Melt infiltration synthesised Ni/MgO catalysts for NH3 decomposition

Details

Supervisors

Gaigneaux, Eric M. ; Gamez Rivera, Sebastian Antonio

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

enIn this work, magnesium oxide synthesised by the hydrothermal method was evaluated as support for a nickel-based catalyst active for ammonia decomposition into hydrogen. The deposition of nickel was performed using the novel melt infiltration method. Both the magnesium oxide textural properties and the nickel dispersion could be modified by changing the parameters of the mentioned methodologies. The temperature and duration of the hydrothermal synthesis and the calcination temperature were reported to influence the texture of the support, while the melt duration influenced the nickel dispersion. Ideal parameters for a high ammonia conversion were identified to be one day of melt duration and two days of melt duration for an uncalcined and calcined mesoporous magnesium oxide support, respectively. With these conditions, catalysts with a high catalytic activity towards ammonia decomposition could be prepared, reaching 97% of conversion at 550°C with a GHSV of 6000 mLNH3/gcatalyst h. The deposition of nickel through melt infiltration allowed the preservation of the MgO specific surface area and porosity when performed on uncalcined support. However, the active phase sintered more easily on the uncalcined support than on the calcined MgO. The dispersion, incomplete reduction and reaction of nickel with the support to form a mixed oxide were found to be the limiting factors of the catalytic activity. Therefore, further studies focused on the dispersion of nickel on magnesium oxide and its reduction treatment are needed.