CN116062708B - Synthetic method of sodium thiosulfate - Google Patents

Abstract

The invention discloses a synthetic method of sodium thiosulfate, which comprises the following steps: taking all substances according to the mol ratio of sulfur, anhydrous sodium sulfite and water of 1:0.95-1.05:5-10, adding the substances into a stirring reactor for reaction, controlling the reaction temperature to be 100-120 ℃, and cooling the obtained liquid after the reaction is finished to obtain sodium thiosulfate crystals. The synthetic method has the advantages of high reaction speed, high yield up to 100%, no need of decolorization, low energy consumption, low production cost and extremely low environmental pollution risk. The synthesized sodium thiosulfate can be directly used for a large-scale heat storage device, and can be used for other traditional applications after refining and purification.

Description

A kind of synthetic method of sodium thiosulfate

Technical Field

The invention belongs to the field of synthetic chemistry, and in particular relates to a green chemical synthesis method of sodium thiosulfate.

Background Art

Sodium thiosulfate, commonly known as "Haibo" or "baking soda", is a colorless transparent crystal. It is easily soluble in water, ammonia and turpentine, but difficult to dissolve in ethanol. It is unstable under acidic conditions and easily decomposes. It can be used as a sulfur source in organic chemistry to produce sulfur-containing compounds. It has strong reducing and coordination abilities and can be used as a fixer in the photographic industry, a dechlorinating agent in the laundry and papermaking industries, a reducing agent in quantitative analysis, and a detergent and disinfectant in medicine. It undergoes a phase change at 48°C, can dissolve in its crystal water, can absorb a large amount of heat, up to 210 J/g, and can be used as a large-scale heat storage material.

In the prior art, sodium thiosulfate is prepared in an aqueous solution. There are two available methods: (1) sodium sulfite and sulfur react in a boiling aqueous solution for several hours, then filter out the unreacted sulfur, and then concentrate and crystallize to obtain sodium thiosulfate pentahydrate; (2) sodium sulfide, sodium carbonate and sulfur dioxide are used to react. The difference between the two processes is that the sulfur in the latter is produced in situ by the reaction of sulfur dioxide (or sodium sulfite - the reaction product of sulfur dioxide and sodium carbonate) with sodium sulfide. Both methods have many steps, and the biggest disadvantage is that the reaction is incomplete and the amount of solvent used is large. Finally, the product needs to be filtered, concentrated and crystallized. Method 2 also requires the production of highly irritating _SO2 , and _Na2S produces malodorous _H2S due to hydrolysis, so it consumes a lot of energy and is not environmentally friendly.

Summary of the invention

Purpose of the invention: The purpose of the present invention is to provide a method for synthesizing sodium thiosulfate which is completely reactive, environmentally friendly and efficient.

Technical solution: The present invention discloses a method for synthesizing sodium thiosulfate, comprising the following steps: taking various substances according to a molar ratio of sulfur, anhydrous sodium sulfite and water of 1:0.95-1.05:5-10, adding them into a stirred reactor for reaction, controlling the reaction temperature to be 100-120°C, cooling the obtained liquid after the reaction is completed, and obtaining sodium thiosulfate crystals, wherein the molar mass of the sulfur is calculated in terms of sulfur atoms.

Preferably, sulfur, anhydrous sodium sulfite and water are prepared in a molar ratio of 1:1:5, and the reaction temperature is controlled at 115-120°C.

More preferably, the reaction temperature is 115°C.

Preferably, the stirring speed of the stirred reactor is 200 to 400 rpm.

Preferably, the catalyst is added at 1% to 5% of the molar amount of anhydrous sodium sulfite.

Preferably, the catalyst is an alkaline substance.

More preferably, the catalyst is at least one of NaOH, Na ₂ CO ₃ and Na ₂ S.

Preferably, the reaction time is 2 to 6 hours.

From a chemical perspective, the synthesis reaction of sodium thiosulfate is as follows:

1/8S ₈ +Na ₂ SO ₃ +5H ₂ O＝Na ₂ S ₂ O ₃ ·5H ₂ O

When the molar ratio of the reactants sulfur, sodium sulfite and water is fed according to the reaction stoichiometric molar ratio S:Na ₂ SO ₃ :H ₂ O=1:0.95-1.05:5-10, water is both a reactant and a solvent for the reaction. The liquid product obtained under the above conditions becomes solid Na ₂ S ₂ O ₃ ·5H ₂ O after cooling, which can be directly used as a heat storage material without purification, and has unparalleled advantages. Because sulfur is a product of desulfurization of petroleum and natural gas, and sodium sulfite is a product of removing SO ₂ in the energy industry (thermal power, heating), it can also be used as a high-value utilization method of sulfur and sodium sulfite.

Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

1. When the synthetic method provided by the present invention feeds materials according to the reaction stoichiometric molar ratio S:Na ₂ SO ₃ :H ₂ O=1:0.95-1.05:5-10, the reactants and products exist in solid form for a long time during the reaction process, and the reaction is complete; in particular, when the reactants are fed according to the stoichiometric molar ratio S:Na ₂ SO ₃ :H ₂ O=1:1:5, after the reaction is completed, all of them are converted into Na ₂ S ₂ O ₃ ·5H ₂ O without evaporation and filtration, which is a reaction with 100% atomic economy and the production capacity per unit container reaches the maximum.

2. The water input in this method is converted into crystal water in Na ₂ S ₂ O ₃ ·5H ₂ O, and the amount of solvent used in the reaction is reduced to a minimum, which is beneficial to the reaction.

3. The production equipment required by the present invention is a common stirring reactor. The reaction is completed in one step, and no toxic and polluting gases such as SO ₂ and H ₂ S are involved. The energy consumption is minimal, and green and environmentally friendly production requirements are achieved. If the product is used as a heat storage material, it does not need to be purified and can be sold or used directly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an X-ray powder diffraction (XRD) pattern of Na ₂ S ₂ O ₃ ·5H ₂ O synthesized in Example 1. FIG.

FIG2 is the XRD patterns of Na ₂ S ₂ O ₃ ·5H ₂ O synthesized in Example 2 and Example 3; wherein A is the XRD pattern of Na ₂ S ₂ O ₃ ·5H ₂ O obtained in Example 2, and B is the XRD pattern of Na ₂ S ₂ O ₃ ·5H ₂ O obtained in Example 3.

DETAILED DESCRIPTION

The technical solution of the present invention is further described below in conjunction with specific embodiments and drawings.

The invention discloses a method for synthesizing sodium thiosulfate. The method uses sulfur, sodium sulfite and a small amount of water as raw materials, reacts for 2 to 6 hours at a reaction temperature of 100 to 120 DEG C, and obtains a target product after cooling. The method is a one-step reaction with an atomic economy of up to 100%, thereby saving production costs and energy consumption to the greatest extent.

Example 1

Accurately weigh 80 g sulfur (2.5 mol S), 315 g anhydrous sodium sulfite (2.5 mol) and 225 mL water (12.5

mol) was added into a stirred reactor, heated to 115°C and stirred at 300 rpm for 5 h. After the reaction, the obtained liquid was transferred to an open product tank and completely converted into Na ₂ S ₂ O ₃ ·5H ₂ O crystals after cooling.

Example 2

Accurately weigh 80 g sulfur (2.5 mol S), 315 g anhydrous sodium sulfite (2.5 mol), 225 mL water (12.5 mol) and 0.05 mol sodium sulfide and add them into a stirred reactor, and react for 2.5 h at 115° C. with a stirring speed of 300 rpm. After the reaction is completed, the resulting liquid is transferred to an open product tank, and Na ₂ S ₂ O ₃ ·5H ₂ O crystals are obtained after cooling.

Example 3

Accurately weigh 80g sulfur (2.5mol S), 315g anhydrous sodium sulfite (2.5mol), 225mL water (12.5mol) and 0.1mol sodium sulfide and add them into a stirred reactor, and react for 2.5h at 120°C with a stirring speed of _250rpm . After the reaction is completed, the obtained liquid is transferred to an open product tank, _{and Na2S2O3 · 5H2O} crystals are obtained after cooling.

Example 4

Accurately weigh 80g sulfur (2.5mol S), 300g anhydrous sodium sulfite (2.38mol), 340mL water (18.9mol) and 0.1mol sodium hydroxide and add _them into a stirred reactor, and react for 3h at 100℃ and a stirring speed of 250rpm. After the reaction is completed, filter and remove the unreacted sulfur while hot, and then immediately transfer the obtained hot solution to an open container, and after cooling _, obtain _Na2S2O3 · _5H2O crystals, and filter and remove the residual solution again, and the obtained liquid is mixed with the unreacted sulfur obtained previously, and directly used for the next batch of synthesis and recycled.

