Graphene catalyst as well as preparation method and application thereof

Abstract

The invention provides a graphene catalyst as well as a preparation method and application thereof. The graphene catalyst can be prepared by hydrolyzing nitrogen-doped fluorinated graphene and then reacting the hydrolyzed nitrogen-doped fluorinated graphene with a transition metal salt, can be used for simultaneously desulfurizing and dewaxing an oil product, and specifically comprises the following steps: uniformly mixing urea peroxide with an aqueous dispersion of the catalyst, and heating and liquefying, so that the catalyst is uniformly dispersed in the urea peroxide along with water, the catalyst comprises the graphene catalyst, thereby forming a premix; enabling the premixed material to be fully mixed and contacted with an oil product to be treated, and enabling the urea peroxide, the water and the graphene catalyst to form a supramolecular network structure; under the action of a catalyst, urea peroxide generates hydroxyl radicals to oxidize sulfur-containing compounds in the oil product into sulfone substances; the supramolecular network structure adsorbs sulfone substances and n-alkane substances in the oil product, so that the oil product is desulfurized and dewaxed at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of oil purification, and specifically relates to a graphene catalyst and a preparation method and application thereof. Background Art

[0002] The purpose of oil desulfurization process is to reduce the content of sulfide in oil products, making the oil products cleaner and more environmentally friendly. Common oil desulfurization processes include hydrodesulfurization, adsorption desulfurization and catalytic desulfurization. These processes can convert organic sulfides in oil products into low sulfide or aqueous compounds through hydrogenation reaction, adsorption separation or catalyst action, thereby improving the quality of oil products. Oxidative desulfurization technology is to oxidize organic sulfur compounds in oil products into sulfones or sulfoxides, mix and stir with oil products carrying oxidants and catalysts in a reactor, and then separate and remove sulfur through filtration, adsorption, extraction and other methods.

[0003] The purpose of oil dewaxing process is to reduce the content of normal alkanes in oil products, so as to reduce the freezing point / pour point of oil products and improve the low-temperature performance of oil products. Common lubricating oil base oil dewaxing processes include cold pressing dewaxing, molecular sieve dewaxing, bacterial dewaxing, solvent dewaxing, catalytic dewaxing and isomerization dewaxing, but these processes have the problem of insufficient dewaxing depth. The cloud point of the obtained paraffin-based lubricating oil base oil is generally around -15℃, the pour point is generally around -20℃, and the low-temperature viscosity is relatively high, which cannot meet the requirements of some lubricating oils with high low-temperature performance. Summary of the invention

[0004] In order to solve all or part of the above-mentioned technologies, the present invention provides the following technical solutions: One of the objects of the present invention is to provide a method for preparing a graphene catalyst, comprising: subjecting a first mixture containing nitrogen-doped fluorinated graphene, an organic base and water to a first reaction, so that at least part of CF in the nitrogen-doped fluorinated graphene is hydrolyzed to form C—OH, thereby obtaining hydroxylated nitrogen-doped graphene; The second mixture containing the hydroxylated nitrogen-doped graphene, a transition metal soluble salt and water is subjected to a second reaction so that the transition metal soluble salt generates a transition metal oxide and is loaded on the graphene, thereby obtaining a graphene catalyst.

[0005] In the preparation method provided by the present invention, by using fluorinated graphene to hydrolyze to obtain oxygen-containing functional groups (such as -OH), the distribution of oxygen-containing functional groups on graphene can be made more uniform, which is beneficial to the subsequent modification of transition metal oxides. The introduction of transition metal oxides further improves the catalytic efficiency of graphene catalysts. In the prepared graphene catalyst, graphene is used as a carrier to load transition metal oxides, and nitrogen doping can change the surface properties of graphene, thereby enhancing the interaction between graphene and transition metal oxides, so that transition metal oxides can be stably and evenly dispersed on the graphene surface, thereby improving catalytic activity. The graphene catalyst has good catalytic activity and catalytic efficiency, and can be used as a catalyst for desulfurization reaction.

[0006] In some embodiments, the first mixture includes, by weight, 1 part of nitrogen-doped fluorinated graphene, 5-20 parts of an organic base, and 50-200 parts of water.

