3 research outputs found
Postsynthesis and Effective Baeyer–Villiger Oxidation Properties of Hierarchical FAU-type Stannosilicate
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.)
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
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