CN114162835A - Production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate from thiourea - Google Patents
Production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate from thiourea Download PDFInfo
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- CN114162835A CN114162835A CN202111329529.4A CN202111329529A CN114162835A CN 114162835 A CN114162835 A CN 114162835A CN 202111329529 A CN202111329529 A CN 202111329529A CN 114162835 A CN114162835 A CN 114162835A
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- thiocyanate
- thiourea
- calcium
- water
- calcium sulfate
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- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 title claims abstract description 72
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 title claims abstract description 58
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 title claims abstract description 36
- VGTPCRGMBIAPIM-UHFFFAOYSA-M sodium thiocyanate Chemical compound [Na+].[S-]C#N VGTPCRGMBIAPIM-UHFFFAOYSA-M 0.000 title claims abstract description 32
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 10
- 238000006243 chemical reaction Methods 0.000 claims abstract description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 25
- SOIFLUNRINLCBN-UHFFFAOYSA-N ammonium thiocyanate Chemical compound [NH4+].[S-]C#N SOIFLUNRINLCBN-UHFFFAOYSA-N 0.000 claims abstract description 22
- ALWXETURCOIGIZ-UHFFFAOYSA-N 1-nitropropylbenzene Chemical compound CCC([N+]([O-])=O)C1=CC=CC=C1 ALWXETURCOIGIZ-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 18
- 238000000926 separation method Methods 0.000 claims abstract description 18
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000002002 slurry Substances 0.000 claims abstract description 10
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims abstract description 9
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims abstract description 9
- 239000000920 calcium hydroxide Substances 0.000 claims abstract description 9
- 239000007788 liquid Substances 0.000 claims abstract description 8
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 4
- 238000001914 filtration Methods 0.000 claims abstract description 4
- 238000010438 heat treatment Methods 0.000 claims abstract description 4
- 239000000463 material Substances 0.000 claims abstract description 4
- 238000001728 nano-filtration Methods 0.000 claims abstract description 4
- 238000001704 evaporation Methods 0.000 claims description 18
- 239000000047 product Substances 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 9
- 230000008020 evaporation Effects 0.000 claims description 9
- 239000012065 filter cake Substances 0.000 claims description 9
- 239000012452 mother liquor Substances 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 6
- 239000011575 calcium Substances 0.000 claims description 6
- 229910052791 calcium Inorganic materials 0.000 claims description 6
- 238000002425 crystallisation Methods 0.000 claims description 6
- 230000008025 crystallization Effects 0.000 claims description 6
- 239000000706 filtrate Substances 0.000 claims description 6
- 238000003825 pressing Methods 0.000 claims description 6
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical class [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 5
- 230000001376 precipitating effect Effects 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 3
- 238000004806 packaging method and process Methods 0.000 claims description 3
- 238000004537 pulping Methods 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000001291 vacuum drying Methods 0.000 claims description 3
- 239000003795 chemical substances by application Substances 0.000 abstract description 2
- 238000005265 energy consumption Methods 0.000 abstract description 2
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 239000000945 filler Substances 0.000 abstract description 2
- 239000000543 intermediate Substances 0.000 abstract description 2
- 239000000575 pesticide Substances 0.000 abstract description 2
- 229920005594 polymer fiber Polymers 0.000 abstract description 2
- 238000009987 spinning Methods 0.000 abstract description 2
- 239000002994 raw material Substances 0.000 description 6
- 239000012141 concentrate Substances 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000001223 reverse osmosis Methods 0.000 description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 description 2
- 235000011152 sodium sulphate Nutrition 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C3/00—Cyanogen; Compounds thereof
- C01C3/20—Thiocyanic acid; Salts thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C335/00—Thioureas, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
- C07C335/02—Thiourea
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Nanotechnology (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to a production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate by thiourea, which comprises the following steps: dissolving ammonium thiocyanate in water, conveying the solution into a reaction kettle by a conveying pump, introducing steam for heating, and starting reaction; preparing calcium hydroxide and water into slurry, introducing steam for preheating, then adding reaction materials, converting unreacted ammonium thiocyanate into calcium thiocyanate in the reaction process, simultaneously generating ammonia gas, absorbing the ammonia gas by using water to produce 25% ammonia water, introducing the rest feed liquid into a separation process, filtering the generated feed liquid through a first stage, and then respectively collecting a calcium thiocyanate concentrated solution and a thiourea concentrated solution through nanofiltration. Compared with the existing production process, the method has the advantages of low cost, simple process, mild reaction conditions, low energy consumption, environmental friendliness, wide and important application of the produced high-purity thiourea in the fields of pesticide and medical intermediates and the like, the high-purity ammonium thiocyanate in the fields of polymer fiber spinning agents and the like, and the nano calcium sulfate in the fields of fillers and the like.
