Process for the co-production of xanthates, thionocarbamates and trithiocarbonate carboxylates and applications

Abstract

The application belongs to the field of flotation reagent preparation, and specifically discloses a method for preparing xanthate by salt water circulation, which comprises the following steps: step (1): subjecting a raw material solution comprising a fatty alcohol, potassium hydroxide, carbon disulfide and water to xanthation reaction; step (2): adding a halo carboxylic acid to the reaction system of step (1) to perform esterification reaction, and then performing oil-water separation to obtain xanthate and potassium halide salt water; and step (3): directly or after solid-liquid separation, the potassium halide salt water is recycled as water source to step (1) for preparation of xanthate. The application further comprises co-production and application of further thioamide and trithiocarbonate carboxylate. The preparation process is simple in operation, high in reaction conversion rate, low in production cost, energy-saving and environment-friendly, easy to realize industrialized production, and the obtained trithiocarbonate carboxylate can assist selective flotation of copper sulfide.

Description

Technical Field

[0001] This invention belongs to the field of mineral pharmaceutical preparation, specifically relating to the preparation and application of xanthate esters, thiocyanates, and trithiocarbonate carboxylates. Background Technology

[0002] Thioamino esters, scientifically known as O-alkyl-N-alkylthiocarbamates, are widely used in the flotation of sulfide ores. They possess advantages such as good flotation selectivity and strong collecting ability, while also exhibiting a certain degree of foaming ability, enabling the flotation separation of minerals such as gold, copper, and lead-zinc ores under low alkalinity conditions. Currently, the synthesis of thioamino esters mainly includes isothiocyanate alcoholysis, one-step catalytic synthesis, electrochemical synthesis, xanthate oxidation ammonolysis, and xanthate esterification-ammonolysis. The isothiocyanate alcoholysis method first synthesizes an isothiocyanate intermediate, which then reacts with an alcohol to obtain thioamino esters. US Patent 4482500 discloses a phase-transfer isothiocyanate alcoholysis method that successfully synthesizes N-allylic-O-alkylthiocarbamate using sodium thiocyanate and allyl chloride as raw materials. However, this process is complex, involves numerous reaction steps, is discontinuous, and has a low yield. The one-step catalytic method uses a catalyst to directly react xanthate with aliphatic amines to prepare thioamino esters. US Patent 3975264 discloses the use of soluble palladium and nickel salts as catalysts to generate isopropyl ester compounds. US Patent 5041599 discloses the use of palladium, rhodium, platinum, and ruthenium as catalysts to generate thiocarbamates. The one-step catalytic method has the advantages of simple process and few reaction steps, but it has disadvantages such as low yield, low value of by-product recycling, difficulty in catalyst recovery, difficulty in subsequent wastewater treatment, and serious environmental pollution. The electrochemical synthesis method mainly uses xanthate, methylamine, and sodium chloride as raw materials for synthesis (LYALIN BV, PETROSYANVA. Electrochemical synthesis of thiocarbamates[J]. Russian Journal of Electrochemistry, 2000, 36(2):164-169). The electrochemical synthesis method has the problem of low current efficiency and is still in the laboratory stage. The xanthate oxidation-ammonolysis method uses an oxidant to oxidize xanthate to obtain dixanthate, and then ammonolyses the dixanthate to obtain thiocarbamates and sulfur. (Li Hua, Liu Guangyi. Research on a new process for the preparation of thiocarbamates [J]. Fine Chemical Intermediates, 2022, 52(01):56-61.). Xanthate esterification-ammonolysis is currently the main method for the industrial production of thiocarbamates. Xanthate is esterified with sodium chloroacetate, and then the resulting alkyl sulfonate is ammonolyzed with aliphatic amines to obtain a mixture of thiocarbamates and thiol compounds. Chinese patent CN106380434B discloses a method for preparing thiocarbamates and producing trithiocarbonates. The xanthate esterification-ammonolysis method has mild conditions, high yield, and high product purity. However, due to the low market demand for the byproduct mercaptoacetic acid and the difficulty in treating sodium-containing wastewater, the large-scale application of this process is limited.

[0003] In the production process of copper sulfide mines, dichromates, Knox-type reagents are commonly used in conjunction with collectors. Since both are toxic, they deteriorate the working environment for workers during production and use, affecting green production in mines. Therefore, it is necessary to find a reagent that can improve the selectivity of copper sulfide ore and other sulfide ores under mild conditions with low alkalinity, reduce production costs, save resources, and promote the development of green mines. Summary of the Invention

[0004] In view of the problems that the brine produced in the existing alkyl xanthate production stage is difficult to handle and that recycling it can easily lead to reaction degradation, the first objective of this invention is to provide a method for preparing xanthate esters by recycling brine, which aims to solve the problems of difficulty in recycling by-product brine and reaction degradation caused by recycling.

