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Open AccessArticle

Effect of Zirconia Polymorph on Vapor-Phase Ketonization of Propionic Acid

Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
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Catalysts 2019, 9(9), 768; https://doi.org/10.3390/catal9090768
Received: 26 August 2019 / Revised: 11 September 2019 / Accepted: 11 September 2019 / Published: 13 September 2019
(This article belongs to the Section Biomass Catalysis)
Vapor-phase ketonization of propionic acid derived from biomass was studied at 300–375 °C over ZrO2 with different zirconia polymorph. The tetragonal ZrO2 (t-ZrO2) are more active than monoclinic ZrO2 (m-ZrO2). The results of characterizations from X-ray diffraction (XRD) and Raman suggest m-ZrO2 and t-ZrO2 are synthesized by the solvothermal method. NH3 and CO2 temperature-programmed desorption (NH3-TPD and CO2-TPD) measurements show that there were more medium-strength Lewis acid base sites with lower coordination exposed on m-ZrO2 relative to t-ZrO2, increasing the adsorption strength of propionic acid. The in situ DRIFTS (Diffuse reflectance infrared Fourier transform spectroscopy) of adsorbed propionic acid under ketonization reaction reveal that as the most abundant surface intermediates, the monodentate propionates are more active than bidentate propionates. In comparison with m-ZrO2, the t-ZrO2 surface favors monodentate adsorption over bidentate adsorption. Additionally, the adsorption strength of monodentate propionate is weaker on t-ZrO2. These differences in adsorption configuration and adsorption strength of propionic acid are affected by the zirconia structure. The higher surface concentration and weaker adsorption strength of monodentate propionates contribute to the higher ketonization rate in the steady state. View Full-Text
Keywords: monoclinic ZrO2; tetragonal ZrO2; ketonization; propionic acid; in situ infrared spectroscopy monoclinic ZrO2; tetragonal ZrO2; ketonization; propionic acid; in situ infrared spectroscopy
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MDPI and ACS Style

Ding, S.; Zhao, J.; Yu, Q. Effect of Zirconia Polymorph on Vapor-Phase Ketonization of Propionic Acid. Catalysts 2019, 9, 768.

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