Iron(0)-Catalyzed Hydrothermal Liquefaction of Switchgrass: the Effects of Co-Catalysts and Reductive Conditions

The effects of a series of co-catalysts: iron(III)chloride, zinc chloride, sodium borate, acetic acid, oxalic acid, 10% Pd-C, sodium carbonate, and Raney-Ni as well as H2 at 200 psi reductive conditions were studied on the iron(0)-catalyzed hydrothermal liquefaction of switchgrass at 210 °C. The addition 10% (w/w) iron(III)chloride as a co-catalyst in 60% aq. ethanol, without a hydrogen atmosphere enhanced the liquefaction yield from 55.7 ± 1.5 to 67.6 ± 2.5%. The use of Pd/C (5% w/w) and Raney-Ni (5% w/w) as co-catalysts could also enhance the liquefaction yields to 67.0 ± 3.0 and 72.3 ± 1.8% respectively, in reactions carried out under hydrogen atmosphere at 200 psi, in H2O, 210 °C, 24 h. GC-MS analysis of the liquefaction products revealed that C5-C10 range partially oxygenated products are formed and the composition of the liquefaction product depends on the co-catalyst used. The thermogravimetric and FT-IR analysis of liquefaction residues indicated that polysaccharide fraction is mainly liquefied in these iron(0)-catalyzed liquefactions of switchgrass at 210 °C.