Hydrogen production from steam reforming of phenol over supported nickel-cobalt catalyst

Abstract

This thesis presents the results of a study of catalytic phenol steam reforming with the aim of hydrogen production using bimetallic nickel-cobalt (Ni-Co) supported on cerium oxide, zirconium dioxide (ZrO2), lanthanum oxide, gamma alumina, and alpha alumina catalysts. Phenol has been selected as a reactant due to the high amount of phenol in bio-oil and is a potential renewable feedstock for hydrogen production. The high cost of noble based catalysts, low activity and performance of non-noble based catalysts, deactivation of catalysts by coke formation, and high temperature requirements for complete phenol conversion are the problems of the previous research. The aim of this research is to develop a highly active and stable catalyst for hydrogen production from the steam reforming of phenol. The physical and chemical properties of the catalysts were characterized in terms of their surface area, crystallinity, reducibility, acidity, basicity, and coke formation. Five prepared catalysts were screened by using a micro-reactor fixed bed at a temperature of 650 oC and atmospheric pressure. The effect of Ni to Co ratio on hydrogen production from phenol steam reforming reaction was then investigated. This was followed by parametric study on the process involving five factors, namely temperature (A), feed flow rate (B), catalyst amount (C), presence of Ni and Co (D), as well as concentration of phenol (E), and the two responses were phenol conversion (Y1) and hydrogen (Y2). The optimum catalytic performance was found to be for the Ni-Co/ZrO2 catalyst with 81.9% of phenol conversion and 80.7% of hydrogen yield at 650 oC. The effect of Ni to Co metal ratio study showed that the 75 wt.% Ni-25 wt.% Co supported on ZrO2 catalyst displayed a superior catalytic activity among all the ratios. The parametric analysis showed that five variables (A, B, C, D and E) and interactions among AE, BE and DE produced significant effects on Y1 and Y2. In the kinetic study, the results suggested that the surface reaction was the rate limiting step by assuming non-dissociative adsorption of phenol and steam using this catalyst. Hence, it is concluded that bimetallic Ni-Co supported on ZrO2 catalyst is able to produce high hydrogen yield and has the potential to tackle the catalyst deactivation by coke.