CN113620293B - Method for preparing methane and carbon dioxide by catalytic cracking of high-concentration organic wastewater - Google Patents
Method for preparing methane and carbon dioxide by catalytic cracking of high-concentration organic wastewater Download PDFInfo
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- CN113620293B CN113620293B CN202110804186.6A CN202110804186A CN113620293B CN 113620293 B CN113620293 B CN 113620293B CN 202110804186 A CN202110804186 A CN 202110804186A CN 113620293 B CN113620293 B CN 113620293B
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Abstract
The invention discloses a method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater, which comprises the following steps: 1) under the conditions of high temperature and high pressure, high-concentration organic wastewater is pumped into a reaction kettle filled with a supported catalyst for treatment, and the airspeed of the raw material is 1-10h ‑1 Preferably 1-4h ‑1 (ii) a 2) Collecting the generated methane and carbon dioxide from a gas outlet end of the reaction kettle; the supported catalyst comprises a carrier and an active component, wherein the carrier is magnetic nano Fe 3 O 4 The active components are Pd and Ag. The method can convert organic carbon in the high-concentration organic wastewater into methane and carbon dioxide and further be used for producing synthesis gas, thereby realizing resource reutilization.
Description
Technical Field
The invention relates to a method for preparing methane and carbon dioxide, in particular to a method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater.
Background
The chemical industry is one of the very important industries of all countries, and plays an important role in the rapid development process of the economy of China, however, various high-concentration organic wastewater can be generated in the chemical production process, such as high-concentration acetone wastewater, propylene glycol wastewater, waste methanol with more impurities and the like generated by a water-based device, organic matters in the wastewater are directly or indirectly discharged to the atmosphere without being recycled, and along with the enhancement of the awareness of people on carbon dioxide emission in recent years, the emission of a large amount of greenhouse gases brought by the high-concentration organic wastewater causes the attention of all countries.
At present, the schemes for treating the high-concentration organic wastewater mainly comprise biochemical treatment or incineration treatment. Usually, the concentration of a certain kind or a certain kind of organic matters in the high-concentration organic matter wastewater is very high (COD is mostly over 20000ppm), and the wastewater needs to be diluted before being sent to biochemical treatment, so that the wastewater treatment amount is greatly increased, and the energy consumption is too high. And incineration treatment not only has high energy consumption, but also can convert most of high-concentration organic matters into carbon dioxide, aggravate greenhouse effect and is not in line with the large background of carbon emission reduction.
With the stricter requirements on carbon emission reduction, how to convert the carbon source in the wastewater into the raw material gas required in production is an important project to be developed urgently for recycling carbon and reducing carbon emission.
Disclosure of Invention
Methane and carbon dioxide are used as two main greenhouse gases, and the chemical utilization of the methane and the carbon dioxide is a good energy-saving and emission-reducing way, so that the current increasingly serious greenhouse effect can be relieved. The synthesis gas prepared by reforming methane and carbon dioxide has a low hydrogen-carbon ratio, the ratio is superior in the practical application process, and the reforming reaction process is a reversible reaction with large reaction heat and can be used as a storage medium of energy, so that the reaction becomes a research hotspot in the current industrial field, for example, a feasible catalyst and reaction conditions for preparing the synthesis gas by catalytic reforming methane and carbon dioxide are discussed in the frequent literature, see [ chemical design communication, 2019, v.45; no.207(09):63-64 ]. The invention aims to solve the technical problem of how to convert organic carbon in high-concentration organic wastewater into methane and carbon dioxide for recycling.
In order to solve the technical problems, the invention provides a method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater. The invention uses Pd-Ag/Fe 3 O 4 @SiO 2 The catalyst with the-SH structure is used for carrying out catalytic treatment on organic wastewater, optimizing and adjusting catalytic reaction conditions, and cracking organic matters in the wastewater into methane and carbon dioxide, so that the problem that the high-concentration organic wastewater is difficult to biochemically treat is solved, and meanwhile, the methane and the carbon dioxide can be used as synthesis gas raw materials, and the resource recycling of a carbon source is realized.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater comprises the following steps:
1) under the conditions of high temperature and high pressure, high-concentration organic wastewater is pumped into a reaction kettle filled with a supported catalyst for treatment, and the airspeed of the raw material is 1-10h -1 (e.g., 2 h) -1 、4h -1 、6h -1 、8h -1 、10h -1 ) Preferably 1-4h -1 ；
2) Collecting the generated methane and carbon dioxide from a gas outlet end of the reaction kettle;
the supported catalyst comprises a carrier and an active component, wherein the carrier is magnetic nano Fe 3 O 4 The active components are Pd and Ag; preferably, the carrier is SiO 2 and-SH jointly modified magnetic nano Fe 3 O 4 Carrier of SiO 2 Is silica and-SH is mercapto.
