WO1993019845A1

WO1993019845A1 - Catalyst for promoting halogen exchange

Info

Publication number: WO1993019845A1
Application number: PCT/GB1993/000648
Authority: WO
Inventors: James Thomson
Original assignee: British Technology Group Ltd
Priority date: 1992-03-28
Filing date: 1993-03-29
Publication date: 1993-10-14
Also published as: EP0632748A1; JPH08500277A

Abstract

A catalyst for promoting halogen exchange in feedstocks such as 1,1,1-trichloroethane to yield chlorofluorohydrocarbons or chlorofluorocarbons is made by halogenating iron oxide Fe3O4 or other non-stoichiometric oxide with SF4 to produce both Lewis acid and Brønsted acid sites. The feedstock is presented to the catalyst with HF to replace chlorine atoms of the feedstock with fluorine.

Description

CATALYST FOR PROMOTING HALOGEN EXCHANGE

This invention relates to a catalyst for promoting halogen exchange, its preparation and its use for halogen exchange and saturation reactions in halocarbons and halohydrocarbons.

Chlorofluorocarbons (CFCs) are widely used in industry as refrigerants, solvents, blowing agents and aerosol propel lants.

However, CFCs have been implicated in the depletion of ozone; it is believed that the CFCs, in themselves inert, diffuse up through the troposphere and concentrate in the upper atmospheric layer or stratosphere, until they are decomposed by ultraviolet radiation with the production of chlorine radicals which consequently initiate catalytic ozone destruction. Hence, there is a need to replace the most environmentally damaging of these compounds, and their use is regulated by the Montreal Protocol. Candidate replacement molecules should ideally contain no chlorine or bromine in their structure. The hydrofluoroalkane molecules CH₃CF₃ (143a), CH₂FCF₃ (134a) and CH₂F₂ (032) are considered as suitable replacement molecules as are to a lesser extent CH₃CF₂Cl (142b) and CH₃CFCl₂ (141b). It is known from US Patent 4873381 to make the hydrofluoroalkane

CH₂F·CF₃ HFA-134a by hydrogenating 1,1-dichlorotetrafluoroethane CCl₂F·CF₃ (114a) at 300°C on 2% palladium supported on fluorinated alumina. The CFC precursor molecules such as CCI₂F·CF₃ (114a) are produced by fluorination of chlorocarbons or chlorohydrocarbons with anhydrous hydrogen fluoride at 350°-450°C in the vapour phase using a fluorinated chromia catalyst. The use of aluminium trifluoride as catalyst is proposed in European Patent Application 0353059A for the fluorination of chloroalkenes such as CCl₂=CH₂ to CCI₂F·CH₃ at up to 120°C. A catalyst produced from fluorinated aluminium oxide to be used for low temperature halogen exchange reactions is suggested in European Patent Application 0439338A but its use is limited to halohydrocarbon substrate molecules, and does not report the bulk production of CFCs using the catalyst under mild conditions. Further, the use of chromia as a catalyst to produce CFCs, as suggested by Blanchard et al. in Applied Catalysis, 59, (1990), 123-128, and in US Patent 4843181, gives a poor yield in some cases and is undesirable since chromium (VI) environments are now thought to be carcinogenic.

It would be desirable to be able to produce CFCs or chlorofluorohydrocarbons (HCFCs) from halocarbon, e.g. chlorocarbon or halohydrocarbon, e.g. chlorohydrocarbon feedstock (i.e. even CFCs from chlorohydrocarbons) in one step under mild conditions

(up to 250°C, or even at room temperature) using an acceptable economic environmentally compatible catalyst.

An aspect of this invention is a method of producing

chlorofluorohydrocarbons, fluorohydrocarbons and/or

halofluorohydrocarbons comprising treating a halohydrocarbon containing a halogen atom (which may or may not be fluorine) with hydrogen fluoride in the present of the catalyst of the invention.

Thus, according to the invention, a catalyst for promoting halogen exchange in halo- or halohydro- carbons or silanes or carbosilanes or silyl-containing compounds, comprises a

non-stoichiometric metal oxide wherein the metal is one or more which can have more than one oxidation state and more than one oxidation state is represented in the oxide in the unit cell, and wherein the oxide is surface-modified to a halohydroxyoxy material which has both Lewis acid characteristics and Brønsted acid characteristics. Preferably the metal oxide has a spinel-related structure (e.g. spinel, defect spinel, inverse spinel), and the metal may be one (or more) of gallium, iron, indium, cobalt, rhodium, ruthenium, thallium, molybdenum and tungsten, most preferably iron and/or cobalt.

