N-methyl-2-pyrrolidone-induced conversion of USY into hollow Beta zeolite and its application in the alkylation of benzene with isobutylene

A new synthetic protocol of hollow structured Beta zeolite via interzeolite conversion with the assistance of N-methyl-2-pyrrolidone (NMP) was reported in this work. The synthesis conditions were optimized to obtain the pure and hollow Beta zeolite from the USY zeolite. In comparison, the solid Beta zeolite with low yield was obtained in the absence of NMP. The important factors in successful synthesis of hollow Beta zeolite were the usage of USY zeolite and the addition of NMP. On the basis of the characterization data, such as XRD, SEM, TEM, and Si-29/Al-27 MAS NMR, a formation mechanism for the synthesis of hollow Beta zeolite from USY was proposed and discussed. The silicon species in the parent USY crystals dissolved firstly, afterwards the primary solid Beta crystals with high SiO2/Al2O3 molar ratio were generated at the earlier stage, finally, the hollow Beta zeolite was formed due to the dissolution-recrystallization of the crystalline nutriments located in the core of the primary solid Beta crystals as well as the consumption of USY. The catalytic performance of alkylation of benzene with isobutylene demonstrated that the obtained hollow Beta catalyst exhibited excellent isobutylene conversion and tert-butylbenzene selectivity against the solid Beta synthesized from an amorphous silica/alumina.