TiO 2 nanobelts with different synthesis methods have been actively pursued for a long time, however, a systematic study corresponding to the fabrication of TiO 2 nanobelts by alkali-hydrothermal method has not been worked out by any research. Here, we systematically study the conditions such as the source of Ti and hydrothermal parameters with the assistance of X-ray diffraction (XRD), scanning electron microscope (SEM), N 2 -sorption measurement and photochemical tests. The XRD and SEM measurements show that the TiO 2 nanobelts exhibit excellent belt-like structures and high crystalline intensity when using tetrabutyl titanate (Ti(OBu) 4 ) as the source of Ti, the volume of 10 mol/L NaOH is 15 mL, the hydrothermal reaction is conducted at 180 °C for 20 h and the heat treatment system is 800 °C for 2 h. The length–diameter ratio of the final obtained sample is about 130 and the specific surface area is 50.4 m 2 /g.
Freeze pretreatment combined with alkaline-hydrothermal method of rice straw for enzymatic hydrolysis was studied. Crystallization stress in the rice stem pores caused by water freezing at −20– −40 °C was modeled to illustrate the destruction mechanism. The stress was calculated as 22.5–38.3 MPa that were higher than the tensile yield stress of untreated stems (3.0 MPa), indicating ice formation damaging pore structure. After freeze at −20 °C, rice straw was further hydrothermally treated at 190 °C with 0.4 M Na 2 CO 3 , achieving 72.0 % lignin removal and 97.2 % cellulose recovery. Glucose yield rose to 91.1 % by 4.3 times after 24 h hydrolysis at 10 FPU loading of Cellic®CTec2 cellulase. The specific surface area of rice straw was 2.6 m 2 /g increased by 1.2 times after freeze. Freeze combined with alkaline-hydrothermal treatment is a green and energy-efficient method for improving enzymatic hydrolysis.
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