Method for synthesizing adipic acid by using biomass platform compound HMF

Abstract

The invention discloses a method for synthesizing adipic acid by utilizing a biomass platform compound HMF. The synthesis method disclosed by the invention comprises the following steps: step 1, carrying out reaction on HMF to obtain a compound I; 2, the compound I is subjected to a reduction reaction to obtain adipic acid. According to the method, adipic acid can be obtained with good yield, raw materials are easy to obtain, post-treatment is simple, and the method is economical and environment-friendly; # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a method for synthesizing adipic acid by utilizing a biomass platform compound HMF. Background Art

[0002] Adipic acid is an important chemical with a wide range of applications, including polyester, coatings, plastics, pharmaceuticals, and daily necessities. Traditional adipic acid production methods include hydrogen peroxide oxidation, sulfuric acid reduction, ammonia oxidation, and oil oxidation. However, the production of adipic acid still faces the following difficulties:

[0003] 1. High cost of raw materials: The raw materials used in traditional methods, such as cyclohexanol and hexenenitrile, are relatively expensive, which limits the large-scale production and widespread application of adipic acid.

[0004] 2. Catalyst selection and efficiency: The catalysts used in traditional methods have limited activity and stability, resulting in low catalytic efficiency, slow reaction rates, and low product purity. Furthermore, some traditional methods require large amounts of catalyst, increasing production costs.

[0005] 3. Environmental impact and waste disposal: Traditional methods generate a lot of waste, which is difficult to post-process. In addition, the chemicals and catalysts used in some methods have adverse effects on the environment, increasing the risk of environmental pollution.

[0006] Therefore, developing a new method for synthesizing adipic acid to overcome the problems existing in traditional methods is of great scientific and engineering significance.

[0007] Biomass platform compounds are renewable resources, such as wood fiber and plant waste, with a wide range of sources and sustainability. Using biomass platform compounds as raw materials for adipic acid can not only reduce dependence on limited petroleum resources, but also reduce carbon emissions and environmental pollution. Among them, 5-hydroxymethylfurfural (HMF) is an important biomass platform compound that can be obtained through acid-catalyzed conversion of biomass. HMF has broad application prospects and can be used for chemical synthesis, biofuel production, and polymer materials. Therefore, using HMF as a raw material to synthesize adipic acid has important economic and environmental value.

[0008] However, the direct synthesis of adipic acid from HMF has not yet been effectively developed. Current research focuses on the conversion and utilization of biomass platform compounds, and direct synthesis methods for adipic acid are still lacking.

[0009] It is of great significance to develop a method for synthesizing adipic acid using biomass platform compounds. In view of this, the present invention is proposed. Summary of the Invention

[0010] The present invention aims to overcome the problems of high raw material costs, low catalytic efficiency, high waste generation, and difficult post-processing in the production of adipic acid in the prior art. Therefore, a method for synthesizing adipic acid using the biomass platform compound HMF is provided. This method has low by-product content and can further produce adipic acid in good yield. The raw materials are readily available, post-processing is simple, and the method is economical and environmentally friendly.

[0011] The present invention provides a method for synthesizing adipic acid, which comprises the following steps:

[0012] Step 1: HMF is reacted to obtain compound I;

[0013] Step 2: Compound I is subjected to reduction reaction to obtain adipic acid;

[0014]

[0015] In one embodiment, the method for synthesizing adipic acid, step 1 comprises the following steps: reacting 5-hydroxymethylfurfural (HMF) in a solvent under the action of a molecular sieve, an acid, and an oxidant to obtain compound I;

[0016] The molar ratio of Si to Al in the molecular sieve is ≤50.

[0017] In some embodiments, in step 1, the molar ratio of Si to Al in the molecular sieve is 1-20, preferably 2.6-15, for example 2.6, 5, 12.5 or 15.

[0018] In some embodiments, in step 1, the molecular sieve is an acidic molecular sieve, preferably 1, 2, 3, 4 or 5 of Y molecular sieve (preferably HY molecular sieve or Na-Y molecular sieve), ZSM-5 molecular sieve, Beta molecular sieve, mcm-22 molecular sieve or mordenite.

[0019] Preferably, the molecular sieve is one, two, three or four of HY molecular sieve, H-ZSM-5 molecular sieve, Beta molecular sieve or Na-Y molecular sieve, and the molar ratio of Si to Al in the molecular sieve is 2.6-15.

