Difunctional composite catalyst for preparing aviation kerosene through direct hydrogenation of carbon dioxide

Abstract

The invention discloses a bifunctional composite catalyst for preparing aviation kerosene through direct hydrogenation of carbon dioxide. The bifunctional composite catalyst is prepared from the H-ZSM-5 zeolite molecular sieve and a composite metal oxide InZnZrOx. Wherein the H-ZSM-5 zeolite molecular sieve is obtained by an inventor through a hydrothermal method, the appearance, the acid strength and the acid amount of the molecular sieve can be accurately controlled through the method, a hierarchical pore structure in a pore channel can be increased, and the selectivity of aviation kerosene components can be well improved; the problems that the diffusion of the heavy carbon aromatic hydrocarbon product in the pore channel of the zeolite molecular sieve is blocked, so that the catalyst is easy to deposit carbon, and the acidic site is covered are solved to a great extent; the composite metal oxide InZnZrOx can be prepared through flexible and efficient coprecipitation, and the problems that in an InZnZrOx / flaky hierarchical pore H-ZSM-5 molecular sieve difunctional composite catalyst, the metal oxide dispersity is low, and the catalytic activity is low are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation kerosene preparation, and in particular relates to a bifunctional composite catalyst used for preparing aviation kerosene by direct hydrogenation of carbon dioxide. Background Art

[0002] With the rapid development of modern society, the demand for air traffic has increased year by year. It is estimated that by 2050, the carbon dioxide emissions from the aviation sector will increase the global carbon dioxide emissions from fossil fuels by 25%. Today, in the face of the global trend of advocating sustainable use of energy and reducing carbon emissions, the aviation industry, as a major carbon emitter, faces tremendous environmental pressure. As the main fuel for aircraft, the production of aviation kerosene is heavily dependent on the refining and processing of crude oil, which is severely limited by the limited fossil resources. In addition, the use of aviation kerosene has also exacerbated the global greenhouse effect, causing sea level rise and frequent extreme weather events, causing serious harm to human society and natural ecosystems. Therefore, it is urgent to develop an environmentally friendly and sustainable aviation kerosene production technology. In this case, the technology of preparing aviation kerosene by direct hydrogenation of carbon dioxide can not only effectively utilize the carbon dioxide emitted by industrial production, but also convert it into aviation kerosene necessary for the aviation industry, realizing the resource recycling of carbon dioxide. Compared with the traditional distillation and cracking production method, this new route shows significant advantages in production efficiency, environmental protection benefits and economic benefits. Therefore, with the continuous breakthroughs in scientific research and technology and the optimization of processes in this field, the direct catalytic hydrogenation of carbon dioxide to produce aviation kerosene is expected to supplement or even gradually replace the traditional fossil energy production route, becoming an important new route to promote the sustainable development of the chemical industry. This will not only help alleviate the problem of climate change, but also be a key step in achieving energy structure transformation and helping the country achieve the strategic goal of "carbon peak and carbon neutrality".

[0003] As we all know, carbon dioxide has a highly stable chemical structure (ΔG = -394.4 kJ / mol), and its conversion requires the cooperation of reducing agents such as hydrogen to achieve the breaking of the CO bond. In recent years, with the continuous development of renewable hydrogen production technology and the continuous progress of clean energy hydrogen production technology, the technology of directly using carbon dioxide to hydrogenate to prepare aviation kerosene has received widespread attention from researchers. At present, the preparation of aviation kerosene by hydrogenation of carbon dioxide is mainly divided into two pathways: the Fischer-Tropsch pathway and the methanol-mediated pathway. The Fischer-Tropsch pathway is to first catalytically convert carbon dioxide into carbon monoxide through the reverse water gas step, and then further catalytically convert carbon monoxide into aviation kerosene component products through the Fischer-Tropsch synthesis step. Among them, because the Fischer-Tropsch pathway follows the Anderson-Schulz-Flory distribution restrictions, it lacks aromatics and cycloalkanes that can improve the energy density of aviation kerosene, and there is an upper limit to the reaction equilibrium. In contrast, the methanol-mediated pathway is to first catalytically convert carbon dioxide into methanol intermediates, and then further dehydrate, polymerize and reform the methanol intermediates into aviation kerosene component products, but because this pathway is not restricted by the Anderson-Schulz-Flory rule, there is no upper limit to the reaction equilibrium. Therefore, the methanol-mediated pathway for the hydrogenation of carbon dioxide to produce aviation kerosene has a higher selectivity for aviation kerosene. However, the current catalyst activity for the preparation of aviation kerosene using the methanol-mediated pathway is generally low. Therefore, the development of high-performance catalysts is still a hot topic in current research.

