Abstract

Abstract In the present study, high surface area amorphous magnesia was synthesized using walnut shell as a template. This green, simple and useful synthetic protocol was based on the precipitation of magnesium nitrate on biomass in an aqueous phase, followed by calcination. Materials were characterized using X-ray diffraction, scanning electron microscopy (SEM) and N2 adsorption/desorption porosimetry, and the results exhibited high surface area for magnesium oxide. Furthermore, the pore size and surface area of these mesoporous materials can be adjusted by varying the biomass/magnesium nitrate ratio. In addition, magnesium oxide was studied as the support of palladium nanoparticles for the aerobic oxidation of alcohols. We have found out that the resulting Pd-loaded material acts as an effective catalytic system for the aerobic oxidation of benzylic and aliphatic alcohols. The catalyst can be recovered and reused three times without loss of activity. Also, to test the catalytic activity of magnesium oxides as a solid catalyst, we selected Meerwein-Ponndorf-Verley reduction of cyclohexanone with 2-propanol over different magnesium oxides.

Highlights

  • Material chemists are interested in magnesium oxide or magnesia (MgO) because of its outstanding properties, such as lowest solubility among the alkaline earth oxides, easy obtainability and cheapness, as well as its textural properties, such as high surface area

  • Walnut shell powder was dispersed into magnesium nitrate solution in deionized water

  • Magnesium oxide prepared in the absence of walnut shell (MgO-0) has the lowest surface area and pore volume (44 m2/g, 0.11 cm3/g), which indicated that the presence of walnut shell is critical for the synthesis of mesoporous alumina (Table 1, entry 1)

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Summary

Introduction

Material chemists are interested in magnesium oxide or magnesia (MgO) because of its outstanding properties, such as lowest solubility among the alkaline earth oxides, easy obtainability and cheapness, as well as its textural properties, such as high surface area. Various methods for the synthesis of high surface area magnesia with controllable textural pro­ perties have been reported, these methods usually use non-aqueous solvent (e.g. ethylene glycol), precipitating agents (e.g. ammonia and urea) and synthetic template (e.g. polymers and mesoporous carbon). These conditions encounter environmental and economical challenges in large-scale application. Reference samples MgO-0 and re-MgO-0 were produced by the same way but without the use of biomass

Catalyst preparation
Characterization
Materials
Oxidation reaction
MPV reduction
Results and discussion
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