SU1161470A1 - Method of obtaining chromium anhydride - Google Patents

Abstract

A method for the preparation of chromic anhydride, which includes reacting sodium bichromate with sulfuric acid when it is heated in excess. and separation of molten sodium bisulfate and chromic anhydride, o. so that, in order to reduce the content of primmes in the product, as well as reduce the loss of chromium in the process, the interaction takes place in three stages: in the first stage, 70-80% of sodium bichrstat of its total amount is used and the process is carried out at 150-170 ° C and molar ratio 1:

Description

ABOUT

The invention relates to a process for the production of chromic anhydride, used, for example, in instrument making, machine tool and mechanical engineering, in the chemical and petrochemical industry, in the production of chromium oxide, catalysts, in the synthesis of rubber and alcohols. The aim of the invention is to reduce the content of impurities in the product and also to reduce the loss of chromium during the process. Example 1. 1156.9 kg of sodium bichromate (67.1% CgOz) are fed to the electrically heated reactor, which accounts for 75% of the total load and 719.6 kg of sulfuric acid (92.5%), which corresponds to the molar ratio Naj CrjO-tH SO. 1: 1.75 The mixture is heated and maintained at for 35 minutes - the first stage of the process. Then, the rest of the sodium bichromate (25% of the total) is 385.7 kg (67.1% CrOs) and 294.1 kg of sulfuric acid (92.5% H2SO4), which corresponds to their molar ratio of Na, Cr2, 0- J iHjSO 1: 1.9. The reaction mass is heated to -158 ° C, held for 30 minutes - the second stage. Next, 120.6 kg of sulfuric acid are introduced to ensure the ratio of Na Cr2O7: H2504 1: 2.08, heated to a temperature of 205 ° C, and incubated for 15 minutes - the third stage. The reaction mass is drained to separate into a settling tank. The chrome anhydride melt is scaled and 1018 kg of technical product are obtained containing, in wt%, CrOj 99.85; SOf 0.035; insoluble residue 0,011. Waste production - sodium bisulfate contains 2.7 wt.% CrO, 1.1 wt.% Cr2.0z. The degree of use of chromium is 98.2%, which indicates a low loss of chromium. Example 2. I1116.7 kg of sodium bichromate (67.1% Cg Oz), which is 70% of the total load, and 624.2 kg of sulfuric acid / 100% NgZO, are fed to the reactor, which corresponds to the molar ratio O 7 : 11280 1g1.7. The mixture is heated and held at 160 s for 40 minutes at the first stage of the process. Then another 478.5 kg of sodium bichromate (30% of 702 charges) and 302.1 kg of sulfuric acid are introduced into the reactor, ensuring the molar ratio .O-T: H2SO 1: 2.92. Heated about 197C and incubated for 30 minutes - the second stage of the process. Next, 197.6 kg of sulfuric acid is added to the molar ratio of Na Cr O: H: 3804 1: 2.10, heated to 208 ° C, held for 10 minutes - the third stage of the process. The reaction mass is drained to separate into a settling tank. The melt of chromic anhydride is boosted to obtain 1050 kg of a technical product containing, in wt.%: CgO3, 99.8; , 03; insoluble residue 0,012. Production waste - sodium bisulfate contains 3.0 ac.% CrO, 1.4 wt.% CrjOj. The degree of use of chromium 9 /, 9%. Example Z. In the reactor, a sub-load of 1300 kg of sodium bichromate (67.1% CrOj), which constitutes 80% of the total charge and 769.6 kg of sulfuric acid (100% H, ..., SO), which corresponds to the molar ratio of components 1 : 1.8. The mixture is heated to and maintained at it for 30 minutes - the first stage of the process. Then another 325 kg of sodium bichromate (67.1% CrOj), which is 20% of the charge, and 208.4 kg of sulfuric acid are introduced into the reactor, ensuring the ratio of Na2Cr207: H2, S04 1: 1.95, is heated to 198 ° C and incubated for 25 minutes - the second stage. Next, 117.6 kg of sulfuric acid are introduced to the ratio of Na2Cr207: H2SO4 1: 2.05, heated to a temperature of 204 ° C, and the third stage is kept for 10 minutes. The reaction mass is poured into the sump. The melt of chromic anhydride is chemized to obtain 1070 kg of technical chromic anhydride containing, in wt.%: CgOz, 99.9; SO 0.04; insoluble residue 0.01. Production waste — sodium bisulfate contains 3.1 wt.% CrOj, 1.3 wt.% CGGO. The degree of use of chromium is 98%. In tab. 1 shows the effects of the molar ratio in the first stage of the process on the quality of chromic anhydride and the loss of the latter.

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with sodium bisulfate (amount of sodium bichromate 75%; temperature

leoc),

In tab. Figure 2 shows the effect of the amount of sodium bichromate added in the first stage of the process on the quality of chromic anhydride and the loss of the latter with sodium bisulfate (mol p61470.44

The ratio of Na2Cr20-: H2SO4 is 1: 1.75, temperature.

In tab. Figure 3 shows the effect of the temperature of the reaction mass in the first 5 stages of the process on the quality of chromic anhydride and the loss of the latter with sodium bisulfate (molar ratio of Na jjCr3.0 .504 1: 1.75; amount of NaiCri04 75%).

Table1

Table 3

Claims (1)

METHOD FOR PRODUCING CHROMIUM ANHYDRIDE, including the interaction with heating of sodium dichromate with sulfuric acid, taken in excess, and the separation of molten sodium bisulfate and chromic anhydride, characterized in that, in order to reduce the content of impurities in the product, as well as to reduce during the loss of chromium, the interaction lead in three stages: in the first stage, 70-80% of sodium dichromate of its total amount is used and the process is carried out at 15O-17O ° C and a molar ratio of Na ₂ Cr _a 0 ₇ : H ₂ S0 ₄ = = 1: (1.7 -1.8), in the second stage at 180-200 ° C, the molar ratio enii Na ₂ Cr _z 0 _7: H ₂ S0 ₊ = 1: (1,90-1,95) and use the remaining quantity of sodium dichromate, in a third step at 2O5-2oo ° C and a molar ratio Na ₂ Nin * Cr _a 0 ₇ : H _a S0 ₄ = 1: (2.05-2.10). .., 1161470>