In a preferred embodiment, the Pd content in the catalyst is Fe in the carrier 3 O 4 0.4 to 1wt%, preferably 0.6 to 0.8wt% of the mass; the Ag content is Fe in the carrier 3 O 4 5.0 to 10 wt.%, preferably 6 to 8 wt.% of the mass.
In a preferred embodiment, the high temperature and high pressure conditions are: 200-.
The adjustment of the temperature, pressure and heating process may be carried out in reactors known in the art.
The invention adopts magnetic nano Fe 3 O 4 The powder is used as a carrier, the carrier is artificially synthesized, the carrier is an effective carrier capable of being prepared into nano particles, and the nano material has the advantages of large specific surface area, many surface active sites, no toxicity, environmental protection and the like. Further using SiO 2 For Fe 3 O 4 After the carrier is modified, the aggregation effect of the nano particles is greatly weakened, so that the suspension stability in a reaction system can be maintained; -SH modification can be used to provide reductionThe active free radical improves the decomposition capability of the catalyst on organic matters.
When the catalyst is used for treating high-concentration organic wastewater, organic matters in the wastewater are provided with-SH on the catalyst under the action of the catalyst][ H ] having reducibility]Attack organic formation [ CH3]，[CH3]By reaction with intermediates to form CH 4 While producing part of CO 2 Taking acetone wastewater as an example, the main catalytic mechanism is as follows:
C 3 H 6 O+[H]→[CH3]+C 2 H 4 O ①
[CH3]+C 2 H 4 O+H 2 02CH 4 +CO 2 +[H] ②
wherein [ H ], [ CH3] represents a reducing radical;
is represented by the formula]Attack organic molecules under the action of catalyst to form [ CH3]Is that the intermediate product further reacts with water to form CH 4 、CO 2 Simultaneously generate [ H ]]And the catalyst is basically free from loss.
In the treatment method of the present invention, various organic substances can be catalytically reacted with the catalyst to convert the organic substances into methane gas. In a preferred embodiment, the organic wastewater is one or more of acetone wastewater, high-aldehyde wastewater, propylene glycol wastewater, acrylic acid wastewater, aniline wastewater, phenol wastewater, preferably acetone wastewater, high-aldehyde wastewater or propylene glycol wastewater;
preferably, the acetone wastewater contains the following main organic components: 20000-35000ppm acetone, 3000-5000ppm methyl methacrylate, 50000-90000ppm total COD (chemical oxygen demand);
preferably, the main organic components and contents in the high-aldehyde wastewater are as follows: acetic acid 18000-;
preferably, the propylene glycol wastewater contains the following main organic components: propylene glycol 30000-50000ppm, total COD 50000-90000 ppm;
preferably, the acrylic acid wastewater comprises the following main organic components in percentage by weight: acrylic acid 15000-25000ppm, propylene glycol 5000-20000ppm, total COD 50000-70000 ppm;
preferably, the phenol wastewater contains the following main organic components: phenol 40000-50000ppm, total COD 70000-100000 ppm;
preferably, the aniline wastewater contains the following main organic components in percentage by weight: aniline 40000-50000ppm and total COD 90000-120000 ppm.
According to the method for treating high-concentration organic wastewater provided by the invention, the high-concentration organic wastewater is preferably derived from acetone wastewater of an aqueous device.
When the organic wastewater is subjected to catalytic cracking, the catalytic cracking can be realized by any reactor known in the field; for example, the acetone wastewater is sent to a catalytic cracking reactor for reaction. In some examples, the operating process conditions of step (1) include: the volume space velocity is 1-10h -1 Preferably 1-4h -1 (ii) a If the volume airspeed is too high, active free radicals cannot be fully converted in a reaction system, organic matters in the acetone wastewater to be treated cannot be fully converted, and the amount of generated methane is small; if the volume space velocity is too low, although the catalytic oxidation effect can be satisfactory, the amount of the catalyst to be used is increased, resulting in an increase in running cost. The reaction temperature is 200-300 ℃, preferably 240-270 ℃, and the reaction pressure is 5-10MPa, preferably 7-9 MPa.
