CN115779811A - Catalytic microchannel reactor for degrading COD (chemical oxygen demand) and preparation method and application thereof - Google Patents
Catalytic microchannel reactor for degrading COD (chemical oxygen demand) and preparation method and application thereof Download PDFInfo
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- 230000003197 catalytic effect Effects 0.000 title claims abstract description 86
- 230000000593 degrading effect Effects 0.000 title claims abstract description 19
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title abstract description 6
- 229910052760 oxygen Inorganic materials 0.000 title abstract description 6
- 239000001301 oxygen Substances 0.000 title abstract description 6
- 239000000126 substance Substances 0.000 title abstract description 6
- 239000002245 particle Substances 0.000 claims abstract description 170
- 239000003054 catalyst Substances 0.000 claims abstract description 73
- 239000000725 suspension Substances 0.000 claims abstract description 45
- 238000005245 sintering Methods 0.000 claims abstract description 26
- 230000003746 surface roughness Effects 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims description 32
- 238000000227 grinding Methods 0.000 claims description 18
- 239000007788 liquid Substances 0.000 claims description 15
- 230000003213 activating effect Effects 0.000 claims description 13
- 230000015556 catabolic process Effects 0.000 claims description 13
- 238000006731 degradation reaction Methods 0.000 claims description 13
- 241000252506 Characiformes Species 0.000 claims description 10
- 230000033444 hydroxylation Effects 0.000 claims description 6
- 238000005805 hydroxylation reaction Methods 0.000 claims description 6
- 239000002612 dispersion medium Substances 0.000 claims description 5
- 239000007800 oxidant agent Substances 0.000 claims description 5
- 230000001590 oxidative effect Effects 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000000243 solution Substances 0.000 description 51
- 230000008569 process Effects 0.000 description 24
- 238000011068 loading method Methods 0.000 description 20
- 238000001514 detection method Methods 0.000 description 17
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 16
- 238000004566 IR spectroscopy Methods 0.000 description 15
- 239000007787 solid Substances 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 13
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 230000009467 reduction Effects 0.000 description 9
- 238000002156 mixing Methods 0.000 description 8
- 238000010438 heat treatment Methods 0.000 description 7
- 239000002609 medium Substances 0.000 description 6
- 239000005416 organic matter Substances 0.000 description 6
- 239000002351 wastewater Substances 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 238000007405 data analysis Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003622 immobilized catalyst Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000010951 particle size reduction Methods 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 238000010586 diagram Methods 0.000 description 1
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- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
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Abstract
The invention relates to the field of microchannel reactors, and discloses a catalytic microchannel reactor for degrading COD (chemical oxygen demand), and a preparation method and application thereof. The catalytic microchannel reactor comprises a microchannel with a catalyst loaded on the inner wall, wherein the surface roughness Ra of the inner wall of the microchannel is less than 3 μm, and the preparation method comprises the following steps: (1) Injecting the catalyst particle suspension into a microchannel in the microchannel reactor, and sintering; (2) And (3) repeating the step (1) until the surface roughness of the inner wall of the microchannel is less than 3 mu m, thus obtaining the catalytic microchannel reactor. The invention can prevent COD from polluting the inner wall of the microchannel by controlling the roughness of the inner surface of the microchannel loaded with the catalyst, thereby prolonging the service life of the catalytic microchannel reactor.
Description
Technical Field
The invention relates to the field of microchannel reactors, in particular to a catalytic microchannel reactor for degrading COD (chemical oxygen demand) and a preparation method and application thereof.
Background
The industrial wastewater containing COD can not meet the discharge requirement, and the problems of high organic matter content and unqualified chromaticity can be solved only by deep oxidation. NaClO and H are commonly used in industry 2 O 2 、O 3 The secondary biochemical effluent is subjected to advanced treatment by using the oxidant, but the problems of low oxidation efficiency, insufficient COD degradation and the like of the oxidant bring difficulties to the downstream use treatment of the treated water.
CN201810577798.4 discloses a method and a device for continuously treating high-salt high-COD organic wastewater by deep catalytic oxidation of a microchannel reactor, wherein the inner wall of a microchannel of the adopted microchannel reactor is coated with gamma-Al 2 O 3 Supported MoO 3 The porous solid catalyst coating can realize the rapid oxidative degradation of organic matters in wastewater by utilizing the micro-channels and the catalyst loaded on the micro-channels, but has the following problems: with the increase of the use times, components (such as suspended matters) in the wastewater, such as COD (chemical oxygen demand) and the like, can be attached to the inner wall of the micro-channel, so that the pollution to the inner wall of the micro-channel is gradually increased, catalytic active sites are covered, the catalytic performance is reduced, and the service life of the micro-channel reactor is influenced.
