Synthesis of High-Silica Erionite Driven by Computational Screening of Hypothetical Zeolites

Abstract

A hypothetical zeolite framework was selected from a database of hypothetical structures and adapted based on structural features relevant for deNOx and MTO catalysis. To attempt the realization of this structure a computational energy-based approach was applied to select relevant OSDAs (organic structure directing agents) molecules with large OSDA-zeolite stabilization energies, leading to the selection of three OSDAs (OSDA1, OSDA2, OSDA3) as potential candidates for the synthesis of the hypothetical zeolite (Hypo#1). Instead of Hypo#1, ERI was found to dominate the experimental product outcome when potassium was used as a mineralizing agent. In the case of OSDA3 a novel high-silica ERI was found. The different ERI products were characterized, intergrowth structures ruled out, and special attention was paid to the compositional and morphological features arising from the use of the different OSDAs. In the specific high-Si product obtained using OSDA3 a distinct tubular to prismatic crystal morphology could be seen. Theoretical stabilization energies calculated for potentially competing phases (Hypo#1, ERI, OFF, CHA among others) could be used to rationaliz e the experimental outcome to a certain extent, but our results show that considering the zeolite-OSDA interaction is probably not sufficient to realize hypothetical frameworks alone, especially for Al-containing zeolites where alkali ions play an important role during crystallization.

Methanol-to-olefins catalysis on ERI-type molecular sieves: towards enhancing ethylene selectivity

“…The synthesis gel molar composition for what is denoted as ERI Zeolite-1 was 1 SiO 2 : 0.167 Al : 0.1 R(OH) 2 (OSDA 7) : 0.3 KOH : 20 H 2 O [66]. In a typical synthesis, using a FAU-type zeolite as a T-atom source, a mixture of OSDA 7 (butane-1,4-bis(trimethylammonium) dihydroxide; synthesis procedure outlined in the SI), NaOH, and DI water were stirred for 0.5 h. Then, Y zeolite (CBV712, Si/Al=6, Zeolyst) was added and this solution was stirred at room temperature for an additional 6 h. The gel was then placed in a Teflon-lined Parr reactor (23 cm 3 ) and heated in a static oven to 135 o C at autogenous pressure for 7 days.…”

“…Thus, the synthesis of phase-pure ERI-type zeolites over a wider range of Si/Al (up to ca. 13) and with different morphologies and particle sizes have now been reported [66][67][68]. We employ some of these OSDAs used to make ERI-type zeolites to synthesize SAPO-17 samples with higher Si/T without the presence of HF.…”

Structure–direction towards the new large pore zeolite NUD-3

“…3 The effort has been rewarded with a large increase in the number of zeolite topologies recognized as unique and viable by the International Zeolite Association (IZA) with a steady rate of over five new topologies accepted per year during the last 40 years. 4 However, it is still generally impossible to predict the target zeolite topology before the synthesis, even when the structural relationship among the various zeolite topologies and their "synthesis descriptors" are studied, 5 or when the SDA is selected by energy minimization calculations to target a specific topology, 6 although some few notable cases of success have been reported. 7 In occasions, a very small change in the SDA brings about a large change in the ability to produce one or another zeolite framework.…”

High Throughput Methods in the Synthesis, Characterization, and Optimization of Porous Materials

“…[33] Following the pioneering work by these groups and others, [23,29,31,[34][35][36] Newsam et al [37] noted the particular difficulty with zeolites in specifying which region of the compositional space to investigate. Even nearly two decades on, the translation between in silico zeolite design to a rigorous synthesis procedure is still difficult [38,39] as a reproducible one-to-one mapping of gel composition to a particular zeolite topology and composition remains elusive. Slight experimental variation can lead to significant and non-trivial effects on the resultant zeolite topology and composition, with the relationship between the contents of the gel and the final crystallized product being difficult to establish.…”

“…[38] Therefore, contemporary HT zeolite work focuses predominantly on a targeting or screening via computational methods prior to synthesis (see Section 3) with novel zeolite discovery through HTS, for example, becoming increasingly infrequent besides a few instances. [39,56] Beyond HTS, HTE focuses on optimization or the benchmarking of catalysts with this avenue similarly involving simulations to pre-screen and flag samples for further investigation. Such developments are to be expected, and indeed welcomed, due to continual increase in computational capabilities coupled with experimental unexplored phase regions increasing in complexity and dimensionality as time increases.…”