A method for co-production of aviation kerosene precursor and carbon nanotubes from waste oil

Abstract

The application discloses a method for co-production of aviation kerosene precursor and carbon nanotubes from waste oil, which comprises the following steps: catalytic pyrolysis: under an inert atmosphere, oil compounds are subjected to catalytic pyrolysis under the action of a catalyst, and products are condensed to obtain non-condensable gas and liquid aviation kerosene precursor; non-condensable gas purification: CO2 and moisture in the non-condensable gas are removed to obtain purified gas; chemical vapor deposition: under the action of a foamed metal catalyst, the purified gas is subjected to chemical vapor deposition to obtain carbon nanotubes. The application realizes preparation of aviation kerosene precursor with hydrocarbon selectivity over 80% through catalytic pyrolysis, and has strong practicability in fuel deoxygenation; through reforming and upgrading of the non-condensable gas, preparation of carbon nanotubes is realized, and the added value of pyrolysis products is greatly improved. The application has a short path and low pollution degree, realizes resource utilization of waste oil, achieves the purpose of environmental protection, and has application value in the fields of energy and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of biomass energy conversion technology, and relates to a method for converting waste oil to co-produce aviation kerosene precursors and carbon nanotubes. Background Technology

[0002] Biomass energy has garnered widespread attention due to its unique renewable and carbon-neutral characteristics. Primarily comprising organic matter including agricultural and forestry crops and their residues, it is currently the only sustainably produced organic carbon source and a renewable energy source that can be converted into liquid fuels, holding broad application value in the future environmental protection and energy sectors. Waste oil is a crucial biomass resource. Current treatment methods, primarily landfilling and incineration, not only harm soil, livestock, and human health but also fail to achieve effective utilization. Therefore, realizing the resource utilization of waste oil is an urgent problem to be solved. Achieving resource utilization of waste oil can both address environmental pollution and transform it into resources for production and daily life, achieving a win-win situation.

[0003] Pyrolysis technology boasts significant advantages such as short pathways, rapid reactions, and the ability to co-produce products. In recent years, it has been developed and applied in the field of waste oil thermal conversion. Under an inert thermal atmosphere, waste oil can be rapidly converted into products such as pyrolysis oil, pyrolysis char, and pyrolysis gas. Pyrolysis oil, in particular, has attracted significant attention due to its fuel value. However, the high oxygen content of the oil obtained from direct pyrolysis makes it difficult to utilize directly. Catalytic pyrolysis deoxygenation is one of the effective ways to directly convert waste oil into usable liquid fuels. Chinese invention patent CN107974266A discloses a method for preparing aviation fuel components through an alcoholysis reaction between waste oil and methanol, under the action of a hydrogenation catalyst. Chinese invention patent CN107573968A utilizes waste oil to remove water and impurities, and then uses a modified catalyst for hydrogenation deoxygenation to prepare high-purity C13-C22 bioalkanes. Patent CN110102279A also reports the application of calcium oxide-modified biochar to catalyze the pyrolysis of oil for deoxygenation to prepare high-quality biofuels.

[0004] Currently, there are many reports on the technology of producing high-quality liquid fuels by pyrolysis of waste oils, but there are no reports on the technology of co-producing functional carbon materials and high-quality oil products using waste oils as raw materials. Summary of the Invention

[0005] The inventors recently discovered that the non-condensable gas produced by the catalytic pyrolysis of oily compounds can be purified and converted into carbon nanotube functional carbon materials through vapor phase chemical deposition, which have good market prospects in the fields of electrical conductivity, thermal conductivity and adsorption.

