Abstract
Commercial silicoaluminophosphate molecular sieves (SAPO-34) received alkali treatment with either NaOH (0.2, 0.01, 0.005, or 0.001 M) or NH4OH (0.005 M). Treatment with NaOH (0.005 M) increased the water adsorption initial rate of SAPO-34 by 1.4-fold. The alkali treatment introduced Na+ adsorption sites into the SAPO-34. The desorption ratio (adsorption at 30°C and desorption at 100°C) was 88.2% higher than the original rate (84.3%). On the other hand, after alkali treatment of SAPO-34 using NH4OH (0.005 M), calcination resulted in the highest desorption ratio at 91.3%. When combined with calcination, alkali treatment with NH4OH introduced H+adsorption sites into SAPO-34, H+ adsorption sites feature low levels of interaction with water, which enhanced the desorption ratio, but decreased the initial adsorption rate. These results indicate that treating commercial SAPO-34 with 0.005 M NaOH enhances both the adsorption and desorption behaviors.
Highlights
In 1984, a novel class of oxide molecular sieves with a crystalline microporous framework, silicoaluminophosphates, was synthesized [1] [2]
Except for Z02-NaOH (0.2 M), these patterns are identical to that of a CHA structure in the literature [11]. These results indicated alkali treatment by the relatively lower NaOH concentration (
The present study examined the effects that alkali treatment (NaOH or NH4OH) exerts on commercial silicoaluminophosphate molecular sieves (SAPO-34)
Summary
In 1984, a novel class of oxide molecular sieves with a crystalline microporous framework, silicoaluminophosphates, was synthesized [1] [2]. These new materials possess properties of both zeolites and aluminophosphetes, which makes. Water diffusivity was enhanced for NaY zeolites via alkali treatment with 1 M of a NaOH solution. This concentration was too high, for the alkali treatment of ZSM-5 zeolites, and the concentration was decreased to an optimum of 0.2 M
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