金属氧化物负载钌催化木质素衍生酚类化合物制备环己醇的研究

Study on preparation of cyclohexanol from lignin-derived phenolic compounds catalyzed by metal oxide-loaded ruthenium

  • 摘要: 本研究采用初湿浸渍法,制备得到一系列钌负载于金属氧化物载体的催化剂(Ru/CeO2、Ru/Nb2O5、Ru/ZrO2、Ru/Al2O3和Ru/CeOx),用于木质素衍生酚类化合物苯酚提质加氢转化为环己醇的研究。通过采用X射线晶体衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等手段对所制备催化剂进行结构和物化特征的表征,发现Ru/CeOx中含有的氧空位可以很好地吸附带有含氧基团的原料,从而有利于苯酚的高效加氢;同时XPS表明,Ru/CeOx中的有效活性中心RuO2和Ru0是催化加氢的活性位点,因此,氧空位和金属活性位点的共同作用使得催化剂有较好的加氢活性。探究了反应温度、压力、时间对加氢效果的影响,发现催化剂能够在140 ℃下使苯酚完全转化,得到目标产物环己醇得率为90.2%,并对催化剂的循环特性进行考察,发现循环使用四次后催化剂仍表现出优异的加氢活性。同时采用GC-MS检测加氢过程的中间产物,进而推断出苯酚加氢过程的反应路径。

     

    Abstract: Hydrodeoxygenation of lignin bio-oil to prepare liquid fuels is a very promising route. In this paper, a series of catalysts (Ru/CeO2, Ru/Nb2O5, Ru/ZrO2, Ru/Al2O3 and Ru/CeOx) supported on metal oxides were prepared by incipient wetness impregnation method, which were used to study the upgrading and hydrogenation of lignin-derived phenolic compounds phenol to cyclohexanol. By means of X-ray crystal diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), the structure and physical and chemical characteristics of the prepared catalyst were characterized. It was found that the oxygen vacancies contained in Ru/CeOx could adsorb the raw materials with oxygen groups well, which was beneficial to the efficient hydrogenation of phenol. At the same time, XPS showed that the effective active centers in Ru/CeOx, RuO2 and Ru0, were active sites for catalytic hydrogenation. Therefore, the combined action of oxygen vacancies and metal active sites made the catalyst have good hydrogenation activity. The effects of reaction temperature, pressure and time on hydrogenation were also investigated. It was found that the catalyst could completely convert phenol at a mild temperature (140 ℃) and the yield of cyclohexanol was 90.2%. The cycle characteristics of the catalyst were investigated, and it was found that the catalyst still showed excellent hydrogenation activity after being recycled for 4 times. At the same time, the intermediate products in the hydrogenation process were detected by GC-MS, and then the reaction path of phenol hydrogenation process was deduced.

     

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