Synthesis and Characterization of Transition and Rare Earth Metals in Beta Zeotypes for the Conversion of Ethanol to Butadiene

Ethanol is an abundant, renewable energy source derived from lignocellulosic sugars from industrial corn processing. Ethanol can be converted into C₄₊ olefins (e.g., butene and butadiene) which are important chemicals for aviation and polymer industries. Existing processes to generate these products are inefficient and expensive. The first step in ethanol oligomerization, ethanol dehydration to ethylene, is an energy-intensive, endothermic process resulting in undesired byproducts and a lower olefin yield. Using a regenerable catalyst for conversion of ethanol directly to C₄₊ olefins from a renewable ethanol source would result in greater sustainability for aviation fuel and polymer production. Zeolites are microporous crystalline materials with ring structures typically comprised of aluminum and silicon. Zeolites have large surface areas, providing numerous sites for reactions to occur. When metals are incorporated into the framework, zeolites serve as multifunctional catalysts that lower the activation energy of chemical reactions, resulting in improved efficiency. Cu-, Zn-, and Y-containing dealuminated Beta (deAlBeta) is an effective zeotype catalyst for ethanol conversion to butene-rich C₃₊ olefins. Lanthanum (La) is in the same group on the periodic table as yttrium (Y), so further investigation is desired to compare reaction rates and product distributions over dealuminated Beta catalysts containing each of these elements. In this work, Beta zeolites were hydrothermally synthesized as H-Beta, dealuminated through treatment with nitric acid, then loaded with La into the framework. La-containing deAlBeta zeotypes were synthesized under various parent Al-Beta support Si/Al ratios and metal weight loadings to identify their influence in ethanol to olefin conversion. La was incorporated into deAlBeta via solid state ion exchange (SSIE) or incipient wetness impregnation (IWI). X-ray diffraction (XRD) was used to assess the crystallinity and identity of the crystal topology. Nitrogen adsorption isotherms were collected to determine micropore volume and surface area of each material. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to determine metal loadings of the catalyst samples. Ethanol conversion to butadiene was probed over La/deAlBeta catalysts by co-feeding ethanol and acetaldehyde to a gas phase packed-bed reactor comprised of powder catalyst samples packed in a tubular quartz reactor. Kinetic data including product formation rates, orders of reaction, and activation energies were measured and found to vary between Y- and La-containing deAlBeta catalysts. This research will demonstrate how catalysts comprised of lanthanum dispersed on dealuminated Beta zeolites can contribute to the sustainability of ethanol to olefins catalysis, therefore providing increasingly economical routes to sustainable aviation fuel.