# Valorization of Waste Tires by Pyrolysis and Activation Processes
###### Abstract  
The problems related to the increase in the generation of discarded tires demonstrate the need for profitable, efficient, cost-effective, and sustainable processes for their waste management. In particular, the valorization of pyrolytic solids for energy storage applications is of interest. In this study, four processes were performed: (1) pyrolysis; (2) chemical activation and pyrolysis; (3) pyrolysis and physical activation; and (4) chemical activation, pyrolysis, and physical activation. The process consisting of chemical activation, pyrolysis, and physical activation yielded 52% solid material with the highest electrical conductivity (2.43 \(\mathrm{\SIUnitSymbolCels  
Waste tire pyrolysis has been the subject of ample research, such as the kinetics of the pyrolysis reaction [11], reactor design, and product characterization [6; 12]. This thermochemical conversion pathway has demonstrated that the recycling of waste tires, accompanied by material and energy recovery, is important from both an economic and environmental aspect [13]. Despite advances in the proper management of waste tires, there are still environmental problems related to their inadequate disposal, probably because the conventional processes are expensive or the products do not have a commercial application [14; 15]. As [PERSON] and [PERSON] [16] reported, economic viability of the pyrolysis process is obtained when the products generated are not limited only to primary products. Furthermore, some authors [14; 17; 18; 19] suggest that the profitability of the pyrolysis of waste tires could depend on the application of the solid fraction.  
Activation processes are used to produce high-quality activated carbon from waste tires [20] and the activation process used plays an important role regarding the commercial applications of this solid product obtained from waste tire pyrolysis. Several investigations analyze the effect of the activation methods with the objective of improving the morphological characteristics of the carbonaceous solid [21; 22]. There are two types of activation process: physical and chemical. The main advantages of physical activation are simplicity and low cost, with steam and CO\({}_{2}\) being the most common agents used [23]. On the other hand, during chemical activation, the tire is impregnated with a chemical agent prior to carbonization. The advantages of this process include a higher carbon yield and better control of porosity [23]. Some chemical agents used in waste tire activation are ZnCl\({}_{2}\), H\({}_{3}\)PO\({}_{4}\)[21], H\({}_{2}\)O\({}_{2}\)[24], KOH [25], and H\({}_{2}\)SO\({}_{4}\)[26]. Different applications have been explored for the pyrolytic solids from waste tires, such as reinforcement on the rubber industry [27], as adsorbents mainly used for the removal of pollutants [28], activated carbon used as catalyst for biodiesel production [2; 29], and recently as anodes in energy storage devices [25; 26]. These studies provide information on the application of the solid fraction as an electrode; however, a complete valorization of all the pyrolytic tire products and an analysis of the effects on their properties of the parameters of the process are still necessary. Chemical composition, a high surface area, and proper porosity formation in the solid fraction are the main factors contributing to their good performance as electrodes [15]. In this study, we explore combinations of waste tire activation, using physical and chemical pathways, and pyrolysis to recover pyrolytic carbon black with suitable properties for its use in energy-storage devices (high surface area, type of pores created, and high electrical conductivity). In addition, liquid and gas products are analyzed with the aim of performing a preliminary analysis of the value of these subproducts.