Thallium oxide is less preferable since thallium is poisonous. The oxides may be used individually, or two or more oxides may be used in conjunction in the catalyst.

Also according to the invention, a method of making a catalyst as set forth above comprises in an inert environment calcining an oxide of a metal or metals which can have more than one oxidation state and more than one oxidation state is represented in the unit cell of the oxide, and then treating the calcined oxide with a halogenating agent containing at least two atoms of halogen, chosen such that the oxygenated product is volatile at the treatment temperature and does not form an oxygenated deposit at the catalyst surface, thus e.g. SF₄, CHCl₃, CCl_4-nF_n (CCl₄ CCl₃F, CCl₂F₂, CF₃CI, CF₄) or C₂Cl_6-nF_n (such as CCI₃CF₃ or CCl₂F-CClF₂), CCl₂=CCl₂ or CF₂=CCl₂, preferably undertaken at from 0°C to 550°C, for long enough to treat the whole surface.

The calcining is preferably performed at from 110°C to 700°C, e.g. 200°C to 300°C, for preferably 2 to 12 hours, in vacuo or under flowing nitrogen. Both Lewis acid sites and Brβtøsted acid sites must be present on the surface of the halogen-treated catalyst, and neither should outnumber the other by more than 20:1, preferably not even by 5:1 or even 2:1. A ratio of 1:1 is ideal but 40 Lewis:60 Brόnsted gives good results.

Higher calcining temperatures tend to increase the ratio of Lewis acid sites to Brønsted acid sites. Where a halogen atom from the halogenating agent co-ordinates to an oxide metal atom which following the calcining is co-ordinatively unsaturated, it forms a Lewis acid site; where a halogen atom from the halogenating agent co-ordinates to an oxide metal atom which despite the calcining remains co-ordinatively saturated, it forms a Brβinsted acid. At reasonable halogenation temperatures, the halogenation is

self-limiting, giving complete surface coverage of all surface metal atoms without attacking the bulk oxide.

The invention thus also provides a method of synthesising a halocarbon or halohydrocarbon (even a halocarbon from a

halohydrocarbon) or silane- or carbosilane- or silyl-containing analogue, preferably at from 20°C to 250°C, comprising contacting a feedstock hydrocarbon or silyl-containing organic which is partly or wholly substituted with halogens which must include a halogen atom other than X, with a catalyst as set forth above in the presence of a source (inorganic or organic) of X, such as HX, where X is the halogen with which it is desired to saturate, or to replace some or all of the halogens in, the feedstock, X preferably being fluorine. Note that even a partly halogenated feedstock can yield a fully halogenated product.

Synthesis is possible at from 0°C or above 20°C, but at above 250°C, CFCs might start to react with the oxide, destroying the catalyst. The synthesis may be in a nitrogen or evacuated environment.

Embodiments of the invention will now be described by way of illustration in the following examples.

Example 1

This example (a summary of several different samples)

describes the preparation of a catalyst using CCl₄, CF₄, CCIF₃ or SF₄ as the halogenating agent.

Numbers of samples of magnetite (Fe₃O₄, 0.5g ), cobalt (II, III) oxide (Cθ3θ₄, 0.5 g), gallia (GaOGa₂O, 0.5 g) and indium oxide (In2θ3, 0.5 g) respectively were thermally preconditioned by calcining at 523K in vacuo. Representatives of all four types of calcined sample were then reacted at room temperature with 4 mmol SF₄ for 6 hours, for testing on all experimental feedstocks.

Further samples of calcined magnetite and cobalt oxide were reacted for 6 hours at 773K with CF₄ and CClF₃ halogenating agents (4 mmol in each case), for testing on 1,1,1-trichloroethane feedstock, which behaved comparably with the other feedstocks. During the

halogenation process, hydrolysis of the halogenating agent occurred to give RO₂, ROX₂ and HX (R = C or S; X = F or Cl) as volatile products. Finally, each of the thermally preconditioned and halogenated oxides were degassed by pumping for 1 hour.

In other samples, 4 mmol CCl₄ was used at 523K, as described later.

Examples 2 to 5 demonstrate the relative reactivities of various feedstocks being dehydrochlorinated on magnetite catalyst. Exchanging chlorine for fluorine while simultaneously exchanging hydrogen for fluorine is a valuable property.

