| With the rapid development of the energy and chemical industry, catalytic hydrotreating technology has been received much attention and been widely studied. Catalysts play an important role in the hydrotreating process and various materials have been developed to improve the catalytic performance. However, in the search for new processes and the improvement of existing processes, the application of alternative materials as catalysts is always of interest. Amongst such materials, nickel phosphites have attracted much attention for hydrotreating due to their unique physical and chemical properties. However, a very wide range of stoichiometries of nickel phosphide can be exhibited and a number of methods have been employed for the preparation of phosphide catalysts. The development of new methods facilitating the control of phase composition, structure and morphology to enhance catalytic performance is an active area of current interest.In this dissertation, nickel phosphide(Ni2P) and novel catalysts(Pd-Ni2P) were prepared and their catalytic properties were investigated by hydrotreating of phenol and bio-oil. The results showed that the two catalysts were active for the hydrogenation of phenol and the major products were benzene and cyclohexane. As temperature increases, the conversion of phenol and selectivity of cyclohexane were increased while the selectivity of benzene was decreased for both catalysts. After reaction for 2 hr, the conversion of phenol over Ni2 P achieved 81.4% with the cyclohexane selectivity of 57.2% at 300℃ and 5 MPa initial pressure. Under the same reaction condition, the conversion of phenol over Pd-Ni2 P achieved 95.4% with the cyclohexane selectivity of 98.0%, which indicated that the catalytic activity was much enhanced by Pd addition. In the cycling experiments, the initial conversion of phenol over Ni2 P was 81.4%, and gradually drops to 48.3% after 5 cycle reactions. On the other hand, the activity of Pd-Ni2 P catalyst slightly decreased throughout the recycling experiment, with the initial conversion of 95.4% and gradually dropping to 84.3%. The properties of bio-oil after hydrotreating over Ni2 P and Pd-Ni2 P have been significantly improved. The oxygen content of bio-oil reduced from 43.1 to 13.5 wt% over Ni2 P and similarly to 8.0 wt% over Pd-Ni2 P catalyst. The water content also decreased from 31.3 to 2.2 and 0.4 wt%, respectively. As a result, the higher heating value(HHV) increased from 22.7 to 43.0 and 44.6 MJ/kg. The physicochemical properties of catalysts were characterized by XRD, TEM and XPS and the results showed that Pd existed on the catalyst surface acted as an electronic acceptor from Ni2 P phase, which could significantly enhance the activity and stability of the catalyst.In addition, a simple solvent thermal method has been developed to prepare nickel phosphide catalysts(Ni12P5). The effect of preparation parameters has been investigated and the catalytic performance was evaluated by hydrotreating of phenol. The results show that when the ratio of nickel chloride and sodium phosphate is 1:5, reacting for 4 h at 200℃ or 12 h at 180℃ Ni12P5 is obtained. The Ni12P5 catalyst is active for the hydrogenation of phenol. Both of the conversion of phenol and selectivity of cyclohexane achieved 100% after 2h at 200℃,5 MPa initial pressure. Furthermore, catalytic hydrotreating of p-nitrophenol over nickel phosphide(Ni12P5) and novel nickel phosphide catalysts(Ag-Ni12P5) were also carried out under mild condition. The effect of Ag loading on the activity of catalysts was investigated. The results showed that with increasing the loading of Ag, the activity of the catalyst firstly increased and then decreased, and the catalyst with 25% Ag loading had the highest activity. The conversion of p-nitrophenol over 25%-Ag-Ni12P5 was almost close to 100% within 8 min. The catalysts was characterized by XRD, TEM, and XPS techniques to investigate the physicochemical properties. The results showed that Ag as an electron donor improved the activity of the catalysts. |
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