A bifunctional carbon-based solid acid catalyst, a preparation method and applications thereof

Abstract

The application discloses a bifunctional carbon-based solid acid catalyst, a preparation method and application, in particular to a bifunctional carbon-based solid acid catalyst which is prepared from a cheap carbon source, a zirconium source and a sulfonating agent through a 'carbonization-coordination-sulfonation' strategy, a large number of Lewis acid sites and acid sites are introduced in the preparation process, and Lewis basic sites are effectively destroyed, which can not only promote the etherification reaction of 5-hydroxymethylfurfural, but also avoid the MPV reduction reaction of 5-hydroxymethylfurfural, thereby ensuring the efficient selective synthesis of 5-ethoxymethylfurfural. In addition, the catalyst prepared by the application exhibits excellent catalytic universality, and can convert 5-hydroxymethylfurfural into corresponding 5-alkoxymethylfurfural in different alcohol systems. More importantly, the catalyst also has good catalytic stability, and still maintains satisfactory catalytic activity after being repeatedly used for several times.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of biomass energy and chemical industry, and particularly relates to a Lewis- Dual-functional carbon-based solid acid catalyst, preparation method and application in high-efficiency synthesis of 5-alkoxymethylfurfural. BACKGROUND

[0002] Converting renewable biomass resources into high-grade bio-based liquid fuels has extremely important scientific significance and practical significance for achieving the carbon peak and carbon neutralization goals. Among different bio-based liquid fuels, 5-alkoxymethylfurfural, which is prepared from 5-hydroxymethylfurfural through etherification, is a kind of furan-based monoether liquid fuel, which has the advantages of high energy density, high octane number, good stability and water insolubility, etc. It can also be mixed with commercial gasoline and exhibits excellent combustion performance. Therefore, 5-alkoxymethylfurfural has very broad application potential and market prospects.

[0003] At present, a large number of research results show that Lewis acid catalysts and acid catalysts can be used to convert 5-hydroxymethylfurfural into 5-alkoxymethylfurfural. For example, when AlCl3 is used as a Lewis acid catalyst, the yield of 5-ethoxymethylfurfural is 82.2% after 3h of reaction at 120℃ (Fuel, 2013, 113: 625-631). When H2SO 4、 Amberlyst-15 and SiO2-SO3H are used as acid catalysts, the yields of 5-ethoxymethylfurfural are 70.0% (Green Chemistry, 2012, 14: 1626-1634), 59.0% (Green Chemistry, 2013, 15: 2379-2383) and 83.8% (RSC Advances, 2013, 3, 12313-12319) after 24h, 12h and 10h of reaction at 100℃, respectively. However, Lewis acid catalysts and acid catalysts alone are difficult to achieve high-efficiency conversion of 5-hydroxymethylfurfural into 5-ethoxymethylfurfural. Based on this, researchers have constructed different Lewis- The yield of 5-ethoxymethylfurfural can reach 88.7% (Journal of Industrial and Engineering Chemistry, 2014, 21:1127-1131) and 83.8% (Catalysis Today, 2019, 325:53-60) by using bifunctional catalysts such as Ag1H2PW and TPA / NbP for 6h and 1h at 120℃. Although the yield of 5-ethoxymethylfurfural is improved, the catalytic selectivity of Ag1H2PW and TPA / NbP and the effect on the synthesis of other 5-alkoxymethylfurfurals are still not ideal. Therefore, it is necessary to design and develop a Lewis- It is still necessary to develop a bifunctional carbon-based solid acid catalyst. SUMMARY

[0004] The technical problems to be solved by the present application are: (1) the catalytic selectivity of existing catalysts for preparing 5-ethoxymethylfurfural from 5-hydroxymethylfurfural is not high; (2) the universality of existing catalysts for catalyzing the synthesis of different 5-alkoxymethylfurfurals is poor. The present application provides a Lewis- The bifunctional carbon-based solid acid catalyst can realize the efficient and selective synthesis of corresponding 5-alkoxymethylfurfurals in various low-carbon alcohols.

[0005] The bifunctional carbon-based solid acid catalyst is a Lewis- The preparation method of the bifunctional carbon-based solid acid catalyst comprises the following steps:

[0006] Step 1, carbonization: obtaining an organic carbon material carrier;

[0007] Step 2, coordination: adding the organic carbon material carrier and a metal zirconium salt into an organic solvent, and reacting under heating, and then washing and drying the product to obtain a metal organic carbon coordination polymer;

[0008] Step 3, sulfonation: adding the metal organic carbon coordination polymer and a sulfonating agent into an organic solvent, and then washing and drying the product to obtain a Lewis- The bifunctional carbon-based solid acid catalyst.

[0009] The step in step 1 comprises the following steps: mixing a carbohydrate with deionized water, and then performing a hydrothermal reaction, and then washing and drying the solid precipitate to obtain the organic carbon material carrier.

[0010] The carbohydrate is one of glucose, fructose, sucrose, chitosan or cellulose, and preferably is glucose; the concentration of the carbohydrate is 50-100g / L; the reaction temperature is 160-220℃; and the reaction time is 6-24h.

