کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6453789 | 1418802 | 2017 | 9 صفحه PDF | دانلود رایگان |
- By Na+-pretreatment of HY (Al/Si = 0.36) zeolite to form H(Na)Y, the surface charge can be positive.
- HAuCl4-derived nanogold can be deposited on H(Na)Y in aqueous solution at pH 6.
- Ultrasmall Au nanoparticles about 1 nm are finely dispersed on Au/H(Na)Y.
- Without any pretreatment, Au/H(Na)Y can possess high catalytic activity for CO oxidation.
In this study, proton-type zeolites Y (HY) with Al/Si ratio of 0.36 were used as a support for deposition of HAuCl4 (in pH 6 solution) to prepare Au/Y catalysts for CO oxidation at 25 °C. The low isoelectric point of HY (â¼pH = 2) made this support inappropriate for loading negatively charged gold complexes, and caused the generation of large gold particles with low catalytic activity. We found that through a Na+ pretreatment of HY to form H(Na)Y, the surface charge can be reversed to positive, thus favoring the deposition. The resulting Au/H(Na)Y, without any high temperature treatment, gave excellent activity in CO oxidation comparable to Au/TiO2. The CO oxidation rate of 0.21 mol CO/mol Auâs remained stable at 25 °C. HRTEM images of the catalyst show highly dispersed gold nanoparticles â¼1 nm confined in the nanocage of H(Na)Y. XPS spectra show high proportion of Au(III) associated with Au-O. The weak Au-O in Au/H(Na)Y is found responsible for the easy reduction in TPR. For comparison, the other alternative procedures of gold deposition were also tried to reverse the surface charge of HY by decreasing the pH of solution. However, high contents of residual Cl in the nano-gold catalyst lead to almost no activity in CO oxidation.
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Journal: Applied Catalysis B: Environmental - Volume 218, 5 December 2017, Pages 506-514