonstrated by the development of intense colors (orange-yellow) upon treatment with dry benzene.



   Alumina alone (after treatment with carbon tetrachloride) gives a yellow color with benzene, but this does not persist on flushing with dry nitrogen.



   Platinum on alumina (after treatment with carbon tetrachloride), however, gives a stable yellow color with benzene and can be stored under dry nitrogen indefinitely.



   The non-reducing conditions used for the chlorination can be inert or oxidizing conditions, the latter being preferred because they provide catalysts which lose their activity more slowly during low temperature isomerization. A suitable method of contacting the alumina is to pass a gaseous stream of the chlorine compound over the alumina, either alone or preferably in a non-carrier gas.

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 reducer. Examples of suitable carrier gases are nitrogen, air or oxygen.



   Non-reducing conditions are essential, since / reducing conditions tend to convert the chlorine compound to hydrogen chloride gas, resulting in an inactive catalyst. The temperature for chlorination can be 149-5930c The tendency to form free aluminum chloride increases with temperature and care should therefore be taken when using the higher temperatures in the range indicated. Since the temperatures used will normally be above the volatilization temperature of aluminum chloride, the formation of free aluminum chloride is readily detected by its occurrence in the gaseous reaction products.

   When treating a compound of alumina and a platinum group metal, care must also be taken to prevent the formation of volatile platinum complexes, the tendency for the formation of such complexes to increase again with an increase in temperature. When dealing with alumina and platinum group metal compounds, the temperature is preferably 149-371 ° C, platinum-on-alumina compounds being more particularly treated at 232-316 µ and palladium compounds. -alumina at 260-343 C. The chlorination reaction is exothermic and the temperatures specified are the initial temperatures used.



   The rate of addition of the chlorine compound is preferably as low as possible to ensure uniform chlorination and to avoid a rapid rise in temperature as a result of the exothermic reaction. The addition rates preferably do not exceed 1.3% by weight of chlorine compound per weight of catalyst per minute. If a carrier gas is used, the flow rate is preferably at least 200 volumes per volume of catalyst per hour and a suitable range is 200 to 1000 vol / vol / hour. The pressure used is suitably atmospheric pressure.

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   The active catalyst is susceptible to hydrolysis in the presence of water and should therefore be stored under anhydrous conditions. Likewise, the materials used in the preparation of the catalyst should also be free of water. The use of the catalysts for low temperature isomerization according to the present invention and. the preparation of these catalysts are illustrated by the following examples.



  EXAMPLE 1.



   65 g of an industrial reforming catalyst, comprising 0.58% by weight of platinum and 0.81% by weight of chlorine, on an alumina support, were brought into contact with 20 g of dry carbon tetrachloride at 300 ° C. Carbon tetrachloride was added dropwise over a half hour period while the catalyst was flushed with dry nitrogen flowing at 250 ml / minute. After reaction, scanning was continued for a further 2 hours.



   The resulting compound contained 12.8 wt% chlorine and 0.49 wt% platinum.



   The catalyst was stored in a properly capped dry vessel and charged to an isomerization reactor under a nitrogen blanket.



   The following operating conditions were used
Catalyst bed temperature 132 C
System pressure 250'l.p.p.c.
 EMI9.1
 



  H2 / hydrocarbon molar ratio 2.5 / 1
Space speed - 0.5 vol./vol./Hre
Catalyst charge 70 ml.



   The feed was a C6 fraction from a light gasoline which had been hydrogenated and subjected to treatment on silica gel before isomerization.



  Impurity rate - benzene not detectable by G.L.C.



   Sulfur 0.00003% by weight
Water 5 parts per million
Bromine number 0.02

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The product which was analyzed by gas chromatography had the composition given in Table I given below.



   TABLE I.
 EMI10.1
 
<tb>



  Product, <SEP>% <SEP> in <SEP> Power <SEP> Hours <SEP> under <SEP> treatment
<tb>
 
 EMI10.2
 weight 't1 4 1 5 1 6! 7 I 27-31 51-55
 EMI10.3
 
<tb> Propane- <SEP> Trace <SEP> - <SEP> - <SEP> - <SEP> Trace-
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> iso-u4 <SEP> - <SEP> 0.5 <SEP> 0.5 <SEP> 0.5 <SEP> 0.5 <SEP> 0.5 <SEP> Trace
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> n-C4 <SEP> - <SEP> Trace- <SEP> - <SEP> Trace <SEP> Trace <SEP> Trace
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> iso-U5 <SEP> Trace <SEP> 2.5 <SEP> 2.5 <SEP> 2 <SEP> 2 <SEP> 2 <SEP> 1.5
<tb>
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> n-C5 <SEP> 2.5 <SEP> 1 <SEP> 0.5 <SEP> 1 <SEP> 1 <SEP> 1 <SEP> 0.5
<tb>
<tb>
<tb> 2,2-dimethylbutane <SEP> 1 <SEP> 28 <SEP> 29.5 <SEP> 28 <SEP> 27 <SEP> 28 <SEP> 27.5
<tb>
<tb>
<tb>
<tb>
<tb> 2,3-dimethylbutane <SEP>) <SEP> 35.5 <SEP> 33,

