The Promoting Effect of Ce on the Performance of Au/CexZr1−xO2 for γ-Valerolactone Production from Biomass-Based Levulinic Acid and Formic Acid

Xiaoling Li,Qi Tian,Jianmei Li,Xudong Liu,Changwei Hu

doi:10.3390/catal8060241

Abstract

The production of γ-valerolactone (GVL) directly from biomass-based levulinic acid (LA) and formic acid (FA) without extra hydrogen source is attractive but challenging, due to the requirement of a highly active and stable catalyst. In present work, Au/CexZr1−xO2 with various Ce/Zr ratios were prepared as the catalyst for GVL production from LA with the equivalent molar FA, and characterized by XRD, Raman-spectra, BET, NH3-TPD, TEM and XPS. It was found that the doped Ce in Au/CexZr1−xO2 catalyst could improve the reduction of Au3+ to metallic Au0, and also promoted the dispersion of Au0, yielding uniform Au0 nanoparticles with a small average particle size of about 2.4 nm, thus enhancing both the decomposition of FA to CO-free H2 and the hydrogenation of LA. Meanwhile, a certain amount of doped Ce (x ≤ 0.4) could facilitate the formation of tetragonal phase (the most desired structure on LA conversion to GVL), and increase the amount of weak and medium-strength acidic sites of catalyst, thereby promoting the dehydration reaction of the intermediate derived from LA hydrogenation. Au/Ce0.4Zr0.6O2 catalyst exhibited the best catalytic activity, achieving 90.8% of LA conversion and 83.5% of GVL yield (TON = 2047.8), with good recyclability, and the activity showed no obvious change after 5 runs.

Highlights

With increasing attention on the production of renewable platform chemicals from biomass, more research has been focused on γ-valerolactone (GVL) production
The Zr 3d5/2 binding energy at around 182.2 eV remains unchanged for all the catalysts. This result is consistent with the result of Eder et al, where it is demonstrated that higher temperature than
The relative concentration of metallic Au0 on Au/Cex Zr1−x O2 is much higher than that in the Au/ZrO2 catalyst, demonstrating that the doped Ce can favor the reduction of Aun+ to Au0

Summary

Introduction

With increasing attention on the production of renewable platform chemicals from biomass, more research has been focused on γ-valerolactone (GVL) production. GVL is considered as one of the most important platform chemicals derived from biomass. GVL can be used as an additive in food, liquid fuels and perfumes [1,2]. It is found that the gasoline with GVL as fuel additive shows similar fuel properties to that with ethanol as an additive. GVL is a precursor to produce gasoline, diesel fuels and other valuable chemicals such as ionic liquid, methyl pentenoate, 1,4-pentanediol, and polymers [3,4,5]. GVL is stable under neutral conditions, and is a safe material for industrial applications [6]

Methods

Results

Conclusion