In a preferred embodiment, the method of preparing the catalyst comprises the steps of:
a. preparation of Fe 3 O 4 @SiO 2 ：
Magnetic nano Fe 3 O 4 Dispersing into constant temperature water of 60-90 ℃, introducing nitrogen and dropwise adding 0.5-3mol/L sodium silicate nonahydrate solution into the dispersion liquid under mechanical stirring; then adjusting pH to 4-6, stirring for 1-5h, separating solid with magnet, and cleaning to obtain SiO 2 Modified carrier Fe 3 O 4 @SiO 2 ；
Preferably, sodium silicate nonahydrate and magnetic nano Fe are added 3 O 4 The mass ratio of (0.9-5.5) to (1);
preferably, the magnetic nano-Fe 3 O 4 Granule of (1)The diameter is 20-30 nm;
b. preparation of Pd-Ag/Fe 3 O 4 @SiO 2 ：
Mixing the above SiO 2 Adding the modified carrier, the metal silver precursor and the metal palladium precursor into an alcohol solution, stirring for 0.5-3h, treating to obtain a solid, and then roasting for 0.5-8h at the temperature of 220 ℃ in the nitrogen atmosphere of 180 DEG to obtain a catalyst intermediate Pd-Ag/Fe loaded with an active component 3 O 4 @SiO 2 ；
Preferably, the metallic silver precursor is one or more of nitrate, sulfate and oxalate of silver;
preferably, the metal palladium precursor is one or more of nitrate, sulfate, trifluoroacetate and oxalate of palladium;
c. preparation of Pd-Ag/Fe 3 O 4 @SiO 2 -SH：
The catalyst intermediate Pd-Ag/Fe 3 O 4 @SiO 2 Activating with acid, washing with water to neutrality, dispersing in benzene solvent, adding mercaptopropyl triethoxysilane and zeolite, and reflux reacting for 12-48 h; stopping the reaction, separating the solid from the magnet, cleaning and drying to obtain the supported catalyst Pd-Ag/Fe 3 O 4 @SiO 2 -SH；
Preferably, the addition amount of the mercaptopropyltriethoxysilane is Fe in the carrier 3 O 4 0.7-3 times of the mass; the zeolite is added in an amount of Fe 3 O 4 0.5-5% of the mass.
The invention can efficiently convert most organic matters in the high-concentration organic wastewater into methane, and simultaneously, the COD content in the treated wastewater is reduced by multiple times, and the wastewater can be sent to biochemical treatment after being slightly diluted; after the reaction is finished, the produced methane gas can be sent to CH 4 With CO 2 The reaction device is used as raw material gas for producing synthesis gas, so that the waste of carbon sources is reduced.
Detailed Description
In order that the technical features and contents of the present invention can be understood in detail, preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention have been described in the examples, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
(1) The main equipment models and raw material sources are as follows:
the waste water storage tank, the static mixer, the waste water delivery pump and the catalytic cracking reactor are purchased from Nicotiana Kogyo chemical equipment Co.Ltd;
a heat collection type constant temperature heating magnetic stirrer, model DF-101S, purchased from Engyu Yuhua instruments manufacturing factory in consolidated City; an electric heating constant temperature air blast drying oven, model DHG-9246A, purchased from Shanghai sperm macro test equipment Co., Ltd; a vacuum drying oven, model DZF-6050, purchased from Shanghai sperm macro experimental facilities, Inc.; peristaltic pumps, model 7518-00, available from MasterFLEX corporation;
taking high-concentration acetone wastewater, high-aldehyde wastewater and propylene glycol wastewater to be treated from an aqueous device, wherein the wastewater is sourced from a Wanhua chemical production device, and phenol wastewater is obtained by self-preparation; conveying the taken wastewater to be treated to a wastewater storage tank, and sampling for analysis; the total COD and the content of the main components in each water quality are shown in the table 1:
TABLE 1 Total COD and Main component content in the respective wastewaters
Tetrahydrate and ferrous chloride, ferric chloride hexahydrate, toluene, ethanol, silver nitrate (AR, 99.8%, molecular weight 170), palladium nitrate dihydrate (AR, 99.5%, molecular weight 261) were purchased from national pharmaceutical group chemical agents ltd; sodium silicate nonahydrate (AR, molecular weight 284.2), mercaptopropyltriethoxysilane was purchased from an avastin reagent net;
31 wt% aqueous hydrochloric acid, 40% sodium hydroxide solution from Wawa Chemicals;
(2) principal analysis and test method
TN analyzer, jena, germany; COD tester, hash corporation;
