Acetic acid pulping of wheat straw under atmospheric pressure

Atmospheric acetic acid pulping of wheat straw was carried out. Pulping con ditions and their effects on pulp properties were investigated in detail, a nd a comparison between acetic acid (AcOH) pulp and soda-anthraquinone (AQ) pulps of wheat straw was made of the chemical composition, strength, and f iber morphology of the pulps. Wheat straw was successfully pulped and fract ionated into pulp (cellulose), acetic acid lignin, and sugars (monosacchari des from hemicellulose), making it easy to utilize them. It was found that among the pulping conditions the dosage of H2SO4 as catalyst was the most n otable, and the extent and rate of delignification could be controlled by v arying the amount of the catalyst. The results also showed that acetic acid pulp was quite different from soda-AQ pulp. About 70% of the ash or 90% of the silica in wheat straw were kept in AcOH pulp. The ash might function a s filler and be beneficial to the printability of paper. It was known that many epidermal cells existed in AcOH pulp in bundles or in single cells. Th ese ash-rich nonfiber cells seemed to hinder the bonding between fibers. Ac OH pulp had lower strength than soda-AQ pulp, which might result mainly fro m the chemical damage of fibers caused by acid, not from the depolymerizati on of cellulose.