WO1980002023A1

WO1980002023A1 - Catalytic processes and catalysts

Info

Publication number: WO1980002023A1
Application number: PCT/GB1980/000051
Authority: WO
Inventors: R Dale; J Rooney
Original assignee: Gallaher Ltd; R Dale; J Rooney
Priority date: 1979-03-28
Filing date: 1980-03-21
Publication date: 1980-10-02
Also published as: EP0025787A1

Abstract

Catalysts comprising a support and copper are used for the catalytic oxidation or oxydehydrochlorination of aliphatic hydrocarbons. The oxydehydrochlorination may be conducted at temperatures of 150 to 350 C and the oxidation at temperatures of 30 to 150 C. The catalysts may comprise a support, copper chemically bonded to the support and a minor amount of a redox couple, such as divalent palladium, for the copper or they may be stable redox catalysts which comprise a support carrying divalent copper and in which the exposed surfaces of the catalyst comprise monovalent copper. The catalysts themselves are new materials.

Description

_ CATALYTIC PROCESSES AND CATALYSTS It. is well known to subject aliphatic hydrocarbons to catalytic oxidation and oxydehydrochlorination processes by passing a gas stream comprising the hydrocarbon over a catalyst. When the intended process is oxidation the gas stream comprises, as its active constituents, the hydrocarbon^'an oxygen. When the intended process is oxydehydrochlorination the gas stream comprises, as its active ingredients, the hydro¬ carbon, oxygen and hydrogen chloride. The oxygen conveniently is introduced in the form of air, so that the gas stream will contain nitrogen, and it may also contain other gaseous materials that do not interfere with the reaction. Although many such processes, and catalysts for use in them, have been proposed they all tend to-suffer from the disadvantage that conversion tends to be rather low or non-specific or that, in order to obtain adequate conversion, temperatures have to be used that are higher than would be desirable.

For instance although it has been proposed to catalytically oxidise ethylene at temperatures as low as 100°C the conversion is low and a mixture of products is obtained and if the temperature is increased degradation products are formed such that it is unsatisfactory or difficult to recycle the unconverted feed stock. Particular difficulties arise in the oxydehydro- chlorination of hydrocarbons since although there is a great commercial need to be able to oxychlorinate, for instance,

^■ j EJCζ/- ethylene (e.g. to produce vinyl chloride) none of the proposed processes are satisfactory on a commercial scale.

It has therefore been our object to devise an improved oxidation or, in particular, oxydehydro¬ chlorination process.

According to the invention a catalytic process for the oxidation or oxydehydrochlorination of an aliphatic hydrocarbon comprises passing a gas stream comprising the hydrocarbon, oxygen and, optionally, hydrogen chloride over a catalyst that is selected from (a) catalysts that comprise a_ support, copper chemically bonded to the support, and a minor amount of a redox couple for the support and (b) catalysts that are stable redox catalysts and which comprise a support carrying divalent copper and in which the exposed surfaces of the catalyst comprises monovalent . copper.

Preferred processes according to the invention are oxydehydrochlorination processes and in particular by the invention it is possible to produce vinyl chloride.

In oxydehydrochlorination processes, the hydro¬ carbon can be an unsaturated hydrocarbon, for instance ethylene, but preferably it is a saturated hydrocarbon. The hydrocarbon preferably contains at least two carbon atoms and the process is of most value applied to hydrocarbons containing up to six carbon atoms. Preferred hydrocarbons are propane, butane, (preferably straight chain) and, especially, ethane. Numerous attempts have been made to subject ethane and other saturated hydrocarbons to catalytic oxydehydrochlorination processes but these processes have generally involved very high temperatures, low conversions and large amounts of unwanted by-products. In the invention we surprisingly find that it is possible to carry out the oxydehydrochlorination process with satisfactory conversions at lower temperatures than normal, for instance temperatures below 350°C and

O preferably below 300°C, often 200-300 C, and in particular that this process results in.little or no formation of unwanted by-products. Any by-products such as benze^'ne that are formed can easily be separated by routine methods. Since by-product formation is very low high overall yields of chlorinated product can be obtained by recycling any unreacted hydrocarbon in the product gas stream.

The oxydehydrochlorination is best conducted by forming a gaseous mixture of the hydrocarbon, hydrogen chloride and air (or pure oxygen or other oxygen providing gas) and passing this gas stream through a reaction tube containing the selected catalyst.

