Preparation method of mesoporous confinement Ru-Ce / SBA-15 catalyst and application of mesoporous confinement Ru-Ce / SBA-15 catalyst in preparation of hydrocarbon liquid fuel

Abstract

The invention provides a preparation method of a mesoporous confinement Ru-Ce / SBA-15 catalyst and application of the mesoporous confinement Ru-Ce / SBA-15 catalyst in preparation of hydrocarbon liquid fuel. The preparation method comprises the following steps: preparing a Ru precursor solution by taking Ce-doped mesoporous SBA-15 as a carrier and taking a certain amount of ethanol as a solvent, and preparing the Ru-Ce / SBA-15 multifunctional catalyst with adjustable acid content and active metal Ru limited range supported in SBA-15 mesopores by combining impregnation and calcination operations and accurately regulating and controlling a metal loading position. The catalyst can be used for preparing hydrocarbon liquid fuel by carrying out catalytic hydrogenolysis on carbon-containing wastes (such as waste plastics and biomass) under mild conditions, and various indexes are obviously superior to those of a traditional commercial noble metal catalyst. The Ru-Ce / SBA-15 multifunctional catalyst provided by the invention is simple in preparation process, low in cost and high in stability, and a new way is provided for designing a next-generation catalyst for preparing hydrocarbon liquid fuel through catalytic hydrogenolysis of carbon-containing waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic conversion of carbon-containing waste to hydrocarbon liquid fuels, and particularly relates to a preparation method of a mesoporous-confined Ru-Ce / SBA-15 catalyst, and also relates to the application of the above mesoporous-confined Ru-Ce / SBA-15 catalyst in the preparation of hydrocarbon liquid fuels. Background Art

[0002] Carbon-containing raw materials (such as polyolefin plastics, biomass, etc.) have good chemical stability due to their strong C-C bonds. This stability has led to a large accumulation of carbon-containing waste, posing a major challenge to the ecological environment. Therefore, developing efficient chemical recycling methods, especially methods for converting carbon-containing waste into liquid fuels, has become a key strategy for resource recovery and environmental remediation. Currently, chemical recycling methods for carbon-containing waste include catalytic pyrolysis, catalytic hydrogenolysis, photocatalysis, electrocatalysis, etc. Among them, catalytic hydrogenolysis has received extensive attention from researchers due to its relatively low reaction temperature and high conversion rate.

[0003] In recent years, researchers have successfully hydrogenolyzed carbon-containing waste such as polyolefins into valuable liquid fuels, lubricants, waxes and other products using catalysts such as Pt / SrTiO 3 , Ru / C, Ru / CeO 2 However, in such catalysts, a large number of metal active sites are irregularly exposed to the open reaction environment, allowing random adsorption of polymer chains on the active sites. The multiple irregular contacts between polymer chains and different catalytic sites result in a wide distribution of hydrogenolysis products (C 7 -C 40 ), thus reducing the selectivity and yield of liquid products. In order to improve the catalyst activity or narrow the product distribution range, a relatively high noble metal loading is often required, which in turn easily leads to excessive production of gaseous products. Therefore, developing new catalysts with specific structures to improve the selectivity of liquid products and thus efficiently produce hydrocarbon liquid fuels with a narrow carbon number distribution remains a huge challenge.

[0004] Given that the adsorption of polymer chains on concave surfaces is more stable than on flat and convex surfaces, by introducing a mesoporous structure to spatially confine the polymer molecular chains, the contact between polymer chains and specific catalytic active sites can be strengthened, enabling precise cleavage of C-C bonds, thereby greatly improving the selectivity of hydrogenolysis products of carbon-containing waste. However, although smaller pore sizes can result in narrower and lower-carbon-number product distributions, they also weaken the diffusivity of reactants, thereby sacrificing some reaction activity.

[0005] In addition to the active metals and the pore structure that provides spatial confinement, the presence of acidic sites in the catalyst can assist the cleavage of CC bonds in carbonaceous waste to a certain extent, promote the hydrogenolysis reaction of carbonaceous waste and improve the product distribution, which provides another way to improve the activity of mesoporous catalysts in the hydrogenolysis reaction of carbonaceous waste.

[0006] Based on this, a method for preparing a multifunctional catalyst with mesopore confinement, adjustable acid content and precise loading of active precious metals inside the mesopores is provided, so that the prepared catalyst can catalyze the hydrogenolysis of carbon-containing waste under mild conditions to efficiently produce hydrocarbon fuels, and improve the selectivity of short-chain hydrocarbon liquid fuels in the product. This has important guiding significance for the production of high-value chemicals in a safe, efficient and low-cost catalytic system, and is also a technical problem that needs to be solved urgently. Summary of the invention

[0007] One of the purposes of the present invention is to provide a method for preparing a mesoporous confined Ru-Ce / SBA-15 catalyst with adjustable acid content and active noble metals accurately loaded inside the mesopores.

[0008] The second object of the present invention is to provide a mesoporous confined Ru-Ce / SBA-15 catalyst with adjustable acid content and active precious metals accurately loaded inside the mesopores.

[0009] The third object of the present invention is to provide a mesoporous confined Ru-Ce / SBA-15 catalyst for use in the preparation of hydrocarbon liquid fuels.

