A CeO2-supported alkaline catalyst for reducing viscosity in heavy oil, its preparation method and its application in reducing viscosity in heavy oil.

Abstract

This invention discloses a CeO2-supported alkaline catalyst for heavy oil viscosity reduction, its preparation method, and its application in heavy oil viscosity reduction, belonging to the fields of rare earth resource utilization and heavy oil extraction technology. The catalyst is prepared by the following method: dissolving metal A salt and metal B salt in water to obtain a mixed metal salt solution; then adding the precipitant buffer solution and the mixed metal salt solution dropwise to hot water, stirring until homogeneous, and heating to react; after the reaction is complete, washing and drying to obtain the alkaline catalyst; dispersing the alkaline catalyst in a cerium salt solution and impregnating it; then adding an oxidant and washing the precipitate; calcining the solid precipitate; after calcination, placing the calcined product in water for hydration, and then drying to obtain the CeO2-supported alkaline catalyst for heavy oil viscosity reduction. The heavy oil catalytic hydrothermal cracking catalyst of this invention is heat-resistant and can effectively reduce the content of heavy oil heavy components, thus showing good application prospects and value in the fields of heavy oil upgrading and extraction technology.

Description

Technical Field

[0001] This invention belongs to the field of rare earth resource utilization and heavy oil extraction technology, specifically relating to a CeO2-supported alkaline catalyst for reducing the viscosity of heavy oil, its preparation method, and its application in reducing the viscosity of heavy oil. Background Technology

[0002] With the depletion of conventional crude oil reserves, their quantity is dwindling, while heavy oil reserves are abundant. However, due to its high viscosity and poor fluidity, it is difficult to extract from the formation. Heavy oil extraction methods include physical methods such as blending with thinner oil and steam injection for thermal recovery. Catalytic hydrothermal cracking technology, a chemical method that can reduce the viscosity of heavy oil through modification, has attracted considerable attention from researchers. This technology can effectively catalyze the breaking of heteroatom chemical bonds in the gums and asphaltenes of heavy oil, fundamentally and irreversibly reducing its viscosity. Currently, the catalysts developed for catalytic hydrothermal cracking technology are all based on acid-catalyzed conversion processes, including nanocatalysts, oil-soluble catalysts, and water-soluble catalysts. Acidic catalysts tend to cause heavy oil to coke during the reaction, reducing or eliminating the catalyst's catalytic activity, and are difficult to achieve viscosity reduction requirements for heavy oils with particularly high gum content. Therefore, developing a highly efficient, stable, and environmentally friendly alkaline catalyst is of great significance.

[0003] Rare earth elements, also known as rare earth metals, possess unique properties such as optical, electrical, and magnetic characteristics due to their special atomic structure. Furthermore, their highly reactive chemical properties allow them to combine with other elements, resulting in a wide variety of new materials with diverse functions and applications. Rare earth metals are currently widely used in electronics, petrochemicals, metallurgy, machinery, energy, light industry, environmental protection, and agriculture. Cerium (Ce) is an important rare earth metal, with important compounds including cerium oxide, cerium hydroxide, cerium dioxide, and high-cerium salts, which have wide applications in glass, flint, ceramics, high-temperature alloys, and luminescent materials.

[0004] In conclusion, the application of rare earth metals to alkaline catalysts to enhance their catalytic performance and promote the upgrading of heavy oil to reduce its viscosity has both practical application value and significance. Summary of the Invention

[0005] This invention provides a CeO2-supported alkaline catalyst for reducing the viscosity of heavy oil, which is prepared by the following method:

[0006] Metal salts A and B were dissolved in water to obtain a mixed metal salt solution. Then, the precipitant buffer and the mixed metal salt solution were added dropwise to hot water, stirred until homogeneous, and heated to react. After the reaction was completed, the solution was washed and dried to obtain an alkaline catalyst. The alkaline catalyst was dispersed in a cerium salt solution and impregnated. Then, an oxidant was added, and the precipitate was washed. The solid precipitate was calcined. After calcination, the calcined product was placed in water for hydration and then dried to obtain a CeO2-supported alkaline catalyst for reducing the viscosity of heavy oil.

