Method for catalyzing co-pyrolysis of microcrystalline cellulose and polystyrene by using bimetal micro-mesoporous composite molecular sieve

Abstract

The invention discloses a method for catalyzing co-pyrolysis of microcrystalline cellulose and polystyrene by using a bimetallic micro-mesoporous composite molecular sieve, and belongs to the field of synthesis of molecular sieve catalytic materials. The invention aims to solve the problems of low aromatic hydrocarbon selectivity and insufficient catalytic efficiency during catalysis of co-pyrolysis of microcrystalline cellulose and polystyrene in the prior art. According to the technical scheme, the preparation method comprises the following steps: firstly, preparing an HZSM-5 / MCM-41 micro-mesoporous composite molecular sieve carrier; and loading a zinc salt and an iron salt on the carrier by adopting an impregnation method, and drying and roasting to obtain the Zn-Fe / HZSM-5 / MCM-41 catalyst. The prepared catalyst is specifically used for catalyzing co-pyrolysis of microcrystalline cellulose and polystyrene, Fe species serve as an efficient deoxidation center, Zn species serve as an aromatization regulation center, the Fe species and the Zn species generate a remarkable synergistic effect, the selectivity and the yield of aromatic hydrocarbon in a product are effectively improved, and the inactivation resistance of the catalyst is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve catalytic material synthesis, and specifically describes a method for synthesizing a bimetallic micro-mesoporous composite molecular sieve catalyst. Background Technology

[0002] Catalytic pyrolysis is a common method for converting organic solid waste (agricultural and forestry waste, plastic waste) into high-value chemicals. This technology can directionally convert organic solid waste into target liquid fuels. The ineffective utilization of biomass and waste plastics leads to the waste of renewable resources and environmental problems; therefore, realizing the high-value energy conversion and utilization of organic solid waste is of significant practical importance. Catalytic co-pyrolysis of oxygen-rich biomass and hydrogen-rich waste plastics can effectively increase the proportion of aromatic hydrocarbons in the products. By using different types of catalysts, the activation energy of the reaction can be effectively reduced, the reaction rate increased, and the target products can be directionally controlled to generate high-value-added liquid fuels such as aromatic hydrocarbons and other hydrocarbon products.

[0003] Zeolite molecular sieves use zeolite as the basic material. Their structure consists of tetrahedra of crystalline silicates or aluminates containing SiO4 and AlO4 connected by oxygen bridges. The pores in the zeolite serve as active centers for the catalyst, providing active sites for the reaction and controlling the adsorption and diffusion processes of molecules, thereby selectively promoting the directional conversion of organic solid waste. In recent years, there has been considerable research on composite molecular sieves. Therefore, the applicant will briefly introduce the existing technical literature relevant to this application. Existing Technical Literature 1: Source: Chen Wenjun. Research on the Preparation of Aromatic Hydrocarbons by Co-catalytic Hydrogenation Pyrolysis of Biomass and Waste Plastics [D]. Zhengzhou University, 2021.; Technical Description: Pd / Trap-HZSM-5 catalysts were prepared using different methods (thermal reduction, chemical reduction, and self-reduction) for the catalytic pyrolysis of pine (PW) and high-density polyethylene (HDPE) to improve the yield of aromatic hydrocarbons. Technical Defect: The catalyst in this method leads to a negative synergistic effect during the catalytic pyrolysis of microcrystalline cellulose (MC) and plastics. Existing technical document 2, source: SUN T, WANG R, XING Y, et al. Preparation of aromatic hydrocarbon-rich bio-oils by catalytic co-pyrolysis of biomass components and plastics based on HZSM-5, MCM-41, and HZSM-5 / MCM-41 [J]. Technical description: The type of feedstock and catalyst used in combination significantly affects the distribution of co-pyrolysis products. The introduction of a catalyst can increase the yield of hydrocarbons in the co-pyrolysis products of biomass components and plastics. Technical drawback: The aromatic hydrocarbon yield of the catalyst in the catalytic co-pyrolysis of microcrystalline cellulose (MC) and polystyrene (PS) remains low.