[0005] A second objective of this invention is to provide a method for preparing thiocyanates based on the aforementioned brine cycle.

[0006] The third objective of this invention is to provide a method for preparing thiocyanates and co-producing trithiocarbonate carboxylates based on the aforementioned brine recycling approach.

[0007] The fourth objective of this invention is to provide the application of the trithiocarbonate-based carboxylate obtained by the preparation method in the selective flotation of copper sulfide ores.

[0008] For the preparation of alkyl xanthates, most existing methods involve xanthation with alcohols, carbon disulfide, and sodium hydroxide, followed by esterification with halocarboxylate salts, and then acidification and oil-water separation to obtain xanthate esters. This process generates a large amount of saturated sodium halide (such as sodium chloride) brine, which is hazardous waste and cannot be directly discharged, and its recovery value is low. Although recycling is a good approach for brine treatment, previous research by the inventors has shown that recycling the brine obtained by this method significantly affects the conversion efficiency of the recycling reaction. To address this problem, this invention, after in-depth research, provides the following improvements:

[0009] A method for preparing xanthate esters by brine recycling, comprising the following steps:

[0010] Step (1):

[0011] A xanthation reaction is carried out on a raw material solution containing fatty alcohol, potassium hydroxide, carbon disulfide, and water.

[0012] Step (2):

[0013] Add halocarboxylic acid to the reaction system of step (1) to carry out esterification reaction, and then separate oil and water to obtain xanthate ester and potassium halide brine;

[0014] Step (3):

[0015] The potassium halide brine, either directly or after solid-liquid separation, is recycled to step (1) for the preparation of xanthate.

[0016] This invention innovatively demonstrates that the novel approach of reacting fatty alcohols, potassium hydroxide, and carbon disulfide with xanthic acid, followed by esterification with halocarboxylic acids, achieves high conversion rates and excellent xanthate yields. More importantly, based on the preparation process described in this invention, the byproduct potassium halide brine can be recycled for the xanthic acid reaction and subsequent esterification reactions, unexpectedly exhibiting excellent cycle stability; for example, it can achieve a reaction yield of over 80% even after four or more cycles. Thus, this invention achieves zero wastewater discharge in the preparation process and recovers potassium salt crystals during the brine recycling stage.

[0017] In this invention, the fatty alcohol is not particularly required; for example, its chemical formula is R1OH, wherein R1 is a C1 to C8 alkyl group.

[0018] The reaction formula for step 1 of this invention is, for example:

[0019]

[0020] Preferably, the molar ratio of fatty alcohol, potassium hydroxide, and carbon disulfide is 1:1 to 2:1 to 2, more preferably 1:1 to 1.2:1 to 1.2;

[0021] Preferably, the initial concentration of potassium hydroxide in the raw material solution is 20% to 50%.

[0022] Preferably, the reaction temperature is 10–50°C, more preferably 20–30°C, and the reaction time is 0.5–5 h.

[0023] In this invention, the halocarboxylic acid in step (2) has no special requirements. Considering the preparation cost and the effect of brine circulation, its chemical formula can be XR. 2 COOH;

[0024] Preferably, the R 2 It is a C1 to C8 alkylene group, and X is a halogen, preferably Cl, Br, I, etc. Considering the material cost, it can be further Cl;

[0025] In this invention, the reaction formula for step (2) is, for example:

[0026]

[0027] Preferably, the halocarboxylic acid is 1 to 1.5 times the amount of the fatty alcohol, more preferably 1 to 1.2 times;

[0028] Preferably, in step (2), the reaction temperature is 50–100°C;

[0029] Preferably, in step (2), the reaction time is 1 to 8 hours;

[0030] In this invention, after the reaction in step (2) is completed, no additional control is required; extraction can be performed directly to efficiently separate xanthate esters. This yields excellent xanthate esters and also improves the reaction stability of the byproduct brine.

[0031] In this invention, the extraction stage can be achieved using conventional hydrophobic solvents, such as diethyl ether, ethyl acetate, etc., or the thiocyanate obtained in this process can be used.

[0032] In this invention, the brine is circulated more than twice. Furthermore, thanks to the excellent circulation reactivity of the brine, and considering the maximization of the economic value of the treatment process, the number of cycles can be further increased to more than three times, or even three to six times.

[0033] In this invention, when the salt concentration reaches saturation during the brine circulation stage, the precipitated salt crystals can be separated using conventional solid-liquid separation methods. These crystals have excellent purity and can be used as potassium salt products.

