The preparation of H3O+/NH4 + -β"-alumina by ion-exchange reactions from K+-β"-alumina in aqueous solutions and molten salts
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H3O+/NH4+ -β"-alumina was synthesized using K+-β"-alumina and two types of ion-exchange mediums, NH4NO3 aqueous solutions and molten NH4NO3 salts, by an ion-exchange reaction in an autoclave and a heating mantle, respectively. In the autoclave reaction, the potassium concentration of the K+-β"-alumina was varied among the [K2O] : [Al2O3] composition ratios of 1 : 4-1 : 8, and the concentrations of the NH4NO3 solution was chosen to be either 1M and 2M, depending on the experiment. Each ion-exchange reaction was carried out at 130, 150 or 180 oC for 2, 4, 6, 8 or 24 h under high pressure. In the heating mantle reaction, the ion-exchange reaction was performed at 180 oC or 200 oC for 2-48 h in molten NH4NO3 salts under atmospheric pressure. After repeating the preceding reaction 5 times with 5 hour re-reactions followed by washing, the highest ion-exchange rate achieved was 90% in the autoclave, and 98% in the heating mantle. The phase stability and phase transformation were analyzed by X-ray diffraction(XRD) and the ion-exchange rate was measured using an inductively coupled plasma(ICP).
Abstract
H3O+/NH4+ -β"-alumina was synthesized using K+-β"-alumina and two types of ion-exchange mediums, NH4NO3 aqueous solutions and molten NH4NO3 salts, by an ion-exchange reaction in an autoclave and a heating mantle, respectively. In the autoclave reaction, the potassium concentration of the K+-β"-alumina was varied among the [K2O] : [Al2O3] composition ratios of 1 : 4-1 : 8, and the concentrations of the NH4NO3 solution was chosen to be either 1M and 2M, depending on the experiment. Each ion-exchange reaction was carried out at 130, 150 or 180 oC for 2, 4, 6, 8 or 24 h under high pressure. In the heating mantle reaction, the ion-exchange reaction was performed at 180 oC or 200 oC for 2-48 h in molten NH4NO3 salts under atmospheric pressure. After repeating the preceding reaction 5 times with 5 hour re-reactions followed by washing, the highest ion-exchange rate achieved was 90% in the autoclave, and 98% in the heating mantle. The phase stability and phase transformation were analyzed by X-ray diffraction(XRD) and the ion-exchange rate was measured using an inductively coupled plasma(ICP).
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