[0007] In some embodiments, the organic base includes one or more of 4-dimethylaminopyridine, tetramethylammonium hydroxide, and tetraethylammonium hydroxide, and the organic base has a high conversion rate of CF hydrolysis to C-OH. Compared with inorganic bases, the organic base has a significantly higher conversion rate of CF hydrolysis to C-OH.

[0008] In some embodiments, the temperature of the first reaction is 140-180°C.

[0009] In some embodiments, the first reaction time is 32-64 hours.

[0010] In some embodiments, the second mixture includes, by weight, 1 part of hydroxylated nitrogen-doped graphene, 0.5-5 parts of a soluble transition metal salt, and 300-500 parts of water.

[0011] In some embodiments, the transition metal soluble salt includes one or more combinations of molybdenum salts, tungsten salts, vanadium salts, iron salts, nickel salts, and cerium salts. That is, the transition metal oxide supported on the graphene can be one or more combinations of molybdenum oxide, tungsten oxide, vanadium oxide, iron oxide, nickel oxide, and cerium oxide.

[0012] In some embodiments, the temperature of the second reaction is 140-180°C.

[0013] In some embodiments, the second reaction time is 12h-24h.

[0014] In some embodiments, a pH adjuster is used to adjust the pH value of the second mixture to 9-10 before the second reaction is performed.

[0015] In some embodiments, the pH adjuster includes one or a combination of ammonia water, tetramethylammonium hydroxide or tetraethylammonium hydroxide.

[0016] In some embodiments, the method further includes: before performing the second reaction, allowing the second mixture to stand for a set time so that the transition metal ions therein are fully adsorbed on the hydroxylated nitrogen-doped graphene and react in situ to form the transition metal oxide.

[0017] In some embodiments, the set time is 24h-48h.

[0018] In some embodiments, the method for preparing the nitrogen-doped fluorinated graphene includes: grinding a third mixture containing 1 part of fluorinated graphite, 1-4 parts of a nitrogen source and 10-30 parts of a dispersant by mass to obtain the nitrogen-doped fluorinated graphene.

[0019] In some preferred embodiments, the nitrogen source is composed of C, H, and N elements or C, H, O, and N elements to avoid introducing other element impurities. For example, the nitrogen source includes one or more of ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium acetate, ammonium oxalate, ammonium citrate, and ammonium succinate.

[0020] In some embodiments, the dispersant includes one or a combination of N-methylpyrrolidone, N,N-dimethylformamide or dimethyl sulfoxide.

[0021] In some embodiments, the grinding process is performed at a rotation speed of 1000-3000 rpm and for a time of 4-6 hours.

[0022] A second object of the present invention is to provide a graphene catalyst, which is prepared by the method described in any of the above technical solutions.

[0023] The third object of the present invention is to provide the application of the graphene catalyst in the desulfurization of oil products.

[0024] In some embodiments, the application includes: using the graphene catalyst and urea peroxide to simultaneously desulfurize and dewax an oil product, for example, a lubricating oil base oil.

[0025] A fourth object of the present invention is to provide a method for simultaneously desulfurizing and dewaxing oil products, comprising: Uniformly mixing carbamide peroxide and a water dispersion of a catalyst and heating and liquefying them, so that the catalyst is uniformly dispersed in the carbamide peroxide along with water, thereby forming a premixed material, wherein the catalyst is the graphene catalyst; The premixed material is fully mixed and contacted with the oil product to be treated, and the urea peroxide, water and graphene catalyst form a supramolecular network structure. Under the action of the catalyst, the urea peroxide generates hydroxyl radicals to oxidize the sulfur-containing compounds in the oil product into sulfone substances; the supramolecular network structure adsorbs the sulfone substances and normal alkane substances in the oil product, thereby achieving simultaneous desulfurization and dewaxing of the oil product.

[0026] With the participation of water, the carbamide peroxide structure cross-links itself to form a network structure, which has hydrogen bonding with the graphene catalyst to form a supramolecular network structure. This supramolecular network structure has a strong adsorption capacity for sulfone substances and normal alkanes.

[0027] The water in the premixed material can not only be used to pre-disperse the graphene catalyst, but also promote the liquefaction of urea peroxide, reduce the heating temperature, and also be used to participate in the formation of a supramolecular network structure.

