Catalytic oxidation of dibromomethane over Ti-modified Co3O4 catalysts: Structure, activity and mechanism

Jian Mei; Wenjun Huang; Zan Qu; Xiaofang Hu; Naiqiang Yan

doi:10.1016/j.jcis.2017.06.077

Catalytic oxidation of dibromomethane over Ti-modified Co₃O₄ catalysts: Structure, activity and mechanism

J Colloid Interface Sci. 2017 Nov 1:505:870-883. doi: 10.1016/j.jcis.2017.06.077. Epub 2017 Jun 23.

Authors

Jian Mei¹, Wenjun Huang¹, Zan Qu¹, Xiaofang Hu¹, Naiqiang Yan²

Affiliations

¹ School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240, PR China.
² School of Environmental Science and Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240, PR China. Electronic address: nqyan@sjtu.edu.cn.

PMID: 28672266
DOI: 10.1016/j.jcis.2017.06.077

Abstract

Ti-modified Co₃O₄ catalysts with various Co/Ti ratios were synthesized using the co-precipitation method and were used in catalytic oxidation of dibromomethane (CH₂Br₂), which was selected as the model molecule for brominated volatile organic compounds (BVOCs). Addition of Ti distorted the crystal structure and led to the formation of a Co-O-Ti solid solution. Co₄Ti₁ (Co/Ti molar ratio was 4) achieved higher catalytic activity with a T₉₀ (the temperature needed for 90% conversion) of approximately 245°C for CH₂Br₂ oxidation and higher selectivity to CO₂ at a low temperature than the other investigated catalysts. In addition, Co₄Ti₁ was stable for at least 30h at 500ppm CH₂Br₂, 0 or 2vol% H₂O, 0 or 500ppm p-xylene (PX), and 10% O₂ at a gas hourly space velocity of 60,000h^-1. The final products were CO_x, Br₂, and HBr, without the formation of other Br-containing organic byproducts. The high catalytic activity was attributed to the high Co³⁺/Co²⁺ ratio and high surface acidity. Additionally, the synergistic effect of Co and Ti made it superior for CH₂Br₂ oxidation. Furthermore, based on the analysis of products and in situ DRIFTs studies, a receivable reaction mechanism for CH₂Br₂ oxidation over Ti-modified Co₃O₄ catalysts was proposed.

Keywords: Catalytic oxidation; Cobalt; Dibromomethane (CH(2)Br(2)); Titania.