Method for preparing p-hydroxycinnamate by catalyzing selective depolymerization of lignin through pillared smectite-loaded copper molybdate

Abstract

The invention discloses a method for preparing p-hydroxycinnamate by catalyzing selective depolymerization of lignin through pillared smectite loaded copper molybdate. The method comprises the following steps: adding a CuMoO / PILCS-x catalyst and an alcohol solvent into organic soluble lignin, reacting for 2-6 hours at the temperature of 130-170 DEG C under the N2 pressure of 0.1-2 MPa, and depolymerizing the lignin to obtain a volatile product mainly comprising p-hydroxycinnamate. According to the method disclosed by the invention, high-selectivity depolymerization of the lignin is realized, the high-added-value chemical p-hydroxycinnamate is obtained, and the purpose of high-value utilization of the lignin is realized. The catalyst used in the method is simple in preparation process and environmentally friendly, efficient conversion of lignin can be achieved in a short preparation period, and a high-selectivity p-hydroxyl cinnamate product is obtained.

Description

Technical Field

[0001] This invention relates to a technology for catalytic depolymerization of lignin to prepare high-value chemicals, and in particular to a method for selectively depolymerizing lignin to prepare p-hydroxycinnamate, belonging to the field of biomass resource utilization. Background Technology

[0002] With the rapid development of human civilization, the excessive consumption of fossil fuels has not only exacerbated the energy shortage problem but also intensified global climate change, causing a series of environmental problems. Therefore, finding and developing efficient renewable resources to replace fossil fuels is urgently needed. Lignocellulose, as a naturally abundant renewable carbon resource with rich reserves, is one of the best alternatives to fossil fuels and a key resource for sustainable bioeconomic development. Its efficient conversion and utilization will effectively achieve synergistic value-added between matter and energy. The main components of lignocellulose include cellulose, hemicellulose, and lignin. Lignin, as the most abundant natural phenolic polymer in the world, is composed of three basic structural units: p-coumarol, coniferyl alcohol, and sinapyl alcohol. The composition ratio of these three monomers varies significantly among lignin from different plant sources: softwood lignin is dominated by coniferyl alcohol (90-95%), while hardwood lignin exhibits a binary dominance of coniferyl alcohol (25-50%) and sinapyl alcohol (50-75%). Herbaceous plant lignin typically contains all three structural units. Lignin is a highly polymeric aromatic amorphous biomolecule formed by the random and disordered bonding of structural units through CO and C-C bonds. Its complex and highly cross-linked structure, containing abundant functional groups such as aliphatic hydroxyl, phenolic hydroxyl, and methoxy groups, gives lignin broad application potential in biomass conversion and materials science. p-Hydroxycinnamic acid (pCA) is an important phenolic acid compound involved in the biocomposition of lignocellulose, mainly comprising p-coumaric acid (pCA), ferulic acid (FA), sinapic acid (SA), and caffeic acid (CA), making lignin a potential source of various aromatic compounds. Given the structural similarity between p-coumaric acid (pCA) and methyl p-hydroxycinnamate (MPC), and the presence of pCA units in lignin (generally linked by ester bonds), lignin becomes the most promising raw material for the mass production of MPC. Designing effective depolymerization strategies to cleave ester bonds to release pCA units followed by esterification is a feasible approach to obtaining MPC from renewable resources.

[0003] Lignin, composed of three methoxyphenylpropene monomers linked by various chemical bonds, is an amorphous macromolecular polymer with a three-dimensional structure. Its complex structure and large molecular weight endow it with a certain resistance to depolymerization. Therefore, the rational design of catalysts to address the problems in lignin depolymerization is one of the key points for achieving efficient conversion. Molybdenum-based catalysts exhibit excellent activity for lignin depolymerization under an inert atmosphere. Meanwhile, montmorillonite clays possess high stability, high specific surface area, high cation exchange capacity, intercalation potential of active species, and reversible swelling properties, making them more suitable for reactions involving larger molecules and representing a novel type of catalyst material.

[0004] p-Methyl coumarate has the following structural formula: As an important derivative of p-hydroxycinnamic acid, it has a wide range of applications in industrial production. It can be used as an important raw material for the preparation of fragrances, pharmaceuticals, cosmetics, food and health products, and is also an intermediate for the synthesis of important drugs. In addition, it plays an important role in immune regulation, protecting the cardiovascular system and nerve cells, preventing and improving diabetes, inhibiting melanin formation and delaying skin aging. It is an aromatic compound with high added value.

[0005] Chinese invention patent CN111072477A discloses a method for preparing p-hydroxycinnamate by copper-catalyzed depolymerization of lignin. This method uses lignin as a raw material, small-molecule alcohols as a reaction medium, and copper metal salt as a catalyst. The reaction is carried out under an inert gas atmosphere of 0.1–2 MPa, at a reaction temperature of 135–175 °C, and for a reaction time of 2–6 h, selectively depolymerizing lignin into monophenolic compounds. Under optimal conditions, the yield of monophenols is 12.45 wt.%, the yield of methyl p-hydroxycinnamate is 9.02 wt.%, and the selectivity is 72.5%. This technology uses copper metal salt as a catalyst for depolymerizing lignin. However, this method suffers from several drawbacks. First, the yield of monophenols is relatively low. Second, as a homogeneous catalyst, copper metal salt presents challenges such as difficulty in separating the catalyst from the product and difficulty in recovering the catalyst itself.

[0006] Chinese invention patent CN107602383A discloses a method for preparing p-hydroxycinnamate by catalyzing the depolymerization of lignin using ionic liquids. The method involves mixing N-methylimidazolium and 1-chloroalkanes in appropriate proportions at room temperature for 12–24 h, then heating to 60–100 °C and continuing stirring for 24–36 h to obtain a mixture. The mixture is then washed with diethyl ether and vacuum dried to obtain an alkylimidazolium chloride. The alkylimidazolium chloride and a metal halide are then mixed at 30–50 °C in a 1:1–2:1 ratio for 3–6 h, followed by extraction with dichloromethane. The resulting solution is then evaporated to remove the solvent and vacuum dried at 60–80 °C for 12–24 h to obtain a halide metal salt ionic liquid [C]. n[min][MCl4]. 5 mmol of a halogen metal salt ionic liquid was mixed with 1 g of organosoluble lignin, and 25 mL of ethanol was added as a solvent. After three N2 displacement reactions, the mixture was heated to 200 °C and reacted at 500 r / min for 4 h to obtain a reaction solution. 150 mL of deionized water was added to the reaction solution, filtered, and the liquid phase was evaporated to dryness. Water was added, and the solution was transferred to a separatory funnel and extracted with ethyl acetate to obtain the biochemical. Under optimal reaction conditions, a conversion rate of 72%, a yield of volatile products of 12 wt.%, and a yield of p-hydroxycinnamate of 7.8 wt.% were obtained. This technology uses an ionic liquid as a catalyst to catalyze the depolymerization of lignin. The yield of p-hydroxycinnamate is relatively low. Furthermore, this technology suffers from problems such as the need for one to two days of stirring and dispersion of chloroalkanes as raw materials, and the slow process of forming alkylimidazolium chloride from the mixture of 1-chloroalkanes and N-methylimidazolium, requiring stirring and reaction at a certain temperature for two to three days. These issues increase the cost of the process due to the long catalyst preparation cycle, the presence of halogens in the reaction process, and the difficulty in separating and processing the products and ionic liquid catalyst dissolved in the solvent. Summary of the Invention

