|关键词||Ru基催化剂 加氢 马来酸二甲酯 丁二酸 铁磁性ni基催化剂|
本文以马来酸酐及其衍生物催化加氢合成丁二酸的Ru基催化剂为核心研究内容，通过样品制备、表征和催化性能评价，获得了高效催化剂；在此基础上对磁性铁负载的Ni基催化剂的加氢性能也进行了探索。主要内容和结论如下： 1）Ru催化剂的制备、表征与催化性能 以RuCl3•nH2O和NaOH为原料，采用沉淀法制备了Ru催化剂，以马来酸二甲酯加氢制丁二酸二甲酯为探针反应，甲醇作溶剂，考察了催化剂制备和预处理条件对催化加氢性能的影响。 在50-70℃*0.4-1.2MPa的低温低压条件下，Ru催化剂显示出很好的马来酸二甲酯加氢活性和重复使用性，实现了高效地合成丁二酸二甲酯，加氢选择性达到100%。 表征数据显示，Ru催化剂前驱体进行焙烧处理时，生成大颗粒的Ru金属和高价钌，其原因是发生了歧化反应：4Ru(OH)3 = Ru0 + 3RuO2 + 6H2O. 动力学研究结果表明，DMM的反应级数在DMM浓度高于0.26mol/L时为零级，浓度在0.015-0.180mol/l时为0.70±0.03级反应，而且在整个DMM浓度范围内加氢反应为压力0.82±0.05级反应，表观活化能为 58.926±2 kJ/mol. 2）负载型Ru催化剂的制备、表征与催化性能 采用吸附-沉淀法制备了负载型Ru/Al2O3催化剂，并详细阐述了其制备化学。考察了催化剂的焙烧和还原条件对催化剂性能的影响。 Ru(OH)3/Al2O3在焙烧处理时，与Ru催化剂相似，也发生歧化反应，但生成 Ru的颗粒较小；这是由于Ru与载体相互作用，使得Ru稳定性增大。因此直接还原处理时，Ru催化剂由于Ru的烧结长大而导致催化活性极低，相反Ru/Al2O3催化剂有较高活性。 采用焙烧-还原活化方式，导致还原后金属Ru晶粒的长大、分散度降低，从而使催化剂活性降低。表明焙烧温度对活性组分Ru金属颗粒大小和分散性的影响较大。焙烧温度小于200℃时，对催化剂活性组分的分布和颗粒大小的影响不大；温度高于300℃以后，还原后催化剂活性组分的颗粒较大、分散度低，催化反应活性低。 结合Ru/Al2O3催化剂XRD, XPS, TPR,等表征，揭示了催化剂与活性之间的关系。结果表明具有催化活性的是晶粒小、分散性好的Ru金属，而不是二氧化钌。 3）磁性铁负载的Ni基催化剂的探索及其马来酸二甲酯加氢性能 采用共沉淀法制备了铁磁性氧化物负载的Ni催化剂，并将其应用到马来酸二烷基酯的加氢中。结果表明其催化活性远高于传统的氧化铝负载的Ni催化剂，虽然其效率仅达到负载Ru催化剂了40%，但磁性氧化物负载的Ni催化剂成本低，而且磁分离使得催化剂从液相反应中回收比传统的过滤、离心更加的容易，显示了良好的开发前景。
This thesis focuses on the development of Ru catalysts. Catalyst samples with excellent activity were prepared, characterized and tested by the hydrogenation of maleate anhydride and its derivatives for the preparation of succinic acid. Additionally, the magnetic oxide supported Ni catalysts were also examined for hydrogenation based on the results of Ru catalyst. The main contents and conclusions are listed as follows: 1) Preparation, characterization and catalytic performance of Ru catalyst Ru catalysts were prepared by precipitation using RuCl3•nH2O and NaOH as reagents. Effects of preparation and pretreating conditions on the catalytic behaviors of the catalysts were investigated using methanol as the solvent, with the hydrogenation of dimethyl maleate to dimethyl succinate as the probe reaction. The characterization data showed that large particles of Ru metal and higher valence Ruthenium species were formed upon calcination of catalyst precursor, which could have resulted from the disproportionation reaction of Ruthenium hydroxide: 4Ru(OH)3 = Ru0 + 3RuO2 + 6H2O. Under the reaction conditions of low temperature (50-70℃) and low pressure (0.4-1.2MPa), Ru catalysts demonstrated both higher catalytic activity and reusability for the selective hydrogenation of dimethyl maleate. Dimethyl succinate was produced effectively with 100% hydrogenation selectivity. It was found that the reaction exhibited an apparent zero-order dependence on DMM concentration at higher than 0.26mol/L, while a reaction order of 0.70±0.03 with respect to DMM was obtained in the range of 0.015-0.180mol/L. However, the reaction order with respect to hydrogen partial pressure was 0.82±0.05 in the tested DMM concentration range. The activation energy was found to be 58.926±2 kJ/mol. 2) Preparation, characterization and catalytic performance of supported Ru catalysts Supported Rucatalysts were prepared utilizing an adsorption-precipitation technique，and the preparation chemistry was investigated in detail. Effects of the calcination and reduction conditions on the catalytic performance were investigated. Similar to that of Ru catalyst, the disproportionation also took place when the Ru(OH)3/Al2O3 were calcined, but the crystal size of the formed Ru metals was comparatively small. This might be attributed to the interaction of Ru with alumina support, thus resulting in the increased stability of Ru/Al2O3. Therefore, when treated by direct reduction, the Ru/Al2O3 catalysts revealed good catalytic activity, while the obtained Ru catalysts showed a substantial activity loss, which could be attributed to the formation of very large Ru metals by sintering. When calcination-reduction treatment instead of direct reduction was applied, comparatively large Ru metal particles accompanied by dispersity loss were observed.The results showed that the calcination temperature played an important role on the particle size and dispersion of Ru metals. When the calcination temperature was lower than 200℃, there existed little impact on the particle size. Upon increasing the calcination temperature above 300℃, catalysts with larger Ru particles and lower Ru dispersions were obtained. The relationship between catalysts and activity has been disclosed based on the results of XRD, XPS, TPR, and the active species is Ru metal with a smaller crystal size and higher dispersity. 3) Investigation on the magnetic oxide supported Ni catalysts and their catalytic performance for the hydrogenation of dimethyl maleate A Ni based catalyst supported on magnetic oxide was prepared by coprecipitation and tested for the hydrogenation of dialkyl maleate. The results indicated that the catalytic activity of Ni/Fe3O4 was much higher than that of Ni/Al2O3. Ni/Fe3O4 catalysts demonstrated about 40% catalytic performance effectivity as compared with supported Ru catalyst, however, the cost of the Ni/Fe3O4 catalysts was significantly less. Furthermore, the magnetic separation renders the recovery of Ni/Fe3O4 catalysts from liquid-phase products much easier than that of cross-flow filtration and centrifugation. These conclusions seem to have identified a potentially good exploration prospect.
|努尔买买提·阿布都克力木. 催化加氢合成丁二酸催化剂研究[D]. 北京. 中国科学院研究生院,2012.|
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