Ni- and Zn-Doping Effects on Cu/SiO2 Catalysts in Nonoxidative Ethanol Dehydrogenation.

Nonoxidative ethanol dehydrogenation opens a pathway for the sustainable production of acetaldehyde and butadiene. One crucial aspect of producing butadiene by the Lebedev process is the high-temperature stability of ethanol to acetaldehyde conversion. However, copper-based catalysts, despite exhibiting high activity and selectivity, suffer from sintering and coking and need to be improved for successful industrial applications. Herein, we show Cu-based (∼2.5 wt %) catalysts doped with Ni and Zn (0.028-0.36 wt %) to improve the catalytic performance of nanoparticles. The catalysts were prepared by hydrolytic sol-gel and dry impregnation methods. STEM analysis determined the nanoparticle sizes in the 1.9-2.8 nm range. Ni-doped catalysts outperformed the parent Cu catalysts in ethanol dehydrogenation activity at lower temperatures (185-220 °C) but suffered from faster deactivation. The Zn-doped catalysts exhibited improved high-temperature stability. For these materials, acetaldehyde selectivity fluctuated around ∼90% and acetaldehyde productivity reached 3.63 g g-1 h-1 at 290 °C and a WHSV of 4.73 h-1. The improved stability of the Zn-doped samples was correlated with lower coke formation (XPS, TG analysis, and Raman spectroscopy).