The Effect of Dealumination on the Framework Stability, Acidity, and Catalytic Performance of SAPO-11 Molecular Sieves

Um Myeong-Heon; Misook Kang

Journal of Industrial and Engineering Chemistry, Vol.11, No.4, 540-549, July, 2005

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The Effect of Dealumination on the Framework Stability, Acidity, and Catalytic Performance of SAPO-11 Molecular Sieves

Um Myeong-Heon , and Misook Kang^{1, †}

Division of Chemical Engineering, Kongju National University, Chungnam 330-717, Korea
¹Industrial Liaison Research Institute, Kyung Hee University, Gyeonggi 449-701, Korea

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This study focused on the framework stability, acidity, and catalytic performance fo dealuminated SAPO-11 molecualr sieves. From the results of XRD and FT-IR analyses, we identified that the framework of SAPO-11 with AEL structure was maintained stably after 48 h of dealumination. In addition, the dealuminated SAPO-11 molecular sieves exhibited higher activation energies toward dehydration and ammonia desorption when compared with those of untreated SAPO-11. The NH3-TPD test confirmed that the number of acid sites on the external surface decreased more than those on the internal surface. To support this hypothesis t-butyl benzene combustion was performed. The combustion performance for t-butyl benzene decreased on the dealuminated samples. On the other hand, as a result of the MTHC process, the C2~C4 paraffin and the C5~hydrocarbons were acquired in higher amounts when compared with C2~C4 olefins; and DME and C1 were obtained in very small amounts on the untreated SAPO-11. However, in the case of dealuminated SAPO-11, methanol conversion increased. In addition, the amounts of produced C5~hydrocarbons and C2~C4 olefin also increased. In particular, for the 48-h dealuminated sample, 90% methanol conversion remained until 4 h. Therefore, in this study, we confirmed that the increase in the Si/Al ratio in SAPO-11 upon dealumination was caccompanied by a decrease in the number of acid sites and an increase in the strength of the Brofnsted acid units. Consequently, this material had a stronger influence on the catalytic performance of the MTHC process.

Keywords:dealumination;SAPO-11;acidity;MTHC process

[References]

Wilson and coworkers, US Patent, 4,310,440 (1982)
Szostak, Molecular sieves: principle of synthesis and identification, Van Nostrand Reinhold, 271 (1989)
Lunsford JH, Tutunjian PN, Chu PJH, Yeh EB, Zakewski DJ, J. Phys. Chem., 93, 2590 (1989)
Kazansky VB, In Structure and Reactivity of Modified Zeolites, Elsevier, Amsterdam, 61 (1984)
Jacobs PA, Catal. Rev.-Sci. Eng., 24, 415 (1985)
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Maher PK, Hunter FD, Scherzer J, Adv. Chem. Ser., 101, 266 (1979)
Kerr T, J. Phys. Chem., 72, 2594 (1968)
Beaumonu R, Barthmeuf D, J. Catal., 44, 170 (1973)
ubelkova LK, Beran S, Malecka A, Mastikhin VM, Zeolites, 9, 12 (1989)
Sohn JR, DeCanio SJ, Frita PO, Lunsford JH, J. Phys. Chem., 90, 4847 (1986)
Karge HG, Dondur V, Weitkamp J, J. Phys. Chem., 95, 283 (1991)
Inui T, Kang M, Appl. Catal. A: Gen., 164(1-2), 211 (1997)
Szostk R, Molecular sieves: principle of synthesis and identification, van Nostrand Reinhold, 205 (1989)
Tapp NJ, Milestone NB, Bibby DM, Zeolites, 8, 83 (1988)
Blackwell CS, Patton RL, J. Phys. Chem., 92, 3965 (1988)
Hunger M, Anderson MW, Ojo A, Pfeifer H, Micro. Mater., 1, 17 (1993)
Prasad S, Vetrivel R, J. Phys. Chem., 96, 3092 (1992)
Kustanovich I, Goldfarb D, J. Phys. Chem., 95, 8818 (1991)
Ozawa T, J. Therm. Anal. Calorim., 5, 563 (1973)
Kerr GT, J. Phys. Chem., 7, 2594 (1968)
Shiralka VP, Saldarriaga CH, Perez JO, Clearfield A, Chen M, Anthony RG, Donohue JA, Zeolites, 9, 474 (1989)
Rajic N, Stojakovic D, Kaucic V, Zeolites, 10, 802 (1990)
Hedge SG, Ratnasamy P, Zeolites, 8, 137 (1988)
Choi BC, Foster DE, J. Ind. Eng. Chem., 11(1), 1 (2005)

[Referenced By]

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[1] Wilson and coworkers, US Patent, 4,310,440 (1982)

[2] Szostak, Molecular sieves: principle of synthesis and identification, Van Nostrand Reinhold, 271 (1989)

[3] Lunsford JH, Tutunjian PN, Chu PJH, Yeh EB, Zakewski DJ, J. Phys. Chem., 93, 2590 (1989)

[4] Kazansky VB, In Structure and Reactivity of Modified Zeolites, Elsevier, Amsterdam, 61 (1984)

[5] Jacobs PA, Catal. Rev.-Sci. Eng., 24, 415 (1985)

[6] Klinowski J, Fyfe CA, Gobbi GC, J. Chem. Soc.-Faraday Trans., 81, 3003 (1985)

[7] Maher PK, Hunter FD, Scherzer J, Adv. Chem. Ser., 101, 266 (1979)

[8] Kerr T, J. Phys. Chem., 72, 2594 (1968)

[9] Beaumonu R, Barthmeuf D, J. Catal., 44, 170 (1973)

[10] ubelkova LK, Beran S, Malecka A, Mastikhin VM, Zeolites, 9, 12 (1989)

[11] Sohn JR, DeCanio SJ, Frita PO, Lunsford JH, J. Phys. Chem., 90, 4847 (1986)

[12] Karge HG, Dondur V, Weitkamp J, J. Phys. Chem., 95, 283 (1991)

[13] Inui T, Kang M, Appl. Catal. A: Gen., 164(1-2), 211 (1997)

[14] Szostk R, Molecular sieves: principle of synthesis and identification, van Nostrand Reinhold, 205 (1989)

[15] Tapp NJ, Milestone NB, Bibby DM, Zeolites, 8, 83 (1988)

[16] Blackwell CS, Patton RL, J. Phys. Chem., 92, 3965 (1988)

[17] Hunger M, Anderson MW, Ojo A, Pfeifer H, Micro. Mater., 1, 17 (1993)

[18] Prasad S, Vetrivel R, J. Phys. Chem., 96, 3092 (1992)

[19] Kustanovich I, Goldfarb D, J. Phys. Chem., 95, 8818 (1991)

[20] Ozawa T, J. Therm. Anal. Calorim., 5, 563 (1973)

[21] Kerr GT, J. Phys. Chem., 7, 2594 (1968)

[22] Shiralka VP, Saldarriaga CH, Perez JO, Clearfield A, Chen M, Anthony RG, Donohue JA, Zeolites, 9, 474 (1989)

[23] Rajic N, Stojakovic D, Kaucic V, Zeolites, 10, 802 (1990)

[24] Hedge SG, Ratnasamy P, Zeolites, 8, 137 (1988)

[25] Choi BC, Foster DE, J. Ind. Eng. Chem., 11(1), 1 (2005)