Xiaohao Liu,Xiaodong Liu,Haiyong Wang,Tianci Xiao,Ying Zhang,Longlong Ma
Efficient conversion of renewable cellulose to high value-added C3 chemicals is a great challenge in the field of biomass valorization. In this work, we found that the combination of Co and Sn could significantly improve the efficiency of cellulose conversion to acetol. 54.4% yield of acetol and 66.6% total yield of C3 products were obtained when using 2%Sn–10%Co/SiO2 (2 wt% Sn content) as a catalyst. However, using the same Sn content of 2%Sn–10%Ni/SiO2, no acetol and only 7.1% yield of C3 products were produced. By studying the effects of different Sn and Co concentrations on cellulose conversion, it was found that the Sn species play an important role in catalyzing glucose conversion to C3 intermediates, while Co mainly played a role in hydrogenation, the same as Ni. The study demonstrated that Sn–Co/SiO2 with low Sn content can convert glucose to C3 intermediates more efficiently than the Sn–Ni/SiO2 catalyst. Moreover, Sn–Co/SiO2 could effectively convert C3 intermediates to acetol at a high temperature which is essential for acetol production from cellulose; but under the same conditions, the Sn–Ni/SiO2 catalyst tended to catalyze the polymerization of C3 intermediates. A series of characterization methods including AAS, TEM, HRTEM, EDS, XRD, ex situ XPS, in situ XPS, and CO2-TPD found that the combination of Sn and Co could significantly increase the noninteger valent SnOx species in the catalyst. These species increased the basicity of the catalyst and were beneficial in catalyzing the isomerization of glucose and the retro-aldol condensation of fructose.
Xiaohao Liu,Xiaodong Liu,Guangyue Xu,Ying Zhang,Chenguang Wang,Qiang Lu,Longlong Ma
Selective conversion of cellulose into high value-added C3 chemicals is a great challenge in biorefinery due to the complicated reaction process. In this work, 61.6% yield of acetol was obtained by one pot conversion of cellulose using Ni–Sn/SiO2 catalysts. A series of characterization methods including TEM, STEM-HAADF, EDS, AAS, XRD, XPS, H2-TPR, Py-FTIR, and CO2-TPD were carried out to explore the structure–activity relationship. The strong basicity of the catalysts was a key factor affecting the production of acetol. In addition, catalysts with the hydrothermally stable L-acid sites and no B-acid sites inhibited side reactions and ensured efficient conversion of cellulose into small molecules. Further studies showed that the formation of the Ni3Sn4 alloy significantly promoted the acetol production, and its weak hydrogenation activity inhibited further conversion of acetol. Noninteger valence tin species (Snδ+ and SnOx) were formed both in Ni3Sn4 and Sn/SiO2. These Sn species were the source of basic sites and the active sites for catalyzing cellulose to acetol. Under the synergistic catalysis of Sn/SiO2 and the Ni3Sn4 alloy, cellulose was efficiently converted into acetol. This work provides guidance for the selective conversion of cellulose into C3 products.
Yan Wan,Congcong Zheng,Xianchi Lei,Mengqi Zhuang,Jinhan Lin,Wenda Hu,Jingdong Lin,Shaolong Wan,Yong Wang
ABSTRACT Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.
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