The Study Of Synthesis Of Polyoxymethylene Dimethyl Ethers

Polyoxymethylene dimethyl ethers is a new excellent oil additive, its high oxygen content and high cetane number can improve the quality of oil, reduce the engine exhaust pollutants, can effectively reduce the smog emissions of pollutants.Currently, raw materials of synthesis of Polyoxymethylene dimethyl ethers normally is methylal and melamine formaldehyde, the price of methylal is more expensive, we use methanol -the lower price,instead of methylal, research the synthesis of Polyoxymethylene dimethyl ethers using methanol and paraformaldehyde, methanol and melamine formaldehyde as raw materials,study the catalyst of the reaction, process conditions optimization and thermodynamics.In catalyst research, through a series of catalyst screening, to methanol and paraformaldehyde, methanol and melamine formaldehyde reaction, ZSM-5 zeolite catalysts have good catalytic activity. It shows that the modification of iron oxide catalysts of ZSM-5 zeolite catalysts is better, load of iron oxide with 1% is advisable.We carry out process conditions optimization experiment with methanol and paraformaldehyde, methanol and melamine formaldehyde as raw materials. The best process condition with Methanol and melamine formaldehyde as the raw material is that, The dosage of ZSM-5 catalyst is 1%, the material ratio of methanol and melamine formaldehyde was 1.2:1 (mol), the temperature is 135 ?, reaction time is 3 h. In this condition the reaction conversion rate is 79.6% and the yield of product is 47.7%. The best process condition with Methanol and paraformaldehyde as raw materials is that, The dosage of ZSM-5 catalyst is 1%, the material ratio of methanol and paraformaldehyde is 1:2.5 (wt), the temperature is 145 ?, reaction time is 3 h, in this condition the reaction conversion rate was 73.5%, the yield of product was 45.6%.Through thermodynamics calculation of the synthesis of PODEn, we find that the first step (melamine formaldehyde hydrolysis reaction) is an endothermic reaction, and each step of polymerization is exothermic reaction, the overall reaction is exothermic reaction, low temperature is favorable to generate the product of high degree polymerization, these with our experimental results are consistent.