[0034] This invention also provides a method for preparing thiocyanate by brine recycling. The method involves recycling xanthate esters using the brine recycling method described in this invention, reacting them with fatty amines via ammonolysis, and then separating the oil and water to obtain thiocyanate esters and aqueous solutions of thioglycolic acid compounds.

[0035] In this invention, the fatty amine can be any primary or secondary amine, for example, with the chemical formula R3-NH2, where R3 is a C1-C8 alkyl, C2-C6 olefin, benzyl or propionitrile, etc., preferably a C1-C8 alkyl; further, the fatty amine can be methylamine, ethylamine, propylamine or butylamine.

[0036] In this invention, the ammonolysis reaction formula is, for example:

[0037]

[0038] Preferably, the fatty amine is 1 to 1.2 times the amount of xanthate.

[0039] Preferably, the ammonolysis reaction temperature is 30–100°C, and the reaction time is preferably 1–5 h.

[0040] The present invention also provides a method for preparing thiocyanate and co-producing trithiocarbonate carboxylate using brine circulation. The thiocyanate is prepared by the brine circulation method described in the present invention, and an aqueous solution of mercapto acid compounds is obtained.

[0041] A second-stage xanthation reaction was carried out by adding caustic alkali and carbon disulfide to an aqueous solution of a mercapto acid compound, and a solution containing trithiocarbonate carboxylate was obtained as a co-product.

[0042] The reaction formula for the second xanthic acid reaction described in this invention is, for example (using KOH as an example of caustic alkali):

[0043]

[0044] Preferably, the molar ratio of mercapto acid compound, caustic alkali, and carbon disulfide is 1:1 to 2:1 to 2, more preferably 1:1 to 1.2:1 to 1.2;

[0045] Preferably, the caustic alkali is sodium hydroxide and / or potassium hydroxide;

[0046] Preferably, the temperature of the second xanthate reaction is 5–80°C, and the reaction time is preferably 2–8 hours.

[0047] This invention enables the recycling of brine and, based on the described preparation method, unexpectedly improves the reaction stability during the preparation stage. This invention achieves high-value recycling of brine, overcoming the problems of wastewater discharge and unsatisfactory stability in the recycling reaction.

[0048] The present invention also provides the application of the trithiocarbonate carboxylate obtained by the preparation method, in combination with a collector, for selective flotation recovery of copper sulfide ore.

[0049] The present invention also found that the trithiocarbonate carboxylate can unexpectedly assist in the selective flotation of copper sulfide ores.

[0050] A further preferred application of the present invention is to combine it with a collector for the selective flotation of copper sulfide ore from a mixture of copper sulfide ore and other sulfide ores.

[0051] The present invention demonstrates that, with the assistance of the aforementioned trithiocarbonate carboxylate, copper sulfide ores can be selectively floated from systems containing copper sulfide ores and other sulfide ores, exhibiting excellent flotation selectivity.

[0052] Preferably, the other sulfide minerals are at least one of lead and zinc sulfide minerals.

[0053] In this invention, the trithiocarbonate carboxylate can be obtained directly using the preparation method of this invention, which is the trithiocarbonate carboxylate and its solution.

[0054] In this invention, the collector is not particularly required and can be any collector capable of collecting copper sulfides, such as at least one of xanthate collectors, sulfur nitrogen collectors, black powder collectors, thiouron ester collectors, and MAC-12.

[0055] Preferably, during the flotation stage, the amount of trithiocarbonate carboxylate used is 20-300 g / t, more preferably 20-50 g / t, and the amount of collector used is 10-200 g / t, more preferably 10-30 g / t.

[0056] Preferably, the pH of the flotation stage is 4–11; more preferably 6–10, and even more preferably 7–10.

[0057] The present invention also shows that, with the assistance of the trithiocarbonate carboxylate, further combined with the combined control of pH in the flotation stage, the flotation selectivity of copper sulfide ores and other sulfide ores can be unexpectedly further improved.

[0058] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0059] (1) This invention innovatively demonstrates that the novel xanthation reaction of fatty alcohols, potassium hydroxide, and carbon disulfide, followed by esterification with halocarboxylic acids, achieves high conversion rates and yields excellent xanthate esters through direct extraction without additional auxiliary treatment. More importantly, based on the preparation process described in this invention, the byproduct potassium halide brine can be recycled for the xanthation reaction and subsequent esterification reactions, unexpectedly exhibiting excellent cycle reaction stability. Furthermore, based on the brine recycling approach described in this invention, multiple components such as xanthate esters, thiocarboxylic acids, and trithiocarbonate carboxylates can be co-produced, achieving zero wastewater discharge during the preparation process.

