Superácidos soportados sobre sílica para isomerización de parafinas cortas

V.M. BENÍTEZ; C.R. VERA; C.L. PIECK; F.G. LACAMOIRE; J.C. YORI; J.M. GRAU; J.M. PARERA

Mérida, Yucatán, México

Simposio; XIX Simposio Iberoamericano de Catálisis; 2004

Instituto Mexicano del Petróleo - UNAM

Oxoanion promoted ZrO2 and TiO2 catalysts are superb isomerization catalysts which are usually prepared in bulk form. High activation temperatures and low sintering resistance yield low surface area materials (< 40 m2g-1). The replication of the structure of these catalysts over silica was studied in this work as a means of increasing the number of available active sites. The dispersion of tungsten-zirconia (WZ), tungsten-titania (WTi), boron-zirconia (BZ) and boron-titania (BTi) over silica (Si, 300 m2g-1) was accomplished by sequentially impregnating Zr and Ti organic compounds and W and B salts. Supported ZrO2 and supported TiO2 had similar sintering resistance, with scarce crystalline growth. Supported ZrO2 crystallized at a high temperature (700 °C) while TiO2 crystallized at a lower temperature (550 °C) indicating that the ZrO2 based materials are the most disperse. The most effective combination for producing active materials in acid catalyzed reactions is WZr. Supported WZr (WZSi) has a bimodal pattern of activity with maxima at 450°C and 750 °C related to surface dehydration and formation of WOx acid species, respectively. n-C6 isomerization reveals that WZSi is less active than bulk WZ in spite of having a much higher surface area (¡Ö150-200 m2 g-1). It has however an improved selectivity, with a total absence of sites with cracking activity. Key words: supported superacids, silica, tungsta-zirconia, n-hexane, isomerization