Disclosure of Invention
The invention provides a catalytic microchannel reactor for degrading COD (chemical oxygen demand) and a preparation method and application thereof, aiming at solving the technical problem that the catalytic performance is influenced by the pollution of COD on the inner wall of a microchannel. The catalytic microchannel reactor can prevent COD from polluting the inner wall of the microchannel by controlling the roughness of the inner wall of the microchannel loaded with the catalyst, thereby prolonging the service life of the catalytic microchannel reactor.
The specific technical scheme of the invention is as follows:
in a first aspect, the invention provides a catalytic microchannel reactor for degrading COD, comprising a microchannel with a catalyst loaded on the inner wall; the surface roughness Ra of the inner wall of the micro-channel is less than 3 mu m.
According to the invention, the catalyst is loaded on the inner wall of the micro-channel, so that the micro-channel has a smaller inner diameter, and the liquid has a larger contact area with the inner wall when flowing in the micro-channel, thereby realizing full contact between the liquid and the catalyst and improving the catalytic effect.
In addition, the team of the invention pays attention to that when the catalytic microchannel reactor loaded with the catalyst is used for degrading COD, COD can be attached to the inner wall of the microchannel, so that the catalytic performance is influenced, and the COD degradation efficiency of the catalytic microchannel reactor is obviously reduced after the catalytic microchannel reactor is continuously used; when used for degrading COD in wastewater, other components (such as suspended matters) in the wastewater may adhere to the inner wall of the microchannel in addition to the COD, resulting in a decrease in COD degradation efficiency. In order to solve the technical problems, the invention controls the surface roughness of the inner wall of the microchannel loaded with the catalyst to be less than 3 μm, and can effectively prevent the reduction of catalytic performance caused by the pollution of COD and other components on the microchannel, thereby prolonging the service life of the catalytic microchannel reactor.
Preferably, the surface roughness Ra of the inner wall of the microchannel is less than 0.5 μm.
Preferably, the catalyst comprises Ni 2 O 3 。
Preferably, the diameter of the micro-channel is 50 μm to 5mm.
In a second aspect, the present invention provides a method for preparing the catalytic microchannel reactor, comprising the following steps:
(1) Injecting the catalyst particle suspension into a microchannel in the microchannel reactor, and sintering;
(2) And (3) repeating the step (1) until the surface roughness of the inner wall of the microchannel is less than 3 mu m, thus obtaining the catalytic microchannel reactor.
According to the invention, after the catalyst particle suspension is injected into the microchannel, the catalyst particles are attached to the inner wall of the microchannel, and then the solid-borne strength is improved by sintering, so that the catalyst is prevented from flowing out of the microchannel together with the liquid to lose efficacy in the use process of the catalytic microchannel reactor. By the mode, the catalyst is directly immobilized on the inner wall of the micro-channel, and the loading capacity of the catalyst can be improved.
In addition, with the increase of the loading times (the repetition times of the step (1)), the surface roughness of the inner wall of the micro-channel is gradually reduced, and the surface roughness is controlled below 3 μm by controlling the loading times, so that the reduction of the catalytic performance caused by the pollution of COD components on the micro-channel can be effectively prevented.
Preferably, the inner wall of the microchannel is subjected to surface hydroxylation by using an activating solution before the step (1).
By carrying out surface hydroxylation on the microchannel before loading the catalyst and loading by utilizing the acting force between the hydroxyl and the catalyst particles, the loading capacity and the solid-supported strength of the catalyst on the inner wall of the microchannel can be improved, so that the efficiency of degrading COD of the catalytic microchannel reactor is improved, and the falling-off of the catalyst in the using process is reduced.
Further, the activating solution is a piranha solution, and the time for surface hydroxylation is 1-2 h.
Preferably, in step (1), the preparation method of the catalyst particle suspension comprises the following steps: and grinding the catalyst particles and dispersing the ground catalyst particles into a dispersion medium to obtain a catalyst particle suspension.
Preferably, the preparation method specifically comprises the following steps:
(I) Injecting the catalyst particle suspension into a microchannel in a microchannel reactor, and sintering, wherein the proportion of the particle size of the catalyst particles is 50-60 nm is not less than 90%;
(II) repeating the step (I) 0-1 time (namely, the step (I) is carried out for 2-3 times in total); then the catalyst particles in the step (I) are changed into particles with the particle size of 30-40 nm, the proportion of the particles is not less than 90 percent, and the step (I) is repeated for 2-3 times; then the catalyst particles in the step (I) are changed into particles with the particle diameter of 15-25 nm, the proportion of the particles is not less than 90 percent, and the step (I) is repeated for 2-3 times.
