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

• Published in: Journal of catalysis 2013-03, Vol.299, p.321-335
• Main Authors: Rashidi, Fereshteh, Sasaki, Takehiko, Rashidi, Ali Morad, Nemati Kharat, Ali, Jozani, Kheirollah Jafari
• Format: Article
• Language: English
• Subjects: absorption; Acidity; active sites; Alumina; aluminum oxide; Boron; Catalysis; Catalysts; catalytic activity; Chemistry; cobalt; CoMoS2 nanocatalysts; comprehensive two-dimensional gas chromatography; Diesel fuel; Diesel fuels; Exact sciences and technology; feedstocks; General and physical chemistry; molybdenum; Nanoalumina support; Nanostructured materials; nitrogen; Phosphorus; Physicochemical properties; porosity; reflectance; sulfur; surface area; Surface defects; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Ultradeep hydrodesulfurization; X-radiation; X-ray photoelectron spectroscopy
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2012.11.012

Schematic of layered structured of small CoMoS2 non crystallites on the surface of Al2O3 supports. Each colored CoMoS2 particle shows a different stacking number: violet=1, blue=2, green=3, and red=4. [Display omitted] ► High surface area mesoporous nanoalumina as a promising support for HDS catalysts. ► Dispersion of high percentage loading of two metals on the nanoalumina is modified. ► Local structure of Co and Mo shells on the nanoalumina support is CoMoS II Type. ► CoMoS II catalytic sites with good quality and high catalytic activity are obtained. ► Coke deposition and pore clogging on the nanoalumina support is decreased. In this paper, new nanocatalysts—CoMoP/nanoAl2O3, CoMoB/nanoAl2O3, CoMo/nanoAl2O3–B2O3, CoMoPB/nanoAl2O3, and CoMoP/microAl2O3—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-γ-Al2O3 [high surface area (403.05m2g−1), cylindrical pore size (104.59Å), large pore volume (1.69cm3g−1), surface defects, and acidic surface] and conventional micro-γ-Al2O3 [surface area (246.20m2g−1), pore volume (0.5cm3g−1), pore size (70.30Å), and neutral surface]—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 nanoAl2O3 support. It was found that CoMoPB/nanoAl2O3 with suitable physicochemical properties—large pore size (101.26Å) and high surface area (247.97m2g−1)—was the highest active catalyst, which enabled it to decrease 13,500ppm (1.35wt%) sulfur of SRLGO feedstock to a sub-10ppm 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