Example 2

Magnetite (0.5 g) was thermally conditioned and fluorinated using SF₄ or CF₄ in a dry Pyrex vacuum vessel as described in Example 1 to give a fluorine content of 3.4 mmol (g catalyst)^-1. After degassing, dry 1,1,1-trichloroethane (4 mmol) was condensed onto the fluorinated iron oxide at 77K. The vessel was allowed to warm up to room temperature and allowed to react for 2 hours. The volatile materials from the reaction were condensed into a Pyrex vaccuum vessel (containing 0.1 g of dry sodium fluoride and 0.75 ml of deuterochloroform CDCl₃) and fitted with an n.m.r. tube and left to stand at room temperature for 1 hour. The volatile materials were then condensed into the n.m.r. tube which was sealed under vacuum. The product distribution of the volatile material was analysed using ¹H and ¹⁹F n.m.r. of the liquid phase. The analyses showed the presence of 1 ,1-dichloro-1-fluoroethane CH₃CCl₂F

(HCFC-141b) 21 mol%, 1-chloro-1,1-difluoroethane CH₃CCF₂ (HCFC-142b) 3 mol%, 1,1,1-trifluoroethane CH₃CF₃ 1 mol%, 1,1,1-trichloroethane CH₃CCI₃ 1.7 mol%, 1,1-dichloroethene 6.6 mol%, 1,1-difluoroethene (CH₂CF₂) 2 mon, 1,2,2-trichloroethene (CHClCCl₂) 1.2 mol%.

The catalyst could be replenished in fluorine with HF, and in a continuous mode of operation N₂ flowing at 30 ml/min through a liquid trap containing 1,1,1-trichloroethane at room temperature is blended with one-third the letter's stoichiometric quantity of HF, and passed over the catalyst, on which the halogen exchange reaction would be continued at room temperature.

Example 3

This (and also Examples 6, 13, 23, 31 and 38) demonstrate saturation.

Magnetite was prepared as described in Example 2. Dry

1,1-dichloroethene was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected from the sample and analysed as described in Example 2. The analysis showed the presence of chlorotrifluoromethane (CFC-13) 2 mol%, 1,1-dichloro-1-fluoroethane (HCFC-141b) 8 mol%,

1-chloro-1,1-difluoroethane (HCFC-142b) 10 mol%,

1,2-dichloro-2,2-difluoroethane (HCFC-132b) 3 mol%,

1,1,2-trichlorotrifluoroethane (CFC-113) 1 mol%. Example 4

Magnetite was prepared as described in Example 2. Dry asym-tetrachloroethane (CH₂ClCCl₃) was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected from the sample and analysed as described in Example 2. The analysis showed the presence of

1,2,2-trichloro-2-fluoroethane (HCFC-131b) 7 mol%,

chlorotrifluoromethane (CFC-13) 2 mol%,

1,2-dichloro-trifluoroethane (HCFC-132b) 1 mol%.

Example 5

Magnetite was prepared as described in Example 2. Dry sym-tetrachloroethane (CHCl₂CHCl₂) was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected from the sample and analysed as described in Example 2. The analysis showed the presence of

1,2,2-trichlorofluoroethane (HCFC-131b), 2 mol%,

1,1,2-trichlorotrifluoroethane (CFC-113) 2 molSJ,

1,1,1-trichloroethane (CFC-113a) 1 mol%.

Example 6

Example 6 demonstrates saturation of a double bond with halogen and illustrates chlorine/fluorine exchange. Magnetite was prepared as described in Example 2. Dry tetrachloroethene

(CCl₂CCl₂) was reacted with the fluorinated surface as described in

Example 2. Volatile material from the reaction was collected from the sample and analysed as described in Example 2. The analysis showed the presence of 1,1,2-trichloro-1-fluoroethane (131b) 2 mol%,

1,2-dichloro-2,2-difluoroethane (HCFC-132) 2 mol%,

1,1-dichloro-2,2,2-trifluoroethane (HCFC-123a) trace,

1-chloro-1,2,2-trifluoroethane (HCFC-133) 3 mol%,

chlorotrifluoromethane 9 mol%, pentafluoroethane (HFA-125) 2 mol%, tetrafluoromethane (HFA-14) trace. Exampl e 7

This Example demonstrates Cl/F exchange and dehydrohalogenation. Magnetite was prepared as described in Example 2. Dry dichloromethane (CH₂Cl₂) was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected from the sample and analysed as described in Example 2. The analysis showed the presence of

chlorotrifluoromethane (CFC-13) 4 mol%,

1,1,2-trichloro-2-fluoroethane (HCFC-131b) 3 mol%,

1,2,2-trichloro-1,2-difluoroethane (HCFC-122) 2 mol%,

dichloro-difluoro-methane (HCFC-12) trace.