[0007] The purpose of this invention is to provide a method for the efficient catalytic depolymerization of lignin to prepare p-hydroxycinnamate, which is simple to prepare, easy to recover and separate, has a short preparation cycle, and is low in cost. The method achieves a lignin conversion rate of up to 34.06-72.16%, a total yield of volatile products of 10.97-23.23 wt.%, a p-hydroxycinnamate yield of 5.15-16.98 wt.%, and a selectivity of 46.95-82.16%.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for selectively depolymerizing lignin to prepare p-hydroxycinnamate using copper molybdate supported by pillared montmorillonite: CuMoO / PILCS-x catalyst and an alcohol solvent are added to organic lignin, and the mixture is reacted at 0.1–2 MPa N2 pressure and 130–170 °C for 2–6 h to depolymerize the lignin and obtain volatile products mainly composed of p-hydroxycinnamate. The CuMoO / PILCS-x catalyst consists of a montmorillonite support and a copper molybdate composite metal oxyacid salt as the active component. The montmorillonite support is a layered aluminosilicate mineral, and x represents the molar ratio of silicon to aluminum in the support, ranging from 2 to 6. The loading amounts of molybdenum and copper as active components are 5–25 wt.% and 14–30 wt.%, respectively.

[0010] To further achieve the objective of this invention, preferably, the preparation method of the CuMoO / PILCS-x catalyst is as follows: deionized water and sodium silicate are stirred and mixed evenly; deionized water, aluminum nitrate nonahydrate, and sodium hydroxide are stirred and mixed evenly, and gradually heated to 90-120°C at room temperature, stirred and kept at this temperature for 0.5-1 h to obtain a PILCS-x slurry; copper acetate monohydrate and urea are mixed with the PILCS-x slurry, and stirred and kept at 90-120°C for 10-12 h, filtered to obtain a filter cake, washed and dried to obtain Cu / PILCS-x solid; ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added to the catalyst. 24 The CuMoO / PILCS-x catalyst was obtained by dissolving CuMoO (·4H2O) in deionized water, adding Cu / PILCS-x support, stirring until homogeneous, letting stand for 10–12 h, drying, and calcining in air at 400–900 °C.

[0011] Preferably, the mass ratio of ammonium molybdate tetrahydrate, sodium silicate, aluminum nitrate nonahydrate, sodium hydroxide, urea, and copper acetate monohydrate is 0.27~2.15:1.68~12:5~14:1:20:4~14.

[0012] Preferably, the uniform mixing of deionized water and sodium silicate involves mixing 80 parts by weight of deionized water with 3.24 to 4.17 parts by weight of sodium silicate; the uniform mixing of deionized water with aluminum nitrate nonahydrate and sodium hydroxide involves mixing 100 parts by weight of deionized water with 2.14 to 4.98 parts by weight of aluminum nitrate nonahydrate and 0.3 to 0.4 parts by weight of sodium hydroxide.

[0013] Preferably, the time for mixing the deionized water and sodium silicate evenly is 0.5 to 1 h; the time for mixing the deionized water, aluminum nitrate nonahydrate, and sodium hydroxide evenly is 0.5 to 1 h.

[0014] Preferably, the filter cake is washed 2-3 times with deionized water; the filter cake is dried by placing the washed filter cake in an oven at 80-120°C.

[0015] Preferably, the mass ratio of lignin to CuMoO / PILCS-x catalyst is 1:0.2~1, and the mass ratio of lignin to alcohol solvent is 1:10~1:20.

[0016] Preferably, the alcohol solvent is any one of methanol, ethanol, n-propanol, and n-butanol.

[0017] Preferably, the organosoluble lignin is extracted by the following method: lignin raw material and extract are added to a reaction vessel, reacted at 100-120℃ for 2-6 h, and then filtered and separated; the filtrate is added to deionized water and filtered to obtain a solid, which is then dried to obtain organosoluble lignin; by mass fraction, the extract is composed of 20-25 parts concentrated sulfuric acid, 3000-4000 parts anhydrous ethanol, and 800-1000 parts deionized water, and 120-150 parts extract are added to 10-15 parts lignin raw material.

[0018] Preferably, the lignin raw material is derived from bagasse, bamboo, or corn stalks.

[0019] The present invention has the following advantages and beneficial effects compared with the prior art:

[0020] (1) This invention addresses the problems of low lignin conversion rate, low yield of products such as p-hydroxycinnamates, and difficulty in separating and recovering catalysts. By modifying montmorillonite clay, a montmorillonite catalyst with abundant acid and basic sites and a large number of mesopores is prepared, which can catalyze the depolymerization of lignin to selectively prepare p-hydroxycinnamates.

[0021] (2) The pillar-supported copper molybdate catalyst used in this invention not only has an adjustable specific surface area, pore size, and malleable interlayer channels, but also possesses excellent catalytic activity. Moreover, the preparation process of this catalyst is simple, has a short cycle, and uses a natural mineral substrate, resulting in low cost and greater environmental friendliness. The reaction conditions for lignin depolymerization are mild. A high yield of p-hydroxycinnamate can be obtained at a reaction pressure of 0.1~2 MPa and a reaction temperature of 130~170℃, achieving efficient and selective depolymerization of lignin under mild conditions.

[0022] (3) The catalyst used in this invention can efficiently catalyze the depolymerization of lignin, while exhibiting high selectivity for p-hydroxycinnamates. The conversion rate of lignin in this method can reach a maximum of 34.06–72.16%, the total yield of volatile products is 10.97–23.23 wt.%, the yield of p-hydroxycinnamates is 5.15–16.98 wt.%, and the selectivity is 46.95–82.16%. The catalyst used in this invention can efficiently catalyze the depolymerization of lignin, while exhibiting high selectivity for p-hydroxycinnamate products. The high selectivity of the catalyst for these high-value-added chemicals not only helps reduce the occurrence of side reactions but also reduces the difficulty of separating the target product. Attached Figure Description

[0023] Figure 1 The XRD patterns of Cu / PILCS-4 and PILCS-4 support in Example 1 of this invention are shown.

[0024] Figure 2 The N2 physical adsorption-desorption isotherm of Cu / PILCS in Example 1 of this invention is shown.

[0025] Figure 3 This is a pore size distribution curve of Cu / PILCS in Example 1 of the present invention.

[0026] Figure 4 The N2 physical adsorption-desorption isotherm of CuMoO / PILCS-x in Example 1 of this invention.

[0027] Figure 5 This is a pore size distribution curve of CuMoO / PILCS-x in Example 1 of the present invention.

[0028] Figure 6 The image shows the XRD pattern of CuMoO / PILCS-x in Example 1 of this invention.

[0029] Figure 7 This is the SEM image of CuMoO / PILCS-x in Example 1 of the present invention.

[0030] Figure 8 This is the GC-MS spectrum of the product obtained by CuMoO / PILCS-x catalytic depolymerization of organosoluble lignin in Example 8 of the present invention.

[0031] Figure 9 The images show the FT-IR spectra of regenerated lignin and native lignin recovered from the CuMoO / PILCS-x catalytic depolymerization reaction of organosoluble lignin in Example 8 of this invention. Detailed Implementation

[0032] To better understand the present invention, the invention will be further described below with reference to the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto.