[0007] In the above technical solution, the metal A salt is selected from nitrates, chlorides, carbonates, sulfates or hydrates of salts of divalent transition metals such as Mg, Cu, Zn, Ni, and Co; the metal B salt is selected from nitrates, chlorides, carbonates, sulfates or hydrates of salts of trivalent transition metals such as Al, Fe, and Cr.

[0008] In the above technical solution, the ion concentration of metal A in the metal salt mixed solution is 0.01~3 mol / L; the ion concentration of metal B is 0.01~1 mol / L; and the molar ratio of metal A to metal B is 16:1~1:1.

[0009] In the above technical solution, the precipitant buffer solution is selected from any one or a mixture of NaOH, Na2CO3, ammonia, potassium hydroxide, potassium carbonate, lithium hydroxide, and lithium carbonate; the concentration of the precipitant buffer solution is 0.01~0.2 g / mL.

[0010] In the above technical solution, the temperature of the hot water is selected from 50~80℃; preferably 70℃.

[0011] In the above technical solution, the heating reaction conditions are: heating at 90~140℃ for 0.5~24h; preferably: heating at 110℃ for 3h.

[0012] In the above technical solution, the cerium salt is cerium chloride, cerium nitrate, cerium oxalate, or their hydrates. The concentration of the cerium salt solution is 0.01~0.1 mol / L; preferably 0.05 mol / L.

[0013] In the above technical solution, the mass ratio of the alkaline catalyst to the cerium salt is 1:3 to 5:1.

[0014] In the above technical solution, the immersion conditions are: immersion at 50~80℃ for 4~72h.

[0015] In the above technical solution, the oxidant is one of hydrogen peroxide, sodium hypochlorite, and persulfate.

[0016] In the above technical solution, the calcination conditions are: calcination at 200~500℃ for 3~12h; preferably: calcination at 250℃ for 6h.

[0017] This invention provides the application of the above-mentioned CeO2 supported alkaline catalyst in reducing the viscosity of heavy oil or improving the efficiency of heavy oil extraction.

[0018] This invention provides a method for catalytic hydrothermal cracking of heavy oil, comprising the following steps:

[0019] Dehydrated heavy oil, CeO2-supported alkaline catalyst, and water are mixed and catalytically reacted under nitrogen conditions. After the reaction is completed, heavy oil with reduced viscosity is obtained.

[0020] In the above-mentioned heavy oil catalytic hydrothermal cracking reaction method, the mass ratio of the dehydrated heavy oil, CeO2 supported alkaline catalyst and water is (10~100):(0.05~0.5):(10~50).

[0021] In the above-mentioned heavy oil catalytic hydrothermal cracking reaction method, the catalytic reaction conditions are: reaction temperature 180~300℃, reaction time 6~72h, and reaction pressure 0.5~8MPa.

[0022] This invention provides a method for reducing the viscosity of heavy oil during heavy oil extraction, comprising the following steps:

[0023] CeO2-supported alkaline catalyst is dispersed in water and stirred to form a suspension. High-temperature steam and the suspension are injected into the oil well together using a high-pressure pump, and the well is left to stand for 10 to 20 days to reduce the viscosity of the heavy oil in the well.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention significantly improves the performance of alkali catalysts in reducing the viscosity of heavy oil by loading CeO2 onto them, thereby greatly enhancing the efficiency of catalytic hydrothermal cracking of heavy oil. The heavy oil catalytic hydrothermal cracking catalyst of this invention is heat-resistant and can effectively reduce the content of heavy components in heavy oil under conditions of 180-300℃ and an initial pressure of 1.0 MPa. This effectively solves the key problem of efficient viscosity reduction of heavy oil using alkali catalysts, opening up new applications for rare earth metals and improving the efficiency of heavy oil extraction, demonstrating good application prospects and value in the fields of rare earth resource utilization and heavy oil extraction technology.