Within a certain range, the surface roughness of the inner wall of the microchannel is reduced along with the increase of the number of times of loading, but when the number of times of loading is increased to a certain degree, subsequently-loaded catalyst particles are easy to be superposed on the immobilized catalyst, which is not beneficial to further reduction of the roughness of the inner wall of the microchannel. Therefore, the present invention is advantageous in that, in the process of repeated loading, the particle size of the catalyst particles is gradually reduced, so that the catalyst particles loaded each time are filled in the gaps between the catalyst particles formed after the previous loading, thereby being advantageous in reducing the surface roughness of the inner wall of the microchannel.
In the process of gradually reducing the particle size of the catalyst particles, if the particle size reduction range is too small, the effect of reducing the roughness of the inner wall of the micro-channel is difficult to effectively play; if the particle size is too large, the gaps between the supported catalyst particles still exist after the catalyst particles are filled into the gaps between the supported catalyst particles, which is formed after the previous loading, and the reduction of the roughness of the inner wall of the micro-channel is also not facilitated.
Preferably, in step (1) or (I), the suspension of catalyst particles has a solids content of from 1 to 10% by weight.
Preferably, in the step (1) or (I), the sintering temperature is 100-400 ℃ and the time is 0.5-2 h.
In a third aspect, the invention provides the use of the catalytic microchannel reactor for the degradation of COD.
Preferably, the application comprises the steps of: and introducing an oxidant solution and the liquid containing COD into the microchannel in the catalytic microchannel reactor together.
Compared with the prior art, the invention has the following advantages:
(1) In the catalytic microchannel reactor, the surface roughness of the inner wall of the microchannel loaded with the catalyst is controlled to be less than 3 mu m, so that COD can be prevented from polluting the inner wall of the microchannel, and the service life of the catalytic microchannel reactor is prolonged;
(2) In the process of preparing the catalytic microchannel reactor, the particle size of catalyst particles is gradually reduced in the process of repeated loading, so that the surface roughness of the inner wall of the microchannel is favorably reduced, and the service life of the catalytic microchannel reactor is prolonged to a greater extent.
Drawings
FIG. 1 is an optical microscopic photograph of a microchannel after the catalyst in example 1 was supported.
FIG. 2 is a schematic diagram of a catalytic microchannel reactor according to the present invention.
The reference signs are: microchannel 1, feed liquor pipe 2, drain pipe 3.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
A catalytic microchannel reactor for degrading COD comprises a microchannel with a catalyst loaded on the inner wall; the surface roughness Ra of the inner wall of the microchannel is less than 3 μm, preferably less than 0.5 μm.
As a specific embodiment, the catalyst comprises Ni 2 O 3 。
As a specific embodiment, the diameter of the micro-channel is 50 μm to 5mm.
A preparation method of the catalytic microchannel reactor comprises the following steps:
(1) Injecting the catalyst particle suspension into a microchannel in the microchannel reactor, and sintering;
(2) And (3) repeating the step (1) until the surface roughness of the inner wall of the microchannel is less than 3 mu m, thus obtaining the catalytic microchannel reactor.
As a specific embodiment, before the step (1), firstly, the inner wall of the micro-channel is subjected to surface hydroxylation by using an activating solution; the activating solution is a piranha solution, and the time of surface hydroxylation is 1-2 h.
As a specific embodiment, in the step (1), the preparation method of the catalyst particle suspension comprises the following steps: after the catalyst particles are ground, catalyst particles are obtained, and the catalyst particles are dispersed in a dispersion medium to obtain a catalyst particle suspension.
As a specific embodiment, the preparation method specifically comprises the following steps:
(I) Injecting the catalyst particle suspension into a microchannel in a microchannel reactor, and sintering, wherein the proportion of the particle size of the catalyst particles is 50-60 nm is not less than 90%;
(II) repeating the step (I) 0-1 times; then the catalyst particles in the step (I) are changed into particles with the particle size of 30-40 nm, the proportion of the particles is not less than 90 percent, and the step (I) is repeated for 2-3 times; then the catalyst particles in the step (I) are changed into particles with the particle diameter of 15-25 nm, the proportion of the particles is not less than 90 percent, and the step (I) is repeated for 2-3 times.
As a specific embodiment, in step (1) or (I), the suspension of catalyst particles has a solid content of from 1 to 10% by weight.
As a specific embodiment, in the step (1) or (I), the sintering temperature is 100-400 ℃ and the time is 0.5-2 h.
The application of the catalytic microchannel reactor in degrading COD.
As a specific embodiment, the application comprises the following steps: and introducing an oxidant solution and the liquid containing COD into the microchannel in the catalytic microchannel reactor together.