[0033] This invention achieves highly efficient depolymerization of lignin by effectively controlling the pore size and acidity / alkalinity of the catalyst by modifying the sodium silicate and aluminum nitrate nonahydrate used in the catalyst support preparation process. The CuMoO / PILCS-x combined molybdenum-based catalyst exhibits excellent activity in lignin depolymerization under an inert atmosphere. Simultaneously, the high stability, high specific surface area, and intercalation potential of montmorillonite clay allow active molybdenum metal species to be intercalated within the montmorillonite clay, thus controlling its structure and making it more suitable for reactions involving larger molecules. This is a novel catalyst material. The present invention provides a method for the selective depolymerization of lignin to prepare p-hydroxycinnamate, using lignin as a raw material. After adding CuMoO / PILCS-x catalyst and an alcohol solvent to the raw material, the reaction is carried out at a N2 pressure of 0.1–2 MPa and a temperature of 130–170°C for 2–6 h, depolymerizing the lignin to obtain volatile products.

[0034] The core feature of this invention is the use of pillar-supported montmorillonite-supported copper molybdate catalyst, expressed as CuMoO / PILCS-x, composed of the support PILCS-x and molybdenum and copper metals. The molybdenum metal loading is 5-25 wt.% of the total catalyst mass, and x represents the molar ratio of silicon to aluminum in the Cu / PILCS-x support, ranging from 2 to 6. The preparation of this CuMoO / PILCS-x is simple, has a short cycle time, and a wide controllable range. Ammonium molybdate tetrahydrate ((NH4)6Mo7O) is used. 24 The Cu / PILCS-x slurry is prepared by dissolving 4H2O in deionized water, adding the carrier Cu / PILCS-x, stirring until homogeneous, allowing to stand for 10–12 h, drying, and calcining in air at 400–900 °C. In this preparation method, Cu / PILCS-x is obtained by referring to relevant technical measures. 1.68–3.92 parts by mass of copper acetate monohydrate and 7–8 parts by mass of urea are added to a white PILCS-x slurry. The slurry is kept at 90–120 °C for 10–12 h. After filtration, a blue filter cake is obtained. The light blue solid obtained after washing and drying is Cu / PILCS-x. In this preparation method, PILCS-x is obtained by referring to relevant technical measures. 80 parts of deionized water are weighed into a beaker, and 3.65~4.17 parts of sodium silicate are added and stirred thoroughly for 0.5~1 h. 100 parts of deionized water are weighed into a beaker, and 2.14~4.98 parts of aluminum nitrate nonahydrate and 0.3~0.4 parts of sodium hydroxide are added and stirred for 0.5~1 h until uniform. The mixture is then gradually heated to 90~120℃ at room temperature, stirred and kept at this temperature for 0.5~1 h to obtain a white PILCS-x slurry.

[0035] In this invention, small-molecule alcohol solvents can effectively dissolve organosoluble lignin and promote the breaking of CO bonds in lignin, participating in esterification and substitution. Importantly, the CuMoO / PILCS-x catalyst of this invention consists of a support PILCS-x and an active component, a copper molybdate composite metal oxoacid salt, wherein the molybdenum metal loading is 5-25 wt.% of the total catalyst mass, and x represents the molar ratio of silicon to aluminum in the Cu / PILCS-x support, ranging from 2 to 6. This catalyst possesses abundant acid-base sites and a suitable mesoporous structure. The synergistic effect between these two elements enhances the ability to break the bonds connecting the basic structural units of lignin. Simultaneously, the suitable pore structure facilitates mass transfer during the catalytic depolymerization process and the shape selection of the target product, thereby promoting the selective depolymerization of lignin to obtain p-hydroxycinnamate products. The present invention discloses a method for selectively depolymerizing lignin to prepare p-hydroxycinnamate, which uses lignin as raw material, adds CuMoO / PILCS-x catalyst and alcohol solvent to the raw material, and reacts at N2 pressure of 0.1~2 MPa and 130~170℃ for 2~6 h to depolymerize lignin and obtain volatile products.

[0036] Preferably, the alcohol solvent can be any one of methanol, ethanol, n-propanol, and n-butanol; the lignin can be any one of bagasse, corn stalks, rice straw, poplar wood, and bamboo; the mass ratio of lignin to CuMoO / PILCS-x catalyst is 1:0.2~1, and the mass ratio of lignin to alcohol solvent is 1:10~1:20.

[0037] The lignin extraction method of this invention is basically the same as that disclosed in the prior art. Specifically, the lignin raw material and the extract are added to a reaction vessel by mass fraction and reacted at 100-120°C for 2-6 hours, followed by filtration and separation. The obtained filtrate is added to deionized water and filtered to obtain a solid, which is then dried to obtain organosoluble lignin. The extract is composed of concentrated sulfuric acid, anhydrous ethanol, and deionized water. The mass concentration of the concentrated sulfuric acid is 95-98%, and 3200-4000 parts of anhydrous ethanol and 800-1000 parts of deionized water are added to every 24-25 parts of concentrated sulfuric acid. 120-150 parts of the extract are added to every 10-15 parts of lignin raw material.

[0038] Example 1: Cu 22 Mo 20 Preparation of O / PILCS-4 catalyst

[0039] Cu 22 Mo 20 The O / PILCS-4 catalyst is achieved through a three-step process:

[0040] (1) The preparation method of carrier PILCS-4 is as follows: 80 mL of deionized water is weighed into a beaker, and 3.86 g of sodium silicate is weighed and stirred thoroughly for 0.5 h; 100 mL of deionized water is weighed into a beaker, 3.10 g of aluminum nitrate nonahydrate and 0.372 g of sodium hydroxide are added and stirred for 0.5 h until uniform. The mixture is then gradually heated to 90-120℃ at room temperature, stirred and kept warm for 0.5 h to obtain white PILCS-4 slurry.

[0041] The prepared PILCS-4 support was characterized by X-ray diffraction to investigate its crystal structure. The results are as follows: Figure 1 As shown, the prepared PILCS-4 support has the typical structural characteristics of montmorillonite group minerals. The peak structure in the X-ray diffraction pattern indicates that the PILCS-4 support is an amorphous crystalline phase. Obvious diffraction peaks of montmorillonite group minerals appear at 2θ = 5.1°, 8.4°, 20.9°, 35.0° and 71.1°, which belong to the (001), (002), (101), (107) and (308) crystal planes of montmorillonite group minerals. Among them, (001) is the characteristic diffraction peak of soapstone, indicating that the preparation process has successfully synthesized soapstone support.

[0042] (2) Cu 22 Preparation method of PILCS-4: Weigh 1.68–3.92 g of copper acetate monohydrate and 7.48 g of urea and add them to a white PILCS-4 slurry. Keep the slurry at 90–120 °C for 12 h. After filtration, a blue filter cake is obtained. Wash and dry the light blue solid obtained, which is Cu. 22 / PILCS-4.

[0043] For the prepared Cu 22 The pore structure of the PILCS-4 catalyst support was characterized by N2 physical adsorption-desorption. Figure 2 and Figure 3 As shown. By Figure 2 It can be seen that Cu 22 The adsorption-desorption isotherms of the PILCS-4 catalyst support are typical type IV isotherms and type H4 hysteresis loops, combined with the pore size distribution diagram. Figure 3 It can be seen that Cu 22 The pore size of / PILCS-4 is mainly mesoporous with a small number of micropores, which facilitates the mass transfer process of lignin macromolecules. Figure 2 It can be seen that Cu 22 The adsorption capacity of the PILCS-4 catalyst support significantly increases in the low-pressure region (P / P0 < 0.1), indicating a strong interaction between the support and nitrogen. This suggests a strong adsorption potential due to the microporous structure of the support. Figure 3The pore size distribution diagram confirms the presence of a partial microporous structure in the carrier; a significant hysteresis loop appears in the relative pressure range of P / P0 = 0.5 to 1.0, indicating that Cu... 22 The PILCS-4 catalyst support contains a mesoporous structure. Figure 3 It can be seen that Cu 22 The PILCS-4 catalyst support has a wide pore size distribution, with micropores concentrated around 2 nm and mesopores ranging from 2 to 33 nm. 22 The total specific surface area of ​​the PILCS-4 catalyst support is 253 m². 2 ·g -1 .