Description
Technical Field
The invention relates to a production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate by thiourea.
Background
In the last hundred years, the direct conversion of ammonium thiocyanate to produce thiourea has been a difficult problem in the industry, and two key points which need to be solved are generally accepted at present: 1. the conversion rate of ammonium thiocyanate is improved; 2. the separation efficiency of ammonium thiocyanate and thiourea is improved. The conversion rate of ammonium thiocyanate is closely related to conditions such as temperature and time, but is more greatly related to factors such as impurities and solvents. Generally, melting is considered by the industry as an effective way to increase the conversion of ammonium thiocyanate, with the highest conversion in the laboratory currently available for reference being typically 45% and conversion in commercial practice typically below 40%. The invention provides a simple liquid phase synthesis method with conversion rate up to 40%, wherein partial raw materials are converted into high-purity thiourea, and unreacted raw materials are further indirectly converted into high-purity sodium thiocyanate and nano calcium sulfate, so that the problem of difficult separation is effectively solved, and the product value is greatly improved.
Disclosure of Invention
In view of the above, the invention aims to provide a production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate from thiourea.
In order to achieve the purpose, the technical scheme is as follows:
1. a production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate by thiourea is characterized by comprising the following steps: the method comprises the following steps:
(1) dissolving ammonium thiocyanate in water, wherein the weight ratio of the ammonium thiocyanate to the water is 1: 1-6: 1, conveying the solution into a reaction kettle by using a conveying pump, starting stirring, introducing steam, heating to 100-150 ℃, starting reaction, and maintaining for 0.5-8 hours;
(2) preparing calcium hydroxide and water into slurry, wherein the weight ratio of the calcium hydroxide to the water is 1: 1-5: 1, introducing steam to preheat the temperature to be 40-100 ℃, then adding the reaction materials in the step (1), reacting for 0.5-8 h, converting unreacted ammonium thiocyanate into calcium thiocyanate in the reaction process, simultaneously generating ammonia gas, absorbing the ammonia gas with water to produce 25% ammonia water, and introducing the rest feed liquid into a separation process, wherein thiourea does not participate in the reaction in the process;
(3) firstly, carrying out primary filtration on the feed liquid generated in the step (2), then carrying out nanofiltration, and respectively collecting a calcium thiocyanate concentrated solution and a thiourea concentrated solution;
(4) evaporating and concentrating the concentrated thiourea solution at the evaporation temperature of 50-135 ℃, then cooling and crystallizing at the crystallization temperature of 20-40 ℃, precipitating a large amount of thiourea, performing centrifugal separation, respectively collecting high-purity thiourea finished products and filtrate, and returning the filtrate to the calcium transferring procedure in the step (2) for preparing slurry;
(5) reacting the concentrated calcium thiocyanate solution generated in the step (3) with a saturated sodium sulfate solution according to a molar ratio of 1: 1.95-1: 2.05 at 40-100 ℃ for 0.5-8 h to generate sodium thiocyanate and calcium sulfate, performing filter pressing separation, and collecting a sodium thiocyanate clear solution and a calcium sulfate filter cake respectively;
(6) collecting the sodium thiocyanate clear solution generated in the step (5), evaporating and concentrating, then cooling and crystallizing, precipitating sodium thiocyanate crystals, performing centrifugal separation, respectively collecting sodium thiocyanate finished products and mother liquor, evaporating and concentrating the mother liquor, and returning to the step 1, wherein the evaporation temperature of sodium thiocyanate is 100-135 ℃, the crystallization temperature is 40-60 ℃, and the evaporation temperature of the mother liquor is 100-135 ℃;
(7) and (3) collecting the calcium sulfate filter cake generated in the step (5), pulping by using condensed water, washing twice, carrying out filter pressing separation, sending the calcium sulfate filter cake collected twice into a double-cone vacuum drying machine for drying at the drying temperature of 100-150 ℃, crushing by using a shaker after drying, packaging to obtain a nano calcium sulfate finished product, and sending washing water into the calcium transferring procedure in the step (2) for preparing slurry after being used for multiple times.