[0028] In some embodiments, the method specifically includes: firstly uniformly mixing the aqueous dispersion of the urea peroxide and the catalyst, and heating to 80-140° C. to melt the urea peroxide into a liquid state, and the graphene catalyst therein is uniformly dispersed in the liquid urea peroxide to form the premixed material.

[0029] In some embodiments, the method further includes: first dispersing the graphene catalyst in water and performing ultrasound to pre-disperse it to form an aqueous dispersion of the graphene catalyst; and then uniformly mixing the aqueous dispersion of the graphene catalyst with the urea peroxide to form the premixed material.

[0030] In some embodiments, the method further includes: performing solid-liquid separation on the product obtained from the reaction to obtain a purified oil product and a solid residue; and separating the sulfone substances and normal alkane substances in the solid residue, and at least recovering the graphene catalyst therein and reusing it.

[0031] In some embodiments, the method specifically includes: heating the solid residue to 50-80°C to liquefy the normal alkane substances therein, dissolving the sulfone substances therein in the liquefied normal alkane substances, and then performing solid-liquid separation. The normal alkane therein can be melted by heating, and the sulfone has a better affinity with the normal alkane and enters the normal alkane phase, thereby being easily separated; the remaining unreacted urea peroxide, urea generated by the reaction, and graphene catalyst can directly enter the next round of oil treatment.

[0032] In some embodiments, a low-sulfur purified oil product is separated by filtration to obtain a filter cake containing normal alkanes, sulfone substances, unreacted urea peroxide, urea generated by the reaction, and a catalyst, and then water is added and heated to 50-80°C to remove the sulfone substances and normal alkanes, and then urea peroxide is added thereto before the next batch of oil products is processed.

[0033] In some embodiments, 20-50 parts of urea peroxide, 0.04-0.4 parts of graphene catalyst and 2-5 parts of water are uniformly mixed by mass to form the premix, and then the premix is ​​fully mixed and contacted with 100 parts of oil to carry out the reaction.

[0034] In some embodiments, the reaction temperature is 50°C-80°C; In some embodiments, the reaction time is 2-6 hours.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The graphene catalyst provided by the present invention has excellent catalytic activity and catalytic efficiency as a catalyst for desulfurization reaction, and is suitable for application in catalytic desulfurization of oil products; the graphene catalyst can also produce a synergistic effect with urea peroxide in the dewaxing process to improve the dewaxing effect; (2) The present invention provides a method for simultaneous desulfurization and dewaxing using the graphene catalyst and urea peroxide, wherein the method has excellent desulfurization and dewaxing effects and high oil purification efficiency; (3) In the simultaneous desulfurization and dewaxing method provided by the present invention, the supramolecular network structure formed by the participation of urea peroxide can adsorb the products of the desulfurization reaction (sulfones, sulfoxides and other sulfone substances), without the need to add additional reagents, thereby reducing costs and reducing the possibility of oil products being contaminated by other reagents, thereby simplifying the process; the normal alkane substances that are by-products of dewaxing can dissolve the products of the desulfurization reaction (sulfones, sulfoxides and other sulfone substances) during catalyst recovery, thereby reducing processing costs and improving production efficiency. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solution of the present invention. The specific functional details disclosed herein should not be interpreted as limiting, but only as the basis for the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in different ways in any appropriate detailed embodiment.

[0037] Unless otherwise specified, the raw materials and reagents used in the specific embodiments of the present invention are all commercially available. The "parts" described in the specific embodiments of the present invention are all parts by mass.

