Method for producing hydrocyanic acid based on temperature and humidity

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to a hydrocyanic acid production method based on temperature and humidity, hydrocyanic acid is prepared from ammonia gas, methane and air through an ammoxidation reaction under the action of a catalyst, and before the ammoxidation reaction, the method further comprises the following steps that the air is dried till the relative humidity is RH, and RH is smaller than or equal to 60%. In the application, before the ammoxidation reaction, the air is dried until the relative humidity is RH, and RH is less than or equal to 60%, so that the adverse effect of moisture in the air on the reaction can be avoided, the synthesis efficiency of hydrocyanic acid is further improved, and the product purity is improved. According to the method, before the ammoxidation reaction, the air is dried, so that moisture in the air can be effectively removed, the risks of equipment corrosion, catalyst medium deactivation, formation of explosive mixed gas and the like caused by the moisture are avoided, and the production safety is improved.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a method for producing hydrocyanic acid based on temperature and humidity. Background Art

[0002] Hydrocyanic acid, also known as hydrogen cyanide, has a molecular formula of HCN and a density of 0.687 g / cm 3 , with a melting point of -13.4℃ (lit.), a boiling point of 26℃, a colorless gas or liquid, and a bitter almond smell. It is a highly toxic chemical. Hydrocyanic acid is an important chemical raw material, which is widely used in many industrial fields. It is mainly used to produce herbicide intermediates such as diphosphine, dyes (indigo), nylon 66 (adiponitrile), feed additives (methionine), chelating agents (EDTA, DTPA), medicines, pesticide intermediates (pantolactone, 2-hydroxyvalerate methyl ester), fluorescent brighteners, insecticides, etc. It is currently an important fine chemical in China.

[0003] There are several traditional methods for synthesizing hydrocyanic acid: Andrussow method (also known as Andrussow method, direct method, etc.), ammonia oxidation method, acrylonitrile by-product method, light oil cracking method, etc. Among them, the Andrussow method is to pass a raw material mixture consisting of methane, ammonia and air (or oxygen) into a wire mesh catalyst bed made of platinum / rhodium / palladium alloy under normal pressure and high temperature conditions for ammonia oxidation reaction. This method has the advantages of simple process, mature technical route, normal pressure, easy implementation, etc., and is a commonly used industrial production method of hydrocyanic acid.

[0004] However, the purity of the product produced by Angle's process needs to be further improved. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a method for producing hydrocyanic acid to further improve the purity of hydrocyanic acid.

[0006] After analyzing the prior art, the inventors found that in the process of producing hydrocyanic acid by the Angle method, moisture in the air will have an adverse effect on the reaction. For example, excessive moisture may participate in some side reactions, reduce the synthesis efficiency of hydrocyanic acid, affect the purity of the product, and may cause equipment corrosion, catalyst medium deactivation, and the formation of explosive mixed gas and other problems.

[0007] To achieve the above objectives, the scheme of this application is as follows:

[0008] The invention provides a method for producing hydrocyanic acid. The hydrocyanic acid is prepared by an ammonia oxidation reaction using ammonia, methane and air as raw materials under the action of a catalyst. Before the ammonia oxidation reaction, the method further comprises the following steps: drying the air to a relative humidity of RH, RH≤60%, preferably 18%-45%, and more preferably 20%-40%.

[0009] Optionally, the drying temperature is 20-60°C, preferably 30-45°C.

[0010] Optionally, the drying time is 1-3 hours, preferably 1.5-3 hours.

[0011] Optionally, during the drying process, the air flow rate is 0.5-2.0 m 3 / min, preferably 0.8-1.8m 3 / min.

[0012] Optionally, concentrated sulfuric acid is used to dry the air.

[0013] Optionally, the catalyst is selected from a binary catalyst platinum / rhodium alloy or a platinum / palladium alloy or a ternary catalyst platinum / rhodium / palladium alloy.

[0014] Optionally, in the binary catalyst platinum / rhodium alloy or platinum / palladium alloy, the mass content of platinum is 90wt%-93wt%.

