碳源对鱼骨式纳米碳纤维及其负载的钯催化剂性能的影响

分别以甲烷、一氧化碳和乙烯为碳源合成了3种鱼骨式结构的纳米碳纤维(FCNF-C1,FCNF-CO和FCNF-C2),并作为载体制备了3种钯催化剂(Pd0.5%),考察了在对苯二甲酸加氢精制中的催化活性,通过N2吸附-脱附、X射线衍射、程序升温脱附、电子透射显微镜及CO化学吸附等方法对载体以及催化剂的结构进行了表征.结果表明,从不同碳源合成的纳米碳纤维(CNF)具有相似的直径和鱼骨式石墨层排列方式,但其物理化学性能差异较大,其中CO作为碳源得到的CNF具有最大的比表面积,最高的石墨化程度和最多的表面含氧基团;不同碳源的鱼骨式CNF负载的钯催化剂的活性为:Pd/FCNF-CO>Pd/FCNF-C1>Pd/FCNF-C2,与Pd分散度的顺序一致.CNF的织构、晶体结构和表面化学等协同载体效应,决定了Pd金属在CNF上的分散状态以及催化性能,而CNF的石墨层排列方式对其影响很小.

Palladium Catalysts Supported on Fishbone Carbon Nanofibers from Different Carbon Sources

Pd catalysts (0.5%Pd) supported on fishbone carbon nanofibers (FCNFs) from different carbon sources for terephthalic acid (TA) hydro-purification were prepared and investigated. CNFs from various carbon sources:CO (FCNF-CO),CH4 (FCNF-C1) and C2H4 (FCNF-C2) have been synthesized and characterized by N2 adsorption,XRD and TPD-MS. It is indicated that though they all possess similar fishbone structure,the FCNF from CO has the largest specific surface area,the highest graphitization degree and a large amount of surface groups,while the FCNF from C2H4 has the least specific surface area,the lowest graphitization degree and moderate surface groups. Pd/CNFs have been synthesized and characterized by TEM,N2 adsorption,XRD and CO chemisorption. The catalytic activity for TA purification follows the sequence:Pd/FCNF-CO>Pd/FCNF-C1>Pd/FCNF-C2,which is in accordance with the sequence of Pd dispersion. It is believed that rather than the graphene arrangement,the synergic support effect of pore structure,crystallinity and the surface chemistry dictates the Pd dispersion on FCNF and the consequent catalytic activity.