甘油氢解制1,3-丙二醇的Pt基催化剂的制备及其性能

发布时间：2018-06-07 15:28

本文选题：甘油 + 氢解　；参考：《扬州大学》2017年硕士论文

【摘要】：生物柴油的不断发展导致了甘油的大量过剩,将廉价的甘油转化为具有更高附加值的化工产品具有重要的意义。在甘油的衍生物中,1,3-丙二醇具有广泛的应用和较高的市场价值。因此,以生物柴油副产物甘油为原料生产1,3-丙二醇对增加生物柴油产业的经济效益具有重要的研究意义。本论文采用分步浸渍法分别制备了 WOx促进的Pt/SiO2,Al2O3改性的Pt-WOx/SiO2,硅掺杂的磷酸铝分子筛SAPO-34负载的Pt-WOx催化剂。论文通过对催化剂的结构、形貌、表面酸性和表面化学态等理化性质的表征,对其甘油氢解制1,3-丙二醇的催化反应性能的测试,来研究催化剂制备方法和其理化性质的关系、催化剂理化性质和其催化性能的关系,揭示甘油在所研究催化剂上的反应机理,为甘油氢解制1,3-丙二醇的工业生产提供基础数据和有益的探索。一、WOx促进的Pt/SiO2催化甘油氢解制1,3-丙二醇本论文采用分步浸渍法制备了不同载体(Zr02、A12O3、Si02)负载的Pt催化剂,同时用WOx对催化剂进行了修饰,考察了载体,WOx前驱体的焙烧温度以及WOx的含量对甘油氢解活性的影响,对制得的催化剂通过低温氮吸附(BJH)、X射线衍射(XRD)、激光共焦拉曼(Raman)、透射电镜(TEM)、高倍透射电镜(HRTEM)、X射线光电子能谱(XPS)等测试手段对样品进行了表征。实验结果表明,以Zr02和A1203为载体负载的Pt基催化剂表现出了对C-O键较强的断裂活性,获得较高的甘油转化率,但是丙二醇的选择性较低;SiO2负载的催化剂则表现出了相对弱的C-O键断裂活性,具有较低的甘油转化率,但是丙二醇(主要为1,2-丙二醇)的选择性较高。在Pt/SiO2中掺杂WOx不仅能够促进Pt/SiO2中氧化态的Pt还原成金属Pt,还能够促进金属Pt在载体表面的分散,降低金属Pt颗粒的尺寸。WOx的掺杂也增加了催化剂中弱酸和中强酸酸性位的数量,促进了 1,3-丙二醇的选择性生成。因此,WOx的掺杂不仅可以提高催化剂的甘油氢解活性,还可以提高1,3-丙二醇的选择性,抑制1,3-丙二醇继续氢解。高分散的WOx有利于Pt-WOx/SiO2的甘油氢解活性和对1,3-丙二醇的选择性;结晶度较好的W03则导致了丙二醇继续氢解生成正丙醇。当Pt的质量分数为2%,WOx的质量分数为10%,焙烧温度为823 K时,Pt-WOx/SiO2催化剂在483 K对甘油的转化率和1,3-丙二醇的选择性分别为26.0%和21.3%。二、Al2O3促进的Pt-WOx/SiO2催化甘油氢解制1,3-丙二醇本论文采用分步浸渍法制备了 Al2O3促进的Pt-WOx/SiO2催化剂,采用BJH、XRD、Raman、TEM、HRTEM、XPS等技术手段对样品进行了表征,研究了 Al2O3前驱体Al(NO3)3的焙烧温度以及Al2O3的含量对Pt-WOx/SiO2催化剂的理化性质和甘油氢解活性、1,3-丙二醇的选择性的影响。研究发现,向载体SiO2中掺杂少量的Al2O3能够增加催化剂表面弱酸酸性位和中强酸酸性位的数量,并提高了表面酸性的强度,促进了双功能催化剂Pt-WOx/SiO2-Al2O3的脱水-加氢反应,加速了甘油氢解和1,3-丙二醇的选择性产生。Al2O3的掺杂还促进了 WOx的分散,增加SiO2载体表面WOx物种的氧缺陷位的数量,降低活性金属Pt的颗粒尺寸,提高了活性组分的分散程度,促进了甘油选择性氢解生成1,3-丙二醇。当Al2O3的含量为5%,其前驱体的焙烧温度为1073 K时,制得的Pt-WOx/SiO2-5%Al2O3(1073 K))催化剂活性最优,对甘油的转化率和1,3-丙二醇的选择性分别为46.1%和26.9%。三、Pt-WOx/SAPO-34选择性氢解甘油制备1,3-丙二醇本论文用分步浸渍法制备了第ⅥB族氧化物(Cr2O3、MoO3、WOx)改性的Pt/SAPO-34,比较了助剂种类和含量对Pt/SAPO-34催化剂的理化性质和甘油氢解性能的影响。论文对优选的Pt-WOx/SAPO-34催化剂在不同的反应温度、压力和停留时间的甘油氢解活性进行了测试。结果表明,第ⅥB族元素中只有W的氧化物对催化剂的甘油氢解活性以及对1,3-丙二醇的选择性具有积极的作用。掺杂的WOx在催化剂中与载体之间表现出较强的相互作用,具有很高的分散程度。掺杂WOx催化剂表面酸性增加,Pt颗粒更加分散,甘油氢解活性和对1,3-丙二醇的选择性提高。当WOx的质量分数为20%时(Pt-20%WOx/SAPO-34)的活性最优,对甘油的转化率和对1,3-丙二醇的选择性分别为48.0%和18.8%。甘油氢解活性随反应温度越高而增加,但是高的反应温度也加剧了产品丙二醇进一步氢解;高的氢压有利于1,3-丙二醇的选择性生成。然而,较长的反应时间会导致催化剂部分失活。总之,Si02担载的Pt-WOx催化剂具有比Al2O3和ZrO2担载的催化剂更高的甘油氢解活性和1,3-丙二醇的选择性,其中WOx通过提高催化剂的表面酸性,促进金属Pt的分散和还原,显著提高了金属Pt活性组分的分散程度,从而促进了甘油的转化和1,3-丙二醇的选择性生成;通过向Pt-WOx/SiO2催化剂中掺杂Al2O3促进了 WOx的分散,增加WOx物种中氧缺位的数量,降低金属Pt颗粒的尺寸,提高催化剂的甘油氢解活性和1,3-丙二醇的选择性;第ⅥB族氧化物中,WOx对Pt/SAPO-34催化剂在甘油选择性氢解反应中表现出积极的促进作用,高分散WOx促进了金属Pt的分散和甘油选择性生成1,3-丙二醇。在本论文所研究的催化剂中,Al2O3促进Pt-WOx/SiO2催化剂表现出了最佳的催化性能。
[Abstract]:The continuous development of biodiesel leads to a lot of excess glycerin. It is of great significance to convert cheap glycerol into chemical products with higher added value. In the derivatives of glycerol, 1,3- propanediol has extensive application and high market value. Therefore, the production of 1,3- propanediol by using the biodiesel byproduct glycerin as raw material is increasing. The economic benefits of adding biodiesel industry have important research significance. In this paper, WOx promoted Pt/SiO2, Al2O3 modified Pt-WOx/SiO2, and silicon doped aluminum phosphate zeolite SAPO-34 supported Pt-WOx catalyst were prepared by stepwise impregnation. The structure, morphology, surface acidity and surface chemical state of the catalyst were studied in this paper. The characterization of the catalytic properties of the glycerol hydrogenolysis of 1,3- propanediol, the relationship between the preparation method of the catalyst and its physicochemical properties, the relationship between the physicochemical properties of the catalyst and its catalytic properties, and the mechanism of the reaction of glycerol on the catalyst studied, which provides the basis for the industrial production of the glycerol hydrogenolysis of 1,3- propanediol. Data and useful exploration. 