Effect of citric acid addition on the morphology and activity of Ni2P supported on mesoporous zeolite ZSM-5 for the hydrogenation of 4,6-DMDBT and phenanthrene

- Small and highly dispersed Ni2P nanoparticles on MZSM-5 were prepared by adding citric acid (CA).
- The mechanism of formation of small Ni2P particles with CA assistance was investigated.
- Small Ni2P particles on MZSM-5 exhibit high hydrogenation activity.

Preparing small, highly dispersed Ni2P particles is important for improving the hydrogenation ability of Ni2P. Here, Ni2P nanoparticles (approximately 4.3 nm) on mesoporous zeolite ZSM-5 (Ni2P/MZSM-5-CA) were prepared using citric acid (CA) as an assistant agent. The formation mechanism of small Ni2P particles when CA was added was investigated by combining UV-vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and temperature-programmed reduction with a transmission electron microscope and CO chemisorption. The results indicated that the formed CA-Ni complex with high viscosity favors the Ni precursor dispersed on the dried catalyst. After calcination, the released Ni species strongly interacted with surface acidic hydroxyl groups on MZSM-5, leading to the formation of Ni2P particles with small sizes and good dispersion under a reducing atmosphere. The reaction rate constants and TOFs over Ni2P/MZSM-5-CA (16.2 × 10−2 μmol g−1 s−1 and 9.7 × 10−4 s−1) are much higher than over Ni2P/MZSM-5 (8.2 × 10−2 μmol g−1 s−1 and 8.3 × 10−4 s−1) in 4,6-dimethyldibenzothiophene hydrodesulfurization. In addition, Ni2P/MZSM-5-CA catalyst shows higher activity than Ni2P catalyst without CA in phenanthrene hydrogenation.

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