CN113617181B - Method and device for removing hydrocarbons in industrial laughing gas by catalytic oxidation method - Google Patents

Method and device for removing hydrocarbons in industrial laughing gas by catalytic oxidation method Download PDF

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Publication number
CN113617181B
CN113617181B CN202110949548.0A CN202110949548A CN113617181B CN 113617181 B CN113617181 B CN 113617181B CN 202110949548 A CN202110949548 A CN 202110949548A CN 113617181 B CN113617181 B CN 113617181B
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laughing gas
hydrocarbon
catalyst
gas
industrial
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CN113617181A (en
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陈剑军
汪民霞
聂俊国
温海涛
徐聪
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Jinhong Gas Co ltd
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Jinhong Gas Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
    • C01B21/22—Nitrous oxide (N2O)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/005—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by heat treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/343—Heat recovery
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/864—Removing carbon monoxide or hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8671—Removing components of defined structure not provided for in B01D53/8603 - B01D53/8668
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24—Nitrogen compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/10—Single element gases other than halogens
    • B01D2257/108—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/502—Carbon monoxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
    • B01D2257/702—Hydrocarbons
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

The invention discloses a device for removing hydrocarbons in industrial laughing gas by a catalytic oxidation method, which is characterized by comprising a gasification system, a heat recovery system and a hydrocarbon removal system which are sequentially connected in series through pipelines, wherein the heat recovery system is connected with a cooling system, and the hydrocarbon removal system is connected with the heat recovery system; the system comprises a heating device and a hydrocarbon removing device, wherein laughing gas is preheated by a heat recovery system and then heated by the heating device to enter the hydrocarbon removing device, and a catalyst is arranged in the hydrocarbon removing device; and the laughing gas after reaction in the dealkylation device circularly flows back to the regenerative system to recycle heat, and finally is cooled by the cooling system. The invention adopts the noble metal-transition metal nitride catalyst for composite use, and the hydrocarbon in the laughing gas is catalyzed, oxidized and removed under the high temperature condition, and meanwhile, the decomposition rate of the laughing gas is inhibited, and the two catalysts are synergistic and mutually promoted, so that the catalytic synergistic effect is realized, and the hydrocarbon in the laughing gas is reduced to below 0.01ppm.

Description

Method and device for removing hydrocarbons in industrial laughing gas by catalytic oxidation method
Technical Field
The invention relates to the technical field of laughing gas purification, in particular to a method and a device for removing hydrocarbons in laughing gas by a catalytic oxidation method.
Background
Laughing gas, which is a powerful greenhouse gas and has a long residence time in the atmosphere and can be transported to the stratosphere, is one of the substances that cause depletion of the ozone layer, has a chemical name nitrous oxide, which is mainly derived from by-products in the production process of adipic acid and nitric acid. Laughing gas is mainly applied to the fields of electronics industry and medicine. Particularly in the electronics industry, electronic grade laughing gas is an indispensable key support material in the manufacture of semiconductor integrated circuits, but has very high purity requirements, at least over 99.999% (5N). Meanwhile, with the continuous development of the electronic industry in China, the electronic grade laughing gas is a necessary basic raw material in the fields of modern photoelectrons, microelectronics, large-scale integrated circuits and optical fiber manufacturing, and obviously, the purity of the electronic grade laughing gas is directly closely related to the quality of downstream products.
At present, the high-purity laughing gas in China mainly depends on import, on one hand, the price is high, and on the other hand, the development of semiconductor technology in China is restricted. The reason is that the purity of laughing gas produced in China is low and the requirements of the production as semiconductor in the photoelectric period cannot be met, so that the development of semiconductor integrated circuits in China is promoted, and the purification technology of the laughing gas in China is urgently needed to be improved.
