Novel technology for concentrating post-MTBE C4

Abstract

The invention discloses a novel technology for concentrating post-MTBE C4. The technology comprises that a C4 raw material is introduced into an extraction absorbing tower through the lower part of the extraction absorbing tower, absorbents are introduced into the extraction absorbing tower through the upper part and the middle part of the extraction absorbing tower and are respectively used as an absorbent 1 and an absorbent 2, the material at the top of the extraction absorbing tower is butane, the material at the bottom of the extraction absorbing tower enters the upper part of an desorption tower 1, the material at the top of the desorption tower 1 enters the upper part of an desorption tower 2, a part of the material at the tower bottom is used as the absorbent 2 for recycle, a part of the material at the tower bottom enters the lower part of the desorption tower 2, the material at the top of the desorption tower 2 is a butene product, the material collected from the middle of the desorption tower 2 is circulated to the lower part of the desorption tower 1 and the material at the desorption tower 2 bottom as the absorbent 1 is recycled. The technology can produce a high-purity butane product and a butylene product under conditions of a low tower bottom temperature and a low liquid-gas ratio and has a butylene recovery rate of 99% or more and an n-butene concentration greater than or equal to 99.9%.

Description

technical field [0001] The invention relates to a new process for concentrating C4 after ether, in particular to an extraction and rectification method for butene and butane. Background technique [0002] At present, the only large-scale production method of methyl ethyl ketone production equipment in the world is the n-butene method, and the carbon four after ether is used as the raw material for the n-butene method to produce methyl ethyl ketone. The process requires fresh n-butene concentration (wt%) ≥ 97%, while ether The concentration (wt%) of n-butene in C4 is generally 40-50%, and most of the others are C4 alkanes, so it is necessary to separate n-butene and alkanes to realize the concentration of butene. [0003] Since 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, and it needs to be separated by extractive distillation, that is, one or more polar components are adde...

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Problems solved by technology

[0004] There are many problems in the existing extraction and absorption process for separating butane and butene: (1) The solubility of conventional solvents to C4 olefins is small, resulting in low mass transfer efficiency in ordinary extraction and absorption towers

(2) The amount of extractant is too large. In order to improve the mass transfer efficiency and ensure the recovery rate of butane and butene, the liquid-gas ratio must be greatly increased. Some existing absorbents have a liquid-gas ratio as high as 20-22. The equipment is huge and the energy consumption is high, which is very uneconomical

If it is operated under pressure, the temperature of the tower will be higher. For example, when using a mixture of morpholine and N-formylmorpholine as a solvent, the temperature at the bottom of the desorption tower will be as high as 210-230°C, which will cause the decomposition or coking of the solvent; if it is operated under normal pressure , Butene cannot be condensed at about 45°C under normal pressure at the top of the tower, it needs cryogenic cooling or compression, and the energy consumption increases a lot

(4) The yield of butene is low, especially when the purity of butene reaches more than 95% in industry, the yield of butene is only about 75%, and the loss is relatively large

Disadvantages of this process On the one hand, the effect of using conventional extractants is not very significant, and there are still many problems existing in existing extraction absorbents. On the other hand, the four-tower process is much more complicated than the two-tower or three-tower process, and the investment, material consumption and energy consumption Basically doubled, but the effect is not much improved

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