CN111100281B - Preparation method of modified graphene oxide catalyst - Google Patents
Preparation method of modified graphene oxide catalyst Download PDFInfo
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- CN111100281B CN111100281B CN201911376234.5A CN201911376234A CN111100281B CN 111100281 B CN111100281 B CN 111100281B CN 201911376234 A CN201911376234 A CN 201911376234A CN 111100281 B CN111100281 B CN 111100281B
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- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
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Abstract
The invention discloses a preparation method of a modified graphene oxide catalyst, which relates to the technical field of catalyst preparation and comprises the following preparation steps: 1) dispersing graphene oxide in a solvent to prepare a graphene oxide solution; 2) carrying out intercalation modification reaction on the graphene oxide solution to prepare a modified graphene oxide solution; 3) carrying out centrifugal washing on the modified graphene oxide solution, and then ultrasonically dispersing in a solvent to prepare a modified graphene oxide dispersion liquid; 4) adding a catalyst into the modified graphene oxide dispersion liquid, reacting to carry out loading of the catalyst, and preparing to obtain a modified graphene oxide catalyst solution; 5) and carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare the modified graphene oxide catalyst. The graphene oxide can remarkably enlarge the interlayer spacing after being modified, and is beneficial to the subsequent loading of a catalyst and the occurrence of interlayer reaction of a graphene composite material.
Description
Technical Field
The invention relates to the technical field of catalyst preparation, in particular to a preparation method of a modified graphene oxide catalyst.
Background
Graphene is a polymer composed of carbon atoms SP2Two-dimensional layered materials consisting of hybrids of only one carbon atom layer thick were first obtained by stripping graphite with adhesive tape by the teaching of Geim of Manchester university, UK. It has excellent physical and chemical performance and specific surface area up to 2630 m2The catalyst has the advantages of high mechanical strength, good biological safety and wide application prospect in the aspect of catalyst loading. However, graphene with a complete structure does not contain any unstable bond, the surface of the graphene is chemically inert, strong van der waals force exists between layers, and the graphene is difficult to disperse in an aqueous phase system or an organic solvent, so that the catalyst is difficult to complex.
Graphene oxide, as a derivative of graphene, is mainly obtained by strong oxidation and intercalation exfoliation of chemical reagents. Compared with graphene, the specific surface area of graphene oxide is similar to that of graphene, and a large number of oxygen-containing functional groups and defects exist on the surface and the edge of graphene oxide, so that conditions are created for dispersion of graphene oxide in a solvent and later chemical modification of graphene oxide. When graphene oxide is used as a catalyst carrier, the defects and functional groups on the surface of the graphene oxide can provide certain complexing sites for the loading of the catalyst, and the agglomeration of the catalyst in a system is reduced, so that the reaction activity of the catalyst is improved. However, in the process of preparing the graphene modified polymer composite material, the graphene oxide serving as a catalyst carrier has limited dispersibility in an organic solvent and poor compatibility with a polymer matrix, and the excellent performance of the graphene modified polymer material is limited to a certain extent.
For example, a chinese patent document discloses "a catalyst for synthesizing propylene carbonate and a preparation method thereof", and publication No. CN104624231B discloses a preparation method of a solid catalyst for synthesizing propylene carbonate, in which graphene oxide is used as a carrier, 1, 2-dibromoethane and triethylamine are used as raw materials, and a solid catalyst for synthesizing propylene carbonate by a cycloaddition reaction of carbon dioxide and propylene oxide can be obtained by a one-step reaction. However, the graphene oxide of the catalyst carrier prepared by the method has limited dispersibility in an organic solvent and poor compatibility with a polymer matrix, and the excellent performance of the graphene modified polymer material is limited.