Example 1
A catalytic microchannel reactor was prepared by the following steps:
(1) Mix Ni 2 O 3 Grinding the particles to a particle size of 20-50 nm;
(2) Ni after grinding 2 O 3 The particles are dispersed in water to prepare Ni with the solid content of 5wt% 2 O 3 A suspension of particles;
(3) Injecting the piranha solution into a microchannel (with the inner diameter of 300 mu m) in the microchannel reactor, and activating the inner surface of the microchannel for 1h;
(4) Ni prepared in the step (2) 2 O 3 Injecting the particle suspension into the microchannel with the activated inner surface in the step (3), then placing the microchannel into a muffle furnace, sintering the microchannel at 350 ℃ for 1h, and performing the injection-sintering process for 5 times in a total cycle to obtain the catalytic microchannel reactor, wherein an optical microscope photo of the microchannel is shown in figure 1. The microchannel obtained in this example was examined for an inner surface roughness Ra =2.62 μm.
The structure of the catalytic microchannel reactor in this example is shown in FIG. 2, comprising microchannel 1; the inner wall of the microchannel 1 is loaded with Ni 2 O 3 A catalyst; the inlet end of the micro-channel 1 is connected with three liquid inlet pipes 2(ii) a The outlet end of the microchannel 2 is connected with a liquid outlet pipe 3.
The catalytic microchannel reactor prepared in the embodiment is used for degrading COD, and the specific process is as follows:
heating a catalytic microchannel reactor to 50 ℃, then respectively and circularly introducing 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm into a microchannel through a liquid inlet pipe at the same time, wherein the flow rates of the two solutions are both 1mL/min, continuously circulating for 1h, and detecting the COD concentration at the outlet end of the microchannel by using a COD detector, wherein the detection result is 0.4ppm. After 20 times of continuous operation (each time of continuous circulation, 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm are circularly introduced, and the continuous circulation is 1 h), the COD concentration at the outlet end of the micro-channel is 5.4ppm, a load layer on the inner surface of the micro-channel is observed by a microscope not to fall off, and the residual quantity of organic matters on the inner surface of the micro-channel is detected to be 22.7mg/dm by infrared spectroscopy (IR) 2 . After the micro-channel is continuously operated for 40 times, the COD concentration at the outlet end of the micro-channel is 8.5ppm, a load layer on the inner surface of the micro-channel is observed by a microscope to be not fallen off, and the residual quantity of organic matters on the inner surface of the micro-channel is 35.7mg/cm by IR detection 2 。
Example 2
A catalytic microchannel reactor was prepared by the following steps:
(1) Mixing Ni 2 O 3 Grinding the particles to a particle size of 20-50 nm;
(2) Ni after grinding 2 O 3 The particles are dispersed in water to prepare Ni with the solid content of 5wt% 2 O 3 A suspension of particles;
(3) Injecting the piranha solution into a microchannel (with the inner diameter of 300 mu m) in the microchannel reactor, and activating the inner surface of the microchannel for 1h;
(4) Ni prepared in the step (2) 2 O 3 And (4) injecting the particle suspension into the microchannel with the activated inner surface in the step (3), then placing the microchannel into a muffle furnace, sintering the microchannel at 100 ℃ for 1h, and performing the injection-sintering process for 10 times in total cycle to obtain the catalytic microchannel reactor. The micro-channel obtained in this example was tested to have an inner surface roughness Ra < 0.5 μm.
The structure of the catalytic microchannel reactor in this example was the same as in example 1.