The gas mixture is conveniently generated by passing a mixture of the hydrocarbons and air or other oxygen providing gas through concentrated aqueous hydrochloric acid and thereby entraining hydrogen chloride in the gas stream.

The degree of oxydehydrochlorination, and in particular the degree of chlorine substitution, can be varied from onochloro substitution to replacement with chlorine of all the hydrogen atoms in the resultant unsaturated molecule by appropriate selection of reaction conditions. The relative proportions of hydrocarbon, oxygen and hydrogen chloride may be varied to optimise the yield of a chosen product. Also the catalyst may significantly affect the degree of oxydehydrochlorina¬ tion at any particular temperature. For instance at a given temperature and with a given gas mixture a catalyst having a support of small pore size may give more- chlorination than a similar catalyst formed on a support having a larger pore size. For instance catalysts on a support having an average pore size below 50 Angstroms, and preferably below 30 Angstroms (for instance 4 to 16 Angstroms, e.g. Zeolite 13X) are preferred when high chlorine substitution is-desired and catalysts on a s.upport having an average pore size above 50 Angstroms and preferably above 100 Angstroms (for instance conventional activated alumina or α-alumina) are preferred when low substitution is desired, e.g. for the formation of vinylchloride from ethylene.

When the starting hydrocarbon is ethane the product may be any of vinylchloride, 1,1-dichloroethylene, cis- or trans-l,2-dichloroethylene, trichloroethylene or tetrachloroethylene. The products can be subjected to subsequent reactions in conventional manner. For instance the higher chlorinated products, such as dichloro- ethylene can be converted to vinylchloride in known manner.

In oxidation processes according to the invention the hydrocarbon should be unsaturated, preferably at a terminal position, and generally contains from 2 to 6 carbon atoms, usually 2 to 4 carbon atoms and is preferably ethylene.

In the invention we surprisingly found that good conversion and high specificity (a high yield of a single chosen product) ^~is^™obtained^~aT^~temperatures much lower than those customarily used in catalytic oxidation processes (e.g. 250°C or more) and that incur the consequential disadvantages of the formation of tars and other undesired by-products. In the invention satisfactory yields are obtained at temperatures much lower than would be expected to be possible, for instance as low as 40°C or even 30°C or ambient. Higher temperatures, up to 100°C or more, generally give better yields without increased by-product formation, but at temperatures of 150°C there is increased tendency for oxidation <to carbon dioxide. The temperature range is therefore generally between 40 and 150°C, preferably 70 to 130°C and most preferably about 100 C. If the reaction conditions are such that the reaction becomes exothermic then cooling or other steps are taken so as to maintain the temperature within the preferred range.

Reaction- of ethylene with air in accordance with the invention can easily be conducted to give high yields of acetaldehyde with substantially nc formation of tars or other inconvenient by-products. Since the reaction product is free of such by-products any ethylene that remains unconverted in the process can easily be recycled for subsequent reaction. Higher terminally unsaturated hydrocarbons generally form the corresponding methyl ketones.

The support for catalysts for use in the oxidation processes preferably has a small average pore size, e.g below 50 Angstroms and preferably below 50 Angstroms, supports having a pore size of 4 to 16 Angstroms (e.g. Zeolite 13X) being preferred. All processes of the invention are preferably conducted by passing the chosen gas stream over the catalyst contained in a tube maintained at substantially atmospheric pressure, although higher or lower pressures may be used if desired. The^*catalyst may be in any form that ensures good contact between the gas stream and the catalyst and may be in traditional catalyst shape but is preferably in granular or powder' form, most preferably in the form of particles below 1 mm in size, often below 10 mesh in size.

In one aspect of the invention the catalysts used in the process comprise a support, copper chemically bonded to the support and a minor amount of a redox couple for the support. A substantial part at least of the copper should be chemically bonded to the support as opposed to being merely adsorbed onto the support as an adsorbed copper salt, e.g. copper chloride. The support should therefore contain sites at which bonding of-copper can occur. The bonding generally is mainly electrovalent. The support can be formed initially with ionically bonded copper in it, for instance by precipitation of aluminium hydroxide gel from an alkaline liquor containing a copper salt followed by drying the gel, but generally the copper is ionically bonded into the support as a result of ion exchange. Accordingly the support should be one that is capable of undergoing

-^J EA^- O ion exchange. Supports such as activated carbon or normal silica can be used but are less satisfactory than supports containing a greater number of ion exchange sites. The support is preferably alumina .. or an alumino silicate, for instance a zeolite.