Disclosure of Invention
The invention provides a preparation method of a modified graphene oxide catalyst, aiming at solving the problems that the existing catalyst carrier is limited in the dispersibility of graphene oxide in an organic solvent, poor in compatibility with a polymer matrix, and limited in excellent performance of a graphene modified polymer material.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a modified graphene oxide catalyst comprises the following preparation steps:
1) dispersing graphene oxide in a solvent to prepare a graphene oxide solution;
2) adding a modifier into the graphene oxide solution for reaction to prepare a modified graphene oxide solution;
3) carrying out centrifugal washing on the modified graphene oxide solution, and then ultrasonically dispersing in a solvent to prepare a modified graphene oxide dispersion liquid;
4) adding a catalyst into the modified graphene oxide dispersion liquid, reacting to carry out loading of the catalyst, and preparing to obtain a modified graphene oxide catalyst solution;
5) and carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare the modified graphene oxide catalyst.
Firstly, dispersing graphene oxide in distilled water to prepare a graphene oxide solution, and then adding a modifier to react to obtain a modified graphene oxide solution; the interlayer spacing of the graphene oxide can be remarkably enlarged after the modification reaction, and the interlayer loading of the catalyst and the entrance of small molecular monomers into the interlayer reaction are facilitated. After modification, centrifugally washing the modified graphene oxide solution, removing residual modifier, and then performing ultrasonic dispersion; then adding a catalyst to complete the loading of the catalyst; and after the reaction is finished, carrying out centrifugal washing and freeze drying to obtain the modified graphene oxide catalyst. The high-dispersity catalyst is beneficial to improving the reaction activity of the catalyst and promoting the layered graphene to be further stripped in the polymerization reaction, the preparation process of the raw materials used for the reaction is mature and easy to obtain, the reaction steps are simple, safe and efficient, the large-scale synthesis application is facilitated, and the catalyst is suitable for the research in the field of graphene modified polymer composite materials.
Preferably, in the step 1), the graphene oxide is dispersed by ultrasonic assistance, the ultrasonic dispersion time is 0.5-2 h, and the concentration of the graphene oxide solution is 1-10 mg/mL.
Preferably, the intercalation agent after intercalation modification in step 2) has carboxyl at the end; the modification steps are as follows: adding 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride into the graphene oxide solution, stirring for reaction, and then adding amino acid powder for reaction at room temperature to prepare the modified graphene oxide solution.
Firstly, adding 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride into a graphene oxide solution, stirring for reaction, activating carboxyl on the surface of graphene oxide, then adding amino acid powder, wherein amino groups on the amino acid can be combined with graphene oxide through amidation, so that the interlayer spacing between graphene is enlarged, and the carboxyl is arranged at the tail end of the amino acid grafted to the graphene after intercalation modification, so that the graphene oxide can be further used for catalyst loading reaction.
Preferably, the intercalation agent after intercalation modification in step 2) has hydroxyl at the end; the modification steps are as follows: adding hexamethylene diamine into the graphene oxide solution, stirring for reaction, then adding alpha-hydroxypropionic acid, and stirring for reaction to prepare the modified graphene oxide solution.
Adding hexamethylene diamine into the graphene oxide solution, wherein an amino group at one end of the hexamethylene diamine can perform an amidation reaction with the surface of the graphene oxide and then be connected to the graphene oxide, an amino group at the other end of the hexamethylene diamine can perform an amidation reaction with alpha-hydroxypropionic acid to be connected, so that the interlayer spacing between the graphene is enlarged, and the tail end of the alpha-hydroxypropionic acid after the reaction has hydroxyl, so that the hexamethylene diamine can be further used for a catalyst loading reaction.
Preferably, the ultrasonic dispersion time in the step 3) is 1-2 h, and the concentration of the modified graphene oxide solution is 1-10 g/mL.
Preferably, the solvent in step 1) and step 3) comprises water.
Preferably, the catalyst in the step 4) is titanium silica sol, and the preparation method of the titanium silica sol comprises the following preparation steps:
a) hydrolyzing a titanium-containing compound in a mixed solution of citric acid and ethanol to obtain titanium sol;
b) hydrolyzing a silicon-containing compound in a mixed solution of hydrochloric acid and ethanol to obtain silica sol;
c) mixing the titanium sol and the silica sol, adding triethyl phosphate, and stirring to obtain the colorless, clear and transparent titanium silica sol catalyst.