[0004] In their study of the methanol-mediated pathway for the production of aviation kerosene by hydrogenation of carbon dioxide, researchers found that H-ZSM-5 molecular sieves have good catalytic activity in the production of aviation kerosene by hydrogenation of carbon dioxide. On the one hand, H-ZSM-5 molecular sieves have a unique three-dimensional pore structure and a moderate pore size, and molecules of a specific size can effectively diffuse and separate in their pores. On the other hand, H-ZSM-5 molecular sieves have strong acid sites, which can promote key reactions such as dehydration and polymerization of alcohol molecules on the surface of the molecular sieve to form higher hydrocarbons. However, during the catalytic reaction of carbon dioxide hydrogenation, the morphology, acidity, and pore structure size of H-ZSM-5 molecular sieves affect the distribution and selectivity of the products of aviation kerosene components; the carbon deposition problem caused by the obstruction of the diffusion of heavy hydrocarbons can also cause pore blockage and inactivation of acid sites, affecting the service life of the catalyst.

[0005] At present, it is still a great challenge to achieve high selectivity and high activity of carbon dioxide hydrogenation to produce aviation kerosene by precisely controlling the morphology, acidity, pore structure size and synergistic catalysis of molecular sieves and front-end metal catalysts through appropriate synthesis methods and process means. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a low-cost, green and environmentally friendly bifunctional composite catalyst with good stability and high catalytic activity for direct hydrogenation of carbon dioxide to prepare aviation kerosene.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The preparation method of the sheet-like multi-level pore H-ZSM-5 zeolite molecular sieve is prepared by the hydrothermal method according to the following operations:

[0009] (1) Dissolve the soft template agent polyethylene glycol in deionized water, add aluminum source and stir;

[0010] (2) slowly adding the silicon source dropwise to the solution obtained in step (1) and continuing stirring;

[0011] (3) slowly adding the organic structure directing agent dropwise to the solution obtained in step (2) and continuing stirring;

[0012] (4) adding an inhibitor to the solution obtained in step (3) and continuing stirring to obtain a precursor solution;

[0013] (5) transferring the precursor solution obtained in step (4) to a hydrothermal reactor for hydrothermal crystallization;

[0014] (6) The crystallized product obtained in step (5) is cooled to room temperature, washed with deionized water for several times, centrifuged to neutrality, and then dried and calcined to obtain a modified sheet-like multi-level porous H-ZSM-5.

[0015] The soft template agent is at least one of hexadecyltrimethylammonium bromide (CTAB), triblock copolymer (P123), polyethylene glycol, and sucrose; the aluminum source is at least one of sodium aluminate, aluminum isopropoxide, sodium aluminum sulfate, aluminum nitrate, and pseudo-boehmite; the inhibitor is at least one of lysine, urea, methanol, ethanol, and glucose; the silicon source is at least one of fumed silica, white carbon black, tetraethyl orthosilicate, and silica sol; the organic structure directing agent is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the stirring time of steps (1) to (3) is 0.5 to 6 hours respectively, and the stirring time of step (4) is 6 to 18 hours; the hydrothermal crystallization temperature of step (5) is 90 to 180° C., and the crystallization time is 1 to 4 days; in step (6): drying is performed at 80 to 120° C., the drying time is 6 to 18 hours, and calcination is performed at 350 to 650° C., and the calcination time is 3 to 12 hours.

[0016] The H-ZSM-5 zeolite molecular sieve obtained by the above preparation method.

[0017] The molar ratio of the components of the above-mentioned H-ZSM-5 zeolite molecular sieve is SiO2 / Al2O3 / organic structure directing agent / soft template agent / inhibitor / H2O=(25-500):1:(5-35):(0.1-10):(5-35):(1000-2000).

