【作者】 赵杰；

【导师】 乐英红； 华伟明；

【作者基本信息】 复旦大学 ， 物理化学， 2008， 博士

【摘要】 SO₄^2-/M_xO_y型固体超强酸,尤其是SO₄^2-/ZrO₂,具有不腐蚀反应装置,环境友好,可在高温下重复使用等优点,近三十年来一直受到国内外催化研究者的广泛关注。与常用的固体酸催化剂相比,它们的最大优点是酸强度高,弥补丁前者在酸强度方面的不足,满足强酸催化反应的需要。而且容易使底物的C-H和C-C键活化,形成碳正离子,促使酸催化反应在相对较低的温度下进行,从而节省能耗,减少副反应,并且有利于生成高辛烷值的支链烃,是一类很有应用潜力的新型绿色催化材料。近年来,随着环境保护要求的提高,人们迫切希望替代石油和化学工业中一些重要反应所使用的环境不友好催化剂,如:HF、H₂SO₄、H₃PO₄和AlCl₃等。固体超强酸能在较低温度下活化共价的C-H和C-C键,且兼具多相催化剂的可再生性和液体超强酸的高活性和高选择性的优点,极有可能成为这些环境不友好催化剂的替代品,创立一批无环境污染的清洁工艺。该体系中又以SO₄^2-/ZrO₂的酸性最强,对其研究也最多。但是SO₄^2-/ZrO₂比表面积和孔容偏小,孔道分布不够单一,这也就限制了它的潜在应用。本论文合成了具有较高热稳定性的介孔SO₄^2-/Al₂O₃-ZrO₂催化剂,其在许多酸催化反应中的活性明显高于传统的SO₄^2-/ZrO₂。首先提出了以介孔γ-Al₂O₃为载体制备负载型介孔SO₄^2-/ZrO₂/γ-Al₂O₃固体超强酸体系,其催化活性明显高于文献中常用的以介孔SiO₂为载体制备的负载型SO₄^2-/ZrO₂和传统的SO₄^2-/ZrO₂催化剂,为介孔固体超强酸的制备提供了新的思路。提出了水热辅助合成非过渡金属氧化物Al₂O₃促进的SO₄^2-/ZrO₂及过渡金属氧化物Fe₂O₃促进的SO₄^2-/ZrO₂固体超强酸,其催化活性明显高于没有经过水热处理的催化剂,为SO₄^2-/ZrO₂型固体超强酸提供了有效的改性方法。同时我们还首先发现了Al₂O₃助剂对SO₄^2-/SnO₂固体超强酸体系的促进作用。论文的第三章采用模板法（以P84为模板剂）,成功合成了经650℃高温焙烧后仍然保持介孔结构的SO₄^2-/Al₂O₃-ZrO₂催化剂（记为MSAZ）,催化剂中Al₂O₃含量高于20wt%,ZrO₂为四方晶相。MSAZ催化剂的孔径分布较均匀,比表面为165-262m²/g,孔容为0.156-0.340cm³/g,表面SO₄^2-含量为7.0-8.4%,远远高于传统的SO₄^2-/ZrO₂（记为CSZ）。催化剂表面既有L酸位,也有B酸位,并且L酸的酸强度高于B酸。MSAZ催化剂比CSZ具有更多的强酸位和超强酸位。催化反应测试的结果显示,在低温正戊烷转化反应、甲苯与苯甲酰氯的苯甲酰化反应及1,3,5-三叔丁基苯的裂解反应中,MSAZ催化剂的催化活性明显高于CSZ催化剂。1,3,5-三叔丁基苯裂解反应的结果展示了介孔MSAZ催化剂相对于微孔沸石的优点和在大分子反应领域中（如:制药、精细化工等）潜在的应用前景。第四章以介孔γ-Al₂O₃为载体,用化学液相沉积法制备了新的负载型介孔SO₄^2-/ZrO₂/γ-Al₂O₃催化剂体系。该催化剂孔径分布较均匀,比表面为217-258m²/g,孔容为0.296-0.352 cm³/g,表面SO₄^2-含量为6.8-7.7%硫含量,明显高于传统的SO₄²-/ZrO₂（记为CSZ）。催化剂中ZrO₂为四方晶相,其酸性和催化活性可以通过改变ZrO₂负载量来调节。催化剂表面具有L酸和B酸位。SO₄^2-/ZrO₂负载于介孔γ-Al₂O₃上,酸强度基本不变,但负载于MCM-41载体上,酸强度明显减弱,且前者酸量大于后者以及CSZ。介孔SO₄^2-/ZrO₂/γ-Al₂O₃催化剂比MCM-41负载的SO₄^2-/ZrO₂和CSZ具有更高的催化活性。固体超强酸催化剂的硫酸化试剂对反应活性的影响顺序如下:（NH₄）₂S₂O₈＞H₂SO₄＞（NH₄）₂SO₄。对于大分子反应,介孔固体超强酸的催化活性明显高于微孔沸石分子筛及传统的SO₄^2-/ZrO₂,在催化大分子反应中表现出良好的应用前景。第五章采用水热辅助方法合成了少量非过渡金属氧化物Al₂O₃促进的SO₄^2-/ZrO₂固体超强酸催化剂。实验结果表明,水热辅助合成有助于增大Al₂O₃促进SO₄^2-/ZrO₂固体超强酸的比表面积,稳定样品表面的硫物种,提高催化剂的酸量,但不会改变Al的配位情况。催化剂表面既具有B酸位又具有L酸位,水热处理后催化剂的B酸位减少,L酸位增加。水热辅助合成有助于提高催化剂的蒎烯异构化活性,其中水热处理一天的催化剂酸量最多,蒎烯异构化活性最高,达到80.8%,比没有经过水热处理的样品（52.3%）活性提高了54%。第六章采用了与第五章相同的水热辅助方法合成了过渡金属氧化物Fe₂O₃促进的SO₄^2-/ZrO₂固体超强酸催化剂。实验结果表明,水热辅助合成有助于增大Fe₂O₃促进SO₄^2-/ZrO₂固体超强酸的比表面积,稳定样品表面的硫物种,抑制氧化锆晶粒长大,有助于提高样品的蒎烯异构化活性。SO₄^2-/ZrO₂中掺杂少量Fe₂O₃可以增加比表面、硫含量,会使氧化锆晶粒变小,可以提高蒎烯异构化活性,其中经过水热处理的含Fe量为2wt%的样品活性最高,达到71.3%,比相同Fe含量但没有经过水热处理的样品（45.8%）活性提高了56%,是SO₄^2-/ZrO₂催化剂2.2倍。第七章我们用共沉淀法制备了掺杂少量Al₂O₃的SO₄^2-/SnO₂。SO₄^2-/SnO₂-Al₂O₃催化剂的比表面为139-150 m²/g,明显大于SO₄^2-/SnO₂催化剂（118 m²/g）。SO₄^2-/SnO₂-Al₂O₃催化剂表面SO₄^2-含量为5.8-8.7 wt%,明显高于SO₄^2-/SnO₂催化剂（5.0wt%）,表明添加少量Al₂O₃能使SO₄^2-/SnO₂催化剂稳定更多的表面硫物种。经500℃高温焙烧后,催化剂中的SnO₂为四方相,随着Al₂O₃含量的增加,SnO₂的衍射峰强度有所减弱,说明Al₂O₃的存在抑制了SnO₂晶粒的长大。SO₄^2-/SnO₂-Al₂O₃催化剂中的Al以六配位形式存在,催化剂表面只有L酸位,且酸性位明显多于SO₄^2-/SnO₂催化剂。考察了催化剂在2-甲氧基萘与乙酸酐的酰化反应中的催化活性。结果发现,SO₄^2-/SnO₂中掺入少量的Al₂O₃可以明显提高2-甲氧基萘酰化反应的活性,掺杂0.2-0.5 mol%的Al₂O₃后,催化剂的活性提高最多,由原来的36.1%提高至58%左右,提高了约60%。活性增加的原因是Al₂O₃助剂可提高催化剂表面SO₄^2-的含量和酸性位数目。更多还原

