Research And Application Of Dimethyl Ether And Oxygen Mixed System

Polyoxymethylene dimethyl ether(PODEn),as an ideal diesel additive,is produced with low-cost materials.It can be used to design or develop catalysts with high selectivity to PODEn,prominent activity and strong stability.In this paper,PODEn is produced in two steps(methyl ether catalytic oxidation and PODEn chain growth step)with reactants of methyl ether and oxygen.The explosive limit of methyl ether with the presence of oxygen was studied and analyzed.The main conclusions are showed follows:The traditional calculation of explosion limit theory is not suitable for calculating the explosion limit of methyl ether in oxygen.The explosion limit of methyl ether in oxygen can be figured out by the formula method or the drawing method.The calculated value ranges from 2.2%to 74.5%.CAT 1-3 is selected as the catalyst in the catalytic oxidation stage of methyl ether.Best results can be achieved when the volume flow ratio of methyl ether and oxygen is 25 than 2,the reaction temperature is 270 degree Celsius,and the reaction pressure is 0.3MPa.This is because carbon deposition of the catalyst decreases after tin loading,which is more conducive to the initiation of the reaction.The optimal reaction pressure and temperature during PODEn chain growth phase is 0.2Mpa and 80 degree Celsius,respectively.Among the various factors influencing the reaction,DMET and acid have negligible influence on the selectivity to reactants,but the adverse effect of water is considerable.In addition,moderate addition of PODE1 can increase the value n in the target product PODEn.By comparing the catalysts used in PODEn chain growth,it was found that HZSM-5(Si/Al=25)and H?(Si/Al=40)have better catalytic effect on the reaction.H?(Si/Al=40)treated with 10%tartaric acid has the best catalytic effect,as this catalyst's pore size and pore volume increase,which is more instrumental to PODEn chain growth.