Hydrothermal Fabrication and Catalytic Performance of Chromium Oxide for Low-concentration NO Oxidation at Ambient Temperature

doi:10.15541/jim20160019

Abstract

Abstract:

The chromic oxide catalysts were synthesized by hydrothermal method using CTAB as surfactant and NH₃·H₂O as precipitant. Physiochemical properties of these catalysts were characterized by X-ray diffraction (XRD), Fourier Transform lufrared specfroscopy (FT-IR), X-ray photoelectron spectroscope (XPS), and transmission electron microscope (TEM). The catalytic NO removal performances for different NO concentrations at room temperature was also investigated. It was shown that under the conditions of space velocity of 60, 000 mL/(g·h) and NO concentration of 1×10^-6, sample of Cr-100 exhibited the best catalytic performance, which maintained 120 h as removal ratio of NO more than 90%. This excellent catalytic performance could be attributed to the surface ions ratio of Cr⁶⁺/Cr³⁺. The FT-IR analysis indicated that catalyst deactivation was due to the active sites of chromic oxide occupied by nitrates, consistent with the results of XPS. Furthermore, the activity tests in different conditions demonstrated that low NO concentration could slow down the rate of nitrate accumulation and prolong the catalyst lifetime.

Key words: hydrothermal, ambient temperature, deactivation, chromic oxide

CLC Number:

X511

WU Mei-Jian, GAO Zhen-Yuan, YUAN Jing, ZHAO Kun-Feng, CAI Ting, YANG Ling, ZHANG Tao, HE Dan-Nong. Hydrothermal Fabrication and Catalytic Performance of Chromium Oxide for Low-concentration NO Oxidation at Ambient Temperature[J]. Journal of Inorganic Materials, 2016, 31(11): 1191-1197.

Figures/Tables 9

Fig. 1 XRD patterns of catalyst synthesized at various hydrothermal temperatures(a) Cr-160; (b) Cr-140; (c) Cr-120; (d) Cr-100U; (e) Cr-100; (f) Cr-80

Fig. 2 TEM (a, c) and HETEM (b, d) images of the chromium oxide catalysts synthesized at different hydrothermal temperatures(a) Cr-100; (b) Cr-100; (c) Cr-160; (d) Cr-160

Fig. 3 XPS spectra of Cr2p of fresh samples prepared at different hydrothermal temperatures and catalyst after NO removal test(a) Cr-100; (b) Cr-100U; (c) Cr-80; (d) Cr-160

Fig. 4 XPS spectra of O1s for fresh and Cr-100 after NO removal test(a) Cr-100; (b) Cr-100U

Table 1 Properties and XPS result of fresh samples prepared at different hydrothermal temperatures and catalyst after NO removal test

Samples	Cr⁶⁺/Cr³⁺	Cr/O	N/Cr	d_XRD/nm
Cr-80	0.37	0.22	-	26.4
Cr-100	0.64	0.32	0	20.7
Cr-100U	0.52	0.34	0.23	22.0
Cr-160	0.23	0.19	-	37.6

Fig. 5 FT-IR spectra of Cr-100 catalysts before and after NO removal test

Fig. 6 (a) The stability tests of NO oxidation at ambient temperature over chromic catalysts and (b) NO2 concentration catalyzed by Cr-100 catalyst(Reaction conditions: mass of catalyst = 0.25 g, total flow rate =500 mL/min, GHSV = 120000 mL/(g·h), NO concentration=5×10-6, temperature=30℃)

Fig. 7 Effect of different initial NO concentrations on NO removal over the Cr-100 catalyst(Reaction conditions: mass of Cr-100 catalyst = 0.25 g, total flow rate = 500 mL/min, GHSV = 120000 mL/(g·h), NO concentration = 2×10-6, 5×10-6, 10×10-6, temperature=30℃)

Fig. 8 The stability tests of NO removal over Cr-100 catalyst(Reaction conditions: mass of Cr-100 catalyst = 0.5 g, total flow rate: = 500 mL/min, GHSV = 60000 mL/(g·h), NO concentration = 1×10-6 , temperature = 30℃)

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