A kind of preparation technology of thionyl chloride

Abstract

The present application relates to the field of chemical synthesis technology, and specifically discloses a preparation process of thionyl chloride. Sulfur, chlorine and sulfur dioxide enter a fixed bed to react, and the mixed gas after the reaction undergoes two sulfur matching reactions to reduce the content of sulfur dichloride in thionyl chloride. The second sulfur matching reaction uses a composite catalyst to promote the decomposition of dichlorothionyl and reduce the content of dichlorothionyl in thionyl chloride. The thionyl chloride prepared by the present application has the advantages of less impurities and high purity.

Description

Technical Field

[0001] The present application relates to the technical field of chemical synthesis, and more specifically, to a preparation process of thionyl chloride. Background Art

[0002] As an important organic chemical intermediate, thionyl chloride is mainly used in the fields of medicine, pesticides, dyes and organic synthesis. At present, there are four main production processes for thionyl chloride, namely sulfur dioxide gas phase method, chlorosulfonic acid method, co-production method and sulfur trioxide gas phase method.

[0003] At present, sulfur dioxide gas phase method is one of the most advanced and mature process technologies for producing thionyl chloride. The sulfur dioxide gas phase method uses liquid chlorine, sulfur and sulfur dioxide as the main raw materials, and continuously synthesizes high-temperature thionyl chloride gas under a certain temperature and in the presence of a catalyst. At this time, the purity of thionyl chloride gas is often low, and it needs to go through condensation, separation, sulfur addition, distillation and other processes to finally obtain high-purity thionyl chloride finished products. However, in the actual production process, due to various reasons, the production of thionyl chloride by sulfur dioxide gas phase method still has problems such as poor product color and low product purity.

[0004] The Chinese patent document with the announcement number CN106698364B discloses a method for producing thionyl chloride. The synthesis gas produced by the reaction of sulfur and chlorine in a synthesis reactor enters a reactor together with sulfur dioxide gas. The crude thionyl chloride generated by the reaction in the reactor directly enters a decomposer in a gaseous form after passing through an absorption tower; the crude thionyl chloride in the gas phase coming out of the decomposer enters a distillation tower, and the gas phase at the top of the distillation tower enters a reflux tank after condensation; the gas phase in the reflux tank enters an evacuation tank through an ejector, and is recycled back to the synthesis reactor, and a qualified thionyl chloride product is extracted in the middle of the distillation tower. The production method of thionyl chloride disclosed in this Chinese patent document has the main advantages of being easy to operate and easy to automate, while reducing the load of the distillation system, but the purity of the produced thionyl chloride is low. Summary of the invention

[0005] In order to further improve the purity of thionyl chloride, the present application provides a preparation process of thionyl chloride.

[0006] The present application provides a preparation process of thionyl chloride, which adopts the following technical scheme:

[0007] A method for preparing thionyl chloride comprises the following steps:

[0008] (1) Sulfur, sulfur dioxide and chlorine are introduced into a fixed bed with activated carbon for reaction;

[0009] (2) The mixed gas after the reaction is introduced into the sulfur preparation kettle, and liquid sulfur is sprayed into the sulfur preparation kettle from the top. The sulfur preparation kettle is filled with activated carbon.

[0010] (3) The crude thionyl chloride is taken out from the middle of the sulfur preparation kettle and enters the condenser, and the liquid crude thionyl chloride is taken out from the bottom of the condenser;

[0011] (4) Liquid crude thionyl chloride is sprayed into the distillation tower from the top. A composite catalyst is attached to the distillation tower, and gaseous crude thionyl chloride is taken out from the middle of the distillation tower.