[0006] The purpose of this invention is to propose a conversion method that can achieve the co-production of aviation kerosene precursors and carbon nanotubes. This method uses the combined application of catalytic pyrolysis and vapor deposition to convert waste oil into hydrocarbon-rich aviation kerosene precursors and non-condensable gases. Then, chemical vapor deposition technology is used to prepare functional carbon nanotubes from the non-condensable gases, effectively improving the added value of the products and the energy utilization efficiency.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for converting waste oils to co-produce aviation kerosene precursors and carbon nanotubes includes catalytic pyrolysis, purification of non-condensable gases, and chemical vapor deposition;

[0009] Catalytic pyrolysis: Under an inert atmosphere, oily compounds undergo catalytic pyrolysis in the presence of a catalyst. The products are then condensed to obtain non-condensable gaseous and liquid aviation kerosene precursors.

[0010] Purification of non-condensable gases: Removing CO2 and moisture from non-condensable gases to obtain purified gas;

[0011] Chemical vapor deposition: Carbon nanotubes are prepared by chemical vapor deposition of purified gas under the action of foam metal catalyst.

[0012] The catalytic pyrolysis described herein is a thermochemical reaction catalyzed by a catalyst under an inert atmosphere and at a pyrolysis temperature.

[0013] The main component of the aforementioned oily compounds is triglycerides.

[0014] The oily compounds mentioned are one or any combination of waste cooking oil, waste animal oil, waste clay oil, expired food oil, soybean oil, sunflower seed oil, and palm oil.

[0015] The inert atmosphere used for the catalytic pyrolysis is one or any combination of nitrogen, argon, helium, neon, krypton, and radon.

[0016] The catalyst used in the catalytic pyrolysis is one or any combination of straw-based biochar, MCM-41 molecular sieve, and SBA molecular sieve.

[0017] The straw-based biochar is one or any combination of wheat straw biochar, rice straw biochar, and corn straw biochar. The straw-based biochar is prepared by the following method: straw is crushed and carbonized at 700℃ for 2 hours under an inert atmosphere; the resulting solid is the straw-based biochar. The straw is wheat straw, rice straw, or corn straw. The inert atmosphere used for preparing the straw-based biochar is one or any combination of nitrogen, argon, helium, neon, krypton, and radon.

[0018] The temperature of the catalytic pyrolysis is 500-700℃, preferably 500-650℃, and more preferably 600℃.

[0019] The products of catalytic pyrolysis are condensed at -30 to 10°C, preferably at -20°C.

[0020] The purification of non-condensable gases involves using chemical reagents to remove CO2 and moisture from the non-condensable gases, thus removing impurities and drying them.

[0021] The chemical reagent is at least one of Ca(OH)2, CaO, NaOH, and KOH.

[0022] Preferably, the non-condensable gas is purified by any two combinations of Ca(OH)2, CaO, NaOH, and KOH.

[0023] The purification of non-condensable gases is carried out at room temperature.

[0024] The purified gas comprises 10-20% hydrogen, 7-25.5% methane, and 40-60% C2-C5 hydrocarbons.

[0025] The chemical vapor deposition process described above uses a foamed metal catalyst to catalyze the purified gas under deposition temperature conditions.

[0026] The active component of the foam metal catalyst is one of nickel, iron and cobalt or any combination thereof.

[0027] Preferably, the foamed metal catalyst is foamed iron, foamed nickel, foamed cobalt, or iron-nickel alloy foam.

[0028] The temperature of the chemical vapor deposition is 750–850°C, preferably 800°C.

[0029] Specifically, the chemical vapor deposition involves the carrier gas and the purified gas entering a vertical pyrolysis furnace simultaneously. Under the action of a foamed metal catalyst, the purified gas comes into contact with the active metal to undergo a chemical vapor deposition reaction. After the reaction is completed, the catalyst is naturally cooled to room temperature, and the carbon nanotube-loaded catalyst is removed. The carbon nanotube-loaded catalyst is then sequentially etched with hydrofluoric acid for 2–3 hours, soaked in hot hydrochloric acid at 80–100°C for 8–10 hours, washed three times with anhydrous ethanol, washed three times with ultrapure water, and dried to obtain carbon nanotubes.

[0030] The carrier gas is one or any combination of nitrogen, argon, helium, neon, krypton, and radon.

