Synthesis and catalytic properties of ZSM-5 zeolite with hierarchical pores prepared in the presence of n-hexyltrimethylammonium bromide

Abstract

Graphical AbstractZSM-5 zeolites with hierarchical pores have been synthesized with n-hexyltrimethylammonium bromide and exhibited superior catalytic performance than the microporous zeolite.ZSM-5 samples with hierarchical pores (macropores, mesopores and micropores) were synthesized in the presence of nhexyltrimethylammonium bromide (HTAB) and tetrapropylammonium hydroxide (TPAOH). The effect of the synthesis conditions including Si/Al ratio, crystallization temperature and time, and the amount of HTAB added to the synthesis system on the final products was examined. The catalytic properties of the hierarchical zeolite were investigated in reactions of Claisen-Schmidt condensation of benzaldehyde and acetophenone, self-condensation of cyclohexanone and methanol conversion. The hierarchical zeolite exhibits superior catalytic performance in Claisen-Schmidt condensation of benzaldehyde and acetophenone, self-condensation of cyclohexanone and has a remarkably high selectivity to dimethyl ether in the methanol conversion reaction at relatively low temperatures, which was attributed to the fast mass transport in the three-dimensional hierarchical pore network. A cooperative assembly mechanism accounting for the formation of the hierarchical zeolite was proposed based on experimental results.

Fibrous silica mesoporous ZSM-5 for carbon monoxide methanation

“…The decrease of both signals in FmZSM-5 may be due to the presence of partial dealumination and the occurrence of the crystallization process. On the other hand, 29 Si MAS NMR spectra of RmZSM-5 and FmZSM-5 exhibited one main signal (at -114 ppm) typically observed for (≡SiO)4Si species, evidencing the highly structured framework and high crystallinity of the ZSM-5 zeolite [15]. Additionally, a weak shoulder signal at -100 ppm was observed, which assigned for (≡SiO)3Si species.…”

In-Situ Synthesis and Characterization of Biodegradable Estolides via Epoxidation from Canola Biodiesel

“…A mesoporous catalyst is favorable for large molecules like epoxidized canola biodiesel and is anticipated to increase the estolide formation via an oxirane ring opening followed by esterification. Earlier studies [11] disclosed that beyond the Si/Al ratio of 32 in the prepared catalysts indicated the decrease in total pore volume; therefore, in the present study, Si/Al ratio was maintained as 32. Presence of pentasil groups in the catalyst is indicated by the IR band ( Figure 2 Figure 3 shows the NH3-TPD profile of aluminosilicates catalyst.…”

“…The moderate and high-intensity desorption regions between the temperatures 300-440 • C and 440-560 • C are due to moderate and strong acidic sites, respectively ( Table 2). The wider desorption peak in the lower intensity area indicates that the zeolite has a higher useful group of weak surface acidic sites [11,15,16]. The XRD pattern of the catalyst is presented in Figure S1.…”

Strategies to Enhance the Catalytic Performance of ZSM-5 Zeolite in Hydrocarbon Cracking: A Review

“…The mesopore diameters can be facilely adjusted from 2 nm to 20 nm by changing the chain length of amphiphilic organosilanes [85]. Bai et al [72] prepared scroll-like ZSM-5 zeolite with micropores, mesopores and macropores by layer-by-layer wrapping of zeolite nanosheets with the assistance of n-hexyltrimethylammonium bromide (HTAB). A coulombic interaction existing between HTAB and the negatively charged aluminosilicate species stabilized the zeolite nanoparticles by decreasing their surface free energy, and facilitates the formation of hierarchical ZSM-5 zeolite at short crystallization time.…”