Synthesis of thermally stable, high surface area anatase–alumina mixed oxides

Abstract

Mixed oxides containing anatase and 5-20 mol% alumina have been synthesized from a precursor sol containing acetic Ž . acid modified titanium isopropoxide and boehmite AlOOH . The resultant oxides retain considerable anatase phase at 10008C and have specific surface area many times higher than that of pure titania. A composite precursor containing titania-20 mol% alumina after calcination at 4508C, has a specific surface area as high as 318 m 2 rg compared to a value of 100 m 2 rg for pure titania prepared under identical conditions. The uniform dispersion of the nanoparticles of alumina in the titania gel matrix causes reduction in the anataseranatase contact points and thus results in a decrease of nucleation sites leading to increase in thermal stability of anatase phase. The high surface area and porosity could arise from the highly branched acetate polymeric gel. The sintered density of compacts derived from mixed oxides is also brought down considerably compared to pure titania counter parts. q

Nanoporous titania–alumina mixed oxides—an alkoxide free sol–gel synthesis

“…These observations clearly evidenced the increase in the anatase-rutile transformation temperature of titanylsulfate-derived nanotitania by the incorporation of boehmite-derived alumina. Similar findings were reported earlier in alkoxide-derived titania by sol -gel methods [6,7,14]. No traces of any aluminium oxides/ hydroxide phases can be found in the XRD patterns of Ti-Al samples on calcination up to 800 jC (Fig.…”

“…1 show the presence only of anatase phase except in pure titania. The rutile fraction calculated from the intensities of the (101) and (110) reflection planes of anatase (I A ) and rutile (I R ) respectively by using the equation W R = 1/1[1 À 1.26(I A /I R )] [6,25] shows that pure titania contains 92% rutile and 8% anatase fraction after calcination at 800 jC. The reduction in the anatase crystallites size with the addition of alumina is more prominent in 800 jC calcined samples.…”

Al2O3 composite agent effects on phase transformation of nanometer TiO2 powder

“…One of the disadvantages of titania used as a support is its poor stability of the active anatase structure at elevated temperatures. Several methods including the preparation of titania nano-composites with alumina, silica, etc., have been reported to reduce the particle size and increase the stability of the anatase structure [8][9][10][11][12]. Recent findings in the active role of titania-alumina support in the hydrodesulfurization catalysts [3] and as photocatalysts [2] necessitate the development of new synthesis procedure resulting in small particle size and enhanced stability of the anatase phase.…”

Photocatalytic Properties of g-C3N4–TiO2 Heterojunctions under UV and Visible Light Conditions

“…When this material was added to TiO 2 , the particle sizes calculated were similar to that of pure TiO 2 , showing that the dopant did not affect the resulting particle sizes. As stated previously, the anatase to rutile (ART) transition generally occurs at around 600–700 °C [46,47,48]. Using the Spurr equation (Equation (2)), it was calculated that undoped TiO 2 retained 100% anatase at 700 °C, with 5% rutile formed at 800 °C.…”