催化裂化催化剂积炭的杂原子组成及其再生转化机理

HETEROATOM COMPOSITION OF COKE DEPOSITED ON CATALYTIC CRACKING CATALYST AND ITS REGENERATION CONVERSION MECHANISM

以不同工艺条件下的催化裂化待生、再生催化剂及催化剂再生烟气为研究对象,分析催化剂积炭的杂原子组成。依据密度泛函理论,利用Gaussian 09软件在B3LYP/def2-TZVP水平下对积炭中典型的含氮、含硫化合物进行几何优化,得到其最稳定构型;以Laplacian键级为判据,研究积炭中杂原子的转化机理。结果表明:催化剂积炭中的含氮化合物主要是吡啶类、吡咯类和季胺类化合物,含硫化合物主要是噻吩类化合物;催化剂再生初期,含氮化合物以∶NH和·CN的形式逸出,主要转化成NH_(3)和HCN;含硫化合物以·HS和∶S等形式逸出,主要转化为H_(2)S、COS;随着再生过程的进行,NH_(3)、HCN和H_(2)S、COS最终分别转化为NO_(x)和SO_(x)。模拟结果与不同再生工艺条件下再生烟气组成一致。

Heteroatom composition of coke deposited on catalytic cracking catalyst and flue gas were analyzed under different process conditions.According to density functional theory,the most stable configurations of typical nitrogen and sulfur compounds in carbon deposits were obtained by using Gaussian 09 software at B3LYP/def2-TZVP level,the Laplacian bond level was used as the criterion,and the conversion mechanism of heteroatom in carbon deposits was studied.The results showed that the nitrogen-containing compounds in coke deposited on catalyst were mainly pyridine,pyrrole and quaternary ammonium compounds,and the sulfur-containing compounds were mainly thiophene compounds.In the initial stage of catalyst regeneration,nitrogen-containing compounds escaped in the form of∶NH and·CN were mainly converted into NH_(3) and HCN,sulfur-containing compounds escaped in the form of·HS and∶S were mainly converted into H_(2)S and COS,and NH_(3),HCN,H_(2)S and COS were finally converted into NO_(x) and SO_(x) respectively.The simulation results were consistent with the flue gas composition under different regeneration process conditions.