[0012] The preparation of the composite catalyst comprises the following steps:

[0013] S1: Evenly mix diammonium hydrogen phosphate, copper source, calcium nitrate and deionized water, add ammonia water, heat up, react for 5 hours, cool to room temperature, age for 24 hours, filter, wash, and dry to obtain copper-doped hydroxyapatite;

[0014] S2: mixing copper-doped hydroxyapatite and starch, granulating, calcining, cooling, loading sulfur, and drying to obtain a composite catalyst;

[0015] (5) The crude gaseous thionyl chloride is then introduced into the finished product condenser, and the liquid product is taken out from the bottom of the finished product condenser to obtain thionyl chloride.

[0016] By adopting the above technical solution, the sulfur dichloride impurities are removed twice, which can improve the purity of thionyl chloride and make thionyl chloride present a clear and transparent appearance. In addition, the entire reaction system is in a cyclic state, which effectively eliminates the generation of three waste pollution problems, while achieving the effect of cost saving, thereby achieving an increase in yield.

[0017] By adopting the technical scheme, a catalyst for promoting the decomposition of dichlorothionyl is prepared, and the catalyst has the characteristic of being insoluble in thionyl chloride, and can efficiently remove dichlorothionyl impurities in thionyl chloride. At the same time, in the process of impurity removal, no new impurities are introduced, and the appearance quality of thionyl chloride can be effectively improved, and the purity of thionyl chloride is increased.

[0018] Preferably, in step (1), the flow rate of chlorine gas is 70-100 m / s. 3 / h, the flow rate of sulfur dioxide is 40-70m 3 / h.

[0019] By adopting the technical scheme, the reaction rate of the reaction is accelerated, thereby improving the production efficiency of thionyl chloride, and it can also ensure that the reactants have a suitable residence time to fully contact and react, thereby improving the conversion rate and product yield, reducing the occurrence of side reactions, and improving the purity of thionyl chloride.

[0020] Preferably, in step (2), the flow rate of the mixed gas is 4600-4800 kg / h, and the flow rate of the liquid sulfur is 360-390 kg / h.

[0021] By adopting the above technical scheme, sulfur can fully react with sulfur dioxide, avoiding the generation of excess sulfur and reducing the occurrence of side reactions. At the same time, the separation rate of impurities can be improved within the flow rate range of the mixed gas, thereby improving the purity of thionyl chloride while ensuring the production efficiency of thionyl chloride.

[0022] Preferably, the temperature in the condenser is 50-60°C.

[0023] By adopting the above technical solution, sulfur dioxide and chlorine are separated in gaseous form, while thionyl chloride is effectively condensed and collected; at this temperature, the separated sulfur dioxide and chlorine still have a small amount of energy, which is convenient for continuing to enter the fixed bed for reaction, saving energy, while removing impurities in thionyl chloride and improving the purity of thionyl chloride.

[0024] Preferably, the temperature in the sulfur preparation kettle and the distillation tower is 85-100°C.

[0025] By adopting the technical scheme, sulfur chloride is condensed and collected, and thionyl chloride is effectively separated in a gaseous form and enters the next stage, thereby avoiding the loss of thionyl chloride in a liquid form, reducing the impurity content in thionyl chloride, and improving the purity and yield of thionyl chloride.

[0026] Preferably, in step S1, the mass ratio of diammonium hydrogen phosphate, copper source and calcium nitrate is (1.7-2.1):1:(6.5-7.3).

[0027] By adopting the above technical solution, the prepared copper-doped hydroxyapatite has good stability, and the appropriate copper doping amount effectively promotes the decomposition of dichlorothionyl, improves the purity of thionyl chloride, and no excess free copper ions enter the thionyl chloride, thereby avoiding new pollution to the thionyl chloride.

[0028] Preferably, in step S1, the copper source is one of copper nitrate, copper phosphate and copper chloride.

[0029] By adopting the above technical solution, copper ions can be fully dissolved and evenly dispersed in the reaction system, which is beneficial for the copper ions to fully contact and react with other reactants, thereby improving the uniformity of copper doping, and then improving the performance and structural stability of copper-doped hydroxyapatite, maintaining good activity throughout the catalytic process, and effectively reducing the impurity content in thionyl chloride.

