CN115055204A

CN115055204A - Catalyst suitable for low-temperature plasma and preparation method and application thereof

Info

Publication number: CN115055204A
Application number: CN202210821163.0A
Authority: CN
Inventors: 边文璟; 竹涛; 韩一伟; 朱繁; 郝景章; 金梦野; 史光; 李加旺
Original assignee: China University of Mining and Technology Beijing CUMTB; MCC Capital Engineering and Research Incorporation Ltd
Current assignee: China University of Mining and Technology Beijing CUMTB; MCC Capital Engineering and Research Incorporation Ltd
Priority date: 2022-07-13
Filing date: 2022-07-13
Publication date: 2022-09-16
Anticipated expiration: 2042-07-13
Also published as: CN115055204B

Abstract

The invention provides a catalyst suitable for low-temperature plasma and a preparation method and application thereof. The catalyst comprises a metal active component and a molecular sieve carrier; the metal active component comprises Mn and Ce and one or more of Co, Cu, Mo, Ni and Fe in terms of atomic molar ratio: mn: ce ═ 1:2:1-1:6: 4. The preparation method of the catalyst comprises the following steps: mixing the molecular sieve carrier with the solution containing metal salt, adding Na ₂ CO ₃ ‑NaHCO ₃ Buffering the solution, aging, drying and roasting to obtain the catalyst. The invention uses coal-based solid waste as raw material to synthesize the low-temperature plasma discharge bodyThe catalyst has simple synthesis process and uses waste to prepare waste; and a low-temperature plasma-double circulation catalyst system is constructed, so that the deep purification of different types of VOCs in the steel industry is realized.

Description

Catalyst suitable for low-temperature plasma and preparation method and application thereof

Technical Field

The invention relates to a catalyst suitable for low-temperature plasma and a preparation method and application thereof, belonging to the technical field of molecular sieve catalysts.

Background

The efficient purification of VOCs (volatile organic compounds) is a key link and a serious challenge in the prevention and control of atmospheric pollution. At present, the high energy consumption and high pollution industries such as ferrous metallurgy, electric energy, chemical industry, waste incineration and mechanical manufacturing industry have rapidly increased scale, so that the problem of regional atmosphere composite pollution caused by discharge of VOCs is more and more severe. Promoting the ultralow emission modification of enterprises in the industries of steel, cement and coking. In 2025, VOCs and NO _x The total emission amount is respectively reduced by more than 10 percent in 2020, and PM2.5 and O are realized ₃ And the pollution of the VOCs in the steel industry is controlled in a coordinated manner. VOCs in the steel industry mainly come from sintering and coking processes. VOCs are formed from volatile substances in raw fuels such as coke and oil-containing scale, and under certain operating conditions, PCDDs and PCDFs are formed simultaneously. For the coking process, the waste gas of VOCs mainly comes from coking, chemical production areas and sewage treatment areas.The main components of VOCs in the coking section comprise benzene series and non-methane total hydrocarbon; the VOCs in the chemical production area mainly comprise benzene series, naphthalene, phenol, non-methane total hydrocarbon, hydrogen sulfide, ammonia and the like. The waste gas in the sewage treatment area mainly comprises benzene series, hydrogen sulfide and ammonia, and has the characteristics of large gas quantity, low concentration, high water content and the like. Therefore, the condition of VOCs waste gas in the steel coking industry is complex, and the characteristic difference of the VOCs waste gas in each section is large.

Aiming at the problem, the synergistic deep purification of different VOCs in the steel industry is realized by utilizing the advantages of the NTP (low temperature plasma) synergistic catalysis technology, such as broad spectrum, high removal efficiency, high energy yield, good economy and the like, on pollutants. At present, in the atmosphere of VOCs mixed flue gas in the steel coking industry, a catalyst is easily affected by sulfur, chlorine and water, so that most of the catalyst is poisoned, and the synergistic effect with NTP is reduced. Under the NTP catalytic coupling system, the molecular sieve is used as a non-carbon-based carrier, and can provide an active space for a catalytic system and disperse active oxides. Meanwhile, the micro-porous and mesoporous characteristics or the specific surface complex structure are provided for a reaction system, so that the supported catalyst is provided with strong stability. In particular, the microporous molecular sieve has larger specific surface area and synergistic action of micro-discharge under the pore diameter of the micropores, so that the microporous molecular sieve has wide application in the pollutant degradation by the transformation of NTP. At present, Mn-based catalytic materials are widely applied in the NTP field, mainly due to the stable structure, higher oxidation-reduction capability and relatively low cost. Is commonly used for SCR-NH ₃ Catalytic oxidation of VOCs, Hg ⁰ Adsorption oxidation, and the like. By to MnO _x The modification is focused on improving the discharge stability and the surface performance of the composite oxide, and the transition and rare earth elements are combined with Mn to form the composite oxide, so that the catalytic performance of a system can be enhanced.

Wang et al utilize CeO ₂ -MnO _x The catalyst adopts IPC (built-in plasma catalytic system) discharge mode to realize the highest toluene removal efficiency and CO ₂ The selectivity was 95.94% and 90.73%, respectively. With CeO alone ₂ And MnO _x In contrast, the combination of Ce and Mn allows the catalyst to have a larger specific surface area, and the interaction between Ce-Mn improves the mobility of oxygen and oxygenThe concentration of vacancies. Under the catalytic coupling reaction system with NTP, O can be reacted ₃ The conversion to more active oxygen takes part in the reaction of toluene, more active oxygen is produced, and the degradation intermediate products adsorbed on the catalyst surface are deeply oxidized by active oxygen to the final products (Chemical Engineering Journal,2017,322: 679-69). Thus, CeO ₂ The catalyst has good oxygen storage capacity, and simultaneously, the catalyst and the NTP have good synergistic effect due to the synergistic effect of Mn and Ce.

CN111921374A discloses a method for catalyzing and degrading chlorobenzene by using a two-stage discharge plasma and a preparation method of a used catalyst. Wherein, the double-stage discharge plasma can better utilize a large amount of active substances and ozone generated in the discharge process, thereby fully utilizing the energy efficiency. The invention emphasizes that Cl element can cause the poisoning of a Co-Mn-O catalytic system in the degradation process of chlorobenzene, and a carrier TiO is adopted ₂ The overall pore structure of the catalyst is improved, and the Cl resistance of the catalyst is improved through the modification of the additive, so that the influence caused by catalyst poisoning is effectively relieved. Through an aging experiment for 50h, the catalyst still maintains higher chlorobenzene degradation efficiency and CO ₂ And (4) selectivity.

However, the above-mentioned article (Chemical Engineering Journal,2017,322:679-69) only considers CeO under conventional laboratory test strips ₂ -MnO _x The catalyst and NTP exhibit good synergy. The smoke components of the actual working conditions of the steel industry are complex, in particular to the sintering and coking processes. The chemical production area and the sintering flue gas contain S, Cl and NH ₃ Component (B) of these elements not only with CeO ₂ -MnO _x Mn in the catalyst reacts to reduce the content of active components and occupy active sites on the surface, and generated aerosol is attached to the surface of the catalyst to block pore channels, so that the catalytic oxidation process is influenced. CN111921374A takes into account the influence of Cl on the catalyst poisoning, and modified TiO is adopted ₂ As a carrier, the pore size distribution of the carrier is improved. But TiO 2 ₂ The photocatalytic synergistic effect of the carrier and low-temperature plasma is examined, and meanwhile, TiO ₂ Does not have a high specific surface area and also has a pore diameter which is not developed. By a series of modificationsAnd correspondingly increases the cost of the whole process.

CN108295866A discloses spinel CoMn for catalytic oxidation of VOCs ₂ O ₄ A catalyst prepared by an oxalic acid sol-gel process. The synthetic catalyst is single crystal phase CoMn ₂ O ₄ The catalyst has the advantages of higher specific surface area, better low-temperature reduction performance and higher oxygen flow performance. CN113385184A discloses a Mn-Co-La composite catalyst for catalyzing and degrading VOCs by low-temperature plasma. By constructing Mn-Co-O solid solution, Co-Mn mixed crystal phase is formed, thereby forming a large amount of lattice defects. And the doped La element enters the Mn-Co-O solid solution crystal lattice to partially replace manganese ions or cobalt ions, so that more crystal lattice defects are formed, the oxygen mobility of the catalyst under the IPC reaction condition is favorably improved, and the oxidative degradation of VOCs is promoted.

