【作者】 谢娟；

【导师】 王延吉； 魏雨；

【作者基本信息】 河北工业大学 ， 化学工艺， 2009， 博士

【摘要】 现有的环己烷氧化制环己酮和环己醇生产工艺普遍存在转化率低、选择性差、工艺复杂、耗能大和对环境污染严重等问题,这就使得研究和开发高效、环境友好的环己烷催化氧化工艺具有重要的理论意义和实用价值。本论文旨在液相条件下,研制一种新型催化剂用于以分子氧(空气)为氧化剂的环己烷选择性氧化反应。这种催化剂不仅能够使反应在相对温和的条件下进行,而且具有较高的催化反应性能。以氯金酸和硼氢化钠为原料,柠檬酸钠作保护剂,在室温条件下一步还原制备出了不同粒径的单分散纳米金颗粒。表征结果显示,制备的金纳米颗粒呈球形,为面心立方结构;柠檬酸钠保护剂的存在不仅提高了粒子的单分散性和稳定性,还在一定程度上抑制了金颗粒的生长,使得颗粒的粒径可控,且分布很窄。紫外-可见吸收光谱反映出,随着粒径的增大,胶体金在可见区的最大吸收峰逐渐向长波方向移动。通过自组装方法制备了Au/SiO2催化剂,并采用X-射线衍射、透射电镜、原子吸收光谱、紫外-可见光谱和氮吸附脱附(比表面积及孔结构分析)对其进行表征。该催化剂在不加任何助剂的条件下,在环己烷催化氧化反应中表现出良好的催化活性。考察了焙烧温度、金含量、反应压力、温度及时间对催化剂活性的影响。结果表明,经500℃焙烧的1% Au/SiO2催化剂,在3.0 MPa空气气氛中于150℃下连续反应4 h时,环己烷转化率约为10.0%,环己酮和环己醇的总选择性约为92.0%。以四苯基卟啉和醋酸盐为原料,合成了四种简单过渡金属配合物。研究发现,可以应用紫外-可见及红外光谱对过渡金属卟啉配合物中心离子的价态及其在周期表中的位置进行初步判断。以空气氧化环己烷制备环己酮和环己醇为探针反应,在不加入任何有机溶剂或助催化剂的条件下考察了金属卟啉用量、反应压力、温度、时间等对其催化活性的影响。结果发现,锰卟啉催化活性最好,在适宜反应条件下,环己烷转化率高达15.4%,环己酮和环己醇的总选择性约为93.9%。以包含巯基和吡啶基官能团的巯基吡啶为桥联剂,实现了Mn(Ⅲ)TPP在金负载量为5%的Au/SiO2催化剂上的固载化,从而得到了一种新型Mn(Ⅲ)TPP-Au/SiO2复合催化剂。首次将其应用于催化空气氧化环己烷反应的实验结果显示,与未固载金属卟啉的5% Au/SiO2催化剂相比,该复合催化剂具有更高的催化活性。在反应温度170℃,空气压力1.5 MPa,反应时间6 h的优化条件下,环己烷转化率与酮醇总选择性分别为5.39%和88.7%。此外,该催化剂还具有可重复使用的特点。更多还原

【Abstract】 The commercial processes of cyclohexane oxidation to cyclohexanone and cyclohexanol generally show many problems, such as low conversion, poor selectivity, complicated technology, high-energy consumption and environmental pollution. So it seems to be of great academic and practical interesting to study and develop highly efficient and environmentally friendly catalytic cyclohexane oxidation processes. The aim of this work is to develop a novel catalyst, which is applied to catalyze selective oxidation of cyclohexane using molecular oxygen (air) as oxidation in liquid-phase. It can not only catalyze the reaction under relatively mild conditions, but also has gotten better catalytic performance.Monodispersed gold nanoparticles with different diameters were successfully synthesized by one step process at room temperature, using HAuCl4 and NaBH4 as the reactants, Na3C6H5O7 as the protecting agent. Characterization results indicate that the as-prepared gold nanoparticles are spherical, and their structure is face center cubic (FCC). Using sodium citrate not only improves monodispersity and stability of Au nanoparticles, but also inhibits the crystal growth, making the particle size is controllable and has a narrow distribution. The peak positions of UV-Vis absorption spectra of colloidal gold shift to the long wavelength as the crystal size increases.Au/SiO2 catalysts were prepared by self-assembly technique. X-ray diffraction (XRD), transmission election microscopy (TEM), atom absorption spectrometry (AAS), ultraviolet-visible spectroscopy (UV-Vis) and nitrogen adsorption/desorption (specific surface area and pore structure analysis) were used to characterize the catalysts. The as-prepared Au/SiO2 catalysts exhibited excellent catalytic performance for selective oxidation of cyclohexane by air in the system without any promoter. The influences of gold content, reaction pressure, reaction temperature, reaction time and calcination temperature of catalyst on the catalytic performance were studied. The conversion of cyclohexane and total selectivity of cyclohexanone and cyclohexanol over the catalyst with 1% gold loading and calcination temperature 500℃, were up to ~10.0% and ~92.0% respectively, under the conditions of reaction temperature 150℃, 3.0 MPa air, reaction time 4 h.Four kinds of simple transition metal complexes were synthesized from tetraphenylporphyrin and transition metal acetate. Results reveal that using UV-Vis and FTIR techniques can determine the valence state and position in the periodic table of the central ions in transition metal porphyrin complexes. The catalytic oxidation of cyclohexane to cyclohexanone and cyclohexanol in air as probe reaction was performed without any organic solvent or cocatalyst, and the influences of the amount of metal porphyrin, reaction pressure, reaction temperature and reaction time on the catalytic activity were investigated. It was found that manganese porphyrin had the highest activity, and a maximum 15.4% of cyclohexane conversion and 93.9% selectivity of cyclohexanone and cyclohexanol could be obtained under the suitable conditions.A Mn(Ⅲ) TPP-Au/SiO2 composite catalyst was obtained by immobilizing Manganese(Ⅲ) porphyrin on Au/SiO2 (5% Au loading) using mercaptopyridine with sulfhydryl and pyridyl groups as bridging agent, and it was used for the aerobic oxidation of cyclohexane for the first time. Experimental results show that the activity of the catalyst was higher than that of the pure 5% Au/SiO2 catalyst. Under the suitable conditions of reaction temperature 170℃, 1.5 MPa air and reaction time 6 h, the conversion of cyclohexane and the total selectivity of cyclohexanone and cyclohexanol were 5.39% and 88.7% respectively. In addition, the catalyst can be used repeatedly.更多还原