[0011] The step 2 is characterized in that the zirconium salt is one of zirconium oxychloride, zirconium tetrachloride or zirconium nitrate, preferably zirconium tetrachloride; the concentration of the zirconium salt in the organic solvent is 10-60 g / L; the mass ratio of the zirconium salt to the organic carbon ligand is 0.5:1-2:1; the reaction temperature is 100-160 DEG C; and the reaction time is 12-36 h.

[0012] The step 3 is characterized in that the sulfonating agent is one of chlorosulfonic acid, methane sulfonic acid, p-toluene sulfonic acid, p-aminobenzenesulfonic acid or concentrated sulfuric acid, preferably chlorosulfonic acid; the concentration of the metal organic carbon coordination polymer in the organic solvent is 10-40 g / L; the mass ratio of the metal organic carbon coordination polymer to the sulfonating agent is 1:1-1:3; and the reaction time is 6-12 h.

[0013] Application of the bifunctional carbon-based solid acid catalyst in catalytic synthesis of 5-alkoxymethylfurfural from 5-hydroxymethylfurfural.

[0014] The application is characterized by comprising the following steps:

[0015] The Lewis- The bifunctional carbon-based solid acid catalyst, the small molecule alcohol and 5-hydroxymethylfurfural are added into a high-pressure reaction kettle, the reaction kettle is sealed and placed in a heating furnace, the reaction kettle is raised to a specified temperature under stirring, and 5-hydroxymethylfurfural is converted into 5-alkoxymethylfurfural through etherification after a certain reaction time.

[0016] The small molecule alcohol is selected from methanol, ethanol, propanol, isopropanol, n-butanol and isobutanol.

[0017] The amount of 5-hydroxymethylfurfural is 1-3 wt% of the amount of the small molecule alcohol, and the Lewis- The amount of the bifunctional carbon-based solid acid catalyst is 10-50 wt% of the amount of 5-hydroxymethylfurfural, the reaction temperature is 80-140 DEG C, and the reaction time is 1-6 h.

[0018] The application further provides a method for eliminating Lewis basic sites in a metal organic carbon coordination polymer.

[0019] Beneficial effects

[0020] The application develops a "carbonization-ligand-sulfonation" strategy to prepare Lewis- In the process of preparing the bifunctional carbon-based solid acid catalyst, the following advantages are achieved: (1) the carbonization process not only prepares a suitable catalyst carrier, but also provides a cheap organic ligand for the catalyst; (2) the ligand process introduces Lewis acid-base active sites (Zr 4+ -O 2-), and can make the Lewis acid and base active sites more uniform; (3) the sulfonation process can destroy the coordination bond, which greatly reduces the Lewis base sites (O 2- ), and retains the Lewis acid sites (Zr 4+ ), and also introduces stronger acid sites (-SO3H). The rich Lewis acid sites and acid sites in the catalyst can significantly synergistically promote the etherification reaction of 5-hydroxymethylfurfural, ensuring efficient synthesis of 5-ethoxymethylfurfural. At the same time, the lack of Lewis base sites can significantly inhibit the transfer hydrogenation reaction of 5-hydroxymethylfurfural, reducing the formation of by-products such as 2,5-dihydroxymethylfuran, thereby greatly increasing the selectivity of 5-ethoxymethylfurfural. In addition, the Lewis- bifunctional carbon-based solid acid catalyst also exhibits excellent catalytic stability and catalytic versatility, not only can be reused multiple times, but also can achieve selective synthesis of various 5-alkoxymethylfurfurals in different alcohols. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the FT-IR spectrum of GHTC-SO3H-1 and Zr-GHTC-SO3H-1 prepared in Comparative Examples 1 and 2.

[0022] Figure 2 is the FT-IR spectrum of GHTC, Zr-GHTC and Zr / GHTC-SO3H prepared in Comparative Examples 3 and 4 and Example 1.

[0023] Figure 3 is the elemental distribution spectrum of Zr / GHTC-SO3H prepared in Example 1.

[0024] Figure 4 is the GC chromatogram of 5-ethoxymethylfurfural prepared by etherification of 5-hydroxymethylfurfural catalyzed by Zr / GHTC-SO3H in Example 2. DETAILED DESCRIPTION

[0025] The technical concept of the present application is to prepare a bifunctional carbon-based solid acid catalyst containing rich Lewis and acid sites and uniform distribution of acid sites by the "carbonization-coordination-sulfonation" strategy. Among them, Zr 4 + is the Lewis acid site, and -SO3H is the acid site, which can together promote the etherification reaction of 5-hydroxymethylfurfural in different alcohols to efficiently generate the corresponding 5-alkoxymethylfurfural. At the same time, the lack of Lewis base sites can significantly inhibit the transfer hydrogenation reaction of 5-hydroxymethylfurfural, reducing the formation of by-products such as 2,5-dihydroxymethylfuran, thereby greatly increasing the selectivity of 5-ethoxymethylfurfural. In addition, the Lewis- 2-The removal of the Lewis basic sites can further inhibit the side reactions such as the transfer hydrogenation of 5-hydroxymethylfurfural, and thus the product selectivity of 5-alkoxymethylfurfural can be improved. Therefore, under the synergistic effect of the multiple active sites, the efficient and selective synthesis of different 5-alkoxymethylfurfurals from 5-hydroxymethylfurfural can be realized through the etherification reaction.

