Acid hydrolysis of some industrial pulps:: effect of hydrolysis conditions and raw material

Dilute acid hydrolysis of pulps was studied by following the decrease in intrinsic viscosity of preparations of microcrystalline cellulose. The decrease in intrinsic viscosity and the loss of weight during hydrolysis at reaction temperatures of 60 and 80degreesC was investigated, using acid concentrations from 0.5 to 4 M and two different acids ( HCl and H2SO4). The same levelling-off degree of polymerisation ( LODP) was reached under all hydrolysis conditions, but a longer time was needed under milder conditions. An appropriate method of determining the intrinsic viscosity at LODP was established and used in this investigation. The greatest difference in LODP was found between a birch prehydrolysed kraft pulp and a mixed hardwood prehydrolysed kraft pulp; the intrinsic viscosities at LODP being 178 and 72 dm(3)/kg, respectively. The effect of the intrinsic viscosity of a given starting material was also investigated, but only a small difference ( 10%) in the LODP was found for pulp samples with very different initial intrinsic viscosities.