Example 5

Accurately weigh 80g sulfur (2.5mol S), 330g anhydrous sodium sulfite (2.62mol), 450mL water (25mol) and 0.12mol sodium carbonate into a stirred reactor, and react for 3h at 100℃ and _250rpm . After the reaction, the obtained liquid is immediately transferred to an open container, and after cooling _{, Na2S2O3} · _5H2O crystals are obtained. The residual solution is filtered to remove the obtained liquid, which can be directly used for the next batch synthesis and recycled.

Example 6

The Na ₂ S ₂ O ₃ ·5H ₂ O synthesized in Example 1 was subjected to an X-ray diffraction experiment using CuKα radiation. FIG1 is a comparative XRD spectrum of the Na ₂ S ₂ O ₃ ·5H ₂ O synthesized in Example 1 and standard Na ₂ S ₂ O ₃ ·5H ₂ O, Na ₂ S ₂ O ₃ ·2H ₂ O, Na ₂ SO ₃ , and sulfur. The experimental results show that when the reaction is carried out at a stoichiometric ratio of 1/8S ₈ +Na ₂ SO ₃ +5H ₂ O=Na ₂ S ₂ O ₃ ·5H ₂ O, a reaction temperature of 115°C, and sufficient stirring for 5 hours, all the sulfur is consumed, and the liquid reaction mixture is completely solidified after cooling. Na ₂ S ₂ O ₃ ·5H ₂ O is the main product of the reaction, and there is a small amount of dehydrated impurity Na ₂ S ₂ O ₃ ·2H ₂ O. This may be due to the fact that during the reaction, some water leaked from the flask which was not sealed tightly.

Example 7

Na ₂ S ₂ O ₃ ·5H ₂ O synthesized in Examples 2 and 3 was subjected to X-ray diffraction experiments using Cu Kα radiation. FIG2 is a comparative XRD spectrum of Na ₂ S ₂ O ₃ ·5H ₂ O synthesized in Example 2 (corresponding to FIG2A ) and Example 3 (corresponding to FIG2B ) with standard Na ₂ S ₂ O ₃ ·5H ₂ O, Na ₂ S·9H ₂ O, Na ₂ SO ₃ , and S _8. The experimental results show that the X-ray diffraction pattern shows only peaks attributable to Na ₂ S ₂ O ₃ ·5H ₂ O, but no characteristic diffraction peaks of S ₈ , Na ₂ SO ₃ and Na ₂ S-9H ₂ O. It can be seen that the addition of sodium sulfide can catalyze the reaction of S ₈ and Na ₂ SO ₃ and shorten the reaction time. Among them, the catalyst works by solubilizing sulfur. Since sulfur is extremely insoluble in water and dissolves very slowly, adding alkaline substances can increase the solubility of sulfur. For example, sodium sulfide can react with sulfur to form sodium polysulfide, thereby playing a catalytic role.

Comparative Example 1

Accurately weigh 80 g sulfur (2.5 mol S), 315 g anhydrous sodium sulfite (2.5 mol) and 225 mL water (12.5 mol) and add them to a stirred reactor. Heat to 125° C. and control the stirring speed to 300 rpm to react for 10 hours. The reactor contains a large amount of unreacted sulfur and anhydrous sodium sulfite. After testing, the reaction conversion rate is less than 80%.

Claims (3)

1. A method for synthesizing sodium thiosulfate, characterized in that it comprises the following steps: taking each substance according to a molar ratio of sulfur, anhydrous sodium sulfite and water of 1:1:5, adding them into a stirred reactor, heating them to 115°C and controlling the stirring speed to 300rpm for reaction for 5h, and after the reaction is completed, cooling the obtained liquid to obtain sodium thiosulfate crystals, wherein the molar mass of the sulfur is calculated as sulfur atoms. 2. A method for synthesizing sodium thiosulfate, characterized in that it comprises the following steps: taking each substance according to the molar ratio of sulfur, anhydrous sodium sulfite, water and sodium sulfide of 1:1:5:0.02-0.05, adding them into a stirred reactor, controlling the stirring speed at 300 rpm at 115°C to react for 2.5 hours, and after the reaction is completed, cooling the obtained liquid to obtain sodium thiosulfate crystals, wherein the molar mass of the sulfur is calculated in terms of sulfur atoms. 3. A method for synthesizing sodium thiosulfate, characterized in that it comprises the following steps: taking each substance according to the molar ratio of sulfur, anhydrous sodium sulfite, water and sodium sulfide of 1:1:5:0.04-0.05, adding them into a stirred reactor, controlling the stirring speed at 250rpm at 120°C to react for 2.5h, and after the reaction is completed, cooling the obtained liquid to obtain sodium thiosulfate crystals, wherein the molar mass of the sulfur is calculated in terms of sulfur atoms.