Synthesis, Characterization, and Catalytic Performance of Highly Dispersed Co-SBA-15

Highly dispersed cobalt on SBA-15 was successfully prepared by a post synthesis grafting of cobalt. Of the cobalt precursors tested, Co(II) acetylacetonate was found to be the best source for high dispersion of cobalt. The Co-SBA-15 catalysts were characterized with different techniques: N-2 physisorption. XRD, TPR, TEM, and X-ray adsorption analysis, The mesoporous structure of SBA-15 was retained after cobalt grafting with LIP to 10 wt % Co loading. There were no large cobalt oxide particles formed, which indicates all the cobalt ions are highly dispersed on the surface and the direct bonding to the silica surfaces results in a high reduction temperature (1123 K) relative to Co oxides. X-ray absorption analysis demonstrates a local Structure of Co ions with all Co ions isolated and bonded with oxygen. XANES analysis requires that the local environment for Co ions be that of either a distorted tetrahedral or all octahedral Structure and the filling of EXAFS data further shows a Co-O bond coordination number of 3.58 +/- 0.48, confirming that the Co is in a distorted tetrahedral environment. The catalytic activity of Co-SBA-15 catalyst was studied for the synthesis of carbon,single walled nanotubes (SWNT). The high reduction stability of Co-SBA-15 is presumed to make a favorable catalyst for this high temperature reaction, Raman spectroscopy and TEM photographs show that good quality carbon SWNT was synthesized by Co-SBA-15. Moreover, Co-SBA-15 has a higher yield of carbon SWNT compared with Co-MCM-41 (C16 alkyl template) under the same reaction conditions.