Preparation method of alkali treatment-ytterbium ion exchange ZSM-5 molecular sieve catalyst and application of alkali treatment-ytterbium ion exchange ZSM-5 molecular sieve catalyst in preparation of phenol by dealkylation of biomass derived alkylphenols

Abstract

The invention relates to the technical field of molecular sieve catalysts, in particular to a preparation method of an alkali treatment-ytterbium ion exchange ZSM-5 molecular sieve catalyst and application of the alkali treatment-ytterbium ion exchange ZSM-5 molecular sieve catalyst in preparation of phenol by dealkylation of biomass derived alkylphenols. According to the method disclosed by the invention, a stepped preparation route of constructing graded pores by virtue of sodium hydroxide / tetrapropylammonium hydroxide synergistic alkali treatment, recovering hydrogen type by virtue of three times of ammonium chloride exchange, and regulating acid by virtue of ytterbium ion exchange is adopted, so that the clearness of the process steps and the accurate control of parameters are realized; a micro-mesoporous hierarchical structure is formed through alkali treatment, so that the mass transfer efficiency is remarkably improved; according to the present invention, the Brnsted / Lewis acid site ratio regulation and control is performed by using the ytterbium ion exchange to form the Lewis acid enrichment surface so as to provide the structure basis for the efficient catalysis, and the uniform process parameters are set at the key nodes such as 550 DEG C calcination and 80 DEG C stirring in the preparation process so as to ensure the batch stability and the feasibility of the amplification implementation;

Description

Technical Field

[0001] This invention relates to the field of molecular sieve catalyst technology, specifically to a method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst and its application in the dealkylation of biomass-derived alkylphenols to produce phenol. Background Technology

[0002] Fossil resources have long served as a vital source of raw materials and energy for human chemical production, but their non-renewable nature and the resulting resource and environmental pressures are becoming increasingly prominent. Biomass, as the only renewable organic carbon resource, boasts advantages such as abundant reserves, wide availability, and sustainable utilization, making it a crucial raw material for replacing some fossil resources in the production of high-value-added chemicals. Lignin, being the only component in natural biomass rich in aromatic structural units, is therefore considered an important renewable resource for the preparation of phenols and other aromatic chemicals, holding significant research importance and application prospects in the field of high-value utilization of biomass.

[0003] Lignin can be transformed into a series of monophenolic compounds through depolymerization, hydrodeoxygenation, and other processes, among which alkylphenols are a relatively important class of intermediate products. Lignin-derived alkylphenols, represented by 4-n-propylphenol, can be further processed through dealkylation reactions to produce phenol and other basic aromatic chemicals. Phenol is an important basic organic chemical raw material, widely used in resins, plastics, synthetic fibers, pharmaceuticals, pesticides, and coatings. Currently, industrial phenol production still mainly relies on fossil resources. Therefore, using lignin-derived alkylphenols as substrates for dealkylation to produce phenol provides an attractive technical route for the green production of phenol and is also an important research direction for the targeted conversion and high-value utilization of lignin.

[0004] Currently, research on the dealkylation of alkylphenols has involved various catalytic systems, including basic oxides, fluorine-modified solid acids, amorphous silicon-aluminum materials, and zeolite molecular sieves. Milnes et al. [J. Appl. Chem. Biotechnol., 1971, 21: 287-296] were among the first to conduct research on alkylphenol dealkylation. Yoshikawa et al. [Catalysis Today, 2020, 347: 110-114], Huang et al. [ACS Catalysis, 2018, 8: 11184-11190], and Zhang et al. [Chinese Journal of Catalysis, 2018, 39: 1445-1452] have also studied the dealkylation conversion of phenols from different catalytic systems. Compared with other catalytic materials, zeolite molecular sieves, due to their regular pore structure, high specific surface area, and abundant acidic sites, show good application potential in the dealkylation of alkylphenols.

[0005] Among various acidic zeolites, ZSM-5 zeolite, due to its MFI topology, suitable pore size, and good thermal and hydrothermal stability, exhibits excellent catalytic activity and phenol selectivity in the dealkylation reaction of alkylphenols, thus becoming one of the most studied catalytic materials in this type of reaction. Verboekend et al. [GreenChemistry, 2016, 18: 297-306] showed that acidic zeolites can catalyze the dealkylation of alkylphenols to produce phenol and lower-carbon olefins; Liao et al. [ACSCatalysis, 2018, 8: 7861-7878] further systematically compared the performance of different acidic zeolites in the dealkylation of 4-n-propylphenol, indicating that ZSM-5 has a better balance between activity, selectivity, and form selectivity.

