Reaction at Interfaces: The Silicoaluminophosphate Molecular Sieve CAL-1
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- 作者：Heloise O. Pastore ; É ; rica C. de Oliveira ; Guilherme B. Superti ; Giorgio Gatti ; Leonardo Marchese
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：February 22, 2007
- 年：2007
- 卷：111
- 期：7
- 页码：3116 - 3129
- 全文大小：551K
- 年卷期：v.111,no.7(February 22, 2007)
- ISSN：1932-7455
文摘
This work reports on the study to determine the best synthesis conditions for the preparation of CAL-1, asilicoaluminophosphate with a chabazite-like structure, prepared from a lamellar aluminophosphate, ALPO-ntu (herein called ALPO-kanemite), and using hexamethyleneimine (HMI) as the structure directing agent(SDA). These studies showed that optimum reaction conditions to obtain CAL-1 depend on the concentrationof silicon desired in the structure. For low silicon concentrations, SiO2/Al2O3 
0.4, no set of adequateconditions was found; the samples prepared were always contaminated with the starting lamellar materials.At SiO2/Al2O3 molar ratios of 0.8 and 1.2, crystalline samples were obtained after 24 h. For siliconconcentrations still larger, an optimum set of reaction conditions could not be determined. The best samplewith SiO2/Al2O3 = 1.6 in the gel was obtained with HMI/Al2O3 = 1.5 only after 48 h of reaction time, andeven then, the crystallinity of the sample thus prepared was poor. The combination of 29Si magic-angle spinningNMR and in situ infrared spectroscopy indicated that, at CAL-1 samples with the lower amount of silicon(
Si = 0.21), protons are found either at the borders of silica patches/islands or inside the aluminosilicatedomains. Characterization showed that HMI was always accompanied by the n-butylammonium cation, theSDA for the ALPO-kanemite, and showed that larger amounts of HMI led to the contamination of the samples.A mechanism involving the full dissolution of ALPO-kanemite to serve as the reactant for the formation ofCAL-1 would not explain the different characteristics of this material in relation to SAPO-34, a structurallysimilar microporous molecular sieve obtained by hydrothermal synthesis of a gel precursor. Therefore, asmall range, molecular level rearrangement of the lamella of the ALPO-kanemite, brought up by the silicon,is proposed to explain the formation of this material.
0.4, no set of adequateconditions was found; the samples prepared were always contaminated with the starting lamellar materials.At SiO2/Al2O3 molar ratios of 0.8 and 1.2, crystalline samples were obtained after 24 h. For siliconconcentrations still larger, an optimum set of reaction conditions could not be determined. The best samplewith SiO2/Al2O3 = 1.6 in the gel was obtained with HMI/Al2O3 = 1.5 only after 48 h of reaction time, andeven then, the crystallinity of the sample thus prepared was poor. The combination of 29Si magic-angle spinningNMR and in situ infrared spectroscopy indicated that, at CAL-1 samples with the lower amount of silicon(Si = 0.21), protons are found either at the borders of silica patches/islands or inside the aluminosilicatedomains. Characterization showed that HMI was always accompanied by the n-butylammonium cation, theSDA for the ALPO-kanemite, and showed that larger amounts of HMI led to the contamination of the samples.A mechanism involving the full dissolution of ALPO-kanemite to serve as the reactant for the formation ofCAL-1 would not explain the different characteristics of this material in relation to SAPO-34, a structurallysimilar microporous molecular sieve obtained by hydrothermal synthesis of a gel precursor. Therefore, asmall range, molecular level rearrangement of the lamella of the ALPO-kanemite, brought up by the silicon,is proposed to explain the formation of this material.