Dehydrochlorination of Intermediates in the Production of Vinyl Chloride over Lanthanum Oxide-Based Catalysts
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Dehydrochlorination of Intermediates in the Production of Vinyl Chloride over Lanthanum Oxide-Based Catalysts Alwies W. A. M. van der Heijden Æ Ad J. M. Mens Æ Rene´ Bogerd Æ Bert M. Weckhuysen
Received: 15 December 2007 / Accepted: 8 February 2008 / Published online: 28 March 2008 Ó The Author(s) 2008
Abstract Lanthanum oxide-based catalysts are active in the elimination of HCl from C2H5Cl, 1,2-C2H4Cl2 and 1,1,2-C2H3Cl3 leading to the formation of their respective chlorinated ethenes. An oxygen-rich catalytic surface may form CO, CO2 and C2HCl as side products, whereas with chlorine-rich catalytic surfaces a stable product distribution is achieved with 100% selectivity towards the formation of ethenes, such as the valuable C2H3Cl intermediate. Keywords Dehydrochlorination Heterogeneous catalysis Lanthanum oxide Chlorinated ethanes Gas phase IR
1 Introduction With an annual production of 45 million tons, chlorine is one of the most important chemicals for numerous commercial products [1]. The reaction with chlorine activates hydrocarbons, making them suitable as building blocks for organic synthesis. Moreover, chlorinated hydrocarbons (CHCs) are used as organic solvents and are persistent, making them heatresistant and relatively inert. On the other hand, the same properties which make these compounds useful in industry make them harmful when emitted into the environment. In the last decades, it was found that CHCs contribute to various environmental effects, such as acid rain formation, ozone layer depletion and the greenhouse effect [2–4]. Also, many
A. W. A. M. van der Heijden A. J. M. Mens R. Bogerd B. M. Weckhuysen (&) Inorganic Chemistry and Catalysis Group, Department of Chemistry, Faculty of Science, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands e-mail: [email protected]
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CHCs are carcinogenic and toxic. Even though the better understanding of the effects of these substances has greatly reduced the use in commercial applications, they are still used and produced in large quantities in industry [5]. More than one third of all chlorine is used for the production of polyvinyl chloride (PVC), the most produced plastic in the world after polyethylene (PE) [1, 5]. C2H3Cl is the monomer of PVC and is industrially prepared from C2H4 and chlorine. C2H4 is chlorinated into 1,2-C2H4Cl2 via oxychlorination and direct chlorination described by Reaction Equations (1) and (2), respectively. 1,2-C2H4Cl2 is then thermally cracked into C2H3Cl as shown in Reaction Equation (3). The oxychlorination process is used to lower chlorine consumption by recycling HCl from the cracking of 1,2-C2H4Cl2, though selectivity towards 1,2C2H4Cl2 is lower than for the direct chlorination process. Overall, the reactions are performed at relatively high selectivity ([98%), but the scale of the process result in the formation of large quantities of by-products [6]. Various chlorinated C1 and C2 are formed in side- reactions and are separated from 1,2-C2H4Cl2 as the so-called light and heavy ends. R
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