Materials for thermohydrolysis of urea in a fluidized bed

Kröcher, Oliver; Elsener, Martin

doi:10.1016/j.cej.2009.04.030

Cited by 18 publications

(7 citation statements)

References 21 publications

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“…During SCR and SNCR, the first steps consist of urea thermolysis -an endothermic reaction which produces isocyanic acid (HCNO) and ammonia (NH 3 ) at 150-300 °C-readily followed by the exothermic hydrolysis of the HCNO into CO 2 and NH 3 (below 200 °C). The production of NH 3 from urea as the final reducing agent of NO ('urea thermohydrolysis' [9]) is the aim of SCR and SNCR, but increasing the water concentration leads to complete HCNO hydrolysis, and further raising the temperature above 450 °C results in ammonia cracking, which generates H 2 , and N 2 . Thus overall, the complete reaction of one mole urea with one mole of water above 450 °C, which can be considered 'steam reforming of urea', produces 3 moles of H 2 , one mole of N 2 and one mole of CO 2 .…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Dupont

Twigg²,

Rollinson

et al. 2013

International Journal of Hydrogen Energy

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The thermodynamic effects of molar steam to carbon ratio (S:C), of pressure, and of having CaO present on the H 2 yield and enthalpy balance of urea steam reforming were investigated.At a S:C of 3 the presence of CaO increased the H 2 yield from 2.6 mol H 2 /mol urea feed at 940 K to 2.9 at 890 K, and decreased the enthalpy of bringing the system to equilibrium. A minimum enthalpy of 180.4 kJ was required to produce 1 mole of H 2 at 880 K. This decreased to 94.0 kJ at 660 K with CaO-based CO 2 sorption and, when including a regeneration step of the CaCO 3 at 1170 K, to 173 kJ at 720 K. The presence of CaO allowed widening the range of viable operation at lower temperature and significantly inhibited carbon formation. The feasibility of producing H 2 from renewable urea in a low carbon future is discussed.

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Section: Introductionmentioning

confidence: 99%

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Dupont

Twigg²,

Rollinson

et al. 2013

International Journal of Hydrogen Energy

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“…Figure illustrates the bonding process and mechanism between isocyanate-related functional groups and surface manganese ions (Mn 3+ ions) of Li-rich Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 cathode materials. First, ammonia (NH 3 ) and isocyanic acid (H–NCO) gas are produced when urea is heated at 200 °C in accordance with the following equation: , Ammonia is an active reducing agent. In the presence of ammonia, oxygen vacancies can be steadily produced on the surface layer of Li-rich oxides. , Moreover, as reported by Doron Aurbach et al, NH 3 treatment could change the surface structure of Li-rich materials, such as the leaching of little Li atoms and the releasing of oxygen .…”

Section: Resultsmentioning

confidence: 99%

Bonding the Terminal Isocyanate-Related Functional Group to the Surface Manganese Ions to Enhance Li-Rich Cathode’s Cycling Stability

Meng

Wang

et al. 2021

ACS Appl. Mater. Interfaces

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Capacity fading of Li-rich cathodes in the cycling process is mainly caused by the irreversible side reactions at the interface of electrode and electrolyte by reason of the lack of a corrosion resistant surface. In this work, isocyanate-related functional groups (−NCO groups and polyamide-like groups) were tightly bonded on the surface of Li-rich oxides through a urea decomposition gas heat-treatment. The surface isocyanate functionalization inhibits the side reaction of PF 5 hydrolysis to give Li x PF y O z and HF species at the surface of Li-rich materials in the cycle process. As compared to the untreated Li-rich sample U0, the samples with the spinel-like layer and isocyanate functionalized surface exhibited an enhanced cycle stability. The capacity retention of the treated sample U3 reached as high as 92.6% after 100 cycles at the current density of 100 mA/g, larger than 66.8% for the untreated sample. Even at a higher current density of 1000 mA/g, sample U3 gives a capacity retention of 81.7% after 300 cycles. The findings of this work reveal the importance of surface isocyanate functionalization in restraining the surface side reactions and also suggest an effective method to design Li-rich cathode materials with better electrochemistry performance.

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“…In order to compare the effects of different oxide catalysts on the pyrolysis reaction of aqueous urea solution and obtain detailed catalytic efficiency values, Kröcher and Elsener tested the catalytic effects of twenty potential catalyst materials on the pyrolysis of aqueous urea solution in a selfmade fluidized bed reactor [44].…”

Section: Catalytic Pyrolysis Of Aqueous Urea Solutionmentioning

confidence: 99%

“…In the above literature [42][43][44], the solvent of urea solution was water, which might affect the catalytic effect of catalysts. Perhaps being aware of it, Bernhard et al carried out experimental tests and kinetic analysis on the catalytic efficiency of stationary catalysts soon afterwards [45].…”

Section: Catalytic Pyrolysis Of Aqueous Urea Solutionmentioning

confidence: 99%

A Review of Urea Pyrolysis to Produce NH₃ Used for NO_x Removal

Wang

Dong

Niu

et al. 2019

Journal of Chemistry

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Urea pyrolysis, from which the denitration reactant ammonia is produced, plays an important role in the urea-based NOx removal process. Research into urea pyrolysis is mostly focused on three parts: urea pyrolysis pathway, catalytic hydrolysis of HNCO, and catalytic pyrolysis of aqueous urea solution. In this paper, detailed overview on research progress of urea pyrolysis was conducted. From the review, it could be concluded that although much research has been carried out, concentration was mainly in analysis of urea pyrolysis products and exploration of catalysts used to improve ammonia yields. Little work has been done on mechanism study and development of a kinetic model with high accuracy, which are still in great need nowadays.

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Materials for thermohydrolysis of urea in a fluidized bed

Cited by 18 publications

References 21 publications

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Bonding the Terminal Isocyanate-Related Functional Group to the Surface Manganese Ions to Enhance Li-Rich Cathode’s Cycling Stability

A Review of Urea Pyrolysis to Produce NH₃ Used for NO_x Removal

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Materials for thermohydrolysis of urea in a fluidized bed

Cited by 18 publications

References 21 publications

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

Bonding the Terminal Isocyanate-Related Functional Group to the Surface Manganese Ions to Enhance Li-Rich Cathode’s Cycling Stability

A Review of Urea Pyrolysis to Produce NH3 Used for NOx Removal

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A Review of Urea Pyrolysis to Produce NH₃ Used for NO_x Removal