Study On Synthesis And Properties Of Surfactants For Diesel Exhaust Gas Treatment Liquids

Urea-Selective Reduction Technology(Urea-SCR)uses NH3 from urea pyrolysis to reduce NOx in exhaust to N2,which can effectively deal with diesel exhaust pollutants.However,in the practical applications process,the urea may pyrolysis incomplete and generate cyanuric acid,biuret and other sediments,which will result in a blockage of the catheter and a reduction in exhaust gas treatment efficiency.Adding non-ionic surfactants can limit the formation of cyanuric acid deposits and optimize the exhaust treatment effect of diesel exhaust gas.The effect of urea sediment inhibitory is greatly affected by the structure-activity relationship,so exploring the structure-activity relationship of surfactants for the design of diesel exhaust gas treatment with urea solution is essential.In this paper,the synthesis of surfactants with different carbon chain structures and EO number and its surface tension and expansion rheology were studied.The effect of inhibit the formation of deposits by surfactant in SCR process were also investigated through the simulated bench test.Thus the relationship between urea sediment removal efficiency and the surfactant structure-activity were explored.First,the aliphatic alcohol,aliphatic alcohol and aliphatic amine polyoxyethylene ether were synthesized by changing the amount of epoxy ethane control of water oil balance(HLB),and studied the cloud point,and solubility of the synthetic surfactants.The results show that the linear polyether of fatty alcohols solubility is poorer,cloud point is generally low;Straight-chain polyether of fatty alcohols solubility is slightly better,the solubility is better with the higher number of EO,and the cloud point will also increases;Straight chain fatty amine polyether has good solubility,and its cloud point is above 90 ?.In addition,with increasing number of epoxy ethane,the cloud point and solubility will be enhanced.Second,in this paper,the surface tension of nonionic surfactants was tested and the surface tension of linear aliphatic amine polyether is relatively high,generally around 35 mN/m;The linear fatty alcohol polyether activity increased,the surface tension decreased,the surface tension is about 30 mN/m;The surface tension of branched fatty alcohol polyether is lower,and it can be reduced to 26.58 mN/m.In addition,as the carbon chain length increases,the surface tension will increase and the surface activity decrease.Third,the rheological properties of nonionic surfactants were measured and the dilatational properties and phase-angle properties were obtained.It was found thatthe linear expansion of the linear aliphatic amine polyether is slightly lower than that of the linear aliphatic polyether.The dilational modulus is 40mN/m;The branched fatty alcohol polyether has higher expansion modulus,and its expansion modulus can reach more than 45mN/m.The phase angles of surfactant are about 10 °,and the strength of interface film is elastic,the phase angle of branched fatty alcohol polyether is higher and the viscosity of membrane is enhanced.Forth,this paper explores the inhibiting effects of sediment with the nonionic surfactants acting as urea solution additives in the SCR system.And through the study,it is found that the polyether surfactants with good proformence of inhibitory effects of sediment are:C12EO10 and the reduction efficiency of urea sedimment is 31.275%,the i-18C20EO and its reduction efficiency of urea sediment is 45.667%,the straight-chain fatty amine polyether's inhibitory effect of urea sediment is relatively balanced,and C18N10EO can promote the sediment reduction efficiency to 41.616%.