Physicochemical characterization of mesoporous zirconia modified with tungstophosphoric acid.

MARIANA PELLIZI, LETICIA MÉNDEZ; MIRTA BLANCO; LUIS PIZZIO

Génova, Italia, del 10 al 14 de mayo del 2009.

Congreso; ABC-6 6th world congress on Catalysis by Acids and Bases; 2009

The development of an effective catalyst is a main point to achieve a successful catalytic process . Among other variables, the pore size must be adequate to facilitate the transport of molecules to or from the active sites. Better transport properties are obtained with mesopores. A very much used method to obtain mesoporous materials is the sol-gel technique, which traditionally is referred to the hydrolisis and condensation of alkoxides, though currently is also used with different precursors . The final porous structure can be adjusted employing an organic compound as pore-forming agent. Different agents, as D-glucose and urea , were utilized. Zirconia (zirconium oxide) is largely used as catalyst support. Its acid properties can be modified by addition of sulfate or tungstate, thus obtaining the quite well studied sulfated or tungstated zirconia, which are materials with high acidity . In a low extent, the addition of Keggin heteropolyacids was studied. The characterization results of zirconia, obtained by sol-gel technique using zirconium isopropoxide as precursor and polyethyleneglycol (PEG) as pore-forming agent, modified with tungstophosphoric acid (TPA) are here presented. After the alkoxide hydrolisis catalysed by HCl, a solution containing PEG is added, and then a TPA solution, whose concentration was varied in order to obtain TPA concentration of 0, 30 and 60 % w/w in the solid. Samples were prepared by TPA addition after 24 h of the gel aging (samples ZrTPA00A, ZrTPA30A and ZrTPA60A), and also adding the TPA solution together with the addition of PEG (samples ZrTPA30B and ZrTPA60B). After that the solids were thermally treated at 100 ºC.