Preparation of vanadium phosphate catalyst precursors for the selective oxidation of butane using α,ω-alkanediols
Vanadium phosphate catalyst precursors were prepared from V 2O 5 and H 3PO 4 or VOPO 4·2H 2O using α,ω-alkanediols (1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol) as both the reducing agent and the solvent. A series of layered VOHPO 4·HO(CH 2) nOH (n = 4-6) materials intercalated with α,ω-alkanediols were obtained. The performance for butane oxidation of the final catalysts formed via the in situ transformation of the VOHPO 4·HO(CH 2) nOH precursors under reaction conditions is described. The final catalysts derived from the alkanediol intercalated materials were found to exhibit relatively low selectivities to maleic anhydride and comprised of V V (VOPO 4) phases with an amorphous V IV phase. However, when a crystalline (V IVO) 2P 2O 7 phase is present, with small amounts of V V phases, as with materials prepared with 1,4-butanediol, the specific and intrinsic catalytic activity are higher.