Study On The Preparation Of Polymethoxy Dimethyl Ether From Suspended Bed

In recent years,exhaust emission of vehicles has brought many problems,so it is urgent to solve the problem of exhaust pollution.Polyoxymethylene dimethyl ethers(PODE_n)are excellent diesel additives,which are blended to the diesel fuel to improve the combustion of diesel,reduce the emissions of pollytant and make the thermal efficiency of engine better.Therefore,PODEn have attracted more and more attention.In this paper,methylal and paraformaldehyde were used as new reaction materials,acidic resin is used as catalyst,beating kettle and suspended bed reactor were connected in series as the whole reaction device,a new process was developed.Furthermore,the synthesis rule of PODE and separation of PODE products were studied.First of all,PODE was intermittently synthesized by this device to verify the feasibility of this process.The effects of beating temperature and pressure,the molar ratio of methylal and paraformaldehyde,catalyst dosage(wt%),reaction temperature and reaction time on the yield and formaldyhede conversion rate were studied.The results show that the use of this process route has a high product yield and formaldehyde conversion rate,so the process is feasible.The results indicated that the reaction condition(the beating temperature was124-125°C,the beating pressure was 0.91 MPa,the molar ratio of methylal and paraformaldehyde was 1:1.5,the amount of catalyst was 9wt%,reaction time was 120 min)were optimal.The yield of PODE_2-6 and PODE_3-6is 26.38wt%and 10.38wt%.Secondly,the effect of molar ratio of methylal and paraformaldehyde,catalyst dosaget(wt%),reaction temperature,reaction time,volume flow rate,the rotational speed of the reactor on the yield of the PODE product and the formaldehyde conversion were studied in the continuous preparation of polymethoxy dimethyl ether.The results showed that the optimum conditions were:the beating temperature is 125°C,the beating pressure is 0.91 MPa,the molar ratio of methylal and paraformaldehyde is 1:1.5,the content of the catalyst is 6wt%of the total amount of the raw materials,the reaction temperature is 105?.The flow rate is1.67 ml/min and the rotational speed of the reactor is 60 r/min.At this time,the yield of PODE_2-6 and PODE_3-6 is respectively reached 43.21wt%and 23.87wt%,the conversion of formaldehyde reaches 52.30%.Finally,the liquid-liquid equilibrium data of water+PODE_1-2+extractants(furfural,isophorone,1-octanol)were measured by liquid-liquid equilibrium kettle method.and the extraction ability of the three kind of extractants was analyzed.In addition,Both NRTL and UNIQUAC thermodynamic model were used to correlate the experimental data for obtaining the binary interaction parameters.The results showed that furfural,isophorone and 1-octanol had excellent extraction effects for separating PODE_1-2 systems,and LLE data were correlated by NRTL and UNIQUAC models with good results in these systems.Thermodynamic data determined by the liquid-liquid equilibrium kettle method provides basic data for the extraction separation of PODE products and water.