[0044] For the prepared Cu 22 X-ray diffraction was performed on the / PILCS-4 support to investigate its crystal structure, and the results are as follows: Figure 1 As shown, distinct diffraction peaks of montmorillonite group minerals were retained at 2θ = 5.1°, 8.4°, 20.9°, 35.0°, and 71.1°, and characteristic diffraction peaks at 2θ = 16.8°, 23.8°, 34.1°, 35.9°, 38.1°, 39.8°, 47.0°, and 53.3° were also observed, belonging to Cu(OH)₂. XRD results indicate that copper ions were introduced into the interlayer of montmorillonite under alkaline conditions via in-situ deposition. After drying, the copper ions in the interlayer intercalation were mainly in the form of Cu(OH)₂, indicating successful copper ion insertion.

[0045] (3) Cu 22 Mo 20 The preparation method of O / PILCS-4 is as follows: 1.5 mL of deionized water is taken, and 0.6 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added. 24 ·4H2O), stir to fully dissolve in deionized water, add carrier Cu 22 After mixing PILCS-4 thoroughly, let it stand for 10–12 hours, dry it, and calcine it in air at 400–900°C to obtain Cu. 22 Mo 20 O / PILCS-4 catalyst solid.

[0046] For the prepared Cu 22 Mo 20 The O / PILCS-4 catalyst was characterized by N2 physisorption-desorption to investigate its pore structure. Results are as follows: Figure 4 and Figure 5 As shown. By Figure 4 It can be seen that Cu 22 Mo 20The adsorption-desorption isotherms of the O / PILCS-4 catalyst are typical type IV isotherms and type H4 hysteresis loops, combined with the pore size distribution diagram. Figure 2 It can be seen that Cu 22 Mo 20 The O / PILCS-4 catalyst has a predominantly mesoporous pore structure with a small number of micropores, which facilitates the mass transfer process of lignin macromolecules. Figure 4 It can be seen that Cu 22 Mo 20 The O / PILCS-4 catalyst exhibits a significant increase in adsorption capacity in the low-pressure region (P / P0 < 0.1), indicating a strong interaction between the support and nitrogen. This is attributed to the strong adsorption potential created by the microporous structure of the support. Figure 5 The pore size distribution diagram confirms the presence of a partial microporous structure in the carrier; a significant hysteresis loop appears in the relative pressure range of P / P0 = 0.7–1.0, indicating that Cu 22 Mo 20 The O / PILCS-4 catalyst exhibits a mesoporous structure. Figure 5 It can be seen that Cu 22 Mo 20 The O / PILCS-4 catalyst exhibits a wide pore size distribution, with micropores concentrated around 1.8 nm and mesopores ranging from 2 to 50 nm. This indicates that during the impregnation process, Cu... 22 In PILCS-4, reversible expansion of the interlayer in ammonium molybdate aqueous solution facilitated the entry of molybdenum metal ions into the interlayer. The copper molybdate composite metal oxyacid salt formed during calcination acted as a pillar within PILCS-4, resulting in a partially macroporous structure. Figure 5 It can be seen that during the calcination process, the portion of the carrier pores occupied by the copper molybdate composite metal oxyacid salt in PILCS-4 and the octahedral sheets of the carrier partially collapsed at high temperatures, resulting in a decrease in specific surface area. However, the microporous structure was basically preserved, and the mesoporous structure showed a concentrated distribution around 14 nm. This indicates that the introduction of molybdenum metal oxide has a positive effect on Cu 22 The structure of / PILCS-4 plays a role in pore size regulation; by adjusting the loading of molybdenum metal, the pore size of the catalyst can be controlled to some extent. 22 Mo 20 The total specific surface area of ​​the O / PILCS-4 catalyst is 71 m². 2 ·g -1 The specific surface area of ​​the micropores is 1 m². 2 ·g -1 The external specific surface area is 70 m². 2 ·g -1 .

[0047] For the prepared Cu 22Mo 20 X-ray diffraction was performed on the O / PILCS-4 support to investigate its crystal structure. The results are as follows: Figure 6 As shown, strong diffraction peaks appeared at 2θ = 9.5°, 15.8°, 19.4°, 22.3°, 23.1°, 23.8°, 24.8°, 26.4°, 26.8°, 27.0°, 34.5°, and 54.1°, which were attributed to the (100), (101), (110), (-102), (0-12), (201), (111), (-202), (-120), (1-21), (-1-22), and (2-41) crystal planes of CuMoO4. This indicates that the copper and molybdenum ions introduced into the interlayer formed copper molybdate composite metal oxyacid salts after calcination, playing the role of active species.

[0048] For the prepared Cu 22 Mo 20 The O / PILCS-4 catalyst was characterized by SEM to investigate its surface morphology. The results are as follows: Figure 7 As shown, a three-dimensional structure formed by the accumulation of nanoparticles can be clearly observed, and columnar metal oxides can also be observed in the pores, which act as pillars. This structure has high stability on the one hand, and is conducive to controlling the pore size of the catalyst on the other hand, which helps to expose more active sites and reduce the resistance to mass transfer, so that the catalyst exhibits high catalytic activity.

[0049] Example 2: Cu 22 Mo 20 Preparation of O / PILCS-2 catalyst

[0050] Cu 22 Mo 20 The O / PILCS-2 catalyst is achieved through a three-step process:

[0051] (1) The preparation method of carrier PILCS-2 is as follows: 80 mL of deionized water is weighed into a beaker, and 3.24 g of sodium silicate is weighed and stirred thoroughly for 0.5 h; 100 mL of deionized water is weighed into a beaker, 4.98 g of aluminum nitrate nonahydrate and 0.372 g of sodium hydroxide are added and stirred for 0.5 h until uniform. The mixture is then gradually heated to 90-120℃ at room temperature, stirred and kept warm for 0.5 h to obtain white PILCS-2 slurry.

[0052] (2) Cu 22The preparation method of PILCS-2 is as follows: Weigh 1.68–3.92 g of copper acetate monohydrate and 7.48 g of urea and add them to a white PILCS-4 slurry. Keep the slurry at 90–120 °C for 12 h. After filtering the slurry, a blue filter cake is obtained. Wash and dry the light blue solid obtained, which is Cu. 22 / PILCS-2.

[0053] (3) Cu 22 Mo 20 The preparation method of O / PILCS-2 is as follows: 1.5 mL of deionized water is taken, and 0.6 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added. 24 ·4H2O), stir to fully dissolve in deionized water, add carrier Cu 22 After mixing PILCS-2 thoroughly, let it stand for 10–12 hours, dry it, and calcine it in air at 400–900°C to obtain Cu. 22 Mo 20 O / PILCS-2 catalyst solid.

