CeO2-graphite carbon composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of crude oil catalysis technologies, and provides a CeO2-graphite carbon composite material and a preparation method and application thereof, and the CeO2-graphite carbon composite material is composed of nanometer CeO2 and graphene or carbon nanotubes growing on the surface of the nanometer CeO2; the nano CeO2 is prepared from cerium chloride heptahydrate, urea and sodium hydroxide through a hydrothermal reaction; graphene or carbon nanotubes grow on the surface of nano CeO2 through a chemical vapor deposition method by taking ethanol as a carbon source and blowing and heating argon, the prepared CeO2 can reach 30-90nm, is narrow in size distribution and is spherical, the graphene or carbon nanotubes directly grow on the surface of CeO2, and the graphene or carbon nanotubes and the CeO2 are tightly combined, so that the dispersibility and catalytic activity of CeO2 are improved, and the preparation method is simple and easy to implement. The viscosity of thickened oil can be obviously reduced when the catalyst is applied to thickened oil hydrothermal cracking.

Description

Technical Field

[0001] This invention relates to the field of crude oil catalysis technology, and more specifically, to a CeO2-graphite carbon composite material, its preparation method, and its application. Background Technology

[0002] Heavy oil is an important unconventional petroleum resource globally, with abundant reserves. However, it generally suffers from high viscosity, poor fluidity, and high development costs, limiting its efficient extraction and utilization. Existing technologies for reducing heavy oil viscosity mainly include thermal recovery, solvent dilution, microbial degradation, and catalytic hydrothermal cracking. Among these, catalytic hydrothermal cracking is considered a promising method for reducing heavy oil viscosity because it can break down and hydrogenate large hydrocarbon molecules under hydrothermal conditions, thereby reducing viscosity.

[0003] Cerium dioxide (CeO2) exhibits certain advantages in heavy oil cracking and hydrogenation reactions due to its unique reversible redox properties and oxygen storage / release capabilities. Existing methods for preparing CeO2-graphite carbon composites mainly include impregnation, hydrothermal methods, sol-gel methods, and deposition-precipitation methods. While these methods can achieve CeO2-graphite carbon composites to some extent, they generally suffer from the following shortcomings: First, CeO2 particles are unevenly distributed on the graphite carbon surface, easily agglomerating, resulting in low utilization of active sites; second, the bonding force between CeO2 and graphite carbon is weak, leading to poor stability of the composite structure; third, particle size and distribution are difficult to control precisely, resulting in insufficient controllability of the interface structure; and fourth, some process conditions are demanding, making large-scale application difficult.

[0004] Therefore, there is an urgent need for a new preparation method that can uniformly deposit and firmly bond graphite carbon and CeO2 particles with high controllability and repeatability, thereby improving the performance of the material and meeting the needs of large-scale preparation. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a CeO2-graphite carbon composite material, its preparation method, and its applications. The CeO2-graphite carbon composite material is synthesized by chemical vapor deposition using ethanol as the carbon source in a tube furnace. The CeO2 obtained by this invention can reach a size of 30-90 nm, has a narrow size distribution, and is spherical. Graphene or carbon nanotubes grow directly on the CeO2 surface, and the two are tightly bonded, improving the dispersibility and catalytic activity of CeO2. When applied to the hydrothermal cracking of heavy oil, it can significantly reduce the viscosity of heavy oil.

[0006] The technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides a CeO2-graphite carbon composite material, which is composed of nano-CeO2 and graphene or carbon nanotubes grown on the surface of nano-CeO2.

[0008] Nano CeO2 is prepared by hydrothermal reaction of cerium chloride heptahydrate, urea and sodium hydroxide; graphene or carbon nanotubes are grown on the surface of nano CeO2 by chemical vapor deposition with ethanol as carbon source and argon purging and heating; the heating temperature is 550-850℃ and the reaction time is 10-70min.

[0009] The heating temperature is 550-850℃, for example, it can be 550℃, 650℃, 700℃, 750℃, 800℃, 850℃, etc.

[0010] The reaction time is 10-70 minutes, for example, 10 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 70 minutes, etc.

[0011] Furthermore, the heating temperature is 650-800℃, and the reaction time is 30-60 min.

[0012] Furthermore, the molar ratio of urea to cerium chloride heptahydrate is (3-5):1.

