Ultrafast synthesis of AFX-Type zeolite with enhanced activity in the selective catalytic reduction of NOx and hydrothermal stability.

Shortening the synthesis time of SSZ-16 (AFX type) zeolite from several days to 2 h has been achieved using an ultrafast synthesis route involving N,N,N',N'-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium (TEBOP) as an organic structure-directing agent (OSDA) in a tubular reactor assisted by seed crystals. Recently, copper exchanged SSZ-16 has been looked upon as one of the few equivalents to SSZ-13 for the selective catalytic reduction of NOx with ammonia (NH3-SCR) from automobile exhausts. Hydrothermal stability is one of the crucial properties for any zeolites that compete for automobile applications. All the samples prepared were analyzed using sophisticated physio-chemical techniques and those prepared from TEBOP were subjected to SCR of NOx reactions. The rapid crystal growth induced by high synthesis temperature bestowed the ultrafast prepared SSZ-16 with high crystallinity and hydrothermal stability as well as enhanced SCR of NOx activity even when aged at 800 °C. Compared to 1,1'-(1,4-butanediyl)bis-4-aza-1-azoniabicyclo[2.2.2]octane dibromide (DABCO), TEBOP was found to be desirable as an OSDA for high crystallinity and hydrothermal stability.

Resolving the Framework Position of Organic Structure-Directing Agents in Hierarchical Zeolites via Polarized Stimulated Raman Scattering.

The direct synthesis of hierarchically intergrown silicalite-1 can be achieved using a specific diquaternary ammonium agent. However, the location of these molecules in the zeolite framework, which is critical to understand the formation of the material, remains unclear. Where traditional characterization tools have previously failed, herein we use polarized stimulated Raman scattering (SRS) microscopy to resolve molecular organization inside few-micron-sized crystals. Through a combination of experiment and first-principles calculations, our investigation reveals the preferential location of the templating agent inside the linear pores of the MFI framework. Besides illustrating the attractiveness of SRS microscopy in the field of material science to study and spatially resolve local molecular distribution as well as orientation, these results can be exploited in the design of new templating agents for the preparation of hierarchical zeolites.

Synthesis of New Microporous Zincosilicates with CHA Zeolite Topology as Efficient Platforms for Ion-Exchange of Divalent Cations.

There is growing interest to develop zeolite materials capable of stabilizing divalent cations such as Cu2+ , Fe2+ , and Ni2+ for catalytic applications. Herein the synthesis of a new microporous zincosilicate with CHA zeolite topology is reported for the first time, by particularly focusing on the mixing procedures of the raw materials to prevent the precipitation of zinc oxides/hydroxides and the formation of impurity phases. The obtained zincosilicate CHA products possess remarkably higher ion-exchange ability for catalytically useful, divalent cations, demonstrated here using Ni2+ as an example, compared to that of aluminosilicate and zincoaluminosilicate analogs. It is anticipated that these zincosilicate CHA materials can be an efficient platform for several important catalytic reactions. In addition, the present finding would provide a general guideline for effective substitution of other heteroatoms into the zeolite frameworks.

Synthesis of zeolites using highly amphiphilic cations as organic structure-directing agents by hydrothermal treatment of a dense silicate gel.

Silicalite-1 and siliceous *MRE zeolite were synthesized with a series of highly amphiphilic ammonium cations as organic SDAs. The relationship between the framework type and the chain length of the amphiphilic cation is explained in terms of the intermolecular N-N distance of the elongated SDA.