the components in the wastewater are analyzed by a liquid chromatography analyzer (LC), Agilent, USA; the contents of carbon dioxide and methane were analyzed by gas chromatography, Agilent, USA
[ PREPARATION EXAMPLE 1 ]
The supported catalyst a was prepared as follows:
(1) preparation of magnetic Nano Fe 3 O 4 ：
Weighing 150g of NaOH, dissolving in 2.5L of water, heating to 80 ℃, and stirring in a nitrogen atmosphere; weighing 2mol of tetrahydrate, ferrous chloride and 4mol of ferric chloride hexahydrate, dissolving in 500mL of water, and adding 8.5mL of 31% hydrochloric acid to obtain a solution; dropwise adding the solution into NaOH solution, and reacting for 30min to obtain Fe 3 O 4 Separating the suspended matter with magnet and washing with clear water to obtain magnetic nanometer Fe 3 O 4 。
(2) Preparation of Fe 3 O 4 @SiO 2 ：
100g of magnetic nano Fe 3 O 4 Dispersing in 500mL constant temperature water of 80 ℃, introducing nitrogen, dropwise adding 664mL and 1mol/L sodium silicate nonahydrate solution into the dispersion under mechanical stirring, adjusting pH to 5, continuously stirring for 3h, separating out solid by using a magnet, and cleaning to obtain SiO 2 Modified carrier Fe 3 O 4 @SiO 2 ；
(3) Preparation of Pd-Ag/Fe 3 O 4 @SiO 2 ：
Mixing the above SiO 2 Adding the modified carrier, 7.9g of silver nitrate and 1.23g of palladium nitrate dihydrate into 300mL of ethanol solution, stirring for 2h, performing rotary evaporation and drying to obtain a solid, and then roasting at 200 ℃ in a nitrogen atmosphere for 3h to obtain a catalyst intermediate Pd-Ag/Fe loaded with an active component 3 O 4 @SiO 2 ；
(4) Preparation of Pd-Ag/Fe 3 O 4 @SiO 2 -SH：
Activating the catalyst intermediate in 300mL of 2mol/L hydrochloric acid for 12 hours, washing the catalyst intermediate to be neutral by using distilled water, then washing the catalyst intermediate by using ethanol and toluene in sequence, and then obtaining Pd-Ag/Fe 3 O 4 @SiO 2 Dispersing the nano material into anhydrous toluene, adding 72g of mercaptopropyltriethoxysilane and 3g of zeolite,heating the mixture to slightly boil and refluxing for 24h, separating out solid by using a magnet after the reaction is finished, and sequentially washing the solid by using toluene, ethanol and distilled water to obtain Pd-Ag/Fe 3 O 4 @SiO 2 -SH。
In the catalyst prepared by the method, the mass contents of Pd and Ag respectively account for Fe 3 O 4 0.5% and 5% of the mass.
[ PREPARATION EXAMPLE 2 ]
The supported catalyst B was prepared as follows:
(1) preparation of magnetic Nano Fe 3 O 4 ：
Weighing 150g of NaOH, dissolving in 2.5L of water, heating to 80 ℃, and stirring in a nitrogen atmosphere; weighing 2mol of tetrahydrate, ferrous chloride and 4mol of ferric chloride hexahydrate, dissolving in 500mL of water, and adding 8.5mL of 31% hydrochloric acid to obtain a solution; dropwise adding the solution into NaOH solution, and reacting for 30min to obtain Fe 3 O 4 Separating the suspended matter with magnet and washing with clear water to obtain magnetic nanometer Fe 3 O 4 。
(2) Preparation of Fe 3 O 4 @SiO 2 ：
100g of magnetic nano Fe 3 O 4 Dispersing in 500mL constant temperature water of 80 ℃, introducing nitrogen, dropwise adding 1L of 1mol/L sodium silicate nonahydrate solution into the dispersion under mechanical stirring, adjusting pH to 5, continuously stirring for 3h, separating out solids by using a magnet, and cleaning to obtain SiO 2 Modified carrier Fe 3 O 4 @SiO 2 ；
(3) Preparation of Pd-Ag/Fe 3 O 4 @SiO 2 ：
Mixing the above SiO 2 Adding the modified carrier, 15.7g of silver nitrate and 2.45g of palladium nitrate dihydrate into 300mL of ethanol solution, stirring for 2h, performing rotary evaporation and drying to obtain a solid, and then roasting at 200 ℃ in a nitrogen atmosphere for 3h to obtain a catalyst intermediate Pd-Ag/Fe loaded with an active component 3 O 4 @SiO 2 ；
(4) Preparation of Pd-Ag/Fe 3 O 4 @SiO 2 -SH：
Taking the catalyst intermediate inActivating in 300mL of 2mol/L hydrochloric acid for 12h, washing with distilled water to neutrality, sequentially washing with ethanol and toluene, and then obtaining Pd-Ag/Fe 3 O 4 @SiO 2 Dispersing the nano material into anhydrous toluene, adding 144g of mercaptopropyltriethoxysilane and 5g of zeolite, heating the mixture to slight boiling and refluxing for 24h, separating out solids by using a magnet after the reaction is finished, and sequentially washing by using toluene, ethanol and distilled water to obtain Pd-Ag/Fe 3 O 4 @SiO 2 -SH。
In the catalyst prepared by the method, the mass contents of Pd and Ag respectively account for Fe 3 O 4 1% and 10% of the mass.
