介孔分子筛固载离子液体复合材料的制备与催化性能研究

The application of mesoporous molecular sieve was limited in the field of catalysis because of its poor hydrothermal stability and weak acidity. The use of ionic liquids was limited in the industrial catalysis due to several disadvantages such as high viscosity, homogeneous reaction and high cost. Mesoporous molecular sieve supported ionic liquid composite as a novel solid catalyst combining the advantageous characteristics of mesoporous molecular sieve and ionic liquid for catalysis reaction will certainly exhibit the unique properties. In this study, the mesoporous molecular sieves with good ordering and adjustable pore size are hydrothermal synthesized by addition of pore-expanding agent and then the modification of mesoporous molecular sieves was carried out by using the suitable modified agent. Mesoporous molecular sieve supported ionic liquid composites were prepared by impregnation, grafting and in situ methods, respectively and characterized their physicochemical properties by various techniques. The catalytic performances of these composites were investigated by using the alkylation of phenol with tert-butyl alcohol and ketalization of cyclohexanone with ethylene as the target reactions. The obtained composites not only have the arranged mesoporous channels, but ionic liquids were uniformly and tightly dispersed into the mesoporous channels and the catalytic activity of the composite is higher than that of sole mesoporous molecular sieve or ionic liquid. There was no apparent loss of catalytic efficiency through eight cycles. The structure-activity relationship is investigated between the mesoporous structure, pore size, ionic liquid and catalytic activity.

介孔分子筛因弱酸性和低水热稳定性限制了它在催化领域的应用，离子液体由于自身的价格、粘度和状态等也限制了它在工业催化中的应用，介孔分子筛固载离子液体将充分发挥二者的优势，变离子液体的均相催化为多相催化，在催化反应中显示出独特的催化活性。本课题首先采用水热法通过添加扩孔剂制备出孔径可调的高有序性介孔分子筛，选用合适的修饰剂对介孔分子筛进行修饰改性，分别采用浸渍法、嫁接法及原位法制备介孔分子筛固载离子液体复合材料，并对所制备的复合材料进行表征，考察复合材料作为固体酸催化剂对苯酚与叔丁醇烷基化反应和环己酮与乙二醇缩酮化反应的催化性能。所制备的复合材料，保留了介孔分子筛的有序孔道，离子液体均匀且牢固地分布在介孔孔道内，催化活性高于单一的介孔分子筛或离子液体，重复使用8次以上催化活性没有明显降低。研究介孔结构、孔径与离子液体和催化活性间的构效关系。

介孔分子筛由于具有孔径适中，大比表面积等特点，因此作为催化剂和催化剂载体具有潜在优势。但是纯硅介孔分子筛几乎没有酸性，也不具有氧化、还原等催化活性，限制了其直接应用。离子液体在某些催化反应中具有高的活性，但是离子液体价格昂贵、粘度高、一般以液态形式存在，限制了离子液体在催化领域的应用。本课题利用离子液体的可设计性，将离子液体引入介孔分子筛，制备介孔分子筛固载离子液体复合材料，并研究其催化性能。.进行了MCM-41、MCM-48和SBA-15三种不同孔道结构的介孔分子筛固载离子液体复合材料的制备与催化性能研究。SBA-15固载离子液体复合材料对环己酮与乙二醇缩酮化反应的催化活性最高。.对MCM-41和SBA-15进行了孔径控制，研究了孔径与催化活性的关系。分别制备了孔径为2.4nm、3.6nm、4.8nm的MCM-41和孔径分别为5nm、8nm、12nm的SBA-15，固载含磺酸基酸性离子液体后，用于催化苯酚与叔丁醇烷基化反应，结果表明，中等孔径的SBA-15固载离子液体后具有高的催化活性与选择性。.以SBA-15为载体，通过原位合成的方法，直接将离子液体在介孔分子筛SBA-15孔道内生成，并负载在介孔分子筛SBA-15上，简化了复合材料的合成步骤，并且制备的复合材料作为固体酸催化剂具有高的催化活性。.对SBA-15进行掺杂改性，并且制备含有B、L双酸中心的离子液体，成功制得了B-L双酸中心离子液体固载介孔分子筛复合材料催化剂，提高了复合材料的酸量和酸强度，使其成为性能优良的固体酸催化剂。另外，研究发现改性的SBA-15固载杂多酸类离子液体显示出更高的固体酸催化活性。.围绕增强复合材料的酸性进行SBA-16固载酸性离子液体复合材料的制备与催化性能研究，研究发现SBA-16型介孔分子筛固载杂多酸离子液体具有高的酸催化活性。.研究结果表明，介孔分子筛固载酸性离子液体可以作为优良的固体酸催化剂，在烷基化、缩酮化以及酯化等酸催化反应中显示出优良的催化活性，特别是SBA系列介孔分子筛固载杂多酸类离子液体显示出更强的酸性和更高的催化活性，催化剂重复使用8次活性没有明显降低，有望在工业上实际应用。