CN117867529A - Method for preparing lactobionic acid by electrocatalytic action of carbon-based nonmetallic catalyst - Google Patents
Method for preparing lactobionic acid by electrocatalytic action of carbon-based nonmetallic catalyst Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 116
- UOQHWNPVNXSDDO-UHFFFAOYSA-N 3-bromoimidazo[1,2-a]pyridine-6-carbonitrile Chemical compound C1=CC(C#N)=CN2C(Br)=CN=C21 UOQHWNPVNXSDDO-UHFFFAOYSA-N 0.000 title claims abstract description 59
- 229940099563 lactobionic acid Drugs 0.000 title claims abstract description 59
- 238000000034 method Methods 0.000 title claims abstract description 37
- 239000003054 catalyst Substances 0.000 title claims abstract description 24
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 23
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 59
- 229920000049 Carbon (fiber) Polymers 0.000 claims abstract description 53
- 239000004917 carbon fiber Substances 0.000 claims abstract description 53
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 50
- 239000004744 fabric Substances 0.000 claims abstract description 42
- GUBGYTABKSRVRQ-QKKXKWKRSA-N Lactose Natural products OC[C@H]1O[C@@H](O[C@H]2[C@H](O)[C@@H](O)C(O)O[C@@H]2CO)[C@H](O)[C@@H](O)[C@H]1O GUBGYTABKSRVRQ-QKKXKWKRSA-N 0.000 claims abstract description 40
- 239000008101 lactose Substances 0.000 claims abstract description 40
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 27
- 238000006243 chemical reaction Methods 0.000 claims abstract description 21
- 238000002360 preparation method Methods 0.000 claims abstract description 17
- 239000012528 membrane Substances 0.000 claims abstract description 15
- 238000005341 cation exchange Methods 0.000 claims abstract description 14
- 125000004433 nitrogen atom Chemical group N* 0.000 claims abstract description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 8
- 239000010439 graphite Substances 0.000 claims abstract description 8
- 239000001301 oxygen Substances 0.000 claims abstract description 8
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 8
- 230000004913 activation Effects 0.000 claims abstract description 6
- 238000001179 sorption measurement Methods 0.000 claims abstract description 6
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims description 24
- 230000003647 oxidation Effects 0.000 claims description 22
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 229920000767 polyaniline Polymers 0.000 claims description 19
- 239000000243 solution Substances 0.000 claims description 17
- 239000004202 carbamide Substances 0.000 claims description 13
- 229910052757 nitrogen Inorganic materials 0.000 claims description 13
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 12
- 230000035484 reaction time Effects 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 12
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 10
- 238000001354 calcination Methods 0.000 claims description 10
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 10
- 229910052755 nonmetal Inorganic materials 0.000 claims description 10
- 238000006555 catalytic reaction Methods 0.000 claims description 9
- -1 hydrogen ions Chemical class 0.000 claims description 9
- 238000006056 electrooxidation reaction Methods 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 6
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 6
- 239000008367 deionised water Substances 0.000 claims description 6
- 229910021641 deionized water Inorganic materials 0.000 claims description 6
- 239000005457 ice water Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 4
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000012141 concentrate Substances 0.000 claims description 3
- 238000009833 condensation Methods 0.000 claims description 3
- 230000005494 condensation Effects 0.000 claims description 3
- 230000018044 dehydration Effects 0.000 claims description 3
- 238000006297 dehydration reaction Methods 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 239000000178 monomer Substances 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 3
- 239000003863 metallic catalyst Substances 0.000 claims 1
- 239000007788 liquid Substances 0.000 abstract description 6
- 238000007086 side reaction Methods 0.000 abstract description 5
