Synthesis of Hierarchically Porous Zeolite Composites with Enhanced Catalytic Activity: Effect of Different Long-Chain Structure Directing Agents

Abstract

A two-section temperature strategy was employed to achieve micromesoporous composites with five kinds of long-chain alkyl quaternary ammonium salts as single template. Zeolites with an ordered twodimensional hexagonal mesopore and crystallized MFI domain were successfully obtained. Gemini quaternary ammonium salt surfactants C 18 N 2 and C 22 N 2 are effective in directing the structure of MCM-41 than CTAB at 100 °C and will transform to lamellar MFI structures at 150 °C gradually. While single quaternary ammonium salts C 18 N and C 22 N direct lamellar M41s at 100 °C and transform to mesoporous structure at a higher temperature of 150 °C, it is possible to get a composite of microporous and mesoporous material with a surface area as high as 1046 m 2 g −1 . Catalytic performance of typical hierarchical zeolites was evaluated by Claisen-Schmidt condensation of bulky reactants. The excellent conversion suggested the synergy effects of improved large molecule diffusion in mesopores and highly separated MFI domains as catalytic centers in the hierarchical zeolites, which can be explained by an appletree model.

Claisen‐Schmidt Condensation using Green Catalytic Processes: A Critical Review

“…These micro/mesoporous composites with high surface area around 1046 m 2 g −1 were also synthesized by Gemini quaternary ammonium salt surfactants such as C 18 N and C 22 N 2 that are more effective than CTAB in MCM‐41 structure directing. C 22 N 2‐3‐2 (49) catalyst gave 80 % conversion and 60 % selectivity of flavanone and 34 % selectivity of chalcone under the same reaction conditions within 12 h. (Scheme ) . Later in 2019, hierarchical MFI/MCM‐41 composites synthesized by a one‐step hydrothermal method using C 22‐6 N as single structure directing agent was reported.…”

“…C 22 N 2-3-2 (49) catalyst gave 80 % conversion and 60 % selectivity of flavanone and 34 % selectivity of chalcone under the same reaction conditions within 12 h. (Scheme 12). [143] Later in 2019, hierarchical MFI/MCM-41 composites synthesized by a one-step hydrothermal method using C 22-6 N as single structure directing agent was reported. HMCs synthesized using C 22-6 N as template with different reaction time in days were designated as HMC-4, HMC-6 and HMC-10.…”

“… Hierarchical aluminosilicate zeolite as acid catalyst for condensation of benzaldehyde with 2‐hydroxyacetophenone …”

“…Hierarchical aluminosilicate zeolite as acid catalyst for condensation of benzaldehyde with 2-hydroxyacetophenone. [143] Scheme 13. trans-Chalcones synthesis catalysed by using clayMontmorillonite KSF. [80] clinoptilolite and applied in CSC reactions for chalcones synthesis.…”