1. WOx promoted Pt/SiO2 catalyzed hydrogenolysis of glycerol to 1,3- propanediol in this paper, a Pt catalyst supported by different carriers (Zr02, A12O3, Si02) was prepared by a stepwise impregnation method. At the same time, the catalyst was modified with WOx, and the roasting temperature of the carrier, the WOx precursor and the effect of the content of WOx on the hydrogenolysis activity of glycerol were investigated. The prepared catalysts were characterized by low temperature nitrogen adsorption (BJH), X ray diffraction (XRD), laser confocal Raman (Raman), transmission electron microscopy (TEM), high transmission electron microscopy (HRTEM), X ray photoelectron spectroscopy (XPS) and other testing methods. Experimental results showed that Pt based catalysts supported by Zr02 and A1203 were compared to C-O bonds. The high conversion rate of glycerol was obtained, but the selectivity of propanediol was lower. The SiO2 supported catalyst showed a relatively weak C-O bond activity, with a lower glycerol conversion rate, but the selectivity of propanediol (mainly 1,2- propanediol) was higher. The doping of WOx in Pt/SiO2 not only promoted the oxidation of Pt/SiO2. The reduction of the state of Pt into metal Pt can also promote the dispersion of metal Pt on the surface of the carrier, and the doping of the size.WOx of the metal Pt particles also increases the number of weak acid and strong acid acid sites in the catalyst, and promotes the selective formation of 1,3- propanediol. Therefore, the doping of WOx can not only improve the hydrogenolysis activity of the glycerol in the catalyst, but also can be raised. The selectivity of high 1,3- propylene glycol inhibits the continued hydrogenolysis of 1,3- propanediol. Highly dispersed WOx is beneficial to the glycerol hydrogenolysis activity of Pt-WOx/SiO2 and selectivity to 1,3- propanediol; the good crystallinity W03 leads to the continued hydrogenolysis of propanediol to propanol. When the mass fraction of Pt is 2%, the mass fraction of WOx is 10%, and the calcination temperature is 823 K, Pt-WO The conversion of glycerol to x/SiO2 catalyst and the selectivity of 1,3- propanediol at 483 K were 26% and 21.3%. two respectively. Al2O3 promoted Pt-WOx/SiO2 catalyzed hydrogenolysis of glycerol to 1,3- propanediol, the Pt-WOx/SiO2 catalyst promoted by Al2O3 was prepared by stepwise impregnation, and the samples were carried out by means of BJH, XRD, Raman, shrinkage, etc. The effects of the calcination temperature of Al2O3 precursor Al (NO3) 3 and the content of Al2O3 on the physical and chemical properties of Pt-WOx/SiO2 catalysts and the selectivity of 1,3- propanediol were investigated. The results showed that a small amount of Al2O3 in the carrier SiO2 could increase the number of weak acid acid sites and strong acid acid sites on the surface of the catalyst and raise the amount of the medium strong acid acid sites. The strength of the surface acidity promoted the dehydration and hydrogenation of the bifunctional catalyst Pt-WOx/SiO2-Al2O3, accelerated