Simply. saturating the support with an aqueous copper salt solution followed by evaporation to dryness in the normal manner usually does not result in optimum ion exchange of copper into the support since the 0 amount of ion exchange copper will be low, the support may include substantial amounts of copper compound that is not chemically bonded to the support and the support may also carry the ions that the copper should have replaced. Preferably the support is impregnated 5 with a solution of a copper salt, ion exchange is permitted to occur, excess solution is removed and the impregnation is then repeated at least once and usually more, e.g. 3 to 6 times. Finally the catalyst is washed and dried. The copper salt solution should not 0 be too concentrated as otherwise the activity may be impaired, the concentration generally being below 50 grams per litre, preferably 20 to 40 grams per litre. The solvent is generally water. Since the anion of the copper salt is removed together with the cation that ^**-^* is being replaced and the excess solution the particular

OMPI salt is not critical, but the nitrate or chloride is generally preferred.

By this, technique, it is ensured that most, and often all, the copper is chemically bonded to the support and even though, as mentioned below, cupric chloride can subsequently be added by a conventional impregnation and dehydration technique the amount is always relatively low compared to the amount of copper that is bonded to the support. At least 501 by weight of the copper on the support, usually at least 70% and preferably at least 90%, is bonded to the support.

The activity of the final catalyst may be inferior if the amount of ionically bonded copper is low,, and in particular if it is significantly below the maximum amount that can be ion exchanged into the support. Preferably the support is chemically substantially saturated with such copper, for instance containing at least 501 and preferably at least 75% of the maximum amount that can be ionically exchanged into the support. Before conducting the ion exchange with the copper solution, the support may have its balancing cations exchanged with lithium or other ions.

Any compound capable of serving as a redox couple with copper may be used. It may consist of a single compound or of a mixture of compounds in which event it is sometimes convenient to look upon one compound of the mixture as the redox couple and another compound of the mixture as a promoter for the redox couple. The redox couple is generally an inorganic compound and this compound and any promoter for it are generally in the form of an acetate or, preferably, a chloride. Suitable promoters include stannic and calcium compourlds but lithium compounds are preferred. Cupric compounds may also be used aspromoter. It is possible that the promotion effect (i.e. improvement in activity) is caused partly and perhaps mainly by the anion, which is preferably chloride, that is introduced with the cation.

Q..-IPI Suitable inorganic compounds as redox couples are noble metal compounds including iridiu , ruthenium or rhodium compounds, generally the trichloride, or palladium compounds. Preferred redox couples include divalent palladium, i.e. Pd 2+. Preferably it is a chloride, generally being introduced onto the support as PdClJ^".

The inclusion of compounds of cerium and/or manganese in the catalyst is often beneficial. The deposition of the redox couple or promoter is best effected by impregnating the support with a solution of the redox couple or promoter and evaporating to dryness. The redox couple and promoter can be impregnated in succession in either order but preferably the redox couple and any promoter^" that is to be introduced are impregnated together from a solution containing both and the support is then evaporated 'to . dryness. This method results in anions in the solution remaining in the support. The solution may be in any suitable solvent, preferably substantially non-aqueous. Methanol and dichloromethane are particularly suitable and may be used as a mixture.

The concentration of the redox couple in the solution is generally below 2% , for instance 0.001 to 1% preferably 0.005 to 0.1% by weight measured as metal, e.g. palladium. The concentration of promoter, measured as metal, in this solution or any other impregnation solution used is generally within the same range.

The catalysts generally comprise from 1 to 10% of chemically bonded copper and a much smaller amount, generally less than 20% by weight based on the weight of copper, of the redox couple, the amount of redox couple being measured as metal when the couple is an inorganic compound. For instance the amount of palladium or other metallic component of redox couple may be from 0.1 or 1% up to 20%, preferably 5. to 20%, based on the weight of copper. Preferred catalysts comprise 2 to 7%, most preferably 3 to 6%, by weight chemically bonded copper and 0.05 to 2%, preferably 0.1 to 0.5% by weight metal of palladium compound or other redox couple. When promoters are included,- the amount is generally from 0.5 to 2.5 parts by.weight of the redox couple, all amounts being measured as metal. Preferably the amount of promoter is about 1 part by weight or sometimes up to 2 parts by weight when the promoter is monovalent, for instance lithium, with double these amounts for higher valent promoters such as calcium.

