CN115677629A - Method for preparing 5-methylfurfural by using iron-based catalyst - Google Patents

Abstract

The invention discloses a green synthesis method for preparing 5-methylfurfural (5-MF) by using 5-hydroxymethylfurfural (HMF) as a raw material. In the preparation process, water doubles as a solvent and a reaction accelerator. The catalyst is a cheap iron-based catalyst, which can be pure iron or contains doping elements, and the molar content of iron is 50-100%; the specific steps are as follows: a certain amount of iron catalyst is loaded into a fixed-bed reactor, and the Inject the reducing gas to carry out the reduction treatment on the catalyst. After the reduction, the aqueous solution of HMF is injected into the reactor with the injection pump, and the carrier gas is passed to make the reactants pass through the catalyst bed more smoothly, and the aqueous solution of the product 5-MF is obtained by the reaction. . The catalyst used in the present invention is easy to prepare, low in price, non-toxic and environmentally friendly, and does not use organic solvents in the reaction process, which can effectively reduce the economic and environmental costs of the synthesis process; the present invention is a method for preparing 5-MF The new green and economical method.

Description

Method for preparing 5-methylfurfural by using iron-based catalyst

technical field

The invention relates to the field of chemical catalysis, in particular to a method for preparing 5-methylfurfural by using an iron-based catalyst to catalyze 5-hydroxymethylfurfural.

Background technique

In recent years, the world's growing demand for renewable energy and chemicals has stimulated research on biomass resources. Biomass resources have the advantages of being environmentally friendly and having a wide range of sources. At the same time, they are also a renewable carbon source that can be converted into solid, liquid or gaseous fuels, so they are very promising. Among numerous biomass-based chemicals, 5-MF (5-methylfurfural) is a very useful chemical substance that can be used as a raw material in medicines, pesticides, cosmetics, and many other chemical processes. According to statistics, more than 70 compounds can be synthesized from 5-MF. In addition, 5-MF is also considered to be a better gasoline additive than other feedstocks such as ethanol due to its low oxygen content, high energy density, and good solubility in hydrocarbons.

As one of the top ten bio-based platform chemicals, HMF (5-hydroxymethylfurfural) contains highly reactive groups such as aldehyde groups, hydroxyl groups, and furan rings in its molecules, and can generate a variety of high added value through a series of catalytic reactions Products, such as 2,5-furandicarbaldehyde, 2,5-furandicarboxylic acid, 5-methylfurfural, 2,5-dimethyltetrahydrofuran, etc. HMF can be prepared by dehydration of glucose or fructose or one-pot hydrolysis/dehydration of cellulose in the presence of a catalyst.

In recent years, more and more attention has been paid to the synthesis of 5-MF (5-methylfurfural) from biomass-derived HMF. Decomposition reaction synthesizes 5-MF. In 2014, Fu Yao et al. reported that in 4 MPa tetrahydrofuran (THF) solution, using W ₂ C/AC as a catalyst, the yield of 5-MF obtained by hydrogenolysis of HMF was 88%. In 2019, the research group also reported the research on the synthesis of dimethylfuran from HMF catalyzed by Fe-NC catalyst in n-butanol solution. In this system, 5-MF was also obtained as a by-product of 22%. Yield. Recently, Han Buxing's group used _{Nb2O5 -} supported single-atom Pt as a catalyst under a _H2 pressure of 4 MPa and tetrahydrofuran as a solvent to obtain a 5-MF yield close to 100%.

Besides _H2 , other H-containing compounds are sometimes used as hydrogen donors for the synthesis of 5-MF. Xia Coast et al. used Pd-PVP/C as the catalyst and formic acid (FA) as the hydrogen source to obtain 80% yield of 5-MF in THF solvent. Recently, Bao Xin and the research group used N-doped carbon layer to coat Au nanocatalyst and renewable formic acid as hydrogen donor, and obtained 95% yield of 5-MF in the case of dioxane as solvent.

Contents of the invention

The technical problem solved by the present invention is: in the prior art, the preparation of 5-MF by HMF hydrogenolysis is usually carried out in an organic solvent, and organic reagents such as high-pressure hydrogen or formic acid are used as hydrogen sources, and noble metal catalyst systems are in the majority, so existing In the process of preparing 5-MF, there are generally disadvantages such as high catalyst cost and the need for organic solvents, and the enterprise's operating costs and environmental protection costs are relatively high.

