Synthesis, Modification, and Consequence of MCM‐22 Zeolite From a Mother Liquor Recycling Procedure for Methanol to Olefins Reaction

ABSTRACT Here, MCM‐22 zeolites were synthesized by a hydrothermal synthesis method using a mother liquor recycling procedure, in which the use of organic templates was greatly reduced with a molar ratio of template to SiO 2 at 0.15 in the zeolite gel precursors. The as‐prepared MCM‐22 zeolites show high crystallinity and flake‐like morphology with a thickness below 100 nm, possessing a high specific surface area of approximately 470 m 2 /g and substantial mesoporous volume of 0.49 cm 3 /g. The oxalic acid treatment was applied to adjust the textural properties of MCM‐22 zeolite as well as the acid sites concentration from 0.43 to 0.22 mmol/g. The selective extraction of extra‐framework aluminum via oxalic acid treatment leads to an increase in the ratio of Brønsted acid site amount to Lewis acid site amount (B/L ratio) from 0.59 to 1. The as‐modified MCM‐22 zeolite shows an enhanced propylene selectivity (44.7%) relative to the MCM‐22 zeolite (35.6%). The eco‐friendly synthesis strategy combined with an effective acid modification method is anticipated to expand the application of MCM‐22 zeolite for designing high‐performance catalysts for methanol to olefins (MTO) reaction.