  5
<tb>
<tb>
<tb> uyclopentane <SEP> 35.5 <SEP> 35.5 <SEP> 33 <SEP> 35 <SEP> 33.5 <SEP> 35 <SEP> 32
<tb>
<tb>
<tb> 2-methylpentane <SEP>)
<tb>
<tb>
<tb>
<tb> 3-methylpentane <SEP> 20 <SEP> 16 <SEP> 16.5 <SEP> 16 <SEP> 17 <SEP> 16 <SEP> 18
<tb>
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> n-C6 <SEP> 33.5 <SEP> 10.5 <SEP> 10.5 <SEP> 10 <SEP> 11 <SEP> 10 <SEP> 11.5
<tb>
<tb>
<tb> methylcyclopentane <SEP> 6 <SEP> 3 <SEP> 3.5 <SEP> 3.5 <SEP> 4 <SEP> 3.5 <SEP> 3.5
<tb>
<tb>
<tb>
<tb>
<tb> cyclohexane <SEP> 1.5 <SEP> 3 <SEP> 3.5 <SEP> 3.5 <SEP> 4 <SEP> 4 <SEP> 5.5
<tb>
 
 EMI10.4
 ir '"rii, Lu 2.



   5 g of an industrial reforming catalyst, comprising 0.58% by weight of platinum and 0.81% by weight of chlorine, on an alumina support, were contacted at 350 ° C. for 15 minutes with a stream of dry nitrogen saturated with carbon tetrachloride, circulating at 250 ml / minute. The nitrogen sweep was then continued for an additional 1 hour.



   Analysis of the resulting compound gave 12.8 wt% chlorine, an acidity (expressed as the chlorine content) of 9.9 wt%, 0.097 wt% hydrogen and 0.017 wt% carbon. there was no significant change in platinum content.



   The catalyst was stored in a properly capped dry vessel and charged to an isomerization reactor under a nitrogen blanket.



   A feed of dry n-hexane (99.9 mole%) was passed along with hydrogen through the reactor, containing 1 ml of catalyst, and the operation was carried out under the following conditions.

 <Desc / Clms Page number 11>

 



   Ambient temperature 20-22-0
Atmospheric pressure
Hydrogen / n-hexane molar ratio 6/1
Space speed of gas 240 vol. /vol./Hre.



   The product which was analyzed by gas chromatography had the composition given in Table II below.



   TABLE II
 EMI11.1
 
<tb> product, <SEP>% <SEP> in <SEP> 1 <SEP> sure <SEP> under <SEP> processing
<tb>
<tb>
<tb> weight <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7
<tb>
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> iso-C4 <SEP> 2.6 <SEP> 1.6 <SEP> 1.6 <SEP> 2.3 <SEP> 1.3 <SEP> 1.9
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> iso-Ce <SEP> 3.7 <SEP> 2.1 <SEP> 2.2 <SEP> 3.1 <SEP> 2.2 <SEP> 2.7
<tb>
<tb>
<tb>
<tb> 2,2-dimethylbutane <SEP> 0.4 <SEP> 0.4 <SEP> 0.5 <SEP> 0.8 <SEP> 0.5 <SEP> 0.6
<tb>
<tb>
<tb>
<tb> 2,3-dimethylbutane <SEP> '<SEP>
<tb>
<tb>
<tb> 2-methylpentane <SEP> 13.7 <SEP> 14.2 <SEP> 14.9 <SEP> 15.6 <SEP> 13.0 <SEP> 13.5
<tb>
<tb>
<tb> 3-methylpentane
<tb>
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> C6 <SEP> 79.6 <SEP> 81.7 <SEP> 80.8 <SEP> 78.2 <SEP> 83.0 <SEP> 81.3
<tb>
 EXAMPLE 3.



   5 g of an industrial reforming catalyst, comprising 0.58% by weight of platinum and 0.81% by weight of chlorine, on an alumina support, were contacted at 200 C for 1 hour with a stream of dry nitrogen saturated with carbon tetrachloride, circulating at 100 ml / minute. The nitrogen sweep was then continued for a further 2 hours. Analysis of the resulting compound gave 0.54 wt% platinum, 10.6 wt% chlorine, acidity (expressed as chlorine content) of 7.3 wt%, 0.19 wt% hydrogen and 0.024% by weight of carbon.



   The activity of the compound was examined using the reactor conditions described in Example 2, but with the reaction temperature at 88-90 ° C. A typical sample analysis of the product after 3 hours of processing gave 56% by weight of C6 isomers present, of which 6.5% by weight were 2,2-dimethylbutane.



    EXAMPLE 4.



   5 g of an industrial reforming catalyst, containing 0.58% by weight of platinum and 0.81% by weight of chlorine, on an alumina support, were contacted with 3 ml of tetrachloride

 <Desc / Clms Page number 12>

 dry carbon at 250 ° C. Carbon tetrachloride was added dropwise over a period of about 15 minutes; during this time the catalyst was flushed with dry nitrogen flowing at 500 ml / minute. After reaction, scanning was continued for a further 1 hour and then 5 ml. of dry benzene was added dropwise over the cooled catalyst. The catalyst developed a deep orange-red color which slowly turned to yellow-orange as the excess benzene was removed by the nitrogen sweep.