[0026] The CeO2-supported alkaline catalyst prepared by this invention has strong thermal stability, requires a small amount of catalyst, has abundant alkaline sites, and exhibits significant catalytic viscosity reduction effect, opening up a new direction for the development of heavy oil catalytic hydrothermal cracking technology. Attached Figure Description

[0027] Figure 1The XRD phase diagram of Zn3Cr1-LDHs is shown. Detailed Implementation

[0028] The heavy oil used in this invention is derived from the Bohai Oilfield and has a density of 0.968 g / cm³. 3 (20℃), viscosity 41525mPa·s (50℃), saturated hydrocarbon content 24.43%, aromatic hydrocarbon content 21.21%, gum content 46.84%, asphaltene content 10.52%.

[0029] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way.

[0030] Example 1

[0031] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Mg3Al1-LDHs) are as follows:

[0032] 2.3077 g of magnesium nitrate hexahydrate and 1.1254 g of aluminum nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was maintained at 9–10. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Mg3Al1-LDHs.

[0033] 1 g of Mg3Al1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (in excess, as hydrogen peroxide reacts with cerium nitrate to produce cerium dioxide) was added. The precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After filtration, it was dried in a drying oven at 70 °C for 12 h to obtain CeO2-Mg3Al1-LDHs.

[0034] Example 2

[0035] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Cu3Al1-LDHs) are as follows:

[0036] 2.1744 g of copper nitrate trihydrate and 1.1254 g of aluminum nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the pH of the solutions was maintained between 9 and 10.5. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h. The precipitate was then ground into powder to obtain Cu3Al1-LDHs.

[0037] 1 g of Cu3Al1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Cu3Al1-LDHs was obtained.

[0038] Example 3

[0039] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Zn3Al1-LDHs) are as follows:

[0040] 2.6776 g of zinc nitrate hexahydrate and 1.1254 g of aluminum nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was maintained at 9–10. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h. The precipitate was then ground into powder to obtain Zn3Al1-LDHs.

[0041] 1 g of Zn3Al1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Zn3Al1-LDHs was obtained.

[0042] Example 4

[0043] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Ni3Al1-LDHs) are as follows:

[0044] 2.6171 g of nickel nitrate hexahydrate and 1.1254 g of aluminum nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 8, and the solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Ni3Al1-LDHs.

[0045] 1 g of Ni3Al1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Ni3Al1-LDHs was obtained.

[0046] Example 5

[0047] The steps for preparing heavy oil viscosity-reducing alkaline catalysts (CeO2-Co3Al1-LDHs) are as follows:

[0048] 2.6193 g of cobalt nitrate hexahydrate and 1.1254 g of aluminum nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was maintained at 9–10. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h. The precipitate was then ground into powder to obtain Co3Al1-LDHs.

[0049] 1 g of Co3Al1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Co3Al1-LDHs was obtained.

[0050] Example 6

[0051] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Mg3Fe1-LDHs) are as follows:

[0052] 2.3077 g of magnesium nitrate hexahydrate and 1.2120 g of ferric nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 13. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Mg3Fe1-LDHs.

[0053] 1 g of Mg3Fe1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Mg3Fe1-LDHs was obtained.

[0054] Example 7

[0055] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Cu3Fe1-LDHs) are as follows:

[0056] 2.1744 g of copper nitrate trihydrate and 1.2120 g of ferric nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 5–6, and the solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Cu3Fe1-LDHs.

[0057] 1 g of Cu3Fe1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Cu3Fe1-LDHs was obtained.

[0058] Example 8

[0059] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Ni3Fe1-LDHs) are as follows:

[0060] 2.6171 g of nickel nitrate hexahydrate and 1.2120 g of ferric nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the pH of the solution was >13, and the solution was stirred at 1000 r / min for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Ni3Fe1-LDHs.

[0061] 1 g of Ni3Fe1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Ni3Fe1-LDHs was obtained.

[0062] Example 9

[0063] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Co3Fe1-LDHs) are as follows:

[0064] 2.6193 g of cobalt nitrate hexahydrate and 1.2120 g of ferric nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was maintained at 9–10. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Co3Fe1-LDHs.

[0065] 1 g of Co3Fe1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Co3Fe1-LDHs was obtained.

