准东煤基活性焦矿物质形态调控及选择性还原NO机制

Great challenges remain in clean and low-cost removal of NO from flue gas. Reduction of NO by coal-based activated cokes is cheap and doesn't need an additional reducing agent. However, this technology suffers from low reaction rate, invalid consumption of the coke, and generation of harmful CO. Based on the differences in catalytic activity of mineral substance of different occurrence modes, regulating of mineral modes to increase reactivities of activated cokes, selectively reduce NO, and generate CO2 is proposed. Main contents of this project are: (1) Transformation mechanism and regulatory method of occurrence modes of sodium during activation of coke. (2) Strengthening mechanism of tiny amounts of active minerals loaded on the activated coke on the oxidation of CO. (3) Effects of interaction of oxygen-containing groups and sodium on the selective reduction of NO. The innovations of this project are: (1) Regulating occurrence modes of sodium to increase the coke reactivity. By regulating the transformation of sodium during carbonization and activation of coal, both concentrating of sodium and maintaining its high catalytic activity can be released. Digging the catalytic capacity of inherent sodium adequately can greatly increase the reactivity of activated coke. (2) Using metals on the activated cokes to strengthen the oxidation of CO and selective reduction of NO. Changing the loading way of metals to reduce the connections between the metals and carbon. This is promising to in-situ catalytic oxidation of CO in the activated coke. Stable oxygen-containing groups promote the selective reduction of NO. The enhancement of selectivity in NO reduction by activated cokes, can be realized by the promotion of sodium in the generation of oxygen-containing groups. The relevant studies are promising to provide theoretical guidance for fast, clean, and efficient reduction of NO by Zhundong coal-based activated cokes.

烟气中NO的清洁、低成本脱除仍面临很大挑战。煤基活性焦还原NO技术具有成本低、无需外加还原介质等优势，但存在反应速率低、活性焦无效消耗高、生成副产物CO等问题。本项目基于高钠准东煤中不同赋存形态矿物质的催化特性差异，提出通过矿物质形态调控来提高活性焦反应性、实现NO选择性还原并生成CO2的技术构想，主要开展以下三方面的研究内容：（1）焦炭活化过程中钠赋存形态转化机制及调控方法；（2）活性焦上加载的微量活性矿物质元素对CO氧化的强化机制；（3）含氧官能团和钠的耦合作用对NO还原选择性的影响。本项目的创新之处在于：（1）提出调控钠的赋存形态来提高活性焦反应性的技术构想；通过调控炭化和活化过程中钠的转化，实现钠在活性焦中富集的同时保持高的催化活性；深度挖掘固有钠的催化潜力，可望大幅提高活性焦的反应活性。（2）提出利用活性焦上金属来强化CO氧化和NO选择性还原；通过调整金属加载方式来弱化金属与碳之间的连接，可望实现CO在活性焦上的原位催化氧化；稳定性含氧官能团可提高NO的选择性还原，利用Na对含氧官能团生成的促进作用，来强化活性焦选择性还原NO。相关研究有望为开发准东煤基活性焦快速、清洁、高效还原NO技术提供理论基础。

煤基活性焦直接还原NO具有成本低、无需外加还原介质等优势。但该技术还面临着反应速率低、二次污染物CO生成、活性焦无效消耗等问题。本项目利用高钠准东煤，提出通过矿物质和官能团的调控/加载来提高活性焦反应性、选择性还原NO并生成CO2的技术构想。项目主要开展了①准东煤基活性焦的理化性能调控、②煤基活性焦还原NO的实验研究、③钠、羧基和羧酸钠加载对char(N)异相还原NO影响的研究、④双金属对活性焦还原NO影响的密度泛函理论研究等内容。.（1）CO2和H2O协同活化。60%CO2/40%H2O活化样品中形成了具有丰富微孔和一些中孔的枝状多孔结构，以及丰富的石墨微晶结构、长程有序的石墨网络、大量含氧和含氮官能团（高达13%）。.（2）CO2和微量K2CO3协同活化。CO2气氛下活性焦上形成了更多的K，可发生插层拓宽芳香层片间距，形成更多的微孔和活性位点，也促进了含氧官能团的保留。CO2和微量K2CO3协同活化样品具有较高的比表面积和孔体积，更多的含氧官能团。.（3）CO2中微量Na2CO3和K2CO3协同活化。样品具有枝状多孔结构和丰富的含氧/含氮官能团。协同活化机制：Na2CO3和K2CO3共掺杂提高了碱金属盐的分散性，有利于微晶内部结构的打开及活化。该研究为制备低成本、低污染、高性能的碳材料提供了一个新的可行途径。.（4）NO-char反应的实验研究。20℃升高至200℃过程中，NO脱除率降低；温度继续升高NO脱除率逐渐上升。归因于温度升高NO脱附增加和NO-char反应速率增加的竞争作用。低烧失率活性焦的活性更高，尤其是协同活化样品。该研究可在低烧失率下获得高活性的焦炭样品。.（5）密度泛函理论分析表明，Na、−COOH和−COONa的掺杂均会提高焦炭模型在NO吸附和还原过程中的反应性，且增强幅度依次提高。Na与COOH的协同作用（−COONa）可促进化学键的断裂，增强焦炭对NO的还原性。.（6）单、双碱金属都促进了NO在焦炭上的还原，但后者的催化活性更高，表现在反应路径缩短，反应能垒降低。这是因为双金属掺杂促进了N-N的形成和N-O的断裂。阐明了双金属高催化作用的机理，为NOx的清洁还原提供了新的思路。