The catalytic microchannel reactor prepared in the embodiment is used for degrading COD, and the specific process is as follows:
heating a catalytic microchannel reactor to 50 ℃, then respectively and circularly introducing 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm into a microchannel through a liquid inlet pipe at the same time, wherein the flow rates of the two solutions are both 1mL/min, and after continuous circulation for 1h, detecting the COD concentration at the outlet end of the microchannel by using a COD detector, wherein the detection result is 0.5ppm. After 20 times of continuous operation (each time of continuous circulation, 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm are circularly introduced, and the continuous circulation is 1 h), the COD concentration at the outlet end of the micro-channel is 0.5ppm, a load layer on the inner surface of the micro-channel is observed by a microscope not to fall off, and the residual quantity of organic matters on the inner surface of the micro-channel is 2.1mg/dm by IR detection 2 . After the micro-channel is continuously operated for 40 times, the COD concentration at the outlet end of the micro-channel is 0.6ppm, a load layer on the inner surface of the micro-channel is observed by a microscope to be not fallen off, and the residual quantity of organic matters on the inner surface of the micro-channel detected by IR is 2.5mg/dm 2 。
Example 3
A catalytic microchannel reactor was prepared by the following steps:
(1) Mixing Ni 2 O 3 Grinding the particles until the proportion of the particles with the particle size of 50-60 nm is 92 percent, dispersing the particles into water to prepare Ni with the solid content of 5wt percent and large particle size 2 O 3 A suspension of particles;
(2) Mixing Ni 2 O 3 Grinding the particles until the proportion of the particles with the particle size of 30-40 nm is 90%, dispersing the particles into water to prepare Ni with the medium particle size and the solid content of 5wt% 2 O 3 A suspension of particles;
(3) Mixing Ni 2 O 3 Grinding the particles until the proportion of the particles with the particle size of 15-25 nm is 90%, dispersing the particles into water to prepare the Ni with small particle size and the solid content of 5wt% 2 O 3 A suspension of particles;
(4) Injecting the piranha solution into a microchannel (with the inner diameter of 300 mu m) in the microchannel reactor, and activating the inner surface of the microchannel for 1h;
(5) Ni with large particle size prepared in the step (1) 2 O 3 Injecting the particle suspension into the microchannel with the activated inner surface in the step (4), then placing the microchannel into a muffle furnace, and sintering the microchannel for 1h at 350 ℃; then Ni with large grain diameter 2 O 3 Changing the particle suspension into Ni with medium particle size prepared in the step (2) 2 O 3 Particle suspension, the injection-sintering process is operated circularly for 2 times; then the medium grain diameter Ni 2 O 3 Changing the particle suspension into the small-particle-size Ni prepared in the step (3) 2 O 3 And (3) circularly operating the injection-sintering process for 2 times by using the particle suspension to obtain the catalytic microchannel reactor. The micro-channel obtained in the embodiment has the inner surface roughness Ra of less than 0.5 μm through detection.
The structure of the catalytic microchannel reactor in this example was the same as in example 1.
The catalytic microchannel reactor prepared in the embodiment is used for degrading COD, and the specific process is as follows:
heating a catalytic microchannel reactor to 50 ℃, then respectively and circularly introducing 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm into a microchannel through a liquid inlet pipe at the same time, wherein the flow rates of the two solutions are both 1mL/min, and after continuous circulation for 1h, detecting the COD concentration at the outlet end of the microchannel by using a COD detector, wherein the detection result is 0.5ppm. After 20 times of continuous operation (each time of continuous circulation, 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm are circularly introduced, and the continuous circulation is carried out for 1 h), the COD concentration at the outlet end of the micro-channel is 0.6ppm, a load layer on the inner surface of the micro-channel is observed by a microscope not to fall off, and the residual quantity of organic matters on the inner surface of the micro-channel is detected by IR to be 2.5mg/dm 2 . After the micro-channel is continuously operated for 40 times, the COD concentration at the outlet end of the micro-channel is 0.6ppm, a load layer on the inner surface of the micro-channel is observed by a microscope to be not fallen off, and the residual quantity of organic matters on the inner surface of the micro-channel detected by IR is 2.6mg/dm 2 。
And (3) data analysis:
examples 1 and 3 were each subjected to 5 times of loading (injection-sintering process), and example 1 used Ni of the same particle size during repeated loading 2 O 3 Particles, whereas example 3 gradually reduced Ni 2 O 3 The particle size of the particles. Example 3 the final microchannel inner surface roughness was significantly lower than example 1; after 20 and 40 continuous runs, the decrease of COD degradation efficiency of example 3 is obviously lower than that of example 1, and the organic residue on the inner surface of the micro-channel is obviously less than that of example 1. The repeated loading method for gradually reducing the particle size of the catalyst is favorable for reducing the surface roughness of the inner wall of the microchannel, so that the catalytic microchannel reactor can still keep higher COD degradation efficiency after being used for a long time.
Example 4
A catalytic microchannel reactor was prepared by the following steps:
(1) Mixing Ni 2 O 3 Grinding the particles until the proportion of the particles with the particle size of 50-60 nm is 92 percent, dispersing the particles into water to prepare Ni with the solid content of 5 weight percent and large particle size 2 O 3 A suspension of particles;
(2) Mixing Ni 2 O 3 Grinding the particles until the proportion of particles with the particle diameter of 45-55 nm is 90%, dispersing the particles into water to prepare Ni with the medium particle diameter and the solid content of 5wt% 2 O 3 A suspension of particles;
(3) Mixing Ni 2 O 3 Grinding the particles until the proportion of the particles with the particle size of 35-45 nm is 91 percent, dispersing the particles into water to prepare the Ni with small particle size and the solid content of 5wt percent 2 O 3 A suspension of particles;
(4) Injecting the piranha solution into a microchannel (with the inner diameter of 300 mu m) in the microchannel reactor, and activating the inner surface of the microchannel for 1h;
(5) Ni with large particle size prepared in the step (1) 2 O 3 Injecting the particle suspension into the microchannel with the activated inner surface in the step (4), then placing the microchannel into a muffle furnace, and sintering the microchannel for 1h at 350 ℃; then Ni with large grain diameter 2 O 3 Changing the particle suspension into Ni with medium particle size prepared in the step (2) 2 O 3 Particle suspension, the injection-sintering process is operated circularly for 2 times; then the medium grain diameter Ni 2 O 3 Changing the particle suspension into the small-particle-size Ni prepared in the step (3) 2 O 3 A suspension of particles ofThe injection-sintering process is circularly operated for 2 times to obtain the catalytic microchannel reactor. The microchannel obtained in this example was examined for an inner surface roughness Ra =1.39 μm.
