Abstract: The advantages of unsupported catalyst in the HDS are obvious and widely paid much attention. In this paper, PEG was added in the process of preparing trimetalic unsupported catalyst by co-precipitation, and the resulting unsupported catalyst was then characterized by XRD, BET, and evaluated in a micro-reactor system to test the optimal amount and the molecular weight of PEG added. Py-IR, SEM, TEM techniques were used to investigate the effect of PEG under optimal conditions on the properties and the HDS activity of the catalyst. The structures of the unsupported Ni-Mo-W catalysts in oxidation state were analyzed by XRD and LRS. The results show that the trimetalic unsupported catalyst prepared by adding PEG with molecular weight of 600 as Mo moles of 20% has the best HDS activity, the HDS rate reaches to 99.8%. Under the best catalyst preparation conditions, the Ni-Mo-W composite has a regular morphology, better distribution of active component, ordered arrangement, optimal pore structure, and fully exposed acid sites. The Ni-Mo-W composite in oxidative state is a new type of Ni-based compound with different Mo and W coordination modes, the bulk and the surface layer of the catalyst are composed of Ni-W, while part of the internal contains Ni-Mo structure.

Key words: trimetalic unsupported catalyst, polyethyleneglycol, inferior diesel, hydrodesulfurization