From the analysis of the existing national conditions in China, the purification of industrial laughing gas is the best technical scheme for obtaining high-purity laughing gas. On one hand, the discharge of laughing gas to the atmosphere is reduced, and on the other hand, the requirements of domestic markets can be met. Chinese patent No. CN105271144A discloses a method for extracting refined N from petrochemical tail gas 2 O equipment and method, and Chinese patent No. 109084527A disclose a laughing gas rectifying and purifying device and a laughing gas rectifying method, which are all aimed at rectifying and purifying industrial-grade laughing gas. However, the purity of laughing gas obtained by the current purification method is low. Analyzing the cause, the impurities except H in industrial laughing gas extracted from the tail gas of petrochemical industry 2 O、CO x 、NO x 、H 2 Besides the impurities, the laughing gas also contains a large amount of hydrocarbon compounds, mainly comprising C2-C4, wherein the content of total hydrocarbon in the purified laughing gas is 15ppm, and the content of total hydrocarbon in the electronic grade is less than or equal to 1ppm. From the following componentsThe hydrocarbon of partial carbon chain in laughing gas can not be removed by adopting the rectification method in the prior art, and the purity of the final laughing gas is affected. Clearly, removal of hydrocarbons from laughing gas is critical to improving technical grade laughing gas. Chinese patent No. CN105271144A discloses a method for extracting refined N from petrochemical industry tail gas 2 In the equipment of O, it is described that ethylene and other impurity gases can be removed, but other hydrocarbons, especially C3 to C4 hydrocarbons, cannot be removed.
Disclosure of Invention
The invention aims to provide a method and a device for removing hydrocarbons in laughing gas by a catalytic oxidation method.
In order to achieve the above object, the present invention has the technical scheme that:
the device for removing hydrocarbons in industrial laughing gas by a catalytic oxidation method comprises a gasification system, a heat recovery system and a hydrocarbon removal system which are connected in series through pipelines in sequence, wherein the heat recovery system is connected with the cooling system, and the hydrocarbon removal system is connected with the heat recovery system; the hydrocarbon removing system comprises a heating device and a hydrocarbon removing device, laughing gas is preheated by a heat returning system and then heated by the heating device to enter the hydrocarbon removing device, a catalyst is arranged in the hydrocarbon removing device, and the catalyst can catalyze and oxidize hydrocarbons and inhibit decomposition of laughing gas.
And the laughing gas after reaction in the dealkylation device circularly flows back to the regenerative system to recycle energy, and finally is cooled by the cooling system.
Preferably, the heat recovery system is a heat recovery heat exchanger, and the cooling system is a cooler.
Preferably, the heating device is an electric heater, and the hydrocarbon removal device is a hydrocarbon removal tower.
In order to achieve another object of the present invention, a method for removing hydrocarbons from industrial laughing gas by using the device for removing hydrocarbons from industrial laughing gas according to the above technical scheme includes: under the condition that the pressure of laughing gas is 1.5-3.0 MPa, the laughing gas is catalyzed by a catalyst at the temperature of 300-480 ℃, and hydrocarbon reacts with oxygen to generate carbon dioxide and water, so that the hydrocarbon in the laughing gas is removed, and meanwhile, the laughing gas can be ensured not to be decomposed under the condition.
Specifically, the method for removing hydrocarbons in industrial laughing gas by catalytic oxidation method comprises the following steps:
(1) Gasifying industrial liquid laughing gas under the pressure of 1.5-3.0 MPa by a gasifier. The gasification can be realized at a temperature of 35 ℃ or above.
(2) The gasified laughing gas flows into a heating device after being preheated by a heat recovery system, is heated to 400-420 ℃, enters a hydrocarbon removal device, the temperature in the hydrocarbon removal device is set to 300-480 ℃, a supported catalyst is arranged in the hydrocarbon removal device, the active components of the catalyst are noble metal and transition metal nitride, hydrocarbon gas in the laughing gas and oxygen react chemically, and after full reaction, the laughing gas returns to the heat recovery system;
(3) Laughing gas flows into a cooling system through a heat recovery system and is cooled.
Preferably, in the step (2), the hydrogen and carbon monoxide impurities in the laughing gas are also fully reacted with oxygen at the same time, so that the hydrogen and carbon monoxide in the laughing gas are removed.
Preferably, step (2) may be cycled multiple times to allow sufficient reaction of the hydrocarbons until the total hydrocarbon content is less than or equal to 0.01ppm.
Preferably, the decomposition rate of laughing gas in the step (2) is less than or equal to 0.3%.
