CN114768700A - Nitric acid reduction device and method for reducing nitric acid - Google Patents
Nitric acid reduction device and method for reducing nitric acid Download PDFInfo
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- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/26—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24
- B01J31/28—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24 of the platinum group metals, iron group metals or copper
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- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/04—Preparation of esters of nitrous acid
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Abstract
The invention relates to the field of raw material recovery, in particular to a nitric acid reduction device and a method for reducing nitric acid, wherein the nitric acid reduction device comprises: the microchannel mixing unit and the microchannel catalysis unit are sequentially connected in series; the micro-channel mixing unit is used for mixing a liquid phase containing nitric acid, methanol and water with a gas containing NO in a cross flow manner; the microchannel catalytic unit is used for carrying out nitric acid reduction catalytic reaction on the mixed material from the microchannel mixing unit. The device can obviously improve the conversion rate of nitric acid and the concentration of the methyl nitrite in the reaction gas by coupling cross-flow mixing and catalytic reaction.
Description
Technical Field
The invention relates to the field of raw material recovery, in particular to a nitric acid reduction device and a nitric acid reduction method.
Background
Ethylene Glycol (MEG) is an important chemical raw material for the manufacture of polyesters (for the further production of dacron, beverage bottles, films), explosives, glyoxal, and as antifreeze, plasticizer, hydraulic fluid and solvent, among others.
The 'coal glycol' is produced by replacing petroleum ethylene with coal, and the process mainly comprises the following steps: coal gasification, synthesis gas purification, carbonylation reaction, esterification reaction, hydrogenation reaction and the like, wherein the principle of partial reaction is as follows:
and (3) carbonylation reaction: 2CH3ONO+2CO＝(COOCH3)2+2NO
Esterification reaction: 2NO +2CH3OH+0.5O2＝2CH3ONO+H2O
Hydrogenation reaction: (COOCH)3)2+4H2＝(CH2OH)2+2CH3OH
Reduction reaction: HNO3+2NO+3CH3OH＝3CH3ONO+2H2O
The regeneration of Methyl Nitrite (MN) plays a very important role in the process route for synthesizing the ethylene glycol, and the regeneration rate of MN is matched with the carbonylation rate of CO so as to ensure the stable and continuous operation of the whole process flow. In the esterification reaction process, the regenerated liquid phase contains methanol, water, nitric acid and the like, wherein the content of the nitric acid is generally 0.5-2%. For the generated wastewater after regeneration, in the prior art, organic matters such as methanol and the like are recovered through gas stripping and distillation, the wastewater containing nitric acid is neutralized by alkali, and then the salt-containing wastewater containing nitrate, nitrite, sodium formate, sodium oxalate, sodium carbonate and the like is discharged into a sewage treatment system.
Disclosure of Invention
The invention aims to solve the problems of low nitric acid conversion rate, low treatment efficiency, large device volume and amplification effect of a nitric acid reduction device in the prior art, and provides a nitric acid reduction device and a method for reducing nitric acid.
In order to achieve the above object, an aspect of the present invention provides a nitric acid reduction apparatus including: the micro-channel mixing unit and the micro-channel catalysis unit are sequentially communicated in series;
the micro-channel mixing unit is used for mixing a liquid phase containing nitric acid, methanol and water with a gas containing NO in a cross flow manner;
the microchannel catalytic unit is used for carrying out nitric acid reduction catalytic reaction on the mixed material from the microchannel mixing unit.
The device can obviously improve the conversion rate of nitric acid and the concentration of the methyl nitrite in the reaction gas by coupling cross-flow mixed reaction and catalytic reaction.
