锰氧化物的还原法制备及其室温催化氧化甲醛研究

发布时间：2018-07-13 19:00

【摘要】：近年来,室内环境质量备受人们的关注,而甲醛污染物在室内环境具有潜伏期长,释放源多,释放持续时间久等特点,去除室内甲醛污染物,改善室内空气质量,与人们身体健康密不可分,引起了人们的广泛关注。甲醛去除方法多种多样,有通风法、生物净化法、吸附法、臭氧氧化法、光催化、低温等离子体技术和催化氧化法等。其中,过渡金属氧化物催化氧化法因其效率高、无污染和廉价等特点成为甲醛去除的研究热点。本文以高锰酸钾作氧化剂,分别选用甲醇和硫酸锰为还原剂,通过简单的氧化还原反应合成系列锰氧化物,并通过在反应体系中加入酸或碱调控锰氧化物催化剂的物理化学性质,进而影响其室温催化氧化降解甲醛的性能。通过扫描电镜(SEM)、X射线衍射(XRD)、拉曼光谱(Raman)、N2-吸附脱附、光电子能谱(XPS)、氢气程序升温还原(H2-TPR)、电感耦合等离子体原子发射光谱(ICP-AES)和原位红外光谱(in situ-FTIR)等表征手段研究了催化剂的物理化学性质,在自行建立的动态、静态测试系统上评价了合成的锰氧化物室温催化氧化降解甲醛的性能,通过分析甲醛催化氧化的中间产物和最终产物,阐述了锰氧化物室温催化氧化甲醛的机理。研究表明,甲醇还原高锰酸钾制备的锰氧化物均属水钠锰矿,反应体系中加入酸,能够使催化剂的比表面积增大,表面吸附氧与晶格氧的比例降低,同时还降低了表面活性氧物种的还原温度和晶格氧的起始还原温度。以2.7 mL甲醇、9 g高锰酸钾和1 mL硫酸为反应条件制备的锰氧化物室温催化氧化甲醛的反应活性最高,甲醛降解率为91%,二氧化碳产率达89%。硫酸锰还原高锰酸钾制备的锰氧化物属于2×2隧道型隐钾锰矿,加碱后制备的锰氧化物为层状水钠锰矿,碱参与硫酸锰和高锰酸钾的反应,能提高催化剂的比表面积和表面吸附氧与晶格氧的比例,降低表面活性氧物种的还原温度和晶格氧的起始还原温度。在高锰酸钾、硫酸锰和氢氧化钠物质量之比为2:3:2的条件下制备的锰氧化物室温催化氧化甲醛的反应活性最高,甲醛降解率为95%,二氧化碳产率为57%。
[Abstract]:In recent years, people pay more attention to indoor environmental quality, and formaldehyde pollutants in indoor environment have the characteristics of long incubation period, many sources of release, long duration of release, and so on, to remove indoor formaldehyde pollutants and improve indoor air quality. It is closely related to the health of people and has aroused widespread concern. There are many ways to remove formaldehyde, such as ventilation, biological purification, adsorption, ozone oxidation, photocatalysis, low-temperature plasma technology and catalytic oxidation. Among them, transition metal oxide catalytic oxidation method has become a hot research area for formaldehyde removal because of its high efficiency, no pollution and low cost. A series of manganese oxides were synthesized by simple redox reaction with potassium permanganate as oxidant and methanol and manganese sulfate as reductants respectively. The physical and chemical properties of manganese oxide catalysts were regulated by adding acid or base to the reaction system, which affected the catalytic oxidation and degradation of formaldehyde at room temperature. By scanning electron microscopy (SEM) X-ray diffraction (XRD), Raman spectroscopy (Raman) and N _ 2-adsorption desorption, Photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), inductively coupled plasma atomic emission spectrometry (ICP-AES) and in situ infrared spectroscopy (in situ FTIR) were used to study the physicochemical properties of the catalysts. The catalytic oxidation of formaldehyde by manganese oxide at room temperature was evaluated by static test system. The mechanism of oxidation of formaldehyde by manganese oxide at room temperature was described by analyzing the intermediate product and final product of catalytic oxidation of formaldehyde. The results show that the manganese oxides prepared by methanol reduction of potassium permanganate are all sodium manganese ores. Adding acid into the reaction system can increase the specific surface area of the catalyst and decrease the ratio of adsorbed oxygen to lattice oxygen on the surface. The reduction temperature of surface active oxygen species and the initial reduction temperature of lattice oxygen are also reduced. Under the conditions of 2.7 mL methanol 9 g potassium permanganate and 1 mL sulfuric acid as the reaction condition, manganese oxide has the highest catalytic activity for formaldehyde oxidation at room temperature, the degradation rate of formaldehyde is 91%, and the yield of carbon dioxide is 89%. Manganese oxide prepared by reduction of potassium permanganate with manganese sulfate belongs to 2 脳 2 tunnel type crypto-potassium manganese ore, and the manganese oxide prepared by adding alkali is layered sodium manganese ore. Alkali takes part in the reaction between manganese sulfate and potassium permanganate. The specific surface area of the catalyst and the ratio of surface adsorbed oxygen to lattice oxygen can be increased, and the reduction temperature of surface active oxygen species and the initial reduction temperature of lattice oxygen can be decreased. Under the condition that the mass ratio of potassium permanganate, manganese sulfate and sodium hydroxide is 2:3:2, the manganese oxide has the highest catalytic activity for formaldehyde oxidation at room temperature, the degradation rate of formaldehyde is 95%, and the yield of carbon dioxide is 57%.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X51

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