聚甲氧基二烷基醚合成文献调研报告

摘 要：聚甲氧基二甲醚是一类分子式为CH3O（CH2O）nCH3 （简写 DMMn， n≥1）的醚类化合物，含氧量高（42 51%）且具有高的十六烷值（>30），能改善柴油的燃烧性能减少排放，因而被认为是理想的柴油含氧添加物。特别是当n=3-8时，DMM3 8具有与柴油相近的性质，平均十六烷值> 76，按20%与柴油调和，碳烟和NOx的排放能分别降低80-90%和50%。DMMn分子中间为低分子量甲醛缩聚物，两端由甲基封端，通常由提供甲基的化合物，如甲醇，二甲醚和甲缩醛，和提供低聚甲醛的化合物，如甲醛，三聚甲醛和多聚甲醛，反应得到。因此，实现从甲醇到DMMn的转化不仅能延长甲醇产业链，消耗过剩的甲醇产能，而且有利于节能减排目标的实现。在早期，以硫酸或者盐酸为催化剂，催化甲醇和甲醛、多聚甲醛或者二氧戊烷反应合成DMMn。BASF公司采用H2SO4或者 CF3SO3H 为催化剂，甲醇、DMM、三聚甲醛和多聚甲醛为原料得到DMM1 10，但是催化剂腐蚀严重，而且原料转化率和DMM3-8的选择性都很低。BP公司采用分子筛或者酸性树脂为催化剂，通过复杂的工艺实现二甲醚和甲醛转化为DMMn，但是，产物中DMM3-8低于10%。近年来，中科院兰州化物所开展了离子液体催化甲醇和三聚甲醛反应合成DMM3-8的研究，产品单程收率达到50%，DMM3-8选择性大于70%。

关键词：聚甲氧基二甲醚 甲醇 甲醛 催化剂 离子液体

Abstract：Polyoxymethylene dimethyl ethers are a kind of ether compounds with the formula CH3O（CH2O）nCH3 （abbreviated to DMMn， n≥1）. DMMn has high oxygen content （42 51%） with a high cetane number （>30） and is regarded as a promising diesel additive， which can improve the combustibility of the diesel oil， enhance the efficiency of combustion， and reduce the release of pollutants. Especially， DMM3 8 exhibits high oxygen content， moderate boiling points， excellent miscibility with diesel oil， and average cetane number of above 76； it was reported that by adding 20% DMM3 8 in the diesel oil， the amounts of powderous pollutants and NOx released upon combustion can be reduced by 80 90% and 50%， respectively. DMMn molecule is composed of formaldehyde oligomer in the midst and methyl in two ends； therefore， DMMn can be synthesized from the compounds providing methyl ends （such as methanol， dimethyl ether， and dimethoxymethane） and those compounds supplying formaldehyde oligomer （such as formaldehyde， trioxymethylene and polyformaldehyde）. As a result， the conversion of methanol to DMMn as an additive of diesel oil may not only extend the methanol industry chain and digest the large surplus production capacity of methanol， but also bring enormous benefits with respect to economics and environmental protection. At early stage， DMMn was obtained from methanol and formaldehyde， polyformaldehyde， or dioxacyclopentane， with sulfuric acid and hydrochloric acid as catalyst. In this respect， BASF Group used H2SO4 or CF3SO3H as catalyst to get DMM1 10， with methanol， DMM， trioxymethylene， and polyformaldehyde as raw materials， but the catalyst is corrosive and the conversion and selectivity to DMM3 8 is low. With zeolites or acidic ion exchange resins as catalyst， BP produced DMMn by conversion of dimethyl ether with formaldehyde through a complicated process； however， the DMM3 8 yield was still lower than 10%. In recent years， Lanzhou Institute of Chemical Physics， Chinese Academy of Sciences has made progress to synthesize DMM3 8 by using ionic liquid as catalyst in a homogeneous reaction system with methanol and trioxymethylene as feed； single-pass yield of DMMn reached 50% with the selectivity to DMM3 8 being 70% 80%.

Key word：Polyoxymethylene dimethyl ethers； Methanol； Formaldehyde； Catalyst； Ionic liquids

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