Example 8

This Example demonstrates Cl/F exchange, fluorination and dehydrohalogenation. Magnetite was prepared as described in

Example 2. Dry chloroform (CHCl₃) was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected from the sample and analysed as described in Example 2. The analysis showed the presence of chlorotrifluoromethane (CFC-13) 3 mol%, trifluoromethane (HFA-23) 4 mol%,

1-chloro-1-fluoroethene 9 mol%.

Example 9

This Example demonstrates isomerisation, which is important as process byproducts would be recycled. Magnetite was prepared as described in Example 2. Dry 1,1,2-trichlorotrifluoroethane

(CCl₂FCClF₂) was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected from the sample and analysed as described in Example 2.

The analysis showed the presence of chlorotrifluoromethane

(CFC-13) 2 mol%, 1,1,1-trichlorotrifluoroethane (CFC-113a) 2 mol%. Example 10

Magnetite was prepared as described in Example 2. Dry

1,1,1-trichlorotrifluoroethane (CCI₃CF₃) was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected and analysed as described in

Example 2. The analysis showed the presence of chlorotrifluoromethane (CFC-13) 4 mol%,

1,1,2-trichlorotrifluoroethane (CFC-113a) 3 mol%,

1,1,-dichlorotetrafluoroethane (CFC-114a) trace, and acetone.

Example 11

This Example demonstrates halogen exchange on completely chlorinated material. Magnetite was prepared as described in Example 2. Dry carbon tetrachloride (CCl₄) was reacted with the fluorinated surface as described in Example 2. Volatile material from the reaction was collected and analysed as described in Example 2. The analysis showed the presence of

trichlorofluoromethane (CFC-11) 5 mo1%, dichlorodifluoromethane (CFC-72) 4 molS», chlorotrifluoromethane and tetrafluoromethane in trace amounts.

Examples 12-21

Cobalt (II, III) oxide was fluorinated as described for magnetite in Example 2. The fluorinated material was reacted with the following range of chlorocarbons and chlorohydrocarbons. The treatment and handling of the reagents are as described in

Examples 2-11.

Example 12

1,1,1-Trichloroethane

Product Distribution:

chlorotrifluoromethane (CFC-13) 1 mol%

1,1-dichloro-1-fluoroethane (HCFC-141b) 10 "

1,1-dichloroethene 6 "

Example 13

1 ,1 -Dichloroethene

Product Distribution :

chlorotrifluoromethane (CFC-13) 0.5 mol %

1 ,1-dichloro-1-fluoroethane (HCFC-141 b) 10

1 -chloro-1 ,1 ,-difl uoroethane (HCFC-141 ) 5

1 ,1-2-trichlorotrifluoroethane (CFC-113) 1

1 ,1 ',1 -trichlorotrifluoroethane (CFC-113a) 2 Example 14

Asym-tetrachloroethane

Product Distribution:

chlorotrifluoromethane (CFC-13) 2 mol% 1,2,2-trichloro-2-fluoroethane (HCFC-131b) 3 " 1,2-dichloro-2,2-difluoroethane (HCFC-132b) 1 "

Example 15

Sym-tetrachloroethane

Product Distribution:

chlorotrifluoromethane (CFC-13) 3 mol%

1,2,2-trichloro-2-fluoroethane (HCFC-131b) 2 "

1,1,2-trichlorotrifluoroethane (HCFC-113) 2 " Example 16

Tetrachloroethene

Product Distribution:

chlorotrifluoromethane (CFC-13) 3 mol%

1,1-dichlorotetrafluoroethane (CFC-114) 2 "

Example 17

Carbon Tetrachloride

Product Distribution:

Trichlorof luoromethane (CFC-11) 3 mol% chlorotrifluoromethane (CFC-13) 2 "

1,1,2-trichlorotrif luoroethane (CFC-113) 2 "

1, 1,1-trichlorotrif luoroethane (CFC-113a) 5 "

Example 18

1,1-Dichloromethane

Product Distribution:

chlorotrifluoromethane (CFC-13) 4 mol%

1,1,1-trichlorotrifluoroethane (CFC-113a) 1 "

