The Study Of Catalytic Synthesis And Application Of Polyoxymethylene Dimethyl Ethers

Polyoxymethylene dimethyl ethers?PODE?made from non-petroleum-based substitude fuel is a new kind of green and environment-friendly diesel fuel additive,which has excellent performance and great application potential because of its high cetane number,high oxygen content and non-intermiscibility gap between diesel.It can improve the diesel fuel's cetane number and combustibility while reduce the emissions of pollutant.In this paper,the green Br?nsted acid ionic liquid [Py N?CH2?3SO3H]HSO4 was synthesized.Then the catalytic activity of the functionalized ionic liquid was investigated in the synthesis of polyoxymethylene dimethyl ethers by the condensation of dimethoxy methane paraformaldehyde.The elementary consists and properties of diesel fuel which blended with polyoxymethylene dimethyl ethers were also been investigated.Firstly,the functionalized disulfonic acid ionic liquid was synthesized by two-step method.After structure characterization of the ionic liquid and its intermediate with FTIR and1 HNMR,the synthesized ionic liquid was the designed one.The ionic liquid has high purity and thermal stability,and the acid intensity is equivalent with concentrated sulfuric acid.It also has high and stable catalytic activity,and after reaction the catalyst and reaction products exist in different phases.Secondly,polyoxymethylene dimethyl ethers were synthesized by the raw material methylal and over ionic liquid paraformaldehyde over acid ionic liquid,and qualitative analysis of PODEnin the products was made by GC-MS.The factors related to reaction activity were investigated,the optimum reaction conditions were found as[Py N?CH2?3SO3H]HSO4 amount of 5%?mass fraction?,feed mole ratio 1,temperature 180?,and reaction time 2h,the yield of PODE2-8 and selectivity to PODE_3-8 reached 51% and51.7%.Compared the yield and selectivity of PODEnsynthesized from different raw material methylal and trioxane,there is no big difference,so the choice of cheap methylal as reactant is more economic.Products were found to follow the Schulz-Flory distribution law.Due tothe restriction of this law,it is difficult to increase the selectivity of the desired product.In addition,with the amount of PODE_3-8 increased in the blended diesel fuel,the oxygen contents in the fuel also increased.The specific valve of increasing is 0.55 percent per unit volume of PODE_3-8 blended in the diesel.The blended diesel fuel has more proper evaporation and atomization than traditional petroleum diesel,and the low temperature fluidity and safety of the blended fuel are higher in the storage,transportation and use process.