半焦负载纳米二元金属催化剂生物质燃气脱焦性能及其抗失活界面作用机制

Bio-tar is the key issue limiting the development of biomass pyrolysis/gasification technology. Recently, the nickel-based catalyst has been given increasing attention since its significant role on the catalytic cracking of tar into small molecules of fuel gas. Unfortunately, the traditional nickel-catalyst is easily subjected to deactivation during the catalytic process reducing the tar-removal performance. Regarding current problems existed on the structure of traditional Ni-catalyst lacking available catalytic sites inside the carrier, we propose to assemble the bimetallic nano-sized nickel-iron/nickel-magnesium in/on biochar carrier in this project. This innovative structure will enhance the interface interactions between the active metals and carrier in order to improve the tar-removal efficiency and anti-deactivation ability. By selecting the optimized proportion of metals, biochar and control parameters, the crystal and micro structures of binary metals and their supporters will be system controlled. We will construct and regulate the multiphase micro-interface to investigate the anti-deactivation mechanism of the new catalyst during the reaction. Besides, evaluating the tar-cracking and deactivation-regeneration performances of catalyst is conducted to build the relationship between catalyst structure and catalytic performance. Finally, the biochar-supported bimetallic nano-catalyst is controllable prepared and optimized. This study aims to elucidate the relationship between the multi-phase micro-interfaces and the performances of tar removal and anti-deactivation of catalyst, which is of significance to protect the nickel-based catalyst with highly efficient and stable operation and promote the efficient use of biomass resources and environmental protection.

生物质燃气焦油是限制生物质热解气化技术发展的瓶颈，镍基催化剂因其显著的焦油催化裂解效率而受到广泛关注。课题针对传统镍基催化剂结构对载体内部缺乏有效利用、催化位点急剧减少而导致催化剂失活、脱焦性能下降等问题，创新提出利用纳米镍铁/镍镁二元金属负载到半焦载体，通过增强纳米催化剂结构中活性组分与载体的多界面作用以提高催化剂脱焦效能和抗失活能力的新思路。考察外在反应条件对纳米金属与载体晶态结构、微结构演变的影响，确定关键影响因素。构建并调控主金属、助金属、载体之间的多相微界面，揭示反应过程中催化剂的抗失活界面作用机制。评估催化剂的焦油催化裂解性能并进行失活再生评价，建立催化剂微观结构与催化效能之间的关联体系，实现半焦负载纳米二元金属催化剂的可控制备和参数优化。本课题旨在解析催化剂结构中多相微界面作用对其焦油催化裂解性能与抗失活特性的影响机制，对促进催化剂高效稳定运行和生物质资源再利用具有重要意义。

生物质燃气焦油是限制生物质热解气化技术发展的瓶颈，本项目面向生物质燃气焦油的定向高效转化重大需求，基于传统镍基催化剂在催化过程中易失活、脱焦性能下降等关键问题，创新提出了利用纳米二元金属负载半焦载体制备得到Ni-Fe催化材料，通过增强纳米催化剂结构中活性组分与载体的多界面作用以提高催化剂脱焦效能和抗失活能力新思路，制备得到多种Ni-Fe基催化材料。结果表明原生生物炭具有丰富的孔隙结构、表面凹凸不平且孔径大小不一；生物炭比表面积303.47 m2/g，平均孔径4.21nm；负载金属后，材料的比表面积和孔径变小，吸附量下降。负载金属均匀分散在生物炭载体表面，并以Fe2O3、NiO、NiFe2O4形式存在。考察了热解温度、二元金属负载量、水蒸汽/生物质炭比例和气体停留时间等因素对催化剂微结构、以及焦油催化裂解性能的影响，明确了关键影响因素。研究发现随着温度的升高，水蒸汽/生物质炭比的提高，气体停留时间的增长，甲苯的催化裂解性能逐渐提高并趋于稳定。在Ni和Fe的负载量都在6%时，甲苯的催化裂解效果最好。正交实验得到最优反应条件：温度为800℃、Ni和Fe的负载量分别为6%、水蒸汽/生物质炭比为1、气体停留时间为0.5s。在此条件下，甲苯的去除率为96.61%，H2、CH4、CO、CO2的相对含量为36.45%、2.9%、16%、5%。构建并调控主金属、助金属、载体之间的多相微界面，揭示了反应过程中催化剂的抗失活界面作用机制。甲苯的催化裂解反应和生物炭的气化反应机理研究表明，二者反应分别符合一阶整体动力学模型和未反应收缩核模型。甲苯在催化裂解过程中生成小分子气体产物，同时产生积碳附在生物炭表面，导致催化材料孔径变小，孔道被灰分和积碳堵塞，吸附量进一步下降，并且金属活性组分被还原为部分Ni和Fe的单质并发生团聚现象。Ni-6-Fe-6/char是最优催化材料，其中NiFe2O4金属合金的存在形式有效限制了催化剂金属被还原为金属Ni单质、Fe单质，进而发生金属团聚导致催化活性失活。本项目对促进高效、抗积碳、低耗催化剂研发和生物质能资源化利用新技术发展提供理论和技术支持。