合成生物柴油Al-MCM-41分子筛负载酸性离子液体催化剂的双酸位调变及界面作用研究

Biodiesel, produced from soybean oil in the presence of ionic liquid catalysts, has drawn more and more attention in recent years, which meet the requirements of green chemistry. But the amount of ionic liquids used in the reaction system was large and it was very difficult to be separated from the reaction mixture. In previous work, it suggested that ionic liquids supported on molecular sieve catalyst had its unique advantages. The catalytic stability of the catalyst had been greatly improved while the catalyst showed better catalytic activity, compared with pure ionic liquid catalysts. On the ground of the study of the ionic liquids supported on Al-MCM-41 molecular sieve catalysts for synthesis of biodiesel from soybean oil by transesterification, this project will investigate how to design and control the acid amount and acid strength of the ionic liquids with different acidic groups and the acidic center and the structure of Al-MCM-41 molecular sieve in order to promote the formation of double acid active sites and improve the catalytic performance, analyze the structure-activity relationship of double acid active sites deeply；and make sure the effect of the interfacial action between ionic liquids and Al-MCM-41 molecular sieve on the catalytic stability in order to control the catalytic behavior and the state of ionic liquids dispersed on the catalyst carrier, which will become the basis for industrial applications.

采用离子液体催化大豆油制备生物柴油，符合绿色化学的要求，成为国内外的研究热点。而该体系中离子液体催化剂尚存在用量大与分离提纯难等问题。前期工作表明分子筛负载离子液体催化剂具有其独特的优势，与单纯离子液体相比，在保持较好催化活性的同时，负载型催化剂稳定性有了很大程度的提高。以大豆油酯交换合成生物柴油的分子筛负载离子液体催化剂研究为基础，进行离子液体及Al-MCM-41分子筛表面酸性基团的调控，促进双酸活性位形成，有效提高催化活性，并深入探讨双酸活性位与催化活性的构效关系；明确离子液体和Al-MCM-41分子筛的界面作用对催化剂稳定性的影响，控制离子液体在载体表面的催化行为，为工业应用奠定基础。

生物柴油作为一种可替代石化柴油的清洁能源，具有环境友好和可再生的优点，备受研究者的关注。本项目致力于基于非均相催化技术制备生物柴油固体催化剂体系的开发，围绕具有双酸中心分子筛负载离子液体催化剂的构筑及催化合成生物柴油而展开。.以硫酸氢根为阴离子，以内磺酸为功能化基团，尝试采用不同的阳离子制备了8种单核离子液体，并以四甲基二胺为阳离子制备了6种双核离子液体。分析表明离子液体催化剂在热稳定性方面表现良好，表现出较强的酸性。以所合成的两种离子液体为催化剂，以大豆油与甲醇的酯交换反应为探针实验考察了其催化活性，从两种体系中各筛选出一种催化活性较高的Brønsted 酸性离子液体，分别为[2-MPYR-BS][HSO4]和[TMHDA-BS][HSO4]。通过单因素实验对酯交换反应条件进行了优化，结果显示[2-MPYR-BS][HSO4]和[TMHDA-BS][HSO4]催化合成生物柴油的收率超过90%，该催化剂连续使用5次依然具有较高的催化活性。.采用不同硅铝比的MCM-41负载离子液体，制备得到一系列负载型双酸位催化剂，并用XRD、FTIR、N2-吸脱附、热重分析及TEM对其进行表征，以大豆油与甲醇的酯交换反应为探针实验考察了其催化活性。结果表明，离子液体成功固载于介孔分子筛并能保持其介孔结构，且在酯交换反应中表现出良好的反应活性。在ILs负载量为30%，醇油物质的量的比为36:1，140℃下反应5h，生物柴油收率在90%以上；而分子筛中Al的引入为活性组分离子液体构建了有益的酸环境，促进了其催化活性的提高；与均相离子液体相比，负载型催化剂能明显提高生物柴油的收率，且回收利用4次生物柴油收率仍接近88%。.釆用密度泛函理论(DFT)对模型油酸甘油酯和甲醇、乙醇的酸催化酯交换反应机理进行研究。采用TS过程发现了四面体过渡态，考察甘油三酯酯键优先发生反应理论，认为端位酯键的酯交换过程是最有利的过程。.对磁性固体催化剂体系CaO/NiFe2O4、CaO/CoFe2O4与CaO-MgO@CoFe2O4等展开研究，结果表明性钙基固体催化剂催化活性较高，生物柴油收率可达95%左右，稳定性良好，连续使用4-5次催化活性没有明显下降，因其具有磁性，在实际生产过程中更加便于回收和再利用。.本项目为基于离子液体固载型催化剂体系及磁性钙基固体催化剂体系的工业化应用奠定了理论基础。