Please cite this article in press as: A. Undri, et al., Carbon from microwave assisted pyrolysis of waste tires, J. Anal. Appl. Pyrol. (2013), http://dx.doi.org/10.1016/j.jaap.2013.06.006 ARTICLE IN PRESS G Model JAAP-3008; No. of Pages 9 Journal of Analytical and Applied Pyrolysis xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Journal of Analytical and Applied Pyrolysis journal h om epage: www.elsevier.com/locate/jaap Carbon from microwave assisted pyrolysis of waste tires Andrea Undri a , Barbara Sacchi b , Emma Cantisani b , Nicola Toccafondi a , Luca Rosi a , Marco Frediani a , Piero Frediani a,∗ a Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 13, Sesto Fiorentino 50019, Firenze, Italy b National Research Council – Institute for Conservation and Valorisation of Cultural Heritage, Via Madonna del Piano, 10, Sesto Fiorentino 50019, Firenze, Italy a r t i c l e i n f o Article history: Received 19 March 2013 Accepted 12 June 2013 Available online xxx Keywords: Tire pyrolysis Microwave assisted pyrolysis Carbon a b s t r a c t A correlation between experimental conditions of microwave assisted pyrolysis (MAP) of tires and some of the characteristics of char are reported. MAP is a complementary or even an alternative methodology to recycle waste polymeric materials. This appealing way was employed in managing waste tires since they contain a high amount of microwave absorbing materials such as metal wires, metal oxides, and carbon, which quickly adsorb microwave radiation (MW) and turn it into heat. Char obtained from MAP of tire was characterized through chemical (ultimate analysis and ion coupled plasma-mass spectroscopy), morphological (BET surface area, scanning electron microscopy), and X-ray diffraction (XRD) analyses. MAP variables such as MW power and tire mass, did not strongly affect the properties of samples. Char contained large amount of amorphous carbon and inorganic compounds formed from additives employed in tires formulation. Hydrocarbons were present only in not-fully pyrolyzed samples. XRD analyses of crystalline phases showed a marked MW effect: different crystalline ZnS forms, spharelite or wurtzite were present due to the different amount of waste tires employed. The presence of these compounds suggested that tires were heated to a temperature higher than the usually accounted. © 2013 Published by Elsevier B.V. 1. Introduction Tires are problematic waste and their recycling is a mandatory issue due to their huge yearly production and their heterogeneous composition [1]. Nowadays there are several technologies suitable and con- venient to deal with waste tires. Retreading is the most environmentally friendly way of recycling used tires allowing an additional life. However this option is not always possible (tire damaged or too old) and may be applied no more than three times. Other physical approaches are also available: direct reuse of old tires as road side barriers, chopped or grinded tires, as feedstock for engineering works, street furniture, filler for new tires production. Otherwise thermal treatments of tires may be employed to recover energy due to their high heating values, equal to com- mercial petroleum coke, with low emission of CO 2 with respect to carbon [2]. Other thermal treatments may be used such as pyrolysis: tires were heated in an oxygen poor or free atmosphere. This methodology may be an interesting way to deal with waste tires because it transforms them into three potentially useful classes of ∗ Corresponding author. Tel.: +39 055 457 3522; fax: +39 055 457 3531. E-mail addresses: piero.frediani@unifi.it, piero.frediani@gmail.com (P. Frediani). products: a char, a liquid and a gas [3,4]. These products can be eas- ily stored, transported and used as a source of chemicals and energy. Nowadays pyrolysis is performed with several heating technologies and apparatus which allow the formation of the three products in different amount and composition. Microwave assisted pyrolysis (MAP) is one of the most appeal- ing approach to pyrolysis due to the considerable advantages of this technology over conventional pyrolysis process. MAP allows a low heating cost [5], a fast and direct heating of any microwave absorbing material, it reduces the pyrolysis time, and enables an improved control over the products properties [6–8]. A large num- ber of materials are able to absorb microwaves (MW) and turn them into heat: water [9], metal powders [9], metal wires [10], flat piece of metals [7], metal oxides [11], and carbonaceous mate- rials [12–14]. The ability of an absorber to turn MW into heat is a specific property of each material, and it is related with the dissi- pation factor (loss tangent), that is the tangent of the ratio between the dielectric loss factor and the dielectric constant of the mate- rial [5,15]. So far spot-points temperature profiles were achieved when heating a multi component material, because each compo- nent is heated in a different way depending on its properties. Indeed high temperature spots were detected in various systems using MW heating [16,17]. In homogeneous metal catalyzed dehalo- genation spot-points of higher temperature were observed in the metal surrounding than in the bulk of the catalyst. [18]. Similar 0165-2370/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.jaap.2013.06.006