赤泥基催化剂原位催化提质煤热解油气及其反应调控机理

High value tar and gas products can be obtained through coal pyrolysis. However, relatively high content of heavy components (boiling point over 360 ℃) in tar results in some key technical problems, such as poor quality of tar and unstable operation of equipment. The key to solve these problems is to decrease the content of heavy components in tar through in-situ catalytic upgrading of pyrolysis oil and gas in the coal pyrolysis process. This project proposes the integrated process coupling comprehensive utilization of red mud derived from alumina production process using Bayer method and catalytic pyrolysis of coal for improving the quality of pyrolysis oil and gas. Low cost and high efficiency red mud based catalysts are prepared through acidizing de-sodium treatment. The effects of composition and structure of catalyst on catalytic upgrading performance of red mud based catalysts will be investigated to obtain the method for preparing red mud based catalysts with desired ability using acidizing treatment. The catalytic reaction mechanism of catalytic upgrading of coal pyrolysis oil and gas over red mud based catalysts will be discussed through evaluating the performance of different catalysts. Furthermore, the char modified by red mud will be studied for catalytic upgrading of coal pyrolysis volatiles and adsorption of heavy metals in waste water to realize the high value-added utilization of the produced char. This study will contribute to coal pyrolysis reaction control and resource utilization of solid wastes by providing feasible methods and theoretical support.

煤热解可获得高价值的焦油和热解气产品，然而焦油中重质组分（沸点高于360℃的馏分）偏高造成了现有热解技术存在焦油品质差以及系统运行不稳定等技术难题。对煤热解产生的油气进行原位催化提质以降低焦油中重质组分含量是解决上述难题的关键。本项目提出将拜耳法生产氧化铝产生的固体废弃物赤泥综合利用与煤催化热解提高热解油气品质过程耦合，对赤泥进行酸化处理脱钠获得高效低成本的赤泥基催化剂，研究赤泥基催化剂制备过程的组成结构变化对催化提质性能的影响，建立酸化处理定向调控赤泥基催化剂性能的方法；通过评价不同赤泥基催化剂对煤热解油气的提质效果，揭示赤泥基催化剂催化提质煤热解油气的基本规律及催化反应机理。研究赤泥改性半焦对热解挥发物的催化裂解作用和对废水中重金属的吸附效果，实现赤泥改性半焦的高价值利用。项目研究可为煤热解过程催化调控和固体废弃物的资源化利用提供可行的方法和理论支撑。

针对现有热解技术存在焦油品质差的问题，本项目以固体废弃物赤泥为原料，构建了煤热解油气提质的低成本赤泥基催化剂（RMCs）。采用固定床反应器，考察了煤热解过程中不同类型RMCs对焦油的催化提质效果，获得了以下主要结果。. (1) 对赤泥进行酸碱处理，制备了不同钠含量的系列RMCs，通过催化剂中钠含量的调控可定向调节催化剂的酸性、孔道特征。在单段固定床反应器中考察了RMCs原位催化煤热解的效果，RMCs中的钠含量对煤催化热解的产物分布具有显著的影响。催化剂中钠含量降低使酸强度增加，导致积碳增加；而钠含量增加抑制了积碳，导致气体生成量增加。酸碱处理是改变RMCs材料物化性质，提高催化提质性能的有效手段。RMCs中氧化铁可以提供晶格氧，促进C-C键的断裂，增加CO和CO2产率；二氧化钛组分有利于焦油中轻质组分含量的提高。.(2) 在两段固定床反应器中考察了RMCs对煤热解挥发物的催化提质效果，与单纯煤热解相比，轻质焦油产率、焦油中轻质组分含量显著提高。此外，在酸碱处理制备赤泥催化剂过程中，增多过滤水洗的次数，可有效降低RMCs中的钠含量，同时增大了催化剂的比表面积，促进了焦油的裂解反应，增加了催化剂孔道内的积碳。.(3) 将赤泥改性半焦、赤泥酸解后的含铁废液分别用作热解挥发物提质、原位催化煤热解的催化剂。赤泥改性半焦比表面积明显增加、具有丰富的金属活性组分，其催化活性优于普通半焦。含铁废液中的Fe、Al活性组分促进了催化氧化反应和重质焦油的裂解，提高了轻质焦油收率和焦油中轻质组分的含量。.本项目可为煤热解过程的反应调控和固体废弃物赤泥的资源化利用提供可行的方法和理论依据。