Ag-Cu催化剂在甘油氢解制丙二醇中的性能研究

发布时间：2018-05-17 13:34

  本文选题：甘油 + 氢解　； 参考：《东南大学》2017年硕士论文

【摘要】：随着当今社会的飞速发展,能源危机成为当今世界面临的重大问题之一。因此,可循环使用的材料受到了人们越来越多的关注。生物柴油生产过程中的主要副产物甘油,被认为是替代石油和天然气来生产许多重要化学工业产品的最可行、最有前途的一种原材料。由于甘油生产的大量过剩以及丙二醇在工业上的广泛应用,甘油氢解制备1,2-丙二醇和1,3-丙二醇有着重要的科研和商业上的意义。根据文献研究,铜基催化剂对C-C键的断裂能力有限,铜基催化剂对甘油氢解有着较高的转化率,对丙二醇有着较高的选择性。但是Cu基催化剂对于甘油氢解制备丙二醇的效果仍然不够理想,因此通过添加其它成分对铜基催化剂进行改性,进一步提高催化剂的活性是当今研究的热点之一。本论文通过浸渍法制备了一系列负载型银铜双金属催化剂,并应用于甘油氢解制丙二醇反应。制得的催化剂采用H2程序升温还原、NH3程序升温脱附、X射线衍射、N2吸脱附、N2O化学吸附、热重分析、电感耦合等离子光谱、扫描电镜以及X射线光电子能谱分析等方法进行表征。实验结果表明,5wt.%银加入到铜基催化剂中,有利于催化剂的还原,提高了催化剂的表面酸性和催化剂中铜颗粒的分布,进而提高了甘油的转化率和丙二醇的产率。当5wt.%银和15wt.%铜同时负载在氧化铝载体表面时,催化剂的酸性更高,分散性更好,铜的表面积更大,因而催化剂的催化效果更佳。另外,文章还详细地研究了金属含量比例、金属浸渍顺序、反应温度、反应压力、反应时间、反应溶剂和溶剂酸碱性对反应影响以及催化剂的重复使用性。当优选的5Ag-15Cu/A1203催化剂在22C℃、3.5 MPa的优选条件下反应8 h时,催化剂对甘油的转化率为66.5%,对1,2-丙二醇的选择性为68.2%,对1,3-丙二醇的选择性为3.1%。为了进一步提高银铜催化剂对1,3-丙二醇的选择性,本论文通过浸渍法制备了不同含量杂多酸和不同种类杂多酸改性的银铜催化剂应用于甘油氢解反应并通过吡啶红外、拉曼衍射等技术进行表征分析。反应结果和表征结果表明,杂多酸的加入能进一步地促进催化剂的还原,提高催化剂的分散性,增强催化剂的表面酸性和B酸酸量,进而提高催化剂对1,3-丙二醇的选择性。与磷钨酸和磷钼酸改性的催化剂相比,硅钨酸改性的银铜催化剂的铜分散性更好,表面的B酸酸量更多,对1,3-丙二醇的选择性更高。当10wt.%硅钨酸改性的5Agl5Cu/A1203催化剂在220℃、3.5 MPa的最佳反应条件下,在200 mL高压釜中反应8 h,催化剂对甘油的转化率为69.6%,对1,2-丙二醇的选择性为35.6%,对1,3-丙二醇的选择性达21.5%。而且硅钨酸改性后的催化剂的重复性有了明显的提高。
[Abstract]:With the rapid development of today's society, the energy crisis has become one of the major problems facing the world. Therefore, people pay more and more attention to recyclable materials. Glycerol, the main by-product of biodiesel production, is considered to be the most feasible and promising raw material instead of oil and natural gas to produce many important chemical industrial products. Due to the excessive production of glycerol and the wide application of propanediol in industry, it is of great scientific and commercial significance to produce 1o 2-propanediol and 1o 3-propanediol by hydrogenolysis of glycerol. According to the literatures, the cleavage ability of the copper-base catalyst to C-C bond is limited, the copper-based catalyst has higher conversion to hydrogenolysis of glycerol and higher selectivity to propylene glycol. However, the effect of Cu-based catalyst on hydrogenolysis of glycerol to propanediol is still not ideal. Therefore, it is one of the hot research topics to further improve the activity of Cu-based catalyst by adding other components to modify the catalyst. In this paper, a series of supported silver and copper bimetallic catalysts were prepared by impregnation method and were used in the hydrogenolysis of glycerol to propylene glycol. The catalyst was characterized by H _ 2 temperature-programmed reduction (H _ 2) temperature programmed desorption of NH _ 3 and X-ray diffraction (XRD) N _ 2 adsorption, thermogravimetric analysis, inductively coupled plasma spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The experimental results show that the addition of 5 wt.% silver into the catalyst is beneficial to the reduction of the catalyst, the surface acidity of the catalyst and the distribution of copper particles in the catalyst, thus increasing the conversion of glycerol and the yield of propylene glycol. When 5wt.% silver and 15wt.% copper are simultaneously loaded on the surface of alumina carrier, the catalyst has higher acidity, better dispersion and larger surface area of copper, so the catalytic effect of the catalyst is better. In addition, the effects of metal content, metal impregnation sequence, reaction temperature, reaction pressure, reaction time, reaction solvent and solvent acidity and alkalinity on the reaction and the reusability of the catalyst were studied in detail. When the optimized 5Ag-15Cu/A1203 catalyst was selected at 22C 鈩，

本文编号：1901576