Dissociation Rates of Urea in the Presence of NiOOH Catalyst: A DFT Analysis
Citations Over TimeTop 10% of 2010 papers
Abstract
Single molecule reactions have been studied between nickel oxyhydroxide, urea, and the hydroxide ion to understand the process of urea dissociation into ammonia, isocyanic acid, cyanate ion, carbon dioxide, and nitrogen. In the absence of hydroxide ions, nickel oxyhydroxide will catalyze urea to form ammonia and isocyanic acid with the rate-limiting step being the formation of ammonia with a rate constant of 1.5 × 10⁻⁶ s⁻¹. In the presence of hydroxide, the evolution of ammonia was also the rate-limiting step with a rate constant of 1.4 × 10⁻²⁶ s⁻¹. In addition, desorption of the cyanate ion presented an energy barrier of 6190 kJ mol⁻¹ suggesting that the cyanate ion cannot be separated from NiOOH unless further reactions occurred. Finally, elementary dissociation reactions with hydroxide ions deprotonating urea to produce nitrogen and carbon dioxide were analyzed. These elementary reactions were investigated along three paths differing in the order that protons were removed and the nitrogen atoms were rotated. The rate-limiting step was found to be the removal of carbon dioxide with a rate constant of 4.3 × 10⁻⁶⁵ s⁻¹. Therefore, the catalyst could be deactivated by the surface blockage caused by carbon dioxide adsorption.
Related Papers
- → Kinetics of the OCN−and HOCN formation from the HNCO + H2O thermal reaction in interstellar ice analogs(2011)44 cited
- → Cyanate as an Active Precursor of Ethyl Carbamate Formation in Sugar Cane Spirit(2015)25 cited
- → Determination of cyanate, and a study of its accumulation in aqueous solutions of urea(1964)99 cited
- → Carbamylation of proteins – mechanism, causes and consequences(2016)3 cited
- → Theoretical study of the mechanism and rate constant of the dimerization of isocyanic acid(1995)11 cited