Preparation, Structural Characteristics and Catalytic Properties of Large-Pore Rare Earth Element (Ce, La)/Al-Pillared Smectites

Ernst Booij1, J. Theo Kloprogge2 and J. A. Rob Van Veen3, †
1 Faculty of Earth Sciences, Free University of Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
2 Hoevenbos 299, 2716 PZ Zoetermeer, The Netherlands
3 Koninklijke/Shell Laboratorium Amsterdam, Badhuisweg 3, PO Box 3003, 1003 AA Amsterdam, The Netherlands
Present address: SRTCA, PO Box 38000, 1030 BN Amsterdam, The Netherlands.

Abstract: Ce/Al- and La/Al-pillared smectites were prepared by cation exchange of bentonite, saponite and laponite with hydrothermally treated (130–160 °C for 16–136 h) solutions containing mixtures of aluminumchlorohydrate (ACH) and Ce3+-/and La3+-salts. After calcination at 500 °C, the pillared products are characterized by basal spacings between 24.8 and 25.7 Å and surface areas of approximately 430 m2 g−1. The products are hydrothermally stable at 500 °C after 2 h in steam. The large basal spacings are due to the formation of a large Ce/La-bearing Al-polyoxocation, whose formation is favored by initially high Al concentrations ≥3.7 M and an OH/Al molar ratio of approximately 2.5. The Ce/Al or La/Al molar ratios can be as low as 1/30. 27Al nuclear magnetic resonance (NMR) spectroscopy has shown that the polyoxocation has a higher Altetrahedral/Aloctahedral ratio than the Keggin structure Al13, which may partly explain the higher stability compared to normal Al-pillared clays. Hydroconversion of n-heptane indicated that the activity of the Pt-loaded pillared products is higher than that of a conventional Pt-loaded amorphous silica-alumina catalyst. Selectivity is strongly dependent on the type of starting clay and its acidity. In industrial hydrocracking of normal feedstock, a Ni/W-loaded Ce/Al-pillared bentonite catalyst showed rapid deactivation due to coke-formation reducing the surface area and the pore volume. Additionally, coke-formation is facilitated by the relatively high iron content of the pillared bentonite (3.43 wt% Fe2O3).

Key Words: Al13 • Bentonite • Hydroconversion • Hydrocracking • Laponite • Montmorillonite • Pillared Clays • REE • Saponite

Clays and Clay Minerals; December 1996 v. 44; no. 6; p. 774-782; DOI: 10.1346/CCMN.1996.0440608
© 1996, The Clay Minerals Society
Clay Minerals Society (www.clays.org)