[0038] Example 1 Embodiment 1 provides a graphene catalyst and a preparation method thereof, which specifically comprises the following steps: (1) 1 part of graphite fluoride, 2 parts of ammonium carbonate and 20 parts of NMP were mixed and stirred uniformly, and treated with a sand mill at 2000 rpm for 5 hours, and then the filtered product was washed with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain nitrogen-doped graphene fluoride slurry; (2) 1 part of nitrogen-doped fluorinated graphene, 10 parts of tetramethylammonium hydroxide, and 100 parts of deionized water were mixed and stirred evenly, ultrasonically treated, and then added into a polytetrafluoroethylene-lined autoclave, reacted at 160° C. for 48 hours, then washed and filtered with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain a hydroxylated nitrogen-doped graphene slurry; (3) 1 part of hydroxylated nitrogen-doped graphene, 2 parts of cerium nitrate and 400 parts of water were mixed and stirred evenly, and the pH value of the mixture was adjusted to 9.5 with tetraethylammonium hydroxide. The mixture was allowed to stand for 24 hours, and then added to a polytetrafluoroethylene-lined high-pressure reactor, reacted at 160°C for 18 hours, and then washed and filtered with deionized water for multiple times to remove impurities, and dried in a vacuum oven at 80°C to obtain cerium (IV) oxide-modified nitrogen-doped graphene, i.e., graphene catalyst.

[0039] Example 1 also provides the use of the above-mentioned graphene catalyst to desulfurize and dewax oil products, specifically including: 100 parts of D130 oil (Qingjiang Petrochemical) were added into the reaction chamber of the circulating fluidized reactor, and 30 parts of urea peroxide, 3 parts of deionized water and 0.1 parts of the graphene catalyst prepared above were added into the high-level tank of the circulating fluidized reactor; The high-level tank is heated to 120°C to melt the urea peroxide therein into liquid, and then the mixed material in the high-level tank is placed in the reaction chamber of the circulating fluidized reactor. The oil product and the mixed material are stirred and reacted in the circulating fluidized reactor in a reciprocating cycle. The reaction temperature is 80°C and the reaction time is 2 hours. After the reaction is completed, the positive pressure filtration method is used to filter twice repeatedly to obtain purified oil and filter cake; the filter cake is returned to the high-level tank and 3 parts of deionized water are added, stirred and heated to 60°C to completely melt the residual normal alkanes in the filter cake into a liquid state, and the sulfone substances in the oil enter the normal alkane phase, and the normal alkanes and sulfone substances are separated into a collection device, and the remaining carbamide peroxide, urea and graphene catalyst are recycled.

[0040] When a new batch of oil products is processed, 8 new portions of urea peroxide are added to the remaining materials, and the mixture is heated to 120°C to melt the urea peroxide (containing urea) into liquid, which is then placed in the circulating fluidized bed reactor to process the new batch of oil products. This process is repeated for 10 batches of oil products.

[0041] Example 2 The only difference between Example 2 and Example 1 is that in the preparation step (2) of the graphene catalyst, tetramethylammonium hydroxide is replaced by 4-dimethylaminopyridine, and the rest is the same as Example 1.

[0042] Example 3 Embodiment 3 provides a graphene catalyst and a preparation method thereof, which specifically comprises the following steps: (1) 1 part of graphite fluoride, 1 part of ammonium nitrate, and 10 parts of NMP were mixed and stirred uniformly, and treated with a sand mill at 1000 rpm for 4 hours, and then the filtered product was washed with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain nitrogen-doped graphene fluoride slurry; (2) 1 part of nitrogen-doped fluorinated graphene, 5 parts of tetramethylammonium hydroxide, and 50 parts of deionized water were mixed and stirred evenly, ultrasonically treated, and then added into a polytetrafluoroethylene-lined high-pressure reactor, reacted at 140°C for 32 hours, then washed and filtered with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain a hydroxylated nitrogen-doped graphene slurry; (3) 1 part of hydroxylated nitrogen-doped graphene, 0.5 part of ferrous sulfate, and 300 parts of water were mixed and stirred evenly, and the pH value of the mixture was adjusted to 9 with tetraethylammonium hydroxide. The mixture was allowed to stand for 36 hours, and then added to a polytetrafluoroethylene-lined high-pressure reactor, reacted at 140°C for 12 hours, and then washed and filtered with deionized water for multiple times to remove impurities, and vacuum dried at 80°C to obtain iron (III) oxide-modified nitrogen-doped graphene, i.e., graphene catalyst.