[0004] To improve catalytic performance, researchers often modify molecular sieves with metals. However, the choice of metal is crucial. For example, Chinese patent CN202310323281.3 discloses a ZSM-5 / MCM-41 catalyst co-modified with zinc (Zn) and aluminum (Al) for the co-pyrolysis of biomass and waste plastics, but it focuses on the co-pyrolysis of corn stalks and polypropylene. However, the co-pyrolysis of microcrystalline cellulose and polystyrene (PS) is also problematic. Compared to common polyolefin plastics (such as PE and PP), PS pyrolysis produces a large amount of styrene monomers, requiring catalysts with efficient hydrogenation, dealkylation, and aromatization capabilities to convert them into more valuable monocyclic aromatic hydrocarbons such as benzene, toluene, and xylene (BTX). Simultaneously, the large amount of oxygen-containing organic matter produced by MC pyrolysis requires catalysts with extremely strong deoxygenation capabilities. The complex intermediates from both raw materials place higher demands on the synergistic effect of the catalyst's active sites.

[0005] Developing a catalyst that can significantly improve the yield of aromatics and optimize product distribution in a microcrystalline cellulose (MC) and polystyrene (PS) feedstock system is a pressing technical challenge in the field. This invention addresses this background by aiming to solve the problems of low aromatic selectivity and insufficient catalytic efficiency of existing catalysts in the catalytic co-pyrolysis of microcrystalline cellulose (MC) and polystyrene (PS) feedstock systems. Summary of the Invention

[0006] To address the problems in the background art, the purpose of this invention is to design a method for preparing bimetallic micro-mesoporous composite molecular sieve catalysts. This method involves combining Zn and Fe metals and loading them onto an HZSM-5 / MCM-41 support. The unique synergistic effect of this composite material is utilized to directionally increase the yield of aromatics in the co-pyrolysis products of MC and PS, especially the yield of high-value monocyclic aromatics, and to directionally increase the proportion of aromatic-rich fuel oil in the co-pyrolysis products of biomass and waste plastics.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The preparation method of the bimetallic micro-mesoporous composite molecular sieve catalyst is as follows: First, prepare a micro-mesoporous composite molecular sieve support (HZSM-5 / MCM-41); then load zinc-iron bimetal onto the support to obtain the Fe-Zn HZSM-5 / MCM-41 catalyst.

[0008] The specific preparation steps are as follows: Microporous phase pretreatment: Prepare a certain amount of alkaline solution as the alkaline phase, and at the same time take a certain amount of ZSM-5 and add it to the prepared alkaline solution for alkaline phase pretreatment. Use a constant temperature water bath for water bath heating, and denote it as solution A.

[0009] Weigh a certain amount of hexadecyltrimethylammonium bromide (CTAB) and add it to deionized water. Stir at a constant speed at room temperature until the solution is completely clear. Record this solution as solution B for later use.

[0010] A certain amount of solution B is added to solution A. After stirring at a constant speed at room temperature, the mixed solution is placed in a high-pressure reactor for digestion. After digestion is complete, the pH of the digestion solution is adjusted, and crystallization continues in the high-pressure reactor.

[0011] After crystallization is complete, the solution is removed and filtered, then placed in an oven to dry to remove excess moisture, and ground into a uniform powder. The powder is then transferred to a muffle furnace for air calcination.

[0012] A certain amount of ammonium chloride solution was prepared and thoroughly mixed with the calcined powder. The mixture was stirred at a constant speed at room temperature to carry out ion exchange. Subsequently, the mixture was filtered and excess moisture was dried. The powder was then ground into powder and transferred to a muffle furnace for air calcination. HZSM-5 / MCM-41 microporous composite molecular sieve was thus obtained.

[0013] The required mass of metal element is determined based on the bimetallic loading. Zinc (Zn) salt and iron (Fe) salt are weighed and dissolved in deionized water to prepare a metal salt solution.

[0014] HZMS-5 / MCM-41 microporous composite molecular sieve was added to a metal salt solution, stirred and sonicated to ensure that metal ions could fully adhere to the surface and interior of the composite molecular sieve.

[0015] The solution from step (7) was dried in an oven to remove excess moisture and then ground into a uniform powder. The powder was then transferred to a muffle furnace for air calcination to obtain the Zn-Fe-HZMS-5 / MCM-41 micro-mesoporous composite molecular sieve catalyst.

