Homogeneous dispersion of Au nanoparticles into mesoporous SBA-15 exhibiting improved catalytic activity for nitroaromatic reduction

Mesoporous silica SBA-15 having pore size (similar to 8 nm) was prepared using Pluronic P123 triblock copolymer followed by its surface modification with 2 wt.% of 3-aminopropyltriethoxysilane (APTES). The Au (1-10 wt.%) impregnation led to the formation of homogeneously dispersed Au nanospheres of size 5-6 nm, and nanorods of length 90-180 nm (and width 6-9 nm) throughout the APTES-modified SBA-15 without any distortion in the long range ordering of mesochannels. It was found that increasing amount (1-10 wt.%) of Au loading followed by calcination at 350 degrees C resulted in change of spherical morphology to rod like Au nanostructures beyond 5 wt.% loading. The surface area (664 m(2)/g) and pore volume (1.33 cm(3)/g) of bare SBA-15 were significantly reduced to 292 m(2)/g and 0.6031 cm(3)/g for Au nanosphere, and 457 m(2)/g and 0.7677 cm(3)/g for Au nanorod dispersed SBA-15, respectively, due to partial filling of mesopores. The catalytic activity of APTES-modified SBA-15 for the reduction of m- and p-dinitrobenzene is abruptly enhanced, after optimum amount (4-10 wt.%) of Au dispersion following a pseudo first order kinetic law that exhibited the best yield and 89% selectivity for m-phenylenediamine and 81% for p-nitroaniline formation, respectively. (C) 2014 Elsevier Inc. All rights reserved.