[0026] The Lewis- The bifunctional carbon-based solid acid catalyst is prepared through a "carbonization-coordination-sulfonation" strategy, and the catalyst takes organic carbon as a carrier, and simultaneously introduces Lewis acidic sites and acidic sites, and lacks Lewis basic sites.

[0027] The Lewis- The preparation method of the bifunctional carbon-based solid acid catalyst typically comprises the following steps:

[0028] Step 1: a certain amount of a carbohydrate and deionized water are stirred and mixed uniformly, and then are added into a reaction kettle, and are reacted at a certain temperature and autogenous pressure for a period of time to generate a solid precipitate; the solid precipitate is separated by filtration, and is repeatedly washed with anhydrous ethanol and deionized water until the filtrate is clear; and the washed solid precipitate is placed in a vacuum drying box for drying, and is dried at 80 DEG C for 12 h to obtain organic carbon.

[0029] Step 2: a certain amount of the organic carbon and a zirconium salt are added into dimethylformamide, are uniformly dispersed by ultrasonic stirring, and then are moved into a reaction kettle, and are reacted at a certain temperature and autogenous pressure for a period of time; after the reaction is completed, the solid precipitate is separated by filtration, and is repeatedly washed with anhydrous ethanol and deionized water until no chloride ion is detected; and the washed solid precipitate is placed in a vacuum drying box for drying, and is dried at 80 DEG C for 12 h to obtain an organic carbon-zirconium coordination polymer.

[0030] Step 3: a certain amount of the organic carbon-zirconium coordination polymer and a sulfonating agent are added into dichloromethane, are uniformly dispersed by ultrasonic stirring, and then are continuously stirred at room temperature for a period of time; after the reaction is completed, the solid precipitate is separated by filtration, and is repeatedly washed with anhydrous methanol and deionized water until no sulfonic acid ion is detected; and the washed solid precipitate is placed in a vacuum drying box for drying, and is dried at 80 DEG C for 12 h to obtain a Lewis- bifunctional carbon-based solid acid catalyst.

[0031] In step 1, the carbohydrate is one of glucose, fructose, sucrose, chitosan or cellulose, and is preferably glucose; the concentration of the carbohydrate is 50-100 g / L; the reaction temperature is 160-220 DEG C; and the reaction time is 6-24 h.

[0032] In step 2, the zirconium salt is one of zirconium oxychloride, zirconium tetrachloride or zirconium nitrate, preferably zirconium tetrachloride; the concentration of the zirconium salt in dimethylformamide is 10-60 g / L, the mass ratio of the zirconium salt to the organic carbon ligand is 0.5:1-2:1, the reaction temperature is 100-160℃, and the reaction time is 12-36 h.

[0033] In step 3, the sulfonating agent is one of chlorosulfonic acid, methane sulfonic acid, p-toluenesulfonic acid, p-aminobenzenesulfonic acid or concentrated sulfuric acid, preferably chlorosulfonic acid; the concentration of the metal organic carbon complex polymer in dichloromethane is 10-40 g / L, the mass ratio of the metal organic carbon complex polymer to the sulfonating agent is 1:1-1:3, and the reaction time is 6-12 h.

[0034] The Lewis- One of the uses of the bifunctional carbon-based solid acid catalyst is in the high-efficiency synthesis of 5-ethoxymethylfurfural.

[0035] The application includes the following steps:

[0036] The Lewis- The bifunctional carbon-based solid acid catalyst, ethanol and 5-hydroxymethylfurfural are added to a high-pressure reaction kettle, which is then sealed and placed in a heating furnace; the reaction kettle is heated to a specified temperature under stirring, and after a certain reaction time, 5-ethoxymethylfurfural is generated through etherification of 5-hydroxymethylfurfural.

[0037] The amount of 5-hydroxymethylfurfural is 1-3 wt% of the amount of ethanol, the amount of the sulfonic acid functionalized zirconium carbon complex catalyst is 10-50 wt% of the amount of 5-hydroxymethylfurfural, the reaction temperature is 80-140℃, and the reaction time is 1-6 h.

[0038] The Lewis- The bifunctional carbon-based solid acid catalyst also has the use of high-efficiency catalysis of the selective synthesis of 5-methoxymethylfurfural, 5-propoxymethylfurfural, 5-isopropoxymethylfurfural, 5-butoxymethylfurfural and 5-sec-butoxymethylfurfural.