[0030] Preferably, in step S2, the mass ratio of copper-doped hydroxyapatite to starch is (15-19.5):1.

[0031] By adopting the technical scheme, the prepared composite catalyst has high porosity and good mechanical strength, which can avoid the composite catalyst from being broken or pulverized during the reaction, extend its service life, and prevent new impurities from entering the thionyl chloride; the high porosity enables the reaction to proceed more fully, the impurity removal rate is high, and the purity of the thionyl chloride is improved.

[0032] Preferably, in step S2, the roasting treatment includes drying, pre-roasting and high-temperature roasting; the drying temperature is 80-100°C, the time is 12-15h, the pre-roasting temperature is 300-400°C, the time is 2-3h, and the high-temperature roasting temperature is 700-800°C, the time is 3-4h.

[0033] By adopting the above technical solution, copper-doped hydroxyapatite crystals can grow in a relatively stable environment, reducing stress and defects caused by too rapid decomposition of starch. At a relatively low temperature in the early stage, the gas generated by the decomposition of starch inside the copper-doped hydroxyapatite particles can escape slowly to form some small pores. As the temperature rises, these small pores will merge and expand to a certain extent, making the final pore size distribution of the copper-doped hydroxyapatite more uniform, increasing the sulfur loading, and thus improving the catalytic performance of the copper-doped hydroxyapatite composite catalyst, effectively removing impurities in thionyl chloride, and thus improving the purity of thionyl chloride.

[0034] Preferably, the heating rate of the pre-calcination is 1.5-2°C / min, and the heating rate of the high-temperature calcination is 8-10°C / min.

[0035] By adopting the above technical scheme, the temperature is slowly increased during pre-baking to gradually carbonize and decompose the starch, and the starch is evenly decomposed into gases such as carbon dioxide and water vapor. These gases can escape gently, which helps to maintain the integrity of the copper-doped hydroxyapatite particles; the temperature is quickly increased during high-temperature calcination, so that the pore structure inside the copper-doped hydroxyapatite particles is further adjusted, and the small pores are appropriately merged and expanded during the rapid heating process, so that the porosity of the composite catalyst is improved, thereby improving the adsorption performance of the composite catalyst, allowing the reactants to be more fully contacted, and improving the removal rate of impurities in thionyl chloride.

[0036] In summary, this application has the following beneficial effects:

[0037] 1. The porous, high specific surface area carrier can increase the contact area between the reactants, so that sulfur dichloride and sulfur can react fully. Compared with directly adding solid sulfur into the distillation tower, it reduces the amount of solid sulfur used, avoids clogging the bottom discharge port of the distillation tower, and improves the yield and purity of thionyl chloride.

[0038] 2. Copper ions are electrophilic, which promotes the polarization of sulfur-chlorine bonds in dichlorothionyl, catalyzes the decomposition of dichlorothionyl, reduces the content of byproduct dichlorothionyl in thionyl chloride, and improves the purity of thionyl chloride. In addition, copper ions replace part of calcium ions and enter the hydroxyapatite crystal structure, which makes them unable to move freely and will not dissolve in thionyl chloride, so new impurities will not be introduced into the product. DETAILED DESCRIPTION

[0039] The present application is further described in detail below with reference to the embodiments.

[0040] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0041] Example 1

[0042] The preparation method of thionyl chloride of the present embodiment comprises the steps:

[0043] (1) Sulfur, sulfur dioxide and chlorine are introduced into a fixed bed with activated carbon for reaction at a temperature of 200°C and a flow rate of sulfur dioxide of 40 m / s. 3 / h, the flow rate of chlorine is 70m 3 / h, the amount of sulfur added is 60kg / h;

