Ru／C催化氢解山梨醇制备C2-C3多元醇

C2～C3多元醇如乙二醇、丙二醇和丙三醇等通常为石油的下游产品。近年来,随着石油价格不断攀升,由山梨醇等可再生资源经催化氢解制备这些小分子醇受到人们的关注。采用山利醇和催化剂Ru／C制备多元醇,并通过活性评价以及TPR、XRD等表征手段确定了催化剂的制备条件,其产物乙二醇、1,2-丙二醇、1,3-丙二醇和丙三醇的选择性分别为28．86％、24．25％、10．97％和9．15％。     

糖醇催化氢解制低级多元醇研究进展

利用糖醇生产低级多元醇可以减少对石油资源的依赖,是可再生资源利用的一个重要研究方向。本文综述了利用糖醇为原料催化氢解制备低级多元醇的研究成果,氢解糖醇可以高选择性得到乙二醇、丙三醇和1,2-丙二醇的混合物。重点介绍了糖醇催化氢解的Retro-aldol、 Retro-Michael反应机理和铜系、镍系、贵金属催化剂,并对糖醇催化氢解的发展前景做了展望,提出开发更为高效稳定的催化体系、降低催化剂制备成本和优化工艺条件将是未来研究工作的重点。     

改性的NiB非晶态合金催化葡萄糖氢解制备低碳二元醇

采用化学还原法制备了NiB非晶态合金催化剂,并引入W、Mo对NiB催化剂进行改性,利用X射线衍射、N₂物理吸附、电感耦合等离子体发射光谱、透射电子显微镜和氢气程序升温脱附等手段表征了催化剂的物理化学性质,考察了其催化葡萄糖氢解制备乙二醇、丙二醇等低碳二元醇的催化性能,并进一步探讨了W在葡萄糖氢解中的作用。结果表明：W、Mo引入NiB非晶态合金可以改变催化剂微结构,促进葡萄糖氢解过程中C-C键的断裂,并催化葡萄糖氢解生成低碳二元醇;W的断键能力要优于Mo,NiWB催化葡萄糖氢解得到的乙二醇和1,2-丙二醇的收率分别为37.0%和11.3%,而NiMoB的乙二醇、1,2-丙二醇收率分别为6.6%和8.9%;W改性的NiB非晶态合金同时具备加氢和断键能力,是一种具有应用前景的糖醇氢解新型催化剂。     

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。     

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。     

甘油氢解制备丙二醇催化剂研究进展

综述了国内外甘油氢解制备丙二醇催化剂的最新研究进展。指出催化剂是甘油氢解制备丙二醇工艺的关键因素,而目前研究中使用较多的有Cu、Ru、Rh、Pt、Ni、Co基催化剂,这些催化剂的类型、组成、载体、制备方法和工艺条件等直接影响催化剂的活性、选择性、稳定性、产物分离难易度和环境污染等。总结指出,甘油氢解制备1,3-丙二醇工艺需要加强高活性和选择性催化剂的基础性研究,而甘油氢解制备1,2-丙二醇工艺在现有比较成熟的催化剂基础上应进一步改进催化体系和催化剂的制备技术,为尽早实现工业化打下基础。     

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。     

HPLC法测定木糖醇及低碳多元醇氢解液的研究

建立了高效液相色谱(HPLC)分析木糖醇及其氢解液的方法,并采用外标法定量分析乙二醇、1,2-丙二醇和1,3-丙二醇。结果表明:最佳分析条件为流动相V(水)∶V(乙腈)=9∶1,pH为5.3,流速为0.600 mL/min,柱温为80℃,进样量为10μL。在此条件下得到木糖醇质量浓度为0.16~100.00 g/L,乙二醇为0.78~50.00 g/L,1,2-丙二醇及1,3-丙二醇为0.39~25.00 g/L,各组分的线性关系R为0.999 7~0.999 9,方法的平均回收率为98.31%~101.11%,相对标准偏差(RSD)为0.85%~2.35%。     

甘油催化氢解制1,3-丙二醇的纳米铜基催化剂

采用共沉淀法制备用于甘油催化氢解制1,3-丙二醇的纳米CuO-TiO₂/SiO₂催化剂,用X射线粉末衍射及扫描电子显微镜对催化剂的结构及形貌进行表征。在微型固定床反应器上考察了纳米催化剂对甘油氢解制备1,3-丙二醇的催化性能,结果表明,在反应温度190 ℃、H₂压力4.5 MPa、n(H₂)∶n(甘油)=50∶1和液空速0.30 h^-1的较佳条件下,甘油转化率为35.66%,1,3-丙二醇选择性达78.18%。     

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。     

Polyol-Derived Alkoxide/Hydroxide Base Catalysts I. Production

A metal methoxide is more expensive than a metal hydroxide and dissolves in methanol releasing a methoxide ion without producing water. The methoxide ion has a higher reaction rate making it more preferred for industrial biodiesel production. This study describes the preparation of alkoxide catalysts from metal hydroxides and non-volatile, non-toxic polyols. Heating aqueous solutions of metal hydroxides and different polyols (1,2-propanediol, 1,3-propanediol, glycerol, xylitol and sorbitol) under vacuum yielded polyol-derived alkoxide base catalysts (PDABC). Comparison of the drying process for respective sodium hydroxide-polyol combinations at two mole ratios of sodium hydroxide to polyol showed that drying at 2:1 mole ratio (metal hydroxide to polyol) was more efficient than that of 3:1. Dehydration of alkaline solutions containing three or more hydroxyl groups (glycerol, sorbitol and xylitol) was faster than drying similar solutions of diols. The empirical formula determined confirmed that the resulting powders contained mono-sodium substituted alkoxides at 1:1, 2:1 and 3:1 (sodium hydroxide: polyol) mole ratio. Fatty acid methyl esters were prepared from canola oil and methanol using glycerol sodium alkylate as a catalyst. The conversion yield of oil to methyl ester was greater than 99 %.     

