钙铝石负载钙铁氧化物协同强化焦油重整与抑制积碳机理

In biomass absorption enhanced reforming gasification, calcium oxide (CaO) can promote tars reforming reactions, however, its enhancement effects are limited and CaO suffers from tar coking which leads to absorbent deactivation. This project proposes a novel methodology to produce synthesized absorbents by simultaneously loading CaO and iron oxide onto mayenite. By this way, we can take the advantages of iron oxide as a tar catalyst and mayenite as the free oxygen carrier, so as to investigate their synergistical functions on the promotion of biomass tar reforming and coke elimination and develop a novel type of CaO absorbent. The main research contents include: (1) We will quantitatively analyze the intermediate products and coke from tar reforming reactions, combining with monitoring transformation of absorbent physical properties, chemical active components and surface functional groups before and after tars reforming, to determine how different components synergistically affect the reaction routes of tars reforming and coke formation, so as to understand the enhancement mechanism for tars reforming and coke elimination and develop the kinetic reaction models. (2) Based on the mechanism research, we will then survey the tar reforming activity of the novel absorbents. The substantial correlations between absorbent preparation parameters such as iron precursors, calcium precursors, iron loading amount and calcination temperature and the tar reforming activity are to be surveyed by incorporating quantitative analysis of tar reforming products and absorbent microscopic characterization, which is significant for optimization of design and preparation of the novel synthesized absorbent. (3) The applicants will perform cyclic reactivity tests for tar reforming and coke elimination as well, to verify the absorbent’s adaptability in long-term application. The results of this project will enrich the tar reforming theory and provide direct reference for the preparation and production of novel absorbent in biomass absorption enhanced gasification technology.

CaO在生物质吸收体气化中能强化焦油重整，但其焦油脱除效果有限且焦油积碳易导致CaO失活。本项目提出钙铝石同时负载CaO和铁氧化物以制备合成吸收剂的新方法，发挥铁氧化物作为催化剂和钙铝石作为自由氧储存体的优点，深入研究“铁氧化物-CaO-钙铝石”协同强化焦油重整和抑制积碳反应机制，开发新型吸收剂。内容包括：(1)定量分析重整中间产物和积碳，结合吸收剂微观物理性质、化学活性成分以及表面官能团变化，明确各组分协同作用下焦油重整和积碳生成路径，阐明强化重整机制，建立反应动力学机理模型；(2) 以机理为依据，开展焦油重整活性研究。结合重整产物定量分析和吸收剂微观表征，揭示钙前驱体、铁前驱体、铁载入量、煅烧温度等制备参数与重整性能的内在联系，优化吸收剂合成方法；(3) 开展焦油循环重整试验，验证吸收剂长期使用适用性。本项目研究可丰富焦油催化重整理论，为新型CaO吸收剂制备提供直接依据。

CaO在生物质吸收体气化中能强化焦油重整，但其焦油脱除效果有限且焦油积碳易导致CaO失活。本项目提出钙铝石同时负载CaO和铁氧化物以制备合成吸收剂的新方法，发挥铁氧化物作为催化剂和钙铝石作为自由氧储存体的优点，深入研究“铁氧化物-CaO-钙铝石”协同强化焦油重整和抑制积碳反应机制，开发了新型复合钙基吸收剂。主要结果如下：.1.在理论研究方面，阐明了新型钙基吸收剂各组分协调强化焦油重整和抑制积碳的机理。协同强化焦油重整机理为：(1) 新型复合吸收剂中的CaO碳酸化吸收CO2，有利于促进焦油水蒸气重整反应的进行，生成更多H2；(2) 新型复合吸收剂中的钙铁石成分对焦油的重整反应具有催化作用，促进了焦油重整和合成气的产生；(3) 新型复合吸收剂中的Ca12Al14O33载体有助于防止吸收剂的烧结和孔隙结构恶化，有利于强化碳酸化吸收CO2的长期反应特性和促进焦油重整脱除。焦油积碳抑制机理：(1) 抑制焦油积碳生成。铁氧化物、CaO、Ca12Al14O33的协同作用促进中间产物茚并抑制焦油缩聚和积碳生成反应；(2)焦油积碳的重整消除。一方面，Ca12Al14O33载体的氧自由基能与焦油积碳发生氧化反应生成CO；另一方面，CaO通过碳酸化反应、钙铁石化学结构及铁氧化物通过“还原-氧化”反应共同促进水煤气变换反应的进行，进而强化积碳水煤气反应。.2．在实际应用方面，所开发的新型吸收剂的循环捕集CO2活性、焦油催化脱除性能、抗积碳能力以及机械强度均得以改善，初步显示出很好的应用潜力。表现在：经过10次循环反应， CaO转化率仅20%左右，而新型吸收剂的CaO转化率仍高于80%；在CaO作用下，1-甲基萘重整产氢率仅为0.05mol/(h·g)、合成气中CO2的浓度为26%、焦油脱除率仅29%、积碳率达46.7mg/g吸收剂，而Ca-Al-Fe存在时，产氢率高达0.17 mol/(h·g)、CO2浓度降低为22%、焦油脱除率高达91%、积碳率降低为仅14.1mg/g吸收剂；此外，CaO吸收剂的机械强度仅24.64kPa，而新型吸收剂的提高到72.70 kPa。