[0044] (2) The mixed gas after the reaction is introduced into the sulfur preparation kettle at a rate of 4600 kg / h. At the same time, liquid sulfur is sprayed into the sulfur preparation kettle from the upper end at a flow rate of 360 kg / h. Activated carbon is attached to the sulfur preparation kettle. The temperature in the sulfur preparation kettle is 85°C. Liquid sulfur chloride is collected from the bottom of the sulfur preparation kettle, enters the sulfur chloride collection tank, and is re-sprayed into the fixed bed of step (1) for reaction;

[0045] (3) crude thionyl chloride is taken out from the middle of the sulfur preparation kettle and enters into a condenser. The temperature in the condenser is 50° C., crude liquid thionyl chloride is taken out from the bottom of the condenser, and a mixed gas of sulfur dioxide and chlorine is taken out from the top. The mixed gas of sulfur dioxide and chlorine is directly introduced into the fixed bed of step (1);

[0046] (4) Liquid crude thionyl chloride is sprayed into the distillation tower from the top. The temperature in the distillation tower is 85°C. A composite catalyst is attached to the distillation tower. Sulfur chloride is taken out from the bottom of the distillation tower, enters the sulfur chloride collection tank and is sprayed back into the fixed bed of step (1) for reaction. Gaseous crude thionyl chloride is taken out from the middle.

[0047] (5) The crude gaseous thionyl chloride is then introduced into a finished product condenser. The temperature in the finished product condenser is 50° C. Sulfur dioxide is extracted from the upper part of the finished product condenser and the extracted sulfur dioxide gas is directly introduced into the fixed bed of step (1). The liquid product is extracted from the bottom to obtain thionyl chloride.

[0048] The preparation method of the composite catalyst of the present embodiment comprises the following steps:

[0049] S1: Take 17g of diammonium hydrogen phosphate, 10g of copper nitrate, 65g of calcium nitrate and 400g of deionized water, mix and stir evenly, add 2.8mL of 25% ammonia water by mass percentage, heat to 85°C, continue stirring and reacting for 5h, cool to room temperature, age for 24h, filter and wash until the pH value of the filtrate is 7, and dry to obtain copper-doped hydroxyapatite;

[0050] S2: 1500g of copper-doped hydroxyapatite and 100g of starch are placed in a granulator. During the granulation process, a carboxymethyl cellulose aqueous solution with a mass percentage concentration of 1.5% is sprayed to obtain particles with an average particle size of 3mm. The particles are placed in a cool and ventilated place for 24h, and then placed in an oven at 100℃ for 12h. The particles are transferred to a muffle furnace for calcination. The temperature is increased to 400℃ at a heating rate of 1.5℃ / min, and the temperature is kept for 2h. The temperature is then increased to 700℃ at a heating rate of 10℃ / min, and the temperature is kept for 4h. The particles are taken out, cooled, and put into a reactor. Hydrogen sulfide and sulfur dioxide gases are introduced. The particles are taken out after 20min and dried to obtain a composite catalyst.

[0051] Example 2

[0052] The preparation method of thionyl chloride of the present embodiment comprises the steps:

[0053] (1) Sulfur, sulfur dioxide and chlorine are introduced into a fixed bed with activated carbon for reaction at a temperature of 250°C and a flow rate of sulfur dioxide of 70 m / s. 3 / h, the flow rate of chlorine is 100m 3 / h, the amount of sulfur added is 80kg / h;

[0054] (2) The mixed gas after the reaction is introduced into the sulfur preparation kettle at a rate of 4800 kg / h. At the same time, liquid sulfur is sprayed into the sulfur preparation kettle from the top at a flow rate of 390 kg / h. Activated carbon is attached to the sulfur preparation kettle. The temperature in the sulfur preparation kettle is 100°C. Liquid sulfur chloride is extracted from the bottom of the sulfur preparation kettle, enters the sulfur chloride collection tank, and is sprayed into the fixed bed again for reaction;

