The Study Of The Coal As Photocatalysts For Synthesizing Of Methanol From CO₂and H₂O

In view of the urgency of energy and environmental, the reduction and effective utilization of greenhouse gas CO2have become worldwide attentive front subject. Photocatalystic synthesis of methanol from CO2and H2O is one of the most prospective ways for CO2conversion. The key point is how to fabricate high efficient and cheap photocatalyst and how it works. In this thesis, photocatalytic properties of coals and coal loaded with transition metal ions for synthesis of methanol from CO2and H2O were studied on the base of the special macromolecular structure and characteristics of coal, and the photocatalytic mechanism was setup on the study of photocatalystic synthesis of methanol using coal model molecuals as photocatalyst.(1) The effect of H/C atomic ratio in coal, radiation time, and amount of coal on yield of methanol in photocatalytic synthesis from CO2and H2O were investigated. The results showed that Shenfu coal (SF coal) and Huating coal with a higher H/C atomic ratio had a better photocatalytic activity. The methanol yield was up to461.32μmol/g using SF coal as catalyst, when the catalyst amont was1.0g/L, and the radiation time was34h. Photocatalytic activity of SF coal decreases after the removal of minerals from it, so that the minerals played an important role in the photocatalytic activity of SF coal.(2) Photocatalysts of SF coal loaded transition metal ions (Cu2+, Fe3+and Ni2+)(M-SF coal) using SF coal as support were prepared by equal volume method.The influences of the ion species, dosage, and the amount of M-SF coal on the yield of methanol in photocatalytic synthesis reaction of CO2and H2O. The results showed that the photocatalytic activity of M-SF coal is improved greatly, and the reactivities are in the order of Cu2+>Fe3+>Ni2+. For the Cu-SF coal, the yield of methanol was818.20μmol/g·cat., when the Cu2+loaded amount was2.0%, the catalyst amount was2.0g/L, and reduction time was10h. (3) The composition and structure of SF coal and M-SF coal were analyzed before and after the photocatalytic reaction. The result showed that SF coal was oxidized in the photocatalytic reaction under UV light, that’s because oxygen-containing functional groups and humic acid content was increased significantly in the reaction residues.(4) Naphthalene, Phenol, Benzoic Acid and Anisole were used as coal modle molecuals, and their structure changes were studied in the photocatalytic synthetic reactions.Based on all of above experiments and results, the photocatalytic mechanism of SF coal and M-SF coal for photocatalytic synthetic methanol reactions from CO2and H2O were established. And a preliminary synergetic mechanism of coal and the transition metal ions loaded on coal were proposed.