[0031] The hydrofluoric acid has a mass fraction of 10%.

[0032] The hot hydrochloric acid is heated to 80-100℃ and has a concentration of 2 mol / L.

[0033] Compared with petroleum-based industrial synthesis routes, the advantages of this invention are:

[0034] 1) This invention uses catalytic pyrolysis of waste oil and vapor phase chemical deposition technology to co-produce aviation kerosene precursors and carbon nanotubes. The pathway is short and the pollution level is low. It realizes both the resource utilization of waste oil and the purpose of environmental protection, taking into account the application value in the fields of energy and environmental protection.

[0035] 2) The method of this invention is based on catalytic pyrolysis and chemical deposition technology, which is convenient and practical. It only requires reaction equipment such as a pyrolysis furnace to realize the technology application, making it easy to promote. Notably, it achieves the preparation of aviation kerosene precursors with a hydrocarbon selectivity of over 80% through pyrolysis catalysis, demonstrating strong practicality in fuel deoxygenation. Furthermore, it achieves the preparation of carbon nanotubes through reforming and upgrading non-condensable gas, significantly increasing the added value of the pyrolysis products. Attached Figure Description

[0036] Figure 1 This is a diagram of a co-production unit for catalytic pyrolysis and chemical vapor deposition.

[0037] Figure 2 This is a distribution diagram of the condensate components after the catalytic pyrolysis of biochar.

[0038] Figure 3 This is a diagram showing the distribution of condensing components and carbon number in aviation kerosene.

[0039] Figure 4 This is a scanning electron microscope (SEM) image of carbon nanotubes. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, further description is provided below with reference to specific embodiments. Those skilled in the art can appropriately improve the process parameters to optimize the invention under the guidance of the invention. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of the present invention.

[0041] Example 1

[0042] like Figure 1As shown, a method for co-producing aviation kerosene precursors and carbon nanotubes from waste oil includes catalytic pyrolysis, non-condensable gas purification, and chemical vapor deposition. A mixture of catalyst and silica sand is packed into a pyrolysis furnace, supported by silica wool to form a catalyst bed. A check valve is opened, and one or any combination of nitrogen, argon, helium, neon, krypton, and radon is introduced. Oily compounds are pumped into the pyrolysis furnace through a sampler. Under an inert atmosphere, the oily compounds undergo catalytic pyrolysis in the presence of the catalyst. The catalytic pyrolysis products are condensed at -20°C to obtain liquid condensable components and non-condensable gases. The condensable components are the aviation kerosene precursors. GC-MS is used to determine the distribution of the condensable components. At room temperature, the non-condensable gases... The condensed components are sequentially purified by passing through a purification device containing lumps or powdered sodium hydroxide and a purification device containing lumps or powdered calcium oxide to remove CO2 and moisture, resulting in purified gas. The composition of the purified gas is determined by GC. The purified gas is then purged with nitrogen and introduced into a vertical pyrolysis furnace. A foamed metal catalyst is formed by supporting the foamed metal catalyst to form a catalyst bed. Under the action of the foamed metal catalyst, the purified gas undergoes a chemical vapor deposition reaction. The remaining gas is collected in a gas collection bag to prevent environmental pollution. After the reaction device cools to room temperature, the foamed metal catalyst loaded with carbon nanotubes is removed. It is first etched with hydrofluoric acid for 2 hours, then soaked in hot hydrochloric acid at 80°C for 8 hours, washed three times with anhydrous ethanol, washed three times with ultrapure water, and dried to obtain carbon nanotubes.

[0043] GC-MS detection conditions: Agilent 7890B-5977B, HP-5MS column, initial temperature 40℃, increased to 330℃ at 10℃ / min, and held for 5 min.

[0044] GC detection conditions: Gas chromatograph GC-2014C, MS-13X and HP-AL / S column, 50℃ for 3 minutes, then increased to 130℃ at 10℃ / min and held for 3 minutes.

