Vibrational infrared spectra of biuret and its thioanalogs. An ab initio SCF/3-21G study

Sullivan, Richard H.; Kwiatkowski, Józef S.; Leszczyński, Jerzy; Jabalameli, Ali

doi:10.1016/0022-2860(93)85018-p

Cited by 11 publications

(19 citation statements)

References 24 publications

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“…The most prominent ATR‐IR features are interpreted as follows: 3050 cm −1 ((HNCO) 3 , ν (NH)), 1045 cm −1 ((HNCO) 3 , ring stretch), 1335 cm −1 (C 2 H 5 N 3 O 2 , ν (CN)), 1410 cm −1 (C 2 H 5 N 3 O 2 , ν (CN)), 1570 cm −1 (C 2 H 5 N 3 O 2 , δ (NH 2 )), 3200 cm −1 (C 2 H 5 N 3 O 2 , ν (NH)), 3400 cm −1 (C 2 H 5 N 3 O 2 , ν (NH)), 1455 cm −1 (CH 4 N 2 O, ν (CN)), 3335 cm −1 (CH 4 N 2 O, ν (NH)); the band at 1685 cm −1 is assumed to result from overlapping features of the three substances . Behind the catalyst only very little deposits were found with 58 % cyanuric acid and 42 % biuret as deduced from HPLC.…”

Section: Resultsmentioning

confidence: 99%

Urea Decomposition in Selective Catalytic Reduction on V₂O₅/WO₃/TiO₂ Catalyst in Diesel Exhaust

et al. 2017

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Selective catalytic reduction (SCR) of NO x by AdBlue and NH3 on monolithic V 2 O 5 /WO 3 /TiO 2 catalyst was studied under flow conditions realistic for diesel exhaust. The tests provided same standard and fast SCR for AdBlue and NH 3 from 150 to 350°C. For standard urea-SCR, axial concentration profiles were checked by monoliths with different lengths evidencing incomplete conversion of urea and isocyanic acid at low temperatures. But SCR was not clearly affected by under-stoichiometric NH 3 as substantiated by kinetic analysis. However, above 250°C, SCR was limited by internal mass transport indicated by Weisz-Prater criterion and lower activation barrier. Formation of deposits was investigated at 175°C and below showing some urea around the nozzle, whereas cyanuric acid and biuret additionally formed around the catalyst.

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Section: Resultsmentioning

confidence: 99%

Urea Decomposition in Selective Catalytic Reduction on V₂O₅/WO₃/TiO₂ Catalyst in Diesel Exhaust

et al. 2017

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“…These atomic motions that dominate in these most are CO stretching and the bending and scissoring motions of the NH and NH 2 groups. 26 In particular, the stretching of the CO groups is likely the main contribution to the new peak that appears at 1780 cm −1 after 20 GPa. The strong peaks between 1500 and 1600 cm −1 are most likely dominated by NH scissoring, bending, CO stretching, and C−N stretching.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

“…Two peaks around 430 and 450 cm –1 appear as two singlets at low pressures, but broaden considerably between 3.3 and 7.8 GPa. These peaks correspond to CO bending, NCN, and N–C stretching and possibly to NH 2 wagging and torsions …”

Section: Resultsmentioning

confidence: 99%

Hydrogen-Bonding Modification in Biuret Under Pressure

Borstad

2017

J. Phys. Chem. A

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Biuret (CHNO) has been studied to 30 GPa by Raman spectroscopy and 50 GPa by X-ray diffraction. Raman peaks exhibit shoulders and splitting that suggests that the molecules undergo reorientation in response to compression. These are observed in three pressure ranges: the first from 3-5 GPa, the second from 8-12 GPa, and finally from 16-20 GPa. The particular modes in the sample that are observed to change in the Raman are strongly linked to the molecular vibrations involving the N-H and the C═O bond, which are most strongly coupled to the hydrogen-bonded lattice structure. The X-ray diffraction suggests that the crystal maintains a monoclinic structure to the highest pressures studied. Although there was a considerable degree of hysteresis observed in some X-ray runs, all the changes observed under pressure are reversible.

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“…High pressure generally favors condensation processes; therefore, the most probable products are oligomers and their byproducts. Dimer and trimer of urea forming during urea thermolysis 32 are ruled out for the absence of their characteristic strong absorption bands: 1325−1365 cm −1 in biuret 33 and above 1750 cm −1 in triuret. 34 In the pyrolysis of urea, biuret further reacts with isocyanic acid (formed by urea decomposition) to give cyanuric acid and ammelide as intermediates in the formation of graphitic carbon nitrides at 820 K. 35 More moderate heating gives cyanuric acid and urea cyanurate (below 700 K) and then carbon nitride oxide (∼720 K).…”

Section: Resultsmentioning

confidence: 99%

Synthesis of High-Quality Crystalline Carbon Nitride Oxide by Selectively Driving the High-Temperature Instability of Urea with Pressure

Dziubek

Citroni

Fanetti³

et al. 2017

J. Phys. Chem. C

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One-step synthesis using only physical tools is an appealing "green" method for the realization of technological materials. High-pressure conditions are particularly suitable in the attainment of extended supramolecular networks and in combination with high-temperature are effective in selecting specific reaction pathways to increase product quality. Here we show how pressures below 3 GPa and temperatures on the order of 420 K are effective for the synthesis, from urea crystal phase IV, of 2D graphitic carbon nitride oxide with enhanced crystalline quality. Angle-dispersive X-ray diffraction and Fourier transform IR spectroscopy show that the reaction becomes less selective at higher pressure with the formation of melamine and ammonium carbamate as byproducts. An anomalous positive slope is shown by the P−T instability boundary, likely arising from unfavorable hydrogen bonding with respect to the topochemical path, making urea an interesting case study for gaining insight into the role of hydrogen bonding in solid-state reactivity.

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Vibrational infrared spectra of biuret and its thioanalogs. An ab initio SCF/3-21G study

Cited by 11 publications

References 24 publications

Urea Decomposition in Selective Catalytic Reduction on V₂O₅/WO₃/TiO₂ Catalyst in Diesel Exhaust

Urea Decomposition in Selective Catalytic Reduction on V₂O₅/WO₃/TiO₂ Catalyst in Diesel Exhaust

Hydrogen-Bonding Modification in Biuret Under Pressure

Synthesis of High-Quality Crystalline Carbon Nitride Oxide by Selectively Driving the High-Temperature Instability of Urea with Pressure

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Vibrational infrared spectra of biuret and its thioanalogs. An ab initio SCF/3-21G study

Cited by 11 publications

References 24 publications

Urea Decomposition in Selective Catalytic Reduction on V2O5/WO3/TiO2 Catalyst in Diesel Exhaust

Urea Decomposition in Selective Catalytic Reduction on V2O5/WO3/TiO2 Catalyst in Diesel Exhaust

Hydrogen-Bonding Modification in Biuret Under Pressure

Synthesis of High-Quality Crystalline Carbon Nitride Oxide by Selectively Driving the High-Temperature Instability of Urea with Pressure

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Product

Resources

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Urea Decomposition in Selective Catalytic Reduction on V₂O₅/WO₃/TiO₂ Catalyst in Diesel Exhaust

Urea Decomposition in Selective Catalytic Reduction on V₂O₅/WO₃/TiO₂ Catalyst in Diesel Exhaust