[0020] More preferably, the molecular sieve is one, two or three of HY molecular sieve, Beta molecular sieve or Na-Y molecular sieve; the molar ratio of Si to Al in the HY molecular sieve is 2.6; the molar ratio of Si to Al in the Beta molecular sieve is 12.5; and the molar ratio of Si to Al in the Na-Y molecular sieve is 15.

[0021] In some embodiments, in step 1, the oxidant is air or oxygen, preferably oxygen.

[0022] In some embodiments, in step 1, the reaction is preferably carried out at a pressure of 1-50 bar, preferably 20-50 bar, such as 20 bar, 30 bar or 50 bar.

[0023] In some embodiments, in step 1, the mass ratio of the HMF to the molecular sieve is 1:(0.01-0.1), preferably 1:(0.01-0.05), for example 1:0.1, 1:0.05, 1:0.04, 1:0.02 or 1:0.01.

[0024] In some embodiments, in step 1, the acid is an inorganic acid, preferably a protonic acid, and more preferably sulfuric acid or hydrochloric acid.

[0025] In some embodiments, in step 1, the molar ratio of the HMF to the acid is 1:(0.1-0.3), preferably 1:(0.126-0.252); for example, 1:0.126 or 1:0.252.

[0026] In some embodiments, in step 1, the solvent is C 1-4 Alcohol solvents, water or C 1-4 Alcohol solvent-water mixed solvent, preferably C 1-4 Alcohol solvent-water mixed solvent.

[0027] The C 1-4 The alcohol solvent is preferably one, two or three of isopropanol, ethanol or methanol.

[0028] The solvent is further preferably a methanol-water mixed solvent. The volume ratio of methanol to water in the mixed solvent is preferably 1:(1-20), for example 1:9.

[0029] In some embodiments, in step 1, the mass-to-volume ratio of the HMF to the solvent is 1:(5-10); for example, 1:5, 1:6 or 1:10; the unit of the mass-to-volume ratio is g / ml.

[0030] In some embodiments, in step 1, the reaction temperature is 60-220°C, preferably 100-150°C, more preferably 110-150°C, for example 110°C, 120°C, 130°C, 140°C or 150°C.

[0031] The progress of the reaction is monitored using conventional monitoring methods in the art, and the end point of the reaction is generally the disappearance of the starting material or the end of the reaction. In some embodiments, in step 1, the reaction time is 1-25 hours, preferably 8-16 hours, for example 8 hours, 10 hours, 12 hours or 16 hours.

[0032] In some embodiments, in step 1, the mass ratio of the HMF to the molecular sieve is 1:0.01, 1:0.05, or 1:0.1; the molecular sieve is one, two, or three of HY molecular sieve, Beta molecular sieve, or Na-Y molecular sieve; the molar ratio of Si to Al in the HY molecular sieve is 2.6; the molar ratio of Si to Al in the Beta molecular sieve is 12.5; and the molar ratio of Si to Al in the Na-Y molecular sieve is 15.

[0033] In some embodiments, in step 1, the reaction further comprises a post-treatment step after completion, and the post-treatment step is preferably distillation, filtration or crystallization; for example, distillation.

[0034] In one embodiment, the method for synthesizing adipic acid, step 2 comprises the following steps: reducing compound I with H2 in a solvent in the presence of a metal catalyst to obtain adipic acid;

[0035]

[0036] The conditions and operations of the reduction reaction may be conventional conditions and operations in the art, and the present invention particularly prefers the following conditions and operations:

[0037] In some embodiments, in step 2, the metal catalyst is 1, 2, 3, 4, 5 or 6 of Pt / C, Pd / C, Ir / C, Ru / C, Au / TiO2 or Ru / TiO2, such as Pt / C, Pd / C, Ir / C or Ru / C.

[0038] In some embodiments, in step 2, the reduction reaction is preferably carried out at a pressure of 1-50 bar, more preferably 20-50 bar, such as 20 bar, 30 bar, 40 bar or 50 bar.

[0039] In some embodiments, in step 2, the mass ratio of the compound I to the metal catalyst is 1:(0.1-0.5), for example, 1:0.1, 1:0.2 or 1:0.5.

