The Physicochemical Analysis of the Interaction Reaction of Potassium Chloride with Ammonium Hydrosulfate

This paper represents the results of exploratory research on the production of ammonium-potassium sulfate salt and by-products. Information on the use of the results of fundamental research for the creation of new technological processes is provided. The increase in the range of products based on ammonium salts is a priority task for the industrial enterprise “KazAzot” JSC (Kazakhstan, Aktau). Another task is to expand the areas of application of products with derivatives based on ammonium hydrosulfate. Furthermore, combined fertilizers can be included in the list of products. The aim of the work is to scientifically substantiate physicochemical transformations in reaction mixtures, such as obtaining ammonium-potassium sulfate-fertilizer with three target components.

The experimental work was conducted in a laboratory shaft electric furnace, with observations of changes in the reaction mass and determination of the pH of the gas phase. The produced products were subjected to an X-ray phase analysis on the diffractometer Miflex 600 (Japan) with CuKɑ. In addition, the physicochemical changes of reaction mixtures and synthesized salts were studied with the help of the derivatograph of the Q-1000/D system by “MOM” F. Paulik, J. Paulik, L. Erdey and LabSys Evo TG-DTA/DTG (Setaram, France), NETZSCH STA 443 F3 in the nitrogen atmosphere. The thermodynamic evaluation of the probability of reactions was obtained using the Astra-4 program complex HCS-5.1 Chemistry (Outokumpu).

It has been established that in the temperature range 157 - 260 °C at equal molar ratios of NH₄HSO₄÷KSO₄ the condensed product of the reaction is a double salt ammonium-potassium sulfate (NH₄KSO₄) and its decomposition into constituent sulfates occurs above 260 °C with simultaneous pyrolysis of ammonium sulfate to complete formation of ammonium hydrosulfate and ammonia. At incomplete pyrolysis of ammonium sulfate in the cooled residue is present (NH₄)₃HS₂O₈, so salt formed from 2 ammonium sulfates: (NH₄)₂SO₄∙NH₄HSO₄ and similarly, the product of incomplete decomposition of ammonium-potassium sulfate - NH₄KSO₄ is KHSO₄∙K₂SO₄.

An increase in the stoichiometric molar ratio in the system «NH₄HSO₄ ÷ KCl» leads to the formation of more complex hydrated salts and the basic salt of ammonium - ammonium sulfate, and, on the contrary, a decrease in the ratio - to a more basic compound of potassium sulfate.