[0060] (2) The technical solution of the present invention adopts the "one-pot method" for production. Through extraction and filtration, multiple products can be separated efficiently, which simplifies the process operation, avoids the loss of raw materials and intermediate products, and reduces costs.

[0061] (3) This invention also produced trithiocarbonate carboxylate, and further research found that it can assist in the flotation of copper sulfide ore, helping to improve its flotation selectivity with other sulfide ores. On this basis, further coordination with pH control during the flotation stage helps to work in conjunction with reagents to further synergistically improve the flotation separation selectivity of copper sulfide ore and other sulfide ores. Attached Figure Description

[0062] Figure 1 This is a flowchart of the synthesis process of the present invention;

[0063] Figure 2The infrared spectrum of the carboxyethyl trithiocarbonate synthesized in Example 1.

[0064] Figure 3 The mass spectrum of the carboxyethyl trithiocarbonate synthesized in Example 1 is shown below.

[0065] Figure 4 The infrared spectrum of O-isopropyl-N-ethyl thiocarbamate synthesized in Example 1.

[0066] Figure 5 The 1H NMR spectrum of the O-tert-butyl-N-ethylthiocarbamate synthesized in Example 4.

[0067] Figure 6 The carbon NMR spectrum of the O-tert-butyl-N-ethyl thiocarbamate synthesized in Example 4.

[0068] Figure 7 Flowchart of the flotation process in Example 8

[0069] Figure 8 The results of the copper-lead flotation separation experiment in Example 8

[0070] Figure 9 This is a flow chart of the copper-lead ore flotation process in Example 9. Detailed Implementation

[0071] The present invention is further illustrated by the following embodiments, but is not limited to these embodiments. All parts and percentages in the examples refer to mass unless otherwise specified.

[0072] In this invention, there are no special requirements for the preparation scale. For example, it can be laboratory scale, pilot-scale, or method scale. As an example of the implementation, unless otherwise stated, the following cases refer to laboratory scale, that is, the weight of the "part" is, for example, 10 to 100g.

[0073] Example 1: Synthesis of O-isopropyl-N-ethylthiocarbamate (Z-200) and co-production of potassium 2-trithiocarbonate.

[0074] Step (1):

[0075] 30.05 parts of isopropanol (99% purity), 66.00 parts of KOH (50% concentration, 85% purity), and 39.97 parts of carbon disulfide (99% purity) were stirred thoroughly and the reaction temperature was controlled at 30°C. After reacting for 3 hours, the mixture was cooled to room temperature. Then, 68.87 parts of chloroacetic acid (70% concentration, 98% purity) were added using a constant pressure dropping funnel. The mixture was heated to 80°C and reacted for 2 hours. After cooling to room temperature, potassium chloride was removed by filtration. The filtrate was extracted with ethyl thiocyanate to obtain an oil phase and an aqueous phase.

[0076] Step (2)

[0077] The oil phase from step (1) was transferred to the reactor, and 32.2 parts of ethylamine aqueous solution (purity of 65% to 70%) were added to the reactor. The temperature was raised to 70°C, and after reacting for 1 hour, it was cooled to room temperature. After oil-water separation, O-isopropyl-N-ethyl thiocarbamate and aqueous phase were obtained.

[0078] Step (3)

[0079] The aqueous phase from step (2) was transferred to a reactor, and 41.88 parts of carbon disulfide with a purity of 99% and 36.31 parts of KOH with a purity of 85% were added. The temperature was raised to 30°C, and the reaction was completed after 2 hours to obtain potassium 2-trithiocarbonate.

[0080] Analysis showed that the purity of O-isopropyl-N-ethylthiocarbamate was 92.05%, with a yield of 96.96% based on potassium isopropyl xanthate, and the purity of potassium 2-trithiocarbonate acetate was 90.77%, with a yield of 86.93% based on potassium isopropyl xanthate.

[0081] The aqueous phase from step (1) is used as an alkaline solution and recycled back to step (1) for reuse in step (1) and subsequent reactions. The reaction conditions during the recycling process are the same as those in steps (1) and (2).

[0082] After one cycle, the purity of the O-isopropyl-N-ethylthiocarbamate product was 90.11%, with a yield of 92.32% based on potassium isopropyl xanthate, and the purity of the 2-trithiocarbonate-based potassium acetate product was 89.27%, with a yield of 85.74% based on potassium isopropyl xanthate.

[0083] After two cycles, the purity of the O-isopropyl-N-ethylthiocarbamate product was 91.45%, with a yield of 93.66% based on potassium isopropyl xanthate, and the purity of the 2-trithiocarbonate-based potassium acetate product was 89.91%, with a yield of 86.69% based on potassium isopropyl xanthate.

