Hydrocracking of the crude oil from thermal pyrolysis of municipal wastes over bi-functional Mo–Ni catalyst

• Overall refining of crude oil from pyrolysis of municipal solid wastes was performed.
• A bi-functional Mo–Ni/SiO2–Al2O3 catalyst was prepared for refining of the crude oil.
• A specific preparation procedure was impregnation–precipitation and sulfurization.
• NiO particle size and dispersion were controlled with urea as precipitator.
• High yield of fuel oil was obtained with a good catalytic stability and regeneration.

Bi-functional Mo–Ni/SiO2–Al2O3 catalyst was prepared by loading bimetal Ni–Mo over large porous and acidic SiO2–Al2O3 substrate via impregnation–precipitation–calcination–sulfurization procedure. Highly dispersed NiO clusters were loaded with urea as a precipitator. The catalytic performance for the hydrocracking of the crude oil from thermally pyrolysis of municipal solid wastes was investigated in a fixed bed reactor. It is found that SiO2–Al2O3 composites with the mid-acidity and large pores were more suitable as the substrate than Al2O3 and Al2O3–Y(Y zeolite). Mo–Ni/SiO2–Al2O3 catalyst with 8 wt% Mo and 14 wt% Ni showed the higher reactivity and higher yield of fuel oil. Moreover, its hydrocracking reactivity could be further improved by partial sulfurization of Ni and Mo. Besides, the bi-functional Mo–Ni/SiO2–Al2O3 showed a good stability, and the deactivated catalyst could be easily regenerated by on-line combustion. Under the optimized conditions of 10 MPa, WHSV 0.3 h−1 and 698 K, the conversion of pyrolysis oil was up to 86% with 66% yield of fuel oil, greatly better than a commercial hydrocracking catalyst. The overall hydrocracking refinement converts most of the olefin, acid, ketones and poly-aromatic presented in the pyrolysis oil into alkanes, alcohols, and alkyl-aromatics, with a significant decrease of N and S contents as well as viscosity.

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