Clean production of corn Stover pulp using KOH+NH ₄OH solution and its kinetics during Delignification

Pulping of corn stover using KOH and NH ₄OH was investigated. The combined alkaline system could effectively remove lignin during pulping. There are three stages of lignin removal during delignification. Approximately 90% of lignin could be removed after the temperature reached 150 °C for over 30 min. The p-hydroxyl phenol groups in lignin could be completely removed during the delignification reaction. The tendency of the increase of the crystalline degree of cellulose is observed with increase of reaction temperature. The kinetics of delignification are found to be first-order with respect to the remained lignin and 0.4 order with respect to the remaining hydroxide concentration. The activation energy of delignification is 23 kJ/mol. The solution obtained from precipitation of lignin is rich in nitrogen, phosphorous, potassium elements and organic matters. Various techniques including FT-IR, GPC, DSC, were applied to characterize the acid precipitated lignin. The result shows that the lignin with the polydispersity of 1.4 still maintains the p-coumaryl, coniferyl, and sinapyl units in its matrix.