[0010] The technical solution adopted by the present invention to achieve one of the purposes is: to provide a method for preparing a mesoporous confined Ru-Ce / SBA-15 catalyst, comprising the following steps: S1, placing the mesoporous SBA-15 carrier in the Ce precursor solution, fully mixing, and then drying and first calcining to obtain a Ce-SBA-15 carrier with acidic sites; S2, using ethanol as solvent to prepare a Ru precursor solution; fully mixing the Ru precursor solution with the Ce-SBA-15 carrier to obtain a first product; in the first product, the volume mass ratio of ethanol to the Ce-SBA-15 carrier is 1.25-5 mL / g; performing a second calcination treatment on the first product to obtain a second product; S3. The second product is placed in a reducing atmosphere and subjected to reduction treatment to obtain a mesoporous confined Ru-Ce / SBA-15 catalyst.

[0011] The overall idea and inventive principle of the present invention are as follows: In order to achieve a low noble metal loading, convert carbon-containing waste into liquid fuel with a high yield under relatively mild reaction conditions, and improve the selectivity of short-chain alkanes, the present invention provides a preparation method of a mesoporous-confined Ru-Ce / SBA-15 catalyst, which mainly involves the following improvements: First, in terms of the selection of the carrier, the present invention uses an SBA-15 carrier with a mesoporous structure, introduces a pore structure, induces polyolefin chains into the pores for reaction, thereby restricting the irregular contact between polyolefin chains and active sites. At the same time, since short-chain alkanes have weak adsorption in the pores, they can avoid excessive cracking reactions after diffusing out of the pores, so that while improving the conversion rate and liquid yield, the generation of gas can be reduced, and thus the selectivity of short-chain alkanes can be improved.

[0012] Second, considering that while the SBA-15 carrier with a mesoporous structure plays a confinement role using a smaller pore diameter, the smaller pore diameter will also hinder the diffusion of reactants and the escape of products, thereby reducing the activity of the catalyst and easily causing excessive cracking. Therefore, this application also adopts a Ce doping step to introduce acidic sites (actually CeO 2 species) on the SBA-15 carrier with a mesoporous structure. The acidic sites can not only promote the adsorption of intermediates on the Ru sites to a certain extent, thereby promoting the hydrogenolysis of polyolefins on Ru, but also alkyl elimination reactions can occur on the acidic sites themselves to produce short-chain olefin products, thereby improving the activity of the catalyst.

[0013] Finally, considering the problem of externally exposed noble metal active sites still existing when using mesoporous materials as carriers to prepare catalysts, in order to maximize the spatial confinement effect of the mesopores, it is crucial to confine the active sites in the pores. Through research in this application, it is found that during the loading process of metal Ru, the type and amount of the precursor solvent determine the impregnation effect: among them, the viscosity and reducibility of the solvent will affect the dispersion effect of the active sites, and the amount of the solvent needs to match the pore volume of the carrier to ensure that the precursor solution is absorbed into the pores as much as possible during the impregnation process, reduce external impregnation, realize the loading of Ru active sites in the pores, and thus effectively play the spatial confinement effect and improve the product distribution. The present invention uses ethanol as the solvent for preparing the Ru precursor solution and controls the volume-mass ratio of ethanol to the Ce-SBA-15 carrier to be 1.25 - 5 mL / g, where the amount of ethanol is equivalent to the pore volume of the carrier (about 1 - 5 times the pore volume of the carrier). During the mixing process of the Ru precursor solution and the Ce-SBA-15 carrier, the Ru precursor solution is fully absorbed by the carrier and diffuses in the pores. During the subsequent calcination process, as the ethanol evaporates, metal Ru slowly precipitates during drying. In addition, the reducibility of ethanol also promotes the reduction of Ru 3+ to Ru 0The reduction reduced the aggregation of Ru particles, thereby achieving the precise impregnation and loading of the active metal Ru.

[0014] In summary, the invention regulates the type and dosage of the precursor solvent during the impregnation process, enabling Ru nanoparticles to be precisely loaded into the pores of the mesoporous SBA-15 support. Meanwhile, the introduction of Ce doping introduces additional acidic sites. The catalyst prepared by the present invention utilizes the mesoporous confinement effect to promote the adsorption stability between the catalyst and the polymer chains, thereby improving the catalytic efficiency and the selectivity of hydrocarbon liquid fuel products. By introducing additional adjustable acidic sites, the catalyst activity and the selectivity for short-chain hydrocarbon liquid fuel products are further improved. Furthermore, under relatively mild conditions, carbon-containing waste (such as low-density polyethylene, etc.) can be highly selectively and efficiently converted into liquid fuels, realizing the resource utilization and high-value utilization of carbon-containing waste.

[0015] Furthermore, in step S1, the average pore diameter of the mesoporous SBA-15 support is 8-9 nm. The key factor for exerting the spatial confinement effect is the size of the support pore diameter. An overly large pore diameter cannot effectively exert the confinement effect, while an overly small pore diameter will hinder the diffusion of reactants and the escape of products, thereby reducing the activity and causing excessive cracking. When the mesoporous (pore diameter of 8-9 nm) SBA-15 is used as the support in the present invention, the comprehensive performance of the catalyst is optimal.

