Surface grafting of FAU/EMT zeolite with (3-aminopropyl)methyldiethoxysilane optimized using Taguchi experimental design

Abstract A series of experiments was conducted to determine optimum conditions for grafting 3-aminopropylmethyldiethoxysilane (APMDES), on structure directing agent (SDA)-free FAU/EMT zeolite using isopropanol (IPA) as solvent to make proper fillers for use in mixed matrix membranes. A Taguchi experimental design L 9 orthogonal array (OA, four factors in three levels) was employed to evaluate effects of temperature ( T : 25, 65, 85 °C), reaction time ( t : 6, 16, 24 h), ratio of APMDES to zeolite (Sil/Zl: 1, 4, 8 ml/g) and ratio of IPA to zeolite (Sol/Zl: 50, 125, 200 ml/g) on the percentages of amine-grafted on zeolite, BET surface area as well as equilibrium isotherm of CO 2 adsorption. In optimizing grafting reaction parameters, a trade-off between percentages of amine-grafted on zeolite and capacity of CO 2 adsorption was needed. Indeed, samples having higher grafted amine exhibited lower CO 2 adsorption capacity, and vice versa. Hence, a grafting index was defined as the product of CO 2 uptake and grafted aminosilane content and used as the response. The obtained results showed that increasing reaction temperature, reaction time and Sil/Zl ratio improved grafting index; however, this index is decreased with increasing Sol/Zl ratio. Analysis of variance (ANOVA) showed that all parameters had significant effects on the response. Sil/Zl ratio and reaction temperature were the most and the least influential factors, respectively.

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