【作者】 王慧颖；

【导师】 景晓燕；

【作者基本信息】 哈尔滨工程大学 ， 应用化学， 2004， 硕士

【摘要】 一定组成的双金属复合氧化物（简称LDO）对烷基化等反应具有良好的催化活性，且通过控制其前体—层状结构双羟基复合金属氧化物（简称LDH）的晶粒尺寸及分布调变孔隙结构可有效地发挥择形作用。但研究发现，成型后的LDO粒子因传质阻力增加导致催化活性降低，同时选择性也受到一定程度的影响。为了解决目前此领域的问题，我们萌发了将稀土元素与双羟基复合金属氧化物组装的构想，以解决催化剂活性降低的问题。 本文采用化学共沉淀法，借鉴催化领域中稀土元素的研究成果，用稀土元素铈取代部分的铝离子进入镁铝水滑石的层状结构中，然后将镍-铁氧体磁性基质与上述水滑石进行组装，合成出颗粒大小均匀的磁性镁铝铈水滑石并对其催化性能进行研究，得出十分有意义的结果。我们通过XRD、振动样品磁强计、TG-DTA、IR等手段对其进行了表征；将其在450～500℃焙烧形成的磁性固体碱用于催化苯甲醛与丙二酸二乙酯Knoevenagel缩合反应，研究发现掺加稀土元素后的磁性水滑石具有更好的催化性能。 （1） 采用共沉淀法制备不同Fe（Ⅲ）：Ni（Ⅱ）：Fe（Ⅱ）摩尔比的磁性基质，应用TEM、振动样品磁强计对其进行研究，我们发现不同Fe（Ⅲ）：Ni（Ⅱ）：Fe（Ⅱ）摩尔比、pH值、温度等因素对磁性基质的粒径和磁学性能影响较大，在不用氮气保护的情况下，Fe（Ⅱ）：Ni（Ⅱ）：Fe（Ⅲ）摩尔比为1：1：4、溶液pH值大于10、温度为40℃、陈化时间为60min的条件下，所制得的磁性基质粒径最小，磁学性能最好。 （2） 采用化学共沉淀法制备出磁性纳米稀土水滑石并对其进行了结构、FT-IR、热学性能、磁学性能及碱强度分析。磁性镁铝铈水滑石的XRD、DTA结果表明，稀土元素铈的加入并没有改变水滑石层状结构的典型特征，而且在Mg²⁺／(Al³⁺+Ce³⁺)摩尔比为3，Al³⁺／Ce²⁺（摩尔比）为7，磁性基质按镁（Ⅱ）／[铁（Ⅱ）+镍（Ⅱ）]（摩尔比）为50加入，溶液pH为9～10，反应温度70±5℃，陈化温度80±5℃，陈化时间8h的条件下，所制得的磁性纳米稀土水滑石结构最好。磁性分析结果表明，镍的加入使磁性基质的磁性强度有所提高，进而影响所制备的磁性镁铝铈水滑石的磁饱和强度，其值随磁性基质含量的增加而线性增加，这一点同磁性镁铝水滑石一致。碱强度分析结果表明了稀土元素的加入对磁性水滑石的碱强度并无明显影响，碱强度仍然处哈尔滨工程大学硕士学位论文于9.3一15.0之间。 （3）磁性镁铝饰水滑石在450⁵00℃焙烧后用于催化苯甲醛与丙酮轻醛缩合反应和苯甲醛与丙二酸二乙醋众oevenagel缩合反应。在苯甲醛与丙二酸二乙酷劫oevenagel缩合反应中，新型的稀土水滑石同原来的磁性镁铝水滑石相比较，饰的引入对反应的最佳条件有所改变:在保持催化剂用量1一2W’t%，反应物配比l一1.2的同时，反应时间缩短为6小时，反应温度降为120℃，而且反应转化率与产物收率都有很大程度的提高（大约提高了10%左右），催化剂反应活性明显得到改善。这一实验结果充分证实了加入稀土元素改善催化剂性能的可行性，同时镍一铁氧体磁性基质提高了与之组装的固体碱的磁饱和强度，从而提高了产物与催化剂的分离率，因此可以更好的利用磁分离技术将催化剂与反应体系进行快速分离，进而提高其回收率。关键词:稀土元素;镁铝饰水滑石;磁性;固体碱;Knoevenagel缩合反应更多还原