[0013] Furthermore, the molar ratio of sodium hydroxide to cerium chloride heptahydrate is (15-25):1.

[0014] Furthermore, the hydrothermal reaction temperature is 120-180℃, and the reaction time is 8-12h.

[0015] Furthermore, the argon flow rate is 200 sccm.

[0016] Secondly, based on the same inventive concept, the present invention provides a method for preparing the CeO2-graphite carbon composite material according to any one of the first aspects, comprising the following steps:

[0017] Nano-CeO2 was prepared and placed in a tube furnace. After being purged with argon and heated, ethanol vapor carried by argon was introduced as a carbon source to carry out a chemical vapor deposition reaction, resulting in CeO2-graphite carbon composite material.

[0018] Furthermore, the preparation method of nano-CeO2 includes the following steps:

[0019] S1. Dissolve cerium chloride heptahydrate and urea in deionized water to form a mixture, add sodium hydroxide solution dropwise and mix well to obtain the reaction precursor solution;

[0020] S2. The precursor solution was subjected to a hydrothermal reaction, and the reaction product was centrifuged, washed, and dried to obtain nano CeO2.

[0021] Thirdly, based on the same inventive concept, the present invention provides the application of CeO2-graphite carbon composite material as described in any one of the first aspects or CeO2-graphite carbon composite material prepared by any one of the preparation methods described in the second aspect in the hydrothermal cracking of heavy oil.

[0022] Furthermore, CeO2-graphite carbon composite material and water were ultrasonically mixed at a mass ratio of 1:1000 to obtain CeO2-graphite carbon composite material dispersion. The CeO2-graphite carbon composite material dispersion was then injected into the reservoir with heavy oil at a mass ratio of 1:1 for heavy oil hydrothermal cracking.

[0023] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0024] 1. A two-step process for preparing CeO2 by hydrothermal method and growing graphene or carbon nanotubes in situ by chemical vapor deposition is adopted, which eliminates the need to synthesize CeO2, graphene or carbon nanotubes separately and then combine them. The process is simplified and facilitates large-scale application.

[0025] 2. The obtained CeO2 particles have a size of 30-90nm and are regularly spherical. Graphene or carbon nanotubes are grown directly on the CeO2 surface, and the two are tightly bonded. The framework effect of graphene or carbon nanotubes effectively inhibits the aggregation of CeO2 particles, greatly improves their dispersibility in the reaction system, and increases the exposure of active sites.

[0026] 3. The redox properties and oxygen storage / release capacity of CeO2, combined with the high specific surface area and excellent conductivity of graphene or carbon nanotubes, result in outstanding catalytic performance in the hydrothermal cracking of heavy oil. This effectively improves the dispersion performance of active components in heavy oil, thereby increasing the contact opportunities between active components and heavy oil molecules and enhancing the quality improvement and viscosity reduction effects.

[0027] 4. The well-organized composite structure ensures stable performance of the catalyst during the reaction process and prevents activity decay due to structural collapse; the preparation process does not require complex equipment, the process can be scaled up, the raw material cost is low, and it is suitable for industrial applications such as heavy oil extraction. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0030] Figure 1 The X-ray diffraction pattern of the product of Embodiment 1 of the present invention;

[0031] Figure 2 The Raman spectrum of the product in Example 1 of this invention;

[0032] Figure 3 Here is a SEM image of the product from Embodiment 1 of the present invention;

[0033] Figure 4 This is a TEM image of the product of Embodiment 3 of the present invention;

[0034] Figure 5 This is a SEM image of the product in Embodiment 4 of the present invention;

[0035] Figure 6 This is a SEM image of the product in Embodiment 5 of the present invention;

[0036] Figure 7 SEM image of Comparative Example 10 of this invention

[0037] Figure 8 This is a SEM image of the product of Comparative Example 1 of this invention;

[0038] Figure 9 This is a SEM image of the product of Comparative Example 2 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0041] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0042] The preparation of nano CeO2 in Examples 1 to 10 below was carried out using the following method:

[0043] Dissolve 0.745g CeCl3·7H2O and 0.48g urea in 20mL of deionized water, then dissolve 2g NaOH in 20mL of deionized water. After complete dissolution, mix the two solutions thoroughly and stir until homogeneous. Add the mixture to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE). Place the reactor in an oven and react at 160℃ for 8 hours. Collect the precipitate using a centrifuge at 12500 rpm and wash several times with pure water. Then, place the solid in an oven and dry at 60℃ for 12 hours. The resulting powder is nano-CeO2.

