Structural Identification of ZnxZryOz Catalysts for Cascade Aldolization and Self-Deoxygenation Reactions [electronic resource]

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Ngôn ngữ: eng

Ký hiệu phân loại: 541.3 Miscellaneous topics in physical chemistry

Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2018

Mô tả vật lý: Size: p. 337-346 : , digital, PDF file.

Bộ sưu tập: Metadata

ID: 263104

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Here, 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, NH
3
/CO
2
temperature programmed desorption (NH
3
/CO
2
-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO
2-
IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn
x
Zr
y
O
z
oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn
2+
species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO
2
particles when the Zn/Zr ratio is smaller than 1/10
when the ratio is above this, both atomically dispersed Zn
2+
and ZnO clusters coexist in mixed Zn
x
Zr
y
O
z
oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO
2
, caused by steam reforming. The incorporation of atomic Zn
2+
into the ZrO
2
framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO
2
, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., 
Zr?o$\curvearrowleft\atop{e\atop?}$Zn
). 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 (C
3

=
-C
6

=
) 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.

1. 09 biomass fuels
2. 10 synthetic fuels
3. 36 materials science
4. 37 inorganic, organic, physical, and analytical chemistry
5. Lewis acid-base pairs

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Structural Identification of Zn<sub>x</sub>Zr<sub>y</sub>O<sub>z</sub> Catalysts for Cascade Aldolization and Self-Deoxygenation Reactions [electronic resource]