[0016] Furthermore, in step (1), the alkaline solution is a sodium hydroxide solution with a concentration of 1.0-2.0 mol / L, and the alkaline pretreatment condition is water bath heating at 40°C for 1.0 hour.

[0017] Furthermore, in step (2), the mass fraction of the CTAB solution can be 10%-15%, and there are no requirements on the mixing method with the alkaline pretreatment solution. The stirring time is 1 h.

[0018] Furthermore, in step (3), the digestion temperature in the high-pressure reactor is 110℃, and the digestion time is 24 h; the crystallization temperature is 110℃, and the crystallization time is 24 h; and before the crystallization step, the pH is adjusted to 8.0-9.0. The inorganic acid used to adjust the pH can be any one of hydrochloric acid, sulfuric acid, or nitric acid, and the inorganic base can be any one of sodium hydroxide or potassium hydroxide. For example, in the example of this invention, the inorganic acid used is nitric acid.

[0019] Furthermore, in step (4), drying is only required to ensure that excess moisture is removed. The temperature of the muffle furnace is 500~600℃, and the roasting time is 6 h.

[0020] Furthermore, in step (5), the concentration of the ammonium chloride solution is 1 mol / L, and the amount is not specifically required, as long as it is completely mixed with the powder after calcination in step 4. The ion exchange time is 30 min, and the temperature of the muffle furnace air calcination is 500~600℃ for 2 h.

[0021] Further, the zinc salt and iron salt mentioned in step (6) are selected from one or more of their respective nitrates, sulfates, or chlorides; the total loading of the Zn and Fe bimetals is 1% to 15% of the total mass of the catalyst. Preferably, when loading zinc and iron metals, ferric nitrate and zinc nitrate are selected, with a total metal loading of 10%, to avoid clogging the internal pores of the molecular sieve due to excessive metal, and the mass ratio of Zn to Fe is 1~3:1~3. Most preferably, the mass ratio of Zn to Fe is 2:2.

[0022] Furthermore, in steps (7) and (8), the equal-volume impregnation method is used, and the amount of deionized water is determined based on the pore volume of the composite molecular sieve carrier as determined in advance.

[0023] Furthermore, in step (9), the temperature of the muffle furnace air calcination is 500~600℃, and the calcination time is 4 h.

[0024] The catalyst is used in a method of catalytic co-pyrolysis of biomass and waste plastics to produce bio-oil rich in aromatic hydrocarbons. The biomass is microcrystalline cellulose, and the waste plastic is polystyrene.

[0025] Furthermore, the catalytic co-pyrolysis was carried out under the following conditions: the reaction temperature was 600℃.

[0026] Compared with existing technologies, the beneficial effects of this invention are as follows: By introducing zinc (Zn) and iron (Fe) bimetallic active centers onto the HZSM-5 / MCM-41 micro-mesoporous composite molecular sieve support, the Fe species acts as a highly efficient deoxygenation center, removing oxygen-containing functional groups; while the Zn species acts as an aromatization regulating center, catalyzing subsequent dehydrogenation, cyclization, and hydrogen transfer reactions. The deoxygenation effect of Fe creates a reaction environment for the aromatization of Zn, producing a synergistic effect, thus specifically targeting the co-pyrolysis of MC and PS, thereby improving its aromatic selectivity, yield, and resistance to deactivation. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The images show the XRD patterns of HZSM-5 molecular sieve, HZSM-5 / MCM-41 composite molecular sieve, and 4Zn-0Fe / 3Zn-1Fe / 2Zn-2Fe / 1Zn-3Fe / 0Zn-4Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading). Figure 1(a) is the wide-angle XRD pattern. Figure 1 (b) is the small-angle XRD pattern.

[0029] Figure 2 TEM images of molecular sieves and composite molecular sieves; among them Figure 2 (a) is a TEM image of HZSM-5 molecular sieve; Figure 2 (b) is a TEM image of MCM-41 molecular sieve. Figure 2 (c) is a TEM image of the HZSM-5 / MCM-41 composite molecular sieve; Figure 2 (d) is a TEM image of 2Zn-2Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading); Figure 2 (e) is a TEM image of the 1Zn-3Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading); Figure 2 (f) is a TEM image of the 3Zn-1Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading); Figure 2 (g) is a TEM image of the 4Zn-0Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading); Figure 2 (h) is a TEM image of 0Zn-4Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading).

