Sulfonyl chloride modified lignin-based carrier loaded with iron phthalocyanine and catalytic lignin depolymerization method

Abstract

The present invention discloses a sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine and a method for catalyzing lignin depolymerization. The sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine has a repeating unit as shown in formula (1): #imgabs0# In formula (1), the wavy line represents the connection of other repeating units as shown in formula (1), M has a structure as shown in formula (2), and R=NH2 or NO2; #imgabs1# Using this catalyst, lignin is catalyzed, oxidatively depolymerized under mild conditions and has good selectivity for phenolic substances in the product.

Description

Technical Field

[0001] The invention relates to the technical field of lignin catalytic depolymerization, and in particular to a method for loading phthalocyanine iron on a sulfonyl chloride-modified lignin-based carrier and catalyzing lignin depolymerization. Background Art

[0002] The papermaking industry produces foul-smelling, toxic black liquor, primarily composed of hemicellulose and lignin, which microorganisms cannot metabolize. Currently, the primary method for treating black liquor is to concentrate it, mix it with pulverized coal from power plants, and then burn it. This wastes resources and creates air pollution. Therefore, the research, development, and comprehensive utilization of lignin in black liquor have become a significant undertaking with significant social and economic benefits.

[0003] Lignin is a three-dimensional network of phenolic polymers found extensively in the cell walls of higher plants. It is composed of three basic aromatic structural units: syringyl (S), guaiacyl (G), and hydroxyphenyl (H). These three basic lignin monomers are primarily connected through C-C and C-O bonds. Depolymerization of lignin, which selectively breaks C-C or C-O bonds in its structure to produce phenols or other small molecule chemicals, is an important approach for achieving large-scale comprehensive utilization of lignin.

[0004] Lignin can be depolymerized through pyrolysis or liquid-phase catalysis. Generally speaking, pyrolysis of lignin requires relatively high reaction temperatures (400-800°C), which are relatively harsh conditions. Compared to pyrolysis, liquid-phase catalytic degradation offers the advantages of milder reaction conditions and higher product selectivity. During liquid-phase catalytic degradation of lignin, C—C or C—O bonds are broken by the catalyst, forming aromatic or other small-molecule chemicals. The key to liquid-phase catalytic depolymerization of lignin is the preparation of an effective catalyst. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for loading phthalocyanine iron on a sulfonyl chloride-modified lignin-based carrier and catalyzing lignin depolymerization, so as to achieve lignin depolymerization.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine, wherein the sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine has a repeating unit as shown in formula (1):

[0008] Formula (1): ,

[0009] In formula (1), the wavy line represents the connection of other repeating units as shown in formula (1), M has the structure shown in formula (2), R = NH2 or NO2, that is, the three Rs are the same and can be selected from NH2 or NO2;

[0010] Formula (2): .

[0011] The black bold short line in formula (2) indicates the bond to the SO2 group.

[0012] The sulfonyl chloride-modified lignin-based carrier-supported iron phthalocyanine is hereinafter referred to as the catalyst of formula (1). A specific structure of the catalyst of formula (1) is shown in the following structural formula.

[0013] .

[0014] A method for preparing the above-mentioned sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine comprises:

[0015]

[0016] The compound represented by formula A and the compound represented by formula B are heated to react in DMF solvent to obtain a sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine as represented by formula (1).

[0017] Preferably, the weight ratio of the compound represented by formula A to the compound represented by formula B is 1:(1-10), and the mixture is ultrasonically treated before the heating reaction, and the heating reaction temperature is 120°C.

[0018] Specifically, the total volume (ml) of the DMF solvent may be 5-50 times the total weight (g) of the compound represented by Formula A and the compound represented by Formula B.

[0019] A method for catalytic lignin depolymerization, comprising:

[0020] Lignin and a sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine as shown in formula (1) are placed in a mixed solvent of water and acetonitrile, the pH value of the solution is in the range of less than 5 and greater than 1, hydrogen peroxide is added, and heating and stirring are carried out to achieve lignin depolymerization.