[0039] Comparative Example 1

[0040] 15 g glucose and 2 g methane sulfonic acid were added into 150 mL deionized water to dissolve, after stirring and mixing uniformly, it was moved into a reaction kettle, and reacted under the autogenous pressure at 180 °C for 10 h to generate a solid precipitate; the solid precipitate was separated by filtration and washed repeatedly with anhydrous ethanol and deionized water until no sulfonic acid ion was detected; the washed solid precipitate was placed in a vacuum drying oven for drying, and dried at 80 °C for 12 h to obtain a sulfonic acid functionalized organic carbon, abbreviated as GHTC-SO3H-1. It was found by FT-IR characterization analysis that ( Figure 1 ), 534 cm -1 a stretching vibration peak belonging to C-S bond, 1227 cm -1 a stretching vibration peak belonging to O=S=O bond, 1704 cm -1 a stretching vibration peak belonging to C=O bond, 3432 cm -1 a stretching vibration peak belonging to O-H bond, which indicates that -COOH, Ph-OH and -SO3H etc. acidic sites are successfully introduced in GHTC-SO3H-1 through the simultaneous process of carbonization and sulfonation.

[0041] Next, 0.25 g 5-hydroxymethylfurfural, 20 mL ethanol and 0.1 g GHTC-SO3H-1 were added into a 100 mL reaction kettle, and the reaction kettle was sealed and placed in a heating furnace; after being heated to 120 °C at a stirring speed of 400 rpm, the conversion rate of 5-hydroxymethylfurfural was 52.7% and the yield of 5-ethoxymethylfurfural was 36.5% after reacting for 2 h, and the selectivity of 5-ethoxymethylfurfural was 69.3%, which indicates that the simple acidic sites cannot effectively catalyze the dehydration etherification reaction of 5-hydroxymethylfurfural, so the yield and selectivity of 5-ethoxymethylfurfural are not high. In the experimental design of this control example, since the first step of simultaneous carbonization and sulfonation needs to be carried out under high-temperature hydrothermal reaction conditions, in order to avoid the decomposition of chlorosulfonic acid in water and other problems, methane sulfonic acid similar to chlorosulfonic acid was used for the reaction, which was used to introduce sulfonic acid groups on the surface of the carbon carrier.

[0042] Control Example 2

[0043] 2 g GHTC-SO3H-1 in Control Example 1 and 2 g zirconium tetrachloride were added into 320 mL dimethylformamide, and after being uniformly dispersed by ultrasonic stirring, it was moved into a reaction kettle and reacted under the autogenous pressure at 120 °C for 24 h to generate a solid precipitate; the solid precipitate was separated by filtration and washed repeatedly with anhydrous ethanol and deionized water until no chloride ion was detected; the washed solid precipitate was placed in a vacuum drying oven for drying, and dried at 80 °C for 12 h to obtain a sulfonic acid functionalized organic carbon zirconium coordination catalyst, abbreviated as Zr-GHTC-SO3H-1. It was found by FT-IR characterization analysis that ( Figure 1), compared with GHTC-SO3H-1, 1704 cm -1 the stretching vibration peak of C=O bond and 3432 cm -1 the stretching vibration peak of O-H bond decreased obviously, at the same time, 462 cm -1 and 650 cm -1 the stretching vibration peak of Zr-O bond appeared, which indicated that Zr-GHTC-SO3H-1 retained the acidic sites and introduced Lewis acid-base sites through coordination process.

[0044] Next, 0.25g 5-hydroxymethylfurfural, 20mL ethanol and 0.1g Zr-GHTC-SO3H-1 were added into 100mL reactor, which was sealed and placed in a heating furnace; under the stirring speed of 400rpm, the temperature was raised to 120℃, after 2h reaction, the conversion of 5-hydroxymethylfurfural was 26.4%, the yield of 5-ethoxymethylfurfural was 4.3%, and the selectivity of 5-ethoxymethylfurfural was 16.3%. In addition, under the action of Zr-GHTC-SO3H-1, 5-hydroxymethylfurfural also underwent obvious transfer hydrogenation reaction, and the transfer hydrogenation product was 2,5-dihydroxymethylfuran, whose yield was 6.8%, which not only indicated that the existence of Lewis basic sites could significantly promote the transfer hydrogenation reaction of 5-hydroxymethylfurfural, but also indicated that the existence of Lewis basic sites could significantly inhibit the dehydration etherification reaction activity of Lewis acid sites and acidic sites, thereby reducing the overall catalytic activity of the catalyst.

[0045] Comparative Example 3

[0046] 15g glucose was added into 150mL deionized water to dissolve, after stirring and mixing uniformly, it was moved into the reactor, and reacted under the autogenous pressure of 180℃ for 10h to generate solid precipitate; after the solid precipitate was separated by filtration, it was repeatedly washed with anhydrous ethanol and deionized water until the filtrate was clear; the washed solid precipitate was placed in a vacuum drying oven for drying, and 80℃ drying for 12h could obtain glucose-based hydrothermal organic carbon, which was abbreviated as GHTC. Through FT-IR characterization analysis, it could be known that Figure 2 ), 1704 cm -1 belonged to the stretching vibration peak of C=O bond, 3432 cm -1 belonged to the stretching vibration peak of O-H bond, which indicated that the glucose-based hydrothermal organic carbon obtained through carbonization process contained rich acidic sites such as -COOH and Ph-OH.