【Abstract】 Layered double metal oxides(LDOs) with certain constitute have ideal catalytic activity to such reaction as alkalization,and they could availably perform function of formation by controlling the grain size of the precursors?Layered double hydrotalcites(LDHs) and by changing their constructional distribute of pores. But we find that the LDO particles have some defects, after formation, their catalytic activity decreases with the increasing of mass transmittion resistance, and their selectivity is influenced to some degree as well. We bourgeon the speculation of assembling rare earth with Layered double hydrotalcites to solve the above problem.In this dissertation, in view of the idea of the application of rare earth catalyst, at first we let the rare earth Ce incorparate into the layer lattice of the Mg-Al hydrotalcites, then we assembled it with magnetic substrates obtaining nickel, so we get magnitic Mg-Al-Ce hydrotalcites of which the grain is even. This dissertation discuss the influence of rare earth Ce on structure and catalytic property of magnitic Mg-Al-Ce hydrotalcites by the measurement of XRD, VSM(Vibrating-sample Magnetometer), TG-DTA, IR ,and so on. We applied calcited products of magnitic Mg-Al-Ce hydrotalcites(calcited at 450~500癈 ) in Knoevenagel condensation of benzaldehyde with diethyl malonate, and compared the results with magnitic Mg-Al hydrotalcites ,then we find the magnitic Mg-Al-Ce hydrotalcites have some advance in catalytic property.(1) We synthesize magnetic substrates with different Fe(III): Ni(II): Fe( II) molar ratio by the method of co-precipitation. Research on magnetic substrates of XRD and VSM shows the bigger influernce of Fe(III): Ni( II): Fe( II) molar ratio, temperature,and pH to grain size and magnetical propertyes. Under the condition of Fe(III): Ni( II): Fe( II) molar ratio being 1:1:4, temperature of 40 C, pH 10, magnetical properties of magnetic substracts are optimum.(2) We synthesize magnitic Mg-Al-Ce hydrotalcites by the method of co-precipitation and study construction, FT-IR, thermal property, magnetical property and basicity. Results of XRD and FT-IR show that the addition of rare earth Ce to hydrotalcites does not change the typical layerer-structure, and we also find when Mg2+ / (Al3++Ce3+) molar ratio being 3, Al3+ / Ce2+ molar ratio being 7, Mg2+/(Fe2++Ni2+)molar ratio being 50, pH 9-10, reaction temperature of70 5C, aging temperature of 80 5 C, aging time of 8 h, the construction of magnitic Mg-Al-Ce hydrotalcites is the best. So we think it practicable that the rare earth Ce incorporated into the layer lattice of the layered materials. Results of VSM show the addition of Ni improve the magnetical properties of magnetic substracts,so the magnetization of samples increase lineally with the content of magnetic substrates,which is same to magnitic Mg-Al hydrotalcites. The analysis of basicity of magnetic solid bases show the addition of rare earth Ce does not influence basicity of solid bases of magnitic Mg-Al-Ce hydrotalcites, and their basicity (Ho) is still between 9.3 and 15.0.(3) We applied calcited products of magnitic Mg-Al-Ce hydrotalcites(calcited at 450-500 C ) in Knoevenagel condensation of benzaldehyde with diethyl malonate, and compared the results with magnitic Mg-Al hydrotalcites ,then we find the addition of rare earth Ce does change the optimized reaction conditions of Knoevenagel condensation(without solvent): without changing the content of catalyst, l~2wt% and reactant ratio(benzaldeehyde/diethyl malonate molar ratio), 1 - 1.2, reaction time reduced 2 hours and reaction temperature decreased to 120 C.In the same time, conversation of diethyl malonate and selectivity of the product is increased 10 persent in general. It showed the addition of rare earth Ce to improve the catalytic property of layered hydrotalcites is practicable again. In addition, because the magnetic substracts contained Ni increase the magnetization of samples, we can separate and recover catalyst of magnetic solid bases from reaction system more easlier.更多还原