Artículos de revistas
Quantification Of Brønsted Acid Sites In Microporous Catalysts By A Combined Ftir And Nh3-tpd Study
Registro en:
Journal Of Physical Chemistry C. , v. 112, n. 18, p. 7193 - 7200, 2008.
19327447
10.1021/jp710613q
2-s2.0-43949131067
Autor
Martins G.V.A.
Berlier G.
Bisio C.
Coluccia S.
Pastore H.O.
Marchese L.
Institución
Resumen
This article reports the use of combined techniques (thermal desorption and spectroscopic analysis) for the characterization of Brønsted sites in microporous solid catalysts. The specific aim was to provide a quantitative determination of sites with slightly different acidities in chabazite-related silicoaluminophosphate (SAPO) materials, which display three bridged hydroxyls, OHA, OHB, and OHC, absorbing at 3630, 3614, and 3600 cm-1, respectively. To this aim, different approaches were employed. First, the total concentration of Brønsted sites was calculated by classical NH3-TPD experiments. Ammonia was preferred to pyridine due to the small kinetic diameter, allowing easy access and diffusion inside the small cavities of chabazite. Second, FTIR spectroscopy was employed to study the adsorption of NH3 and CO. The Lambert - Beer equation, using extinction coefficients from the literature, was employed to estimate the total amount of Brønsted sites involved in the formation of NH4 + ammonium ions or in CO/H+ adducts. The agreement among the data obtained by the three methods, which is excellent, is discussed critically. The fraction of each acid group in samples with different Brønsted site densities and strength distributions was determined with great accuracy. This finally allowed calculation of the extinction coefficients of the three hydroxyls of the H-SAPO-34 catalysts, which were εA = εB = 3.9 cm μmol-1 and εC = 6.0 cm μmol-1. It is proposed that these values are of general use for determining the distribution of acid sites of SAPOs and zeolites whose hydroxyls absorb in the same range of wavenumbers. © 2008 American Chemical Society. 112 18 7193 7200 Wojciechowski, B.W., Corma, A., (1986) Catalytic Cracking: Catalyst, Chemistry, and Kinetics, , Marcel Dekker: New York Stocker, M., (1999) Microporous Mesoporous Mater, 29, p. 3 Xu, Y., Grey, C.P., Thomas, J.M., Cheetham, A.K., (1990) Catal. Lett, 4, p. 251 Marchese, L., Chen, J.S., Wright, P.A., Thomas, J.M., (1993) J. Phys. Chem, 97, p. 8109 Martins, G.A.V., Berlier, G., Coluccia, S., Pastore, H.O., Superti, G.B., Gatti, G., Marchese, L., (2007) J. Phys. Chem. C, 111, p. 330 Barthomeuf, D., (1994) Zeolites, 14, p. 394 Bordiga, S., Regli, L., Cocina, D., Lamberti, C., Bjorgen, M., Lillerud, K.P., (2005) J. Phys. Chem. B, 109, p. 2779 Smith, L. Cheetham, A. K. Morris, R. E. Marchese, L. Thomas, J. M. Wright, P. A. Chen, J. Science (Washington, DC, U.S.) 1996, 271, 799Sastre, G., Lewis, D.W., (1998) J. Chem. Soc, Faraday Trans, 94, p. 3049 Zubkov, S.A., Kustov, L.M., Kazansky, V.B., Girnus, I., Fricke, R., (1991) J. Chem. Soc., Faraday Trans, 87, p. 897 Lok, B.M., Messina, C.A., Patton, R.I., Gajek, R.T., Cannon, T., Flannigen, E.M., (1984), U.S. Patent 4,440,871, example 32Cheng, S., Tzeng, J., Hsu, B., (1997) Chem. Mater, 9, p. 1788 Martins, G.A.V., Pastore, H.O., (2005) Stud. Surf. Sci. Catal, 158, p. 335 Pastore, H.O., Martins, G.A.V., Superti, G.B., Marchese, L., Strauss, M., Brazilian Patent PI0601669-3, 2006Lisi, L., Marchese, L., Pastore, H.O., Frache, A., Ruoppolo, G., Russo, G., (2003) Top. Catal, 22, p. 95 Marchese, L., Frache, A., Gatti, G., Coluccia, S., Lisi, L., Ruoppolo, G., Russo, G., Pastore, H.O., (2002) J. Catal, 208, p. 479 Coluccia, S., Marchese, L., Martra, G., (1999) Microporous Mesoporous Mater, 30, p. 43 Smith, L., Cheetham, L., Marchese, L., Gianotti, E., Thomas, J.M., Wrigth, P.A., Chen, J., (1996) Catal. Lett, 41, p. 13 Zecchina, A., Bordiga, S., Spoto, G., Marchese, L., Petrini, G., Leonfanti, G., Padovan, M., (1992) J. Phys. Chem. B, 96, p. 4991 Zecchina, A., Bordiga, S., Spoto, G., Scarano, D., Petrini, G., Leofanti, G., Padovan, M., Otero Areàn, C., (1992) J. Chem. Soc., Faraday Trans, 88, p. 2959 Knözinger, H., Huber, S., (1998) J. Chem. Soc., Faraday Trans, 94, p. 2047 Makarova, M.A., Wilson, A.E., van Liemt, B.J., Mesters, C.M.A.M., de Winter, A.W., Williams, C., (1997) J. Catal, 172, p. 170 Makarova, M.A., Ojo, A.F., Karim, K., Hunger, M., Dwyer, J., (1994) J. Phys. Chem. B, 98, p. 3619 Makarova, M.A., Karim, K., Dwyer, J., (1995) Microporous Mater, 4, p. 243 Morterra, C., Garrore, E., Bolis, V., Fubini, B., (1987) Spectrochim. Acta, Part A, 43, p. 1577 Barzetti, T., Selli, E., Moscotti, D., Forni, L., (1996) J Chem. Soc., Faraday Trans, 92, p. 1401 Selli, E., Forni, L., (1999) Microporous Mesoporous Mater, 31, p. 129 Datka, J., Marek, G., (2006) Catal. Today, 114, p. 205 Zecchina, A., Marchese, L., Bordiga, S., Pazè, C., Gianotti, E., (1997) J. Phys. Chem. B, 101, p. 1128 Bortnovsky, O., Melichar, Z., Sobalìk, Z., Wichterlovà, B., (2001) Microporous Mesoporous Mater, 42, p. 97 Man, P.P., Briend, M., Peltre, M.J., Lamy, A., Beaumier, P., Barthomeuf, D., (1991) Zeolites, 11, p. 563