[0054] Example 3: Cu 22 Mo 20 Preparation of O / PILCS-6 catalyst

[0055] Cu 22 Mo 20 The O / PILCS-6 catalyst is achieved through a three-step process:

[0056] (1) The preparation method of carrier PILCS-6 is as follows: 80 mL of deionized water is weighed into a beaker, and 4.17 g of sodium silicate is weighed and stirred thoroughly for 0.5 h; 100 mL of deionized water is weighed into a beaker, 2.14 g of aluminum nitrate nonahydrate and 0.372 g of sodium hydroxide are added and stirred for 0.5 h until uniform. The mixture is then gradually heated to 90-120℃ at room temperature, stirred and kept warm for 0.5 h to obtain white PILCS-6 slurry.

[0057] (2) Cu 22 The preparation method of PILCS-6 is as follows: 1.68–3.92 g of copper acetate monohydrate and 7.48 g of urea are weighed and added to a white PILCS-6 slurry. The mixture is kept at 90–120°C for 12 h. After filtration, a blue filter cake is obtained. The light blue solid obtained after washing and drying is Cu. 22 / PILCS-6.

[0058] (3) Cu 22 Mo 20The preparation method of O / PILCS-6 is as follows: 1.5 mL of deionized water is taken, and 0.6 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added. 24 ·4H2O), stir to fully dissolve in deionized water, add carrier Cu 22 After mixing PILCS-6 thoroughly, let it stand for 10–12 hours, dry it, and calcine it in air at 400–900°C to obtain Cu. 22 Mo 20 O / PILCS-6 catalyst solid.

[0059] Example 4: Cu 14 Mo 20 Preparation of O / PILCS-4 catalyst

[0060] Cu 14 Mo 20 The O / PILCS-4 catalyst is achieved through a three-step process:

[0061] (1) The preparation method of carrier PILCS-4 is as follows: 80 mL of deionized water is weighed into a beaker, and 3.86 g of sodium silicate is weighed and stirred thoroughly for 0.5 h; 100 mL of deionized water is weighed into a beaker, 3.10 g of aluminum nitrate nonahydrate and 0.372 g of sodium hydroxide are added and stirred for 0.5 h until uniform. The mixture is then gradually heated to 90-120℃ at room temperature, stirred and kept warm for 0.5 h to obtain white PILCS-4 slurry.

[0062] (2) Cu 14 The preparation method of PILCS-4 is as follows: 1.68 g of copper acetate monohydrate and 7.48 g of urea are weighed and added to the obtained white PILCS-4 slurry. The mixture is kept at 90-120℃ for 12 h. After filtration, a blue filter cake is obtained. The light blue solid obtained after washing and drying is Cu. 14 / PILCS-4.

[0063] (3) Cu 14 Mo 20 The preparation method of O / PILCS-4 is as follows: 1.5 mL of deionized water is taken, and 0.6 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added. 24 ·4H2O), stir to fully dissolve in deionized water, add carrier Cu 14 After mixing PILCS-4 thoroughly, let it stand for 10–12 hours, dry it, and calcine it in air at 400–900°C to obtain Cu. 14 Mo 20 O / PILCS-4 catalyst solid.

[0064] Example 5: Cu26 Mo 20 Preparation of O / PILCS-4 catalyst

[0065] Cu 26 Mo 20 The O / PILCS-4 catalyst is achieved through a three-step process:

[0066] (1) The preparation method of carrier PILCS-4 is as follows: 80 mL of deionized water is weighed into a beaker, and 3.86 g of sodium silicate is weighed and stirred thoroughly for 0.5 h; 100 mL of deionized water is weighed into a beaker, 3.10 g of aluminum nitrate nonahydrate and 0.372 g of sodium hydroxide are added and stirred for 0.5 h until uniform. The mixture is then gradually heated to 90-120℃ at room temperature, stirred and kept warm for 0.5 h to obtain white PILCS-4 slurry.

[0067] (2) Cu 26 The preparation method of PILCS-4 is as follows: 3.36 g of copper acetate monohydrate and 7.48 g of urea are weighed and added to the obtained white PILCS-4 slurry. The mixture is kept at 90-120℃ for 12 h. After filtration, a blue filter cake is obtained. The light blue solid obtained after washing and drying is Cu. 26 / PILCS-4.

[0068] (3) Cu 26 Mo 20 The preparation method of O / PILCS-4 is as follows: 1.5 mL of deionized water is taken, and 0.6 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added. 24 ·4H2O), stir to fully dissolve in deionized water, add carrier Cu 20 After mixing PILCS-4 thoroughly, let it stand for 10–12 hours, dry it, and calcine it in air at 400–900°C to obtain Cu. 26 Mo 20 O / PILCS-4 catalyst solid.

[0069] Example 6: Cu 22 Preparation of Mo5O / PILCS-4 catalyst

[0070] Cu 20 The Mo5O / PILCS-4 catalyst was obtained through a three-step method:

[0071] (1) The preparation method of carrier PILCS-4 is as follows: 80 mL of deionized water is weighed into a beaker, and 3.86 g of sodium silicate is weighed and stirred thoroughly for 0.5 h; 100 mL of deionized water is weighed into a beaker, 3.10 g of aluminum nitrate nonahydrate and 0.372 g of sodium hydroxide are added and stirred for 0.5 h until uniform. The mixture is then gradually heated to 90-120℃ at room temperature, stirred and kept warm for 0.5 h to obtain white PILCS-4 slurry.

[0072] (2) Cu 22 The preparation method of PILCS-4 is as follows: 2.80 g of copper acetate monohydrate and 7.48 g of urea are weighed and added to the obtained white PILCS-4 slurry. The mixture is kept at 90-120℃ for 12 h. After filtration, a blue filter cake is obtained. The light blue solid obtained after washing and drying is Cu. 22 / PILCS-4.

[0073] (3) Cu 22 The preparation method of Mo5O / PILCS-4 is as follows: 1.5 mL of deionized water is taken, and 0.1 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added. 24 ·4H2O), stir to fully dissolve in deionized water, add carrier Cu 20 After mixing PILCS-4 thoroughly, let it stand for 10–12 hours, dry it, and calcine it in air at 400–900°C to obtain Cu. 22 Mo5O / PILCS-4 catalyst solid.

[0074] Example 7: Cu 22 Mo 25 Preparation of O / PILCS-4 catalyst

[0075] Cu 22 Mo 25 The O / PILCS-4 catalyst is achieved through a three-step process:

[0076] (1) The preparation method of carrier PILCS-4 is as follows: 80 mL of deionized water is weighed into a beaker, and 3.86 g of sodium silicate is weighed and stirred thoroughly for 0.5 h; 100 mL of deionized water is weighed into a beaker, 3.10 g of aluminum nitrate nonahydrate and 0.372 g of sodium hydroxide are added and stirred for 0.5 h until uniform. The mixture is then gradually heated to 90-120℃ at room temperature, stirred and kept warm for 0.5 h to obtain white PILCS-4 slurry.

[0077] (2) Cu 22The preparation method of PILCS-4 is as follows: 2.80 g of copper acetate monohydrate and 7.48 g of urea are weighed and added to the resulting white PILCS-4 slurry. The mixture is kept at 90–120 °C for 12 h. After filtration, a blue filter cake is obtained. The light blue solid obtained after washing and drying is Cu. 22 / PILCS-4.