[0084] After three cycles, the purity of the O-isopropyl-N-ethylthiocarbamate product was 90.33%, with a yield of 90.36% based on potassium isopropyl xanthate, and the purity of the 2-trithiocarbonate-based potassium acetate product was 88.98%, with a yield of 86.65% based on potassium isopropyl xanthate.

[0085] After four cycles, the purity of the O-isopropyl-N-ethylthiocarbamate product was 90.07%, with a yield of 87.29% based on potassium isopropyl xanthate, and the purity of the 2-trithiocarbonate-based potassium acetate product was 86.41%, with a yield of 82.07% based on potassium isopropyl xanthate.

[0086] Potassium 2-trithiocarbonate was recrystallized and characterized; its infrared spectrum is shown below. Figure 2 Its mass spectrometry is shown in Figure 3 The O-isopropyl-N-ethyl thiocarbamate product was washed with saturated brine, purified by distillation, and then characterized. Its infrared spectrum is shown in [insert image here]. Figure 4 .

[0087] Table 1. Analysis of Infrared Spectra of O-Isopropyl-N-Ethiocarbamate

[0088]

[0089] Table 22 - Infrared spectra of potassium trithiocarbonate.

[0090]

[0091] Comparative Example 1

[0092] Compared with Example 1, the only difference is that in step (1), an equimolar amount of NaOH is used to replace the KOH. Other operations and parameters are the same as in Example 1, and its cycle performance is verified in the same way.

[0093] The results showed that the purity of O-isopropyl-N-ethylthiocarbamate was 90.33%, and the yield based on sodium isopropyl xanthate was 89.35%. The purity of sodium 3-trithiocarbonate acetate was 88.05%, and the yield based on sodium isopropyl xanthate was 89.15%.

[0094] After one cycle, the purity of O-isopropyl-N-ethylthiocarbamate was 57.13%, with a yield of 42.02% based on sodium isopropyl xanthate, and the purity of sodium 3-trithiocarbonate acetate was 50.06%, with a yield of 49.77% based on sodium isopropyl xanthate.

[0095] After two cycles, the purity of the O-isopropyl-N-ethylthiocarbamate product was 28.12%, with a yield of 20.05% based on sodium isopropyl xanthate, and the purity of the 3-trithiocarbonate sodium acetate product was 30.03%, with a yield of 19.55% based on sodium isopropyl xanthate.

[0096] After three cycles, the purity of the O-isopropyl-N-ethylthiocarbamate product was 15.46%, with a yield of 12.63% based on sodium isopropyl xanthate, and the purity of the 3-trithiocarbonate sodium acetate product was 10.05%, with a yield of 9.79% based on sodium isopropyl xanthate.

[0097] Therefore, it can be seen that the water recycling performance of this type of reaction using sodium hydroxide is not ideal.

[0098] Comparative Example 2

[0099] Compared to Example 1, the only difference is that in step 1, an equimolar amount of potassium chloroacetate is used to replace the chloroacetic acid. The operation and parameters are the same as in Example 1.

[0100] Analysis showed that the purity of the O-isopropyl-N-ethylthiocarbamate product was 81.33%, and the yield based on potassium isopropyl xanthate was 82.45%. It is evident that the reaction efficiency of this product is inferior to that of the present invention.

[0101] Example 2: Synthesis of O-ethyl-N-ethylthiocarbamate and co-production of potassium 4-trithiocarbonate butyrate

[0102] 24.25 parts of 95% pure ethanol, 66.00 parts of 50% KOH (85% purity), and 39.97 parts of 99% pure carbon disulfide were thoroughly stirred and the reaction temperature was controlled at 30°C. After reacting for 2 hours, the mixture was cooled to room temperature. Then, 85.79 parts of 70% 4-chlorobutyric acid (98% purity) were added using a constant pressure dropping funnel. The mixture was heated to 80°C and reacted for 2.5 hours. After cooling to room temperature, potassium chloride was removed by filtration, and the filtrate was extracted with ethyl thiocyanate. The oil phase was transferred to a reactor, and 37.19 parts of an aqueous ethylamine solution (65%–70% purity) were added. The mixture was heated to 75°C and reacted for 1 hour. After cooling to room temperature, the oil and water were separated to obtain O-ethyl-N-ethylthiocarbamate. The aqueous phase was then transferred to a reactor, and 41.88 parts of carbon disulfide (99% purity) and 36.31 parts of flake KOH (85% purity) were added. The mixture was heated to 30°C and reacted for 2 hours to obtain potassium 4-trithiocarbonate butyrate. Analysis showed that the purity of the O-ethyl-N-ethylthiocarbamate product was 90.33%, with a yield of 88.18% based on potassium ethyl xanthate. The purity of the 4-trithiocarbonate butyrate product was 85.66%, with a yield of 89.49% based on potassium ethyl xanthate.