[0045] Example 2

[0046] Based on the catalytic pyrolysis apparatus and non-condensable gas purification apparatus of Example 1, the effects of different catalysts on the preparation of deoxygenated fuel from waste soybean oil by catalytic pyrolysis were tested.

[0047] Preparation of straw-based biochar: Straw is crushed to 0.1-0.2 mm and carbonized at 700℃ for 2 hours under a nitrogen atmosphere. The resulting solid is straw-based biochar.

[0048] Both SBA-15 and MCM-41 molecular sieves are commercially available catalysts.

[0049] Test conditions: 2g of catalyst was mixed with 5g of quartz sand to form a catalyst bed; the temperature was 600℃; the nitrogen flow rate was 200mL / min; and the WHSV of the oil was 3h. -1After the catalytic pyrolysis products are condensed at -20℃, the non-condensable components are then purified by passing sodium hydroxide and calcium oxide sequentially to remove CO2 and moisture, yielding purified gas.

[0050] Table 1 shows that the yield of the condensable component exceeded 55% under different catalysts, while the yield of the non-condensable component exceeded 30%. Table 2 shows that after purification, the non-condensable gases from waste soybean oil under different catalysts mainly consisted of H2, CH4, CO, and C2-C5 low-carbon hydrocarbons. The high content of C2-C5 low-carbon gases indicates that the non-condensable gases contain abundant carbon sources and can be used as raw materials for further reforming and upgrading.

[0051] Table 1. Effects of catalysts on the condensate components of waste soybean oil from catalytic pyrolysis

[0052] Wheat straw-based biochar 55.89 42.26 Corn straw-based biochar 59.42 37.26 Rice straw-based biochar 58.16 35.69 MCM-41 molecular sieve 63.26 31.02 SBA-15 molecular sieve 65.20 32.64

[0053] Table 2. Components of non-condensable gases formed after catalytic cracking and purification of waste oils

[0054] Wheat straw-based biochar 14.03 7.82 20.37 57.78 Corn straw-based biochar 12.25 8.49 23.65 55.61 Rice straw-based biochar 11.11 10.62 22.56 55.71 MCM-41 molecular sieve 19.14 12.02 18.74 50.10 SBA-15 molecular sieve 13.87 25.12 20.62 40.39

[0055] Example 3

[0056] To test the potential of producing aviation kerosene from the condensed components obtained by catalytic pyrolysis.

[0057] Based on the catalytic pyrolysis apparatus of Example 1, different oil compounds whose main component is triglycerides were selected as raw materials, and wheat straw-based biochar (same as in Example 2) was used as the catalyst. Test conditions: 2g of catalyst was mixed with 5g of quartz sand to form the catalytic bed; the temperature was 600℃; the nitrogen flow rate was 200mL / min; and the oil WHSV was 3h. -1 The condensate components after catalytic pyrolysis of five oily compounds were analyzed according to the GC-MS detection conditions of Example 1.

[0058] Taking cooking oil as an example, such as Figure 3 As shown, the selectivity of acid-ester compounds in the condensate obtained from the catalytic pyrolysis of wheat straw-based biochar was 2.56%, while the selectivity of hydrocarbons reached 87.83%, indicating that the condensate obtained from catalytic pyrolysis has a good deoxygenation effect. Further comparison of the hydrocarbons in the condensate with those in aviation kerosene (GB 6537-2018) shows that... Figure 4 As shown, the condensate and aviation kerosene are basically consistent in terms of carbon number. The condensate has more C8 and below and more C13, while aviation kerosene has more C8-C13. However, the difference in C8-C13 content between the two is no more than 9%, indicating that the condensate obtained from the catalytic pyrolysis of catering oil can be used as a precursor for aviation kerosene.