[0006] Although ZSM-5 exhibits good catalytic performance in alkylphenol dealkylation, traditional microporous ZSM-5 still suffers from problems such as significant diffusion restriction, easy retention of reaction intermediates and products inside the pores, and easy carbon deposition and deactivation, thereby reducing the accessibility of acidic sites and affecting catalyst activity and stability. To address these issues, previous studies have attempted to construct hierarchical ZSM-5 through alkali treatment or desilication to shorten the diffusion path and reduce pore blockage. Liao et al. [ACSSustainableChemistry&Engineering, 2020, 8: 8713-8722] reported that hierarchical ZSM-5 can effectively improve product diffusion and enhance catalyst stability, while also pointing out that increasing the density and strength of Lewis acid sites helps to further improve dealkylation performance. In addition to pore structure regulation, the distribution of acidic sites, especially the synergistic effect of Brønsted acid sites and Lewis acid sites, is also considered a key factor affecting the activity and selectivity of alkylphenol dealkylation. Studies by Du et al. [Chinese Journal of Catalysis, 2013, 34: 1599-1607] have shown that rare earth cation exchange can replace H+ ions at Brønsted acid sites, thereby inhibiting dehydroxylation under high-temperature conditions, reducing skeletal aluminum loss, and improving the hydrothermal stability of zeolites. Wang et al. [Journal of Rare Earths, 2007, 25: 321-328] pointed out that the introduction of metal cations can increase the number of acid sites, acid strength, and the ratio of Lewis acids to Brønsted acids. Therefore, while hierarchical pore modification can improve mass transfer, it may not simultaneously achieve synergistic optimization of the type, number, and strength of acid sites. Furthermore, the reaction microenvironment, especially the presence of water, also significantly affects the dealkylation behavior of alkylphenols. Verboekend et al. [GreenChemistry, 2016, 18: 297-306] found that introducing an appropriate amount of water into the reaction feed can significantly improve the stability of ZSM-5 in the dealkylation of alkylphenols and inhibit coke formation. Bocus et al. [ACSCatalysis, 2022, 12: 14227-14242] further pointed out through theoretical research that the presence of water helps to promote the competitive adsorption of water and phenol and form water-mediated hydrogen bond chains, thereby shortening the residence time of phenolic compounds in the zeolite channels and inhibiting condensation coke formation. It can be seen that the dealkylation reaction of alkylphenols is not only affected by the pore structure, but also closely related to the distribution of acidic sites and the reaction microenvironment.

[0007] However, existing ZSM-5 catalytic systems still have some shortcomings. First, traditional microporous ZSM-5 still suffers from significant diffusion limitations, easily leading to the retention of reaction intermediates and products within the pores, resulting in coking and deactivation. Second, while simply constructing a hierarchical pore structure can improve mass transfer, it may not simultaneously achieve synergistic optimization of the type, quantity, and strength of acid sites. For alkylphenol dealkylation reactions, the distribution and synergistic effect of Brønsted and Lewis acid sites directly influence C–C bond breaking, phenol desorption, and side reactions. Therefore, how to further regulate the distribution of acid sites while maintaining the ZSM-5 framework structure, especially enhancing the Lewis acid effect which is beneficial to dealkylation reactions, remains a problem that needs to be solved by existing technologies. On the other hand, rare earth ion exchange can regulate the acid type, acid strength, and acid site distribution on the molecular sieve surface, showing potential for improving dealkylation activity and selectivity. However, in the existing technology, there are still few studies on the synergistic use of alkali treatment to construct hierarchical pores loaded with rare earth ion exchange to regulate acidity for the continuous gas-phase dealkylation of 4-n-propylphenol to phenol. In particular, there is a lack of systematic technical solutions that use Yb as the acid-regulating center and take into account diffusion performance, acid regulation and regeneration stability.

[0008] Therefore, it is necessary to develop a modified ZSM-5 catalyst with both hierarchical pore structure and optimized acid site distribution for the efficient dealkylation of lignin-derived 4-n-propylphenol to phenol, which has significant research value and application prospects. If hierarchical channels can be constructed through alkali treatment, and further combined with rare earth ion exchange to regulate the Brønsted / Lewis acid site distribution, it is expected to simultaneously solve problems such as limited mass transfer, coking deactivation, and insufficient phenol yield, thus providing a new technical solution for the green preparation of phenol from biomass sources. Summary of the Invention

[0009] Technical problems to be solved To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst and its application in the dealkylation of biomass-derived alkylphenols to phenol, which can effectively solve the problems of limited mass transfer, coking and deactivation, and insufficient phenol yield in existing technologies.

[0010] Technical solution To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst, comprising the following preparation method: S1. Pretreatment of ZSM-5-P molecular sieve yields pretreated ZSM-5-P molecular sieve. S2. The pretreated ZSM-5-P molecular sieve is subjected to alkali treatment to construct hierarchical pores, and the resulting ZSM-5 molecular sieve with hierarchical pores is denoted as hierarchical pore ZSM-5 molecular sieve. S3. The hierarchical ZSM-5 molecular sieve in S2 is subjected to ammonium chloride ion exchange and calcination to restore the hydrogen form. The result is denoted as hydrogen form hierarchical molecular sieve ZSM-5-4. S4. The hydrogen-type hierarchical porous molecular sieve ZSM-5-4 is modified by ytterbium ion exchange to obtain the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst.