In a second aspect, the invention provides a method of reducing nitric acid in a nitric acid reduction unit according to the invention, the method comprising: and (2) enabling a liquid phase containing nitric acid, methanol and water to enter the micro-channel mixer through a liquid phase feed inlet, enabling a gas containing NO to enter the micro-channel mixer through a gas phase feed inlet, carrying out gas-liquid cross-flow mixing and carrying out a primary reaction, enabling the obtained mixed phase to enter a micro-channel catalytic unit for catalytic reaction, and optionally detecting the catalytic reaction material in a detection unit.
According to the method, a liquid phase is injected from a liquid phase feed inlet, a gas phase is injected from a gas phase feed inlet, the liquid phase containing nitric acid, methanol and water and NO-containing gas are subjected to cross-flow mixing reaction in a micro-channel mixer to form methyl nitrite, and because the reaction is not balanced, the gas-liquid mixed phase is continuously sent to a micro-channel catalytic unit for further reaction, and finally, the gas-liquid mixed phase reaches a detection unit to detect the final reaction component. The method can obviously improve the conversion rate of the nitric acid and the concentration of the methyl nitrite in the reaction gas.
Drawings
Fig. 1 is a schematic view of the configuration of a nitric acid reduction apparatus for treating a bottom solution of an esterification column according to a preferred embodiment of the present invention.
Description of the reference numerals
11 liquid phase feed inlet and 12 gas phase feed inlet
13 microchannel mixing unit 14 microchannel catalytic unit
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
The invention provides a nitric acid reduction device, comprising: the micro-channel mixing unit and the micro-channel catalysis unit are sequentially communicated in series;
the micro-channel mixing unit is used for mixing a liquid phase containing nitric acid, methanol and water with a gas containing NO in a cross flow manner;
the micro-channel catalytic unit is used for carrying out nitric acid reduction catalytic reaction on the mixed material from the micro-channel mixing unit.
According to a particularly preferred embodiment of the invention, the microchannel mixing unit comprises a liquid phase feed opening and a gas phase feed opening which are arranged at different positions.
According to a particularly preferred embodiment of the invention, the nitric acid reduction device further comprises a detection unit, wherein the detection unit is communicated with the discharge port of the microchannel catalytic unit and is used for detection and material component detection.
In the present invention, the detection unit may be a conventional choice in the art as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the detection unit comprises a detection cell.
According to a particularly preferred embodiment of the present invention, the nitric acid reduction plant, wherein the microchannel catalytic unit comprises a single-pass reactor.
According to a particularly preferred embodiment of the present invention, the microchannel mixer comprises a multistage T-shaped cross-flow channel.
In the present invention, the number of stages of the microchannel mixer is not particularly required as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the number of stages of the microchannel mixer is 4 to 10. By adopting the above-described preferred embodiment, the concentration of methyl nitrite can be further increased.
In the present invention, there is no particular requirement on the size of the microchannel mixer as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the size of the microchannel mixer is 50 to 1000 μm. By adopting the above preferred embodiment, the concentration of methyl nitrite can be further increased.
In order to further increase the concentration of methyl nitrite, according to a preferred embodiment of the present invention, the size of the microchannel mixer is 150-300 μm.
In the present invention, the size of the microchannel catalyst unit is not particularly required as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the size of the microchannel catalyst unit is 1000-2000 μm. By adopting the above-described preferred embodiment, the concentration of methyl nitrite can be further increased.
In order to further increase the concentration of methyl nitrite, according to a preferred embodiment of the invention, the size of the microchannel catalytic unit is 1200-1400 microns.
The invention provides a method for reducing nitric acid in a nitric acid reduction device, which comprises the following steps: and (2) enabling a liquid phase containing nitric acid, methanol and water to enter the micro-channel mixer through a liquid phase feed inlet, enabling a gas containing NO to enter the micro-channel mixer through a gas phase feed inlet, carrying out gas-liquid cross-flow mixing and carrying out a primary reaction, enabling the obtained mixed phase to enter a micro-channel catalytic unit for catalytic reaction, and optionally detecting the catalytic reaction material in a detection unit.
