碱性氮化物对催化裂化催化剂结焦作用的研究

发布时间：2018-12-27 06:25

【摘要】：原油的重质化、劣质化程度在不断加剧,焦化蜡油(CGO)与页岩油成为FCC扩大原料、增加效益的新途径。然而,CGO与页岩油中的氮化物会导致产物焦炭收率升高,催化剂失活严重。传统的氮化物中毒机理侧重于氮化物与酸性位的作用,但氮化物在催化裂化过程对生焦所起的作用认识不够深刻,氮化物对FCC催化剂中毒机理仍需补充与完善。本文以模型化合物为原料,着重考察了不同碱性氮化物对模型化合物催化裂化生焦反应的影响。当N元素的添加量为500 ug/g时,吡啶对邻二甲苯的生焦起到抑制作用,这与吡啶易与酸性位结合而难以发生亲电取代反应有关。大分子氮化物(喹啉、吖啶)对邻二甲苯的生焦具有促进作用。当N元素的添加量为2000 ug/g时,喹啉促进邻二甲苯生焦的作用因B酸损失增多而被掩盖。喹啉对甲基环己烷、1-己烯的生焦具有促进作用,然而与邻二甲苯为原料相比,这种促进作用并不明显。大分子碱性氮化物对焦炭的贡献不仅与其自身的吸附有关。在催化裂化反应的过程中,氮化物首先吸附到L酸位上,形成“结焦点”,诱导芳烃化合物快速吸附到“结焦点”上,然后发生缩合生焦的反应,从而导致焦炭产率的增加。该机理的提出改变了传统的氮化物对催化剂毒害作用的认识,为新型抗氮催化剂的制备提供了重要的理论基础。结焦剂的红外表征与X射线光电子能谱证明了焦炭多层结构的存在,与普通芳烃化合物相比,由于氮化物在催化剂表面具有较强的吸附作用,所以氮化物主要位于焦炭多层结构的最内层。结焦剂的再生行为表明,焦炭的多层结构与NOX的生成密不可分,位于焦炭多层结构内层的N原子是NOX的主要贡献者,这为催化裂化再生如何控制NOX的排放提供了重要的理论基础。
[Abstract]:The heavy and inferior degree of crude oil is getting worse and worse. (CGO) and shale oil have become a new way to expand the raw material and increase the benefit of FCC. However, CGO and nitride in shale oil can increase the coke yield and deactivate the catalyst seriously. The traditional mechanism of nitride poisoning is focused on the effect of nitride and acid site, but the role of nitride on coke generation in FCC process is not deep enough, and the poisoning mechanism of nitride to FCC catalyst still needs to be supplemented and perfected. In this paper, the effects of different basic nitrides on the catalytic cracking coking of model compounds were investigated. When the addition amount of N is 500 ug/g, pyridine inhibits the coking of o-xylene, which is related to the easy binding of pyridine with acid site and the difficulty of electrophilic substitution reaction. Macromolecular nitrides (quinoline, acridine) promote coke production of o-xylene. When the addition amount of N was 2000 ug/g, the effect of quinoline on coke production of o-xylene was masked by increasing the loss of B acid. Quinoline can promote the coking of methylcyclohexane and 1-hexene, but this effect is not obvious compared with that of o-xylene. The contribution of macromolecular basic nitride to coke is not only related to its own adsorption. In the process of catalytic cracking reaction, nitrides are first adsorbed to L acid sites to form a "junction focus", which induces the aromatics to rapidly adsorb to the "junction focus", and then the reaction of condensation and coking takes place, which leads to the increase of coke yield. This mechanism has changed the understanding of the toxic effect of the traditional nitride on the catalyst and provided an important theoretical basis for the preparation of the new nitrogen-resistant catalyst. Infrared characterization of coking agent and X-ray photoelectron spectroscopy (XPS) proved the existence of multi-layer structure of coke. Compared with ordinary aromatic compounds, nitride has strong adsorption on the surface of catalyst. So the nitride is mainly located in the innermost layer of the multi-layer structure of coke. The regeneration behavior of coking agent shows that the multilayer structure of coke is closely related to the formation of NOX. The N atom located in the inner layer of coke multilayer structure is the main contributor of NOX. This provides an important theoretical basis for how to control the emission of NOX in FCC regeneration.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE624.91

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