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采用新鲜的及再生的MoO_3-NiO/γ-Al_2O_3催化剂,催化生物质四氢糠醇合成吡啶,考察其催化性能的差异及催化剂失活的原因,并通过氮气物理吸附测试(BET)、元素分析仪(EA)、场发射扫描电子显微镜(SEM)、场发射透射电子显微镜(TEM)、X射线衍射分析仪(XRD)、激光拉曼光谱仪(LRS)、X射线光电子能谱仪(XPS)、热重分析仪(TG)以及吡啶原位红外吸收光谱仪(PY-IR)对失活催化剂进行表征分析。发现失活催化剂有两种形态的碳,即无定形碳和石墨化碳,催化剂失活的原因不是活性组分的变化或流失,而是由积碳引起的。积碳堵塞了催化剂的孔道和比表面积,并且覆盖了活性组分以及酸性位,降低了活性位点的有效利用率。针对催化失活,尝试了在线燃烧的方法使失活催化剂在空气中再生,发现再生后的催化剂与新鲜催化剂的催化活性基本一致,并且也可以保持50 h内吡啶收率大于80%。
The fresh and regenerated MoO_3-NiO / γ-Al_2O_3 catalyst was used to catalyze the synthesis of pyridine from biomass tetrahydrofurfuryl alcohol. The differences of catalytic performance and catalyst deactivation were investigated. The results of nitrogen physical adsorption (BET), elemental analysis (EA), field emission scanning electron microscopy (SEM), field emission transmission electron microscopy (TEM), X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (TG) and pyridine in situ infrared absorption spectrometer (PY-IR) were used to characterize the inactivated catalyst. The deactivated catalyst was found to have two forms of carbon, namely, amorphous carbon and graphitized carbon. The deactivation of the catalyst was not caused by the change or loss of the active components, but by the carbon deposition. Coke deposits clog the pores and specific surface area of the catalyst and covers the active components as well as the acidic sites, reducing the effective utilization of active sites. In order to catalyze the inactivation, an in-line combustion method was tried to regenerate the deactivated catalyst in the air. The catalytic activity of the regenerated catalyst was almost the same as that of fresh catalyst, and the yield of pyridine in 50 h was also maintained at more than 80%.