[0018] The bifunctional composite catalyst for direct hydrogenation of carbon dioxide to prepare aviation kerosene is made of the above-mentioned H-ZSM-5 zeolite molecular sieve and the composite metal oxide InZnZrOx, wherein x is the amount of oxygen, which varies with the addition amount of In, Zn, and Zr, and varies due to the different oxygen proportions in In2O3, ZnO, and ZrO2.

[0019] The composite metal oxide InZnZrOx and H-ZSM-5 zeolite molecular sieve are mechanically mixed and tableted according to a mass ratio of (0.25-4):1, and then sieved to 20-40, 40-60, 80-100 or 100-120 mesh particles for preparation.

[0020] The composite metal oxide InZnZrOx consists of In2O3, ZnO and ZrO2, wherein the mass percentage of In2O3 and ZnO in the composite metal oxide is 5.0-15.0wt.%, and the balance is ZrO2.

[0021] The composite metal oxide InZnZrOx was prepared as follows

[0022] (1) Dissolving the corresponding nitrates of In2O3, ZnO and ZrO2 in deionized water and stirring until completely dissolved to obtain a precursor solution;

[0023] (2) preparing a corresponding amount of alkaline carbonate according to the amount of the required composite metal oxide, and dissolving the alkaline carbonate in deionized water to obtain an alkaline carbonate solution;

[0024] (3) slowly adding the precursor solution obtained in step (1) dropwise to the alkaline carbonate solution obtained in step (2) until the reaction is complete, and continuing stirring;

[0025] (4) The mixed solution obtained in step (3) is cooled, filtered, washed, dried and calcined in sequence to obtain the composite metal oxide InZnZrOx.

[0026] In step (1), the mass ratio of In2O3, ZnO and ZrO2 is 1:(1-10):(1-10); in step (2), the alkaline carbonate is (NH3)2CO3, and the concentration of the alkaline carbonate solution is 0.1-0.8 mol / L; in step (3), the alkaline carbonate solution is at 40-80°C, and the reaction is completed by adding dropwise until the pH reaches 6-10, and stirring is continued for 0.5-4h; in step (4), the drying is carried out at 90-110°C, and the drying time is 5-16h; and the calcination is carried out at 350-550°C, and the calcination time is 2-8h.

[0027] The above-mentioned bifunctional composite catalyst is used for direct hydrogenation of carbon dioxide to produce aviation kerosene.

[0028] In view of the problems existing in the preparation of aviation kerosene, the inventors have developed a bifunctional composite catalyst for the direct hydrogenation of carbon dioxide to prepare aviation kerosene, which is made of the above-mentioned H-ZSM-5 zeolite molecular sieve and the composite metal oxide InZnZrOx. Among them, the H-ZSM-5 zeolite molecular sieve is obtained by the inventor using a hydrothermal method, which can accurately control the appearance, acid strength and acid amount of the molecular sieve and increase the multi-level pore structure in the pores, which can well improve the selectivity of aviation kerosene components and greatly improve the problems of easy carbon deposition and acid site coverage of the catalyst caused by the diffusion obstruction of heavy carbon aromatic products in the zeolite molecular sieve pores; the composite metal oxide InZnZrOx can be prepared by flexible and efficient coprecipitation, which solves the problems of low dispersion and low catalytic activity of metal oxides in the bifunctional composite catalyst of InZnZrOx / flaky multi-level pore H-ZSM-5 molecular sieve.

[0029] Compared with the prior art, the present invention has the following outstanding features:

[0030] 1. Use a flexible and efficient co-precipitation method to synthesize metal oxide InZnZrOx catalysts with high dispersion and high activity, and use a simple and controllable hydrothermal method to synthesize a flaky multi-level porous ZSM-5 molecular sieve catalyst to combine into a bifunctional composite catalyst.

[0031] 2. InZnZrOx / flaky multi-level pore ZSM-5 molecular sieve bifunctional composite catalyst Due to the multi-level pore structure in the flaky ZSM-5 molecular sieve, it is beneficial for the catalytically generated products to flow and diffuse in the molecular sieve pores in a timely manner, thereby reducing the catalyst deactivation caused by carbon deposition and increasing the service life of the catalyst.

