Selective hydrocracking of poly-aromatics to mono-aromatics in a catalyst grading system of NiMo/Al2O3-HY and NiMo/Beta

Selective hydrocracking of poly-aromatic hydrocarbons (PAHs) to mono-aromatic hydrocarbons (MAHs) over zeolite-supported non-noble metal catalysts is an effective way to upgrade light cycle oil (LCO). However, it is still a challenge to increase the yield of MAHs. Herein, we report that a catalyst grading system consisting of NiMo/A30Y50 (upper catalyst layer) and NiMo/Beta(25) (lower catalyst layer) can efficiently convert 1-methylnaphthalene (1-MN, representative of PAHs in LCO) into MAHs. Experimental and characterization studies reveal that NiMo/Beta(25) can facilitate the conversion of intermediates of 1-MN hydrocracking (mainly methyl tetralins and indanes) into MAHs, mainly due to its good textural property, high Brønsted acidity and high MoS2 dispersion. Under the experimental condition of 400 °C, 6 MPa, H2/1-MN molar ratio = 6 and weight hourly space velocity of 1-MN (WHSV) = 1 h−1, the NiMo/A30Y50 – NiMo/Beta(25) catalyst grading system can realize 99.9% conversion of 1-MN and 63.8% selectivity of MAHs, which outperforms the performance of most catalysts reported in the literature. Moreover, even if the presence of NH3 in the reaction system, this catalyst grading system can give rise to 98.3% conversion of 1-MN and 52.7% selectivity of MAHs at 420 °C, 6 MPa, H2/1-MN molar ratio = 6 and WHSV = 1 h−1. The findings of this study offer new opportunities for the valorization of LCO.