高芳烃高含氮重油催化转化反应基础研究

Fluid catalytic cracking is a major method for converting heavy oil into light products. In China, the processing capacity of FCC units has over 200 million tons per year. As the crude oil becomes heavier and more inferior, the feedstock of FCC units also becomes more inferior. The increase of aromatic and nitrogen contents of feedstock would lead to the decrease of conversion. However, due to the lack of understanding of the reaction mechanism, this problem still not be solved effectively. Thus, the blending ratio of inferior feedstock is very low. In view of the previous research exist some problems, such as always use the small molecule model compounds and the deficiency of the reactor, this project firstly used the combined separation method and advanced analysis methods to separate and characterize the key components for restricting the conversion of heavy oil. A novel reactor was designed to investigate the pre-cracking and catalytic cracking mechanism of heavy oil. Furthermore, the retardation effect of basic nitrogen compounds, neutral nitrogen compounds and aromatics, separated from the feedstock, on the conversion of feedstock will be analyzed. The effects of reaction temperature and zeolite poor restriction on the conversion process of feedstock will also be studied. To further understand the effect of reaction temperature and the concentration of basic nitrogen compounds, neutral nitrogen compounds and aromatics on the competing adsorption and diffusion behavior, the molecular simulation technology will be introduced. Finally, a novel process for controlling the reactions of nitrogen compounds and enhancing the catalytic conversion will be carried out in a pilot-scale riser FCC apparatus, and the controlling conversion theory of heavy oil with high aromatic and nitrogen content will be proposed. All these will lay the foundation for the development of novel FCC technology, which can enhance the conversion of heavy oil, improve the product quality, and increase the yield of light olefins.

作为重油轻质化的重要手段，我国催化裂化年加工能力已超2亿吨。但随着原油的重质、劣质化，催化裂化原料日益变差，特别是芳烃和氮含量升高后带来的转化难问题一直没能有效解决，导致催化裂化掺炼劣质原料比例严重受限。鉴于之前研究多采用小分子模型化合物代表性不足和反应器存在缺陷等问题，本项目采用组合分离方法和先进分析手段对制约重油转化的关键组分进行有效分离和精确表征；通过设计新反应器研究重油预裂化、催化裂化反应历程，分析分离出大分子碱性（BN）、中性含氮化合物（NN）和芳烃（Ar）对原料转化的阻滞作用及反应温度和分子筛孔道限制的影响；采用分子模拟技术研究不同温度、浓度下BN、NN和Ar在分子筛中的竞争吸附与扩散行为；在提升管中试平台上建立原位控制含氮化合物反应、强化重油催化转化的新工艺方法，提出高芳烃高含氮重油的控制转化理论，为开发集重油高效转化、油品质量升级及增产低碳烯烃于一身的创新工艺技术奠定基础。

本研究立足于对高芳烃高含氮原料分析结构和转化机理的深入理解，为此类原料的高附加值转化奠定基础。首先利用傅里叶变换离子回旋共振质谱、红外光谱以及核磁共振，对三种焦化蜡油及其亚组分中的氮化物和芳烃的组成与结构进行了精细表征，获得了碱性含氮化合物、非碱性含氮化合物和芳烃的组成与结构信息，深入认识了高芳烃高含氮重油的催化裂化反应特性以及氮元素在催化裂化过程中的迁移规律。明确了缩合度较低（DBE值小于10），分子尺寸较小的含氮化合物是造成原料转化率降低、产品分布变差的关键组分；含氮化合物的分子结构和大小是影响其进入催化剂分子筛孔道难易、导致催化剂活性中心中毒轻重的关键。丰富了石油组成与转化化学的应用基础理论。其次，研究了高芳烃高含氮重油及其窄馏分中大分子碱性含氮化合物、中性含氮化合物和芳烃对Y 型和ZSM-5 型分子筛催化剂的毒害作用机制和对原料转化的阻滞作用。明晰了FCC催化剂的基质和分子筛对含氮化合物转化的贡献：催化剂的基质对含氮化合物的转化不会产生明显影响；而分子筛因其具有酸性特征，使缩合度较低、分子较小的含氮化合物在其表面缩合生焦，并结合氮化物和芳烃在不同分子筛上吸附与扩散规律，为抗氮催化剂的设计明确了方向。最后，提出了高芳烃高含氮重油的控制转化理论——通过适宜高温、大剂油比、短反应时间和分子筛的孔道限制效应，抑制氮化物对催化剂的毒害作用，并在实验室提升管中试装置上考察了高温、大剂油比、短停留时间方案，长停留时间方案和高催化剂活性方案对强化焦化蜡油催化转化的效果，明确了通过适宜高温、大剂油比、短反应时间和分子筛的孔道限制效应，可以有效强化高芳烃高含氮原料的催化转化，为开发集重油高效转化、油品质量升级及增产低碳烯烃于一身的创新工艺技术奠定基础。同时，上述研究成果为两段提升管催化裂化/裂解加工高芳烃高含氮原料技术的开发与优化以及工业应用奠定了理论基础。