[0032] 3. InZnZrOx / flaky multi-level pore ZSM-5 molecular sieve bifunctional composite catalyst has excellent aviation kerosene component selectivity in the reaction of carbon dioxide hydrogenation to produce aviation kerosene. Under optimized reaction conditions, it can achieve a maximum aviation kerosene selectivity of 81.72% among hydrocarbons. The catalyst also has the advantages of low cost, green environmental protection, good stability and high activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the XRD diagram of the flaky multi-level pore H-ZSM-5 molecular sieve of Example 5 with different urea addition amounts. In the figure: ZSM-5-(1), ZSM-5-(4), ZSM-5-(7), and ZSM-5-(10) correspond to the preparation products with urea addition amounts of 1g, 4g, 7g, and 10g, respectively.

[0034] Figure 2 This is the SEM image of the flaky multi-level pore H-ZSM-5 molecular sieve of Example 5 with different urea addition amounts, in which: a, b, c, d are H-ZSM-5-(1), H-ZSM-5-(4), H-ZSM-5-(7), and H-ZSM-5-(10), respectively.

[0035] Figure 3 This is the XRD diagram of the flaky multi-level pore H-ZSM-5 molecular sieve with different silicon-to-aluminum ratios of Example 6. In the diagram: ZSM-5-(50), ZSM-5-(150), ZSM-5-(250), and ZSM-5-(350) correspond to the preparation products with 0.340g, 0.113g, 0.068, and 0.049g of aluminum isopropoxide added, respectively.

[0036] Figure 4 These are SEM images of the flaky multi-level pore H-ZSM-5 molecular sieves of Example 6 with different silicon-to-aluminum ratios, wherein: a, b, c, and d are H-ZSM-5-(50), H-ZSM-5-(150), H-ZSM-5-(250), and H-ZSM-5-(350), respectively. DETAILED DESCRIPTION

[0037] Example 1

[0038] The first step is to prepare the composite metal oxide InZnZrOx, comprising the following steps:

[0039] According to the configuration ratio of each element, 1.32g of In(NO3)3·4H2O, 1.82g of Zn(NO3)2·6H2O and 17.4g of Zr(NO3)4·5H2O were weighed and dissolved in deionized water and stirred until completely dissolved to obtain a precursor solution. Then 9.2g of (NH3)2CO3 was fully dissolved in deionized water, and slowly added to the above precursor solution while vigorously stirring at 70°C, and the pH was controlled within the range of 8 to 10. Then, the obtained suspension was stirred for 2h at 70°C. After cooling to room temperature, filtering, and washing with deionized water, it was dried in an oven at 105°C for 8h, and then calcined in a muffle furnace at a heating rate of 2°C / min from room temperature to 500°C for 3h to obtain a composite metal oxide catalyst InZnZrOx.

[0040] The second step is to prepare a sheet-like multi-level pore H-ZSM-5 zeolite molecular sieve, which includes the following steps:

[0041] After 4.67g of PEG-2000 is fully dissolved in a beaker filled with deionized water, 0.477g of aluminum isopropoxide is added and stirred at room temperature for 1h. Then, 24.30g of tetraethyl orthosilicate is slowly added dropwise and stirring is continued for 2h. Then, 18.98g of tetrapropylammonium hydroxide is slowly added dropwise and stirring is continued for 2h, and then 5.60g of urea is added and stirring is continued for 12h to obtain a precursor solution. The obtained precursor solution is transferred to a hydrothermal reactor and hydrothermally crystallized at 160-180℃ for 1-3d. After cooling to room temperature, washing with deionized water, and centrifuging to neutrality, it is dried at 105℃ for 12h, and then calcined in a muffle furnace at 550℃ for 6h at a heating rate of 2℃ / min to obtain an H-ZSM-5 zeolite molecular sieve with a lamellar multi-level pore structure.

[0042] In the third step, the composite metal oxide InZnZrOx prepared in the first step and the flaky multi-level porous H-ZSM-5 zeolite molecular sieve prepared in the second step are mixed evenly in a mass ratio of 1:1, pressed into tablets, and sieved into particles to prepare an InZnZrOx / flaky multi-level porous H-ZSM-5 bifunctional composite catalyst with aviation kerosene catalytic activity.

[0043] In the fourth step, the InZnZrOx / lamellar multi-level porous H-ZSM-5 bifunctional composite catalyst prepared above is placed in the constant temperature zone of a fixed bed reactor to evaluate the catalytic reaction of carbon dioxide hydrogenation to produce aviation kerosene.

