Researchers from the Dalian Institute of Chemical Physics in China have developed a new catalyst with enhanced selectivity for a chemocatalytic approach they developed earlier for the production of cellulosic ethanol.

In the original process, cellulose is first converted into methyl glycolate (MG) in methanol with the promotion of a tungsten-based catalyst and oxygen atmosphere; the formed MG is then hydrogenated to ethanol over a supported copper catalyst. However, the total yield of ethanol from cellulose was only ~30% (yield of MG ~60%, with subsequent selectivity to ethanol of ~50%).

To enhance the ethanol selectivity for this two-step approach, the researchers have now developed a 0.1Pt-Cu/SiO₂ single-atom alloy catalyst; they obtained 76.7% maximum selectivity of ethanol with this new system. A paper on their work is published in RSC journal Green Chemistry.

… the commercial production of cellulosic ethanol is still facing economic and technical barriers due to the high cost of pretreatment as well as the low efficiency of enzymes. Therefore, it is highly desired to develop an alternative method to production of cellulosic ethanol.

… In the present work, we report a new catalyst which is composed of Cu and Pt to form a single-atom alloy (SAA) structure. In this SAA structure, all the Pt atoms are sufficiently isolated with the surrounding Cu atoms, which offers unique advantage of promoting hydrogen activation without causing the C-C cleavage side reaction caused by the Pt nanoparticles, thus affording significantly enhanced selectivity to ethanol as well as promising stability in the MG hydrogenation reaction.

—Yang et al.

In their study, they found that compared to the Cu/SiO₂ catalyst, the 0.1Pt-Cu/SiO₂ catalyst exhibited a higher ethanol selectivity; the MG was converted completely at 493 K and the ethanol selectivity arrived at the highest value of 76.7% at 503 K—20 K less than the Cu/SiO₂ catalyst. Further reaction tests of the Pt-Cu/SiO₂ catalyst with different Pt loadings showed that the optimum content of Pt was 0.1 wt%; lower or higher Pt loadings all resulted in decreased ethanol selectivity.

The team attributed the enhanced performance to the SAA structure.

On one hand, the introduction of Pt improved the dispersion of Cu and increased the Cu+/Cu0 ratio; on the other hand, the single atoms of Pt promoted the activation of H₂ while minimized the C-C cleavage reactions. Thus, MG could be converted to ethanol at a reduced temperature and the ethanol selectivity could be enhanced remarkably. The Pt-Cu SAA strategy presented in this work can be extended to other important reaction systems where C=O and C-O hydrogenation are involved.

—Yang et al.

Resources

• Chao-Jun Yang, Zhi-Li Miao, Fan Zhang, Lin Li, Yan-Ting Liu, Ai-Qin Wang and Tao Zhang (2018) “Hydrogenolysis of methyl glycolate to ethanol over Pt-Cu/SiO2 single-atom alloy catalyst: a further step from cellulose to ethanol” Green Chem. doi: 10.1039/C8GC00309B