Zhang Xiaoxin

Fischer-Tropsch Synthesis over Skeletal Co@HZSM-5 Core-Shell Catalysts

We used skeletal Co as the core to prepare a skeletal Co@HZSM-5 core-shell catalyst by growing an HZSM-5 membrane on skeletal Co via hydrothermal synthesis. The physicochemical properties of the catalyst were determined using elemental analysis, N2 physisorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and NH3 desorption. In gas-phase Fischer-Tropsch synthesis (FTS), the skeletal Co@HZSM-5 core-shell catalyst was more efficient than a physically mixed skeletal Co-HZSM-5 catalyst in cracking long-chain hydrocarbons, giving higher selectivity for C5-C11 gasoline products. The thickness of the zeolite shell on the skeletal Co@HZSM-5 core-shell catalyst was easily tuned by adjusting the hydrothermal time. At a suitable zeolite shell thickness, the long-chain hydrocarbons were cracked completely, with high FTS activity, leading to high selectivity for the gasoline fraction. Increasing the reaction temperature resulted in higher以骨架Co为内核,通过水热合成在其表面包覆HZSM-5分子筛膜,制备了具有核壳结构的骨架Co@HZSM-5催化剂.采用元素分析、氮物理吸附、粉末X射线衍射、扫描电子显微镜、氨脱附等手段对催化剂的物理化学性质进行了表征.在气相费托合成反应中,骨架Co@HZSM-5核壳催化剂显示了比物理混合的骨架Co-HZSM-5催化剂更好的催化裂解作用,故C5-C11汽油段产物选择性高.通过改变水热时间,对分子筛膜厚进行了调节,发现适当的分子筛膜厚在保证催化剂具有较高活性的前提下,使长链费托合成产物完全裂解,高选择性地得到汽油段产物.提高反应温度有利于费托合成反应的进行以及分子筛上裂解效率的提高,但产物分布向短链烃方向移动.在水热4天制备的骨架Co@HZSM-5核壳催化剂上及反应温度为250°C时,得到了最佳反应结果,汽油段产物选择性达79%,说明费托合成活性中心与催化裂解酸中心之间形成了良好的协同作用.