Mesoporous-molecular-sieve-supported nickel sorbents for adsorptive desulfurization of commercial ultra-low-sulfur diesel fuel

摘要

A high-performance nickel-based sorbent was developed by loading nickel on a mesoporous molecular sieve, MCM-48, for adsorptive desulfurization (ADS) of commercial ultra low sulfur diesel (ULSD) for fuel cell applications. The prepared sorbents were characterized by the N2 adsorption-desorption. X-ray diffraction (XRD), H2 chemisorption, and transmission electron microscope (TEM), and the ADS performance was evaluated in a fixed-bed flow sorption system at 220 °C using a commercial ULSD with a sulfur content of 14.5 ppmw. Effects of the ultrasonic aid in incipient wetness impregnation (IW1), nickel loading amount and support materials on the sorbent performance were examined. It was found that the incipient wetness impregnation with the ultrasonic aid improved significantly the ADS performance of the sorbent by increasing the dispersion of nickel on the surface. Using MCM-48 as a support with 20 wt% nickel loading (Ni20/MCM-48) can lead to an excellent nickel-based sorbent with a breakthrough capacity of 2.1 mg-S/g-sorb for ADS of the ULSD at a breakthrough sulfur level of 1 ppmw. The alkyl dibenzothiophenes are likely adsorbed on the sorbent surface directly through an interaction between the sulfur atom and the exposed nickel atoms, and a part (～6%) of the adsorbed alkyl dibenzothiophenes react further with the surface nickel to release the corresponding hydrocarbons. The desulfurization reactivity of the alkyl dibenzothiophenes is dependent on not only the number, but also the size of the alkyl substituents at the 4- and 6-positions of alkyl dibenzothiophenes.