Kinetic modeling of urea decomposition and byproduct formation

Krum, Kristian; Patil, Rituja; Hashemi, Hamid; Wang, Ze; Li, Songgeng; Glarborg, Peter; Wu, Hao

doi:10.1016/j.ces.2020.116138

Cited by 17 publications

(16 citation statements)

References 27 publications

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“…The model includes a water evaporation model and a kinetic reaction scheme to describe urea decomposition and byproduct formation. The kinetic model includes formation and decomposition of biuret, CYA, ammelide, and triuret, as described in recent work (Krum et al 2020). The initial UWS droplet is characterized by a specified uniform size d 0 , temperature T l,0 , and species mass fraction Y u,0 .…”

Section: Modeling Workmentioning

confidence: 99%

“…Bernhard et al (2011) studied evaporation of urea in a flow reactor and measured urea in the gas phase, indicating that urea evaporation may be important. However, in a recent study Krum et al (2020) could not detect gas-phase urea in a combined thermogravimetric analysis (TGA) / Fourier transformed infrared spectroscopy (FTIR) study. Additionally, they showed that gaseous HNCO and NH 3 can recombine into condensable products at lower temperatures, offering an alternative reaction path to urea in the recondensed species.…”

Section: Introductionmentioning

confidence: 99%

“…In the present work, a model for UWS depletion including byproduct formation is presented. A kinetic reaction model based on non-ionic species is adopted from previous work (Krum et al 2020), and combined with an energy balance based on the work of Abramzon and Sirignano (1989). The kinetic model of Krum et al (2020) was developed to describe TGA mass loss data for urea at medium heating rate conditions (up to 500 o C/min.…”

Section: Introductionmentioning

confidence: 99%

“…A kinetic reaction model based on non-ionic species is adopted from previous work (Krum et al 2020), and combined with an energy balance based on the work of Abramzon and Sirignano (1989). The kinetic model of Krum et al (2020) was developed to describe TGA mass loss data for urea at medium heating rate conditions (up to 500 o C/min. ), while earlier models (Ebrahimian et al, 2012;Gan et al, 2016) employed kinetic parameters derived based on low heating rate TGA data (≤20 o C/min.).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Modeling the decomposition and byproduct formation of a urea-water-solution droplet

Krum

Allingham

Poulsen

et al. 2021

Chemical Engineering Science

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Section: Modeling Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Modeling the decomposition and byproduct formation of a urea-water-solution droplet

Krum

Allingham

Poulsen

et al. 2021

Chemical Engineering Science

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“…The evolution of products was found to be in fairly good agreement with simulations. Subsequent experimental studies were performed to improve this model by revisiting kinetic data and including phase-change reactions. − …”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of the Thermal Decomposition of Urea Derivatives

et al. 2022

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An extensive theoretical study of the thermal decomposition of alkyl- and phenylureas, which are widely used in the pesticides, pharmaceuticals, and materials industries, has been carried out using electronic structure calculations and reaction rate theories. Enthalpies of formation and bond dissociation energies (BDE) of 11 urea derivatives have been calculated using different levels of theory (CBS-QB3, CCSD(T)/CBS//M06-2X/6-311++G(3df,2pd), and CBS-QM062X) according to the size of the system. Potential energy surfaces for the unimolecular decomposition pathways of these urea derivatives were also systematically computed for the first time. Several pericyclic reactions can be envisaged, as a function of the size and the nature of the N substituents, and all of these pathways were explored. Our calculations show that these compounds are solely decomposed by four-center pericyclic reactions, yielding substituted isocyanates and amines, and that initial bond fissions are not competitive. Based on the set of urea derivatives studied, a new reaction rate rule for their thermal decomposition was defined and involves the nature of the transferred H atom (primary or secondary/alkyl or benzyl) and the nature of the N-atom acceptor (primary, secondary, or tertiary). This new reaction rate rule allows us to determine the product branching ratios in the thermal decomposition of a given urea derivative and its total rate of decomposition. Applications on urea derivatives used in the chemical industry are presented and illustrate the usefulness of this new rate rule that allows to predict the previously unknown thermal decomposition kinetics of a large number of these compounds.

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Flame retardant polyvinyl alcohol film with self‐releasing carbon dioxide and ammonia from phytic acid and urea

Wu,

Lai,

Nan

et al. 2024

J of Applied Polymer Sci

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This paper utilizes the reaction of phytic acid (PA) and urea (UM) in polyvinyl alcohol (PVA) solution to synthesize flame retardant gasses (CO2, NH3) for the preparation of PVA composite films containing flame retardant microbubbles. The flame retardancy of PVA composite films was assessed using methods including limiting oxygen index (LOI), vertical burning (UL 94), and cone calorimetry. The results indicated an increase in the LOI of the PVA composite film containing flame retardant microfoam from 20% to 30% compared with the pure PVA film, and that UL 94 reached VTM‐0. Furthermore, its peak exothermic rate and total exothermic amount were reduced by 36.25% and 38.92%, respectively, compared with the pure PVA film. The investigation of the flame‐retardant mechanism employed thermogravimetric‐infrared (TG‐IR), scanning electron microscopy (SEM), Raman spectroscopy, and infrared spectroscopy. The results demonstrate that the CO2 and NH3 flame retardant microbubbles within the composite film render it less ignitable at the initial stage, and that the internal UM of the composite film continues to decompose, releasing CO2 and NH3 upon heating. In addition, the acidic substances decomposed by PA during combustion promote the dehydration, cross‐linking, and cyclization of PVA, generating chemical structures such as POC, POP, and PO4 with enhanced thermal stability. This encourages the formation of a continuous, dense charcoal layer and impedes the transfer of oxygen and heat into the interior.

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Kinetic modeling of urea decomposition and byproduct formation

Cited by 17 publications

References 27 publications

Modeling the decomposition and byproduct formation of a urea-water-solution droplet

Modeling the decomposition and byproduct formation of a urea-water-solution droplet

Theoretical Study of the Thermal Decomposition of Urea Derivatives

Flame retardant polyvinyl alcohol film with self‐releasing carbon dioxide and ammonia from phytic acid and urea

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