[ PREPARATION EXAMPLE 3]
The supported catalyst C was prepared as follows:
(1) preparation of magnetic Nano Fe 3 O 4 ：
Weighing 150g of NaOH, dissolving in 2.5L of water, heating to 80 ℃, and stirring in a nitrogen atmosphere; weighing 2mol of tetrahydrate, ferrous chloride and 4mol of ferric chloride hexahydrate, dissolving in 500mL of water, and adding 8.5mL of 31% hydrochloric acid to obtain a solution; dropwise adding the solution into NaOH solution, and reacting for 30min to obtain Fe 3 O 4 Separating the suspended matter with magnet and washing with clear water to obtain magnetic nanometer Fe 3 O 4 。
(2) Preparation of Fe 3 O 4 @SiO 2 ：
100g of magnetic nano Fe 3 O 4 Dispersing in 500mL constant temperature water at 80 ℃, introducing nitrogen, dropwise adding 832mL of 1mol/L sodium silicate nonahydrate solution into the dispersion under mechanical stirring, adjusting pH to 5, continuously stirring for 3h, separating out solids by using a magnet, and cleaning to obtain SiO 2 Modified carrier Fe 3 O 4 @SiO 2 ；
(3) Preparation of Pd-Ag/Fe 3 O 4 @SiO 2 ：
Mixing the above SiO 2 Adding the modified carrier, 11.06g of silver nitrate and 1.72g of palladium nitrate dihydrate into 300mL of ethanol solution, stirring for 2h, performing rotary evaporation and drying to obtain a solid, and then roasting at 200 ℃ in a nitrogen atmosphere for 3h to obtain the catalystCatalyst intermediate Pd-Ag/Fe loaded with active component 3 O 4 @SiO 2 ；
(4) Preparation of Pd-Ag/Fe 3 O 4 @SiO 2 -SH：
Taking the middle of the catalyst, activating the middle of the catalyst in 300mL of 2mol/L hydrochloric acid for 12 hours, washing the middle of the catalyst to be neutral by using distilled water, then washing the middle of the catalyst by using ethanol and toluene in sequence, and then obtaining Pd-Ag/Fe 3 O 4 @SiO 2 Dispersing the nano material into anhydrous toluene, adding 108g of mercaptopropyltriethoxysilane and 2g of zeolite, heating the mixture to slight boiling and refluxing for 24h, separating out solids by using a magnet after the reaction is finished, and sequentially washing by using toluene, ethanol and distilled water to obtain Pd-Ag/Fe 3 O 4 @SiO 2 -SH。
In the catalyst prepared by the method, the mass contents of Pd and Ag respectively account for Fe 3 O 4 0.7% and 7% of the mass.