Under the conditions of continuous discharge IPC and PPC (external plasma catalytic system) systems, the pollution degradation by free radicals is a main reaction process, and the catalyst is required to have better oxygen storage-evolution capacity, so that oxygen transmission and O can be accelerated ₃ Conversion capability, more oxygen active free radicals and hydroxyl free radicals are provided for reaction, and simultaneously, the by-product O can be reduced ₃ And (5) discharging. In CN108295866A, the spinel catalyst system with a single crystal phase has high oxygen flow performance, but the oxygen storage capacity of the Co-Mn system is weaker. Meanwhile, in a Mn-Co-La solid solution system in CN113385184A, only Mn provides catalytic active sites, and the performance is insufficient due to the insufficient active sites.

Disclosure of Invention

In order to solve the above technical problems, the present invention aims to provide a catalyst suitable for low temperature plasma, and a preparation method and an application thereof. The catalyst suitable for low-temperature plasma provided by the invention can realize deep purification of different types of VOCs in the steel industry.

In order to achieve the above object, the present invention firstly provides a catalyst suitable for low temperature plasma, the catalyst comprising a metal active component and a molecular sieve support; the metal active component comprises Mn and Ce and one or more of Co, Cu, Mo, Ni and Fe in terms of atomic molar ratio, wherein the metal active component comprises one or more of Co, Cu, Mo, Ni and Fe in combination: mn: ce ═ 1:2:1-1:6:4 (i.e., 1 (2-6): 1-4)).

In the above catalyst suitable for low temperature plasma, preferably, the metal active component includes Mn and Ce, and one or a combination of Mo, Co and Cu, in terms of atomic molar ratio, and one or a combination of Mo, Co and Cu: mn: ce ═ 1:2:1-1:6: 4. More preferably, the metal active component comprises Mn, Ce and Mo, in atomic molar ratios, Mo: mn: ce ═ 1:2:1 to 1:6:4, and particularly preferably, Mo: mn: ce ═ 1:2:1-1:2:3 (i.e., 1:2 (1-3)); or the metal active component comprises Mn, Ce and Co, in terms of atomic molar ratio, Co: mn: ce ═ 1:2:1-1:6:4, more preferably, Co: mn: ce ═ 1:2:1-1:2:3 (i.e., 1:2 (1-3)); or the metal active component comprises Mn, Ce and Cu, in terms of atomic molar ratio, Cu: mn: ce ═ 1:2:1-1:6:4, and more preferably, Cu: mn: ce ═ 1:2:1-1:2:3 (i.e., 1:2 (1-3)).

In the catalyst suitable for low-temperature plasma, preferably, the molecular sieve support comprises one or more of a 13X molecular sieve, a ZSM-type molecular sieve, an MCM-type molecular sieve, and the like. More preferably, the molecular sieve support is a 13X molecular sieve.

In the catalyst suitable for low-temperature plasma, preferably, the content of the metal active component is 10% to 30% by weight based on the total weight of the catalyst, and the content of the metal active component is based on the weight of the metal oxide.

In the catalyst suitable for low-temperature plasma, preferably, the 13X molecular sieve is prepared by the following steps: carrying out classification treatment on the fly ash; then mixing the graded fly ash, an aluminum source, a silicon source, a hard template, seed crystals and NaOH in water to obtain a mixed solution; stirring the mixed solution, and then aging to obtain initial gel; and crystallizing the initial gel, and at least drying and roasting to obtain the 13X molecular sieve.

In the catalyst applicable to low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the fly ash includes fluidized bed fly ash.

In the above catalyst to which low-temperature plasma is applied, preferably, in the step of preparing the 13X molecular sieve, the classification treatment includes hydrochloric acid washing and/or sodium hydroxide washing. More preferably, the classification process includes: firstly, carrying out hydrochloric acid pickling on the fly ash, and then carrying out sodium hydroxide alkaline washing. Wherein, the hydrochloric acid pickling conditions comprise: adopting concentrated hydrochloric acid with the mass fraction of 20-36.5%, the solid-liquid ratio is 1:1-5:1, the reaction temperature is 60-90 ℃, and stirring and reacting for 1-3 h; the sodium hydroxide alkaline washing conditions comprise: the solid-liquid ratio is 1:3-1:6 (excessive sodium hydroxide), the alkalinity of the sodium hydroxide solution is more than 10 (the pH value is about more than 12), the reaction temperature is 70-100 ℃, and the stirring reaction is carried out for 1-3h (sealing). The speed of rotation of the stirrer can be adjusted as is customary to the person skilled in the art. The invention carries out classification treatment on the fly ash to purify the Al source and the Si source.

In the above catalyst applicable to low temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the aluminum source includes an aluminum soluble inorganic salt, such as sodium metaaluminate (NaAlO) ₂ ) One or more of aluminum sulfate, aluminum nitrate and the like.

In the above catalyst suitable for low temperature plasma, preferably, in the preparation step of the 13X molecular sieve, the silicon source includes a silicon-soluble inorganic salt, such as sodium silicate (Na) ₂ SiO ₃ ) Tetraethoxysilane, silica sol, water glass, kaolin and ultrafine SiO ₂ And the like, or combinations thereof.

In the catalyst suitable for low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the hard template includes one or a combination of carbon nanotubes, porous silicon templates, carbon black and the like.

In the above catalyst suitable for low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the seed crystal comprises a 13X molecular sieve seed crystal, and the pore volume of the 13X molecular sieve seed crystal is 0.1-0.4cm ³ Per g, pore diameter of 1.4-2.5nm, and the crystal size is 1.2-1.5 μm.

In the catalyst to which low-temperature plasma is applied, it is preferable that in the step of preparing the 13X molecular sieve, 75 to 80 parts by weight of the classified fly ash, 1 to 3 parts by weight of the aluminum source, the silicon source, the hard template, 6 to 8 parts by weight of the seed crystal, and 5 to 20 parts by weight of NaOH (which is solid sodium hydroxide) are mixed in water. The amounts of the aluminum source and the silicon source added are calculated so that the silica-alumina ratio of the initial gel is 3 to 11, and are not limited herein.

In the catalyst applicable to low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the alkalinity of the mixed solution is 8 to 10.

In the catalyst using low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the temperature for stirring the mixed solution is room temperature to 60 ℃, more preferably 40 to 60 ℃, and the stirring time is 20min to 1 h. The rotation speed of the stirring is slow stirring, and the specific speed can be adjusted by the ordinary skilled person. The stirring can be performed by adopting a heat collection type magnetic stirrer.

In the catalyst applicable to low-temperature plasma, preferably, in the preparation step of the 13X molecular sieve, the aging temperature is 70-90 ℃ and the aging time is 6-12 h.

In the above catalyst suitable for low temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the molar ratio of silica to alumina in the initial gel is 3 to 11, more preferably 4 to 6.

In the catalyst suitable for low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the crystallization temperature is 120-. The crystallization may be carried out in a high pressure autoclave with a polytetrafluoroethylene liner. After crystallization is finished, conventional steps of suction filtration, washing and the like can be carried out until the pH value of the filtrate is neutral, and then subsequent drying and roasting are carried out.

In the catalyst using low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the drying temperature is 75-115 ℃ and the drying time is 6-12 h. The drying may be carried out in an oven.

In the catalyst suitable for low-temperature plasma, preferably, in the preparation step of the 13X molecular sieve, the calcination temperature is 450-550 ℃ and the calcination time is 3-6 h. The firing may be performed in a muffle furnace.

In the catalyst applicable to low-temperature plasma, preferably, in the step of preparing the 13X molecular sieve, the step (1) further comprises tabletting and sieving with a 40-60 mesh sieve after roasting to obtain the 13X molecular sieve.

In the above catalyst suitable for low temperature plasma, preferably, the 13X molecular sieve has a crystal size of 1.2-1.5 μm, a pore diameter of 1.5-2nm, and a pore volume of 0.14-0.4cm ³ A specific surface area of 300-700m ² (ii) in terms of/g. More preferably, the 13X molecular sieve has a crystal size of 1.2-1.5 μm, a pore diameter of 1.5-2nm, and a pore volume of 0.2-0.4cm ³ A specific surface area of 600-700m ² /g。

According to an embodiment of the present invention, preferably, the catalyst suitable for low temperature plasma is prepared by the following steps:

mixing a molecular sieve carrier with a solution containing a metal salt to obtain a dispersion liquid; mixing Na ₂ CO ₃ -NaHCO ₃ Adding a buffer solution into the dispersion liquid, aging, and at least drying and roasting to obtain the catalyst suitable for the low-temperature plasma; wherein the solution containing the metal salt is a solution containing a Mn salt, a Ce salt and one or more of a Co salt, a Cu salt, a Mo salt, a Ni salt and a Fe salt, and in the solution containing the metal salt, one or more of Co, Cu, Mo, Ni and Fe are combined in terms of atomic molar ratio: mn: ce ═ 1:2:1-1:6: 4.

