TPD and TPR Studies of Vanadyl Pyrophosphate Catalysts derived from VOPO4·2H2O Precursor
Y.H. Taufiq-Yap1, K.C. Waugh2 and C.P. Ho1
Chemistry, Universiti Putra
2Department of Chemistry, University of Manchester Institute of Science and Technology, PO Box 88, Manchester, M60 1QD, United Kingdom
Three vanadyl pyrophosphate catalysts synthesised via VOPO4·2H2O have been calcined for 40, 100 and 132 hours at 673 K in a reaction flow of n-butane/air. These catalysts were denoted VPD40, VPD100 and VPD132. The nature of oxidants in/on these catalysts has been investigated by using temperature-programmed techniques. One peak maximum was found desorbed in O2 temperature programmed desorption (TPD) at 992 K for VPD40 with a total amount of oxygen desorbed of 2.4´1020 mol´g-1. However an increased of calcination duration to 100 and 132 hours produced one oxygen peak desorbed at 986 K with a total amount of oxygen desorbed doubled to 4.4´1020 mol´g-1. Temperature programmed reduction with H2 resulted in the removal of ~ 10 times more than the lattice oxygen which can be desorbed thermally with the development of a new low reduction peak at ~ 840 K.