[0078] (3) Cu 22 Mo 25 The preparation method of O / PILCS-4 is as follows: 1.5 mL of deionized water is taken, and 0.8 g of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is added. 24 ·4H2O), stir to fully dissolve in deionized water, add carrier Cu 20 After mixing PILCS-4 thoroughly, let it stand for 10–12 hours, dry it, and calcine it in air at 400–900°C to obtain Cu. 22 Mo 25 O / PILCS-4 catalyst solid.

[0079] Example 8: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0080] Lignin extraction: Weigh 10.0 g of sugarcane bagasse raw material and 120 mL of extract, add them to a 250 mL hydrothermal reactor, and react in an oven at 110℃ for 4 h. After cooling to room temperature, filter and wash with ethanol, collect the filtrate and washings, add 500 mL of deionized water to precipitate lignin. Filter through a 0.22 μm filter membrane, air dry in a fume hood, and grind into powder to obtain organosoluble sugarcane bagasse lignin. The extract consists of 24 g of 98% concentrated sulfuric acid, 3200 mL of anhydrous ethanol, and 800 mL of deionized water.

[0081] Catalytic depolymerization of lignin: 100 mg of extracted organic-soluble bagasse lignin and 100 mg of Cu were weighed sequentially. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reactor. The reactor was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID. The reaction solution was filtered to obtain a filtrate, and deionized water was added to a final volume of 200 mL. The mixture was allowed to stand for approximately 24 h to precipitate unreacted lignin. After filtration and drying, regenerated lignin was obtained.

[0082] Gas chromatography-mass spectrometry (GC-MS) was used (HP-INNOWAX column: 30 m × 0.25 mm × 0.25 μm, column flow rate 2 mL·min). -1 The split ratio is 4:1. The heating program is: 50℃ held for 1 min, then increased by 10℃ per minute. -1 The product was qualitatively analyzed and quantitatively calculated by heating at a rate of 280℃ and holding for 20 min. The GC-FID results of the product are as follows: Figure 8 As shown in Table 1.

[0083] Table 1. GC-MS Analysis of Volatile Products

[0084] Calculation results show that in Cu 22 Mo 20 Under the action of O / PILCS-4 catalyst, the conversion rate of lignin reached 62.35%, the total yield of volatile products was 23.23%, and the yield and selectivity of hydroxycinnamate products were 16.98% and 73.03%, respectively.

[0085] Unreacted lignin was collected to obtain regenerated lignin. Infrared spectroscopy was used to characterize both primary and regenerated lignin to study the structural changes of lignin before and after the catalytic depolymerization reaction. The FT-IR results of lignin are shown below. Figure 9 As shown, 3436 cm -1 Belongs to the stretching vibration of OH; 2920, 2850 cm -1 These correspond to the stretching vibrations of CH in methyl and methylene groups, and the stretching vibration of CO in methoxy groups, respectively; 1718 cm⁻¹ -1 Attributable to stretching vibrations of C=O in non-conjugated ketones, carbonyl groups, and ester groups; 1331 and 1126 cm⁻¹ −1 The absorption peaks at 1596, 1508, 1424, and 834 cm⁻¹ correspond to the stretching vibrations of CO in the lilac unit (S) and CH in the benzene ring, respectively. −1 The absorption peaks at 1271 and 1231 cm⁻¹ should be attributed to the stretching vibrations of the aromatic core benzene ring structure; −1 The peak at this location belongs to the guaiac-based unit (G); 1166 cm⁻¹ −1 This corresponds to the stretching vibration at C=O in the P-CA structure. (From...) Figure 8 It can be seen that lignin retains its main molecular structure after catalytic depolymerization, exhibiting a molecular structure of 3436 cm⁻¹. -1 The OH stretching vibration peaks at 2920 and 2850 cm⁻¹ are also observed. -1 The CH stretching vibrations of the methyl and methylene groups, as well as the C=O absorption peaks in the methoxy group, did not show significant changes. However... Figure 8It also shows 1166 cm. -1 The infrared absorption peak belonging to the PCA structure almost completely disappeared, indicating that the pCA structural units were broken down during the lignin depolymerization process, which further confirms the results of GC-MS product analysis.

[0086] Example 9: Cu 22 Mo 20 O / PILCS-2 catalyzes lignin depolymerization

[0087] The difference between this embodiment and embodiment 8 is that:

[0088] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-2 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID.

[0089] The calculation results show that the conversion rate of lignin is 50.91%, the total yield of volatile products is 17.55%, and the yield and selectivity of hydroxycinnamate products are 13.69% and 77.97%, respectively.

[0090] Example 10: Cu 22 Mo 20 O / PILCS-6 catalyzes lignin depolymerization

[0091] The difference between this embodiment and embodiment 8 is that:

[0092] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-6 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0093] The calculation results show that the conversion rate of lignin is 54.76%, the total yield of volatile products is 19.85%, and the yield and selectivity of hydroxycinnamate products are 14.58% and 73.48%, respectively.

[0094] Example 11: Cu 14 Mo 20O / PILCS-4 catalyzes lignin depolymerization

[0095] The difference between this embodiment and embodiment 8 is that:

[0096] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 14 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0097] The calculation results show that the conversion rate of lignin is 60.47%, the total yield of volatile products is 20.20%, and the yield and selectivity of hydroxycinnamate products are 16.48% and 81.59%, respectively.

[0098] Example 12: Cu 26 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0099] The difference between this embodiment and embodiment 8 is that:

[0100] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 26 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0101] The calculation results show that the conversion rate of lignin is 57.62%, the total yield of volatile products is 18.44%, and the yield and selectivity of hydroxycinnamate products are 15.15% and 82.16%, respectively.

[0102] Example 13: Cu 22 Mo 25 O / PILCS-4 catalyzes lignin depolymerization

[0103] The difference between this embodiment and embodiment 8 is that:

[0104] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 25O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0105] The calculation results show that the conversion rate of lignin is 58.77%, the total yield of volatile products is 18.98%, and the yield and selectivity of p-hydroxycinnamate products are 14.79% and 77.90%, respectively.

[0106] Example 14: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0107] The difference between this embodiment and embodiment 8 is that:

[0108] Weigh out 100 mg of the extracted organic soluble sugarcane bagasse lignin and 40 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0109] The calculation results show that the conversion rate of lignin is 49.96%, the total yield of volatile products is 16.70%, and the yield and selectivity of hydroxycinnamate products are 12.92% and 77.34%, respectively.

[0110] Example 15: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0111] The difference between this embodiment and embodiment 8 is that:

[0112] Weigh out 100 mg of the extracted organic soluble sugarcane bagasse lignin and 60 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0113] The calculation results show that the conversion rate of lignin is 52.93%, the total yield of volatile products is 18.74%, and the yield and selectivity of hydroxycinnamate products are 13.59% and 72.53%, respectively.

[0114] Example 16: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0115] The difference between this embodiment and embodiment 8 is that:

[0116] Weigh out 100 mg of the extracted organic soluble sugarcane bagasse lignin and 80 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0117] The calculation results show that the conversion rate of lignin is 60.75%, the total yield of volatile products is 21.21%, and the yield and selectivity of hydroxycinnamate products are 15.92% and 75.08%, respectively.

[0118] Example 17: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0119] The difference between this embodiment and embodiment 8 is that:

[0120] Weigh out 100 mg of the extracted organic-soluble bagasse lignin and 120 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0121] The calculation results show that the conversion rate of lignin is 56.38%, the total yield of volatile products is 18.06%, and the yield and selectivity of hydroxycinnamate products are 14.06% and 77.85%, respectively.

[0122] Example 18: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0123] The difference between this embodiment and embodiment 8 is that:

[0124] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 2 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID.

