Developments and structures of mesopores in alkaline-treated ZSM-5 zeolites

Abstract

ZSM-5 zeolites with SiO 2 /Al 2 O 3 molar ratio of 24 were treated in 0.05 M aqueous sodium hydroxide solution at 325 K in different periods. The samples were characterized by means of nitrogen adsorption at 77 K, field emission scanning electron microscopy, X-ray diffractometry, and Fourier transform infrared spectroscopy. Analysis of the experimental results showed that the alkaline treatment periods have influence on the developments and structures of mesopores in the alkaline-treated ZSM-5 zeolites. Alkaline treatment initially develops mesopores mainly from the boundary portion of MFI zeolites to the bulk, while prolonged treatment destroys the mesopores, and an optimum mesoporosity is obtained by the treatment for 1.5 h. On the other hand, crystallinities and short-range order in alkaline treated zeolites have remained virtually unchanged according to the examination from X-ray diffractometry and Fourier transform infrared spectroscopy.

Characterization of Acidity and Porosity of Zeolite Catalysts by the Equilibrated Thermodesorption of n-Hexane and n-Nonane

“…The micropore volumes determined for the acidic zeolites are slightly lower than the literature data of 0.16-0.17 cm 3 /g for ZSM-5 [4,17,18], 0.28-0.29 cm 3 /g for Fig. 5 Adsorption isobar of n-hexane on HZSM-5 (15) determined by averaging the integrated desorption and adsorption profiles and its temperature derivative (heating/cooling rate 5°C/min) Fig.…”

Modification of MOR by desilication treatments: Structural, textural and acidic characterization

“…This treatment has resulted in a promising methodology to produce extended mesoporosity in zeolites crystals, without impacting on the acidity [11]. In recent years, several publications on this subject have emerged, especially focused on MFI type zeolite, for which detailed studies of the effect of the experimental parameters on the mesoporosity development have been made [11][12][13][14].…”

Tannin-immobilized mesoporous silica bead (BT–SiO2) as an effective adsorbent of Cr(III) in aqueous solutions

“…In addition, the pore size distribution of BT-SiO 2 is mainly in the range of 8.0-20.0 nm and a major peak is located at 11.0 nm (Fig. 3 inserts), which suggests that most of the pores inside the BT-SiO 2 adsorbent are in mesoporous structure [34,35]. It is generally accepted that mesoporous adsorbent has much higher adsorption rate compared with corresponding microporous or nonporous adsorbent, because the permanent mesoporous structure provides adsorbates an easy access to the adsorption sites, and thus decreases the mass transfer resistance during adsorption process [36,37].…”