[0047] ​Next, 0.25 g of 5-hydroxymethylfurfural, 20 mL of ethanol and 0.1 g of GHTC were added to a 100 mL reaction kettle, which was then placed in a heating furnace after being sealed; under a stirring speed of 400 rpm, the temperature was raised to 120°C, and after 2 h of reaction, the conversion rate of 5-hydroxymethylfurfural was 6.9%, the yield of 5-ethoxymethylfurfural was 2.1%, and the selectivity of 5-ethoxymethylfurfural was 30.4%, which not only indicates that the pure acidic sites cannot effectively catalyze the dehydration etherification reaction of 5-hydroxymethylfurfural, but also indicates that the relatively weak acidic sites cannot effectively promote the formation of 5-ethoxymethylfurfural.

[0048] Comparative Example 4

[0049] 2 g of GHTC in Comparative Example 3 and 2 g of zirconium tetrachloride were added to 320 mL of dimethylformamide, and after being uniformly dispersed by ultrasonic stirring, they were moved into a reaction kettle, and a solid precipitate was generated under a self-generated pressure of 120°C for 24 h of reaction; the solid precipitate was separated by filtration and repeatedly washed with anhydrous ethanol and deionized water until no chloride ions were detected; the washed solid precipitate was placed in a vacuum drying box for drying, and 80°C drying for 12 h yielded an organic carbon-zirconium coordination catalyst, abbreviated as Zr-GHTC. Through FT-IR characterization analysis, it can be seen that Figure 2 ), compared with GHTC, the stretching vibration peak intensity of C=O bond at 1704 cm -1 and the stretching vibration peak intensity of O-H bond at 3432 cm -1 decreased significantly, and at the same time, the stretching vibration peaks of Zr-O bond at 462 cm -1 and 650 cm -1 appeared, which indicates that Zr-GHTC introduced rich Lewis acid-base sites through the coordination process.

[0050] Next, 0.25 g of 5-hydroxymethylfurfural, 20 mL of ethanol and 0.1 g of Zr-GHTC were added to a 100 mL reaction kettle, which was then placed in a heating furnace after being sealed; under a stirring speed of 400 rpm, the temperature was raised to 120°C, and after 2 h of reaction, the conversion rate of 5-hydroxymethylfurfural was 15.6%, the yield of 2,5-dihydroxymethylfuran was 8.3%, and the yield and selectivity of 5-ethoxymethylfurfural were 0, which indicates that in the absence of acidic sites, the main function of Lewis acid-base sites is to promote the transfer hydrogenation reaction of 5-hydroxymethylfurfural to generate 2,5-dihydroxymethylfuran.

[0051] Comparative Example 5

[0052] GHTC-SO3H-2 and GHTC-SO3H-1 have the same structure and active sites, which shows that -COOH, Ph-OH and -SO3H are successfully introduced into GHTC-SO3H-2 through the step-by-step process of carbonization and sulfonation. acidic sites.

[0053] Next, 0.25 g of 5-hydroxymethylfurfural, 20 mL of ethanol and 0.1 g of GHTC-SO3H-2 were added to a 100 mL reaction kettle, and the reaction kettle was sealed and placed in a heating furnace. After the temperature was raised to 120°C at a stirring speed of 400 rpm and reacted for 2 h, the conversion rate of 5-hydroxymethylfurfural was 49.3%, the yield of 5-ethoxymethylfurfural was 32.9%, and the selectivity of 5-ethoxymethylfurfural was 66.7%. This shows that pure acidic sites cannot effectively catalyze the dehydration etherification of 5-hydroxymethylfurfural, so the yield and selectivity of 5-ethoxymethylfurfural are not high.

[0054] Comparative Example 6

[0055] GHTC-SO3H-2 and 2 g of zirconium tetrachloride were added to 320 mL of dimethylformamide, and after ultrasonic stirring and dispersion, the mixture was transferred to a reaction kettle and reacted at 120°C for 24 h under autogenous pressure to form a solid precipitate. The solid precipitate was separated by filtration and repeatedly washed with anhydrous ethanol and deionized water until no chloride ions were detected. The washed solid precipitate was placed in a vacuum drying oven and dried at 80°C for 12 h to obtain a sulfonic acid functionalized organic carbon zirconium coordination catalyst, which is abbreviated as Zr-GHTC-SO3H-2. FT-IR characterization analysis shows that Zr-GHTC-SO3H-2 and Zr-GHTC-SO3H-1 have the same structure and active sites, which shows that Zr-GHTC-SO3H-2 retains acidic sites while also introducing Lewis acid-base sites through the step-by-step strategy of "carbonization, sulfonation and coordination".