   The nitrogen flushing was continued for 12 hours and then the compound was transferred to a dry container and stored under dry nitrogen. '
Under these storage conditions, the yellow catalyst was found to be stable for a period exceeding 3 weeks.



   Analysis of this benzene-treated compound gave 0.54 wt% platinum, 9.8 wt% chlorine, an acidity (expressed as chlorine content) of 8.2 wt%, 0.20 % by weight of hydrogen and 0.59% by weight of carbon.



   After 2 weeks of storage, the activity of the compound was examined using the atmospheric reactor conditions described in Example 2. Analyzes of typical samples of the product over the first 17 hours of processing gave 12%. by weight of C6 isomers present. In this way, the. that the compound had been treated with benzene did not adversely affect the isomerization activity.



    EXAMPLE 5.



   5 gr of an industrial reforming catalyst consisting of P, 58% by weight of platinum and 0.81% by weight of chlorine, on an alumina support, was contacted at 300 C with a current! of dry nitrogen carrying vapor of methylene chloride, for half an hour. The nitrogen circulation rate was 250 ml / minute. After reaction, the nitrogen flushing was continued for a further 1 hour and then the catalyst, after cooling in dry nitrogen, was stored in a vessel.

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 dry suitably corked.



   Analysis of the resulting compound gave 0.54 wt% platinum, 9.5 wt% chlorine, acidity (expressed as the chlorine content) of 6.4 wt%, 0.65 wt% carbon , 0.11; % by weight of hydrogen.



   The catalyst (1 ml) was charged to an isomerization reactor under a sheet of dry nitrogen and a feed of dry n-hexane was passed along with hydrogen under the following conditions. :
Atmospheric pressure
Reaction temperature: ambient, 22-24 C
Hydrogen / n-hexane molar ratio 6/1
Space speed of gas 200 vol./vol./Hre.



   Catalyst charge 1 ml
N-hexane feed (99.9 mole% purity)
The product which was analyzed by gas chromatography had the composition shown in the following Table III.



   TABLE III
 EMI13.1
 Product,% by weight t¯¯¯¯Hours under treatment ¯¯¯¯¯¯¯¯¯¯¯¯¯! 3! 4 <5t6t7t 25 hydrocarbons t; 1-C4 1.3 0.9 0.5 0, 3 Hydrocarbon trace C '1.7 0 $ 8 0.4 0.2 I trace 2,2-dimethylbiitane 4.1 4.9 4.3 3.0 2.2 - 0.1 2,3-dimethylbutene 2- methylp iitan 35 7 39.0 39.9 37.2 33.3 9.3 3.-rWei (hylpentane) hydrocarbons n-06 57.1 53.6 54eg 59.2 64.5 9oe6
After 25 hours of treatment at room temperature, 22-24 C, the reaction temperature was raised to 220 C in about 1 hour. Analyzes of the product at various temperatures during this period are given in Table IV below.

 <Desc / Clms Page number 14>

 



    TABLE IV
 EMI14.1
 Products,; ¯¯¯Reaction temperature, OC% by weight F22 * i 3 '<63 1 103 "! I 120 f 157! 17501 215- hydrocarbons 1- 4! O, 1! Oel 0.1 0.2 2 , 5 6.1 20.6
 EMI14.2
 
<tb> hydrocarbons <SEP> C5 <SEP> - <SEP> - <SEP> - <SEP> - <SEP> Track <SEP> 0.2 <SEP> 0.9 <SEP> 3.4
<tb>
<tb>
<tb>
<tb> 2,2-dimethylbutane <SEP> # 0.1 <SEP> 0.3 <SEP> 0.4 <SEP> 0.5 <SEP> 1.0 <SEP> 4.7 <SEP> 9, 2 <SEP> 11.8
<tb>
<tb>
<tb> 2,3-dimethylbutane
<tb>
<tb>
<tb>
<tb> 2-methylpentane <SEP> 9.3 <SEP> 11.3 <SEP> 12.5 <SEP> 13 <SEP> 14.7 <SEP> 19.7 <SEP> 24.5 <SEP> 28 , 0
<tb>
<tb>
<tb>
<tb> 3-methylpentane <SEP>)
<tb>
 
 EMI14.3
 n-C6 hydrocarbons 90.6 88.3 87.1 $ 86.5 1.1 73.0 59.3 36.1
 EMI14.4
 .And. & JMtr.Lt. And U.



   5 g of an industrial reforming catalyst, comprising 0.58% by weight of platinum and 0.81% by weight of chlorine, on an alumina support, were contacted at 300 ° C. with a dry nitrogen course carrying chloroform vapor, circulating at 250 ml / minute. The chloroform had been previously washed well with distilled water to remove the alcoholic stabilizer and then re-dried. After 10 minutes of reaction, volatiles began to emerge from the catalyst bed and the chlorination treatment was stopped; only the nitrogen sweep was continued for an additional hour.



