PREPARATION OF A LIGNIN-DERIVED PASTING OIL

By studying the effects of time and temperature on the hydrotreating of cresol, alone and with lignin added, in a tubing bomb reactor and a stirred autoclave, conditions have been found under which a lignin-derived pasting oil can be produced. The unanticipated formation of high boiling cresol degradation products, mostly anthracenes, made production of the pasting oil more difficult than expected; however, using conditions of intermediate severity, anthracenes formation was minimized and sufficient lignin depolymerization was obtained. Vacuum distillation appeared to be the best method for separating cresol from the acetone soluble product, being more efficient and more selective than extraction with hexane. The initial samples of pasting oil still contained cresol and cresol-derived products; however, repeated hydrotreating of this material with more lignin, followed by removal of low boiling products by distillation, should result in a pasting oil that is almost wholly lignin-derived. Once catalyst testing begins, recycle of the high boiling product will be used to provide pasting oil for subsequent experiments. © 1990 Humana Press Inc.