Effect of oxidation processing on the preparation of post-hydrothermolysis acid from cotton stalk.

The typical properties and yield of the refined hydrothermolytic acid (RHTA) and refined hydrothermolytic oxidation acid (RHOA) respectively prepared from cotton stalk by the hydrothermolysis process with and without hydrogen peroxide at 180-280 °C were investigated. The pH of RHOA at 180-260 °C is lower than that of RHTA. The yield of RHOA prepared at 180-280 °C is higher than that of RHTA except 230 °C. Besides, the variation trend of RHOA yield at 180-260 °C is in accordance with that of RHTA yield at 200-280 °C. The composition of RHTA and RHOA were determined using gas chromatography and mass spectrometry. The acids content of RHOA at 200 °C reaches the maximum. The phenols of RHOA at 200-230 °C is significantly higher than that of RHTA. Under oxidation atmosphere, the formation of ketones is inhibited and the secondary reactions of furan derivatives is promoted. Overall, the oxidation processing can alleviate the severe hydrothermolysis conditions for preparing post-hydrothermolysis acid.

Study on an alternative approach for the preparation of wood vinegar from the hydrothermolysis process of cotton stalk.

The yield and pH of the refined aqueous product (RAP) prepared by the hydrothermolysis of cotton stalk (CS) were investigated using response surface methodology with the variation of three parameters: CS/water ratio of 0.05-0.15w/w, temperature of 180-280 °C, and retention time of 0-30 min. At the best formulation (0.05w/w, 264.36 °C and 0 min), the yield and pH of RAP were 82.8% and 3.95, respectively. Additionally, the organic compounds contained in RAP prepared under the respective optimal formulation (pH: 0.05w/w, 251.43 °C and 0 min, yield: 0.05w/w, 280.00 °C and 0 min) were determined by gas chromatography and mass spectrometry. The results show that the kinds of compounds in RAP are identical or similar to those in the wood vinegar (WV), but their contents is slightly higher than that of the WV. In sum, it is feasible that RAP has the enormous potential to be utilized as WV probably because of its higher quality and value than WV.