   Analysis at the resulting compound gave 0.40 wt% platinum, 12.6 wt% chlorine, acidity (expressed as te
 EMI14.5
 of chlorine) of 9.4% by weight, 0.11% by weight of carbon, 0.09% by weight of hydrogen.



   The catalyst (1 ml) was charged to an isomerization reactor under a sheet of dry nitrogen and a dry feed of n-hexane was passed through it along with hydrogen under the pressure. processing conditions given in Example 5, except as regards the gas space velocity which is given in the following Table V, together with the composition of the product, as analyzed by gas chromatography.

 <Desc / Clms Page number 15>

 



  TABLE V
 EMI15.1
 
<tb> Spatial <SEP> speed
<tb>
<tb>
<tb> of <SEP> gas <SEP> 250 <SEP> v / v / Hre <SEP> 125 <SEP> v / v / Hre
<tb>
<tb>
<tb> Time
<tb>
 
 EMI15.2
 Reaction temperature Ambient, 20-22 * U 20-.22 C tion Hours under treatment- 1 1/2 2 3 1/2 4 5 6 ment - .1. 1 - 1
 EMI15.3
 i-04 'hydrocarbons 4 1 8 1 l 5 l 5 5 4% by weight 4 4.1 3.8 1.3 1.5 1.5 5.4 4.0 hydrocarbons i-C5'% by weight 5.5 3 , 2 1.9 2.0 1.8 5.4 5.1
 EMI15.4
 2,2-dimethylbutne, o @ 8 0.2 0 l 0.1 t0.1 .0.5 0.6% by weight 2,3-dimethylbutane
 EMI15.5
 2-methylpentane) 12.0 8.9 7.0 7.3 7.2 11.5 11.9 3-methylpentane% by weight
 EMI15.6
 n-C6 'hydrocarbons 77 5 84y9 89 4 89 1 89.4 77.1 78s4% by weight EXAMPLE 7.



   The preparation of a catalyst, again using chloroform, was carried out as in Example 6, except that the reaction temperature was 220 ° C. and the reaction time was about 1/2 hour.



   Analysis of the resulting compound gave 0.57 wt% platinum, 9.0 wt% chlorine, acidity (expressed as chlorine content) of 7.1 wt%, 0.17 wt% carbon. , 0.17% by weight of hydrogen.



   A load of 1 ml of catalyst was tested for its isomerization activity, using the feedstock and processing conditions of Example 5, except for the gas space velocity which is given. in Table VI below, together with the composition of the product as analyzed by gas chromatography.

 <Desc / Clms Page number 16>

 



    TABLE VI
 EMI16.1
 
<tb> Speed <SEP> spa-
<tb>
<tb> tiale <SEP> of <SEP> gas <SEP> 250 <SEP> v / v / Hre <SEP> 125 <SEP> v / v / Hre
<tb>
<tb> V / VHre
<tb>
 
 EMI16.2
 reacSon Ambiant, 22 - 24 C 22 - 24-C Hauraa aoua 1 l2 î / ffi'1 /! 17 j la 19 20 21 hydrocarbons 170001 - - - 002 Q; np 17 0.9 0.1 - - 0.3 0.2 0.2 hydrocarbons 1 0 Trace i-G5,% enpalds '-'-' "- 2,2-dimethylbu-3'2 0 5 Trace Trace Trace Trace 0 lOI 0 l
 EMI16.3
 
<tb> 2,3-dimethylbu-:

  
<tb> tane
<tb>
 
 EMI16.4
 2-methylpentane) 2,) 16.9 8.5 4.9 4.9 4, 6.4 7.6 7.3 3-methylpentane)
 EMI16.5
 
<tb>% <SEP> in <SEP> weight
<tb>
 n- - C6 hydrocarbons,% by weight. 60.6 80.7 91.3 95.5 95.1 93.2 93.3 92.1 92.4
After 21 hours of processing at the processing temperature, 22-24 C, the reaction temperature was raised to 110 U over a period of about 2 hours. Of. Analyzes of product at various temperatures in this period are given in Table VII below.



   TABLE VII
 EMI16.6
 
<tb> Product <SEP> Reaction <SEP> temperature <SEP>, <SEP> C
<tb>
 
 EMI16.7
 9enyoida 4 i 30 '1 4 1 50 "1 60 1 700 80 95 il = *
 EMI16.8
 
<tb> hydrocar-
<tb>
<tb> bures <SEP> C1- <SEP> 0.2 <SEP> 0.2 <SEP> 0.2 <SEP> 0.2 <SEP> 5.7 <SEP> 5.3 <SEP> 3, 4 <SEP> 2.3 <SEP> 2.5 <SEP> 3.3
<tb>
<tb>
<tb> C4
<tb>
<tb>
<tb> hydrocar-
<tb>
<tb> bures <SEP> i- <SEP> - <SEP> - <SEP> - <SEP> - <SEP> 0.1 <SEP> 8.6 <SEP> 6.6 <SEP> 3.7 < SEP> 2.3 <SEP> 4.4
<tb>
<tb>
<tb> C5
<tb>
<tb> 2,2-dim-
<tb>
 