Preferably, the catalyst is Al 2 O 3 As a carrier, the active ingredient is supported on Al 2 O 3 The active component accounts for 0.1 to 15.0 percent of the total mass of the catalyst. Preferably, the active ingredient accounts for 5-10% of the total mass of the catalyst.
Preferably, the active ingredient is a mixture of a noble metal and a transition metal nitride, the transition metal nitride comprising 3 to 8% of the active ingredient, preferably the transition metal nitride comprising 8% of the active ingredient.
In the prior art, H in laughing gas is generally removed by an adsorption method or a fractionation method 2 O、CO 2 、 NO x Such impurities, however, the total hydrocarbon content of the laughing gas (THC) is reduced to 15ppmParticularly the propylene and propane of hydrocarbons are hardly removed. Meanwhile, the laughing gas also comprises trace amounts of other hydrocarbon compounds, which cannot be removed by the method in the prior art, so that the purity of the laughing gas is limited to be improved.
The laughing gas has a boiling point of 88.49 ℃ and is colorless and sweet, is a gaseous oxidant, is very stable at normal temperature and normal pressure, can be decomposed into oxygen and nitrogen at a high temperature of 650 ℃, and starts to be decomposed at a temperature of 350 ℃ under the condition of a catalyst. The general total hydrocarbon content of industrial laughing gas is 15ppm, and the laughing gas is stored in liquid state under the conditions of-25 ℃ and 1.5-3.0 MPa.
The invention adopts the catalytic oxidation method to catalyze and oxidize hydrocarbon including hydrocarbon in industrial laughing gas into carbon dioxide and water, thereby removing the difficult-to-remove part in the laughing gas and directly realizing medical grade or food grade. And then removing carbon dioxide, water and other impurities from the laughing gas with the hydrocarbon removed and a fractionating tower in the prior art, thus obtaining the high-purity electronic-grade laughing gas. The prior art directly uses the technical proposal of direct impurity removal of the fractionating tower, because the presence of hydrocarbons leads to the difficulty of reaching 5N grade.
The technical problem to be solved by the technical scheme of the invention is how to inhibit the decomposition of laughing gas while removing hydrocarbon impurities.
The active component of the catalyst used in the invention is a mixture of noble metal and transition metal nitride, inorganic porous medium alumina is used as a carrier, trace hydrocarbon in laughing gas raw material gas and combustible components such as hydrogen, carbon monoxide and the like are oxidized under the catalysis of noble metal catalysis to generate carbon dioxide and water, so that the quality standard requirement (below 1 ppm) in high-purity laughing gas is met, and the precision of laughing gas after hydrocarbon removal can reach the standards of food grade and medicine grade.
On the other hand, the active ingredient of the catalyst used in the present invention is a mixture of a noble metal, which is mainly used as a catalyst for hydrocarbon oxidation, and a metal nitride, which is an inhibitor for suppressing decomposition of laughing gas at high temperature.
The smile catalytic decomposition principle is as follows: 2N 2 O(g)→2N 2 (g)+O 2 +82kJ/mol. In the standard state, about 82kJ of heat is generated per mole of nitrous oxide decomposition, but energy is input to the nitrous oxide decomposition to convert the molecular state of laughing gas into an active state in which chemical reaction occurs, so as to initiate the decomposition reaction. N (N) 2 O is an asymmetric molecule, the bond groups of N-N and N-O in the structure are about 2.7 and 1.6 respectively, and the N-O bond is easier to open; while opening the N-O bond requires about 250 to 270 kJ.mol-1 of activation energy, N 2 O is decomposed into N 2 And O 2 . Obviously N 2 The O decomposition reaction requires a large amount of heat energy to be consumed. Therefore, the invention improves the N-O bond energy by the catalysis of the transition metal nitride, thereby improving the activation energy of the decomposition reaction and inhibiting N 2 O is decomposed under the reaction conditions of the present invention.
Meanwhile, noble metal/alumina has a catalytic effect on synthesizing laughing gas by nitrogen and oxygen, and inhibits the decomposition reaction of the laughing gas from the reverse reaction direction of decomposition. Therefore, under the dual actions of metal palladium and metal nitride, the activation energy required by nitrogen and oxygen to generate the laughing gas is reduced, and the inhibition effect on the thermal decomposition of the laughing gas is formed, so that the laughing gas cannot realize the decomposition reaction under the conditions of 300-480 ℃ and 1.5-3.0 MPa.
