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

Zeolitesβ, 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＞Hβ＞HMCM-22＞HM. The performance of the zeolites has been largely improved after the modification. Naphthalene conversion rate reaches 97% and 60%, andβ,β′-selectivity 66% and 70% for CuHY and CuH?, 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. 129Xe NMR results demonstrate that the two types of the pore channels in CuHβ 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 initio quantum chemical calculations.