Distribution of Effective Ferrierite Active Sites for Skeletal Isomerization of n‐Butene to Isobutene

Abstract

In this study, the effective active sites of aged ferrierite(FER) were confirmed to be located in the 10‐membered ring (10‐MR) pore mouths by modification with ammonium hexafluorosilicate((NH4)2SiF6 )and long‐term experiments. Analysis of SiO2/Al2O3 ratios showed that aluminum atoms were selectively removed from the FER surface after the modification with (NH4)2SiF6. Comparison of the catalytic properties before and after modification showed that the catalytic activity of aged FER depended only on the amount of acid sites located in the 10‐MR pore mouths. Monitoring of the change in acid amount with reaction time and the difference between aged and deactivated FER showed that aged FER retained only weak acid sites, and its deactivation was caused by carbon deposition on the 10‐MR pore mouth acid sites. Therefore, the catalytic performance of FER can be improved by increasing the number of 10‐MR pore mouths.

Monomolecular mechanisms of isobutanol conversion to butenes catalyzed by acidic zeolites: Alcohol isomerization as a key to the production of linear butenes

“…The observed [linear alkenes]/[isobutene] ratio of alkenes formed as products of the isobutanol dehydration was found to be much higher compared to the equilibrium distribution (4.9 [10] and 3.2 [13] at 523 K versus 0.7 at equilibrium). These results may seem counterintuitive at first glance, as ferrierite is a very efficient catalyst for the skeletal isomerization of linear butenes to isobutene [14,15,16,17]. Thus, starting from alcohols or directly from the corresponding alkenes, selectivities are fully inverted.…”

Synthesis of Nano‐Hierarchical Ferrierite with Sole Template and Its Catalytic Application in n‐Butene Skeletal Isomerization

“…As we all know,catalytic performances of zeolite are closely related to its texture and acid properties.According to Table ,although S2 and SC had simlar HF , the Vext and Smes of S2 were significantly larger that these of SC,which indicated S2 was hierarchical FER ,but SC was traditional micropore FER .According to Figure , S2 and SC shown similar total acid amount because they had similar SiO 2 /Al 2 O 3 ratio(Table3), which leaded to that S2 and SC shown similar initial activity.Pyridine molecules can only adsorb on the outer surface and near the pore mouths of the 10‐MR channels under the conditions of low temperature and short‐term adsorption,So the results of PY‐IR were used to express acid amount located in 10‐MR mouths.According to Figure ,the acid amount located in 10‐MR pore mouths of S2 was much higher than SC because S2 had much more 10‐MR pore mouths because of its smaller crystal size(Figure ).According to the previous results about FER, the stable n ‐butene conversion depended directly on the acid amount located in 10‐MR pore mouths,therefore the stable n ‐butene conversion much higher than that of SC.…”

Molecular Views on Mechanisms of Brønsted Acid-Catalyzed Reactions in Zeolites

“…676 The behavior of the ferrierite zeolite was experimentally investigated in details in that respect, as a high selectivity (>80%, higher than the equilibrium distribution) for linear butenes starting from isobutanol was measured. 624,625 Conversely, it is known that ferrierite is a very efficient catalyst for the skeletal isomerization of linear butenes to isobutene (section 5.5), 436,442,692,693 which seems contradictory with the results obtained for isobutanol dehydration. It was moreover shown that in similar reaction conditions, butene isomerization is much slower than isobutanol dehydration.…”

“…On catalysts such as alumina, isobutanol dehydration produces exclusively the expected isobutene isomer. ,, However, variable yields of linear butenes are obtained with zeolite catalysts, that depend on the zeolite topology, and on operating conditions . The behavior of the ferrierite zeolite was experimentally investigated in details in that respect, as a high selectivity (>80%, higher than the equilibrium distribution) for linear butenes starting from isobutanol was measured. , Conversely, it is known that ferrierite is a very efficient catalyst for the skeletal isomerization of linear butenes to isobutene (section ), ,,, which seems contradictory with the results obtained for isobutanol dehydration. It was moreover shown that in similar reaction conditions, butene isomerization is much slower than isobutanol dehydration. , For all these reasons, the a posteriori isomerization of isobutene into linear butenes cannot explain the formation of linear butenes from isobutanol.…”