Mordenite Nanorods Prepared by an Inexpensive Pyrrolidine‐based Mesoporogen for Alkane Hydroisomerization

Abstract

We report the synthesis of hierarchical mordenite zeolite nanorods in one step using inexpensive mono‐quaternary ammonium N‐cetyl‐N‐methylpyrrolidinium (C16NMP) as mesoporogen to the synthesis gel. The presence of a small amount of C16NMP results in the formation of 0.6–1 μm rods‐like crystals oriented along the c‐axis with a high mesoporous volume (0.12 cm3 g−1) and external surface area (∼90 m2 g−1) compared to bulk mordenite. Acidity characterization shows that the presence of C16NMP during mordenite formation leads to a redistribution of aluminum in the zeolite framework: the amount of Brønsted acid sites in the side‐pockets (8MR channels) is increased at the expense of those in the 12MR main channels. As these latter acid sites are the ones involved in the conversion of alkene intermediates in bifunctional hydroconversion of alkanes, an optimized hierarchical mordenite prepared with C16NMP displays a more ideal hydrocracking selectivity than bulk MOR prepared solely with sodium.

Mild dealumination of template-stabilized zeolites by NH4F

“…The starting material is a MOR zeolite prepared with a charged C 16 NMP (Ncetyl-N-methylpyrrolidinium cation) as the SDA. 42 The use of this amphiphilic SDA results in a hierarchical pore structure with potential benefits to catalysis. We demonstrated that, after loading of Pd nanoparticles, this zeolite shows improved performance in bifunctional n-hexadecane hydroconversion compared to bulk MOR zeolite because of a reduced amount of acid sites in the main 12-membered ring channels as well as the presence of mesopores.…”

“…A conventional MOR sample denoted as MOR-H (hierarchical) was synthesized according to the procedure described in our previous report. 42 The sample constituted a highly crystalline MOR zeolite with a Si/Al ratio of 9 (Fig. 10).…”

Hierarchically Porous (Alumino)Silicates Prepared by an Imidazole-Based Surfactant and Their Application in Acid-Catalyzed Reactions

“…An observed lattice distance of 1.33 nm is attributed to the [110] plane (Figure 13c, insert) and points to nanorods oriented parallel to the c -axis. 25,62,63 As discussed in our previous work, 25 the hydrophilic head group of the SDA molecule is likely located in the 8 MR side-pockets or at the interface between the 8MR and 12MR channels, while the hydrophobic tail is blocking crystal growth in the a - and b -directions.…”

“…The samples exhibited similar catalytic behavior, namely, a low selectivity to cracking products up to n -hexadecane conversion of 80% (Figure 12c), explained by the relatively weak acidity 25 of the amorphous materials (Table S4). The Pd/Com-ASA displayed a slightly “M-shaped” distribution of cracked product (Figure 12d), whereas the Pd/Al-LS sample showed a more symmetric distribution of cracked products at 50% conversion.…”

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

“…This last decrease caused a better hydrocracking selectivity since 12-MR acid sites are otherwise involved in the conversion of alkene intermediates. [274] In contrast to previous template-assisted methods, another synthesis strategy is possible, which falls under the concept of kinetic regulation. Herein, the hierarchical zeolite is synthesized without using a template, but by controlling the zeolite crystallization process so that a balance between nucleation and crystal growth is achieved.…”