Synthesis Of Acid-catalyzed Diesel Fuel Additive POM DME

Polyoxymethylene dimethyl ether (PODE) is a new kind of diesel fuel additi-ve,which has excellent performance and strong potential application prospects. It cannot only improve the cetane number of diesel fuel and reduce the emissions ofparticulate matter and NOx, but also can improve the combustion efficiency of dieseloil, while without changing the engine structure. But the synthesis technology ofPODE is far from mature at the moment.There are some problems such as low yieldsof products,high cost of process,etc.Furthermore, law of the nature of the reactionsuch as PODE product distribution and the reaction mechanism are not clear.In this paper, firstly, we studied the acid catalysis synthesis of PODE frommethylal and paraformaldehyde, compared and screened the acid catalyst, and studiedthe reaction rule. The main results showed as follows: the cation exchange resin andsulfuric acid had the best catalytic performance, of which the PODE yields were57.3%and55.4%,respectively.And it was found that cation exchange resin withexchange capacity of1.62mmol/g had the best catalytic performance. In addition,mechanism studies revealed that PODE was generated by methylal and paraformalde-hyde met the chain growth mechanism, and the composition distribution of PODEaccorded with Anderson-Schulz-Flory distribution.Secondly, we studied the synthesis of PODE from methylal and trioxymethyleneunder the catalysis of solid acid. The results showed as follows: solid acid catalyst,such as zeolite molecular sieve, had better performance than liquid acid. And thehigher the relative L acid/B acid ratio of zeolites was,the greater the reactivity of themwas. And it was found that a big surface area of molecular sieves was beneficial toimprove their activity,while the particle size of molecular sieve had no big effect.Forthe catalyst of cation exchange resin, the smaller the exchange capacity of it was, thebetter the catalytic activity was.The study on the distribution of the reaction productsindicated that: PODE product distribution satisfied the approximate rule:2yPODE4=yPODE3+yPODE5=yPODE2+yPODE6(y was on behalf of yields).Based on the detailedanalysis, we stochastically proposed a conventionnal reaction mechanism(suitable formost of solid acid) and a special reaction mechanism (applicable to a few solid acidsuch as HMCM-49) which both contained the overall insertion of trioxymethylene.Finally, we studied how the impurities of raw material, such as water and meth- anol, and some component influenced on the synthesis of PODE, the results showedthat: adding PODE2to the raw material could help to improve the content PODE3andPODE4in the product; the presence of water and methanol in raw material couldlower the yields of PODE product, so the content of them should be kept as small aspossible.