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CO oxidation and 4-nitrophenol reduction over ceria-promoted platinum nanoparticles impregnated with ZSM-5 zeolite
Journal of Rare Earths ( IF 5.2 ) Pub Date : 2021-07-17 , DOI: 10.1016/j.jre.2021.07.009
Zeinhom M. El-Bahy 1 , Mohammed T. Alotaibi 2 , Salah M. El-Bahy 2
Affiliation  

Active new ceria-promoted platinum supported on ZSM-5 catalysts were prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), transform electron microscopy (TEM), temperature programmed desorption (TPD), and FTIR of CO adsorption. The samples were prepared by the incipient wetness impregnation method and calcined at 500 °C. The XRD patterns and FTIR spectra prove that the zeolite framework is kept unaltered after metal loadings. TEM images prove the presence of Pt nanoparticles with particle size starting from 14 to 27 nm. The FTIR data suggest the formation of Pt–O–Ce linkage. In-situ FTIR of CO adsorption over reduced samples proves the presence of Pt0 only, and no Ptn+–CO species are detected. The prepared catalysts were tested in both oxidation reaction (CO oxidation) in the gas phase and in reduction reaction (4-nitrophenol reduction) in the aqueous medium. Firstly, CO oxidation by O2 results in the formation of a CO2 peak at 2347 cm−1 as the only CO oxidation product in the studied frequency range. The intensity of the CO2 peak increases after the addition of Ce, and it is 4 times higher in Pt1Ce0.5ZSM-5 than that in the Ce-free sample. According to the FTIR data and previous reports, the increase in the catalytic activity may be due to the formation of Pt–O–Ce linkage. Secondly, Ce-promoted Pt1ZSM5 also exhibits enhanced catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol by NaBH4 in the aqueous medium. The first-order rate constant of the reduction increases ≈13 times after incorporating equal ratios of Pt and Ce (Pt1Ce1ZSM-5), and the activation energy (Ea) decreases to 40% of that in the reaction over Pt1ZSM-5.



中文翻译:

用 ZSM-5 沸石浸渍的二氧化铈促进的铂纳米粒子上的 CO 氧化和 4-硝基苯酚还原

制备了负载在 ZSM-5 催化剂上的新型二氧化铈促进的活性铂,并通过 X 射线衍射 (XRD)、傅里叶变换红外光谱 (FTIR)、变换电子显微镜 (TEM)、程序升温脱附 (TPD) 和 FTIR 对其进行了表征。 CO吸附。样品采用初湿浸渍法制备,并在 500 ℃下煅烧。XRD 图案和 FTIR 光谱证明沸石骨架在金属负载后保持不变。TEM 图像证明了 Pt 纳米粒子的存在,其粒径从 14 到 27 nm。FTIR 数据表明 Pt-O-Ce 键的形成。还原样品上 CO 吸附的原位FTIR 证明仅存在 Pt 0,而没有 Pt n +-CO 物种被检测到。制备的催化剂在气相中的氧化反应(CO氧化)和水性介质中的还原反应(4-硝基苯酚还原)中进行了测试。首先,O 2对CO的氧化导致在2347 cm -1处形成CO 2峰,这是所研究频率范围内唯一的CO氧化产物。添加Ce后CO 2峰的强度增加,Pt 1 Ce 0.5 ZSM-5 的强度是无Ce样品的4倍。根据 FTIR 数据和之前的报道,催化活性的增加可能是由于 Pt-O-Ce 键的形成。其次,Ce-promoted Pt 1ZSM5还表现出增强的对NaBH 4在水性介质中将4-硝基苯酚还原为4-氨基苯酚的催化活性。在加入等比例的 Pt 和 Ce (Pt 1 Ce 1 ZSM-5)后,还原的一级速率常数增加了 ≈13 倍,并且活化能 ( E a ) 降低到 Pt 反应的 40% 1 ZSM-5。

更新日期:2021-07-17
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