CONICET | Buscador de Institutos y Recursos Humanos

Approximately one billion waste tires are generated annually worldwide. Catalytic pyrolysis of this residue is a promisingalternative for recycling, fuel recovery, and even obtaining higher economic value products. Here, catalysts based onheteropolyacids (HPA) supported on TiO2 (H3PW12O40/TiO2) were evaluated to yield a pyrolytic liquid enriched inaromatic compounds such as BTX and p-cymene. The nature and content of the acid sites were determined throughFT-IR spectra of adsorbed pyridine. In these spectra, six bands were detected; the signals at 1545 and 1635 cm-1 wereassociated with protonate pyridine bonded to Brønsted acid sites (BAS), while those found at 1445, 1575, and 1610 cm1 were ascribed to pyridine coordinately bonded to the Lewis acid sites (LAS). Then, the acid site content was calculatedusing the vibration bands at 1445 cm-1for LAS and 1545 cm-1for BAS. Activity experiments were carried out in TGAFTIR equipment and a fixed bed reactor (12 mm ID stainless steel tubular reactor) between 400 and 600 °C under100 mL min− 1 constant nitrogen flow rate. The gaseous products were condensed at the exit of the reactor, and thecomposition of pyrolytic oils was determined by QP2010SE Shimadzu GC/MS. TGA measurements confirmed thecatalyst´s stability at working temperatures. The primary compounds of waste tire pyrolysis were D,L-limonene, andisoprene. In contrast, catalysts favored the formation of target compounds compared with the uncatalyzed reaction.TGA-FTIR studies confirmed the presence of aromatic compounds through bands observed between 1500 and 1600cm−1, usually ascribed to the C=C stretching, mainly on catalysts with higher content of HPA ( > 15%). Moreover,pyrolysis reactions performed in a fixed bed showed that the higher the HPA content, the greater the favoring of thecracking reactions. Catalysts with low TPA loading (< 5%) promoted the formation of p-cymene by secondary reactionson D,L-limonene, while intermediate concentrations (between 15 and 30%) favored aromatization reactions leading toBTX. p-Cymene is mainly formed through isomerization reactions of aliphatic terpene driving to its isomers, terpinoleneand α- and γ-terpinene, whose subsequent dehydrogenation gives rise to these aromatic terpenes. On the other hand,the C-C bond breaking of the D,L-limonene ring in the β-position could contribute to BTX formation, as described in [1].The acidity results indicated a direct correlation between acidic properties and catalytic activity. A higher BAS/LAS ratio,related to a higher HPA content, favored the cracking and aromatization reactions leading to BTX. On the contrary, alower BAS/LAS ratio coming mainly from the support promoted to a greater extent isomerization reactions leading to pcymene

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