Highly effective sulfated zirconia nanocatalysts grown out of colloidal silica at high temperature

A large surface-to-volume ratio is a prerequisite for highly effective catalysts. Making catalysts in the form of nanoparticles provides a good way to achieve the aim. However, agglomeration of nanoparticles during the preparation and utilization of nanocatalysts remains a formidable problem. Here, we present a novel approach in which nano units of catalysts are formed in the matrix of a colloidal carrier, with assistance of a cross-linking agent, and then grow out of the carrier upon calcination at high temperature. This ensures that the catalysts not only do not agglomerate, but also have a low cost and high catalytic efficiency due to the large surface-to-volume ratio and the absence of carbon deposition. The technique is demonstrated by the successful preparation of a binary nanocatalyst that consists of a silica nanoparticle core and a sulfated zirconia (SZ) nanocrystal shell (JML-1). The synthesis was achieved by converting sulfated zirconia (SZ) and silica solutions into a composite gel by means of sol-gel processing in the presence of triethoxysilane as the cross-linking agent, followed by heating at 50 degrees C and calcining at 550 degrees C. Relative to other catalysts, such as pure SZ, non-nanodispersed SZ over silica (SZ/SiO2), and zeolites Y, Beta, and ZSM-5, JML-1 exhibits superior catalytic activity in many reactions. For example, the activity of JML-1 in the production of gasoline by alkylation of 1-butene with isobutene remained at 95% or higher after 20 h of reaction and was over 90% after being regenerated five times. In sharp contrast, SZ and SZ/SiO2 give a high activity only for 2 h and the initial activity of zeolites Beta and ZSM-5 are about 88 and 60%, respectively. These findings demonstrate that non-agglomerated nanoparticles anchored onto a carrier surface can be prepared and the technique provides a versatile route to new highly effective nanocatalyst systems.