The noble metals are not fully filled with d electron orbitals, the surfaces are easy to adsorb reactants, and the strength is moderate, so that the noble metals are favorable for forming intermediate active compounds, and therefore, the noble metals have higher catalytic activity and can catalyze and oxidize hydrocarbons and other easily-oxidized substances such as hydrogen, carbon monoxide and the like. Meanwhile, the transition metal nitride can also have the function of catalytic oxidation, and after being mixed with noble metal, the transition metal nitride is loaded into alumina to form a uniform porous medium, and can be fully contacted with gas to complete catalytic oxidation reaction.
It is evident that the effect of the catalytic action of the mixture of noble metal and transition metal nitride is not a simple superposition, but rather a result of a mutual synergistic effect.
The reaction process comprises the following steps:
H 2 +O 2 →H 2 O
CO+O 2 →CO 2
C m H n +O 2 →CO 2 +H 2 O
C m H n O K +O 2 →CO 2 +H 2 O。
obviously, in the presence of metallic palladium, not only hydrocarbon in industrial laughing gas is oxidized into water and carbon dioxide, but also other hydrocarbon is subjected to catalytic oxidation reaction, so that the purification of the first part is realized, and the standards of food grade and medicine grade and 2N-3N laughing gas are achieved. The electronic grade laughing gas of 5N grade (99.999%) can be realized only by using the purification process in the prior art.
By adopting the technical scheme, the invention has the following technical effects:
1. the noble metal-transition metal nitride catalyst is used in a compound way, hydrocarbons in the laughing gas are removed by catalytic oxidation at high temperature, meanwhile, the decomposition rate of the laughing gas is inhibited, the two catalysts are synergistic, and the two catalysts are mutually promoted and have catalytic synergistic effects, so that the hydrocarbons in the laughing gas are reduced to below 0.01ppm, medical grade or food grade laughing gas is directly obtained, and a foundation is laid for preparing 5N-grade electronic grade laughing gas.
2. The method removes the laughing gas by catalytic oxidation and simultaneously removes the combustible gas impurities such as hydrogen, carbon monoxide and the like in the laughing gas by catalytic oxidation, so that the impurity content of the hydrogen and the carbon monoxide is reduced to 0.1ppm, and the standard of the electronic grade laughing gas is met.
3. The process flow is simple, the heat is recovered by a heat regenerator circulation preheating method, the energy is saved, and the energy consumption is reduced.
Drawings
FIG. 1 is a schematic diagram of a device for removing hydrocarbons from laughing gas according to embodiment 1 of the present invention.
FIG. 2 is a schematic diagram of the process flow of hydrocarbons in laughing gas according to example 1 of the present invention.
Wherein, 1 a gasifier; 2, a heat regenerator; 3 an electric heater; 301 an electric heating rod; 4a hydrocarbon removal tower; 5. a cooler; 501 inlet; 502 outlet.
Detailed Description
The following description of the embodiments of the present invention will clearly and fully describe the technical solutions of the embodiments of the present invention in conjunction with the specific contents of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
The invention adopts industrial laughing gas as raw material, directly removes hydrocarbons, and then is assisted with an adsorption device in the prior art to realize the production and processing of high-purity laughing gas. The device for removing hydrocarbons in industrial laughing gas comprises a gasification system, a heat recovery system and a hydrocarbon removal system which are connected in sequence through pipelines. The heat recovery system is connected with the cooling system, and the hydrocarbon removal system is connected with the heat recovery system; wherein, the heat recovery system can recover heat; the hydrocarbon removal system is connected with the heat regenerator; the hydrocarbon removing system comprises a heating device and a hydrocarbon removing device, wherein laughing gas is preheated by a heat returning system and then heated by the heating device to enter the hydrocarbon removing device, and a catalyst is arranged in the hydrocarbon removing device; and the laughing gas after reaction in the dealkylation device is circulated and flows back to the regenerative system, and finally is cooled by the cooling system. Preferably, the gasification system is a gasifier, the heating device is an electric heater, the hydrocarbon removal device is a hydrocarbon removal tower, the heat recovery system is a heat regenerator, and the cooling system is a circulating water condenser.