The structure of the catalytic microchannel reactor in this example was the same as in example 1.
The catalytic microchannel reactor prepared in the embodiment is used for degrading COD, and the specific process is as follows:
heating a catalytic microchannel reactor to 50 ℃, then respectively and circularly introducing 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm into a microchannel through a liquid inlet pipe at the same time, wherein the flow rates of the two solutions are both 1mL/min, and after continuous circulation for 1h, detecting the COD concentration at the outlet end of the microchannel by using a COD detector, wherein the detection result is 0.5ppm. After 20 times of continuous operation (each time of continuous circulation, 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm are circularly introduced, and the continuous circulation is carried out for 1 h), the COD concentration at the outlet end of the micro-channel is 2.8ppm, a load layer on the inner surface of the micro-channel is observed by a microscope not to fall off, and the residual quantity of organic matters on the inner surface of the micro-channel is 11.7mg/dm by IR detection 2 . After the micro-channel is continuously operated for 40 times, the COD concentration at the outlet end of the micro-channel is 4.3ppm, a load layer on the inner surface of the micro-channel is observed by a microscope to be not fallen off, and the residual quantity of organic matters on the inner surface of the micro-channel detected by IR is 17.9mg/dm 2 。
And (3) data analysis:
in examples 3 and 4, the repeated loading method of gradually reducing the particle size of the catalyst is adopted, and the reduction range of the particle size is smaller in example 4. Compared with example 3, the micro-channel obtained finally in example 4 has larger roughness of the inner surface, and after 20 times and 40 times of continuous operation, the reduction range of COD degradation efficiency is larger, and the organic matter residue on the inner surface of the micro-channel is higher. It is indicated that in the process of gradually reducing the particle size of the catalyst, if the particle size reduction range is too small, the effect of reducing the roughness of the inner wall of the micro-channel and further preventing COD from polluting the micro-channel is difficult to be effectively exerted.
Example 5
A catalytic microchannel reactor was prepared by the following steps:
(1) Mixing Ni 2 O 3 Grinding the particles until the proportion of the particles with the particle size of 50-60 nm is 92 percent, dispersing the particles into water to prepare Ni with the solid content of 5 weight percent and large particle size 2 O 3 A suspension of particles;
(2) Mix Ni 2 O 3 Grinding the particles until the proportion of the particles with the particle size of 15-25 nm is 90%, dispersing the particles into water to prepare the Ni with small particle size and the solid content of 5wt% 2 O 3 A suspension of particles;
(3) Injecting the piranha solution into a microchannel (with the inner diameter of 300 mu m) in the microchannel reactor, and activating the inner surface of the microchannel for 1h;
(4) Ni with large particle size prepared in the step (1) 2 O 3 Injecting the particle suspension into the microchannel with the activated inner surface in the step (4), then placing the microchannel into a muffle furnace, and sintering the microchannel for 1h at 350 ℃; then Ni with large grain diameter 2 O 3 Changing the particle suspension into the small-particle-size Ni prepared in the step (2) 2 O 3 And (3) circularly operating the injection-sintering process for 4 times by using the particle suspension to obtain the catalytic microchannel reactor. The microchannel obtained in this example was examined to have an inner surface roughness Ra =1.52 μm.
The structure of the catalytic microchannel reactor in this example was the same as in example 1.
