MOFs衍生炭负载的钴基催化剂的廉价制备及其CO加氢催化性能

以对苯二甲酸（H₂BDC）为配体、乙酸钴为Co源、水作溶剂，通过共沉淀法合成了金属有机框架材料（Co-BDC MOFs）；以其为前驱体分别在乙炔和氩气氛下采用化学气相沉积法制备了核壳结构Co@C催化剂。结合XRD、氮吸附、SEM、TEM、XPS、TGA和Raman光谱等手段对Co@C催化剂的结构和组成进行了表征，考察了该催化剂在费托合成反应中的活性及稳定性。结果表明，炭化气氛对炭层结构的石墨化程度有较大影响，而对金属Co核的物相结构和粒径影响较小；乙炔气氛有助于形成多孔的石墨炭壳，从而促进烃链的生长，Co@C-C₂H₂催化剂上的C₅₊烃产物选择性高达82.66%，反应过程中催化剂物相由单相金属Co转变为金属Co与Co₂C的混合相，且无失活现象发生，表明Co₂C具有较高的费托反应催化活性。

Low-cost preparation of carbon-supported cobalt catalysts from MOFs and their performance in CO hydrogenation

With terephthalic acid (H₂BDC) as ligand and cobalt acetate as Co source, metal-organic frameworks (Co-BDC MOFs) were synthesized in water by co-precipitation; after that, core-shell Co@C catalysts were prepared by chemical vapor deposition (CVD) of Co-BDC MOFs in acetylene and Ar atmosphere. The structure, composition and properties of Co@C catalysts were characterized by XRD, nitrogen physisorption, SEM, TEM, XPS, TGA and Raman spectroscopy and their catalytic performance in Fischer-Tropsch synthesis (FTS) were investigated in a fixed-bed tubular reactor. The results demonstrated that the carbonization atmosphere has an important influence on the graphitization degree of carbon shell, whereas has little effect on the phase and size of Co core. The pore of graphite shell is significantly improved by CVD in acetylene, which can enhance the selectivity to heavier hydrocarbons (C₅₊) for CO hydrogenation; in particular, the Co@C-C₂H₂ catalyst shows a high selectivity of 82.66% to the C₅₊ hydrocarbons. As the carbon shell can effectively inhibit the cobalt nanoparticles from migration and agglomeration during the FTS reaction, the Co species were well distributed in both the fresh and spent catalysts and no significant sintering and deactivation are observed for the Co@C catalysts upon the FTS tests. During the FTS reaction, the active phase changes from metallic Co to a mixture of metallic Co and Co₂C, whilst the catalytic activity of Co@C-C₂H₂ keeps almost unchanged, suggesting that Co₂C may also be an active phase for the Fischer-Tropsch synthesis.