4TH International Congress on Technology - Engineering & SCIENCE - Kuala Lumpur - Malaysia (2017-08-05)
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Synthesis And Characterization Of Vanadium Incorporated Al-PILCs
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PILCs have the possibility of application both as catalyst support and adsorbent because of their own peculiar properties. For the pillared structure, stable structure, functional high surface area as well as the amount and distribution of catalytic active centers (metal/metal combinations) and acid centers (Lewis and Brönsted) are also important in reaction temperatures and they are potential environmental catalyst for air pollution control and organic conversion. These properties are easily arranged by the correct choice of pillar agent(s). The Al-polyoxocation, i.e., Keggin ion-Al13 has a well-defined chemical composition, structure and charge, and it is thermally stable in PILCs respectively. Second metal incorporation by post-synthesis by ion exchange or impregnation and isomorphous replacement of aluminum in the Keggin ions resulted in improvements of catalytic properties. Vanadium shows high activity especially for oxidation reactions [1,2]. In this study, by using Hancili White (HW) bentonite from Middle Anatolian as the host and keeping the “base(OH)/metal(Al)†ratio as 2.0 Al-PILC was obtained as support [3]. By use of vanadyl sulphate hydrate (VOSO4xH2O) or sodium metavanadate (NaVO3), and wet impregnation (WI), washing after wet impregnation (WWI) and impregnation from solution (I) methods, vanadium was loaded as active compound in two different amounts to the Al-pillared clay that was pre-calcined at 573 K. After then the samples were calcined at 573 K and 773 K [4]. Loading of vanadium caused decreases in the XRD peak intensity and the basal spacing belonging Al-PILC and vanadium incorporated samples with basal spacing values from 1.75 to 1.35 nm were obtained. The nitrogen adsorption/desorption study showed that, the highest surface area after support, was observed for NaVO3 loaded by impregnation from solution and calcined at 573 K and the lowest surface area was observed for NaVO3 loaded by wet impregnation and calcined at 773 K. NaVO3 loading resulted higher V/Si ratio than the other vanadium source did. It was seen from XPS analysis vanadium was bonded with 2p3/2. X-ray photoelectron spectroscopy (XPS) results showed that Al/Si ratio decreased from 0.46 down to 0.35 by vanadium impregnation. The layered structure of Al-PILC and the placement of vanadium particles between these layers and onto the clay particles’ surface were observed in the TEM analyses. Fast dehydration till 3000C temperature, then decreases in mass loss and solid-solid reaction with hydroxylation at 900º C were observed in TGA/DTA analyses of samples. A high endothermic peak below 1500C and an exothermic peak above 8000C were observed for all PILCs. The consistence of V-O-Al and V-O-Si bonds and Bronsted and Lewis acid centers were observed in FTIR results.
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Aylin Tecimer, Suna Balcı
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