Effect of hetero atom on dispersion of NiMo phase on M-SBA-15 (M = Zr, Ti, Ti-Zr)

NiMo catalysts were prepared on different hetero atom doped SBA-15 supports for hydrotreatment evaluation. The nature of the hetero atom (Ti, Zr and TiZr) was observed to have a profound impact on the final molybdenum phase formed after calcination of the catalysts. Mo L-3 edge XANES analysis of the catalysts along with results from Raman and XRD, show that Zr-SBA-15 support is able to disperse the Molybdenum oxide phase better than the other supports. The formation of bulk phases viz., MoO3 and NiMoO4 is accelerated in pure SBA-15 supports. Evidence of Mo present as tetrahedral MoO4 units was only found in TiZr-SBA-15 support. The presence of tetrahedral Mo species on TiZr-SBA-15 support was attributed to be due to the relative positive charge on the Zr site arising from the electronegative difference between Ti and Zr leading to [MoO4](2-) stabilization. Sulfidation studies of the catalysts revealed that formation of active NiMoS phase is maximum in Zr-SBA-15 support and minimum in the SBA-15 supported catalysts. The low sulfidation of Mo in SBA-15 and TiZr-SBA-15 was due to the presence of bulk MoO3 phase. The hydrotreating activities were in confirmation with the characterization studies, with NiMo/Zr-SBA-15 and NiMo/Ti-SBA-15 exhibiting highest HDS and HDN conversions respectively. (C) 2012 Elsevier B. V. All rights reserved.