Method for removing alkyne in carbon 4 fraction by selective hydrogenation

Abstract

The invention relates to a method for removing alkyne in carbon 4 fraction by selective hydrogenation, comprising the steps of: introducing a liquid inside a tower in an appropriate position below a feedboard to a C4 alkyne hydrogenation reactor; and after reaction, returning a material flow to a rectifying column to remove alkyne in separation process. By adjusting a liquid phase extraction position and reflux ratio of a debutanizer, butadiene entering the C4 hydrogenation reactor is low in concentration, high in EA and VA concentration so as to reduce the reaction probability of converting butadiene to butane and butane conversion, improve the selectivity of converting C4 alkyne to butadiene to realize productive butadiene and remove the alkyne. Meanwhile, C4 alkyne hydrogenation is performed on a fixing bed outside the tower, the catalyst is easier to regenerate and change so as to meet the requirements of long term operation of ethylene unit. The invention can reduce the concentration of alkyne in C4 fraction entering the butadiene extracting device, lower a part of energy consumption of secondary extraction, save C4 hydrocarbon for dilution and reduce the environmental pollution.

Description

technical field [0001] The invention belongs to a method for selectively removing alkynes from unsaturated compounds, in particular to selectively hydrogenating and removing alkynes in 1,3-butadiene from a mixture of unsaturated compounds, and belongs to the field of petrochemical industry. Background technique [0002] 1,3-butadiene, as a raw material for synthetic rubber, is mainly separated from the by-product C4 fraction of cracking ethylene. The C4 fraction includes almost all the various isomers of C4alkanes, alkenes, dienes and alkynes, and a small amount of C3 and C5 hydrocarbons. Synthetic rubber requires the total content of alkynes to be less than 20ppm, of which vinyl acetylene VA is less than 5ppm. At present, the process of separating 1,3-butadiene is mainly solvent extraction method. This method obtains 99.5% of 1,3-butadiene through first extraction, second extraction, de-light rectification tower, and de-heavy rectification tower. , of which the second ext...

AI Technical Summary

Problems solved by technology

The advantages of the fixed-bed selective hydrogenation process are: easy operation, catalyst regeneration and replacement, and the disadvantages are: due to the high concentration of butadiene in the raw material, the selectivity is not high, and the loss of butadiene is large

The disadvantages are: since the reaction temperature is limited by the pressure of the debutanizer, the reaction temperature range is small, and there are few means to adjust the performance of the catalyst; when the debutanizer runs for a period of time, the surface of the catalyst deposits polymer, the catalyst activity decreases, and the catalyst regenerates , It is difficult to replace, and the running time of the debutanizer cannot meet the requirements of long-term operation of the ethylene plant

However, the reacted material is sent to above the feed position of the distillation tower, so that the liquid load on the plate between the feed position in the distillation tower and the position where the reacted material enters increases, and the diameter of the distillation tower increases; on the other hand, due to the lower position The material returns to a high place, and the material is mixed back, which is not conducive to the separation of C4 and C5. If a certain separation requirement is to be achieved, the number of theoretical plates and actual plates of the distillation column must be increased.

For the debutanizer of the existing ethylene plant, it cannot meet the requirements. It is necessary to replace the distillation tower with a large diameter and a high number of plates to achieve the purpose of this patent, and the investment cost will increase.

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