Method for in situ high activity odh catalyst

A process for preparing a catalyst comprising mixed oxides of MoVNbTe comprising the following steps:

• i) forming an aqueous solution of ammonium heptamolybdate (tetrahydrate) and telluric acid in a molar ratio of Mo:Te 1:0.14 to 1:0.20, at a temperature from 30° C. to 85° C. and adjusting the pH of the solution to 6.5 to 8.5, with a nitrogen-containing base to form soluble salts of the metals;
• ii) stirring the pH adjusted solution for a time of not less than 15 minutes;
• iii) adjusting the pH of the resulting solution to from 4.5 to 5.5, with an acid, and stirring the resulting solution at a temperature of 75° C. to 85° C. until it is homogeneous;
• iv) preparing an aqueous 0.30 to 0.50 molar solution of vanadyl sulphate at a temperature from room temperature to 80° C.;
• v) mixing the solutions from steps i) and iv) together to provide a molar ratio of V:Mo from 1.00:1 to 1.67:1;
• vi) preparing a solution of H2C2O4 and Nb2O5xH2O in a molar ratio from 3:1:1 to 6.5:1;
• vii) adding the solution from step vi) to the solution of step v) to provide a molar ratio of Mo:Nb from 5.56:1 to 7.14:1 to form a slurry;
• viii) heating the resulting slurry in an autoclave under an inert gas, air, carbon dioxide, carbon monoxide and mixtures thereof at a pressure of not less than 1 psig at a temperature from 140° C. to 190° C. for not less than 6 hours.