The effect of metal ions as co-catalysts on acidic ionic liquid catalyzed single-step saccharification of corn stover in water

• Mn2+, Fe3+, Co2+ co-catalysts enhances TRS yields in the corn stover hydrolysis.
• Hydrolysis using Mn2+ co-catalyst gave the highest TRS yield of 90.2% at 160 °C.
• Except Cr3+, all other metal chloride co-catalysts improved the glucose yields.

The effects of adding Cr3+, Mn2+, Fe3+, Co2+ Ni2+, Cu2+, Zn2+ and La3+ chlorides as co-catalysts to 1-(1-propylsulfonic)-3-methylimidazolium chloride acidic ionic liquid catalyzed saccharification of corn stover in aqueous medium was studied at 140–170 °C, by measuring the total reducing sugar (TRS) and glucose yields. The samples with Mn2+, Fe3+, Co2+ as co-catalysts produced higher TRS yields compared to the sample without the metal ions. The Mn2+ produced the highest catalytic effect enhancements and produced TRS yields of 68.0%, 72.9%, 90.2% and 87.9% at 140, 150, 160 and 170 °C respectively; whereas the corn stover samples without the Mn2+ produced TRS yields of 42.9%, 52.3%, 54.4% and 53.5% at the same four temperatures. At higher temperatures of 160 and 170 °C, all metal ions studied produced significant enhancements in glucose yields, except Cr3+. The addition of La3+ as a co-catalyst produced the highest glucose yield improvement.