Mg²⁺-derived mesoporous ultra-high silica twelve-membered-ring basic zeolites: straightforward synthesis and catalytic performance

Abstract

Mg 2+ -derived mesoporous ultra-high silica twelve-membered-ring zeolites with multiple topologies (MOR, BEA and MTW) were straightforwardly synthesized by a one-pot route, where the crucial step was the cohydrolysis/condensation of silica source and magnesium salt under moderate acidic conditions. SiO 2 /Al 2 O 3 ratios can be adjusted from ∼30 to as high as 410, thus generating superior basicity that was further improved by the incorporation of Mg species. A mesoporous structure was self-formed without the assistance of any template or special strategy. Catalysis tests showed high activity of these zeolites in a typical base reaction, Knoevenagel condensation, even for the bulky substrates due to the enhanced mass transfer arising from the mesopores. This methodology provides a promising approach towards target synthesis of valuable Mg 2+ -derived mesoporous ultra-high silica zeolites with tunable acid/base properties, which can even act as an efficient mesoporous zeolitic solid base.

Synthesis and Characterization of Al-TON Zeolite Using a Dialkylimizadolium as Structure-Directing Agent

“…The XRD patterns of samples obtained in three and seven days in static were normalized (marked with *) for better visualization. These results show that when [C 4 MI]Cl is used as the structure-directing agent, the zeolite crystallizes faster, both in stirring and static modes and without aging the synthesis gel (however, in the IZA methodology, it is debatable whether the aging step is beneficial) 20 . This behavior could be explained by the strong interaction of the charge of the ionic liquid with the zeolitic charge imposed by aluminum, whereas the 1,8-diaminooctane possibly interacts by van der Waals forces, without compensating for the charges of the zeolite framework.…”

“…In addition to the molecular sieving, the presence of heteroatoms in different zeolitic structures may confer different properties to the zeolites, such as acidity, ion exchange, redox properties, among others. [3][4][5][6][7] Certain zeolites require organic molecules (organic structure-directing agent, OSDA) for their crystallization to be thermodynamically favorable, and several molecule groups have been studied. [8][9][10] Depending on the characteristics of these organic molecules (size, flexibility, and hydrophobicity), zeolites with different structural characteristics can be obtained.…”

“…This definition was recently expanded with the discovering of some special extra-large pore zeolites as, for example, ITQ-37 1 (a mesoporous chiral zeolite) and ITQ-43 2 (hierarchical meso-microporous zeolite), with pore size in the range of 2-4 nm. The zeolite structure is based on TO 4 units in which T (Si, Al, Ti, Ge, etc.) is coordinated to four oxygen atoms in a tetrahedral geometry.…”

Construction of Acid–Base Synergetic Sites on Mg‐bearing BEA Zeolites Triggers the Unexpected Low‐Temperature Alkylation of Phenol

“…[47,48] Am ore significant shift of the O1sa nd Si 2p signals occurs for Mgb(50) than for Mg (im) -b and Mg (ex) -b,s uggesting that in situ incorporated Mg species favors more negative Os pecies, in accordance with our previous observations. [49,50] The basicity of zeolitesi sc losely related to the negativity of Os peciesa nd more negative Os pecies usuallym ean enhanced basicity. [45] In the CO 2 temperature-programmed desorption( TPD) curves, the Mgb(n)s amples demonstrate three CO 2 desorption peaks in the ranges of 110-130 8C, 270-300 8C, and 500-520 8C, respectively identifiedt ot he weak, medium, and strong basic sites (Figure2C).…”

Synthesis of titanosilicate pillared MFI zeolite as an efficient photocatalyst

“…[6][7][8] Inclusion of the mesoporosity to the microporous zeolites, i.e., synthesis of hierarchical meso-/microporous zeolites, is a strategy to improve the catalyst utilization by promoting active site accessibility and mass transport for reactions involving bulky molecules. 7,[9][10][11] Different methods have been developed to create hierarchical meso-/microporous zeolites during the past decade. [12][13][14][15][16][17] Synthesis of two-dimensional (2D) layered zeolites followed by pillaring of the resulted 2D structures is an example of these synthesis methods.…”