Molecular Active Sites in Heterogeneous Ir-La/C-Catalyzed Carbonylation of Methanol to Acetates.
We report that when Ir and La halides are deposited on carbon, exposure to CO spontaneously generates a discrete molecular heterobimetallic structure, containing an Ir-La covalent bond that acts as a highly active, selective, and stable heterogeneous catalyst for the carbonylation of methanol to produce acetic acid. This catalyst exhibits a very high productivity of ∼1.5 mol acetyl/mol Ir·s with >99% selectivity to acetyl (acetic acid and methyl acetate) without detectable loss in activity or selectivity for more than 1 month of continuous operation. The enhanced activity can be mechanistically rationalized by the presence of La within the ligand sphere of the discrete molecular Ir-La heterobimetallic structure, which acts as a Lewis acid to accelerate the normally rate-limiting CO insertion in Ir-catalyzed carbonylation. Similar approaches may provide opportunities for attaining molecular (single site) behavior similar to homogeneous catalysis on heterogeneous surfaces for other industrial applications.
†Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
Ja Hun
JH
Kwak
†Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
Robert
R
Dagle
‡Eastman Chemical Company, Kingsport, Tennessee 37660, United States.
Gerald C
GC
Tustin
‡Eastman Chemical Company, Kingsport, Tennessee 37660, United States.
Joseph R
JR
Zoeller
§Oak Ridge National Laboratory, Oak Ridge, Tennessee 37871, United States.
Lawrence F
LF
Allard
†Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.|⊥The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, United States.
Yong
Y
Wang
acetic acid; carbonylation; catalysis; heterogeneous iridium catalyst; methanol; molecular active sites