The catalytic microchannel reactor prepared in the embodiment is used for degrading COD, and the specific process is as follows:
heating a catalytic microchannel reactor to 50 ℃, then respectively and circularly introducing 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm into a microchannel through a liquid inlet pipe at the same time, wherein the flow rates of the two solutions are both 1mL/min, continuously circulating for 1h, and detecting the COD concentration at the outlet end of the microchannel by using a COD detector, wherein the detection result is 0.4ppm. After 20 times of continuous operation (each time of continuous circulation, 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm are circularly introduced, and the continuous circulation is carried out for 1 h), the COD concentration at the outlet end of the micro-channel is 3.6ppm, a load layer on the inner surface of the micro-channel is observed by a microscope not to fall off, and the residual quantity of organic matters on the inner surface of the micro-channel is 15.0mg/dm by IR detection 2 . After the continuous operation for 40 times, the COD at the outlet end of the micro-channel is concentratedThe degree is 5.0ppm, the load layer on the inner surface of the channel observed by a microscope does not fall off, and the residual quantity of organic matters on the inner surface of the micro-channel detected by IR is 20.8mg/dm 2 。
And (3) data analysis:
examples 3 and 5 both used a repetitive loading method of gradually decreasing the catalyst particle size, with the particle size decreasing in example 5 being larger. Compared with example 3, the micro-channel obtained finally in example 5 has larger roughness of the inner surface, and after 20 times and 40 times of continuous operation, the reduction range of COD degradation efficiency is larger, and the organic matter residue on the inner surface of the micro-channel is higher. It is indicated that in the process of gradually reducing the particle size of the catalyst, if the reduction of the particle size is too large, after the catalyst particles loaded each time are filled into the gaps of the catalyst particles formed after the last loading, larger gaps still exist among the immobilized catalyst particles, which causes the roughness of the inner surface of the microchannel to be higher, and further causes the COD degradation efficiency of the catalytic microchannel reactor to be reduced to a larger extent after the catalytic microchannel reactor is used for a long time.
Comparative example 1
50mL of 200ppm COD solution was taken, 50mL of 500ppm NaClO solution was added, and degradation was carried out at 50 ℃. Sampling after 30min, and detecting by using a COD detector, wherein the COD is 30ppm.
Comparative example 2
A catalytic microchannel reactor was prepared by the following steps:
(1) To Ni 2 O 3 Grinding the particles to obtain Ni with the particle size of 20-50 nm 2 O 3 A particle;
(2) Ni after grinding 2 O 3 The particles are dispersed in a dispersion medium to prepare Ni with the solid content of 5wt% 2 O 3 A suspension of particles;
(3) Injecting the piranha solution into a microchannel (with the inner diameter of 300 mu m) in the microchannel reactor, and activating the inner surface of the microchannel for 1h;
(4) Ni prepared in the step (2) 2 O 3 And (4) injecting the particle suspension into the microchannel with the activated inner surface in the step (3), then placing the microchannel into a muffle furnace, and sintering the microchannel at 350 ℃ for 1h to obtain the catalytic microchannel reactor. After the detection, the detection result shows that,the microchannel inner surface roughness Ra =4.55 μm obtained in the present comparative example.
The structure of the catalytic microchannel reactor in this comparative example was the same as in example 1.
The catalytic microchannel reactor prepared in the comparative example is used for degrading COD, and the specific process is as follows:
heating a catalytic microchannel reactor to 50 ℃, then respectively and circularly introducing 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm into a microchannel through a liquid inlet pipe at the same time, wherein the flow rates of the two solutions are both 1mL/min, and after continuous circulation for 1h, detecting the COD concentration at the outlet end of the microchannel by using a COD detector, wherein the detection result is 0.5ppm. After 20 times of continuous operation (20 mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol aqueous solution with the initial concentration of 200ppm are circularly introduced in each operation and continuously circulated for 1 h), the COD concentration at the outlet end of the micro-channel is 11.3ppm, a load layer on the inner surface of the channel is observed by a microscope not to fall off, and the residual organic matter amount on the inner surface of the micro-channel is 47.1mg/dm by IR detection 2 . After the micro-channel is continuously operated for 40 times, the COD concentration at the outlet end of the micro-channel is 14.7ppm, a load layer on the inner surface of the micro-channel is observed by a microscope to be not fallen off, and the residual quantity of organic matters on the inner surface of the micro-channel detected by IR is 52.3mg/dm 2 。
Comparative example 3
A catalytic microchannel reactor was prepared by the following steps:
(1) To Ni 2 O 3 Grinding the particles to obtain Ni with the particle size of 20-50 nm 2 O 3 Particles;
(2) Ni after grinding 2 O 3 The particles are dispersed in a dispersion medium to prepare Ni with the solid content of 5wt% 2 O 3 A suspension of particles;
(3) Injecting the piranha solution into a microchannel (with the inner diameter of 300 mu m) in the microchannel reactor, and activating the inner surface of the microchannel for 1h;
(4) Ni prepared in the step (2) 2 O 3 Injecting the particle suspension into the microchannel with the activated inner surface in the step (3), then placing the microchannel into a muffle furnace, sintering the microchannel at 350 ℃ for 1h, and injecting and sintering the microchannelThe process was operated 3 times in total cycles to obtain a catalytic microchannel reactor. The microchannel obtained in the present comparative example was examined for an inner surface roughness Ra =3.31 μm.