[0044] Example 1

[0045] This embodiment provides a CeO2-graphite carbon composite material, the preparation method of which includes the following process:

[0046] 0.2 g of CeO2 was loaded into a ceramic boat and placed in the isothermal zone of a tube furnace. The furnace was then heated to 750 °C at a heating rate of 10 °C / min under an Ar atmosphere. Ethanol vapor was introduced into the quartz tube through a flowing Ar stream (200 sccm), and the temperature was maintained at 750 °C for 30 min. This yielded a CeO2-graphite carbon composite material.

[0047] Please refer to Figure 1-3 , Figure 1 The X-ray diffraction pattern of the CeO2-graphite carbon composite material in this embodiment is shown. The 2θ peaks are located at 28.5°, 33.1°, 47.5°, 56.3°, 59.1°, 69.4°, 76.7° and 79.0°, respectively, belonging to the (111), (200), (220), (311), (222), (400), (331) and (420) planes, respectively. The synthesis is a CeO2-graphite carbon composite catalyst with CeO2 as the main component.

[0048] Depend on Figure 2 As can be seen, the CeO2-graphite carbon composite material sample prepared in this embodiment shows a clear D band (approximately 1358 cm⁻¹). -1 ) and G-band (approximately 1580cm) -1 This confirms the existence of carbon nanomaterials. And I D / I G A ratio of 0.82 indicates the synthesis of carbon nanotubes with a high degree of graphitization. (The text abruptly ends here.) Figure 3 The presence of carbon nanotubes confirms the successful synthesis of CeO2-graphite carbon composite material, with the carbon nanotubes having a diameter of approximately 40 nm and the CeO2 having a size between 45 and 65 nm.

[0049] Example 2

[0050] This embodiment provides a CeO 2-The graphite carbon composite material differs from Example 1 only in that the heating and holding temperatures are both 550°C.

[0051] Example 3

[0052] This embodiment provides a CeO 2- The graphite carbon composite material differs from Example 1 only in that the heating and holding temperatures are both 650°C.

[0053] Please refer to Figure 4 ,Depend on Figure 4 It can be seen that the CeO2-graphite carbon composite material prepared in this embodiment has a layer of graphene wrapped around CeO2, and the size of CeO2 is between 30-40nm.

[0054] Example 4

[0055] This embodiment provides a CeO2-graphite carbon composite material, which differs from Example 1 only in that the heating temperature and holding temperature are 700℃.

[0056] Please refer to Figure 5 ,Depend on Figure 5 It can be seen that the CeO2-graphite carbon composite material prepared at the temperature of this embodiment will generate a small amount of carbon nanotubes, with CeO2 size between 35-50nm.

[0057] Example 5

[0058] This embodiment provides a CeO2-graphite carbon composite material, which differs from Example 1 only in that the heating temperature and holding temperature are 800℃.

[0059] Please refer to Figure 6 ,Depend on Figure 6 It can be seen that the CeO2-graphite carbon composite material prepared in this embodiment grows large-sized carbon nanotubes, and the particle size increases, with the CeO2 size being between 70-90 nm.

[0060] Example 6

[0061] This embodiment provides a CeO2-graphite carbon composite material, which differs from Example 1 only in that the heating temperature and holding temperature are 850°C.

[0062] Example 7

[0063] This embodiment provides a CeO2-graphite carbon composite material, which differs from Example 1 only in that it is held at 750°C for 10 minutes.

[0064] Example 8

[0065] This embodiment provides a CeO2-graphite carbon composite material, which differs from Example 1 only in that it is held at 750°C for 20 minutes.

[0066] Example 9

[0067] This embodiment provides a CeO2-graphite carbon composite material, which differs from Example 1 only in that it is held at 750°C for 45 minutes.

[0068] Example 10

[0069] This embodiment provides a CeO2-graphite carbon composite material, which differs from Example 1 only in that it is held at 750°C for 60 minutes.

[0070] Please refer to Figure 7 ,Depend on Figure 7 It can be seen that the carbon nanotube diameter of the CeO2-graphite carbon composite material prepared in this embodiment has increased to between 50-60 nm, and the CeO2 size has also increased to between 65-80 nm.

