Hydrothermally treated corncob as solid acid catalyst for facile hydrolysis of starch from avocado seed

Corncob residue has been successfully utilized to create a heterogeneous acid catalyst. The catalyst was developed through a two-step process. It began by carbonizing the corncob particles under hydrothermal condition at 200 °C for 10 h, and it was then followed by hydrothermal sulfonation using the concentrated H 2 SO 4 at 150 °C for 10 h. Based on the SEM image of synthesized catalyst, the corncob-derived sulfonated solid catalyst (CC-HT-S) exhibited the irregular surface shape with the random size of pores after sulfonation. Meanwhile, the FT-IR analysis indicated the presence of –SO 3 H by showing the absorption band at 1030 and 1190 cm −1 for CC-HT-S. It was supported by increase in the acid density of CC-HT-S as 5.6-fold was observed higher than the untreated corncob. The CC-HT-S was further performed in the hydrolysis of starch from avocado seed to produce glucose. The optimum total reducing sugar (TRS) concentration of 5.8 g/L was obtained by hydrolyzing 4 g starch of avocado seed at 100 °C for 50 min. There was no significant reduction in catalyst activity following five consecutive reaction runs. Therefore, the developed CC-HT-S catalyst utilized in hydrolysis process for TRS production showed the potential performance to be applied in larger scale.