[0040] In some embodiments, in step 2, the mass-to-volume ratio of the compound I to the solvent is 1:(60-700); for example, 1:60 or 1:700; the unit of the mass-to-volume ratio is g / ml.

[0041] In some embodiments, in step 2, the temperature of the reduction reaction is 80-160°C, preferably 90-160°C, such as 90°C, 95°C, 100°C or 160°C.

[0042] The progress of the reaction is monitored using conventional monitoring methods in the art, and the reaction endpoint is generally the disappearance of the starting material or the end of the reaction. In some embodiments, in step 2, the reduction reaction time is 1-20 hours, preferably 5-16 hours, for example 5 hours, 6 hours, 8 hours or 16 hours.

[0043] In some embodiments, in step 2, the solvent is C 1-4 The alcohol solvent is preferably one, two or three of isopropanol, ethanol or methanol, such as isopropanol, ethanol or methanol.

[0044] In some embodiments, in step 2, after the reduction reaction is completed, a post-treatment step is further included, and the post-treatment step is preferably distillation, filtration or crystallization; for example, filtration.

[0045] In some embodiments, in step 2, the reduction reaction further comprises a purification step, and the purification step is preferably rotary evaporation, extraction and acidification.

[0046] The present invention also provides a method for synthesizing compound I, which comprises the following steps:

[0047] Under the action of molecular sieves, acid and oxidant, 5-hydroxymethylfurfural (HMF) reacts in a solvent to obtain compound I;

[0048]

[0049] The molar ratio of Si to Al in the molecular sieve is ≤50.

[0050] The reaction conditions and operations are preferably the same as those in step 1 described above.

[0051] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0052] The reagents and raw materials used in the present invention are commercially available.

[0053] The positive progress of the present invention is that the synthesis method of the present invention has the advantage of less by-products, and further, adipic acid can be obtained in high yield under low-cost molecular sieve catalysis, which significantly reduces production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a physical picture of the product collected in Example 1. DETAILED DESCRIPTION

[0055] The present invention is further described below through specific examples.

[0056] The present invention is described in detail below with reference to specific examples, but the present invention is not limited to these examples. At the same time, the examples only provide some conditions for the preparation method of a catalyst and its application, but do not mean that these conditions must be met to achieve this purpose.

[0057] HPLC separation and detection conditions are as follows:

[0058] Instrument: Agilent 1260 high performance liquid chromatograph;

[0059] Chromatographic column: Aminex HPX-87H column (7.8×300mm);

[0060] Mobile phase: A is H2O, B is 5mM H2SO4;

[0061] The flow rate was 0.9 mL / min, the detection wavelength was 210 nm, the column temperature was 50°C, the elution gradient was shown in the table below, and the percentages are volume percentages.

[0062] Time (minutes) Mobile phase A (%) Mobile phase B (%) 0-10 90 10 10-15 80 20 15-30 60 40

[0063] Example 1:

[0064] Step 1: Dissolve 10g of 5-hydroxymethylfurfural in 50mL of isopropanol, add 0.5g of molecular sieve HY (Si / Al=2.6) catalyst and 1mol% of sulfuric acid, and fill with 30bar of O2. The reaction temperature is controlled at 120°C and the reaction time is 8 hours. After the reaction is completed, the solvent is removed by distillation to obtain 2,5-diketo-adipic acid (yield 86%, retention time 9min). The by-products are: (yield is 1%, retention time is 19min), (yield is 4%, retention time is 28min), (yield is 6%, retention time is 13min) and humins (yield is 3%, no retention time, which is the result of carbon balance calculation).

[0065] Step 2: Dissolve 0.5 g of 2,5-diketo-adipic acid in 30 mL of ethanol, add 0.1 g of Pt / C as a metal catalyst, and introduce 25 bar of H2. The reaction temperature is controlled at 100°C for 6 hours. After the reaction, the catalyst is separated by filtration to obtain a mixed solution. The mixed solution is then separated by HPLC to obtain an adipic acid solution containing 96% adipic acid (retention time 7 minutes). The byproducts include: (content is 1%, retention time is 16min), (content 1%, retention time 9min) and (Content is 2%, retention time is 11min).

