SSZ-13 Crystallization by Particle Attachment and Deterministic Pathways to Crystal Size Control

Abstract

Many synthetic and natural crystalline materials are either known or postulated to grow via nonclassical pathways involving the initial self-assembly of precursors that serve as putative growth units for crystallization. Elucidating the pathway(s) by which precursors attach to crystal surfaces and structurally rearrange (postattachment) to incorporate into the underlying crystalline lattice is an active and expanding area of research comprising many unanswered fundamental questions. Here, we examine the crystallization of SSZ-13, which is an aluminosilicate zeolite that possesses exceptional physicochemical properties for applications in separations and catalysis (e.g., methanol upgrading to chemicals and the environmental remediation of NO(x)). We show that SSZ-13 grows by two concerted mechanisms: nonclassical growth involving the attachment of amorphous aluminosilicate particles to crystal surfaces and classical layer-by-layer growth via the incorporation of molecules to advancing steps on the crystal surface. A facile, commercially viable method of tailoring SSZ-13 crystal size and morphology is introduced wherein growth modifiers are used to mediate precursor aggregation and attachment to crystal surfaces. We demonstrate that small quantities of polymers can be used to tune crystal size over 3 orders of magnitude (0.1-20 μm), alter crystal shape, and introduce mesoporosity. Given the ubiquitous presence of amorphous precursors in a wide variety of microporous crystals, insight of the SSZ-13 growth mechanism may prove to be broadly applicable to other materials. Moreover, the ability to selectively tailor the physical properties of SSZ-13 crystals through molecular design offers new routes to optimize their performance in a wide range of commercial applications.

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

“…Table lists the physicochemical properties of SSZ‐13‐T and SSZ‐13‐TF samples, in which both have the Si/Al ratio around 17, which is characteristic of zeolite SSZ‐13 . The BET surface area of SSZ‐13‐TF microspheres is 623 m 2 g −1 , indicating that the SSZ‐13‐TF microsphere particles were well crystallized.…”

“…Templated SSZ‐13 crystals (denoted as SSZ‐13‐T) were prepared using conventional hydrothermal methods similar to procedures described by Rimer and others, with a molar composition of 20 choline chloride:10 Na 2 O:2.6 Al 2 O 3 :100 SiO 2 :4400 H 2 O. Differently in this study, aluminum isopropoxide and choline chloride were used as aluminum source and organic template, respectively.…”

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

“…Often it is desirable to tune crystal size or introduce mesoporosity in Lewis acid zeolites to allow better diffusion to and from active sites and decrease the chance of pore blockage owing to deposition of side products. To this end, Rimer et al (30,31) have shown that zeolite growth modifiers are capable of modulating zeolite crystal structure. Ouyang et al (32) show that delaminated Sn-DZ-1, an MWW framework material with Sn postsynthetically incorporated into surface-accessible sites, has higher activity for the BV oxidation of 5-bromo-2-adamontanone with H 2 O 2 than Sn-Beta.…”

Synthesis and crystal growth mechanism of ZSM-22 zeolite nanosheets

“…2a1). 21 Moreover, some nanorods with lengths in the micrometer scale are observed at the outer surface of those amorphous aggregates (Fig. 2a1, a2).…”