[0016] Furthermore, in step S1, the loading amount of metal Ce relative to the mesoporous SBA-15 support is 1 wt% - 9 wt%; the acid amount of the Ce-SBA-15 support with acidic sites is 0.075 - 0.4 mmol / g. In the present invention, Ce doping introduces CeO 2 species. XPS characterization shows that in this catalyst, Ce exists as Ce 4+ / Ce 3+ . The existence of the latter indicates the presence of oxygen vacancies on the catalyst surface, which means it can provide Lewis acid sites. The acid amount is determined by NH 3 -TPD characterization, and the acid amount of the catalyst increases with the increase of the Ce doping amount.

[0017] Furthermore, in step S1, the Ce precursor solution includes an aqueous solution of CeCl 3 or Ce(NO 3 ) 3 . During the drying treatment, the temperature of the vacuum drying oven is 60-100 °C, and the heating time is 6-12 h.

[0018] Further, in step S1, the temperature of the first calcination treatment is 200 - 400 °C, and the time is 2 - 6 h. Preferably, the temperature of the first calcination treatment is 300 - 400 °C, and the time is 3 - 5 h.

[0019] Further, in step S2, the Ru precursor solution is prepared from an aqueous solution of RuCl 3 and ethanol. In the present invention, considering that the anhydrous RuCl 3 raw material is prone to moisture absorption, resulting in difficult precise quantification and easy Ru loading fluctuations, it is therefore formulated as an aqueous solution for storage. In addition, in order to reduce the adverse effects of the water present in the aqueous solution of RuCl 3 on the impregnation of metallic Ru and the confined loading in the pores, the present invention defines that the concentration of the aqueous solution of RuCl 3 is not less than 5 wt%. Under this condition, in the Ru precursor solution, the volume ratio of ethanol to water is higher than 5:1. As the main solvent, ethanol can not only ensure the dispersion effect of the active metal Ru in the pores, but also play a reducing role to ensure the precise loading of the active metal Ru, thereby improving the activity of the catalyst.

[0020] Further, in step S2, the loading amount of metallic Ru relative to the mesoporous SBA - 15 support is 0.1 wt% - 5 wt%. Preferably, the loading amount of metallic Ru relative to the mesoporous SBA - 15 support is 0.5 wt% - 2 wt%.

[0021] In some preferred embodiments, the loading amount of metallic Ru relative to the mesoporous SBA - 15 support is 1 wt%, and the loading amount of metallic Ce relative to the mesoporous SBA - 15 support is 5 wt% - 9 wt%.

[0022] Further, in step S2, the temperature of the second calcination treatment is 200 - 400 °C, and the time is 2 - 6 h. Preferably, the temperature of the second calcination treatment is 300 - 400 °C, and the time is 3 - 5 h.

[0023] In the present invention, the impregnation and calcination of the Ce precursor and the Ru precursor on the support are carried out in steps. Such an operation can avoid the Ru sites being covered by a high loading amount of Ce during the mixed impregnation process, which affects the catalyst activity, and ensure that Ru, as the main active site for polyolefin hydrogenolysis, better exerts its catalytic effect. Further, in terms of the control of the conditions for the first calcination and the second calcination, too low a temperature may lead to incomplete decomposition of the cerium precursor and insufficient reduction of ruthenium, thereby reducing the catalyst activity; while too high a calcination temperature will cause the rapid evaporation of the precursor, making the active sites unable to be fully dispersed. Appropriate calcination temperature and time can ensure that the prepared catalyst has high activity and stability.

[0024] Further, in step S3, the reducing atmosphere is a mixed gas of hydrogen and argon, and the volume percentage of hydrogen is 5%-10%; the temperature of the reduction treatment is 200-400 °C, and the time is 2-4 h.

[0025] The technical solution adopted to achieve the second object of the present invention is: to provide a mesoporous-confined Ru-Ce / SBA-15 catalyst prepared by the preparation method according to the first object of the present invention.

[0026] The mesoporous-confined Ru-Ce / SBA-15 catalyst prepared by the present invention is in the form of a gray powder. Using mesoporous SBA-15 as the carrier, relative to the weight of the carrier, the loading amount of metal cerium is 1-9 wt%, and the loading amount of metal ruthenium is 0.1-5 wt%. The mesoporous-confined Ru-Ce / SBA-15 catalyst has certain acidic sites, and the acid amount is 0.05-0.4 mmol / g. It has a mesoporous structure, with an average pore diameter of 8-9 nm and a pore volume of 1-1.3 cm 3 / g, and the specific surface area is 450-500 m 2 ·g -1 .

[0027] The technical solution adopted to achieve the third object of the present invention is: to provide an application of the mesoporous-confined Ru-Ce / SBA-15 catalyst according to the second object of the present invention in preparing hydrocarbon liquid fuels: using the mesoporous-confined Ru-Ce / SBA-15 catalyst to catalytically hydrogenolyze carbon-containing waste to prepare hydrocarbon liquid fuels; the carbon-containing waste includes waste plastics and / or biomass.

