Method for continuously preparing dimethyl 2, 6-naphthalate slice

Abstract

The invention provides a method for continuously preparing dimethyl 2, 6-naphthalate slices, which comprises the following steps: adding crude dimethyl 2, 6-naphthalate and absolute methanol into a high-pressure reaction kettle to obtain recrystallized dimethyl 2, 6-naphthalate; and melting the dimethyl 2, 6-naphthalate, continuously rectifying the dimethyl 2, 6-naphthalate in a rectifying tower to obtain molten dimethyl 2, 6-naphthalate, and enabling the molten dimethyl 2, 6-naphthalate to flow into a granulating and slicing device to obtain a flaky solid. Wherein the high-pressure reaction kettle and the rectifying tower are respectively and additionally provided with a heat tracing heat preservation device. According to the present invention, the 2, 6-NDC crude ester is prepared by using the recrystallization and the continuous rectification slicing process, such that the refining efficiency can be improved, the high-pressure reaction kettle and the rectification device are subjected to whole-process heat tracing, the stable and smooth discharging of the 2, 6-NDC can be ensured, the blocking of the filter plate due to condensation can be avoided, the yield of the obtained high-purity 2, 6-NDC is high and can achieve 92%, and the purity is more than 99.95%. The rectified 2, 6-NDC fraction can be directly pumped into a slicing system to realize continuous production of flaky 2, 6-NDC products, so that the situation that 2, 6-NDC is heated and melted again and unnecessary energy consumption is increased is avoided.

Description

technical field [0001] The invention relates to the field of new coal chemical materials, in particular to a method for continuously preparing slices of dimethyl 2,6-naphthalenedicarboxylate. Background technique [0002] my country's coal reserves are abundant. In today's increasingly tight energy environment, as a measure to increase the comprehensive utilization of heavy components in coal, petroleum and other energy sources, it is of great significance to develop a high value-added route for naphthalene. Dimethyl 2,6 naphthalate (NDC) is a key intermediate for some high-end specialty polyesters, and its main purpose is to synthesize polyethylene 2,6 naphthalate (PEN). PEN material is an emerging functional polymer resin material with superior performance, mainly composed of 2,6 naphthalene dicarboxylic acid (2,6-NDA) or 2,6-NDC and ethylene glycol esterification or transesterification and then polycondensation. Compared with the widely used polyethylene terephthalate (P...

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Problems solved by technology

After the material is transferred to the suction filter device, when it meets the filter plate at room temperature, the material will partially condense and block the filter plate, which will lead to unstable and smooth discharge, low operating efficiency, and high-purity 2,6-NDC. low yield

[0007] 2. In the intermittent recrystallization method used in the purification of 2,6-NDC, the amount of recrystallization solvent consumed is relatively large. During the process of material transfer, the solvent will volatilize into the air and cause air pollution.

[0009] 4. At present, 2,6-NDC is purified by vacuum distillation. The distillation temperature is too high (>270°C), which will easily lead to decarboxylation of 2,6-NDC and generate 2-naphthoic acid methyl ester as a by-product. Color deterioration

[0010] 5. The 2,6-NDC fraction from distillation / rectification will quickly solidify and form large pieces under normal temperature cooling, which is not easy to break. It needs to be melted or dissolved again for subsequent reprocessing and granulation, which will increase unnecessary energy. consumption

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