[0011] Furthermore, the preprocessing method in S1 is as follows: The ZSM-5-P molecular sieve was calcined in air at 550℃ for 5.5 hours to obtain the pretreated ZSM-5-P molecular sieve.

[0012] Furthermore, the method for constructing hierarchical pores using alkali treatment in S2 is as follows: S2.1. Prepare an alkaline solution with a total hydroxyl concentration of 0.2 mol / L by mixing sodium hydroxide solution and tetrapropylammonium hydroxide solution; S2.2 Weigh 3~6g of pretreated ZSM-5-P molecular sieve and pour it into 90~180mL of alkaline solution. Stir at 80℃ for 4h and immediately transfer to ice water for quenching. After centrifugation to separate the solid components, wash with deionized water until neutral. Then dry at 60℃ for 12h and finally calcine at 550℃ in air atmosphere for 5.5h. The result is hierarchical pore ZSM-5 molecular sieve.

[0013] Furthermore, the method for ammonium chloride ion exchange and calcination to restore the hydrogen form in S3 is as follows: The hierarchical porous ZSM-5 molecular sieve in S2 was immersed in 90-180 mL of 0.5 mol / L ammonium chloride solution and ion exchange was carried out at 80 °C and 300 r / min. After each exchange, the sieve was separated and exchanged again. After three ion exchange-washing cycles, the sieve was calcined at 550 °C in air for 5.5 h to obtain the hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

[0014] Furthermore, the method for ytterbium ion exchange modification treatment in S4 is as follows: 1-2 g of hydrogen-type hierarchical porous molecular sieve ZSM-5-4 and a calculated amount of ytterbium nitrate pentahydrate were added to 15-30 mL of deionized water and mixed. After stirring at room temperature for 24 h, the mixture was dried at 80 °C for 12 h and finally calcined at 550 °C in air for 5.5 h. The resulting product is the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst (i.e., yYb / ZSM-5-4, preferably y=1, meaning that the weight of ytterbium accounts for 1% of the total weight of hydrogen-type hierarchical porous molecular sieve ZSM-5-4, i.e., 1Yb / ZSM-5-4). The weight of ytterbium accounts for 0.52-13.0% of the total weight of hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

[0015] Comparative catalyst preparation: Using the same method as above, lanthanum or cerium ion-exchanged 1La / ZSM-5-4 and 1Ce / ZSM-5-4 can be further prepared as comparative samples.

[0016] An application of an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst prepared according to the aforementioned method in the dealkylation of biomass-derived alkylphenols to phenol, wherein the method of application is as follows: 0.5 g of alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst with a mesh size of 40-80 mesh was placed in the middle section (15-17 cm) of a reactor with a length of 30 cm and an inner diameter of 1 cm. After being fixed with quartz wool, nitrogen gas was introduced at a flow rate of 15 mL / min. A mixture of 4-n-propylphenol and water from biomass-derived alkylphenols was fed into the reactor at a molar ratio of 1:6 by a high-pressure injection pump at a feed flow rate of 0.017-0.050 mL / min. The preheating section of the fixed-bed reactor was maintained at 453 K, and the reaction section was maintained at 573-673 K for the dealkylation reaction.

[0017] Under optimized process conditions, 1Yb / ZSM-5-4 exhibits the best performance in the dealkylation reaction of 4-n-propylphenol: at 623 K, the phenol yield can reach 63.35%; after increasing the temperature to 673 K, the phenol yield can reach up to 80.35%, and the phenol selectivity can reach 96.86%. Stability tests show that the catalyst maintains high activity after continuous operation for 48 h, and its activity can be significantly restored after regeneration by calcination in air at 550 °C for 5.5 h, indicating that it has good regenerability.

[0018] Catalyst structure and mechanism of action: After alkali treatment, the molecular sieve ZSM-5-P transforms from a single microporous structure to a hierarchical micro-mesoporous structure, significantly increasing the total specific surface area, mesoporous surface area, and pore volume. While maintaining the MFI topology, it improves substrate and product diffusion. Following ytterbium ion exchange, the proportion of Lewis acids on the catalyst surface increases, while the Brønsted / Lewis acid ratio decreases. The Lewis acid sites enhance the adsorption and polarization of 4-n-propylphenol, promoting the breaking of the Caryl–C (sp3) bond between the aromatic ring side chain and the benzene ring, thereby improving the dealkylation reaction activity. DFT calculations show that 1Yb / ZSM-5-4 has a higher adsorption energy for 4-n-propylphenol and exhibits a more favorable bond breaking barrier change.

