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DEACTIVATION MECHANISM OF γ-Al2O3 BASED CATALYSTS FOR THE CATALYTIC HYDROLYSIS OF CARBONYL SULFIDE IN PRESENCE OF HCl
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摘要: 随着钢铁行业超低排放的推进,实施高炉煤气脱硫迫在眉睫。高炉煤气中含硫组分主要为羰基硫(COS),常采用γ-Al2O3基催化剂将COS催化水解为H2S再进一步脱除,但是煤气中的HCl组分容易导致催化剂失活。采用浸渍法在γ-Al2O3上负载碱金属Na、K制备铝基水解催化剂,在固定床-气相色谱联用装置上,考察水解催化剂在含HCl气氛的失活机理。在120 ℃、150000 h-1空速条件下测试COS的水解效率。结果表明:Na/Al2O3和K/Al2O3催化剂的活性及抗氯性能均高于γ-Al2O3,且Na/Al2O3的抗氯性高于K/Al2O3。活性组分Na、K增加了催化剂的碱性中心,促进了COS水解反应,提高了催化剂活性;Na、K优先与HCl反应生成金属氯化物,减弱了HCl对载体组分的氯化作用,提高了催化剂的抗氯性。探明了Na/Al2O3和K/Al2O3催化剂在含HCl气氛的失活机理。HCl占据了催化剂的中强碱性中心(M—O),与碱金属活性组分反应生成了金属氯化物(M—Cl),降低了催化剂的活性。Na/Al2O3催化剂在HCl气氛中的Na流失量显著低于K/Al2O3催化剂中K的流失量,提高了Na/Al2O3催化剂的抗氯性。Abstract: With the implementation of ultra-low emissions in the iron and steel industry, applying blast furnace gas desulfurization technology is very urgent. The sulfur-containing component in blast furnace gas mainly is carbonyl sulfide (COS), and the catalytic hydrolysis method on the γ-Al2O3-based catalyst is usually selected to generate H2S and then further removed. However, the hydrolysis catalyst is easily deactivated in the presence of HCl from the blast furnace gas. In this work, the γ-Al2O3-based catalyst was prepared by the impregnation method supported with alkali metals, Na or K, as an active component. The effect of HCl on the hydrolysis activity and deactivation mechanism of the catalyst was investigated through the combined platform of a fixed-bed reactor and gas chromatography. The hydrolysis efficiency of COS was tested at 120 ℃, gas hourly space velocity (GHSV) of 150000 h-1. The results showed that hydrolysis efficiency and chlorine resistance on catalysts Na/Al2O3 and K/Al2O3 were higher than that on γ-Al2O3, and the chlorine resistance on Na/Al2O3 was higher than that on K/Al2O3. The active components, Na and K increased the content of alkaline centers of the catalyst, promoted the COS hydrolysis reaction and improved the catalyst activity. The active component Na or K preferentially reacts with HCl to form metal chloride, weakens the chlorination effect of HCl on the support components and improves the chlorine resistance of the catalyst. The deactivation mechanism of Na/Al2O3 and K/Al2O3 catalysts in the presence of HCl was investigated. HCl occupied the medium-strong alkaline center (M—O) of the catalysts and reacted with the active components of alkali metals to form metal chloride (M—Cl), and then reduced the catalyst activity. The loss of Na in Na/Al2O3 in the presence of HCl was significantly lower than K in K/Al2O3, which improved the chlorine resistance of Na/Al2O3 catalyst.
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