Catalytic Pyrolysis-Gasification of Waste Tire and Tire Elastomers for Hydrogen Production

Abstract

Hydrogen production from waste tires was investigated using a two-stage pyrolysis-gasification reactor and Ni−Mg−Al (1:1:1) as a catalyst. In addition, the elastomer constituents most commonly used in tires, natural rubber (NR), styrene−butadiene rubber (SBR), and butadiene rubber (BR), were also investigated. Experiments were conducted at a pyrolysis temperature of 500 °C and gasification temperature of 800 °C. The results showed that the gas and hydrogen yield were increased for the tire and elastomer constituents during pyrolysis-gasification. However, there was a dramatic increase in H 2 and CO concentrations as well as a consequent decrease in CH 4 and C 2 −C 4 concentrations when the Ni−Mg−Al catalyst was applied to the pyrolysis-gasification process. For example, hydrogen production increased from 0.68 to 5.43 wt % for the catalytic steam pyrolysis-gasification of waste tire in the presence of Ni−Mg−Al catalyst. The highest hydrogen production (15.26 wt %) was obtained for the BR feedstock. Reacted catalysts were characterized using a variety of methods, including temperature-programmed oxidation (TPO) and scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDXS). The SEM results showed that large amounts of filamentous carbons were observed for the reacted Ni−Mg−Al catalysts derived from all the feedstocks. The total amount of coke deposition on the reacted catalyst, calculated from TPO experiments, was lowest for the BR feedstock (7.0 wt %) and was 31, 21.8, and 18.4 wt % for the waste tire, NR, and SBR samples, respectively.