Catalytic effects of NaOH and ZrO2 for partial oxidative gasification of n-hexadecane and lignin in supercritical water☆

Partial oxidative gasification of n-hexadecane (n-C16) and organosolv-lignin (lignin) was studied by use of a batch type reactor in supercritical water: 673 K, 0.52 cm−3 of water density (40 MPa of water pressure at 673 K), and 0.3 of O/C ratio for the n-C16 experiments; 673 K, 0.35 cm−3 of water density (30 MPa of water pressure at 673 K), and 1.0 of O/C ratio for the lignin experiments. The experiments without O2 were also conducted for lignin (lignin decomposition). For all the cases (n-C16 partial oxidation, lignin decomposition, lignin partial oxidation), NaOH or zirconia (ZrO2) was added in the system as catalysts. Through n-C16 studies, the catalytic effect of NaOH and ZrO2 on partial oxidation in supercritical water were examined. In the case of lignin partial oxidation, we studied the possibility of partial oxidation in supercritical water for gasification technique of wastes. The yield of H2 from n-C16 and lignin with zirconia was twice as same as that without catalyst at the same condition. The H2 yield with NaOH was 4 times higher than that without catalyst. Thus, a base catalyst has a positive effect on partial oxidation of n-C16 and lignin to produce H2. The catalytic effect of NaOH and ZrO2 was found to be enhancement of decomposition of intermediate (aldehyde and ketone) into CO, through n-C16 studies. In the case of lignin studies, the enhancement of decomposition of the carbonyl compounds by catalytic effect of NaOH and ZrO2 inhibit char formation and promotes CO and thus H2 formation.