Pyrolysis of urea and guanidinium salts to be used as ammonia precursors for selective catalytic reduction of NOx

Sandoval-Rangel, Ladislao; Rosa, Javier Rivera De la; Lucio–Ortiz, Carlos J.; Castaldi, Marco J.

doi:10.1016/j.jaap.2015.04.007

Cited by 20 publications

(9 citation statements)

References 42 publications

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“…However, according to the previous study [29], N-containing compounds might also undergo polymerization to form solid residues. Therefore, the effects of both solid residues and H 2 O during pyrrole pyrolysis are worthy of investigation in a future work.…”

Section: Discussionmentioning

confidence: 99%

Theoretical Investigation of the Formation Mechanism of NH3 and HCN during Pyrrole Pyrolysis: The Effect of H2O

et al. 2018

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Coal is a major contributor to the global emission of nitrogen oxides (NOx). The NOx formation during coal utilization typically derives from the thermal decomposition of N-containing compounds (e.g., pyrrolic groups). NH3 and HCN are common precursors of NOx from the decomposition of N-containing compounds. The existence of H2O has significant influences on the pyrrole decomposition and NOx formation. In this study, the effects of H2O on pyrrole pyrolysis to form NOx precursors HCN and NH3 are investigated using the density functional theory (DFT) method. The calculation results indicate that the presence of H2O can lead to the formation of both NH3 and HCN during pyrrole pyrolysis, while only HCN is formed in the absence of H2O. The initial interaction between pyrrole and H2O determines the N products. NH3 will be formed when H2O attacks the C2 position of pyrrole with its hydroxyl group. On the contrary, HCN will be generated instead of NH3 when H2O attacks the C3 position of pyrrole with its hydroxyl group. In addition, the DFT calculations clearly indicate that the formation of NH3 will be promoted by H2O, whereas the formation of HCN is inhibited.

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Section: Discussionmentioning

confidence: 99%

Theoretical Investigation of the Formation Mechanism of NH3 and HCN during Pyrrole Pyrolysis: The Effect of H2O

et al. 2018

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“…To shine some light onto urea pyrolysis, many thermogravimetric and calorimetric studies have been conducted, often in combination with the analysiso fe volved gases and/or pyrolysis residues by meanso fv ibrational spectroscopy,m ass spectrometry or chromatography,a sw ell as thermochemical modelling of the decompositionr eaction. [7,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] Severals tudies explicitly reveal the distinct influence of pyrolysis parameters, such as heating rate, initial sample mass and crucible shape on decomposition temperature,t otal mass loss and pyrolysis residues formed. [5,9,41,42] Thism ight be traced back to the complex mix of different reaction products and intermediates during urea pyrolysis (the specific compositioni sd etermined by the exact pyrolysis parameters), many of which can furtherr eact with each other to form different intermediates.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Biuret—A Crucial Reaction Intermediate for Understanding Urea Pyrolysis To Form Carbon Nitrides: Crystal‐Structure Elucidation and In Situ Diffractometric, Vibrational and Thermal Characterisation

Groß

Höppe

2020

Chemistry A European J

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The crystal structure of biuret was elucidated by means of XRD analysiso fs ingle crystalsg rown through slow evaporation from as olution in ethanol. It crystallises in its own structure type in space group C2/c (a = 15.4135(8) , b = 6.6042(3) , c = 9.3055(4) , Z = 8). Biuret decomposition was studied in situ by means of temperature-programmed powder XRD and FTIR spectroscopy,t oi dentify ac o-crystalline biuret-cyanuric acidp hase as ap reviously unrecognised reaction intermediate. Extensive thermogravimetric studies of varying crucibleg eometry,h eatingr ate and initial sample mass reveal that the concentration of reactive gases at the interfacet ot he condensed sample residues is ac rucial parameter for the prevailing decompositionp athway.T aking these findings into consideration, as tudy on the optimisation of carbon nitride synthesis from urea on the gram scale, with standard solid-state laboratory techniques, is presented. Finally,aserendipitously encountered self-coating of the crucible inner walls by graphite during repeateds ynthetic cycles, which prove to be highly beneficial for the obtained yields,i sr eported.

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“…Examples for repurposed hardware to facilitate this kind of task can be found in the literature. [1][2][3] Direct coupling of the reaction vessel to gas chromatography/mass spectrometry (GC/MS) 4 and thermal conductivity detectors 5 was reported for gaseous samples, along with manual sampling of the solid residue for Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) analyses. 4 Manual sampling by pipette can also be an option for reactions in the liquid phase in open systems.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3] Direct coupling of the reaction vessel to gas chromatography/mass spectrometry (GC/MS) 4 and thermal conductivity detectors 5 was reported for gaseous samples, along with manual sampling of the solid residue for Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) analyses. 4 Manual sampling by pipette can also be an option for reactions in the liquid phase in open systems. 6 Switching a valve to redirect circulating fluid to another instrument for analysis reduces the required manual labor.…”

Section: Introductionmentioning

confidence: 99%

Modifying an ÄKTApurifier System for the Automated Acquisition of Samples for Kinetic Modeling of Batch Reactions

2020

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Pyrolysis of urea and guanidinium salts to be used as ammonia precursors for selective catalytic reduction of NOx

Cited by 20 publications

References 42 publications

Theoretical Investigation of the Formation Mechanism of NH3 and HCN during Pyrrole Pyrolysis: The Effect of H2O

Theoretical Investigation of the Formation Mechanism of NH3 and HCN during Pyrrole Pyrolysis: The Effect of H2O

Biuret—A Crucial Reaction Intermediate for Understanding Urea Pyrolysis To Form Carbon Nitrides: Crystal‐Structure Elucidation and In Situ Diffractometric, Vibrational and Thermal Characterisation

Modifying an ÄKTApurifier System for the Automated Acquisition of Samples for Kinetic Modeling of Batch Reactions

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