Yoo, K Kashfi, R Gopal, S Smirniotis, PG Gangoda, M Bose, RN 2024-01-21T08:38:45Z 2024-01-21T08:38:45Z 2021-09-01 2003-06-19 1387-1811 https://pubs.kist.re.kr/handle/201004/138460 Synthesis of ZSM-12 using tetraethylammonium bromide (TEABr) as the template was investigated. Among the various parameters that affect the crystallization of ZSM-12, aluminum content of the gel, OH-/SiO2 and TEA/SiO2 ratios were the important determinants. Systematic variations of these parameters revealed that the TEABr-assisted synthesis had many similarities to the synthesis using TEAOH template reported earlier, with the exception that the OH-/SiO2 ratios had to be maintained at lower values. Furthermore, the OH-/SiO2 ratios favorable for ZSM-12 formation lie in a very narrow range. The source of alkalinity also affected the rate of crystallization and the composition of the product. The crystallization was found to be faster and better incorporation of aluminum in the zeolite framework was obtained when NaOH was used to provide alkalinity rather than KOH. Successful synthesis of highly crystalline ZSM-12 samples with Si/Al ratio around 30 was achieved using a minimal amount of relatively inexpensive TEABr (TEA/SiO2 = 0.125). Aluminum-27 NMR spectroscopy unambiguously revealed that all aluminum atoms are incorporated in the zeolite framework in tetrahedral coordination. The NMR line-widths of aluminum signals of the calcined samples were significantly larger than those with template incorporated samples. Spin-lattice relaxation times, conventional and rotating frame, as well as magic angle spinning (MAS) cross-polarization data with variable contact time support that there is a significant proton reservoir in the aluminum framework. The NMR data indicate that many distorted tetrahedral sites are formed upon removal of the template and some of these sites contain Al-OH moieties. (C) 2003 Elsevier Science Inc. All rights reserved. English ELSEVIER SCIENCE BV MULTIPLE-QUANTUM MAS CROSS-POLARIZATION QUADRUPOLAR NUCLEI ZEOLITE-BETA VANADIUM-SILICATE SPECTROSCOPY ALUMINUM ALUMINOSILICATES RESOLUTION MECHANISM TEABr directed synthesis of ZSM-12 and its NMR characterization Article 10.1016/S1387-1811(03)00317-2 1 MICROPOROUS AND MESOPOROUS MATERIALS, v.60, no.1-3, pp.57 - 68 MICROPOROUS AND MESOPOROUS MATERIALS 60 1-3 57 68 scie scopus 000183748700006 Chemistry, Applied Chemistry, Physical Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Science & Technology - Other Topics Materials Science Article MULTIPLE-QUANTUM MAS CROSS-POLARIZATION QUADRUPOLAR NUCLEI ZEOLITE-BETA VANADIUM-SILICATE SPECTROSCOPY ALUMINUM ALUMINOSILICATES RESOLUTION MECHANISM ZSM-12 hydrothermal synthesis tetraethylammonium bromide (TEABr) template low Si/Al NMR characterization of ZSM-12 Al-27NMR relaxation times