[0021] The volume ratio of water to acetonitrile can be 6:1-1:1, and the total volume (ml) of the mixed solvent can be 50-250 times the weight (g) of the lignin.

[0022] Preferably, based on the weight of lignin, the weight ratio of the sulfonyl chloride modified lignin-based carrier loaded with iron phthalocyanine is 0.5 wt % to 6 wt %.

[0023] Preferably, based on the weight of lignin, the weight ratio of the sulfonyl chloride modified lignin-based carrier loaded with iron phthalocyanine is 3.5 wt %.

[0024] Preferably, the heating temperature is 120-150° C., and the reaction time is 40-200 min.

[0025] Preferably, the heating temperature is 135° C., the reaction time is 120 min, and the pH value of the solution is adjusted to 3 with sulfuric acid.

[0026] Preferably, the concentration of the hydrogen peroxide is 2.5×10 -2 -20×10 -2 mol / L.

[0027] Preferably, the concentration of the hydrogen peroxide is 15×10 -2 mol / L.

[0028] Compared with the prior art, the beneficial effects of the present invention include at least:

[0029] The invention prepares a novel sulfonyl chloride modified lignin-based carrier loaded with iron phthalocyanine, and adopts the catalyst to carry out catalytic oxidative depolymerization of lignin under mild conditions and good selectivity of phenolic compounds in the depolymerization product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FT-IR spectra of the compound of formula B and the catalyst of formula (1) according to the embodiment of the present invention.

[0031] Figure 2 1 is a BET analysis chart of compound A of the embodiment of the present invention and the catalyst of formula (1).

[0032] Figure 3 This is an analysis chart of the effect of catalyst content on liquid product yield and phenol selectivity in the examples of the present invention.

[0033] Figure 4 This is an analysis chart of the effect of H2O2 concentration on the yield of liquid products and phenol selectivity in the examples of the present invention.

[0034] Figure 5 This is an analysis chart of the effect of reaction time on the yield of liquid phase products and phenol selectivity in the examples of the present invention.

[0035] Figure 6 It is a picture of the ethyl acetate soluble portion in Examples 5-9 of the present invention.

[0036] Figure 7 It is the GC-MS spectrum of the ethyl acetate extraction product in Example 5-9 of the present invention.

[0037] Figure 8 This is the FT-IR spectrum of the ethyl acetate extraction product in Examples 5-9 of the present invention.

[0038] Figure 9 1 is the SEM image of the solid residue obtained at different reaction times in Example 18 of the present invention. DETAILED DESCRIPTION

[0039] Example embodiments will now be described more fully. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concepts of the example embodiments to those skilled in the art.

[0040] In the embodiment, the main reagents used include: potassium hydroxide (KOH, purity ≥98%), sodium hydroxide (NaOH, purity ≥97%), sulfuric acid (H2SO4, concentration 98%), ferric chloride hexahydrate (FeCl3·6H2O), ethanol (C2H5OH, 99.9%), hydrogen peroxide (H2O2), thionyl chloride (SOCl2), 4-nitrophthalic acid (C8H5NO6), urea (CO(NH2)2), sodium sulfide (NaS2·9H2O) and N, N-dimethylformamide (C3H7NO), all of which are commercially available.

[0041] Example 1: Preparation of compound of formula A

[0042]

[0043] The lignin in the embodiment (as shown in Formula A1) was recovered from papermaking black liquor, and then a lignin-based carbon sulfonyl chloride derivative (compound of Formula A) was synthesized through three steps of carbonization, sulfonation and chlorination.