 EMI16.9
 thylbutz- 0.1 0.1 0.1 0.2 0.2 0.4 1.3 1.3 1.2 1.2
 EMI16.10
 
<tb> do
<tb>
<tb>
<tb> 2,3-dim-
<tb>
<tb>
<tb> thylbuta-
<tb>
<tb>
<tb> do
<tb>
 
 EMI16.11
 2-methyl-7.3 7.5 8.4 8.8 9.3 8t6 12o3 17.4 19.6 19.9;

   
 EMI16.12
 
<tb> pentane
<tb>
<tb> 3-methyl- (
<tb>
<tb> pentane <SEP> (<SEP> - <SEP>
<tb>
 
 EMI16.13
 . , hYrocarb4 .92.2 91.2 9p, g 84.7 77, l 76.3 75.2 74.4 71.2
 EMI16.14
 
<tb> res <SEP> n-C6
<tb>
   EXAMPLE 8.



   A solution of 4 kg of aluminum isopropoxide in 20 l of Analar benzene was prepared, and 8 l was added thereto rapidly. deionized water. The mixture was stirred for 30 minutes and the

 <Desc / Clms Page number 17>

 benzene layer was decanted. A further 8 L of deionized water was added and the remaining benzene was decanted after 30 minutes of stirring. The sludge was filtered under vacuum and then transformed back to slurry with 4 L of deionized water. The mixture was stirred for 1 hour and filtered under vacuum a second time to give 8451 g of hydrogel.



   A 3300 gram portion of the hydrogel was mixed with 15 ml of deionized water, and stirred for 2 hours. A solution of 4 g of palladium chloride in 250 ml of 0.5N hydrochloric acid was prepared, and slowly added to the stirred slurry. The slurry was stirred for 1 hour and then 750 ml of deionized water saturated with hydrogen sulfide was added. The mixture was stirred for 30 minutes and then evaporated to dryness in an air oven at 100 ° C., which gave 456.5 g of dried hydrate. The hydrate was ground in a mortar with a pestle, which gave 247.5 g of granular material, between 8 and 16 mesh B.S.S.

   The ground hydrate was calcined at 450 0 for 2 hours, giving a production of 161.9 g of alumina-palladium base. The amounts used were estimated to give a palladium content of 0.7% by weight on the calcined base.



   A charge of 51.6 gr (70 ml) of the base was placed in a glass reactor and heated to 570 F in a stream of 15 liters of dry nitrogen per hour, these conditions being maintained throughout the treatment. . The base was purged at 570 ° F for 2 hours and then 16 grams of dried carbon tetrachloride was added dropwise over a 20 minute period. The catalyst was purged for a further 30 minutes and then discharged, giving a production of 54 g.



   The catalyst was tested under fixed bed downflow conditions. The feedstock used was a dried, desulfurized and dearomatized C6 fraction from a C5 / C6 light refinery gasoline. The processing conditions used were as follows:

 <Desc / Clms Page number 18>

 Temperature 270 F
 EMI18.1
 Pressure 300 * 1.P.P.C- Hydrogen molar ratio /
 EMI18.2
 hydrocarbons 2.5 / 1
Space speed 0.5 vol./vol./Hre.



   The analyzes of the feedstock and of the product, obtained by gas chromatography, are given in the following Table VIII:
TABLE VIII
 EMI18.3
 
<tb> Hours <SEP> under <SEP> treatment <SEP> Food <SEP> 15 <SEP> 54-58
<tb>
 
 EMI18.4
 ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯tation ¯¯¯¯¯
 EMI18.5
 
<tb> Paraffins <SEP> C1-C4 '% <SEP> in <SEP> weight <SEP> - <SEP> 0.5 <SEP> Trace
<tb>
<tb>
<tb> Paraffins <SEP> Ce <SEP>, <SEP>% <SEP> in <SEP> weight <SEP> 3.5 <SEP> 2.0 <SEP> 3.0
<tb>
<tb>
<tb> Paraffins <SEP> C6 '<SEP>% <SEP> in <SEP> weight <SEP> 88.0 <SEP> 90.0 <SEP> 88.0
<tb>
 
 EMI18.6
 lvphthenes, by weight 8.5 7.5 9.0
 EMI18.7
 
<tb> Total, <SEP>% <SEP> in <SEP> weight <SEP> 100.0 <SEP> 100.0 <SEP> 100.0
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Fraction <SEP> C6
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2,2-dimethylbutane,% <SEP> in <SEP> weight <SEP> 1,

  0 <SEP> 28.0 <SEP> 29.5
<tb>
<tb>
<tb>
<tb>
<tb> 2,3-dimethylbutane) '
<tb>
<tb>
<tb> 2-methylpentane <SEP>)% <SEP> in <SEP> weight <SEP> 39.5 <SEP> 41.5 <SEP> 40.5
<tb>
<tb>
<tb> Uyclopentane
<tb>
<tb>
<tb>
<tb>
<tb> 3-methylpentane, <SEP>% <SEP> in <SEP> weight <SEP> 18.5 <SEP> 18.0
<tb>
<tb>
<tb>
<tb>
<tb> n-hexane, <SEP>% <SEP> in <SEP> weight <SEP> 22.0 <SEP> 12.0 <SEP> 12.0
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Total, <SEP>% <SEP> in <SEP> weight <SEP> 100.0 <SEP> 100.0 <SEP> 100.0
<tb>
 
 EMI18.8
 KlliMPL1 !: 9.



