甲烷无氧芳构化反应中Co助剂对Mo／HZSM-5

 甲烷在Co－Mo／HZSM－5催化剂上进行无氧芳构化反应的评价结果表明，Co的添加大大提高了Mo／HZSM－5催化剂在反应过程中的稳定性．BET实验证明，反应后的积炭对Co－Mo／HZSM－5催化剂孔道堵塞的程度较小．对积炭催化剂进行的一系列程序升温表面反应（如TPH，TPCO2和TPO）结果表明，TPO谱上有两个峰温明显不同的烧炭峰，Co的添加明显抑制了高温积炭的生成．H2主要与高温积炭发生反应，这部分积炭是催化剂失活的主要原因；CO2对低温积炭的影响则尤为明显．TEM结果表明，积炭催化剂上存在丝状积炭物种．碳丝不能与H2反应，但能被CO2除去．Co的添加促进了丝状积炭物种的生成，碳丝并不是导致催化剂失活的因素．

Effect of Co Additive on Formation of Coke Deposits in Methane Dehydro-Aromatization over Mo/HZSM-5 Catalyst

Methane dehydro-aromatization (MDA) in the absence of gas-phase oxygen is one of the promising routes for direct conversion of methane into fuels and chemicals, particularly into aromatics such as benzene and toluene. MDA under non-oxidative conditions was carried out over Co-Mo/HZSM-5 catalyst, and the result suggested that the addition of Co dramatically improved the stability of Mo/HZSM-5 catalyst. Furthermore, the chemical nature and physical properties of the coke deposits formed on Co-Mo/HZSM-5 catalyst were studied by various temperature-programmed surface reactions (TPSR), such as TPH, TPCO_2 and TPO, combining with TGA and TEM. The results were compared with those obtained over Mo/HZSM-5 catalyst. The TPO profiles recorded during the procedure of coke burning-off showed two peaks. The TPH experiments had effect on the coke burning-off only at high temperature. However, TPCO_2 mainly resulted in the diminishing of the coke burning-off at low temperature. The TEM pictures gave evidence that a lot of filamentous carbon formed on the surface of coked catalysts during the course of TPSR, and this kind of coke deposits was not a contributor to the deactivation of catalyst. Hydrogen had no ability to react with carbon filaments, but TPCO_2 experiment could eliminate them completely.