[0044] Specifically, lignin was first carbonized in a tube furnace under N2 protection. Lignin and KOH were placed in a nickel pan (weight ratio of 1:(0.5-3), 1:2 in this example) and then placed in the center of the tube furnace. The furnace was heated to 550°C at a heating rate of 15°C / min and held for 90 minutes. After the reaction, the resulting black sample was washed with hot water, filtered, and then dried at 105°C for 12 hours to obtain carbonized lignin. Next, the carbonized lignin was sulfonated in a three-necked round-bottom flask under N2 protection. The carbonized lignin and H2SO4 were mixed in a round-bottom flask at a weight ratio of 1:(5-13) and reacted at 150°C for 6 hours. The resulting black sample (designated sulfonated lignin, as shown in Formula A2) was washed with water, filtered, and finally dried at 105°C for 12 hours. Finally, the synthesis of the compound represented by Formula A can refer to the known method for preparing sulfonyl chloride from sulfonic acid compounds. Specifically, the compound represented by A2 is added to an excess SOCl2 solution and reacted at 90°C for 24 hours. After the reaction is completed, the residual SOCl2 is distilled off, and the solid product (as represented by Formula A) is washed, dried, and set aside.

[0045] Example 2: Structure of the compound of formula B

[0046]

[0047] The structure of the compound of formula B is shown in the above structure, wherein R = NH2 or NO2. The compound can be prepared by known methods, and its preparation method will not be repeated here.

[0048] Example 3: Preparation of the catalyst of formula (1)

[0049]

[0050] The compound of formula A and the compound of formula B prepared above (wherein, in this embodiment and the following embodiments, R is NH2, and the weight ratio is 1:1.2) are added to DMF solvent, the total volume (ml) of the solvent is 5 times the total weight (g) of the compound represented by formula A and the compound represented by formula B, a small amount of water can be added to the solvent (for example, the volume of water is 5% of the volume of DMF), and ultrasonic treatment is performed for 2 hours, and then the mixture is stirred at 120°C for 72 hours. Finally, the reaction mixture is filtered to obtain a solid, which is washed with water and acetone and dried at 65°C to obtain a black-blue powder catalyst (catalyst of formula (1), R is NH2).

[0051] Example 4-18: Catalytic Oxidative Depolymerization of Lignin

[0052] First, an appropriate amount of the catalyst of formula (1) (the weight ratio of the catalyst to lignin is 0 wt% to 4.5 wt%) is dispersed in a mixed solvent of water and acetonitrile (the volume ratio of the two is 4:1), and the total volume (ml) of the mixed solvent is 100 times the weight (g) of the lignin. Second, lignin (1 g) is added to the above mixture, and the pH of the mixture is adjusted to 3.0 with sulfuric acid. Subsequently, the mixture is vibrated for 20-30 minutes to fully disperse the catalyst of formula (1) and lignin. Finally, the mixture is transferred to a 150 ml reactor and H2O2 (the concentration of H2O2 is 0 mol / L to 20×10 -2 mol / L) was added to the reaction mixture, and the mixture was stirred at 135°C for 40-200 minutes. After the reaction, the solid residue and liquid product were separated by centrifugation. The liquid product was extracted with ethyl acetate to obtain the ethyl acetate-soluble material for analysis.

[0053] For specific reaction conditions in Examples 4-18, see Table 1.

[0054]

[0055] Result analysis:

[0056] The chemical functional groups of the catalysts were analyzed using a Nicolet IS10 Fourier transform infrared spectroscopy (FTIR) instrument. The BET surface area was measured using N adsorption / desorption isotherms (Quantachrome autosorb IQ-C analyzer). The surface structure of the catalysts was analyzed using a Hitachi S-3400 scanning electron microscope (SEM) (Hitachi, Japan).

[0057] The depolymerization product was analyzed using an Agilent 6890A / 5973N instrument equipped with an HP-5MS (30m×0.25mm×0.25μm) column. The following analytical conditions were used: 2 μL of sample was injected into the system at 40°C and maintained at 40°C for 2 minutes. The temperature was then increased to 150°C at a rate of 5°C / min and held for 2 minutes. The temperature was then increased to 280°C at a rate of 8°C / min and held for 5 minutes. The elemental composition of the product was analyzed using an elemental analyzer (EA).