According to a particularly preferred embodiment of the invention, the process is described in which the microchannel catalytic unit is loaded with a nitrate chemical reduction catalyst.
In the present invention, the nitrate chemical reduction catalyst may be conventionally selected in the art as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the nitrate chemical reduction catalyst comprises an active component and a carrier, and the active component comprises, in mass percent, in the catalyst: pd0.1-1%, Cu 2-4%, Ce 0.01-0.02%; the carrier is porous stainless steel. By adopting the foregoing preferred embodiment, the content of methyl nitrite can be further increased.
The invention provides a preparation method of a nitrate radical chemical reduction catalyst, which comprises the following steps:
1) preparation of catalyst precursor: putting catalyst precursor A macroporous polystyrene resin into PdCl after ultrasonic treatment2And Ce (NO)3)3Soaking in the soaking solution for 1-5h, preferably soaking in equal volume, separating the complex after the reaction is finished, and drying to obtain a catalyst precursor B; and (2) soaking the catalyst precursor B in a mixed solution of sodium hydroxide and hydrazine hydrate, reacting for 0.5-5h, and separating a complex to obtain a catalyst precursor C, wherein the mass ratio of the sodium hydroxide to the hydrazine hydrate is preferably 10-30: 1, the volume ratio of the catalyst precursor B to the mixed solution of sodium hydroxide and hydrazine hydrate is 15-20: 1;
2) preparing a composite catalyst: soaking the catalyst precursor C in EDTA saturated solution for 1-20 hr, separating, preferably soaking in the same volume, and drying to obtain catalyst precursor D; soaking the catalyst precursor D in ultrasonically treated copper sulfate soaking liquid (with the concentration of 5-10 wt%) for 1-5h, separating a complex after the reaction is finished, and drying to obtain a catalyst precursor E; soaking the catalyst precursor E in a mixed solution of sodium hydroxide and hydrazine hydrate, preferably, the mass ratio of the sodium hydroxide to the hydrazine hydrate is 20-35: 1, the volume ratio of the catalyst precursor E to the mixed solution of sodium hydroxide and hydrazine hydrate is 5-15: and 1, drying to obtain the nitrate chemical reduction catalyst.
By adopting the preferred catalyst production method, the catalyst formation rate and the catalyst efficiency can be further improved.
According to a particularly preferred embodiment of the invention, the microchannel catalytic unit is loaded with catalyst by means of pressure loading.
According to the invention, the resin fine powder loaded with the catalyst is pressed into the baked stainless steel meshes on the surface in a pressurizing manner, so that the micro reaction channel modified by the surface catalyst is prepared, and the yield of methyl nitrite can be further improved.
In the present invention, as long as the object of the present invention can be achieved, there is no particular requirement for the operating conditions in the microchannel mixer, and according to a particularly preferred embodiment of the present invention, the operating conditions in the microchannel mixer include: the feeding amount of the liquid phase containing nitric acid, methanol and water is 5-160L/h.
According to a particularly preferred embodiment of the invention, the operating conditions in the microchannel mixer comprise: the ratio of the NO-containing gas to the liquid-phase feed flow of nitric acid, methanol and water is 10-50: 1. by adopting the above preferable embodiment, the yield of methyl nitrite can be further improved.
In order to further increase the yield of methyl nitrite, according to a preferred embodiment of the present invention, the feed flow ratio of the NO-containing gas to the liquid phase containing nitric acid, methanol and water is 20-30: 1.
According to a particularly preferred embodiment of the invention, the operating conditions in the microchannel mixer further comprise: the temperature is 70-80 ℃. By adopting the above preferred embodiment, the yield of methyl nitrite can be further improved.
In the present invention, there is NO particular requirement for the residence time of the NO-containing gas and the liquid phase containing nitric acid, methanol and water in the microchannel mixer as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the residence time of the NO-containing gas and the liquid phase containing nitric acid, methanol and water in the microchannel mixer in the method for reducing nitric acid is in the range of 30 to 200 ms. By adopting the above preferred embodiment, the production rate of methyl nitrite can be further improved.