[0030] Figure 3 The attached diagram shows the N2- adsorption / desorption process of the 2Zn-2Fe / 1Zn-3Fe / 3Zn-1Fe / 4Zn-0Fe / 0Zn-4Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading) in the embodiments of the present invention.

[0031] Figure 4 This is a mapping diagram of the 2Zn-2Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading) in an embodiment of the present invention. Detailed Implementation

[0032] Example 1: HZSM-5 / MCM-41 composite molecular sieve: 20 ml of 2.0 mol / L NaOH solution was prepared as the alkaline phase. Simultaneously, 4 g of ZSM-5 (Tianjin Nankai University Catalyst Co., Ltd., silicon-to-aluminum ratio 25 mol / mol) was weighed and added to the prepared NaOH solution for alkaline pretreatment. The solution was heated in a constant temperature water bath at 40℃ for 60 min, and this solution was denoted as Solution A. 50 ml of a 10% (w / w) hexadecyltrimethylammonium bromide (CTAB) solution was added to Solution A. After uniform stirring at room temperature, the mixture was placed in a high-pressure reactor and digested at 110℃ for 24 h. After digestion, the solution was cooled to room temperature, and the internal pH was adjusted to the target value of 8.5. Crystallization continued in the reactor at 110℃ for 24 h. After crystallization, the solution was removed, filtered, and then dried in an oven for 2 h. The powder was then transferred to a muffle furnace and calcined in air at 550℃ for 6 h. A 1 mol / L ammonium chloride solution was thoroughly mixed with the calcined powder, and the mixture was stirred at a constant speed at room temperature to carry out ion exchange. The mixture was then filtered, excess moisture was dried, and the powder was ground into powder. The powder was then transferred to a muffle furnace and calcined in air at 550℃ for 2 h. This yielded the HZSM-5 / MCM-41 composite molecular sieve.

[0033] according to Figure 1 As shown in the wide-angle X-ray diffraction (XRD) pattern, when 2θ is between 7-25°, the prepared HZSM-5 / MCM-41 composite molecular sieve sample exhibits obvious MFI topological diffraction peaks. The sample has good crystallinity and no impurities, indicating that the microporous structure is still retained in the sample. Figure 1 The small-angle X-ray diffraction (XRD) pattern shown in b indicates that the sample exhibits diffraction peaks corresponding to the hexagonal crystal plane structure, suggesting that the sample has a regular and ordered hexagonal mesoporous structure.

[0034] Depend on Figure 2 Transmission electron microscopy (TEM) tests show that HZSM-5 molecular sieve has a smooth surface, uniform dispersion, and exhibits a blocky morphology; MCM-41 molecular sieve exhibits a uniform particle morphology, with uniform channels and a well-ordered structure; while the HZSM-5 / MCM-41 composite molecular sieve retains the blocky structure of HZSM-5 molecular sieve and also possesses the uniform channels and well-ordered structure of MCM-41.

[0035] Therefore, while retaining the original microporous structure, the sample successfully introduced a mesoporous structure, thus preparing the HZSM-5 / MCM-41 composite molecular sieve. At the same time, compared with pure HZSM-5 molecular sieve, the introduction of mesoporous structure leads to a weakening of the intensity of the MFI characteristic diffraction peak, indicating that the framework structure of HZSM-5 molecular sieve is etched by NaOH.

[0036] Example 2: 4Zn-0Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading): Weigh 1 g of dried HZSM-5 / MCM-41 composite molecular sieve (preparation method consistent with Example 1) and place it in a beaker. Then weigh 0.4552 g of Zn(NO3)2·6H2O and add 0.8 mL of deionized water (according to BET test, the pore volume of the prepared HZSM-5 / MCM-41 composite molecular sieve is 0.8 ml / g, so 0.8 mL of deionized water is needed for equal impregnation when weighing 1 g of carrier). Stir for 30 min and sonicate for 20 min to ensure uniform mixing and obtain a metal salt solution. Add 1 g of HZSM-5 / MCM-41 microporous composite molecular sieve to the metal salt solution, stir for 12 h and sonicate for 20 min to ensure that metal ions can fully adhere to the surface and interior of the composite molecular sieve. The solution was dried in an oven at 105℃ for 12 h to remove excess moisture, and then calcined in a muffle furnace at 550℃ for 4 h to obtain a 4Zn-0Fe HZMS-5 / MCM-41 microporous composite molecular sieve catalyst with a loading of 10% and a Zn to Fe metal mass ratio of 4:0.

