飞行时间质谱调查超声膨胀条件下低碳烷烃芳构化反应

Investigation of Light Alkane Aromatization Under Supersonic Jet Expansion Condition by Using Time of Flight Mass Spectroscopy

在超声膨胀条件下,调查了甲烷和丙烷烃在3%Mo/HZSM-5催化剂上芳构化反应,其反应物和产物直接由飞行时间质谱检测。发现在相同的催化剂上观察到结果与大气压条件下的结果完全不同,萘是主要产品。在低温下芳烃化合物形成与丙烷C3H7自由基在布朗斯特酸性位上偶联密切相关。在700℃初始的诱导期期间,13CHO中间体被形成,并且Mo O3被转化为Mo2C。即CH4在Mo2C/HSM-5脱氢是速度控制步骤,而后期烷基芳构化反应能在更低的温度范围内进行。

Methane and propane dehydroaromatization over the 3% Mo/HZSM-5 catalyst under supersonic jet expansion （SJE） condition was investigated by direct monitoring of the reactant and products using time-of-flight mass spectrometry （TOF-MS）. The results observed over the same catalyst were different from that at atmospheric pressure, naphthalene was the major product, and the formation of the aromatic compounds at relatively low temperature was a result of coupling of C3H7 radicals from propane on Bronsted acidic sites. During the initial induction period at 700 oC, 13CHO was formed and MoO3 was converted to Mo2C. The dehydrogenation of methane over Mo2C/ZSM-5 is the rate-determining step, and the later aromatization of alkyl group can be conducted at much lower temperature.