[0066] Example 10

[0067] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Mg3Cr1-LDHs) are as follows:

[0068] 2.3077 g of magnesium nitrate hexahydrate and 1.2004 g of chromium nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 13. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Mg3Cr1-LDHs.

[0069] 1 g of Mg3Cr1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Mg3Cr1-LDHs was obtained.

[0070] Example 11

[0071] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Cu3Cr1-LDHs) are as follows:

[0072] 2.1744 g of copper nitrate trihydrate and 1.2004 g of chromium nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 8-9. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Cu3Cr1-LDHs.

[0073] 1 g of Cu3Cr1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Cu3Cr1-LDHs was obtained.

[0074] Example 12

[0075] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Zn3Cr1-LDHs) are as follows:

[0076] 2.6776 g of zinc nitrate hexahydrate and 1.2004 g of chromium nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 9. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h. The precipitate was then ground into powder to obtain Zn3Cr1-LDHs.

[0077] Its XRD phase diagram is as follows Figure 1 As shown. Figure 1 The XRD diffraction angles were 11°, 23°, 34°, 59°, 60°, and 70°, indicating that the synthesized Zn3Cr1-LDHs material has a layered structure and good metal dispersion.

[0078] 1 g of Zn3Cr1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Zn3Cr1-LDHs was obtained.

[0079] Example 13

[0080] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Ni3Cr1-LDHs) are as follows:

[0081] 2.6171 g of nickel nitrate hexahydrate and 1.2004 g of chromium nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 8-9. The solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Ni3Cr1-LDHs.

[0082] 1 g of Ni3Cr1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Ni3Cr1-LDHs was obtained.

[0083] Example 14

[0084] The steps for preparing a heavy oil viscosity-reducing alkaline catalyst (CeO2-Co3Cr1-LDHs) are as follows:

[0085] 2.6193 g of cobalt nitrate hexahydrate and 1.2004 g of chromium nitrate nonahydrate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution A. 1 g of sodium hydroxide and 0.1587 g of anhydrous sodium carbonate were dissolved in 20 mL of deionized water and sonicated for 10 min, denoted as solution B. Simultaneously, solutions A and B were added dropwise to 100 mL of deionized water at 70 °C. During titration, the solution pH was 7-8, and the solution was stirred at 1000 rpm for 0.5 h. The entire solution was then transferred to a polytetrafluoroethylene (PTFE) container and heated at 110 °C for 3 h. After the PTFE container cooled, the solution was filtered and washed until neutral. The precipitate was then transferred to a 70 °C drying oven and dried for 12 h, then ground into powder to obtain Co3Cr1-LDHs.

[0086] 1 g of Co3Cr1-LDHs powder was dispersed in 30 mL of cerium nitrate solution (0.05 mol / L) and impregnated at 70 °C for 12 h. Then, 30 mL of 30% hydrogen peroxide (excess) was added, and the precipitate was washed and filtered three times with deionized water. The solid was placed in a muffle furnace and calcined at 250 °C for 6 h. The calcined product was then hydrated in deionized water for 2 h and filtered. After drying in a drying oven at 70 °C for 12 h, CeO2-Co3Cr1-LDHs was obtained.

[0087] I. Catalytic hydrothermal cracking reaction of heavy oil

[0088] 50g of dehydrated heavy oil was weighed and added to a reactor, along with 0.1g of powdered catalyst and 21g of water. After sealing the high-pressure reactor, nitrogen was introduced to purge the air from the reactor three times, and then the pressure was maintained at 1.0MPa for 12 hours. The reactor was then heated to 250℃ and reacted for 8 hours. After the reaction was completed, the temperature was lowered, the gas was vented, and the heavy oil in the reactor was transferred to a beaker to obtain the heavy oil obtained after the alkali-catalyzed hydrothermal cracking reaction. The viscosity reduction rate of the heavy oil after the alkali-catalyzed hydrothermal cracking reaction was tested using a rheometer, and the test results are shown in Table 1.

