甘油氢解制备1,2-丙二醇和1,3-丙二醇催化剂研究进展

随着生物质甘油下游综合利用研究的兴起,甘油氢解反应已成为研究热点。甘油氢解反应工艺的关键技术是氢解催化剂,对近年来甘油氢解制备1,2-丙二醇和1,3-丙二醇的催化剂研究进展进行综述。通过分析甘油氢解制备1,2-丙二醇和1,3-丙二醇催化剂的组成和工业应用情况,对未来可能实现工业化的催化剂体系前景进行展望。     

甘油氢解制备1,2-丙二醇催化剂的研究进展

由于生物柴油产业的蓬勃发展而造成副产物甘油的大量过剩,迫使人们努力寻求甘油转化为高附加价值产物的有效途径。本文综述了国内外甘油氢解制1,2-丙二醇催化剂以及机理研究的新进展。指出催化剂是甘油氢解制1,2-丙二醇的关键因素,目前甘油氢解反应中以Cu、Ni、Ru、Pt、Rh基催化剂使用较多,其中Cu基催化剂的研究最为广泛,载体、助剂、制备方法、反应溶剂、甘油氢解条件等对Cu基催化剂的活性、选择性、寿命、产物分离难度等具有较大影响。为进一步改善催化剂的综合性能,需要加强对甘油氢解机理和催化剂制备技术的基础性研究。多金属催化剂、复合多功能催化剂和甘油原位氢解反应因其自身优势颇受关注,而催化剂的失活机理及再生性能考察是值得深入研究的新课题。     

甘油氢解制备1,3-丙二醇催化剂研究进展

甘油具有很高的含氧量(O/C=1),对于多元醇和碳水化合物来说,二级C-O键的选择性裂解是将生物质转化为增值化学品的重要策略,所以氢解还原是甘油化学转化中最重要的反应之一。在由甘油氢解所得产品中,1,3-丙二醇的工业价值较高,但有关甘油氢解制备1,3-丙二醇的研究成果还是较少,并且对反应机理没有统一的结论。本文从催化甘油氢解制备1,3-丙二醇的不同体系的催化剂入手,对不同催化体系催化甘油催化氢解制备1,3-丙二醇催化剂的研究现状、反应机理进行总结及分析,发现存在甘油转化率低,副产物多,1,3-丙二醇产率低等问题,而且催化剂的使用寿命短等问题仍然是工业化道路上的一大难题,但因1,3-丙二醇较高的工业价值,未来甘油氢解反应催化材料的研究方向还是会主要集中在催化制备1,3-丙二醇上。     

甘油催化氢解制1,2-丙二醇的研究进展

综述了甘油催化氢解制1,2-丙二醇的研究进展。除了Ru、Cu等催化剂,Ag和Co催化剂也对甘油氢解反应有催化活性。载体、制备方法以及使用环境等都对催化剂性能有一定影响。其中,Cu催化剂价格相对低廉,对1,2-丙二醇选择性较高,可回收利用,满足工业化需求。最后对原位氢解机理和直接氢解机理进行解释说明。     

复合分子筛对甘油催化氢解反应的研究

本文主要采用共沉淀法制备了多种类型的铜基催化剂,并考察了甘油催化氢解制备1,2-丙二醇的反应性能。介绍了复合分子筛的铜基催化剂对甘油氢解催化氢解反应的影响。将MCM58-Beta型分子筛进行改性,磷钨酸改性后对反应效果最佳,此时甘油转化率为91.8%、1,2-丙二醇选择性为41.1%。     

氧化硅载体对Ir-Re双金属的结构及其催化甘油氢解的影响

采用3 种氧化硅载体KIT-6、G-6 和FS 制备了Ir-Re 双金属催化剂,并应用于甘油选择性氢解制备1,3-丙二醇,采用TEM、XRD、H₂-TPR、CO-DRIFTS 和NH3-TPD 等手段详细表征了催化剂结构,并探讨其构效关系。研究结果表明: 3 种催化剂表面的Ir-Re 双金属催化剂均形成了Ir-Re 合金结构, 合金化程度为Ir-Re/KIT-6 > Ir-Re/FS > Ir-Re/G-6;载体表面羟基含量显著影响Ir-Re 纳米粒子的分散度及其与载体的相互作用。Ir-Re/FS 的金属分散度最高,甘油氢解的初始活性最高但稳定性最差;而具有良好合金结构的Ir-Re/KIT-6 在甘油氢解中表现出良好的氢解活性和最高的1,3-丙二醇选择性。     

甘油催化氢解制备丙二醇催化剂研究进展

简要概括了近些年生物柴油副产物甘油催化氢解制备丙二醇催化剂研究新进展,对甘油氢解分别采用贵金属催化体系和过渡金属催化体系的催化活性和选择性以及可能的机理进行了解释说明。采用贵金属Pt/WO3负载型催化剂、ReO x改性的Rh/SiO2、Ir/SiO2催化剂、贵金属催化体系中加入有机溶剂以及采用Cu-STA(硅钨酸)/SiO2的气相催化工艺等方式都能得到相对较多的1,3-丙二醇(收率最高为38%)。高分散的纳米铜基催化剂对甘油氢解有着较高的活性、选择性和稳定性,具有工业应用前景。纳米钴催化剂具有特定的形态和良好的催化效果颇受关注。     

