(583bk) Identification of Activities of CuO Species in CuO-CeO2/Y Catalysts for HCl Oxidation

Identification of activities of CuO Species
in CuO-CeO₂/Y
Catalysts for HCl
Oxidation

Zhaoyang Fei^1,2,
Rui Cao², Xian Chen², Jihai Tang², Mifen Cui
², Xu Qiao^1,2*

(1. State Key Laboratory of Materials-Oriented Chemical
Engineering, Nanjing University of Technology, Nanjing, Jiangsu 210009, China 2.
College of Chemistry and Chemical Engineering, Nanjing University of
Technology, Nanjing, Jiangsu 210009, China;)

Key words£ºHCl oxidation; CuO-CeO₂/Y
catalysts; CuO species; catalytic
activity

Catalytic oxidation of HCl to Cl₂
is an energy-efficient and environmentally friendly way to recycle chlorine
from by-product HCl in chlorine-related chemical industry. The transition metal
catalysts, especially copper-based compounds, display high
catalytic activity in this process ^[1]. Previous research
found that CuO-CeO₂ composite catalysts showed novel catalytic
activity and the copper species were the mainly activity component
^[2]. In the present work, a series of Y-zeolite supported (¦Öwt%)CuO-(13%)CeO₂
catalysts were prepared by impregnation method. The states of copper species
were investigated.
The results show that different copper species showed obvious activity
diversity.

The XRD results (Fig.1) show that peaks attributed
to the CuO were not detected in the catalysts with low CuO content(below 6wt%),
indicating all copper species were highly dispersed on the support. With the
increase of CuO content, the crystalline CuO has formed. This result is also testified
by the TPR results (Fig.2): ¦Á₂ peak interpreted as the reduction of small CuO crystallites appears in
CuO(12)-CeO₂(13)/Y catalyst.

Fig. 1 The XRD patterns of the catalysts         Fig.
2 The TPR profiles of the catalysts      Fig. 3
The catalytic performances of the catalysts

The reduction behavior of CuO(2)-CeO₂(13)/Y
catalyst is similar to that of CuO(12)-CeO₂(13)/Y
after acid treatment, indicating both catalysts possess the same type of
copper species. Only copper ions in CeO₂ lattice exist in the catalyst
after acid treatment, so it can be assumed that copper ions existed in CeO₂
lattice when copper content below 2wt%, which contribute remarkably to the
catalytic activity. With the increasing of CuO content, the conversion of HCl
increases greatly which can be ascribed to the dispersed copper species. When
CuO content is above 6wt%, the small CuO crystallites are formed,which make little contribution to the
activity of the catalysts.

Finally, comparing the
conversion of HCl over catalysts with different CuO content, it can be
concluded that the activities of different copper species are in this order: copper
ions existed in CeO₂ lattice (17.3 g_HCl∙h^-1∙g_CuO)>dispersed
CuO (9.4 g_HCl∙h^-1∙g_CuO)> bulk CuO (1.0 g_HCl∙h^-1∙g_CuO).

REFERENCES

[1] C. Mondelli, A. P. Amrute, T.
Schmidt, J. P¨¦rez-Ram¨ªrez. A delafossite-based copper catalyst for sustainable
Cl₂ production by HCl oxidation. Chem. Commun., 2011, 47,
7173-7176.

[2] Zhaoyang Fei, Rui Cao, Xian
Chen, Jihai Tang, Mifen Cui, Xu Qiao. Synergetic effects of CuO-CeO₂
catalysts in HCl oxidation. The 3rd International Conference on Sustainable
Chemical Product and Process Engineering (SCPPE 2013).