The lactic acid (LA) production from corn stover using Lewis acid catalysts was
optimized. Initially, an equimolar mixture of Al(III)/Sn(II) was used as a catalytic system
at 190 ◦C with 5 wt% biomass. Increasing the catalyst concentration led to higher LA
production, showing the optimal results at 16 mM. A low catalyst concentration mainly
produced furfural and HMF, dehydration products from the corn stover sugars. Higher
catalyst concentration increased LA yield but also produced the degradation of the glucose
dehydration products into levulinic and formic acids, reducing LA selectivity. Al(III)
was essential for LA formation, while Sn(II) was less effective due to its lower solubility,
shown by the presence of Sn(II) in the solid residue after treatments. A total of 16 mM
Al(III) yielded the highest LA levels at 190 ◦C, 7.4 g/L, and 20.7% yield. Increasing the
temperature to 210 ◦C accelerated the LA production while also achieving the lowest energy
consumption, which was 0.47 kWh/g LA at the highest LA production point. However,
longer treatments at this temperature caused LA degradation. AlCl3 has been identified as
an ideal catalyst for biomass conversion to LA, being inexpensive and low in toxicity.