The structure of the catalytic microchannel reactor in this comparative example was the same as in example 1.
The catalytic microchannel reactor prepared in the comparative example is used for degrading COD, and the specific process is as follows:
heating a catalytic microchannel reactor to 50 ℃, then respectively and circularly introducing 20mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol water solution with the initial concentration of 200ppm into a microchannel through a liquid inlet pipe at the same time, wherein the flow rates of the two solutions are both 1mL/min, and after continuous circulation for 1h, detecting the COD concentration at the outlet end of the microchannel by using a COD detector, wherein the detection result is 0.6ppm. After 20 times of continuous operation (20 mL of NaClO solution with the initial concentration of 500ppm and 20mL of ethanol aqueous solution with the initial concentration of 200ppm are circularly introduced in each operation and continuously circulated for 1 h), the COD concentration at the outlet end of the micro-channel is 10.1ppm, a load layer on the inner surface of the channel is observed by a microscope not to fall off, and the residual organic matter quantity on the inner surface of the micro-channel is 42.1mg/dm by IR detection 2 . After the micro-channel is continuously operated for 40 times, the COD concentration at the outlet end of the micro-channel is 14.1ppm, a load layer on the inner surface of the micro-channel is observed by a microscope to be not fallen off, and the residual quantity of organic matters on the inner surface of the micro-channel is 58.7mg/dm by IR detection 2 。
And (3) data analysis:
in comparative example 2, comparative example 3, example 1 and example 2, the roughness of the inner surface of the catalytic microchannel reactor was reduced in order; after 20 and 40 consecutive runs, the decrease of COD degradation efficiency of example 1 was significantly lower than that of comparative examples 2 and 3, the decrease of example 2 was significantly lower than that of example 1, and the residual organic matter amount on the inner surface of the microchannel of example 1 was significantly lower than that of comparative examples 2 and 3, and example 2 was significantly lower than that of example 1. The method has the advantages that the roughness of the inner surface of the micro-channel can be reduced through multiple times of loading, and after the roughness is reduced to a certain degree, the micro-channel is favorably prevented from being polluted by COD along with the increase of the loading times and the reduction of the roughness of the inner surface of the micro-channel, so that the catalytic micro-channel reactor can still keep higher COD degradation efficiency after being used for a long time, and has longer service life.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (10)
1. A catalytic microchannel reactor for degrading COD is characterized by comprising a microchannel with a catalyst loaded on the inner wall; the surface roughness Ra of the inner wall of the micro-channel is less than 3 mu m.
2. The catalytic microchannel reactor of claim 1, wherein the catalyst comprises Ni 2 O 3 。
3. The catalytic microchannel reactor of claim 1, wherein the diameter of the microchannel is from 50 μm to 5mm.
4. A method of making a catalytic microchannel reactor as claimed in any one of claims 1~3 comprising the steps of:
(1) Injecting the catalyst particle suspension into a microchannel in the microchannel reactor, and sintering;
(2) And (2) repeating the step (1) until the surface roughness of the inner wall of the micro-channel is less than 3 mu m, thus obtaining the catalytic micro-channel reactor.
5. The method of claim 4, wherein step (1) is preceded by surface hydroxylation of the inner wall of the microchannel using an activating solution.
6. The method according to claim 5, wherein the activating solution is a piranha solution, and the surface is hydroxylated for 1 to 2h.
7. The method according to claim 4, wherein in the step (1), the method for preparing the catalyst particle suspension comprises the steps of: and grinding the catalyst particles and dispersing the ground catalyst particles into a dispersion medium to obtain a catalyst particle suspension.
8. The preparation method according to claim 4, comprising the following steps:
(I) Injecting the catalyst particle suspension into a microchannel in a microchannel reactor, and sintering, wherein the proportion of the particle size of the catalyst particles is 50-60nm is not less than 90%;
(II) repeating step (I) 0~1 times; changing the catalyst particles in the step (I) into particles with the particle size of 30-40nm of not less than 90%, and repeating the step (I) for 2~3 times; and (3) changing the catalyst particles in the step (I) into particles with the particle size of 15-25nm, wherein the proportion of the particles is not less than 90%, and repeating the step (I) 2~3 times.
9. Use of a catalytic microchannel reactor according to any one of claims 1~3 for the degradation of COD.
10. Use according to claim 9, characterized in that it comprises the following steps: and introducing an oxidant solution and the liquid containing COD into the microchannel in the catalytic microchannel reactor together.
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