In the preparation of titanium silicasols, the titanium-containing compounds are hydrolyzed to form Ti (OH)4Hydrolysis of molecules with silicon-containing compounds to form Si (OH)4The molecules are dehydrated and condensed to generate a network system catalyst with a Ti-O-Si bond structure, and the titanium silicasol prepared by the method is treatedThe catalyst has high catalytic activity in a nano-scale, citric acid is required to be added during the preparation of the titanium silicasol, the citric acid has the function of inhibiting hydrolysis, and redundant hydroxyl in the citric acid molecule can be combined with hydroxyl and carboxyl at the tail end of an intercalator and modified graphene oxide in the later period in the catalyst loading process to prevent the agglomeration of the citric acid; triethyl phosphate is added when the titanium sol and the silica sol are mixed, so that the stability and the catalytic activity of the catalyst are adjusted through the chemical coordination of phosphoric acid.
When the modified graphene oxide is used as a catalyst carrier, the titanium silicasol enters the modified graphene oxide layers through an ion exchange process similar to that between layered silicate layers, and hydroxyl and carboxyl at the tail end of the intercalation agent and oxygen-containing groups on the modified graphene oxide can be condensed with hydroxyl in titanium silicasol catalyst molecules to generate C-O-Ti or C-O-Si bonds, so that the catalyst molecules are fixed on the surface and between layers of the modified graphene oxide, the loading of the catalyst is completed, the defects and functional groups on the surface of the modified graphene oxide can also prevent the agglomeration among the catalyst particles, and the stability of the catalyst is improved.
Preferably, the molar ratio of titanium to silicon in the titanium silica sol is 1-9: 1.
When the titanium-silicon catalyst with the molar ratio is used in polymerization reaction, the catalytic action on side reaction is small, and the hue of the product is favorably improved.
Preferably, the mass ratio of the citric acid to the titanium-containing compound is (3.76-11.3):100, and the mass ratio of the triethyl phosphate to the titanium-containing compound is (3.57-10.7): 100.
The addition amount of citric acid and triethyl phosphate is small, the hydrolysis inhibition effect is reduced, and the catalyst stability is poor; if the addition amount is too high, the combination of the catalyst and the modified graphene oxide is influenced;
preferably, the mass ratio of titanium to modified graphene oxide in the modified graphene oxide catalyst in the step 5) is 0.01-2: 100.
The titanium content in the modified graphene oxide catalyst is more suitable for polymerization reaction catalysis within the range.
Therefore, the invention has the following beneficial effects: (1) the interlayer spacing of the modified graphene oxide can be remarkably enlarged after the modification of the graphene oxide, so that the subsequent loading of a catalyst and the occurrence of interlayer reaction of a graphene composite material are facilitated; (2) the modified graphene oxide has a large number of defects on the surface, and can be used as an active site for a complex catalyst, so that the dispersion performance of the catalyst is improved, the interlayer catalytic reaction can be promoted, and the preparation of a high-dispersity graphene modified polymer composite material is facilitated; (3) the titanium silicasol prepared by a sol-gel method is used as a catalyst, is in a nano-scale size, has high catalytic activity, and can prevent agglomeration among catalyst particles due to the defects and functional groups on the surface of the modified graphene oxide when the modified graphene oxide is loaded on the modified graphene oxide, thereby improving the stability of the catalyst; (3) the preparation process of the raw materials used in the reaction is mature and easy to obtain, the reaction steps are simple, safe and efficient, large-scale synthesis and application are facilitated, and the method is suitable for researches on aspects of graphene modified polymer composite materials and the like.
Drawings
Fig. 1 is an XRD spectrum of the modified graphene oxide catalyst prepared in example 1 of the present invention.
