Tunable KIT-6 Mesoporous
Sulfonic Acid Catalysts for
Fatty Acid Esterification
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Abstract
We report the first catalytic application of pore-expanded
KIT-6
propylsulfonic acid (PrSO<sub>3</sub>H) silicas, in fatty acid esterification
with methanol under mild conditions. As-synthesized PrSO<sub>3</sub>H-KIT-6 exhibits a 40 and 70% enhancement in turnover frequency (TOF)
toward propanoic and hexanoic acid esterification, respectively, over
a PrSO<sub>3</sub>H-SBA-15 analogue of similar 5 nm pore diameter,
reflecting the improved mesopore interconnectivity of KIT-6 over SBA-15.
However, pore accessibility becomes rate-limiting in the esterification
of longer chain lauric and palmitic acids over both solid acid catalysts.
This problem can be overcome via hydrothermal aging protocols which
permit expansion of the KIT-6 mesopore to 7 nm, thereby doubling the
TOF for lauric and palmitic acid esterification over that achievable
with PrSO<sub>3</sub>H-SBA-15