水热合成法制备焦绿石型三氧化钨的研究

发布时间：2018-04-29 23:15

本文选题：水热反应 + 焦绿石型　；参考：《中南大学》2011年硕士论文

【摘要】：焦绿石型三氧化钨(WO3·0.5H_2O)以扭曲的WO6八面体为结构基元、通过W-O刚性骨架的角顶构筑形成具有圆环孔道的层状结构,由于其具有分子筛的网状结构和介稳性,在材料科学领域拥有广泛的应用前景,同时在钨冶炼领域,能够作为制备氧化钨的中间体,有希望减少钨工艺流程,实现碱液循环。目前,通过利用水热法制备焦绿石型氧化钨已经能够保证一定的反应率,但是含钨酸钠的水热体系结构比较复杂,限制了该法的推广应用。因此,如何强化和优化水热反应过程,制备出比较符合工业要求的焦绿石型氧化钨产品,对于实现工业化生产具有重要的意义。鉴于WO3易溶于钨酸钠溶液,起到改变水热体系pH值的作用,本文主要选择三氧化钨为添加剂制备焦绿石型氧化钨,并辅以二氧化碳、草酸预处理钨酸钠溶液,详细地研究了不同条件下所得产品的结构形态以及溶液反应率,对影响反应过程的各项因素进行了分析。根据实验数据以及红外谱图分析手段,初步探讨了水热法制备焦绿石型三氧化钨的反应机理。研究结果表明： (1)单独利用三氧化钨为添加剂能够稳定水热体系的pH,并且制得焦绿石型氧化钨产品,其反应率能达到80%以上。而以草酸、CO2预处理钨酸钠溶液后,则利于改变反应速率,将反应时间由原来的24h以上缩短至8h以内。 (2)进一步证明了碱性体系下也能够制得焦绿石型三氧化钨产品,所需要pH范围拓展至3.5～8.9之间。 (3)经XRD、SEM等检测手段分析,所制得的产品均具有良好的立方体结构,颗粒的粒径平均尺寸都在1μm左右。 (4)以三氧化钨为添加物的产品具有较好的分散性,但是,产品中容易夹带Na元素,用少量稀盐酸进行洗涤能基本去除Na元素。 (5)采用红外检测初步认为W_2O_7~(2-)是制备焦绿石型氧化钨的生长基元,探讨了钨酸钠溶液在水热反应过程中以及酸化过程中多组分平衡情况,对水热反应机理提出了合理的假设。
[Abstract]:Pyrochlore tungsten trioxide (WO _ 3) 0.5H _ 2O) takes the twisted WO6 octahedron as the structural unit, and forms a layered structure with a circular pore channel through the angle-top of the W-O rigid skeleton. Because of its network structure and dielectric stability of molecular sieve, It has a wide application prospect in the field of material science. At the same time, it can be used as the intermediate for the preparation of tungsten oxide in the field of tungsten smelting. It is hopeful to reduce the tungsten technological process and realize the lye circulation. At present, pyrochlore tungsten oxide can be prepared by hydrothermal method, but the structure of hydrothermal system containing sodium tungstate is complex, which limits the application of the method. Therefore, how to strengthen and optimize the hydrothermal reaction process and prepare pyrochlore tungsten oxide products which meet the industrial requirements is of great significance for the realization of industrial production. In view of the fact that WO3 is soluble in sodium tungstate solution and plays a role in changing pH value of hydrothermal system, pyrochlorite type tungsten oxide is prepared by tungsten trioxide as additive, and sodium tungstate solution is pretreated with carbon dioxide and oxalic acid. The structure morphology and solution reaction rate of the products obtained under different conditions were studied in detail. The factors affecting the reaction process were analyzed. Based on the experimental data and infrared spectrum analysis, the reaction mechanism of pyrochlore tungsten trioxide prepared by hydrothermal method was preliminarily discussed. The results show that: 1) the pH of hydrothermal system can be stabilized by using tungsten trioxide as additive alone, and pyrochlore type tungsten oxide can be prepared. The reaction rate of pyrochlorite type tungsten oxide can reach more than 80%. When sodium tungstate solution was pretreated with oxalic acid CO _ 2, the reaction rate was changed, and the reaction time was shortened from more than 24 h to less than 8 h. 2) it is further proved that pyrochlorite tungsten trioxide products can also be prepared in alkaline system, and the required pH range is extended to 3.58.9. The results show that all the products have good cube structure and the average particle size is about 1 渭 m. (4) the product with tungsten trioxide as additive has good dispersibility, however, Na element is easily entrained in the product, and the Na element can be basically removed by washing with a small amount of dilute hydrochloric acid. (5) it is preliminarily considered that W _ S _ 2O _ 2 _ 7 ~ (2) is the growth unit of pyrochlore type tungsten oxide by infrared detection. The multicomponent equilibrium of sodium tungstate solution during hydrothermal reaction and acidification is discussed, and the reasonable hypothesis of hydrothermal reaction mechanism is put forward.
【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：O614.613

【引证文献】