A preferred way of making the catalysts comprise impregnating zeolite with an aqueous copper salt solution, permitting ion exchange to occur, removing the excess solution and repeating the impregnation at least twice, preferably then washing and drying the support, impregnating the support with a solution providing 0.1 to 0.5%, measured^' as^' metal and based on

2- the weight of catalyst, PdCl. and a substantially equal amount lithium chloride or up to twice the amount of calcium chloride or stannic chloride, and evaporating the catalyst to dryness.

The catalyst is preferably used without any of the chemical after treatments normally used in the prior art, e.g high temperature reduction. However we have found that the activity of the catalyst can often be increased by subsequently heating it under moderate conditions, namely 100 to 200 C preferably for half to 4 hours. Lower temperatures do not seem to increase activity and higher temperatures tend to damage the catalyst. The temperature is preferably at least 120°C and preferably the heating is conducted for from 1 to 3 hours at about 150 C.

Particular improvement may be obtained if the catalyst is contacted with water vapour for at least 15 Or 30 seconds at the specified temperature at the end of the heating. The contact with water _%yapour is generally for at least 5 minutes, usually at least 10 minutes but it is generally unnecessary for the contact to be longer than 20 minutes.

A convenient way of carrying out the activation is to conduct most of the heating under vacuum in a closed vessel and then to introduce sufficient water vapour to raise the pressure to atmospheric and complete the heating in this atmosphere.

Instead of activating by heating in the presence of steam activation may also be achieved by exposing the catalyst resulting from substantially dry heating to atmospheric moisture for 1 to 2 days or activation may be completed during use of the catalyst. For instance it may be heated immediately prior to use. The catalyst generally has a blue colour. The contact with moisture may reduce the colour intensity of the catalyst and as soon as this has been observed the contact with water vapour can be terminated. The amount of water vapour absorbed for optimum activation is generally at least 10 mg per gram catalyst. Preferably the amount is at least 25 mg, most preferably 50 to 100 mg, per gram catalyst. Amounts above 200 mg per gram are usually unnecessary.

It is well known that some redox catalysts containing copper will contain copper mainly in the diyalent state but that some of the copper will pass through a transient monovalent stage during the catalytic process. However in a second aspect of the invention we have found that good results are obtained when the catalysts are ones that are stable redox catalysts and comprise a support carrying divalent copper and in which the exposed surfaces of the catalysts comprise monovalent copper. Thus instead of merely permitting monovalent copper to be formed as a transient intermediate "during use, improved results are obtained if a stable redox catalyst is formed which is a product comprising a support carrying divalent copper, the exposed surface of the deposit comprising substantially monovalent copper. By saying that the catalyst is stable we mean that it is preformed, before use in the desired catalytic process,

OMPI and is capable of being stored for significant periods of time, for instance many hours or days or weeks, before use, for instance in a impermeable packet.

The substantially monovalent copper on the surface is in intimate contact with divalent copper, which forms a substrate for the substantially monovalent copper. Preferably substantially all the copper on the surface is in substantially monovalent form since although some divalent copper can be tolerated it tends to reduce the activity of the catalyst. The amount of monovalent copper should be low, compared to the amount of divalent copper, and may be provided by, for instance, a mono- molecular layer. The amount should not be more than the amount required to form a layer a few molecules thick on the divalent copper.

The presence of bivalent copper in the catalyst can be observed by electron spin resonance measurements .(ESR) . The valency state of the copper in the surfaces can be determined by electron spectroscopy chemical analysis (ESCA) . By referring to the surface comprising substantially monovalent copper we mean that the copper is in a valency state lower than divalent copper but substantially above zerovalent, as determined by ESCA, and preferably has an electron binding energy substantially equivalent to that of monovalent copper although it may have a valency state slightly higher, for instance about

1.2. Preferably the surface, as determined by ESCA is substantially free of divalent copper. The analysis may be by, for example, a Vacuum Generators E.S.C.A. 3 Spectrometer in which the base pressure of the analyser

_g chamber is 1 x 10 Torr and of the sample chamber is

_7 1 x 10 Torr. Observation of the Cu2p doublet shows the binding energy for Cu2p3/2. Divalent copper (CuO) has a binding energy of about 933.6 eV. In the catalysts used in the invention the bindin energy is preferably between 932.2 and 933.4, most preferably

932.5 to 933.3.