In order to further increase the methyl nitrite production rate, according to a preferred embodiment of the present invention, the residence time of the NO-containing gas and the liquid phase containing nitric acid, methanol and water in the microchannel mixer is 60 to 80 ms.
In the present invention, as long as the object of the present invention can be achieved, there is no particular requirement on the conditions of the microchannel catalytic unit reduction reaction, and according to a particularly preferred embodiment of the present invention, the operating conditions of the microchannel catalytic unit reduction reaction include: the temperature is 60-100 ℃. By adopting the above preferred embodiment, the yield of methyl nitrite can be further improved.
According to a particularly preferred embodiment of the invention, the operating conditions of the microchannel catalytic unit reduction reaction include: the residence time of the mixed liquid is 100-500 ms.
In order to further increase the rate of methyl nitrite production, according to a preferred embodiment of the present invention, the operating conditions of the catalytic unit reduction reaction include: the temperature is 75-78 ℃, and the retention time of the mixed liquid is 200-260 ms.
According to a particularly preferred embodiment of the invention, the operating conditions of the catalytic unit reduction reaction comprise: the mass ratio of the mixed liquid to the catalyst is 1000-2000: 1.
by adopting the above preferable embodiment, the yield of methyl nitrite can be further improved.
In the present invention, the liquid phase containing nitric acid, methanol and water is not particularly limited as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the liquid phase containing nitric acid, methanol and water contains 1 to 5 mol% of nitric acid, 32 to 75 mol% of methanol and 10 to 50 mol% of water.
According to a particularly preferred embodiment of the invention, the nitric acid content by weight in the liquid phase comprising nitric acid, methanol and water is preferably from 1.5 to 2.1 mol%; the methanol content is preferably 40 to 65 mol%, and the total content of the remaining components including NO and methyl nitrite is 0 to 30 mol%.
In order to further increase the conversion rate of nitric acid, according to a preferred embodiment of the present invention, the liquid phase containing nitric acid, methanol and water is a waste liquid at the bottom of the esterification tower of the coal-to-ethylene glycol reaction.
In the present invention, the NO volume content of the nitrogen-containing gas is not particularly limited as long as the object of the present invention can be achieved, and according to a particularly preferred embodiment of the present invention, the NO volume content of the nitrogen-containing gas is 5 to 15 mol%. By adopting the above preferable embodiment, the yield of methyl nitrite can be further improved.
According to a particularly preferred embodiment of the invention, the nitrogen-containing gas has a NO content of 6 to 9 mol% by volume.
In order to further improve the conversion rate of nitric acid, according to a preferred embodiment of the present invention, the NO-containing gas is an esterification recycle gas generated in a reaction process of preparing ethylene glycol from coal.
The present invention is illustrated by the following examples, which are not intended to limit the scope of the invention.
In the following examples, the preparation method of the nitrate chemical reduction catalyst includes:
1) preparation of catalyst precursor: placing macroporous polystyrene resin as a catalyst precursor A in PdCl subjected to ultrasonic treatment2And Ce (NO)3)3Soaking the catalyst in the soaking solution for 2h in a medium volume, separating a complex after the reaction is finished, and drying to obtain a catalyst precursor B; the catalyst precursor B is immersed in a mixed solution of sodium hydroxide and hydrazine hydrate, and the mass ratio of the sodium hydroxide to the hydrazine hydrate is 20: 1, reacting for 2 hours, and separating a complex to prepare a catalyst precursor C, wherein the volume ratio of the catalyst precursor B to a mixed solution of sodium hydroxide and hydrazine hydrate is 18: 1;
2) preparing a composite catalyst: soaking the catalyst precursor C in EDTA saturated solution for 5 hr, separating and drying to obtain catalyst precursor D; soaking the catalyst precursor D in copper sulfate soaking solution (with the concentration of 8 weight percent) subjected to ultrasonic treatment for 2 hours, separating a complex after the reaction is finished, and drying to obtain a catalyst precursor E; soaking the catalyst precursor E in a mixed solution of sodium hydroxide and hydrazine hydrate, wherein the mass ratio of the sodium hydroxide to the hydrazine hydrate is 30:1, the volume ratio of the catalyst precursor E to the mixed solution of sodium hydroxide and hydrazine hydrate is 10: 1, and then dried to obtain a nitrate chemical reduction catalyst (the catalyst composition comprises, in mass percent, 0.2% of Pd, 3.5% of Cu, and 0.01% of Ce). And pressing the fine powder of the nitrate radical chemical reduction catalyst into the roasted stainless steel meshes on the surface in a pressurizing way to prepare the micro reaction channel modified by the surface catalyst.
