| The molding method is the key technonogy for low-temperature SCR (Selective Catalytic Reduction) catalysts used in SCR process. In this work, the cordierites were used as the substrates. The TiO2 coating and ZSM-5 coating were prepared by in-situ precipitation and in-situ synthesized hydrothermal method respectively. The optimum preparation parameters were screened. X-ray diffraction (XRD), Scanning electron microscope (SEM), and Specific surface area (BET) were applied for characterization. The adhesion strength and the low-temperature SCR activities of monolithic catalysts were examined by using ultrasonic oscillation and gas simulation system respectively.The Cr-V/TiO2/cordierites were prepared by in-situ precipitation combined with impregnation. The results showed that the TiO2 coating adhered to the cordierite closely and uniformly. Adhesion was enhanced by the loading of active components. The monolithic catalysts presented the similar high SCR activity and sulfur resistance stability as the powder catalyst. If the loading of the active component, Cr-V, was at least 5% by weight, the catalyst achieved excellent SCR activity, with an NOx conversion above 90%, in the temperature range 160-300℃. The Cr-V/TiO2/cordierite monolithic catalysts had relatively high stability in the presence of 0.01% SO2.The Mn-Ce/ZSM-5/cordierites were prepared by in-situ hydrothemal synthesis combined with impregnation. The optimal preparation parameters of ZSM-5/cordierite (Si/Al mole ratio=300) were as follows:cordierites were pretreated by 37% hydrochloric acid solution; the Si/TPAOH mole ratio was 1:0.2 with the pH 10-11. The ZSM-5 coating could well adhere onto the cordierite surface without dropping easily. The catalytic activity test results showed that the Mn-Ce/ZSM-5/cordierite monolithic catalysts presented excellent low-temperature DeNOx performance, with an NOx conversion above 80%, in the temperature range 140-220℃. |
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