负载型CuO/γ-Al2O3催化剂结构与催化甘油氢解性能

采用浸渍法制备了CuO/γ-Al2O3催化剂,通过BET、XRD、XPS和TPR方法表征催化剂上CuO的分布与化学形态,结合固定床催化甘油氢解制备1,2-丙二醇试验.结果表明,催化剂表面高度分散缺电子状态的Cu物种是甘油氢解制备1,2-丙二醇的活性中心.采用浸渍法制备的铜基催化剂具有较好的甘油氢解制备1,2-丙二醇性能...     

Cu基催化剂催化甘油氢解制备丙二醇

在间歇釜式反应器中考察Cu基催化剂在不同酸性条件下的甘油催化氢解反应性能,采用γ-Al₂O₃、SiO₂和SiC酸碱性不同的载体研究催化剂催化活性和选择性的影响,结果表明,3种载体的Cu基催化剂均对1,2-丙二醇的生成有较高的催化活性和选择性,但只有弱酸性SiO₂为载体时生成1,3-丙二醇。研究在底物中添加H₂SO₄（B酸）对甘油氢解反应性能的影响,发现质子酸的存在有利于1,3-丙二醇的生成,但易导致副反应发生,使1,2-丙二醇选择性大幅降低。研究用磷钨酸改性的Cu/SiO₂催化剂对甘油氢解反应的催化活性的影响,发现磷钨酸的加入有利于甘油氢解为1,3-丙二醇,且酸性越强,越容易发生副反应。随着Cu/HWP/SiO₂催化剂焙烧温度的升高,酸性减弱,丙二醇选择性提高,推测出质子酸作用下Cu基催化剂的甘油氢解反应机理。     

甘油催化氢解制备丙二醇的研究现状

随着生物柴油产业的快速发展,作为生物柴油副产物的甘油逐渐过剩,合理有效地利用甘油能促进生物柴油产业的良性发展。丙二醇(1,2-丙二醇和1,3-丙二醇)是重要的化工中间体,具有较高的经济价值,利用可再生的甘油催化氢解制备丙二醇替代传统的石化路线符合绿色化学的要求,因而具有广阔的应用前景。简述了利用甘油催化氢解制备丙二醇的研究背景,详细分析了甘油催化氢解的机理(包括脱水-加氢机理、脱氢-加氢机理、直接氢解机理和螯合机理),从催化剂的角度综述了甘油催化氢解制备丙二醇的研究现状和取得的研究成果,并提出了未来甘油氢解的研究方向。     

Recent Advances in Catalytic Conversion of Glycerol

The article underlines and discusses the state-of-the-art accomplishments in the catalytic conversion of glycerol (1,2,3-propanetriol) to fuels and value-added chemicals in the past five years (2008–2012). The reactions include steam reforming, aqueous-phase reforming, hydrogenolysis, oxidation, dehydration, esterification, etherification, carboxylation, acetalization, and chlorination. Typical products are hydrogen, propanediols, dihydroxyacetone, glyceric acid, acrolein, glyceride, polyglycerol, glycerol carbonate, acetals, ketals, and epichlorohydrine. Recent studies on the catalysts, reaction conditions, and possible pathways are primarily discussed. They indicate that major breakthroughs are achieved by the use of multifunctional catalysts, process intensification and integrated reactions. Literature survey suggests that future work on the catalytic conversion of glycerol for commercial goals particularly requires new catalysts, innovative reactor engineering, and close multidisciplinary partnership.     

甘油氢解合成1,2-丙二醇铜锌铝催化剂的性能

采用共沉淀法制备了铜锌铝类水滑石前驱体,经焙烧和还原后制得铜基催化剂。采用XRD、H₂-TPR、H₂-TPD、NH₃-TPD和CO₂-TPD等表征手段并结合甘油氢解反应评价,研究了类水滑石前驱体的老化对催化剂结构和性能的影响,考察了反应条件对催化剂甘油氢解反应性能的影响。结果表明,老化有利于形成结构更为完整的类水滑石前驱体,但对铜物种的还原性能未造成显著影响。与由未老化前驱体制备的催化剂相比,由老化前驱体制备的铜锌铝催化剂具有较大Cu表面及较大酸量,但表面碱中心数量较低,从而该催化剂具有较好的甘油氢解活性及稳定性。在220 ℃、H₂压力3.0 MPa、n(H₂)/n(甘油)为18.9、甘油重时空速1.26 h^-1及质量分数为60%甘油水溶液的条件下,经老化前驱体制备的铜锌铝催化剂上甘油转化率接近100%、1, 2-丙二醇选择性约为96%。     