[0058] The surface structure of the solid residue was analyzed by Hitachis-3400 scanning electron microscope.

[0059] The liquid product yield is calculated as follows:

[0060] Liquid product (wt%) = W 液相产物 / W 木质素 ×100%.

[0061] Where W 木质素 and W 液相产物 represent the weight of lignin and the weight of liquid product, respectively.

[0062] The selectivity of phenolic compounds was expressed as the ratio of the peak area of ​​the corresponding product to the total area of ​​the liquid phase products.

[0063] Figure 1 is the FT-IR spectrum of the compound of formula B and the catalyst of formula (1) according to the embodiment of the present invention, referring to Figure 1 , line a represents the compound of formula B, and line b represents the catalyst of formula (1). Figure 1 The FT-IR spectrum shows that the characteristic peak of iron phthalocyanine appears at 1320 cm -1 、1120 cm -1 , 740 cm -1 This is attributed to the vibration of the phthalocyanine ring. The spectrum of the catalyst of formula (1) clearly shows similar characteristic bands, indicating that the phthalocyanine iron is bonded to the compound of formula A. At 900 cm -1 A new SN stretching vibration characteristic peak appeared nearby, indicating that iron phthalocyanine was successfully introduced into the compound of formula A through chemical reaction.

[0064] Reference Figure 2 , line a represents the compound of formula A, line b represents the catalyst of formula (1), and Table 2 shows the porous structure characterization results of compound A and catalyst of formula (1).

[0065]

[0066] Reference Figure 2 When P / P0 is lower than 0.2, a steep slope can be seen, which confirms that the two N2 adsorption-desorption isotherms are consistent with the type I adsorption isotherm and the H4 type hysteresis loop, which also proves that there are a large number of micropores in the sample. The detailed specific surface area and pore structure parameters of the compound of formula A and the catalyst of formula (1) are shown in Table 2. The catalyst sample of formula (1) exhibits a lower specific surface area and pore volume. When iron phthalocyanine is loaded on the compound of formula A, the BET specific surface area increases from 643.67 m 2 / g decreased to 638.98 m 2 / g, and at the same time, the pore volume increased from 0.337 cm 3 / g decreased to 0.291 cm 3 The decrease in BET surface area and pore volume may be due to the blocking of some pores of the support by iron phthalocyanine.

[0067] The depolymerization efficiency of lignin and the composition and properties of the liquid product are affected by reaction conditions, such as catalyst content, reaction time, etc. Examples 4-18 investigated the effects of specific reaction conditions on the depolymerization efficiency of lignin.

[0068] Figure 3 This is an analysis of the effects of catalyst content on liquid product yield and phenol selectivity in the examples of the present invention. Most reactions are influenced by the active sites and basic properties of the catalyst. Based on this, referring to Examples 4-9, the present invention utilizes six different catalyst concentrations: 0 wt%, 0.5 wt%, 1.5 wt%, 2.5 wt%, 3.5 wt%, and 4.5 wt%. Figure 3 As can be seen, with increasing catalyst content, both the liquid product yield and phenol selectivity increased compared to the uncatalyzed degradation process. When 3.5 wt% catalyst was used, the maximum liquid product yield was 38.94%, and the phenol selectivity also reached a peak of 32.58%. When the catalyst content increased to 4.5 wt%, both the liquid product yield and phenol selectivity decreased.

[0069] These results indicate that the appropriate catalyst dosage has a certain effect on the yield of liquid products and phenol selectivity. Once the catalyst dosage exceeds the optimal value, the yield of liquid products and phenol selectivity may decrease.