[0028] Further, the carbon-containing waste is low-density polyethylene; the application includes: mixing low-density polyethylene and the mesoporous-confined Ru-Ce / SBA-15 catalyst according to a mass ratio of (1-2):(0.01-0.025), and under the conditions of a H 2 pressure of 2-5 MPa, a temperature of 260-320 °C, and a stirring rate of 100-400 rpm, performing a catalytic hydrogenolysis reaction for 6-36 h to obtain a standard product of liquid mixed hydrocarbons with a concentrated carbon chain length of C 8 -C 38 ; in the standard product of liquid mixed hydrocarbons, the proportion of short-chain alkanes in the range of C 7 -C 25 is 65%-99%.

[0029] Compared with the prior art, the beneficial effects of the present invention are: (1)The preparation method of a mesoporous-confined Ru-Ce / SBA-15 catalyst provided by the present invention uses ethanol as a solvent. Through precise impregnation operations, it ensures the uniform dispersion of ruthenium nanoparticles inside the mesopores of SBA-15. By utilizing the mesoporous confinement effect, it effectively guides polymer chains into the catalytic pores, which can promote the selective cleavage of C-C bonds and thereby improve the selectivity of short-chain alkanes. In addition, before loading the active component ruthenium, the mesoporous SBA-15 support is doped with cerium in the present invention, providing additional acidic sites and significantly improving the performance of the catalyst.

[0030] (2)The present invention prepares a mesoporous-confined Ru-Ce / SBA-15 catalyst with low loading, high dispersion, and adjustable acidity. This catalyst reduces the loading amount of the noble metal Ru, greatly improves the atomic utilization efficiency, reduces the consumption of the noble metal compared with commercial Ru / C catalysts, and saves the production cost.

[0031] (3)The mesoporous-confined Ru-Ce / SBA-15 catalyst prepared by the present invention is used for catalytic hydrogenolysis of carbon-containing waste to prepare hydrocarbon liquid fuels, and has the advantages of mild reaction conditions and high product selectivity. Among them, the mild reaction temperature not only extends the service life of the catalyst but also improves the economy of the reaction process. In addition, the lower reaction pressure is beneficial to reducing the consumption of hydrogen and improving the safety of the reaction. Further, the stability experiment shows that the catalyst can be recycled, improving the catalyst utilization rate and reducing the use cost. The present invention provides theoretical guidance for catalytic hydrogenolysis of carbon-containing waste to prepare hydrocarbon liquid fuels under mild conditions and has good application prospects. Description of the Drawings

[0032] Figure 1 It is a general process schematic diagram of the preparation method and application of a mesoporous-confined Ru-Ce / SBA-15 catalyst provided by the embodiment of the present invention; Figure 2 It is a high-resolution transmission electron microscopy image of the 1%Ru-7%Ce / SBA-15 catalyst prepared in Example 1; Figure 3 It is a high-angle annular dark-field scanning transmission image of 1%Ru-7%Ce / SBA-15 prepared in Example 1; Figure 4 It is the N 2 adsorption-desorption isotherm diagram of 1%Ru-7%Ce / SBA-15 prepared in Example 1; Figure 5 It is the pore size distribution diagram of 1%Ru-7%Ce / SBA-15 prepared in Example 1; Figure 6 It is the wide-angle XRD diagram of 1%Ru-7%Ce / SBA-15 prepared in Example 1; Figure 7 NH₃-TPD curve of 1%Ru-7%Ce / SBA-15 prepared in Example 1; Figure 8 Product distribution diagram of LDPE hydrogenolysis catalyzed by the catalysts prepared in Example 1, Examples 3 - 6 and Comparative Example 2.

[0033] Figure 9 Product distribution diagram of LDPE hydrogenolysis catalyzed by the catalyst prepared in Comparative Example 3; Figure 10 Reaction rate comparison diagram of LDPE hydrogenolysis catalyzed by the catalysts provided in Example 1 and Comparative Example 5; Figure 11 Product distribution diagram of LDPE hydrogenolysis catalyzed by different catalysts in Comparative Example 5; Figure 12 Product distribution diagram of LDPE hydrogenolysis catalyzed by the catalyst prepared in Example 1 at different reaction times. Detailed implementation manners

[0034] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0036] The embodiments of the present invention provide a preparation method of a mesoporous-confined Ru-Ce / SBA-15 catalyst, comprising the following steps: Step 1: Place the mesoporous SBA-15 support in the Ce precursor solution, mix well, and then perform drying treatment and the first calcination treatment to obtain a Ce-SBA-15 support with acidic sites. Among them, the average pore diameter of the mesoporous SBA-15 support is 8 - 9 nm; the loading amount of metal Ce relative to the mesoporous SBA-15 support is 1 wt% - 9 wt%; the acid amount of the Ce-SBA-15 support with acidic sites is 0.075 - 0.4 mmol / g. The Ce precursor solution includes CeCl 3 or Ce(NO 3 ) 3 aqueous solution; the temperature of the first calcination treatment is 200 - 400 °C, and the time is 2 - 6 h.