The purpose of the present invention is to provide a method for synthesizing 5-MF from HMF by using iron as the main active component of the catalyst and using water as a solvent and a hydrogen donor to catalyze HMF. Inexpensive catalytic hydrogenolysis of HMF to synthesize 5-MF.

It is characterized in that, comprising the following steps:

(1) Reduction process: the iron-based catalyst is placed in the reactor, and the reducing gas is introduced to perform reduction and activation treatment;

(2) reaction process: pass into the aqueous solution containing 5-hydroxymethylfurfural in the reactor, obtain the aqueous solution containing 5-methylfurfural after the reaction;

Wherein, the metal element in the iron-based catalyst includes iron element and doping element, and the doping element is selected from one or both of V, Cr, Mn, Co, Ni, Zn, Cu, Al and Mg elements. More than one species, the amount of the iron element accounts for 50-100% of all the metal elements in the iron-based catalyst.

Preferably, the doping element is zinc.

Preferably, the amount of iron element accounts for 80-100% of all metal elements.

The reduction gas contains H ₂ or CO, the content is 20-100%, the reduction temperature is 400-600° C., and the reduction time is 2-4 hours.

Preferably, the reduction temperature is 400-500°C.

Preferably, the flow rate of the reducing gas is 20-50ml/min, and the space velocity of the reducing gas is 12000-30000h ^-1 .

During the reaction process, the 5-hydroxymethylfurfural aqueous solution is injected into the reactor with a sample pump, the concentration of 5-hydroxymethylfurfural is 1-60mg/ml, the injection rate is 1-3ml/h, and the weight hourly space velocity is 0.015 ～0.3h ^-1 , and the carrier gas is passed through, the reaction temperature is 220～300°C, and the product is reacted to obtain an aqueous solution containing 5-methylfurfural.

Preferably, in the aqueous solution containing 5-hydroxymethylfurfural, the concentration of 5-hydroxymethylfurfural is 10-20 mg/ml.

Preferably, the reaction temperature is 240-300°C.

Preferably, the carrier gas introduced in the reaction is one or a combination of non-oxidizing gases such as H ₂ , N ₂ , Ar, and He.

Preferably, the flow rate of the carrier gas used in the reaction process is 20-50ml/min.

Compared with existing technology, main advantage of the present invention is:

(1) Use cheap iron-based catalysts, and the preparation method is simple, and the spent catalysts are non-toxic and environmentally friendly, which can effectively reduce the cost of the 5-MF synthesis process;

(2) Water is used as a solvent and a hydrogen donor in the reaction process, and other organic solvents and hydrogen donors such as formic acid are not needed, so the entire reaction process is green and environmentally friendly.

Description of drawings

Fig. 1 is the experimental result of the cycle life of the catalyst described in Example 15 of the present invention.

Detailed ways

In a preferred embodiment, the preparation and reaction method of the present invention comprises the following steps:

The catalyst can be prepared by a common sol-gel method. The specific method is: Weigh an appropriate amount of iron nitrate and other metal nitrates (V, Cr, Mn, Co, Ni, Cu, Zn, Mg or Al, etc.) In a milliliter of ethylene glycol, it was stirred at 40°C for 2 hours, then at 80°C for 1.5 hours, then dried overnight in an oven at 120°C, and the obtained solid was calcined in flowing air at 500°C for 4 hours. A series of FeMx catalysts with different molar ratios of Fe:M were prepared using this method, where M is the doping element (V, Cr, Mn, Co, Ni, Cu, Zn, Mg or Al, etc.), and x is the doping metal mole percentage.

Put a certain amount of iron-based catalyst into the fixed-bed reactor, and pass in reducing gas to reduce the catalyst. After the reduction, use the injection pump to inject the 5-hydroxymethylfurfural aqueous solution into the reactor, and pass it at a certain flow rate. The carrier gas is reacted to obtain an aqueous solution containing 5-methylfurfural. Among them, water doubles as a solvent and a reaction accelerator. The reducing gas used is _H2 or CO, and the reducing temperature is 400-600°C.

The present invention will be further described in detail below in conjunction with the embodiments. The described embodiments are not all, but only a part of the embodiments of the present invention. Within the scope of the present invention, no creative changes are made, and all belong to the protection scope of the present invention.

In the following examples, the information of the equipment used is as follows:

Electric heating furnace (Jiangsu Ruipu Electric Equipment Factory, model: RP-800); gas chromatograph (Agilent, model: 7820A).

The iron salts and other nitrates used were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 5-hydroxymethylfurfural and other organic reagents were purchased from Sinopharm Chemical Reagent Co., Ltd.