[0089] Table 1. Viscosity Reduction Effect of Various Catalysts on Heavy Oil Hydrothermal Cracking

[0090]

[0091] As shown in Table 1, the CeO2-supported alkaline catalysts prepared in this invention all exhibit good viscosity-reducing effects on heavy oil, with a maximum effect of 86%. During the hydrothermal cracking of heavy oil, the CS bonds in the gums and asphaltenes break, generating small molecule compounds. Furthermore, the π-π conjugation between asphaltenes macromolecules is also disrupted. Alkaline catalysis can promote the breaking of heteroatom chemical bonds in gum and asphaltenes molecules, thereby achieving the purpose of viscosity reduction.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for catalytic hydrothermal cracking of heavy oil, characterized by, The steps are as follows: The dehydrated thick oil, the CeO2 supported base catalyst and water are mixed, and the catalytic reaction is carried out under the condition of nitrogen, and the thick oil with reduced viscosity is obtained after the reaction is completed; The mass ratio of the dehydrated thick oil, the CeO2 supported base catalyst and water is (10-100):(0.05-0.5):(10-50); the catalytic reaction conditions are as follows: the reaction temperature is 180-300 DEG C, the reaction time is 6-72h, and the reaction pressure is 0.5-8 MPa; The CeO2 supported base catalyst is prepared by the following method: The metal A salt and the metal B salt are dissolved in water to obtain a metal salt mixed solution; then the precipitant buffer solution and the metal salt mixed solution are added dropwise into hot water, stirred uniformly, and heated to react; after the reaction is completed, the base catalyst is obtained by washing and drying; and the base catalyst is dispersed in a cerium salt solution for impregnation; Then, an oxidizing agent is added, and the precipitate is washed; The solid precipitate is calcined, the calcined product is placed in water for hydration after the calcination is completed, and then dried to obtain a thick oil viscosity reduction CeO2 supported base catalyst; The metal A salt is a nitrate, a chloride, a carbonate or a sulfate of a divalent transition metal or a hydrate thereof; and the metal B salt is a nitrate, a chloride, a carbonate or a sulfate of a trivalent transition metal or a hydrate thereof.

2. A method of reducing the viscosity of heavy oil during heavy oil recovery, characterized by, The steps are as follows: The CeO2 supported base catalyst is dispersed in water, stirred to form a suspension, the high-temperature steam and the suspension are injected into the oil well by using a high-pressure pump, and the well is stewed for 10-20 days to reduce the viscosity of the thick oil in the oil well; The CeO2 supported base catalyst is prepared by the following method: The metal A salt and the metal B salt are dissolved in water to obtain a metal salt mixed solution; then the precipitant buffer solution and the metal salt mixed solution are added dropwise into hot water, stirred uniformly, and heated to react; after the reaction is completed, the base catalyst is obtained by washing and drying; and the base catalyst is dispersed in a cerium salt solution for impregnation; Then, an oxidizing agent is added, and the precipitate is washed; The solid precipitate is calcined, the calcined product is placed in water for hydration after the calcination is completed, and then dried to obtain a thick oil viscosity reduction CeO2 supported base catalyst; The metal A salt is a nitrate, a chloride, a carbonate or a sulfate of a divalent transition metal or a hydrate thereof; and the metal B salt is a nitrate, a chloride, a carbonate or a sulfate of a trivalent transition metal or a hydrate thereof.

3. The method according to claim 1 or 2, characterized in that, The precipitant buffer solution is selected from any one or a mixed solution of NaOH, Na2CO3, ammonia water, potassium hydroxide, potassium carbonate, lithium hydroxide and lithium carbonate.

4. The method according to claim 1 or 2, characterized in that, The heating reaction condition is that the heating is carried out at 90-140 DEG C for 0.5-24h.

5. The method according to claim 1 or 2, characterized in that, The cerium salt is cerium chloride, cerium nitrate, cerium oxalate or a hydrate thereof.

6. The method of claim 1 or 2, wherein, The oxidizing agent is one of hydrogen peroxide, sodium hypochlorite and peroxymonosulfuric acid.

7. The method according to claim 1 or 2, characterized in that, The calcination condition is that the calcination is carried out at 200-500 DEG C for 3-12h.

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