[0103] Example 3: Synthesis of O-ethyl-N-isopropylthiocarbamate and co-production of potassium 2-trithiocarbonate.

[0104] 24.25 parts of 95% pure ethanol, 66.00 parts of 50% KOH (85% purity), and 39.97 parts of 99% pure carbon disulfide were thoroughly stirred and the reaction temperature was controlled at 25°C. After reacting for 3 hours, the mixture was cooled to room temperature. Then, 68.87 parts of 70% chloroacetic acid (98% purity) were added using a constant pressure dropping funnel. The mixture was heated to 80°C and reacted for 2.5 hours. After cooling to room temperature, potassium chloride was removed by filtration, and the mixture was extracted with ethyl thiocyanate. The oil phase was transferred to a reactor, and 30.16 parts of isopropylamine (98% purity) were added. The mixture was heated to 85°C and reacted for 2 hours. After cooling to room temperature, the oil and water were separated to obtain O-ethyl-N-isopropylthiocarbamate. The aqueous phase was then transferred to a reactor, and 41.88 parts of carbon disulfide (99% purity) and 36.31 parts of flake KOH (85% purity) were added. The mixture was heated to 40°C and reacted for 2 hours to obtain potassium 2-trithiocarbonate. Analysis showed that the purity of the O-ethyl-N-isopropylthiocarbamate product was 92.19%, with a yield of 96.11% based on potassium ethyl xanthate. The purity of the potassium 2-trithiocarbonate was 89.08%, with a yield of 90.80% based on potassium ethyl xanthate.

[0105] Example 4: Synthesis of O-tert-butyl-N-ethylthiocarbamate and co-production of potassium 2-trithiocarbonate.

[0106] 37.06 parts of 99% pure tert-butanol, 66.00 parts of 50% KOH (85% purity), and 39.97 parts of 99% pure carbon disulfide were thoroughly stirred and the reaction temperature was controlled at 30°C. After reacting for 3 hours, the mixture was cooled to room temperature. Then, 68.87 parts of 70% chloroacetic acid (98% purity) were added using a constant pressure dropping funnel. The temperature was raised to 75°C, and the mixture was reacted for 2.5 hours. After cooling to room temperature, potassium chloride was removed by filtration. The filtrate was extracted with ethyl thiocyanate, and the oil phase was transferred. The mixture was transferred to a reactor, and 32.2 parts of an aqueous ethylamine solution (65%–70% purity) were added. The temperature was raised to 80°C, and the reaction was allowed to proceed for 2.5 hours. After cooling to room temperature, oil and water separation was performed to obtain O-tert-butyl-N-ethylthiocarbamate. The aqueous phase was then transferred to another reactor, and 41.88 parts of carbon disulfide (99% purity) and 36.31 parts of flake KOH (85% purity) were added. The temperature was raised to 40°C, and the reaction was allowed to proceed for 2 hours, yielding potassium 2-trithiocarbonate. Analysis showed that the O-butyl-N-butylthiocarbamate product had a purity of 91.86% and a yield based on potassium butyl xanthate of 90.65%. The 2-trithiocarbonate potassium acetate product had a purity of 91.05% and a yield based on potassium butyl xanthate of 89.78%. The O-tert-butyl-N-ethylthiocarbamate product was washed with saturated brine, purified by distillation, and then characterized. Its NMR spectroscopy was performed. 1H, 13 The C-spectrums are shown below. Figure 5 .

[0107] Table 3. Analysis of NMR Spectra

[0108]

[0109] Example 5: Synthesis of O-butyl-N-propylthiocarbamate and co-production of potassium 2-trithiocarbonate.

[0110] 37.06 parts of 99% pure n-butanol, 66.00 parts of 50% KOH (85% purity), and 38.15 parts of 99% pure carbon disulfide were thoroughly stirred and the reaction temperature was controlled at 30°C. After reacting for 3 hours, the mixture was cooled to room temperature. Then, 68.87 parts of 70% chloroacetic acid (98% purity) were added using a constant pressure dropping funnel. The temperature was raised to 75°C, and the mixture was reacted for 2.5 hours. After cooling to room temperature, potassium chloride was removed by filtration, and the mixture was extracted with ethyl thiocyanate. The filtrate was collected, and the oil phase was transferred to a reactor. 30.16 parts of n-propylamine (98% purity) were added to the reactor, the temperature was raised to 70°C, and the reaction was carried out for 3 hours. After cooling to room temperature, oil and water were separated to obtain O-butyl-N-propylthiocarbamate. The aqueous phase was then transferred to a reactor, and 41.88 parts of carbon disulfide (99% purity) and 36.31 parts of flake KOH (85% purity) were added. The temperature was raised to 35°C, and the reaction was completed after 2 hours to obtain potassium 2-trithiocarbonate. Analysis showed that the purity of the O-butyl-N-propylthiocarbamate product was 89.95%, with a yield of 93.22% based on potassium butyl xanthate. The purity of the potassium 2-trithiocarbonate was 90.14%, with a yield of 85.18% based on potassium butyl xanthate.