The pressure condition of the hydrocarbon removing equipment is 1.5-3.0 MPa. As shown in FIG. 1, technical grade laughing gas liquid (-25 ℃ C., 1.5-3.0 MPa) is added into a gasifier 1 for gasification, and the gasification temperature is 35 ℃. The gasified laughing gas enters the heat regenerator 2 through a raw material inlet positioned in the middle of the heat regenerator 2 for preheating, and the temperature of the gas flowing out of the heat regenerator 2 is about 250 ℃. The preheated gas enters the electric heater 3, the electric heater 3 controls the heating power of the electric heating rod 301 by adjusting the current, the gas is heated to be quickly heated to 420-430 ℃, then enters the dealkylation tower 4, the temperature in the dealkylation tower 4 is constant to 425+/-5 ℃, a catalyst is arranged in the tower, the gas is fully contacted with the catalyst, hydrocarbon impurities in the gas react with oxygen, the reacted gas flows back into the regenerator 2 from an outlet at the bottom of the dealkylation tower 4, the temperature of the purified gas is reduced in the regenerator 2, the heat of the gas is recovered by the reflux 2, the temperature of the gas is reduced to 150-160 ℃ and enters the condenser 5 for cooling, the condenser is selected as a circulating water cooler, the outer wall of the cooler 5 is reduced by cold water through the inlet 501, the cold water flows out from the outlet 502 at the upper end, the heat of the condenser is taken away, and the temperature of the gas is reduced. The cooled gas flows out from the outlet of the condenser, is filled into bottles or is continuously purified according to the requirement, and enters the fractionator for rectification, so as to remove impurities such as water, carbon dioxide and the like.
The heat in the heat regenerator 2 in the invention is derived from the heat of the purified gas, and the purified gas is returned to the heat regenerator 2 to collect the heat, so that the heat is collected and used for continuously preheating the industrial-grade laughing gas raw material to be purified.
The active ingredients of the catalyst used in the invention are noble metal and transition metal nitrides, alumina is used as a carrier, and the active ingredients are loaded on the surface of a porous medium of the alumina to increase the surface area, thereby being beneficial to the dispersion of the active ingredients and enabling the active ingredients to be fully contacted with gas. Ultrafine particles are adopted, so that the ultrafine particles can be uniformly distributed, the contact area with gas can be increased, and meanwhile, the interaction between the noble metal and the oxide carrier of the supported noble metal catalyst taking aluminum oxide as the carrier can form a synergistic effect to promote the catalytic activity of active ingredients. The preparation method can adopt the methods of jet milling, ball milling and the like to control the particle size of the active ingredient of the powder to be 80-150 microns, then the powder is uniformly mixed and then is loaded on an alumina carrier, and the alumina carrier can adopt a layered or honeycomb carrier. The loading method may be a method of the prior art.
The active component of the catalyst accounts for 0.1-15% of the total mass of the catalyst, preferably the active component of the catalyst accounts for 5-10% of the total mass of the catalyst. Wherein the transition metal nitride accounts for 3-10% of the active component by mass, and preferably the transition metal nitride accounts for 5-8% of the active component by mass.
As a preferred embodiment, the noble metal may be selected from one or more of palladium, platinum, rhodium, gold, silver.
As a preferred embodiment, the transition metal nitride may be selected from at least one of cobalt, nickel, cadmium, copper, iron, vanadium, zinc, manganese.
Referring to fig. 2, the process flow of the present invention comprises the following steps: (1) The industrial liquid laughing gas (-25 ℃, 1.5-3.0 MPa) is gasified by a gasifier. (2) The gasified laughing gas flows into a heating device after being preheated by a heat regenerator, is heated and heated, and enters a hydrocarbon removal device, a catalyst is arranged in the hydrocarbon removal device, the active components of the catalyst are transition metal nitrides, hydrocarbon compounds including hydrocarbon gases in the laughing gas, hydrogen and carbon monoxide react with oxygen chemically under the action of the catalyst, and after full reaction, the laughing gas returns to the heat regenerator to recover energy; this step may be cycled through multiple times. (3) After the combustible impurity components in the laughing gas are completely reacted, the purified laughing gas flows into a cooling system through a heat regenerator to be cooled; (4) Collecting purified laughing gas, and filling bottles or further entering a fractionating tower for impurity removal according to the requirement to obtain the laughing gas with higher purity. The laughing gas after the process can reach 3N level.
