Deep Hydrodesulfurization of Dibenzothiophenes Over NiW Sulfide Catalysts Supported on Sol–Gel Titania–Alumina

Abstract

This work showed that the use of Al 2 O 3 -TiO 2 as carriers has a positive effect on the activity of supported NiW catalysts in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene carried out in a batch reactor at 320°C and total H 2 pressure of 5.5 MPa. Two Al 2 O 3 -TiO 2 mixed oxides with Al/Ti atomic ratios of 10 and 2 were synthesized by sol-gel method together with the pure Al 2 O 3 synthesized as reference support. For NiW/ Al 2 O 3 -TiO 2 and NiW/Al 2 O 3 catalysts, a metal load of 17 and 5.5 wt% of W and Ni were considered respectively. It was found that both Al 2 O 3 -TiO 2 -supported catalysts exhibited higher activity than alumina-supported one. The catalyst with a largest TiO 2 content (NiW/AT2) demonstrated to be 23 % more active with respect to NiW/Al 2 O 3 . Solids were characterized by temperature-programmed reduction (TPR), high resolution transmission electronic microscopy and X-ray photoelectronic spectroscopy (XPS) techniques. A decrease in support-metal interaction (from TPR) was observed when Ti content increased, which could lead to a higher amount of NiWS phase (from XPS). Besides, a slight increase in the slabs length in WS 2 was observed for titania-containing catalyst with respect to NiW/Al 2 O 3 , indicating that the dispersion can still be optimized. The atomic ratio Al/Ti = 2 of the NiW/Al 2 O 3 -TiO 2 catalyst proved to be a potential substitute for current catalysts for sulfur reduction in ultra-clean diesel.

Effect of Metal Loading in Unpromoted and Promoted CoMo/Al2O3–TiO2 Catalysts for the Hydrodeoxygenation of Phenol

“…The obtained gel was aged for 24 h at 273 K. Subsequently, it was dried at 333 K. Finally, the dried gel was calcined for 3 h at 773 K with a rate of 3 K min −1 . AT2 support textural properties were: S BET = 359 m 2 g −1 , V p = 1.1 cm 3 g −1 , Dp = 7.7 nm, and PZC = 7.6, as previously reported by [32,34] The promoted CoMo catalyst series were impregnated following four different molar Co/(Co + Mo) ratios: 0.1, 0.2, 0.3, and 0.4. For monometallic catalysts, the Mo (or Co) solution was impregnated on AT2 support and was macerated at room conditions for 12 h. After that, it was dried at 393 K and calcinated at 673 K for 5 h. For the promoted catalyst, the Mo calcined materials were impregnated with the cobalt solution and the heat treatment was repeated.…”

“…One possible way is to modify Al-based mixed oxides, such as Al 2 O 3 -TiO 2 (AT). This mixed oxide has been proposed as an alternative support to take advantage of the combined properties of alumina and titania [27][28][29][30][31][32][33]. It had displayed notorious improvements in the textural and physicochemical properties in comparison to alumina or titania supports [30][31][32][33][34].…”

“…This mixed oxide has been proposed as an alternative support to take advantage of the combined properties of alumina and titania [27][28][29][30][31][32][33]. It had displayed notorious improvements in the textural and physicochemical properties in comparison to alumina or titania supports [30][31][32][33][34]. Particularly, CoMoS supported over sol-gel synthetized Al 2 O 3 -TiO 2 catalysts with an Al/Ti = 2 ratio (called "AT2") showed that the interactions between the metal oxide phases and the support enhance the formation of the sulfided active phases compared to alumina, leading to higher activities [32,[35][36][37].…”

“…It had displayed notorious improvements in the textural and physicochemical properties in comparison to alumina or titania supports [30][31][32][33][34]. Particularly, CoMoS supported over sol-gel synthetized Al 2 O 3 -TiO 2 catalysts with an Al/Ti = 2 ratio (called "AT2") showed that the interactions between the metal oxide phases and the support enhance the formation of the sulfided active phases compared to alumina, leading to higher activities [32,[35][36][37]. In a previous work of the HDO of phenol, it was shown that CoMo/AT2 was twice as active and was more selective to the DDO route than CoMo/Al 2 O 3 catalyst [34].…”

Recent Insights in Transition Metal Sulfide Hydrodesulfurization Catalysts for the Production of Ultra Low Sulfur Diesel: A Short Review

“…Early studies showed for example that Mo over Al/Ti = 1 and Ti/(Ti + Zr) = 0.8 supports lead to the highest activities among tested catalysts for hydrocracking and coal-derived liquids upgrading [69]. For the HDS of DBT, several reports have been published using Al/Ti = 2 to obtain the highest activity [4,35,52,55] among materials prepared by the sol-gel method.…”