Process for obtaining seed hull commodities including cellulosic fibers

Abstract

Cellulosic fibers are removed from seed hulls such as cottonseed hulls by a process including (a) in the absence of mechanical action sufficient to cause degradation of fiber properties, contacting the seed hulls which comprise both cellulosic fibers (linters and hull fibers) and non-fibrous hull components with an alkaline solution and an oxygen-containing gas until the cellulosic fibers are substantially free of the non-fibrous hull components, and (b) recovering the cellulosic fibers from the non-fibrous hull components so as to produce readily washable cellulosic fibers having substantially unimpaired mechanical properties. The cellulosic fibers may then be washed and separated according to known fiber fractionation procedures. The cellulosic fibers produced according to this improved process have substantially unimpaired mechanical properties and contain substantially no polyphenolic materials or extraneous color components. The process provides a more selective and complete removal of polyphenolic materials and extraneous color material requiring less alkali and resulting in higher carbohydrate yields than prior art processes. The process eliminates or significantly alleviates the noise and respiratory dangers of certain known mechanical delinting processes. Other seed hull commodities may also be obtained. These other seed hull commodities include hull residue containing xylan which may be further treated to produce xylose and xylitol. Xylose is produced by hydrolyzing the xylan such as by dilute sulfuric acid treatment. Xylitol may be produced by catalytically hydrogenating xylose hydrolyzate solution and then crystallizing xylitol directly from the hydrogenated hydrolyzate solution.