Pyrolysis of waste rubber tires with palladium doped zeolite

Abstract

This paper investigates the pyrolysis of waste rubber tires using zeolite-based heterogeneous catalysts. The catalytic activity of Hbeta and Pd/Hbeta was studied by examining the pyrolysis product yields. The gas yield from non-catalytic pyrolysis was at 20% while the use of Hbeta increased the gas yield to 28%. Doping Hbeta with Pd noble metal made a significant enhancement in hydrocarbon cracking producing a gas yield of 37%. The enhanced catalytic activity of Pd/Hbeta was due to dehydrogenation-hydrogenation reactions induced by the Pd metal sites. The incorporation of Pd into zeolite Hbeta led to appreciable improvements in the morphology of the catalyst. Pd-doping increased the surface area from 434 m2/g to 450 m2/g. The pore size also increased from 2.96 nm to 3.69 nm with a smaller crystallite size of 1.59 nm. The MO4 tetrahedra structure was preserved in Pd/Hbeta with the acidity characterized by hydroxyl groups (OH) at FTIR absorption bands of 631 cm−1.