[0015] Optionally, in the three-way catalyst platinum / rhodium / palladium alloy, the mass content of platinum is 92wt%-93wt%.

[0016] Optionally, the molar ratio of the ammonia to the methane is 1:1.05-1.15.

[0017] Optionally, after the ammoxidation reaction, the method further comprises the following steps: using the sulfuric acid solution obtained after drying to absorb excess ammonia in the reaction system.

[0018] Beneficial effects of the present invention:

[0019] In the present application, before the ammoxidation reaction, the air is dried (dried to a relative humidity of RH, RH≤60%), which can avoid the adverse effect of moisture in the air on the reaction, thereby improving the synthesis efficiency of hydrocyanic acid and the purity of the prepared hydrocyanic acid.

[0020] In the present application, the air is dried before the ammoxidation reaction, which can effectively remove moisture from the air, avoid the risks of equipment corrosion, catalyst medium deactivation, formation of explosive mixed gas, etc. caused by moisture, and improve production safety.

[0021] The present application ensures the stable operation of the entire hydrocyanic acid synthesis system by adjusting the temperature, humidity and flow rate, reduces the occurrence of reaction abnormalities caused by environmental factors or fluctuations in reaction conditions, and improves the yield and purity of the produced hydrocyanic acid.

[0022] The present application ingeniously utilizes the dehydration property of concentrated sulfuric acid for air drying, and uses the diluted sulfuric acid after absorbing water to absorb excess ammonia, thereby realizing the recycling of sulfuric acid, reducing production costs, and having good environmental benefits.

[0023] In the present application, the purity of hydrocyanic acid can be further improved by drying the air at a temperature of 25-55°C.

[0024] In this application, the air flow rate is controlled to be 0.5-2.0m 3 / min, especially 0.8-1.8m 3 / min, which helps to further improve the yield and purity of hydrocyanic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0026] Figure 1 This is a process flow chart of this application. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] An embodiment of the present invention provides a method for producing hydrocyanic acid, wherein hydrocyanic acid is prepared by an ammoxidation reaction using methane, ammonia and air as raw materials in the presence of a catalyst, wherein the molar ratio of ammonia to methane is 1:1.05-1.15, and the catalyst is selected from a binary catalyst platinum / rhodium alloy or a platinum / palladium alloy or a ternary catalyst platinum / rhodium / palladium alloy;

[0029] Before the ammoxidation reaction, the following steps are also included:

[0030] At 20-60℃, use concentrated sulfuric acid to dry the air for 1-3h until the relative humidity is RH, RH≤60%; during the drying process, the air flow rate is 0.5-2.0m 3 / min.

[0031] In another embodiment of the present invention, after the ammoxidation reaction, the method further comprises the following steps: using the sulfuric acid solution obtained after drying to absorb excess ammonia in the reaction system.

[0032] In the following description, numerous details are discussed to provide a more thorough explanation of embodiments of the present invention; however, it is apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details.

[0033] Example 1

[0034] like Figure 1 As shown, this embodiment provides a method for producing hydrocyanic acid, wherein a concentrated sulfuric acid dryer is used as a dryer, the dryer is provided with an air inlet, a sulfuric acid inlet, an air outlet, a temperature regulating component, a humidity sensor and a sulfuric acid outlet, the air inlet is connected to an air inlet pipe, the air outlet is connected to the reactor through an outlet pipe, flow meters are provided on the air inlet pipe and the outlet pipe, the reactor is provided with a methane inlet, an ammonia inlet, a platinum / rhodium alloy wire mesh catalyst bed and a synthesis gas outlet, the synthesis gas outlet is connected to a deamination device, the deamination device is connected to the sulfuric acid outlet, and the deamination device can be a static mixer, a falling film absorption tower, etc.;

[0035] The specific steps of the production method of hydrocyanic acid are as follows:

[0036] The temperature of the dryer was set at 20°C, concentrated sulfuric acid was introduced into the dryer, and the 3 / min flow rate into the dryer, and the humidity data of the dried air is recorded in real time by the humidity sensor. After 2 hours, the dried air (relative humidity RH is 55%) is transported to the reactor, and ammonia and methane are introduced into the reactor. The volume ratio of ammonia, methane and dried air entering the reactor is 1:1.05-1.15:5-7;

[0037] In the reactor, ammonia, methane and air react at a temperature of 1050° C. in the presence of a binary platinum / rhodium alloy wire mesh catalyst bed (the mass content of platinum in the platinum / rhodium alloy is 93wt%) to carry out an ammonia oxidation reaction, and a sulfuric acid solution containing moisture in the air (i.e., the sulfuric acid solution obtained after drying) is used to absorb the unreacted ammonia. After the reaction is completed, the purity of the hydrocyanic acid in the product is detected by chromatography. The results are shown in Table 1.

[0038] Example 2

[0039] The difference between this embodiment and embodiment 1 is that the temperature of the dryer is set to 30° C. and the relative humidity of the air after drying is 28%.

[0040] After the reaction was completed, the purity of the hydrocyanic acid in the product was detected by chromatography, and the results are shown in Table 1.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that the temperature of the dryer is set to 40° C. and the relative humidity of the air after drying is 19%.

[0043] After the reaction was completed, the purity of the hydrocyanic acid in the product was detected by chromatography, and the results are shown in Table 1.

[0044] Example 4

[0045] The difference between this embodiment and embodiment 1 is that the temperature of the dryer is set to 50° C., and the relative humidity RH of the air after drying is 16%.

[0046] After the reaction was completed, the purity of the hydrocyanic acid in the product was detected by chromatography, and the results are shown in Table 1.

[0047] Example 5

[0048] The difference between this embodiment and embodiment 1 is that the temperature of the dryer is set to 60° C., and the relative humidity RH of the air after drying is 14%.

[0049] After the reaction was completed, the purity of the hydrocyanic acid in the product was detected by chromatography, and the results are shown in Table 1.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 1 is that the air is not dried.

[0052] After the reaction was completed, the purity of the hydrocyanic acid in the product was detected by chromatography. The results are shown in Table 1.

[0053] Table 1 Purity test results

[0054] Group Drying temperature, ℃ Relative humidity of air after drying, % Purity of hydrocyanic acid, % Example 1 20 55 5.1 Example 2 30 28 6.5 Example 3 40 19 7.8 Example 4 50 16 8.1 Example 5 60 14 8.4 Comparative Example 1 -- -- 1.5

[0055] As can be seen from Table 1, compared with Comparative Example 1 (the air was not dried before the ammoxidation reaction), the purity of hydrocyanic acid in Examples 1-5 (the air was dried before the ammoxidation reaction) increased significantly. This result shows that drying the air (drying to a relative humidity of RH, RH≤60%) before the ammoxidation reaction can avoid the adverse effect of moisture in the air on the reaction, thereby improving the synthesis efficiency of hydrocyanic acid and improving the purity of the product.

[0056] As can be seen from Table 1, compared with Example 1 (the relative humidity of the air after drying is 55%), the purity of hydrocyanic acid in Examples 2-4 (the relative humidity of the air after drying is 16%-28%) is significantly increased. This result shows that drying the air at a temperature of 25-55°C until the relative humidity of the air is 15%-30% can further improve the purity of hydrocyanic acid.

[0057] It can be seen from Table 1 that the failure to dry the air in Comparative Example 1 will seriously affect the conversion efficiency of the catalyst in the reactor, and the high water content in the air will cause the catalyst to be oxidized and deactivated, resulting in catalyst loss.

[0058] Example 6

[0059] The difference between this embodiment and embodiment 1 is that the air flow rate is 0.5m when entering the dryer. 3 / min, the temperature of the dryer was set to 40°C, and the relative humidity of the air after drying was 16%.

[0060] After the reaction was completed, the yield of hydrocyanic acid was calculated according to the formula: yield (%) = molar amount of hydrocyanic acid / molar amount of ammonia feed × 100%. The purity of hydrocyanic acid in the product was detected by chromatography. The results are shown in Table 2.

