Influence of process variables on the properties of pulp obtained by ethanol pulping of wheat straw

Abstract

The influence of independent variables in the cooking of wheat straw with ethanol-water mixtures (ethanol concentration, cooking time and temperature) on various properties of the pulp (yield and holocellulose, α-cellulose and lignin contents) was studied with a view to determining the best operating conditions to obtain quality pulp (pulp with high holocellulose and α-cellulose contents and a low lignin content). The results were fitted to a second-order polynomial function using a BMDP system package and a 2 m central composite design. In this way, equations that reproduce yield and the holocellulose and α-cellulose contents with errors less than 3.5% and lignin content with errors less than 15% were derived. Additional equations were obtained that relate dependent variables to the treatment severity parameter, R o and reproduce the experimental yields and holocellulose, α-cellulose and lignin contents with errors less than 10, 4, 4 and 15%, respectively. Obtaining pulp with high holocellulose and α-cellulose contents and a low lignin content, entails using a high temperature (190°C) and ethanol concentration (80%) for a long time period (2 h).