[0071] Comparative Example 1

[0072] This comparative example provides a nano CeO2, prepared using the same method as the nano CeO2 in Example 1, to verify the effect of single nano CeO2 on the hydrothermal pyrolysis of heavy oil.

[0073] Please refer to Figure 8 ,Depend on Figure 8 As can be seen, the nano CeO2 particles are approximately spherical in shape, with a size between 10-20 nm. Due to their small size, these CeO2 particles tend to aggregate significantly, leading to a decrease in catalytic activity.

[0074] Comparative Example 2

[0075] This comparative example provides a high-temperature calcined CeO2 material, which differs from Example 1 only in that ethanol is not added, in order to verify the effect of the material obtained by high-temperature calcination of CeO2 without adding ethanol as a carbon source on the hydrothermal cracking of heavy oil.

[0076] Please refer to Figure 9 ,Depend on Figure 9 It can be seen that after high-temperature calcination, the CeO2 particles increase in size to between 70-100 nm.

[0077] To better understand the present invention, the following performance evaluation was performed on the products of the above embodiments and comparative examples:

[0078] Test Example 1

[0079] This test example 1 evaluates the viscosity-reducing performance of the products prepared in the above embodiments and comparative examples for heavy oil. The specific process is as follows:

[0080] 80g of heavy oil was placed in a 500mL reactor, and water was added at an oil-to-water ratio of 1:1. The mass ratio of heavy oil to catalyst was 1:0.005. The reactor was heated to 240℃ and reacted for 24 hours with stirring at 350 rpm. After the reaction, the oil sample was removed from the reactor, and its viscosity was measured at 50℃ using a viscometer. During the measurement, the torque was maintained between 30% and 70%, and the changes in the SRAR composition of the oil sample were analyzed.

[0081] The viscosity reduction rate (Δη) of the heavy oil viscosity reducing catalyst is calculated by the following formula:

[0082]

[0083] Where η0 is the viscosity before the reaction, and η is the viscosity after the reaction.

[0084] To visually evaluate the effect of CeO2-graphite carbon composite material on viscosity reduction of heavy oil, the viscosity of the heavy oil after hydrothermal cracking in the examples and comparative examples was measured at 50°C after oil-water separation, and the viscosity reduction effect was compared. The test results are shown in Table 1.

[0085] Table 1. Viscosity reduction rate of heavy oil in each group after catalytic reaction.

[0086] sample Viscosity reduction rate / % Example 1 71.96％ Example 2 65.70％ Example 3 69.75％ Example 4 69.95％ Example 5 67.44％ Example 6 65.58％ Example 7 66.54％ Example 8 68.66％ Example 9 67.52％ Example 10 64.69％ Comparative Example 1 63.03％ Comparative Example 2 58.80％

[0087] As shown in Table 1, in Examples 1-6, the viscosity reduction effect increased from 65.7% to 71.96% and then decreased to 65.58% with increasing temperature. In Examples 1 and 7-10, the viscosity reduction effect increased from 66.54% to 71.96% and then decreased to 64.69% with increasing time. The viscosity reduction effect of all examples was higher than that of Comparative Examples 1 and 2, confirming the excellent catalytic performance of the CeO2-graphite carbon composite material. In particular, the CeO2-graphite carbon composite material obtained under the conditions of Example 1 is the best catalyst for heavy oil hydrothermal cracking, with a viscosity reduction of 71.96%.

[0088] Test Example 2

[0089] Test Example 2 evaluates the performance of the four components of heavy oil in the products prepared in the above embodiments and comparative examples.

[0090] To evaluate the internal changes of heavy oil after catalytic hydrothermal cracking, a four-component performance evaluation was conducted to observe the effect of CeO2-graphite carbon composite material on the viscosity of heavy oil. The results are shown in Table 2.