[0059] As shown in Table 3, similar to the condensate obtained by catalytic pyrolysis of catering oil, the yields of condensate obtained by catalytic pyrolysis of palm oil, waste clay oil, expired edible oil, and sunflower seed oil all exceeded 63%, the hydrocarbon selectivity all exceeded 81%, and the C8-C13 selectivity all exceeded 69%. This indicates that the condensate obtained by catalytic pyrolysis of different oil compounds under the action of catalysts all have the potential to be used as precursors for aviation kerosene.

[0060] Table 3. Effects of different oily compounds on condensed components

[0061] Catering oil 70.06 87.83 72.36 Palm oil 63.52 87.66 73.02 Waste white clay oil 64.33 83.95 69.56 Expired cooking oil 68.26 86.38 71.23 Sunflower seed oil 67.84 81.26 75.95

[0062] Example 4

[0063] The effects of different carrier gases (i.e., different inert gas atmospheres) on the properties of the condensate components prepared by catalytic pyrolysis were tested. Taking catering oil as an example, wheat straw-based biochar (same as in Example 2) was used as the catalyst. The test conditions were the same as in Example 3, except that the type of carrier gas was adjusted, and the carrier gas flow rate was 200 mL / min.

[0064] The results are shown in Table 4. It can be seen that the yield of the condensed components all exceeded 64%, and the hydrocarbon selectivity exceeded 81%, indicating that the condensed components prepared under different inert gas atmospheres all have good deoxygenation effects.

[0065] Table 4. Effect of carrier gas on condensate composition

[0066] <![CDATA[N2]]> 70.06 87.83 Ar 64.34 86.72 He 66.82 82.69 Ne 65.44 81.24

[0067] Example 5

[0068] The effect of different catalytic pyrolysis temperatures on the properties of the condensed components was tested. Taking catering oil as an example, wheat straw-based biochar was used as the catalyst, and the test conditions were the same as in Example 3.

[0069] The results are shown in Table 5. The yields of the condensed components varied slightly at different catalytic pyrolysis temperatures, but all yields exceeded 50%, indicating that the suitable catalytic pyrolysis temperature is 500–700℃. When the catalytic pyrolysis temperature is 500–650℃, the yields all exceed 60%, and the particularly preferred catalytic pyrolysis temperature is 600℃.

[0070] Table 5. Effect of catalytic pyrolysis temperature on condensed components

[0071]

[0072]

[0073] Example 6

[0074] Commercially available nickel foam (99.8% purity, 1.7 g / cm³ bulk density) was used. 3 Using a vertical pyrolysis furnace as the reaction apparatus, nickel foam was placed in the furnace and activated at 800°C for 1 hour, after which the temperature was kept constant. The non-condensable components obtained from the catalytic pyrolysis of catering oil in Example 3 were sequentially passed through conical flasks containing NaOH solid and CaO solid to obtain purified gas. The purified gas was tested according to the GC detection conditions in Example 1. The main components and contents (mass fraction) of the purified gas were: H2 11.98%, CO 16.74%, CH4 17.93%, and C2-C5 low-carbon hydrocarbons 53.35%. The purified gas was produced by nitrogen (flowing...) Purified gas (purging gas at a flow rate of 200 mL / min) was introduced into the pyrolysis furnace. Under the catalytic action of nickel foam, the purified gas underwent chemical vapor deposition at 800°C for 2 hours. Nitrogen gas was then continuously introduced at a flow rate of 200 mL / min. After natural cooling to room temperature, the nickel foam loaded with carbon nanotubes was removed. The nickel foam loaded with carbon nanotubes was then successively etched with hydrofluoric acid (10% by mass) for 2 hours and soaked in hot hydrochloric acid (80°C, 2 mol / L) for 8 hours to remove any impurities and nickel foam that may have remained during the chemical vapor deposition process. It was then washed three times with anhydrous ethanol and three times with ultrapure water, and dried. The resulting solid was the carbon nanotube. The average diameter and thickness of the carbon nanotubes prepared in this example was 31.86 nm.

[0075] Example 7

[0076] The effects of different catalysts on the properties of carbon nanotubes were tested.

