Study On Effect Of Ionic Liquids In The Process Of CH₄ Conversion Under Plasma

A considerable amount of research work has been devoted to the investigation of efficienttechnology for natural gas which is an altemative energy source to petroleum. Methane as amajor component of natural gas is difficult to activate because it is one of the most stablemolecules and it is restricted in thermodynamics. The high temperature of normal methanetransformed methods is usually 700～900℃which not only brings on methane excessoxidation to CO_x(X=0, 1, 2), but also leads catalyst to lose activities because of pulverization,sintering and losing active components.The ionic liquids are new type of green environment-friendly reagent, which have uniqueproperties such as a wide range of liquidus temperature, nonvolatile, nonflammable, goodionic conductivity and large electrochemical window and its adjustable structure. Today theionic liquids are widely used in analytical chemistry, electrochemistry, heterogeneouscatalysis and organic or inorganic synthesis. In the thesis, we firstly used ionic liquids ascatalyst in the methane conversion reaction by nonequilibruim plasma technology. On onehand, it is useful improving reaction efficiency. On the other hand, it offers the reparation thatthe solid catalysts are easy coking to lose activity in the methane conversion by plasma. Themain investigations are shown on the following.1,Methane is transformed to C₂ hydrocarbon (C₂H₄,C₂H₆,C₂H₂) products through thedirect current high voltage plasma technology. The effects of parameters of the flowrate of methane, the peak voltage and the discharge gap were investigated. For CH₄coupling reaction, the conversion of CH₄ increased while the flow rate and thedischarge gap reduced and the peak plasma increased. The best condition of the reactionis flow rate 15ml/min, peak voltage 14KV and discharge gap 8mm.2,The series of ionic liquids were synthesized according to the formula [Rmim]⁺X^- (R=C₄～C₈; X=HSO₄,PF₆,Br,CF₃COO,BF₄), and the properties were analysed aboutconductance, electrochemistry window, acidity and basicity and polarization.3,The effect of the ionic liquids which were used as catalyst put in the plasma zone and the verge of plasma zone was studied. The optimal condition was that the spacebetween ionic liquid surface and down electrode was 2～5mm when the ionic liquid wasin the verge of plasma zone.4,The effect of the ionic liquids [Rmim]⁺X^- (R=C4～C8; X=HSO4,PF₆,Br,CF₃COO,BF₄) was studied. It was found the conversion of methane and the yield of C₂hydrocarbon increased with increasing acidity: HSO₄^-＞PF₆^-＞Br^-＞CF₃COO＞BF₄^- of theionic liquids [C₆mim]⁺X^- and there was no evidence influence of the ionic liquids[Rmim]Br (R=C₄～C₈).5,The effect of parameters of the flow rate of methane, the peak voltage and the dischargegap were investigated in the ionic liquid [C₈mim]⁺HSO₄^-. The optimal condition wasflow rate 10ml/min, peak voltage 14KV and discharge gap 8mm.6,It was found that the coke formed in the DC high voltage plasma reaction. The SEManalysis of the coke showed the coke was congregated like batt and distributed anomaly,and the diameter of the granule was nanometer.