CrOx modified particles size and electronic density of Ni catalyst on ZSM-23 for enhanced hydroisomerization performance of long-chain n-alkanes

Abstract

CrOx-doped Ni catalysts with different Ni/Cr mass ratios on ZSM-23 (NimCrn/ZSM-23) were synthesized using a simple initial wet impregnation method. The influence of CrOx on Ni in the NimCrn/ZSM-23 catalysts was investigated by combining XPS, IR-CO, H2-TPR, TEM, and EDX mapping. The obtained results suggested that an intimate contact was formed between Ni and CrOx in the catalysts. The CrOx-modified NiOx species strongly interacted with ZSM-23, facilitating the formation of small sized Ni nanoparticles. Meanwhile, the electronic density around Ni on the catalyst was increased due to the presence of adjacent CrOx. The reaction rate and TOFs over Ni2.0Cr2.0/ZSM-23 (1.13 × 10-2 mol•g-1•h−1 and 6.8 × 10-2 s−1) are much higher than over Ni2.0/ZSM-23 (0.88 × 10-2 mol•g-1•h−1 and 6.2 × 10-2 s−1) in the n-hexadecane hydroisomerization, illustrating the promotion of CrOx in the Ni-based catalyst. The Ni2.0Cr2.0/ZSM-23 catalyst exhibited the highest iso-hexadecanes yield of 82.9 %, as compared to Pt/ZSM-23 catalyst (78.9 %).