Ni/La2O2CO3催化剂对山梨醇氢解产物的选择性调控

采用共沉淀法制备了具有协同稳定作用的Ni/La₂O₂CO₃催化剂，用于山梨醇选择性氢解为小分子醇的研究。采用X射线衍射、氢气程序升温还原、CO₂程序升温脱附和扫描电镜对催化剂进行了表征。考察了不同配比Ni、La的加氢位点和碱性调控对山梨醇氢解产物的影响。结果表明，Ni、La摩尔比为2：3时，山梨醇转化率达到98.6%，C₂~C₃多元醇的产率达到43.8%，催化剂经2次反应后对山梨醇的转化率仍高达90%。探究了催化剂从酸性到碱性调变过程中，山梨醇氢解的产物分布，并提出了反应路径。     

Polyol-Derived Alkoxide/Hydroxide Base Catalysts II: Transesterification Reactions

Biodiesel, fatty acid methyl ester (FAME), was produced by transesterification of canola oil with methanol in the presence of a series of alkoxide/hydroxide base catalysts produced from glycerol, 1,2-propanediol, 1,3-propanediol, xylitol, or sorbitol produced by dehydration reaction of sodium hydroxide in the presence of polyols. Transesterification reactions proceeded efficiently in the presence of sodium alkoxide catalysts prepared at three different mole ratios of sodium hydroxide to glycerol (1:1, 2:1, and 3:1). The production of methyl ester during the course of the reaction was determined repeatedly and the reaction progress was compared with that achieved in a reaction catalyzed by freshly prepared anhydrous sodium methoxide as a standard catalyst. Sodium alkoxide/hydroxide catalysts activity during the first 2 min of the reaction was in the order of: sorbitol < xylitol < sodium methoxide < 1,2-propanediol < 1,3-propanediol < glycerol regardless of the mole ratio of sodium hydroxide to glycerol. All catalysts showed a higher methyl ester accumulation at higher ratios of sodium hydroxide to polyol and had the following order 1:1 < 2:1 < 3:1 (sodium hydroxide:glycerol). Several of these catalysts were as powerful as sodium methoxide in catalyzing the transesterification reaction at the same mole concentration. All alkoxide/hydroxide catalysts resulted in a high FAME accumulation (>95 wt%) in a single transesterification batch reaction.     

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO_x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO_x with metal Ru particles can form “MoO_x-Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.     

Hydrogenolysis of sorbitol to glycols over carbon nanofiber supported ruthenium catalyst

Sorbitol hydrogenolysis was carried out over a carbon nanofiber supported ruthenium catalyst prepared by incipient wetness impregnation. The carbon nanofiber supported ruthenium catalyst was shown to have an attracting behavior when compared with a commercial activated carbon supported ruthenium catalyst, especially in terms of selectivity to glycols. The preferable hydrogen partial pressure for sorbitol hydrogenolysis was ca. 8.0 MPa, lower than that usually reported in previous works. Slightly soluble calcium hydroxide, which was used as a basic promoter, remarkably increased the selectivity to glycols, as compared with the soluble sodium hydroxide. The variation of product selectivity with catalyst amount indicated that glycerol was the initial C3 polyol product while propylene glycol was derived from glycerol. The parametric investigation was further focused on the intrinsic features of sorbitol hydrogenolysis.     

Hydrogenolysis of Glycerol to Propanediol Over Ru: Polyoxometalate Bifunctional Catalyst

Ruthenium-doped (5 wt%) acidic heteropoly salt Cs_2.5H_0.5[PW₁₂O₄₀] (CsPW) is an active bifunctional catalyst for the one-pot hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in liquid phase, providing 96% selectivity to 1,2-PDO at 21% glycerol conversion at 150 °C and an unprecedented low hydrogen pressure of 5 bar. Rhodium catalyst, 5%Rh/CsPW, although less active, shows considerable selectivity to 1,3-PDO (7.1%), with 1,2-PDO being the main product (65%).     

纳米CuO/SiO_2催化甘油氢解制备1,2-丙二醇反应研究

采用共沉淀法制备了纳米CuO/SiO2催化剂,在固定床反应器上考察了纳米催化剂对甘油催化加氢制1,2-丙二醇（1,2-PDO）的催化活性。结果表明,在反应温度200℃,反应压力1.0 MPa,n（H2）∶n（甘油）=30∶1,液空速0.30 h-1的条件下,甘油转化率100%,1,2-PDO选择性98.71%。