【作者】 钱晓巍；

【导师】 张宁；

【作者基本信息】 南昌大学 ， 工业催化， 2011， 硕士

【摘要】 作为一类新型催化材料,铌化合物由于其独特的性能引起了国内外学者的广泛关注。它们可以作为催化剂的活性组分、助剂或载体使用,其催化作用主要源于其独特的酸性及氧化还原性。它们在许多领域都有着广泛应用,如脱水、脱氢、水合、水解、氧化脱氢、环氧化、氨氧化、甲基氧化偶联、酯化、烷基化、异构化；缩合；碳氢化合物的歧化、氢化、NO的分解与还原、加氢脱硫/脱氮、光催化、环境污染治理等等。我国具有十分丰富的铌矿资源,但在铌化合物的基础研究及应用开发方面尚处于起步阶段。因此,进一步研究铌系催化剂,对开发新型高效、绿色环保的新型催化体系,具有十分重要的理论价值和社会意义。本文以五氯化铌NbCl5为铌源,采用前驱体法、水热法和溶胶-凝胶法分别制备了铌负载型含钛硅基分子筛Nb/Ti-MCM-41催化剂、铌基介孔分子筛Nb-MCM-41催化剂和离子掺杂(Nb,I,N)型TiO2催化剂,通过XRD, N2吸附-脱附,FT-IR, UV-vis, TG, XPS等表征技术对其进行了结构分析；并通过紫外光下降解溶液中亚甲基蓝反应(Nb/Ti-MCM-41),双氧水苯酚羟基化反应(Nb-MCM-41)和可见光下催化处理阿奇霉素制药废水中有机残留物反应(离子掺杂型TiO2)来分别考察它们的催化活性。催化剂表征结果显示,Nb/Ti-MCM-41和Nb-MCM-41系列催化剂都保持了MCM-41介孔材料的性质,拥有大的比表面积和均匀分布的孔径。Nb/Ti-MCM-41催化剂中,通过浸渍负载的Nb物种均匀的分散在催化剂的表面,但有少量沉积在分子筛孔内；而Nb-MCM-41系列中的Nb原子则顺利的进入了骨架结构中；通过XPS分析可知,掺杂离子(Nb,I,N)都进入到了半导体TiO2的晶格中,TiO2的晶相也随掺杂离子的不同而发生变化。实验结果表明,在紫外光下降解亚甲基蓝反应过程中,助剂Nb的加入可使得Ti-MCM-41催化剂对有机物分子的吸附和降解性能都有所提高。催化剂中反应活性最佳的Nb/MCM-41,在暗反应阶段对亚甲基蓝的吸附高达83%,在光反应阶段也表现出了好的降解活性。Nb-MCM-41催化苯酚羟基化反应中,对产物苯二酚而言,固液比为50：1的条件下,最佳反应条件为：催化剂中Si/Nb=48,反应温度55℃,催化剂用量0.1 g,反应时间6 h,苯二酚选择性最高为96%；产物中邻苯二酚与对苯二酚(CAT/HQ)的比可达到80。所有离子掺杂型TiO2在催化处理阿奇霉素废水中的有机物时都表现出了一定的活性。其中,活性最佳的为I-N-TiO2,可见光下反应12 h后对目标废水COD的去除率高达57.2%,活性最差的为Nb-TiO2,仅2.7%。更多还原

【Abstract】 To be a new kind of catalytic materials, niobium compound has aroused extensive concern in the domestic and international academics due to its unique structure and excellent properties. They can be used as a catalyst of the active component, promoter or carrier, Niobic acid and compounds containing niobium are applied in a wide range of catalysis fields for their unique acidic property, oxidizing and thermal stability. Such as:dehydration, dehydrogenation, hydration, hydrolysis, epoxidation, ammoxidation, hydroisomerization, esterification, alkylation, condensation, disproportionation, desulfurization, denitrification, photocatalytic reactions and so on. China boasts abundant niobium mineral resources for the development of niobium industry with the advantaged superiority. However, currently the research of theoretical basis, analytical methods, development and application prospects about niobium-based compounds is still at the starting stage. So, It has an important theoretical referenced value and practical significance to explore the catalytic systems of high efficient, clean and green.In this study, using NbCls as precursor, three kinds of Nb-based catalyst were prepared. There are Nb/Ti-MCM-41, Nb-MCM-41 and (Nb, I, N) doped TiO2, which synthesized by precursor method, hydrothermal method and sol-gel method, respectively. The samples were characterized by XRD, N2 adsorption-desorption, FT-IR, UV-vis, TG, XPS and the reasons of formation also discussed. The catalytic activity of as-prepared samples were evaluated in the photodegradation of methylene blue under UV-light, hydroxylating phenol reaction, and the visible-light photodegradation of Azithromycin pharmaceutical wastewater, respectively.The X-ray diffraction patterns indicate that the modified materials (Nb/Ti-MCM-41 and Nb-MCM-41) retain the standard MCM-41 structure. The Nb deposited into the structure of Ti-MCM-41. Whereas, to Nb-MCM-41, the Nb atoms are present in the framework instead. XPS study shows that the dopants (Nb, I, N) have been doped into the bulk of TiO2.Nb/Ti-MCM-41 shows a significant MB elimination efficiency under UV light, duo to its porosity, huge specific surface area and the promoting effect of niobium dispersed into the structure. During a 3-hour reaction, Nb/MCM-41 demonstrates the best adsorption and photocatalytic activity (83% of MB decolored at the dark adsorption) as compared with other samples.The catalytic activity of Nb-MCM-41 toward hydroxylation of phenol in aqueous medium was evaluated using H2O2 as the oxidant at 80℃.The effects of reaction parameters such as Si/Nb ratios, temperature, catalyst amount, and time were also investigated. The results show that the optimal reaction condition is a 100 mg L-1 catalyst dosage, Si/Nb=48, reaction temperature of 55℃and a 6-h reaction time. the Nb-MCM-41-48 showes nearly 96% benzenediol selectivity and high CAT/HQ ratio, to 80 times.The XRD patterns reveal that the mono-doped samples display only anatase phase, whereas the codoped I-N-TiO2 exhibits a mixed-phase (anatase and rutile phase). All the doped TiO2 were applied in the treatment of Azithromycin pharmaceutical wastewater(APW), and they demonstrates different activity for the photocatalytic treatment of APW under visible light. After a 12-hour reaction, I-N-TiO2 demonstrated the best photocatalytic activity of APW (57% APW degradation percentage). On the contrary, the wost one the Nb-TiO2, with the only 2.7% APW degradation percentage.更多还原