[0091] Table 2 Evaluation data of four components of heavy oil

[0092] oil sample Saturated fraction Aromatic components gelatin Asphalt crude 28.41％ 26.71％ 32.75％ 12.13％ Example 1 25.32％ 34.63％ 27.61％ 12.44％ Example 2 25.23％ 33.62％ 28.48％ 12.67％ Example 3 24.87％ 33.53％ 28.85％ 12.85％ Example 4 24.75％ 33.39％ 29.02％ 12.84％ Example 5 24.98％ 33.43％ 28.86％ 12.73％ Example 6 24.92％ 33.46％ 28.85％ 12.77％ Example 7 24.96％ 33.49％ 28.92％ 12.61％ Example 8 25.07％ 33.52％ 28.82％ 12.59％ Example 9 25.54％ 32.56％ 29.18％ 12.72％ Example 10 24.31％ 33.04％ 29.85％ 12.80％ Comparative Example 1 24.14％ 33.87％ 30.22％ 11.77％ Comparative Example 2 27.97％ 29.33％ 30.14％ 12.56％

[0093] As shown in Table 2, the resin content decreased in all pyrolysis samples compared to crude oil, indicating that resins are susceptible to thermal and catalytic transformation. Asphaltene content increased slightly in all cases, except for a slight decrease in the oil sample treated with raw CeO2, suggesting that CeO2 may promote the cracking or transformation of some resins. Saturated components decreased in all pyrolysis samples, with the largest decrease observed in raw CeO2.

[0094] In contrast, the aromatic content increased significantly in all catalyst-treated samples, with the most significant increase in CeO2-graphite carbon in Example 1. Among all examples, CeO2-graphite carbon in Example 1 resulted in the largest reduction in gum content (down to 27.61%) and the highest aromatic content (34.63%), demonstrating its superior ability to promote the conversion of gum into lighter aromatics.

[0095] The viscosity reduction does not depend on a single SARA component, but rather on the overall compositional distribution of each component. The viscosity reduction rates of the nano-CeO2 catalysts in Comparative Examples 1 and 2 are lower than those in the above examples, indicating that the prepared CeO2-graphite carbon composite material is superior to CeO2 in reducing viscosity in heavy oil. Furthermore, Example 1 shows the best effect, further improving the viscosity reduction rate. Combined with the data from Test Example 1, the scheme in Example 1 is the most preferred scheme in this application.

[0096] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0097] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A CeO2-graphite carbon composite material, characterized in that, The CeO2-graphite carbon composite material is composed of nano-CeO2 and graphene or carbon nanotubes grown on the surface of the nano-CeO2. The nano-CeO2 is prepared by hydrothermal reaction of cerium chloride heptahydrate, urea and sodium hydroxide; the graphene or carbon nanotubes are grown on the surface of nano-CeO2 by chemical vapor deposition with ethanol as carbon source and argon purging and heating; the heating temperature is 550-850℃ and the reaction time is 10-70min.

2. The composite material according to claim 1, characterized in that, The heating temperature is 650-800℃, and the reaction time is 30-60min.

3. The composite material according to claim 1, characterized in that, The molar ratio of urea to cerium chloride heptahydrate is (3-5):

1.

4. The composite material according to claim 1, characterized in that, The molar ratio of sodium hydroxide to cerium chloride heptahydrate is (15-25):

1.

5. The composite material according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 120-180℃ for 8-12 hours.

6. The composite material according to claim 1, characterized in that, The argon gas flow rate is 200 sccm.

7. A method for preparing a CeO2-graphite carbon composite material according to any one of claims 1 to 6, characterized in that, The preparation method of the CeO2-graphite carbon composite material includes the following steps: Nano-CeO2 was prepared and placed in a tube furnace. After being purged with argon and heated, ethanol vapor carried by argon was introduced as a carbon source to carry out a chemical vapor deposition reaction, resulting in CeO2-graphite carbon composite material.

8. The method according to claim 7, characterized in that, The preparation method of the nano CeO2 includes the following steps: S1. Dissolve cerium chloride heptahydrate and urea in deionized water to form a mixture, add sodium hydroxide solution dropwise and mix well to obtain the reaction precursor solution; S2. The precursor solution is subjected to a hydrothermal reaction, and the reaction product is centrifuged, washed, and dried to obtain nano CeO2.

9. The application of a CeO2-graphite carbon composite material according to any one of claims 1 to 6 or a CeO2-graphite carbon composite material prepared by the preparation method according to any one of claims 7 to 8 in the hydrothermal cracking of heavy oil.

10. The application according to claim 9, characterized in that, The CeO2-graphite carbon composite material and water were ultrasonically mixed at a mass ratio of 1:1000 to obtain a CeO2-graphite carbon composite material dispersion. The CeO2-graphite carbon composite material dispersion was then injected into the reservoir with heavy oil at a mass ratio of 1:1 for heavy oil hydrothermal cracking.

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