A novel chemical
looping (CL) process was demonstrated
to produce
acetaldehyde (AA) via oxidative dehydrogenation (ODH) of ethanol.
Here, the ODH of ethanol takes place in the absence of a gaseous oxygen
stream; instead, oxygen is supplied from a metal oxide, an active
support for an ODH catalyst. The support material reduces as the reaction
takes place and needs to be regenerated in air in a separate step,
resulting in a CL process. Here, strontium ferrite perovskite (SrFeO3−δ) was used as the active support, with both
silver and copper as the ODH catalysts. The performance of Ag/SrFeO3−δand Cu/SrFeO3−δwas
investigated in a packed bed reactor, operated at temperatures from
200 to 270°C and a gas hourly space velocity of 9600
h–1. The CL capability to produce AA was then compared
to the performance of bare SrFeO3−δ(no catalysts)
and materials comprising a catalyst on an inert support, Cu or Ag
on Al2O3. The Ag/Al2O3catalyst was completely inactive in the absence of air, confirming
that oxygen supplied from the support is required to oxidize ethanol
to AA and water, while Cu/Al2O3gradually got
covered in coke, indicating cracking of ethanol. The bare SrFeO3−δachieved a similar selectivity to AA as Ag/SrFeO3−δbut at a greatly reduced activity. For the
best performing catalyst, Ag/SrFeO3−δ, the
obtained selectivity to AA reached 92–98% at yields of up to
70%, comparable to the incumbent Veba-Chemie process for ethanol ODH,
but at around 250°C lower temperature. The CL-ODH
setup was operated at high effective production times (i.e., the time
spent producing AA to the time spent regenerating SrFeO3−δ). In the investigated configuration with 2 g of the CLC catalyst
and 200 mL/min feed flowrate ∼5.8 vol % ethanol, only three
reactors would be required for the pseudo-continuous production of
AA via CL-ODH.