SDA-Free Hydrothermal Synthesis of High-Silica Ultra-nanosized Zeolite Y

Abstract

Despite having been used in hydrocracking processes for decades, zeolite Y is still nowadays the subject of intense research aiming at improving its physicochemical properties. Here, and for the first time, the synthesis of zeolite Y nanocrystals prepared in organic template-free medium, featuring both extremely reduced dimensions (mean diameter below 30 nm) and a high silicon to aluminum ratio (Si/Al ≈ 2.2), is reported. The singularity of the protocol lies in the progressive adding of a silica source during synthesis combined with the use of prolonged aging times. These high-silica ultra-nanosized zeolite Y crystals display excellent textural properties (V micropore = 0.33 cm3/g and S BET = 830 m2/g), comparable to their microsized counterparts. In this work, the extensive study of the influence of various parameters (i.e., gel composition, aging time, and crystallization conditions) intended for the optimization of the synthesis protocol is also presented.

Template‐Free Synthesis of Hierarchical SSZ‐13 Microspheres with High MTO Catalytic Activity

“…Several aluminosilicate zeolites, including ZSM‐5, ECR‐1, Beta, Y, and EMT‐type molecular sieve, have been reported to be synthesized without organic templates. For example, Xiao et al .…”

Organic‐Free, ZnO‐Assisted Synthesis of Zeolite FAU with Tunable SiO2/Al2O3 Molar Ratio

“…[4] However,z eolite FAUi sn ormally synthesized with relatively low SiO 2 /Al 2 O 3 molar ratio and then, the interaction between CO 2 and the zeolitei st oo strong to desorbC O 2 .T o lessen the gas-solid interaction whilst maintain ag ood adsorption capacity,z eolite FAUw ith relatively high SiO 2 /Al 2 O 3 molar ratio is demanded. [7][8][9] Consequently, an attempt to challenge this SiO 2 /Al 2 O 3 molar ratio limit is significant both theoretically and practically. [5] Additionally,z eolites with different SiO 2 /Al 2 O 3 molar ratios are preferable for the separation of CO 2 /CH 4 mixtures with different feed pressures.…”

“…Thereinto, the organic-free methodu sually ensure zeolite FAUw ith SiO 2 /Al 2 O 3 molar ratio below 4, but difficult to guarantee ap roduct with higherS ic ontent. [7][8][9] Consequently, an attempt to challenge this SiO 2 /Al 2 O 3 molar ratio limit is significant both theoretically and practically.Conventionally,z eolite FAUw ith different SiO 2 /Al 2 O 3 molar ratio can be synthesized with the aid of either seeds, [10] or OSDAs such as TMAOH, [11] tetraethylammonium hydroxide (TEAOH), [12] and crown-ethers. [13] Besides,m uch attention has been paidt od esigning new OSDA in order to achieve a "hand-in-glove" fit between the template and zeolite pores.…”

“…Thereinto, the organic-free methodu sually ensure zeolite FAUw ith SiO 2 /Al 2 O 3 molar ratio below 4, but difficult to guarantee ap roduct with higherS ic ontent. [7][8][9] Consequently, an attempt to challenge this SiO 2 /Al 2 O 3 molar ratio limit is significant both theoretically and practically.…”

Hollow Y zeolite single crystals: synthesis, characterization and activity in the hydroisomerization of n-hexadecane

“…Low diffusivity increases the residence time of molecules in the porosity, which can dramatically influence the catalytic activity as well as selectivities, for example by favoring over-cracking reactions in acid-catalysis. Molecular transport in zeolite frameworks can be improved by decreasing the mean diffusion length, for example by working with crystals as small as possible [7][8][9][10]. However, nanometric crystals are not always easy to synthesize and, in the particular case of Y zeolite, they are generally less stable than the corresponding micrometric counterparts [9,11].…”