Abstract
Zeolite Cs-ABW nanocatalyst has been hydrothermally synthesized without using any harmful organic template. The zeolite nanocrystal with very high solid yield (81.88%) can be obtained within 60 min and at 180 $^{\circ}$C (∼ 20 atm), conditions that are much faster and gentler than the existing synthesis methods. The orthorhombic Cs-ABW nanocrystals (mean size of 32 nm) have high aluminum content (Si/Al ratio $=$ 1.14) and possess high basicity. The nanocrystals also exhibit better catalytic activity than conventional homogeneous catalysts in the Henry (nitroaldol) reaction of benzaldehyde with nitroethane under microwave heating conditions. The nanocatalyst does not suffer from coking and leaching problems. It can be reused without loss of reactivity even after five consecutive runs under the described reaction conditions.
Highlights
The Henry or nitroaldol reaction is one of the famous coupling reactions in organic chemistry to incorporate an alkylnitro group into a carbonyl compound. 1 It is a versatile reaction for synthesizing a variety of useful fine chemicals and pharmaceutical intermediates. 2 Essentially, the Henry reaction is made possible only in the presence of a base catalyst
Synthesis of Cs-ABW zeolite nanocrystals Nanocrystalline Cs-ABW zeolite has been synthesized via hydrothermal treatment at 180 ?C
The HT-10m solid was amorphous according to X-ray diffraction (XRD) results (Figure 1a)
Summary
The Henry or nitroaldol reaction is one of the famous coupling reactions in organic chemistry to incorporate an alkylnitro group into a carbonyl compound. 1 It is a versatile reaction for synthesizing a variety of useful fine chemicals and pharmaceutical intermediates. 2 Essentially, the Henry reaction is made possible only in the presence of a base catalyst. 2 Essentially, the Henry reaction is made possible only in the presence of a base catalyst. Homogeneous catalysts such as NaOH, KOH, Na 2 CO 3 , pyridine, and amines are known to display unique catalytic performances in various reactions. 8,9 Very recently, we successfully studied the nucleation and crystal growth of Cs-ABW zeolite nanocrystals in an organic-template-free hydrosol system using microscopy and spectroscopy techniques. In the present study, nanosized Cs-ABW zeolite is crystallized under rapid and safer hydrothermal conditions using an organotemplate-free system. Characterization and catalytic performance of the synthesized Cs-ABW in the Henry reaction of benzaldehyde with nitroethane are reported
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