Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene Over ZnMeIIIFeO4 Catalysts: Effect of Trivalent Metal (MeIII)

Abstract

ZnMe III FeO 4 catalysts with different trivalent metal (Me III = Fe, Al, Cr, Mn, and Co) were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. Successful formation of ZnMe III FeO 4 catalysts was confirmed by XRD and ICP-AES analyses. Catalytic performance of ZnMe III FeO 4 catalysts in the oxidative dehydrogenation of n-butene strongly depended on the identity of trivalent metal (Me III ). Acid properties of ZnMe III FeO 4 catalysts were measured by NH 3 -TPD experiments, with an aim of correlating the catalytic performance with the surface acid property of the catalysts. It was revealed that yield for 1,3-butadiene increased with increasing surface weak-acid density of ZnMe III FeO 4 catalyst. Among the catalysts tested, ZnFeFeO 4 catalyst with the largest surface weak-acid density showed the best catalytic performance in the oxidative dehydrogenation of n-butene.

Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene over Sulfated ZnFe2O4 Catalyst

“…This means that surface acid-base property of ZnFe 2 O 4 catalyst plays a very important role in the oxidative dehydrogenation of n-butene. It has been reported in our previous works [11,19,21,25,26] that the catalytic performance of ZnFe 2 O 4 catalyst in the oxidative dehydrogenation of n-butene was closely related to the surface acid density of the catalyst.…”

“…1 Typical reaction mechanism for the oxidative dehydrogenation of n-butene over ferrite-type catalyst [18,19] impregnated sample was dried overnight at 100°C, and then it was calcined at 470°C for 1 h to yield the sulfated ZnFe 2 O 4 catalyst. The sulfated ZnFe 2 O 4 catalyst was denoted as ZnFe 2 O 4 (X), where X represents the molar concentration of ammonium sulfate solution used for sulfation.…”

“…are reduced to Fe 2? [18,19]. Furthermore, two Fe cations serve as an essential weak-acid center where acid-base interaction (formation of p-bonding or activation of C-H bond) occurs [22].…”

“…Although fundamental reaction mechanism has not been clearly elucidated, many researchers agree that the oxidative dehydrogenation of n-butene to 1,3-butadiene over ZnFe 2 O 4 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.…”

“…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-oxy intermediate to form 1,3-butadiene, (step 5) desorption of 1,3-butadiene, and (step 6) dissociation of oxygen on the gas phase to make up oxygen vacancy in the catalyst and reoxidation of multivalent cations [16,20,21].…”