(387f) Atomically Dispersed Metal Sites in Multifunctional Zeolite Catalyst for Cascade Ethanol Conversion to C3-C6 Olefins
Ethanol to higher olefins (C3-C6 olefins) provides a unique approach for renewable commodity chemicals and is also a critical step for renewable jet and diesel production. This reaction has been proposed to involve complex cascade dehydrogenation to acetaldehyde, aldol condensation to form new C-C bond and further reactions to produce higher olefins. Multifunctional sites are needed to cooperate together to reach an optimum activity and product selectivity. In this talk, we will discuss a new zeolite supported multifunctional catalyst to enable this type of chemistry, where all the introduced metals are atomically dispersed at high metal loading (~6.5 wt.%). The active metal sites will be discussed from the findings of in situ X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) studies. These metals are found to introduce different types of Lewis acid sites, which show unique function in the cascade reaction of ethanol conversion to olefins. These isolated metal sites showed high reactivity towards the desired products while minimizing selectivity to side products, such as ethylene and diethyl ether. The proper combination of these sites can achieve C3-C6 olefins productivity of 0.57 golefins gcat-1 h-1 and high olefins yield of 88%. This catalyst also shows good thermal stability and can be regenerated after long-term reaction at 300 °C and under reducing environment.