Ammonium sulfide organosolv pulping

Abstract

The use of ammonium sulfide in aqueous ethanol and methanol was investigated for pulping of wood. Hemlock chips required 21% ammonium sulfide (equivalent to 19% Na2O) at 180°C to become delignified to the kappa range 35–50. The yields exceeded those of conventional kraft pulps by 14% on dry wood basis. Over 75% of the original glucomannan was recovered in the pulp as the consequence of end group stabilization by ammonium sulfide. The intrinsic viscosity of the pulps, measured in cadoxen was 10.65 dl/g — approximately double the value for softwood kraft pulps. The pulps were readily bleached and possessed higher tensile and burst strengths but lower tear strengths than kraft pulps. Ammonium sulfide pulps from cottonwood were likewise obtained in high yields and with adequate strength properties.