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000000926 separation method Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 238000007210 heterogeneous catalysis Methods 0.000 description 2
- 238000002329 infrared spectrum Methods 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- KJFMBFZCATUALV-UHFFFAOYSA-N phenolphthalein Chemical compound C1=CC(O)=CC=C1C1(C=2C=CC(O)=CC=2)C2=CC=CC=C2C(=O)O1 KJFMBFZCATUALV-UHFFFAOYSA-N 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 238000004448 titration Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000000909 electrodialysis Methods 0.000 description 1
- 238000004128 high performance liquid chromatography Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- SWGJCIMEBVHMTA-UHFFFAOYSA-K trisodium;6-oxido-4-sulfo-5-[(4-sulfonatonaphthalen-1-yl)diazenyl]naphthalene-2-sulfonate Chemical compound [Na+].[Na+].[Na+].C1=CC=C2C(N=NC3=C4C(=CC(=CC4=CC=C3O)S([O-])(=O)=O)S([O-])(=O)=O)=CC=C(S([O-])(=O)=O)C2=C1 SWGJCIMEBVHMTA-UHFFFAOYSA-K 0.000 description 1
Abstract
The invention discloses a method for preparing lactobionic acid by using a carbon-based nonmetallic catalyst in an electrocatalytic way, wherein an anode electrode and a cathode electrode are arranged on two sides of an electrolytic tank with a cation exchange membrane arranged in the middle, the anode electrode takes sheet carbon fiber cloth as a carbon skeleton, and nitrogen-doped graphene oxide is modified on the surface of the carbon skeleton; the cathode electrode is a graphite electrode; lactose is injected into one side of the anode of the electrolytic cell, wherein the concentration of the lactose is 1mol/L to 1.5mol/L; after being electrified, the anode electrode is used as a carbon fiber cloth surface of a carbon skeleton and nitrogen atoms doped on the surface of graphene to activate and electrolyze oxygen generated by the activation and the oxidization of lactose to lactobionic acid; forming single lactobionic acid at one side of the anode electrode; by constructing adsorption of O 2 And the activated solid-liquid interface can promote lactose to be oxidized into lactobionic acid, the reaction process is mild, the side reaction is inhibited, and the electrooxygen is improvedConversion and current efficiency of the process for the preparation of lactobionic acid.
Description
Technical Field
The invention relates to the technical field of lactobionic acid preparation, in particular to a method for preparing lactobionic acid by using a carbon-based nonmetallic catalyst in an electrocatalytic manner.
Background
The invention discloses a method for preparing lactobionic acid by electrooxidation of lactose to lactobionic acid in application number CN112030190A, which mainly comprises the following steps: the anode and the cathode electrode are graphite, and water in the middle interface layer of the bipolar membrane is ionized into H under the action of a direct current electric field + And OH (OH) - Ions, H + Enters the cathode chamber through the SSBS-g-AA positive film and is hydrolyzed with OH generated by water - Binding to generate H 2 O, and OH formed - Enters an anode chamber through SBS-g-DMAEMA negative film, and combines with H+ generated in the process of generating lactobionic acid through lactose electrooxidation to generate H 2 O, thereby promoting the reaction in the forward direction. KBr is the medium of indirect electrocatalytic oxidation reaction, br - Oxidized to Br at the anode 2 Subsequently lactose is oxidized to lactobionic acid, which itself is reduced to Br - . As is clear from the reaction process, on one hand, side reactions exist, which cause low current efficiency, and on the other hand, bromine ions are introduced into the product, so that the separation is inconvenient.
Disclosure of Invention
The invention aims to provide a method for preparing lactobionic acid by electrocatalytic action by using a carbon-based nonmetallic catalyst, which comprises the following steps of constructing and adsorbing O 2 And the activated solid-liquid interface can promote the oxidation of lactose into lactobionic acid, the reaction process is mild, the side reaction is inhibited, and the conversion rate and the current efficiency in the process of preparing lactobionic acid by electrooxidation are improved.
