Complete oxidation of o-xylene over Pd/Al(2)O(3) catalyst at low temperature

TLDR: In this article, a simplified mechanism for the catalytic oxidation of o-xylene over Pd/Al(2)O(3) was proposed, based on the behavior of adsorbed species.

About: This article is published in Catalysis Today.The article was published on 2008-12-15 and is currently open access. It has received 107 citations till now. The article focuses on the topics: Catalytic oxidation & Catalysis.

Figures

Fig. 9. GC/MS chromatograms for gaseous organic products of o-xylene total oxidation over 1% Pd/Al2O3 catalyst. Reaction conditions: 20% O2/N2 balance, total flow rate 100 mL min 1, GHSV 50,000 h 1, (a) for 100 ppm o-xylene at 130 8C, (b) for 100 ppm, o-xylene at 160 8C and (c) for 1000 ppm o-xylene at various reaction temperatures.

Fig. 11. o-Xylene TPO spectra over the g-Al2O3 support and the 1% Pd/Al2O3 catalyst. o-Xylene TPO conditions: total flow rate 50 mL min 1, 20% O2/N2 balance, heating rate 20 8C min 1, (A) over g-Al2O3 support and (B) over 1% Pd/Al2O3 catalyst.

Fig. 10. In situ DRIFTS of o-xylene oxidation over 1% Pd/Al2O3 catalyst at different temperatures. Reaction conditions: o-xylene 100 ppm, total flow rate 100 mL min 1, 20%O2/ N2 balance.

Table 1 The surface areas of g-Al2O3 and g-Al2O3 supported noble metal catalysts

Fig. 1. o-Xylene conversions of Al2O3 supported 1% noble metal catalysts at various temperatures. Reaction conditions: o-xylene 100 ppm, 20% O2/N2 balance, total flow rate 100 mL min 1, GHSV 50,000 h 1.

Fig. 3. o-Xylene conversions of Pd/Al2O3 catalysts with various Pd loadings. Reaction conditions: o-xylene 100 ppm, 20% O2/N2 balance, total flow rate 100 mL min 1, GHSV 50,000 h 1.

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Complete oxidation of o-xylene over pd/al2o3 catalyst at low temperature" ?

The mechanism of o-xylene oxidation was studied with respect to the behavior of adsorbed species on Pd/Al2O3 surface examined by in situ DRIFTS and the gas products detected by the online GC/MS. 

Q2. What is the effect of the adsorption on the catalyst?

The orientation change of the adsorbed ring structure from parallel to tilt (vertical) [16,35,36] and/or more molecules with an aromatic ring structure adsorbed on the catalyst could contribute to the increase of intensity. 

Q3. What are the advantages of noble metal catalysts over metal oxides?

The advantages of noble metal catalysts over metal oxides include superior specific activity and high selectivity, which makes them as the best candidates for low temperature complete oxidation of VOCs. 

Q4. What are the commonly used supports for Pt and Pd?

In the case of metal oxide supported Pt and Pd catalyst, the commonly used supports are Al2O3, ZrO2, CeO2, SiO2 and TiO2 and so on [3,8–10]. 

Q5. What is the effect of the temperature on the band intensities of the aromatic ring?

the band intensities due to aromatic ring structure (1610, 1587, 1489 and 1465 cm 1) increased, which denoted some species with an aromatic ring structure was still existed on the catalyst surface at this temperature. 

Q6. What is the active species in the Pd/Al2O3 catalyst?

At about 110 8C, the 100 ppm o-xylene can be completely oxidized into CO2 and H2O over 1% Pd/Al2O3 at a GHSV of 10,000 h1. XRD patterns show that the metallic 

Q7. What catalysts were prepared using the wet impregnation technique?

The Al2O3 supported noble metal (Pd, Pt, Rh, Au and Ag) catalysts were prepared via the wet impregnation technique with g-Al2O3 and an aqueous solution containing appropriate amount of Pd(NO3)2, H2PtCl6, RhCl3, AuCl3 and AgNO3, respectively. 

Q8. What is the effect of Pd loading on catalytic activity?

the authors think that the enhanced catalytic activities could be due to the increase of the number of Pd active species in higher Pd loading catalysts, despite of the aggregation of the metallic Pd. 

Q9. What is the main reason for the study of VOCs?

During the last decades, the complete oxidation of VOCs has been widely studied over either supported noble metals or metal oxides catalysts in view of developing catalytic oxidation applications [3–7]. 

Q10. What is the GHSV of Pd/Al2O3 catalyst?

Pd species plays an important role for the catalytic oxidation of oxylene over Pd/Al2O3 catalyst, and a further discussion about the active species of Pd/Al2O3 catalyst for o-xylene catalytic oxidation will be given in their next work. 

Q11. How much Pd was added to the catalyst?

over the 1% Pd/Al2O3 catalyst, a large amount of CO2 was produced around 140 8C with the rising temperature, indicating that addition of 1% 

Q12. What is the effect of the surface area of the catalysts?

That is, the variations in the surface areas of these catalysts can be considered as a negligible factor for the different catalytic activities of o-xylene oxidation.