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

Abstract

Abstract:One of the fundamental issues in catalysis is to identify the catalytic active site. Due to its prominent pore topology and acidity, ferrierite (FER) zeolite has attracted extensive interest in various catalytic reactions such as isomerization of butenes. However knowledge on the active Brönsted acid site is still absent. In the present study, we perform extensive density functional theory calculations to explore the distribution and strength of the Brönsted acid sites and their potential catalytic activity for the double-bond isomerization of 1-butene to 2-butene. We employ a two-layered ONIOM scheme (our Own N-layered Integrated molecular Orbital + molecular Mechanics) to describe the structure and energetic properties of FER zeolite. We find that the hydrogen bond could improve the stability of Brönsted acid sites effectively, and, as a result, Al4-O6-Si2 and Al4-O-(SiO) 2 -Al4 are the most stable sites for 1-Al substitution and 2-Al substitution, respectively. We further find that the Brönsted acid strength tends to decrease with the increase of Al contents and increase when the distance between the Al atoms is increased in 2-Al substitution. Finally it is demonstrated that the strength of acid sites determines the catalytic activity for the double bond isomerization of 1-butene to 2-butene.

New trends in improving gasoline quality and octane through naphtha isomerization: a short review

“…However, due to their lower activity, they are operated at a higher temperature [19]. Ferrierite (FER) zeolite catalyst has noticeable pore size and acidity, thus involved in various catalytic reactions such as isomerization of butenes [2,20]. Table 4 shows the maximum tolerances of contaminants like sulfur, water, C 7 + , and benzene bearing on the catalyst [8].…”

Advances in the Synthesis of Ferrierite Zeolite

“…Since the first synthetic preparation of FER zeolites in the 1960s, many efforts have been made in the synthesis and modification of FER zeolites in the past decades considering the important industrial application of FER zeolite in skeletal isomerization of n-butene. Therefore, FER zeolites with different elementary composition, morphology, hierarchical structure, acid strength, and catalytic properties have been successfully prepared using different synthesis methods [12,[19][20][21][22][23][24][25].…”