Oxidative-organosolvent delegification of wheat straw

Abstract

Urgency of the research. Expansion of the raw material base of the pulp and paper industry of Ukraine takes place through the use of alternative types of vegetable raw materials, namely wheat straw, and the improvement of environmentally friendly oxidative-organosolvent technology for the production of straw pulp. Target setting. Methods for the delignification of vegetable raw materials using the oxidant – hydrogen peroxide – are currently available. The disadvantage of these methods is the high consumption of the oxidant, which constitutes 90 % by weight of absolutely dry raw material that significantly increases the cost of technical cellulose. Therefore, it is necessary to improve the technological parameters of the delignification process of wheat straw with hydrogen peroxide in acetic acid. Actual scientific researches and issues analysis. Recent open-access publications have been reviewed, including literature on oxidative-organosolvent delignification methods of plant material using peroxoacids. Uninvestigated parts of general matters defining. Investigation of technological parameters of oxidative-organosolvent delignification for the reduction of oxidant consumption and determination of optimal values of temperature and duration of the delignification process of wheat straw with the mixture of hydrogen peroxide in acetic acid. The research objective. Investigation of straw pulp production method in order to reduce the consumption of cooking reagents while increasing the physical- mechanical properties and yield of the target product. The statement of basic materials. A method of obtaining straw pulp from wheat straw shreddings in acetic acid media with the hydrogen peroxide consumption 50 % by weight of absolutely dry raw material was investigated. The content of the main components in the raw vegetable material was determined. The effect of the delignification conditions, namely the temperature and cooking duration, on the yield of the fibrous semi-finished product, the content of residual lignin and the content of cellulose was studied. It was shown that the increase of temperature from 70 °C to 90 °C and duration of vegetable raw materials processing from 60 to 180 min lead to the decrease in yield by 28 %, the content of residual lignin by 6.5 %, while the cellulose content in the fibrous semi-finished product increased by 21 %. Calculated regression equations adequately described the experimental data and could be used as a mathematical model of the delignification process of wheat straw by hydrogen peroxide in acetic acid media. Optimal values of technological parameters of the wheat straw cooking process were determined using the method of multicriterion optimization of the delignification conditions. Conclusions. Calculated regression equations adequately described the production process of straw cellulose by hydrogen peroxide delignification in acetic acid. Established optimal technological parameters provided obtaining a final product with high quality indicators (yield 78.2%, residual lignin content 3.6%, cellulose content 65.4%, breaking length – 6200 m, punching resistance 210 kPa, tearing resistance – 425 mN, folding endurance 625 n.d.b.).