Ambient Temperature Formaldehyde Oxidation on the Pt/Na-ZSM-5 Catalyst: Tuning Adsorption Capacity and the Pt Chemical State

Abstract

Catalytic oxidation is believed to be the most efficient method for indoor formaldehyde purification. Herein, we reported that the Pt/Na-ZSM-5 catalyst with low Pt loading (0.16 wt %) prepared by depositing Pt on Na+ ion-exchanged ZSM-5 could completely oxidize 300 ppm formaldehyde in 2.5 vol % H2O at 32 °C and maintain its activity during the 62 h-long stability test. Multiple characterizations revealed that the presence of Na species significantly enhanced formaldehyde adsorption ability and made Pt species tend to exist in the form of metal Pt through electron transfer from Na to Pt, which promoted the activation of oxygen and opened a new efficient formaldehyde oxidation pathway, namely, direct decomposition of formate. The synergistic effects resulted in the TOF of Pt(0.16)/Na-ZSM-5 being about nine times higher than that of Pt(0.50)/ZSM-5. Our study showed that utilizing an alkali metal to tune the surface acidity/basicity of the support and the state of the supported noble metal was a promising way to improve the intrinsic catalytic performance and reduce noble metal usage.

Regulating Encapsulation of Small Pt Nanoparticles inside Silicalite-1 Zeolite with the Aid of Sodium Ions for Enhancing n-Hexane Reforming

“…When Na is added, a peak appears near 1072.4 eV, which is assigned to the formation of an −O−Na linkage that stabilizes the Pt atoms, and the peak intensity gradually increases with the increase in Na content. 59 Although the Na content of Pt@Sil-1-6Na is higher than that of Pt@Sil-1-4Na, the peak intensities of both Pt@Sil-1-6Na and Pt@Sil-1-4Na are the same. More quantitative data for the surface content and bulk content of Pt and Na based on the XPS and ICP are listed in Table 1.…”

“…There is no signal for Pt/Sil-1 and Pt@Sil-1 catalysts, indicating that there is no Na on the catalyst surface. When Na is added, a peak appears near 1072.4 eV, which is assigned to the formation of an −O–Na linkage that stabilizes the Pt atoms, and the peak intensity gradually increases with the increase in Na content . Although the Na content of Pt@Sil-1-6Na is higher than that of Pt@Sil-1-4Na, the peak intensities of both Pt@Sil-1-6Na and Pt@Sil-1-4Na are the same.…”

“…Moreover, compared with Pt@Sil-1, all of the Pt@Sil-1-xNa samples exhibit an obvious red shift to a low wavenumber. The obvious red shift phenomenon strongly suggests a higher surface electron density over the Pt atoms in the Pt@Sil-1-xNa catalyst because of electron donation from the Na species 59,64 and smaller particle size of Pt in Pt@Sil-1-xNa. For the Pt@Sil-1 catalyst, Pt is located at the defect of Sil-1 zeolite, which contains a large number of hydroxyl groups (−O−H).…”

Redispersion of Pt nanoparticles encapsulated within ZSM-5 at high temperature oxygen for partial oxidation of methane

“…Generally, PtO x is reduced at 100 ℃-300 ℃, but the reduction of Pt 2+ and Pt 4+ coordinated with -(-O-Si≡) y of ZSM-5 requires about 450 ℃ and 550 ℃ [41,42]. However, the reduction peak of pure ZSM-5 did not appear in the H 2 -TPR process.…”

Effect of Hydroxyl Groups on Metal Anchoring and Formaldehyde Oxidation Performance of Pt/Al2O3

“…The alkali metals can be electronic or structural promoters, improving the activity of catalysts markedly . Previous literature studies have reported that alkali metal doping generates noble metal–alkali–O x –(OH) y species, which could be active sites for water-gas shift reactions. ,, In addition, alkali metal addition induces a decrease in the particle size of noble metal particles as well as increases the dispersion of the noble metals and surface OH groups, resulting in a promotion effect on HCHO oxidation. − To our knowledge, researchers have mainly focused on the interaction between noble metals and alkali metals, but the interaction between alkali metals and the supports has not been fully explored. Therefore, it is necessary to study how alkali metals interact with supports and further affected noble metal anchoring so that the catalytic promotion mechanism of alkali metals can be understood.…”