[0125] The calculation results show that the conversion rate of lignin is 57.17%, the total yield of volatile products is 18.13%, and the yield and selectivity of hydroxycinnamate products are 11.84% and 65.31%, respectively.

[0126] Example 19: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0127] The difference between this embodiment and embodiment 8 is that:

[0128] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 3 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID.

[0129] The calculation results show that the conversion rate of lignin is 60.09%, the total yield of volatile products is 20.80%, and the yield and selectivity of hydroxycinnamate products are 13.87% and 66.68%, respectively.

[0130] Example 20: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0131] The difference between this embodiment and embodiment 8 is that:

[0132] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 5 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID.

[0133] The calculation results show that the conversion rate of lignin is 63.94%, the total yield of volatile products is 21.28%, and the yield and selectivity of hydroxycinnamate products are 15.36% and 72.18%, respectively.

[0134] Example 21: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0135] The difference between this embodiment and embodiment 8 is that:

[0136] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 150 °C for 6 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID.

[0137] The calculation results show that the conversion rate of lignin is 64.15%, the total yield of volatile products is 19.77%, and the yield and selectivity of p-hydroxycinnamate products are 14.94% and 75.57%, respectively.

[0138] Example 22: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0139] The difference between this embodiment and embodiment 8 is that:

[0140] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 140 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0141] The calculation results show that the conversion rate of lignin is 48.85%, the total yield of volatile products is 15.70%, and the yield and selectivity of hydroxycinnamate products are 10.93% and 69.62%, respectively.

[0142] Example 23: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0143] The difference between this embodiment and embodiment 8 is that:

[0144] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 160 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. One mL of the reaction solution was then analyzed by GC-MS-FID.

[0145] The calculation results show that the conversion rate of lignin is 67.58%, the total yield of volatile products is 18.48%, and the yield and selectivity of p-hydroxycinnamate products are 14.80% and 80.09%, respectively.

[0146] Example 24: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0147] The difference between this embodiment and embodiment 8 is that:

[0148] Weigh out 100 mg of the extracted organic soluble bagasse lignin and 100 mg of Cu in sequence. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reaction vessel. The reaction vessel was sealed, and the air inside was purged three times with high-purity nitrogen. The reaction was carried out at 170 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID.

[0149] The calculation results show that the conversion rate of lignin is 72.16%, the total yield of volatile products is 18.45%, and the yield and selectivity of hydroxycinnamate products are 13.75% and 74.53%, respectively.

[0150] Example 25: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0151] The difference between this embodiment and embodiment 8 is that:

[0152] (1) Extraction of lignin: Weigh 10.0 g of bamboo raw material and 120 mL of extract, add them to a 250 mL hydrothermal reactor, and react in an oven at 110 °C for 4 h. After cooling to room temperature, filter and wash with ethanol, collect the filtrate and washings, add 500 mL of deionized water to precipitate lignin. After filtering through a 0.22 μm filter membrane, air dry in a fume hood, and grind into powder to obtain organosoluble bamboo lignin. The extract consists of 24 g of 98% concentrated sulfuric acid, 3200 mL of anhydrous ethanol and 800 mL of deionized water.

[0153] (2) Catalytic depolymerization of lignin: 100 mg of the organosoluble bamboo lignin extracted in step (1) and 120 mg of Cu were weighed sequentially. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reactor. The reactor was sealed, and the air inside was replaced three times with high-purity nitrogen. Nitrogen gas was then introduced at 1.0 MPa, and the reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID. The reaction solution was filtered to obtain a filtrate, and deionized water was added to a final volume of 200 mL. The mixture was allowed to stand for approximately 24 h to precipitate unreacted lignin. After filtration and drying, regenerated lignin was obtained.

[0154] The calculation results show that the conversion rate of lignin is 49.89%, the total yield of volatile products is 15.68%, and the yield and selectivity of p-hydroxycinnamic acid products are 7.93% and 50.57%, respectively.

[0155] Example 26: Cu 22 Mo 20 O / PILCS-4 catalyzes lignin depolymerization

[0156] The difference between this embodiment and embodiment 8 is that:

[0157] (1) Extraction of lignin: Weigh 10.0 g of corn stalk raw material and 120 mL of extract, add them to a 250 mL hydrothermal reactor, and react in an oven at 110 °C for 4 h. After cooling to room temperature, filter and wash with ethanol, collect the filtrate and washing liquid, add 500 mL of deionized water to precipitate lignin. After filtering through a 0.22 μm filter membrane, air dry in a fume hood, and grind into powder to obtain organosoluble corn stalk lignin. The extract consists of 24 g of 98% concentrated sulfuric acid, 3200 mL of anhydrous ethanol and 800 mL of deionized water.

[0158] (2) Catalytic depolymerization of lignin: 100 mg of the organosoluble corn straw lignin extracted in step (1) and 120 mg of Cu were weighed sequentially. 22 Mo 20 O / PILCS-4 catalyst and 15 mL of anhydrous methanol were added to a 50 mL reactor. The reactor was sealed, and the air inside was replaced three times with high-purity nitrogen. Nitrogen gas was then introduced at 1.0 MPa, and the reaction was carried out at 150 °C for 4 h. After the reaction was completed and cooled to room temperature, the reaction solution was removed, and dimethyl phthalate (DMT) was added as an internal standard. 1 mL of the reaction solution was analyzed by GC-MS-FID. The reaction solution was filtered to obtain a filtrate, and deionized water was added to a final volume of 200 mL. The mixture was allowed to stand for approximately 24 h to precipitate unreacted lignin. After filtration and drying, regenerated lignin was obtained.

[0159] The calculation results show that the conversion rate of lignin is 34.06%, the total yield of volatile products is 10.97%, and the yield and selectivity of p-hydroxycinnamic acid products are 5.15% and 46.95%, respectively.

[0160] As can be seen from the above embodiments, the present invention achieves highly efficient and selective depolymerization of lignin using a pillar-supported montmorillonite-supported copper molybdate catalyst system. Under the conditions of N2 pressure of 0.1~2 MPa, reaction temperature of 130~170℃, and reaction time of 2~6 h, the conversion rate of lignin in this method can reach up to 34.06~72.16%, the total yield of volatile products is 10.97~23.23 wt.%, the yield of p-hydroxycinnamate is 5.15~16.98 wt.%, and the selectivity is 46.95~82.16%. In the embodiments, the yields of methyl p-hydroxycinnamate from organically soluble corn cob and bamboo lignin are 5.15% and 7.93%, respectively. Although these yields seem low, they are already quite considerable compared to lignin-derived raw materials such as corn cob and bamboo. Lignin is composed of three basic structural units: p-coumarol, coniferol, and sinapyl alcohol. These three structures vary considerably from lignin of different sources. In bagasse, corn stalk, and bamboo lignin, the H-unit content of bagasse lignin is generally 15-20%, while that of corn stalk and bamboo lignin is generally 5-10%. p-Coumaric acid (pCA) and methyl p-hydroxycinnamate (MPC) have similar structures, and the p-coumaric acid content largely determines the yield of MPC. The above yields demonstrate that the catalyst of this invention achieves good depolymerization effects on corn stalk lignin and bamboo lignin. It should be noted that, for bagasse raw materials, the yield of MPC in this invention exceeds 10%, far higher than existing technologies. Overall, this invention demonstrates excellent depolymerization ability for organosoluble lignin from various sources.