[0019] Beneficial effects Compared with known public technologies, the technical solution provided by this invention has the following beneficial effects: 1. This invention achieves clear process steps and precise parameter control through a step-by-step preparation route of "sodium hydroxide / tetrapropylammonium hydroxide synergistic alkali treatment to construct hierarchical pores - ammonium chloride three-stage exchange to restore hydrogen form - ytterbium ion exchange to adjust acidity". This route not only retains the MFI topology of zeolite molecular sieves, but also forms a micro-mesoporous hierarchical structure through alkali treatment, which significantly improves mass transfer efficiency. Combined with the ytterbium ion exchange to regulate the ratio of Brønsted / Lewis acid sites, a Lewis acid-enriched surface is formed, providing a structural basis for efficient catalysis. The preparation process sets uniform process parameters at key nodes such as calcination at 550℃ and stirring at 80℃ to ensure batch stability and the feasibility of scale-up implementation.

[0020] 2. In the gas-phase dealkylation reaction of 4-n-propylphenol to phenol, the catalyst prepared in this invention exhibits significant performance advantages over unexchanged or lanthanum / cerium exchanged samples. Specifically, under preheating at 453 K and reaction temperature range of 573-673 K, the phenol yield reaches a maximum of 80.35% and the selectivity reaches 96.86% through the synergistic control of nitrogen carrier gas at 15 mL / min, water-to-substrate molar ratio of 1:6, and feed flow rate of 0.017-0.050 mL / min. This performance improvement is due to the promotion of substrate diffusion by the hierarchical pore structure and the directional enhancement of Lewis acid sites by ytterbium exchange, which synergistically optimize the catalytic cycle of substrate adsorption-bond breaking-product desorption.

[0021] 3. The catalyst in this invention maintains high activity during a continuous 48-hour fixed-bed reaction. After deactivation, it can be regenerated by air calcination at 550°C, meeting the requirements of continuous industrial production. This stability is due to both the structural preservation of the MFI framework during alkali treatment and the stabilizing effect of Yb ion exchange on acid sites, forming a closed-loop process adaptability of "catalysis-deactivation-regeneration".

[0022] 4. The entire process from preparation to application in this invention embodies the precise design of process parameters. At the preparation end, the hierarchical pore structure is precisely controlled by parameters such as 0.2 mol / L total hydroxyl concentration alkaline solution, 3-6 g catalyst dosage, and 90-180 mL solution volume. At the application end, the characteristics of the continuous fixed-bed reactor are matched by parameters such as 40-80 mesh catalyst particle size, 453 K preheating temperature, and 573-673 K reaction range, forming an integrated process condition optimization system for "preparation-application".

[0023] In summary, this invention achieves efficient, stable, and renewable application of catalysts in the dealkylation of biomass-derived alkylphenols to phenol through four-dimensional innovation in preparation process, structural regulation, performance optimization, and process adaptation, demonstrating significant technological advancement and industrial application value. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0025] Figure 1 The XRD patterns of ZSM-5-P zeolite before and after modification according to the present invention are shown below. Figure 2 Nitrogen adsorption-desorption isotherms of catalysts treated under different conditions according to the present invention; Figure 3 The diagram shows the pore size distribution of the catalysts treated under different conditions according to the present invention. Figure 4 The following are pyridine infrared spectral characterization diagrams of different catalysts of the present invention; Figure 5 The diagram shows the stability and regeneration performance of the 1Yb / ZSM-5-4 catalyst of this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] The present invention will be further described below with reference to embodiments.

[0028] Example 1 This embodiment describes a method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst, comprising the following preparation method: S1. Pretreatment of ZSM-5-P molecular sieve yields pretreated ZSM-5-P molecular sieve. S2. The pretreated ZSM-5-P molecular sieve is subjected to alkali treatment to construct hierarchical pores, and the resulting ZSM-5 molecular sieve with hierarchical pores is denoted as hierarchical pore ZSM-5 molecular sieve. S3. The hierarchical ZSM-5 molecular sieve in S2 is subjected to ammonium chloride ion exchange and calcination to restore the hydrogen form. The result is denoted as hydrogen form hierarchical molecular sieve ZSM-5-4. S4. The hydrogen-type hierarchical porous molecular sieve ZSM-5-4 is modified by ytterbium ion exchange to obtain the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst.

[0029] Furthermore, the preprocessing method in S1 is as follows: The ZSM-5-P molecular sieve was calcined in air at 550℃ for 5.5 hours to obtain the pretreated ZSM-5-P molecular sieve.

