Microwave Assisted Pyrolysis of Waste Tires: Study and Design of Half-Cells SOFCs with Low Environmental Impact
Authors: Passaponti Maurizio , Rosi Luca , Frediani Marco , Salvietti Emanuele , De Luca Antonio , Giaccherini Andrea , Innocenti Massimo 
Published: February 2020

Scope Scrap tires are problematic waste and their recycling is a mandatory issue due to their huge yearly production and their heterogeneous composition [1]. Currently, a great deal of effort to promote the recycling of tires has been made and the use of waste tires as a valuable source of energy and chemical substances was encouraged [2]. Among several technologies for tires recycling, pyrolysis [3] has been exploited. Recently our group reported microwave assisted pyrolysis (MAP) of waste tires demonstrating the correlation between the characteristics of char from pyrolysis and the experimental conditions of the process. Different re-uses has been proposed for pyrolytic char, mainly as activated carbon after conversion, for the capture of pollutant gases from flue gas streams. In order to establish novel application for the solid residual from MAP we have evaluated the potential electrocatalytic efficiency of a collection of char from MAP in Oxygen Reduction Reaction (ORR). The basic idea comes from the consideration that the presence of different metals, together with a high carbon content are mandatory requirements for catalysts for ORR.

 Catalytic activity of char obtained from MAP of waste tires as oxygen reduction catalyst was studied in alkaline medium using the rotating disk (RRDE) electrochemical technique. The presence and combination of different metals in char object of study, each on them acting on different steps of Oxygen Reduction reaction (ORR), produces synergic catalytic effects. Notably, the materials show from the good to excellent electrons value (n) measured at -0.75 V for the ORR; this is indicative of prevailing ¾ e- reduction process. This result is a promising base for further developments, in order to improve the efficiency of future low-cost catalysts to be used in renewable energy technologies.

The Perovskite oxides La1−x
Sr
x
Co1−y
Fe
y
O3–
δ (LSCF) as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) have been extensively investigated. Recent studies show that cathode performances can be improved by metal surface modification or B-site substitution on LSCF.The development of intrinsically mixed conducting perovskites, such as derivatives of ferrites and cobaltiti, it constitutes an interesting field for the design and development of more and more efficient materials. Although the specific reaction mechanism needs to be further investigated, the promoting effect of metal species in enhancing oxygen surface exchange and oxygen bulk diffusion is well recognized. In the present investigation, recent progresses on metals of transitions from Map as promotion of LSCF are discussed focusing on two main aspects, the different synthesis approaches used and the effects of metal promotion on structural properties, oxygen vacancies content and cathodic performances. Associated with increased catalytic, the novelty of the work lies in the fact that the char obtained from microwave assisted pyrolysis of waste tires represent a low-cost and ”green” source of metals needed for the IT-SOFCs cathode, and not only: MAP transforms tires in three useful classes of products: a solid, a liquid and a gas. Liquid to its hydrocarbon [4] composition can be use as fuel in SOFCs.

[1] J. D. Martınez, N. Puy, R. Murillo, T. Garcia, M. V. Navarro, A. M. Mastral, Waste tyre pyrolysis – A review, Renewable and Sustainable Energy Reviews 23 (2013) 179–213.

[2] Progress in used tyres management in the European Union: A review

[3] M. Labakil, M. Jeguirim, Thermochemical conversion of waste tyres-a review, Environmental Science and Pollution Research (2016) DOI 10.1007/s11356-016-7780-0.

[4] A. Undri, L. Rosi, M.Frediani, P Frediani - Upgraded fuel from microwave assisted pyrolysis of waste tires, Fuel January 2014, Pages 600–608