Patent ID: 7157406

Claim:
A process for the preparation of zirconium dioxide catalyst or carrier consisting essentially of at least 85% by weight of the monoclinic modification of said zirconium dioxide and not more than 15% by weight of its tetragonal modification, which comprises: preparing a concentrated aqueous acidic solution of a zirconium salt selected from the group consisting of zirconium chloride and zirconium nitrate; adding this initially prepared solution gradually to a basic water/ammonia mixture at a temperature of about 20 to 60° C. such that the pH value is slowly reduced from its initial upper limit of 14 until the addition is completed at a final pH value of from 8 down to not less than 6, the precipitate being recovered essentially free of ammonium salts, and subsequently drying and calcining the recovered precipitate at temperatures of from 300 to 600° C. and at pressures of from 0.5 to 5 bar.