Catalytic Conversion of Cellulose to Levulinic Acid by Metal Chlorides

Lincai Peng,Yan Gong,Junhua Zhang,Lu Lin,Beixiao Zhang,Junping Zhuang

doi:10.3390/molecules15085258

Lincai Peng, Yan Gong + Show 4 more

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https://doi.org/10.3390/molecules15085258

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Abstract

The catalytic performance of various metal chlorides in the conversion of cellulose to levulinic acid in liquid water at high temperatures was investigated. The effects of reaction parameters on the yield of levulinic acid were also explored. The results showed that alkali and alkaline earth metal chlorides were not effective in conversion of cellulose, while transition metal chlorides, especially CrCl3, FeCl3 and CuCl2 and a group IIIA metal chloride (AlCl3), exhibited high catalytic activity. The catalytic performance was correlated with the acidity of the reaction system due to the addition of the metal chlorides, but more dependent on the type of metal chloride. Among those metal chlorides, chromium chloride was found to be exceptionally effective for the conversion of cellulose to levulinic acid, affording an optimum yield of 67 mol % after a reaction time of 180 min, at 200 °C, with a catalyst dosage of 0.02 M and substrate concentration of 50 wt %. Chromium metal, most of which was present in its oxide form in the solid sample and only a small part in solution as Cr3+ ion, can be easily separated from the resulting product mixture and recycled. Finally, a plausible reaction scheme for the chromium chloride catalyzed conversion of cellulose in water was proposed.

Highlights

Cellulose is abundantly available, and is considered as a promising alternative to non-renewable natural resources for the sustainable supply of fuel and chemicals in the future
This is due to the faster dehydration of fructose to HMF than that of glucose, which already been shown in previous studies [18,19]
The results showed that alkali and alkaline earth metal chlorides did not lead effectively to the conversion of cellulose, and there was no significant difference with the blank

Summary

Introduction

Is considered as a promising alternative to non-renewable natural resources for the sustainable supply of fuel and chemicals in the future. One attractive approach is the single-step conversion of cellulose to levulinic acid (LA, Figure 1) by acid-catalyzed hydrolysis. Researchers have reported the conversion of biomass into LA using a dilute mineral acid such as HCl and H2SO4 as catalyst [4,5,6,7]. These hydrolysis reactions were effective, the use of the mineral acid causes serious pollution and promotes equipment corrosion and being difficult to recover from the reaction products for recycling [8]. Wang et al [10] used sulfated TiO2 as a solid acid catalyst to hydrolyze cellulose into LA, the highest yield achieved under their optimal experimental conditions was only 27.2 mol %

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