[0070] Figure 4 This is an analysis of the effect of H2O2 concentration on the yield of liquid products and the selectivity of phenols in the examples of the present invention. Referring to Examples 8 and 10-14, six different levels of H2O2 concentration (0 mol / L, 2.5×10 -2 mol / L、5×10 -2 mol / L、10×10 -2 mol / L、15×10 -2 mol / L, 20×10 -2 mol / L), using 3.5 wt% catalyst, the reaction was carried out at 135℃ and pH 3.0 for 120 min. As the H2O2 concentration increased from 0 mol / L to 20×10 -2 mol / L, the yield of liquid products and the selectivity of phenolic compounds also showed similar trends. -2 mol / L, the yield of liquid products and the selectivity of phenolic compounds increased with the increase of hydrogen peroxide concentration. When the H2O2 concentration was 15×10 -2 mol / L, the highest yield was 38.94%, and the highest selectivity for phenolic compounds was 32.58%. Further increasing the H2O2 concentration did not significantly change the yield of liquid products, but the selectivity for phenolic compounds decreased significantly.

[0071] Figure 5 This is an analysis chart of the effect of reaction time on the yield of liquid products and the selectivity of phenols in the examples of the present invention. Referring to Examples 8 and 15-18, Figure 5 As can be seen, as the reaction time increases to 2 hours, the yield of the liquid product and the selectivity of phenolic compounds gradually increase, reaching their maximum values ​​at 2 hours. As the reaction time is further extended to 160 minutes and 200 minutes, the yield of the liquid product and the selectivity of phenolic compounds begin to decrease. At 200 minutes, both the yield of the liquid product and the selectivity of phenolic compounds reach their lowest values, indicating that reaction times exceeding 2 hours are detrimental to the reaction.

[0072] The reaction process and properties of the liquid products at five different catalyst concentrations (0.5 wt%, 1.5 wt%, 2.5 wt%, 3.5 wt%, and 4.5 wt%) in Examples 5-9 were analyzed. Specifically, the obtained liquid product was extracted with ethyl acetate, and the ethyl acetate soluble matter was found to be Figure 6 , GC-MS analysis of product composition, the results are shown in Figure 7 .

[0073] Figure 6 All samples (0.5 wt%, 1.5 wt%, 2.5 wt%, 3.5 wt%, 4.5 wt%, corresponding to samples a to e) showed different colors. As the catalyst content increased, the color changed from light yellow to dark brown. Figure 7 It can be seen that the depolymerization products obtained when using different catalyst concentrations are significantly different. The detected products mainly include phenolic compounds, esters and aldehydes. The detailed information of the depolymerization products is summarized in Table 3.

[0074]

[0075]

[0076]

[0077] Table 3 shows that chemical substances such as ethyl propionate, butyl acetate, acetosyringone, phenol, and 2,6-bis(1,1-dimethylethyl)-naphthalene account for a large proportion of the total integrated area. 2,4-di-tert-butylphenol was observed to be a significant component of the products obtained at different catalyst concentrations. At a catalyst concentration of 0.5 wt%, the primary compound in the product was 2,3-dihydro-benzofuran, accounting for 13.72% of the total integrated area; followed by ethyl propionate, at 5.54%; and 2,4-di-tert-butylphenol, at 3.01%. At a catalyst concentration of 1.5 wt%, 2,3-dihydro-benzofuran accounted for the majority of the total integrated area, at 48.16%, followed by ethyl propionate and 2,4-di-tert-butylphenol, at 17.42% and 10.12%, respectively. Compounds 3-hydroxy-4-methoxybenzaldehyde and eicosane accounted for 5.38% and 3.09% of the total integrated area, respectively. When the catalyst concentration was 2.5 wt%, 3.5 wt%, and 4.5 wt%, ethyl propionate accounted for the largest proportions of the total integrated area, at 65.18%, 51.59%, and 59.06%, respectively. This was followed by 2,4-di-tert-butylphenol, which accounted for 15.73%, 14.84%, and 17.08%, respectively.

