Catalysis Today 190 (2012) 133–143 Contents lists available at SciVerse ScienceDirect Catalysis Today jou rn al h om epage: www.elsevier.com/locate/cattod Amphiphilic magnetic composites based on layered vermiculite and fibrous chrysotile with carbon nanostructures: Application in catalysis Ana Paula C. Teixeira a , Aluir D. Purceno a , Aline S. Barros a , Bruno R.S. Lemos a , José D. Ardisson b , Waldemar A.A. Macedo b , Evelisy C.O. Nassor a , Camila C. Amorim c , Flávia C.C. Moura a , Manuel G. Hernández-Terrones d , Flaysner M. Portela d , Rochel M. Lago a,∗ a Departamento de Química, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil b Laboratório de Química de Nanoestruturas, Centro de Desenvolvimento da Tecnologia Nuclear - CDTN/CNEN, MG 31270-901, Brazil c Departamento de Engenharia Ambiental e Sanitária, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil d Instituto de Química, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil a r t i c l e i n f o Article history: Received 30 September 2011 Received in revised form 21 December 2011 Accepted 31 January 2012 Available online 22 March 2012 Keywords: Chrysotile Vermiculite Carbon nanofibers Amphiphilic Biodiesel a b s t r a c t This work describes the synthesis and catalytic applications of magnetic composites based on carbon nanotubes and nanofibers prepared by CVD (chemical vapor deposition) using two natural materials with special morphology, i.e. layered vermiculite clay and fibrous chrysotile. Extensive characterization by XRD, Mössbauer, Raman, SEM, TEM, TG/DTA, contact angle showed that the composites are made mainly of carbon nanotubes and nanofibers fixed on the surface of the layered or fibrous matrix contain- ing also carbon coated iron or cobalt cores responsible for the magnetic properties of the composites. The combination of hydrophilic Si and Al oxides surface with the hydrophobic carbon nanostructure produced amphiphilic materials with remarkable effect on the interaction and separation of two phases system, e.g. oil and water. For example, immiscible oil/water mixtures can be easily emulsified in the presence of the amphiphilic composites producing a much more efficient interface. It is demonstrated that this emul- sification is very important for the biodiesel synthesis and hydrolysis of soybean oil. After reaction, the emulsion can be easily broken by a simple magnetic separation process. This emulsion–demulsification process can be also used for biodiesel purification and wastewater treatment. The composites are also used to prepare a magnetically recoverable supported Pd catalyst for the hydrogenation of the model molecule 1,5-COD. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Natural minerals based on silicates and aluminosilicates are very attractive materials for applications in catalysis and adsorption. These materials show good mechanical and thermal stability, acid and basic sites due to the Si and Al oxides and redox properties due to the presence of transition metals, especially Fe. Moreover, these minerals exist in different morphologies and textures that can be modified by mechanical and chemical controlled processing. Two of these materials are chrysotile and vermiculite. Chrysotile [Mg 3 Si 2 O 5 (OH) 4 ] is a magnesium silicate formed by hydrothermal alteration of olivines [(Mg,Fe) 2 SiO 4 )] and pyroxenes [(Ca,Na,Fe)(Mn,Cr,Al)(Si,Al) 2 O 6 )]. A special feature of chrysotile is the form of long thin microfibers/strings, which are able to orientate themselves in several different directions. Individual fibers tend to become entangled both within themselves and with adjacent fibers, ∗ Corresponding author. Tel.: +55 31 3409 5775; fax: +55 31 3409 5700. E-mail addresses: rochel@ufmg.br, rochellago@yahoo.com.br (R.M. Lago). forming an intricate mesh. Only few applications of chrysotille in catalysis have been found in the literature, such as support for metallocene [1], porphyrin [2,3], elimination of detergents [4] and generation of free radical [5]. The clay mineral vermiculite is a very interesting layered material with many potential industrial and environmental applications. Vermiculite can be modified by two processes, i.e. acid leaching and pillaring, to produce catalysts for different reactions. Some of these applications are in organic synthesis [6–9], removal of contaminants [10–17], hydrocarbon conversion [18,19], hydrogenation [20] and as support for ionic liquid [21]. In this work, a novel approach to use natural inorganic mate- rials such as chrysotile and vermiculite in catalytic applications is developed. In this approach carbon nanofibers/nanotubes are produced by catalytic CVD on the surface of chrysotile and ver- miculite to prepare magnetic amphiphilic composites. A schematic representation of the different composites preparation is shown in Fig. 1. These composites have several special features. They are amphiphilic due to the simultaneous presence of hydrophobic 0920-5861/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2012.01.042