室温氧化气氛下金属改性的锆系超强酸催化氧化环己烷反应研究

【作者】 王静静；

【导师】 王博；

【作者基本信息】 陕西师范大学 ， 物理化学， 2008， 硕士

【摘要】 近年来环境问题引起了人们的高度重视。固体酸代替液体酸催化有机反应是实现环境友好的一条重要途径，符合绿色化学的发展方向。而SO₄^2-／M_xO_y型固体超强酸在多种重要的烷烃催化反应中都显示出了很高的活性，而且具有易于分离、易再生、不腐蚀反应器、环境污染少及热稳定性好等优点，是一种非常有应用前景的催化剂。已有研究表明，在还原条件下，SO₄^2-／M_xO_y型固体超强酸对烷烃的异构化、烷基化反应具有很好的催化活性。相比之下，在氧化条件下，对此类催化剂催化烷烃反应研究的不多。本课题就是在此基础上提出的。即以SO₄^2-／ZrO₂-CuO、SO₄^2-／ZrO₂-Co₂O₃和SO₄^2-／ZrO₂-V₂O₅三类固体超强酸为例，研究SO₄^2-／M_xO_y型固体超强酸在温和氧化气氛中（室温，以空气作氧化剂）对烷烃的催化反应情况，以开发经济环保的含氧衍生物的合成方法。本论文的实验中用共沉淀方法和沉淀--浸渍法分别制备了SO₄^2-／ZrO₂-CuO、SO₄^2-／ZrO₂-Co₂O₃和SO₄^2-／ZrO₂-V₂O₅三种催化剂，并应用于室温空气氧化的温和条件下对环己烷催化氧化反应的研究。产物的定性和定量分析通过UV-vis分光光度计和GC-MS表征获得。实验结果表明，与单纯金属氧化物组分的SO₄^2-／ZrO₂催化结果相比，添加第二金属氧化物组分CuO和Co₂O₃的SO₄^2-／ZrO₂-CuO和SO₄^2-／ZrO₂-Co₂O₃二元金属氧化物固体超强酸对催化环烷烃直接合成邻苯二甲酸二丁酯有很好的效果。而且对于SO₄^2-／ZrO₂-Co₂O₃催化剂来说，产物中酯的种类，除了邻苯二甲酸二丁酯，还有乙二酸环己基十三烷基酯，但酯的总体产率低于SO₄^2-／ZrO₂-CuO。从而开发了一种由环烷烃直接制备芳香酯的环保经济方法。而SO₄^2-／ZrO₂-V₂O₅催化环己烷反应的主产物是C₁₄-C₂₈的直链烷烃，酯类产物含量不高。在常温条件下环烷烃直接转化成长直链烃反应的实现，不仅对提高十六烷值，推进清洁柴油的生产具有十分重要的意义，而且对石油形成过程的研究提供了很有价值的实验依据。此外，本论文还对上述三种催化剂的表面性质进行了系统的表征。反应前的催化剂采用X-射线衍射仪（XRD）、傅立叶变换红外光谱仪（FT-IR）进行表征。通过XRD分析可知，经过高温锻烧后的催化剂的晶型由无定型转变为四方晶型，形成的活性中心并具有较强的催化活性，并且CuO、Co2O₃和V₂O₅在催化剂中处于高度分散状态。通过红外光谱分析表明其存在O=S=O，具有酸中心，且催化剂易吸水。反应后的催化剂表面特征通过XPS光电子能谱进行表征，得出催化剂中除加入的改性金属氧化物略有价态变化外，其他元素基本没有什么变化，这也说明通过适当的活化处理后，本实验所制备的催化剂具有很好的重复使用性。更多还原

【Abstract】 In recent years, environmental problem has drawn increasing attention. Solid acid catalyst instead of liquid acid is one of the most important ways with the direction of the development of green chemistry. The SO₄^2-/M_xO_y solid acid has been proved to be a useful and active catalyst in many kinds of important catalytic reaction of alkane. Furthermore, the kind of catalyst, that has several advantages such as easy separation, good reusability of the catalyst, non corrosion to the reactor and usage of environmental friendly, play an important role in the chemical and petroleum industries.From the prevenient studies by other researchers, many large volume applications based on SO₄^2-/M_xO_y solid acid are reported in the literature, especially in the petroleum industry for alkylation and isomerization reactions in the reductive ambience. In the contrast, the effect of the kind of catalysts on oxidation of alkane under mild condition has been paid little attention. The content of this subject study is presented on the basis of the status. In the thesis, SO₄^2-/ZrO₂-CuO, SO₄^2-/ZrO₂-Co₂O₃ and SO₄^2-/ZrO₂-V₂O₅ were synthesized and their application in the oxidation of cyclohexane under mild condition （room temperature and atmospheric pressure） was investigated. The aim to the study was for the development of the synthetical methods to oxygenous ramification, which was economical and environmentally friendly.In the paper, the catalytical activity to the samples of SO₄^2-/ZrO₂-CuO, SO₄^2-/ZrO₂-Co₂O₃ and the sample of SO₄^2-/ZrO₂-V₂O₅, which prepared by precipitation method and precipitation-impregnation method, respectively, were investigated in the oxidation of cyclohexane under mild condition （room temperature, air as the oxidant）. Qualitative and quantitative analysis of each product was performed by UV-vis spectra and gas chromatography-mass spectrometry （GC-MS） system. The results show that, compared to non-metal oxide modified sulfate zirconia, the yield of ester obviously increased at overall products when the metal oxide CuO and Co₂O₃ were added to solid acid. The main products to the sample of SO₄^2-/ZrO₂-CuO were dibutyl phthalate. And another kind of ester, except for phthalate ester, named cyclohexyl triclecyl oxalate, was found in the products solvent to the sample of SO₄^2-/ZrO₂-Co₂O₃. But the yield of the ester with SO₄^2-/ZrO₂-Co₂O₃ was lower than that of SO₄^2-/ZrO₂-CuO. The one-step esterification reaction, that offers several advantages such as economical and environmental friendly, is necessary for ester chemosynthesis industry from the environment standpoint. In the case of SO₄^2-/ZrO₂-V₂O₅, the main products were long line alkane, and the content of ester in the overall products was low. The realization of direct transformation from cyclohexane into long line alkane was very significant, not only for the production of environmentally friendly diesel oil in high octane number, but also for the research of the petroleum forming process. Otherwise, the three kinds of catalysts were well characterized in this work. The catalyst before the reaction was characterized by means of X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FTIR）. XRD analysis shows that after the high-temperature burning, catalyst ZrO₂ changed from amorphous to crystalline quartet, formed an active site and had strong catalytic activity. CuO Co₂O₃ and V₂O₅ was in the highly fragmented state in catalyst. Solid acid catalyst can not be product without burning. IR spectra show the existence of O=S=O, acid center and catalyst which is easy-absorbent. The catalysts after the reaction was investigated by means of X-ray photoelectron spectroscopy （XPS）, the result displayed that the binding energies of all of the elements are almost unchanged after the reaction, except C element, indicating the stability of the structure of the modified catalyst and also suggesting that the solid acid may be recycling applied after appropriate activation.更多还原