Oxidation of propane to give acrylic acid using catalysts in a mixture of crystalline phases

A method for preparing acrylic acid from propane, characterized in that a gas mixture comprising propane, steam and, optionally, an inert gas and/or molecular oxygen, is passed over a catalyst conferring good selectivity, comprising a crystalline catalyst phase:

• satisfies the formula (I):
• TeaMo1VbNbcOx (I)
• in which
• a is between 0.1 and 2 limits included;
• b is between 0 and 1 limits included;
• c is between 0 and 0.2 limits included;
• x and y represent the quantity of oxygen bound to the other elements and depends on their oxidation states,
• and corresponds to a hexagonal lattice structure of which the X-ray diffraction spectrum, diffraction angles (2θ) measured using the copper Kα1 and Kα2 lines as an X-ray source, with a 0.02° step, has a peak at the diffraction angle 28.2° and lattice parameters a=0.729 (±0.02) nm×p, p being an integer from 1 to 4;
• c=0.400 (±0.01) nm×q, q being an integer from 1 to 2;
• α=90°, Y=120°,
• or of a monoclinic structure Te2MoO7 or Te0.2MoOx,
• combined with a crystalline catalyst phase for activating the propane.