Thiophene Hydrodesulfurization over Alumina-Supported Molybdenum Carbide and Nitride Catalysts: Adsorption Sites, Catalytic Activities, and Nature of the Active Surface

On the surface sites of MoP/SiO2 catalyst under sulfiding conditions: IR spectroscopy and catalytic reactivity studies

“…The band at 2045 cm −1 shifts to higher frequencies when the treatment temperature is increased, e.g., to 2047 cm −1 at 373 K, to 2049 cm −1 at 473 K, to 2055 cm −1 with a shoulder at 2090 cm −1 at 573 K, and to 2100 cm −1 at 673 K. Meanwhile, a shoulder at ca. 2055 cm −1 can still be distinguished for the sample treated at 673 K. The appearance of the band at 2100 cm −1 indicates the sulfidation of the phosphide surface because this is a characteristic band of CO adsorbed on sulfided Mo catalyst and has been assigned to linearly adsorbed CO on cus Mo 2+ sites [21,23,27]. The results show that the surface of the MoP/SiO 2 catalyst is partially sulfided when treated with the thiophene/H 2 mixture at 673 K. A separate detection of the changes of thiophene itself during the treatments at different temperatures shows that thiophene becomes reactive with hydrogen on the MoP/SiO 2 catalyst at and above 373 K. Thus, the gradual sulfidation of MoP/SiO 2 catalysts can be ascribed to the HDS of thiophene [31][32][33][34].…”

“…2 and 3). The assignment of this IR band can be well aided by a number of related studies of CO adsorption on Mo-based catalysts [23][24][25][26][27][28][29]. Decanio and Storm [35] investigated the adsorption of CO on mildly reduced Mo/Al 2 O 3 catalysts with different Mo loadings.…”

“…According to the preparation process, the passivated MoP/SiO 2 sample reduced at 923 K can be regarded as fresh molybdenum phosphide on silica. Therefore, adsorbed CO on fresh MoP/SiO 2 exhibits a characteristic band at 2045 cm −1 that can be due to adsorbed CO on Mo sites [23][24][25][26][27][28][29] on the surface of MoP. The fresh sample is denoted as MoP/SiO 2 on which following experiments will be carried out.…”

“…The HDN and HDS activities of Mo nitride and carbide catalysts are initially high but decline with time in the presence of sulfur-containing compounds, which was explained mainly by the irreversible sulfidation of these catalysts [21][22][23] under reaction conditions. However, it is interesting to note that molybdenum phosphide catalysts show quite stable activities in hydrotreating reactions in the presence of sulfur-containing feedstock, and in some cases even exhibit increased activities with reaction time [7,8,14,15,18,19].…”

Hydrodesulfurization of 4,6-DMDBT on a multi-metallic sulfide catalyst with layered structure

“…In order to achieve ultra-deep desulfurization, many researches have been conducted including development of novel phosphide, carbide, and nitride catalysts, and improvement of existing sulfide catalysts by doping with noble metals and loading into zeolites [15][16][17][18]. In recent years, an unsupported NiMoW tri-metallic HDS catalyst, called NEBULA, has been drawing much attention, [19][20][21] because its HDS activity is much higher than those of other conventional catalysts.…”