[0066] The adipic acid solution obtained by HPLC separation in step 2 is further subjected to rotary evaporation, extracted with triethylamine, and the extract is acidified to pH = 2 after rotary evaporation, separated and dried to obtain Figure 1 The white solid adipic acid (0.42 g, purity 98%) is shown, and the isolated yield of adipic acid can reach 90%.

[0067] Example 2:

[0068] Step 1: Dissolve 10 g of 5-hydroxymethylfurfural in 50 mL of methanol, add 0.4 g of H-ZSM-5 (Si / Al=15) molecular sieve catalyst and 1 mol% sulfuric acid, and purge with 30 bar of O2. The reaction temperature is controlled at 130°C for 10 hours. After completion of the reaction, the solvent is removed by distillation to obtain 2,5-diketo-adipic acid with a yield of 74%.

[0069] Step 2: Dissolve 0.5 g of 2,5-diketo-adipic acid in 30 mL of isopropanol, add 0.1 g of Pd / C as a metal catalyst, and introduce 20 bar of H2. The reaction temperature is controlled at 90°C for 5 hours. After the reaction, the catalyst is separated by filtration to obtain a mixed solution, which is then separated by HPLC to obtain an adipic acid solution. The adipic acid solution is further subjected to rotary evaporation, extraction, acidification, and drying to obtain a white solid adipic acid. The specific operation is as described in Example 1; the isolation yield can reach 95%.

[0070] Example 3:

[0071] Step 1: Dissolve 10g of 5-hydroxymethylfurfural in 60mL of ethanol, add 0.1g of Beta (Si / Al = 12.5) molecular sieve catalyst and 1mol% sulfuric acid, and purge with 50bar of O2. The reaction temperature is controlled at 110°C for 12 hours. After completion of the reaction, the solvent is removed by distillation to obtain 2,5-diketo-adipic acid with a yield of 86%.

[0072] Step 2: Dissolve 0.5 g of 2,5-diketo-adipic acid in 350 mL of methanol, add 0.25 g of Ir / C as a metal catalyst, and introduce 30 bar of H2. The reaction temperature is controlled at 95°C for 8 hours. After the reaction, the catalyst is separated by filtration to obtain a mixed solution, which is then separated by HPLC to obtain an adipic acid solution. The adipic acid solution is further subjected to rotary evaporation, extraction, acidification, and drying to obtain a white solid adipic acid. The specific operation is as described in Example 1; the isolation yield can reach 90%.

[0073] Example 4:

[0074] Step 1: Dissolve 5g of 5-hydroxymethylfurfural in 50mL of isopropanol, add 0.1g of molecular sieve HY (Si / Al=5) catalyst and 1mol% sulfuric acid, and purify with 20bar of oxygen. The reaction temperature is controlled at 140°C for 16 hours. After completion of the reaction, the solvent is removed by distillation to obtain 2,5-diketo-adipic acid with a yield of 62%.

[0075] Step 2: Dissolve 0.5 g of 2,5-diketo-adipic acid in 30 mL of ethanol, add 0.05 g of Pt / C as a metal catalyst, and introduce 20 bar of H2. The reaction temperature is controlled at 160°C for 16 hours. After completion of the reaction, the catalyst is separated by filtration to obtain a mixed solution, which is then separated by HPLC to obtain an adipic acid solution. The adipic acid solution is further subjected to rotary evaporation, extraction, acidification, and drying to obtain a white solid adipic acid. The specific operation is as described in Example 1; the isolation yield can reach 90%.

[0076] Example 5:

[0077] Step 1: Dissolve 10g of 5-hydroxymethylfurfural in 50mL of methanol, add 1g of HY (Si / Al=2.6) molecular sieve catalyst and 1mol% hydrochloric acid and fill with 20bar O2. Reaction temperature control At 150°C, the reaction time is 10 hours. After the reaction is completed, the solvent is removed by distillation to obtain The yield of 2,5-diketoadipic acid was 85%.

[0078] Step 2: Dissolve 0.5 g of 2,5-diketo-adipic acid in 30 mL of isopropanol, add 0.1 g of Pt / C as a metal catalyst, and introduce 40 bar of H2. The reaction temperature is controlled at 100°C for 16 hours. After completion of the reaction, the catalyst is separated by filtration to obtain a mixed solution, which is then separated by HPLC to obtain an adipic acid solution. The adipic acid solution is further subjected to rotary evaporation, extraction, acidification, and drying to obtain a white solid adipic acid. The specific operation is as described in Example 1; the isolation yield can reach 89%.