Example 1
The liquid phase containing nitric acid, methanol and water comes from waste liquid at the bottom of the coal-to-ethylene glycol reaction esterification tower, wherein the weight content of the nitric acid is 1.6 mol%, the weight content of the methanol is 62.2 mol%, the weight content of the water is 16.3 mol%, the total content of components such as NO and methyl nitrite is 17.5 mol%, and the temperature is 74 ℃. The nitrogen-containing gas is esterification recycle gas generated in the reaction process of preparing ethylene glycol from coal, wherein the volume content of nitric oxide is 8 mol%, and the rest is gases such as nitrogen dioxide, nitrogen and the like, and the temperature is 74 ℃. The feed rate of the liquid phase containing nitric acid, methanol and water was 30L/h, and the feed flow ratio of the nitrogen-containing gas to the liquid phase containing nitric acid, methanol and water was 20: 1. the nitrate chemical reduction catalyst (preparation method is as above) comprises the following components in percentage by mass: pd0.2%, Cu 3.5% and Ce0.01%, wherein the mass ratio of the mixed liquid to the catalyst is 1200: 1. the microchannel mixer was 150 microns in size and comprised 8 stages of T-shaped cross flow channels. The microchannel catalytic unit has a size of 1200 microns.
Introducing a liquid phase containing nitric acid, methanol and water from a liquid phase feed inlet through an injection pump, introducing nitrogen-containing gas from a gas phase feed inlet through an injection pump, mixing the gas phase and the liquid phase in an 8-stage T-shaped microchannel, carrying out reduction reaction to form methyl nitrite, continuously sending the gas-liquid mixed phase into a microchannel catalytic reaction section for further reaction because the reaction is not balanced, and finally detecting the final reaction component in a detection cell. The residence time of the nitrogen-containing gas and the liquid phase containing nitric acid, methanol and water in the microchannel mixer was 70ms and the residence time in the microchannel catalytic reactor was 200 ms.
In the detection cell of this example, the volume content of MN (methyl nitrite) in the reaction gas is 10.2 mol%; the concentration of nitric acid in the reducing solution was 195 ppm.
Example 2
The liquid phase containing nitric acid, methanol and water comes from waste liquid at the bottom of an esterification tower of a coal-to-ethylene glycol reaction, wherein the weight content of the nitric acid is 1.2 mol%, the weight content of the methanol is 61.2 mol%, the weight content of the water is 20.5 mol%, the total content of components such as NO and methyl nitrite is 17.1 mol%, and the temperature is 75 ℃. The nitrogen-containing gas is esterification recycle gas generated in the reaction process of preparing the ethylene glycol from the coal, wherein the volume content of the nitric oxide is 8mol percent, and the rest is gases such as nitrogen dioxide, nitrogen and the like, and the temperature is 76 ℃. The feed rate of the liquid phase containing nitric acid, methanol and water was 82.5L/h, and the feed flow ratio of the nitrogen-containing gas to the liquid phase containing nitric acid, methanol and water was 25: 1. the nitrate chemical reduction catalyst comprises the following components in percentage by mass: pd0.6%, Cu 2.7% and Ce0.02%, wherein the mass ratio of the mixed liquid to the catalyst is 1500: 1. the microchannel mixer was 220 micron in size and comprised 6 stages of T-shaped cross flow channels. The microchannel catalytic unit has a size of 1300 microns.
