低阶煤挥发分二次反应与焦油组成协同调控机制

A high content of heavy fraction in tar results in a poor quality of the tar, which hinders the application of pyrolysis technology for cascade utilization of low rank coal. In view of a common problem which exists in the process of secondary reaction control for high quality tar production, in this project, three ways are used to strengthen the regulating of composition and structure of tar by controlling the secondary reaction of volatiles.(1)Pretreatment, catalytic pyrolysis and mixed coal pyrolysis are used to strengthen the controlling of the composition and structure of volatiles. The influence of volatile compositions on tar quality will be elucidated and the controlling mechanism of volatile compositions on secondary reactions will be revealed.(2) The secondary reaction of volatiles can be directly influenced by controlling the pyrolysis atmosphere and temperature. The influences of atmosphere and temperature on the tar characteristics are deep analyzed and the reforming mechanism of active gas on the ring-opening for polycyclic aromatic hydrocarbons will be elucidated.(3)The secondary reaction will be affected by carrying out the catalytic cracking of volatile. The relationship between the composition and structure of catalyst and tar quality was studied, and the synergistic controlling mechanism of catalyst on the secondary reaction and tar composition will be revealed. .Based on that, a theoretical technology for improving the fraction of light tar from low rank coal will be developed.

焦油中重质组分含量直接影响焦油的品质，进而决定着低阶煤热解分级利用技术的应用。挥发分二次反应调控是解决煤热解制备高品质油品的共性问题。项目通过挥发分二次反应调控，强化热解焦油组成与结构的控制，从而提高热解焦油的品质。通过预处理、催化热解等方法，强化挥发分组成和结构的控制，探索挥发分组成对焦油组成和结构的影响规律，揭示挥发分组成对二次反应的调控机制；通过气氛和温度直接干预挥发分的二次反应，解析气氛和温度对焦油组成的影响规律，解析活性气体对多环芳烃的开环重整机理；通过催化剂直接干预挥发分二次反应，探索催化剂的组成和结构对焦油品质的影响规律，揭示催化剂对挥发分二次反应调控机制，为低阶煤热解油品品质强化方法提供科学依据。

本项目针对低阶煤热解过程中存在焦油品质差的难题，通过调控挥发物逸出过程中的二次裂解行为及煤样预处理等方式抑制焦油重质组分的生成、促进重质组分向轻质组分转化，从而实现焦油品质提升的目的。结果表明，γ- Al2O3平均孔径大、酸性适中，有利于重质组分模型化合物芘的裂解。在采用机械法制备的Ni/Al2O3催化剂作用下，甲苯-芘体系液体产物收率最高，析碳率最低。助剂Ce对重质组分芘的裂解率影响较小，然而对抗积碳性能有利。优选的Ni-Ce/Al2O3可显著抑制和丰煤热解焦油重质组分的生成，降幅约22%。.引入水蒸气可明显提升Ni-Ce/Al2O3催化剂对重质组分芘的裂解率，于S/C=0.15时达到最大值98.93%，同时水蒸气抑制了积碳的生成。根据产物生成规律提出了芘较为明显的裂解路径之一是向萘转化，D2O的同位素实验验证了水蒸气引入后产生了更多H·，促进了芘的裂解，从而使得萘产率明显增加。在甲烷气氛下，液体产率和芘裂解率均随CH4气速增加而下降，即甲烷气体的引入不利于芘的裂解。.ZrO2/Al2O3催化剂时促进了芘的裂解，且随Zr基催化剂焙烧温度的增加而下降，随Zr含量增加先增加后减小。原因在于一方面是ZrO2可促使H2O分解产生活性氢，来稳定芘裂解产生的自由基，另一方面Zr基催化剂本身可通过活化芘的Car-H裂解成环数更少的芳香化合物。在S/C=0.12，Zr含量为23.9%的Zr基催化剂条件下，芘的裂解率从1h的96.16%降至8h的94.75%，对萘、氧芴和菲的裂解率下降。.煤样的预处理可影响挥发物的释出。浸渍镍盐煤样热解焦油中重质组分含量降低，其中NiSO4的效果最好。洗油和喹啉溶胀煤样孔道增加，有利于挥发物扩散，故溶胀煤样热解焦油沥青产率降低。上述研究为低阶煤热解焦油品质调控提供了理论依据。