[0111] Example 6: Synthesis of O-isobutyl-N-propylthiocarbamate and co-production of potassium 2-trithiocarbonate.

[0112] 37.06 parts of isobutanol (99% purity), 66.00 parts of KOH (50% concentration, 85% purity), and 39.97 parts of carbon disulfide (99% purity) were thoroughly stirred and the reaction temperature was controlled at 30°C. After reacting for 3 hours, the mixture was cooled to room temperature. Then, 68.87 parts of chloroacetic acid (70% concentration, 98% purity) were added using a constant pressure dropping funnel. The temperature was raised to 80°C, and after reacting for 3 hours, the mixture was cooled to room temperature. The potassium chloride was removed by filtration, and the filtrate was extracted with ethyl thiocyanate. The oil phase was transferred to a reactor, and 36.94 parts of n-propylamine (99% purity) were added. The temperature was raised to 80°C, and the reaction was carried out for 3 hours. After cooling to room temperature, the oil and water were separated to obtain O-isobutyl-N-propylthiocarbamate. The aqueous phase was then transferred to a reactor, and 41.88 parts of carbon disulfide (99% purity) and 36.31 parts of flake KOH (85% purity) were added. The temperature was raised to 30°C, and the reaction was carried out for 3 hours to obtain potassium 2-trithiocarbonate. Analysis showed that the purity of the O-isobutyl-N-propylthiocarbamate product was 91.07%, and the yield based on potassium isobutylxanthate was 92.97%. The purity of the potassium 2-trithiocarbonate was 90.55%, and the yield based on potassium isobutylxanthate was 86.63%.

[0113] Example 7: Synthesis of O-isobutyl-N-isobutylthiocarbamate and co-production of potassium 2-trithiocarbonate.

[0114] 37.06 parts of isobutanol (99% purity), 66.00 parts of KOH (50% concentration, 85% purity), and 38.15 parts of carbon disulfide (99% purity) were thoroughly stirred and the reaction temperature was controlled at 30°C. After reacting for 2 hours, the mixture was cooled to room temperature. Then, 69.21 parts of 2-chloropropionic acid (80% concentration, 98% purity) were added using a constant pressure dropping funnel. The mixture was heated to 90°C and reacted for 3 hours. After cooling to room temperature, potassium chloride was removed by filtration, and the mixture was extracted with ethyl thiocyanate. The oil phase was transferred to a reactor, and 36.94 parts of isobutylamine (99% purity) were added. The mixture was heated to 90°C and reacted for 3 hours. After cooling to room temperature, the oil and water were separated to obtain O-isobutyl-N-isopropylthiocarbamate. The aqueous phase was then transferred to a reactor, and 41.88 parts of carbon disulfide (99% purity) and 36.31 parts of flake KOH (85% purity) were added. The mixture was heated to 30°C and reacted for 3 hours to obtain potassium 2-trithiocarbonate. Analysis showed that the purity of the O-isobutyl-N-isopropylthiocarbamate product was 90.05%, with a yield of 93.32% based on potassium isobutyl xanthate. The purity of the potassium 2-trithiocarbonate was 87.28%, with a yield of 84.71% based on potassium isobutyl xanthate.

[0115] Example 8: Separation of copper-lead sulfide ores by flotation with potassium 2-trithiocarbonate-based acetate

[0116] The flotation machine operates at a speed of 1650 r / min and is used for the flotation of copper-lead sulfide ores with a particle size between 0.074 mm and 0.038 mm. The flotation process flow is as follows: Figure 7 As shown in the figure. The dosage of potassium 2-trithiocarbonate was 30 mg / L, the dosage of Z-200 was 20 mg / L, and the dosage of pine oil was 10 mg / L. After stirring for 30 seconds and aerating for 30 seconds, the flotation time was 3 minutes. The pH of the pulp was varied, and the recovery rates of each mineral component were calculated at different pulp pH values. The results are shown in the figure. Figure 8 As shown. By Figure 8 It was found that potassium 2-trithiocarbonate acetate had a strong inhibitory effect on galena when pH > 4. When the pulp pH was 8.2, the flotation recovery rate of chalcopyrite in the froth product was 85.65%, and the recovery rate of galena was 9.35%. This achieved flotation separation of the two minerals under low alkalinity conditions.