[0030] Furthermore, the method for constructing hierarchical pores using alkali treatment in S2 is as follows: S2.1. Prepare an alkaline solution with a total hydroxyl concentration of 0.2 mol / L by mixing sodium hydroxide solution and tetrapropylammonium hydroxide solution; S2.2 Weigh 3g of pretreated ZSM-5-P molecular sieve and pour it into 90mL of alkaline solution. Stir at 80℃ for 4h and immediately transfer to ice water for quenching. After centrifugation to separate the solid components, wash with deionized water until neutral. Then dry at 60℃ for 12h and finally calcine at 550℃ in air atmosphere for 5.5h. The result is hierarchical pore ZSM-5 molecular sieve.

[0031] Furthermore, the method for ammonium chloride ion exchange and calcination to restore the hydrogen form in S3 is as follows: The hierarchical porous ZSM-5 molecular sieve in S2 was immersed in 90 mL of 0.5 mol / L ammonium chloride solution and ion exchange was carried out at 80 °C and 300 r / min. After each exchange, the sieve was separated and exchanged again. After three ion exchange-washing cycles, the sieve was calcined at 550 °C in air for 5.5 h to obtain the hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

[0032] Furthermore, the method for ytterbium ion exchange modification treatment in S4 is as follows: 1g of hydrogen-type hierarchical molecular sieve ZSM-5-4 and a calculated amount of ytterbium nitrate pentahydrate were added to 15mL of deionized water and mixed. The mixture was stirred at room temperature for 24h, dried at 80℃ for 12h, and finally calcined at 550℃ in air for 5.5h. The resulting product is the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst (i.e., yYb / ZSM-5-4, preferably y=1, i.e., 1Yb / ZSM-5-4), wherein the weight of ytterbium accounts for 0.52% of the total weight of hydrogen-type hierarchical molecular sieve ZSM-5-4.

[0033] Comparative catalyst preparation: Using the same method as above, lanthanum or cerium ion-exchanged 1La / ZSM-5-4 and 1Ce / ZSM-5-4 can be further prepared as comparative samples.

[0034] An application of an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst prepared according to a method for preparing such catalysts in the dealkylation of biomass-derived alkylphenols to phenol, wherein the method of application is as follows: 0.5 g of alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst with a mesh size of 40 mesh was placed in the middle section (15 cm) of a reactor with a length of 30 cm and an inner diameter of 1 cm. After being fixed with quartz wool, nitrogen gas was introduced at a flow rate of 15 mL / min. A mixture of 4-n-propylphenol and water from biomass-derived alkylphenols was fed into the reactor at a molar ratio of 1:6 by a high-pressure injection pump at a feed flow rate of 0.017 mL / min. The preheating section of the fixed-bed reactor was maintained at 453 K, and the reaction section was maintained at 573 K for the dealkylation reaction.

[0035] Example 2 This embodiment describes a method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst, comprising the following preparation method: S1. Pretreatment of ZSM-5-P molecular sieve yields pretreated ZSM-5-P molecular sieve. S2. The pretreated ZSM-5-P molecular sieve is subjected to alkali treatment to construct hierarchical pores, and the resulting ZSM-5 molecular sieve with hierarchical pores is denoted as hierarchical pore ZSM-5 molecular sieve. S3. The hierarchical ZSM-5 molecular sieve in S2 is subjected to ammonium chloride ion exchange and calcination to restore the hydrogen form. The result is denoted as hydrogen form hierarchical molecular sieve ZSM-5-4. S4. The hydrogen-type hierarchical porous molecular sieve ZSM-5-4 is modified by ytterbium ion exchange to obtain the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst.

[0036] Furthermore, the preprocessing method in S1 is as follows: The ZSM-5-P molecular sieve was calcined in air at 550℃ for 5.5 hours to obtain the pretreated ZSM-5-P molecular sieve.

[0037] Furthermore, the method for constructing hierarchical pores using alkali treatment in S2 is as follows: S2.1. Prepare an alkaline solution with a total hydroxyl concentration of 0.2 mol / L by mixing sodium hydroxide solution and tetrapropylammonium hydroxide solution; S2.2 Weigh 6g of pretreated ZSM-5-P molecular sieve and pour it into 180mL of alkaline solution. Stir at 80℃ for 4h and immediately transfer to ice water for quenching. After centrifugation to separate the solid components, wash with deionized water until neutral. Then dry at 60℃ for 12h and finally calcine at 550℃ in air atmosphere for 5.5h. The result is hierarchical pore ZSM-5 molecular sieve.