[0078] Notably, as the catalyst concentration increases to 3.5 wt%, the total proportion of phenolic compounds reaches its maximum, and the types of phenolic compounds also change. The phenolic compounds obtained include phenol, 2-methoxyphenol, 2,4-di-tert-butylphenol, 2,3-dimethoxyphenol, 3,4-dimethoxyphenol, and 2,6-dimethoxyphenol, which account for the largest proportion of the total integrated area, at 14.84%; 2,6-dimethoxyphenol accounts for 10.78% of the total integrated area. Compounds 2,3-dimethoxyphenol and 3,4-dimethoxyphenol account for relatively small proportions of the total integrated area, appearing only at 3.5 wt% catalyst. For 2,4-di-tert-butylphenol, its proportion increases from 3.01% to 17.08% as the catalyst content increases from 0.5 wt% to 4.5%, indicating that the catalyst promotes the production of 2,4-di-tert-butylphenol. With respect to phenol, as the catalyst dosage increases from 0.5 wt% to 4.5 wt%, its proportion first increases from 0.16% to 4.22%. At 4.5 wt%, the proportion of phenol decreases to 3.7%. No 2,6-dimethoxyphenol is observed at 0.5 wt% and 1.5 wt% catalyst dosages. However, as the catalyst dosage increases from 2.5 wt% to 3.5 wt%, the proportion of 2,6-dimethoxyphenol increases, reaching 2.15% and 10.78%, respectively. When the catalyst concentration is further increased to 4.5 wt%, the proportion of 2,6-dimethoxyphenol decreases to 0.9%. When the catalyst dosage is 1.5 wt%, 2.5 wt%, and 3.5 wt%, respectively, the proportion of 2-methoxyphenol is 0.61%, 0.72%, and 1.56%, respectively. When the catalyst dosage is further increased to 4.5%, the proportion decreases to 0.61%.

[0079] To further confirm Figure 6 The chemical functional group characteristics of the degradation products of each sample were analyzed by FT-IR. The results are as follows Figure 8 shown.

[0080] like Figure 8 As shown in Figure 3, the products have similar chemical functional groups and the positions of the vibration peaks are basically the same, which indicates that the main components of the depolymerization products have similar structures. -1 The broad band at 2938 and 2841 cm is attributed to the stretching vibration peaks of OH, =CH and NH in aromatic or aliphatic groups, indicating the presence of phenols or benzene rings in the product; -1 The peak at 1702 cm is attributed to the asymmetric stretching vibration of methyl and methylene CH, indicating the presence of saturated aliphatic hydrocarbons in the product; -1 The small and broad bands near 1590 and 1505 cm are attributed to the stretching vibration of C=O in ketone or carboxylic acid derivatives;-1 The peaks near 1273 and 1120 cm are attributed to the vibration of the C=C bond in the aromatic skeleton. This result shows that the aromatic skeleton structure of lignin is well preserved in the product. -1 The peak at is assigned to the Ar-O bond of methoxyphenol.

[0081] The elemental compositions of the products of Examples 5-9 were analyzed, and the results are shown in Table 4.

[0082]

[0083] Elemental analysis results show that the carbon content of the product increased compared to lignin, reaching its highest level when the catalyst dosage was 3.5 wt%. The hydrogen content was slightly higher, while the oxygen content was lower, reaching a minimum of 21.8% in the product with a 3.5 wt% catalyst dosage. Furthermore, the heating value (HHV) of the product increased, from 20.5 MJ / kg for lignin to 23.3-30.2 MJ / kg for the product, reaching a maximum of 30.2 MJ / kg.

[0084] For Example 18, SEM analysis was used to study the changes in the microstructure of lignin at different depolymerization times (40 min, 80 min, 120 min, and 150 min). The results are as follows: Figure 9 shown. Figure 9 Figure a is lignin, 40min corresponds to Figure 9 Figure b, 80min corresponds to Figure 9 Figure c, 120min corresponds to Figure 9 Figure e, 150min corresponds to Figure 9 f graph of .

