Nanostructured Pd-Cu Catalysts Supported on Zr-Al and Zr-Ti for Synthesis of Vinyl Acetate

摘要

Renewable ethylene can be obtained by dehydration of bio-ethanol and used for production of vinyl acetate (VAM) through reaction with acetic acid (AcOH), using Pd-Cu catalysts. In the present manuscript, structural characterizations of Pd-Cu/ZrO2 catalysts show that these systems present cubic structure with different spatial distributions. Particularly, it is shown that combustion of ethylene and acetic acid can be inhibited below 180 degrees C, maximizing the rates of VAM formation, when the catalysts are modified with Ti+4. The effects of AcOH concentration on rates of VAM formation show that higher AcOH concentrations favor the formation of undesired byproducts, while lower AcOH concentrations favor effects related to O-2 mobility, which can lead to surface decomposition. VAM formation is favored, with selectivities ranging from 0.8 to 1.0. XPS results indicate the existence of metallic Pd, CuO species and Zr species, in agreement with IR results. DRIFTS results also show that different Pd-acetate intermediates can be present, depending on the electronic effects associated to Pd-Cu and Zr species.