Ultradeep hydrodesulfurization of diesel fuels using highly efficient nanoalumina-supported catalysts: Impact of support, phosphorus, and/or boron on the structure and catalytic activity

In this paper, new nanocatalysts-CoMoP/nanoAl(2)O(3), CoMoB/nanoAl(2)O(3), CoMo/nanoAl(2)O(3)-B2O3, CoMoPB/nanoAl(2)O(3), and CoMoP/microAl(2)O(3)-were prepared by a wet co-impregnation method on micro- and nanostructured alumina supports. The effects of physicochemical and chemical properties of the supports new mesoporous nano-gamma-Al2O3 [high surface area (403.05 m(2) g(-1)), cylindrical pore size (104.59 angstrom), large pore volume (1.69 cm(3) g(-1)), surface defects, and acidic surface] and conventional micro-gamma-Al2O3 [surface area (246.20 m(2) g(-1)), pore volume (0.5 cm(3) g(-1)), pore size (70.30 angstrom), and neutral surfacel and of phosphorus (P) and boron (B) addition on the local structure and hydrodesulfurization (HDS) activity of CoMoS catalytic sites were studied in hydrodesulfurization reactions of straight-run light gas-oil (SRLGO). Porosity, morphological, and structural characterizations of the supports and nanocatalysts were done by informative techniques such as nitrogen physisorption, Mo and S X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy-energy dispersive X-ray (HRTEM-EDX), Mo- and Co-extended X-ray absorption fine structure (EXAFS), Co X-ray absorption near-edge structure (XANES), and diffuse reflectance spectroscopy-ultraviolet-visible (DRS-UV-vis). The characterization results showed that dispersion of Co and Mo to form the CoMoS II phase is improved on the nanoAl(2)O(3) support. It was found that C0M0PB/nanoAl(2)O(3) with suitable physicochemical properties large pore size (101.26 angstrom) and high surface area (247.97 m(2)g(-1))-was the highest active catalyst, which enabled it to decrease 13,500 ppm (1.35 wt%) sulfur of SRLGO feedstock to a sub-10 ppm transparent diesel fuel. The HDS catalytic activity of the most refractive substituted dibenzothiophene (DBT) compounds in the feed followed the sequence 4,6-dimethyl-DBT < 2,4-dimethy1-6-ethyl-DBT < 4,6-diethyl-DBT < 2,4,6,8-tetramethyl-DBT < 4-methyl-DBT determined by comprehensive two-dimensional gas chromatography (GC x GC-SCD) analysis. It was confirmed that the HDS reaction and catalytic activity of the CoMoS sites is controlled particularly by pore size, surface area, acidity, and the surface properties of the support. (C) 2012 Elsevier Inc. All rights reserved.