Research of the process of obtaining potassium dihydrophosphate using diethylamine

. The article studies the physico-chemical analysis of the conversion process of local raw materials of potassium chloride and extraction phosphoric acid obtained on the basis of phosphorites of Central Kyzylkums, in the presence of diethylamine. As a product, potassium dihydrogen phosphate was obtained, which is used as a complex fertilizer in many branches of the chemical industry and in agriculture. The influence of technological parameters on the conversion process is investigated.


Introduction
Large-capacity production inorganic substances: mineral fertilizers, soda, as well as a number of others products inorganic chemistry are the most important components o f chemical industry.Technologies for obtaining fertilizers with a high concentration of useful minerals are of interest in terms of reducing their energy intensity and simplifying the hardware and technological scheme.Dihydrophosphate and potassium metaphosphate are highly concentrated complex fertilizersthe total concentration of useful components P 2 O 5 + K 2 O in anhydrous salts is: KH 2 PO 4 -86,8%; K 2 HPO 4 -94,8%; K 3 PO 4 -100%; KPO 3 -91%.Potassium metaphosphate (KPO 3 ) is a highly effective, practically non-hygroscopic and non-sedimentary fertilizer, non-toxic for seeds [1][2][3].
Receipt dihydrogen phosphate potassium from chloride potassium by reactions it does not occur in an aqueous medium, and when the resulting hydrochloric acid is extracted with amyl alcohol [4][5][6], the equilibrium shifts to the right KCl + H 3 PO 4 KH 2 PO 4 + HCl (extr.amil.alcohol), but i t requires evaporation uterine solutions for allocation dihydrophosphate potassium, which accompanied significant expense of thermal energy.In addition, rectification cleaning of the extractant used is required [7][8][9] The use of amines makes it possible to obtain potassium dihydrophosphate by reaction immediately in crystalline form, due to the high salting effect of amine salts on potassium dihydrogen phosphate.The crystalline product remains to be filtered, rinsed and dried.The optimal conditions for the salting of the product in reactions (4-5) are determined by the physicochemical properties of the corresponding multicomponent water-salt system containing one of the types of amines, and by analogy extends to the construction of other technological processes for obtaining fertilizers in water-salt systems with salting [10][11][12][13][14][15][16].

Experimental
Potassium dihydrogen phosphate is obtained as a result of the following heterogeneous reaction: We conducted a study on the production of potassium dihydrogen phosphate based on potassium chloride with extraction phosphoric acid (EPA) obtained from Central Kizylkum phosphorites in the presence of diethylamine in a flask with three necks.During the study, the effect of EPA norms on the formation of dihydrophosphate, diethylamine, the duration of the process on the conversion process and product yield was studied (table 1).Experimental data show that with an increase in the rate of EPA from 80 to 100%, the product yield increases and reaches a maximum value of 67.97%.A further increase in the rate of EPA to 140% sharply reduces the yield to 24.91%.This character of the dependence of the product yield on the EPA rate is explained by the fact that at a rate of 100%, potassium monophosphate is formed and the yield is 100%, and a further increase in the EPA rate leads to an increase in the solubility of KH 2 PO 4 in phosphoric acid and decreases.

Equations and mathematics
In experiment 9, the yield of the product at a rate of 120% is 11.74% less than at a rate of 100% and in experiment 10 it is 35.58% less than at a 140% rate.The process was influenced (Pic. 1) by the molar ratio of potassium chloride to diethylamine.
In experiment 9, the product yield at a rate of 120% is 11.74% less than at a rate of 100%, and in experiment 10 it is 35.58% less than at a 140% rate.The process was influenced (Pic.1) by the molar ratio of potassium chloride to diethylamine At a molar ratio of 1:0.80, the product yield was 41.99%, and at 1:1.20, the yield was 10.32% less compared to a molar ratio of 1:1.00.At a ratio of 1:1, the product yield was the highest -67.97% in the experiments.After the completion of the conversion process, the solid and liquid phases were subjected to chemical and physicochemical analysis.
Pic. 3 graphically presents experimental data on the effect of duration on product yield.The nature of the curves has z figurative shows that in the interval of 15-30 minutes there is a relatively smooth increase in the yield of the product from 58.71 to 60.49%.Further, with an increase in the duration of the conversion to 60 minutes, there is an almost abrupt increase in the yield of the product to 67.97% over which time period 7; 8 min.A further increase in the duration of the conversion has practically no effect on the yield of the product.The kinetic data of Table 2 show that at a temperature of 30 0 C, with an increase in the conversion time from 15 to 90 minutes, under otherwise identical conditions, the product yield increases.The maximum product yield of 67.61% is achieved at a 100% rate of extraction phosphoric acid and practically the same values of the ratio of liquid and solid phases (L:S).Under the same conditions, the maximum filtration rate in the solid and liquid phases was recorded, amounting to 747.95 and 4305.79 kg/m 2 h, respectively.
According to the results of chemical analysis (table 2), it can be concluded that certain fluctuations in the content of components in the solid and liquid phases after the end of the conversion process, there are certain fluctuations.The limits of the content of components in the solid phase were the following wt.%:K  The data show that after the filtration process, the precipitate needs to be washed more thoroughly.
Differential thermal analysis and thermographic changes were performed on a synchronous thermal analyzer START 1600 manufactured by the German company Linsize, measurements were carried out at a speed of 20C (min in an oxidizing environment (Pic.5 a and b)).
As shown by DTA sample 4, in the temperature range of 250-275, a deep endothermic doublet effect is observed, which corresponds to a minimum at 257 and 270ºС.Which correspond to staged dehydration potassium dihydrophosphate with the formation of potassium methophosphate (KPO 4 ) through potassium pyrophosphate ( K 2 H 2 P 2 O 4 ).
As shown by X-ray diffraction analysis (Pic.4) of the samples consists of minerals potassium dihydrogen phosphate more than 99.0% and potassium chloride not more than 1.0% (Table 3).The structure of KH 2 RO 4 crystals is tetragonal.Sieve analysis and the diameter of the particle size of the crystals is average d -mm.  1.   1.

Conclusions
Based on X-ray phase analysis, the mineralogical composition was determined.The average mineralogical composition of samples 2-5 was as follows: KH 2 RO 4 -99.2%;COP l -0.75%.Thus, the experimental studies carried out have established the optimal technological parameters for the production of potassium dihydrogen phosphate : the rate of extraction phosphoric acid is 100%; pH suspension 3.71; conversion duration -45 minutes; ratio W :T = 5.60:1; humidity -4.45%.The same conditions are optimal for the filtration rate of the conversion pulp.

Fig. 1 .
Fig. 1.Influence of the norm (molar ratio) of EPA on the yield of potassium dihydrogen phosphate

Fig. 3 .
Fig. 3. Effect of conversion duration on product yield

6 E3SFig. 5 .
Fig. 5. Derivatogram of samples .a -general view, b -analysis of TG and DSC The sample numbers correspond to those in Table1.

Table 1 .
Impact of technological parameters on process c c chloride conversion potassium EFC in the presence of DEA

Table 1 ,
Pic. 3).The graph (Pic. 1) of the dependence of the product yield on the EPA norm has a parabolic character.

Table . 2
. Chemical composition of solid and liquid phases after conversions