Wherein, more preferably, the solution containing the metal salt is a solution containing a combination of a Mn salt and a Ce salt, and one or more of a Co salt, a Cu salt and a Mo salt, and in the solution containing the metal salt, one or more of Mo, Co and Cu are combined in terms of atomic molar ratio: mn: ce ═ 1:2:1-1:6: 4. Particularly preferably, the solution containing the metal salt is a solution containing a Mn salt, a Ce salt, and a Mo salt, and in the solution containing the metal salt, in terms of atomic molar ratio, Mo: mn: ce ═ 1:2:1-1:6: 4; most preferably, Mo: mn: ce ═ 1:2:1-1:2: 3; or the solution containing a metal salt is a solution containing a Mn salt, a Ce salt, and a Co salt, and in the solution containing a metal salt, in terms of atomic molar ratio, Co: mn: ce ═ 1:2:1-1:6: 4; most preferably, the molar ratio, in atomic terms, of Co: mn: ce ═ 1:2:1-1:2: 3; or the solution containing the metal salt is a solution containing a Mn salt, a Ce salt, and a Cu salt, and in the solution containing the metal salt, in terms of atomic molar ratio, Cu: mn: ce ═ 1:2:1-1:6: 4; most preferably, the molar ratio, in terms of atomic mole ratios, of Cu: mn: ce ═ 1:2:1-1:2: 3.

According to an embodiment of the present invention, preferably, the catalyst suitable for low temperature plasma has a crystal size of 1.2-2.5 μm, a pore diameter of 1.7-2.6nm, and a pore volume of 0.2-0.36cm ³ A specific surface area of 360- ² (ii) in terms of/g. More preferably, the catalyst suitable for low temperature plasma has a crystal size of 1.2-2.5 μm, a pore diameter of 1.7-2.6nm, and a pore volume of 0.2-0.36cm ³ A specific surface area of 420- ² /g。

According to an embodiment of the present invention, preferably, the catalyst suitable for low temperature plasma has a combination of metal active components of spinel X-Mn-O (crystal phase structure) and fluorite Ce-O (crystal phase structure), wherein X is Mo, Co, Cu, Ni or Fe; more preferably, the low temperature plasma-compatible catalyst has a combination of metal active components of spinel X-Mn-O (crystal phase structure) and fluorite Ce-O (crystal phase structure), where X is Mo, Co or Cu.

The second aspect of the present invention provides a preparation method of the catalyst suitable for low temperature plasma, which comprises the following steps:

mixing a molecular sieve carrier with a solution containing a metal salt to obtain a dispersion liquid; mixing Na ₂ CO ₃ -NaHCO ₃ Adding a buffer solution into the dispersion liquid, aging, and at least drying and roasting to obtain the catalyst suitable for low-temperature plasma; it is composed ofWherein the solution containing the metal salt is a solution containing a combination of a Mn salt and a Ce salt, and one or more of a Co salt, a Cu salt, a Mo salt, a Ni salt and a Fe salt, and in the solution containing the metal salt, one or more of Co, Cu, Mo, Ni and Fe in terms of atomic molar ratio: mn: ce ═ 1:2:1-1:6: 4.

In the above preparation method, preferably, the solution containing a metal salt is a solution containing a Mn salt and a Ce salt, and one or a combination of several of a Co salt, a Cu salt, and a Mo salt, and in the solution containing a metal salt, one or a combination of several of Mo, Co, and Cu is in terms of atomic molar ratio: mn: ce ═ 1:2:1-1:6: 4. More preferably, the solution containing a metal salt is a solution containing a Mn salt, a Ce salt, and a Mo salt, and in the solution containing a metal salt, in terms of atomic molar ratio, Mo: mn: ce ═ 1:2:1-1:6: 4; particularly preferably, Mo: mn: ce ═ 1:2:1-1:2: 3; or the solution containing the metal salt is a solution containing a Mn salt, a Ce salt, and a Co salt, and in the solution containing the metal salt, in terms of atomic molar ratio, Co: mn: ce ═ 1:2:1-1:6: 4; particularly preferably, the molar ratio of Co: mn: ce ═ 1:2:1-1:2: 3; or the solution containing the metal salt is a solution containing a Mn salt, a Ce salt, and a Cu salt, and in the solution containing the metal salt, in terms of atomic molar ratio, Cu: mn: ce ═ 1:2:1-1:6: 4; particularly preferably, the molar ratio of Cu: mn: ce ═ 1:2:1-1:2: 3.

In the above-mentioned production method, preferably, the total concentration of the metal salts in the metal salt-containing solution is 0.001 to 0.003M. The solvent in the solution may be absolute ethanol.

In the above preparation method, preferably, the Mn salt includes manganese nitrate and/or manganese acetate, and the like.

In the above-described production method, preferably, the Ce salt includes cerium acetate, cerium nitrate, or the like.

In the above preparation method, preferably, the Co salt includes cobalt acetate and/or cobalt nitrate, and the like.

In the above-described production method, preferably, the Cu salt includes copper acetate, copper nitrate, or the like.

In the above preparation method, preferably, the Mo salt includes molybdenum acetate and/or molybdenum nitrate, and the like.

In the above-described production method, preferably, the Ni salt includes nickel acetate, nickel nitrate, or the like.

In the above preparation method, preferably, the Fe salt includes iron acetate and/or iron nitrate, and the like.

In the above preparation method, preferably, the molecular sieve support comprises one or a combination of several of 13X molecular sieve, ZSM type molecular sieve, MCM type molecular sieve, and the like. More preferably, the molecular sieve support is a 13X molecular sieve. More preferably, the 13X molecular sieve is prepared by the above 13X molecular sieve preparation steps of the present invention.

In the above preparation method, preferably, the ratio of the molecular sieve support to the total amount of the metal salt in the solution containing the metal salt is such that the content of the metal active component is 10% to 30% based on the total weight of the catalyst, and the content of the metal active component is based on the weight of the metal oxide. Namely, the dosage ratio of the molecular sieve carrier and the metal salt solution in the preparation process is calculated according to the metal loading in the prepared catalyst.

In the above preparation method, preferably, the molecular sieve support is mixed with a solution containing a metal salt, and the mixture is subjected to ultrasonic treatment for 20 to 60 minutes to obtain the dispersion. The ultrasonic treatment time is too long to hydrolyze the metal solution into gel flocs, so the preparation method of the invention preferably adopts the ultrasonic treatment time of 20-60min, and the power and frequency of the ultrasonic treatment can be adjusted by the ordinary skilled person. Further, more preferably, the above preparation method may further include the steps of: one or two drops of nitric acid solution are added dropwise during ultrasonic treatment.

In the above-mentioned production method, preferably, the Na ₂ CO ₃ -NaHCO ₃ The concentration of the buffer solution is 0.3-0.5mol/L (the concentration is Na) ₂ CO ₃ And NaHCO ₃ Total concentration of (c). More preferably, the Na ₂ CO ₃ -NaHCO ₃ In a buffer solutionNa ₂ CO ₃ And NaHCO ₃ In a molar ratio of 1:1 to 3: 1.

In the above-mentioned production method, preferably, Na is added ₂ CO ₃ -NaHCO ₃ A buffer solution is added to the dispersion to bring the pH of the dispersion to 8-10 (more preferably 8-9).

In the above preparation method, preferably, the aging temperature is 75 to 90 ℃ and the aging time is 18 to 24 hours. More preferably, the aging is carried out in an oil bath.

In the above-mentioned production method, after the aging is completed, the conventional steps such as washing and separation may be carried out. For example, deionized water and absolute ethyl alcohol can be used for repeatedly washing and aging the obtained product to be neutral, and suction filtration can be adopted for separation.

In the above preparation method, preferably, the drying temperature is 85-120 ℃ and the drying time is 8-16 h.

In the above preparation method, preferably, the roasting process is: heating to 120-140 ℃ at the rate of 3-6 ℃/min, keeping the temperature for 0.5-1h, then heating to 500-600 ℃ at the rate of 3-6 ℃/min, and keeping the temperature for 2-4 h.

In the above preparation method, after calcination, the calcined product may be subjected to conventional tabletting, sieving, etc. to finally obtain the catalyst suitable for low temperature plasma.

