Equilibria in the Ammonium Carbamate-Urea-Water System

Evidence of Surface Catalytic Effect on Cosmic Dust Grain Analogs: The Ammonia and Carbon Dioxide Surface Reaction

“…Once delivered on our planet, both ammonium carbamate and carbamic acid can further evolve under the primitive Earth environment. It was discovered that ammonium carbamate can be converted into urea CO(NH2)2 and water in a temperature range between 135º and 200º C (Clark, Gaddy, & Rist 1933). Formamide and urea was also produced in interstellar ice analogues by UV irradiation of a HNCO ice (Raunier et al 2004) or a CH3OH:NH3 ice mixture (Nuevo et al 2010).…”

Structure, hydrogen bonding and thermal expansion of ammonium carbonate monohydrate

“…It is known from laboratory analogue experiments that the organic molecules produced photochemically in Titan's dense N 2 /CH 4 atmosphere may be hydrolyzed in aqueous ammonia to form both urea and amino acids (Poch et al, 2012). Further hydrolysis of urea would be expected to form ammonium carbonates (Clark et al, 1933); on Earth, this process is mediated in soils with the aid of bacterial urease, whereafter the carbonate breaks down to ammonia and water (e.g. Chin & Kroontje, 1963).…”

TiO2 Nanoparticles Supported on Hierarchical Meso/Macroporous SiO2 Spheres for Photocatalytic Applications

“…For instance, basic amino acids, such as arginine or lysine, keep the reaction under weakly basic conditions leading to spherical particles with dendritic pores [18,45]. The same particles can be obtained with urea, whose thermal decomposition above 70°C maintains the solution pH between 7 and 9.5, depending on the urea concentration [46]. Nevertheless, the increase in urea concentration rises the nucleation rate leading to smaller particles.…”