Influence of Water Adsorbing Polymer Addition on Urea Synthesis From Recovered Ammonia and Carbon Dioxide in Porous Hollow Silica Spheres

Abstract This work investigated influence of addition of water absorbing polymer into porous hollow silica spheres on urea synthesis from recovered ammonia and carbon dioxide in nanospaces of the hollow spheres including catalytically active copper species. Recovered ammonia and carbon dioxide tended to increase with increasing the amount of sodium polyacrylate, and the recovered compounds as well as physisorbed water decreased after urea synthesis reaction identified from the results of DRIFT spectra and EDX analyses. Urea yield in the hollow spheres increased with increasing the amount of sodium polyacrylate and the maximum yield was observed in the sample prepared with 0.03 g of sodium polyacrylate. From the result of DTA, endothermic peaks assigned as phase transition and decomposition of urea were observed and the peak temperatures were relatively high compared with pristine urea probably due to nanoconfinement effect.