Method for preparing diphenylmethane dicarbamic acid ester in double solvent system

A technology of phenylcarbamate and dicarbamate, which is applied in the field of liquid acid-catalyzed synthesis of diphenylmethane dicarbamate, can solve the problems of many by-products, low reaction efficiency, and large reaction mass transfer resistance. Achieve the effect of reducing reaction resistance, promoting catalytic activity and good effect

Inactive Publication Date: 2009-05-27
INST OF PROCESS ENG CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Most liquid acid catalysts use water as a solvent. The catalyst liquid acid and the methyleneation reagent formaldehyde are in the water phase, while the raw material MPC is not easily soluble in water to form a new organic liquid phase. The mass transfer resistance of the liquid-liquid two-phase reaction is relatively large. low reaction efficiency
The liquid acid catalyst uses water as the solvent. After the reaction is completed, the unreacted raw material MPC and the product MDC are mixed together, which is difficult to separate and recycle.
Therefore, this type of method is not suitable for producing the raw material MDC for preparing pure MDI, because there are many by-products, separation and purification are difficult, and it is not suitable for large-scale industrial production

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] Add 7.55g methyl phenylcarbamate (MPC) in the 100ml there-necked flask equipped with thermometer, condensing reflux tube and constant pressure dropping funnel, mass concentration is 96% sulfuric acid 14ml (the molar ratio with MPC is 5: 1) , a mass concentration of 15% acetic acid aqueous solution 50ml (about 7 times the MPC quality), magnetic stirring heating, when the temperature was raised to 50 ° C, dropwise add a mass concentration of 37% formaldehyde solution 2.0ml (with MPC The molar ratio is 1:2), after the formaldehyde is added dropwise, the temperature is raised to 95°C, and 0.2ml of formaldehyde aqueous solution is added after 1 hour, and the reaction is carried out under normal pressure for 3 hours, then the heating is stopped, left to cool to room temperature, filtered, washed with water, Drying gave a solid product and combined filtrates. The resulting solid and filtrate were analyzed by high-performance liquid chromatography, and the results were: the con...

Embodiment 2

[0019] 48ml of the obtained filtrate after the solid is separated in Example 1 is used as catalyst and solvent, and is added to a 100ml three-necked flask together with 6.04g MPC, stirred and heated to 50°C, and the constant pressure funnel is added dropwise with a mass concentration of 37% formaldehyde solution 1.5ml, after adding formaldehyde dropwise, raise the temperature to 95°C, add 0.15ml formaldehyde aqueous solution after 1 hour, react under normal pressure for 3 hours, stop heating, let stand to cool to room temperature, filter, wash with water, and dry to obtain a solid product. The resulting solid and filtrate were analyzed by high-performance liquid chromatography, and the results were: the conversion rate of methyl phenylcarbamate was 95.74%, and the yield of methyl diphenylmethane dicarbamate was 80.65%, of which 4,4'-diphenyl Methane dicarbamate methyl ester accounts for 88.93%, 2,4'-diphenylmethane dicarbamate methyl ester yield rate is 7.75%, and the rest are ...

Embodiment 3

[0021] Take by weighing 6.04g methyl phenylcarbamate in the 50ml there-necked flask that thermometer, condensing reflux tube and constant pressure dropping funnel are equipped with, adding mass concentration is 38% hydrochloric acid 10ml (with the mol ratio of MPC being 3: 1) and Dilute with water to 30ml of formic acid solution (about 5 times the mass of MPC) with a mass concentration of 25%, stir and heat up to 50°C, and dropwise add 2ml of formaldehyde solution with a mass concentration of 37% (with the molar mass of MPC) Ratio is 1:1.5), after adding formaldehyde dropwise, heat up to 90°C, react under normal pressure for 5 hours, stop heating, let it stand to cool to room temperature, filter, wash with water, and dry to obtain a solid product, and the obtained solid and filtrate are subjected to high-efficiency Liquid chromatography analysis. The result is: the conversion rate of methyl phenylcarbamate is 91.60%, and the yield of diphenylmethane dicarbamate is 78.94%, wher...

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PUM

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Abstract

The invention relates to a method for synthesizing diphenylmethane diurethane through catalysis of liquid acid in a composite solvent system, in particular for synthesizing 4,4,-diphenylmethane diurethane. In the composite component solvent system, a phenyl carbamate reagent and a methylenation reagent are catalyzed and condensed through liquid organic acid; a composite component solvent can well promote catalytic activity of the liquid acid; and in the process of synthesizing the diphenylmethane diurethane by one-step reaction, the conversion rate of phenyl carbamate as a raw material reaches 97.46 percent, the yield of diphenylmethane diurethane is 86.93 percent, the selectivity of 4,4,- diphenylmethane diurethane in a product can reach 91.56 percent, and only a few byproducts are generated. After the reaction is completed, an MDC product can be separated through filtering and washing; the solvent can be recycled; after recycling, the yield of the MDC can still reach over 80 percent; and the method has good effect and does not cause the waste of the raw materials and the solvent.

Description

technical field [0001] The invention relates to a method for synthesizing diphenylmethane dicarbamate by liquid acid catalysis in a composite solvent system. Background technique [0002] Diphenylmethane diisocyanate (MDI) is an important raw material for the synthesis of polyurethane. It is also used in the synthesis of metal adhesives, glass fibers, colored coatings and various artificial leathers. It is used in the fields of construction, automobiles, ships, aviation, electronics, shoemaking and daily necessities. It has a wide range of applications, and the demand at home and abroad has grown rapidly in recent years. Diphenylmethane dicarbamate (MDC) is an important intermediate for the non-phosgene synthesis of MDI. Therefore, it is an urgent need for the development of modern industry to provide a method for cleanly synthesizing MDC with application value, and it will certainly produce good social benefits. [0003] The reaction of phenylcarbamate and methyleneation ...

Claims

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Application Information

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IPC IPC(8): C07C271/28C07C269/02
Inventor 李会泉裴义霞游志敏张懿
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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