[0055] (3) crude thionyl chloride is taken out from the middle of the sulfur preparation kettle and enters into a condenser. The temperature in the condenser is 60° C. crude thionyl chloride is taken out from the bottom of the condenser, and a mixed gas of sulfur dioxide and chlorine is taken out from the top. The mixed gas of sulfur dioxide and chlorine is directly introduced into the fixed bed of step (1);

[0056] (4) Liquid crude thionyl chloride is sprayed into the distillation tower from the top. The temperature in the distillation tower is 100°C. A composite catalyst is attached to the distillation tower. Sulfur chloride is taken out from the bottom of the distillation tower, enters the sulfur chloride collection tank and is sprayed back into the fixed bed of step (1) for reaction. Gaseous crude thionyl chloride is taken out from the middle.

[0057] (5) The crude gaseous thionyl chloride product is then introduced into a finished product condenser at a temperature of 60°C, sulfur dioxide is extracted from the upper portion, and the extracted sulfur dioxide gas is directly introduced into the fixed bed of step (1), and a liquid product is extracted from the bottom of the finished product condenser to obtain thionyl chloride.

[0058] The preparation method of the composite catalyst of the present embodiment comprises the following steps:

[0059] S1: Take 21g of diammonium hydrogen phosphate, 10g of copper phosphate, 73g of calcium nitrate and 400g of deionized water, mix and stir evenly, add 3.2mL of 25% ammonia water by mass percentage, heat to 85°C, continue stirring and reacting for 5h, cool to room temperature, age for 24h, filter and wash until the pH value of the filtrate is 7, and dry to obtain copper-doped hydroxyapatite;

[0060] S2: 1950g of copper-doped hydroxyapatite and 100g of starch are placed in a granulator. During the granulation process, a carboxymethyl cellulose aqueous solution with a mass percentage concentration of 1.5% is sprayed to obtain particles with an average particle size of 3mm. The particles are placed in a cool and ventilated place for 24h, and then placed in an oven at 80℃ for 15h. The particles are transferred to a muffle furnace for calcination. The temperature is increased to 300℃ at a heating rate of 2℃ / min, and the temperature is kept for 3h. The temperature is then increased to 800℃ at a heating rate of 8℃ / min, and the temperature is kept for 3h. The particles are taken out, cooled, and put into a reactor. Hydrogen sulfide and sulfur dioxide gases are introduced. The particles are taken out after 25min and dried to obtain a composite catalyst.

[0061] Example 3

[0062] The preparation method of thionyl chloride of the present embodiment comprises the steps:

[0063] (1) Sulfur, sulfur dioxide and chlorine are introduced into a fixed bed with activated carbon for reaction at a temperature of 250°C and a flow rate of sulfur dioxide of 50 m / s. 3 / h, the flow rate of chlorine is 90m 3 / h, the amount of sulfur added is 65kg / h;

[0064] (2) The mixed gas after the reaction is introduced into the sulfur preparation kettle at a rate of 4700 kg / h. At the same time, liquid sulfur is sprayed into the sulfur preparation kettle from the top at a flow rate of 370 kg / h. Activated carbon is attached to the sulfur preparation kettle. The temperature in the sulfur preparation kettle is 90°C. Liquid sulfur chloride is taken from the bottom of the sulfur preparation kettle, enters the sulfur chloride collection tank and is sprayed into the fixed bed again for reaction;

[0065] (3) crude thionyl chloride is taken out from the middle of the sulfur preparation kettle and enters into a condenser. The temperature in the condenser is 52° C. crude thionyl chloride is taken out from the bottom of the condenser, and a mixed gas of sulfur dioxide and chlorine is taken out from the top. The mixed gas of sulfur dioxide and chlorine is directly introduced into the fixed bed of step (1);

[0066] (4) Liquid crude thionyl chloride is sprayed into the distillation tower from the top. The temperature in the distillation tower is 90°C. A composite catalyst is attached to the distillation tower. Sulfur chloride is taken out from the bottom of the distillation tower, enters the sulfur chloride collection tank and is sprayed back into the fixed bed of step (1) for reaction. Gaseous crude thionyl chloride is taken out from the middle.