In order to solve the technical problem, the technical scheme of the invention is as follows: a method for preparing lactobionic acid by using a carbon-based nonmetallic catalyst comprises the steps of placing an anode electrode and a cathode electrode on two sides of an electrolytic tank with a cation exchange membrane in the middle, wherein the anode electrode takes sheet carbon fiber cloth as a carbon skeleton, and nitrogen-doped graphene oxide is modified on the surface of the sheet carbon fiber cloth; the cathode electrode is a graphite electrode;
lactose is injected into one side of the anode of the electrolytic cell, wherein the concentration of the lactose is 1mol/L to 1.5mol/L;
electrolytic oxidation at 25 ℃ to 40 ℃ for 180min to 240min;
oxidation current density of 20 mA.cm -2 To 35mA cm -2 ；
After being electrified, the anode electrode is used as a carbon fiber cloth surface of a carbon skeleton and nitrogen atoms doped on the surface of graphene to activate and electrolyze oxygen generated by the activation and the oxidization of lactose to lactobionic acid;
hydrogen ions generated by the anode electrode enter one side of the cathode electrode through a cation exchange membrane between the anode electrode and the cathode electrode and are combined with hydroxyl generated on the surface of the cathode electrode into water molecules through the solution;
a single lactobionic acid is formed at one side of the anode electrode.
Preferably, the preparation method of the anode electrode comprises the following steps:
s11, arranging the cleaned carbon fibers in strong acid for soaking, and loading-COOH on the surface of the carbon fiber cloth;
s12, modifying graphene oxide by using polyaniline;
s13, placing urea and graphene oxide with polyaniline modified on the surface into deionized water, and stirring to obtain-NH (NH) -urea 2 Forming an amide bond by dehydration condensation of-COOH on the edge of carbon fiber cloth and polyaniline-modified graphene oxide, wherein the graphene oxide passes through-NH of urea 2 The chemical bond is connected with the carbon fiber cloth;
s14, placing the carbon fiber cloth-urea-polyaniline modified graphene oxide self-assembled structure obtained in the S13 in a polytetrafluoroethylene reaction kettle for hydrothermal reaction, and calcining to obtain nitrogen-doped carbon fiber cloth and graphene oxide serving as anode electrodes. The invention effectively and uniformly dopes nitrogen atoms on the surface of the graphene oxide through the loaded polyaniline to promote O 2 Molecular adsorption and activation.
Preferably, the method for modifying graphene oxide by polyaniline in S12 comprises the following steps:
s121, placing 100mg of graphene oxide into deionized water, adding 10ml of HCl with the concentration of 1mol/L, uniformly stirring, dropwise adding excessive 0.4. 0.4m L aniline, and performing ultrasonic dispersion for 1h;
s122, placing the mixed solution in an ice water bath, respectively adding 30 and m L of HCl with the concentration of 1mol/L and 0.25g of ammonium persulfate, uniformly mixing, and introducing argon protective atmosphere;
and S123, maintaining an ice-water bath, soaking for 24 hours, and cleaning by using ethanol to remove excessive unreacted aniline, so as to obtain polyaniline-modified graphene oxide.
Preferably, in S121, aniline and graphene oxide are uniformly distributed on the surface of graphene oxide through the adsorption action of pi-pi bonds, and aniline monomers are polymerized to form chain polyaniline under the action of ammonium persulfate.
Preferably, the reaction time for forming an amide bond in S13 is 6 hours to 12 hours. The invention provides sufficient reaction time in the S12 process to promote the formation of amide bonds and ensure the sufficient formation of the resulting covalent bonds.
Preferably, the temperature of the hydrothermal reaction in S14 is 120 ℃ to 140 ℃ and the reaction time is 12 hours to 18 hours. The invention forms relatively stable carbon fiber cloth-polyaniline modified graphene oxide through hydrothermal reaction.
Preferably, the calcination in S14 is performed under nitrogen protection, including a first stage and a second stage; wherein the technological parameters of the first stage are as follows: heating to 250-300 deg.c and maintaining for 2-4 hr;
the technological parameters of the second stage are as follows: continuously heating to 750-800 ℃, and preserving heat for 2-4 hours to obtain the nitrogen-doped graphene oxide.
Preferably, the pH of the solution on the anode side is maintained between 5.8 and 6.8 during the electrochemical oxidation of lactose to lactobionic acid. H continuously generated at one side of anode in the invention + The water molecules are continuously combined with OH-contact on one side of the cathode through the cation exchange membrane by diffusion, the pH value of the whole reaction system is relatively little changed, and the influence on lactose oxidation is small.
