CS252393B1 - A method for reducing or removing calcium from pentaerythritol solutions - Google Patents

Abstract

A method for reducing or removing calcium from pentaerythritol solutions is provided. The crude pentaerythritol solution is treated with a mixture of carbon dioxide and ammonia or its aqueous solution, or with ammonium carbonate or bicarbonate. The conversion of calcium into a water-insoluble salt is most often carried out after the previous removal of colored compounds from the crude pentaerythritol solution with solid adsorbents, for example activated carbon. The suspension of adsorbent and calcium carbonate is separated, most preferably by filtration.

Description

The present invention provides a method of reducing or removing calcium ion from so-called " calcium " of crude pentaerythritol processed in the process of its recrystallization.

The crude pentaerythritol obtained by fractional crystallization of the solutions produced in the pentaerythritol-enriched reaction step enriched in pentaerythritol and / or calcium formate by recycling the mixed salts or aqueous solutions from the pentaerythritol and calcium formate separation stage, contains a formate-dependent separation. Inorganic impurities, in this case calcium cations, have a negative effect on the quality of technical pentaerythritol. They cause haze of alkyd resins (Miiller H. Fette Seizen - Austrichnutel 58, 174 (1956), Gourley S. Dunlop W., Journal of the Oil Color Chemists Association 40, 40 (1957). The presence of calcium formate also has a very negative effect on melting temperature. and the stability of the technical pentaerythritol, which is converted into varnishes at elevated temperatures to decompose.

Calcium formate, which negatively affects the quality of technical pentaerythritol, remains partially in the crystalline state or in water-soluble form in the cake moisture in the raw pentaerythritol.

The most important way to reduce its content in crude pentaerythritol is to recrystallize it in deionic water most often by dissolving the crude pentaerythritol in steam condensate and / or in a solution unsaturated to pentaerythritol at temperatures of 80-110 ° C. Complete removal of the calcium cation can be achieved on cation exchangers (U.S. Pat. No. 100,891).

A method of removing alkali metal formate by electrodialysis is known (US Pat. No. 3,779,883). A method of precipitating a calcium cation into a water-insoluble form by treatment with phosphoric acid and oxalic acid is then employed, followed by filtration of the precipitate. Reduction of the crystalline calcium formate content is also achieved by washing the cake of crude pentaerythritol with deionic water, aqueous solution containing pentaerythritol (mother liquors from the recrystallization of crude pentaerythritol), or reducing the concentration of crystalline formate in a slurry of crude pentaerythritol by adding water from pentaerythritol.

Of these, the combined process for reducing calcium ion content is most commonly used by washing the raw pentaerythritol cake with steam condensate and / or mother liquor from recrystallizing the crude pentaerythritol and removing residual calcium on the cation exchangers, or by precipitation with oxalic acid or phosphoric acid followed by filtration of oxalate.

A disadvantage of the cation exchanger process is that the cation exchanger regenerates a considerable amount of acidic waste water (most often the regeneration is carried out with hydrochloric acid), after which neutralization increases the amount of waste water from the pentaerythritol production plant. More preferably, oxalic acid or phosphoric acid is used in the calcium removal step, problems are encountered in securing them.

In the study of the possibility of removing calcium from crude pentaerythritol solutions, it has been found that waste products from other productions may be advantageously used to remove calcium.

Claims (2)

It is an object of the present invention to reduce or remove calcium ion from pentaerythritol solutions which are prepared by dissolving crude pentaerythritol in steam condensate and / or mother liquor from the recrystallization of crude pentaerythritol. It is characterized in that a solution of crude pentaerythritol which is saturated to pentaerythritol at temperatures of 70 to 100 ° C and contains 7.10 .alpha. Of 0.23 mole of calcium formate is impregnated with a mixture of carbon dioxide and ammonia in an amount of one mole of calcium formate. From the solution, the calcium ion is precipitated to insoluble calcium carbonate, which is subsequently separated from the solution, most often by filtration. In the case where a step of refining to reduce or remove the color of the solution is included in the recrystallization of crude pentaerythritol (removal of color compounds from the condensation reaction of formaldehyde alone), it is preferable to carry out a process of reducing or removing colorants After decolourizing the solution, the calcium ion is subsequently precipitated by treatment with a mixture of carbon dioxide and ammonia, and the adsorbent / calcium carbonate suspension is separated from the solution, most often by filtration. Depending on the amount or excess of the ammonia carbon dioxide mixture, the stoichiometric amount required to precipitate calcium decreases the calcium content or completely removes it from the crude pentaerythritol solution. Ammonium carbonate or ammonium hydrogen carbonate may be used as a precipitating agent instead of a mixture of carbon dioxide and ammonia. Preferably, a mixture of carbon dioxide and aqueous ammonia solution is used for this purpose, most often as a waste product from aqueous scrubbers of ammonia production. Compared with the previously used methods of reducing or removing calcium from crude pentaerythritol solutions, the advantage of the process according to the invention is the utilization of waste, cheap products from other technologies, improvement of ecological conditions (elimination of cation exchanger regeneration by acid and thus acid regeneration waste solution). Example 1 Κ 200 g of an aqueous solution of pentaerythritol with a calcium content of 0,34% by weight at room temperature under atmospheric pressure, 5 g of a 25% aqueous ammonia solution is added and the mixture is treated with 0.9 g of CO2 for 5 min. After filtration of the calcium carbonate, the presence of calcium was not detected in the filtrate complexometrically. Example 2 To 200 g of an aqueous solution of pentaerythritol with a calcium content of 0.34% by weight. 1.63 g of ammonium carbonate are added at room temperature under atmospheric pressure and stirring. After filtration of the calcium carbonate, the presence of calcium in the filtrate was not complexometric. SUBJECT Method for reducing or removing calcium from solutions of pentaerythritol prepared by dissolving crude pentaerythritol in steam condensate and / or mother liquor from the recrystallization of crude pentaerythritol, characterized in that an aqueous solution of crude pentaerythritol containing 7.10 ⁴ to 0.23 moles of calcium formate is treated carbon dioxide and ammonia, or an aqueous solution thereof, or ammonium carbonate or bicarbonate in an amount of 0.7 to 5 moles, preferably 0.8 to 1 moles, of said compounds per mole of calcium formate, and the resulting calcium carbonate is separated by filtration, preferably together with adsorbents of sugars and color compounds present in the crude pentaerythritol solution.