Conversion of carbohydrate biomass to methyl levulinate with Al2(SO4)3 as a simple, cheap and efficient catalyst

doi:10.1016/j.catcom.2014.02.021

Catalysis Communications

Volume 50, 5 May 2014, Pages 13-16

https://doi.org/10.1016/j.catcom.2014.02.021 Get rights and content

Highlights

•
Al₂(SO₄)₃ is efficient for carbohydrate conversion to methyl levulinate (MLE).
•
Al₂(SO₄)₃ provides L and B acid sites to catalyze carbohydrate conversion to MLE.
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Other mono-, di- and polysaccharides can also be converted to MLE efficiently.

Abstract

Al₂(SO₄)₃ was developed as a simple and efficient catalyst for the synthesis of methyl levulinate (MLE) from carbohydrate biomass including fructose, glucose, mannose, sucrose, cellobiose, starch, and cellulose. The maximum MLE yield of 64% from glucose could be obtained at 160 °C for 150 min. Important roles of Al^3 + and Brønsted acid sites generated by the hydrolysis/methanolysis of Al^3 + were elucidated. The reaction process was revealed using in situ real-time attenuated total reflection infrared spectroscopy. Al₂(SO₄)₃ can be regenerated easily and reused at least four times without the loss of activity.

Graphical abstract

Table graphic

Introduction

With the gradual consumption of fossil resources, great effort is paid to convert abundant and renewable biomass resources into chemicals and fuels. As one of the most important chemicals derived from biomass resources, levulinate esters showed numerous potential applications either in flavoring and fragrance industries or as a blending component in biodiesel [1], [2]. Additionally, the ester and carbonyl functional groups also enable levulinate esters to be used as substrates for various kinds of condensation and addition reactions in organic chemistry [3]. Production of levulinate esters from cheap, abundant, and renewable biomass resources has attracted much attention in recent years. For example, levulinate esters were obtained from direct conversion of cellulosic biomass [4], [5], [6], [7], [8] or from platform compounds derived from cellulose and hemicellulose, such as glucose [9], [10], levulinic acid (LA) [11], 5-chloromethylfurfural [12], [13], and furfuralcohol [14].

Various acid catalysts including mineral acids (HCl, H₂SO₄, etc.) [4], [10] and solid acids (sulfated metal oxides [9], heteropolyacids [2], [5], sulfonic resins [15], [16], zeolites [9], etc.) were employed for conversion of carbohydrates to LA or its esters. In general, carbohydrates are first dehydrated to 5-hydroxymethylfurfural (HMF) or its derivatives, which are then rehydrated to LA or its esters [9], [17], [18]. It is believed that the generation of HMF or its derivatives from fructose is much easier than from glucose [19], [20], [21], [22]. With glucose as starting material, a catalyst being able to isomerize glucose to fructose might show good performance to obtain high yield of LA or its esters. It can be concluded from literature that Lewis acids are effective for isomerization of aldose [23], [24] while dehydration of fructose to LA or its esters is catalyzed by Brønsted acids [9], [25], [26], [27]. Accordingly, a catalyst combined both Lewis and Brønsted acidity should be appropriate for transformation of glucose to LA or its esters. Similar strategy was utilized in conversion of carbohydrates such as cellulose, sucrose, corn starch, or glucose. For example, Ya'aini and coworkers used hybrid catalyst Cr/HY to catalyze glucose conversion in water to LA; 62% of LA yield was obtained at 160 °C for 180 min [28]. Tominaga et al. employed mixed-acid systems consisting In(OTf)₃ and p-toluenesulfonic acid as Lewis and Brønsted acids to synthesize methyl levulinate (MLE) from cellulose in methanol; MLE yield reached 70% at 180 °C for 5 h, which was higher than In(OTf)₃ (42%) or p-toluenesulfonic acid (20%) being solely used under the same reaction conditions [6]. Recently, Mao and Wu et al. studied the co-catalysis effect of Al salts and acid ionic liquid on the conversion of sucrose or corn starch to MLE. It was found that the combination of Al salts and acid ionic liquid was efficient for the formation of MLE [29], [30].

In the present work, single component Al₂(SO₄)₃ was developed as catalyst for the conversion of various carbohydrates to MLE in methanol at the absence of any co-catalyst. The catalytic mechanism of Al₂(SO₄)₃ in the conversion of carbohydrate to MLE was studied.

Section snippets

Glucose conversion to MLE catalyzed by various acid catalysts

Various catalysts were tested in the conversion of glucose to MLE in methanol (Table 1). MLE yield was low when mineral acid such as H₂SO₄ or HCl was used as catalyst although glucose was completely converted (Table 1, entries 2 and 4). Zeolites, such as H-β, H-MOR, or H-ZSM-5, and sulfonic resin of Amberlyst 15 exhibited lower MLE yield than mineral acids (Table 1, entries 6–9). Only H-USY gave higher MLE yield than mineral acids (Table 1, entry 5). When fructose was used as substrate,

Conclusions

Al₂(SO₄)₃ was found to be an efficient and recyclable catalyst for the conversion of glucose to MLE in methanol under comparably mild conditions (160 °C, 150 min). Al₂(SO₄)₃ could provide Lewis and Brønsted acid site through Al^3 + and the hydrolysis/methanolysis of Al^3 + at the same time, which related to the isomerization of glucose to fructose and dehydration of fructose to MLE, respectively. Fructose, mannose, sucrose, cellobiose, and starch can also be converted to MLE effectively at 160 °C for

Acknowledgments

We are grateful to the National Natural Science Foundation of China (Grant: U1304209; J1210060) and the Undergraduate Innovation Education Project of Zhengzhou University for the financial support (Grant: 2013sjxm008).

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Short CommunicationConversion of carbohydrate biomass to methyl levulinate with Al2(SO4)3 as a simple, cheap and efficient catalyst

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Glucose conversion to MLE catalyzed by various acid catalysts

Conclusions

Acknowledgments

Bioresour. Technol.

Carbohydr. Res.

Appl. Energy

Ind. Crop. Prod.

Appl. Catal. A

Microporous Mesoporous Mater.

Catal. Commun.

J. Catal.

Microporous Mesoporous Mater.

Bioresour. Technol.

J. Catal.

Green Chem.

ChemCatChem

ACS Symp. Ser.

Ind. Eng. Chem. Res.

Green Chem.

Molecules

Angew. Chem. Int. Ed.

Short Communication
Conversion of carbohydrate biomass to methyl levulinate with Al₂(SO₄)₃ as a simple, cheap and efficient catalyst