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Catalytic oxidation of tricholoethylene over Cr/ZSM‐5/PSSF zeolite membrane catalysts prepared by chemical vapor deposition

Zhang, Yong, Zhang, Huiping, Yan, Ying
Journal of chemical technology and biotechnology 2019 v.94 no.5 pp. 1585-1592
X-ray diffraction, X-ray photoelectron spectroscopy, adsorption, ammonia, catalysts, catalytic activity, chromium, desorption, mass transfer, nitrogen, oxidation, oxides, oxygen, scanning electron microscopy, trichloroethylene, vapors, volatile organic compounds, zeolites
BACKGROUND: Chemical vapor deposition (CVD) is a promising catalyst preparation method owing to high dispersion and small particles of metallic oxides. Besides, the ZSM‐5 zeolite membrane is used to treat volatile organic compounds (VOCs) due to relatively high contact efficiency, lower bed pressure drop and mass transfer resistance than granular ZSM‐5, giving good stability of the metal catalysts. However, Cr modified ZSM‐5 zeolite membrane prepared by CVD for trichloroethylene (TCE) catalytic oxidation was still not well‐studied. In the present study, a series of Cr(x)/ZSM‐5/PSSF (x = 1, 3, 5 and 7) catalysts with different Cr loadings was prepared by CVD and further characterized by nitrogen gas (N₂) adsorption and desorption, X‐ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature‐programmed desorption (NH₃‐TPD) and X‐ray photoelectron spectroscopy (XPS), as well as catalytic performance for TCE oxidation. RESULTS: The results showed that the Cr₂O₃ species were uniformly dispersed on the surface of ZSM‐5/PSSF, and that the Cr(1)/ZP catalyst exhibited the best catalytic activity for TCE oxidation owing to more Cr⁶⁺ species and adsorbed oxygen. It also demonstrated that the Cr(1)/ZP catalyst shows superior catalytic performance for TCE oxidation, giving a T₉₀ that is about 62 °C (c.15%) lower than 1% Cr/ZSM‐5 particle catalyst. Furthermore, it exhibited an excellent stability after online testing at 440 °C for 30 h, and then dropped from 91% to 62% after 95 h, finally remaining at 62% after 120 h. CONCLUSION: The study demonstrated that Cr/ZSM‐5 zoelite membrane catalysts prepared by CVD show better catalytic behavior and stability for catalytic oxidation of TCE than Cr/ZSM‐5 zoelite catalysts. © 2019 Society of Chemical Industry