Boron doping g-C3N4 supported Cu2O for photocatalytic reforming of xylose into lactic acid

Abstract

Photocatalytic reforming of biomass has a broad prospects in the green and efficient production of high-value chemicals, which was in line with the sustainable development. Herein, we proposed a new photocatalytic system to produce lactic acid from xylose by using boron doping carbon nitride supported cuprous oxide (g-C3N4-B-Cu2O) under a weak alkaline system. The UV–vis and photoluminescence (PL) characterization showed that the introduction of boron and Cu2O into C3N4 not only improved the catalyst UV–visible light absorption range, but promote the separation ability of photogenerated electron holes, which was beneficial for lactic acid forming. The poisoning experiments indicated that the free radicals such as 1O2,·OH,·O2- and h+ were the key active substances in the process of xylose photocatalytic reforming into lactic acid, and with the sacrificial agents such as benzoquinone (BQ), ethylene diamine tetraacetic acid (EDTA), isopropyl (IPA), and tryptophan (Trp) use, the yield of lactic acid significantly reduced. Remarkably, the maximum lactic acid yield of this work was 91.2 %, and it was obtained at 60 ℃ for 120 min with 99.3 % xylose conversion. More importantly, the g-C3N4-B-Cu2O photocatalyst exhibited the satisfied stability, and can be reused at least for nine times with the lactic acid yield loss less than 2.3 %. Finally, the plausible reaction pathway for xylose photocatalytic reforming to lactic acid over g-C3N4-B-Cu2O were also investigated in this work.