FCC再生器中NOx的生成机理及其原位CO还原研究

The process of regeneration of fluid catalytic cracking (FCC) catalyst is the main source of NOx emission in petroleum refining industry. It’s due to the oxidation of nitrogen-containing compounds from FCC coke, where the basic nitrogen-containing molecules in FCC feed tend to be deposited on the acid sites of the FCC catalyst and further transformed into carbonaceous via a series of polymerization and dehydrogenation reactions. Regarding to the big issue of current environmental protection, it’s thus significantly important to develop FCC NOx emission control technology. In this project, composition and structure of FCC coke will be studied in particular, combining TPD technology and molecular simulation to understand the mechanism of the NOx formation during FCC regeneration. Then, the reaction process of the reduction reaction between CO and NO under typical FCC oxidation regeneration condition will be investigated using in-situ generated CO resource in the FCC process. So obtained surface reaction mechanism can be used as the guidance for the design and modification of novel FCC catalyst with well catalytic properties for the reaction between CO and NOx. Therefore, two kinds of pollutants can be eliminated simultaneously during the FCC process, and this project will provide reference and guidance for the design of novel emission reduction technology for FCC regeneration process.

流化催化裂化（FCC）催化剂再生过程是炼厂NOx排放的主要来源，其原因在于裂化过程中沉积于催化剂上的含N化合物在催化剂再生时被氧化而最终转化为氮氧化物（NOx）。因此，发展FCC催化剂再生过程NOx的控制技术意义重大。本课题首先对典型FCC待生催化剂焦炭的组成、结构及程序升温条件下含N化合物的迁移行为与转移过程进行研究，结合分子模拟技术，获得FCC催化剂再生过程NOx生成过程机理；然后基于FCC催化剂再生过程会产生大量CO的现象，通过研究NOx与CO在不同氧化再生条件下的相互作用过程，获得相关表面反应过程机理并用于指导FCC催化剂的改性而赋予其同时催化CO原位还原NOx的性能，从而最终实现在再生过程中对两种污染物进行同时消除的目的。为发展FCC再生过程新型减排技术的工艺设计等提供参考与指导。

当前世界原油趋向于重质化的趋势不可逆转。而随着经济的不断发展和环保意识的增强，原油的重质化与市场对轻质油品需求之间的矛盾日益突出。流化催化裂化工艺（FCC）是可将重质油裂解成小分子馏分，但同时也容易生成焦炭沉积在催化剂表面从而导致催化剂失活。工业上常用高温氧化燃烧的方法脱除催化剂表面焦炭使催化剂再生，在此过程中会形成如NOx，CO和SOx等多种污染物，由此而导致的大气环境污染问题也日益严重。本项目通过对FCC工业结焦催化剂的研究，考察了结焦催化剂热解产物生成趋势，热解过程焦炭结构和性质迁移规律，解释了FCC再生过程燃料型NOx的生成机理，推导了该过程NO生成的主要路径，得到了FCC工业结焦催化剂再生工况条件对其性能的影响机制。并在此基础上，设计合成了系列无氧或有氧条件下脱硝催化体系，实现了NOx和CO的同时脱除，解释了NOx和CO的脱除反应机理，阐释了催化剂设计与调控规律，获得了催化剂构效关系和作用机制。项目研究成果可为本领域相关研究工作提供理论参考和技术借鉴，所合成的系列催化剂有进一步工业应用的潜力。