甲醛净化用高效二氧化钛纳米管催化剂的可控制备及应用

Poor activity caused by the nonuniform dispersion of active components is found in the purification of formaldehyde over titania nanotube arrays (TNAs) catalysts. Supercritical fluid deposition (SCFD) and the pre-modification of TNAs by chemical methods are proposed to improve the dispersion of active components. The chemical reaction between the pre-modified groups and the active components, the excellent penetration capacity of supercritical fluid as well as its zero surface tension, would benefit the dispersion. The effect of the pre-modification and the deposition conditions on noble metals dispersion and the catalyst activity would be studied. The catalytic oxidation mechanism of formaldehyde and the composition-structure-activity relationship of the catalyst would be explored by in-situ DRIFTS, SEM, TEM, chemisorption, etc. Then the catalytic oxidation mechanism of formaldehyde would be illustrated, and the catalyst preparation process and formaldehyde oxidation process would be optimized. A method based on the chemical reaction between noble metals and the pre-modified groups is developed to controllably and uniformly disperse noble metals over TNAs, and finally the TNAs catalyst with high activity for formaldehyde oxidation is prepared. This project would provide basic data and lay a technology foundation for the application of TNAs catalyst in air purification. And it also provides a good reference for controllable and uniform dispersion of active components over ordered structure carriers and the study of the composition-structure-activity relationship.

针对二氧化钛纳米管阵列(TNAs)催化剂因活性组分分散不均导致其在甲醛催化氧化中活性不高的问题，本研究提出采用化学的方法对TNAs表面进行预修饰，并结合超临界流体沉积技术，利用预修饰基团与活性组分之间的化学作用及超临界流体超强的渗透能力和零表面张力，将活性组分均匀分散在TNAs上。通过考察预修饰过程和沉积工艺对贵金属分散及其催化活性的影响，并结合原位漫反射红外光谱、SEM、TEM及化学吸附等表征手段对甲醛氧化反应机理及催化剂组成/结构/功效关系的研究，揭示甲醛催化氧化反应机理，优化催化剂制备工艺和甲醛催化氧化工艺，建立一种基于贵金属与TNAs表面预修饰基团之间化学作用的可控均匀分散方法，最终制备出对甲醛催化氧化具有高效活性的TNAs催化剂。本研究为TNAs催化剂在空气净化中的应用提供基础数据和奠定技术基础，同时为在规整结构载体上可控均匀负载活性组分及其组成/结构/功效关系的研究提供参考。

用于甲醛净化的催化剂主要有贵金属催化剂和非贵金属催化剂，非贵金属催化剂成本低、资源丰富，但其活性不如贵金属催化剂，而贵金属催化剂的主要问题在于因活性组分分散不均导致其活性不够，且其成本较高，因此降低贵金属负载量并提高其在载体上的分散度是提高催化活性同时降低成本的一个重要途径。.本项目通过阳极氧化法制备出通透的二氧化钛纳米管阵列结构，采用热碱法对其表面进行预修饰，利用预修饰基团与贵金属组分之间的化学作用以及超临界流体的零表面张力以及高扩散等特性，将极少量的贵金属组分均匀地分布到纳米管表面。探索了热碱处理工艺以及超临界流体沉积工艺对催化性能的影响，获得了较佳的热碱预处理工艺和沉积工艺，将0.1wt%的Pt负载于纳米管阵列上，在室温条件下实现了对甲醛的完全催化氧化。采用原位漫反射红外光谱对甲醛氧化反应进行了在线监测，提出了反应机理，确定了甲酸盐的分解为该反应的关键步骤，分析认为催化剂体系中应含Pt或其他对甲酸盐分解具有促进作用的组分。本项目所设计的TNAs催化剂对室温条件下甲醛的氧化具有优异的催化活性，为TNAs催化剂在空气净化中的应用提供基础数据和奠定技术基础，为新型甲醛等VOCs催化氧化催化剂的设计和开发提供思路和方法。