Supported catalyst for the oxidation of acrolein into acrylic acid

A catalyst active in the oxidation of acrolein into acrylic acid, which comprises a silica or alumina support and from 15 to 80% by weight, with respect to the catalyst, of a catalytically active part having the following chemical composition

• Mo.sub.a V.sub.b W.sub.c Cu.sub.d X.sub.x O.sub.y
• wherein X is Cr, Mn, Fe, Co, Ni, Zn, Cd, Al or Sb and wherein for a=12, b ranges from 4 to 8, c ranges from 1 to 4, d ranges from 2 to 5, x ranges from 0 to 1 and y ranges from about 17 to about 72;
• said active part having an amorphous and bidimensional structure with an interplanar distance of 3.98 A, as measured by X rays;
• and an IR spectrum with a somewhat broad band at 860 cm.sup.-1 attributable to the tetrahedral coordination of the oxygen atoms with respect to the metal atoms;
• and said catalyst being obtained by impregnating the support with an aqueous solution of decomposable salts of the metals of said active part, drying the thus impregnated support and activating at high temperature the support thus dried, the activation stage being carried out firstly in an oxidizing atmosphere and then in an inert atmosphere, the cycle of impregnation, drying and activation being then repeated at least one time and the activation of the last cycle being followed by a thermal treatment in an oxidizing atmosphere.