[ PREPARATION EXAMPLE 4 ]
A supported catalyst D was prepared in substantially the same manner as in preparation example 1: except that no palladium nitrate was added in step 3, the catalyst prepared was noted as: Ag/Fe 3 O 4 @SiO 2 -SH。
[ PREPARATION EXAMPLE 5 ]
A supported catalyst E was prepared in substantially the same manner as in preparation example 1: except that the modification treatment in step 2 was not performed, the catalyst prepared was noted as: Pd-Ag/Fe 3 O 4 @SH。
[ PREPARATION EXAMPLE 6 ]
A supported catalyst F was prepared in substantially the same manner as in preparation example 1: except that the modification treatment in step 4 was not performed, the catalyst prepared was noted as: Pd-Ag/Fe 3 O 4 @SiO 2 。
[ PREPARATION EXAMPLE 7 ]
A supported catalyst G was prepared in substantially the same manner as in preparation example 1: except that the modification treatment in step 2 and step 4 was not performed, and the catalyst obtained was recorded as: Pd-Ag/Fe 3 O 4 。
[ example 1 ]
The reaction kettle is filled with a catalyst A, and the acetone wastewater 1O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst A into a reaction kettle, pressurizing the reaction kettle to 7MPa, and raising the temperature to 250 ℃;
(2) starting a feeding pump, and pumping the acetone wastewater 1O into a reaction kettle for reaction; space velocity of 2h -1 Under the action of the catalyst A, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 47% of methane and 53% of carbon dioxide. The components in the wastewater after catalytic cracking were analyzed, and COD was 16000ppm, acetone was 6000ppm, and methyl methacrylate was 2000 ppm.
[ example 2 ]
The reaction kettle is filled with a catalyst B, and the acetone wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst B into a reaction kettle, pressurizing the reaction kettle to 7MPa, and raising the temperature to 250 ℃;
(2) starting a feeding pump, and pumping the acetone wastewater 2O into a reaction kettle for reaction; space velocity of 2h -1 Under the action of the catalyst B, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 50% methane and 50% carbon dioxide. The components in the wastewater after catalytic cracking were analyzed, COD 13000ppm, mainly containing 5000ppm acetone and 1500ppm methyl methacrylate.
[ example 3]
The reaction kettle is filled with a catalyst C, and the acetone wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst C into a reaction kettle, pressurizing the reaction kettle to 7MPa, and raising the temperature to 250 ℃;
(2) starting a feeding pump, and pumping the acetone wastewater 2O into a reaction kettle for reaction; space velocity of 2h -1 Under the action of the catalyst C, organic matters in the wastewater carry out free radical reaction,methane and carbon dioxide are generated, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 65% of methane and 35% of carbon dioxide. The waste water after catalytic cracking was analyzed for its components, COD 9000ppm, mainly containing 3500ppm of acetone and 900ppm of methyl methacrylate.
[ example 4 ]
The reaction kettle is filled with a catalyst A, and the high-aldehyde wastewater 1O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst A into a reaction kettle, pressurizing the reaction kettle to 5MPa, and raising the temperature to 200 ℃;
(2) starting a feeding pump, and pumping the high-aldehyde wastewater 1O into a reaction kettle for reaction; space velocity of 1h -1 Under the action of the catalyst A, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 45% of methane and 55% of carbon dioxide. The waste water after catalytic cracking was analyzed for its components, COD 12000ppm, mainly containing 9000ppm of acetic acid and 1200ppm of formaldehyde.
[ example 5 ]
The reaction kettle is filled with a catalyst B, and the high-aldehyde wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst B into a reaction kettle, pressurizing the reaction kettle to 5MPa, and raising the temperature to 200 ℃;
(2) starting a feeding pump, and pumping the high-aldehyde wastewater 2O into a reaction kettle for reaction; space velocity of 1h -1 Under the action of the catalyst B, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 50% methane and 50% carbon dioxide. The waste water after catalytic cracking was analyzed for its components, COD 9000ppm, mainly containing 7000ppm acetic acid and 800ppm formaldehyde.
[ example 6 ]
The reaction kettle is filled with a catalyst C, and the high-aldehyde wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst C into a reaction kettle, pressurizing the reaction kettle to 5MPa, and raising the temperature to 200 ℃;
(2) starting a feeding pump, and pumping the high-aldehyde wastewater 2O into a reaction kettle for reaction; space velocity of 1h -1 Under the action of the catalyst C, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 60% of methane and 40% of carbon dioxide. The waste water after catalytic cracking was analyzed for its components, COD 7000ppm, containing mainly 5500ppm acetic acid and 300ppm formaldehyde.
[ example 7 ]
The reaction kettle is filled with a catalyst A, and the propylene glycol wastewater 1O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst A into a reaction kettle, pressurizing the reaction kettle to 10MPa, and raising the temperature to 300 ℃;
(2) starting a feeding pump, and pumping the propylene glycol wastewater 1O into a reaction kettle for reaction; space velocity of 5h -1 Under the action of the catalyst A, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 44% of methane and 56% of carbon dioxide. The waste water after catalytic cracking was analyzed for components, COD 13000ppm, containing mainly 7000ppm propylene glycol.
