Influence of the Formation of Ternary Oxide of Pd and Na Supported on Alumina Catalysts for the Room Temperature Hydrode
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Influence of the Formation of Ternary Oxide of Pd and Na Supported on Alumina Catalysts for the Room Temperature Hydrodechlorination of Chlorobenzene J. Vinod Kumar Æ N. Lingaiah Æ N. Seshu Babu Æ V. Pavan Kumar Æ P. S. Sai Prasad
Received: 21 April 2009 / Accepted: 11 June 2009 / Published online: 30 June 2009 Ó Springer Science+Business Media, LLC 2009
Abstract A series of Pd/Na modified Al2O3 catalysts was prepared by deposition–precipitation method. These catalysts were characterized by X-ray diffraction, temperature programmed reduction, X-ray photoelectron spectroscopy, N2 adsorption, CO pulse chemisorption and SEM-EDAX. The characterization data reveal the formation of a ternary oxide of Pd with Na for the catalysts at an optimum Pd to Na ratio. The activity of the catalysts studied for the room temperature hydrodechlorination of chlorobenzene, is also found to be maximum at this ratio. Keywords Hydrodechlorination Deposition– Precipitation Palladium Sodium Na2Pd3O4
1 Introduction Chlorinated hydrocarbon (CHC) is a generic term given to a compound containing chlorine, carbon and hydrogen. The term can be used to describe industrial chemicals such as polychlorinated biphenyls (PCB), chlorine waste products such as chlorobenzene, dioxins and furans and organochlorine pesticides such as lindane and DDT. The C–Cl bond, common to all organo-Cl compounds, is strong and gives high stability to these compounds. For this reason, several organo-CHC compounds have been synthesized
J. Vinod Kumar N. Lingaiah N. Seshu Babu V. Pavan Kumar P. S. Sai Prasad (&) Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Hyderabad 500607, India e-mail: [email protected] N. Lingaiah e-mail: [email protected]
and used extensively for years in industrial and agricultural applications. For the same reason, these molecules tend to stay in the environment for a longer time, and threaten to contaminate aquatic and soil systems [1, 2]. The human and environmental health risks of chlorinated hydrocarbons depend on the compound in question. Several methods have been employed to destruct or convert these environmental hazards to value added compounds. Among these techniques catalytic hydrodechlorination provides a promising non-destructive alternative technology whereby the chlorinated waste is converted into products with commercial value [3–8]. An important aspect in this view is the selection of catalyst for catalytic hydrodechlorination (HDC). Among several catalysts reported in literature, supported Pd catalyst seems to be promising due to its high ability in replacing chlorine atoms with hydrogen [9–11]. The most important problem that is commonly encountered in catalytic hydrodechlorination is strong catalyst deactivation. Some authors suggest that coke deposition or metal particle sintering or the formation of HCl during the course of reaction may be the possible reason for catalyst deactivation [12–15]. However, it is widely accepted that the HCl formation is the main reas
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