Catalytic effects of NaOH and ZrO_2 for partial oxidative gasification of n-hexadecane and lignin in supercritical water

摘要

Partial oxidative gasification of n-hexadecane (n-C_(16)) 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-C_(16) 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-C_(16) partial oxidation, lignin decomposition, lignin partial oxidation), NaOH or zirconia (ZrO_2) was added in the system as catalysts. Through n-C_(16) studies, the catalytic effect of NaOH and ZrO_2 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 H_2 from n-C_(16) and lignin with zirconia was twice as same as that without catalyst at the same condition. The H_2 yield with NaOH was 4 times higher than that without catalyst. Thus, a base catalyst has a positive effect on partial oxidation of n-C_(16) and lignin to produce H_2. The catalytic effect of NaOH and ZrO_2 was found to be enhancement of decomposition of intermediate (aldehyde and ketone) into CO, through n-C_(16) studies. In the case of lignin studies, the enhancement of decomposition of the carbonyl compounds by catalytic effect of NaOH and ZrO_2 inhibit char formation and promotes CO and thus H_2 formation.