Effect of metal addition to Ni/activated charcoal catalyst on gasification of glucose in supercritical water

Supercritical Water Gasification of Municipal Sludge: A Novel Approach to Waste Treatment and Energy Recovery

“…Catalytic SCWG studies can be divided into two categories based on the types of catalyst used: supported and unsupported catalysis (Lee, 2011). Supported catalysts can include the Noble metals (viz., Ru, Rh, Pd, Ir, and Pt) or lower-cost, common metals (viz., Re, Sn, Pb, W, Mo, Zn, Cr, and Ni) (Chang et al, 1993).…”

“…Supported catalysts can include the Noble metals (viz., Ru, Rh, Pd, Ir, and Pt) or lower-cost, common metals (viz., Re, Sn, Pb, W, Mo, Zn, Cr, and Ni) (Chang et al, 1993). Supported catalysts usually consist of various metals (including oxides and ores) dispersed on fixed-bed supports or particles made of ceramic, carbon, or metal oxide (Ding et al, 1996;Lee, 2011). High-performance ceramics (e.g., Al2O3, ZrO2, SiO2, Si3N4, Ce2O3, and TiO2) have been used as supports for catalysts in SCW (Azadi et al, 2011;Ding et al, 1996;Lee, 2011).…”

“…Supported catalysts usually consist of various metals (including oxides and ores) dispersed on fixed-bed supports or particles made of ceramic, carbon, or metal oxide (Ding et al, 1996;Lee, 2011). High-performance ceramics (e.g., Al2O3, ZrO2, SiO2, Si3N4, Ce2O3, and TiO2) have been used as supports for catalysts in SCW (Azadi et al, 2011;Ding et al, 1996;Lee, 2011). All of these ceramics are, however, subject to thermal creep at much lower temperatures than when exposed to hightemperature gases, thereby allowing the supported catalyst particles to contact each other, then sinter, weld, or polish, rendering them inactive (Bermejo & Cocero, 2006b;Hyde et al, 2001).…”

“…It is known, however, that soluble salts and insoluble metals catalytically react in different ways (mainly solubilization, mineralization, and oxidation), and a number of researchers have pointed out that there is no straightforward explanation in the literature for the kinetic mechanisms governing these synergistic processes (Azadi & Farnood, 2011;Bernardi et al, 2010;Lu et al, 2010). Catalytic in-situ effects resulting from sludge-entrained inorganic species have been studied as alternatives to conventional catalysts (Lee, 2011). This approach makes use of the antisolvent effect of supercritical water, wherein catalytically active salts and metals present in the sludge matrix actually produce catalyst precursors on the fly, such as activated carbon and trace reactive metals (Marques et al, 2011).…”

“…Tars and sulfur edicts commonly released from sludge during gasification also present a threat to long-term catalyst stability (Afif et al, 2011;Elliott, 2008;Izumizaki et al, 2005;Zhang et al, 2011). Tarry deposits and sulfur poisons dramatically impact metal catalyst effectiveness and resulting gas yield volume, even though they have little discernable effect on gas fraction and composition (Afif et al, 2011;Lee, 2011). Some catalyst regeneration was evident with the flushing of sulfur-poisoned catalysts with subcritical water (at 250-300°C), which removed up to 75% of the sulfur (Elliott, 2008).…”