[0056] Next, 0.25 g of 5-hydroxymethylfurfural, 20 mL of ethanol and 0.1 g of Zr-GHTC-SO3H-2 were added to a 100 mL reaction kettle, which was sealed and placed in a heating furnace; after being heated to 120°C at a stirring speed of 400 rpm for 2 h, the conversion rate of 5-hydroxymethylfurfural was 31.1%, the yield of 2,5-dihydroxymethylfuran was 7.4%, the yield of 5-ethoxymethylfurfural was 3.9%, and the selectivity of 5-ethoxymethylfurfural was 12.5%, which indicated that the presence of Lewis basic sites not only promoted the transfer hydrogenation reaction of 5-hydroxymethylfurfural, but also significantly inhibited the dehydration etherification reaction activity of Lewis acidic sites and acidic sites, thereby reducing the overall catalytic activity of the catalyst.

[0057] Comparative Example 7

[0058] 15 g of glucose, 2 g of methane sulfonic acid and 2 g of zirconium tetrachloride were added to 150 mL of deionized water and dissolved, and after being stirred and mixed uniformly, they were transferred into a reaction kettle and reacted at a self-generated pressure of 180°C for 10 h to generate a solid precipitate; after being separated by filtration, the solid precipitate was repeatedly washed with anhydrous ethanol and deionized water until no sulfonic acid group and chloride ion were detected; the washed solid precipitate was placed in a vacuum drying box for drying, and 80°C drying for 12 h yielded a sulfonic acid functionalized organic carbon zirconium coordination catalyst, which was abbreviated as Zr-GHTC-SO3H-3. Through FT-IR characterization analysis, it can be seen that the stretching vibration peak at 534 cm -1 belongs to the C-S bond, the stretching vibration peak at 1227 cm -1 belongs to the O=S=O bond, the stretching vibration peak at 1704 cm -1 belongs to the C=O bond, the stretching vibration peak at 3432 cm -1 belongs to the O-H bond, and the stretching vibration peaks at 462 cm -1 and 650 cm -1 belong to the Zr-O bond, which indicates that through the one-pot strategy of “carbonization, sulfonation and coordination”, Zr-GHTC-SO3H-3 can also introduce a large number of acidic sites and Lewis acid-base sites.

[0059] Next, 0.25 g of 5-hydroxymethylfurfural, 20 mL of ethanol, and 0.1 g of Zr-GHTC-SO3H-3 were added to a 100 mL reactor. The reactor was sealed and placed in a heating furnace. The temperature was raised to 120 °C with stirring at 400 rpm. After 2 h of reaction, the conversion rate of 5-hydroxymethylfurfural was 19.5%, the yield of 2,5-dihydroxymethylfuran was 4.5%, the yield of 5-ethoxymethylfurfural was 2.9%, and the selectivity of 5-ethoxymethylfurfural was 14.9%. This indicates that the presence of Lewis basic sites not only promoted the transfer hydrogenation reaction of 5-hydroxymethylfurfural but also significantly inhibited the reaction of Lewis acidic sites and... The dehydration and etherification reaction activity of acidic sites reduces the overall catalytic activity of the catalyst. In this comparative example, since the carbonization-sulfonation-coordination simultaneous reaction is carried out under high-temperature hydrothermal conditions, methanesulfonic acid, which has similar properties to chlorosulfonic acid, was used for the reaction to introduce sulfonic acid groups onto the surface of the carbon support in order to avoid problems such as the decomposition of chlorosulfonic acid upon contact with water.

[0060] Example 1

[0061] 2g of Zr-GHTC from Reference Example 4 and 3g of chlorosulfonic acid were added to 100mL of dichloromethane. After ultrasonic stirring and uniform dispersion, the mixture was stirred and reacted at room temperature for 10h. After the reaction, the solid precipitate was separated by filtration and repeatedly washed with anhydrous methanol and deionized water until no sulfonate and chloride ions were detected. The washed solid precipitate was dried in a vacuum drying oven at 80℃ for 12h to obtain the sulfonic acid-functionalized organic carbon zirconium coordination catalyst, abbreviated as Zr / GHTC-SO3H. FT-IR characterization analysis showed that ( Figure 2 Compared to Zr-GHTC, Zr / GHTC-SO3H has a higher concentration at 534 cm⁻¹. -1 The stretching vibration peak of the CS bond appeared at 1227 cm⁻¹. -1 The appearance of stretching vibration peaks of O=S=O bonds indicates that the sulfonation process introduced -SO3H and other bonds into Zr / GHTC-SO3H. Acidic sites. More importantly, Zr / GHTC-SO3H at 1704 cm⁻¹ -1 The stretching vibration peak of the C=O bond and 3432 cm⁻¹ -1 The stretching vibration peak intensity of the OH bond at 462 cm⁻¹ increased significantly, and at the same time, the peak intensity at 462 cm⁻¹ increased significantly. -1 650cm -1 The stretching vibration peak of the Zr-O bond was significantly weakened, indicating that the sulfonation process also reduced the Lewis base sites in Zr / GHTC-SO3H by partially disrupting the Zr-O bond linkage. In other words, the "carbonization-coordination-sulfonation" strategy ensured both the presence of Lewis acidic sites and the presence of Lewis base sites. Introduction and uniform distribution of acid sites Figure 3 ), and the Lewis basic sites were also greatly destroyed.

