CATALYTIC HYDROPYROLYSIS OF LIGNIN - INFLUENCE OF REACTION CONDITIONS ON THE FORMATION AND COMPOSITION OF LIQUID PRODUCTS

Catalytic hydropyrolysis of different lignins has been studied under various reaction conditions. With a palladium catalyst on active charcoal, liquid products (oil) up to 80 wt% were obtained and the solid residue amounted to only 1 wt%. Nickel-molybdenum on aluminosilica catalysts led to oil yields of about 65 wt%, containing larger amounts of monomeric phenols. Therefore, nickel-molybdenum catalysts were selected to study the influence of the reaction conditions. Under initial hydrogen pressures ranging from 3 to 12 MPa the yield of oil increased from 18.4 wt% to 63.2 wt%. Reaction time had only a slight influence on the product yields, while increasing reaction temperatures promoted fragmentation to monomeric compounds. About one third of the oil was detectable by gas chromatography. The composition of this monomeric fraction did not change under the influence of changing process parameters. The main components of this fraction were phenol and cresols. Some alkylated phenols were found in minor amounts. Guaiacol was found only at a reaction temperature of 350-degrees-C. In none of the nickel-molybdenum experiments were catechols detected.