[0044] Activation conditions: at a space velocity of 3600 mL (h·g cat) in an argon atmosphere, the temperature was raised from room temperature to 320°C at a rate of 10°C / min, and the activation time was 2h. After the activation, the activation gas argon was switched to the feed gas and introduced into the fixed bed reactor, and the reaction temperature was adjusted to 320°C and the reaction pressure was adjusted to 3MPa for catalytic evaluation. The gaseous reaction products were directly analyzed and detected online by chromatography, where H2, N2, and CO2 were detected by TCD detector, and hydrocarbons and oxygen-containing compound products were detected by FID detector; the liquid products were analyzed and detected by GC-MS. The results are shown in Table 1.

[0045] Example 2

[0046] The difference from Example 1 is that the weight of In(NO3)3·4H2O in the first step is 1.66 g. The other operations, synthesis conditions and methods, and catalytic evaluation methods are the same as those in Example 1. The catalytic evaluation results are shown in Table 1.

[0047] Example 3.

[0048] The difference from Example 2 is that the soft template in the second step is replaced by 13.33 g of PEG-8000. Other synthesis conditions and methods, and catalytic evaluation methods are the same as those in Example 1. The catalytic evaluation results are shown in Table 1.

[0049] Table 1 Effect of different examples on the catalytic performance of CO2 hydrogenation

[0050]

[0051]

[0052] The results show that in Examples 1 and 2, by changing the proportion of each element in the composite metal oxide, the CO2 hydrogenation conversion rate of the bifunctional composite catalyst decreased from 11.81% to 7.92%, and the product aviation kerosene C 8-16 The selectivity of the composite metal oxide increased from 79.65% to 81.72%. The proportion of each element in the composite metal oxide had a significant effect on the catalytic performance. In Examples 2 and 3, by using different soft templates, the CO2 hydrogenation conversion rate of the bifunctional composite catalyst decreased from 7.92% to 6.93%, and the product aviation kerosene C 8-16 The selectivity increased from 81.72% to 80.82%. Different soft templates have an effect on the activity of the catalyst and the selectivity of the product.

[0053] Example 4

[0054] In the first step, the composite metal oxide InZnZrOx prepared in Example 2 and the sheet-shaped multi-level pore H-ZSM-5 zeolite molecular sieve prepared in Example 1 were weighed in different mass ratios. The ratios were set to 1:3, 1:2, 1:1, 2:1, and 3:1 respectively. After weighing and mixing the powders in different mass ratios, the catalyst particles were obtained by tableting and sieving.

[0055] In the second step, the catalyst is loaded into the constant temperature zone of the fixed bed to evaluate the catalytic reaction of carbon dioxide hydrogenation.

[0056] Activation conditions: At atmospheric pressure, at a space velocity of 3600 mL (h·g cat ) in a pure Ar atmosphere for 2 h. Reaction conditions: The reaction gas was a mixture of H2 / CO2 / N2 = 72 / 24 / 4, with a space velocity of 3600 mL (h·g cat ), the reaction temperature was 320℃, the reaction pressure was 3MPa, and the effects of different mass ratios of composite metal oxide InZnZrOx and lamellar multi-level pore H-ZSM-5 zeolite molecular sieve on the catalytic performance of carbon dioxide hydrogenation to produce aviation kerosene were investigated. The catalytic evaluation results are shown in Table 2.

[0057] Table 2 Effect of InZnZrOx / lamellar multi-level pore H-ZSM-5 molecular sieve mass ratio on CO2 hydrogenation catalytic performance

[0058]

[0059]

[0060] The results show that the different mass ratios of metal oxides and molecular sieves in the bifunctional catalyst have a significant effect on the catalytic performance of CO2 hydrogenation. When the mass ratio is 1:1, the CO2 hydrogenation conversion rate of the catalyst is similar to that of the product aviation kerosene C. 8-16 The selectivity is optimal.

[0061] Example 5

[0062] The first step is to prepare the composite metal oxide InZnZrOx, comprising the following steps:

[0063] According to the configuration ratio of each element, 0.83g of In(NO3)3·4H2O, 0.91g of Zn(NO3)2·6H2O and 8.7g of Zr(NO3)4·5H2O were weighed and fully dissolved in deionized water to obtain a precursor solution. Then, 4.6g of (NH3)2CO3 was fully dissolved in deionized water and slowly added dropwise to the above solution at 70°C while vigorously stirring, and the pH was controlled within the range of 8 to 10.

