Analytical pyrolysis and semicontinuous catalytic hydropyrolysis of Organocell lignin

Abstract Analytical pyrolysis—gas chromatography FID has been applied to simulate technical flash pyrolysis using milled wood lignin (MWL) and Organocell lignin (OCL) derived from a sulfur-free pulping process. Although OCL yielded less unsaturated compounds than MWL the composition of phenolic compounds is still complex. In a search for technically viable ways of lignin utilization, OCL was subjected to catalytic hydropyrolysis in a semicontinuous reactor system which permits the continuous removal of valuable products from the reaction zone. Thus, a light-oil fraction was collected in a high-pressure condenser and a middle-oil fraction remained in the reactor during the whole reaction time. Residence times, hydrogen pressures and the effect of catalyst were studied. Hydrogen pressure was the most significant parameter with respect to overall oil yields and simplification of phenol composition. Total oil yields of > 80% were obtained at 14 MPa, 360 min residence time using a mixture of nickel oxide and chromium oxide supported on aluminium/silicon oxide as catalyst. By quantitative determination of the monophenols with capillary GC, about 12.3% wt., based on lignin, of low molecular weight phenols could be detected in the light-oil fraction. Elemental analysis of the light- and middle-oil fraction was performed. The influence of different process parameters on oxygen content and H/C ratio is demonstrated.