Environmental-friendly method used for preparation of potassium nitrite and regent-grade potassium nitrite, and combined production of regent-grade sodium oxalate

Abstract

The invention relates to an environmental-friendly method used for preparation of potassium nitrite and regent-grade potassium nitrite, and combined production of regent-grade sodium oxalate. The environmental-friendly method comprises following steps: (1) potassium hydroxide and oxalic acid are mixed at a weight ratio of 1.5-1.6:1 so as to obtain an aqueous solution 1; (2) sodium nitrite is prepared into an aqueous solution 2, and the aqueous solution 2 is filtered, wherein the weight of sodium nitrite accounts for 1.6 times of the weight of oxalic acid used in step (1); (3) the aqueous solution 1 is heated to 85 DEG C, the aqueous solution 2 is added with stirring, and an obtained mixture is subjected to heat preservation at a temperature of 80 DEG C for 30min; (4) the mixture is filtered, filtrate and precipitate are collected respectively, and are processed so as to obtain products. According to the environmental-friendly method, double decomposition is adopted; the solubility of sodium oxalate is much lower than that of potassium carbonate and potassium oxalate, so that sodium oxalate is taken as a decomposing agent. It can be observed from a picture in the invention that solubility of the obtained sodium oxalate is very low, and changes little with temperature changing, and the solubility of potassium nitrite is relatively high, so that reaction of potassium oxalate with sodium nitrite is used, and industrial potassium nitrite standards can be achieved via one-time synthesis.

Description

technical field [0001] The invention belongs to the chemical industry, the food industry and the chemical reagent industry, in particular to an environment-friendly method for preparing potassium nitrite, reagent-grade potassium nitrite and co-production of reagent-grade sodium oxalate. technical background [0002] Potassium nitrite is a food coloring agent and color-retaining agent allowed to be used in my country. It can produce special flavor during the color-protecting process, so it is widely used in food, especially in meat as a color-protecting agent and flavoring agent. Potassium nitrite is also It can inhibit a variety of anaerobic Clostridium, especially Clostridium botulinum, so it is allowed to be used as a preservative for various canned meat and products in my country. Potassium nitrite is also a reducing agent in organic synthesis, and can also be used in the manufacture of aniline dyes and azo dyes. It is also used in the separation of nickel and cobalt in me...

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Problems solved by technology

[0003] At present, there are two industrial methods for preparing potassium nitrite: absorption method and reduction method. One is to use potassium hydroxide solution to absorb nitric oxide, and KOH+NO→KNO 2 , the side reaction is KOH+NO 2 → KNO 3 , at the same time, when NO gas is prepared by decomposition method, it will cause great environmental pollution

The reduction method is to heat potassium nitrate and lead powder together, KNO 3 +Pb→KNO 2 +PbO, the use of metal lead pollutes the environment, and the disadvantage is that there are many by-products, including a large amount of potassium nitrate and sodium nitrite, which are difficult to separate and purify

[0004] Steps of the preparatory group of a college in Tianjin (1) Inorganic salt industry 1979.3 Using sodium nitrite and potassium carbonate as raw materials for double decomposition reaction to prepare potassium nitrite, using the difference in solubility of sodium carbonate and potassium nitrite for repeated crystallization, the process is relatively cumbersome

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