   A load of 56 gr (70 ml) of an industrial aluminum compound. platinum lead comprising 0.572 wt% platinum and 0.81 wt% chlorine on alumina, in the form of 1/16 inch extruded rods, was placed in a glass reactor and set up a circulation of dry nitrogen gas of 15 l / hour. The temperature of the catalyst bed was raised to 570 ° F and maintained at that level throughout the process.



   The base was purged with dry nitrogen gas for
 EMI18.9
 2 hours at 570oF, and then 17 g of dried chloroform was added dropwise over a period of 18 minutes. The catalyst was further purged for 1 hour and then discharged, giving a production of 49 g.

 <Desc / Clms Page number 19>

 



   The catalyst was checked under the same conditions and using the same feedstock as in Example 8, with the results given in the following Table IX.



   TABLE IX.
 EMI19.1
 
<tb>



  Hours <SEP> under <SEP> processing <SEP> Power supply - <SEP> 5 <SEP> - <SEP> 8 <SEP> 23 <SEP> - <SEP> 26 <SEP>
<tb>
 
 EMI19.2
 ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ tion ¯¯¯ ¯¯¯¯¯
 EMI19.3
 
<tb> Pumps <SEP> ition
<tb>
<tb> Paraffins <SEP> C1-C4 <SEP>, <SEP>% <SEP> in <SEP> weight- <SEP> Trace <SEP> Trace
<tb>
<tb> Paraffins <SEP> Ce <SEP>, <SEP>% <SEP> in <SEP> weight <SEP> 3.5 <SEP> 2.0 <SEP> 3.0
<tb>
<tb> Paraffins <SEP> U <SEP>, <SEP>% <SEP> in <SEP> weight <SEP> 88.0 <SEP> 89.5 <SEP> 89.5
<tb>
 
 EMI19.4
 Naphtenes,% by weight 8.5 8.5 7.5
 EMI19.5
 
<tb> Total, <SEP>% <SEP> in <SEP> weight <SEP> 100.0 <SEP> 100.0 <SEP> 100.0
<tb>
<tb>
<tb>
<tb>
<tb> Fraction <SEP> C6
<tb>
<tb>
<tb>
<tb>
<tb> 2,2-dimethylbutane, <SEP> in <SEP> weight <SEP> 1.0 <SEP> 24.0 <SEP> 24.0
<tb>
<tb>
<tb>
<tb> 2,3-dimethylbutane <SEP>) '
<tb>
<tb>
<tb> 2-methylpentane <SEP>)

  % <SEP> in <SEP> weight <SEP> 39.5 <SEP> 42.0 <SEP> 42.5
<tb>
 
 EMI19.6
 cyclopentane)
 EMI19.7
 
<tb> 3-methylpentane, <SEP>% <SEP> in <SEP> weight <SEP> 22.0 <SEP> 19.5 <SEP> 19.5
<tb>
<tb> n-hexane <SEP>, <SEP>% <SEP> in <SEP> weight <SEP> 37.5 <SEP> 14.5 <SEP> 14.0
<tb>
<tb>
<tb>
<tb> Total, <SEP>% <SEP> in <SEP> weight <SEP> 100.0 <SEP> 100.0 <SEP> 100.0
<tb>
 
 EMI19.8
 X: PiPi, 10.



   80 ml (65 gr) of an industrial alumina-platinum compound, comprising 0.572% by weight of platinum and 0.81% by weight of chlorine on alpine, was placed in a glass reactor and made there circulate 40 l / hour of dry nitrogen gas for 4 hours. 6 ml were added. of trichlorobromomethane in 13 minutes by letting it fall into the nitrogen circulation. The temperature of the catalyst bed was 512 F. The catalyst was purged with nitrogen for an additional 2 hours and then discharged.



  The catalyst production was 69 g and this catalyst had a chlorine content of 8.6% by weight and a bromine content of 1.35% by weight.



   The catalyst was tested under fixed bed downflow conditions. The feedstock used was a dried, desulfurized and dearomatized C6 fraction from a light C5 / C6 refinery gasoline. The operating conditions used were as follows:

 <Desc / Clms Page number 20>

 
Temperature 270 F
Pressure 250 l.p.p.c.



   Hydrogen / hydrocarbon molar ratio 2.5 / 1
Space speed 2 vol./vol./hre.



   Analyzes of feedstock and product, obtained by gas chromatography, are given in the following Table X.



   PAINTINGS.
 EMI20.1
 



  Hours under treatment Food 3 ¯ 12 18 - 21 ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ 3 - 6 9 - 12 18-21
 EMI20.2
 
<tb> <SEP> recovery from <SEP> liquid <SEP> no
<tb>
<tb> stabilized, <SEP> in <SEP> weight- <SEP> 88.5 <SEP> 93.0 <SEP> 98.5
<tb>
 
 EMI20.3
 hydrocarbons 1-5 by weight 2.5 3.0 3.5 35 2e2-dimethylbutane,% by weight 2 11.0 11.5 9t5
 EMI20.4
 
<tb> naphthenes <SEP> C6 <SEP> '<SEP>% <SEP> in <SEP> weight <SEP> 8 <SEP> 6.5 <SEP> 8.5 <SEP> 7.0
<tb>
   EXAMPLE 11.



