Co-liquefaction Of Lignite, Wheat Straw And Waste Plastics Via Subcritical Water

This paper reports the co-liquefaction properties of Jingoulignite （JG）, wheat straw （WS） and waste plastic in differentliquefaction conditions. The effect of temperature, pressure, time,solvent and different additives on liquefaction products duringco-liquefaction were studied. The transformation behavior of sulfurduring co-liquefaction was also investigated. Furthermore, thescanning electron microscope （SEM） analysis, the infraredspectroscopic （IR） analysis and1H NMR analysis were done in orderto study further the mechanism of co-liquefaction of Jingou lignite,wheat straw and waste plastic. The main conclusions are asfollows:1. The co-liquefaction properties of Jingou lignite, wheat strawand poly （ethylene terephthalate）（PET）（1） Compared with tetralin, using subcritical water as solventcan get higher total conversion rate during co-liquefaction of Jingoulignite, wheat straw and PET. （2） There exists obvious synergistic effect duringco-liquefaction of Jingou lignite, wheat straw and PET; and whenthe blending ration of lignite, wheat straw and PET is5/4/1, the oilyield is the highest; the total conversion of co-liquefaction of threeof them is higher than that of co-liquefaction of lignite with wheatstraw or with PET.（3） During co-liquefaction via subcritical water:（a） the totalconversion increases when the temperature increases from260℃to300℃and then decreases; b. when adding Fe₂O₃and S, the totalconversion increases with the temperature increasing, and the totalconversion is the maximum at320℃; c. when adding tourmaline，the total conversion increases when the temperature increasesfrom260℃to300℃and then decreases, and the total conversionis the maximum at300℃; while for oil, with the increasing of thetemperature, the oil yield decreases. Adding tourmaline and FeS isconducive to ring opening reaction during liquefaction process, andit is also good to reducing the H（ar）content in the oil.（4） When the residence time increases from10minutes to60minutes, the total conversion increases slowly （except40minutes）;with the initial pressure increasing from2MPa to5MPa, the totalconversion also increases （except3MPa）.（5） The traditional catalyst for coal liquefaction has no obvious catalysis for co-liquefaction of lignite, wheat straw and PET viasubcritical water.2. The transformation behavior of sulfur during co-liquefactionof Jingou lignite, wheat straw and PET（1） More sulfur will transfer into the residuals, and only verylittle sulfur will come into the oil, asphaltene, preasphaltene andgas during co-liquefaction if use sub-critical water as solventinstead of tetralin.（2） The sulfur content in residuals decreases when thetemperature increases from260℃to300℃, and then increaseswhen the temperature increases from300℃to320℃, and theminimum sulfur content in residuals is90.7%at300℃; whenadding Fe₂O₃and S, With increasing of temperature, the sulfurcontent in residuals decreases continuously.（3） With increasing of the initial pressure, the sulfur content inthe residuals increases （not including3MPa）.（4） More sulfur will transfer into the residuals if addingtourmaline or FeS into the mixtures during co-liquefaction; whileadding Fe₂O₃and S will promote more sulfur to transfer into theother liquefaction products such as oil, asphaltene, preasphalteneand gas.（5） The H₂S content is always higher than COS content in the gas during co-liquefaction of lignite, wheat straw and PET. With thetemperature increasing, the content of H₂S and COS in the gas alsoincrease when adding Fe₂O₃and S or without additives.