[0037] Example 3: 0Zn-4Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading): 1 g of dried HZSM-5 / MCM-41 composite molecular sieve (preparation method is the same as in Example 1) was weighed and placed in a beaker. The subsequent operations were the same as in Example 2, except that 0.7235 g of Fe(NO3)3·9H2O metal salt was weighed. The other operations were the same as in Example 2. Finally, a 0Zn-4Fe HZSM-5 / MCM-41 microporous composite molecular sieve catalyst with a Zn and Fe metal mass ratio of 0:4 and a loading of 10% was obtained.

[0038] according to Figure 3 The N2- adsorption / desorption curves shown indicate that the hysteresis loops of the 4Zn-0FeHZSM-5 / MCM-41 and 0Zn-4FeHZSM-5 / MCM-41 composite molecular sieves are both of the "H4" type. This is characterized by the adsorption branches showing micropore filling characteristics in the low-pressure region and mesopore filling characteristics in the high-pressure region, indicating that both samples exhibit micropore-mesopore characteristics.

[0039] Example 4: 2Zn-2Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading): 1 g of dried HZSM-5 / MCM-41 composite molecular sieve (preparation method is the same as in Example 1) was placed in a beaker. The subsequent operations were the same as in Example 2, except that 0.3617 g of Fe(NO3)3·9H2O and 0.2276 g of Zn(NO3)2·6H2O were weighed. The other operations were the same as in Example 2, and a 2Zn-2Fe HZSM-5 / MCM-41 microporous composite molecular sieve catalyst with a loading of 10% and a Zn to Fe metal mass ratio of 2:2 was obtained.

[0040] Figure 4 The figure shows the mapping of Fe and Zn elements in the 2Zn-2Fe HZSM-5 / MCM-41 composite molecular sieve. It can be seen that Zn ions are in the form of particles and are uniformly dispersed on the catalyst surface, while Fe ions are uniformly distributed on the catalyst surface in the form of nanoclusters or small particles. The contents of the two metal elements are shown in Table 1. It can be found that the metal loading ratio of all samples is close to the initial calculated value, which indicates that the catalyst has successfully loaded the two metals and the metal ratio can be freely adjusted.

[0041] Example 5: 1Zn-3Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading): 1 g of dried HZSM-5 / MCM-41 composite molecular sieve (preparation method is the same as in Example 1) was placed in a beaker. The subsequent operations were the same as in Example 2, except that 0.5426 g of Fe(NO3)3·9H2O and 0.1138 g of Zn(NO3)2·6H2O were weighed. The other operations were the same as in Example 2, and a 1Zn-3Fe HZSM-5 / MCM-41 microporous composite molecular sieve catalyst with a loading of 10% and a Zn to Fe metal mass ratio of 1:3 was obtained.

[0042] Example 6: 3Zn-1Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading): 1 g of dried HZSM-5 / MCM-41 composite molecular sieve (preparation method is the same as in Example 1) was placed in a beaker. The subsequent operations were the same as in Example 2, except that 0.1809 g of Fe(NO3)3·9H2O and 0.3413 g of Zn(NO3)2·6H2O were weighed. The other operations were the same as in Example 2, and a 3Zn-1Fe HZSM-5 / MCM-41 microporous composite molecular sieve catalyst with a loading of 10% and a Zn to Fe metal mass ratio of 3:1 was obtained.

