Fabrication of β-Zeolite Nanocrystal Aggregates for the Alkylation of Benzene and Cyclohexene

Abstract

A dual-template strategy with poly(ethylene glycol) (PEG) and cetyltrimethylammonium bromide (CTAB) was employed to synthesize the β-zeolite nanocrystal aggregates with ultrafine and hierarchical structure (micropores combined with intra-mesopores and inter-mesopores), and the particle size of aggregates and the nanocrystal size of β-zeolites can be systematically tailored by tuning the molar ratios of CTAB/PEG. In the alkylation between benzene and cyclohexene, the β-zeolite nanocrystal aggregates synthesized in the presence of PEG exhibited outstanding activity and resistance to deactivation under harsh reaction conditions, and the lifetime of β-5C4P was extended by 4.3 times compared with the commercial nanosized βzeolite, indicating that the additional PEG played the role of crystal growth inhibitors to reduce the size of nanocrystals, which increased the amount of accessible external Brønsted acid sites and effectively enhanced the diffusion properties. The experimental data for the spent β-zeolites revealed that the deactivation of zeolites was attributed to the blocking of channels and the loss of active sites occurred due to the inevitable side reactions. In addition, the resultant β-zeolite nanocrystal aggregates also presented robust regeneration performance, which identified a facile and effective route to directly prepare β-zeolite nanocrystal aggregates with excellent catalytic properties in the alkylation of aromatics.

Production of Renewable p-Xylene from 2,5-Dimethylfuran and Ethylene over MWW Zeolite Catalysts

“…As reported in the literatures, , the band at ∼1545 cm –1 can be related to pyridine adsorption at Brønsted acid sites, and the band at ∼1455 cm –1 can be assigned to pyridine adsorption at Lewis acid sites. The band appearing at ∼1445 cm –1 can be attributed to pyridine H-bonded to OH groups on the surface of the material through the N atom. , Therefore, the adsorption peak at ∼1445 cm –1 should not be counted, and the Py-FTIR spectra were deconvoluted. The results are given in Table .…”

“…The Brønsted and Lewis acid properties were identified by Py-FTIR, as shown in Figure 3b and Table 1. As reported in the literatures, 39,40 the band at ∼1545 cm −1 can be related to pyridine adsorption at Brønsted acid sites, and the band at ∼1455 cm −1 can be assigned to pyridine adsorption at Lewis acid sites. The band appearing at ∼1445 cm −1 can be attributed to pyridine H-bonded to OH groups on the surface of the material through the N atom.…”

“…The band appearing at ∼1445 cm −1 can be attributed to pyridine H-bonded to OH groups on the surface of the material through the N atom. 39,40 Therefore, the adsorption peak at ∼1445 cm −1 should not be counted, and the Py-FTIR spectra were deconvoluted. The results are given in Table 1.…”

Morphology and Microstructural Optimization of Zeolite Crystals Utilizing Polymer Growth Modifiers for Enhanced Catalytic Application

“…al. reported that hierarchical β-zeolite nanocrystal aggregates with intra-mesopores and inter-mesopores could be fabricated by using PEG 2000 and cetyltrimethylammonium bromide (CTAB) as dual templates in the presence of tetraethylammonium hydroxide (TEAOH) [54]. They found that the morphology and porosity of the resulting β-zeolites could be adjusted by tuning the amount of PEG 2000.…”