Preferably, as oxidation of lactose to lactobionic acid proceeds, water is consumed to form a concentrate of the anode side solution.
By adopting the technical scheme, the invention has the beneficial effects that:
the invention uses a carbon-based nonmetallic catalyst which is connected to the surface of carbon fiber cloth through chemical bonds as an anode electrode of an electrolytic tank, and a cathode electrode is a graphite electrode; the anode electrode and the cathode electrode are arranged on two sides of an electrolytic tank with a cation exchange membrane arranged in the middle, wherein the anode electrode takes sheet carbon fiber cloth as a carbon skeleton, and the surface of the anode electrode is modified with nitrogen doped graphene oxide; in the lactose oxidation process, the graphene oxide doped with nitrogen atoms on the surface of the anode electrode effectively activates oxygen generated in the electrolyzed water into O of a solid-liquid interface by improving the electron conductivity 2- After the power is on, the anode electrode is used as the carbon fiber cloth surface of the carbon skeleton and the nitrogen atoms doped on the surface of the graphene to activate and electrolyze to produce oxygen which is used as an active group to oxidize lactose into lactobionic acid, and the catalyst used in the invention has different valence changes different from metal ions, so that the reaction process is mild, side reactions are inhibited, and the conversion rate and the current efficiency in the process of preparing the lactobionic acid by electrooxidation are improved;
the concentration of lactose injected into one side of the anode of the electrolytic tank is 1mol/L to 1.5mol/L, the electrolytic oxidation is carried out for 180min to 240min at the temperature of 25 ℃ to 40 ℃, and the oxidation current density is 20 mA.cm -2 To 35mA cm -2 The conversion rate of lactose is approximately 80%, and hydrogen ions generated by the anode electrode during the electrolysis process enter to the cathode electrode side through a cation exchange membrane between the anode electrode and the cathode electrode, and are combined with hydroxyl groups generated on the surface of the cathode electrode into water molecules through a solution, so that single lactobionic acid is formed on the anode electrode side. The invention greatly reduces the use of alkaline substances such as potassium hydroxide or sodium carbonate and the like, and also greatly reduces the workload of subsequent substance separation and concentration;
according to the preparation method, the graphene oxide doped with nitrogen atoms is connected to the surface of the carbon fiber cloth through chemical bonds, and most of carboxyl groups of the graphene oxide are specific structural characteristics existing at the edge of a graphene oxide lamellar structure, in order to effectively enlarge a catalytic area in the preparation process, the urea is used for respectively forming amide bonds with the carbon fiber cloth and the graphene oxide which are soaked by strong acid to form carboxyl groups, the graphene oxide is distributed along the surface of the carbon fiber cloth through the amide bonds, the carbon fiber cloth has certain rigidity, the structure is stable, urea in the preparation process is positioned between the carbon fiber cloth and the graphene oxide, and nitrogen element doping and structural stability are synchronously formed by matching with subsequent calcination;
the invention provides a method for preparing lactobionic acid by using a carbon-based nonmetallic catalyst in an electrocatalytic way, which has heterogeneous catalysis and strong adaptability.
Drawings
FIG. 1 is an infrared spectrum of polyaniline-modified graphene oxide in example 1 of the present invention;
FIG. 2 is an SEM image of carbon fiber cloth-nitrogen doped graphene oxide prepared in example 1 of the present invention;
FIG. 3 is an SEM image of a single carbon fiber of the carbon fiber cloth-nitrogen doped graphene oxide prepared in example 1 of the present invention;
FIG. 4 is a schematic diagram of an electrocatalytic production of lactobionic acid using a carbon-based non-metal catalyst according to the present invention;
FIG. 5 is a liquid chromatogram of lactobionic acid obtained in example 1 of the present invention.
In the figure:
an electrolytic cell 1; an anode electrode 2; a cathode electrode 3; a cation exchange membrane 4; a collection unit 5.
Detailed Description
In order to further explain the technical scheme of the invention, the invention is explained in detail by specific examples.