Introducing a liquid phase containing nitric acid, methanol and water from a liquid phase feed inlet through an injection pump, introducing nitrogen-containing gas from a gas phase feed inlet through an injection pump, mixing the gas phase and the liquid phase in a 6-stage T-shaped microchannel, carrying out reduction reaction to form methyl nitrite, continuously sending the gas-liquid mixed phase into a microchannel catalytic reaction section for further reaction because the reaction is not balanced, and finally detecting the final reaction component in a detection cell. The residence time of the nitrogen-containing gas and the liquid phase containing nitric acid, methanol and water in the microchannel mixer was 60ms and the residence time in the microchannel catalytic reactor was 230 ms.
In the detection cell of this embodiment, the volume content of MN (methyl nitrite) in the reaction gas is 9.1 mol%; the concentration of nitric acid in the reducing solution was 223 ppm.
Example 3
The liquid phase containing nitric acid, methanol and water comes from waste liquid at the bottom of the esterification tower of the coal-to-ethylene glycol reaction, wherein the weight content of the nitric acid is 0.9 mol%, the weight content of the methanol is 58 mol%, the weight content of the water is 19 mol%, the total content of components such as NO, methyl nitrite and the like is 19.1 mol%, and the temperature is 76 ℃. The nitrogen-containing gas is esterification recycle gas generated in the reaction process of preparing ethylene glycol from coal, wherein the volume content of nitric oxide is 6 mol%, and the rest is gases such as nitrogen dioxide, nitrogen and the like, and the temperature is 78 ℃. The feeding amount of the liquid phase containing nitric acid, methanol and water is 160L/h, and the feeding flow ratio of the nitrogen-containing gas to the liquid phase containing nitric acid, methanol and water is 30: 1. the nitrate chemical reduction catalyst comprises the following components in percentage by mass: pd0.9%, Cu 3.8%, and Ce0.02%, wherein the mass ratio of the mixed solution to the catalyst is 1900: 1. the microchannel mixer was 300 microns in size and comprised 10 stages of T-shaped cross-flow channels. The microchannel catalytic unit has a size of 1400 microns.
Introducing a liquid phase containing nitric acid, methanol and water from a liquid phase feed inlet through an injection pump, introducing nitrogen-containing gas from a gas phase feed inlet through an injection pump, mixing the gas phase and the liquid phase in a plurality of groups of T-shaped microchannels, carrying out reduction reaction to form methyl nitrite, continuously sending the gas-liquid mixed phase into a microchannel catalytic reaction section for further reaction because the reaction is not balanced, and finally reaching a detection pool to detect the final reaction components. The residence time of the nitrogen-containing gas and the liquid phase containing nitric acid, methanol and water in the microchannel mixer was 80ms and the residence time in the microchannel catalytic reactor was 260 ms.
In the detection cell of this embodiment, the volume content of MN (methyl nitrite) in the reaction gas is 7 mol%; the concentration of nitric acid in the reducing solution was 263 ppm.
Example 4
The process of example 1 was followed except that the nitrate chemical reduction catalyst contained, in mass percent: pd0.3%, Cu 4% and Ce0.025%.
In the detection cell of this example, the volume content of MN (methyl nitrite) in the reaction gas was 8.6 mol%; the concentration of nitric acid in the reducing solution was 291 ppm.
Example 5
The process of example 1 was followed except that the nitrogen-containing gas was fed at a flow ratio to the liquid phase comprising nitric acid, methanol and water of 40: 1.
in the detection cell of this embodiment, the volume content of MN (methyl nitrite) in the reaction gas is 7.6 mol%; the concentration of nitric acid in the reducing solution was 310 ppm.