[0043] The desulfurization and dewaxing process of Example 3 specifically includes: 100 parts of D130 oil (Qingjiang Petrochemical) were added into the reaction chamber of the circulating fluidized reactor, and 20 parts of urea peroxide, 2 parts of deionized water and 0.04 parts of the prepared graphene catalyst were added into the high-level tank of the circulating fluidized reactor; The high-level tank is heated to 120°C to melt the urea peroxide therein into liquid, and then the mixed material in the high-level tank is placed in the reaction chamber of the circulating fluidized bed reactor. The oil product and the mixed material are stirred and reacted in a reciprocating cycle in the circulating fluidized bed reactor. The reaction temperature is 50°C and the reaction time is 2 hours.

[0044] The rest is implemented in the same manner as in Example 1.

[0045] Example 4 Embodiment 4 provides a graphene catalyst and a preparation method thereof, which specifically comprises the following steps: (1) 1 part of graphite fluoride, 4 parts of ammonium citrate, and 30 parts of NMP were mixed and stirred uniformly, and treated with a sand mill at 3000 rpm for 6 hours, and then the filtered product was washed with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain nitrogen-doped graphene fluoride slurry; (2) 1 part of nitrogen-doped fluorinated graphene, 20 parts of tetramethylammonium hydroxide, and 200 parts of deionized water were mixed and stirred evenly, ultrasonically treated, and then added into a polytetrafluoroethylene-lined autoclave, reacted at 180°C for 64 hours, then washed and filtered with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain a hydroxylated nitrogen-doped graphene slurry; (3) 1 part of hydroxylated nitrogen-doped graphene, 5 parts of nickel nitrate and 500 parts of water were mixed and stirred evenly, the pH value of the mixture was adjusted to 10 with tetraethylammonium hydroxide, and the mixture was allowed to stand for 48 hours. Then, it was added to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 180°C for 24 hours. Then, it was washed and filtered with deionized water for multiple times to remove impurities, and vacuum dried at 80°C to obtain nickel oxide (III) modified nitrogen-doped graphene, i.e., graphene catalyst.

[0046] The oil desulfurization and dewaxing of Example 4 specifically includes: 100 parts of D130 oil (Qingjiang Petrochemical) were added into the reaction chamber of the circulating fluidized reactor, and 50 parts of urea peroxide, 5 parts of deionized water and 0.4 parts of the prepared graphene catalyst were added into the high-level tank of the circulating fluidized reactor; The high-level tank is heated to 120°C to melt the urea peroxide therein into liquid, and then the mixed material in the high-level tank is placed in the reaction chamber of the circulating fluidized bed reactor. The oil product and the mixed material are stirred and reacted in a reciprocating cycle in the circulating fluidized bed reactor. The reaction temperature is 65°C and the reaction time is 2 hours.

[0047] The rest is implemented in the same manner as in Example 1.

[0048] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the graphene catalyst prepared by the present invention is not added during the desulfurization and dewaxing of the oil product, and the rest is implemented in the same manner as Example 1.

[0049] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the catalyst used in Comparative Example 2 is the hydroxylated nitrogen-doped graphene prepared in step (2) of Example 1, that is, the catalyst is not modified by metal elements, and the rest is implemented in the same way as Example 1.

[0050] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the catalyst used in Comparative Example 3 is not nitrogen-doped. The specific preparation process is as follows: (1) 1 part of graphite fluoride and 20 parts of NMP were mixed and stirred uniformly, and processed by a sand mill at 2000 rpm for 5 hours, and then the filtered product was washed with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain a fluorinated graphene slurry; (2) 1 part of fluorinated graphene, 10 parts of tetramethylammonium hydroxide, and 100 parts of deionized water were mixed and stirred evenly, ultrasonically treated, and then added into a polytetrafluoroethylene-lined autoclave, reacted at 160° C. for 48 hours, then washed and filtered with deionized water and anhydrous ethanol for multiple times to remove impurities, and concentrated to obtain a hydroxylated graphene slurry; (3) 1 part of hydroxylated graphene, 2 parts of cerium nitrate and 400 parts of water were mixed and stirred evenly, the pH value of the mixture was adjusted to 9.5 with tetraethylammonium hydroxide, and the mixture was allowed to stand for 24 hours. Then, it was added to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 160°C for 18 hours. Then, it was washed and filtered with deionized water several times to remove impurities, and vacuum dried at 80°C to obtain cerium (IV) oxide modified graphene.

