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. 2023 Dec 20;9(1):714-718.
doi: 10.1021/acsomega.3c06534. eCollection 2024 Jan 9.

Thermochemical Properties of Synthesized Urea from Recovered Ammonia and Carbon Dioxide in Well-Ordered Nanospaces of Hollow Silica Spheres

Tetsuo Umegaki  1 , Yoshiyuki Kojima  1
Affiliations

Thermochemical Properties of Synthesized Urea from Recovered Ammonia and Carbon Dioxide in Well-Ordered Nanospaces of Hollow Silica Spheres

Tetsuo Umegaki et al. ACS Omega. .

Abstract

The present work investigated the thermochemical properties of urea synthesized in well-ordered nanospaces of porous hollow silica spheres' shells from recovered ammonia and carbon dioxide in aqueous solution. Thermochemical behaviors of the urea synthesized in well-ordered nanospaces of the hollow spheres' shells prepared with 1-dodeclyamine were analyzed from the results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and endothermic peaks assigned as the phase transition and decomposition were observed at ca. 440 and 514 K, respectively, which were higher than those of pristine urea (405 and 408 K, respectively), probably because of the nanoconfinement effect. The decomposition behavior was also confirmed by the result of diffuse reflectance infrared Fourier transform (DRIFT) spectra of the samples treated at various temperatures up to 573 K, and the decomposition of urea synthesized in the well-ordered nanospaces of the hollow spheres' shells started at 468 K and completed up to 533 K.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Scheme of urea synthesis in the nanospaces of the shell of porous hollow silica spheres.
Figure 2
Figure 2
Thermogravimetric analyses of urea-encapsulated porous hollow silica spheres prepared with (a) 1-dodecylamine, (b) 1-dodecane, (c) 1-dodecanol, and (d) urea-encapsulated commercial silica. Synthesis conditions of encapsulated urea: (a) 16 h and (b–d) 5 h at 323 K under a 0.5 MPa argon atmosphere.
Figure 3
Figure 3
Differential thermal analyses of urea-encapsulated porous hollow silica spheres prepared with (a) 1-dodecylamine, (b) 1-dodecane, (c) 1-dodecanol, and (d) urea-encapsulated commercial silica. Synthesis conditions of encapsulated urea: (a) 16 h and (b–d) 5 h at 323 K under a 0.5 MPa argon atmosphere.
Figure 4
Figure 4
(A) Near- and (B) mid-DRIFT spectra of urea-encapsulated porous hollow silica spheres prepared with 1-dodecylamine treated under a 0.5 MPa argon atmosphere for 16 h (a) without heat treatment and with heat treatment at (b) 383, (c) 468, (d) 533, and (e) 573 K in a nitrogen atmosphere.
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