1,2,2-trichloro-2-fluoroethane (HCFC-131b) 1.5 " Example 19

Chloroform

Product Distribution:

chlorotrifluoromethane (CFC-13) 5 mol%

1 ,1 , 2-trichlorotrifluoroethane (CFC-113) 5 "

1 ,1 ,1-trichlorotrifluoroethane (CFC-113a) 6 "

1 ,1 ,dichlorotetrafluoroethane (CFC-114) 2 "

Example 20

1 ,1 ,2-Trichlorotrifluoroethane

Product Distribution:

chlorotrϊfluoroethane 1 mol%

1 ,1 ,1-trichlorotrifluoroethane (CFC-113a) 5 "

hexaf luoroethane (CFC-116) 1 "

Example 21

1,1,1-Trichlorotrifluoroethane

Product Distribution:

chlorotrifluoromethane (CFC-13) 2 mol%

1,1,2-trichlorotrιfluoroethane (CFC-113) 4 "

hexafluoroethane (CFC-116) 1 "

Examples 22-31

Gallium oxide (Ga₂O₃, 0.5 g) was calcined at 523K for 6 hours in vacuo. The calcined material was fluorinated at ambient temperatures using SF₄ (4 mmol) as described in Example 1. After degassing, the sample was reacted with the following range of chlorohydrocarbons and chlorocarbons after which the volatile material from the reaction was analysed using ¹H and ¹⁹F n.m.r. as described in Example 2. It should be noted that in the case where the substrate reagent was a chlorohydrocarbon, a deep purple colouration of the catalyst was observed over -he first 15 minutes of reaction. Example 22

1,1,1-Trichloroethane

Product Distribution:

1,1-dichloro-1-fluoroethane (CH₃CCl₂F,HCFC-141b) 12 mol% 1-chloro-1,1-difluoroethane (CH₃CClF₂,HCFC-I42b)) 3 " 1,1,1-trifluoroethane (CH₃CF₃,HFA-143a) 2 "

1,1-dichloroethene (CH₂CCl₂) 5 "

1,1,1-trichloroethane (CH₃CCl₃) 72.9 " 1-chloro-1,1,1-trifluoromethane (CFC-13) 5.1 " acetone trace

Example 23

1,1,Dichloroethene

Product Distribution:

1,1-dichloro-1-fluoroethane (HCFC-141b) 11.56 mol%

1-chloro-1,1-difluoroethane (HCFC-142a) 2.0 " 1-chloro-1,1,1-trifluoromethane (CFC-13) 5.1 "

1,1 -dichloroethene 81.0 " Example 24

Dichloromethylene

Product Distribution:

1,1-dichloro-1-fluoroethane (HCFC-141b) 9 mol%

1-chloro-1,1-difluoroethane (HCFC-142b) 15 " 1,2-dichloro-2,2-difluoroethane (HCFC-132b) 11 "

1,1,2-trichloro-trifluoroethane (CFC-113) 3 "

1,1,1-trichloroethane trace dichloromethane 61 asym-tetrachloroethane trace

Example 25

Asym-tetrachloroethane

Product Distribution:

1,1,1-triehlorotrifluoroethane (CFC-113a) 15 mol% 1,2,2-trichloro-2-fluoroethane (HCFC-131b) 1 " asym-tetrachloroethane 83 " Example 26

Sym-tetrachloroethane

1,2,2-trichloro-2-fluoroethane (HCFC-131b) trace

Example 27

1,1,2-trichlorotrifluoroethane (CFC-113)

Product Distribution:

1,1,1-trichlorotrifluoroethane (CFC-113a) 6.7 mol%

1-chlorotrifluoromethane (CFC-13) 6.0 " unreacted 113 77.0 "

Example 28

1,1.1-trichlorotrifluoroethane (CFC-113a)

Product Distribution:

1,1,2-trichlorotrifluoroethane (CFC-113) 1 mol% hexafluoroethane (CFC-116) 1 " trifluoroethane trace asym-tetrachloroethane 1 " unreacted 113a 96 "

Example 29

Carbon Tetrachloride

Product Distribution:

1,1,1-trichlorofluoromethane (CFC-11) 14 mol% 1,1,-dichlorodifluoromethane (CFC-12) 2 mol%

1-chlorotrifluoromethane (CFC-13) 2 "

Example 30

Chloroform

Product Distribution:

Chlorotrifluoromethane (CFC-13) 2 mol%

1,1-dichloro-2,2-difluoroethane (HCFC-132b) 4 "

1-chloro-2,2,2-trifluoroethane (HCFC-133a) 2.5 "

1,2,2,2-tetrafluoroethane (HFA-134a) 4 " Example 31

Tetrachloroethene

Product Distribution:

Chlorotrifluoromethane (CFC-13) 3 mol%

1,2,2-trichloro-2-fluoroethane (HCFC-131) 5 "

1,2,-dichloro-2,2-difluoroethane (HCFC-132b) 2 "

1,1,2-trichlorotrifluoroethane (CFC-113) 1 "

1,1,1,-trichlorotrifluoroethane (CFC-113a) 2 " Examples 32-39

Indium oxide (In₂O₃, 0.5 g) was pretreated and reacted with the following substrate molecules as otherwise described for

Examples 22-31. It should be noted that when a chlorohydrocarbon substrate molecule was used, a slight discolouration of the initially light yellow indium oxide surface to a light orange colour was observed.

Example 32

1,1,1-Trichloroethane

Product Distribution:

1,1-dichloro-1-fluoroethane (HCFC-141b) 12 mol%

1-chloro-1,1-difluoroethane (HCFC-142b) 2 "

1,1,1-trifluoroethane (HCFC-143a) 2 "

1,1-dichloroethene 4 "

1-chloro-1-fluoroethene trace

1,1,1-trichloroethane 78 "

Example 33

Chloroform

Product Distribution:

chlorotrifluoromethane (CFC-13) 9 mol%

1,1-difluoroethene (CH₂CF₂) 3 "

dichloromethane 3 "

unreacted chloroform 84 "

acetone 1 " Example 34

Dichloroethane

Product Distribution :

1 ,1 ,2-trichlorotrifluoroethane (CFC-113) trace

Example 35

1 ,1 ,2-trιchlorotrifluoroethane (CFC-113)

Product Distribution:

1 ,1 ,1-trichlorotrifl uoroethane (CFC-113a) 4 mol% hexafluoroethane (CFC-116) 0.5 " chlorotrifluoromethane (CFC-13) trace

1 ,1 ,1-trichloroethane 1 " acetone 3 " chloral trace

Example 36

Carbon Tetrachloride

Product Distribution:

trichlorofluoromethane (CFC 11) 0.5 mol% 1,1,2-trichlorotrifluoroethane (CFC-113) 5 "

1,1,1-trichlorotrifluoroethane (CFC-113a) 6 "

Example 37

1,1,1-trichlorotrifluoroethane

Product Distribution:

1,1,2-trichlorotrifluoroethane (CFC-113) 3 mol% hexafluoroethane (CFC-116) trace

Example 38

Tetrachloroethene

chlorotrifluoromethane (CFC 13) 1 mol% 1,1,2-trichloro-2-fluoroethane (HCFC-131) 3 " 1,1,2-trichlorotrifluoroethane (CFC-113) 3 " 1,1,1-trichlorotrifluoroethane (CFC-113a) 5 " Example 39

Asym-tetrachloroethane

1 ,1 ,2-trichlorotrifl uoroethane (CFC-113) 2 mol%

1 , 1 , 1 -tri chlorotri f l uoroethane ( CFC-113a) 5 "

Exampl e 40

Magnetite (Fe₃O₄, 0.5 g) was calcined at 343K in vacuo and coated with gallium chloride (0.2 g) by treating gallia with CCl₄ at

523K as described in Example 1. The vapour of GaCl₃ was allowed to condense on the dried magnetite and the system heated to 343K in vacuo. to give a coating of gallium chloride on magnetite. The gallium chloride coated magnetite was then reacted with SF₄ (4 mmol) at ambient temperature followed by degassing the sample by pumping at room temperature. 1,1,1-trichloroethane (3 mmol) was condensed onto the treated oxides and allowed to react at room temperature and collected as described in Example 2. The product distribution from the volatile materials showed the presence of

1,1-dichloro-1-fluoroethane (HCFC-141b) 12 mol%,

1-chloro-1,1-difluoroethane (HCFC-142b) 5mol%,

1,1,1-trifluoroethane (HFA-143a) 5 mol%,

chlorotrifluoromethane (CFC-13) 2 mol%,

1,1,2-trichlorotrifluoroethane (CFC-113) 3 mol%.

Example 41

Gallium oxide catalyst.