In the above preparation method, preferably, the prepared catalyst suitable for low temperature plasma has a crystal size of 1.2-2.5 μm, a pore diameter of 1.7-2.6nm, and a pore volume of 0.2-0.36cm ³ A specific surface area of 360- ² /g。

In the preparation method, the prepared catalyst suitable for low-temperature plasma is preferably powder, and the particle size of the catalyst powder is 40-60 meshes.

In a third aspect, the present invention provides a use of the above catalyst suitable for low temperature plasma as a catalyst in purifying VOCs by using low temperature plasma.

In the above application, preferably, the low temperature plasma is a Dielectric Barrier (DBD) discharge low temperature plasma.

In the above application, preferably, the low-temperature plasma employs an internal plasma catalytic system (IPC) and/or an external plasma catalytic system (PPC).

In the above application, preferably, the discharge parameters of the internal plasma catalysis system (IPC) and the external plasma catalysis system (PPC) are respectively: the discharge voltage is 11-18kV, and the discharge frequency is 200-300 Hz. More preferably, the discharge voltage is 17-18 kV.

In the application, the space velocity is preferably 20000-40000h ^-1 。

In the above application, preferably, the VOCs include one or a combination of several of benzene series, naphthalene, phenol, dioxin, trichlorobenzene, malodorous gas, and the like. Wherein the benzene series mainly comprises toluene, and the malodorous gas mainly comprises H ₂ S and/or NH ₃ And the like. The present invention attributes persistent organic pollutants to VOCs as well.

In the above application, the conversion of the benzene-based compound is preferably 98% or more, more preferably 99% or more.

In the above application, the conversion rate of dioxin and/or trichlorobenzene is preferably 84% or more.

In the above application, preferably, the conversion rate of the malodorous gas is 99% or more.

The invention provides a catalyst suitable for low-temperature plasma and a preparation method and application thereof. The catalyst provided by the invention can be applied to purification and treatment of VOCs in the steel industry. The catalyst suitable for low-temperature plasma provided by the invention is preferably a metal-loaded molecular sieve catalyst prepared by synthesizing a carrier 13X molecular sieve through hydrothermal method directional regulation and control and then performing coprecipitation. Then, the invention constructs a low-temperature plasma catalysis coupling system, develops a degradation experiment for degrading main VOCs pollutants in the steel industry by the coupling system, and mainly comprises dioxin-like substances, benzene series substances and malodorous gases (NH) ₃ And H ₂ S), and the like.

The invention surrounds the situation that the steel industry has various VOCs types and great difficulty in emission reduction, prevention and controlThe characteristics of broad spectrum, high removal efficiency, good economy and the like of the low-temperature plasma technology on pollutants are fully utilized; and a low-temperature plasma catalysis coupling technology is adopted to realize the cooperative control of multiple pollutants. The invention mainly develops around three key technologies: 1. the invention discloses a microporous structure effect, which takes coal-based solid waste fly ash as a raw material, directionally regulates and controls a carrier 13X molecular sieve by a hydrothermal method, and prepares Mo (or Co or Cu or Ni or Fe) by a coprecipitation method _a Mn _b Ce _c O _x catalyst/13X (preferably Mo (or Co or Cu) _a Mn _b Ce _c O _x a/13X catalyst). The catalyst has stronger surface discharge and pore diameter micro discharge in a low-temperature plasma discharge system, and strengthens the low-temperature plasma discharge effect. 2. The invention has the advantages that the catalyst not only has good catalytic activity and S, Cl resistance of the spinel structure catalyst, but also has fluorite CeO under a low-temperature plasma reaction system by constructing the metal combination of spinel structure Mo (or Co or Cu or Ni or Fe) -Mn-O (preferably Mo (or Co or Cu) -Mn-O) and fluorite Ce-O ₂ Has strong oxygen storage capacity. 3. The mass transfer strengthening effect of the multistage reaction is generated under a low-temperature plasma discharge system ₃ The Mo (or Co or Cu or Ni or Fe) -Mn (preferably Mo (or Co or Cu) -Mn) and Mn-Ce-O in the synergistic double-circulation system are converted into active oxygen free radicals at high speed, so that the number of free radicals in the reaction system is increased, and the high-efficiency and rapid removal of various pollutants is realized.

The catalyst suitable for low-temperature plasma and the preparation method and application thereof provided by the invention have the following beneficial effects:

1. the coal-based solid waste is used as a raw material to synthesize the catalyst suitable for the low-temperature plasma discharge system, the synthesis process is simple, the waste is prepared from the waste, and the resource saving is realized;

2. constructing a low-temperature plasma-dual cycle catalyst system, and realizing the deep purification of different kinds of VOCs in the steel industry under the synergistic action of a plurality of effects of a microporous structure effect, a metal combination effect and a multistage reaction mass transfer enhancement effect, wherein benzene series substances are(toluene), dioxins (trichlorobenzenes) (which attribute persistent organic pollutants to VOCs) and mixed malodors (H) ₂ S and NH ₃ ) The conversion rates respectively reach 99 percent, 84 percent and 100 percent; provides theoretical guidance for VOCs synergetic and integrated treatment in the steel industry.

Drawings

FIG. 1 is a scanning electron microscope image of the fly ash used as the raw material in examples 1 and 2.

FIG. 2N of the catalyst and 13X molecular sieve carrier prepared in examples 1 and 2 ₂ Adsorption and desorption isotherm graphs.

FIG. 3 shows Cu prepared in example 1 ₁ Mn ₂ Ce ₃ O _x X-ray diffraction pattern of/13X catalyst.

FIG. 4 shows Co prepared in example 2 ₁ Mn ₂ Ce ₃ O _x X-ray diffraction pattern of/13X catalyst.

FIG. 5a is Cu prepared in example 1 ₁ Mn ₂ Ce ₃ O _x An X-ray photoelectron spectrum O1s diagram of the/13X catalyst.

FIG. 5b shows Co prepared in example 2 ₁ Mn ₂ Ce ₃ O _x An X-ray photoelectron spectrum O1s diagram of the/13X catalyst.

FIG. 6 shows Cu prepared in example 1 ₁ Mn ₂ Ce ₃ O _x Scanning electron micrographs of the/13X catalyst.

FIG. 7 shows Co prepared in example 2 ₁ Mn ₂ Ce ₃ O _x Scanning electron micrographs of the/13X catalyst.

FIG. 8 is N of the catalyst prepared in comparative example 1 ₂ Adsorption and desorption isotherm graphs.

FIG. 9 is a graph showing the effect of different catalysts and different discharge voltages on toluene conversion in IPC discharge mode.

FIG. 10a is a graph showing the effect of different catalysts and different discharge voltages on carbon dioxide selectivity in IPC discharge mode.

FIG. 10b is a graph showing the effect of different catalysts and different discharge voltages on carbon balance in IPC discharge mode.

Fig. 11 is a graph of the catalytic stability of the four catalysts prepared in comparative example 1.

FIG. 12a shows different catalysts, different energy densities vs. H in PPC discharge mode ₂ Graph of the effect of S conversion.

FIG. 12b shows different catalysts, different energy densities versus NH in PPC discharge mode ₃ Graph of the effect of conversion.

FIG. 13 is a graph showing the effect of different catalysts and different discharge voltages on the trichlorobenzene conversion in the IPC discharge mode.

FIG. 14 is a graph of the results of multiple cycle stability tests for different catalysts.

Detailed Description

The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.