[0051] According to the same method as Example 1, the cerium oxide modified graphene prepared in Comparative Example 3 was used for desulfurization and dewaxing.

[0052] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the catalyst used in Comparative Example 4 is cerium oxide-modified graphene, and the specific preparation method is as follows: 1 part of graphene oxide, 2 parts of cerium nitrate and 400 parts of water were mixed and stirred evenly, the pH value of the mixture was adjusted to 9.5 with tetraethylammonium hydroxide, and the mixture was allowed to stand for 24 hours. Then, it was added to a polytetrafluoroethylene-lined high-pressure reactor and reacted at 160°C for 18 hours. Then, it was washed and filtered with deionized water several times to remove impurities, and vacuum dried at 80°C to obtain cerium oxide (IV) modified graphene.

[0053] In the same manner as in Example 1, desulfurization and dewaxing were carried out using the cerium (IV) oxide modified graphene of Comparative Example 4.

[0054] Comparative Example 5 Comparative Example 5 uses sodium percarbonate as an oxidant, as follows: 100 parts of D130 oil, 30 parts of sodium percarbonate, 3 parts of deionized water, and 0.1 parts of graphene catalyst (the same as the graphene catalyst used in Example 1) were added into a circulating fluidized reactor, and the reaction was stirred and reacted in a reciprocating cycle at a reaction temperature of 80° C. for 2 hours. After the reaction was completed, the mixture was filtered twice repeatedly by positive pressure filtration to obtain a purified oil.

[0055] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that in the preparation step (2) of the graphene catalyst, tetramethylammonium hydroxide is replaced by inorganic base sodium hydroxide. The specific step (2) of Comparative Example 6 is: 1 part of nitrogen-doped fluorinated graphene, 10 parts of sodium hydroxide, and 100 parts of deionized water were mixed and stirred evenly, ultrasonically treated, and then added into a polytetrafluoroethylene-lined high-pressure reactor, reacted at 160°C for 48 hours, then washed and filtered with deionized water and anhydrous ethanol several times to remove impurities, and concentrated to obtain hydroxylated nitrogen-doped graphene slurry.

[0056] It was found that the inorganic base sodium hydroxide could not hydrolyze the CF bond, so subsequent operations could not be performed.

[0057] Comparative Example 7 The only difference between Example 7 and Example 1 is that in the preparation step (2) of the graphene catalyst, tetramethylammonium hydroxide is replaced by triethylamine, and the rest is implemented in the same manner as Example 1.

[0058] Elemental analysis was performed on the fluorinated graphite, the intermediate product nitrogen-doped fluorinated graphene, and the intermediate product hydroxylated nitrogen-doped graphene used in preparing the graphene catalyst in Example 1. The element content in the sample was determined by an elemental analyzer, wherein the C, H, and N elements were determined by a high temperature combustion method, the F element was determined by an oxygen bottle combustion-thorium nitrate titration method, and the O element was the remaining amount.

[0059] Table 1 Element contents of samples at each stage in the process of preparing graphene catalyst in Example 1

[0060] The content of each element of the hydroxylated nitrogen-doped graphene prepared in Example 1, Example 2, Comparative Example 6 and Comparative Example 7 was tested, and the test results are shown in Table 2: Table 2 Content of each element in hydroxylated nitrogen-doped graphene in Examples 1-2 and Comparative Examples 6-7

[0061] According to Table 2, compared with comparative example 6 in which an inorganic base is used to catalyze the hydrolysis of CF to C-OH, the conversion rate of CF is higher when an organic base is used; and compared with triethylamine, tetramethylammonium hydroxide and 4-dimethylaminopyridine have better effects. In addition, tetraethylammonium hydroxide and tetramethylammonium hydroxide have similar structures and comparable effects.

[0062] The present invention detects the sulfur content in the original oil and the oil after the desulfurization and dewaxing process of the relevant embodiments and comparative examples according to SH / T 0689-2000. The detection results are shown in Table 3.