   5 g of a platinum-alumina catalyst, containing 0.58% by weight of platinum and 0.01% by weight of chlorine, were purged at 385 C with nitrogen for 30 minutes, before being placed in
 EMI20.5
 reaction at 3.5 l: with dilluorodichloroinethane gas, circulating at 50 ml / minute, for 5 minutes. The resulting compound was then purged for a further 1 hour with dry nitrogen.



   On analysis, 3.2% by weight of fluorine, 6.5% by weight of chlorine and 0.51% by weight of platinum were obtained.



   The catalyst was checked for isomerization activity using the feedstock and processing conditions used in Example 3. Typical sample analysis of the product after 3 hours of processing gave 50%. by weight of C6 isomers present, of which 5% by weight consisted of 2,2-dimethylbutane.



    EXAMPLE 12.



   40 ml (26.5 gr) of an industrial compound of platinum and alumina, containing -0.74% by weight of platinum, 0.35% by weight of fluorine and 0.35% by weight of chlorine, on alumina, were dried for 2 hours at 600 F in a circulation of 40 liters of nitrogen.

 <Desc / Clms Page number 21>

 dry te per hour, then reduced for 2 hours at 600 F in a circulation of 40 liters of dry hydrogen per hour. Then treated with 14.4 ml (23 g) of carbon tetrachloride over a period of 2 1/2 hours in a stream of 40 liters of dry nitrogen per hour at a temperature of 600 F. The catalyst was purged with nitrogen for an additional 2 hours and then discharged.

   The chlorine content of the catalyst was 4.1% by weight.



   The catalyst was checked for isomerization activity using a feedstock similar to that of Example 10, under the following conditions
Temperature 270 F
 EMI21.1
 Pressure 2501.p.p.c.



   Hydrogen / hydrocarbon molar ratio 2.5 / 1
Space speed 1.5 vol./vol./Hre.



   The analyzes of the feedstock and of the product, obtained by gas chromatography, are given in the following Table XI.



   TABLE XI
 EMI21.2
 Hours under food treatment) - 6 12 - 15 24 - 27 ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯tation 12-15 2 / * "27
 EMI21.3
 
<tb> <SEP> recovery from <SEP> liquid <SEP> no
<tb>
<tb>
<tb> stabilized, <SEP> $ <SEP> in <SEP> weight <SEP> - <SEP> 96.8 <SEP> 89.7 <SEP> 86.3
<tb>
<tb>
<tb>
<tb> hydrocarbons <SEP> C1-C5 '<SEP>% <SEP> in <SEP> weight <SEP> 2.5 <SEP> 6 <SEP> 4.5 <SEP> 5
<tb>
<tb>
<tb>
<tb> 2,2-dimethylbutane,% <SEP> in <SEP> weight <SEP> 2 <SEP> 6.5 <SEP> # <SEP> 5
<tb>
 
 EMI21.4
 waphthensa 06 w% wt 8 8.5 9.5 10 EXAMPLE 13.



   6.5 g of aluminum hydrate, prepared by hydrolysis of aluminum isopropoxide, were heated in dry nitrogen circulating at 100 ml / minute for 1 hour at 400 C. The alumina thus produced had a BET surface area of 390 m2 / g and, on analysis, it gave 0.04% by weight of carbon, 0.87% by weight of hydrogen and 0.03% by weight of chlorine.



   This alumina was then reacted with a stream of nitrogen saturated with carbon tetrachloride in vapor, circulating at 100 ml / minute for 30 minutes at 300 0. Chlorinated alumina

 <Desc / Clms Page number 22>

 The resultant had a BET surface area of 310 m2 / g, and on analysis it gave 0.02 wt% carbon, 0.2 wt% hydrogen and 10.30 wt% chlorine.



   The catalyst was checked for isomerization activity using a feed of dry n-hexane (99.9 mole%) under the following conditions.



   Temperature 24 C
Atmospheric pressure
Hydrogen / n-hexane molar ratio 6.2 / 1
Gas space speed 170 vol./vol./Hre.



   An analysis of the product after 1 hour of treatment shows the following composition:
Isobutane% by weight 2.9 Isopentane '"13.0 n-pentane -
2,2-dimethylbutane "6.0
2,3-dimethylbutane)
2-methylpentane) "33.8
 EMI22.1
 3-dimethylpentane) n-hexane "44.3
The activity, however, was not maintained for such a long time as with similar catalysts additionally containing a platinum group metal.



   The following examples show the preparation of inactive catalysts and illustrate the particular nature of the present invention.



     EXAMPLE 14.