The invention has the beneficial effects that:
the method adopts ammonium thiocyanate as a raw material, partially directly converts the ammonium thiocyanate into thiourea, partially converts calcium hydroxide into calcium thiocyanate and ammonia gas, separates the calcium thiocyanate into a calcium thiocyanate concentrated solution and a thiourea concentrated solution by using a reverse osmosis membrane, then converts the calcium thiocyanate into sodium thiocyanate and nano calcium sulfate by using sodium sulfate as a raw material, and directly concentrates the thiourea concentrated solution to produce high-purity sodium thiocyanate;
compared with the existing production process, the method has the advantages of low cost, simple process, mild reaction conditions, low energy consumption and environmental friendliness, and the product produced by the method has three types of high-purity thiourea, high-purity sodium thiocyanate and nano calcium sulfate, wherein the high-purity thiourea is used in the fields of pesticide and medical intermediates and the like, the high-purity ammonium thiocyanate is used in the fields of polymer fiber spinning agents and the like, and the nano calcium sulfate is widely and importantly applied in the fields of fillers and the like.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Please refer to fig. 1:
a production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate by thiourea comprises the following steps:
(1) dissolving ammonium thiocyanate in water, wherein the weight ratio of the ammonium thiocyanate to the water is 1: 1-6: 1, conveying the solution into a reaction kettle by using a conveying pump, starting stirring, introducing steam, heating to 100-150 ℃, starting reaction, and maintaining for 0.5-8 hours;
(2) preparing calcium hydroxide and water into slurry, wherein the weight ratio of the calcium hydroxide to the water is 1: 1-5: 1, introducing steam to preheat the temperature to be 40-100 ℃, then adding the reaction materials in the step (1), reacting for 0.5-8 h, converting unreacted ammonium thiocyanate into calcium thiocyanate in the reaction process, simultaneously generating ammonia gas, absorbing the ammonia gas with water to produce 25% ammonia water, and introducing the rest feed liquid into a separation process, wherein thiourea does not participate in the reaction in the process;
(3) firstly, carrying out primary filtration on the feed liquid generated in the step (2), then carrying out nanofiltration, and respectively collecting a calcium thiocyanate concentrated solution and a thiourea concentrated solution;
(4) evaporating and concentrating the concentrated thiourea solution, cooling and crystallizing, precipitating a large amount of thiourea, performing centrifugal separation, respectively collecting high-purity thiourea finished products and filtrate, and returning the filtrate to the calcium transferring procedure in the step (2) for preparing slurry; the evaporation temperature is 50-135 ℃, and the cooling crystallization temperature is 20-40 ℃;
(5) reacting the concentrated calcium thiocyanate solution generated in the step (3) with a saturated sodium sulfate solution according to a molar ratio of 1: 1.95-1: 2.05 at 40-100 ℃ for 0.5-8 h to generate sodium thiocyanate and calcium sulfate, performing filter pressing separation, and collecting a sodium thiocyanate clear solution and a calcium sulfate filter cake respectively;
(6) collecting the clear sodium thiocyanate solution generated in the step (5), evaporating and concentrating, cooling and crystallizing to separate out sodium thiocyanate crystals, performing centrifugal separation, respectively collecting a sodium thiocyanate finished product and mother liquor, and evaporating and concentrating the mother liquor to return to the step 1; the evaporation temperature of the sodium thiocyanate is 100-135 ℃, the crystallization temperature is 40-60 ℃, and the evaporation temperature of the mother liquor is 100-135 ℃;
(7) and (3) collecting the calcium sulfate filter cake generated in the step (5), pulping by using condensate water, washing twice, performing filter pressing separation, sending the calcium sulfate filter cake collected twice into a double-cone vacuum drying machine for drying at the suitable drying temperature of 100-150 ℃, crushing by using a shaker after drying, and packaging to obtain a finished product of the nano calcium sulfate, wherein after the washing water is used for multiple times, the washing water is sent into the calcium conversion procedure in the step (2) for preparing slurry.