Example 6
The process of example 1 was followed except that the feed temperature of the nitrogen-containing gas and the liquid phase containing nitric acid, methanol and water was 65 ℃.
In the detection cell of this example, the volume content of MN (methyl nitrite) in the reaction gas was 8.1 mol%; the concentration of nitric acid in the reducing solution was 262 ppm.
Example 7
The process of example 1 was followed except that the residence time of the nitrogen-containing gas and the liquid phase containing nitric acid, methanol and water in the microchannel mixer was 30ms and the residence time in the microchannel catalytic reactor was 100 ms.
In the detection cell of this example, the volume content of MN (methyl nitrite) in the reaction gas was 8.1 mol%; the concentration of nitric acid in the reducing solution was 255 ppm.
Example 8
The procedure is as in example 1, except that the nitric oxide content is 10 mol%.
In the detection cell of this example, the volume content of MN (methyl nitrite) in the reaction gas was 7.9 mol%; the concentration of nitric acid in the reducing solution was 255 ppm.
Example 9
The process of example 1 was followed except that the microchannel mixer ruler included 3 stages of T-shaped cross-flow channels.
In the detection cell of this embodiment, the volume content of MN (methyl nitrite) in the reaction gas is 7.9 mol%; the concentration of nitric acid in the reducing solution was 301 ppm.
Example 10
The process of example 1 was followed except that the microchannel mixer size was 400 microns and the microchannel catalytic unit size was 1500 microns.
In the detection cell of this embodiment, the volume content of MN (methyl nitrite) in the reaction gas is 8.1 mol%; the concentration of nitric acid in the reducing solution was 263 ppm.
Example 11
The process of example 1 was followed except that the mass ratio of the mixed liquor to the catalyst in the microchannel catalytic unit was 2200: 1.
in the detection cell of this example, the volume content of MN (methyl nitrite) in the reaction gas was 7.7 mol%; the concentration of nitric acid in the reducing solution was 402 ppm.
Comparative example 1
The process of example 1 was followed except that: no microchannel catalytic unit was added.
In the detection pool of the comparative example, the volume content of MN (methyl nitrite) in the reaction gas is 8.5 mol%; the concentration of nitric acid in the reducing solution was 525 ppm.
Comparative example 2
The process of example 1 was followed except that a plate reactor was used to reduce the nitric acid. The specific method comprises the following steps: the nitric acid waste liquid is stripped and distilled to recover organic matters such as methanol, the waste water containing nitric acid is neutralized by alkali, and then the salt-containing waste water containing nitrate, nitrite, sodium formate, sodium oxalate, sodium carbonate and the like is discharged into a sewage treatment system.
In the detection cell of the comparative example, the volume content of MN (methyl nitrite) in the reaction gas is 6.5 mol%; the concentration of nitric acid in the reducing solution was 752 ppm.
Comparative example 3
The process of example 1 was followed except that: no microchannel mixing unit was added.
In the detection pool of the comparative example, the volume content of MN (methyl nitrite) in the reaction gas is 5.1 mol%; the concentration of nitric acid in the reducing solution was 503 ppm.
Compared with the comparative example 2, the method has the advantages of small occupied area, small investment and good treatment effect; compared with comparative examples 1 and 3, the method of the invention has the advantages of high conversion rate of the methyl nitrite and low concentration of nitric acid in the reducing solution, wherein the conversion rate of the methyl nitrite is improved by 50% in the preferred example 1 compared with the comparative example 3 which is a non-coupling scheme.
