Skeletal Isomerization of 1-Butene on 10-Member Ring Zeolite Catalysts

Shape Selectivity of HFER Zeolites as Responsible for the Positive Effect of Their Si/Al Ratio on the Selectivity to n-Butene Isomerization into Isobutene

“…In particular, the selectivity to isobutene of the fresh samples is generally poor and a high selectivity can be obtained only after a partial deactivation caused by the trapping of heavy products within the zeolite micropores. Over the fresh HFER sample, propene and pentenes are the main by-products, which is typical of a bimolecular mode of n-butene transformation, actually a mechanism involving successively n-butene dimerization, octene isomerization then cracking [6][7][8][9][10][11][12][13][14][15]. 13 C labelling experiments confirm the predominance of this bimolecular mechanism [16][17][18].…”

“…A large variety of catalysts based on alumina [1][2][3][4][5] or on medium pore size zeolites [6][7][8][9][10][11][12] have been found as active and selective for the skeletal isomerization of nbutene. However, the best catalyst seems to be the protonic form of ferrierite (HFER); indeed, this zeolite is capable of operating in the absence of water at relatively low temperature (623 K) with a high selectivity to isobutene and a high stability.…”

Investigations into the origin of the remarkable catalytic performance of aged H-ferrierite for the skeletal isomerization of 1-butene to isobutene

“…First, a recent series of studies by van Donk et al [17,36,40,41] has shown that the 10-ring pore mouth inlets of aged H-FER are still accessible for 1-butene molecules, even in the case of deposition of high amounts (e.g., 6.8 wt%) of coke in the zeolite pores. Second, pore mouth shape selectivity allows us to explain the data of O'Young et al [42] wherein H-FER is more selective than ZSM-23, despite the fact that the free diameter (5.2 Å) at the FER channel intersection is slightly larger than that (4.8 Å) of 10-ring channels in ZSM- 23. Third, we found that the isomerization activities of two H-FER zeolites with similar Si/Al ratios but notably different crystal sizes and thus different numbers of 10-ring pore mouths per unit weight are significantly different from each other (see below).…”

The Distribution and Strength of Brönsted Acid Sites on the Multi-Aluminum Model of FER Zeolite: A Theoretical Study

“…Due to its prominent pore structure and Brönsted acidity, it has been proved to be an efficient catalyst for butene isomerization [8,9]. Extensive experimental and theoretical studies have been performed to understand the underlying origin of the high reactivity of FER [8][9][10][11]. Although it is generally believed that the Brönsted acid site is the active site for the isomerization process and that the unique pore structure plays an important role in the reactivity, the properties of the catalyst, such as the acid strength, acid density, and the location of the acid sites and their effect on the reactivity are still unclear in the literature.…”

“…Furthermore, FER zeolite is also reported to exhibit high selectivity and stability for isomerization reactions, which has been attributed to its specific pore structure and mild acidity [21]. The effect of the pore structure on reactions has been studied in detailed [11,22], but the influence of the various local configurations on Brönsted acid sites has been mentioned rarely. Therefore it is necessary to study the distribution of different amount of Al atoms and the acid strength of Brönsted acid sites in FER zeolite.…”