Method for extracting, rectifying and separating butane from butylene by ternary mixed solvent

Abstract

The invention provides a method for extracting, rectifying and separating butane from butylene by a ternary mixed solvent. The ternary mixed solvent is the ternary mixed solvent of N-methylpyrrolidone, methyl ethyl ketone and water. The advantages of the N-methylpyrrolidone, the methyl ethyl ketone and the water are integrated; the N-methylpyrrolidone and the water have high selectivity; the methyl ethyl ketone has good solubility on carbon; the water and the methyl ethyl ketone have low boiling points; and the three solvents make the best of both worlds, and achieve efficient separation on the butane and the butylene.

Description

technical field [0001] The invention relates to a method for extracting and rectifying separation of butane and butene by using N-methylpyrrolidone, methyl ethyl ketone and water as solvents. Background technique [0002] The boiling points of butane and butene are close, and the relative volatility is close to 1. It is difficult to separate by ordinary rectification. Therefore, the extraction and rectification method is often used for separation, that is, a polar component, that is, a solvent component, is added to the upper part of the rectification tower. , to increase the relative volatility of butane and butene in the tower, and improve the separation efficiency. There are many polar solvents that can be used for extraction and distillation to separate butane and butene, such as nitrogen-formyl morpholine, morpholine, mixture of nitrogen-formyl morpholine and morpholine, sulfolane, nitrogen-methylpyrrolidone, methyl ethyl ketone and A mixture of N-formylmorpholine, a m...

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Problems solved by technology

[0005] (2) The morpholine solvent system using morpholine and N-formylmorpholine as solvents, this solvent system is the earliest butane and butene separation solvent introduced from abroad and adopted in China, but the solvent system is used to strip the still The temperature is high, about 210°C, and the energy consumption is relatively large. Butene is easy to polymerize to form a high polymer during the purification process, causing losses. The generated high polymer remains in the solvent, which reduces the efficiency of the solvent. Therefore, the circulating solvent must be Continuous regeneration, the regeneration process causes a large amount of solvent loss, and fresh solvent must be continuously replenished, and the price of morpholine and N-formylmorpholine is relatively high, so the production cost of this solvent system is very high, and it is no longer considered in new equipment now The solvent system

[0006] (3) The methyl ethyl ketone solvent system using methyl ethyl ketone and N-formylmorpholine as solvents. This solvent system is developed domestically. See the document "Method for Separation of Butane and Butene by Extraction and Rectification of Methyl Ethyl Ketone Series Mixed Solvents" (ZL: 00136535.5 ), the characteristic of this solvent system is that the solvent has good solubility to butane and butene, there is no three-phase state in the tower, the operation of the tower is stable, the bottom of the stripping tower is stable and moderate, about 160 ° C, and can be reboiled in the middle The heat of the circulating solvent is recovered by the device, and the disadvantage is that the selectivity of the solvent is low, and the solvent circulation ratio is higher than that of the acetonitrile solvent system and lower than that of the morpholine solvent system

[0008] There are also some research results on the solvent system for extracting and rectifying the separation of butane and butene, but they have not been industrialized in China, such as: patent "a method for separating butane and butene with multiple mixed solvents" (ZL200810159239.8) Using a multicomponent mixture of ionic liquid, nitrogen-formylmorpholine, and methyl ethyl ketone as a solvent, extractive distillation is used to separate butane and butene. The results show that the separation efficiency is much higher than that of using methyl ethyl ketone and N-formylmorpholine. solvent, and the extractive distillation column is easy to operate and easy to control

However, during the actual operation of this process, the temperature of the stripping tower is relatively high, and the loss of ionic liquid is relatively large during the operation process, especially when the ionic liquid is discharged together with heavy substances during solvent regeneration, resulting in high operating costs for this process.

Another example: DMF solvent system, see literature " with extractive distillation method separation C4 research progress of alkane and olefin " (Guangxi Chemical Industry, 1996,28 (2) 20-24,28), all can not satisfy industrialization because of various reasons Require

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