In conclusion, the invention can obviously improve the conversion rate of nitric acid and the concentration of the methyl nitrite in the reaction gas through catalytic reaction and cross-flow mixed reaction.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (10)
1. A nitric acid reduction apparatus, comprising: the microchannel mixing unit and the microchannel catalysis unit are sequentially connected in series;
the micro-channel mixing unit is used for cross-flow mixing of a liquid phase containing nitric acid, methanol and water and a gas containing NO;
the microchannel catalytic unit is used for carrying out nitric acid reduction catalytic reaction on the mixed material from the microchannel mixing unit.
2. The nitric acid reduction plant of claim 1, wherein,
the micro-channel mixing unit comprises a liquid phase feed inlet and a gas phase feed inlet which are arranged at different positions; and/or
The nitric acid reduction device also comprises a detection unit, wherein the detection unit is communicated with the discharge hole of the microchannel catalysis unit and is used for detecting and discharging components of materials;
preferably, the detection unit comprises a detection cell.
3. The nitric acid reduction apparatus of claim 1 or 2, wherein,
the microchannel catalytic unit comprises a single-tube reactor; and/or
The microchannel mixer comprises a multi-stage T-shaped cross-flow channel, preferably comprises 4-10 stages of T-shaped cross-flow channels; and/or
The size of the microchannel mixer is 50-1000 microns, preferably 150-300 microns; and/or
The size of the microchannel catalysis unit is 1000-2000 microns, preferably 1200-1400 microns.
4. A method of reducing nitric acid in a nitric acid reduction unit according to any one of claims 1 to 3, comprising: and (2) enabling a liquid phase containing nitric acid, methanol and water to enter the micro-channel mixer through a liquid phase feed inlet, enabling a gas containing NO to enter the micro-channel mixer through a gas phase feed inlet, carrying out gas-liquid cross-flow mixing and carrying out a primary reaction, enabling the obtained mixed phase to enter a micro-channel catalytic unit for catalytic reaction, and optionally detecting the catalytic reaction material in a detection unit.
5. The method according to claim 4, wherein the microchannel catalytic unit is loaded with a nitrate chemical reduction catalyst, the catalyst comprising an active component and a carrier, the active component being present in the catalyst in an amount comprising, in mass percent: pd0.1-1%, Cu 2-4%, Ce 0.01-0.02%; the carrier is polystyrene resin; preferably, the filling is performed by pressurized filling.
6. The process of claim 4 or 5, wherein the operating conditions in the microchannel mixer comprise:
the feeding amount of the liquid phase containing nitric acid, methanol and water is 5-160L/h;
the flow ratio of the NO-containing gas to the liquid phase feed containing nitric acid, methanol and water is 10-50: 1, preferably 20-30: 1;
the temperature is 70-80 ℃.
7. Process according to any one of claims 4-6, wherein the residence time of the NO-containing gas and the liquid phase comprising nitric acid, methanol and water in the microchannel mixer is in each case 30-200ms, preferably in each case 60-80 ms.
8. The method of any of claims 4-7, wherein the operating conditions of the microchannel catalytic unit comprise: the temperature is 60-100 ℃, preferably 75-78 ℃, the retention time of the mixed solution is 100-500ms, preferably 200-260ms, and the mass ratio of the mixed solution to the catalyst is 1000-2000: 1.
9. the method according to any one of claims 4 to 8,
the molar content of the nitric acid in the liquid phase containing the nitric acid, the methanol and the water is 1-5 mol%, and preferably 0.9-2.1 mol%; the methanol content is 32 to 75 mol%, preferably 40 to 65 mol%; the water content is 10-50 mol%, and the total content of the rest components including NO and methyl nitrite is 0-30 mol%;
preferably, the liquid phase containing nitric acid, methanol and water is waste liquid at the bottom of the esterification tower of the coal-to-ethylene glycol reaction.
10. The method of any one of claims 4-9,
the NO volume content of the NO-containing gas is 5-15 mol%, preferably 6-9 mol%;
preferably, the NO-containing gas is esterification recycle gas generated in the reaction process of preparing the ethylene glycol from coal.
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