Activated carbon (AC) catalyst supports prepared from hydrolysis lignin were modified to contain Sn, Al, and Cr oxides.
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The modified metal oxide AC catalysts converted > 94 % of glucose in aqueous solution.
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The lactic acid yield was highest with a combination of Sn and Al oxides on AC supports.
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Besides the active metal oxides, the preparation technique of AC affected the lactic acid yield.
Abstract
In this study, heterogeneous biomass-based activated carbon-supported metal oxide catalysts were prepared and tested for lactic acid production from glucose in aqueous solution. Activated carbons were produced from hydrolysis lignin by chemical (ZnCl2) or steam activation and modified with a nitric acid treatment and Sn, Al, and Cr chlorides to obtain carbon-based metal oxide catalysts. The modification of the carbon support by nitric acid treatment together with Sn and Al oxides led to an increase in lactic acid yield. The highest lactic acid yield (42 %) was obtained after 20 min at 180 °C with the Sn/Al (5/2.5 wt.%) catalyst on steam-activated carbon treated by nitric acid. Reusability of the catalyst was also studied with the conclusion that the deposition of carbonaceous byproducts and leaching of Al oxides led to a decrease in catalyst selectivity to lactic acid.