[0062] Next, 0.25 g of 5-hydroxymethylfurfural, 20 mL of ethanol and 0.1 g of Zr / GHTC-SO3H were added into a 100 mL reaction kettle, and the reaction kettle was placed in a heating furnace after being sealed; under the stirring speed of 400 rpm, the temperature was raised to 120°C, and after 2 h of reaction, the conversion rate of 5-hydroxymethylfurfural was 100.0%, and the yield and selectivity of 5-ethoxymethylfurfural were 88.4%, which indicated that the synergistic effect of Lewis acid sites and The synergistic effect of Lewis acid sites and can efficiently promote the dehydration etherification reaction of 5-hydroxymethylfurfural to generate 5-ethoxymethylfurfural. At the same time, the destruction and lack of Lewis basic sites also avoid the transfer hydrogenation reaction of 5-hydroxymethylfurfural and the formation of 2,5-dihydroxymethylfuran (the yield of 2,5-dihydroxymethylfuran is 0), which further improves the selectivity of 5-ethoxymethylfurfural. Correspondingly, if the synthesis sequence of “carbonization-sulfonation-ligand” in Comparative Examples 1, 2, 5, 6 and 7 (regardless of step synthesis or one-pot synthesis) is adopted, a large number of Lewis basic sites will be introduced, which will lead to the occurrence of MPV transfer hydrogenation reaction, and then reduce the yield and selectivity of the target product.

[0063] Example 2

[0064] Next, 0.25 g of 5-hydroxymethylfurfural, 20 mL of ethanol and 0.1 g of Zr / GHTC-SO3H were added into a 100 mL reaction kettle, and the reaction kettle was placed in a heating furnace after being sealed; under the stirring speed of 400 rpm, the temperature was raised to 120°C, and after 2 h of reaction, the conversion rate of 5-hydroxymethylfurfural was 100.0%, and the yield and selectivity of 5-ethoxymethylfurfural were 88.4%, which indicated that the synergistic effect of Lewis acid sites and Figure 4 ), which indicated that the optimization of the reaction conditions was beneficial to further improve the catalytic activity of the catalyst and promote the formation of the target product. More importantly, when the Zr / GHTC-SO3H was repeatedly used for 4 times under the same reaction conditions, the conversion rate of 5-hydroxymethylfurfural could still reach 98.5%, and the yield and selectivity of 5-ethoxymethylfurfural could reach 90.2% and 91.6%, which indicated that the Zr / GHTC-SO3H exhibited good catalytic stability.

[0065] In order to better highlight the effectiveness of the “carbonization-ligand-sulfonation” strategy in the present application, the catalytic performance of the Zr / GHTC-SO3H prepared in Example 1 was compared with other catalysts, and the specific results are shown in Table 1. As can be seen from Table 1, in the Zr / GHTC-SO3H provided by the present application, the Zr 4+is the Lewis acid site, -SO3H is acid sites, which can jointly promote the etherification of 5-hydroxymethylfurfural in ethanol to generate 5-ethoxymethylfurfural efficiently. At the same time, O 2- The removal of (Lewis basic site) can also inhibit the transfer hydrogenation and other side reactions of 5-hydroxymethylfurfural, thereby improving the product selectivity of 5-ethoxymethylfurfural. Therefore, under the synergistic action of the multiple active sites of Zr / GHTC-SO3H, 5-ethoxymethylfurfural can be synthesized efficiently and selectively from 5-hydroxymethylfurfural through etherification, and the catalytic performance is obviously better than that of other catalysts in Table 1.

[0066] Table 1

[0067]

[0068] In order to further demonstrate the effectiveness of the "carbonation-ligand-sulfonation" strategy in the present application, the catalytic universality of Zr / GHTC-SO3H in Example 1 in different alcohol systems is also studied, and the specific results are shown in Examples 3-7.

[0069] Example 3

[0070] 0.25g of 5-hydroxymethylfurfural, 20mL of methanol and 0.1g of Zr / GHTC-SO3H were added into a 100mL reaction kettle, and the reaction kettle was sealed and placed in a heating furnace; under the stirring speed of 400rpm, the temperature was raised to 100℃, after 2h of reaction, the conversion rate of 5-hydroxymethylfurfural was 100.0%, and the yield and selectivity of 5-methoxymethylfurfural was 91.6%.

[0071] Example 4

[0072] 0.25g of 5-hydroxymethylfurfural, 20mL of methanol and 0.1g of Zr / GHTC-SO3H were added into a 100mL reaction kettle, and the reaction kettle was sealed and placed in a heating furnace; under the stirring speed of 400rpm, the temperature was raised to 100℃, after 2h of reaction, the conversion rate of 5-hydroxymethylfurfural was 100.0%, and the yield and selectivity of 5-methoxymethylfurfural was 91.6%.

