水溶液对光催化煤脱硫实验的影响

Effect of aqueous solution on photocatalytic coal desulfurization experiment

为提高燃煤中硫的脱除率,采用光催化氧化法脱硫,利用30%过氧化氢(H_(2)O_(2))作为氧化剂、SiO_(2)作为光催化剂,加入1 g水溶液,使其在紫外灯照射下反应,或者在紫外光照射后加入1 g水溶液,观察煤中硫含量的变化。结果表明:水溶液可以增加氧化物质,提高溶剂的氧化性,H_(2)O_(2)-SiO_(2)-H_(2)O光催化处理后煤样的无机硫脱除率达到40%左右,有机硫脱除率最大可以达到9.69%。加入过氧化氢会优先去除无机硫,但是过量的过氧化氢反而会捕获羟基自由基导致体系的氧化性减弱,脱硫率降低;光照结束后加入水溶液时煤的有机硫脱除率提高,说明水溶液在一定程度上可以促进光催化煤脱硫。FTIR和XPS分析表明光催化对噻吩、砜和亚砜的脱除效果好;模拟分析表明水溶液可以在紫外光辐射下产生羟基自由基;而噻吩内部为负电性区域,外部区域呈正电性,羟基自由基的氧原子附近所在区域呈负电性,所以高电负性羟基自由基容易攻击噻吩等高电子云密度点,使其氧化成极性更大的物质,最后通过萃取将其与煤分离。

To improve the removal rate of sulfur in coal,using 30%hydrogen peroxide(H_(2)O_(2))as the oxidant and SiO_(2)as the photocatalyst,the photocatalytic desulfurization of coal by adding 1 g aqueous solution as the reagent and the solvent before or after ultraviolet lamp irradiation was investigated under the normal temperature and pressure.The results show that adding an aqueous solution can increase the oxidizing substances in the solution and improve the oxidizing ability of the solvent.After treatment with H_(2)O_(2)-SiO_(2)-H_(2)O,the removal rate of inorganic sulfur in coal samples reaches about 40%,and the maximum removal rate of organic sulfur reaches 9.69%.Adding hydrogen peroxide will preferentially remove inorganic sulfur,but excessive hydrogen peroxide will capture hydroxyl free radicals,weakening the oxidation of the system and reducing the desulfurization rate.In addition,adding water after the end of illumination improves the organic sulfur desulfurization rate of coal,indicating that an aqueous solution can promote photocatalytic coal desulfurization to a certain extent.FTIR and XPS analysis reveales an excellent photocatalytic removal of thiophene,sulfone,and sulfoxide.The simulation finds that an aqueous solution can produce hydroxyl radicals under ultraviolet radiation.Then,the inside area of thiophene is negatively charged,and the outside is positively charged,while the hydroxyl radical near the oxygen atom in the region is electronegative.Therefore,hydroxyl radicals with high electronegativity tend to attack high electron cloud density points such as thiophene and oxidize them to substances with greater polarity.Eventually,it can be separated from the coal by extraction.