The effect of K and acidity of NiW-loaded HY zeolite catalyst for selective ring opening of 1-methylnaphthalene

Bi-functional catalysts were prepared using HY zeolites with various SiO₂/Al₂O₃ ratios for acidic function, NiW for metallic function, and K for acidity control. 1-Methylnaphthalene was selected as a model compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction was investigated using the prepared bi-functional catalysts with different levels of acidity in a fixed bed reactor system. In NiW/HY catalysts without K addition, the acidity decreased with the SiO₂/Al₂O₃ mole ratio of the HY zeolite. Ni_1.1 W_1.1/HY(12) catalyst showed the highest acidity but slightly lower yields for the selective ring opening than Ni_1.1W_1.1/HY(30) catalyst. The acidity of the catalyst seemed to play an important role as the active site for the selective ring opening of 1-methylnaphthalene but there should be some optimum catalyst acidity for the reaction. Catalyst acidity could be controlled between Ni_1.1W_1.1/HY(12) and Ni_1.1W_1.1/HY(30) by adding a moderate amount of K to Ni_1.1W_1.1/HY(12) catalyst. K_0.3Ni_1.1W_1.1/HY(12) catalyst should have the optimum acidity for the selective ring opening. The addition of a moderate amount of K to the NiW/HY catalyst must improve the catalytic performance due to the optimization of catalyst acidity.