SU4354A1 - Method for continuous production of potassium chlorate and potassium chloride by the action of chlorine on potash - Google Patents

Description

The effect of chlorine on the hydrates of alkali and alkaline-earth metals, as well as on carbonates of alkali metals, was studied by Berzelius in 1785, and was studied in detail by Ge-Lussac in 1842. The method of obtaining potassium potassium from potash from the time of Berzelius was abandoned and and apparently

It was not of scientific interest, however, the process of obtaining bertolet salt directly from potash with simultaneous production of potassium chloride as a by-product deserves attention in the USSR, where the only source of potassium is plant potash, from which chloride is specially prepared by treatment with hydrochloric acid. potassium. On the other hand, with large production and consumption of caustic soda, large amounts of chlorine obtained simultaneously cannot be used in a consistent manner, and thus.

The production of chemical salt from electrolytic chlorine makes economic sense. At the same time, due to the significant demand for chlorine and bleaching salts, the entire amount of chlorine produced simultaneously with caustic soda cannot be used exclusively for the production of potassium chlorate by chemical means. Finally, the production of potassium salt directly electrolytically has its very large advantages and needs correspondingly large quantities of potassium chloride. Thus, under the conditions of the USSR, it is most appropriate to combine chemical and electrochemical production of bertolet salt with chemical production directly from potash and to produce potassium chloride, which is the aim of the invention.

The chemistry of the process of chlorine on caustic alkali and alkali metal carbonates can be divided into two points; 1) chlorine absorption and formation of hypochlorite

2MON -f 2Ci MCI + MCIO + H, 0 ... Q,., 5 ..,., .... Q, 3 ,, Q 3MC1O 2MC1 -f MCiO:, j ° - g -f- lh .and

zm, with, + for, - zmaots-zms14-zso, 1z .., 4-5ms14-zso

the snake MClOn -h 2MCI / -jH-bt-i-MLlU, .- i-i) /vii..u "

Since the formation of chlorate occurs through the intermediately formed hypochlorite, its output depends on the rational formation and even more favorable decomposition of hypochlorite into chlorate. The stationary concentration of hypochlorite prepared during the chlorination process of a caustic or carbonated alkali solution and the decomposition of hypochlorite into chlorate and chloride are affected by the following factors: 1) temperature, 2) light, 3) alkalinity of the solution, 4) concentration of the initial caustic or carbonic alkali , 5} chloride concentration, 6) carbonic acid, 7) beat the flow of chlorine and 8) concentration of it. Bhadari (Zeitschr. F. Anorg. Chetn. 13,385) and Foerster (Journ, prakt. Chem. 63, 141) proved that with an increase in temperature, under other equal conditions, the decomposition of hypochlorite goes faster and, moreover, it goes stagnantly The solution becomes less, because at a higher temperature per unit of time, the formed C of hypochlorite decomposes more than at a low temperature. The very same decomposition proceeds with a side reaction with the release of oxygen according to the formula:

2MaO- 2MS1 + O.2.

Further, Bhadari proved that at high temperature and equality of other conditions, hypochlorite per unit of time decomposes the more, the greater the concentration of hypochlorite. The amount of released oxygen increases

and 2) decomposition of the resulting hypochlorite into chlorate and chloride. The whole process can be schematically represented by the following formulas:

with increasing hypochlorite concentration and heating time. The experiments of the authors with carbonates lead to the same conclusions.

The concentration of hypochlorite increases, as shown by the experiments of the authors, when chlorinating in cold with a decrease in the initial concentration of potash, and at boiling with an increase in the current of chlorine passed by the solution. The alkalinity of the medium has a great influence on the rate of decomposition of hypochlorite and the side reaction with the release of oxygen, and it is: the greater the alkalinity of the medium, the less per unit time under other equal conditions hypochlorite decomposes. The side reaction with oxygen evolution increases with decreasing alkalinity of the medium.

The presence of chloride on the decomposition of hypochlorite; 1. Apparently causes catalytic plp iS (Foerstor uncl Joire. Journ. Prakl. Chem. 59, 53), where, all other things being equal, it accelerates the process of the conversion of hypochlorite to chlorate and reduces the side reaction with BI.I oxygen separation. The presence of free carbon dioxide also accelerates the transition of hypochlorite to chlorate, and although carbonic acid is stronger than the hypochlorite, nevertheless, the authors' experiments showed that an excess of CO2 does not noticeably increase the side reaction with oxygen evolution. An excess of chlorine in the decomposition of hypochlorite into chlorate has, as it were, two different catalytic values. On the one hand, an excess of chlorine contributes to the formation of HOO, which oxidizes hypochlorite according to the formula: -H-2CH1O + C1O 2H + 2a + C1O3, while the concentration of HCCO, according to the formula: i2H + 2Cl1O 2CH1O, remains constant. On the other hand, an excess of chlorine contributes to the self-decomposition of hypochlorite according to the formula ssGo-- aOzN-2C1. These reactions during the formation of chlorate are very important, as they proceed without loss of oxygen. Experiments with carbonates, in general, fully confirmed the catalytic role of an excess of chlorine. When chlorinating a solution of potash with a weak current, chlorine, but such that the solution is saturated with it, t, -e. so that chlorine is delivered to a unit of time more than during this period the solution of potash can absorb, the rate of decomposition of hypochlorite is many times less than in experiments, where chlorine with a stronger stream passed through the same solution. During the chlorination process, the same factors act on the course of the reactions, with the only difference being that during the chlorination of carbonates, all the time SOL is released, which at the beginning of the process is more or less, depending on the temperature, is released in a free form, part of it reaction with a solution of not yet chlorinated potash, forming bicarbonate. Then, having reached the moment when the whole carbonate is converted into bicarbonate, bicarbonate is chlorinated, copiously liberates CO.,. Then the bicarbonate disappears, and the remaining hypochlorite from the action of chlorine and heat passes into chlorate. All calculations for determining the output from the theory were based on the assumption that the process of chlorinating potash should proceed according to the formula: ЗКОСОа + ЗСЬ КСЮз - {-. 5Ка - {- ЗСО2. Chlorination in the cold was carried out at room temperature (10-15) in a flask with a capacity of 5COc. After a certain period of time, two or two samples were taken with a pipette. In one, it was determined the amount of KCIO, in the other, the CCSU;) the sample was taken while the liquid remained homogeneous. The chlorine rate was counted by the bubbles in the washing line with H., SO. |, At which the current of chlorine 100-150 bubbles per minute was considered weak, 150 is 250 average, and when the number of bubbles per minute is more than 250, it is considered strong. With cold chlorination, a large amount of hypochlorite remains at the end of the process, very slowly under these conditions, which decomposes. To translate it into chlorate, in one of the experiments, the hypochlorite decomposed by transmission, the average chlorine current during slow naphelania first to 40 and then to 80 ° and then to boil, and in other experiments, only by boiling, without passing chlorine. At the end of the experiment, the KClO.-i-f-KCl obtained was determined by analyzing the reaction liquid. With an average current of chlorine and a small concentration of the initial solution of potash, the process of formation of hypochlorite goes faster than chlorate, the maximum of the one and the other is reached almost simultaneously. With the same average chlorine current, the limiting amount of formed and not changing during the process of hypochlorite is the greater, the lower the concentration of the taken potash solution. Chlorate is best when most potash goes into chlorate in the cold, it happens