Example 1
The embodiment discloses a carbon-based nonmetal catalyst applied to electrocatalytic preparation of a lactobionic acid anode electrode, wherein the preparation method of the anode electrode comprises the following steps:
s11, the surface density after cleaning is 200g/m 2 The carbon fibers are arranged in strong acid for soaking, and the surfaces of the carbon fiber fabrics are loaded with-COOH;
wherein the volume ratio of the strong acid to the concentrated sulfuric acid is 1:3, the heating temperature is 80 ℃, and the soaking time is 4 hours; the size of the carbon fiber cloth is 4cm x 4cm;
s12, modifying graphene oxide by using polyaniline;
the method for modifying graphene oxide by polyaniline comprises the following steps:
s121, placing 50mg of graphene oxide into 100ml of deionized water, adding 10ml of HCl with the concentration of 1mol/L, uniformly stirring, dropwise adding excessive 0.3. 0.3m L aniline, and performing ultrasonic dispersion for 1h;
aniline and graphene oxide are uniformly distributed on the surface of the graphene oxide through the adsorption action of pi-pi bonds, and aniline monomers are polymerized to form chain polyaniline under the action of ammonium persulfate.
S122, placing the mixed solution in an ice water bath, respectively adding 15m L of HCl with the concentration of 1mol/L and 0.15g of ammonium persulfate, uniformly mixing, and introducing argon protective atmosphere;
and S123, maintaining an ice-water bath, soaking for 24 hours, and cleaning by using ethanol to remove excessive unreacted aniline, so as to obtain polyaniline-modified graphene oxide.
S13, placing urea and graphene oxide with polyaniline modified on the surface into deionized water, and stirring to obtain-NH (NH) -urea 2 Forming an amide bond by dehydration condensation of-COOH on the edge of carbon fiber cloth and polyaniline-modified graphene oxide, wherein the graphene oxide passes through-NH of urea 2 The chemical bond is connected with the carbon fiber cloth;
the reaction time for forming an amide bond in S13 was 12 hours. The invention provides sufficient reaction time in the S12 process to promote the formation of amide bonds and ensure the sufficient formation of the resulting covalent bonds. The infrared spectrum of the polyaniline-modified graphene oxide prepared in the embodiment is shown in fig. 1.
S14, placing the carbon fiber cloth-urea-polyaniline modified graphene oxide self-assembled structure obtained in the S13 in a polytetrafluoroethylene reaction kettle for hydrothermal reaction, and calcining to obtain nitrogen-doped carbon fiber cloth and graphene oxide serving as anode electrodes. The invention effectively and uniformly dopes nitrogen atoms on the surface of the graphene oxide through the loaded polyaniline to promote O 2 Molecular adsorption and activation.
The temperature of the hydrothermal reaction in S14 is 130 ℃, and the reaction time is 15 hours. The invention forms relatively stable carbon fiber cloth-polyaniline modified graphene oxide through hydrothermal reaction, the morphology of which is shown in figure 2, and the fiber surface of the carbon fiber cloth is attached with a modifying substance.
The calcination in S14 is performed under the protection of nitrogen, and comprises a first stage and a second stage; wherein the technological parameters of the first stage are as follows: heating to 250 ℃, and preserving heat for 4 hours;
the technological parameters of the second stage are as follows: continuing to heat up to 750 ℃, and preserving heat for 4 hours to obtain the nitrogen-doped graphene oxide loaded on the carbon fiber cloth, as can be seen from fig. 2 and 3, graphene oxide sheets are uniformly attached to the fiber surface of the carbon fiber cloth in the embodiment, and a certain gap is formed between the nitrogen-doped graphene oxide sheets, so that a richer solid-liquid interface is formed in the lactose catalysis process conveniently.
Example 2
This example discloses a carbon-based nonmetallic catalyst applied to electrocatalytic preparation of a lactobionic acid anode electrode, and the preparation method of the anode electrode, which is mainly different from example 1 as follows:
the reaction time for forming an amide bond in S13 was 9 hours.
The temperature of the hydrothermal reaction in S14 is 140 ℃, and the reaction time is 12 hours.
