铋和镍对钒磷氧化物催化剂性能的影响(英文)

Vanadium phosphorus oxide (VPO) catalysts were synthesized by the dihydrate method which involved the two steps for the preparation of the dihydrate (VOPO4 2H2 O) and the precursor hemi-hydrate (VOHPO4 0.5H2 O). Bi and Ni salt were added into the mixture of VOPO4 2H2 O and isobu-tanol, and the obtained precursors were calcined in a flow of a n-butane/air mixture to produce the promoted VPO catalysts. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorp-tion- desorption, inductively coupled plasma-atomic emission spectroscopy, scanning electron mi-croscopy (SEM), and H2 temperature-programmed reduction (H2 -TPR). Their catalytic properties were tested using a fixed-bed microreactor. All the catalysts gave main XRD peaks at 2θ = 22.9°, 28.5°, and 30.0°, attributing to the (020), (204), and (221) planes of the pyrophosphate phase (VO)2 P2 O7, respectively. The promoted catalysts have smaller crystallite size and higher specific surface areas. SEM micrographs revealed the formation of more prominent plate-like crystallites that were arranged as rosette clusters. H2 -TPR results showed that the promoted catalysts had lower reduction peak temperatures and possessed higher amounts of V5+-O2– and V4+-O– pairs, which gave higher selectivity and activity in the selective oxidation of n-butane to maleic anhydride.