[0073] Example 5

[0074] 0.25g of 5-hydroxymethylfurfural, 20mL of methanol and 0.1g of Zr / GHTC-SO3H were added into a 100mL reaction kettle, and the reaction kettle was sealed and placed in a heating furnace; under the stirring speed of 400rpm, the temperature was raised to 100℃, after 2h of reaction, the conversion rate of 5-hydroxymethylfurfural was 100.0%, and the yield and selectivity of 5-methoxymethylfurfural was 91.6%.

[0075] Example 6

[0076] 0.25 g of 5-hydroxymethylfurfural, 20 mL of butanol and 0.1 g of Zr / GHTC-SO3H were added to a 100 mL reaction kettle, which was sealed and placed in a heating furnace after sealing; under the stirring speed of 400 rpm, the temperature was raised to 130℃, after 4h reaction, the conversion rate of 5-hydroxymethylfurfural was 100.0%, and the yield and selectivity of 5-butoxymethylfurfural was 92.9%.

[0077] Example 7

[0078] 0.25 g of 5-hydroxymethylfurfural, 20 mL of butanol and 0.1 g of Zr / GHTC-SO3H were added to a 100 mL reaction kettle, which was sealed and placed in a heating furnace after sealing; under the stirring speed of 400 rpm, the temperature was raised to 130℃, after 4h reaction, the conversion rate of 5-hydroxymethylfurfural was 100.0%, and the yield and selectivity of 5-butoxymethylfurfural was 92.9%.

[0079] As can be seen from Examples 1 and 3-7, Zr / GHTC-SO3H prepared by the "carbonization-ligand-sulfonation" strategy not only can catalyze the efficient synthesis of 5-ethoxymethylfurfural in ethanol, but also can catalyze the efficient synthesis of 5-methoxymethylfurfural, 5-propoxymethylfurfural, 5-isopropoxymethylfurfural, 5-butoxymethylfurfural and 5-sec-butoxymethylfurfural in methanol, propanol, isopropanol, butanol and sec-butanol, showing good catalytic universality.

[0080] References:

[0081] [1] Green Chemistry, 2016, 18: 5884-5889.

[0082] [2] Catalysis Science Technology, 2013, 3: 2104-2112.

[0083] [3] RSC Advances, 2021, 11: 33969-33979.

[0084] [4] Journal of Industrial and Engineering Chemistry, 2014, 21: 1127-1131.

[0085] [5] Fuel, 2021, 303: 121227.

Claims

1. Use of a Lewis-Bronsted bifunctional carbon-based solid acid catalyst in the catalytic synthesis of 5-alkoxymethylfurfural from 5-hydroxymethylfurfural, characterized in that, The preparation method of the Lewis-Brønsted dual-functional carbon-based solid acid catalyst comprises the following steps: Step 1, carbonization: obtaining an organic carbon material carrier; Step 2, coordination: adding the organic carbon material carrier and a metal zirconium salt into an organic solvent, and reacting under heating, and then washing and drying the product to obtain a metal organic carbon coordination polymer; Step 3, sulfonation: adding the metal organic carbon coordination polymer and a sulfonating agent into an organic solvent, uniformly dispersing under ultrasonic stirring, and then continuously stirring and reacting at room temperature for a period of time; washing and drying the product to obtain the Lewis-Brønsted dual-functional carbon-based solid acid catalyst; The step 1 comprises the following steps: mixing a carbohydrate and deionized water, and then performing a hydrothermal reaction, washing and drying the solid precipitate to obtain the organic carbon material carrier; the carbohydrate is glucose; the concentration of the carbohydrate is 50-100 g / L, the reaction temperature is 160-220 DEG C, and the reaction time is 6-24 h; In the step 2, the zirconium salt is zirconium tetrachloride; the concentration of the zirconium salt in the organic solvent is 10-60 g / L, the mass ratio of the zirconium salt to the organic carbon material carrier is 0.5:1-2:1, the reaction temperature is 100-160 DEG C, and the reaction time is 12-36 h; In the step 3, the sulfonating agent is chlorosulfonic acid; the concentration of the metal organic carbon coordination polymer in the organic solvent is 10-40 g / L, the mass ratio of the metal organic carbon coordination polymer to the sulfonating agent is 1:1-1:3, and the reaction time is 6-12 h; The Lewis-Brønsted dual-functional carbon-based solid acid catalyst, a small molecule alcohol and 5-hydroxymethylfurfural are added into a high-pressure reaction kettle, the reaction kettle is sealed and placed in a heating furnace; the reaction kettle is heated to a specified temperature under stirring, and after a certain reaction time, the 5-hydroxymethylfurfural is converted into 5-alkoxymethylfurfural through an etherification reaction; The small molecule alcohol is selected from methanol, ethanol, propanol, isopropanol, n-butanol or isobutanol.

2. Use according to claim 1, characterized in that, The amount of the 5-hydroxymethylfurfural is 1-3 wt% of the amount of the small molecule alcohol, the amount of the Lewis-Brønsted dual-functional carbon-based solid acid catalyst is 10-50 wt% of the amount of the 5-hydroxymethylfurfural, the reaction temperature is 80-140 DEG C, and the reaction time is 1-6 h.

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