Preparation of sulfur lignin

The thermal degradation of lignin occurs over a wide temperature range, from about 420-773 K. Several practical ways exist for the preparation of sulfur lignin. These are summarized in Table I. 

The synthesis of sulfur lignin is relatively simple, and on a large scale its preparation becomes less expensive than the preparation of synthetic polymers currently used in the semiconductor industry. 

Further Preparative Reactions. When pulps are to be used in the production of materials that do not retain the original fiber stmcture, such as rayon or ceUulose acetate film, the lignin, hemiceUulose, and other components must be reduced to the lowest possible concentrations. A surfactant (ionic or nonionic) is often added during a hot, weakly alkaline extraction step after chlorination. Another approach, sometimes used in addition to the surfactant step, is to treat the pulp with 6—10% NaOH after most of the oxidative bleaching is finished. This treatment removes most of the hemiceUulose. In most purification plants the final stage includes use of sulfuric acid chelators are optional. 

Table I. Some of the methods to prepare sulfur lignin at the temperature of 473-513 K...

Matsushita Y., Iwatsuki A., Yasuda S., Application of cationic polymer prepared from sulfuric acid lignin as a retention aid for usual rosin sizes to neutral papermaking, 7. Wood Sci, 50(6), 2004, 540-544. 

Sulfur dioxide is used in great quantities in the manufacture of sulfuric acid, sulfurous acid, and sulfites. It destroys fungi and bacteria, and is used as a preservative in the preparation of dried prunes, apricots, and other fruits. A solution of calcium hydrogen sulfite, Ca(HSOs)2, made by reaction of sulfur dioxide and calcium hydroxide, is used in the manufacture of paper pulp from wood. The solution dissolves lignin, a substance that cements the cellulose fibers together, and liberates these fibers, which are then processed into paper. 

Alkaline-extracted/acid hydrolysis (AH/NaOH) lignin samples were prepared by subjecting aspen wood flour to a one hour cook at 120°C in 0.05N sulfuric acid (22), followed by mixing the clarified supernatant with 1% w/w NaOH at 25°C with a Waring blender. The insoluble lignins were precipitated by addition of acid and water washes (32% yield). 

---