Catalytic pyrolysis of waste rubber -

Abstract

The waste crisis striking most countries has made it crucial to consider treatment methods that would leave minimal impact on the environment. Statistics show that rubber tires contribute to a significant portion of waste on local and global scales. Different techniques have been developed to cope with waste tires, one of which is pyrolysis. This work aims at enhancing two types of pyrolysis, namely thermal pyrolysis and solar pyrolysis, by using different catalysts. Thermal pyrolysis temperature is fixed at 590 ̊C, whereas solar pyrolysis is conducted at an irradiation between 900-1100 W-m2. Nine catalysts are synthesized based on the acidic Hbeta zeolite structure, Hbeta, Pd-Hbeta, Pt-Hbeta, Pd-Pt-Hbeta and on the semi-conductor TiO2 photo active catalyst, TiO2, Pd-TiO2, Pt-TiO2, Pd-Pt-TiO2, and Bi2O3-SiO2-TiO2. Thermal pyrolysis results highlighted the enhancement effect of palladium noble metal that gave the highest pyrolytic gas yield of 37.02percent, while Hbeta zeolite gave 27.89percent only. On the other hand, solar pyrolysis with photocatalytic Pd-TiO2 produced the highest gas yield of 40.94percent. The pyrolysis oil samples were collected and characterized using GC-MS to determine the carbon chain length which is found to decrease to C9-C12 gasoline range under Pd-Hbeta and Pd-TiO2. Meanwhile, catalyst behavior and activity were investigated using several techniques including; BET isotherm, SEM, EDX, and XRD. The highest surface area for Hbeta zeolite based catalysts was 449 m²-g for Pd-Hbeta zeolite. While the semi-conductor TiO2 based catalyst, Pd-Pt-TiO2 gave a surface area of 130.9 m²-g. Palladium metal produced the highest dispersion on the support surface and inside the pores. The bimetallic Hbeta zeolite catalyst and the tri-metallic Bi2O3-SiO2-TiO2 catalyst had a layered structure as detected by SEM. Palladium noble metal doping showed a significant enhancement for both Hbeta acidic surface and photo active semi-conductor TiO2. Pd- Hbeta zeolite provoked the dehydrogenation-hydrogenati