[0064] Then, the obtained suspension was stirred for 2 h at 70 °C, cooled to room temperature, filtered, washed with deionized water, dried at 105 °C for 10 h, and then calcined at 500 °C in a muffle furnace at 2 °C / min for 3 h to obtain a composite metal oxide catalyst InZnZrOx.

[0065] The second step is to prepare the flaky multi-level pore H-ZSM-5 zeolite molecular sieve with different urea addition amounts, including the following steps:

[0066] After fully dissolving 3.33g of PEG-2000 in 4 beakers filled with deionized water, add 0.34g of aluminum isopropoxide to each of the 4 beakers and stir at room temperature for 1h. Then, slowly drop 17.36g of tetraethyl orthosilicate into each of the 4 beakers and continue stirring for 2h. Then, slowly drop 13.56g of tetrapropylammonium hydroxide into each of the 4 beakers and continue stirring for 2h. Finally, add 1g, 4g, 7g and 10g of urea to each of the 4 beakers and continue stirring for 14h.

[0067] Next, the obtained precursor solutions were transferred to four hydrothermal reactors respectively and hydrothermally crystallized at 160-180°C for 1-3 days. After being cooled to room temperature, washed with deionized water, and centrifuged to neutrality, they were dried at 105°C for 12 hours and then transferred to a muffle furnace and calcined at a heating rate of 2°C / min from room temperature to 550°C for 6 hours to obtain H-ZSM-5(1), H-ZSM-5(4), H-ZSM-5(7) and H-ZSM-5(10) zeolite molecular sieves with lamellar multi-level pore structures and different urea addition amounts.

[0068] Figure 1 2 is the XRD diagram of the product obtained in Example 5. The flaky multi-level porous H-ZSM-5 products with different urea addition amounts all have characteristic peaks of typical MFI zeolite molecular sieves. Figure 2 is a SEM picture of the product obtained in Example 5, and the product all exhibits a flaky hexagonal structure.

[0069] In the third step, the composite metal oxide InZnZrOx prepared in the first step and the flaky multi-level pore H-ZSM-5 (1), H-ZSM-5 (4), H-ZSM-5 (7) and H-ZSM-5 (10) zeolite molecular sieves with different urea addition amounts prepared in the second step are mixed uniformly in a mass ratio of 1:1, pressed into tablets, and sieved into particles to prepare a bifunctional composite catalyst with aviation kerosene catalytic activity.

[0070] The fourth step is to place the bifunctional composite catalyst prepared above in the constant temperature zone of a fixed bed reactor to evaluate the catalytic reaction of carbon dioxide hydrogenation to aviation kerosene. Activation conditions: at a space velocity of 3600 mL (h·g cat) in an argon atmosphere, the temperature was raised from room temperature to 320°C at a rate of 9°C / min, and the activation time was 2h. After the activation, the activation gas argon was switched to the feed gas and introduced into the fixed bed reactor, and the reaction temperature was adjusted to 320°C and the reaction pressure was adjusted to 3MPa for catalytic activity evaluation. The effect of the flaky multi-level porous H-ZSM-5 prepared with different urea addition amounts on the catalytic performance of carbon dioxide hydrogenation to produce aviation kerosene was investigated, and the catalytic evaluation results are shown in Table 3.

[0071] Table 3 Effect of urea addition amount of flaky multi-level pore H-ZSM-5 molecular sieve on the catalytic performance of CO2 hydrogenation

[0072]

[0073] The results show that the amount of urea added during the synthesis of the flake-like multi-level pore H-ZSM-5 molecular sieve has a significant effect on the catalytic performance of CO2 hydrogenation. When the amount of urea added during the synthesis of the flake-like multi-level pore H-ZSM-5 molecular sieve is 4 g, the CO2 hydrogenation conversion rate of the catalyst is similar to that of the product aviation kerosene C. 8-16 The selectivity is optimal.

[0074] Example 6

[0075] The difference from Example 5 is that in the second step, a sheet-like multi-level pore H-ZSM-5 zeolite molecular sieve with different silicon-aluminum ratios is prepared, and the composite metal oxide InZnZrOx used is the same as that in Example 5.

