Inhibiting Fe–Al Spinel Formation on a Narrowed Mesopore-Sized MgAl2O4 Support as a Novel Catalyst for H2 Production in Chemical Looping Technology

Ali Hafizi,Mohammad Rahimpour

doi:10.3390/catal8010027

Abstract

In this paper, the structure of Al2O3 is modified with magnesium to synthesize MgAl2O4 as an oxygen carrier (OC) support. The surface properties and structural stability of the modified support are improved by the incorporation of magnesium in the structure of the support and additionally by narrowing the pore size distribution (about 2.3 nm). Then, iron oxide is impregnated on both an Al2O3 support and a MgAl2O4 support as the oxygen transfer active site. The XRD results showed the formation of solely Fe2O3 on the MgAl2O4 support, while both Fe2O3 and Fe3O4 are detected in the synthesized Fe2O3-Al2O3 structure. The synthesized samples are investigated in chemical looping cycles, including CO reduction (as one of the most important side reactions of chemical looping reforming), at different temperatures (300–500 °C) and oxidation with steam at 700 °C for hydrogen production. The obtained results showed the inhibition of Fe–Al spinel formation in the structure of the Fe2O3-MgAl2O4 OC. In addition, H2 with a purity higher than 98% is achievable in oxidation of the OC with steam. In addition, the activity and crystalline change of the Fe2O3-MgAl2O4 OC is investigated after 20 reduction-oxidation cycles.

Highlights

The production of hydrogen from primary resources, such as methane and water, is industrially developed [1,2,3,4]
Iron oxide was impregnated on a magnesium-modified alumina support for the transference of pure lattice oxygen
The synthesized MgAl2 O4 with a narrow pore size distribution centered at 2.3 nm revealed a better performance on the formation of Fe2 O3 on the support’s surface in comparison with Al2 O3

Summary

Introduction

The production of hydrogen (as an energy carrier) from primary resources, such as methane and water, is industrially developed [1,2,3,4]. Hydrogen with high purity can be applied in different applications, such as fuel cells. Most hydrogen production processes need further purification with the purpose of preventing electrode poisoning [5]. One-step pure hydrogen production has attracted attention during the past few years [6,7]. The chemical looping technique (CLT) is known as a novel process for hydrogen production from different sources. The principal reactions involved in the chemical looping steam methane reforming (CL-SMR) process are as follows [10,11]: Fuel reactor: CH4 + Mex Oy → CO + 2H2 + Mex Oy−1

Methods

Results

Conclusion