   70 ml (54.9 g) of the platinum-alumina compound, used in Example 10, was dried at 570 F for 2 hours in a cir-. circulation of 30 liters of hydrogen per hour. 4 ml were then added. of carbon tetrachloride to the flow of hydrogen over 4 3/4 minutes and the catalyst was purged with continued flow of hydrogen for 2 hours. During the addition of carbon tetrachloride, appreciable amounts of hydrochloric gas were detected in the outgoing gases. The catalyst production was 56.3 gr and the chlorine content was 5.8% by weight.

 <Desc / Clms Page number 23>

 



   The catalyst was checked for isomerization activity using a feed similar to that of Example 10 under the following conditions:
Temperature 270 F
Pressure 250 l.p.p.c.



   Hydrogen / hydrocarbon molar ratio 2.5 / 1
Space speed 1 vol./vol./Hre.



   The production of 2,2-dimethylbutane in the period of 2 to 20 hours of treatment was only 2% by weight, i.e. the same amount as that of the feed, indicating that the catalyst was inactive for low temperature isomerization.



   Similar results were obtained when hydrogen chloride gas was used in nitrogen instead of carbon tetrachloride and hydrogen.



    EXAMPLE 15.



   Example 14 was repeated except that instead of a flow of carbon tetrachloride and hydrogen, chlorine gas was passed over the catalyst at a rate of 3.5 liters per hour for 3 hours. . When checked under the isomerization conditions of Example 14, the catalyst was again inactive.



    EXAMPLE 16.



   5 gram portions of the platinum-alumina compound, used in Example 1, were treated with nitrogen circulating at 100 ml / min and containing a number of chlorine-containing hydrocarbons. The hydrocarbons used and the treatment conditions were as follows: (a) tetrachloroethane 20 minutes at 300 C (b) 1,2-dichloroethane 30 minutes at 350 C (c) tetrachlorethylene 30 minutes at 300 C (d) chloride methyl 30 minutes at 260 C (e) methyl chlorura 30 minutes at 370 ° C.



   Pure methyl chloride gas flowing at 100 ml / minute and not a mixture of nitrogen and chlorinated hydrocarbon was used in (d) and (e).

 <Desc / Clms Page number 24>

 



   All of these catalysts were inactive for the isomerization of n-hexane at temperatures below 400 °, although an analysis of the catalysts produced in (a) and (e) shows that they had a markedly increased content of. chlorine, the catalyst produced in (a) having a chlorine content of 4% by weight and the catalyst produced in (e) having a chlorine content of 5.2% by weight. s
It will be understood that the treatment conditions used for the isomerization in Examples 2, 3, 4, 5, 6, 7, 11 and 13 do not necessarily represent the optimum conditions.

   In some cases, conditions were deliberately chosen to give a rigorous test for catalyst activity rather than for maximum isomerization. Thus, although conversions under conditions encompassing low reaction temperature (20-24 C), short contact time (gas space velocities of 125 to 250 vol / vol / hr) and pressures atmospheres are low, they in fact represent a high catalytic activity because the conditions used were exceptionally specific.



   CLAIMS.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

1. A process for the isomerization of paraffinic hydrocarbons C4 and higher, boiling in the boiling range of gasoline, comprising contacting paraffinic hydrocarbons in the presence of hydrogen at a temperature below 204. C with a catalyst prepared by contacting alumina with a compound of the general formula: EMI24.1 in which X and Y are the same or different and are chosen from H, 01, Br, F or SC1, or in which X and Y together form oxygen or sulfur, under non-reducing conditions and at a temperature such that chlorine is fixed by the alumina without the production of free aluminum chloride. <Desc / Clms Page number 25> 2. The process of claim 1, wherein the catalyst contains a small proportion of a metal or a metal compound having hydrogenating activity and selected from groups Via or VIII of the Periodic Table. 3. A method according to claim 2, wherein the! metal is a metal of the platinum group. 4. A process according to claim 3, wherein the platinum group metal is platinum or palladium. 5. A process according to claim 3 or 4, wherein the amount of metal is 0.01 to 5% by weight, preferably 0.1 to 2% by weight. 6. A process according to any one of claims 1 to 5, wherein the feed contains a major portion of pentanes and / or hexanes. 7. A process according to any one of claims 1 to 6, wherein the isomerization temperature is 50 to 400 F, preferably 150 to 350 F. 8. A process according to any one of claims 1 to 7, wherein the isomerization pressure is from atmospheric pressure to 2000 pounds per square inch, the space velocity is from 0.5 to 10 vol./vol./ Hre. and the hydrogen / hydrocarbon molar ratio is 0.01 to 20/1. 9. A process according to claim 8, wherein the isomerization pressure is 225 to 1000 pounds per square inch, the space velocity is 0.2 to 5 vol./vol./Hre. and the molecular hydrogen / hydrocarbon ratio is 1.5 to 15/1. 10. A process according to any one of claims 1 to 9 wherein the catalyst contains 1 to 15% by weight of chlorine. 11. The process of claim 10, wherein the catalyst contains 2 x 10-4 to 3.5 x 10-4 grams of chlorine per m2 of surface area. 12. A process for the isomerization of paraffinic hydrocarbons <Desc / Clms Page number 26> ques C4 and higher, as described above, in particular in the examples given.