n‐octane reforming over alumina‐supported Pt, Pt–Sn and Pt–W catalysts
Tóm tắt
Pt, Pt–Sn and Pt–W supported on γ‐Al2O3 were prepared and characterized by H2 chemisorption, TEM, TPR, test reactions of n‐C8 reforming (500°C), cyclohexane dehydrogenation (315°C) and n‐C5 isomerization (500°C), and TPO of the used catalysts. Pt is completely reduced to Pt0, but only a small fraction of Sn and of W oxides are reduced to metal. The second element decreases the metallic properties of Pt (H2 chemisorption and dehydrogenation activity) but increases dehydrocyclization and stability. In spite of the large decrease in dehydrogenation activity of Pt in the bimetallics, the metallic function is not the controlling function of the bifunctional mechanisms of dehydrocyclization. Pt–Sn/Al2O3 is the best catalyst with the highest acid to metallic functions ratio (due to its lower metallic activity) presenting a xylenes distribution different from the other catalysts. The acid function of Pt–Sn/Al2O3 is tuned in order to increase isomerization and cyclization and to decrease cracking, as compared to Pt and Pt–W.
Tài liệu tham khảo
Y.-X. Li, K.L. Klabund and B.H. Davis, J. Catal. 128 (1991) 1.
R. Srinivasan, L.A. Rice and B.H. Davis, J. Catal. 129 (1991) 257.
B.H. Davis and G.J. Antos, in: Catalytic Naphtha Reforming, eds. G.J. Antos, A.M. Aitani and J.M. Parera (Dekker, New York, 1995) ch. 5, p. 153.
V. Haensel, US Patent 2 957 819, UOP (1960).
J.L. Contreras, Ph.D. thesis, Universidad Autónoma Metropolitana Iztapalapa, M´exico (1960).
J.L. Contreras, G.A. Fuentes and E.M.M. Domínguez, in: Anal. XV Simp. Iberoam. Catal., Córdoba, Argentina, 1996, Vol. I, p. 1.
A. Kadkhodayan and A. Brenner, J. Catal. 117 (1989) 311.
C.L. Rollinson, The Chemistry of Chromium, Molybdenum and Tungsten, Pergamon Texts in Inorganic Chemistry, Vol. 21 (Pergamon, Oxford, 1973) p. 767.
A.K. Aboul-Gheit and S.M. Abdel-Hamid, in: Preparation of Catalysts VI. Scientific Bases for the Preparation of Heterogeneous Catalysts, eds. G. Poncelet et al. (Elsevier, Amsterdam, 1995) p. 1131.
T.F. Garetto, A. Borgna, E. Benvenuto and C.R. Apesteguía, in: XII Symp. Iberoam. Catal., Rio de Janeiro, Brasil, 1990, Vol. I, p. 585.
H. Lieske, G. Lietz, H. Spindler and J. Volter, J. Catal. 81 (1983) 8.
K. Kunimore, Y. Ikeda, M. Soma and T. Uchijima, J. Catal. 79 (1983) 185.
G. Den Otter and F.M. Dautzenberg, J. Catal. 53 (1978) 116.
S. Stagg, W. Alvarez, D. Resasco, J.M. Parera and C.A. Querini, in: Anal. XV Symp. Iberoam. Catal., Córdoba, Argentina, 1996, Vol. II, p. 1061.
J.S. M'Boungou, J.L. Schmitt, G. Maire and F. Garin, Catal. Lett. 10 (1991) 391.
R. Burch and L.C. Garla, J. Catal. 71 (1981) 360.
E. Iglesia, J.E. Baumgartner, F.H. Ribeiro and M. Boudart, J. Catal. 131 (1991) 523.
R.B. Levy and M. Boudart, Science 181 (1973) 547.
B.H. Davis and P. Venuto, J. Catal. 15 (1969) 363.
P. Mériaudeau and C. Naccache, Catal. Rev. Sci. Eng. 39 (1997) 5.
J.M. Parera and N.S. Fígoli, in: Catalytic Naphtha Reforming, eds. G.J. Antos, A.M. Aitani and J.M. Parera (Dekker, New York, 1995) ch. 3.
H.B. Davis, G.A. Westfall and R.W. Naylor, J. Catal. 42 (1976) 238.
M. Boudart, A. Aldag, J.E. Benson, N.A. Dougharty and C.G. Harkins, J. Catal. 6 (1966) 92.
G.A. Mills, H. Heinemann, T.H. Milliken and A.G. Oblad, Int. Eng. Chem. 45 (1953) 134.
C.A. Querini, N.S. Fígoli and J.M. Parera, Appl. Catal. 52 (1989) 249.
J.H. Sinfelt, J. Catal. 29 (1973) 308.