Paper-making cellulose fibres, xylose and furfural recovery - from annual plant residues, esp. straw, by oxalic acid extn., giving little waste matter

摘要

Fibrous material suitable for paper and cardboard prodn. xylose and/or furfural are obtd. by (a) treating residues from annual plants, contg. woody cellulose fibres, hemicellulose and =10 wt. % lignin, w.r.t. dry matter, at 80-125 degrees C (110-120 degrees C) with a 1-5% (3%) aq. oxalic acid soln., until 50-75% of the hemicellulose has gone into soln., (b) sepg. the cellulose fibres from the liquid, washing with water and opt. drying, (c) using the liquid sepd. from the fibres for a further extn., (d) adding Ca++ to the wash water obtd. in (b) and sepg. the pptd. Ca oxalate, (e) recovering xylose and/or furfural in known way from the residual liquid, (f) converting the Ca oxalate to CaSO4 and oxalic acid with a large excess of H2SO4, spg. the CaSO4, and recovering oxalic acid from the residual liquid by evapn. and crystallisation, (g) using the oxalic acid again in the extn., and (h) using the liquid, freed from oxalic acid in step (f), after diluting with water and making up with H2SO4. Process leaves little waste matter. Valuable by-prods. are obtd. The process involves a closed, system, needing addn. only of a Ca cpd., and supplementary amts. of H2SO4 and oxalic acid.