[0043] according to Figure 1 The XRD pattern shown and Figure 2The TEM image shown in df shows that the 2Zn-2Fe (1Zn-3Fe, 3Zn-1Fe) HZSM-5 / MCM-41 composite molecular sieve still combines both microporous and mesoporous structures. However, due to the introduction of Zn and Fe, the Si atoms in the support are replaced by Zn and Fe in the mesoporous structure, resulting in increased interplanar spacing and cell volume. This causes the diffraction peaks corresponding to the hexagonal crystal structure in the sample to shift to the left. The introduction of metals still allows the sample to maintain a high diffraction peak intensity, and no metal oxide peaks appear, indicating successful loading of bimetals. However, this does not lead to a decrease in the crystallinity of the sample, indicating that the original crystal structure has not been destroyed. At the same time, compared with the HZSM-5 / MCM-41 composite molecular sieve, the loading of metal ions does not change the basic morphology of its surface; they are simply uniformly distributed on the surface and in the pores of the catalyst.

[0044] Comparative Example 1: The difference between Comparative Example 1 and Example 4 is that Fe is replaced with Al, while the other operations are the same as in Example 4.

[0045] 2Zn-2Al HZSM-5 / MCM-41 composite molecular sieve (10% loading): Take 1 g of dried HZSM-5 / MCM-41 composite molecular sieve (preparation method is the same as in Example 1) and place it in a beaker. The subsequent operations are the same as in Example 4, except that 0.2276 g of Zn(NO3)2·6H2O and 0.696 g of Al(NO3)3·9H2O were weighed. The other operations are the same as in Example 2, and a 2Zn-2Al HZSM-5 / MCM-41 microporous composite molecular sieve catalyst with a loading of 10% and a Zn to Al metal mass ratio of 2:2 is obtained.

[0046] Table 1 shows the basic properties of HZSM-5 molecular sieve, MCM-41 molecular sieve, HZSM-5 / MCM-41 composite molecular sieve and 4Zn-0Fe / 3Zn-1Fe / 2Zn-2Fe / 1Zn-3Fe / 0Zn-4Fe HZSM-5 / MCM-41 composite molecular sieve (10% loading) in the examples of this invention.

[0047] Table 1. Basic properties of catalysts:

[0048] As shown in Table 1, metal loading leads to a decrease in the pore surface area, pore volume, and pore size of the catalyst. This may be due to the metal filling, which changes the intergranular gaps of the catalyst and thus alters its pore surface area. Additionally, some metal ions may block the pores of the catalyst, which will change the pore volume and pore size of the catalyst.

[0049] Example 7: The above examples and comparative examples were evaluated by using pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS) to catalytically pyrolyze microcrystalline cellulose (MC) and polystyrene (PS), and the aromatic hydrocarbon yield was calculated to assess the performance of the bimetallic micro-mesoporous molecular sieve prepared in this invention. Specifically, the following were included: The rapid pyrolysis reaction temperature was 600℃, and the reaction time was 10 s; the raw material mass ratio was M. MC M PS =1:1 and M 催化剂 M MCPS =5:1; For non-catalytic pyrolysis, weigh 0.1 mg of MCPS feedstock and place it in a sample cup; for catalytic pyrolysis, thoroughly mix 0.1 mg of MCPS feedstock with 0.5 mg of catalyst, and then place a sample weighing 0.6 mg in the sample cup. When the furnace temperature rapidly rises to the specified temperature, manually place the sample into the heating zone. The pyrolysis products are analyzed online by GC / MS (QP2010 Ultra, Shimadzu, Japan). The injection port temperature is set to 250℃, and chromatographic analysis is performed using an Rtx-5M capillary column. The carrier gas is helium (99.999%), the column flow rate is 1.27 mL / min, and the split ratio is 100:1. The initial furnace temperature is set to 50℃ and held for 5 min. Then the temperature is increased to 260℃ at a rate of 10℃ / min and held for 10 min. The GC / MS interface temperature and ion source temperature are 280℃ and 230℃, respectively. The mass spectrometry range was 35 ≤ m / z ≤ 500. Chromatographic peaks were identified by comparing spectra with those in the NIST11 and F-Search PY-1110E-181 spectral libraries, as well as with previous research data. This allowed for the determination of the content and variations of various products in non-catalytic pyrolysis and CCP.

[0050] Table 2 shows the hydrocarbon yields of microcrystalline cellulose and polystyrene (MCPS) under catalytic and non-catalytic pyrolysis conditions in the examples of this invention.

