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Preparation of VPO-catalysts on supports of different nature
|Volodymyr Sydorchuk , Elena Diyuk , Valeriy Zazhigalov|
Institute of Sorption and Problems of Endoecology NAS of Ukraine, 13 Gen Naumova Str., Kyiv 03164, Ukraine
Vanadium-phosphorus oxide systems (VPO) are catalysts for oxidative transformations of hydrocarbons. Vanadyl hydrophosphate (VHP), precursor of catalyst, is not formed as a rule at deposition of VPO on supports. It was offered following new pathways for preparation of mesoporous supported VPO-catalysts by means barothermal synthesis (BTS) in organic and aqueous medium under 170 C: 1) introduction of nonporous fumed oxides or carbon nanotubes in reaction mixture on various stages of VPO synthesis; this route permits to obtain needed phase and to regulate its porous structure in wide limits; first it was prepared supported VPO-catalysts aerogel type on base of C-nanotubes; 2) precipitation on porous solids of different nature: silica gel, phosphates of Ti and Zr, active carbon; in latter case synthesis was carried out in aqueous medium without reducing agent; 3) deposition on preliminary modified silica with organic grafted layer which is potential reducing reagent at VPO preparation; such supported catalysts have residual organic groups on surface which are thermostable on air to 350 C; synthesis of VPO on oxidized carbon allows to increase both louding of active phase and its dispersity in two times; 4) mechanochemical deposition of ready VHP on fumed oxides and phosphates. All suggested approaches permit to prepare on surface of supports necessary phase of VHP in nanodisperse state; size of crystallites according to XRD data has following values: 33-35 nm for bulk samples, 30 nm for method 4, 23-26 nm for method 1, 20 nm for method 3, 6-15 nm on carbon surface. VHP is formed with various relation for intensities of crystalline patterns of (001) and (220) planes: 0,39-1,69. This relation determines primary surface orientation of planes and hence catalytic properties of VPO in diverse processes.
Presentation: Poster at E-MRS Fall Meeting 2006, Symposium B, by Volodymyr Sydorchuk
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-14 10:01 Revised: 2009-06-07 00:44