[0077] The test conditions were the same as in Example 6, except that the catalyst was adjusted to be iron foam (purity 99.8%, bulk density 0.8 g / m³). 3 Cobalt foam (purity 99.9%, specific surface area 200g / m²) 2 Its bulk density is 0.5 g / m³ 3 Iron-nickel alloy foam (iron to nickel mass ratio 1:1, purity 99.9%, bulk density 0.5-0.8 g / m³) 3 The results are shown in Table 6. The catalyst has a slight impact on the carbon nanotube yield and the thickness of the monolayer. Considering both the carbon nanotubes and the average diameter thickness, nickel foam is the preferred catalyst for vapor deposition.

[0078] Table 6. Effect of active metals in catalysts on carbon nanotubes

[0079] Foamed iron 1.92 33.23 Nickel foam 2.05 31.86 Cobalt foam 1.82 35.69 Iron-nickel alloy foam 2.53 36.26

[0080] Example 8

[0081] The effect of different deposition temperatures on the properties of carbon nanotubes was tested.

[0082] The test conditions were the same as in Example 6. This example only adjusted the deposition temperature. The results are shown in Table 7. It shows that the carbon nanotubes prepared at different deposition temperatures are slightly different. Considering both the yield and the average diameter of the carbon nanotubes, the preferred temperature is 800℃.

[0083] Table 7. Effect of deposition temperature on carbon nanotubes

[0084] 750 1.82 32.09 800 2.05 31.86 850 1.98 33.47

Claims

1. A method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds, characterized in that: include: Catalytic pyrolysis: Under an inert atmosphere, oily compounds undergo catalytic pyrolysis in the presence of a catalyst. The products are condensed to obtain non-condensable gaseous and liquid aviation kerosene precursors. The oily compounds are one or any combination of waste catering oil, waste animal oil, waste clay oil, expired food oil, soybean oil, sunflower seed oil, and palm oil. The catalyst used in the catalytic pyrolysis is one or any combination of MCM-41 molecular sieve and SBA molecular sieve. The temperature of the catalytic pyrolysis is 500–650°C. Purification of non-condensable gases: The non-condensable components are sequentially purified by sodium hydroxide and calcium oxide to remove CO2 and moisture, resulting in purified gas; the purified gas contains 10-20% hydrogen, 7-25.5% methane, and 40-60% C2-C5 hydrocarbons; Chemical vapor deposition: Carrier gas and purified gas are simultaneously introduced into a vertical pyrolysis furnace. Under the action of foamed metal catalyst, the purified gas comes into contact with the active metal and undergoes a chemical vapor deposition reaction. After the reaction is completed, the catalyst is naturally cooled to room temperature and the carbon nanotube-loaded catalyst is removed. The carbon nanotube-loaded catalyst is then successively etched with hydrofluoric acid for 2-3 h, soaked in hot hydrochloric acid at 80-100℃ for 8-10 h, washed three times with anhydrous ethanol and three times with ultrapure water, and dried to obtain carbon nanotubes.

2. The method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds according to claim 1, characterized in that: The inert atmosphere used for the catalytic pyrolysis is one or any combination of nitrogen, argon, helium, neon, krypton, and radon.

3. The method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds according to claim 1, characterized in that: The temperature of the catalytic pyrolysis is 600℃.

4. The method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds according to claim 1, characterized in that: The products of catalytic pyrolysis are condensed at -30 to 10°C.

5. The method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds according to claim 1, characterized in that: The products of catalytic pyrolysis are condensed at -20°C.

6. The method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds according to claim 1, characterized in that: The active component of the foam metal catalyst is one of nickel, iron and cobalt or any combination thereof.

7. The method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds according to claim 1, characterized in that: The temperature for chemical vapor deposition is 750–850°C.

8. The method for co-producing aviation kerosene precursors and carbon nanotubes by converting oily compounds according to claim 7, characterized in that: The chemical vapor deposition temperature is 800℃.

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