[0038] Furthermore, the method for ammonium chloride ion exchange and calcination to restore the hydrogen form in S3 is as follows: The hierarchical porous ZSM-5 molecular sieve in S2 was immersed in 180 mL of 0.5 mol / L ammonium chloride solution and ion exchange was carried out at 80 °C and 300 r / min. After each exchange, the sieve was separated and exchanged again. After three ion exchange-washing cycles, the sieve was calcined at 550 °C in air for 5.5 h to obtain the hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

[0039] Furthermore, the method for ytterbium ion exchange modification treatment in S4 is as follows: 2g of hydrogen-type hierarchical porous molecular sieve ZSM-5-4 and a calculated amount of ytterbium nitrate pentahydrate were added to 30mL of deionized water and mixed. After stirring at room temperature for 24h, the mixture was dried at 80℃ for 12h and finally calcined at 550℃ in air for 5.5h. The resulting product is the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst, in which the weight of ytterbium accounts for 13.0% of the total weight of hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

[0040] Comparative catalyst preparation: Using the same method as above, lanthanum or cerium ion-exchanged 1La / ZSM-5-4 and 1Ce / ZSM-5-4 can be further prepared as comparative samples.

[0041] An application of an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst prepared according to a method for preparing such catalysts in the dealkylation of biomass-derived alkylphenols to phenol, wherein the method of application is as follows: 0.5 g of 80-mesh alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst was placed in the middle section (17 cm) of a reactor with a length of 30 cm and an inner diameter of 1 cm. After being fixed with quartz wool, nitrogen gas was introduced at a flow rate of 15 mL / min. A mixture of 4-n-propylphenol and water from biomass-derived alkylphenols was fed into the reactor at a molar ratio of 1:6 by a high-pressure injection pump at a feed flow rate of 0.050 mL / min. The preheating section of the fixed-bed reactor was maintained at 453 K, and the reaction section was maintained at 673 K for the dealkylation reaction.

[0042] Example 3 This embodiment describes a method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst, comprising the following preparation method: S1. Pretreatment of ZSM-5-P molecular sieve yields pretreated ZSM-5-P molecular sieve. S2. The pretreated ZSM-5-P molecular sieve is subjected to alkali treatment to construct hierarchical pores, and the resulting ZSM-5 molecular sieve with hierarchical pores is denoted as hierarchical pore ZSM-5 molecular sieve. S3. The hierarchical ZSM-5 molecular sieve in S2 is subjected to ammonium chloride ion exchange and calcination to restore the hydrogen form. The result is denoted as hydrogen form hierarchical molecular sieve ZSM-5-4. S4. The hydrogen-type hierarchical porous molecular sieve ZSM-5-4 is modified by ytterbium ion exchange to obtain the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst.

[0043] Furthermore, the preprocessing method in S1 is as follows: The ZSM-5-P molecular sieve was calcined in air at 550℃ for 5.5 hours to obtain the pretreated ZSM-5-P molecular sieve.

[0044] Furthermore, the method for constructing hierarchical pores using alkali treatment in S2 is as follows: S2.1. Prepare an alkaline solution with a total hydroxyl concentration of 0.2 mol / L by mixing sodium hydroxide solution and tetrapropylammonium hydroxide solution; S2.2 Weigh 5g of pretreated ZSM-5-P molecular sieve and pour it into 150mL of alkaline solution. Stir at 80℃ for 4h and immediately transfer to ice water for quenching. After centrifugation to separate the solid components, wash with deionized water until neutral. Then dry at 60℃ for 12h and finally calcine at 550℃ in air atmosphere for 5.5h. The result is hierarchical pore ZSM-5 molecular sieve.

[0045] Furthermore, the method for ammonium chloride ion exchange and calcination to restore the hydrogen form in S3 is as follows: The hierarchical porous ZSM-5 molecular sieve in S2 was immersed in 150 mL of 0.5 mol / L ammonium chloride solution and ion exchange was carried out at 80 °C and 300 r / min. After each exchange, the sieve was separated and exchanged again. After three ion exchange-washing cycles, the sieve was calcined at 550 °C in air for 5.5 h to obtain the hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

[0046] Furthermore, the method for ytterbium ion exchange modification treatment in S4 is as follows: 2g of hydrogen-type hierarchical porous molecular sieve ZSM-5-4 and a calculated amount of ytterbium nitrate pentahydrate were added to 30mL of deionized water and mixed. After stirring at room temperature for 24h, the mixture was dried at 80℃ for 12h and finally calcined at 550℃ in air for 5.5h. The resulting product is the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst, in which the weight of ytterbium accounts for 6.0% of the total weight of hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

[0047] Comparative catalyst preparation: Using the same method as above, lanthanum or cerium ion-exchanged 1La / ZSM-5-4 and 1Ce / ZSM-5-4 can be further prepared as comparative samples.

[0048] An application of an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst prepared according to a method for preparing such catalysts in the dealkylation of biomass-derived alkylphenols to phenol, wherein the method of application is as follows: 0.5 g of 50-mesh alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst was placed in the middle section (16 cm) of a reactor with a length of 30 cm and an inner diameter of 1 cm. After being fixed with quartz wool, nitrogen gas was introduced at a flow rate of 15 mL / min. A mixture of 4-n-propylphenol and water from biomass-derived alkylphenols was fed into the reactor at a molar ratio of 1:6 by a high-pressure injection pump at a feed flow rate of 0.030 mL / min. The preheating section of the fixed-bed reactor was maintained at 453 K, and the reaction section was maintained at 623 K for the dealkylation reaction.