Fig. 2 is an XRD spectrum of the modified graphene oxide catalyst prepared in example 3 of the present invention.
Fig. 3 is an FTIR spectrum of the modified graphene oxide catalyst prepared in example 1 of the present invention.
Figure 4 is a TGA spectrum of the modified graphene oxide catalyst prepared in example 1 of the present invention.
Fig. 5 is an XPS spectrum of the modified graphene oxide catalyst prepared in example 1 of the present invention.
FIG. 6 is a transmission electron micrograph of GO/PET nanocomposite prepared according to example 1 of the present invention.
Fig. 7 is an XRD spectrum of the graphene oxide catalyst prepared in comparative example 1 of the present invention.
Fig. 8 is an XPS spectrum of the modified graphene oxide catalyst prepared in comparative example 2 of the present invention.
Detailed Description
The invention is further described with reference to specific embodiments.
Example 1: a preparation method of a modified graphene oxide catalyst comprises the following preparation steps:
1) dispersing 1g of graphene oxide in 1000mL of water and carrying out ultrasonic treatment for 0.5 h to prepare a graphene oxide solution of 1 mg/mL;
2) adding 5g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride into 100mL of graphene oxide solution, stirring for reaction for 0.5-1.5h, then adding 6g of amino acid powder, and reacting at room temperature for 25h to prepare 1mg/mL of modified graphene oxide solution;
3) carrying out centrifugal washing on the modified graphene oxide solution, and then dispersing the modified graphene oxide solution in water by ultrasonic for 1 h to prepare a modified graphene oxide dispersion solution;
4) adding 0.042g of titanium silicasol catalyst into the modified graphene oxide dispersion liquid for reaction for 4 hours, and carrying out catalyst loading to prepare a modified graphene oxide catalyst solution; the preparation method of the titanium silicasol catalyst comprises the following steps:
a) weighing 8.5 g of tetrabutyl titanate, and hydrolyzing in a mixed solution of 1 mol/L, 0.48g of citric acid and 15.5 mL of ethanol to obtain titanium sol;
b) weighing 1.3 g of tetraethoxysilane, and hydrolyzing in a mixed solution of 1 mol/L, 2.5 mL of hydrochloric acid and 15.5 mL of ethanol to obtain silica sol;
c) mixing titanium sol and silica sol, adding 0.71 g of triethyl phosphate, and stirring to obtain a colorless, clear and transparent titanium silica sol catalyst; the molar ratio of titanium to silicon in the titanium silicasol catalyst is 4: 1;
5) and carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare the modified graphene oxide catalyst, wherein the mass ratio of titanium to modified graphene oxide in the modified graphene oxide catalyst is 0.1: 100.
Example 2: a preparation method of a modified graphene oxide catalyst comprises the following preparation steps:
1) dispersing 3g of graphene oxide in 1000mL of water and carrying out ultrasonic treatment for 1 h to prepare a 3 mg/mL graphene oxide solution;
2) adding 5.3 g of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride into 100mL of graphene oxide solution, stirring for reaction for 0.5-1.5h, then adding 6.5 g of amino acid powder, and reacting for 25h at room temperature to prepare a modified graphene oxide solution of 3 mg/mL;
3) carrying out centrifugal washing on the modified graphene oxide solution, and then dispersing in water by ultrasonic for 1.2 h to prepare a modified graphene oxide dispersion liquid;
4) adding 0.013 g of titanium silicasol catalyst into the modified graphene oxide dispersion liquid for reaction for 2 hours, and carrying out catalyst loading to prepare a modified graphene oxide catalyst solution; the preparation method of the titanium silicasol catalyst comprises the following steps:
a) weighing 8.5 g of tetrabutyl titanate, and hydrolyzing in a mixed solution of 1 mol/L, 0.32 g of citric acid and 15.5 mL of ethanol to obtain titanium sol;
b) weighing 5.2 g of tetraethoxysilane, and hydrolyzing in a mixed solution of 1 mol/L, 2.5 mL of hydrochloric acid and 15.5 mL of ethanol to obtain silica sol;
c) mixing titanium sol and silica sol, adding 0.3 g of triethyl phosphate, and stirring to obtain a colorless, clear and transparent titanium silica sol catalyst; the molar ratio of titanium to silicon in the titanium silicasol catalyst is 1: 1;
5) and carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare the modified graphene oxide catalyst, wherein the mass ratio of titanium to modified graphene oxide in the modified graphene oxide catalyst is 0.01: 100.
