“Physico-chemical nanomaterials science”

The influence of the metal ions modification on physic-chemical properties VPO catalyst in n-pentane oxidation
Kiziun O.V., Zazhigalov V.O.
Institute for Sorption and Problems of Endoecology of National Academy of Sciences of Ukraine, Naumova 13, Kyiv-164, 03164 Ukraine. 

VPO catalysts are known as the catalytic systems for selective transformation of  inert paraffins [1], particularly n-butane to maleic anhydride (MA) and n-pentane to maleic and phthalic anhydrides (PhA) at al. A development of catalytic properties of the VPO composition is possible by means of the introduction of additives of a various nature 
Experimental. Basic VPO composition and VPMeO samples modified by ions of Me=Bi, La, Mo, Te, Fe, W, Zr, Ті, Ag, Ni were synthesized in organic solution medium of n-butanol with V2O5 and H3PO4 (the atomic ratio P/V=1.15 and Me/V=0.05-0.40) by known method [2]. The synthesized samples were investigated by means of X-ray phase analysis (XRD), X-ray photoelectron spectroscopy (XPS), differential thermal analysis (DTA), scanning electron microscopy (SEM). Types of acidic centers on the VPMeO surface were defined by dimethylpyridine and 2,6-dimethylpyridine adsorption methods.
Results. The XRD data show that all the investigated samples before activation in the stream of reactant contained the VOHPO4•0.5H2O precursor phase.  VPMoO patterns are the exception in which the (NH4)3PO4MoO3 phase are forming with character reflections. Results of DTA show an influence of additives on the crystallization stage of (VO)2P2O7 phase in VPMeO samples. SEM data of VPMeO patterns show that all additives have the effect on morphology of VPO matrix. XPS results show introduction of additives changes O 1S-electrons binding energy. This fact can influence on the rate of paraffin transformation. The additives introduction influences on acid-base properties of the surface of VPMeO catalysts. It was established that a change of these properties regulates the selectivity of anhydrides, particularly the selectivity of PhA and MA formation in partial oxidation of n-pentane.  

1.	Centi G., Golinelli G., Busca G. Modification of the surface 
pathways in alkane oxidation by selective doping of Bronsted acid sites of  vanadyl pyrophosphate // J Phys Chem. - 1990. - 94. - P. 6813-6819.
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