Study of the products of melamine (C3N6H6) treated at high pressure and high temperature

Yao, Liming; Li, F. Y.; Li, J. X.; Jin, Chunming; Yu, Richeng

doi:10.1002/pssa.200421177

Cited by 20 publications

(12 citation statements)

References 26 publications

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“…According to literature reports on the thermal decomposition of melamine under conventional heating conditions A C H T U N G T R E N N U N G ( 300 8C), melamine would become a linear branching or cyclic condensate with release of ammonia. [31,34,35] This thermal decomposition process is clearly different to that of COA C H T U N G T R E N N U N G (NH 2 ) 2 . Indeed, for the TGA curve of melamine (C 3 H 6 N 6 ), only one decomposition process is observed (see Figure 4 II), suggesting that melamine quickly condenses and sublimates completely under rapid heating.…”

Section: Resultsmentioning

confidence: 89%

Urea as a New and Cheap Nitrogen Source for the Synthesis of Metal Nitride Clusterfullerenes: The Role of Decomposed Products on the Selectivity of Fullerenes

Jiao

Zhang

et al. 2012

Chemistry A European J

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By using urea as the new nitrogen source, for the first time, Sc-based metal nitride clusterfullerenes (NCFs), Sc(3)N@C(2n) (2n=80, 78, 70, 68), have been synthesized successfully. The optimum molar ratio of Sc(2)O(3)/CO(NH(2))(2)/C for the synthesis of Sc NCFs is 1:3:15. The yield of Sc(3)N@C(80)(I(h) +D(5h)) per gram of Sc(2)O(3), using CO(NH(2))(2) as the new nitrogen source, was quantitatively compared to those obtained when using the reported nitrogen sources, including N(2), NH(3), and guanidinium thiocyanate. We find that there is a clear difference on the selectivity of Sc-based NCFs within the extract mixture obtained from one rod and accumulative two rods. According to discharging experiments and XRD analysis, we conclude that NH(3) generated in situ from the decomposition of CO(NH(2))(2) is mainly responsible for the formation of Sc-based NCFs when using only one rod, whereas in the second rod CO(NH(2))(2) would decompose into melamine during discharging of the first rod. Thus, the selectivity of fullerenes is clearly dependent on the decomposed product of CO(NH(2))(2). Finally the difference in the decomposition behavior of CO(NH(2))(2) and melamine was studied in detail and a possible decomposition process of CO(NH(2))(2) during discharging was proposed. Accordingly, the difference in the selectivity and yield of Sc NCFs for CO(NH(2))(2) and melamine was interpreted.

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Section: Resultsmentioning

confidence: 89%

Urea as a New and Cheap Nitrogen Source for the Synthesis of Metal Nitride Clusterfullerenes: The Role of Decomposed Products on the Selectivity of Fullerenes

Jiao

Zhang

et al. 2012

Chemistry A European J

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“…Montigaud et al [9] demonstrated that pyrolysis of melamine at 2.5 GPa and 800 • C in presence of hydrazine leads to formation of a bi-dimensional honeycomb-type structure close to those expected for the theoretical graphitic-like g-C 3 N 4 . Similar syntheses successfully producing g-C 3 N 4 and closely related byproducts utilizing pure melamine have also been achieved [8,10]. Synthesis of C-N nanotubes was also observed in high-pressure catalytic pyrolysis of melamine with NaN 3 -Fe-Ni at 35 MPa and 650 • C [11].…”

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confidence: 67%

Evolution of Interatomic and Intermolecular Interactions and Polymorphism of Melamine at High Pressure