Example 3: a preparation method of a modified graphene oxide catalyst comprises the following preparation steps:
1) dispersing 6g of graphene oxide in 1000mL of water, and performing ultrasonic treatment for 1.5h to prepare a graphene oxide solution of 6 mg/mL;
2) adding 10g of hexamethylenediamine into the graphene oxide solution, stirring and reacting for 4 hours at 80 ℃, then adding 10g of alpha-hydroxypropionic acid, and stirring and reacting for 4 hours to prepare a modified graphene oxide solution, and preparing to obtain a 6 mg/mL modified graphene oxide solution;
3) carrying out centrifugal washing on the modified graphene oxide solution, and then dispersing in water by ultrasonic for 1.8 h to prepare a modified graphene oxide dispersion liquid;
4) adding 2.381 g of titanium silicasol catalyst into the modified graphene oxide dispersion liquid for reaction for 6 hours, and carrying out catalyst loading to prepare a modified graphene oxide catalyst solution; the preparation method of the titanium silicasol catalyst comprises the following steps:
a) weighing 8.5 g of tetrabutyl titanate, and hydrolyzing in a mixed solution of 1 mol/L, 0.61 g of citric acid and 15.5 mL of ethanol to obtain titanium sol;
b) weighing 0.86 g of tetraethoxysilane, and hydrolyzing in a mixed solution of 1 mol/L, 2.5 mL of hydrochloric acid and 15.5 mL of ethanol to obtain silica sol;
c) mixing titanium sol and silica sol, adding 0.49 g of triethyl phosphate, and stirring to obtain a colorless, clear and transparent titanium silica sol catalyst; the molar ratio of titanium to silicon in the titanium silicasol catalyst is 6: 1;
5) and carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare the modified graphene oxide catalyst, wherein the mass ratio of titanium to modified graphene oxide in the modified graphene oxide catalyst is 1: 100.
Example 4: a preparation method of a modified graphene oxide catalyst comprises the following preparation steps:
1) dispersing 10g of graphene oxide in 1000mL of water and carrying out ultrasonic treatment for 2 h to prepare a 10 mg/mL graphene oxide solution;
2) adding 15 g of hexamethylenediamine into the graphene oxide solution, stirring and reacting for 5 hours at 90 ℃, then adding 15 g of alpha-hydroxypropionic acid, stirring and reacting for 5 hours to prepare a modified graphene oxide solution, and preparing the modified graphene oxide solution of 10 mg/mL;
3) carrying out centrifugal washing on the modified graphene oxide solution, and dispersing in water by ultrasonic for 2 h to prepare a modified graphene oxide dispersion liquid;
4) adding 7.91 g of titanium silicasol catalyst into the modified graphene oxide dispersion liquid for reaction for 8 hours, and carrying out catalyst loading to prepare a modified graphene oxide catalyst solution; the preparation method of the titanium silicasol catalyst comprises the following steps:
a) weighing 8.5 g of tetrabutyl titanate, and hydrolyzing in a mixed solution of 1 mol/L, 0.96 g of citric acid and 15.5 mL of ethanol to obtain titanium sol;
b) weighing 0.58 g of ethyl orthosilicate, and hydrolyzing in a mixed solution of 1 mol/L, 2.5 mL of hydrochloric acid and 15.5 mL of ethanol to obtain silica sol;
c) mixing titanium sol and silica sol, adding 0.91 g of triethyl phosphate, and stirring to obtain a colorless, clear and transparent titanium silica sol catalyst; the molar ratio of titanium to silicon in the titanium silicasol catalyst is 9: 1;
5) and carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare the modified graphene oxide catalyst, wherein the mass ratio of titanium to modified graphene oxide in the modified graphene oxide catalyst is 2: 100.