[0051] Table 2 Hydrocarbon yield under different conditions:

[0052] Table 2 shows the hydrocarbon yields of MCPS obtained under different conditions in this embodiment. Compared with the non-catalytic pyrolysis of MCPS, the hydrocarbon content in all catalytic pyrolysis products of MCPS increased significantly. Among them, the yield of aromatic hydrocarbons (Ahs) in the catalytic pyrolysis products of MCPS prepared by the bimetallic micro-mesoporous composite molecular sieve of this invention increased significantly, indicating that it has good selectivity for aromatic hydrocarbons. The decrease in hydrocarbon yield of 1Fe-3Zn HZSM-5 / MCM-41 and 3Fe-1Zn HZSM-5 / MCM-41 may be due to the small pore size caused by the filling of Zn and Fe, which affects the catalytic reaction. Compared with the single metal Fe catalyst, the yield of monocyclic aromatic hydrocarbons (MAHs) of 1Fe-3ZnHZSM-5 / MCM-41 is improved, showing the potential of bimetallic synergy. However, when the ratio of Fe to Zn is not right, its catalytic activity may be lower than that of the single metal Zn catalyst.

[0053] As shown in Table 2, the AHs and MAHs contents in the products reached their highest levels during the rapid catalytic pyrolysis of 2Fe-2Zn HZSM-5 / MCM-41 and MCPS, with an AHs increase of 22.2%, which is significantly better than other catalysts. Furthermore, it exhibits the best selectivity for MAHs. Therefore, when the mass ratio of Zn to Fe is 2:2, the bimetallic composite molecular sieve shows a significant synergistic effect and is suitable for the rapid catalytic pyrolysis of MCPS, thereby optimizing the composition of the fuel oil in the pyrolysis products.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for co-pyrolyzing microcrystalline cellulose and polystyrene using a bimetallic micro-mesoporous composite molecular sieve, characterized in that... A bimetallic micro-mesoporous molecular sieve catalyst, designated Zn-Fe HZSM-5 / MCM-41, was prepared by loading zinc and iron active metals onto the HZSM-5 / MCM-41 micro-mesoporous composite molecular sieve as a support. The catalyst was used to catalyze the co-pyrolysis of microcrystalline cellulose and polystyrene to prepare bio-oil rich in aromatic hydrocarbons.

2. The method according to claim 1, characterized in that, The catalyst includes the following preparation steps: (1) Preparation of HZSM-5 / MCM-41 micro-mesoporous composite molecular sieve support: ZSM-5 molecular sieve was pretreated with alkaline phase, and hexadecyltrimethylammonium bromide template agent was added and mixed. Then, hydrothermal treatment was carried out, followed by a first calcination, then ammonium chloride solution ion exchange and a second calcination to obtain HZSM-5 / MCM-41 micro-mesoporous composite molecular sieve support; (2) Weigh the zinc salt and iron salt and dissolve them in deionized water to prepare a metal salt solution; add the HZSM-5 / MCM-41 micro-mesoporous composite molecular sieve support to the metal salt solution for impregnation, dry and calcine the impregnated product, load the zinc salt and iron salt onto the composite molecular sieve support prepared in step (a) to obtain the bimetallic micro-mesoporous composite molecular sieve catalyst; wherein the mass ratio of Zn to Fe is 1~3: 1~3.

3. The method according to claim 2, characterized in that, The conditions for alkaline pretreatment in step (1) are: using a sodium hydroxide solution with a concentration of 1.0-2.0 mol / L, and heating in a water bath at 40°C for 1.0 hour; the conditions for hydrothermal treatment are: the digestion temperature and crystallization temperature are both 110°C, and the digestion time and crystallization time are both 24 hours; and before crystallization, the pH value is adjusted to 8.0-9.

0.

4. The method according to claim 2, characterized in that, The temperature of the first roasting in step (1) is 500~600℃, the temperature of the second roasting is 500~600℃, and the temperature of the final roasting in step (2) is 500~600℃.

5. The method according to claim 1, characterized in that, The zinc salt and iron salt are selected from one or more of their respective nitrates, sulfates or chlorides; the total loading of the Zn and Fe bimetals is 1% to 15% of the total mass of the catalyst.

6. The method according to claim 5, characterized in that, The total loading of the Zn and Fe bimetals is 10%.

7. The method according to claim 2, characterized in that, The mass ratio of Zn to Fe is 2:2.

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