共查询到19条相似文献,搜索用时 62 毫秒
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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。 相似文献
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从总体流程、反应器类型、催化剂种类、分离方法和特点几方面总结了糖醇催化氢解为低级多元醇的工艺技术研究国内外现状,并对该工艺的研究方向作一展望. 相似文献
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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。 相似文献
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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%。 相似文献
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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。 相似文献
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采用HPLC、LC-MS、GC-MS等分析手段对不同工艺条件下Ni/W2C催化葡萄糖加氢转化的中间产物及终产物进行定性定量分析,研究了葡萄糖加氢转化过程的反应机制和历程。研究发现:葡萄糖加氢转化过程中同时平行发生了加氢、异构和逆向羟醛缩合(氢解)三类反应;葡萄糖发生加氢反应能够得到六元醇且其不会再进一步转化,发生逆向羟醛缩合反应主要生成乙二醇(C2产物),发生异构反应则可生成果糖,其进行逆向羟醛缩合的产物则为1,2-丙二醇和甘油(C3产物);高浓度葡萄糖条件下,其异构产物果糖发生脱水反应生成的5-HMF浓度过高发生聚合,进而导致结焦。根据葡萄糖加氢转化的反应网络,提出了调控反应过程中C2产物和C3产物分布的策略,并通过增加催化剂用量来加快果糖脱水的竞争反应速率(加氢、氢解),进而实现了高浓度(10%,质量分数)葡萄糖的加氢转化。此外,葡萄糖加氢转化过程中存在明显的浓度效应,反应物浓度越低,越有利于发生逆向羟醛缩合反应,反之则有利于发生加氢反应。 相似文献
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采用TPR-TPO联用技术对溶胶-凝胶法制备的Cu/SiO_2催化剂进行表征,计算出催化剂的还原活化能E_a=55.04 kJ·mol^(-1),指前因子A=4.24×10~6s^(-1)。在反应压力4.0 MPa,空速0.46 h^(-1)、n(H_1):n(甘油)=10:1和催化剂用量5.0g的条件下,考察温度对甘油催化氢解性能的影响,220℃时,1,2-丙二醇收率最高,达96%。同时,根据TPR-TPO表征结果,将经历一次还原过程和还原-氧化-再还原过程活化的催化剂分别用于甘油催化氢解反应,还原-氧化-再还原过程较还原过程活化的催化剂收率提高11%。 相似文献
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Hydrogenolysis of biomass-derived glycerol is an alternative route to sustainable production of propylene glycol. Cu–ZnO catalysts
were prepared by coprecipitation with a range of Cu/Zn atomic ratio (0.6–2.0) and examined in glycerol hydrogenolysis to propylene
glycol at 453–513 K and 4.2 MPa H2. These catalysts possess acid and hydrogenation sites required for bifunctional glycerol reaction pathways, most likely involving
glycerol dehydration to acetol and glycidol intermediates on acidic ZnO surfaces, and their subsequent hydrogenation on Cu
surfaces. Glycerol hydrogenolysis conversions and selectivities depend on Cu and ZnO particle sizes. Smaller ZnO and Cu domains
led to higher conversions and propylene glycol selectivities, respectively. A high propylene glycol selectivity (83.6%), with
a 94.3% combined selectivity to propylene glycol and ethylene glycol (also a valuable product) was achieved at 22.5% glycerol
conversion at 473 K on Cu–ZnO (Cu/Zn = 1.0) with relatively small Cu particles. Reaction temperature effects showed that optimal
temperatures (e.g. 493 K) are required for high propylene glycol selectivities, probably as a result of optimized adsorption
and transformation of the reaction intermediates on the catalyst surfaces. These preliminary results provide guidance for
the synthesis of more efficient Cu–ZnO catalysts and for the optimization of reaction parameters for selective glycerol hydrogenolysis
to produce propylene glycol. 相似文献
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The renewability of bio-glycerol has made it an attractive platform for the production of diverse compounds. Selective hydrogenolysis of glycerol to propylene glycol (PG) is one of the most promising routes for glycerol valorization, since this compound is an important chemical intermediate in a number of applications. In this article, advancements in the catalytic conversion of glycerol into propylene glycol are reviewed, which include advances in process development, effects of preparation and activation methods on catalytic activity and stability, and the performance of various types of catalysts. The feasibility of using bio-hydrogen and the challenges of utilizing crude glycerol for glycerol hydrogenolysis are also discussed. 相似文献
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采用共沉淀法制备了氧化铕(Eu2O3)促进的Cu—ZnO催化剂,通过X射线衍射(XRD)、N2O脉冲吸附等手段对所制备的催化剂物化性质进行表征,考察了它们在连续流动固定床反应器中甘油氢解反应的催化性能,讨论了反应液中水的质量分数及还原温度对Eu2O3促进的Cu—ZnO催化性能的影响.结果表明:引入Eu203不改变甘油氢解反应的产物分布,但能显著提高催化剂的稳定性;减少反应液中水含量及降低还原温度有利于提高催化剂的稳定性;稀土Eu2O3能够增强Cu—ZnO的抗水氧化能力,使催化剂表面Cu^0难被水氧化而不易失活。 相似文献
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Long Huang Yu‐Lei Zhu Hong‐Yan Zheng Yong‐Wang Li Zhi‐Yong Zeng 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(12):1670-1675
BACKGROUND: The conversion of glycerol to value‐added derivatives is now critical, owing to the large surplus of glycerol from biodiesel production. The main objective of this work is to develop a novel process for converting solvent‐free glycerol to 1,2‐propanediol. RESULTS: Several catalysts were screened for aqueous‐phase hydrogenolysis of glycerol in an autoclave. The most effective catalysts (Ni/Al2O3, Cu/ZnO/Al2O3) were further tested for vapor phase hydrogenolysis in a fixed‐bed. Ni/Al2O3 did not prove as effective for the production of 1,2‐propanediol because of the high selectivity to CH4 and CO. Over Cu/ZnO/Al2O3, glycerol was mainly converted to the desired 1,2‐propanediol and the reaction intermediate acetol. The production of 1,2‐propanediol was favoured at higher hydrogen pressure. At 190 °C and 0.64 MPa, near complete conversion of glycerol was achieved with 1,2‐propanediol selectivity up to 92%. In addition, a higher concentration (between 43.4% and 0.8%) of acetol was detected and an approximately stoichiometric relationship was found between acetol and 1,2‐propanediol. CONCLUSION: 1,2‐propanediol can be produced with high yields via the vapor phase hydrogenolysis of glycerol over Cu/ZnO/Al2O3. Furthermore, the mechanism of 1,2‐propanediol formation is suggested to proceed mainly through an acetol route over Cu/ZnO/Al2O3. Copyright © 2008 Society of Chemical Industry 相似文献
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研究了并流共沉淀法制备的CuO-ZnO催化剂在山梨醇催化氢解反应中的催化性能,考察了催化剂制备时不同沉淀温度和不同pH对催化剂性能的影响。采用XRD、H2-TPR和SEM等手段对催化剂及其前驱体的分散状态、还原性能和表面形貌进行了表征。结果表明,沉淀pH显著影响催化剂的分散程度和表面形貌,而沉淀温度则影响催化剂及其前驱体中CuO、ZnO的分散状态和分子组成形式;当 pH=8.0和沉淀温度为70 ℃时,催化剂的活性最佳。 相似文献
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