1. A process for recovering the inorganic waste liquid generated by the thermolysis of fluoro-reaction of diazonium salt in substituted arylhydrocarbon hydrogen fluoride includes such steps as adding NaHF to said inorganic waste liquid₂、HF、H₂O and organic impurities, characterized in that the process comprises the steps of:

step one, adding H into the inorganic layer waste liquid₃BO₃Cooling to room temperature, and filtering out and recovering crystallized solid organic matters;

step two, adding activated carbon or activated carbon fiber into the residual solution after the solid organic matter is filtered out for adsorption and decoloration, and obtaining colorless transparent liquid after decoloration;

regulating the pH value of the decolored colorless transparent liquid to 2-4, supplementing hydrogen fluoride for regulation if the pH value is more than 4, and supplementing equivalent boric acid and caustic soda for regulation if the pH value is less than 2;

and step four, obtaining white crystalline solid sodium fluoborate after concentration and drying.

2. The method according to claim 1, wherein the inorganic layer waste liquid is an inorganic layer waste liquid obtained after hydrogen fluoride is recovered by distillation after the pyrolysis fluorination reaction is finished.

3. The method of claim 1, wherein H is added₃BO₃Adding water to make the content of sodium fluoborate lower than 50 wt%.

4. The method of claim 1, wherein H is H₃BO₃The addition amount of (A) is 0.98-1.0 times of the equivalent of sodium ions in the solution.

5. The method according to claim 1, wherein the activated carbon or activated carbon fiber is added in an amount of 5 to 15 wt% based on the amount of boric acid added.

6. The method of claim 1, wherein the solid organic is an azo compound.

7. The method according to claim 1, wherein the temperature for the adsorption decoloring in the second step is 50 to 100 ℃.

Background

It is well known that the reaction process for preparing fluoro substituted aromatic hydrocarbons from diazonium hydrogen fluoride salts of substituted benzenes is:

in the formula, the position of the substituent R is not limited, the number of the substituent R is not limited to one, and the substituent R is alkyl or halogen.

After the fluorination reaction was carried out, the mixture was allowed to stand for separation. The organic layer contains, in addition to the fluoro-substituted aromatic hydrocarbon as the main reaction product, an organic by-product substituted phenol, an azo compound, a polymer thereof, and the like. The inorganic layer mainly contains excess hydrogen fluoride, sodium bifluoride, water, and the like.

The composition of the inorganic layer is relatively complex. Therefore, the existing manufacturers of fluoro-substituted aromatic hydrocarbon at home and abroad take the recycling of the inorganic layer as a super problem, only part of hydrogen fluoride can be recycled, and the rest of hydrogen fluoride is treated as waste. The existing treatment methods comprise the following two methods:

firstly, concentrated sulfuric acid is added into the inorganic layer to recover hydrogen fluoride:

2NaHF₂+H₂SO₄(concentrated) → Na₂SO₄+4HF

After rectifying and recovering part of hydrogen fluoride, the residual sodium sulfate containing hydrogen fluoride and sodium bifluoride is treated as waste salt. Obviously, this is only a recovery of part of the hydrogen fluoride and does not allow an efficient treatment and comprehensive utilization of the waste salts.

Secondly, after distilling the hydrogen fluoride, adding caustic soda into the distillation residual liquid to neutralize to neutrality, and performing spray drying to recover the sodium fluoride. However, no standard sodium fluoride product has been obtained so far, only the inorganic layer waste liquid is converted into waste solid.

NaHF₂+HF+NaOH→NaF+H₂O

People try to refine the unqualified sodium fluoride product to meet the quality standard, but the water solubility is too low, the energy consumption in the refining process is too high to be compensated, and the industrialization process cannot be realized. The purification of reject sodium fluoride has to be abandoned.

Disclosure of Invention

Aiming at the technical problems, the invention provides a process for recovering inorganic layer waste liquid generated in the process of replacing the diazonium salt pyrolysis fluorination reaction of arene hydrogen fluoride.

The method provided by the invention is a brand new process for preparing sodium fluoroborate by a sodium bifluoride method.

The technical scheme of the invention is as follows:

H₃BO₃+NaHF₂+2HF→NaBF₄+3H₂O

a process for recovering the inorganic waste liquid generated by the thermolysis of fluoro-reaction of diazonium salt in substituted arylhydrocarbon hydrogen fluoride includes such steps as adding NaHF to said inorganic waste liquid₂、HF、H₂O and organic impurities, the process comprising the steps of:

step one, adding H into the inorganic layer waste liquid₃BO₃Cooling to room temperature, and filtering out and recovering crystallized solid organic matters;

step two, adding activated carbon or activated carbon fiber into the residual solution after the solid organic matter is filtered out for adsorption and decoloration, and obtaining colorless transparent liquid after decoloration;

regulating the pH value of the decolored colorless transparent liquid to 2-4, supplementing hydrogen fluoride for regulation if the pH value is more than 4, and supplementing equivalent boric acid and caustic soda for regulation if the pH value is less than 2;

and step four, obtaining white crystalline solid sodium fluoborate after concentration and drying.

Based on the above scheme, preferably, the inorganic layer waste liquid refers to an inorganic layer waste liquid obtained after hydrogen fluoride is recovered by distillation after the pyrolysis fluorination reaction is finished.

Based on the scheme, preferably, water is supplemented firstly, and then H is quantitatively added₃BO₃The content of sodium fluoroborate is made lower than 50 wt%, and water is added to make the generated sodium fluoroborate fully soluble in water (especially in winter).

