CN1120147C - Method for inhibiting and eliminating discolouration of 3-chloropropene product - Google Patents

Abstract

The present invention discloses a method for inhibiting and eliminating the discoloration of 3-chloropropene products, which is characterized in that 3-chloropropene products can be prevented from discoloration, namely to keep colorless 3-chloropropene products for a long time without discoloration; discolored 3-chloropropene products can be changed into colorless products, and after being changed into colorless products, the 3-chloropropene products can be kept for a long time without discoloration. The method mainly comprises: excessive carbonate is added into 3-chloropropene products (the added carbonate can be Li2CO3, Na2CO3, K2CO3, CaCO3, MgCO3, BaCO3, etc.). Free hydrochloric acid and Fe<2+> ions in 3-chloropropene products are effectively reduced, so that the purpose of inhibiting and eliminating the discoloration of 3-chloropropene products is achieved. If used for treating 3-chloropropene products, the method of the present invention has the advantages of favorable effect and simple operation and can be widely used in large-scale industrialized production.

Description

Method for inhibiting and eliminating discoloration of 3-chloropropene product

The invention relates to a method for inhibiting and eliminating the discoloration of a 3-chloropropene product.

The pure 3-chloropropene product should be colorless. But if Fe in the 3-chloropropene product²⁺If the ion content is higher, the product is easy to change color at the temperature of over 20 ℃. Typically turning yellow, yellow-green, red-brown, black-brown, etc. within two weeks. We can conclude by a large number of experiments and according to modern coordination chemistry theory that: the main reason for causing the discoloration of the 3-chloropropene product is the 3-chloropropene and Fe²⁺The reaction produces a coloured complex which can be written as [ Fe (H)₂O)_m(3AC)_n]²⁺. Wherein 3AC represents 3-chloropropene, n represents 3-chloropropene and Fe²⁺M represents water and Fe²⁺Coordination number of (2). The values of m and n may be taken to be 0, 1, 2, 3, 4, 5, 6, however, n + m.ltoreq.6.

As known from literature search, at present, few research literatures report the discoloration of 3-chloropropene products. The applicant's patent application (application No.: 00126643.8) on 20/10/2000 of "a method for solving discoloration of 3-chloropropene" mainly emphasizes that free acid and metallic Fe in 3-chloropropene product are washed away with water as much as possible²⁺And a colored complex formed by ferrous ions and 3-chloropropene. The method solves the problem that the 3-chloropropene product has good color change effect, but needs a certain amount of water, soft water or deionized water to wash the product, has large workload, and needs to increase certain washing equipment investment.

The invention aims to utilize carbonate (such as Li) with weak alkalinity₂CO₃、Na₂CO₃、K₂CO₃、CaCO₃、MgCO₃、BaCO₃Etc.) react with free hydrochloric acid in the 3-chloropropene product to reduce the free acid content and react with Fe in the 3-chloropropene²⁺Ion reaction to produce FeCO₃And (4) precipitating. With CO₃ ^2-Can be used in combination with [ Fe (H)]₂O)_m(3AC)_n]²⁺3-chloropropene is replaced by reaction. A series of chemical reactions are as follows:

thereby inhibiting and eliminating the discoloration of the 3-chloropropene product.

In order to achieve the purpose, the invention adopts the following technical scheme:

adding an excess of carbonate, usually Li, to the 3-chloropropene product₂CO₃、Na₂CO₃、K₂CO₃、CaCO₃、MgCO₃、BaCO₃And the like, and one of them is optional. Stirred or shaken and then allowed to stand. The stirring or shaking time is generally 1 to 30 minutes, and the standing time is more than 1 hour. Elimination of 3-chloropropene productionFree acid and Fe in the product²⁺And colored complexes [ Fe (H)₂O)_m(3AC)_n]²⁺。

The detailed technical scheme of the invention is as follows:

addition of excess carbonate (usually Li) to the 3-chloropropene product without discoloration₂CO₃、Na₂CO₃、K₂CO₃、CaCO₃、MgCO₃、BaCO₃) Eliminating free acid in 3-chloropropene product and preventing Fe in storage²⁺Production of (a vessel for storing 3-chloropropene product is typically a ferrous product); simultaneously making Fe in 3-chloropropene product²⁺Conversion to FeCO₂. Thereby preventing the product from being damagedFormation of coloured complexes [ Fe (H) during storage₂O)_m(3AC)_n]²⁺Further inhibit the discoloration of the 3-chloropropene product.