[0079] Example 6:

[0080] Step 1: Dissolve 10g of 5-hydroxymethylfurfural in 50mL of methanol, add 1g of Na-Y (Si / Al=15) molecular sieve catalyst and 1mol% sulfuric acid, and purge with 20bar of O2. The reaction temperature is controlled at 150°C for 10 hours. After completion of the reaction, the solvent is removed by distillation to obtain 2,5-diketo-adipic acid with a yield of 89%.

[0081] Step 2: Dissolve 0.5 g of 2,5-diketo-adipic acid in 30 mL of isopropanol, add 0.1 g of Pt / C as a metal catalyst, and introduce 40 bar of H2. The reaction temperature is controlled at 100°C for 16 hours. After completion of the reaction, the catalyst is separated by filtration to obtain a mixed solution, which is then separated by HPLC to obtain an adipic acid solution. The adipic acid solution is further subjected to rotary evaporation, extraction, acidification, and drying to obtain a white solid adipic acid. The specific operation is as described in Example 1; the isolation yield can reach 91%.

[0082] Example 7:

[0083] Step 1: Dissolve 10 g of 5-hydroxymethylfurfural in 50 mL of methanol and water (V 甲醇 :V 水 =1:9) was added to a mixed solution of 0.1 g of Beta (Si / Al = 12.5) molecular sieve catalyst and 1 mol% sulfuric acid, and 50 bar of oxygen was introduced. The reaction temperature was controlled at 110°C for 12 hours. After completion of the reaction, the solvent was removed by distillation to obtain 2,5-diketo-adipic acid with a yield of 96%.

[0084] Step 2: Dissolve 0.5 g of 2,5-diketo-adipic acid in 350 mL of methanol, add 0.25 g of Ir / C as a metal catalyst, and introduce 30 bar of H2. The reaction temperature is controlled at 95°C for 8 hours. After the reaction, the catalyst is separated by filtration to obtain a mixed solution, which is then separated by HPLC to obtain an adipic acid solution. The adipic acid solution is further subjected to rotary evaporation, extraction, acidification, and drying to obtain a white solid adipic acid. The specific operation is as described in Example 1; the isolation yield can reach 94%.

Claims

1. A method for synthesizing adipic acid, characterized in that: It includes the following steps, Step 1: HMF is reacted to obtain compound I; Step 2: Compound I is subjected to reduction reaction to obtain adipic acid; 2. The method for synthesizing adipic acid according to claim 1, wherein Step 1 comprises the following steps: reacting HMF in a solvent under the action of molecular sieves, acid and oxidant to obtain compound I; The molar ratio of Si to Al in the molecular sieve is ≤50.

3. The method for synthesizing adipic acid according to claim 2, wherein One or more of the following conditions are met: (1) In step 1, the oxidant is air or oxygen; (2) In step 1, the molar ratio of Si to Al in the molecular sieve is 1-20; (3) In step 1, the molecular sieve is an acidic molecular sieve; (4) In step 1, the reaction pressure is 1-50 bar; (5) In step 1, the mass ratio of the HMF to the molecular sieve is 1:(0.01-0.1); (6) In step 1, the acid is an inorganic acid; (7) In step 1, the molar ratio of the HMF to the acid is 1:(0.1-0.3); (8) In step 1, the solvent is C 1-4 Alcohol solvents, water or C 1-4 Alcohol solvent-water mixed solvent; (9) In step 1, the mass-to-volume ratio of the HMF to the solvent is 1:(5-10), and the unit of the mass-to-volume ratio is g / ml; (10) In step 1, the reaction temperature is 60-220°C; (11) In step 1, the reaction time is 1-25 hours; In step (12) , after the reaction is completed, a post-processing step is further included, and the post-processing step is distillation, filtration or crystallization.

