钴基金属有机框架催化剂在苯甲醇氧化反应中的性能研究

发布时间：2018-09-18 07:28

【摘要】：苯甲醛作为重要的化工原料及有机合成反应中间体,在工业应用领域占据重要位置。如今工业上采用的苯甲醛制备方法,存在着工艺过程繁琐,产率低且不符合绿色化学反应过程,因此寻找绿色环保、原子利用率高的制备方法成为现代科学研究的热点。苯甲醇氧化反应是重要的化工反应,也是制备苯甲醛最为常用的方法之一。在苯甲醇氧化反应中,氧气作为氧化剂且副产物仅为水,进而减少了对环境的污染。金属有机框架(MOFs)材料由于其具有大的比表面积、多孔性、孔径尺寸的可调性及结构多样性,成为催化领域的研究热点。MOFs材料由金属节点和有机配体构成,在催化反应中,金属节点和有机配体可以作为活性中心,除此以外,还可以根据反应的需要引入一些催化活性中心。在本论文中主要以不同金属为节点,选用合适的有机配体与其配位组成结构多样的MOFs材料,并将这些材料用于氧气为氧化剂,催化氧化苯甲醇制苯甲醛的反应中。分析结果如下:一、金属有机框架M(bdc)(ted)_(0.5)(M=Co,Zn,Ni,Cu)催化剂的制备及在选择性氧化苯甲醇反应中的应用采用溶剂热法合成金属有机框架材料M(bdc)(ted)_(0.5)(M=Co,Zn,Ni,Cu,bdc=对苯二甲酸,ted=三乙烯二胺),同时对该材料进行了XRD、FI-IR、N_2吸附-脱附、TG及SEM等表征,最终的催化剂记为M(bdc)(ted)_(0.5)。以苯甲醇催化氧化反应为探针反应,考察了在相同的反应条件下,相同有机配体不同金属节点的MOFs材料对苯甲醇氧化反应性能的影响。实验结果表明:四种金属催化剂,以Co金属为节点的催化剂显现出的催化性能最好。在氧气为氧化剂时,反应8 h后,转化率为81.8%,选择性接近100%。同时,Co(bdc)(ted)_(0.5)催化剂表现出了明显的溶剂效应,在DMF溶剂中转化率及选择性最好,可能是由于DMF与Co~(2+)之间的配位相互作用,进而影响了催化剂活性中心的配位能力。中断和循环实验结果表明:热过滤催化剂后,苯甲醇的转化率没有明显上升,且催化剂经三次循环使用后催化活性没有明显降低,进一步说明催化剂具有较好的循环稳定性。二、金属有机框架M-BTC(M=Co,Cu,Fe)催化剂的制备及在催化氧化苯甲醇反应中性能的研究以均三苯甲酸为配体与过渡金属(Co,Cu,Fe)合成的金属有机框架材料M-BTC(M=Co,Cu,Fe)。经XRD、FI-IR、N_2吸附-脱附、XPS、TG及SEM表征,发现不同过渡金属制备的MOFs结构及形貌不完全相同。通过比较三种不同金属节点催化剂在苯甲醇氧化反应中的催化性能时,发现在相同的反应条件下Co-BTC催化剂的催化活性高于其他两种金属催化剂。同时对该反应进行了不同反应条件的催化测试。实验结果表明:以空气为氧化剂,反应10 h后,在DMF溶剂中催化剂Co-BTC的催化活性最好,苯甲醇转化率为92.9%,苯甲醛选择性为97.1%。同时对催化剂进行了重复实验和热过滤实验,结果表明:催化剂经三次循环使用后催化活性没有明显降低,热过滤催化剂后,苯甲醇的转化率变化不明显,说明该催化剂结构较为稳定。由于反应中以空气为氧化剂,更好的与绿色化学相符合。
[Abstract]:Benzaldehyde, as an important chemical raw material and intermediate of organic synthesis reaction, occupies an important position in the field of industrial application. Nowadays, the preparation methods of benzaldehyde used in industry have many disadvantages, such as tedious process, low yield and inconsistent with green chemical reaction process. Therefore, it is necessary to look for green environmental protection and high atom utilization methods. Benzyl alcohol oxidation is an important chemical reaction and one of the most commonly used methods to prepare benzaldehyde. In the oxidation of benzyl alcohol, oxygen acts as an oxidant and the by-product is only water, thus reducing environmental pollution. Metal-organic frameworks (MOFs) materials have large specific surface area, porous, and porous. MoFs are composed of metal nodes and organic ligands. In catalytic reactions, metal nodes and organic ligands can be used as active centers. In addition, some catalytic active centers can be introduced according to the needs of the reaction. The results are as follows: 1. Preparation of metal organic frameworks M (bdc) (ted) (0.5) (M = Co, Zn, Ni, Cu) catalysts and selective oxidation of benzyl alcohol to benzaldehyde. The metal-organic framework material M (bdc) (ted) (0.5) (M = Co, Zn, Ni, Cu, BDC = terephthalic acid, Ted = triethylenediamine) was synthesized by solvothermal method. The material was characterized by XRD, FI-IR, N 2 adsorption-desorption, TG and SEM. The final catalyst was recorded as M (bdc) (ted) (0.5). The catalytic oxidation of benzyl alcohol was used as a probe reaction. The effects of MOFs with different metal nodes of the same organic ligand on the oxidation of benzyl alcohol were investigated under the same reaction conditions. The results showed that the catalytic performance of the four metal catalysts with Co metal nodes was the best. The conversion rate was 81.8% and the selectivity was close to 1.8% after 8 h reaction with oxygen as oxidant. At the same time, Co (bdc) (ted) (0.5) catalyst showed obvious solvent effect, and the best conversion and selectivity in DMF solvent, probably due to the coordination interaction between DMF and Co ~ (2+), which affected the coordination ability of the active sites of the catalyst. The interruption and cycling experiments showed that the conversion of benzyl alcohol after the thermal filtration catalyst was carried out. The catalytic activity of the catalyst did not decrease after three cycles, which further indicated that the catalyst had good cyclic stability. 2. Preparation of metal-organic framework M-BTC (M=Co, Cu, Fe) catalyst and its performance in catalytic oxidation of benzyl alcohol using pyromellitic acid as ligand and transition metal (Co, C, Fe) M-BTC (M = Co, Cu, Fe) synthesized by u, Fe was characterized by XRD, FI-IR, N_2 adsorption-desorption, XPS, TG and SEM. It was found that the structure and morphology of M OFs prepared by different transition metals were not identical. By comparing the catalytic performance of three metal nodal catalysts in the oxidation of benzyl alcohol, it was found that Co was under the same reaction conditions. The catalytic activity of - BTC catalyst was higher than that of the other two metal catalysts. The catalytic tests under different reaction conditions were carried out. The results showed that the catalytic activity of Co-BTC catalyst in DMF solvent was the best after 10 h reaction with air as oxidant. The conversion of benzyl alcohol was 92.9% and the selectivity of benzaldehyde was 97.1%. The results of repeated experiments and thermal filtration showed that the catalytic activity of the catalyst did not decrease significantly after three cycles of use, and the conversion of benzyl alcohol did not change significantly after the thermal filtration catalyst, indicating that the catalyst structure was relatively stable.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ244.1

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