A kind of purification method of cyclohexene liquid crystal intermediate

Abstract

The invention relates to a method for purifying a cyclohexene-based liquid crystal intermediate, which is suitable for the liquid crystal intermediate containing a cyclohexene group that needs to be catalytically hydrogenated and reduced by precious metals, specifically the liquid crystal intermediate containing a cyclohexene group Put the crude product to be purified into a kettle-type container with stirring, heating, and heat preservation functions, add a non-polar solvent to dissolve, put in a mixture of polar adsorbent and non-polar adsorbent for adsorption, and absorb at the set temperature and speed of stirring and adsorption Purification is carried out under the time; after stirring adsorption purification, the adsorbent and the product solution are separated by filtration, the product solution is concentrated to remove the solvent, and then recrystallized and purified to obtain the final product. The purification method of the cyclohexene liquid crystal intermediate of the present invention adopts a temperature-controllable and time-controlled kettle-type container, and adopts a polar adsorbent and a non-polar adsorbent at the same time, and the liquid crystal intermediate obtained by it is in the catalytic hydrogenation reaction It can be hydrogenated faster, has less residue of olefinic impurities, and is not easy to catalyze poisoning.

Description

technical field [0001] The invention belongs to the technical field of purification of liquid crystal compounds, and in particular relates to a method for purifying a cyclohexene liquid crystal intermediate. Background technique [0002] Liquid crystal displays using liquid crystal compositions are widely used in displays such as instruments, computers, and televisions, and liquid crystal compositions, as one of the important optoelectronic materials of liquid crystal displays, play an important role in improving the performance of liquid crystal displays. At present, a large number of liquid crystal compounds with different molecular structures have appeared on the market, from biphenylnitriles, esters, oxygen-containing heterocycles, and pyrimidine ring liquid crystal compounds to cyclohexylbenzenes, phenylacetylenes, and ethyl bridges. Class, terminal alkenyl liquid crystals and various fluorine-containing aromatic ring liquid crystal compounds, etc., continuously meet th...

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Problems solved by technology

[0006] However, in the current preparation process of liquid crystal monomers containing cyclohexane groups, the main problem is: when synthesizing cyclohexenyl intermediates through Grignard reactions, the purification of crude products is not enough, resulting in hydrogenation and reduction by metal catalysts in the next step. For cyclohexene, the noble metal catalyst is poisoned due to the impurity of the hydrogenation substrate, which makes the hydrogenation reaction incomplete, the reaction is too long, and the cyclohexenyl intermediate remains too much; in addition, some cyclohexane liquid crystals containing fluorine benzene The intermediate will also produce fluorine impurities due to the long hydrogenation reaction time, which will affect the product yield and purity; at the same time, the substrate of the hydrogenation reaction is impure, which will cause excessive consumption of precious metal catalyst usage, and the precious metal catalyst will be used because of It is easy to be poisoned, the activity is greatly reduced, and basically cannot be applied again, which increases the cost of the process

[0007] At present, when processing and purifying liquid crystal intermediates containing cyclohexene groups in the liquid crystal material industry, the crude cyclohexene intermediates are mainly dissolved and then filtered by column chromatography through silica gel polar adsorbents. The dissolved cyclohexene When the crude olefin intermediate flows through the chromatographic column, the time for the adsorption and removal of impurities by the chromatographic column is not enough, and various impurities cannot be effectively adsorbed and removed, thereby affecting the subsequent hydrogenation reaction; at the same time, only a single method for removing polar impurities is used Silica gel-based adsorbents cannot effectively remove non-polar impurities with low polarity. Substrates after these conventional purification treatments generally suffer from slow hydrogenation, incomplete reaction, many residual alkene impurities, and easy catalysts in subsequent hydrogenation reactions. Problems such as poisoning cannot be applied mechanically, which increase the preparation cost of this type of liquid crystal monomer

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