【Abstract】 SO₄^2-/M_xO_y type solid superacids,especially SO₄^2-/ZrO₂,have attracted much attention in the last 30 years,because they are noncorrosive,environmentally friendly and reusable at high temperatures.Compared with traditional solid acid catalysts,the typical feature of these solid superacids is that they are highly acidic.Thus,they make up the deficiency in acid strength for the former acid catalysts,and meet the requirement for the strong acid-catalyzed reactions.Mover,they are easy to activate C-H and C-C bonds of the substrates,and catalyze the reaction at relatively low temperatures.As a result,energy can be saved and side reactions are decreased.Also branched hydrocarbons with high octane number are favored to produce.Therefore, they are recognized as a class of novel catalytic materials which are green and have potential application.Recently,with the increasing of environmental constrains,the environmental unfriendly catalysts used in petrochemical industry,such as HF,H₂SO₄,H₃PO₄ and AlCl₃,are urgent to be substituted by new clean catalysts.Solid superacids are capable of activating the covalent C-H and C-C bonds at lower temperatures,and reveal all the advantages of heterogeneous catalysts such as regenerability coupled with the benefits of liquid superacids such as high activity and selectivity.They are possible to become the substitute of those environmentally unfriendly catalysts,and thus a number of environmental friendly processes may be established.In these solid superacids,the acidity of SO₄^2-/ZrO₂ is strongest,and the research of this kind of solid superacid catalysts is also most broad.However,for the SO₄^2-/ZrO₂ type solid superacid catalysts,the relatively small surface area and pore volume and non-uniform pore size limits their potential applications.In the present dissertation,we prepared mesoporous sulfated Al₂O₃-ZrO₂ catalysts with higher hydrothermal stability,and the catalysts are more active than the conventional SO₄^2-/ZrO₂ for various acid-catalyzed reactions.We put forward for the first time to prepare a novel mesoporous solid superacid system by loading sulfated zirconia into mesostructuredγ-Al₂O₃.The novel mesoporous solid superacids exhibit superior catalytic performances to mesostructured SiO₂ supported sulfated zirconia that were often studied in the literature as well as traditional sulfated zirconia catalysts, affording a new pathway for the preparation of mesoporous solid superacids.We advanced a method of hydrothermal assistant synthesis for preparing non-transition metal oxide Al₂O₃ and transition metal oxide Fe₂O₃ promoted SO₄^2-/ZrO₂ solid superacid catalysts.Their catalytic activities are distinctly higher than the corresponding catalysts without hydrothermal assistant treatment,supplying an effective modification method for SO₄^2-/ZrO₂ solid superacid catalysts.At the same time,we discover for the first time the promoting effect of Al₂O₃ on SO₄^2-/SnO₂ solid superacid.In the third chapter of this thesis,mesoporous sulfated Al₂O₃-ZrO₂（MSAZ） catalysts with large surface areas and pore volumes after calcination at high temperature（650℃） and with higher Al₂O₃ content than 20wt%were successfully prepared from a template of block