[ example 8 ]
The reaction kettle is filled with a catalyst B, and the propylene glycol wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst B into a reaction kettle, pressurizing the reaction kettle to 10MPa, and raising the temperature to 300 ℃;
(2) starting a feeding pump, and pumping the propylene glycol wastewater 2O into a reaction kettle for reaction; space velocity of 5h -1 Under the action of the catalyst B, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 49% of methane and 51% of carbon dioxide. The components in the wastewater after catalytic cracking were analyzed, COD was 10000ppm, and mainly contained 5500ppm of propylene glycol.
[ example 9 ]
The reaction kettle is filled with a catalyst C, and the propylene glycol wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst C into a reaction kettle, pressurizing the reaction kettle to 10MPa, and raising the temperature to 300 ℃;
(2) starting a feeding pump, and pumping the propylene glycol wastewater 2O into a reaction kettle for reaction; space velocity of 5h -1 Under the action of the catalyst C, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 58% methane and 42% carbon dioxide. The components in the wastewater after catalytic cracking were analyzed, and COD was 6500ppm, and contained mainly 3500ppm of propylene glycol.
[ example 10 ]
The reaction kettle is filled with a catalyst A, and the phenol wastewater 1O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst A into a reaction kettle, pressurizing the reaction kettle to 10MPa, and raising the temperature to 300 ℃;
(2) starting a feeding pump, and pumping the phenol wastewater 1O into a reaction kettle for reaction; space velocity of 5h -1 Under the action of the catalyst A, organic matters in the wastewater undergo a radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 42% of methane and 58% of carbon dioxide. The components in the wastewater after catalytic cracking are analyzed, COD is 20000ppm, and the wastewater mainly contains 10000ppm of phenol.
[ example 11 ]
The reaction kettle is filled with a catalyst B, and the phenol wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst B into a reaction kettle, pressurizing the reaction kettle to 10MPa, and raising the temperature to 300 ℃;
(2) starting a feeding pump, and pumping the phenol wastewater 2O into a reaction kettle for reaction; space velocity of 5h -1 Under the action of the catalyst B, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 49% of methane and 51% of carbon dioxide. The components in the wastewater after catalytic cracking are analyzed, COD 16500ppm mainly contains 8000ppm phenol.
[ example 12 ]
The reaction kettle is filled with a catalyst C, and the phenol wastewater 2O is subjected to catalytic cracking according to the following reaction conditions:
(1) loading the prepared catalyst C into a reaction kettle, pressurizing the reaction kettle to 10MPa, and raising the temperature to 300 ℃;
(2) starting a feeding pump, and pumping the phenol wastewater 2O into a reaction kettle for reaction; space velocity of 5h -1 Under the action of the catalyst C, organic matters in the wastewater undergo a free radical reaction to generate methane and carbon dioxide, gas is collected at a gas outlet end of the reaction kettle, and the components of the gas are analyzed to be 56% of methane and 44% of carbon dioxide. The components in the wastewater after catalytic cracking were analyzed, and COD was 12000ppm and phenol was contained mainly at 5800 ppm.
Comparative example 1
Acetone wastewater 1 o was treated in the same manner as in example 1 except that: catalyst a was replaced with catalyst D. The gas was collected at the gas outlet end of the reactor and analyzed for composition of 20% methane and 80% carbon dioxide. The waste water after catalytic cracking was analyzed for components, COD 40000ppm, containing mainly 16000ppm acetone, 2700ppm methyl methacrylate.
Comparative example 2
Acetone wastewater 1 o was treated in the same manner as in example 1 except that: catalyst a was replaced with catalyst E. The gas was collected at the gas outlet end of the reactor and analyzed for composition of 32% methane and 68% carbon dioxide. The components in the wastewater after catalytic cracking were analyzed, and COD was 30000ppm, which mainly contained 12500ppm of acetone and 2000ppm of methyl methacrylate.
Comparative example 3
Acetone wastewater 1 o was treated in the same manner as in example 1 except that: catalyst a was replaced with catalyst F. The gas was collected at the gas outlet end of the reactor and analyzed for composition of 0.8% methane, 99.2% carbon dioxide. The waste water after catalytic cracking was analyzed for its components, COD 65000ppm, containing mainly 27000ppm acetone and 3000ppm methyl methacrylate.
Comparative example 4
Acetone wastewater 1 o was treated in the same manner as in example 1 except that: catalyst a was replaced with catalyst G. The gas was collected at the gas outlet end of the reactor and analyzed for composition of 0.5% methane, 99.5% carbon dioxide. The waste water after catalytic cracking was analyzed for components, COD 70000ppm, containing mainly 29000ppm acetone and 3200ppm methyl methacrylate.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and additions can be made without departing from the method of the present invention, and these modifications and additions should also be regarded as the protection scope of the present invention.