Based on the above scheme, preferably, H₃BO₃The addition amount of (A) is 0.98-1.0 times of the equivalent of sodium ions in the solution. The equivalent of sodium ion is calculated according to the addition of sodium nitrite in the diazotization reaction process.

Based on the scheme, the adding amount of the activated carbon or the activated carbon fiber is preferably 5 wt% to 15 wt% of the adding amount of the boric acid.

Based on the above scheme, preferably, the solid organic compound is an azo compound.

Based on the scheme, preferably, in the second step, the temperature for adsorption decoloring is 50-100 ℃.

The method provided by the invention is different from the technical process of the existing sodium fluoborate preparation method, and expensive raw materials of fluoboric acid and sodium carbonate are not needed, so that the qualified fine sodium fluoborate is prepared, and inorganic layer waste liquid generated in the technical process of replacing aromatic hydrocarbon diazonium fluoride salt pyrolysis fluorination reaction which is difficult to treat is treated, thereby achieving the best effect of killing two birds with one stone.

Advantageous effects

The invention has the following two characteristics:

1, the problem of treating the inorganic layer waste liquid of the diazonium salt pyrolysis reaction of substituted aromatic hydrogen fluoride is solved creatively, and the waste is changed into valuable.

1.1 adding boric acid into the inorganic layer waste liquid to increase the polarity of the inorganic layer waste liquid, and filtering out and recycling the precipitated solid organic matters.

1.2 adsorbing and decolorizing the filtrate with active carbon or active carbon fiber, and performing harmless incineration treatment on the filtered waste solids.

1.3 evaporating and drying the decolored inorganic aqueous solution to prepare the sodium fluoborate with high quality.

2 creatively opens up a new process for synthesizing the sodium fluoborate.

2.1 the process for synthesizing sodium fluoroborate by using sodium bifluoride, hydrogen fluoride and boric acid as initial raw materials.

2.2 the process aims at utilizing waste, not only solves the problem of inorganic layer waste liquid treatment, but also fully reduces the preparation cost of the sodium fluoborate, and has obvious economic benefit and social benefit.

2.3 the preparation of sodium fluoroborate by this process is controlled by adjusting the pH as an end point. If the pH value is higher, the hydrogen fluoride is supplemented for adjustment, and if the pH value is lower, the equivalent weight of boric acid and caustic soda is supplemented.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example one

150g of waste liquid of fluorination reaction inorganic layer containing NaHF after recovering hydrogen fluoride by distillation was taken₂ 78g(1.258mol)， HF 23.5g(1.175mol)，H₂44.5g of O and 4g of organic impurities.

30g of water was added with stirring, and then H was added₃BO₃77.5g (1.25mol), cooling to room temperature, filtering out and recycling crystallized 4g of solid organic matter (for other use), adding 10g of activated carbon, heating to 80 ℃, filtering, supplementing HF to the filtered colorless transparent liquid to adjust the pH value to 2-4, concentrating and drying to obtain 138g of white crystallized solid sodium fluoborate with the purity of 98.5%.

Example two

In pilot scale, the phenyl hydrogen fluoride diazonium salt is prepared by adding sodium nitrite into the hydrosulfide salt of aniline, fluorobenzene is prepared by pyrolytic fluoro reaction, and the initial charging proportion of various materials is as follows: 9.3kg (100mol) of aniline, 7.0kg (101.6mol) of sodium nitrite and 32kg (1600mol) of hydrogen fluoride, and distilling to recover the hydrogen fluoride to obtain the inorganic layer waste liquid.

The recovered inorganic layer waste liquid is 13.2kg, and the main components and contents in the inorganic layer waste liquid are as follows: such as NaHF₂6.2kg, HF 3kg, water 3.6kg, and the sum of other impurities is 0.4 kg.

2kg of water was added with stirring, and then H was added₃BO₃6.2kg (100mol), cooling to room temperature, filtering out crystallized 0.2kg solid organic matter, recovering (for other use), adding 0.8kg active carbon, heating to 80 deg.C, filteringAnd supplementing HF into the filtered colorless transparent liquid to adjust the pH value to 2-4, and concentrating and drying to obtain 11kg of white crystalline solid sodium fluoborate with the purity of 98.2%.

Example three

In pilot scale, the phenyl hydrogen fluoride diazonium salt is prepared by adding sodium nitrite into the hydrosulfide salt of aniline, fluorobenzene is prepared by pyrolytic fluoro reaction, and the initial charging proportion of various materials is as follows: 9.3kg (100mol) of aniline, 6.3kg (101.6mol) of sodium nitrite and 32kg (1600mol) of hydrogen fluoride, and distilling to recover hydrogen fluoride to obtain inorganic layer waste liquid.

The recovered inorganic layer waste liquid is 15kg, and the main components and contents in the inorganic layer waste liquid are as follows: such as NaHF₂6.2kg, HF 4.8kg, water 3.6kg, and the sum of other impurities is 0.4 kg.

2.5kg of water was added with stirring, and then H was added₃BO₃6.2kg (100mol), cooling to room temperature, filtering out crystallized 0.2kg solid organic matter, recovering (for other use), adding 0.8kg active carbon, heating to 80 deg.C, filtering, and filtering to obtain colorless transparent liquid with strong acidity, wherein the weight ratio of the colorless transparent liquid is 3.1: adding boric acid and caustic soda according to the weight ratio of 1, adjusting the pH value to 2-4, and concentrating and drying to obtain 12.1kg of white crystalline solid sodium fluoborate with the purity of 98.1%.