Abstract
The synthesis of the ZSM-5 and beta zeolites in their nanosized form has been achieved by using simple alkyl-substituted mono-cationic cyclic ammonium cations as OSDA molecules. The particular combination of a cyclic fragment and a short linear alkyl-chain group (preferentially C4) within the monocationic OSDA molecules allows directing the crystallization of nanosized zeolites with excellent solid yields (above 90%). Interestingly, the formation of the nanosized ZSM-5 and beta zeolites mostly depends on the size and nature of the cyclic fragment of the OSDA molecule, resulting in all cases in nanocrystalline solids with homogeneous distributions of particle sizes (∼10-25 nm) and controlled Si/Al molar ratios (∼15-30). The achieved nanosized ZSM-5 and beta zeolites have been extensively characterized by different techniques to study their physico-chemical properties, such as chemical composition, pore accessibility or Brønsted acidity, among others. Moreover, the catalytic properties of the nanosized ZSM-5 and beta zeolites have been evaluated for different chemical reactions, including methanol-to-olefins (MTO) in the case of ZSM-5, and alkylation of benzene with propylene to obtain cumene and oligomerization of light olefins to liquid fuels in the case of beta, observing in all cases improved catalytic activity and product selectivity towards target products when compared to related catalysts.
Highlights
Zeolites are microporous crystalline materials with pores and cavities with uniform size and shape in the molecular range ($3–15 A), which can be prepared with different pore topologies, chemical compositions, and/or crystal sizes.[1,2] This large versatility has allowed their industrial implementation in diverse applications, including gas adsorption and separation, oil conversion, petrochemistry and for the preparation of chemicals and ne chemicals.[3,4,5] More recently, there has been a signi cant scienti c and commercial interest in the synthesis of zeolites for environmental purposes.[6]Some of the zeolite properties can be tuned during their preparation
The catalytic properties of the nanosized ZSM-5 and beta zeolites have been evaluated for different chemical reactions, including methanol-to-olefins (MTO) in the case of ZSM-5, and alkylation of benzene with propylene to obtain cumene and oligomerization of light olefins to liquid fuels in the case of beta, observing in all cases improved catalytic activity and product selectivity towards target products when compared to related catalysts
The synthesized nanozeolites clearly show a better catalytic performance, including both, catalyst lifetime and product selectivities towards the desired products, as compared to other related zeolites. These monocationic dual-function-based organic structure directing agent (OSDA) molecules that combine a cyclic fragment and a butyl alkyl group have been rarely explored in the literature for zeolite synthesis, and we believe that the results presented here could pave the way for a general and efficient synthesis approach to direct the crystallization of other nanosized zeolites by properly selecting the cyclic/alkyl groups
Summary
Zeolites are microporous crystalline materials with pores and cavities with uniform size and shape in the molecular range ($3–15 A), which can be prepared with different pore topologies, chemical compositions, and/or crystal sizes.[1,2] This large versatility has allowed their industrial implementation in diverse applications, including gas adsorption and separation, oil conversion, petrochemistry and for the preparation of chemicals and ne chemicals.[3,4,5] More recently, there has been a signi cant scienti c and commercial interest in the synthesis of zeolites for environmental purposes.[6]. The synthesized nanozeolites clearly show a better catalytic performance, including both, catalyst lifetime and product selectivities towards the desired products, as compared to other related zeolites These monocationic dual-function-based OSDA molecules that combine a cyclic fragment and a butyl alkyl group have been rarely explored in the literature for zeolite synthesis, and we believe that the results presented here could pave the way for a general and efficient synthesis approach to direct the crystallization of other nanosized zeolites by properly selecting the cyclic/alkyl groups
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