Characteristics and desulfurization-regeneration properties of sol-gel-derived copper oxide on alumina sorbents

Mesoporous alumina supported copper oxide granular sorbents were synthesized by the sol-gel method using different raw materials. The copper loading in the sorbents was varied from 5 to 20-wt.% CuO. The effect of the copper content on the surface area of the sorbents and dispersion of the active species was studied. Samples with <14 wt.% CuO did not show any crystalline copper containing phase. For CuO/γ-Al₂O₃ with 8 wt.% CuO, most of the copper species consisted of Cu²⁺ ions and no sulfide species were found. The optimum temperature for operation of the sol-gel derived sorbents was 400°C at which more than 85% of the initial sulfation capacity is maintained up to three sulfation-regeneration cycles. The pore structure, crush strength, sulfation capacity and regeneration properties of the sol-gel derived sorbents were studied and compared with those of the similar commercial sorbents used in pilot scale fluidized-bed copper oxide process for flue gas treatment. The sol-gel-derived mesoporous copper oxide coated alumina granules, with a surface area of 220-248 m²/g, pore volume of 0.46-0.48 cm³/g, and pore diameter of 6.7-8.8 nm, offer higher surface area, more uniform pore size distribution, and higher crush strength than the commercially available sorbents for the copper oxide process. For similar copper oxide content the sol-gel derived sorbents showed superior sulfation and regeneration properties than the commercial sorbents, in terms of sulfation capacity, regenerability, and SO₂ concentration in the regenerated effluent.