[0037] Step 2: Prepare a Ru precursor solution using ethanol as the solvent; fully mix the Ru precursor solution with the Ce-SBA-15 support to obtain a first product; in the first product, the volume-mass ratio of ethanol to the Ce-SBA-15 support is 1.25 - 5 mL / g; perform a second calcination treatment on the first product to obtain a second product. Among them, the Ru precursor solution is prepared from an aqueous solution of RuCl 3 and ethanol, and the concentration of the aqueous solution of RuCl 3 is not less than 5 wt.%. The loading amount of metallic Ru relative to the mesoporous SBA-15 support is 0.1 wt% - 5 wt%. The temperature of the second calcination treatment is 200 - 400 °C, and the time is 2 - 6 h.

[0038] Step 3: Place the second product in a reducing atmosphere (a mixed gas of H 2 and Ar, and the volume percentage of hydrogen is 5% or 10%), and perform a reduction treatment at a temperature of 200 - 400 °C for 2 - 4 h to obtain a mesoporous-confined Ru-Ce / SBA-15 catalyst.

[0039] The present invention will be further described below in conjunction with specific embodiments, but it is not a limitation of the present invention.

[0040] The main parameters and variables of the examples and comparative examples of the present invention are shown in Table 1.

[0041] Table 1

[0042] Example 1 A preparation method of a mesoporous-confined Ru-Ce / SBA-15 catalyst, comprising the following steps: Step 1: Dissolve 43.4 mg of Ce(NO 3 ) 3 in 10 mL of deionized water, add 200 mg of SBA-15 to the Ce(NO 3 ) 3 solution, and stir vigorously to make it mix evenly. Dry the obtained mixture in a vacuum drying oven at 60 °C for 12 h to obtain a white solid. Grind the obtained solid into fine powder, and then place it in a tubular furnace and calcine it at 350 °C in an air atmosphere for 4 h to obtain a Ce-SBA-15 support.

[0043] Step 2: Dissolve 0.041 mL of a 10 wt% aqueous solution of RuCl 3 in 0.5 mL of ethanol, add 200 mg of the Ce-SBA-15 support, and stir vigorously to ensure the uniform dispersion of the Ru precursor to obtain a pale yellow mixture.

[0044] Step 3: Place the light yellow mixture in a tubular furnace and calcine it at 300 °C for 5 h in an air atmosphere, and then reduce it at 300 °C for 2 h in a 10% H 2 / Ar atmosphere. The obtained gray powder is the Ru-Ce / SBA-15 catalyst.

[0045] A series of characterizations were carried out on the 1%Ru-7%Ce / SBA-15 catalyst prepared in Example 1. The actual Ru loading was 0.36% and the actual Ce loading was 5.75% obtained by ICP test, denoted as 1%Ru-7%Ce / SBA-15. The 1%Ru-7%Ce / SBA-15 catalyst prepared in Example 1 has obvious mesoporous channel structure characteristics, and the elements Ce, O, and Si are evenly dispersed on the SBA-15 support (as Figure 2 shown). It can be seen from the high-angle annular dark-field scanning transmission image that there are a large number of small bright spots distributed on the support, and the signal of Ru perfectly overlaps with the signal of the SBA-15 channel, indicating that Ru nanoparticles are precisely loaded inside the mesopores of SBA-15 (such as the bright spots in Figure 3 ). Through the N 2 adsorption-desorption curve, it was found that the specific surface area of the 1%Ru-7%Ce / SBA-15 catalyst is 461.1 m 2 ·g -1 , the pore volume is 1.3 cm 3 / g, it has a mesoporous structure, and the average pore size distribution is about 8.7 nm (as Figure 4 and Figure 5 shown).

[0046] The XRD pattern of the 1%Ru-7%Ce / SBA-15 catalyst prepared in Example 1 is as Figure 6 shown. Four well-resolved small diffraction peaks observed at 28.6 nm, 33.1 nm, 47.5 nm, and 56.3 nm correspond to the (111), (200), (220), and (311) crystal planes of CeO 2 , respectively. At the same time, only the (101) and (100) crystal plane signals of tiny Ru nanoparticles are shown, further confirming the uniform distribution and high dispersion of Ru nanoparticles in the pores. Three NH 3 desorption peaks near 100, 375, and 550 °C in the ammonia temperature-programmed desorption (NH 3 -TPD) curve (as Figure 7 shown) correspond to weak acid, medium acid, and strong acid sites respectively, and the total acidity is 0.33 mmol / g.

[0047] Example 2 Same as Example 1, only change the 10 wt% RuCl in Step 2 3The dosage of the aqueous solution was replaced with 0.205 mL, and the prepared catalyst was denoted as 5%Ru-7%Ce / SBA-15.

[0048] Example 3 Same as Example 1, only the dosage of Ce(NO 3 ) 3 in Step 1 was replaced with 6.2 mg, and the prepared catalyst was denoted as 1%Ru-1%Ce / SBA-15.

[0049] Example 4 Same as Example 1, only the dosage of Ce(NO 3 ) 3 in Step 1 was replaced with 18.6 mg, and the prepared catalyst was denoted as 1%Ru-3%Ce / SBA-15.

[0050] Example 5 Same as Example 1, only the dosage of Ce(NO 3 ) 3 in Step 1 was replaced with 31 mg, and the prepared catalyst was denoted as 1%Ru-5%Ce / SBA-15.

