Chromia based fluorination catalyst
A chromia-based fluorination catalyst comprising at least one additional metal selected from zinc, nickel, aluminum and magnesium in which from 0.1 to 8.0% by weight of the catalyst is in the form of one or more crystalline compounds of chromium and/or one or more crystalline compounds of the at least one additional metal. The catalyst can be used in processes for producing a fluorinated hydrocarbon.
1. A chromia-based fluorination catalyst consisting of:
amorphous chromia;
zinc oxide in a total amount of zinc of from 0.5 to 25% by weight of the catalyst; and
crystalline chromium oxide in a total amount of from 0.1 to 2.5% by weight of the catalyst;
which catalyst is supported or unsupported.
2. A catalyst according to claim 1 having a surface area of at least 50 m2/g.
3. A catalyst according to claim 2 having a surface area of from 70 to 250 m2/g.
4. A catalyst according to claim 1 having a sulphate content of less than 10% w/w.
5. A method for producing a catalyst as defined in claim 1 , which method comprises heat treating an amorphous catalyst precursor at a temperature of from 300 to 600° C. for a period of from 1 to 12 hours in an atmosphere of nitrogen or an atmosphere having an oxygen level of from 0.1 to 10% v/v in nitrogen.
6. A method for prefluorinating a catalyst according to claim 1 , which method comprises heat treating the catalyst at a temperature of from 250 to 500° C. for a period of from 1 to 16 hours at atmospheric or superatmospheric pressure in the presence of hydrogen fluoride.
7. A process for producing a fluorinated hydrocarbon, which process comprises reacting a halogenated hydrocarbon with hydrogen fluoride in the presence of a catalyst as defined in claim 1 .
8. A process for producing a fluorinated hydrocarbon, which process comprises reacting a halogenated hydrocarbon with hydrogen fluoride in the presence of a catalyst produced according to the method of claim 6 .
9. A process according to claim 7 that is carried out at elevated temperature in the vapour phase.
10. A process according to claim 7 for the production of 1,1,1,2-tetrafluoroethane or penta-fluoroethane.