According to the specific embodiment of the present invention, preferably, the catalyst suitable for low temperature plasma of the present invention is prepared by the following steps:

(1) preparation of 13X molecular sieve carrier:

the method comprises the following steps of (1) adopting fluidized bed coal ash as a raw material, and firstly carrying out classification treatment on the coal ash to purify an Al source and a Si source; the classification processing includes: firstly, carrying out hydrochloric acid pickling on the fly ash, and then carrying out sodium hydroxide alkaline washing; wherein, the hydrochloric acid pickling conditions comprise: adopting concentrated hydrochloric acid with the mass fraction of 20-36.5%, the solid-liquid ratio is 1:1-5:1, the reaction temperature is 60-90 ℃, and stirring and reacting for 1-3 h; the sodium hydroxide alkaline washing conditions comprise: the solid-liquid ratio is 1:3-1:6 (excessive sodium hydroxide), the alkalinity of the sodium hydroxide solution is more than 10, the reaction temperature is 70-100 ℃, and the stirring reaction is carried out for 1-3h (sealing); the rotational speed of the stirring can be adjusted as is customary by the person skilled in the art; after the hydrochloric acid washing is carried out on the fly ash, the conventional steps of separating, washing and the like can be carried out, and then the sodium hydroxide alkali washing is carried out;

then according to the weight portion, 75-80 portions of coal ash after grading treatment are mixed with 1-3 portions of aluminium source, silicon source, hard template, 6-8 portions of seed crystal and 5-2 portions of NaOH (which is solid sodium hydroxide)0 part by weight of aluminum source and silicon source are mixed in deionized water, and the adding amount of the aluminum source and the silicon source is such that the silicon-aluminum ratio of the initial gel is 3-11 (more preferably 4-6), a mixed solution is obtained, and the alkalinity of the mixed solution is 8-10; wherein the aluminum source comprises sodium metaaluminate (NaAlO) ₂ ) One or more of aluminum sulfate, aluminum nitrate and the like, wherein the silicon source comprises sodium silicate (Na) ₂ SiO ₃ ) Tetraethoxysilane, silica sol, water glass, kaolin and ultrafine SiO ₂ The hard template comprises one or more of carbon nano tube, porous silicon template, carbon black and the like, the seed crystal comprises a 13X molecular sieve seed crystal, and the pore volume of the 13X molecular sieve seed crystal is 0.1-0.4cm ³ Per g, the aperture is 1.4-2.5nm, and the crystal size is 1.2-1.5 μm; slowly stirring the mixed solution by using a heat collection type magnetic stirrer at room temperature to 60 ℃ (more preferably 40 to 60 ℃), wherein the stirring time is 20min to 1 h; aging for 6-12h at 70-90 deg.C to obtain initial gel; then transferring the initial gel to a high-pressure reaction kettle with a polytetrafluoroethylene lining, and crystallizing for 48-64h at the temperature of 120-; then, carrying out suction filtration and washing until the pH value of the filtrate is neutral; drying at 75-115 ℃ for 6-12h in an oven, roasting at 550 ℃ for 3-6h in a muffle furnace at 450-; the crystal particle size of the 13X molecular sieve is 1.2-1.5 mu m, the pore diameter is 1.5-2nm, and the pore volume is 0.14-0.4cm ³ A specific surface area of 300-700m ² (ii)/g; more preferably, the 13X molecular sieve has a crystal size of 1.2-1.5 μm, a pore diameter of 1.5-2nm, and a pore volume of 0.2-0.4cm ³ A specific surface area of 600-700m ² /g；

(2) Preparation of the catalyst:

mixing the 13X molecular sieve carrier prepared in the step (1) with a solution containing metal salt, and carrying out ultrasonic treatment for 20-60min to obtain a dispersion liquid; wherein the solution containing the metal salt is a solution containing a Mn salt, a Ce salt and one or more of a Co salt, a Cu salt and a Mo salt, and in the solution containing the metal salt, the molar ratio of atoms of one or more of Mo, Co and Cu is as follows: mn: ce ═ 1:2:1-1:6: 4; more preferably, the solution containing a metal salt is a solution containing a Mn salt, a Ce salt, and a Mo salt, and in the solution containing a metal salt, in terms of atomic molar ratio, Mo: mn: ce ═ 1:2:1-1:6: 4; particularly preferably, Mo: mn: ce ═ 1:2:1-1:2: 3; or the solution containing the metal salt is a solution containing a Mn salt, a Ce salt, and a Co salt, and in the solution containing the metal salt, in terms of atomic molar ratio, Co: mn: ce ═ 1:2:1-1:6: 4; particularly preferably, the molar ratio of Co: mn: ce ═ 1:2:1-1:2: 3; or the solution containing the metal salt is a solution containing a Mn salt, a Ce salt, and a Cu salt, and in the solution containing the metal salt, in terms of atomic molar ratio, Cu: mn: ce ═ 1:2:1-1:6: 4; particularly preferably, the molar ratio of Cu: mn: ce ═ 1:2:1-1:2: 3;

the total concentration of the metal salt in the solution containing the metal salt is 0.001-0.003M, and the solvent in the solution is absolute ethyl alcohol; the Mn salt comprises manganese nitrate and/or manganese acetate and the like, the Ce salt comprises cerium acetate and/or cerium nitrate and the like, the Co salt comprises cobalt acetate and/or cobalt nitrate and the like, the Cu salt comprises copper acetate and/or copper nitrate and the like, and the Mo salt comprises molybdenum acetate and/or molybdenum nitrate and the like;

na was added using a Buchner funnel at a rate of about 1 drop/s ₂ CO ₃ -NaHCO ₃ A buffer solution is slowly added dropwise to the dispersion, the Na ₂ CO ₃ -NaHCO ₃ The concentration of the buffer solution is 0.3-0.5mol/L (the concentration is Na) ₂ CO ₃ And NaHCO ₃ Total concentration of) the Na ₂ CO ₃ -NaHCO ₃ Na in buffer solution ₂ CO ₃ And NaHCO ₃ In a molar ratio of from 1:1 to 3:1, so that the pH of the dispersion is from 8 to 10 (more preferably from 8 to 9);

then aging in oil bath for 18-24h at 75-90 ℃; then repeatedly washing the aging product to be neutral by using deionized water and absolute ethyl alcohol, and performing suction filtration; then drying for 8-16h at 85-120 ℃ in an oven, then heating to 140 ℃ at the speed of 3-6 ℃/min in a muffle furnace, keeping for 0.5-1h, then heating to 600 ℃ at the speed of 3-6 ℃/min, and keeping for 2-4 h; then tabletting and sieving by a 40-60 mesh sieve to obtain the catalyst suitable for low-temperature plasma.

The total metal loading is 10-30% of the total weight of the catalyst suitable for low-temperature plasma, and the loading is the weight of metal oxide.

The prepared catalyst suitable for low-temperature plasma has crystal particle size of 1.2-2.5 μm, pore diameter of 1.7-2.6nm, and pore volume of 0.2-0.36cm ³ A specific surface area of 360- ² (ii)/g; more preferably, the catalyst suitable for low temperature plasma has a crystal size of 1.2-2.5 μm, a pore diameter of 1.7-2.6nm, and a pore volume of 0.2-0.36cm ³ A specific surface area of 420- ² /g。

Example 1

This example provides a catalyst suitable for low temperature plasma, which is prepared by the following steps:

(1) preparation of 13X molecular sieve carrier:

pretreatment of raw materials: the fluidized bed fly ash is used as a raw material, an SEM image of the raw material is shown in figure 1, the fly ash is not serious in sintering phenomenon and is in spherical distribution, and the element distribution is measured by XRF and is shown in table 1; firstly, carrying out classification treatment on the fly ash to purify an Al source and a Si source; the classification processing includes: firstly, carrying out hydrochloric acid pickling on the fly ash, and then carrying out sodium hydroxide alkaline washing; wherein, the hydrochloric acid pickling conditions comprise: adopting concentrated hydrochloric acid with the mass fraction of 20-36.5%, the solid-liquid ratio is 1:1-5:1, the reaction temperature is 60-90 ℃, and stirring and reacting for 1-3 h; the sodium hydroxide alkaline washing conditions comprise: the solid-liquid ratio is 1:3-1:6 (excessive sodium hydroxide), the alkalinity of the sodium hydroxide solution is more than 10, the reaction temperature is 95 ℃, and the stirring reaction is carried out for 1h (plugging); the speed of rotation of the stirrer can be adjusted as is customary to those skilled in the art; after the fly ash is subjected to hydrochloric acid washing, the conventional steps of separation, washing and the like can be carried out, and then sodium hydroxide alkali washing is carried out;

TABLE 1 chemical composition of raw fly ash

Chemical composition	SiO ₂	Al ₂ O ₃	Fe ₂ O ₃	MgO	CaO	Na ₂ O	K ₂ O
								Mass fraction (%)	43.53	35.343	4.132	1.091	7.4	0.129	0.436

Preparing a molecular sieve carrier: then, according to the parts by weight, mixing 75-80 parts of pulverized fuel ash after grading treatment with 1-3 parts of aluminum source, silicon source and hard template, 6-8 parts of seed crystal and 5-20 parts of solid NaOH in deionized water, wherein the adding amount of the aluminum source and the silicon source is such that the silicon-aluminum ratio of the initial gel is 4-5, so as to obtain a mixed solution, and the alkalinity of the mixed solution is 8-10; wherein the aluminum source is sodium metaaluminate (NaAlO) ₂ ) The silicon source is sodium silicate(Na ₂ SiO ₃ ) The hard template is a carbon nano tube, the seed crystal is a 13X molecular sieve seed crystal, and the pore volume of the 13X molecular sieve seed crystal is 0.1-0.4cm ³ G, the aperture is 1.4-2.5nm, and the crystal size is 1.2-1.5 mu m; slowly stirring the mixed solution by adopting a heat collection type magnetic stirrer at 40-60 ℃ for 30 min; aging for 6-12h at 70-90 deg.C to obtain initial gel; then transferring the initial gel into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and crystallizing for 48 hours at 180 ℃; then, carrying out suction filtration and washing until the pH value of the filtrate is neutral; drying in an oven at 100 ℃ for 12h, roasting in a muffle furnace at 450 ℃ for 6h, tabletting, and sieving with a 40-60-mesh sieve to obtain a 13X molecular sieve carrier;