[0067] (5) The crude gaseous thionyl chloride is then introduced into a finished product condenser. The temperature in the finished product condenser is 52° C. Sulfur dioxide is extracted from the upper part of the finished product condenser and the extracted sulfur dioxide gas is directly introduced into the fixed bed of step (1). The liquid product is extracted from the bottom to obtain thionyl chloride.

[0068] The preparation method of the composite catalyst of the present embodiment comprises the following steps:

[0069] S1: Take 20g of diammonium hydrogen phosphate, 10g of copper chloride, 70g of calcium nitrate and 400g of deionized water, mix and stir evenly, add 3mL of 25% ammonia water by mass percentage, heat to 85°C, continue stirring and reacting for 5h, cool to room temperature, age for 24h, filter and wash until the pH value of the filtrate is 7, and dry to obtain copper-doped hydroxyapatite;

[0070] S2: 1750g of copper-doped hydroxyapatite and 100g of starch are placed in a granulator. During the granulation process, a carboxymethyl cellulose aqueous solution with a mass percentage concentration of 1.5% is sprayed to obtain particles with an average particle size of 3mm. The particles are placed in a cool and ventilated place for 24h, and then placed in an oven at 95℃ for 13h. The particles are transferred to a muffle furnace for calcination. The temperature is increased to 380℃ at a heating rate of 1.7℃ / min, and the temperature is kept for 2.5h. The temperature is then increased to 750℃ at a heating rate of 9℃ / min, and the temperature is kept for 3.5h. The particles are taken out, cooled, and put into a reactor. Hydrogen sulfide and sulfur dioxide gases are introduced. The particles are taken out after 25min and dried to obtain a composite catalyst.

[0071] Comparative Example 1

[0072] The preparation method of the thionyl chloride of this comparative example comprises the following steps:

[0073] (1) Sulfur, sulfur dioxide and chlorine are introduced into a fixed bed with activated carbon for reaction at a temperature of 200°C and a flow rate of sulfur dioxide of 40 m / s. 3 / h, the flow rate of chlorine is 70m 3 / h, the amount of sulfur added is 60kg / h;

[0074] (2) The mixed gas after the reaction is introduced into the sulfur preparation kettle at a rate of 4600 kg / h. At the same time, liquid sulfur is sprayed into the sulfur preparation kettle from the upper end at a flow rate of 360 kg / h. Activated carbon is attached to the sulfur preparation kettle. The temperature in the sulfur preparation kettle is 85°C. Liquid sulfur chloride is collected from the bottom of the sulfur preparation kettle, enters the sulfur chloride collection tank, and is re-sprayed into the fixed bed of step (1) for reaction;

[0075] (3) crude thionyl chloride is taken out from the middle of the sulfur preparation kettle and enters into a condenser. The temperature in the condenser is 50° C., crude liquid thionyl chloride is taken out from the bottom of the condenser, and a mixed gas of sulfur dioxide and chlorine is taken out from the top. The mixed gas of sulfur dioxide and chlorine is directly introduced into the fixed bed of step (1);

[0076] (4) Liquid crude thionyl chloride is sprayed into the distillation tower from the top. The temperature in the distillation tower is 85°C. A composite catalyst is attached to the distillation tower. Sulfur chloride is taken out from the bottom of the distillation tower, enters the sulfur chloride collection tank and is sprayed back into the fixed bed of step (1) for reaction. Gaseous crude thionyl chloride is taken out from the middle.

[0077] (5) The crude gaseous thionyl chloride is then introduced into a finished product condenser. The temperature in the finished product condenser is 50° C. Sulfur dioxide is extracted from the upper part of the finished product condenser and the extracted sulfur dioxide gas is directly introduced into the fixed bed of step (1). The liquid product is extracted from the bottom to obtain thionyl chloride.

