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„µ¦—¼—Ž´Â°¤Ã¤Áœ¸¥œÃ‡¦Š¦oµŠŽ¸Ã°Å¨˜rœ·— H-ZSM-5 ×¥¦³Á¸¥ª·›¸ ONIOM
The Adsorption of Ammonia on the H-ZSM-5 Zeolite: an ONIOM Study
¥³Ã„p³ µÁ¦È¤—µÁ³1* ¨³°»¬µ °o œš°Š2
Yako Karemdabeh1* and Usa Onthong2
š‡´—¥n °
„µ¦«¹„¬µ„µ¦—¼ —Ž´Â°¤Ã¤Áœ¸¥œÃ‡¦Š¦o µŠŽ¸Ã°Å¨˜rœ·— H-ZSM-5 Áž}œ˜´ ª—¼—Ž´—oª¥ª·›¸„µ¦‡Î µœª–
šµŠÁ‡¤¸‡°¤¡·ªÁ˜°¦r ץčo ¦³Á¸¥ª· ›¸ ONIOM ‡Îµœª– Hartree-Fock (HF) ¨³ Density Functional Theory
(DFT) š¸É ¦³—´„µ¦‡Î µœª– HF/6-31G(d,p) ¨³ B3LYP/6-31G(d,p) ¤¸‡nµ¡¨´ŠŠµœ„µ¦—¼—Ž´ (adsorption energy)
Ášnµ„´ -16.18, -17.06 kcal/mol Î µ®¦´Â‹Îµ¨°Š 5T-quantum cluster ¨³ 12T ONIOM2 model (T= tetrahedron)
¤¸‡nµ¡¨´ŠŠµœ„µ¦—¼—Ž´ (adsorption energy) Ášnµ„´ -23.59, -24.41 kcal/mol ˜µ¤¨Îµ—´ ץ°¤Ã¤Áœ¸¥‹³™¼„ H-
ZSM-5 ަØÁœ˜š¸É°³˜°¤ÅœÃ˜¦Á‹œ °ŠÂ°¤Ã¤Áœ¸¥ n ŠŸ¨Ä®o°³˜°¤ÅœÃ˜¦Á‹œ¤¸ ‡ªµ¤®œµÂœnœ °Š°·Á¨È„˜¦°œ
¨—¨Š ‹µ„„µ¦‡Îµœª–œ´œ»œªnµŽ¸ ðŨ˜rœ·— H-ZSM-5 µ¤µ¦™—¼—°¤Ã¤Áœ¸¥Å—o Ž¹ÉŠŸ¨„µ¦‡Îµœª–š¸Éŗo¤¸‡ªµ¤
°—‡¨o°Š„´ Ÿ¨„µ¦š—¨°Š
‡ÎµÎµ‡´ : „µ¦—¼—Ž´ Á‡¤¸‡°¤¡·ªÁ˜°¦r Ž¸Ã°Å¨˜rœ·— H-ZSM-5
Abstract
An ONIOM (Our-own-N-layered Integrated molecular Orbital + molecular Mechanics) method has been
employed to investigate the interaction of ammonia on H-ZSM-5 zeolite using Hartree-Fock (HF) and density
functional theory (DFT) approaches. Full optimization of all clusters and their complexes were optimized at HF/6-
31G(d,p) and B3LYP/6-31G(d,p) theoretical levels. The adsorption energy of NH3 on H-ZSM-5 calculated by the
5T quantum cluster is -16.18, -17.06 kcal/mol, whereas, the 12T ONIOM2 model gives the adsorption energy of
-23.59, -24.41 kcal/mol, respectively. The reaction mechanism of ammonia on H-ZSM-5 is found to bound to the
Bronsted acid site of H-ZSM-5. The result of adsorption process indicates that the ammonia is preferentially
bonded to the Bronsted acid site of H-ZSM-5. Our findings are in agreement with experimental data.
Keywords: Adsorption, Computational chemistry, H-ZSM-5 zeolite, ONIOM
1 °µ‹µ¦¥r µ µª·š¥µ«µ˜¦r ‡–³ª·š¥µ«µ˜¦r ¨³Áš‡Ã¨Ãœ¥¸ ¤®µª·š¥µ¨´¥°· ¨µ¤¥³¨µ ž{˜˜µœ¸ 94160
Department of Chemistry, Faculty of Science and Technology, Islamic Yala University, Phattani, 94160
Corresponding author : Ú¦«´¡šr/Ú¦µ¦ 0-7341-8651 E-mail:yakotsu088@hotmail.com
2 Ÿ«. —¦. ®œn ª¥ª·‹´¥Á‡¤¸‡°¤¡· ªÁ˜°¦r ‡–³ª·š¥µ«µ˜¦r ¤®µª· š¥µ¨´¥š´„¬·– ¡´š¨»Š 93110
Asst. Prof. Dr., Computational Chemistry Research Unit, Faculty of Science, Thaksin University, Phatthalung, 93110