Process for the transformation of a vanadium/phosphorus mixed oxide catalyst precursor into the active catalyst for the production of maleic anhydride

A process for the transformation of a vanadium and phosphorus mixed oxide catalyst precursor into an active catalyst for the synthesis of maleic anhydride,

• wherein the precursor comprises vanadyl acid orthophosphate hemihydrate of formula (VO)HPO4·0.5H2O as main component and the active catalyst comprises vanadyl pyrophosphate of formula (VO)2P2O7 as main component, and
• wherein the process comprises the steps of:
• a) initial heating of the precursor to an initial temperature of 170-190° C. and holding at the initial temperature for 1-10 minutes, in an atmosphere composed of 100% by volume of air;
• b′) optional heating of the precursor from the initial temperature to a calcination temperature TC1 of 320-380° C. and holding at the temperature TC1 for 0.5-3 hours, in an atmosphere selected from an atmosphere composed of 10%-50% by volume of air and 50%-90% by volume of steam, and an atmosphere composed of 20%-40% by volume of air, 5%-15% by volume of steam and 45%-75% by volume of an inert gas;
• b) further heating of the precursor from the initial temperature or, if step b′) is carried out, from the calcination temperature TC1 to a calcination temperature TC2 of 390-460° C. and holding at the temperature TC2 for 0.5-3 hours, in an atmosphere which
• 1. has the same composition as the atmosphere of step b′), if step b′) is carried out,
• 2. is composed of 20%-40% by volume of air, 5%-15% by volume of steam and 45%-75% by volume of an inert gas, if step b′) is not carried out;
• c) heating of the precursor from the calcination temperature TC2 to a calcination temperature TC3 of 470-550° C. and holding at the calcination temperature TC3 for 0.5-3 hours, in an atmosphere composed of 100% by volume of an inert gas;
• and
• d) cooling the active catalyst obtained in step c).