[0161] p-Hydroxycinnamate esters are typical representatives of polyphenolic compounds. Hydroxycinnamic acid has many biological functions, including antioxidant, anti-inflammatory, anti-cancer, blood sugar regulation, blood lipid regulation, prevention of neurodegenerative diseases, and maintenance of intestinal barrier integrity. Therefore, it is often used in the pharmaceutical field as an intermediate for anticancer drugs, coronary heart disease drugs, and in the synthesis of the adrenaline esmolol. Due to its antibacterial, preservative, and food flavoring functions, p-hydroxycinnamic acid is widely used in the food industry, often as a natural food preservative, flavoring agent, nutritional supplement, and sensory additive. p-Hydroxycinnamic acid can also be used as a natural ingredient in skin care and cosmetic products, and as a raw material for the synthesis of highly conductive polymers in fields such as liquid crystal displays.

[0162] Chinese invention patent CN111072477B uses copper metal salt as a catalyst. Under optimal conditions, the yield of monophenol is 12.45 wt.%, the yield of methyl p-hydroxycinnamate is 9.02 wt.%, and the selectivity is 72.5%. The yield of methyl p-hydroxycinnamate is less than 10%. Although copper metal salt, as a homogeneous catalyst, has strong catalytic activity and selectivity, a fast reaction rate, and relatively sensitive reaction conditions, it suffers from problems such as the catalyst and product being simultaneously dissolved in the solvent and difficult to separate; the catalyst itself dissolving in the solvent and requiring the addition of precipitating agents to precipitate the metal salt for recovery, resulting in a complex recovery process; and the potential for leakage of metal ion solution leading to metal pollution. This invention utilizes pillared montmorillonite-supported copper molybdate, employing inexpensive montmorillonite group minerals as a carrier. Through simple in-situ deposition and impregnation with loaded active metals, a heterogeneous catalyst was successfully prepared. The pore structure was controllably adjusted, significantly reducing mass transfer resistance and exposing abundant active sites, enabling highly efficient catalytic depolymerization of lignin to selectively prepare p-hydroxycinnamate products. Catalyst recovery and separation are simple, making it suitable for rapid industrial applications. In particular, the pillared montmorillonite-supported copper molybdate catalyst used in this invention allows for the introduction of metals into the montmorillonite interlayer via in-situ deposition. After the catalytic reaction, the catalyst and reaction solution can be separated simply by filtration. This process is simple, has minimal environmental pollution, and can achieve highly efficient and selective depolymerization of lignin under mild conditions.

[0163] Chinese invention patent CN107602383B, under optimal reaction conditions, achieves a conversion rate of 72%, a total yield of volatile products of 12 wt.%, and a yield of 7.8 wt.% for p-hydroxycinnamate. This technology uses ionic liquids as catalysts to catalyze the depolymerization of lignin. However, the ionic liquid catalysts used require a long time to form imidazolium alkyl halide salts, and the ionic liquids also dissolve in the solution. The catalyst and reaction solution are difficult to separate, resulting in a long catalyst preparation cycle and a lengthy subsequent separation process, increasing the cost of the process. In contrast, this invention uses a pillar-supported montmorillonite-supported copper molybdate catalyst. Through simple in-situ deposition and impregnation of active metals, active metals can be loaded onto montmorillonite in just 24 hours. This leverages the efficient cleavage of CO bonds by molybdenum metal under a nitrogen atmosphere and the enhanced activity of copper metal. This catalyst is heterogeneous, requiring only simple filtration to separate the catalyst from the reaction solution. It offers advantages such as a simple preparation process, milder reaction conditions, and a streamlined subsequent separation process.

[0164] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the selective depolymerization of lignin catalyzed by copper molybdate supported on pillared montmorillonite to prepare p-hydroxycinnamate, characterized in that, After adding CuMoO / PILCS-x catalyst and alcohol solvent to organic lignin, the reaction is carried out at N2 pressure of 0.1~2 MPa and 130~170℃ for 2~6 h to depolymerize the lignin and obtain volatile products mainly composed of p-hydroxycinnamate. The CuMoO / PILCS-x catalyst is composed of montmorillonite support and copper molybdate composite metal oxyacid salt active component. The montmorillonite support is a layered aluminosilicate mineral, and x represents the molar ratio of silicon to aluminum in the support, which is 2~6. The loading of molybdenum and copper active components is 5~25 wt.% and 14~30 wt.%, respectively.

2. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 1, characterized in that, The preparation method of the CuMoO / PILCS-x catalyst is as follows: deionized water and sodium silicate are stirred and mixed evenly; deionized water, aluminum nitrate nonahydrate, and sodium hydroxide are stirred and mixed evenly, and gradually heated to 90-120°C at room temperature, stirred and kept at the temperature for 0.5-1 h to obtain a PILCS-x slurry; copper acetate monohydrate and urea are mixed with the PLICS-x slurry, and stirred and kept at 90-120°C for 10-12 h, filtered to obtain a filter cake, washed and dried to obtain Cu / PILCS-x solid; ammonium molybdate tetrahydrate is fully dissolved in deionized water, the Cu / PILCS-x support is added and stirred evenly, and after standing for 10-12 h, it is dried and calcined in air at 400-900°C to obtain the CuMoO / PILCS-x catalyst.

3. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 2, characterized in that, The mass ratio of ammonium molybdate tetrahydrate, sodium silicate, aluminum nitrate nonahydrate, sodium hydroxide, urea, and copper acetate monohydrate is 0.27~2.15:1.68~12:5~14:1:20:4~14.

4. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 2, characterized in that, The deionized water and sodium silicate are mixed evenly by stirring 80 parts by weight of deionized water and 3.24 to 4.17 parts by weight of sodium silicate; the deionized water, aluminum nitrate nonahydrate, and sodium hydroxide are mixed evenly by stirring 100 parts by weight of deionized water, 2.14 to 4.98 parts by weight of aluminum nitrate nonahydrate, and 0.3 to 0.4 parts by weight of sodium hydroxide.

5. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 2, characterized in that, The time for mixing the deionized water and sodium silicate evenly is 0.5~1 h; the time for mixing the deionized water, aluminum nitrate nonahydrate, and sodium hydroxide evenly is 0.5~1 h.

6. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 2, characterized in that, The filter cake is washed 2-3 times with deionized water; the filter cake is dried by placing the washed filter cake in an oven at 80-120℃.

7. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 1, characterized in that, The mass ratio of lignin to CuMoO / PILCS-x catalyst is 1:0.2~1, and the mass ratio of lignin to alcohol solvent is 1:10~1:

20.

8. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 1, characterized in that, The alcohol solvent is any one of methanol, ethanol, n-propanol, and n-butanol.

9. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 1, characterized in that, The organosoluble lignin is extracted by the following method: lignin raw material and extract are added to a reaction vessel and reacted at 100-120℃ for 2-6 h, followed by filtration and separation; the filtrate is added to deionized water and filtered to obtain a solid, which is then dried to obtain organosoluble lignin; by mass fraction, the extract consists of 20-25 parts concentrated sulfuric acid, 3000-4000 parts anhydrous ethanol, and 800-1000 parts deionized water, and 120-150 parts extract are added to 10-15 parts lignin raw material.

10. The method for preparing p-hydroxycinnamate by selective depolymerization of lignin catalyzed by pillared montmorillonite-supported copper molybdate according to claim 9, characterized in that, The lignin raw material is derived from bagasse, bamboo, or corn stalks.

Images