镁铝水滑石基双功能催化剂的构筑与催化碳烟燃烧机理研究

Developing high activity catalyst for soot combustion is one of the most efficient approaches for the removal of particulate material from diesel emission. During soot catalytic combustion, the adsorption of NOx on the catalyst is unclearly, inducing that the soot combustion mechanism is not well understood. This problem restricts the development of catalytic diesel particulate filter (CDPF). In this proposal, the preparation conditions will be manipulated to construct the MgAl hydrotalcite-derived support with different basic sites. Afterwards, noble metals such as Au, Pt and Pd will be loaded, forming bi-functional catalyst with basic sites and oxidation sites. The soot catalytic is used as a probe reaction. Combining in-situ DRIFTS and experiments, the microcosmic and macroscopic adsorption of NOx on the bi-functional catalyst are investigated when soot is existing or not. Meanwhile, the effect of the adsorption behavior on the soot combustion is also elucidated. Finally, the structure-performance and the reaction mechanism are determined and the catalyst with the best activity is selected. This project could provide theoretical guidance on the design of bi-functional catalysts. It is of great value and significance for the development of CDPF technique.

开发高性能碳烟燃烧催化剂是降低柴油车尾气中碳烟颗粒（PM）排放的最有效手段之一。在碳烟催化燃烧过程中，氮氧化物（NOx）小分子在催化剂活性位点的吸附行为不明确，导致催化机理不清，成为催化型柴油颗粒过滤器（CDPF）催化剂技术开发的瓶颈。针对上述难题，本项目设计合成水滑石基双功能催化剂，拟通过调变水滑石基前驱体的制备参数，构筑不同强度碱性位点的MgAl水滑石基载体，并负载贵金属（Au、Pt、Pd），形成具有碱性位和氧化位的双功能催化剂；以碳烟催化燃烧为目标反应，结合原位红外光谱技术和实验研究，阐明有无碳烟存在时NOx在双功能催化剂位点上微观分子水平吸附行为和宏观吸附储存量，以及吸附行为对碳烟燃烧反应的影响机制，揭示NOx气氛下碳烟催化燃烧反应机理。上述研究将为双功能催化剂的设计提供理论指导，对CDPF催化剂技术的开发具有重要的理论价值和实用意义。

开发高性能碳烟燃烧催化剂是降低柴油车尾气中碳烟颗粒（PM）排放的最有效手段之一。本项目从水滑石基载体的原料配比、沉淀环境和焙烧温度三方面探索了镁铝水滑石基载体的制备条件，并负载贵金属Pd和Ag，通过调控催化剂上氧化位和碱性位的数量和分布，构建了贵金属负载的镁铝水滑石基双功能催化剂。重点探究了合成条件对载体碱性位点的影响，为水滑石基载体的可控合成提供技术方案。开发了Pd-K系列水滑石基双功能催化剂。负载碱金属K，以增强和改变镁铝水滑石基载体的碱性分布。并改变贵金属Pd的负载量，从而调变氧化位的数量，达到协同催化目的。筛选了贵金属的负载量，1%的负载量样品效果能够最优。开发了Ag-K系列水滑石基双功能催化剂。负载贵金属Ag，以提供碳烟催化燃烧的氧化位。通过对比有无碱金属K负载，从而调变镁铝水滑石基载体的碱性位分布和数量，达到协同催化的目的。当Ag、K共负载时，在紧接触或松接触条件下，催化剂的碳烟氧化能力达到最优。为工业上催化型颗粒捕集器的开发提供技术方案。