【作者】 翁志焕；

【导师】 蹇锡高；

【作者基本信息】 大连理工大学 ， 高分子材料， 2008， 博士

【摘要】 多金属氧酸盐（多酸）作为氧化催化剂已被广泛应用于各种均相和非均相催化体系中。多酸非常重要的一个优点就是它的催化性能可以方便地通过改变反荷阳离子、杂原子和多原子来调节;另一优点是具有良好的热稳定性,可适用于300～350℃的催化反应环境。但多酸在实际应用中也存在着不可回避的问题:作为均相催化剂,其不易从体系中回收;作为非均相催化剂,其表面积比较低。解决上述问题对多酸的推广应用具有重要的意义。本文首先采用有机季铵盐修饰多酸得到了反应控制相转移磷钼酸盐催化剂Q₃PMo₄O₁₆（Q=[C₇H₇N（CH₃）₃]⁺）。在氧化剂H₂O₂的作用下,不可溶的Q₃PMo₄O₁₆可转变为可溶的催化活性中心Q₃PMo₄O₂₄而进入反应溶液参与催化反应;当反应结束H₂O₂消耗完毕后,催化剂又恢复为Q₃PMo₄O₁₆而从体系中沉淀出来。这样催化剂在反应过程中既表现出了均相催化的特点,而在反应结束后又可以像非均相催化剂那样方便地被回收。将此催化剂应用于醇类液相催化氧化反应中,发现其对芳香醇和脂肪族仲醇的催化活性高于脂肪族伯醇。当H₂O₂与苯甲醇的摩尔比为0.75时,苯甲醇基于H₂O₂的转化率可以达到92.8%,主产物苯甲醛的选择性大于99%,反应后催化剂的回收率为87.6%（wt%）,同时催化剂循环使用三次其催化活性无明显降低。制备了另一种反应控制相转移磷钨酸盐催化剂Q₉PW₉O₃₄（Q=[C₇H₇N（CH₃）₃]⁺）。FF-IR和³¹P NMR的表征结果表明:这种催化剂在H₂O₂的作用下可降解为更小的可溶的活性物种[PW₄O₂₄]^3-,当H₂O₂消耗掉时,活性物种又可转变为初始的不溶性的催化剂而从体系中沉淀出来。将催化剂应用于苯甲醇的液相氧化反应中,当H₂O₂与苯甲醇的摩尔比为0.9时,反应0.5h,苯甲醇基于H₂O₂的转化率不低于95.0%,苯甲醛的选择性都大于99%,同时催化剂循环使用三次其催化活性得到良好的保持。通过动力学实验,得到了Q₃PMo₄O₁₆和Q₉PW₉O₃₄催化氧化苯甲醇的反应速率方程分别为:dc/dt=k[BzOH][Q₃PMo₄][H₂O₂]和dc/dt=k[BzOH]^0.5[Q₉PW₉]^0.5[H₂O₂]^0.5,两个催化体系的反应活化能分别为48.6kJ/mol和27.0kJ/mol。并建立了Q₃PMo₄O₁₆催化体系的动力学数学模型。以季铵化的杂萘联苯基聚芳醚砜酮（QAPPESK）为载体,负载一系列杂多阴离子得到了非均相化的杂多酸催化剂。当反应物与H₂O₂的摩尔比为1:1时,在液相催化氧化苯甲醇的反应中,催化剂QAPPESK-PW₉的活性最高,反应6h,苯甲醇的转化率为92.1%,苯甲醛的选择性为98.2%;而在环己烯的氧化反应中QAPPESK-PMo₄是较合适的催化剂,反应4h,环己烯的转化率为95.7%,环氧环己烷的选择性为96.0%。对QAPPESK-PW₉和QAPPESK-PMo₄进行FT-IR、XRD和TG表征,分析结果显示:杂多阴离子均以分子水平均匀地分布在载体上,其在聚合物表面并未形成结晶相;聚合物载体和杂多阴离子的结构在反应后都得到了很好的保持。将QAPPESK-PW₉和QAPPESK-PMo₄分别循环使用五次,其催化活性无明显降低,催化剂均未发生明显的杂多阴离子溶脱现象。将交联聚苯乙烯D201作为负载[PW₉O₃₄]^9-和[PMo₄O₂₄]^3-的载体,通过FT-IR、UV、XRD、TG和EPMA的详细表征:发现杂多阴离子同样是以分子水平负载到载体上,并无明显的堆积现象;在反应中,载体和杂多阴离子都表现出了良好的稳定性,其结构在反应后并未发生变化。其中D201-PMo₄在液相氧化环己烯的反应中表现出了较高的催化活性,反应6h,环己烯的转化率为89.5%,主产物的选择性为90.5%。将催化剂循环使用五次,其催化活性无明显降低。相对于D201,以QAPPESK为载体的催化剂在氧化苯甲醇的反应中表现出了更高的催化活性。更多还原