(2) preparation of the catalyst:

mixing the 13X molecular sieve carrier prepared in the step (1) with a solution containing metal salt, and carrying out ultrasonic treatment for 60min to obtain a dispersion liquid; wherein the solution containing the metal salt is a solution containing a Mn salt, a Ce salt and a Cu salt; the total concentration of the metal salts in the solution containing the metal salts is 0.001-0.003M, and the molar ratio of the metal ions in the solution is Cu: mn: ce 1:2: 3; the solvent in the solution is absolute ethyl alcohol; the Mn salt is Mn (CHCOO) ₂ The Ce salt is Ce (NO) ₃₎₃ ·6H ₂ O, the Cu salt is Cu (NO) ₃ ) ₂ ·3H ₂ O；

Na was added at a Buchner funnel speed of about 1 drop/s ₂ CO ₃ -NaHCO ₃ A buffer solution is slowly added dropwise to the dispersion, the Na ₂ CO ₃ -NaHCO ₃ The concentration of the buffer solution is 0.3-0.5mol/L (the concentration is Na) ₂ CO ₃ And NaHCO ₃ Total concentration of) the Na ₂ CO ₃ -NaHCO ₃ Na in buffer solution ₂ CO ₃ And NaHCO ₃ In a molar ratio of 1:1 to 3:1, so that the pH value of the dispersion is 8 to 9;

then aging in oil bath for 18-24h at 75-90 ℃; then repeatedly washing the aging product to be neutral by using deionized water and absolute ethyl alcohol, and performing suction filtration; then dried in an oven at 120 ℃ for 12h and then in a muffle furnace at 5 DEG CHeating to 130 ℃ at a speed of/min, keeping the temperature for 0.5h to remove residual water, heating to 500-550 ℃ at a speed of 5 ℃/min, and keeping the temperature for 4 h; then tabletting and sieving by a 40-60 mesh sieve to obtain the catalyst suitable for low-temperature plasma, which is marked as Cu ₁ Mn ₂ Ce ₃ O _x and/13X. To prepare the obtained Cu ₁ Mn ₂ Ce ₃ O _x The total metal loading was 20% based on the total weight of the/13X catalyst and was based on the weight of metal oxide.

Example 2

This example provides a catalyst suitable for low temperature plasma, which is prepared substantially in the same manner as in example 1, except that: the solution containing the metal salt is a solution containing a Mn salt, a Ce salt and a Co salt; the total concentration of the metal salts in the solution containing the metal salts is 0.001-0.003M, and the molar ratio of the metal ions in the solution is Co: mn: ce 1:2: 3; the solvent in the solution is absolute ethyl alcohol; the Mn salt is Mn (CHCOO) ₂ Said Ce salt is Ce (NO) ₃₎₃ ·6H ₂ O, the Co salt is Co (NO) ₃ ) ₂ ·6H ₂ And O. The catalyst prepared in this example and suitable for low temperature plasma was recorded as Co ₁ Mn ₂ Ce ₃ O _x and/13X. To prepare the obtained Co ₁ Mn ₂ Ce ₃ O _x The total metal loading was 20% based on the total weight of the/13X catalyst and was based on the weight of metal oxide.

N reaction of the catalysts prepared in examples 1 and 2 and 13X molecular sieve carrier ₂ Isothermal adsorption-desorption, XRD, SEM, XPS analysis, the results are as follows.

TABLE 2 specific surface area, pore volume and pore diameter of catalyst and molecular sieve support

Sample name	S _BET (m ² /g)	Pore volume (cm) ³ /g)	Average pore diameter (nm)
				13X molecular sieve	634.8	0.24	1.57
Cu ₁ Mn ₂ Ce ₃ O _x /13X	426.216	0.2689	2.37
				Co ₁ Mn ₂ Ce ₃ O _x /13X	561.1451	0.3537	2.531

FIG. 2 shows the catalysts prepared in examples 1 and 2 and N on 13X molecular sieve support ₂ Adsorption and desorption isotherm graphs. Table 2 shows the specific surface area, pore volume and pore diameter of the catalyst prepared in examples 1 and 2 and the 13X molecular sieve support. FIG. 3 shows Cu prepared in example 1 ₁ Mn ₂ Ce ₃ O _x XRD pattern of/13X catalyst. FIG. 4 shows Co prepared in example 2 ₁ Mn ₂ Ce ₃ O _x XRD pattern of/13X catalyst. FIG. 5a is Cu prepared in example 1 ₁ Mn ₂ Ce ₃ O _x O1s diagram for the/13X catalyst; FIG. 5b shows Co prepared in example 2 ₁ Mn ₂ Ce ₃ O _x O1s diagram of/13X catalyst. FIG. 6 shows Cu prepared in example 1 ₁ Mn ₂ Ce ₃ O _x SEM image of/13X catalyst. FIG. 7 shows Co prepared in example 2 ₁ Mn ₂ Ce ₃ O _x SEM image of/13X catalyst.

It can be seen that examples 1 and 2 of the present invention successfully produced Cu ₁ Mn ₂ Ce ₃ O _x catalyst/13X, Co ₁ Mn ₂ Ce ₃ O _x a/13X catalyst. Cu prepared in examples 1 and 2 of the present invention ₁ Mn ₂ Ce ₃ O _x catalyst/13X, Co ₁ Mn ₂ Ce ₃ O _x catalyst/13X, all presenting a single spinel Co (Cu) ₁ Mn ₂ O ₄ Crystal phase structure and single fluorite CeO ₂ The crystal phase structure, and the crystal form of the carrier 13X molecular sieve is regular, and the carrier has larger specific surface area and developed aperture. In addition, in the catalyst, the metal active component is stably loaded on the surface of the molecular sieve carrier and has more chemisorption oxygen, so that the catalyst has Mo (or Co or Cu) -Mn and Mn-Ce-O synergistic double circulation, the mass transfer process of active free radical oxygen on the surface of the catalyst can be accelerated, the reaction rate is improved, the 'multi-component synergistic effect' of metal is realized, and the catalyst and low-temperature plasma show good synergistic effect.

Comparative example 1

This comparative example provides a binary catalyst prepared essentially the same as example 1 except that: the solution containing the metal salt is a solution containing a Cu salt, a Ce salt or a Co salt and a Mn salt; the total concentration of metal salts in the solution containing metal salts is 0.001-0.003M, and the molar ratio of metal ions in the solution is Co or Ce or Cu: mn is 1: 1; the solvent in the solution is absolute ethyl alcohol; the Mn salt is Mn (CHCOO) ₂ The Ce salt is Ce (NO3) 3.6H 2O, the Co salt is Co (NO3) 2.6H 2O, and the Cu salt is Cu (NO) ₃ ) ₂ ·3H ₂ And (O). The difference is that: a ZSM-5 type molecular sieve is adopted as a carrier, has a mesoporous structure and is commercially available in catalyst factories of Tianjin university. The catalyst prepared in this comparative example was noted as CoMn/13X, MnCe/13X, CuMn/13X, MnCe/ZSM-5. The total metal loading was 20% based on the total weight of the catalyst prepared, and the loading was based on the weight of metal oxide.

Table 3 shows the specific surface area, pore volume and pore diameter of the catalyst prepared in comparative example 1. N of catalyst prepared in comparative example 1 ₂ The adsorption and desorption isotherms are shown in FIG. 8.

TABLE 3 specific surface area, pore volume and pore diameter of comparative catalysts

Sample name	S _BET (m ² /g)	Pore volume (cm) ³ /g)	Average pore diameter (nm)
				CuMn/13X	397.7	0.25	1.41
MnCe/13X	443.5	0.36	1.5
				MnCe/ZSM-5	376	0.29	1.44
CoMn/13X	425.3	0.31	1.47

Example 3

This example provides Cu suitable for low temperature plasma prepared in examples 1 and 2 ₁ Mn ₂ Ce ₃ O _x catalyst/13X, Co ₁ Mn ₂ Ce ₃ O _x the/13X catalyst is respectively used as a catalyst in the purification of VOCs by using low-temperature plasma.

