Synthetic Zeolites Modified with Salts of Transition Metals in the Reaction of Chemisorption-catalytic Oxidation of Sulphur Dioxide by Air Oxygen

The effect of the nature and concentration of d-metal salts attached to synthetic zeolites NaA and KA on the kinetic and stoichiometric parameters of the chemisorption-catalytic oxidation of sulphur dioxide with air oxygen at ambient temperature was studied. It was found that the adsorption capacity of NaA zeolite relative to SO2 is 100 times higher than that of KA zeolite; the time of protective action of NaA and KA zeolites increases upon modification with transition metal salts and with an increase of their content in the compositions. It was shown that the formation of inner and outer sphere complexes and the relationship between them is determined by the nature and concentration of metal ions and by the nature of the carrier. It was proven that the chemisorption-catalytic process ends with the oxidation of SO2 to H2SO4.

Preparation of NaA Zeolite from High Iron and Quartz Contents Coal Gangue by Acid Leaching—Alkali Melting Activation and Hydrothermal Synthesis

In this study, NaA zeolite was successfully synthesized from coal gangue with high contents of iron and quartz as the main raw material. The results show that most iron ions can be removed from coal gangue after calcination at 700 °C for 2 h, leaching in hydrochloric acid with a mass fraction of 20% for 7 h and a liquid-solid ratio of 3.5:1. When m (acid leached residue of calcined gangue):m (Na2CO3) = 1.1 and melting at 750 °C for 2 h, the quartz and other aluminosilicates turn into nepheline, which dissolve in water. Finally, the optimum conditions of synthesis NaA zeolite are as follows: n(SiO2)/n(Al2O3) = 2.0, n(Na2O)/n(SiO2) = 2.1, n(H2O)/n(Na2O) = 55, aging at 60 °C for 2 h, and crystallization at 94 °C for 4 h. This shows that the high iron and quartz contents coal gangue can be used for the synthesis of NaA zeolite.

Novel preparation of low-cost support for NaA zeolite membrane by utilizing natural clay

The membrane support is the basis for the preparation and application of the zeolite membrane and its cost and properties directly determine the performance of the zeolite membrane as well as its industrial applications. In this paper, the direct synthesis of NaA zeolite membrane on a novel low-cost support via an in situ reaction by utilizing natural clay can enable a significant reduction in manufacturing costs. During the preparation of the support for the NaA zeolite membrane, additives, such as Al2O3, Al(OH)3 and AlF3, were combined with kaolin clay and used as alumina precursors. Using the resulting porous mullite support, the effects of the firing temperature on the permeability and pore structure of the support were investigated extensively. The results of the experiment showed that silica in the natural clay was reacted by the Al2O3 precursor additives, producing a needle-like mullite in situ that served as a rigid skeleton porous structure for the support. Thus, a network porous structure of the mullite support could be formed during sintering process. The prepared network porous structure mullite supports exhibited a high pure water permeance of 3324 L m2 h1 bar1, open porosity of 41.8% and a mean pore size of 1.36 µm which was ideal for the preparation of the NaA zeolite membrane.

The effect of guest cations on proton conduction of LTA zeolite

The as-synthesized NaA zeolite with the proton conductivity of 9.12 × 10−3 S cm−1 (80 °C, 100% RH) can show unique cations effects on proton conduction property with different guest cations substituted (e.g. Li+, K+, Mg2+, Ca2+ and Sr2+).