Hydrogen production from partial oxidation of iso-octane over Ni/Ce 0.75Zr 0.25O 2 and Ni/β″-Al 2O 3 catalysts

Abstract

In this study, the partial oxidation of iso-octane over Ni/Ce 0.75Zr 0.25O 2 and Ni/β″-Al 2O 3 catalysts was investigated. The results indicated that Ni/Ce 0.75Zr 0.25O 2 is more active than Ni/β″-Al 2O 3. The partial oxidation products were mainly H 2 and CO for Ni/Ce 0.75Zr 0.25O 2 catalyst, with hydrogen selectivity up to 53% in the temperature range of 550–800 °C with a C/O feed ratio of 1. The H 2/CO ratio was in the range of 1.3–1.7 depending on the operating temperature. At temperatures above 700 °C, the presence of methane was detected. The main products of iso-octane partial oxidation over Ni/β″-Al 2O 3 catalyst were CO 2 and i-C 4H 8 at temperatures below 650 °C while H 2 and CO along with small amount of hydrocarbons such as CH 4, C 2H 4, C 2H 6 and C 3H 6 were obtained at temperatures above 650 °C, yielding a H 2/CO ratio of about 1.3. As a result, the hydrogen selectivity was lower than that of Ni/Ce 0.75Zr 0.25O 2 catalyst. For both catalysts, the carbon dioxide and carbon monoxide selectivities were decreased whilst the hydrogen and hydrocarbons selectivities were increased with increasing C/O feed ratio. The Ni/Ce 0.75Zr 0.25O 2 catalyst can be operated over a wider C/O feed ratio range than the Ni/β″-Al 2O 3 catalyst, resulting in less amount of carbon formed. The presence of steam in the feed yielded a larger amount of hydrogen and less amount of coke formation. Since the iso-octane conversion of both catalysts remained unchanged after a prolonged reaction time, a decrease in H 2 selectivity for Ni/β″-Al 2O 3 catalyst may be attributed to the phase change of β″-Al 2O 3 in the presence of steam.