[0063] Table 3 Sulfur content in oil products and desulfurization efficiency

[0064] According to Table 3, compared with Comparative Example 3, the desulfurization effect of Example 1 is improved, indicating that nitrogen doping in the graphene catalyst can improve the catalytic performance. Comparing Comparative Example 3 and Comparative Example 4, it can be seen that the desulfurization effect of Comparative Example 3 is better than that of Comparative Example 4, indicating that the structure obtained by hydrolysis of fluorinated graphene is more conducive to metal oxide loading, thereby improving the catalytic performance of the graphene catalyst. Comparing Example 1 and Comparative Example 7, it can be seen that compared with Example 1, the desulfurization effect of Comparative Example 7 is significantly reduced, indicating that incomplete hydrolysis of CF bonds in graphene will affect the metal oxide loading, resulting in reduced catalytic performance.

[0065] In Example 1 of the present invention, the graphene catalyst is recycled by post-processing the filter cake. Ten batches of oil products are treated according to the recycling method of Example 1. The sulfur content and desulfurization efficiency of each batch of purified oil products are shown in Table 4.

[0066] Table 4 Effect of recycling 10 batches of oil products

[0067] According to Table 4, the graphene catalyst recovered and reused by post-treatment of the filter cake can still maintain an excellent desulfurization effect during multiple cycles.

[0068] The present invention tests the pour points of the original oil product and the purified oil products treated by the relevant examples and comparative examples according to GB / T 510-1983. The test results are shown in Table 5.

[0069] Table 5 Pour point of oil products

[0070] According to Table 4, the pour point of the purified oil can be reduced to -80°C by using the method of Example 1 of the present invention for combined desulfurization and dewaxing, which shows that the method of Example 1 has excellent dewaxing effect and the purified oil obtained can meet the use environment of extremely low temperature. Compared with Comparative Examples 1-4, the dewaxing effect of Example 1 is better, which shows that the graphene catalyst of the present invention can not only catalyze the desulfurization reaction, but also promote the improvement of the dewaxing effect. Combining Examples 1 and 2 with Comparative Examples 1-4, it is shown that the improvement of the dewaxing effect of the graphene catalyst is mainly due to the fact that the loading of metal oxides promotes the formation of a network-like supramolecular structure, thereby maximally adsorbing normal alkanes in the oil. Comparative Example 5 uses sodium percarbonate as an oxidant. Combining Tables 4 and 5, although Comparative Example 5 can also achieve a good desulfurization effect, the pour point of the oil does not decrease at this time, which shows that the dewaxing effect cannot be achieved by changing the oxidant.

[0071] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all aspects and are not intended to limit the present invention, the scope of the present invention is defined only by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0072] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0073] Although the present invention has been described with reference to illustrative embodiments, it will be appreciated by those skilled in the art that various other changes, omissions and / or additions may be made without departing from the spirit and scope of the present invention and that the elements of the embodiments may be replaced by substantial equivalents. In addition, many modifications may be made without departing from the scope of the present invention to adapt specific circumstances or materials to the teachings of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for performing the present invention, but it is intended that the present invention will include all embodiments within the scope of the appended claims. In addition, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another element.

Claims

1. A method for preparing a graphene catalyst, characterized in that: include: subjecting a first mixture containing nitrogen-doped fluorinated graphene, an organic base and water to a first reaction, so that at least part of CF in the nitrogen-doped fluorinated graphene is hydrolyzed to form C—OH, thereby obtaining hydroxylated nitrogen-doped graphene; The second mixture containing the hydroxylated nitrogen-doped graphene, a transition metal soluble salt and water is subjected to a second reaction so that the transition metal soluble salt generates a transition metal oxide and is loaded on the graphene, thereby obtaining a graphene catalyst.

2. The preparation method according to claim 1, characterized in that: The first mixture comprises, by mass, 1 part of nitrogen-doped fluorinated graphene, 5-20 parts of an organic base, and 50-200 parts of water; And / or, the organic base includes one or more of 4-dimethylaminopyridine, tetramethylammonium hydroxide, and tetraethylammonium hydroxide; And / or, the temperature of the first reaction is 140-180°C and the time is 32-64h; And / or, the second mixture comprises, by mass, 1 part of hydroxylated nitrogen-doped graphene, 0.5-5 parts of a soluble transition metal salt, and 300-500 parts of water; And / or, the transition metal soluble salt includes one or a combination of molybdenum salt, tungsten salt, vanadium salt, iron salt, nickel salt, and cerium salt; And / or, the temperature of the second reaction is 140-180°C and the time is 12h-24h; And / or, a pH adjuster is used to adjust the pH value of the second mixture to 9-10, and then the second reaction is carried out. Preferably, the pH adjuster includes one or more of ammonia water, tetramethylammonium hydroxide or tetraethylammonium hydroxide.

