Sulfonic acid-functionalized silica-coated magnetic nanoparticle catalysts

Four different sulfonic acids are grafted onto silica-coated magnetic nanoparticle supports, yielding magnetic, solid acid catalysts. The hybrid organic/inorganic sulfonic acid catalysts are evaluated in test reactions in terms of activity and recyclability and compared with commercially available heterogeneous acidic resins and homogeneous sulfonic acids. The magnetic, solid acid catalysts exhibit comparable activity to the other commercial and homogeneous catalysts. Recovery tests confirm the presence of surface-bound sulfonic acid functionalities in three of the four catalysts. These results illustrate the utility of magnetic nanoparticles, as a heterogeneous support for the simple recovery of sulfonic acid catalysts. (c) 2007 Elsevier Inc. All rights reserved.