【Abstract】 Polyoxometallates（heteropoly acids）have been widely employed as oxidation catalysts in various homogeneous and heterogeneous reactions.One of the great advantages of polyoxometallates catalysts is that their oxidation catalytic properties can be controlled in a systematic way by changing the identity of charge compensating counter-cations,heteroatoms, and framework polyatoms.Another advantage that makes polyoxometallates promising catalysts is their great thermal stability,so they can be used under the middle high temperature catalytic conditions（300～350℃）.However,there are some problems for polyoxometallates in the application:as homogeneous catalyst,it is difficult to recover the catalyst from the system;and as heterogeneous catalyst,their surface area is very low.So it is very important to resolve above mentioned problems for the application of polyoxometallates.Firstly,a reaction-controlled phase-transfer catalyst Q₃PMo₄O₁₆（Q=[C₇H₇N（CH₃）₃]⁺）is synthesized by using quaternary ammonium salt to modify the polyoxometallates.Under the action of H₂O₂,the insoluble Q₃PMo₄O₁₆formed soluble catalytic activity species Q₃PMo₄O₂₄ to catalyze the oxidation reaction;after the H₂O₂ are consumed up,the catalyst can deposit from the system as Q₃PMo₄O₁₆.Therefore,in the reaction,the catalyst not only shows the feature of homogeneous catalyst,but also can be recovered easily as heterogeneous catalyst. This catalyst is employed in the liquid phase oxidation of alcohols.It is found that the aromatic alcohols and aliphatic sec alcohol can be catalyzed oxidation more efficiently than aliphatic primary alcohol.When the molar ratio of H₂O₂ to benzyl alcohol is 0.75,the conversion based on H₂O₂ reaches 92.8%,the selectivity of main product benzaldehyde is not less than 99%,the recovery ratio is 87.6%（wt%）,moreover,the catalyst can be recycled three times without decreasing the activity obviously.Then,another reaction-controlled phase-transfer polyoxotungstate catalyst Q₉PW₉O₃₄ （Q=[C₇H₇N（CH₃）₃]⁺）is prepared.The results of characterizing with FT-IR and ³¹P NMR indicating that after it reacts with H₂O₂,the catalyst depolymerizes into one smaller active species[PW₄O₂₄]^3-which is soluble in the reaction medium,when the oxidant H₂O₂ is consumes up,the soluble species polymerizes into insoluble larger compounds with Keggin-structure framework.The catalyst is utilized in the liquid phase oxidation of benzyl alcohol,when the molar ratio of H₂O₂ to benzyl alcohol is 0.9,after 0.5h,the conversion based on H₂O₂ is not less than 95.0%,the selectivity of benzaldehyde is over 99%,the catalyst is recycled three times and the activity is maintained well. Through kinetic experiments,the reaction rate equations of liquid phase catalytic oxidation of benzyl alcohol with Q₃PMo₄O₁₆and Q₉PW₉O₃₄are obtained,respectively.The equations as follows:dc/dt=k[BzOH][Q₃PMo₄][H₂O₂]and dc/dt=k[BzOH]^0.5[Q₉PW₉]^0.5 [H₂O₂]^0.5.The reaction activation energy of these two catalytic systems are 48.6 kJ/mol and 27.0 kJ/mol,respectively.And the kinetic mathematical model of catalytic system with O₃PMo₄O₁₆is built.Some supported polyoxometallates catalysts are prepared by supporting a series of polyoxometallates on the quaternary ammonium poly(phthalazinone ether sulfone ketone.In the liquid phase oxidation of benzyl alcohol,when the molar ratio of substrates to H₂O₂ is 1, the catalytic activity of QAPPESK-PW₉ is the highest,the conversion of benzyl alcohol reaches 92.1%,and the selectivity of benzaldehyde is 98.2%within 6h.And in the catalytic oxidation of cyclohexene,QAPPESK-PMo₄ is confirmed to be the best catalyst,the conversion and selectivity of cyclohexene oxidation reaction are 95.7%and 96.0%, respectively within 4 h.The studies of characterization of QAPPESK-PW₉ and QAPPESK-PMo₄ with FT-IR,XRD and TG demonstrate that:the heteropoly anions are finely dispersed on the polymer support,they do not form crystal phase on the support surface; the structure of polymer support and heteropoly anions are maintained well during the reaction.The QAPPESK-PW₉ and QAPPESK-PMo₄ can be recycled five times without decreasing the catalytic activity,indicating that no leaching of the active species occurred during the reaction.The crosslinked polystyrene D201 is employed as the support of[PW₉O₃₄]^9-and [PMo₄O₂₄]^3-.The catalysts are characterized with FT-IR,UV,XRD,TG and EPMA,and it is found that the heteropoly anions do not form crystal phase on the support surface,during the reaction,the polymer support and heteropoly anions show high stability,their structure are both maintained well.The D201-PMo₄ shows higher catalytic activity than D201-PW₉,within 6h,the conversion of cyclohexene reaches 89.5%,and the selectivity of main product is 90.5%.The catalyst can be recycled five times without decreasing the activity obviously.The catalyst with QAPPESK as support shows higher catalytic activity than that with D201 as support.更多还原