Claims (11)
1. A method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater is characterized by comprising the following steps:
1) under the conditions of high temperature and high pressure, high-concentration organic wastewater is pumped into a reaction kettle filled with a supported catalyst for treatment, and the airspeed of the raw material is 1-10h -1 ；
2) Collecting the generated methane and carbon dioxide from a gas outlet end of the reaction kettle;
the supported catalyst comprises a carrier and an active component, wherein the carrier is magnetic nano Fe 3 O 4 The active components are Pd and Ag;
the carrier is SiO 2 and-SH jointly modified magnetic nano Fe 3 O 4 Carrier of SiO 2 Is silica and-SH is mercapto.
2. The method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater according to claim 1, wherein the space velocity of the raw material in the step 1) is 1-4h -1 。
3. The method as claimed in claim 1, wherein the Pd content in the catalyst is Fe in carrier 3 O 4 0.4-1wt% of mass; the Ag content is Fe in the carrier 3 O 4 5.0-10wt% of the mass.
4. The method as claimed in claim 1, wherein the Pd content in the catalyst is Fe in carrier 3 O 4 0.6-0.8wt% of the mass; the Ag content is Fe in the carrier 3 O 4 6-8wt% of the mass.
5. The method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater according to any one of claims 1 to 4, wherein the high-temperature and high-pressure conditions are as follows: 200 ℃ and 300 ℃ and 5-10 MPa.
6. The method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater according to claim 5, wherein the high-temperature and high-pressure conditions are as follows: 240 ℃ and 270 ℃ at 7-9 MPa.
7. The method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater according to any one of claims 1 to 4, wherein the organic wastewater is one or more of acetone wastewater, high-aldehyde wastewater, propylene glycol wastewater, acrylic acid wastewater, aniline wastewater and phenol wastewater.
8. The method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater according to any one of claims 1 to 4, wherein the preparation method of the catalyst comprises the following steps:
a. preparation of Fe 3 O 4 @SiO 2 ：
Magnetic nano Fe 3 O 4 Dispersing into constant temperature water of 60-90 ℃, introducing nitrogen and dropwise adding 0.5-3mol/L sodium silicate nonahydrate solution into the dispersion liquid under mechanical stirring; then adjusting pH to 4-6, stirring for 1-5h, separating solid with magnet, and cleaning to obtain SiO 2 Modified carrier Fe 3 O 4 @SiO 2 ；
b. Preparation of Pd-Ag-Fe 3 O 4 @SiO 2 ：
Mixing the above SiO 2 Adding the modified carrier, the metal silver precursor and the metal palladium precursor into an alcohol solution, stirring for 0.5-3h, treating to obtain a solid, and then roasting at the temperature of 180-220 ℃ in a nitrogen atmosphere for 0.5-8h to obtain a catalyst intermediate Pd-Ag/Fe loaded with an active component 3 O 4 @SiO 2 ；
c. Preparation of Pd-Ag/Fe 3 O 4 @SiO 2 -SH：
The catalyst intermediate Pd-Ag/Fe 3 O 4 @SiO 2 Activating with acid, washing with water to neutrality, dispersing in benzene solvent, adding mercaptopropyl triethoxysilane and zeolite, and reflux reacting for 12-48 h; stopping the reaction, separating the solid from the magnet, cleaning and drying to obtain the supported catalyst Pd-Ag/Fe 3 O 4 @SiO 2 -SH。
9. The method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater according to claim 8, wherein sodium silicate nonahydrate and magnetic nano Fe are added in step a 3 O 4 The mass ratio of (0.9-5.5) to (1).
10. The method for preparing methane and carbon dioxide by catalytically cracking high-concentration organic wastewater according to claim 8, wherein in the step b, the metallic silver precursor is one or more of nitrate, sulfate and oxalate of silver; the metal palladium precursor is one or more of nitrate, sulfate, trifluoroacetate and oxalate of palladium.
11. The method for preparing methane and carbon dioxide by catalytic cracking of high concentration organic wastewater as claimed in claim 8, wherein in step c, the addition amount of mercaptopropyltriethoxysilane is Fe in carrier 3 O 4 0.7-3 times of the mass; the zeolite is added in an amount of Fe 3 O 4 0.5-5% of the mass.
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