Platinum loaded on fibrous ZSM-5 for cumene hydrocracking

Abstract

Recently, the need to create a versatile hydrocracking catalyst is a major concern in oil and gas industry. The increasing demand for valuable middle distillates has placed hydrocracking as the most important secondary process. Cumene hydrocracking is an ideal hydrocracking reaction due to the minimum amount of side reactions. A novel ZSM-5 catalyst with fibrous morphology (FZSM- 5) and platinum loaded on FZSM-5 (Pt/FZSM-5) were successfully prepared by using a microemulsion system with ZSM-5 seed assisted crystallization and impregnation method for cumene hydrocracking. XRD and FESEM/TEM-EDX analyses showed that the FZSM-5 possesses ZSM-5 structure and a spherical morphology with evenly distributed dendrimeric silica fibers. In addition, FZSM-5 exhibited intrinsic mesopores at 3-5 and 10-20 nm, which led to an increase in the surface area up to 42% compared with ZSM-5 seed. Pyridine FTIR result showed the presence of a large number of Lewis acid sites and a small number of Brönsted acid sites. These acid sites were further increased after protonation and introduction of platinum. In addition, the protonation and introduction of Pt on FZSM-5 increased the rate of cumene conversion up to 0.303 µmole/s g-cat at 623 K with 92% product yield in which the product equally distribute to benzene and propylene. This activity of Pt/HFZSM-5 in cumene hydrocracking was almost 1.5-fold higher than that of Pt/HZSM-5 (0.161 µmole/s g-cat) with 72% product yield. The high activity of Pt/HFZSM-5 towards cumene hydrocracking could be attributed to the unique morphology of FZSM-5 which increase the accessibility of the active sites and facilitated the hydrogen spillover phenomena assisted by the presence of a large number of Lewis acid sites and platinum metal. This new fibrous ZSM-5 catalyst open a big potential in general heterogeneous catalytic reaction, especially in the hydrocracking process.