The industrial production of VOCs by steel mainly comprises: benzene series, naphthalene and phenol. Toluene was selected as the target contaminant for the reaction. The IPC discharge mode is adopted, and the reaction conditions are set as follows: toluene with the concentration of 600ppm is introduced, and the space velocity is 40000h ^-1 Water content: 50 percent, the particle size of the catalyst is 40-60 meshes, the loading amount of the metal active component is 20 percent (taking the total weight of the catalyst as a reference), the discharge voltage is 11-18kV, and the discharge frequency is 300 Hz. The gas flow rate is set to be 1L/min through the empty tower gas velocity and the residence time.

For comparison, the MnCe/13X catalyst prepared in comparative example 1 and the 13X molecular sieve prepared in example were used as a comparison of the degradation effects. Fig. 9, fig. 10a and fig. 10b show the reaction results, where fig. 9 is a graph showing the influence of different catalysts and different output voltages on the toluene conversion rate, fig. 10a is a graph showing the influence of different catalysts and different output voltages on the carbon dioxide selectivity, and fig. 10b is a graph showing the influence of different catalysts and different output voltages on the carbon balance. It can be seen that Co ₁ Mn ₂ Ce ₃ O _x the/13X catalyst has higher toluene conversion rate, and the toluene conversion rate eta (Co) is higher when the voltage is 18kV ₁ Mn ₂ Ce ₃ O _x /13X)，η(Cu ₁ Mn ₂ Ce ₃ O _x 13X) can respectively reach 99.4 percent and 98.2 percent. Co ₁ Mn ₂ Ce ₃ O _x /13X，Cu ₁ Mn ₂ Ce ₃ O _x S of/13X _CO2 And CB reached 93.8% and 99.1%, 87.6% and 95.8%, respectively, achieving almost complete conversion of toluene.

For comparison, catalytic performance experiments were conducted using the four catalysts prepared in comparative example 1. The IPC discharge mode is adopted, and the reaction conditions are set as follows: toluene with the concentration of 600ppm is introduced, and the space velocity is 40000h ^-1 Water content: 50 percent, the particle size of the catalyst is 40-60 meshes, the loading amount of the metal active component is 20 percent (taking the total weight of the catalyst as a reference), and the discharge frequency is 300 Hz. The stability of the four catalysts in the catalytic system was measured at input voltages of 16kV and 18kV, alternating every 5h, and the performance of the catalyst stability is shown in fig. 11. After 20h continuous working condition experiments, compared with the prepared MnCe/ZSM-5, the MnCe/13X has larger specific surface area and pore volume, and meanwhile, in the 20h test, good stability can be kept. It can be seen that the 13X molecular sieve obtained by the specific preparation method is used as a carrier, and has more excellent technical effects.

Example 4

The steel industry sewage treatment process VOCs mainly comprises: benzene series, malodorous gas (NH) ₃ And H ₂ S), selecting mixed malodorous gas (NH) ₃ And H ₂ S) as the target contaminant of the reaction. In this embodiment, the malodorous gas has a small concentration and a large amount of gas, so the PPC discharge mode is adopted mainly to reduce the concentration of the by-products. The MnCe/13X catalyst prepared in comparative example 1 was used as a comparison for degradation effect.

Setting the initial concentration, C _o (H ₂ S)＝240mg/m ³ ，C _o (NH ₃ )＝120mg/m ³ The space velocity is 40000h ^-1 Discharge voltage 11-18kV, discharge frequency 200Hz, gas flow 5L/min, corresponding energy density: SED is 80J/L-300J/L, water content: 50 percent. Experimental result H ₂ S and NH ₃ The conversion is shown in fig. 12a and 12 b. When SED is at 288J/L, the conversion rate of mixed malodors reaches a maximum. Wherein Co ₁ Mn ₂ Ce ₃ O _x The maximum conversion of the/13X catalyst was 99.8%. 99.3%, almost complete removal was achieved. The conversion in NTP (Non-thermal Plasma, i.e. low temperature Plasma reactor without catalyst filling) mode was the lowest, only 78.2%, 82.4%.

Example 5

The sintering procedure VOCs in the steel industry mainly comprises the following steps: selecting trichlorobenzene as a dioxin substitute as a target pollutant, and controlling the initial concentration C of the trichlorobenzene by adopting an IPC (International patent medicine) discharge mode _tcb ＝10mg/m ³ Gas velocity Q2L/min, mixed gas: NO, SO ₂ HCl with concentration of 240ppm, 140ppm and 100ppm respectively, and space velocity of 40000h ^-1 The discharge frequency is 300Hz, and the discharge voltage is 11kV-17 kV. As shown in FIG. 13, when the discharge voltage reached 17kV, the trichlorobenzene conversion efficiency in the mixed pollutant system reached the highest, and the conversion rate was 84.98% or more, which resulted in stable emission of trichlorobenzene up to the standard.

Example 6

In the operating conditions for degrading mixed malodorous gases in the PPC mode, the durability of the catalyst is a key factor. In a reaction system for catalyzing and degrading mixed malodorous gas by low-temperature plasma, SO is contained in the generated by-products ₄ ^2- 、SO ₃ ^2- And NH ₄ ⁺ The formed aerosol can adhere to the surface of the catalyst, resulting in catalyst deactivation. This example therefore investigates the tolerance of the catalyst in the PPC discharge mode.

Setting the initial concentration C of the mixed malodorous gas _o (H ₂ S)＝240mg/m ³ ，C _o (NH ₃ )＝120mg/m ³ SED is 300(J/L), gas flow is 5L/min, and space velocity is 40000h ^-1 The system operation period is 5 cycles. Each cycle was 5 hours. The MnCe/13X catalyst prepared in comparative example 1 was used for comparison. The results are shown in fig. 14, and the experimental results show that the overall conversion of the catalyst to mixed malodors is maintained above 82%, wherein Co of the examples of the invention is Co ₁ Mn ₂ Ce ₃ O _x catalyst,/13X, Cu ₁ Mn ₂ Ce ₃ O _x Catalyst for NH 13X ₃ And H ₂ The overall S conversion was maintained above 86%, which was higher than 82.1% and 82.5% of the MnCe/13X catalyst of comparative example 1.

Claims

1. A catalyst suitable for low-temperature plasma, which comprises a metal active component and a molecular sieve carrier; the metal active component comprises Mn and Ce and one or more of Co, Cu, Mo, Ni and Fe in terms of atomic molar ratio, wherein the metal active component comprises one or more of Co, Cu, Mo, Ni and Fe in combination: mn: ce ═ 1:2:1-1:6: 4.

2. The catalyst suitable for low-temperature plasma according to claim 1, wherein the metal active component comprises Mn and Ce, and one or more of Mo, Co and Cu, in terms of atomic molar ratio: mn: ce ═ 1:2:1-1:6: 4;

preferably, the metal active component comprises Mn, Ce and Mo, in atomic molar ratios, Mo: mn: ce ═ 1:2:1-1:6: 4; more preferably, Mo: mn: ce ═ 1:2:1-1:2: 3;

or the metal active component comprises Mn, Ce and Co, in terms of atomic molar ratio, Co: mn: ce ═ 1:2:1-1:6: 4; more preferably, the molar ratio, in atomic terms, of Co: mn: ce ═ 1:2:1-1:2: 3;

or the metal active component comprises Mn, Ce and Cu, in terms of atomic molar ratio, Cu: mn: ce ═ 1:2:1-1:6: 4; more preferably, the molar ratio, in terms of atomic mole ratio, of Cu: mn: ce ═ 1:2:1-1:2: 3.

3. The catalyst applicable to low-temperature plasma according to claim 1, wherein the molecular sieve support comprises one or a combination of 13X molecular sieve, ZSM type molecular sieve and MCM type molecular sieve; preferably, the molecular sieve support is a 13X molecular sieve.

4. The catalyst suitable for low-temperature plasma according to claim 1, wherein the content of the metal active component is 10% to 30% by weight based on the total weight of the catalyst, and the content of the metal active component is based on the weight of metal oxide.

