A flow-through reactor for hemicelluloses extraction with hot pressurized water was scaled with a factor of 73. System performance was evaluated by comparing the temperature profile, extraction yield and kinetics of the two systems, performing experiments at 160 and 170 degrees C, 11 barg for 90 min, using catalpa wood as raw material. Hemicellulose yields were 33.9% and 38.8% (lab scale 160 degrees C and 170 degrees C) and 35.7% and 41.7% (pilot scale 160 degrees C and 170 degrees C). The pilot reactor was upgraded by designing a manifold system capable to provide samples with different liquid residence time during the same experiment. Tests at 140, 150, 160 and 170 degrees C were carried for 90 min. Increasing yields (9.3-40.6%) and decreasing molecular weights (4078-1417 Da) were obtained at increasing the temperature. Biomass/water ratio of 1/27 gave total average concentration of xylose of 0.4 g/L (140 degrees C) to 1.8 g/L (170 degrees C).