Comparative example 1: a preparation method of a graphene oxide catalyst comprises the following preparation steps:
1) dispersing 1g of graphene oxide in 1000mL of water and carrying out ultrasonic treatment for 0.5 h to prepare a graphene oxide solution of 1 mg/mL;
2) adding 0.042g of titanium silicasol catalyst into the graphene oxide solution to react for 4 hours, and carrying out catalyst loading to prepare a modified graphene oxide catalyst solution; the preparation method of the titanium silicasol catalyst comprises the following steps:
a) weighing 8.5 g of tetrabutyl titanate, and hydrolyzing in a mixed solution of 1 mol/L, 0.48g of citric acid and 15.5 mL of ethanol to obtain titanium sol;
b) weighing 1.3 g of tetraethoxysilane, and hydrolyzing in a mixed solution of 1 mol/L, 2.5 mL of hydrochloric acid and 15.5 mL of ethanol to obtain silica sol;
c) mixing titanium sol and silica sol, adding 0.71 g of triethyl phosphate, and stirring to obtain a colorless, clear and transparent titanium silica sol catalyst; the molar ratio of titanium to silicon in the titanium silicasol catalyst is 4: 1;
3) and carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare the modified graphene oxide catalyst, wherein the mass ratio of titanium to modified graphene oxide in the modified graphene oxide catalyst is 0.1: 100.
Comparative example 2: the difference from example 1 is that the preparation method of the titanium silicasol catalyst comprises the following steps:
a) weighing 8.5 g of tetrabutyl titanate, and hydrolyzing in a mixed solution of 1 mol/L and 15.5 mL of ethanol to obtain titanium sol;
b) weighing 1.3 g of tetraethoxysilane, and hydrolyzing in a mixed solution of 1 mol/L, 2.5 mL of hydrochloric acid and 15.5 mL of ethanol to obtain silica sol;
c) mixing the titanium sol and the silica sol to obtain a colorless, clear and transparent titanium silica sol catalyst; the molar ratio of titanium to silicon in the titanium silicasol catalyst is 4: 1.
XRD characterization is performed on the modified graphene oxide catalyst prepared in example 1, and the result is shown in fig. 1, where the spectrum shows that the diffraction angle of the original graphene oxide is 2 Ө =11.11oAnd the distance between the (001) crystal planes of the graphene oxide is 0.796 nm. And the diffraction angle of the modified graphene oxide catalyst is shifted to 2 Ө =10.66 at a low angleoThe distance between crystal planes corresponding to graphene oxide (001) is 0.829 nm, which indicates that the interlayer distance of graphene oxide is enlarged after modification and catalyst loading.
XRD characterization is performed on the modified graphene oxide catalyst prepared in example 3, and the result is shown in figure 2, wherein the spectrum shows that the 2 Ө diffraction angle of the modified graphene oxide after being modified and loaded by the catalyst is 11.11 of the original 2 Ө diffraction angleoMove to low angle 7.66oThe interplanar spacing corresponding to the (001) crystal plane of graphene oxide was shifted from 0.796 nm to 1.153 nm, indicating that the interlayer spacing of graphene oxide was enlarged after modification and catalyst loading.
FTIR characterization of the modified graphene oxide catalyst prepared in example 1 is performed, and the result is shown in FIG. 3, which shows that the patterns are 3426, 1721, 1613 and 1065 cm-1The characteristic peaks appearing at (b) mainly correspond to the stretching vibration peaks of O-H (free water), C = O, C = C and C-O groups in GO. And outside 650 to 750, 1100, and 960 cm-1Characteristic absorption peaks of Ti-O-Ti, Si-O-Si, or Si-O-Ti, etc. of the catalyst appear nearby. FTIR spectra of modified graphene oxide catalystsThe successful modification and loading of the graphene oxide catalyst is demonstrated.