Gallium oxide (0.5 g) was transferred to a dry Pyrex vacuum vessel fitted with a PTFE stopper and calcined in vacuo at 523K for 8 hours. Carbon tetrachloride (0.2 ml) was degassed and stored under darkness over 3A molecular sieves in a dry Pyrex vacuum vessel, prior to being transferred at 77K in vacuo onto the calcined gallium oxide sample. The system was reacted at 423K for 6 hours and the volatile materials from the reaction were analysed using a Perkin-Elmer 1750 FTIR spectrometer fitted with a data station. The infrared spectrum of the volatile materials from the reaction showed the ,presence of hydrogen chloride, carbon dioxide, phosgene, and unreacted carbon tetrachloride. The chlorine treated gallium oxide material was degassed by pumping at room temperature for 2 hours. Meanwhile a quantity of 1 ,1,1-trichloroethane was transferred to a dry Pyrex vacuum vessel, degassed and stored in the dark over activated 3A molecular sieves. An aliquot of the

1,1,1-trichloroethane (0.2 ml) was condensed at 77K onto the chlorine-treated gallium oxide sample and left to warm up to room temperature. The chlorinated gallium oxide material turned

immediately deep purple in colour. The 1 ,1,1-trichloroethane was allowed to react with the chlorine treated gallium oxide for a further 30 minutes. The volatile material from the reaction was analysed by infrared, and showed the presence of 1 ,1-dichloroethene, hydrogen chloride, carbon tetrachloride and trace quantities of 1,1,1-trichlorethane. The sample was degassed by pumping at room temperature. The treated solid retained the deep purple

colouration. The organic layer was not weakly bound to the chlorine treated gallium oxide surface.

Example 42

Chlorine promoted magnetite (Fe₃O₄)

Magnetite (0.5 g) was transferred to a dry Pyrex vacuum vessel as described in Example 41. The iron oxide material was calcined at 523K for 8 hours. Carbon tetrachloride (0.2 ml) was transferred in vacuo to the vacuum vessel as described for the gallium oxide system in Example 41. The CCl₄ was reacted with the calcined magnetite material at 523K for 6 hours. The volatile materials from the reaction were analysed using infrared (Perkin-Elmer 1750 FTIR, fitted with data station), and showed the presence of hydrogen chloride, phosgene, carbon dioxide and unreacted carbon

tetrachloride. The chlorine-treated magnetite was degassed by pumping at room temperature for 1 hour prior to reaction with

1 ,1,1-trichloroethane (0.2 ml) as described for the gallium oxide system. The volatile materials from the reaction were analysed using infrared and showed the presence of 1,1-dichloroethene, hydrogen chloride, and carbon tetrachloride. Owing to the intrinsic blaςk colour of the magnetite material, the colour of the organic layer was not apparent. The ready ability of the chlorine-treated magnetite to dehydrochlorinate 1,1,1-trichloroethane was evidence of the generation of strong Lewis acid sites at the chlorinated iron oxide surface.

Example 43

Indium oxide catalyst.

Indium oxide (0.5 g) was transferred to a dry Pyrex vacuum vessel fitted with a PTFE stopper and calcined in. vacuo at 523K for 8 hours. Sulphur tetrafluoride (7 mmol, Air Products) was transferred at 77K in vacuo onto the calcined indium oxide sample. The system was allowed to react for 2 hours and the volatile materials from the reaction were analysed using a Perkin-Elmer 1750 FTIR spectrometer fitted with a data-station. The spectrum of the volatile materials from the reaction showed the presence of sulphur dioxide, thionyl fluoride, silicon tetrafluoride (generated from the reaction of hydrogen fluoride with the Pyrex vessel), and unreacted sulphur tetrafluoride.

The fluorine treated indium oxide was degassed by pumping for 2 hours. A quantity of 1,1,1-trichloroethane was transferred to a dry Pyrex vacuum vessel, degassed and stored in the dark over activated 3A molecular sieves. An aliquot of the

1,1,1-trichlorethane (7 mmol) was condensed at 77K onto the

fluorine-treated indium oxide sample and left to warm up to room temperature. The fluorinated indium oxide material immediately turned light orange in colour. The 1,1,1-trichoroethane was allowed to react with the fluorine treated indium oxide for a further 1 hour. The volatile material from the reaction was transferred in vacuo to a dry vacuum vessel, containing activated sodium fluoride and deuterochloroform (0.75 ml) and fitted with a side-arm and n.m.r. tube. The volatile material was analysed using ¹⁹F and ¹H liquid phase n.m.r. The n.m.r. spectra confirmed the presence of

