Three important elements of Zr, Mo and Zn were introduced into the VPO precursor derived in the aqueous medium, and the effects of the introduced elements on the physico chemical properties of the VPO base such as the...Three important elements of Zr, Mo and Zn were introduced into the VPO precursor derived in the aqueous medium, and the effects of the introduced elements on the physico chemical properties of the VPO base such as the surface area, phase composition and catalytic performance were studied accordingly. The modulated samples were also subject to further mechanical milling in order to change the surface state and particle size of the samples. It was found that both the combination of different additives and the mechanical milling would obviously affect surface area and morphology of the modulated samples. The added components and the mechanical milling reduced the complexity of the phase composition and increased the content of the (VO)2P2O7 phase. The combination of Mo and Zn components showed the best positive promotion effect and the following milling process can enhance this effect further. It was also found that the catalytic performance could also be improved somewhat by treating the catalyst at regular intervals with the fresh air during the reaction.展开更多
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 an...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.展开更多
文摘Three important elements of Zr, Mo and Zn were introduced into the VPO precursor derived in the aqueous medium, and the effects of the introduced elements on the physico chemical properties of the VPO base such as the surface area, phase composition and catalytic performance were studied accordingly. The modulated samples were also subject to further mechanical milling in order to change the surface state and particle size of the samples. It was found that both the combination of different additives and the mechanical milling would obviously affect surface area and morphology of the modulated samples. The added components and the mechanical milling reduced the complexity of the phase composition and increased the content of the (VO)2P2O7 phase. The combination of Mo and Zn components showed the best positive promotion effect and the following milling process can enhance this effect further. It was also found that the catalytic performance could also be improved somewhat by treating the catalyst at regular intervals with the fresh air during the reaction.
基金supported by the Ministry of Science,Technology and Innovation of Malaysia
文摘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.