[0051] Example 6 Same as Example 1, only the dosage of Ce(NO 3 ) 3 in Step 1 was replaced with 55.8 mg, and the prepared catalyst was denoted as 1%Ru-9%Ce / SBA-15.

[0052] Comparative Example 1 This comparative example used a commercially available Ru / C catalyst with a 5 wt% loading.

[0053] Comparative Example 2 The difference between this comparative example and Example 1 was that the catalyst preparation method did not include Step 1 of introducing acidic sites by Ce doping. Instead, mesoporous SBA-15 was directly used for Steps 2 and 3 of catalyst preparation, and the prepared catalyst was denoted as 1%Ru / SBA-15.

[0054] Comparative Example 3 The difference between this comparative example and Example 1 was as follows: The catalyst was prepared using the traditional impregnation method, which specifically included the following steps: 0.205 mL of 10 wt% RuCl 3 aqueous solution was added to 10 mL of deionized water, and 200 mg of SBA-15 support was added. The mixture was vigorously stirred to make it homogeneous. The resulting mixture was dried in a vacuum drying oven at 60 °C for 12 h to obtain a white solid. The obtained solid was ground into fine powder and calcined in an air atmosphere at 300 °C for 5 h, and then in 10% H2 Reduce it at 300 °C for 2 h in an Ar atmosphere. The prepared catalyst is denoted as i / o-5%Ru / SBA-15.

[0055] Comparative Example 4 The difference between this comparative example and Example 1 is that in Step 1, the dosage of Ce(NO 3 ) 3 is replaced with 31 mg, and the calcination temperature is replaced with 300 °C. In Step 2, the solvents for preparing the Ru precursor solution are respectively replaced with a mixed solution of deionized water and ethanol, ethylene glycol, methanol, n-propanol, isopropanol, and n-butanol with the same volume and an alcohol-to-water ratio of 5:1 to prepare a series of catalysts.

[0056] Comparative Example 5 In this comparative example, different catalysts are prepared by loading the active component Ru on other supports at a loading amount of 1 wt%, and are respectively denoted as Ru / C, Pt / C, Pd / C, Ru / CeO 2 , Ru / SiO 2 and Ru-Ce / SiO 2 .

[0057] Application performance test Using low-density polyethylene as the raw material for testing carbon-containing waste, the application performance of the catalysts prepared in each example and comparative example was tested. The specific test method is as follows: Step 1: According to the mass ratio of low-density polyethylene raw material to catalyst of 100:1, load 1 g of low-density polyethylene and 10 mg of the catalyst prepared in each example or comparative example into a batch reactor, mix evenly and seal.

[0058] Step 2: Replace the gas in the reactor with H 2 five times at room temperature, and then fill it with high-purity hydrogen at 2 - 5 MPa. Heat the reactor to 260 - 320 °C, and keep it warm for 6 - 36 h under magnetic stirring at 100 - 400 rpm, then stop heating.

[0059] Step 3: Cool the reactor at room temperature, open the gas release valve to collect the gas in the reactor, and analyze the gas products using a gas chromatograph (GC).

[0060] Step 4: Open the reactor, use excessive dichloromethane to rinse and dissolve the products in the reactor. After vacuum filtration, separate the liquid part containing mixed alkanes and the solid part containing unreacted polyethylene and the catalyst. Rotate and evaporate the soluble liquid part to remove dichloromethane, then dissolve the remaining alkane products with 20 mL of dichloromethane to obtain a colorless or light yellow standard product, and analyze the liquid products using a gas chromatograph-mass spectrometer (GC-MS). Wait for the solid part to dry naturally and then weigh it.

[0061] In the above application performance test, the conversion rate, liquid product yield, and selectivity of products with different carbon numbers were calculated using the following formulas: Conversion rate (wt%) = × 100% Liquid product yield (wt%) = × Conversion rate (wt%) Selectivity of products with different carbon numbers (wt%) = × 100% (1) Influence of Ce doping and preparation method on catalytic performance The catalysts prepared in Examples 1-6 and Comparative Examples 1-3 were kept at a temperature of 300 ° °C, a hydrogen pressure of 3 MPa, and a stirring speed of 200 rpm for 18 h. The composition and content of the obtained products are shown in Table 2 below.

[0062] Table 2

[0063] As can be seen from Table 2 above, By comparing the test results of Examples 1 and 2, it can be seen that the liquid yield in the products increases significantly with the increase of the loading amount of the active metal Ru. The Ru-Ce / SBA catalyst prepared in Example 2 with the Ru loading increased to 5% still has good activity, and can achieve the complete conversion of LDPE in a relatively short time and obtain a concentrated product distribution. By comparing the test results of Example 2 with the commercial 5% Ru / C catalyst provided in Comparative Example 1, it can be seen that under the premise of the same Ru loading, the performance of the 5% Ru-7% Ce / SBA-15 catalyst prepared by the present invention is significantly higher than that of the commercial Ru / C catalyst.