[0078] The preparation method of the composite catalyst of this comparative example comprises the following steps: mixing 40g of activated carbon, 5g of copper nitrate and 50g of deionized water, uniformly dispersing by ultrasonication, filtering, drying the filter residue, putting it into a reactor, introducing hydrogen sulfide and sulfur dioxide gas, taking it out after 20 minutes, and drying it to obtain the composite catalyst.

[0079] Comparative Example 2

[0080] The preparation method of the thionyl chloride of this comparative example comprises the following steps:

[0081] (1) Sulfur, sulfur dioxide and chlorine are introduced into a fixed bed with activated carbon for reaction at a temperature of 200°C and a flow rate of sulfur dioxide of 40 m / s. 3 / h, the flow rate of chlorine is 70m 3 / h, the amount of sulfur added is 60kg / h;

[0082] (2) The mixed gas after the reaction is introduced into the sulfur preparation kettle at a rate of 4600 kg / h. At the same time, liquid sulfur is sprayed into the sulfur preparation kettle from the upper end at a flow rate of 360 kg / h. Activated carbon is attached to the sulfur preparation kettle. The temperature in the sulfur preparation kettle is 85°C. Liquid sulfur chloride is collected from the bottom of the sulfur preparation kettle, enters the sulfur chloride collection tank, and is re-sprayed into the fixed bed of step (1) for reaction;

[0083] (3) crude thionyl chloride is taken out from the middle of the sulfur preparation kettle and enters into a condenser. The temperature in the condenser is 50° C., crude liquid thionyl chloride is taken out from the bottom of the condenser, and a mixed gas of sulfur dioxide and chlorine is taken out from the top. The mixed gas of sulfur dioxide and chlorine is directly introduced into the fixed bed of step (1);

[0084] (4) Liquid crude thionyl chloride is sprayed into the distillation tower from the top. The temperature in the distillation tower is 85°C. A catalyst is attached to the distillation tower. Sulfur chloride is taken out from the bottom of the distillation tower, enters the sulfur chloride collection tank and is sprayed back into the fixed bed of step (1) for reaction. Gaseous crude thionyl chloride is taken out from the middle.

[0085] (5) The crude gaseous thionyl chloride is then introduced into a finished product condenser. The temperature in the finished product condenser is 50° C. Sulfur dioxide is extracted from the upper part of the finished product condenser and the extracted sulfur dioxide gas is directly introduced into the fixed bed of step (1). The liquid product is extracted from the bottom to obtain thionyl chloride.

[0086] The preparation method of the catalyst of this comparative example comprises the following steps:

[0087] S1: 17g of diammonium hydrogen phosphate, 75g of calcium nitrate and 400g of deionized water were mixed and stirred evenly, 2.8mL of 25% ammonia water was added, the temperature was raised to 85°C, the reaction was continued with stirring for 5h, the mixture was cooled to room temperature, aged for 24h, filtered and washed until the pH value of the filtrate was 7, and dried to obtain hydroxyapatite;

[0088] S2: 1500g of hydroxyapatite and 100g of starch are placed in a granulator. During the granulation process, a carboxymethyl cellulose aqueous solution with a mass percentage concentration of 1.5% is sprayed to obtain particles with an average particle size of 3mm. The particles are placed in a cool and ventilated place for 24h, and then dried in an oven at 100℃ for 12h. The particles are transferred to a muffle furnace for calcination. The temperature is increased to 400℃ at a heating rate of 1.5℃ / min, and the temperature is kept for 2h. The temperature is then increased to 700℃ at a heating rate of 10℃ / min, and the temperature is kept for 4h. The particles are taken out, cooled, and put into a reactor. Hydrogen sulfide and sulfur dioxide gases are introduced. The particles are taken out after 20min and dried to obtain a catalyst.

[0089] Performance testing

[0090] 1. Copper ion content detection

[0091] Inductively coupled plasma mass spectrometry was used.

