Direct Synthesis of Nano‐Ferrierite along the 10‐Ring‐Channel Direction Boosts Their Catalytic Behavior

Abstract

Ferrierite zeolites with nanosized crystals and external surface areas higher than 250 m 2 ·g -1 have been prepared at relatively low synthesis temperature (120ºC) by means of the collaborative effect of two Organic Structure Directing Agents (OSDA). In this way, hierarchical porosity is achieved without the use of post-synthesis treatments that usually involve leaching of T atoms and solid loss. Adjusting the synthesis conditions it is possible to decrease the crystallite size in the directions of the 8-and 10-ring channels, [010] and [001] respectively, increasing the number of pores accessible and reducing their average pore length to 10-30 nm. The small crystal size of the nano-ferrierites results in an improved accessibility of reactants to the catalytic active centers and enhanced product diffusion, leading to higher conversion and selectivity with lower deactivation rates for the oligomerization of 1-pentene into longer-chain olefins.Zeolites are microporous silico-aluminates with crystalline structures presenting well defined channels and cavities of molecular dimensions, [1] widely employed as adsorbents, ion exchangers and for gas separation or refining, petrochemical and environmental catalytic applications [2] due to their molecular sieve and shape selectivity effects [3] . Nevertheless, based on confinement effects, a new concept and methodology for the "Ab initio" synthesis of zeolites for preestablished catalytic reactions has been reported very recently [4] . In processes dealing with bulky molecules, their microporous structure may impose diffusional problems and underuse of the overall micropore volume, directly affecting activity, selectivity and deactivation rate. Among the different approaches proposed to increase the accessibility to the zeolites active sites [5] , the generation of inter-crystalline mesoporosity by reducing the crystallite size from the micro-to the nanoscale [5d, 6] has been thoroughly explored in the last years.Ferrierite [FER] is a zeolite with a bidirectional microporous structure formed by interconnected medium (10-ring, 4.2 x 5.4 Å) and small (8-ring, 3.5 x 4.8 Å) pores. Along the 8-ring channels a cavity is formed, accessible only through 8-ring windows, and known as the FER cage [7] . This zeolite, highly stable towards thermal, hydrothermal and chemical treatments, has been applied as catalyst in different processes, such as isomerization of n-butenes [8] and others [9] .Although highly selective, the topology and pore dimensions of ferrierite limits the reaction to the active sites closer to the crystal surface and results in fast deactivation due to pore blocking with coke precursors. One possible solution would be to decrease the diffusional path lengths. Thus, a delaminated FER, ITQ-6, was obtained by delamination of a layered precursor (PREFER) [10] , following a procedure similar to the one used for preparing zeolite ITQ-2 [6] . When efficiently delaminated, ITQ-6 is highly active for the conversion of bulky reactants [10b] due to its high external sur...

Advances in the Synthesis of Ferrierite Zeolite

“…The long carbon chain in the surfactant limited the crystal growth of FER zeolites along three dimensions, and thus produced the aluminosilicate FER nanocrystals with sizes in the range of 10-20 nm ( Figure 4A). Because of the reduction of crystal size along the [001] direction, the access to Brønsted acid sites increased, which enhanced its catalytic activity as well as lifetime in oligomerization of 1-pentene to liquid fuels reaction ( Figure 4B) [7]. Very similarly, Xu et al reported a successful size control strategy of aluminosilicate FER zeolite by adding cetyltrimethyl ammonium bromide (CTAB) into the synthesis system containing Pi as the organic template.…”

“…Zeolites are crystalline microporous materials which have been widely applied on an industrial scale in heterogeneous catalysis, adsorption, separation and ion exchange in the past decades [1][2][3][4][5]. Among them, Ferrierite (FER) zeolite is one of the industrialized types, which has excellent catalytic properties in skeletal isomerization of n-alkene, methanol to olefin, N 2 O decomposition, CO 2 hydrogenation, dehydration of methanol or ethanol, dimethyl ether carbonylation, and so on [6][7][8][9][10][11][12][13][14][15][16].…”

Advances in the synthesis and application of the SSZ-39 zeolite

“…In order to enhance mass transfer, great efforts have been made for improving mass transfer in SSZ-39 zeolites such as generation of mesoporosity and preparation of SSZ-39 nanocrystals. 5,45–54…”

Preparation of Aluminosilicate Ferrierite Zeolite Nanosheets with Controllable Thickness in the Presence of a Sole Organic Structure Directing Agent

“…FER zeolite is a medium-pore zeolite containing 10-Membered Ring (10-MR) channels (0.42 × 0.54 nm) in the [001] direction and 8-MR channels (0.35 × 0.48 nm) in the [010] direction [25][26][27][28][29][30][31]. Aluminosilicate FER zeolite, which is represented by ZSM-35, shows distinguished catalytic performances in many reactions, such as skeletal isomerization, high-olefin catalytic cracking, carbonylation of dimethyl ether, methanol to olefins, and NO x reduction [25,26,[32][33][34][35][36][37][38][39][40] To further enhance the catalytic performance, the preparation methods for aluminosilicate FER zeolites with controllable morphology and crystal sizes are particularly attractive. Corma et al prepared FER nanocrystals with sizes of 10-20 nm using piperidine and surfactant as dual templates [25].…”

“…Aluminosilicate FER zeolite, which is represented by ZSM-35, shows distinguished catalytic performances in many reactions, such as skeletal isomerization, high-olefin catalytic cracking, carbonylation of dimethyl ether, methanol to olefins, and NO x reduction [25,26,[32][33][34][35][36][37][38][39][40] To further enhance the catalytic performance, the preparation methods for aluminosilicate FER zeolites with controllable morphology and crystal sizes are particularly attractive. Corma et al prepared FER nanocrystals with sizes of 10-20 nm using piperidine and surfactant as dual templates [25]. Meanwhile, FER nanoneedles with a diameter of 10 nm were developed by adding choline as an organic template [41].…”