Selective Liquid-phase Hydrodechlorination of Chlorotrifluoroethylene over Palladium-Supported Catalysts: Activity and D
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Selective Liquid-phase Hydrodechlorination of Chlorotrifluoroethylene over Palladium-Supported Catalysts: Activity and Deactivation Bao-Chuan Meng • Zhao-Yang Sun • Jin-Peng Ma • Gui-Ping Cao • Wei-Kang Yuan
Received: 8 December 2009 / Accepted: 10 May 2010 / Published online: 22 May 2010 Ó Springer Science+Business Media, LLC 2010
Abstract Liquid-phase hydrodechlorination of chlorotrifluoroethylene (CTFE) to trifluoroethylene (TrFE) with molecular hydrogen was studied over palladium-supported catalysts. BaSO4, Al2O3 and activated carbon (AC) were used as supports, respectively. The results showed that the Pd/AC catalysts exhibit higher activity than Pd/BaSO4 and Pd/Al2O3. The treatment of activated carbon with HNO3 led to a considerable increase of surface functional groups containing oxygen atoms, which resulted in a higher dispersion of palladium on the supports and enhancement of catalytic activity. The stability of the catalyst was investigated, one reason for the inhibition was the accumulation of NaCl on the surface of Pd/AC that blocks the pores of carbon support. The activity of Pd/AC could partially recovered by washing with water. The other irreversible deactivation of the catalyst are from the change of particle size and the pore structure, leaching of Pd, a decrease of BET surface area and Pd surface area of Pd/AC catalyst. Keywords Trifluoroethylene Activated carbon Pd/AC catalyst HNO3 pretreatment Deactivation
1 Introduction Chlorinated organic compounds exhibit high toxicity and form a class of environmentally undesirable compounds that are produced by a wide range of industrial processes as
B.-C. Meng Z.-Y. Sun J.-P. Ma G.-P. Cao (&) W.-K. Yuan East China University of Science and Technology, UNILAB Research Center of Reaction Engineering, State-key Laboratory of Chemical Engineering, Shanghai 200237, China e-mail: [email protected]
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by-products [1]. Catalytic hydrodechlorination of chlorinated organic compounds over noble metal catalysts has been recognized as a facile and efficient procedure to eliminate these compounds [2, 3]. Among noble metals in Group VIII known for those procedures, palladium was reported to be the most active metal that catalyze selective replacing of chlorine with hydrogen. As Pd not only promotes C–Cl bond cleavage efficiently, but also shows poisoning resistance [4, 5]. Heterogeneous catalytic hydrodechlorination is conventionally carried out in either gas [6–8] or liquid phase [2, 3, 9]. The hydrogen source can be molecular hydrogen [3, 6, 10] or other hydrogen donors such as alcohols, 2-propanol [11, 12], sodium hypophosphite, sodium borohydride [13], as well as proaromatic compounds [14]. Trifluoroethylene (TrFE), produced by catalytic hydrodechlorination of chlorotrifluoroethylene (CTFE), is an important chemical intermediate for synthesis of many useful compounds. For example, 1,1,1,2-tetrafluoroethane (HFC-134a) is known as the best alternative of freons. It also can copolymerize with olefins, for instance, the copolymerization product of Tr
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