[0049] Performance testing 1. The structural characteristics of the catalyst were analyzed by alkali treatment and different Yb ion exchange effects, and the data obtained are recorded in Table 1. 2. The density and properties of acidic sites of different Yb ion exchange catalysts were analyzed, and the data obtained are recorded in Table 2; 3. The dealkylation of 4-n-propylphenol to phenol was tested under different catalysts and reaction conditions, and the data obtained are recorded in Table 3; Table 1. Structural characteristics analysis of catalysts treated with alkali and with different Yb ion exchange pairs. catalyst <![CDATA[S total (m 2 / g)]]> <![CDATA[S micro (m 2 / g)]]> <![CDATA[S meso (m 2 / g)]]> <![CDATA[V total (cm 3 / g)]]> <![CDATA[V micro (cm 3 / g)]]> <![CDATA[V meso (cm 3 / g)]]> ZSM-5-P 331.20 199.02 132.18 0.191 0.107 0.084 ZSM-5-4 440.01 200.21 239.79 0.452 0.107 0.345 0.2Yb / ZSM-5-4 433.88 187.31 246.57 0.453 0.100 0.353 1Yb / ZSM-5-4 415.29 183.01 232.29 0.445 0.098 0.347 1.8Yb / ZSM-5-4 407.13 174.71 232.42 0.425 0.093 0.332 5Yb / ZSM-5-4 323.12 144.48 178.64 0.338 0.077 0.261 Table 2. Acidic site density and properties of the Yb / ZSM-5 catalyst. catalyst B / L WA (μmol / g) SA (μmol / g) TA (μmol / g) ZSM-5-P 0.66 52.34 519.33 571.67 ZSM-5-4 0.58 413.00 163.35 576.35 0.2Yb / ZSM-5-4 0.73 318.54 270.45 588.99 1Yb / ZSM-5-4 0.38 317.82 298.13 615.95 1.8Yb / ZSM-5-4 0.48 312.95 288.79 601.74 5Yb / ZSM-5-4 0.49 309.04 275.92 584.96 Table 3 Performance of 4-n-propylphenol dealkylation to phenol under different catalysts and reaction conditions Group Catalyst / Variable Temperature / °C Water-oil ratio <![CDATA[WHSV / h -1 ]]> Phenol yield / % Phenol selectivity / % Different metals ZSM-5-4 350 6 4.4 35.04 95.32 Different metals 1La / ZSM-5-4 350 6 4.4 33.70 92.63 Different metals 1Ce / ZSM-5-4 350 6 4.4 31.20 92.98 Different metals 1Yb / ZSM-5-4 350 6 4.4 63.35 97.33 Yb load ZSM-5-P 350 6 4.4 21.21 99.06 Yb load 0Yb / ZSM-5-4 350 6 4.4 35.04 99.05 Yb load 0.2Yb / ZSM-5-4 350 6 4.4 17.65 99.08 Yb load 0.5Yb / ZSM-5-4 350 6 4.4 21.47 99.08 Yb load 0.8Yb / ZSM-5-4 350 6 4.4 29.48 99.06 Yb load 1.0Yb / ZSM-5-4 350 6 4.4 63.35 99.03 Yb load 1.2Yb / ZSM-5-4 350 6 4.4 54.02 99.05 Yb load 1.5Yb / ZSM-5-4 350 6 4.4 52.55 99.05 Yb load 1.8Yb / ZSM-5-4 350 6 4.4 52.46 99.02 Yb load 2.6Yb / ZSM-5-4 350 6 4.4 41.56 99.03 Yb load 5.0Yb / ZSM-5-4 350 6 4.4 37.29 99.03 Yb load 10Yb / ZSM-5-4 350 6 4.4 35.65 99.11 Water-oil ratio 0 350 0 4.4 26.73 85.66 Water-oil ratio 2 350 2 4.4 51.96 88.87 Water-oil ratio 4 350 4 4.4 56.30 90.66 Water-oil ratio 6 350 6 4.4 64.75 92.71 Water-oil ratio 8 350 8 4.4 64.16 92.79 Water-oil ratio 10 350 10 4.4 65.09 93.29 reaction temperature 1Yb / ZSM-5-4 300 6 4.4 21.57 83.26 reaction temperature 1Yb / ZSM-5-4 325 6 4.4 46.60 89.35 reaction temperature 1Yb / ZSM-5-4 350 6 4.4 63.35 94.96 reaction temperature 1Yb / ZSM-5-4 375 6 4.4 74.53 94.83 reaction temperature 1Yb / ZSM-5-4 400 6 4.4 80.35 96.86 WHSV 1Yb / ZSM-5-4 350 6 2.0 67.12 93.85 WHSV 1Yb / ZSM-5-4 350 6 3.2 63.68 93.08 WHSV 1Yb / ZSM-5-4 350 6 4.4 62.90 93.05 WHSV 1Yb / ZSM-5-4 350 6 5.2 56.50 95.27 WHSV 1Yb / ZSM-5-4 350 6 6.0 47.79 90.82 Note: a) Conditions for investigating different metals and Yb loadings: T=350℃, H2O / 4-n-PP=6:1, WHSV=4.4h -1 .

