(756c) Kinetic Study of Ethane Aromatization: Influence of Metal Function on the Early-Stage Reactivity and Stability

The unprecedented increase in NGLs production benefits the global chemical sector by shifting the raw materials from naphtha to the cheaper light alkanes. Consequently, the production of aromatic BTX (benzene, toluene, and xylene) is reduced, which requires the development of “on-purpose” techniques for light alkanes aromatization. In order to provide a knowledge basis for the design of efficient catalysts for ethane aromatization, our recent study focuses on the effect of metal species chemical compositions and their synergy with the zeolite host on the reactivity and stability of the catalysts. Here, we will discuss the effect of metal function, namely Ni_xGa_y, Pt, Zn, and Re, on the early-stage induction catalytic behavior, “steady-state” deactivation kinetics, and the back-transient products’ decay kinetics. With the Ni, Ga, and Ni/Ga modified HZSM-5 catalysts as the examples, we show the metal function has a significant effect on the early-stage catalytic behavior, as well as the “steady-state” rate for BTX and deactivation kinetics. The Ni/HZSM-5 produces only methane and coke with almost 100% ethane conversion during the early-stage (initial ⁓5 min); the formation of olefins and aromatics was observed after 10 min and reached the steady-state after 15 min. Such a significant induction period was not found for the Ni-Ga/HZSM-5 and Ga/HZSM-5 catalysts. In terms of deactivation kinetics, results from a typical coking induced kinetic model are shown as an example. The kinetic parameters for different deactivation kinetic models were evaluated. Besides the Ni/Ga catalytic system, the Pt, Zn, and Re modified HZSM-5 catalysts were also evaluated by the transient/steady-state deactivation kinetics. Additionally, the chemical properties of the metal species have been extensively characterized by TEM, STEM-EDS, XRD, XPS, XAS, NH₃-/propylamine-TPD, and etc. We conclude that the metal function is the key to the reactivity and stability of the catalyst during ethane aromatization.