[0092] 2. Sulfur dichloride content test

[0093] Using liquid chromatography, add excess anhydrous ethanol to the test sample, then introduce excess ammonia gas, centrifuge, and take the oil and ester layer for chromatographic analysis.

[0094] 3. Test of sulfur dichloride and thionyl chloride content

[0095] Gas chromatography was used, and the chromatographic column was a 3.2m×3.1mm glass column filled with OC-210.

[0096] The test data of the content of each component of Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 are shown in Table 1 below:

[0097] Table 1 Test data of each component content

[0098]

[0099] It can be seen from the analysis of Examples 1-3 and Comparative Examples 1-2 in combination with Table 1 that after the crude thionyl chloride product is subjected to secondary impurity removal using the composite catalyst, the thionyl chloride has a high purity and no new impurities are introduced.

[0100] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A preparation process for thionyl chloride, characterized in that, The steps include: (1) Sulfur, sulfur dioxide and chlorine are introduced into a fixed bed with activated carbon for reaction; (2) The mixed gas after the reaction is introduced into the sulfur preparation kettle, and liquid sulfur is sprayed into the sulfur preparation kettle from the top. The sulfur preparation kettle contains activated carbon. (3) The crude thionyl chloride is taken out from the middle of the sulfur preparation kettle and enters the condenser, and the liquid crude thionyl chloride is taken out from the bottom of the condenser; (4) Liquid crude thionyl chloride is sprayed into the distillation tower from the top. A composite catalyst is attached to the distillation tower, and gaseous crude thionyl chloride is taken out from the middle of the distillation tower. The preparation of the composite catalyst comprises the following steps: S1: Evenly mix diammonium hydrogen phosphate, copper source, calcium nitrate and deionized water, add ammonia water, heat up, react for 5 hours, cool to room temperature, age for 24 hours, filter, wash, and dry to obtain copper-doped hydroxyapatite; S2: mixing copper-doped hydroxyapatite and starch, granulating, calcining, cooling, loading sulfur, and drying to obtain a composite catalyst; (5) The crude gaseous thionyl chloride product is then introduced into the finished product condenser, and the liquid product is taken out from the bottom of the finished product condenser to obtain thionyl chloride; The copper source is one of copper nitrate, copper phosphate and copper chloride.

2. A preparation process for thionyl chloride according to claim 1, characterized in that, In step (1), the flow rate of chlorine gas is 70-100m 3 / h, the flow rate of sulfur dioxide is 40-70m 3 / h.

3. A preparation process for thionyl chloride according to claim 1, characterized in that, In the step (2), the flow rate of the mixed gas is 4600-4800 kg / h, and the flow rate of the liquid sulfur is 360-390 kg / h.

4. A preparation process for thionyl chloride according to claim 1, characterized in that, The temperature in the condenser and the finished product condenser is 50-60°C.

5. A preparation process for thionyl chloride according to claim 1, characterized in that, The temperature in the sulfur preparation kettle and the distillation tower is 85-100°C.

6. A preparation process for thionyl chloride according to claim 1, characterized in that, In the step S1, the mass ratio of diammonium hydrogen phosphate, copper source and calcium nitrate is (1.7-2.1):1:(6.5-7.3).

7. A preparation process for thionyl chloride according to claim 1, characterized in that, In step S2, the mass ratio of copper-doped hydroxyapatite to starch is (15-19.5):

1.

8. A preparation process for thionyl chloride according to claim 1, characterized in that, In step S2, the roasting treatment includes drying, pre-roasting and high-temperature roasting; the drying temperature is 80-100°C, the time is 12-15h, the pre-roasting temperature is 300-400°C, the time is 2-3h, and the high-temperature roasting temperature is 700-800°C, the time is 3-4h.

9. A process for preparing thionyl chloride according to claim 8, characterized in that, The heating rate of the pre-calcination is 1.5-2°C / min, and the heating rate of the high-temperature calcination is 8-10°C / min.

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