Preparation, characterization and catalytic properties of Ti-rich Ti-YNU-1

Ti-rich Ti-YNU-1 has been successfully prepared by using acid-treated Fe-YNU-1 as silica source. Its Ti/Si molar ratio was increased from 0.0065 maximally achieved by the conventional method (Appl. Catal. A (2011), 401, 37–45) to 0.012. The diffuse reflectance UV–vis spectroscopy reveals that most of Ti species had a tetrahedral coordination. This is further substantiated by the presence of a broad band at 930 cm−1, which is characteristic for the incorporation of Ti in the framework. As a result, the prepared Ti-rich Ti-YNU-1 gave considerably higher conversions of both 1-hexene and cyclohexene than the sample prepared by the conventional method. Nevertheless, the increase degree of 1-hexene conversion was much higher than that of cyclohexene conversion with increasing Ti content, suggesting that most of additional Ti species were incorporated into the intralayer sinusoidal 10-membered ring channels, while a few was inserted into the interlayer supercages. Removal of most of occluded templating molecules and framework Fe species or Ti species from the postsynthesized lamellar Fe- or Ti-MWW precursor by acid treatment is necessary for the formation of Fe- or Ti-YNU-1.

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► Ti-rich Ti-YNU-1 was prepared using highly acid-treated Fe-YNU-1 as silica source.
► Ti-rich YNU-1 shows high activity for the oxidation of both linear and bulky alkenes.
► Removal of most of templating and metal species by acid treatment is necessary for forming YNU-1.
► Postsynthesis conditions of the lamellar precursor influence the formation of YNU-1.