Surface chemical modification of zeolites and their catalytic performance for naphthalene alkylation

Zeolites β, Y and mordenite are modified with organic and inorganic cupric salts using a liquid phase deposit method, and their catalytic performance and the dispersion states of copper on the zeolites are characterized by using naphthalene isopropylation reaction and ¹²⁹Xe NMR, respectively. The experimental results indicate that naphthalene conversion on the catalysts decreases in the order of HY>H β >HMCM-22>HM. The performance of the zeolites has been largely improved after the modification. Naphthalene conversion rate reaches 97% and 60%, and ββ ∼-selectivity 66% and 70% for CuHY and CuH β, respectively. Metal surfactants, such as hexanoic and octanoic copper, play a positive role in modifying the external surface and pore structure of zeolitesβ and Y. ¹²⁹ Xe NMR results demonstrate that the two types of the pore channels in CuH β are unimpeded for xenon atoms, and there is a fast chemical exchange between two xenon atoms located in different adsorption sites; Cu²⁺ ion is a strong adsorption site for xenon atoms and it is a strong active center as well; Cu²⁺ and Cu⁺+ ions coexist in channels of zeolites, which are in agreement with the conclusions from ab iniiio quantum chemical calculations.