Highly selective catalytic conversion of furfural to ¦Ã-butyrolactone
Tiefeng Wang* and Xiaodan Li, Yafei Li
Beijing Key Laboratory of Green Reaction Engineering and Technology
Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
*Corresponding author: wangtf@tsinghua.edu.cn
The depletion of fossil fuel reserves and growing demand for energy are drawing efforts to find alternative sources of energy and organic carbon. Biomass-derived molecules can serve as renewable substitutes for petroleum-based building blocks to produce fuels and chemicals.1 Furfural, a renewable platform compound produced by hydrolysis and dehydration of xylan contained in lignocellulose, has already been used to produce fine chemicals such as furfuryl alcohol, tetrahydrofurfuryl alcohol, furan, and furfural resin in industry.2-4 During the past decades, novel technologies and processes have been developed for furfural production. This will necessarily promote the further utilization of furfural to produce more value-added chemicals.
One of the most promising products is ¦Ã-butyrolactone (GBL), which has wide applications in the fields of solvents, medicine, spice and fine organic synthesis.5 Currently, GBL is mainly produced by dehydrocyclization of 1,4-butanediol (BDO) and hydrogenation of maleic anhydride, but they usually have problems of harsh operating conditions, complicated process, and environmental pollution.6 Therefore, it is attractive to sustainably produce GBL from a renewable biomass-derived molecule with high atom economy. This work reports a two-step process to produce GBL from furfural with 2(5H)-furanone as the intermediate. In the first step, furfural was oxidized to 2(5H)-furanone with a promising yield over 60%. In the second step, the purified 2(5H)-furanone was further hydrogenated to GBL using SiO2 supported metal catalysts.
The catalytic oxidation of furfural to 2(5H)-furanone was studied using hydrogen peroxide as the oxidant and formic acid as the catalyst. A 60-62% yield of 2(5H)-furanone, with a total yield of diacids (i.e., maleic acid and succinic acid) in the range of 15-20% as by-products, was obtained in a bi-phasic system using 1,2-dichloroethane or ethyl acetate as the solvent. The good solubility in the organic phase and the strong oxidizing nature of performic acid, which was the real active oxidant generated from formic acid and hydrogen peroxide, contributed to the promising yield of 2(5H)-furanone.7
Having obtained 2(5H)-furanone by furfural oxidation, we next turn to the hydrogenation of 2(5H)-furanone to GBL. With only one more additional C=C bond than GBL, 2(5H)-furanone is an ideal intermediate for converting furfural to GBL. The selective hydrogenation of the C=C bond in 2(5H)-furanone was first studied in a liquid phase over a series of SiO2 supported monometallic catalysts (M = Pt, Pd, Rh, Ru, Ni, Co and Cu) prepared by incipient wetness impregnation. The catalyst activity followed the trend of Pd0.5/SiO2 ~ Rh0.5/SiO2 > Ru0.5/SiO2 > Pt0.5/SiO2, and Ni4.5/SiO2 > Co4.5/SiO2 > Cu4.5/SiO2. Furthermore, the initial TOF for 2(5H)-furanone hydrogenation over these monometallic catalysts showed a volcano-type dependence on their metal d-band center values, with Pd having the highest activity.8 This correlation further guided our design of non-noble metal-based bimetallic catalysts to reduce cost.
Ni was shown to be active and selective for the hydrogenation of the C=C bond in 2(5H)-furanone. The activity and selectivity of a metal catalyst can be significantly altered by incorporating a second metal due to electronic and geometric effects.9 Thus, a series of Ni-based bimetallic catalysts, Ni-M/SiO2 (M= Fe, Co, Cu and Zn), were prepared and evaluated for the selective hydrogenation of 2(5H)-furanone to GBL. Among the prepared bimetallic catalysts, Ni-Fe/SiO2 showed the best performance. The effect of addition of Fe on the catalyst performance was further studied with different Ni/Fe ratios. It was found that the introduction of a suitable amount of Fe significantly enhanced the activity while maintaining the selectivity of the Ni/SiO2 catalyst. Characterization measurements by XRD, BET, TEM and chemisorption were used to investigate the promotional effect of Fe, showing that the formation of NiFe alloy, optimized reducibility and metal particle size distribution contributed to the enhanced catalytic performance of the Ni-Fe/SiO2 bimetallic catalyst.
In summary, a two-step process was developed for producing GBL from furfural, providing a new strategy for converting biomass-derived platform compound to high value-added fine chemicals. In the oxidation step, the highest yield of the intermediate, 2(5H)-furanone, was obtained in a bi-phasic system with formic acid as the catalyst, ethyl acetate as the solvent, and hydrogen peroxide as the oxidant. In the subsequent hydrogenation step, a series of Group VIII monometallic catalysts were first investigated and their catalytic performances were correlated with intrinsic properties of the metals, based on which an efficient non-noble bimetallic catalyst, Ni-Fe/SiO2, was further designed.
References
[1] P. Gallezot, Chem. Soc. Rev., 2012, 41, 1538.
[2] D. M. Alonso, J. Q. Bond and J. A. Dumesic, Green Chem., 2010, 12, 1493.
[3] J. P. Lange, E. van der Heide, J. van Buijtenen and R. Price, ChemSusChem, 2012, 5, 150.
[4] S. Dutta, S. De, B. Saha and Md. I. Alam, Catal. Sci. Technol., 2012, 2, 2025.
[5] X. Li, Y. Y. Cui, X. L. Yang, W. L. Dai and K. N. Fan, Appl. Catal. A, 2013, 458, 63.
[6] J. R. Ebner and V. M. Francetti, Chem. Rev., 1988, 88, 55.
[7] X. D. Li, X. C. Lan and T. F. Wang, Catal. Today, 2016, 276, 97.
[8] X. D. Li, X. C. Lan and T. F. Wang, Green Chem., 2016, 18, 638.
[9] S. Zafeiratos, S. Piccinin and D. Teschner, Catal. Sci. Technol., 2012, 1787.
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