5. The catalyst suitable for low-temperature plasma according to claim 3, wherein the 13X molecular sieve is prepared by the following steps: carrying out classification treatment on the fly ash; then mixing the graded fly ash, an aluminum source, a silicon source, a hard template, seed crystals and NaOH in water to obtain a mixed solution; stirring the mixed solution, and then aging to obtain initial gel; crystallizing the initial gel, and at least drying and roasting to obtain the 13X molecular sieve;

preferably, the fly ash comprises fluidized bed fly ash;

preferably, the fractionation treatment comprises hydrochloric acid pickling and/or sodium hydroxide caustic washing; more preferably, the classification process includes: firstly, carrying out hydrochloric acid pickling on the fly ash, and then carrying out sodium hydroxide alkaline washing; wherein, the hydrochloric acid pickling conditions comprise: adopting concentrated hydrochloric acid with the mass fraction of 20-36.5%, the solid-liquid ratio is 1:1-5:1, the reaction temperature is 60-90 ℃, and stirring and reacting for 1-3 h; the sodium hydroxide alkali washing conditions comprise: the solid-liquid ratio is 1:3-1:6, the alkalinity of the sodium hydroxide solution is more than 10, the reaction temperature is 70-100 ℃, and the stirring reaction is carried out for 1-3 h;

preferably, the source of aluminum comprises an aluminum soluble inorganic salt; more preferably, the aluminum source comprises one or a combination of sodium metaaluminate, aluminum sulfate and aluminum nitrate;

preferably, the silicon source comprises a silicon-soluble inorganic salt; more preferably still, the first and second liquid crystal compositions are,the silicon source comprises sodium silicate, ethyl orthosilicate, silica sol, water glass, kaolin and superfine SiO ₂ One or a combination of several of them;

preferably, the hard template comprises one or a combination of several of carbon nanotubes, porous silicon templates and carbon black;

preferably, the seed crystal comprises a 13X molecular sieve seed crystal, and the pore volume of the 13X molecular sieve seed crystal is 0.1-0.4cm ³ Per g, the aperture is 1.4-2.5nm, and the crystal size is 1.2-1.5 μm;

preferably, 75-80 parts by weight of the classified fly ash, 1-3 parts by weight of an aluminum source, a silicon source, a hard template, 6-8 parts by weight of seed crystal and 5-20 parts by weight of NaOH are mixed in water;

preferably, the alkalinity of the mixed solution is 8-10;

preferably, the temperature for stirring the mixed solution is room temperature to 60 ℃, more preferably 40 to 60 ℃, and the stirring time is 20min to 1 h;

preferably, the aging temperature is 70-90 ℃, and the aging time is 6-12 h;

preferably, the molar ratio of silica to alumina in the initial gel is 3 to 11;

preferably, the crystallization temperature is 120-180 ℃, and the crystallization time is 48-64 h;

preferably, the drying temperature is 75-115 ℃, and the drying time is 6-12 h;

preferably, the roasting temperature is 450-550 ℃, and the time is 3-6 h;

preferably, the prepared 13X molecular sieve has the crystal particle size of 1.2-1.5 mu m, the pore diameter of 1.5-2nm and the pore volume of 0.14-0.4cm ³ A specific surface area of 300-700m ² /g。

6. The catalyst for low temperature plasma according to claim 1, wherein the catalyst for low temperature plasma has a crystal size of 1.2-2.5 μm, a pore diameter of 1.7-2.6nm, and a pore volume of 0.2-0.36cm ³ A specific surface area of 360- ² /g；

Preferably, the catalyst suitable for low-temperature plasma has a combination of metal active components of spinel X-Mn-O and fluorite Ce-O, wherein X is Mo, Co, Cu, Ni or Fe; more preferably, the low temperature plasma-compatible catalyst has a combination of metal active components of spinel X-Mn-O and fluorite Ce-O, where X is Mo, Co, or Cu.

7. A method for preparing the catalyst suitable for low-temperature plasma according to any one of claims 1 to 6, comprising the steps of:

mixing a molecular sieve carrier with a solution containing a metal salt to obtain a dispersion liquid; mixing Na ₂ CO ₃ -NaHCO ₃ Adding a buffer solution into the dispersion liquid, aging, and at least drying and roasting to obtain the catalyst suitable for the low-temperature plasma; wherein the solution containing the metal salt is a solution containing a Mn salt, a Ce salt and one or more of Co salt, Cu salt, Mo salt, Ni salt and Fe salt, and in the solution containing the metal salt, in terms of atomic molar ratio, one or more of Co, Cu, Mo, Ni and Fe is/are combined: mn: ce ═ 1:2:1-1:6: 4.

8. The production method according to claim 7, wherein the solution containing the metal salt is a solution containing a Mn salt and a Ce salt, and one or a combination of several of a Co salt, a Cu salt, and a Mo salt, and in the solution containing the metal salt, one or a combination of several of Mo, Co, and Cu is: mn: ce ═ 1:2:1-1:6: 4;

preferably, the solution containing a metal salt is a solution containing an Mn salt, a Ce salt, and a Mo salt, and in the solution containing a metal salt, Mo: mn: ce ═ 1:2:1-1:6: 4; more preferably, Mo: mn: ce ═ 1:2:1-1:2: 3;

or the solution containing a metal salt is a solution containing a Mn salt, a Ce salt, and a Co salt, and in the solution containing a metal salt, in terms of atomic molar ratio, Co: mn: ce ═ 1:2:1-1:6: 4; more preferably, the molar ratio, in atomic terms, of Co: mn: ce ═ 1:2:1-1:2: 3;

or the solution containing the metal salt is a solution containing a Mn salt, a Ce salt, and a Cu salt, and in the solution containing the metal salt, in terms of atomic molar ratio, Cu: mn: ce ═ 1:2:1-1:6: 4; more preferably, the molar ratio, in terms of atomic mole ratio, of Cu: mn: ce ═ 1:2:1-1:2: 3;

preferably, the total concentration of metal salts in the metal salt-containing solution is 0.001 to 0.003M.

9. The production method according to claim 7 or 8, wherein the Mn salt comprises manganese nitrate and/or manganese acetate;

preferably, the Ce salt comprises cerium acetate and/or cerium nitrate;

preferably, the Co salt comprises cobalt acetate and/or cobalt nitrate;

preferably, the Cu salt comprises copper acetate and/or copper nitrate;

preferably, the Mo salt comprises molybdenum acetate and/or molybdenum nitrate;

preferably, the Ni salt comprises nickel acetate and/or nickel nitrate;

preferably, the Fe salt comprises iron acetate and/or iron nitrate;

preferably, the molecular sieve carrier comprises one or more of a 13X molecular sieve, a ZSM type molecular sieve and an MCM type molecular sieve in a multi-combination manner; more preferably, the molecular sieve support is a 13X molecular sieve;

preferably, mixing the molecular sieve carrier with a solution containing metal salt, and carrying out ultrasonic treatment for 20-60min to obtain the dispersion liquid;

preferably, the Na ₂ CO ₃ -NaHCO ₃ The concentration of the buffer solution is 0.3-0.5 mol/L;

preferably, Na is added ₂ CO ₃ -NaHCO ₃ Adding a buffer solution into the dispersion liquid to ensure that the pH value of the dispersion liquid is 8-10;

preferably, the aging temperature is 75-90 ℃ and the aging time is 18-24 h;

preferably, the drying temperature is 85-120 ℃, and the drying time is 8-16 h;

preferably, the roasting process is as follows: heating to 140 ℃ at the rate of 3-6 ℃/min, keeping the temperature for 0.5-1h, then heating to 600 ℃ at the rate of 3-6 ℃/min, and keeping the temperature for 2-4 h;

preferably, the prepared catalyst suitable for low-temperature plasma is powder, and the particle size of the catalyst powder is 40-60 meshes.

10. Use of the low temperature plasma compatible catalyst of any one of claims 1-6 as a catalyst in the purification of VOCs using low temperature plasma;

preferably, the low-temperature plasma is dielectric barrier discharge low-temperature plasma;

preferably, the low-temperature plasma adopts a built-in plasma catalytic system and/or an external plasma catalytic system;

preferably, the discharge parameters of the built-in plasma catalysis system and the external plasma catalysis system are respectively as follows: the discharge voltage is 11-18kV, and the discharge frequency is 200-300 Hz; more preferably, the discharge voltage is 17-18 kV;

preferably, the space velocity is 20000- ^-1 ；

Preferably, the VOCs comprise one or more of benzene series, naphthalene, phenol, dioxin, trichlorobenzene and malodorous gas; wherein the benzene series comprises toluene, and the malodorous gas comprises H ₂ S and/or NH ₃ ；

Preferably, the conversion rate of the benzene series is more than 98%, more preferably more than 99%;

preferably, the conversion rate of the dioxin and/or trichlorobenzene is over 84 percent;

preferably, the conversion rate of the malodorous gas is 99% or more.