The copper containing deposit in the catalyst may be physically adsorbed onto the support but is preferably bonded to the support e.g. as described above.. Preferably the catalyst includes also a redox couple for copper, this redox couple generally being present as a minor amount compared to the amount of copper. Preferably therefore the catalyst which has substantially mono¬ valent copper on its exposed surfaces is a catalyst made from the materials and by the methods described in detail above. The activation by heating, especially in the presence of moisture vapour, appears to result in the formation of substantially monovalent copper. Broadly the monovalent copper catalysts are best made by heating a catalyst comprising a support carrying a deposit comprising divalent copper under conditions such as to convert the exposed surface of the deposit to monovalent copper compound, preferably while leaving the underlying copper in the divalent state.

To promote the formation of substantially monovalent copper the catalyst may be reduced during or after its formation. For instance a reducing agent such as stannous tin, cerium as Ce 3+ or thallium Tl1+ may be deposited before the redox couple. The amount of reducing agent is generally very small, e.g. 0.01 to

10%, usually 0.5 to 2% measured as metal by weight of copper. It may be ion exchanged onto the support with the copper or after the copper or may be deposited onto the copper by evaporation of a solution containing the reducing agent, generally before depositing the redox couple and any promoter for the redox couple. Instead of or in addition to producing monovalent copper by activation, e.g. with steam as described above, and/or by including an inorganic reducing agent, the divalent copper can be reduced by a gaseous reducing agent, for instance carbon monoxide. This is generally affected before the deposition of any redox couple and promoter.

The catalysts described above in both aspects of the invention are themselves novel materials. They are

OM useful not only for the processes described but also for other processes, such as pollution control, for instance in an automobile exhaust, production of hydrogen by the water gas reaction and carbon monoxide oxidation. They are particularly satisfactory in the low temperature catalytic oxidation of carbon monoxide to carbon dioxide with the result that they are of value incorporation in smoking products or filters for smoking products. Thus they may be used as the catalytic component of the smoking products or filters as described in British Patent Specification No. 2,014,376.

In the following Examples, Examples 1 to 7 illustrate the novel catalysts and their production while the remaining examples illustrate processes according to the invention. Example 1

Zeolite 13X was immersed in" an aqueous solution of ^•30 g/1 cupric nitrate, left to soak in that solution to permit ion exchange to occur and was then separated from the remaining solution. The separated product was then immersed in fresh solution and the whole process".repeated until it has been given three immersions. Analysis showed at that time that the catalyst contained from 3 to 6% copper based on the dry weight. The product was then washed with water and dried. It was then immersed in sufficient of a solution of Na-PdCl. in equal parts methanol and methylene dichloride to provide 0.5% Pd, measured as metal, in the catalyst, and the product dried at room temperature. A typical solution contains 7.5 mg Pd, as Na₂PdCl₄, in 100 ml solvent. Different samples of this catalyst were then heated in air for two hours at various temperatures between 25 C and 300°C. As a guide to the activity of these catalysts a standard activity test was used in this and the following examples and consisted of passing a gas stream containing carbon monoxide and oxygen over the .catalyst at ambient temperature and observing the degree of conversion of carbon monoxide to

-^JREX^ OMPI carbon dioxide. It was found that the greatest activity was obtained with catalysts in which the heating had been conducted at temperatures of between 100 and 200 C with best results being obtained when the heating was at 150°C. Example 2

The process of Example 1 was repeated using various palladium concentrations and with the incorporation of various promoters in the palladium solution and the 0 catalyst content of palladium and promoters was as follows

CATALYST

A 13X/Cu/0.25% Pd as Pd ClJ^"

B It tt 1! 1! ft tl tl + 0. 25% Li as LiCl

C tt t t tt I t tt It t l. + 0 . 5% Sn^{4 +} as SnCl₄ ^" D It I t t t It t t tt I t ^• + 0. 5 % Cu^{2 +} as CuCl₂ E 13X/Cu/0. 1% Pd as PdCl^^" F tt II It It t l tt + 0. 25% Li ⁺ as LiCl

