焦油催化裂解与甲烷催化重整耦合提质过程及机理研究

Shanxi province is one of the largest coal coking production provinces in China. Coal tar, as the main by-product of coal coking and an important pyrolysis product of low-rank coal, however, usually contains high content of heavy components, low content and yield of high-value light tar, which is difficult to be treated and may lead to some operational troubles. Moreover, low yield of light tar is usually obtained in the catalytic upgrading of coal tar when no additional hydrogen is supplied. To upgrade the tar, regulate the qualities of tar and gases, in this project, an integrated process by catalytic cracking of tar with catalytic methane reforming is proposed based on the fact that Ni-based catalyst can simultaneously catalyze the cracking of coal tar and the reforming of methane. The quality and quantities of light tar are expected to be upgraded through the stabilization of free radicals from catalytic cracking of tar by the active radicals from methane reforming (•CHx, •H). The effects of the approaches of catalytic reforming of methane and operational parameters in integrated process on the quality and yields of tar and gases are investigated. A new pyrolysis-time of flight mass spectrometry combined with vacuum ultraviolet photoionization/electron impact ionizations is used to in-situ analyze the reaction products. The mechanism of upgrading the tar in the integrated process is explored by analyzing the difference of products in catalytic cracking of tar and integrated process, combined with the isotopic tracing technique. By this project, we expect to obtain the general rules to regulate the distribution of coal tar and gases in the integrated process, the optimal upgrading conditions for high contents and yield of light tar, and the act mechanism between catalytic cracking of coal tar and catalytic methane reforming. The prospective results of this project will provide a new approach to upgrade the coal tar, and an alternative route to utilization of methane-rich coke oven gas. This research will be helpful for us to understand the cracking of coal tar, regulate the products distribution of tar and gases, and further process the coal tar.

山西是煤焦生产大省，煤焦油是焦化过程主要副产品及中低阶煤热解的重要产品。本项目针对煤焦油中重质组分含量高和焦油催化裂解轻质化过程油收率低等问题，利用Ni基催化剂可同时催化焦油裂解和甲烷重整的特点，提出将焦油催化裂解与甲烷催化重整过程相耦合，以期借助甲烷重整过程中产生的富氢活性自由基来稳定焦油裂解形成的自由基，达到焦油提质和调控油气品质的目的。通过研究不同甲烷催化重整方式和耦合过程参数对油气品质的影响，获得焦油催化裂解与甲烷催化重整耦合过程油气调控的基本规律和具有高轻质组分含量与收率的提质工艺；通过热解-真空紫外单光子/电子轰击双电离与飞行时间质谱系统对反应产物的原位检测，结合同位素示踪技术，阐明耦合过程焦油轻质化的作用机理。该项目的开展为重质焦油轻质化提供新方法，也为富含甲烷气的焦炉煤气利用提供新方向，研究工作对认识焦油催化裂解规律及过程调控、煤焦油深加工具有重要的理论意义和实际应用价值。

本项目针对传统热解焦油重质组分含量高、轻质组分含量低和焦油催化裂解过程焦油产率低等问题，将传统焦油催化裂解和甲烷催化重整过程相耦合，以甲烷催化重整过程中产生的富氢活性自由基（•H和•CHx）来稳定焦油裂解形成的自由基，达到焦油提质的目的。研究结果表明，该方法可实现轻质焦油含量与收率的大幅提高，焦油品质显著提升。不同类型的催化剂（分子筛、Ni基和炭基催化剂）均可实现对煤热解焦油的催化提质，尤以Ni含量为5 wt.%的Ni/Al2O3和活性炭（AC）提质效果最佳。轻质焦油含量和收率得到大幅提高。当甲烷二氧化碳重整与热解焦油原位催化裂解耦合时，以5Ni/Al2O3作为提质催化剂，焦油中轻油、酚油、萘油、洗油和蒽油的含量分别提高120%，110%，51% 和32%，重质组分含量由47.2 wt.%降至19.2 wt.%，平均分子量由279 amu降至193 amu。以AC为提质催化剂时，轻质焦油产率提高45%。.以AC为载体制备5 wt.%的Ni/AC催化剂，650 oC时轻质焦油含量由52.8 wt.%提高到96.5 wt.%，轻质焦油产率提高52.5%，平均分子量由279 amu降至160 amu。甲烷水蒸气重整与热解焦油原位催化裂解耦合同样提高焦油品质。Ni/AC可使轻质焦油产率提43%。热解与重整温度、催化剂用量、气体流量等同样影响焦油耦合提质效果。该方法不仅适用于热解焦油的原位催化提质，同样可以实现离线热解焦油的催化提质。对Ni基催化剂与碳基催化剂结合，提高了其抗积碳性能；通过添加Mo助剂进行改性，提高了其抗硫能力。.利用原位热解-真空紫外单光子电离与飞行时间质谱，认识了煤热解和催化热解过程初级产物的生成规律和催化作用形式；结合同位素示踪分析，证明了甲烷催化重整产生的•H和•CHx参与了轻质焦油的形成，正是这些小分子自由基的作用使得耦合提质过程限制提高了轻质焦油含量与收率。这些研究成果揭示了焦油催化裂解和甲烷催化重整耦合提高焦油品质的具体作用机制；为降低热解焦油重质组分含量、提升焦油品质和调控热解过程中的油气品质等具有重要的指导作用和实际应用价值。也为生物质热解过程产物品质提高提供一种新思路。

内容获取失败，请点击重试