The calcination in S14 is performed under the protection of nitrogen, and comprises a first stage and a second stage; wherein the technological parameters of the first stage are as follows: heating to 300 ℃, and preserving heat for 2 hours;
the technological parameters of the second stage are as follows: heating to 800 deg.C, and maintaining for 2 hr.
Example 3
This example discloses a carbon-based nonmetallic catalyst applied to electrocatalytic preparation of a lactobionic acid anode electrode, and the preparation method of the anode electrode, which is mainly different from example 1 as follows:
the reaction time for forming an amide bond in S13 was 6 hours.
The temperature of the hydrothermal reaction in S14 is 120 ℃, and the reaction time is 18 hours.
The calcination in S14 is performed under the protection of nitrogen, and comprises a first stage and a second stage; wherein the technological parameters of the first stage are as follows: heating to 250 ℃, and preserving heat for 2 hours;
the technological parameters of the second stage are as follows: heating to 750 deg.c and maintaining for 2 hr.
Example 4
The embodiment discloses a method for preparing lactobionic acid by electrochemical preparation of an anode electrode, which is prepared in the embodiment 1, as shown in fig. 4, the device comprises two sides of an electrolytic tank 1, an anode electrode 2, a cathode electrode 3 and a cation exchange membrane 4 arranged between the two, wherein the anode electrode 2 takes sheet carbon fiber cloth as a carbon skeleton, and the surface of the sheet carbon fiber cloth is modified with nitrogen doped graphene oxide; the cathode electrode 3 is a graphite electrode;
lactose is injected into one side of the anode of the electrolytic tank 1, wherein the concentration of lactose is 1 mol/L;
electrolytic oxidation at 25 ℃ to 40 ℃ for 180min;
oxidation current density of 20 mA.cm -2 ；
After being electrified, the anode electrode is used as a carbon fiber cloth surface of a carbon skeleton and nitrogen atoms doped on the surface of graphene to activate and electrolyze oxygen generated by the activation and the oxidization of lactose to lactobionic acid;
hydrogen ions generated by the anode electrode enter one side of the cathode electrode 3 through a cation exchange membrane 4 between the anode electrode 2 and the cathode electrode 3 and are combined with hydroxyl radicals generated on the surface of the cathode electrode 3 into water molecules through a solution;
a single lactobionic acid is formed on one side of the anode electrode 2.
The hydrogen gas generated at the cathode side in this embodiment enters the collection unit 5.
In this example, the pH of the solution on the anode side was maintained between 5.8 and 6.8 during the electrochemical oxidation of lactose to lactobionic acid. H continuously generated at one side of anode in the invention + The water molecules are continuously combined with OH-contact on one side of the cathode through the cation exchange membrane by diffusion, the pH value of the whole reaction system is relatively little changed, and the influence on lactose oxidation is small.
In this example, as oxidation of lactose to lactobionic acid proceeds, water is consumed to form a concentrate of the anode side solution.
Example 5
This example discloses a method for electrochemical production of lactobionic acid using the anode electrode prepared in example 2, and the difference between this example and example 4 further comprises:
lactose is injected into one side of the anode of the electrolytic cell, wherein the concentration of the lactose is 1.2 mol/L;
electrolytic oxidation at 25 ℃ to 40 ℃ for 210min;
oxidation current density of 30mA cm -2 。
Example 6
This example discloses a method for electrochemical production of lactobionic acid using the anode electrode prepared in example 3, and the difference between this example and example 4 further comprises:
lactose is injected into one side of the anode of the electrolytic cell, wherein the concentration of lactose is 1.5mol/L;
electrolytic oxidation at 25 ℃ to 40 ℃ for 240min;
oxidation current density of 35 mA.cm -2 。
Comparative example
The main difference between this comparative example and example 4 is that the anode electrode is a graphite electrode, the solution on the anode side comprises 1mol/L lactose solution, and the remaining process parameters are the same as in example 4.
