Influence of reaction time on mesoporous MgO based CO2 Capture

“The effect of reaction time was then investigated based on the sample with 0.1 g SDS. As shown in Figure 4a, with prolonging the reaction time, the CO2 capacity steadily increased from 0.94 to 0.96 mmol g−1 between six and 12 h and subsequently there was a noticeable decline from 0.96 to 0.55 mmol g−1 between 12 to 72 h. Figure 4b shows the XRD patterns of the synthesized samples. When the reaction time was no longer than 18 h, all samples formed mainly MgO (JCPDS 45-0946) with some MgCO3 (JCPDS 08-0479) impurity observed. With a further prolonging of the reaction time, the MgCO3 content steadily increased. Particularly for the 72 h sample, the majority phase became MgCO3 and the sharp and intense peaks indicated their highly crystalline nature. The major determinant lies in the degree of the urea hydrolysis process. With longer reaction time, the formation of MgCO3 was preferred, which led to a decreased CO2 capture capacity. Table 4 demonstrates clearly that all the samples possess high specific surface area in the range of 204.0 to 375.2 m2 g‒1, and small average pore size of 1.82 to 2.19 nm.”


Figure 4. (a) The influence of reaction time on the CO2 capture capacity; (b) XRD spectra of MgO compounds at different reaction times.”


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