Kinetic modeling of xylan hydrolysis in co- and countercurrent liquid hot water flow-through pretreatments

► Declining xylan hydrolysis rate constant is superior to constant hydrolysis rate constant. ► Direct xylooligomer degradation is necessary to describe observed degradation behavior. ► Countercurrent flowthrough pretreatment performs better than cocurrent pretreatment. ► Temperature gradient along the reactor axis is beneficial to reduce xylan degradation. ► Biomass bed shrinking increases exit xylooligomer concentration compared to non-shrinking.