The invention adopts ammonium thiocyanate as a raw material, partially directly converts the ammonium thiocyanate into thiourea, partially converts calcium hydroxide into calcium thiocyanate and ammonia gas, separates the calcium thiocyanate into a calcium thiocyanate concentrated solution and a thiourea concentrated solution by using a reverse osmosis membrane, then converts the calcium thiocyanate into sodium thiocyanate and nano calcium sulfate by using sodium sulfate as a raw material, and directly concentrates the thiourea concentrated solution to produce high-purity sodium thiocyanate.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (1)
1. A production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate by thiourea is characterized by comprising the following steps: the method comprises the following steps:
(1) dissolving ammonium thiocyanate in water, wherein the weight ratio of the ammonium thiocyanate to the water is 1: 1-6: 1, conveying the solution into a reaction kettle by using a conveying pump, starting stirring, introducing steam, heating to 100-150 ℃, starting reaction, and maintaining for 0.5-8 hours;
(2) preparing calcium hydroxide and water into slurry, wherein the weight ratio of the calcium hydroxide to the water is 1: 1-5: 1, introducing steam to preheat the temperature to be 40-100 ℃, then adding the reaction materials in the step (1), reacting for 0.5-8 h, converting unreacted ammonium thiocyanate into calcium thiocyanate in the reaction process, simultaneously generating ammonia gas, absorbing the ammonia gas with water to produce 25% ammonia water, and introducing the rest feed liquid into a separation process, wherein thiourea does not participate in the reaction in the process;
(3) firstly, carrying out primary filtration on the feed liquid generated in the step (2), then carrying out nanofiltration, and respectively collecting a calcium thiocyanate concentrated solution and a thiourea concentrated solution;
(4) evaporating and concentrating the concentrated thiourea solution at the evaporation temperature of 50-135 ℃, then cooling and crystallizing at the crystallization temperature of 20-40 ℃, precipitating a large amount of thiourea, performing centrifugal separation, respectively collecting high-purity thiourea finished products and filtrate, and returning the filtrate to the calcium transferring procedure in the step (2) for preparing slurry;
(5) reacting the concentrated calcium thiocyanate solution generated in the step (3) with a saturated sodium sulfate solution according to a molar ratio of 1: 1.95-1: 2.05 at 40-100 ℃ for 0.5-8 h to generate sodium thiocyanate and calcium sulfate, performing filter pressing separation, and collecting a sodium thiocyanate clear solution and a calcium sulfate filter cake respectively;
(6) collecting the sodium thiocyanate clear solution generated in the step (5), evaporating and concentrating, then cooling and crystallizing, precipitating sodium thiocyanate crystals, performing centrifugal separation, respectively collecting sodium thiocyanate finished products and mother liquor, evaporating and concentrating the mother liquor, and returning to the step 1, wherein the evaporation temperature of sodium thiocyanate is 100-135 ℃, the crystallization temperature is 40-60 ℃, and the evaporation temperature of the mother liquor is 100-135 ℃;
(7) and (3) collecting the calcium sulfate filter cake generated in the step (5), pulping by using condensed water, washing twice, carrying out filter pressing separation, sending the calcium sulfate filter cake collected twice into a double-cone vacuum drying machine for drying at the drying temperature of 100-150 ℃, crushing by using a shaker after drying, packaging to obtain a nano calcium sulfate finished product, and sending washing water into the calcium transferring procedure in the step (2) for preparing slurry after being used for multiple times.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111329529.4A CN114162835B (en) | 2021-11-11 | 2021-11-11 | Production process for co-producing high-purity sodium thiocyanate and nano calcium sulfate by thiourea |
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| CN114162835B CN114162835B (en) | 2023-12-01 |
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3723604A (en) * | 1970-03-05 | 1973-03-27 | Glanzstoff Ag | Process for removing thiourea as an impurity from alkali-and alkaline earth-metal rhodanides |
| JPS61270212A (en) * | 1986-02-20 | 1986-11-29 | Nissan Chem Ind Ltd | Production of calcium thiocyanate |
| US4832930A (en) * | 1988-05-02 | 1989-05-23 | Tekatch William M | Decomposition of ammonium thiocyanate |
| US20030060662A1 (en) * | 1998-03-24 | 2003-03-27 | Balakrishnan Srinivasa | Process for the preparation of thiourea |
| CN108423906A (en) * | 2018-03-16 | 2018-08-21 | 山西瑞赛科环保科技有限公司 | A kind of wastewater treatment method of substituting thioureido production |
| CN108424379A (en) * | 2018-03-16 | 2018-08-21 | 山西瑞赛科环保科技有限公司 | A kind of clean preparation method for substituting thioureido |
| CN109052429A (en) * | 2018-10-16 | 2018-12-21 | 河北诚信九天医药化工有限公司 | A kind of production technology of high-quality sodium sulfocyanate |
| CN112876393A (en) * | 2021-01-19 | 2021-06-01 | 浙江工业大学 | Method for continuously synthesizing and purifying thiourea by using ammonium thiocyanate |
-
2021
- 2021-11-11 CN CN202111329529.4A patent/CN114162835B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3723604A (en) * | 1970-03-05 | 1973-03-27 | Glanzstoff Ag | Process for removing thiourea as an impurity from alkali-and alkaline earth-metal rhodanides |
| JPS61270212A (en) * | 1986-02-20 | 1986-11-29 | Nissan Chem Ind Ltd | Production of calcium thiocyanate |
| US4832930A (en) * | 1988-05-02 | 1989-05-23 | Tekatch William M | Decomposition of ammonium thiocyanate |
| US20030060662A1 (en) * | 1998-03-24 | 2003-03-27 | Balakrishnan Srinivasa | Process for the preparation of thiourea |
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| CN112876393A (en) * | 2021-01-19 | 2021-06-01 | 浙江工业大学 | Method for continuously synthesizing and purifying thiourea by using ammonium thiocyanate |
Non-Patent Citations (1)
| Title |
|---|
| 唐立靖等: "微细浸染型金矿硫脲-硫氰酸铵浸出研究", 黄金科学技术, vol. 23, no. 4, pages 97 - 101 * |
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