[0076] The preparation of flaky multi-level pore H-ZSM-5 zeolite molecular sieves with different silicon-aluminum ratios of 50, 150, 250 and 350 comprises the following steps:

[0077] In the first step, 3.33 g of PEG-2000 was fully dissolved in 4 beakers filled with deionized water, and then 0.340 g, 0.113 g, 0.068 g, and 0.049 g of aluminum isopropoxide were added to the 4 beakers, respectively, and stirred at room temperature for 1 hour. Then, 17.36 g of tetraethyl orthosilicate was slowly added dropwise to the 4 beakers, and stirring was continued for 2 hours. Then, 13.56 g of tetrapropylammonium hydroxide was slowly added dropwise to the 4 beakers, and stirring was continued for 2 hours. Finally, 3.33 g of urea was added to the 4 beakers and stirred for 14 hours.

[0078] The obtained precursor solutions were transferred to four hydrothermal reactors respectively and hydrothermally crystallized at 160-180°C for 1-3 days. After being cooled to room temperature, washed with deionized water, and centrifuged to neutrality, they were dried at 105°C for 12 hours, and then transferred to a muffle furnace and calcined at a heating rate of 2°C / min from room temperature to 550°C for 6 hours to obtain flaky multi-level pore H-ZSM-5 (50), H-ZSM-5 (150), H-ZSM-5 (250) and H-ZSM-5 (350) zeolite molecular sieves with different silicon-aluminum ratios. Figure 3 3 is the XRD diagram of the product obtained in Example 6. The flaky multi-level pore H-ZSM-5 products with different silicon-aluminum ratios all have characteristic peaks of typical MFI zeolite molecular sieves. Figure 4 : is the SEM picture of the product obtained in Example 6, and the product all presents a flaky hexagonal structure.

[0079] In the second step, the composite metal oxide InZnZrOx prepared in Example 5 and the flaky multi-level pore H-ZSM-5 (50), H-ZSM-5 (150), H-ZSM-5 (250) and H-ZSM-5 (350) zeolite molecular sieves with different silicon-aluminum ratios of 50, 150, 250 and 350 prepared in the above step are mixed uniformly in a mass ratio of 1:1, pressed into tablets, and sieved into particles to prepare a bifunctional composite catalyst with aviation kerosene catalytic activity.

[0080] In the third step, the bifunctional composite catalyst prepared in the above steps was placed in the constant temperature zone of a fixed bed reactor to evaluate the catalytic reaction of carbon dioxide hydrogenation to aviation kerosene. Activation conditions: at a space velocity of 3600 mL (h·g cat ) in an argon atmosphere, the temperature was raised from room temperature to 320°C at a rate of 10°C / min, and the activation time was 2h. After the activation, the activation gas argon was switched to the feed gas and introduced into the fixed bed reactor, and the reaction temperature was adjusted to 320°C and the reaction pressure was adjusted to 3MPa for catalytic activity evaluation. The effect of the flaky multi-level porous H-ZSM-5 prepared with different silicon-aluminum ratios on the catalytic performance of carbon dioxide hydrogenation to produce aviation kerosene was investigated, and the catalytic evaluation results are shown in Table 4.

[0081] Table 4 Effect of Si / Al ratio of H-ZSM-5 molecular sieve with hierarchical pores on catalytic performance of CO2 hydrogenation

[0082]

[0083]

[0084] The results show that the different Si-Al ratios of the flake-type multi-level pore H-ZSM-5 molecular sieves have a significant effect on the catalytic performance of CO2 hydrogenation. With the increase of Si-Al ratio, the acid content and acid strength of the molecular sieve decrease, and the CO2 hydrogenation conversion rate is significantly related to the product aviation kerosene C. 8-16The selectivity also decreases.

