Oxidative Dehydrogenation of n -Butene to 1,3-Butadiene over Sulfated ZnFe 2 O 4 Catalyst
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Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene over Sulfated ZnFe2O4 Catalyst Howon Lee • Ji Chul Jung • In Kyu Song
Received: 7 October 2009 / Accepted: 13 October 2009 / Published online: 24 October 2009 Ó Springer Science+Business Media, LLC 2009
Abstract Oxidative dehydrogenation of n-butene to 1,3butadiene over sulfated ZnFe2O4 catalyst was carried out in a continuous flow fixed-bed reactor. The effect of sulfation on the catalytic performance of ZnFe2O4 was investigated. Sulfated ZnFe2O4 catalyst showed a better catalytic performance than ZnFe2O4 catalyst in the oxidative dehydrogenation of n-butene. Acid–base property of sulfated ZnFe2O4 catalyst was measured by TPD experiment, with an aim of correlating the catalytic performance with the surface acid–base property of the catalyst. It was revealed that the catalytic performance of sulfated ZnFe2O4 catalyst was closely related to the surface weak-acid density of the catalyst. The enhanced acidity of sulfated ZnFe2O4 catalyst was responsible for its high catalytic performance in the oxidative dehydrogenation of n-butene. Thus, sulfation served as an efficient method for improving catalytic performance of ZnFe2O4 in the oxidative dehydrogenation of n-butene. Keywords Zinc ferrite n-Butene 1,3-Butadiene Oxidative dehydrogenation Sulfated zinc ferrite
1 Introduction Oxidative dehydrogenation of n-butene has attracted much attention as a promising process for producing 1,3-butadiene [1–3]. A number of catalysts have been employed for the oxidative dehydrogenation of n-butene, including
H. Lee J. C. Jung I. K. Song (&) School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University, Shinlim-dong, Kwanak-ku, Seoul 151-744, South Korea e-mail: [email protected]
bismuth molybdate catalyst [4–7], vanadium-containing catalyst [8], Cu–Mo catalyst [9], and ferrite-type catalyst [10–13]. Among these catalysts, ZnFe2O4 catalyst has been recognized as the most efficient catalyst for the oxidative dehydrogenation of n-butene [14, 15]. Many attempts have been made to find major factors determining the catalytic performance in the oxidative dehydrogenation of n-butene [16–18]. Although fundamental reaction mechanism has not been clearly elucidated, many researchers agree that the oxidative dehydrogenation of n-butene to 1,3-butadiene over ZnFe2O4 catalyst follows the reaction mechanism by way of p-allyl-oxy intermediate based on the Mars–van Krevelen mechanism [18, 19]. Typical reaction mechanism for the oxidative dehydrogenation of n-butene over ferrite-type catalyst is shown in Fig. 1 [18, 19]. Reaction mechanism for the oxidative dehydrogenation of n-butene by way of p-allyl-oxy intermediate consists of six sequential elementary steps; (step 1) surface hydroxylation of lattice oxygen (in the presence of steam), (step 2) chemisorption of n-butene and activation of C–H bond, (step 3) abstraction of a-hydrogen from n-butene to form p-allyl-oxy intermediate, (step 4) abstraction of one more hydrogen from p-allyl-ox
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