Abstract
The effects of desilication (DS) of the zeolite β on the hydrocracking of polycyclic aromatics were investigated using the Ni2P/β catalysts. The Ni2P/β catalysts were obtained by the temperature-programmed reduction (TPR) method, and the physical and chemical properties were examined by N2 physisorption, X-ray diffraction (XRD), 27Al magic angle spinning–nuclear magnetic resonance (27Al MAS NMR), extended X-ray absorption fine structure (EXAFS), isopropyl amine (IPA) and NH3 temperature-programmed desorption (TPD), CO uptake, and thermogravimetric analysis (TGA). The catalytic activity was examined at 653 K and 6.0 MPa in a continuous fixed bed reactor for the hydrocracking (HCK) of model compounds of 1-methylnaphthalene (1-MN) and phenanthrene or a real feedstock of pyrolysis fuel oil (PFO). Overall, the Ni2P/DS-β was observed as more active and stable in the hydrocracking of polycyclic aromatics than the Ni2P/β catalyst. In addition, the Ni2P/β suffered from the coke formation, while the Ni2P/DS-β maintained the catalytic stability, particularly in the presence of large polycyclic hydrocarbons in the feed.
Highlights
Pyrolysis fuel oil (PFO), the by-product of naphtha cracking process, has been used as a low valued fuel oil as a heating source due to high content of polyaromatic hydrocarbon
This result implies that the mesopore reduces the coke formation due to the enhanced accessibility of large aromatics towards active sites, resulting in a promotion of the hydrocracking activity
Catalyst exhibited higher BTX yield than the Ni2P/β catalyst at the same reaction conditions in. These results indicate that the catalytic activity for hydrocracking of polycyclic aromatics depends on presence of 3-ring polycyclic aromatics
Summary
Pyrolysis fuel oil (PFO), the by-product of naphtha cracking process, has been used as a low valued fuel oil as a heating source due to high content of polyaromatic hydrocarbon. NiMo/USY and NiW/USY catalysts exhibit good activity in hydrocracking reactions, but require high temperatures of around 773–1073 K and H2 pressures of around 8.0–15.0 MPa. Besides, the catalysts tend to undergo rapid deactivation by coke formation on the strong acid sites in the zeolite [11,12,13,14]. Our recent studies revealed that a Ni2 P supported on zeolite β shows a good activity in the hydrocracking of naphthalene and 1-methyl naphthalene at 673 K and 3.0–5.5 MPa [29,30], in which a bifunctional catalytic activity and inter-particulate porosity contribute to the high conversion. Catalysts 2020, 10, 47 larger-sized polycyclic hydrocarbons in real feedstock, like pyrolysis fuel oils, the microporosity of zeolites can limit the diffusion of the molecules, causing coke formation. Pyrolysis fuel oils as a real feedstock were used in the feed for hydrocracking (HCK) over the Ni2 P/DS-β
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