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Paramétrages

Paramétrages

1. WO1986004049 - PROCEDE DE PREPARATION DE FLUORURES ULTRAPURS DE METAUX LOURDS

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique
CLAIMS

What is Claimed is:

1. A process for the preparation of an ultrapure heavy metal fluoride whose heavy metal component
behaves as a pseudo-noble metal of improved purity
from its heavy metal oxide comprising the steps of:
a) reacting the oxide of said heavy metal with a predetermined amount of aqueous hydrofluoric acid to form a solid reaction product;
b) drying said solid reaction product under controlled heating to form a hydrated fluoride of said chosen heavy metal having a predetermined amount of hydration; and
c) exposing said hydrated heavy metal fluoride to a reactive atmosphere comprising hydrofluoric acid vapor in a carbon dioxide reactive carrier gas, and a selected halide compound in the gas phase at a predetermined elevated temperature for a predetermined period of time to thereby further increase anion purity.

2. The process set forth in Claim 1 wherein said selected halide compound in the gas phase is chosen from the group consisting of carbon tetrachloride, chlorofluoromethane derivatives or other higher halo-carbon derivatives.

3. The process of Claim 1 wherein exposing said hydrated heavy metal fluoride to a reactive atmosphere further comprises:
a) exposing said hydrated heavy metal fluoride to a reactive atmosphere of hydrofluoric acid vapor in a carbon dioxide reactive carrier gas while simultaneously raising the temperature of said reaction mixture to a maximum of approximately 900°C; and b) at approximately 900°C, cooling the
reaction mixture whereupon carbon tetrachloride gas is introduced into the reaction mixture while still gradually reducing the temperature of the reaction mixture.

4. The process of Claim 1 wherein exposing said hydrated heavy metal fluoride to a reactive atmosphere further comprises:
a) exposing said hydrated heavy metal fluoride to a reactive atmosphere of hydrofluoric acid vapor in a reactive carbon dioxide carrier gas while simultaneously raising the temperature of said reaction mixture up to approximately 900°C; and
b) at approximately 900°C cooling the reaction mixture whereupon a chlorofluoromethane derivative gas or other higher halo-carbon derivative gas is introduced into said reaction mixture while still gradually reducing the temperature of said reaction mixture.

5. The process of Claims 1, 2, 3 or 4 wherein the heavy metal is lead.

6. The process of Claim 4 wherein the chloro-fluoromethane derivative is dichlorodifluoromethane .

7. The process of Claim 4 wherein the chloro-fluoromethane derivative is trichlorofluoromethane.

8. The product produced by the process of Claims

1, 3 or 4.

9. A process for the preparation of ultrapure lead fluoride of improved purity from lead oxide
comprising the steps of:
a) reacting lead oxide with approximately two times the theoretical stoichiometric amount of
aqueous hydrofluoric acid to form a solid reaction
product ;
b) drying said solid reaction product under controlled heating to form hydrated lead fluoride,
PbF2-xH20 with x < 1;
c) exposing the hydrated lead fluoride to a reactive atmosphere of 10-30 volume percent of hydrofluoric acid vapor at a flow rate of lcc/sec in a carbon dioxide reactive carrier gas while simultaneously raising the temperature of the reaction mixture to a maximum of
approximately 900°C;
d) at approximately 900°C, cooling the
reaction mixture and thereafter introducing 10-30 volume percent of carbon tetrachloride gas at a flow rate of lcc/sec into said reaction mixture; and
e) further cooling the reaction mixture to completion to thereby produce a lead fluoride product of improved anion purity.