The Study On The Synthetic Technology Of DMM_3-8 As Diesel Additives

Polymethoxy dimethyl ethers,referred to as DMMn or PODEn(n=3~8),is known as a kind of polyether materials,As a new type of diesel fuel additives,it has high containing of oxygen(42~48%)and hexadecane value(?78).When added DMM3-8(WDMM3-8=10%?20%)in diesel,It can reduce exhaust emissions of soot and nitrogen oxides significantly,improve the combustion characteristics of diesel fuel,reduce the solidifying point of diesel oil and improve the thermal efficiency of diesel engine.DMM3-8 is internationally recognized as a new environmentally friendly diesel fuelblend for reducing fuel consumption and the smoke emissions,and its study on the synthetic technology is a research hotspot in recent years.The synthesis of DMM3-8 has made greatly progress in the lab test,however,its industrial production has been no big breakthrough because there are many disadvantages in the literature methods,for example,expensive raw materials,low product yield and high production cost,etc.By optimizing the reaction conditions and comparing with the two synthesis routes of DMM3-8,a suitable process for industrialized production was determined.Route one:Using methylal and trioxymethylene as raw materials for the synthesis of DMM3-8(1)Catalysts were screened.According to the literature,Amberlyst 46 is the catalyst with highest catalytic efficiency for the synthesis of DMM3-8,but this catalyst is very expensive.Through the study of the catalytic efficiency of solid acid catalysts,p-toluene sulfonic acid,various metal oxide solid acid and the strong acid cationic exchange resin on the reaction,it was found that the catalytic efficiency of resin A was similar to Amberlyst 46.The resin A catalyst has the advantages of high catalytic efficiency,economy and can be reused for many times(more than 15 times),and it is very suitable for the industrial production.(2)The reaction conditions were optimized by studying the effects of the appropriate proportion of trioxane and methylal,reaction temperature,reaction time,the appropriate proportion of trioxane with the paraphrase liquid and other factors on the reaction.Route two:Using methylal and paraformaldehyde as raw materials for the synthesis of DMM3-8(1)Though the study of the effect of resin A and other catalysts on the reaction,it was found that the catalytic efficiency of resin A was equal to Amberlyst 46,and the resin A catalyst could be used in this route also.(2)The reaction conditions were optimized by studying the effects of the appropriate proportion of paraformaldehyde and methylal,reaction temperature,reaction time,dosage of catalyst and the appropriate proportion of paraformaldehyde and the paraphrase liquid and other factors on the reaction.Through the comparison the yield of product,the price of raw material and reaction conditions of the two synthesis routes of DMM3-8,the paper finally finalized the synthetic route of paraformaldehyde and methylal as raw materials which is more suitable for the industrial production.This route has the advantages of mild reaction conditions,raw materials and catalyst economic and easy to be got,no wastes and so on.