Preparation of CexZr1-xO2 with Combined Composition for Improved Pd-only Three-way Catalyst

doi:10.15541/jim20170387

Abstract

Abstract:

Two special CeO₂-ZrO₂ composites with combined compositions were prepared by a simple sequential precipitation method. The effect of the combination styles on properties of the supported Pd-only three-way catalysts was investigated by means of X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption/desorption, H₂-temperature programmed reduction (H₂-TPR), and oxygen storage capacity measurement (OSC). The results reveal that the structural and textural properties are modified for the two catalysts with compositional heterogeneity. Combined configuration facilitates the formation of Ce³⁺ and lattice defects, resulting in improved oxygen mobility, due to strong interaction between the noble metal and the support as well as the synergistic function inside the support. Consequently, the corresponding catalysts show amplified operation windows for the conversions of CO, C₃H₈ and NO before and after aging, indicating promising application in purification of automobile exhaust gases.

Key words: combined composition, sequential precipitation, Pd-only three-way catalyst, catalytic performance

CLC Number:

TQ174

LI Hong-Mei, LAN Li, CHEN Shan-Hu, LIU Da-Yu, WANG Wei, CHEN Yao-Qiang. Preparation of Ce_xZr_1-_xO₂ with Combined Composition for Improved Pd-only Three-way Catalyst[J]. Journal of Inorganic Materials, 2018, 33(7): 798-804.

Figures/Tables 9

Fig. 1 XRD patterns of (a) fresh and (b) aged catalysts

Fig. 2 Raman spectra of (a) fresh and (b) aged catalysts

Table 1 Textural properties of fresh and aged catalysts

Sample	Surface area /(m²•g^-1)		Pore volume /(ml•g^-1)		Average pore radius/nm
Sample	fresh	aged	fresh	aged	fresh	aged
Pd/Ce65i	125	26	0.29	0.15	4.6	11.2
Pd/Ce35i	122	25	0.26	0.14	4.3	11.0
Pd/Ce65	131	23	0.24	0.12	3.6	10.9
Pd/Ce35	117	17	0.25	0.11	4.0	13.9

Fig. 3 Pore size distributions of the fresh catalysts.

Table 2 XPS results of fresh and aged catalysts

Samples	Atomic concentration/%				Ce/Zr	(Ce³⁺/Ce) /%
Samples	Ce3d	Zr3d	Pd3d	O1s	Ce/Zr	(Ce³⁺/Ce) /%
Pd/Ce65i-F	7.5	13.7	1.2	77.6	0.5	21.2
Pd/Ce35i-F	8.5	13.9	1.2	76.4	0.6	19.0
Pd/Ce65-F	11.3	9.2	1.7	77.8	1.2	18.9
Pd/Ce35-F	5.8	16.3	1.4	76.5	0.4	18.7
Pd/Ce65i-A	7.0	13.4	1.2	78.4	0.5	20.7
Pd/Ce35i-A	6.9	13.9	1.1	78.1	0.5	18.9
Pd/Ce65-A	8.4	9.9	1.4	80.3	0.8	18.2
Pd/Ce35-A	6.0	15.8	0.8	77.4	0.4	17.7

Fig. 4 TPR profiles of (a) fresh and (b) aged catalysts

Fig. 5 OSC values of fresh and aged catalysts

Fig. 6 Conversion curves of CO, C3H8 and NO as a function of air/fuel ratio (λ) of fresh and aged catalysts

Fig. 7 Schematics of the combination modes of Pd/CeO2-ZrO2 catalysts prepared from sequential precipitation route

References 19

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Preparation of Ce_xZr_1-_xO₂ with Combined Composition for Improved Pd-only Three-way Catalyst

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