Lignin and related compounds. VI. A study of variables affecting the hydrogenolysis of spruce wood lignin using a rhodium-on-charcoal catalyst

The effect of reaction conditions on the hydrogenolysis of spruce wood lignin over a rhodium-on-charcoal catalyst has been studied and monitored by the yields of the three major degradation products, 1, 2, and 5. Variables included: initial pressure of hydrogen, amount of catalyst, and acidity–basicity of the media. Little variation occurred under moderate acidic or basic conditions with yields of 18–20% of lignin recovered as monomers. Under strongly acidic or basic conditions both yields and relative abundances changed appreciably. Initial hydrogen pressures less than 500 psig resulted in slightly decreased yields in some cases. In strongly alkaline media similar results were obtained with or without added hydrogen provided the catalyst were present.