3. The preparation method according to claim 2, characterized in that: Also includes: Before carrying out the second reaction, the second mixture is allowed to stand for a set time so that the transition metal ions therein are fully adsorbed on the hydroxylated nitrogen-doped graphene and react in situ to form transition metal oxides; Preferably, the set time is 24h-48h.

4. The preparation method according to claim 3, characterized in that: The preparation method of the nitrogen-doped fluorinated graphene comprises: grinding a third mixture containing 1 part of fluorinated graphite, 1-4 parts of a nitrogen source and 10-30 parts of a dispersant by mass to obtain the nitrogen-doped fluorinated graphene.

5. The preparation method according to claim 4, characterized in that: The nitrogen source is composed of C, H, and N elements or C, H, O, and N elements. More preferably, the nitrogen source includes one or more of ammonium carbonate, ammonium bicarbonate, ammonium nitrate, ammonium acetate, ammonium oxalate, ammonium citrate, and ammonium succinate. And / or, the dispersant includes one or a combination of N-methylpyrrolidone, N,N-dimethylformamide or dimethyl sulfoxide; And / or, the grinding process is performed at a rotation speed of 1000-3000 rpm and for a time of 4-6 hours.

6. A graphene catalyst, characterized in that: It is prepared by the method described in any one of claims 1 to 5.

7. Use of the graphene catalyst according to claim 6 in desulfurization and dewaxing of oil products; Preferably, the application includes: The graphene catalyst and urea peroxide are used to simultaneously desulfurize and dewax oil products.

8. A method for simultaneous desulfurization and dewaxing of oil products, characterized in that: include: Uniformly mixing carbamide peroxide and a water dispersion of a catalyst and heating and liquefying them, so that the catalyst is uniformly dispersed in the carbamide peroxide along with water, thereby forming a premixed material, wherein the catalyst comprises the graphene catalyst according to claim 6; The premixed material is fully mixed and contacted with the oil product to be treated, and the urea peroxide, water and graphene catalyst form a supramolecular network structure; under the action of the catalyst, the urea peroxide generates hydroxyl radicals to oxidize the sulfur-containing compounds in the oil product into sulfone substances; the supramolecular network structure adsorbs the sulfone substances and normal alkane substances in the oil product, thereby achieving simultaneous desulfurization and dewaxing of the oil product.

9. The method according to claim 8, characterized in that Also includes: Firstly, the graphene catalyst is dispersed in water and ultrasonicated to pre-disperse it to form an aqueous dispersion of the graphene catalyst; then, the aqueous dispersion of the graphene catalyst is uniformly mixed with the urea peroxide to form the premixed material; And / or, the urea peroxide and the aqueous dispersion of the catalyst are first uniformly mixed, and heated to 80-140° C. to melt the urea peroxide into a liquid state, and the graphene catalyst therein is uniformly dispersed in the liquid urea peroxide to form the premixed material; And / or, the method further comprises: performing solid-liquid separation on the product obtained from the reaction to obtain a purified oil product and a solid residue; and separating the sulfone substances and normal alkane substances in the solid residue, and at least recovering the graphene catalyst therein and reusing it; preferably, separating the sulfone substances and normal alkane substances in the solid residue specifically comprises: heating the solid residue to 50-80°C to liquefy the normal alkane substances therein, and dissolving the sulfone substances therein in the liquefied normal alkane substances, and then performing solid-liquid separation.

10. The method according to claim 8 or 9, characterized in that: By weight, 20-50 parts of urea peroxide, 0.04-0.4 parts of graphene catalyst and 2-5 parts of water are uniformly mixed to form the premixed material, and then the premixed material is fully mixed and contacted with 100 parts of oil product to carry out the reaction; And / or, the reaction temperature is 50°C-80°C; And / or, the reaction time is 2-6h.

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