3 research outputs found

    Postsynthesis and Effective Baeyer–Villiger Oxidation Properties of Hierarchical FAU-type Stannosilicate

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    Sn–Y zeolite, with hierarchical pore systems and extremely low Al content, was successfully prepared via a convenient postsynthetic route which involves proper predealumination and subsequent (NH<sub>4</sub>)<sub>2</sub>SnCl<sub>6</sub> treatment under mild aqueous condition. The Sn ions were incorporated into the framework of properly dealuminated Y zeolite through reacting with the defect sites generated in the industrial steaming treatment, the first-step acid treatment, and the second Sn incorporation process under acidic conditions. The acidic medium achieved by adding HCl in the Sn incorporation process affected not only the amount of incorporated Sn and residual Al but also the coordination state of inserted Sn ions. Compared with hydrothermally synthesized Sn-Beta, postsynthesized Sn–Y zeolite exhibited outstanding catalytic performances in the Baeyer–Villiger oxidation reactions of ketones especially when bulky <i>tert</i>-butyl hydroperoxide was employed as the oxidant due to an open pore structure of 3-dimensional 12-membered ring (12-MR) channels of FAU topology as well as the dealumination-derived intracrystal mesoporosity. Moreover, alkali metal ions modification was shown to be an effective approach for enhancing the selectivity of lactones

    Anthocyanin Accumulation and Molecular Analysis of Correlated Genes in Purple Kohlrabi (Brassica oleracea var. <i>gongylodes</i> L.)

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    Kohlrabi (Brassica oleracea var. <i>gongylodes</i> L.) is an important dietary vegetable cultivated and consumed widely for the round swollen stem. Purple kohlrabi shows abundant anthocyanin accumulation in the leaf and swollen stem. Here, different kinds of anthocyanins were separated and identified from the purple kohlrabi cultivar (Kolibri) by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry. In order to study the molecular mechanism of anthocyanin biosynthesis in purple kohlrabi, the expression of anthocyanin biosynthetic genes and regulatory genes in purple kohlrabi and a green cultivar (Winner) was examined by quantitative PCR. In comparison with the colorless parts in the two cultivars, most of the anthocyanin biosynthetic genes and two transcription factors were drastically upregulated in the purple tissues. To study the effects of light shed on the anthocyanin accumulation of kohlrabi, total anthocyanin contents and transcripts of associated genes were analyzed in sprouts of both cultivars grown under light and dark conditions

    Bolaform Molecules Directing Intergrown Zeolites

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    Understanding of epitaxial and rotational intergrowth is particularly important for the design and synthesis of hierarchically structured zeolites. Herein, we propose a new route for fabricating hierarchical MTW- and MFI-type zeolites with intergrown structures by tuning the methylene chain lengths between the two N-heterocycles in bolaform quaternary ammonium structure-directing agents (SDAs). MTW-type zeolites with 66.4° rotational intergrowth and MFI-type zeolites with 90° rotational intergrowth were synthesized with methylene chain lengths of 4–6 and 7–9, respectively. A possible theoretical evidence of the geometrical match between SDAs and zeolite structures was proposed by the binding energy obtained by molecular mechanics calculations. It is speculated that the bolaform SDAs are located in the straight 12-membered ring (MR) channels along the <i>b</i> direction of MTW topology, directing the intergrown structure by sharing the (310) plane. The bolaform SDAs located in the intersections of straight 10-MR channels and sinusoidal 10-MR channels of MFI topology directed the intergrown structure by sharing the (010) plane. The hierarchical zeolite catalysts prepared using this strategy, characteristic of hybrid micro- and mesoporosities, proved to be useful for tandem cracking reactions involving bulky molecules
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