[0061] Example 7

[0062] The difference between this embodiment and embodiment 1 is that the air flow rate is 1.0m when entering the dryer. 3 / min, the temperature of the dryer was set to 40°C, and the relative humidity of the air after drying was 20%.

[0063] After the reaction was completed, the yield of hydrocyanic acid was calculated according to the formula: yield (%) = molar amount of hydrocyanic acid / molar amount of ammonia feed × 100%. The purity of hydrocyanic acid in the product was detected by chromatography. The results are shown in Table 2.

[0064] Example 8

[0065] The difference between this embodiment and embodiment 1 is that the air flow rate is 1.5m / s when entering the dryer. 3 / min, the temperature of the dryer was set to 40°C, and the relative humidity of the air after drying was 27%.

[0066] After the reaction was completed, the yield of hydrocyanic acid was calculated according to the formula: yield (%) = molar amount of hydrocyanic acid / molar amount of ammonia feed × 100%. The purity of hydrocyanic acid in the product was detected by chromatography. The results are shown in Table 2.

[0067] Example 9

[0068] The difference between this embodiment and embodiment 1 is that the air flow rate is 2.0m when entering the dryer. 3 / min, the temperature of the dryer was set to 40°C, and the relative humidity of the air after drying was 45%.

[0069] After the reaction was completed, the yield of hydrocyanic acid was calculated according to the formula: yield (%) = molar amount of hydrocyanic acid / molar amount of ammonia feed × 100%. The purity of hydrocyanic acid in the product was detected by chromatography. The results are shown in Table 2.

[0070] Table 2 Yield and purity test results

[0071] Group <![CDATA[The flow rate of air, m 3 / min]]> Yield, % Purity of hydrocyanic acid, % Example 6 0.5 70 5.1 Example 7 1.0 97 8.5 Example 8 1.5 89 7.0 Example 9 2.0 70 5.1

[0072] From Table 2, we can see that in 0.5-2.0m 3 / min, with the increase of air flow rate, the yield and purity of hydrocyanic acid both showed a trend of first increasing and then decreasing. When the air flow rate was 1.0m 3 / min, the yield and purity of hydrocyanic acid are the highest. This result shows that the flow rate of controlled air is 0.5-2.0m 3 / min, especially 0.8-1.8m 3 / min, which helps to further improve the yield and purity of hydrocyanic acid.

[0073] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for producing hydrocyanic acid, wherein the hydrocyanic acid is prepared by ammonia oxidation reaction with ammonia, methane and air as raw materials in the presence of a catalyst, characterized in that: Before the ammoxidation reaction, the method further comprises the following steps: drying the air to a relative humidity of RH, RH≤60%.

2. The method for producing hydrocyanic acid according to claim 1, wherein The drying temperature is 20-60°C.

3. The method for producing hydrocyanic acid according to claim 1, wherein The drying time is 1-3 hours.

4. The method for producing hydrocyanic acid according to claim 1, characterized in that: During the drying process, the air flow rate is 0.5-2.0m 3 / min.

5. The method for producing hydrocyanic acid according to claim 4, characterized in that: During the drying process, the air flow rate is 1.0-2.0m 3 / min.

6. The method for producing hydrocyanic acid according to claim 1, characterized in that: The air is dried using concentrated sulfuric acid solution.

7. The method for producing hydrocyanic acid according to claim 1, characterized in that: The catalyst is selected from a binary catalyst platinum / rhodium alloy or a platinum / palladium alloy or a ternary catalyst platinum / rhodium / palladium alloy.

8. The method for producing hydrocyanic acid according to claim 6, characterized in that: The molar ratio of the ammonia to the methane is 1:1.05-1.

15.

9. The method for producing hydrocyanic acid according to claim 8, characterized in that: After the ammoxidation reaction, the method further comprises the following steps: using the sulfuric acid solution obtained after drying to absorb excess ammonia in the reaction system.

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