4. The method for synthesizing adipic acid according to claim 3, wherein One or more of the following conditions are met: (1) In step 1, the oxidant is oxygen; (2) In step 1, the molar ratio of Si to Al in the molecular sieve is 2.6-15; (3) In step 1, the molecular sieve is one, two, three, four or five of Y molecular sieve, ZSM-5 molecular sieve, Beta molecular sieve, mcm-22 molecular sieve or mordenite; (4) In step 1, the reaction pressure is 20-50 bar; (5) In step 1, the mass ratio of the HMF to the molecular sieve is 1:(0.01-0.05); (6) In step 1, the acid is a protonic acid; (7) In step 1, the molar ratio of the HMF to the acid is 1:(0.126-0.252); (8) In step 1, the solvent is C 1-4 Alcohol solvent-water mixed solvent; (9) In step 1, the reaction temperature is 100-150°C; (10) In step 1, the reaction time is 8-16 hours; In step (11) , after the reaction is completed, a post-processing step is further included, and the post-processing step is distillation.

5. The method for synthesizing adipic acid according to claim 4, wherein One or more of the following conditions are met: (1) In step 1, the molecular sieve is one, two, three or four of HY molecular sieve, H-ZSM-5 molecular sieve, Beta molecular sieve or Na-Y molecular sieve, and the molar ratio of Si to Al in the molecular sieve is 2.6-15; Preferably, the molecular sieve is one, two or three of HY molecular sieve, Beta molecular sieve or Na-Y molecular sieve; the molar ratio of Si to Al in the HY molecular sieve is 2.6; the molar ratio of Si to Al in the Beta molecular sieve is 12.5; the molar ratio of Si to Al in the Na-Y molecular sieve is 15; (2) In step 1, the acid is sulfuric acid or hydrochloric acid; (3) In step 1, the solvent is a methanol-water mixed solvent; the volume ratio of methanol to water in the mixed solvent is preferably 1:(1-20), for example 1:9; And (4) in step 1, the reaction temperature is 110-150°C.

6. The method for synthesizing adipic acid according to claim 2, wherein: In step 1, the molecular sieve is one, two or three of HY molecular sieve, Beta molecular sieve or Na-Y molecular sieve; the molar ratio of Si to Al in the HY molecular sieve is 2.6; the molar ratio of Si to Al in the Beta molecular sieve is 12.5; the molar ratio of Si to Al in the Na-Y molecular sieve is 15; The mass ratio of the HMF to the molecular sieve is 1:(0.01-0.1).

7. The method for synthesizing adipic acid according to claim 1, wherein Step 2 comprises the following steps: in the presence of a metal catalyst, in a solvent, reducing compound I with H2 to obtain adipic acid; 8. The method for synthesizing adipic acid according to claim 7, wherein One or more of the following conditions are met: (1) In step 2, the metal catalyst is one, two, three, four, five or six of Pt / C, Pd / C, Ir / C, Ru / C, Au / TiO2 or Ru / TiO2; (2) In step 2, the pressure of the reduction reaction is 1-50 bar; (3) In step 2, the mass ratio of the compound I to the metal catalyst is 1:(0.1-0.5); (4) In step 2, the mass-to-volume ratio of the compound I to the solvent is 1:(60-700), and the unit of the mass-to-volume ratio is g / ml; (5) In step 2, the temperature of the reduction reaction is 80-160°C; (6) In step 2, the reduction reaction time is 1-20 hours; (7) In step 2, the solvent is C 1-4 Alcohol solvents; (8) In step 2, after the reduction reaction is completed, a post-processing step is further included, wherein the post-processing step is distillation, filtration or crystallization; In step (9) 2, the reduction reaction further includes a purification step after completion, wherein the purification step includes rotary evaporation, extraction and acidification.

9. The method for synthesizing adipic acid according to claim 8, wherein One or more of the following conditions are met: (1) In step 2, the metal catalyst is Pt / C, Pd / C, Ir / C or Ru / C; (2) In step 2, the pressure of the reduction reaction is 20-50 bar; (3) In step 2, the temperature of the reduction reaction is 90-160°C; (4) In step 2, the reduction reaction time is 5-16 hours; In step (5) 2, after the reduction reaction is completed, a post-processing step is further included, and the post-processing step is filtration.

10. A method for synthesizing compound I, characterized in that: It includes the following steps, Under the action of molecular sieves, acid and oxidant, 5-hydroxymethylfurfural (HMF) reacts in a solvent to obtain compound I; The molar ratio of Si to Al in the molecular sieve is ≤50; The reaction conditions and operations can be the same as those described in any one of claims 3 to 5.

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