The technical scheme and technical effects of the invention for removing hydrocarbons in industrial-grade laughing gas are further described by specific examples.
Example 1
(1) The industrial liquid laughing gas (-25 ℃, 1.5-3.0 MPa) is gasified in the gasifier 1, and the gasification temperature is 35 ℃.
(2) The gasified laughing gas flows into the electric heater 3 after being preheated to 250 ℃ by the heat regenerator 2, the current of the electric heater 3 is regulated, the gas is quickly heated to 400+/-5 ℃ and then enters the dealkylation tower, the dealkylation tower 3 is internally provided with a catalyst, the active components of the catalyst are metal palladium and copper nitride, the content of the catalyst is 1% of the total mass percentage of the catalyst, and the copper nitride accounts for 15% of the mass percentage of the mixture of the metal palladium and the copper nitride.
The hydrocarbon including hydrocarbon gas in the laughing gas and the hydrogen and the carbon monoxide react with the oxygen under the action of the catalyst, and after the full reaction, the laughing gas returns to the regenerator 2;
(3) After the combustible impurity components in the laughing gas are completely reacted, the purified laughing gas flows into a cooling system through a heat regenerator to be cooled;
(4) Collecting purified laughing gas and detecting.
Example 2
The difference from example 1 is that the catalyst active ingredient content is 0.1% by mass of the total catalyst, and copper nitride is 8% by mass of the mixture of metallic palladium and copper nitride.
Example 3
The difference from example 1 is that the catalyst active ingredient content is 5% by mass of the total catalyst, and the copper nitride is 8% by mass of the mixture of metallic palladium and copper nitride.
Example 4
The difference from example 1 is that the catalyst active ingredient content is 3% by mass of the total catalyst, and the copper nitride accounts for 8% by mass of the mixture of metallic palladium and copper nitride.
Example 5
The difference from example 1 is that the catalyst active ingredient content is 5% by mass of the total catalyst, and copper nitride is 10% by mass of the mixture of metallic palladium and copper nitride.
Example 6
The content of the catalyst active ingredient was 5% by mass of the total catalyst, and copper nitride was 5% by mass of the mixture of metallic palladium and copper nitride, differing from example 3.
Example 7
The content of the catalyst active ingredient was 15% by mass of the total catalyst, and copper nitride was 8% by mass of the mixture of metallic palladium and copper nitride, as distinguished from example 3.
Example 8
The content of the catalyst active ingredient was 8% by mass of the total catalyst, and copper nitride was 8% by mass of the mixture of metallic palladium and copper nitride, as distinguished from example 3.
Example 9
The difference from example 3 is that the temperature of the gas in the dealkylation column is 300.+ -. 5 ℃.
Example 10
The difference from example 3 is that the temperature of the gas in the dealkylation column is 420.+ -. 5 ℃.
Example 11
The difference from example 3 is that the temperature of the gas in the dealkylation column is 480.+ -. 5 ℃.
Example 12
The catalyst is distinguished from example 3 in that the active ingredients are rhodium metal and copper nitride, the content of which is 5% of the total mass of the catalyst, and the copper nitride is 8% of the mass of the mixture of palladium metal and copper nitride.
Example 13
The catalyst is distinguished from example 3 in that the active ingredients are rhodium metal and nickel nitride, the content of which is 5% of the total mass of the catalyst, and the nickel nitride is 8% of the mass of the mixture of rhodium metal and nickel nitride.
Example 14
The difference from example 3 is that the catalyst has active ingredients of metallic palladium and nickel nitride, the content of which is 5% of the total mass of the catalyst, and the nickel nitride accounts for 8% of the mass of the mixture of metallic palladium and nickel nitride.
Example 15
The difference from example 3 is that the catalyst has active ingredients of metallic palladium and cobalt nitride, the content of which is 5% of the total mass of the catalyst, and the cobalt nitride accounts for 8% of the mass of the mixture of metallic palladium and cobalt nitride.
