费托合成CeO2助Co/SiO2催化剂的失活

在固定床反应器上考察了原粒度(1～3mm)CeO2助Co/SiO2催化剂的费托反应性能,提出了催化剂失活的机理,并采用程序升温还原、X射线衍射和X射线光电子能谱对催化剂进行了表征.结果表明,在1.5MPa,488K和400h-1条件下进行的300h稳定性实验中,原粒度CeO2助Co/SiO2催化剂上的CO平均转化率达到41%,液态烃选择性达到85%,液态烃中C10 烃的质量含量占88%以上.反应器出口的催化剂中有少量的CoO和Co2SiO4生成.催化剂的失活过程受动力学控制而非热力学控制,催化剂的失活机理为:高分散的纳米Co离子在反应器出口高水蒸气压力的作用下,以CoO为中间物种,与水合SiO2作用生成Co2SiO4,即Co H2O→CoO H2,SiO2 H2O→OSi(OH)2,2CoO OSi(OH)2→Co2SiO4 H2O.

Deactivation of CeO2-Promoted Co/SiO2 Fischer-Tropsch Catalysts

The catalytic performance of the CeO₂-Co/SiO₂ catalyst was investigated for Fischer-Tropsch synthesis on a lab-scale fixed-bed reactor filled with 1.5 L catalyst (1–3 mm) for 300 h under the reaction conditions of 1.5 MPa, 488 K, and 400 h⁻¹. The catalyst was characterized by temperature-programmed reduction, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy. The catalyst exhibited a CO conversion of 41%, a C₅₊ selectivity of 85%, and a CH₄ selectivity of 10%. XRD results revealed the presence of CoO and cobalt silicate species on the catalyst that was located near the outlet of the reactor after reaction. It was proposed that the cobalt silicate species was formed through reaction 2Co + SiO₂ + 2H₂O→Co₂SiO₄ + 2H₂ via a CoO intermediate, which was kinetically restricted under typical Fischer-Tropsch synthesis conditions.