【作者】 宋海岩；

【导师】 王祥生； 李钢；

【作者基本信息】 大连理工大学 ， 工业催化， 2010， 博士

【摘要】 金催化逐渐成为国内外的研究热点。人们已成功制备出MCM-41和SBA-15等中孔分子筛负载型纳米金催化剂,但关于HMS系列分子筛负载型金催化剂却鲜有报道。以Ti-HMS为催化剂,H2O2为氧化剂,可以实现燃油中大分子硫化物的深度氧化脱除。但反应中部分H2O2受热分解,其有效利用率大大降低。为解决上述问题,本论文以Ti-HMS为载体,采用一系列方法,进行了负载型双功能催化剂Au/Ti-HMS的合成,并将其用于催化H2／O2直接合成H2O2,以及原位H2O2氧化脱硫的研究。论文的主要内容如下：采用沉积沉淀(DP)法制备了Au/TS-1和Au/Ti-HMS,考察了二者在H2／O2直接法合成H2O2反应中催化性能的异同。研究发现,Au/TS-1在水中能获得更高的H2O2产率,而Au/Ti-HMS则更适合在甲醇中合成H2O2。通过H2-TPR技术确定了直接法合成H2O2的活性中心为Au0物种。Au/TS-1和Au/Ti-HMS在甲醇溶剂中催化H2O2氢解／分解速率均明显低于水做溶剂,并且金催化H2O2的氢解比分解更容易自发进行。采用DP法制备Au/Ti-HMS,载体的有序中孔结构受到明显影响,因此开发出原位法进行Au/Ti-HMS的合成,并比较了制备方法对载体结构及催化性能的影响。结果表明,原位法样品的载体蠕虫状中孔结构和骨架钛保持完好,并能有效地催化原位H2O2氧化脱除模拟燃料中的大分子硫化物,对4,6-二甲基二苯并噻吩的脱除率可达到93%。氨水DP法样品的载体中孔有序度降低,但其中孔结构依然保持完整,纳米金粒子尺寸较小,比原位法样品更能快速脱除苯并噻吩和二苯并噻吩。尿素DP法样品载体的中孔结构被水热条件破坏严重,但仍具有骨架钛结构,仅能实现苯并噻吩和二苯并噻吩的脱除,而对4,6-二甲基二苯并噻吩的氧化则完全失活。原位H2O2氧化脱硫过程中,H2O2的生成与硫化物被H2O2氧化过程同步发生。同Ti-HMS/市售H2O2氧化脱硫相比,原位H2O2氧化脱硫技术实现了H2O2的有效利用、产物的“零排放”以及工艺的简化。原位法催化剂的活性金组分在反应中出现流失,表现了较差的重复使用性能。进而开发出原位还原法合成Au/Ti-HMS。研究表明,合成中NaBH4/Au摩尔比控制在1.25：1并引入盐酸,能显著提高载体的中孔有序度,并获得尺寸较小且分布均匀的纳米金颗粒。金颗粒被牢固地镶嵌于载体的多重孔道之间,使其在直接法合成H2O2,以及催化原位H2O2氧化脱除苯并噻吩和二苯并噻吩等反应中能够重复使用多次而未失活。更多还原

【Abstract】 Gold catalysis gradually becomes a focal research all over the world. Gold nanoparticles supported on mesoporous molecular sieves MCM-41 and SBA-15 have been prepared successfully. But there are few reports on HMS supported gold catalysts. Oxidative desulfurization of bulky sulfur compounds in diesel over Ti-HMS/H2O2 has been made a considerable progress. However, the continuous decomposition of commercial H2O2 during heated reaction seriously cuts down its effective availability. To resolve the above problems, a bifunctional catalyst Au/Ti-HMS is synthesized by a series of methods, and is used in the oxidative desulfurization by in-situ-H2O2 directly synthesized from H2/O2. The main contents of this paper are as follows.Au/TS-1 and Au/Ti-HMS prepared by deposition-precipitation (DP) method were used in the direct synthesis of H2O2 from H2/O2 to investigate the similarities and differences of their catalytic performance. It is shown that Au/TS-1 obtains a higher productivity of H2O2 in water solvent, whereas Au/Ti-HMS is more suitable to synthesize H2O2 in methanol solvent. The Au0 species act as the active sites during synthesis of H2O2, which is confirmed by H2-TPR technique. Both Au/TS-1 and Au/Ti-HMS obtain lower decomposition rate and hydrogenation rate of H2O2 in methanol solvent than in water. The hydrogenation of H2O2 occurs much more spontaneously than the decomposition.The ordered mesoporous structure of the support was seriously influenced during the DP preparation of Au/Ti-HMS. Therefore, Au/Ti-HMS was synthesized by an in situ method, and the effects of different preparation method on the structure of support and the catalytic performance of catalyst were investigated. It is shown that Au/Ti-HMS (In situ) maintains the wormlike mesoporous structure and the framework Ti successfully. It achieves effective in-situ-H2O2-oxidation of bulky sulfur compounds in model oil and especially obtains 93% removal rate for 4,6-dimethyldibenzothiophene. Au/Ti-HMS (NH3 DP) still possesses intact mesopores of HMS in spite of the decrease of mesopores ordering. In addition, it possesses smaller gold nanoparticles and achieves more effective removal of benzothiophene and dibenzothiophen than Au/Ti-HMS (In situ). For Au/Ti-HMS (Urea DP), the mesoporous structure of the support is seriously damaged in hydrothermal condition. It can only achieve the removal of benzothiophene and dibenzothiophen due to the existence of framework Ti, whereas, it has no catalytic activity for the removal of 4,6-dimethyldibenzothiophene. The formation of H2O2 and in-situ-H2O2 oxidation occur as a simultaneous process. Compared with Ti-HMS/commercial H2O2 method, the in-situ-H2O2-ODS technique achieves effective utilization of H2O2, zero emission and process simplification.Au/Ti-HMS(In situ) showed a poor reusability due to the loss of gold active sites during reactions. Therefore, an in-situ-reduction method was adopted to synthesize Au/Ti-HMS. It is shown that the sample with 1.25:1 of NaBH4/Au molar ratio and addition of HC1 possesses mesoppres with high order, as well as small and uniformly dispersed gold nanoparticles which were strongly embedded between the channels of the support. The catalyst exhibits attractive stability and recycled performance in the direct synthesis of H2O2 and in the in-situ-H2O2 oxidation of benzothiophene and dibenzothiophen.更多还原