Wetting Effect Of Ionic Liquids On Coal Dust And Its Influence On Coal Oxidation Property

Mine dust and coal spontaneous combustion restrict the safe and sustainable development of the coal industry seriously.At present,the study of wetting agent or surfactant to enhance the wettability becomes hot spot of mine dust control.Room temperature ionic liquids?referred to as ionic liquids?have excellent solubility,designability of structure and dissolving and swelling capacity to coal as the hot spots currently in the field of green chemistry.Based on the wettability of enhanced coal,this paper analyzes and studies the wettability of amphiphilic ionic liquids to enhance the coal's wettability,and analyzes the impact on the oxidation properties of coal.This paper provides evidence for the search of new materials that can significantly enhanced the coal wettability and weaken the coal oxidation activity.Firstly,the critical micelle concentration?CMC?of four kinds of imidazolium-based ILs,such as[HOEMIm][BF₄],[HOEMIm][NTf₂],[C₁₂MIm]Br,[C₁₄MIm]Br and two kinds of quaternary ammonium salt ILs[N_8,8,8,1]Cl and[N_2,2,2,2]Cl are measured by ultraviolet spectrophotometry.The surface tension and wettability of coal experiments show the surface tension at different concentrations of CMC,5%and 20%of ILs.As well as W²-t plot show the surface tension from the CMC to 20%is basically the same and lower than water.[N_8,8,8,1]Cl?[C₁₂MIm]Br and[C₁₄MIm]Br have higher wettability,followed by[HOEMIm][NTf₂]and[HOEMIm][BF₄].It shows good wet performance about CMC and 5%concentrations of[C₁₂MIm]Br,5%and 20%concentrations of[HOEMIm][BF₄],[HOEMIm][NTf₂]and[N_8,8,8,1]Cl.It is inferred that the wettability of ILs are related to the relative molecular mass,and the greater the relative molecular mass is,the more obvious amphipathic structure is.The effects of ILs of 20%concentration on the oxidation characteristics of coal and the microstructure evolution process are studied by means of TG-DTA,temperature-programmedexperimentandFTIR.TG-DTAand temperature-programmed experiments can characterize the inhibition of oxidative activity of these ILs directly and effectively.IR can further reveal the influences of functional groups after treatment.The thermal stability of ILs is analyzed b y TG-DTA.[HOEMIm][NTf₂]and[HO EMIm][BF₄]are good thermal stability and[N_8,8,8,1]Cl and[N_2,2,2,2]Cl are worse thermal stability.TG results show the loss weight of[HOEMIm][BF₄]-tc is less than raw coal after 440°C.DTA results show that the temperature reaching the maximum weight loss rate is delayed about 40°C.The[HOEMIm][BF₄]-tc's trough temperature moves towards the high temperature relative to the untreated coal,and the DTA value is smaller.It indicate that[HOEMIm][BF ₄]delays the oxidation process of the coal,reduces the rate of the exothermic reaction and weakens the coal oxidation activity.The temperature-programmed experimental results show that the 20%concentration of[HO EMIm][BF₄]has an inhibition between 55%and 75%.It has an inhibitory effect on coal oxidation and raises the activative energy of oxidation reaction.So[HOEMIm][BF₄]has the best effect of inhibiting coal oxidation activity.IR results show that ILs have different degrees of damage to O-H and C-O bonds in coal.The greater the damage,the more beneficial the inhibition of the oxidation activity of coal is.We infer that[HOEMIm][NTf₂]and[HOEMIm][BF₄]are more effective to inhibite coal oxidation activity combined with the quantitative analysis of the decrease of CH₂/CH₃ ratio and relative content of hydrogen bonds A_hy/A_ar,and the increase of aromaticity of A_ar/A_al.In summary,[HO EMIm][BF₄]of 20%centration is the most suitable among all ILs for inhibiting the oxidation activity of coal.It can both wet coal and inhibit the oxidation activity of coal effectively.