Example 16
The difference from example 3 is that the catalyst has active ingredients of metal platinum and cobalt nitride, the content of which is 5% of the total mass of the catalyst, and the cobalt nitride accounts for 8% of the mass of the mixture of the metal platinum and the cobalt nitride.
Example 17
The difference from example 3 is that the catalyst has active ingredients of metal platinum and copper nitride, the content of which is 5% of the total mass of the catalyst, and the copper nitride accounts for 8% of the mass of the mixture of the metal platinum and the copper nitride.
Example 18
The difference from example 3 is that the catalyst has active ingredients of metallic silver and copper nitride, the content of which is 5% of the total mass of the catalyst, and the copper nitride accounts for 8% of the mass of the mixture of metallic silver and copper nitride.
The laughing gas purified in examples 1-17 was subjected to detection of total hydrocarbon content and detection of decomposition rate of laughing gas.
Comparative example 1
The difference from example 1 is that the catalyst in the dealkylation column is only metallic palladium/alumina.
Comparative example 2
The difference from example 1 is that the catalyst in the dealkylation column is only cobalt nitride/alumina.
The total hydrocarbon content detection method comprises the following steps: see GB/T8984-2008 for gas chromatography for determination of carbon monoxide, carbon dioxide and hydrocarbons in a gas.
Detection instrument: the Shimadzu gas chromatograph GC-14C, a hydrogen Flame Ionization (FID) detector was used.
Chromatographic column: GDX-104, 1m long, 4mm inside diameter, column temperature 90 ℃.
Detector temperature: 100 ℃.
Gas: high-purity hydrogen with the flow rate of 33-60 mL/min.
Carrier gas: the flow rate of the high-purity oxygen is 4.8-10 mL/min.
Purification column for carrier gas oxygen: the length of the catalyst was 20cm and the inner length was 4cm, and a platinum and palladium mixture was supported on an alumina carrier in an amount of 0.3% based on the carrier and used at 350 ℃.
Laughing gas decomposition rate detection: and respectively detecting the content of nitrogen in the laughing gas raw material and the purified laughing gas to calculate the decomposition rate of the laughing gas.
The results of the measurements are shown in Table 1.
As is clear from Table 1, the total hydrocarbon content was reduced from 15ppm to 0.01ppm or less in the raw material, and the combustible gases of carbon monoxide and hydrogen were also reduced to 0.1ppm, because carbon monoxide and hydrogen were also catalyzed to undergo oxidation-reduction reaction to produce carbon dioxide and water.
Specifically, from examples 1 to 6, it was found that example 3 had the best effect of removing hydrocarbons and removing carbon monoxide and hydrogen, while the decomposition rate of laughing gas was the lowest, examples 8 and 6 times. Namely, the content of the active component of the catalyst is 5 percent of the total mass of the catalyst, and the best implementation mode is that the copper nitride accounts for 8 percent of the mass of the mixture of the metallic palladium and the copper nitride.
Example 2 and example 4 have the same copper nitride content, but have the ability to remove hydrocarbons, remove other combustible gases, and inhibit the decomposition rate of laughing gas, and obviously, there is a synergistic effect between metallic palladium and copper nitride, mutually reinforcing, and promoting both the hydrocarbon removal and the inhibition of the decomposition of laughing gas.
Examples 6 and 7 show that merely increasing the catalyst content does not increase the efficiency of the hydrocarbon removal and decrease the decomposition rate of laughing gas.
As can be seen from examples 2 to 8, the higher the catalyst content, the more preferably the copper nitride content is 8% by mass of the active ingredient, whereas the 10% tends to decrease. When the content of copper nitride is 5% by mass of the active ingredient, the decomposition rate of laughing gas is the lowest.
The decomposition rates of laughing gas in example 3 and examples 7-9 were respectively: 0.071%, 0.089%, 0.071% and 0.266%, the temperature of the dealkylation column was 400 ℃, 300 ℃, 420 ℃ and 480 ℃, respectively. It can be seen that the effect of the dealkylation is better as the temperature increases, but the decomposition rate of laughing gas increases as it is, and the decomposition rate of laughing gas is close to 400-420 ℃ and 300 ℃ but increases rapidly when the temperature reaches 480 ℃.
