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Title: Structural identification of Zn xZr yO z catalysts for Cascade aldolization and self-deoxygenation reactions

Abstract

Complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH3/CO2 temperature programmed desorption (NH3/CO2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn xZr yO z oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn2+ and ZnO clusters coexist in mixed Zn xZr yO z oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO2, caused by steam reforming. The incorporation of atomic Zn2+ into the ZrO2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., ). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated tomore » the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C3=-C6=) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1439651
Report Number(s):
PNNL-SA-134337
Journal ID: ISSN 0926-3373; 49339; KP1704020
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Catalysis. B, Environmental; Journal Volume: 234; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Baylon, Rebecca A. L., Sun, Junming, Kovarik, Libor, Engelhard, Mark, Li, Houqian, Winkelman, Austin D., and Wang, Yong. Structural identification of ZnxZryOz catalysts for Cascade aldolization and self-deoxygenation reactions. United States: N. p., 2018. Web. doi:10.1016/j.apcatb.2018.04.051.
Baylon, Rebecca A. L., Sun, Junming, Kovarik, Libor, Engelhard, Mark, Li, Houqian, Winkelman, Austin D., & Wang, Yong. Structural identification of ZnxZryOz catalysts for Cascade aldolization and self-deoxygenation reactions. United States. doi:10.1016/j.apcatb.2018.04.051.
Baylon, Rebecca A. L., Sun, Junming, Kovarik, Libor, Engelhard, Mark, Li, Houqian, Winkelman, Austin D., and Wang, Yong. Mon . "Structural identification of ZnxZryOz catalysts for Cascade aldolization and self-deoxygenation reactions". United States. doi:10.1016/j.apcatb.2018.04.051.
@article{osti_1439651,
title = {Structural identification of ZnxZryOz catalysts for Cascade aldolization and self-deoxygenation reactions},
author = {Baylon, Rebecca A. L. and Sun, Junming and Kovarik, Libor and Engelhard, Mark and Li, Houqian and Winkelman, Austin D. and Wang, Yong},
abstractNote = {Complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH3/CO2 temperature programmed desorption (NH3/CO2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed ZnxZryOz oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn2+ and ZnO clusters coexist in mixed ZnxZryOz oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO2, caused by steam reforming. The incorporation of atomic Zn2+ into the ZrO2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., ). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated to the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C3=-C6=) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.},
doi = {10.1016/j.apcatb.2018.04.051},
journal = {Applied Catalysis. B, Environmental},
number = C,
volume = 234,
place = {United States},
year = {Mon Oct 01 00:00:00 EDT 2018},
month = {Mon Oct 01 00:00:00 EDT 2018}
}