Effects Of Acid Pretreatment And Halide Additives On Thermal Solvent Extraction Of Long-flame Coal

In this paper,Yulin long-flame coal was used as the investigated object.Cyclohexanone was chosen as the extraction solvent.Then the effects of acid pretreatment and halide additives on long-flame coal were investigated.It was found that both methods had positive effects on improving the extraction yields.The experiment content and conclusions were listed in the following part.The HCl and H2SO4 solutions with different concentration were used as the acid pretreatment solvents,and the coal examples were treated for 2 hours.The mass ratio of coal to acid solvent was 1:3.The extraction yields got a maximum value with the increasing of the acid concentration.The coal treated by 0.5mol/L HCl solution was extracted by cyclohexanone at 300? for 2h.The extraction yield of toluene soluble fraction(Y-TS)increased from 10.1% to 44.9%,and the extraction yield of toluene insoluble tetrahydrofuran soluble fraction(Y-TIFS)increased from 6.2% to 12.4%,leading to the total extraction yield(Y-T)increase from 16.3% to 57.3%.The increments of the three yields were 34.8%,6.2% and 41% respectively.As to the coal treated by 0.3mol/L H2SO4,the Y-TS,Y-TIFS,Y-T increased 39.7%,1% and 40.7% from 10.1%,6.2%,16.3% to 49.8%,7.2% and 57% respectively.In terms of the general solubilizing effect of the pretreatment,HCl showed better performance than H2SO4.When a certain amount of anhydrous CaCl2 or anhydrous AlCl3 was added to the thermal extraction at 300? for 2h,the solubility of long-flame coal was improved.When 0.5% CaCl2 was added,Y-TS,Y-TIFS,Y-T increased from 10.1%,6.2%,16.3% to 26.5%,10% and 36.5% respectively,and the increments were 16.4%,3.8% and 20.2%.When 0.5% AlCl3 was added,the three extraction yields of long-flame coal increased from 10.1%,6.2%,16.3% to 27.9%,10.7% and 38.6% with the increments of 17.8%,4.5% and 22.3%.On the whole,the solubilizing effect of AlCl3 was better than that of CaCl2.It could be found from the infrared spectrum that the types of functional groups had little changed after extraction.But the relative amounts of hydroxyl containing compounds,aromatic hydrocarbons and their derivatives decreased.The cyclohexanone extracts of the coal samples pretreated by 0.3mol/L H2SO4 solution and exteacts with 0.5% AlCl3 addition respectively were detected by GC/MS analysis.It was found that both methods could promote the effect of fracturing the part of covalent bond in coal to change the ingredients of extracts.Compounds containing oxygen were the main extracts,and the relative content was less than the blank sample.The former was reduced by 13.69%,and the latter decreased by 16.62%.The relative contents of hydrocarbon compounds and the compounds containing three-membered ring increased compared with the blank sample.The former method increased by 11.8% and 24.41% and the latter method increased by 18.53% and 22.41%.The range of molecular weight of extracts was expanded from 100-200 to 100-300.