Steam-assisted transformation of natural kaolin to hierarchical ZSM-11 using tetrabutylphosphonium hydroxide as structure-directing agent: synthesis, structural characterization and catalytic performance in the methanol-to-aromatics reaction

Transforming natural kaolin into pure-phase hierarchical aggregates of nano ZSM-11 has been achieved by using a novel tetrabutylphosphonium hydroxide as a structure-directing agent via steam-assisted crystallization. The hierarchical ZSM-11 possesses a small particle size (about 240 nm), large surface area (428 m2 g−1), and abundant mesopores (0.30 cm3 g−1). Moreover, the hierarchical ZSM-11 exhibits prolonged catalytic lifetime and promoted aromatic selectivity in the methanol-to-aromatics reaction. The superior catalyst stability is attributed to the better capacity of accommodating the coke and a lowered coking rate.