Process for the preparation of perfluoropolyethers acyl-fluoride ended by reduction of the corresponding peroxidic perfluoropolyethers

A process for the preparation of perfluoropolyethers having at least one —COF end group of formula:

• T-CFX′—O—Rf—CFX—COF (I)
• wherein:
• T is equal to COF, F, C1-C3 perfluoroalkyl;
• X, X′, equal to or different from each other, are F or —CF3;
• Rf is selected from:
• —(C2F4O)m(CF2CF(CF3)O)n(CF2O)p(CF(CF3)O)q—
• wherein:
• the sum n+m+p+q ranges from 2 to 200,
• the (p+q)/(m+n+p+q) ratio is lower than or equal to 10:100, preferably comprised between 0.5:100 and 4:100,
• the n/m ratio ranges from 0.2 to 6, preferably from 0.5 to 3;
• m, n, p, q, are equal to or different from each other and when m, n range from 1 to 100, preferably from 1 to 80, then p, q range from 0 to 80, preferably from 0 to 50;
• the units with n, m, p, q indexes being statistically distributed along the chain,
• —(CF2CF2CF2O)r—
• wherein r ranges from 2 to 200,
• —(CF(CF3)CF2O)s—
• wherein s ranges from 2 to 200,
• by reduction of the corresponding perfluoropolyethers containing peroxidic bonds, using gaseous hydrogen in the presence of a catalyst comprising metals of the VIII group supported on metal fluorides, optionally in the presence of perfluorinated solvents inert at a temperature from 20° C. to 140° C., preferably from 80° C. to 130° C. and at a pressure between 1 and 50 atm, preferably between 1 and 10 atm.