Synthesis and Characterization of Novel Phyto-Mediated Catalyst, and Its Application for a Selective Oxidation of (VAL) into Vanillin under Visible Light

Afnan Al-Hunaiti,Deeb Taher,Ibrahim Bsoul,Tareq Hussein,Qassem Mohaidat,Sami Mahmood

doi:10.3390/catal10080839

Abstract

Here, we report an efficient and highly selective oxidation of lignin model substrate using phyto-mediated ZnFe2O4 nanoparticle using Boswellia carterii extract. The nanocatalyst with an average size of 8 nm showed excellent photocatalytic activity of the synthesized carbonyl containing products under visible light irradiation. The catalytic activity and selectivity towards oxidation of vanillyl alcohol to vanillin with selectivity up to 99% at conversion over 98% and turn-over frequency values up to 1600 h−1 were obtained in the presence of H2O2 and base. The cubic spinel nano-ZnFe2O4 catalyst was characterized by powder-XRD, FESEM, HR-TEM and Mössbauer analysis. The demonstrated catalyst was robust and stable under the reaction conditions. Furthermore, it was easy to be separated from the reaction mixture and be reused for subsequent reactions up to 5 times without significant reactivity or selectivity loss.

Highlights

The upsurge need of alternative sources for fine chemicals take the burden off the dependency on depleted traditional non-renewed sources and might have environmental benefits [1,2,3]
The oxidative depolymerization has been viewed as a promising method for the conversion of lignin to small phenolic compounds such as vanillin, syringaldehyde and p-hydroxybenzaldehyde [11,12,13,14,15,16,17]
Different studies stressed out that plant metabolites like polyphenols are natural reducing agents and a capping agent used for metallic nanoparticles stabilization [37]

Summary

Introduction

The upsurge need of alternative sources for fine chemicals take the burden off the dependency on depleted traditional non-renewed sources and might have environmental benefits [1,2,3]. The valorization of lignin compounds by converting lignin into valuable fine chemicals and fuels has become an appealing approach. Several strategies to produce lignin derivatives, including pyrolysis, hydro processing and oxidation were reported [7,8,9,10,11]. In comparison to thermal and hydro processing strategies, which require high energy input, oxidation strategies are gaining intensive attentions because they can be implemented under mild and environmentally friendly conditions [11,12,13,14,15,16,17,18,19,20,21,22,23,24,25].

Methods

Results

Conclusion