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以过氧化氢氧化淀粉制备水溶性羧基淀粉(OST),通过红外光谱、滴定法、粘度和水溶性测试表征OST结构与性能.选择溶解性最高、羧基含量42.1%OST(OST42.1)用于还原氯金酸获得纳米金颗粒,通过溶胶负载制备纳米金催化剂.利用紫外-可见光谱、透射电镜、X衍射和低温N2物理吸附表征所制备的催化剂的微观结构与性能.结果表明,随着OST42.1浓度由5 g/L上升40 g/L时,纳米金颗粒直径呈先降低而上升的趋势,在20 g/L时还原所得纳米金颗粒负载量和颗粒平均直径分别为0.5%和1.8 nm,比表面积和容积率分别为353.01 m2/g和0.293 cm3/g.以20 g/L的OST42.1制备的催化剂,用于催化丙烯环氧化反应,转化率、氢气效率和丙烯环氧化选择性分别达到18.5%,31.1%和68%.其原因在于OST42.1在水中具有溶解度高和粘度低等优点, 以均相还原氯金酸能增加纳米金颗粒负载量及降低直径,提高丙烯气相环氧化效率.研究表明,高水溶性的羧基淀粉能有效还原氯金酸,获得高催化活性的纳米金颗粒,在丙烯气相环氧化领域中具有广泛的应用.

Oxidized starch (OST) with high carboxyl contents (CC) ranging from 18.9% to 42.1% were prepared by H2O2 depending on the H2O2/starch molar ratios.Gold nanoparticles (Au NPs) was fabricated via OST with 42.1% CC (OST42.1) reducing the chloroauric acid,respectively,then Au NPs was embedded into the Titanium silicalite (TS).The effects of preparation conditions on the catalytic performance of propylene epoxidation were evaluated.Both structure and soluble performance of OST were studied.TS/Au was characterized by UV-Vis,TEM,XRD and BET.Furthermore,effect of TS/Au catalyzed the propylene epoxidation was assessed to explore the relationship between the structure and performance of the catalysts.The results showed that when the concentration of OST42.1 increased from 20 g/L to 40 g/L,the diameter of Au NPs presented a trend that first decreased and then increased.When concentration of OST42.1 was 20 g/L,Au NPs could achieve 0.5% with 1.8 nm averaged diameter.BET surface area (SBET) and adsorption pore volume (Vp) of TS/Au-20 (fabricated by 20 g/L OST42.1) was 353.01 m2/g and 0.293 cm3/g, respectively.When this most active catalyst was employed,conversion rate,H2 efficiency and PO selectivity was 18.5%,31.3% and 68%,respectively.OST42.1 exhibited better solubility property and lower viscosity in water,which was easy to control the structure and morphology of Au NPs.As a result,the size of Au NPs decreased and Au NPs content increased,which were attributed to improving conversion rate and the selectivity of propylene epoxidation significantly.The results revealed that TS/Au catalyst prepared by OST42.1 had a potential application in propylene epoxidation.