Thermal Decomposition of Carbon Precursors in Decorated AFI Zeolite Crystals

Abstract

Mass spectrometry and thermogravimetric analysis are used to explore the thermal decomposition of carbon precursors (primarily the tripropylammonium cations) occluded within AlPO(4)-5 (AFI) crystals prepared in various media (in the presence or absence of F(-) ions, Si(4+) substations of P(5+)), with the aim to fabricate high-density 0.4-nm single-walled carbon nanotubes (SWNTs). It has been found that the tripropylammonium precursors exist in the as-synthesized crystals in three different forms: tripropylammonium fluoride, hydroxide, and tripropylammonium cation compensating for the negative charge of the framework. The latter is bonded to the framework by strong chemical interaction and its decomposition takes place by a series of beta-elimination reactions to give propylene and ammonia, with the stepwise formation of dipropylammonium and n-propylammonium cations. The 0.4-nm SWNTs filling density was found to be higher than that resulting from the carbon precursor of tripropylammonium fluoride and hydroxide, because of the strong adsorption force of the channel walls to pyrolysate, as evidenced by the clear and strong radial breathing modes in Raman spectra.

Two kinds of graphene-based composites for photoanode applying in dye-sensitized solar cell

“…After careful observation the patterns of the GSCT and GTNTs, obvious distinction of the low-frequency region implies the different interaction between the graphene-SCT and grapheneTNTs. The similar profile in the low-frequency range of the SCT and GSCT suggests physical interaction between the graphene and SCT (LBL self-assembly process is based on electrostatic force in this case), while the broadening peak of the GTNTs indicates the formation of chemical bond between the graphene and TNTs during the hydrothermal reaction [20].…”

“…Synthesis process of the GTNTs is shown as Scheme 1a, and the details (including fabricating pure TNTs) are according to our recent work [20].…”

“…The detailed characterizations including XPS, XRD, FTIR, UVevis diffuse reflectance spectra of the GTNTs have been done in elsewhere [20].…”

Intergrowth Structure of Zeolite Crystals as Determined by Optical and Fluorescence Microscopy of the Template‐Removal Process

“…To accomplish this, zeolites are calcined after synthesis to remove the template and allow reactant molecules to enter the channel system. Thermal decomposition of template molecules in different molecular sieves has been studied extensively mainly by thermoanalytical techniques, [16,17] mass spectrometry, [18,19] and NMR spectroscopy. [20] These methods are bulk techniques, which average information over the whole catalyst sample.…”

Aligned High Density Semi‐Conductive Ultra‐Small Single‐Walled Carbon Nanotubes

“…The carbon nanotubes were formed by pyrolysis between 450 °C and 800 °C of the organic template used in the synthesis of AlPO‐5. The process was optimized by using different organic templates and pyrolysis conditions . The sample obtained at 800 °C showed the best performance and was selected for more detailed analysis.…”