ZnO对CuO-ZnO/Al2O3催化剂催化甘油氢解性能的影响

以氧化铝为载体,采用浸渍法制备了负载型CuO-ZnO/Al2O3催化剂,通过XRD、XPS、TPR手段表征催化剂上CuO和ZnO的分布和化学形态。结果表明,CuO-ZnO/Al2O3催化剂催化甘油氢解反应中,CuO是活性组分,ZnO的引入可以降低CuO与载体氧化铝的相互作用强度,有利于CuO的还原,提高催化剂甘油氢解活性;催化剂表面呈缺电子状态的Cu物种是甘油氢解的活性中心。当活性组分CuO质量分数为12%,n(Cu)∶n(Zn)=1∶1.5时,CuO-ZnO/Al2O3催化剂催化甘油氢解活性最高,甘油转化率可达97.82%,对1,2-丙二醇选择性达94%。     

高活性Cu/SiO2催化剂上甘油氢解制1,2-丙二醇

采用蒸氨法制备了不同Cu负载量的Cu/SiO₂催化剂,并在连续固定床上催化甘油氢解。通过氮气物理吸附、X射线衍射、透射电镜、氧化亚氮-氢气滴定等手段对催化剂进行了表征。结果表明制备过程中形成的层状硅酸铜使催化剂具有大比表面积、较高的铜分散度以及较强的金属载体相互作用,因而在甘油氢解反应中表现出较好的时空收率和稳定性。此外,研究发现水对催化剂稳定性具有负面作用,而低转化率的情况下催化剂表面冗余的甘油可能是导致催化活性降低的一个重要因素。     

Characterization and catalytic properties of the CuO/SiO2 catalysts prepared by precipitation-gel method in the hydrogenolysis of glycerol to 1,2-propanediol: Effect of residual sodium

The effect of residual sodium on the CuO/SiO₂ catalysts prepared by precipitation-gel (PG) method has been investigated in correlation with the detailed characteristics of active component performance and catalytic performance in glycerol hydrogenolysis. Characterization of the catalysts showed that the residual sodium had a negative effect on the chemical–physical properties of the catalysts, such as the BET surface area, the dispersion of copper, and the reducibility of Cu²⁺ species as well as the adsorbility of reactant molecules. As a consequence, the conversion and selectivity of the catalysts in glycerol reactions generally decreased with increasing sodium content. The leaching of sodium from catalyst surface as a base could, however, on the one hand, weakly promote the activity of the catalyst, and on the other hand, could help retard the leaching of the active copper component and reduce the deactivation rate of the catalyst. The glycerol hydrogenolysis reaction is supposed to be a structure-sensitive reaction, in which copper particle sizes lower than a critical limit or those that did not fulfill a certain ensemble requirement were not active for glycerol reaction. Such details explained the lower TOFs of the catalysts with much smaller sizes. A certain amount of sodium is deduced to be needed for CuO/SiO₂ catalyst to exhibit both high catalytic activity and good stability. In addition, a reaction mechanism based on the effect of sodium on the activity and selectivity in glycerol hydrogenolysis has been proposed.     

Deactivation of CuZn Catalysts Used in Glycerol Hydrogenolysis to Obtain 1,2-Propanediol

Different CuZn catalysts were prepared by coprecipitation method with Cu/Zn atomic ratio of 0.2, 0.4, 1.0, 2.5 and 6.0. Monometallic Zn and Cu catalysts and a bimetallic catalyst (Cu/Zn?=?2.5) prepared by physical mixture of the precursors were also studied. These catalysts were tested in the glycerol hydrogenolysis reaction and the higher yields to 1,2-propanediol were achieved for Cu/Zn atomic ratio?≥?1 samples. The deactivation of a representative catalyst (Cu/Zn?=?1) was evaluated and its yield to 1,2 propanediol decreases until ca 40% after five runs. To explain this behavior, fresh and used catalysts were characterized by different techniques. Chemical analysis of solid catalysts and liquid reaction medium confirmed the leaching of Zn species under our reaction conditions. This process promotes Cu sintering which is proposed as the actual reason of the observed deactivation in the glycerol hydrogenolysis for this catalytic system.     

Production of Biomass-Derived Chemicals and Energy: Chemocatalytic Conversions of Glycerol

The growing production of biodiesel as a renewable source-based fuel leads to an increased amount of glycerol. Thus, it is a favorable starting material to obtain highly functionalized products. From a variety of catalytic reactions three examples, namely glycerol oxidation, glycerol hydrogenolysis and aqueous-phase reforming, were chosen for detailed studies in our group. The experimental focus for the oxidation of glycerol was set on preparation and detailed examination of supported Pt–Bi catalysts in batch reactions as well as in continuous experiments using a trickle bed reactor. For aqueous-phase reforming of glycerol to hydrogen the addition of tin to supported platinum catalysts was investigated. Ruthenium and copper based catalysts could be successfully applied in the hydrogenolysis of glycerol to 1,2-propanediol.