【作者】 张倩；

【导师】 郭峰；

【作者基本信息】 大连理工大学 ， 环境工程（专业学位）， 2021， 硕士

【摘要】 由于化石资源减少,人类开发各种形式的可再生能源来寻求可持续发展。生物质作为一种可再生碳源,由于其环境友好、资源丰富,被认为是传统化石资源的理想替代品。糠醛是从木质纤维素中得到的重要的高附加值生物平台化合物,糠醛通过催化氧化可以得到马来酸、富马酸、2（5H）-呋喃酮和琥珀酸等附加值更高的化学产品。开发新型催化剂来提高糠醛的转化率和氧化产物的选择性有重要意义。本文制备了一种双功能固体酸催化剂杂多酸双金属盐及其负载型催化剂,以1,2-二氯乙烷为有机溶剂,过氧化氢为氧化剂,催化糠醛选择性氧化得到马来酸、富马酸和2（5H）-呋喃酮。首先,通过对不同金属取代的磷钨杂多酸双金属盐的筛选,发现相对于金属离子如K⁺、Fe³⁺、Co²⁺,Sn⁴⁺取代的磷钨酸铯盐催化剂对糠醛的氧化具有更高的选择性。扫描电镜、透射电镜、X射线衍射和傅立叶变换红外光谱等表征结果表明,Sn⁴⁺、Cs⁺的引入没有改变磷钨酸的Keggin结构,Sn⁴⁺更多地取代了杂多酸催化剂表面的H⁺。本论文设计合成的固体酸H₁Cs₁Sn_0.25PW催化剂同时具有布朗斯特酸性、路易斯酸性和氧化性,催化活性高且易于分离,十分适合用于催化氧化糠醛。对糠醛在杂多酸双金属盐催化剂上的选择性氧化的反应条件进行了优化,在最佳反应温度（50℃）和时间（2 h）,糠醛和过氧化氢的最佳摩尔比为1:6下,马来酸得到最高的产率44.2%和选择性61.9%。催化剂经五次回收重复使用依然保持良好的催化活性。然后,制备了g-C₃N₄负载型杂多酸盐催化剂,研究了其对糠醛氧化反应选择性的影响。通过X射线衍射和傅立叶变换红外光谱的表征结果可以看到磷钨铯锡盐负载到了g-C₃N₄。本文最后探讨了使用杂多酸双金属盐做催化剂,过氧化氢做氧化剂,选择性氧化糠醛的机理。将实验结果和催化剂表征结果相结合,发现铯锡磷钨酸盐保持了杂多酸的Keggin结构,分布于杂多酸表面的Sn⁴⁺有助于促进糠醛的Baeyer-Villiger氧化反应,从而提高了马来酸的选择性。更多还原

【Abstract】 Due to reduction of fossil resources,various forms of renewable energy have been developed to seek sustainable development.As a renewable carbon energy source,biomass is considered as an ideal substitute for traditional fossil resources because of its environmental friendliness and abundant reserves.Furfural is an important biological platform compound with high added value obtained from lignocellulose.Through catalytic oxidation of furfural,higher added value chemical products such as maleic acid,fumaric acid,2（5H）-furanone and succinate can be obtained.It is of great significance to develop new catalysts to improve the conversion of furfural and the selectivity of oxidation products.This paper mainly introduces the study of heteropoly acid bimetallic salts and their supported catalysts in the selective oxidation of furfural.The oxidation of furfural was carried out in a water/organic two-phase system with1,2-dichloroethane as the solvent,heteropolyacid bimetallic salt as the catalyst and hydrogen peroxide as the oxidant.Firstly,through the screening of different metal-substituted phosphotungstic heteropoly acids,it was found that Sn⁴⁺substituted cesium phosphotungstate catalysts have higher selectivity for the catalytic oxidation of furfural than other metal ions such as K⁺,Fe³⁺,Co²⁺.The results of SEM,TEM and XRD showed that the Keggin structure of phosphotungstic acid was not changed by the introduction of Sn⁴⁺and Cs⁺,and Sn⁴⁺replaced more H⁺on the surface of heteropoly acid catalyst.The heteropolyacid bimetallic salt catalyst H₁Cs₁Sn_0.25PW designed and synthesized in this paper has Bronsted acid,Lewis acid and oxidizability.The catalyst is very suitable for catalytic oxidation of furfural because of its high catalytic activity.It is easy to separate and can be recycled and reused.The reaction conditions for selective oxidation of furfural on heteropoly acid bimetallic salt catalyst were optimized.Under the optimal molar ratio of furfural and hydrogen peroxide of 1:6,maleic acid has the highest yield（44.1%）and selectivity（61.9%）under optimized conditions（50?°C,2 h）.The catalyst still maintained good catalytic activity after five times of recycling and reuse.Then,g-C₃N₄ supported heteropoly acid salt catalysts were prepared and their effects on the selectivity of furfural oxidation were studied.Through XRD and FT-IR characterizations,it can be seen that the H₁Cs₁Sn_0.25PW is loaded to g-C₃N₄.Finally,the mechanism of selective oxidation of furfural by using heteropoly acid bimetallic salt as catalyst and hydrogen peroxide as oxidant was discussed.Combining the experimental results with the catalyst characterization results,it was found that the cesium tin phosphotungstate maintained the Keggin structure of the heteropoly acid,and the Sn⁴⁺distributed on the surface of heteropoly acid was helpful to promote the Baeyer-Villiger oxidation of furfural,thereby improving the selectivity of maleic acid.更多还原