Zeolite RHO Synthesis Accelerated by Ultrasonic Irradiation Treatment

Abstract

In recent years, there are increasing interest on applying ultrasonic irradiation for the synthesis of zeolite due to its advantages including remarkable shortened synthesis duration. In this project, the potential of ultrasonic irradiation treatment on the synthesis of zeolite RHO was investigated. Ultrasonic irradiation treatment time was varied from 30 to 120 minutes for the synthesis of zeolite RHO. The zeolite RHO solid samples were characterized with X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and nitrogen adsorption-desorption analysis. The application of ultrasonic irradiation treatment in this study has accelerated the synthesis of zeolite RHO where the synthesis duration has been significantly shortened to 2 days compared to 8 days required by conventional hydrothermal heating without ultrasonic irradiation treatment. Highly crystalline zeolite RHO crystals in truncated octahedron morphology were successfully formed.

Modified Zeolite/Polysulfone Mixed Matrix Membrane for Enhanced CO2/CH4 Separation

“…Besides, a low intensity absorption peak identified at 794 cm −1 can be connected to Si-Al-O symmetrical stretching vibration. The characteristic absorption peak of double eight-ring external linkage in zeolite RHO was revealed at 588 cm −1 and 634 cm −1 [29,38]. As observed from Figure 5b for NH 2 -RHO, the absorption peak ranging from 3650-3200 cm −1 showed an increasing broadness compared to that of zeolite RHO.…”

“…The observed FTIR spectra differences between zeolite RHO and NH 2 -RHO are also indicated in Figure 5. As can be seen in Figure 5a for zeolite RHO, the FTIR spectrum portrayed a strong absorption peak in the range of 1250-950 cm −1 , which corresponds to Si-O and Al-O tetrahedra asymmetrical stretching vibration in the zeolite RHO particle [29,37]. Intense absorption peaks located in the range of 3650-3200 cm −1 and 1640 cm −1 indicated the presence of O-H stretching of adsorbed water molecules and O-H bending of lattice water in the zeolite RHO sample [38].…”

“…Zeolite RHO was synthesized by following the method reported in our previous work [29]. A precursor solution with molar composition of 3 Na SiO 2 : 110 H 2 O was prepared by dissolving sodium hydroxide in deionized water at room temperature.…”

Coarse-Grained Model for the Hydrothermal Synthesis of Zeolites

“…We expect the solvation strength ε to be much smaller than the strength of attraction between T particles, ε TT = 12.378 kcal mol –1 , and even weaker than the T and S attraction, ε TS = 1.6 kcal mol –1 . In next section, we tune ε to capture the demixing of a water-rich phase and a silica-rich phase in the synthesis mixture and the dehydration of the zeolite upon heating to ∼500–550 K. − …”

“…There are several effective routes for the preparation of zeolitic materials. − The most widely used is hydrothermal synthesis (HS). − In this route, tetraethylorthosilicate (TEOS) and an organic structure-directing agent (SDA), typically a tetraalkylammonium cation, are mixed in water under alkaline conditions in an autoclave at temperatures that typically range from 70 to 200 °C. ,,− HS of zeolites involves multiple processes: ,,− first, the polymerization of silica that leads to self-aggregation of silica and SDA species into amorphous aggregates; − second, the crystallization of the amorphous aggregates into zeolites; ,,,− and third, the growth of the zeolite crystals through a combination of oriented attachment of aggregates and the addition of monomers or oligomers to them. ,, Finally, the desorption of water from the pores of the zeolite with heat treatment. − Although different synthesis conditions and SDAs result in the formation of different crystal polymorphs, the processes of polymerization, crystal nucleation and growth, and water desorption are common to the HS of all zeolites.…”