Since lactose used in the present invention has a solubility of 1mol/L or more, the concentration is high compared with that of general chemical conversion, and the lactobionic acid content in the solutions after conversion of examples 4 to 6 and comparative examples are measured by back titration methods, respectively, as follows:
firstly adding a certain molar amount of M and ensuring excessive sodium hydroxide, wherein part of M1 is used for salifying with lactobionic acid, the rest is M2, and phenolphthalein is used as an indicator to make the indicator appear purple red; titrating the reaction solution to be neutral by using the sulfuric acid standard solution with the determined concentration, namely, the solution becomes colorless, namely, the titration end point is obtained; the amount of free sodium hydroxide M2 was determined and the concentration of lactobionic acid based on m1=m-M2 was determined, and the specific data are shown in table 1.
Table 1 lactobionic acid concentrations and conversion obtained in examples 4 to 6 and comparative example
The anode side conversion solutions obtained in examples 4 to 6 were separated by electrodialysis, and the HPLC chart was shown in FIG. 5. As can be seen from FIG. 5, the present invention produced single lactobionic acid.
The invention uses a carbon-based nonmetallic catalyst which is connected to the surface of carbon fiber cloth through chemical bonds as an anode electrode of an electrolytic tank, and a cathode electrode is a graphite electrode; the anode electrode and the cathode electrode are arranged on two sides of an electrolytic tank with a cation exchange membrane arranged in the middle, wherein the anode electrode takes sheet carbon fiber cloth as a carbon skeleton, and the surface of the anode electrode is modified with nitrogen doped graphene oxide; in the lactose oxidation process, the graphene oxide doped with nitrogen atoms on the surface of the anode electrode effectively activates oxygen generated in the electrolyzed water into O of a solid-liquid interface by improving the electron conductivity 2- After the power is on, the anode electrode is used as the carbon fiber cloth surface of the carbon skeleton and the nitrogen atoms doped on the surface of the graphene to activate and electrolyze to produce oxygen which is used as an active group to oxidize lactose into lactobionic acid, and the catalyst used in the invention has different valence changes different from metal ions, so that the reaction process is mild, side reactions are inhibited, and the conversion rate and the current efficiency in the process of preparing the lactobionic acid by electrooxidation are improved;
the concentration of lactose injected into one side of the anode of the electrolytic tank is 1mol/L to 1.5mol/L, the electrolytic oxidation is carried out for 180min to 240min at the temperature of 25 ℃ to 40 ℃, and the oxidation current density is 20 mA.cm -2 To 35mA cm -2 The conversion rate of lactose is approximately 80%, and hydrogen ions generated by the anode electrode during the electrolysis process enter to the cathode electrode side through a cation exchange membrane between the anode electrode and the cathode electrode, and are combined with hydroxyl groups generated on the surface of the cathode electrode into water molecules through a solution, so that single lactobionic acid is formed on the anode electrode side. The invention greatly reduces the use of alkaline substances such as potassium hydroxide or sodium carbonate and the like and also greatly reduces the subsequent substancesThe workload of mass separation and concentration; according to the preparation method, the graphene oxide doped with nitrogen atoms is connected to the surface of the carbon fiber cloth through chemical bonds, and most of carboxyl groups of the graphene oxide are specific structural characteristics existing at the edge of a graphene oxide lamellar structure, in order to effectively enlarge a catalytic area in the preparation process, the urea is used for respectively forming amide bonds with the carbon fiber cloth and the graphene oxide which are soaked by strong acid to form carboxyl groups, the graphene oxide is distributed along the surface of the carbon fiber cloth through the amide bonds, the carbon fiber cloth has certain rigidity, the structure is stable, urea in the preparation process is positioned between the carbon fiber cloth and the graphene oxide, and nitrogen element doping and structural stability are synchronously formed by matching with subsequent calcination; the invention provides a method for preparing lactobionic acid by using a carbon-based nonmetallic catalyst in an electrocatalytic way, which has heterogeneous catalysis and strong adaptability.