TGA characterization of the modified graphene oxide catalyst prepared in example 1 was performed, and the results are shown in fig. 4, which shows that for graphene oxide, the mass loss is divided into three stages, with water being removed within 150 ℃; decomposition of 150 ℃ and 240 ℃ mainly oxygen-containing functional groups to generate CO and CO2And water, etc.; after 250 ℃ pyrolysis of the carbon chain skeleton predominates. The oxygen content in the graphene oxide is approximately 40 wt% of the total mass. For the modified graphene oxide catalyst, the heat loss curve shows similar weight loss tendency. Removing water within 140 ℃, and the weight loss is about 2.3 wt%; 140 ℃ and 240 ℃ are mainly used for the falling and decomposition of the grafted modifier molecules and the oxygen-containing functional groups of GO, and the weight loss is about 51.4 wt%; after 250 ℃ pyrolysis of the carbon chain skeleton predominates.
The modified graphene oxide catalyst prepared in example 1 was subjected to XPS characterization, and the result is shown in fig. 5, and the spectrum shows that only two characteristic peaks exist in GO, an O1s characteristic peak at 530.8 ev, and a C1s characteristic peak at 283.9 ev. And in addition to the existence of characteristic peaks of O1s and C1s in the modified graphene oxide catalyst, the existence of peaks of Ti2p and Si2p from the catalyst at 457.6 ev and 101.7 ev proves that the modified graphene oxide catalyst is successfully prepared. Compared with graphene oxide, the modified graphene catalyst has the advantage that the relative content of oxygen element is reduced, and is mainly caused by partial thermal reduction of GO in the modification and loading processes.
Compounding the modified graphene oxide catalyst prepared in the embodiment 1 with PET to prepare a GO/PET nano composite material, and performing performance standard, wherein the preparation method comprises the steps of weighing 3.86 g of the modified graphene oxide catalyst prepared in the embodiment 1, adding the modified graphene oxide catalyst into 396.8 g of ethylene glycol solution, and performing ultrasonic treatment for 1 hour to disperse the modified graphene oxide catalyst; then weighing 664 g of terephthalic acid (PTA) and adding the terephthalic acid (PTA) into the ethylene glycol solution dispersed with the modified graphene oxide catalyst for pulping; adding the mixture into a 2L polyester reaction kettle after the pulping is finished, and carrying out esterification reaction at about 248 ℃; heating to 278 ℃ until water is distilled off, and vacuumizing to perform polycondensation reaction; the polycondensation vacuum is about 25 pa, the polycondensation time is 2.5 h, and the GO/PET nano composite material is obtained after discharging when the rated power is reached. The content of graphene oxide in the composite material is 0.5 wt%, and the content of titanium element in the catalyst is 5 ppm. The viscosity of the composite slice was 0.64 dL/g as measured by Ubbelohde viscometer, and the melting point of the graphene/polyester nanocomposite slice was 252.7 ℃ as measured by differential scanning calorimetry. The TEM characterization of the composite material slice is performed, and the result is shown in fig. 6, which shows that the sheet diameter of graphene in the composite material is about 1 um, the graphene has good compatibility with the polymer matrix, no obvious agglomeration phenomenon exists between particles, and the graphene modified polymer composite material has good dispersibility, and is beneficial to the performance of the graphene modified polymer composite material.
The difference between comparative example 1 and example 1 is that the graphene oxide in comparative example 1 is not modified by intercalation during preparation, and the XRD characterization result is shown in fig. 7, which shows that the original graphene oxide has a diffraction angle of 2 Ө =11.11oThe interplanar spacing corresponding to the (001) crystal plane of graphene oxide was 0.796 nm. After the graphene oxide supports the catalyst, the position of a diffraction peak of the graphene oxide basically has no obvious change, which shows that the catalyst exists as an amorphous complex system in the graphene oxide, has low content and has no obvious influence on the crystal orientation of the graphene oxide.
