The depletion of fossil fuels is a growing concern in the aviation industry, which currently relies on non-renewable resources. Ethanol is a promising option in the production of sustainable aviation fuel (SAF) as an abundant renewable feedstock. Ethanol can be catalytically upgraded to C4 olefins, such as butene, which is an important intermediate in the production of SAF. Existing processes typically proceed through an energy-intensive two-step pathway via ethanol dehydration to ethylene followed by oligomerization to butene. However, ethanol can be transformed to butene in a single step over dealuminated Beta zeolite (deAlBeta) impregnated with metals such as Cu, Zn, and Y (CuZnY/deAlBeta). Although this pathway is desirable due to its sustainability, a major limitation is the rapid deactivation of the catalyst arising from Cu sintering and pore blocking at the C-C coupling (Y) site. In this study, we aim to gain an understanding of the identity and deactivation mechanism of the adsorbed species present on spent CuZnY/deAlBeta catalysts. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was performed to identify the functional groups present in the coke on spent CuZnY/deAlBeta samples. Probe molecules were added to silica support, and DRIFTS spectra were collected at increasing temperatures to differentiate between similar IR bands. We detected no peaks attributed to cyclic structures, pointing to the pore-blocking of active sites by aliphatic carbon species likely derived from unreacted ethanol or ethanol derived species. In addition, the zero-length column technique (ZLC) was used to study the adsorption and diffusion behavior of various intermediates in deAlBeta. Catalyst was packed in a quartz reactor tube and saturated with an analyte gas of interest, then switched to an inert carrier gas to extract a desorption curve and diffusion coefficients. The resulting data can help us understand how mass transport within crystallites may impact product distributions and catalyst deactivation. Together, these studies expand on research into the deactivation pathways of trimetallic ethanol-to-olefins catalysts and contribute to the development of new pathways to renewable jet fuel.
