纳米铜基催化剂结构及其催化生物质基多元醇选择氢解性能研究

The production of highly value-added ethylene glycol and propylene glycol by selective hydrogenolysis of biomass-derived polyols is one of the important ways to high-value utilization of biomass. This application selects copper as the main active component, which itself exhibits both high activity in alcohol-OH group dehydrogenation and C=O bond hydrogenation but low activity in C-C bond cleavage. By using optimized synthesis method, Cu-based nanocatalysts were prepared with controlled size and structure. Under the promotion of alkali additives and / or the synergy effect of alkaline catalyst support, biomass-derived xylitol and sorbitol were hydrogenolyzed to the target glycols with high activity and high selectivity. The structure-activity relationship of the copper-based catalysts in the hydrogenolysis of biomass-derived polyols was revealed by the studying of the effects of catalyst composition, microstructure and the surface properties of the catalysts on the catalytic activity and selectivity. In order to elucidate the reaction pathway and the mechanism of the selective hydrogenolysis of polyols, the non-steady-state species and the surface adsorbed species were identified, and the catalytic active sites were also characterized. The effective ways to adjust of the catalytic reaction pathway were initially established. Combination with the density functional theory calculations, the microscopic structure, which is benefit for the activation and conversion of polyols, was constructed, and the new and more effective catalyst systems were designed from the molecular / atomic level. These studies also provide some theoretical basis for the creation of new catalysts for the hydrogenation (activation) and transformation of specific polyols.

通过生物质基多元醇选择氢解制备高附加值的乙二醇和丙二醇是生物质高值化利用中的一条重要途径。本申请以同时具有较高醇-OH基脱氢活性和C=O键加氢活性而自身C-C键裂解活性较低的金属铜为主活性组分，采用优化的合成方法，制备尺寸和结构可控的Cu基纳米催化剂，在碱助剂的促进作用和/或碱性载体的协同作用下，将生物质基木糖醇和山梨醇高活性和高选择性地氢解为目标二元醇。研究催化剂的组成、微观结构、表面性质等对催化剂活性和选择性的影响规律，揭示铜基催化剂在生物质基多元醇选择氢解反应中的构效关系。借助对非稳态物种、表面吸附态物种的鉴别和对催化剂活性位的表征，认识多元醇选择氢解反应的路径和机理，初步建立调控催化反应路径的有效方法。结合密度泛函理论计算，构筑有利于多元醇活化和转化的微观结构，从分子/原子水平上设计合成新的更有效的催化剂体系，同时也为针对特定多元醇加氢活化和转化的新型催化剂的创制提供理论基础。

通过生物质基多元醇选择氢解制备高附加值的乙二醇和丙二醇是生物质高值化利用中的一条重要途径。以同时具有较高醇-OH基脱氢活性和C=O键加氢活性而自身C-C键裂解活性较低的金属Cu为主活性组分，研究了系列不同结构、尺寸和组成纳米Cu催化剂在生物质基木糖醇选择氢解制备乙二醇和1,2-丙二醇反应中的性能，发现Cu/SiO2-Ca(OH)2双功能催化剂体系可以高效催化木糖醇氢解制备目标二元醇，取得与文献报道Ni、Ru基催化剂相近甚至更好的结果，同时可以显著抑制不必要C-C键裂解副产物如甲烷的生成。Cu/SiO2催化剂的活性和选择性强烈受控于Cu颗粒尺寸，显示铜催化剂催化木糖醇氢解反应的结构敏感特性。同时催化剂的活性和选择性也受反应动力学条件如反应温度、压力、pH、反应液浓度等影响。这些Cu颗粒尺寸和反应动力学条件的影响与先前报道的木糖醇氢解制二元醇的反应路径一致，说明总反应速率受控于Cu催化剂上木糖醇脱氢生成木糖中间体，而二元醇的选择性则依赖于Ca(OH)2高效催化木糖逆羟醛缩合生成乙醇醛和甘油醛以及它们随后加氢生成二元醇的速率要胜过与Ca(OH)2发生副反应生成乙醇酸和乳酸。基于如上研究和认识，设计制备了新型高效Cu-Ni/SiO2双金属催化剂体系，同时提高了催化剂的C-OH脱氢和C=O加氢活性，在200 ℃和8MPa的较温和反应条件下取得81%的目标二元醇收率，该结果是目前国内外文献报道的最好结果之一。研究了催化剂的循环使用稳定性，发现Cu的烧结和强吸附物种对活性位的覆盖是催化剂失活的主要原因，通过焙烧和还原处理可以有效恢复催化活性。研究工作为设计制备更加高效稳定的纳米铜基高碳多元醇氢解催化剂和优化二元醇生成工艺条件指明了方向。.此外，基于纳米Cu优异的C-O键/C=O键氢解/加氢性能，以纳米Cu-SiO2基复合物催化剂实现了CO2经环碳酸酯高效间接多相催化加氢制备甲醇同时联产二元醇（收率均>97%)，催化剂的活性明显受表面酸碱性、Cu颗粒尺寸和价态影响，表面Cu0和Cu+的协同催化对获得高的甲醇收率起到至关重要的作用；以无Cr的价廉Cu-Mg3AlO4.5水滑石结构双功能催化剂实现生物糠醇（醛）高效环醚C-O键氢解制1,2-戊二醇和1,5-戊二醇，在413 K和6 MPa H2的温和反应条件下，取得80%的戊二醇总收率，显示良好的工业开发潜力。