Separation method for coal-based fischer-tropsch olefin

Abstract

The invention relates to a method for separating olefin from coal-based fischer-tropsch synthesis light distillate oil. The method comprises the following steps of (1) conducting deacidification treatment on fischer-tropsch light distillate oil raw materials; (2) absorbing the deacidification-treated distillate oil to remove a carbonyl compound; (3) ensuring that the distillate oil after deacidification enters a de-lighting tower, a component with a carbon number less than n is separated from the top of the de-lighting tower, a bottom component enters a de-weighting tower, a component with a carbon number greater than n is taken off from the bottom of the de-weighting tower, and a component with a carbon number of n is separated from the top of the de-weighting tower; (4) ensuring that thecomponent of the carbon number of the n enters an extractive distillation tower and is in reverse contact with an extracting agent, a non-polar alkane is separated from the top of the tower, and theextracting agent and the target olefin are distilled from the bottom into a recovery tower; (5) ensuring that the target olefin is distilled off from the top of the recovery tower, and the extractingagent is distilled off from a tower kettle and recycled to the extractive distillation tower. Due to the preparation of the high carbon number olefin, and negative pressure distillation is used for preventing olefin cracking, which ensures the structural integrity of the olefin.

Description

technical field [0001] The invention relates to a separation method suitable for Fischer-Tropsch olefins, in particular to a method for separating olefins from coal-based Fischer-Tropsch alkenes. Background technique [0002] High-carbon olefins are important and commonly used organic petrochemical raw materials. They can be used as detergents, oil additives, surfactants and pharmaceutical intermediates. They can also be used as high-quality comonomers to produce high-grade polyolefin resins. [0003] The existing olefin preparation technologies are divided into two categories: one is the coal-based route, and the other is the petroleum route (also known as ethylene oligomerization). The coal-based route refers to the separation of alkanes from coal-based light distillates to obtain olefins. The commonly used methods include molecular sieve adsorption process and extractive distillation process; the petroleum route refers to the preparation of olefins by ethylene oligomeriza...

AI Technical Summary

Problems solved by technology

There are deficiencies in the existing preparation and separation methods, which are as follows: (1) The traditional separation of coal-based alkanes and olefins adopts the method of molecular sieve adsorption, which is limited by the life of the molecular sieve and needs to be periodically shut down for molecular sieve regeneration. High cost, poor production continuity, low production efficiency, and low purity of olefins obtained

(2) The extraction agent selected by the existing extraction and rectification process is a low-boiling extraction agent, which can only separate substances below C8, and cannot meet the requirements for the separation of Fischer-Tropsch alkanes and olefins above C8

(3) The carbon number of olefins obtained by the ethylene oligomerization route can only be from C4-C8, and only even-numbered carbon products can be produced, which has poor product diversity and high production costs

However, the composition of raw materials in actual production is much more complex and contains many impurities. It is very difficult to obtain raw materials that meet the requirements of this method. This method cannot be applied to the olefin separation process of coal-based Fischer-Tropsch synthesis light distillate oil. Oxygenated compounds in olefins will affect the separation of alkanes, and the presence of oxygenated compounds will affect the quality of products, which are extremely toxic to the catalysts used in the synthesis process of downstream products, so for the actual separation process put forward more stringent requirements

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