Directing gel: An effective method tailoring morphology of MWW zeolites and their catalytic performance in liquid-phase alkylation of benzene with ethylene

• Directing gel was obtained at the end of induction period.
• Directing gel showed regular shape but no typical diffraction peaks of MWW zeolites.
• Directing gel samples presented irregular MWW sheets packed in disorder.
• HMI/SiO2 of directing gel is the key to increase the number of Brønsted acid sites.
• The ethylene conversion was increased without obvious loss of EB selectivity.

The directing gel method was developed to tailor morphology, textural property, acidity and catalytic performance of MWW catalysts. Directing gel was defined as large amounts of crystal precursors without any typical diffraction peaks corresponding to MWW zeolites. The synthesis of directing gel was stopped at the end of induction period, and then additional materials were added to further crystallization. Via directing gel method, not only did the final MWW zeolites possess high crystallinity, but also the morphology were remarkably changed into irregular MWW sheets packed in disorder, which was completely different from rose-like shape of the reference MCM-22 via conventional hydrothermal synthesis. Besides morphology tailoring, the textural property (esp. external surface area and pore volumes) and acid sites of final MWW zeolites were also improved. The increases of ethylene conversion of directing gel catalysts were attributed to the better accessibility of active centers jointly induced by their morphology, textural property and acidity.

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