6 tl I I II It II tt + 0. 5 % Sn^{4 +} as SnCI₄

H " " 0.25% Pd " + 0. 5% Ca as CaCl₂

When the activity was determined as in Example 1 catalysts B,C,D,F,G and H had higher and longer lasting activity than catalysts A and E, catalysts B, D and H 5 being particularly satisfactory. The processes necessary for the manufacture of catalysts B and H were repeated but with varying amounts of lithium and calcium and it was found that the values of lithium and calcium quoted in catalysts B and H were optimum. Example 3

The process of Example 1 was repeated and samples of the resultant catalyst were subjected to different treatments after the heating and the activity determined as in Example ^"1. It was found that activity increased 5 upon storage in a stoppered bottle but increased more if it was exposed to the atmosphere for 24 hours after • the heating., The best increase in activity was caused by including steam in the atmosphere towards the end of the heating. Example 4 Zeolite molecular sieve, type 13X, was ion exchanged in triplicate with 3% aqueous cupric nitrate, washed with distilled water and dried in air at about 35 C. A solution containing Na₂PdCl, and Li Cl in 50/50 methanol/meth lene chloride (or methanol alone) was applied and allowed to evaporate leaving a free flowing powder having Pd and Li loadings of between 0.1% and 0.-51.

The catalyst was activated by first heating in a bottle for 1\ hours at 150 C after which time a small sample tube is introduced and the bottle sealed with a rubber septum. Water at the rate of from 50 to 100 mg/g of catalyst was added through the septum via a syringe into the empty tube, where it evaporated. The contents were maintained at 150°C for a further 15 minutes. The resultant catalyst had good activity when determined as in Example 1.

Better results could be obtained when the activation was conducted by heating the catalyst in a closed tube while applying vacuum to about 1 millimetre mercury for the desired period and then introducing water into the vessel, while under vacuum, and then heating the water, the temperature and the amount of water being such that the pressure in the vessel is substantially 1 atmosphere, due substantially entirely to the water vapour in the vessel.

Electron spin resonance examination of the catalyst before the heating steps showed that the catalyst contained divalent copper and ESCA determination, at this stage showed that there was substantially no monovalent copper present on the surface. ESCA determination of the catalyst that had been activated by heating and steaming at 150 C showed that the surface consisted substantially only of substantially monovalent

O PI_ copper, the recorded binding energy for Cu2P3/3 being 933.25. ESCA showed no significant trace of divalent copper, but ESR showed the presence of divalent copper. Example 5 The process of Example 1 was repeated but modified by contacting the ion exchanged zeolite with a solution containing stannous chloride before contact with the palladium solution. The stannous chloride solution was evaporated to dryness. The amount of stannous chloride was about 1% based on the amount of copper in the support. Similar results could be

3+ 1+ obtained using solutions of Ce or Tl instead of stannous chloride. Example 6 The process of Example 1 was repeated but with some modifications. Cupri.c chloride was used instead of cupric nitrate. The process was repeated until the support had been given five immersions and analysis then showed that the catalyst contained from 5 to 6% copper based on the dry weight. The methanol/methylene dichloride solution contained, in addition to the palladium compound, stannic chloride in an amount sufficient to provide 0.5% measured as Sn. The product was dried at room temperature and then heated at 150 C for two hours while exposed to the ambient atmosphere. Example 7

The process of Example 2 is repeated, to form catalysts 7A to 7H, but using α-alumina (having a pore size well in excess of 100 Angstroms) instead of Zeolite 13X. Example 8

A gas mixture was formed of one part by volume ethylene and three parts by volume air and passed through a tube containing catalyst A of Example 2 in particulate form having a mesh size of 30 to 60 mesh. The tube and the catalyst was held at a temperature ill the range 70 to 100°C, generally around 100°C. The resultant gas mixture contained acetaldehyde in high yield, and was substantially free of tarry residue and other by-products . Although the conversion of ethylene was high a little remained unreacted and could easily be recycled.

_* Results as good as or better than this are obtainable when catalyst A is replaced by any of the other catalysts identified in Examples 1 to 6, while the catalysts of Example 7, having a larger pore size, gave less satisfactory yields . When propylene is subjected to the same reaction acetone is. formed in good yield and butylene-1 ^• forms methyl propyl ketone .

Example 9

A mixture of equal amounts by volume of air and ethane was bubbled through concentrated aqueous hydrochloric acid to produce a gas mixture of air, ethane and hydrogen chloride.

