Effect of phosphorus on novel bifunctional additives for enhancing the production of propylene and removal of SO2 in FCC process

✍ Scribed by Xiaoling Xu; Chunyi Li; Honghong Shan

• Publisher: Elsevier Science
• Year: 2011
• Tongue: English
• Weight: 697 KB
• Volume: 340
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/j.molcata.2011.03.014

✦ Synopsis

Magnesium-aluminate spinels were introduced into the matrix of typical propylene additives (ZSM-5 as the active component) to obtain a series of novel bifunctional additives for enhancing the production of propylene and removal of SO 2 . Their performance as additives to a commercial equilibrium USY FCC catalyst for VGO (vacuum gas oil) cracking and activity in oxidative adsorption of SO 2 under similar FCC regenerator conditions were investigated. The bottleneck of the novel bifunctional additives is that the substitution of MgAl 2 O 4 for Kaolin clay in propylene additives causes the migration of Mg 2+ into ZSM-5 zeolite, which evidently lowers the activity of ZSM-5 as an FCC additive. However, pretreating MgAl 2 O 4 with phosphoric acid either by extraction or by impregnation method which weakened the interaction between MgAl 2 O 4 and ZSM-5 during the steaming and calcination processes, respectively, was proved to be effective in enhancing the efficiency of ZSM-5 for increasing propylene yield. Concurrently, the unusally high hydrogen transfer activity of MgAl 2 O 4 in VGO cracking, which also contributed to the decrease in ZSM-5 activity, was sharply reduced by P doping. Moreover, the phosphorus modification also promoted the SO 2 uptake capacity of bifunctional additives.