Claims (9)
1. A method for electrocatalytic production of lactobionic acid using a carbon-based non-metallic catalyst, characterized in that: the anode electrode and the cathode electrode are arranged on two sides of an electrolytic tank with a cation exchange membrane arranged in the middle, wherein the anode electrode takes sheet carbon fiber cloth as a carbon skeleton, and the surface of the anode electrode is modified with nitrogen doped graphene oxide; the cathode electrode is a graphite electrode;
lactose is injected into one side of the anode of the electrolytic cell, wherein the concentration of the lactose is 1mol/L to 1.5mol/L;
electrolytic oxidation at 25 ℃ to 40 ℃ for 180min to 240min;
oxidation current density of 20 mA.cm -2 To 35mA cm -2 ；
After being electrified, the anode electrode is used as a carbon fiber cloth surface of a carbon skeleton and nitrogen atoms doped on the surface of graphene to activate and electrolyze oxygen generated by the activation and the oxidization of lactose to lactobionic acid;
hydrogen ions generated by the anode electrode enter one side of the cathode electrode through a cation exchange membrane between the anode electrode and the cathode electrode and are combined with hydroxyl generated on the surface of the cathode electrode into water molecules through the solution;
a single lactobionic acid is formed at one side of the anode electrode.
2. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as defined in claim 1, wherein: the preparation method of the anode electrode comprises the following steps:
s11, arranging the cleaned carbon fibers in strong acid for soaking, and loading-COOH on the surface of the carbon fiber cloth;
s12, modifying graphene oxide by using polyaniline;
s13, placing urea and graphene oxide with polyaniline modified on the surface into deionized water, and stirring to obtain-NH (NH) -urea 2 Forming an amide bond by dehydration condensation of-COOH on the edge of carbon fiber cloth and polyaniline-modified graphene oxide, wherein the graphene oxide passes through-NH of urea 2 The chemical bond is connected with the carbon fiber cloth;
s14, placing the carbon fiber cloth-urea-polyaniline modified graphene oxide self-assembled structure obtained in the S13 in a polytetrafluoroethylene reaction kettle for hydrothermal reaction, and calcining to obtain nitrogen-doped carbon fiber cloth and graphene oxide serving as anode electrodes.
3. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as defined in claim 2, wherein: the method for modifying graphene oxide by polyaniline in S12 comprises the following steps:
s121, placing 100mg of graphene oxide into deionized water, adding 10ml of HCl with the concentration of 1mol/L, uniformly stirring, dropwise adding excessive 0.4ml of aniline, and performing ultrasonic dispersion for 1h;
s122, placing the mixed solution into an ice water bath, respectively adding 30ml of HCl with the concentration of 1mol/L and 0.25g of ammonium persulfate, uniformly mixing, and introducing argon protective atmosphere;
and S123, maintaining an ice-water bath, soaking for 24 hours, and cleaning by using ethanol to remove excessive unreacted aniline, so as to obtain polyaniline-modified graphene oxide.
4. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as claimed in claim 3, wherein: in S121, aniline and graphene oxide are uniformly distributed on the surface of the graphene oxide through the adsorption action of pi-pi bonds, and aniline monomers are polymerized to form chain polyaniline under the action of ammonium persulfate.
5. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as defined in claim 2, wherein: the reaction time for forming an amide bond in S13 is 6 hours to 12 hours.
6. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as defined in claim 2, wherein: the temperature of the hydrothermal reaction in S14 is 120-140 ℃ and the reaction time is 12-18 hours.
7. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as defined in claim 2, wherein:
the calcination in S14 is performed under the protection of nitrogen, and comprises a first stage and a second stage; wherein the technological parameters of the first stage are as follows: heating to 250-300 deg.c and maintaining for 2-4 hr;
the technological parameters of the second stage are as follows: continuously heating to 750-800 ℃, and preserving heat for 2-4 hours to obtain the nitrogen-doped graphene oxide.
8. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as defined in claim 1, wherein: during the electrochemical oxidation of lactose to lactobionic acid, the pH of the solution on the anode side is maintained between 5.8 and 6.8.
9. A method of preparing lactobionic acid by electrocatalytic catalysis using a carbon based non-metal catalyst as defined in claim 1, wherein: as oxidation of lactose to lactobionic acid proceeds, water is consumed to form a concentrate of the anode side solution.
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