Abstract:

In the solid-solid mixing pyrolytic process,the ash or bed material may influence the pyrolytic behaviors of the oil shale.Thus,pyrolysis of oil shale mixed with four metal oxides Al₂O₃,MgO,CaO and Fe₂O₃ were investigated.The results showed that CaO had a strong influence to the yields of products,and particularly promotes the formations of shale oil and char,while decreases the yield of gas product.On the contrary,Al₂O₃ in acidic property can most distinctly promote the devolatilization of oil shale with an augmented yields of shale oil,water and gas products.Comparatively,the effects of MgO and Fe₂O₃ to product yields were much weaker.All of the four metal oxides can promote the formation of H₂,CH₄ and C₂ hydrocarbons.The content of CO₂ decreased extremely for CaO,while all other metal oxides played promoting role to the formation of CO₂.H₂ and CH₄ can be most distinctly increased for Fe₂O₃ and Al₂O₃,respectively.The content of aromatics in shale oil can be augmented by all of the four metal oxides and the effect of Fe₂O₃ was most significant.For the components of chain hydrocarbons,the short-chain (C₆-C₁₂) alkanes and alkenes were promoted for both of CaO and MgO,while only the short-chain alkanes were increased under the effect of Al₂O₃.It was deduced that the alkalinic CaO and MgO firstly reacted with the fatty acids of the organic matters,forming a fatty acid salt.Then,a decarboxylating step was followed in the way of releasing CaCO₃,simultaneously generating intermediates that could be converted to both of alkanes and alkenes.However,under the acidic Al₂O₃,the decarboxylation product was CO₂,determined a prevalent alkane product.

Key words: oil shale, shale ash, pyrolysis, metal oxide, catalysis

摘要：

通过固定床反应器，对4种金属氧化物（Al₂O₃、MgO、CaO、Fe₂O₃）对油页岩热解所得油、气产率及成分的影响进行了研究。结果显示，碱性CaO对油、水、气、焦产率分布影响较为突出，可提高页岩油与半焦产率，并降低热解气产率；而酸性较强的Al₂O₃可同时提高页岩油、热解气和热解水的产率，有利于促进挥发分的析出；比较而言，MgO和Fe₂O₃的作用相对较弱。4种金属氧化物均可提高热解气中H₂、CH₄和C₂的产率；CaO作用下CO₂含量降低，而其他金属氧化物对CO₂的产生有不同程度的促进作用；Fe₂O₃可促进H₂产生；Al₂O₃作用下CH₄含量有所增加。4种金属氧化物均可促进页岩油中芳香烃的产生，并且CaO和MgO两种碱土金属氧化物作用下，短链（C₆~C₁₂）烷烃和烯烃含量均增加，而掺混Al₂O₃时页岩油中仅短链（C₆~C₁₂）烷烃含量增加。对此机理进行推测认为，碱性CaO和MgO首先与以脂肪酸形式存在的有机质进行酸碱反应，得到脱羧活性更高的羧酸盐，后者脱羧所得中间产物具有生成烷烃或烯烃两条可能路径，同时得到碳酸盐；而在具有Lewis酸特征的Al₂O₃作用下，脱羧产物为CO₂，并同时得到饱和烃产物。

关键词: 油页岩, 页岩灰, 热解, 金属氧化物, 催化