Abstract:

The polyethylene glycol (PEG) solution was examined in the presence of zirconium oxide supported nickel catalysts (Ni/ZrO₂) in sub- and supercritical water (350—430℃ and 24 MPa) in a continuous reactor with the residence time of 60—300 s. As a result, the main gaseous products were hydrogen, carbon monoxide, methane and carbon dioxide. When PEG was gasified with 90 g 15% Ni/ZrO₂ at 430℃, 24 MPa, residence time 300 s, 70.14 mol H₂ was produced by gasifying 1 kg PEG, which was 5.1 times of the hydrogen yield produced without catalyst, 2.6 times of the hydrogen yield produced catalyzed with 90 g ZrO₂, the R_TOC(TOC removal efficiency), R_CG(carbon gasification ratio) and R_HG(hydrogen gasification ratio) were 88.84%, 88.50% and 169.40% respectively. The amount of gases increased with an increase in nickel loading on zirconium oxide.When the mass fraction of Ni rose to 15% from 5%,the R_TOC, R_CG and R_HG rose to 58.66%,58.16% and 112.49% from 45.31%,44.55% and 78.25% respectively at 410℃,24 MPa, residence time 180 s. Higher temperature and longer residence time had positive effect on gasification and increase hydrogen yield. The gasification efficiency and H₂ yield decreased with the increase of PEG concentration, but CO₂ yield increased initially and then decreased and CH₄ yield increased because the water-gas shift reaction was restrained and the methanation reaction was accelerated with the increase of PEG concentration.The experiment proved that Ni/ZrO₂ showed good catalytic activity, especially in hydrogen production. For the same reaction efficiency, reaction temperature can be lowered by about 80℃.