Claims

1. A method for preparing a sheet-like multi-level pore H-ZSM-5 zeolite molecular sieve, characterized in that The hydrothermal method was used to prepare the following: (1) Dissolve the soft template agent polyethylene glycol in deionized water, add aluminum source and stir; (2) slowly adding the silicon source dropwise to the solution obtained in step (1) and continuing stirring; (3) slowly adding the organic structure directing agent dropwise to the solution obtained in step (2) and continuing stirring; (4) adding an inhibitor to the solution obtained in step (3) and continuing stirring to obtain a precursor solution; (5) transferring the precursor solution obtained in step (4) to a hydrothermal reactor for hydrothermal crystallization; (6) The crystallized product obtained in step (5) is cooled to room temperature, washed with deionized water for several times, centrifuged to neutrality, and then dried and calcined to obtain a modified sheet-like multi-level porous H-ZSM-5.

2. The method for preparing the H-ZSM-5 zeolite molecular sieve according to claim 1, characterized in that: The soft template agent is at least one of hexadecyltrimethylammonium bromide, triblock copolymer, polyethylene glycol, and sucrose; the aluminum source is at least one of sodium aluminate, aluminum isopropoxide, sodium aluminum sulfate, aluminum nitrate, and pseudo-boehmite; the inhibitor is at least one of lysine, urea, methanol, ethanol, and glucose; the silicon source is at least one of fumed silica, white carbon black, tetraethyl orthosilicate, and silica sol; the organic structure directing agent is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; the stirring time of steps (1) to (3) is 0.5 to 6 hours respectively, and the stirring time of step (4) is 6 to 18 hours; the hydrothermal crystallization temperature of step (5) is 90 to 180° C., and the crystallization time is 1 to 4 days; in step (6): drying is performed at 80 to 120° C., the drying time is 6 to 18 hours, and calcination is performed at 350 to 650° C., and the calcination time is 3 to 12 hours.

3. The H-ZSM-5 zeolite molecular sieve obtained by the preparation method according to claim 1 or 2.

4. The H-ZSM-5 zeolite molecular sieve according to claim 3, characterized in that The molar ratio of its constituent substances is SiO2 / Al2O3 / organic structure directing agent / soft template agent / inhibitor / H2O=(25-500):1:(5-35):(0.1-10):(5-35):(1000-2000).

5. A bifunctional composite catalyst for direct hydrogenation of carbon dioxide to produce aviation kerosene, characterized in that It is made of the H-ZSM-5 zeolite molecular sieve described in claim 4 and the composite metal oxide InZnZrOx.

6. The bifunctional composite catalyst according to claim 6, characterized in that: The composite metal oxide InZnZrOx and the H-ZSM-5 zeolite molecular sieve are mechanically mixed in a mass ratio of (0.25-4):1, tableted, and then sieved into particles for preparation.

7. The bifunctional composite catalyst according to claim 6, characterized in that: The composite metal oxide InZnZrOx consists of In2O3, ZnO and ZrO2, wherein the mass percentage of In2O3 and ZnO in the composite metal oxide is 5.0-15.0wt.%, and the balance is ZrO2.

8. The bifunctional composite catalyst according to claim 6, characterized in that The composite metal oxide InZnZrOx is prepared by the following operation (1) Dissolving the corresponding nitrates of In2O3, ZnO and ZrO2 in deionized water and stirring until completely dissolved to obtain a precursor solution; (2) preparing a corresponding amount of alkaline carbonate according to the amount of the required composite metal oxide, and dissolving the alkaline carbonate in deionized water to obtain an alkaline carbonate solution; (3) slowly adding the precursor solution obtained in step (1) dropwise to the alkaline carbonate solution obtained in step (2) until the reaction is complete, and continuing stirring; (4) The mixed solution obtained in step (3) is cooled, filtered, washed, dried and calcined in sequence to obtain the composite metal oxide InZnZrOx.

9. The bifunctional composite catalyst according to claim 6, characterized in that: In the step (1), the mass ratio of In2O3, ZnO and ZrO2 is 1:(1-10):(1-10); in the step (2), the alkaline carbonate is (NH3)2CO3, and the concentration of the alkaline carbonate solution is 0.1-0.8 mol / L; in the step (3), the alkaline carbonate solution is at 40-80°C, and the reaction is completed by adding dropwise until the pH reaches 6-10, and stirring is continued for 0.5-4h; in the step (4), the drying is carried out at 90-110°C, and the drying time is 5-16h; and the calcination is carried out at 350-550°C, and the calcination time is 2-8h.

10. The bifunctional composite catalyst according to claims 5 to 10 is used for direct hydrogenation of carbon dioxide to produce aviation kerosene.

Images