1,1-dichloro-1-fluoroethane, 1-chloro-1,1-d,fluoroethane,

1,1,1-trifluoroethane, 1,1-dichloroethene and unreacted

1,1,1-trichloroethane. Example 44

Cobalt oxide (Co(II)Co(III)O₃)

Cobalt oxide (0.5 g) was transferred to a dry vacuum vessel as described in Example 41. The cobalt oxide material was calcined at 523K for 8 hours. Carbon tetrachloride (7 mmol) was transferred in vacuo to the vacuum vessel as described for the gallium oxide system in Example 41. The CCl₄ was reacted with the calcined cobalt oxide material at 523K for 6 hours. The volatile materials from the reaction were analysed using infrared (Perkin-Elmer 1750 FTIR, fitted with data-station), and showed the presence of hydrogen chloride, phosgene, carbon dioxide and unreacted carbon

tetrachloride. The chlorine-treated cobalt oxide was degassed by pumping at room temperature for 2 hours prior to being reacted with 1,1,1-trichloroethane as dsecribed for the gallium oxide system in Example 41. The volatile materials were analysed using infrared and showed the presence of 1,1-dichloroethene, hydrogen chloride and carbon tetrachloride. Owing to the intrinsic black colour of the cobalt oxide material no colour change in the solid was observed. The ready ability of the chlorine-treated cobalt oxide to

dehydrochlorinate 1,1,1-trichloroethane was evidence of the generation of strong Lewis acid sites at the chlorinated cobalt oxide surface.

Claims

1. A catalyst for promoting halogen exchange in halo- or halohydro- carbons, -carbosilanes, or -silanes or silyl-containing compounds, comprising a non-stoichiometric metal oxide wherein the metal is one or more which can have more than one oxidation state and more than one oxidation state is represented in the oxide in the unit cell, and wherein the oxide is surface-modified to a

halohydroxyoxy material which has both Lewis acid characteristics and Brønsted acid characteristics.

2. A catalyst according to Claim 1, wherein the oxide has a spinel-related structure.

3. A catalyst according to Claim 1 or 2, wherein the metal is one or more of gallium, iron, indium, cobalt, rhodium, ruthenium, thallium, molybdenum and tungsten.

4. A catalyst according to Claim 3, wherein the oxide is of iron and/or cobalt.

5. A catalyst according to any preceding claim, wherein the surface carries Lewis acid sites and Brønsted acid sites, neither of which outnumbers the other by more than 20:1.

6. A method of making a catalyst according to any preceding claim, comprising in an inert environment calcining an oxide of a metal or metals which can have more than one oxidation state and more than one oxidation state is represented in the unit cell of the oxide, and then treating the calcined oxide with a halogenating agent whose molecule contains at least two atoms of halogen, chosen such that the oxygenated product is volatile at the treatment temperature and does not form an oxygenated deposit at the catalyst surface.

7. A method according to Claim 6, wherein the calcining is performed at from 110°C to 700°C.

8. A method according to Claim 6 or 7, wherein the calcining is performed for 2 to 12 hours.

9. A method according to Claim 6, 7 or 8, wherein the treatment with halogenating agent is performed at from 0°C to 550°C.

10. A method according to any of Claims 6 to 9, wherein the halogenating agent is SF₄, CHCl₃, CCl_4-nF_n (CCl₄ CCI₃F, CCl₂F₂, CF₃CI, CF₄) or C₂Cl_6-nF_n (such as CCI₃CF₃ or CCl₂F-CClF₂), CCl₂=CCl₂ or CF₂-CCl₂.

11. A method of synthesising a halocarbon or halohydrocarbon or its silane or carbosilane or silyl-containing analogue, comprising contacting a feedstock hydrocarbon (silane) which is partly or wholly substituted with halogens, with a catalyst according to any of Claims 1 to 5 or made by a method according to any of Claims 6 to 10, in the presence of a source of X where X is the halogen wi th which it is desired to saturate, or to replace some or all of the halogens in, the feedstock..

12. A method according to Claim 11, wherein X is fluorine.

13. A method according to Claim 11 or 12, when performed at from 0°C or 20°C to 250°C.

14. A halocarbon or halohydrocarbon or silane analogue synthesised by a method according to Claim 11, 12 or 13.