[0064] By comparing the test results of Examples 1, 3-6 and Comparative Example 2, it can be seen that the liquid yield in the products increases slightly with the increase of the Ce loading. When the Ru loading is 1%, the best effect is obtained when the Ce loading is 7%. Excessive Ce loading will instead reduce the catalyst activity.

[0065] Furthermore, Figure 8 shows the product distribution after the hydrogenolysis of LDPE by the catalysts prepared in Example 1, Examples 3-6 and Comparative Example 2. In addition to the high liquid yield, the distribution of liquid products in the application of the catalysts prepared by the present invention is significantly concentrated in the range of C 7 -C 25 , accounting for 84% of the liquid products.

[0066] Figure 9The product distribution after hydrogenolysis of LDPE by the catalyst prepared in Comparative Example 3 is shown. By comparing the test results of the catalyst prepared by the traditional impregnation method in Example 1 and Comparative Example 3, the preparation method provided by the present invention can accurately locate Ru in the pores of the mesoporous support, significantly improving the selectivity of the product.

[0067] The above test results show that the Ru-Ce / SBA-15 catalyst prepared by the preparation method provided by the present invention can greatly improve the hydrogenolysis efficiency of low-density polyethylene and increase the liquid fuel yield.

[0068] (2) Influence of the type of precursor solvent on catalytic performance The catalyst prepared in Comparative Example 4 was kept at a hydrogen pressure of 3 MPa, a temperature of 300 °C, and a stirring speed of 200 rpm for 18 h. The composition and content of the obtained products are shown in Table 3 below.

[0069] Table 3 Results of catalytic hydrogenolysis of low-density polyethylene by 1%Ru-5%Ce / SBA-15 prepared using different alcohols

[0070] As can be seen from Table 3 above, In the preparation method of the 1%Ru-7%Ce / SBA-15 catalyst, compared with other alcohols, using ethanol as the solvent, the viscosity and reducibility of ethanol can affect the dispersion effect of the active sites. By adjusting the amount of the solvent to match the pore volume of the support, it can be ensured that the precursor solution is absorbed into the pores as much as possible during the impregnation process, reducing external impregnation, realizing the loading of Ru active sites in the pores, thereby effectively exerting the spatial confinement effect, improving the product distribution, and further enhancing the catalytic performance of the catalyst.

[0071] (3) Influence of the type of support on catalytic performance The catalysts provided in Example 1 and Comparative Example 5 were kept at a hydrogen pressure of 3.5 MPa, a temperature of 280 °C, and a stirring speed of 200 rpm for 18 h, and the reaction rates of the catalysts were tested. The comparison chart of the test results is as Figure 10 shown. As can be seen from Figure 10 Under the condition that the mass ratio of the catalyst to low-density polyethylene is 1:100, the 1%Ru-7%Ce / SBA-15 catalyst provided in Example 1 of the present invention has a significantly higher reaction rate (defined as the mass of LDPE converted or the mass of liquid products produced per unit time per unit mass of Ru) compared with other catalysts, which is 549.38 g p ·g Ru -1 ·h -1 .

[0072] Further, under the conditions of a hydrogen pressure of 3.5 MPa, a temperature of 280 °C, a stirring speed of 200 rpm, and heat preservation for 18 h, the catalysts prepared in Example 1 were tested for their catalytic performance with those of Comparative Example 2 and Comparative Example 5, namely Ru / SiO 2 and Ru-Ce / SiO 2 , and the results are shown in Table 4 below and Figure 11 as follows.

[0073] Table 4

[0074] As can be seen from Table 4 and Figure 11 , regardless of whether SBA-15 or SiO 2 is used as the carrier, a higher liquid yield is obtained on the Ce-doped catalyst, indicating that Ce doping significantly improves the activity of the catalyst and the selectivity of the product. In addition, compared with the case where SiO 2 is used as the carrier, the product distribution is significantly shifted towards the short-chain alkane range of C 7 -C 25 when SBA-15 is used as the carrier, highlighting the improvement of the selectivity of short-chain hydrocarbon liquid products by mesoporous confinement.

[0075] (IV) Influence of application conditions on catalytic performance The H 2 pressure, reaction temperature, and reaction time of the catalyst prepared in Example 1 were respectively changed during the application performance test, and the three-phase products and yields obtained by catalytic hydrogenolysis are shown in Table 5, Table 6, and Table 7 respectively.

[0076] Table 5 Yields under different H 2 pressures (reaction temperature 280 °C, reaction time 18 h)

[0077] Table 6 Yields at different reaction temperatures (H 2 pressure 3 MPa, reaction time 18 h)

[0078] Table 7 Yields at different reaction times (H 2 pressure 3.5 MPa, temperature 280 °C)

[0079] As can be seen from Tables 5-7, in the application of the catalyst provided by the present invention, increasing the H 2Pressure and reaction temperature are conducive to the catalytic hydrogenolysis of low-density polyethylene, but too high a reaction temperature will also lead to a rapid increase in gas products. The reaction time is a key factor affecting the yield and conversion rate. Prolonging the reaction time is beneficial to the hydrogenolysis of low-density polyethylene. After prolonging the reaction time to 36 h, with a Ru loading of 1%, a liquid yield of 72.6% and a gas yield of 7.8% (solid conversion rate of 80.4%) were obtained. Not only is the overall conversion rate higher than that of the commercial 5% Ru / C catalyst (solid conversion rate of 75.9% and gas yield of 21%), but also the gas yield is significantly lower, with obvious advantages.