2018

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Melamine (C 3 H 6 N 6 ; 1,3,5-triazine-2,4,6-triamine) is an aromatic substituted s-triazine, with carbon and nitrogen atoms forming the ring body, and amino groups bonded to each carbon. Melamine is widely used to produce laminate products, adhesives, and flame retardants, but is also similar chemically and structurally to many energetic materials, including TATB (2,4,6-triamino-1,3,5trinitrobenzene) and RDX (1,3,3,. Additionally, melamine may be a precursor in the synthesis of superhard carbon-nitrides, such as β-C 3 N 4 . In the crystalline state melamine forms corrugated sheets of individual molecules, which are stacked on top of one another, and linked by intra-and inter-plane N-H hydrogen bonds. Several previous high-pressure X-ray diffraction and Raman spectroscopy studies have claimed that melamine undergoes two or more phase transformations below 25 GPa. Our results show no indication of previously reported low pressure polymorphism up to approximately 30 GPa. High-pressure crystal structure refinements demonstrate that the individual molecular units of melamine are remarkably rigid, and their geometry changes very little despite volume decrease by almost a factor of two at 30 GPa and major re-arrangements of the intermolecular interactions, as seen through the Hirshfeld surface analysis. A symmetry change from monoclinic to triclinic, indicated by both dramatic changes in diffraction pattern, as well as discontinuities in the vibration mode behavior, was observed above approximately 36 GPa in helium and 30 GPa in neon pressure media. Examination of the hydrogen bonding behavior in melamine's structure will allow its improved utilization as a chemical feedstock and analog for related energetic compounds. Crystals 2018, 8, 265 2 of 20stacked on top of one another. When used as a salt or mixed with resins, melamine is an effective fire retardant, in part due to the release of flame-smothering nitrogen gas when burned [2]. When combined with formaldehyde, melamine forms a very durable thermosetting plastic used in a broad variety of kitchenware and household goods [3]. Despite its stability and flame-retardant properties, melamine is also very closely related, both structurally and chemically, to the widely used molecular explosives RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), TATB (2,4,6-triamino-1,3,5-trinitrobenzene), and to 2,4,6-trinitro-1,3,5-triazine, a hypothetical new explosive [4] which has not yet been successfully synthesized [5,6]. As a curiously stable cousin of these explosives, melamine is a worthwhile target of investigation in the search for new energetic materials with enhanced safety and stability while maintaining sufficient explosive potential [7].The primary motivation for studying the high-pressure behavior of melamine ultimately stems from its intermediate position between energetic species and ultra-hard materials; for instance, melamine may be a functional precursor for synthesis of a hypothetical β-C 3 N 4 phase, with a β-Si 3 N 4 structure, predicted to be a super-hard materia...

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“…46 No g-C 3 N 4 material, which has a relatively strong ~1320 cm -1 band, was formed either. [3][4][5][6] We also investigated thermal decomposition of melamine on TiO 2 in the closed cell with 5 Torr of O 2 initially. The infrared spectral result is shown in Figure S4.…”

Section: Cyanamide Dicyandiamide and Cyanuric Acid On Tiomentioning

confidence: 99%

“…C 3 N 4 . [3][4][5][6][7] As shown in Scheme 1a, melamine can be prepared by mildly heating cyanamide (H 2 N-C≡N) or dicyandiamide ((H 2 N) 2 C=N-C≡N). 8,9 However, upon thermal treatment at a temperature higher than 300 o C, melamine starts to predominantly undergo deamination, instead of ring-breaking process.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Thermal and Photochemical Reaction Pathways of Melamine on TiO₂

Lin

Chien

et al. 2015

J. Phys. Chem. C

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Fourier transform infrared spectroscopy was employed to study the thermal and photochemical reactions of melamine ((H 2 N) 3 (C 3 N 3 )) on TiO 2. Also tested was the adsorption of urea, cyanamide (H 2 N-C≡N), dicyandiamide ((H 2 N) 2 C=N-C≡N) and cyanuric acid ((OH) 3 (C 3 N 3 )) for identifying possible reaction intermediates. It was found that the thermal decomposition of melamine starts with N-H bond scission, possibly forming the intermediates such as (H 2 N) 2 (C 3 N 3 )NH-and (H 2 N)(C 3 N 3 ) (NH) 2 -. Further loss of hydrogen atoms and ring-opening from these intermediates lead to the formation of -NCO (isocyanate) and -N 3 (azide) on the surface. The TiO 2 -mediated photochemical reaction of melamine proceeds via different mechanism, forming dicyandiamide. These thermal and photochemical reaction pathways of melamine on TiO 2 are reported for the first time. They are different from previous studies showing the processes of polymerization, and substitution of NH 2 by OH to form cyanuric acid and urea.

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Study of the products of melamine (C₃N₆H₆) treated at high pressure and high temperature

Cited by 20 publications

References 26 publications

Urea as a New and Cheap Nitrogen Source for the Synthesis of Metal Nitride Clusterfullerenes: The Role of Decomposed Products on the Selectivity of Fullerenes

Urea as a New and Cheap Nitrogen Source for the Synthesis of Metal Nitride Clusterfullerenes: The Role of Decomposed Products on the Selectivity of Fullerenes

Evolution of Interatomic and Intermolecular Interactions and Polymorphism of Melamine at High Pressure

Comparison of the Thermal and Photochemical Reaction Pathways of Melamine on TiO₂

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Study of the products of melamine (C3N6H6) treated at high pressure and high temperature

Cited by 20 publications

References 26 publications

Urea as a New and Cheap Nitrogen Source for the Synthesis of Metal Nitride Clusterfullerenes: The Role of Decomposed Products on the Selectivity of Fullerenes

Urea as a New and Cheap Nitrogen Source for the Synthesis of Metal Nitride Clusterfullerenes: The Role of Decomposed Products on the Selectivity of Fullerenes

Evolution of Interatomic and Intermolecular Interactions and Polymorphism of Melamine at High Pressure

Comparison of the Thermal and Photochemical Reaction Pathways of Melamine on TiO2

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Study of the products of melamine (C₃N₆H₆) treated at high pressure and high temperature

Comparison of the Thermal and Photochemical Reaction Pathways of Melamine on TiO₂