copolymer（P84）.Zirconia in MSAZ catalysts is tetragonal crystalline.The pore diameters are narrow in distribution.The surface area of MSAZ catalysts is 165-262m²/g,the pore volume is 0.156-0.340cm³/g and surface SO₄^2- content is 7.0-8.4%,which are much higher than those of conventional sulfated zirconia（labeled as CSZ）.The nature of acid sites present on the MSAZ catalysts is Lewis and Brφnsted type,and the strength of Lewis acid sites is stronger than that of Brφnsted ones.MSAZ catalysts have greater number of strong and very strong acid sites than CSZ.Catalytic tests show that mesoporous sulfated Al₂O₃-ZrO₂ catalysts exhibit higher activities than conventional sulfated zirconia for conversion of n-pentane at low temperature,Friedel-Crafts benzoylation of toluene with benzoyl chloride and dealkylation of 1,3,5-tri-tert-butyl-benzene.Catalytic evaluation for the dealkylation of 1,3,5-tri-tert-butyl-benzene shows that mesostructured MSAZ catalysts elucidate the advantages evidently over microporous zeolites and provide potential application for catalyzing bulky molecules such as those encountered in the production of pharmaceuticals and fine chemicals.In the fourth chapter,we have shown that novel mesoporous SO₄^2-/ZrO₂/γ-Al₂O₃ catalysts were successfully synthesized via chemical liquid deposition method using the carrier of mesostructuredγ-Al₂O₃.The pore diameters of the catalysts are narrow in distribution,the surface area is 217-258m²/g,the pore volume is 0.296-0.352 cm³/g,and the surface sulfate content is 6.8-7.7%,which are evidently higher than those of conventional sulfated zirconia（labeled as CSZ）.Zirconia in the catalysts exhibits only the tetragonal phase.The acidity and catalytic activity can be adjusted via changing the loading of ZrO₂.Both Lewis and Brφnsted acid sites are present on the catalysts.Mesostructuredγ-Al₂O₃ supported sulfated zirconia catalysts have the equivalent acid strength to sulfated zirconia,but have stronger acid strength than MCM-41 supported sulfated zirconia.Moreover,the number of acid sites is higher on the former catalysts than on the latter one and CSZ.Hence,the novel mesoporous solid superacids are more active than MCM-41 supported sulfated zirconia and sulfated zirconia for various acid-catalyzed reactions.The different sulfating agents lead to different sulfate contents,which explains the differences in acidity and catalytic reactivity,the order is（NH₄）₂S₂O₈＞H₂SO₄＞（NH₄）₂SO₄.The catalytic activity of mesoporous solid superacids is evidently higher than microporous zeolites and conventional sulfated zirconia in catalyzing bulky molecules.In the fifth chapter,non-transition metal oxide Al₂O₃ promoted SO₄^2-/ZrO₂ solid superacid catalysts were synthesized through hydrothermal assistant treatment method. The results indicate that hydrothermal assistant synthesis is helpful for increasing the surface areas of Al₂O₃ promoted SO₄^2-/ZrO₂ solid superacid catalysts,stabilizing the sulfate species on surface of the catalysts,and enhancing the acid amount