金属氧化物对油页岩热解产物收率及组成分布的影响

Effects of metal oxides on yields and compositions of products from pyrolysis of oil shale

通过固定床反应器,对4种金属氧化物(Al_2O_3、MgO、CaO、Fe_2O_3)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Al_2O_3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Fe_2O_3的作用相对较弱。4种金属氧化物均可提高热解气中H_2、CH_4和C2的产率;CaO作用下CO_2含量降低,而其他金属氧化物对CO_2的产生有不同程度的促进作用;Fe_2O_3可促进H_2产生;Al_2O_3作用下CH_4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Al_2O_3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Al_2O_3作用下,脱羧产物为CO_2,并同时得到饱和烃产物。

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.