Research On Desulfurization From Coal By Photocatalytic Enhancement Of IL-H₂O₂ And Its Mechanism

The main restrictive factor affecting the utilization of coal resources is the existence of sulfur in coal.The unclean combustion of coal will produce a large amount of harmful substances,mainly sulfide and carbon dioxide.The former will damage people’s health and deteriorate the environment.Such as acid rain,which will not only corrode buildings,destroy the soil environment,but also affect agricultural production;the latter leads to the rise of global temperature and the greenhouse effect.In this paper,the common catalyst TiO₂/SiO₂,the hydroxyl modified catalyst TiO₂/SiO₂and the acidic ionic liquid 1-carboxymethyl-3-methylimidazole hydrogen sulfate[HO₂MMim][HSO₄]were mixed with the oxidant H₂O₂solution to enhance coal desulfurization by photocatalysis.Through capture agent experiment,FTIR,XPS and TG-FTIR analysis experiment to discuss the coal desulfurization and the effects of catalyst,ionic liquid and oxidizer on desulfurization rate.Finally,through computer simulation results to analyze the mechanism of organic sulfur oxidative removal in the process of photocatalytic enhanced IL-H₂O₂coal desulfurization.The desulfurization experiment of photocatalytic oxidation of bituminous coal with mixed reagents of different mass ratios showed that the desulfurization rate of organic sulfur and inorganic sulfur of coal was relatively low under the avoiding light condition,when introducing light source,the desulfurization rate is improved.After adding the catalyst,the desulfurization has been greatly increased.The organic desulfurization rate of coal-[HO₂MMim][HSO₄]-H₂O₂-TiO₂（3:1:10:3）is 24.03%,while coal-[HO₂MMim][HSO₄]-H₂O₂-SiO₂（3:1:10:4）is 16.28%and the overall desulfurization effect is weaker than that of TiO₂,indicating that TiO₂has stronger catalytic oxidation than SiO₂.The organic desulfurization rate of coal-[HO₂MMim][HSO₄]-H₂O₂-hydroxyl modified SiO₂（3:1:10:3）is 21.71%,using coal-[HO₂MMim][HSO₄]-H₂O₂-hydroxyl modified TiO₂（3:1:10:3）can reach 22.48%.It shows that the hydroxyl modified TiO₂has better catalytic performance than hydroxyl modified SiO₂.This mainly attributed to the hydroxyl attached to the surface of the hydroxyl modified catalyst,which increases the concentration of·OH in the system,thereby enhancing the photocatalytic activity.Adding tert-butanol,H₂O₂and ethanol as the capture agents of·OH,e^-and H⁺,respectively,to judge the main active radicals in the desulfurization process.The experimental results show that·OH is the main contribution radical with the organic sulfur desulfurization of coal decreased significantly after adding tert-butanol in the whole desulfurization process.Through the FTIR analyzed the organic sulfur functional groups,oxygen-containing functional groups and methylene groups in the raw coal and the treated coal with different mass ratios.The result shows that the vibration intensity of the absorption peak of S-Fe in the coal sample is obviously weakened after photocatalytic treatment and the vibration intensity of organic sulfur-CH,-S-S-absorption peaks in coal treated with hydroxyl modified catalyst Coal-[HO₂MMim][HSO₄]-H₂O₂-TiO₂（3:1:10:3）isweakerthan Coal-[HO₂MMim][HSO₄]-H₂O₂-hydroxyl-modified TiO₂（3:1:10:3）.Therefore,the coal desulfurization effect of using hydroxyl-modified TiO₂as a photocatalyst is better than that of ordinary TiO₂to remove thiols and thioether organic sulfurs.After the experiment,the hydroxyl-modified catalyst is easy to recover,and the desulfurization effect of organic sulfur is slightly reduced by recycling,the stability is strong.Therefore,it is easier to remove organic sulfur such as mercaptans,sulfide by using hydroxyl-modified TiO₂as a photocatalyst than TiO₂as a photocatalyst and has long service life.The XPS analysis results showed that there may be two directions,one is the organic sulfur oxidation,the other is organic sulfur converts into inorganic sulfur in the photocatalytic enhanced IL-H₂O₂system.The·OH is main oxidizing substance to improve the desulfurization rate of coal,which is consistent with the analysis results of.It is proved once again that using hydroxyl modified TiO₂as photocatalyst has a better desulfurization effect to thiophene than that of TiO₂.Through Materials Studio and COSMOtherm simulation analysis,it is found that thiophene is easier to be removed by direct oxidation of hydroxyl radical.The addition of ionic liquid can reduce the energy barrier of electron transition and make electron transition more easily;adding H₂O₂makes it easier for those with high chemical potential to enter to enter the reaction with low chemical potential,which enhances the extraction effect of ionic liquids.TG-DSC-DDSC analysis shows that the heat released by coal combustion is slightly reduced than raw coal due to the removal of sulfur-containing structure,when coal sample enhanced with photocatalytic IL-H₂O₂desulfurization due to the removal of sulfur-containing structure.The thermal risk experiment shows that the photocatalytic enhanced coal desulfurization is an exothermic process.When heated to 65°C and 80°C,the temperature in the reactor exceeds the set temperature,indicating that there will be heat accumulation during the reaction process.If the heat cannot be removed in time,there will be potential safety hazards.