Discovery of new MWW family zeolite EMM-10: Identification of EMM-10P as the missing MWW precursor with disordered layers

We the report discovery of zeolite EMM-10, a new member of the MWW family, and its layered zeolite precursor, EMM-10P. The latter is closely related to the layered precursor MCM-22P but its layers are stacked without vertical alignment. The layers are believed to be twisted off-register or otherwise disordered in-plane but still hydrogen bonded through silanols. The proposed structural disorder is concluded from the X-ray powder diffraction pattern, which is very similar to that of MCM-22P but lacks the discrete interlayer reflections, especially (1 0 1) and (1 0 2). EMM-10P complements the series of three distinct, as-synthesized MWW materials, viz: MCM-22P, MCM-49 and MCM-56, all differing in packing of the MCM-22 monolayers. The EMM-10P precursor was synthesized using a diquaternary ammonium template while the preceding three materials were obtained with hexamethyleneimine as the structure directing agent. Upon calcination EMM-10P partially converts to an ordered MWW structure but, to a large extent, the stacking disorder persists while the layers fuse together. Basic characterization including sorption, electron diffraction, electron microscopy, NMR, and swellability with surfactants, reveals properties similar to MCM-22. EMM-10, therefore, represents a further extension of the already uniquely diverse MCM-22 zeolite family, and corresponds to an anticipated structure variation. It has also broader fundamental implications, illustrating the growing contribution of disordered structures among zeolites and the need for better characterization tools and methods.

EMM-10P – ‘missing’ disordered analogue of layered zeolite precursor MCM-22P.Figure optionsDownload as PowerPoint slideResearch highlights
► New precursor with disorder in stacking of H-bonded MWW layers is synthesized.
► Complements MCM-22P/MCM-22 pair as previously missing member of the MCM-22 family.
► 4th distinct material crystallized with MWW structure.
► Detailed structural characterization by electron diffraction and multi-nuclear NMR.