Polymethoxydialkyl ether (PODE) is a kind of oligoether compound which is produced by acetalization reaction. When both ends of poden are blocked by methoxy, it is called polymethoxydimethyl ether (dmm3-8, molecular formula CH3O (CH2O) nch3). Compared with DME and dmm1, dmm3-8 has higher viscosity and boiling point, so mixing with diesel does not need to change the existing engine Oil supply system.
When the polycondensation molecular unit is controlled at n = 3-6, dmm3-8 has a good miscibility with diesel oil, with an average cetane number of over 76 and a boiling point of 156-268 ℃, which is just in the range of diesel oil. It overcomes the shortage of DME and dmm1 as fuel components, fully meets the requirements of clean diesel oil blending and components, and is considered to be a promising environmental protection diesel oil component.
In addition to being an excellent oil additive, DMMN can also be used as an excellent medium boiling point solvent with the following advantages: 1. Solubility. It has a strong dissolving power and can be completely miscible with hydrocarbons and alcohol, ether, acetone, etc. It is a good substitute for aromatic solvent (toluene, xylene, trimethylbenzene), DMF (dimethylformamide), methanol, glycol butyl ether and halogenated hydrocarbon.2. Amphiphilic solvent. At 16 ℃, 32.3% (WT) of dmmn was dissolved in water and 4.3% (WT) of water was dissolved in product. At the same time, it has good solubility in alkane, arene, ether, ketone aldehyde ester and halogenated hydrocarbon and can be used as compatibilizer. 3. Toxicity: the toxicity of organic solvents is the lowest, with slight toxicity, sulfur-free and aromatics free. Biodegradable. 4. Low cost.
In this technology, methanol is used as the basic raw material, methanol oxidation is used to prepare formaldehyde, formaldehyde and methanol polymerization are used to prepare methylal, methylal and formaldehyde are used as raw materials for reactive distillation to prepare polymethoxydimethyl ether, and typical separation technology is used to separate products. The fixed bed catalyst technology is used in this process, which has mild reaction conditions, long catalyst life, high conversion rate and good selectivity.
The technical route adopted in each stage is as follows:
(1) The technology of silver formaldehyde + tail gas circulation was used. The technology has been widely used in industrial plants, and the investment cost is relatively low. Using tail gas circulation technology can improve the formaldehyde yield.
(2) The technology of catalyst distillation and pressure swing distillation is used in the synthesis of methylal to prepare high concentration methylal. At present, the technology has mature operation.
(3) The synthesis of polymethoxydimethyl ether is based on methanol, and formaldehyde and methylal are used as reaction materials to prepare polymethoxydimethyl ether. At present, it is industrialized, mature and stable.