Trimodal Porous Hierarchical SSZ-13 Zeolite with Improved Catalytic Performance in the Methanol-to-Olefins Reaction

Chabazite zeolites with trimodal porosity (native micropores of the CHA framework, an additional network of larger micropores of similar to 0.5 nm, and mesopores) were synthesized by adding diquarternary ammonium type surfactant C22-4-4 cations and fluoride anions in the synthesis of SSZ-13 zeolite. The hierarchical SSZ-13 zeolites are fully crystalline and exhibit similar acidity as bulk SSZ-13 zeolite. The increased diffusion rate in the hierarchical SSZ-13, proven by uptake experiments of bulky molecules and selective staining by thiophene oligomers, resulted in much slower catalyst deactivation in the methanol-to-olefins (MTO) reaction. Confocal fluorescent images of spent hierarchical SSZ-13 zeolites reveal homogeneous distribution of carbonaceous deposits, indicating that the micropore space has been completely utilized during the MTO reaction.