This gas mixture was passed through a reaction tube containing catalyst A of Example 2 in the form of particles having a mesh size of 30 to 60 mesh, the tube and the catalyst being maintained at a temperature of about 280°C.

A very high yield of higher chlorinated products

(mainly tetrachloroethylene but with some trichloroethy- lene) was obtained, together with ^• smaller amounts of lower chlorinated products such as vinylchloride and dichloroethylene and a very little benzene.

Results as good as this, and often better, are obtainable when catalyst A is replaced with any of the other catalysts identified in Examples 1 to 6.

Example 10

The process of Example 9 was repeated using catalyst A of Example 7 instead of catalyst A of Example

2. The product was mainly vinylchloride, but contained also small amounts of di-, tri- and tetra-chloroethylenes.

Good conversion was obtained in a single pass, but by recycling the unreacted ethylene very high overall • yields of vinylchloride can be obtained.

Claims

1. A catalytic process for the oxidation or oxydehydrochlorination of an aliphatic hydrocarbon comprisin passing a gas stream comprising the hydrocarbon, oxygen and optionally hydrogen chloride over a catalyst characterised in that the catalyst is selected from (a) catalysts that comprise a support, copper chemically bonded to the support and a minor amount of a redox couple for the support and (b) catalysts that are stable redox catalysts and which comprise a support carrying divalent copper and in which the exposed surfaces of the catalyst comprise monovalent copper.

2. A process according to claim 1 in which the catalyst comprises a support, copper chemically bonded to the support and a minor amount of a redox couple for the support.

3. A process according to claim 2 in which substantial all the copper is chemically bonded to the support and the support is substantially saturated chemically with the copper.

4. A process according to claim 2 in which the redox couple comprises divalent palladium.

5. A process according to claim 2 in which the catalyst comprises 1 to 10% copper and less than 20%, based on the weight of copper, of redox couple.

6. A process according to claim 2 in which the catalys comprises 2 to 7% by weight copper and 0.05.to 2% redox couple and in which the support is a zeolite.

7. A process according to claim 2 including stannic, lithium or calcium ions as promoter.

8. A process according to claim 7 in which the weight of promoter, measured as metal, is 0.5 to 2.5 times the weight of redox couple, measured as metal.

9. A process according to claim 7 in which the

2- redox couple is provided as PdCl. and any promoter is introduced as chloride.

10. A process according to claim 2^".in which the catalyst is formed by impregnating the support with a solution of a cupric salt, permitting ion exchange to occur, removing excess solution and repeating the impregnation at least once, and then depositing the redox couple by impregnating the resultant support with a solution providing the redox couple and evaporating the solution to dryness, and the catalyst is then activated by heating at 100 to 200°C for half to 4 hours.

11. A process according to claim 10 in which the

. activation of the catalyst has been improved by contacting the catalyst with water vapour at the end of the heating.

12. A process according to claim 2 in which the

^• copper is mainly divalent but the exposed surfaces of the catalyst comprise monovalent copper.

13. An oxydehydrochlorination catalytic process according to claim 1 in which the hydrocarbon is a saturated aliphatic hydrocarbon containing 2 to 6 carbon atoms and the active constituents of the gas stream are hydrocarbon, oxygen and hydrogen chloride.

14. A process according to claim 13 conducted at a temperature of 150 to 350°C.

15. A process according to claim 13 conducted at a temperature of 200 to 300°C.

16. A process according to claim 13 in which the support has a pore size above 100 Angstroms.

17. A process according to claim 13 in which the hydrocarbon is ethane.

18. A catalytic oxidation process according to claim 1 in which the hydrocarbon is a terminally unsaturated aliphatic hydrocarbon containing 2 to 6 carbon atoms and the active constituents of the gas stream are the hydrocarbon and oxygen.

19. A process according to claim 18 conducted at a temperature of 30 to 150°C.

20. A process according to claim 18 conducted at a temperature of 40 to 100°C.

21. A process according to claim 18 in which the suppo has a pore size below 50 Angstroms.

22. A process according to claim 18 in which the hydrocarbon is ethylene.

23. A novel catalyst comprising a support, copper chemically,bonded to the supprt and a minor amount of redox couple for the copper.

24. A novel catalyst that is a stable redox catalyst and which comprises a support carrying divalent copper and in which the exposed surfaces of the catalyst comprise monovalent copper.

-^JRE

_. OMPI