the doping of glycerol and the selectivity of 1,3- propanediol, and promoted the dispersion of WOx, increased the number of oxygen defects in the WOx species on the SiO2 carrier, reduced the particle size of the active metal Pt, and increased the activity of the active metal Pt. The dispersion of the component promotes the selective hydrogenolysis of glycerol to 1,3- propanediol. When the content of Al2O3 is 5% and the calcination temperature of the precursor is 1073 K, the Pt-WOx/SiO2-5%Al2O3 (1073 K)) catalyst has the best activity, and the selectivity for glycerol conversion and 1,3- propanediol is 46.1% and 26.9%. three respectively, and Pt-WOx/SAPO-34 is selective hydrogenolysis. The preparation of 1,3- propanediol with glycerol in this paper was prepared by stepwise impregnation method for the modified Pt/SAPO-34 of the first B group (Cr2O3, MoO3, WOx). The effects of the type and content of the additives on the physicochemical properties of the Pt/SAPO-34 catalyst and the properties of the glycerol hydrogenolysis were compared. The selected Pt-WOx/ SAPO-34 catalysts were at different reaction temperatures, pressure and residence time. The activity of glycerol hydrogenolysis was tested. The results showed that only W oxide in the sixth B group had positive effect on the glycerol hydrogenolysis activity of the catalyst and the selectivity of 1,3- propanediol. The doped WOx showed strong interaction with the carrier in the catalyst, and had a high degree of dispersion. The doping of WOx catalyst was very high. With the increase of surface acidity, the Pt particles are more dispersed, the hydrogenolysis activity of glycerol and the selectivity to 1,3- propanediol are increased. When the mass fraction of WOx is 20% (Pt-20%WOx/SAPO-34), the conversion rate of glycerol and the selectivity to 1,3- propanediol, respectively, 48% and 18.8%. glycerol, increase with the higher reaction temperature, but high The reaction temperature also aggravates the further hydrogenolysis of the product propanediol; high hydrogen pressure is beneficial to the selective formation of 1,3- propanediol. However, the longer reaction time will lead to partial deactivation of the catalyst. In a word, the Si02 supported Pt-WOx catalyst has higher glycerol hydrogenolysis activity and the selectivity of 1,3- propanediol than the catalysts supported by Al2O3 and ZrO2. By increasing the surface acidity of the catalyst, WOx promoted the dispersion and reduction of metal Pt, significantly increased the dispersion of the active component of the metal Pt, thus facilitated the conversion of glycerol and the selective formation of 1,3- propanediol. By doping Al2O3 to the Pt-WOx/SiO2 catalyst, the dispersion of WOx was promoted and the number of oxygen vacancies in WOx species was increased. The size of metal Pt particles is reduced, the hydrogenolysis activity of the catalyst and the selectivity of 1,3- propanediol are improved. In the sixth B oxide, WOx has a positive effect on the selective hydrogenation of glycerol to Pt/SAPO-34 catalyst. High dispersion WOx promotes the dispersion of metal Pt and the selectivity of glycerol to produce 1,3- propanediol. In the catalyst studied, Al2O3 promoted the Pt-WOx/SiO2 catalyst to exhibit the best catalytic performance.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;O623.413

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