Comparative example 2 is different from example 1 in that citric acid and triethyl phosphate were not used in preparing the titanium silica sol catalyst, and the modified graphene oxide catalyst prepared was characterized, and the results are shown in fig. 8: it can be seen from the figure that, compared with the position of the peak in the XPS spectrum of the modified graphene oxide supported catalyst in example 1 in fig. 5, the XPS spectrum of the modified graphene oxide supported catalyst in comparative example 2 has no obvious characteristic peak related to the titanium-silicon catalyst, which indicates that the catalyst has poor stability and the loading effect on the modified graphene oxide is poor.
Claims (8)
1. A preparation method of a modified graphene oxide catalyst is characterized by comprising the following preparation steps:
1) dispersing graphene oxide in a solvent to prepare a graphene oxide solution;
2) carrying out intercalation modification reaction on the graphene oxide solution to prepare a modified graphene oxide solution;
3) carrying out centrifugal washing on the modified graphene oxide solution, and then ultrasonically dispersing in a solvent to prepare a modified graphene oxide dispersion liquid;
4) adding a catalyst into the modified graphene oxide dispersion liquid, reacting to carry out loading of the catalyst, and preparing to obtain a modified graphene oxide catalyst solution;
5) carrying out centrifugal washing and freeze drying on the modified graphene oxide catalyst solution to prepare a modified graphene oxide catalyst;
the tail end of the intercalation modified intercalator in the step 2) is provided with carboxyl, and the modification step is as follows: adding 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride into the graphene oxide solution, stirring for reaction, and then adding amino acid powder for reaction at room temperature to prepare a modified graphene oxide solution; or the tail end of the intercalation modified intercalator in the step 2) is provided with hydroxyl, and the modification step is as follows: adding hexamethylenediamine into the graphene oxide solution, stirring for reaction, and then adding alpha-hydroxypropionic acid, and stirring for reaction to prepare a modified graphene oxide solution;
the catalyst in the step 4) is titanium silicasol.
2. The preparation method of the modified graphene oxide catalyst according to claim 1, wherein the graphene oxide is dispersed in the step 1) by ultrasonic assistance, the ultrasonic dispersion time is 0.5-2 h, and the concentration of the graphene oxide solution is 1-10 mg/mL.
3. The preparation method of the modified graphene oxide catalyst according to claim 1, wherein the ultrasonic dispersion time in the step 3) is 1-2 hours, and the concentration of the modified graphene oxide solution is 1-10 g/mL.
4. The method of claim 1, wherein the solvent in step 1) and step 3) comprises water.
5. The preparation method of the modified graphene oxide catalyst according to claim 1, wherein the preparation method of the titanium silica sol comprises the following preparation steps:
a) hydrolyzing a titanium-containing compound in a mixed solution of citric acid and ethanol to obtain titanium sol;
b) hydrolyzing a silicon-containing compound in a mixed solution of hydrochloric acid and ethanol to obtain silica sol;
c) mixing the titanium sol and the silica sol, adding triethyl phosphate, and stirring to obtain the colorless, clear and transparent titanium silica sol catalyst.
6. The method according to claim 5, wherein the molar ratio of titanium to silicon in the titanium silica sol is 1-9: 1.
7. The method for preparing a modified graphene oxide catalyst according to claim 5, wherein the mass ratio of the citric acid to the titanium-containing compound is (3.76-11.3):100, and the mass ratio of the triethyl phosphate to the titanium-containing compound is (3.57-10.7): 100.
8. The method for preparing a modified graphene oxide catalyst according to claim 1, wherein the mass ratio of titanium to modified graphene oxide in the modified graphene oxide catalyst in the step 5) is 0.01-2: 100.
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