As more attention is focused toward carbon dioxide emissions into the environment, conversion of CO2 to useful chemicals can utilize the extra carbon dioxide captured from power plant stack gas, instead of sequestration. The mainstream method of producing carbonates and carbamates utilizes toxic phosgene. The cycloaddition of carbon dioxide to epichlorohydrin, or other epoxides, can produce carbonates without the use of phosgene. A catalyst with high surface area, Lewis acid sites, and an affinity for carbon dioxide is required to develop carbonates using carbon dioxide. A cobalt doped metal-organic framework-5 (Co21-MOF-5) was developed to test the cycloaddition reactions with carbon dioxide. The crystalline structure of developed Co21-MOF-5 crystals matched those reported. An average Langmuir surface area of 594 m2/g was developed. Of the reactions tested, using epichlorohydrin as a precursor at 80 °C and 7 bar over four hours produced the best result with a conversion of 43.3% and 100% selectivity for the carbonate. Using the precursor of styrene oxide under the same conditions produced a conversion of 55% with 35% selectivity to the carbonate. Reactions involving epichlorohydrin at higher temperatures did not show any measureable amounts of the desired product and could not be reproduced. Further investigation into using Co21-MOF-5 to produce a carbamate yielded a conversion of 25% with 100% selectivity, but a collapse of the catalyst crystalline structure.
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Cobalt MOF-5 : a novel catalyst for CO2 conversion to carbonates.
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