[0117] Example 9: Separation of copper-lead sulfide ores by flotation with potassium 2-trithiocarbonate-based acetate

[0118] A copper-lead ore sample from Jiangxi Province has a copper grade of 0.55% and a lead grade of 2.21%. The experimental procedure was as follows: grinding to a fineness of -200 mesh (65%), followed by one roughing and one scavenging process. The lime dosage was 1200 g / t. The flotation process flow diagram is shown below. Figure 9 The flotation results are shown in Table 4. The table shows that using potassium 2-trithiocarbonate acetate for copper-lead ore beneficiation yields better flotation performance compared to traditional depressants.

[0119] Table 4. Results of flotation experiments in Example 11

[0120]

[0121] In summary, the trithiocarbonate carboxylate of the present invention can assist collectors in selectively collecting copper sulfide ores and improve the flotation selectivity of copper sulfide ores and other sulfide ores.

Claims

1. A method for preparing thiocyanates and co-producing trithiocarbonate carboxylates using brine recycling, characterized in that, Xanthate esters were prepared by brine circulation. The obtained xanthate esters and fatty amines were subjected to ammonolysis, followed by oil-water separation to obtain thiouric acid esters and aqueous solutions of mercapto acid compounds. Then, caustic alkali and carbon disulfide were added to the aqueous solution of mercapto acid compounds to carry out a second-stage xanthation reaction, and a solution containing trithiocarbonate carboxylate was co-produced. The steps for preparing xanthate esters using brine recycling include: Step (1): A xanthation reaction is carried out on a raw material solution containing fatty alcohol, potassium hydroxide, carbon disulfide, and water. Step (2): Add halocarboxylic acid to the reaction system of step (1) to carry out esterification reaction, and then separate oil and water to obtain xanthate ester and potassium halide brine; Step (3): The potassium halide brine, either directly or after solid-liquid separation, is recycled to step (1) for the preparation of xanthate.

2. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, The chemical formula of the fatty alcohol is R1OH, wherein R1 is a C1-C8 alkyl group.

3. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 2, characterized in that, The molar ratio of fatty alcohol, potassium hydroxide, and carbon disulfide is 1:1~2:1~2.

4. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 3, characterized in that, The molar ratio of fatty alcohol, potassium hydroxide, and carbon disulfide is 1:1~1.2:1~1.

2.

5. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, The initial concentration of potassium hydroxide in the raw material solution is 20% to 50%.

6. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, In step (1), the reaction temperature is 10~50℃ and the reaction time is 0.5~5h.

7. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, In step (2), the chemical formula of the halocarboxylic acid is XR. 2 COOH; The R mentioned 2 It is a C1~C8 alkylene group, and X is a halogen; The amount of halocarboxylic acid is 1 to 1.5 times that of fatty alcohol.

8. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 7, characterized in that, In step (2), X is Cl; The amount of halocarboxylic acid is 1 to 1.2 times that of fatty alcohol.

9. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 7, characterized in that, In step (2), the reaction temperature is 50~100℃; In step (2), the reaction time is 1 to 8 hours.

10. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 7, characterized in that, In step (3), the salt water is circulated more than twice.

11. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 10, characterized in that, The saline solution is circulated at least three times.

12. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 11, characterized in that, The saline solution is circulated 3 to 6 times.

13. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, The chemical formula of the fatty amine is R3-NH2, where R3 is a C1-C8 alkyl group.

14. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 13, characterized in that, The amount of fatty amines is 1 to 1.5 times that of xanthate.

15. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 13, characterized in that, The amount of fatty amines is 1 to 1.2 times that of xanthate.

16. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, The ammonolysis reaction temperature is 30~100℃, and the reaction time is 1~5h.

17. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, The molar ratio of mercapto acid compounds, caustic alkalis, and carbon disulfide is 1:1~2:1~2.

18. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 17, characterized in that, The molar ratio of mercapto acid compounds, caustic alkalis, and carbon disulfide is 1:1~1.2:1~1.

2.

19. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, The caustic alkali is sodium hydroxide and / or potassium hydroxide.

20. The method for preparing thiocyanates and co-producing trithiocarbonate carboxylates by brine recycling as described in claim 1, characterized in that, The second stage of xanthation reaction takes place at a temperature of 5~80℃ for 2~8 hours.

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