[0085] from Figure 9 As can be seen from Figure a, lignin has a relatively smooth and dense surface structure. When the reaction time is extended to 40 min ( Figure 9 (b), the smooth surface was slightly damaged, some shallow pits were observed, and a small amount of scum was deposited on the lignin surface, indicating that the depolymerization of lignin started from the surface; further reaction to 80min ( Figure 9 Figure c shows that the surface damage is aggravated and some deeper pits appear. Zoom in and observe ( Figure 9 d), more fragments were found attached to the surface or in the pits, indicating that the main reaction at this stage was lignin depolymerization. When the reaction time was extended to 120 min ( Figure 9 e), slight agglomeration can be observed, indicating that with the increase of reaction time, the coupling and polycondensation of the intermediate products begin to become obvious. When the reaction time is further increased to 150 min ( Figure 9(f) Agglomeration can be observed, indicating that a longer time promotes the coupling and polycondensation reactions of the intermediates.

[0086] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the invention without departing from the principles and purpose of the present invention. All such changes shall fall within the scope of protection of the claims of the present invention.

Claims

1. A sulfonyl chloride modified lignin-based carrier loaded with iron phthalocyanine, characterized in that: The sulfonyl chloride modified lignin-based carrier-loaded phthalocyanine iron is used as a catalyst for lignin depolymerization reaction. The sulfonyl chloride modified lignin-based carrier-loaded phthalocyanine iron has a repeating unit as shown in formula (1): Formula (1): , In formula (1), the wavy line represents the connection of other repeating units shown in formula (1), M has the structure shown in formula (2), R = NH2 or NO2; Formula (2): .

2. A method for preparing a sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine as claimed in claim 1, characterized in that: include: ； The compound represented by formula A and the compound represented by formula B are heated to react in DMF solvent to obtain a sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine as represented by formula (1). The compound represented by formula A is synthesized by carbonizing, sulfonating and chlorinating lignin in three steps.

3. The method for preparing the sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine according to claim 2, characterized in that: The weight ratio of the compound represented by formula A to the compound represented by formula B is 1:(1-10). Before the heating reaction, the mixture is ultrasonically treated. The heating reaction temperature is 120°C.

4. A method for catalyzing lignin depolymerization, characterized in that: include: Lignin and the sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine as shown in formula (1) of claim 1 are placed in a mixed solvent of water and acetonitrile, the pH value of the solution is in the range of less than 5 and greater than 1, hydrogen peroxide is added, and heating and stirring are carried out to achieve oxidative depolymerization of the lignin.

5. The method for catalytic lignin depolymerization according to claim 4, characterized in that: Based on the weight of lignin, the weight ratio of the sulfonyl chloride modified lignin-based carrier loaded with iron phthalocyanine is 0.5wt%-6wt%.

6. The method for catalytic depolymerization of lignin according to claim 5, characterized in that: Based on the weight of lignin, the weight ratio of the sulfonyl chloride-modified lignin-based carrier loaded with iron phthalocyanine is 3.5 wt %.

7. The method for catalytic depolymerization of lignin according to claim 4, characterized in that: The heating temperature is 120-150°C and the reaction time is 40-200 minutes.

8. The method for catalytic lignin depolymerization according to claim 7, characterized in that: The heating temperature was 135° C., the reaction time was 120 min, and the pH value of the solution was adjusted to 3 with sulfuric acid.

9. The method for catalytic lignin depolymerization according to claim 4, characterized in that: The concentration of the hydrogen peroxide is 2.5×10 -2 -20×10 -2 mol / L.

10. The method for catalytic lignin depolymerization according to claim 9, characterized in that: The concentration of the hydrogen peroxide is 15×10 -2 mol / L.

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