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Correlation of urea precipitation temperature with phase formation, morphology, and catalytic activity for CO2 conversion of CeO2
(2025-08-01)
Seeharaj, Panpailin
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Duangtanon, Jenjira
;
Sreemueang, Chanakan
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Noppharat, Phetchphalin
;
Kulthananat, Tachatad
This study proposes a simple method for tailoring the morphology and activity of cerium oxide (CeO<inf>2</inf>) catalysts in converting carbon dioxide (CO<inf>2</inf>) and methanol to green organic carbonate, dimethyl carbonate (DMC), to utilize and reduce CO<inf>2</inf> emissions. CeO<inf>2</inf> was prepared by urea precipitation at 85, 105, and 125 °C for 2 h, then calcining at 600 °C for 2 h. The phase structure and morphology of CeO<inf>2</inf> correlated with the urea hydrolysis rate. A low degree of supersaturation at 85 °C led to heterogeneous precipitation of cerium oxycarbonate (Ce<inf>2</inf>O(CO<inf>3</inf>)<inf>2</inf>.H<inf>2</inf>O) and CeO<inf>2</inf> with spherical morphology, while a higher degree of supersaturation at 105 °C and 125 °C resulted in homogeneous precipitation of single-phase Ce<inf>2</inf>O(CO<inf>3</inf>)<inf>2</inf>.H<inf>2</inf>O with spindle and elongated octahedral morphology, respectively. The spindle-shaped CeO<inf>2</inf> prepared at 105 °C with a predominant surface (111) facet showed the highest catalytic activity, with a DMC yield of 18.81 mmol.g<inf>cat</inf>−1. The enhanced catalytic efficiency of spindle-shaped CeO<inf>2</inf> was due to the high concentration of surface-active defect sites of exposed cerium cations and oxygen vacancies, which optimized the number of acid–base sites in adsorbing and activating CO<inf>2</inf> and methanol to produce DMC.
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Modification of acid–base properties of metal-doped ZnO catalysts for the transesterification of propylene carbonate with methanol to dimethyl carbonate
(2025-04-01)
Ieamviteevanich, Pimchanok
;
Kim-Lohsoontorn, Pattaraporn
;
Seeharaj, Panpailin
This study investigated the effect of metal dopants on the surface properties of ZnO-based catalysts for the transesterification of propylene carbonate (PC) with methanol to produce dimethyl carbonate (DMC). A series of metal-doped ZnO nanocatalysts (M-ZnO, where M is Ca2+, Cu2+, Ce3+, La3+, and Y3+ with the mol ratio of Zn2+/Mx+ = 4) were prepared by a simple co-precipitation method followed by calcining in air at 673 K for 5 h. Introducing different metal cations into the ZnO system decreased crystallite size and created surface defects of exposed cations and oxygen vacancies, increasing surface-active acid and basic sites. The catalytic performance for DMC production was ranked as follows: Ca-ZnO < Cu–ZnO < ZnO < Ce-ZnO < Y-ZnO < La-ZnO. La-ZnO showed the highest performance of all catalysts, with 67% PC conversion, 67% DMC selectivity, and 45% DMC yield. The improvement of catalytic activity was correlated with an increase in the concentration of moderate and strong acid–base functionalities on the La-ZnO surfaces for participating in the reaction of PC and methanol to form DMC.
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Platelet Ceria Catalysts from Solution Combustion and Effect of Iron Doping for Synthesis of Dimethyl Carbonate from CO2
(2025-01-01)
Rusta, Nicoletta
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Mameli, Valentina
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Ricci, Pier Carlo
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Porcu, Stefania
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Seeharaj, Panpailin
Solution combustion (SC) remains among the most promising synthetic strategies for the production of crystalline nanopowders from an aqueous medium, due to its easiness, time and cost-effectiveness, scalability and eco-friendliness. In this work, this method was selected to obtain anisometric ceria-based nanoparticles applied as catalysts for the direct synthesis of dimethyl carbonate. The catalytic performances were studied for the ceria and Fe-doped ceria from SC (CeO<inf>2</inf>-SC, Ce<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf>-SC) in comparison with the ceria nanorods (CeO<inf>2</inf>-HT, Ce<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf>-HT) obtained by hydrothermal (HT) method, one of the most studied systems in the literature. Indeed, the ceria nanoparticles obtained by SC were found to be highly crystalline, platelet-shaped, arranged in a mosaic-like assembly and with smaller crystallite size (≈6 nm vs. ≈17 nm) and higher surface area (80 m2 g−1 vs. 26 m2 g−1) for the undoped sample with respect to the Fe-doped counterpart. Although all samples exhibit an anisometric morphology that should favor the exposition of specific crystalline planes, HT-samples showed better performances due to higher oxygen vacancies concentration and lower amount of strong basic and acid sites.
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Improvement of surface properties of metal doped-CeO2 nanospindle catalysts for direct synthesis of dimethyl carbonate from CO2 and methanol
(2023-06-01)
Seeharaj, Panpailin
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Saenman, Thanita
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Phiwhom, Thanabat
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Muangsuwan, Chutanan
;
Srinives, Sira
To utilize carbon dioxide (CO<inf>2</inf>) which is the main greenhouse gas, this study developed effective metal doped-CeO<inf>2</inf> nanospindle catalysts for conversion of CO<inf>2</inf> and methanol into dimethyl carbonate (DMC). Ce<inf>0.9</inf>M<inf>0.1</inf>O<inf>2</inf> nanospindles (where M is a transition metal, i.e., Zr, Fe, Cu and Co) were prepared by a template-free hydrothermal method. The substitution of different valence and size cations, including Zr4+, Fe3+, Cu2+ and Co2+, for Ce4+ sites in the fluorite CeO<inf>2</inf> lattice induced the defect formation of surface-active sites of exposed Ce3+ and oxygen vacancies through the charge compensation and redox pair reactions. Ce<inf>0.9</inf>Fe<inf>0.1</inf>O<inf>2</inf> solid solution with well-preserved spindle shaped morphology showed the highest catalytic performance by giving DMC yield at 3.56 mmol.g<inf>cat</inf>−1 with 100% DMC selectivity. The improvement of catalytic activity was attributed to the higher proportion of surface defect sites and variation of acid-base properties caused by the integration of Fe dopants into CeO<inf>2</inf> ionic system.

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