Pulping of lignocellulose with aqueous alcohol and alkaline earth metal salt catalyst

In a process for converting lignocellulosic plant material to the form of separated fibers in which the plant material is cooked in a confined chamber at elevated pressure in the absence of added oxygen with an initially neutral or acidic aqueous mixture of a lower aliphatic alcohol having one to three carbon atoms at elevated temperature, the improvement which consists essentially of the steps of;

• (a) cooking fragmented lignocellulose with an aqueous solvent mixture containing a major volume proportion of the alcohol and containing a catalytic amount of a magnesium, calcium or barium salt or mixtures thereof which promotes separation of the fibers from the lignocellulose material in the solvent mixture at elevated temperatures as a primary catalyst in amount dissolved therein at an elevated temperature between 145.degree. C. and 240.degree. C., the salt including anions selected from the group consisting of chloride, nitrate and sulphate which is soluble in at least the catalytic amount in the mixture to form magnesium, calcium and barium ions and a catalytic amount of an acidic compound as a secondary catalyst wherein the catalytic amount of the salt is between about 0.005 and 0.5 molar and the catalytic amount of the acid compound is between about 0.0001 and 0.01 normal and wherein the amount of the acid is 10% or less than the weight of the salt;
• (b) maintaining the cooking process at the cooking temperature for at least 2 minutes and sufficient to effect at least partial depolymerization and dissolution of lignin and hemicellulose and other cell wall constituents encrusting the cellulose fibers and to render the fibers separable from each other in a liquor residue containing deissolved lignin materials and sugars to produce a pulp which has a Tappi 0.5 CuEn viscosity of 14 or above;
• and
• (c) recovering the separated fibers, lignin materials and sugars from the liquor residue.

In a process for converting lignocellulosic plant material to the form of a separable-fiber cellulosic residue in which the plant material is cooked in a confined chamber at elevated pressure in the absence of added oxygen with an initially neutral or acidic aqueous mixture of a lower aliphatic alcohol having one to three carbon atoms at elevated temperature, the improvement consists essentially of the steps of:

• (a) cooking fragmented lignocellulosic material with an aqueous solvent mixture containing a major volume proportion of alcohol and containing a magnesium, calcium or barium salt or mixtures thereof which promotes separation of the fibers from the lignocellulosic material in the solvent mixture at elevated temperatures as a primary catalyst in a catalytic amount dissolved therein in a concentration of between about 0.005 and 0.5 molar, the salt including anoins selected from the group comsisting of the chloride, nitrate and sulphate and which is soluble in at least the catalytic amount in the mixture to form magnesium, calcium and barium ions, and with a catalytic amount of a strong acid as a secondary catalyst in concentration between about 0.0001 to and 0.01 Normal, at an elevated temperature between 145.degree. C. and 240.degree. C.;
• (b) maintaining the cooking process at the cooking temperature for at least 2 minutes and sufficient to effect at least partial depolymerization and dissolution of the lignin and hemicellulose and other fiber cell wall constituents encrusting the cellulose fibers to produce a separable-fiber cellulosic residue to produce a pulp which has a Tappi 0.5 CuEn viscosity of 14 or above;
• and
• (c) recovering the cellulosic residue, lignin and sugars from the liquor residue.