[0080] Furthermore, Figure 12 Figure 5 shows the product distribution after the hydrogenolysis of LDPE by the catalyst prepared in Example 1 for different times, indicating that as time goes by, the yields of liquid and gas products continuously increase, and the product distribution gradually shifts to short-chain hydrocarbons. After reacting for 36 h, the liquid products are concentrated in the C 7 -C 25 range, with a proportion as high as 99.3%.

[0081] The above test results show that the catalyst provided by the present invention can efficiently catalyze the hydrogenolysis of carbon-containing waste to prepare hydrocarbon liquid fuels under low noble metal loading and mild reaction conditions by appropriately prolonging the reaction time.

[0082] (V) Recycling performance test The catalyst of Example 1 used for catalytic hydrogenolysis was recycled, that is, the solid collected after the previous reaction was supplemented with low-density polyethylene to 1 g and the experiment was repeated (insulated for 18 h under the conditions of a hydrogen pressure of 3.5 MPa, a temperature of 280 °C, and a stirring speed of 200 rpm). The test results are shown in Table 8 below.

[0083] Table 8 Recycling performance test results of 1% Ru-7% Ce / SBA-15

[0084] As can be seen from Table 8, After five cycles, the liquid yield of the catalyst prepared in Example 1 for catalytic hydrogenolysis of low-density polyethylene can still reach 32.2 wt%, indicating that the catalyst prepared by the present invention not only has high catalytic efficiency, but also has excellent stability and reusability.

[0085] The above are only preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention accordingly. Those skilled in the art should be able to realize that all equivalent replacements and obvious changes made by using the content of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a mesoporous confined Ru-Ce / SBA-15 catalyst, characterized in that: The following steps are involved: S1, placing the mesoporous SBA-15 carrier in the Ce precursor solution, fully mixing, and then drying and first calcining to obtain a Ce-SBA-15 carrier with acidic sites; S2, using ethanol as solvent, preparing a Ru precursor solution; The Ru precursor solution and the Ce-SBA-15 carrier are fully mixed to obtain a first product; in the first product, the volume mass ratio of ethanol to the Ce-SBA-15 carrier is 1.25-5 mL / g; the first product is subjected to a second calcination treatment to obtain a second product; S3. The second product is placed in a reducing atmosphere and subjected to reduction treatment to obtain a mesoporous confined Ru-Ce / SBA-15 catalyst.

2. The preparation method according to claim 1, characterized in that In step S1, the average pore size of the mesoporous SBA-15 carrier is 8-9 nm, and the pore volume is 1-1.3 cm 3 / g; the loading amount of metal Ce relative to the mesoporous SBA-15 carrier is 1 wt%-9wt%; the acid amount of the Ce-SBA-15 carrier with acidic sites is 0.075-0.4 mmol / g.

3. The preparation method according to claim 1, characterized in that In step S1, the Ce precursor solution includes an aqueous solution of CeCl3 or Ce(NO3)3; the temperature of the first calcination treatment is 200-400 °C and the time is 2-6 h.

4. The preparation method according to claim 1, characterized in that In step S2, the Ru precursor solution is prepared from an aqueous solution of RuCl3 and ethanol; the concentration of the aqueous solution of RuCl3 is not less than 5 wt%.

5. The preparation method according to claim 1, characterized in that In step S2, the loading amount of metal Ru relative to the mesoporous SBA-15 carrier is 0.1 wt%-5wt%.

6. The preparation method according to claim 1, characterized in that In step S2, the temperature of the second calcination treatment is 200-400 ° C, and the time is 2-6 h.

7. The preparation method according to claim 1, characterized in that In step S3, the reducing atmosphere is a mixed gas of hydrogen and argon, with the volume percentage of hydrogen being 5%-10%; the temperature of the reduction treatment is 200-400 °C, and the time is 2-4h.

8. A mesoporous confined Ru-Ce / SBA-15 catalyst, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. The use of the mesoporous confined Ru-Ce / SBA-15 catalyst for preparing hydrocarbon liquid fuel according to claim 8, characterized in that: The mesoporous confined Ru-Ce / SBA-15 catalyst is used to catalyze the hydrogenolysis of carbon-containing waste to prepare hydrocarbon liquid fuel; the carbon-containing waste includes waste plastics and / or biomass.

10. The use according to claim 9, characterized in that: The carbon-containing waste is low-density polyethylene; The application comprises: mixing low-density polyethylene and mesoporous confined Ru-Ce / SBA-15 catalyst in a mass ratio of (1-2):(0.01-0.025), and performing catalytic hydrogenolysis reaction for 6-36 h under the conditions of H2 pressure of 2-5 MPa, temperature of 260-320 °C, and stirring rate of 100-400 rpm to obtain carbon chain length C8-C 38 , concentrated distribution of liquid mixed hydrocarbon standard products; In the liquid mixed hydrocarbon standard product, C7-C 25 The mass percentage of short chain alkanes ranges from 65% to 99%.

Images