Synthesis and properties of nanostructured sol-gel sorbents for simultaneous removal of sulfur dioxide and nitrogen oxides from flue gas.

摘要

Regenerative, alumina-supported, copper-based sorbent/catalysts provide a promising technique for simultaneous removal of SO₂ and NO _x from flue gas. These sorbents can remove over 90% of SO₂ and 70+% of NO_x while generating no wastes, reducing energy consumption, and producing valuable by-products. The lack of a cost-effective sorbent with low attrition rate and good reactivity has been the main hurdle to commercialization of this copper oxide process. Developing such a sorbent is the focus of this dissertation.; This work examines using sol-gel techniques rather than traditional processes to produce γ-alumina and copper coated 7-alumina granular sorbents. Important modifications to the established sol-gel synthesis process were made, which minimized generated wastes and reduced preparation time and sorbent cost.{09}A laboratory scale semi-continuous process providing a basis for large-scale synthesis was developed.; The effect of the copper content on the surface area and dispersion of the active species on sol-gel-derived sorbents coated by the one step and wet-impregnation methods was studied. The sol-gel-derived sorbents showed superior sulfation and regeneration properties than the existing commercial sorbents used in the copper oxide process in terms of sulfation capacity, fast regeneration, recovery of sorption capacity, and SO₂ concentration in the regenerated effluent.; The optimum temperature for NO reduction by NH₃ over sol-gel-derived CuO/γ-Al₂O₃ was found to be 350°C for both fresh and sulfated catalysts. This was also the optimum operating temperature for simultaneous removal of SO₂ and NO_x from simulated flue gas. At 350°C, the adsorption capacity of the sol-gel sorbent/catalyst was higher than UOP's sorbent, and very close to the capacity of ALCOA's sorbent, while the catalytic activity for NO reduction of the sol-gel-derived CuO/γ-Al ₂O₃ sorbent fell between the commercial sorbents.; The new mesoporous sol-gel-derived materials showed larger surface area, better mechanical strength, and more uniform dispersion of the copper species than existing commercially available sorbents. The superior mechanical properties, better cost effectiveness, and comparable efficiency for simultaneous removal of SO₂ and NO_x of the sol-gel-derived CuO/γ-Al ₂O₃ sorbents with respect to the commercial ones make them a good option for use in the copper oxide process for combined removal of SO₂ and NO_x from flue gas.