| It is an important direction that levulinic acid converted into?-valerolactone by Ru/C catalysts.Water is the by-product in the process of levulinic acid conversion.Therefore,water is used as the solvent.However,at the conditions of water system and high temperature reaction,Ru/C catalysts are facing the challenge of poor stability.In this dissertation,the highly stable catalyst with inserting metal nanoparticles into porous carbon channels,introducing heteroatom functional groups and encapsulation confines were designed and prepared for the conversion of levulinic acid.The results were detailly presented as follow:?1?Ru nanoparticles well dispersed on the surface of carbon spheres have been developed by the introduction of nitrogen-doping.The incorporation of the N-dopant with in the carbon matrix effectively improved the dispersion of Ru NPs.It was found that the presence of graphite N was responsible for the high dispersion of Ru NPs.Through adjusting the carbonization temperature from 400 to 850?,we discovered that the absolute content of graphite N could be modulated from 3.2 to 22.4 mg·g-1.As a result,the dispersion of Ru NPs was improved from 29.8%to 70.9%.The Ru/N-CS-850 catalyst revealed excellent catalytic performance?LA conversion>99%?for the hydrogenation of levulinic acid to?-valerolactone,also exhibited very high stability after 4 runs.?2?A confinement structured catalyst was prepared by in-situ encapsulating Ru NPs to double shell hollow carbon nanospheres?DSC?.Ru-DSC catalyst had excellent stability in the hydrogenation of levulinic acid,and there was no obvious deactivation after 6 runs.The content of pyridine nitrogen on the shell layer was controlled by changing the precursor of the shell layer carbon.The pyridine nitrogen content in the shell carbon layer of Ru-DSC-CTS catalyst calcined from chitosan as the precursor was the highest one,which was 29.2 mg·g-1.The pyridine nitrogen in the support made the catalyst basic and could interact with acidic levulinic acid to increase the concentration of levulinic acid,resulting in the improvement of performance.Under the hydrogen pressure of 4 MPa and temperature of 70?,the LA conversion rate of Ru-DSC-CTS was higher than 99%and GVL selectivity was more than 99%.?3?Ru NPs embedded on mesoporous carbon was prepared,and the Ru-MC showed excellent catalytic performance at the temperature of 70? and hydrogen pressure of 4 MPa after reaction for 2 h,a high LA conversion of 99%,excellent cycle stability and thermal stability was observed.There was no obvious deactivation after6 runs,and Ru NPs were not sintered under the heat treatment at 600?.The incorporated structure improved the interaction between Ru NPs and carbon matrix,contributing to enhancing the anti-loss and anti-sintering ability of Ru NPs,and the excellent stability of Ru-MC.?4?Ru-DSC catalysts were used in hydrogen evolution reaction at 1.0 M KOH electrolyte.The over potential of Ru-DSC-I was 73.5 m V at the current density of 10m A·cm-2,and the TOF value was 64.5 s-1 at 100 m A·cm-2.Furthermore,the activity of Ru-DSC-I did not decrease after 500 cycles.The better performance of Ru-DSC-I for hydrogen evolution reaction was mainly attributed to the considerable electrochemical surface area. |
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