of catalysts, but the coordinate circumstance of Al remains unchanged.The nature of acid sites present on the catalysts is Lewis and Brφnsted type,and after hydrothermal treatment, the number of Lewis acid sites increases and that of Brφnsted ones decreases. Hydrothermal assistant synthesis can enhance the catalytic activity ofα-pinene isomerization reaction.The acid amount and catalytic acidity forα-pinene isomerization is highest after 1 day hydrothermal treatment.The conversion is 80.8%, increased by 54%in comparison with the corresponding untreated sample（52.3%）.In the sixth chapter,transition metal oxide Fe₂O₃ promoted SO₄^2-/ZrO₂ solid superacid catalysts were synthesized through hydrothermal assistant treatment method. The results clearly indicate that hydrothermal assistant synthesis is also helpful for increasing the surface area of Fe₂O₃ promoted SO₄^2-/ZrO₂ solid superacid catalysts, stabilizing the surface sulfate species,restraining the growth of ZrO₂ crystallites, enhancing the catalytic activity ofα-pinene isomerization reaction.Incorporation of small amounts of Fe₂O₃ into SO₄^2-/ZrO₂ results in higher surface areas,more surface SO₄^2- content and smaller crystallite size of ZrO₂.Hence,the catalytic activity ofα-pinene isomerization reaction is improved.The activity of the catalyst containing 2wt%Fe is highest.The conversion reaches 71.3%,increased by 56%compared with the corresponding sample without hydrothermal assistant treatment（45.8%）,and is 2.2 times as high as SO₄^2-/ZrO₂. In the seventh chapter,we prepared small amounts of Al₂O₃ doped SO₄^2-/SnO₂ through co-precipitation method.SO₄^2-/SnO₂-Al₂O₃ catalysts have distinctively larger surface area（ranging from 139 to 150m²/g） than SO₄^2-/SnO₂（118m²/g）.The content of SO₄^2- on the surface of SO₄^2-/SnO₂-Al₂O₃ catalysts is 5.8-8.7wt%),obviously higher than SO₄^2-/SnO₂（5.0wt%）,showing that incorporation of small amounts of Al₂O₃ can stabilize more sulfur species on the surface of SO₄^2-/SnO₂.SnO₂ in the catalysts is tetragonal crystalline after calcination at 500℃.As the Al₂O₃ content is increased,the intensity of characteristic diffractive peaks of SnO₂ decreases progressively.This result demonstrates that the growth of SnO₂ crystallites is inhibited in the presence of Al₂O₃.There is only six-coordinate aluminum species in the SO₄^2-/SnO₂-Al₂O₃ catalysts.Only Lewis acid sites are present on the catalysts,and the number of acid sites is increased after incorporation of Al₂O₃ into SO₄^2-/SnO₂.Benzoylation of 2-Methoxynaphthalene with acetic anhydride was used as a test reaction to investigate the activities of the catalysts.The results indicate that incorporation of Al₂O₃ into SO₄^2-/SnO₂ can enhance the catalytic activity.The activity of SO₄^2-/SnO₂ increases most after doping 0.2-0.5 mol%Al₂O₃,increased by about 60%（from 36.1%to 58%）. The reason for activity enhancement is that the surface SO₄^2- content and number of acid sites of SO₄^2-/SnO₂ catalysts are increased after incorporation of small amounts of Al₂O₃.更多还原