Adding an excess of carbonate (usually Li) to the discolored 3-chloropropene product₂CO₃、Na₂CO₃、K₂CO₂、CaCO₃、MgCO₃、BaCO₃) To make Fe in 3-chloropropene product²⁺And coloured complexes [ Fe (H)₂O)_m(3AC)_n]²⁺Conversion to FeCO₃Thereby rendering the product colorless; simultaneously, free acid in the 3-chloropropene product is eliminated, and Fe in the storage process is prevented²⁺The production of (the vessel used for storing the 3-chloropropene product is generally a ferrous product) gives rise again to the coloured complex [ Fe (H)₂O)_m(3AC)_n]²⁺Discoloring the product. The purpose of inhibiting and eliminating the discoloration of the 3-chloropropene product is achieved.

The addition of sodium carbonate is preferred to the addition of lithium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate and barium carbonate. Because the sodium carbonate not only has easily obtained raw materials and moderate cost, but also can easily convert the complex of iron in the 3-chloropropene into FeCO₃。

The 3-chloropropene product treated by the method is colorless in appearance, and the free acid content and Fe in the product²⁺The content is obviously reduced, the product is placed for more than half a year without color change, and the product has no strict requirements on the packaging material of the product.

The present invention is described in further detail below by way of specific examples.

Example 1: in a 1 cubic meter reaction vessel, 500kg of 3-chloropropene product which has become brownish yellow is added, 3kg of sodium carbonate is slowly added, stirring is carried out for 15 minutes, and standing is carried out for 15 hours.

And (3) testing results: after treatment with sodium carbonate, the acidity of the free acid (calculated as HCl) in the product was reduced from 0.006% to 0, Fe²⁺The content is reduced from 0.12mg/L to 0.002 mg/L; the appearance becomes colorless, and the product remains colorless after half a year of storage.

Example 2: 500kg of yellowish 3-chloropropene product is added to a 1-cubic meter reactor, 2kg of calcium carbonate is slowly added, the mixture is stirred for 10 minutes and isleft for 8 hours.

And (3) testing results: after treatment with calcium carbonate, the acidity of the free acid (calculated as HCl) in the product was reduced from 0.005% to 0, Fe²⁺The content is reduced from 0.10mg/L to 0.002 mg/L; the appearance of the product turns colorless, and the product is preserved for half a yearIt is still colorless after use.

Example 3: 160kg of a 3-chloropropene product which is temporarily colorless in appearance, was placed in an iron drum having a volume of 200 l, 300 g of sodium carbonate were added, the iron drum was shaken slightly, allowed to stand and then stored.

And (3) testing results: the 3-chloropropene product in the barrel is colorless or does not change color after being placed for 6 months, the acidity (calculated by HCl) of free acid in the tested product is 0, and Fe²⁺The content is 0.002 mg/L; for 3-chloropropene of the same quality placed in another iron barrel, the 3-chloropropene product in the barrel becomes brownish red after two months because no sodium carbonate is added for treatment, and Fe in the tested product²⁺The content is 0.26 mg/L.

Claims (2)

1. A method for inhibiting and eliminating the discoloration of 3-chloropropene product is characterized in that excessive carbonate is added into the 3-chloropropene product to eliminate free acid and Fe in the 3-chloropropene product²⁺And coloured complexes [ Fe (H)₂O)_m(3AC)_n]²⁺Coloured complex [ Fe (H)₂O)_m(3AC)_n]²⁺In the formula (I), 3AC represents 3-chloropropene, n represents 3-chloropropene and Fe²⁺M represents water and Fe²⁺The coordination number of (b), m and n may be taken to be 0, 1, 2, 3, 4, 5, 6, however, n + m.ltoreq.6; wherein the carbonate is Li₂CO₃、Na₂CO₃、K₂CO₃、CaCO₃、MgCO₃、BaCO₃。

2. The method according to claim 1, characterized in thatCharacterized in that the carbonate adopts Na₂CO₃The effect is optimal and the economy is the most.