[0050] b) Water-oil ratio test conditions: catalyst 1Yb / ZSM-5-4, T=350℃, WHSV=4.4h -1 .

[0051] c) Temperature conditions for the test: catalyst was 1Yb / ZSM-5-4, H2O / 4-n-PP ratio was 6:1, and WHSV was 4.4 h. -1 .

[0052] d) WHSV testing conditions: catalyst is 1Yb / ZSM-5-4, T=350℃, H2O / 4-n-PP=6:1.

[0053] 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 will 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 preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst, characterized in that, The preparation method includes: S1. Pretreatment of ZSM-5-P molecular sieve yields pretreated ZSM-5-P molecular sieve. S2. The pretreated ZSM-5-P molecular sieve is subjected to alkali treatment to construct hierarchical pores, and the resulting ZSM-5 molecular sieve with hierarchical pores is denoted as hierarchical pore ZSM-5 molecular sieve. S3. The hierarchical ZSM-5 molecular sieve in S2 is subjected to ammonium chloride ion exchange and calcination to restore the hydrogen form. The result is denoted as hydrogen form hierarchical molecular sieve ZSM-5-4. S4. The hydrogen-type hierarchical porous molecular sieve ZSM-5-4 is modified by ytterbium ion exchange to obtain the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst.

2. The method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst according to claim 1, characterized in that, The preprocessing method in S1 is as follows: The ZSM-5-P molecular sieve was calcined in air at 550℃ for 5.5 hours to obtain the pretreated ZSM-5-P molecular sieve.

3. The method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst according to claim 1, characterized in that, The method for constructing a hierarchical pore structure using alkali treatment in S2 is as follows: S2.

1. Prepare an alkaline solution with a total hydroxyl concentration of 0.2 mol / L by mixing sodium hydroxide solution and tetrapropylammonium hydroxide solution; S2.2 Weigh 3~6g of pretreated ZSM-5-P molecular sieve and pour it into 90~180mL of alkaline solution. Stir at 80℃ for 4h and immediately transfer to ice water for quenching. After centrifugation to separate the solid components, wash with deionized water until neutral. Then dry at 60℃ for 12h and finally calcine at 550℃ in air atmosphere for 5.5h. The result is hierarchical pore ZSM-5 molecular sieve.

4. The method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst according to claim 1, characterized in that, The method for ammonium chloride ion exchange and calcination to restore the hydrogen form in S3 is as follows: The hierarchical porous ZSM-5 molecular sieve in S2 was immersed in 90-180 mL of 0.5 mol / L ammonium chloride solution and ion exchange was carried out at 80 °C and 300 r / min. After each exchange, the sieve was separated and exchanged again. After three ion exchange-washing cycles, the sieve was calcined at 550 °C in air for 5.5 h to obtain the hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

5. The method for preparing an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst according to claim 1, characterized in that, The method for ytterbium ion exchange modification in S4 is as follows: 1-2 g of hydrogen-type hierarchical porous molecular sieve ZSM-5-4 and a calculated amount of ytterbium nitrate pentahydrate were added to 15-30 mL of deionized water and mixed. After stirring at room temperature for 24 h, the mixture was dried at 80 °C for 12 h and finally calcined at 550 °C in air for 5.5 h. The resulting product is the alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst, wherein the weight of ytterbium accounts for 0.52-13.0% of the total weight of hydrogen-type hierarchical porous molecular sieve ZSM-5-4.

6. The application of an alkali-treated ytterbium ion-exchange ZSM-5 molecular sieve catalyst prepared according to any one of claims 1-5 in the dealkylation of biomass-derived alkylphenols to phenol, characterized in that, The method of application is as follows: 0.5 g of alkali-treated ytterbium ion exchange ZSM-5 molecular sieve catalyst with a mesh size of 40-80 mesh was placed in the middle section of the reactor. After being fixed with quartz wool, nitrogen gas was introduced at a flow rate of 15 mL / min. A mixture of 4-n-propylphenol and water from biomass-derived alkylphenols was fed into the reactor at a molar ratio of 1:6 by a high-pressure injection pump at a feed flow rate of 0.017-0.050 mL / min. The preheating section of the fixed-bed reactor was maintained at 453 K, and the reaction section was maintained at 573-673 K for the dealkylation reaction.

Images