solid KCI, cool to more than} low t, then a significant amount of chlorate can be isolated; for this, it is necessary to add so much so that when cooled, the chloride is not released, and then, after suction from the mother liquor and washing with a saturated solution of chlorate, a pure chlorate free of potassium chloride will be obtained. To do this, it is necessary to take for chlorination a certain empirically determined concentration of potash in a saturated solution.

KC1Oz + KC1,

Since, with an excessive concentration of potash, the excess of chlorate formed cannot be dissolved in the liquid even at boiling, and therefore, during hot filtration, chlorate will be filtered out along with the chloride. On the contrary, with an insufficient concentration of potash, in addition to the undesirability of a low concentration, due to a decrease in yield, the process of separate crystallization becomes more difficult, due to a slight loss of chlorate with the addition of water inevitable for the purity of the product. A suitable concentration of potash in a solution of KC1 + KS1Oz, saturated at 15 °, is 2.685

equivalent At this concentration of the solution, the temperature for the first crystallization and filtration from KC1 is 75-82 °. The temperature of the second crystallization for the release of chlorate is 15-17.5 ° C. Before the second crystallization, an increase of 18-20% water is sufficient for these concentrations.

Thus, by the action of chlorate on potash solution, it is possible to achieve almost quantitative conversion of potash to chlorate and chloride without the formation of chloride by-side by decomposing hypochlorite with the release of oxygen. Achieving such a result is possible under the conditions that favor the formation of hypochlorite and its non-decomposition into chloride and oxygen, on the other hand, conditions

supportive of its termination in chlorate and chloride. These conditions are reduced to maintaining the period of saturation with chlorine as far as possible in the cold, the second stage, with a gradual rise in temperature, and most importantly with the maximum excess of gaseous chlorine. An excess of chlorine gas, and it is an increase in its partial occurrence above the solution at a total atmospheric pressure can accelerate the process of turning hypochlorite into chlorate more than twice.

Due to the fact that the solution of potassium bicarbonate, saturated with carbonic acid, very eagerly and quantitatively absorbs chlorine, it is possible to convert riorauia into chlorate and chloride in the form of a continuous process with completely quantitative utilization of chlorine and release of pure chlorate-free carbon kyoyuta from the reaction system. Due to the different solubility of potassium chlorate and potassium chloride and the change in these solubilities with temperature, it is possible by correct selection of the initial composition of the reaction mixture to achieve separate precipitation of each of the two reaction products of the potassium chloride salt and potassium chloride in crystalline form, and thus avoid as the need for special separation of these salts, and all special evaporation of solutions. At the same time, the mother liquor after the release of potassium chloride from it (at 80 EO / o) and bertolet salt (at 15) goes back into reaction with the addition of a new portion of potash and is removed from the cycle only when foreign matter accumulates in it.

Ed.

Claims (2)

1. Method for continuous production of potassium chlorate and potassium chloride by the action of chlorine on potash, immediately giving both salts in solid form without evaporation or freezing of solutions, which differs the fact that chlorine acts on a solution of potash at such a concentration that at the 13th end potassium chloride at a high temperature drops out in solid form, and to convert the potash to bertolette salt without decomposing the hypochlorite into potassium chloride and oxygen, the first stage of the process of saturation of potash with chlorine is the time of which bicarbonate is formed and the maximum concentration of hypochlorite is obtained, carried out at a moderate current of chlorine and possibly low temperature, in the second stage, in order to achieve the possible acidity of the solution, vuyuschey transition hypochlorite chlorate salt (chlorate), the solution temperature gradually increased, simultaneous skipping 1yu maximum excess chlorine. 2. Acceptance of the method according to claim 1, characterized in that the solution of potassium chloride and potassium chloride obtained at 80-90 is diluted with 18-20% water and cooled to 5 to isolate the potassium salt, then saturated with potassium and treated with chlorine, as as indicated in paragraph 1, bringing the temperature to 80-90 at the end of the reaction to terminate the reaction of precipitating potassium chloride in solid form, and with the resulting solution proceed as indicated above.