This specification discloses an operational continuous process to convert lignin as found in ligno-cellulosic biomass before or after converting at least some of the carbohydrates. The process comprises thermally treating the ligno-cellulosic biomass and then subjecting the thermally treated ligno-cellulosic biomass to a step of fiber shives reduction to produce a low viscosity slurry. The continuous process has been demonstrated to create slurry, raise the slurry to ultra high pressures, deoxygenate the lignin in a reactor over a catalyst which not a fixed bed without producing char. The conversion products of the carbohydrates or lignin can be further processed into polyester intermediates for use in polyester preforms and bottles.