In conclusion, at 300-480 ℃, the decomposition rate of laughing gas is lower than 0.3% in the presence of a catalyst, and the total hydrocarbon content after hydrocarbon removal is lower than 0.01ppm.
Examples 10-16 are comparative examples of catalytic action of mixtures of different noble metals with transition metal nitrides under the same conditions. As can be seen from the results of Table 1, the effect of the dealkylation was more similar in the same case. Specifically, the palladium metal effect is better, rhodium and platinum are less, and the catalysis effect of the copper nitride is stronger than that of other transition metal nitrides such as nickel nitride and cobalt nitride after being mixed with the copper nitride.
As is clear from the results of the tests of comparative example 1 and comparative example 2 in Table 1, the total hydrocarbon content, hydrogen gas content and carbon monoxide content of laughing gas in the presence of only a single catalyst were higher than those in the presence of both catalysts. In particular, the decomposition rate of laughing gas reached 3% in the presence of only the transition metal nitride, whereas the decomposition rate of laughing gas was only 2.81% when the two catalysts were mixed under the same conditions (example 1). While the total hydrocarbon content reaches 3ppm only in the presence of metallic palladium, the total hydrocarbon content can be removed to below 0.01ppm when the two are simultaneously used. That is, noble metals, in addition to catalyzing the oxidation of hydrocarbons, carbon monoxide and hydrogen, are also capable of inhibiting laughing gas decomposition in conjunction with transition metal nitrides and vice versa.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. A method for removing hydrocarbons in industrial laughing gas by a catalytic oxidation method is characterized in that under the condition of the pressure of 1.5-3.0 MPa, the hydrocarbons, carbon monoxide and hydrogen react with oxygen to generate carbon dioxide and water through catalysis at 300-480 ℃ to remove the hydrocarbons in the laughing gas, wherein the active component of the catalyst is a mixture of noble metal and transition metal nitride, the active component of the catalyst accounts for 0.1-15% of the total mass of the catalyst, the transition metal nitride accounts for 3-10% of the active component by mass, the noble metal is one or more selected from palladium, platinum, rhodium, gold and silver, and the transition metal nitride is at least one selected from cobalt, nickel, cadmium, copper, iron, vanadium, zinc and manganese.
2. The method for removing hydrocarbons from industrial laughing gas by catalytic oxidation according to claim 1, comprising the steps of:
(1) Gasifying industrial liquid laughing gas through a gasifier under the pressure of 1.5-3.0 MPa;
(2) Preheating gasified laughing gas by a heat recovery system, flowing into a heating device, heating to 400-420 ℃, entering a hydrocarbon removal device, arranging a supported catalyst in the hydrocarbon removal device, carrying out chemical reaction on hydrocarbon gas in the laughing gas and oxygen at the temperature of 300-480 ℃ in the hydrocarbon removal device, and returning the laughing gas to the heat recovery system after full reaction;
(3) Laughing gas flows into a cooling system through a heat recovery system, and is cooled and collected.
3. The method for removing hydrocarbons from industrial laughing gas by catalytic oxidation according to claim 2, wherein in step (2), hydrogen and carbon monoxide in laughing gas are also fully reacted with oxygen at the same time, and hydrogen and carbon monoxide in laughing gas are removed.
4. The method for removing hydrocarbons from technical-grade laughing gas by catalytic oxidation according to claim 2, wherein the step (2) can be circulated for a plurality of times to enable the hydrocarbons to fully react until the total hydrocarbon content is less than or equal to 0.01ppm.
5. The method for removing hydrocarbons from industrial-grade laughing gas by catalytic oxidation according to claim 2, wherein the decomposition rate of laughing gas in step (2) is less than or equal to 0.3%.
6. The method for removing hydrocarbons from industrial laughing gas by catalytic oxidation according to any one of claims 1-5, wherein the catalyst is Al 2 O 3 As a carrier, the active ingredient is supported on Al 2 O 3 Is carried on a carrier of (a).
7. The method for removing hydrocarbons from industrial laughing gas by catalytic oxidation according to claim 1, wherein the transition metal nitride accounts for 3-8% of the active ingredient by mass.
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