Example 1

Weigh 5 mmol of ferric nitrate and add it to 10 ml of ethylene glycol, stir at 40°C for 2 hours, then stir at 80°C for 1.5 hours at a stirring speed of 600 rpm, and then dry in an oven at 120°C for 12 hours. The obtained solid was calcined in flowing air at 500° C. for 4 hours to prepare an iron oxide catalyst Fe ₂ O ₃ .

Weigh 200 mg of iron oxide catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% H ₂ /Ar gas mixture with a flow rate of 35 ml/min, and the gas space velocity is 21000 h ^-1 , put the catalyst Restore at 500°C for 2 hours, then cool down to 280°C, inject HMF aqueous solution with a concentration of 12.6mg/ml into the reaction tube with a syringe pump, the injection rate is 1ml/h, the weight hourly space velocity is 0.063h ^-1 , and pass through The argon of 20ml/min is used as the carrier gas to make the reactant pass through the catalyst bed layer more smoothly. After 1.5 hours of reaction, the condensed liquid phase product is collected and analyzed by gas chromatography. The conversion rate of HMF is 92.0%. 5-MF The selectivity of is 68.4%, and the yield of 5-MF is 62.9%.

Example 2

Weigh 200mg of iron oxide catalyst into the middle of the reaction tube, install the reaction tube in an electric heating furnace, feed high-purity hydrogen with a flow rate of 20ml/min, the gas space velocity is 12000h ^-1 , and reduce the catalyst at 500°C for 2 hour, then lower the temperature to 300°C, use a syringe pump to inject HMF aqueous solution with a concentration of 10mg/ml into the reaction tube, the injection rate is 1ml/h, the weight hourly space velocity is 0.05h ^-1 , and the carrier gas is nitrogen at 20ml/min. After 1.5 h, the condensed liquid phase product was collected and analyzed by gas chromatography. The conversion rate of HMF was 98.2%, the selectivity of 5-MF was 66.4%, and the yield of 5-MF was 65.2%.

Example 3

Weigh 200 mg of iron oxide catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed 50 vol% H ₂ /Ar mixed gas with a flow rate of 50 ml/min, and the gas space velocity is 30000 h ^-1 , and put the catalyst Restore at 600°C for 2 hours, then lower the temperature to 300°C, inject HMF aqueous solution with a concentration of 12.6mg/ml into the reaction tube with a syringe pump, the injection rate is 2ml/h, the weight hourly space velocity is 0.126h ^-1 , and the carrier gas is 20ml/min of hydrogen, after 1.5h of reaction, the condensed liquid phase product was collected and analyzed by gas chromatography. The conversion rate of HMF was 37.7%, the selectivity of 5-MF was 43.4%, and the yield of 5-MF was 16.4%. %.

Example 4

Weigh 200 mg of iron oxide catalyst and put it into the middle of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% CO/Ar gas mixture with a flow rate of 20 ml/min, and a gas space velocity of 12000 h ^-1 , place the catalyst in the Restore at 400°C for 2 hours, then cool down to 220°C, inject HMF aqueous solution with a concentration of 20mg/ml into the reaction tube with a syringe pump, the injection rate is 1ml/h, the weight hourly space velocity is 0.1h ^-1 , and the carrier gas is 40ml/ Min of hydrogen, after 1.5 hours of reaction, the condensed liquid phase product was collected and analyzed by gas chromatography. The conversion rate of HMF was 77.3%, the selectivity of 5-MF was 62.1%, and the yield of 5-MF was 48.0%.

Example 5

Weigh 200 mg of iron oxide catalyst and put it into the middle of the reaction tube, install the reaction tube in the fixed bed reactor of the electric heating furnace, and feed 50 vol% H ₂ /Ar mixed gas with a flow rate of 20 ml/min, and the gas space velocity is 12000 h ^{- 1.} Reduce the catalyst at 500°C for 4 hours, then lower the temperature to 240°C, inject HMF aqueous solution with a concentration of 12.6mg/ml into the reaction tube with a syringe pump, the injection rate is 1ml/h, and the weight hourly space velocity is 0.063h ^-1 , the carrier gas is hydrogen at 50ml/min, and the condensed liquid phase product is collected after 1.5h of reaction and analyzed using a gas chromatograph. The conversion rate of HMF is 86.1%, and the selectivity of 5-MF is 70.3%. The yield was 60.5%.

Example 6

Weigh 2.5mmol of ferric nitrate and 2.5mmol of chromium nitrate and add them to 10ml of ethylene glycol, stir at 40°C for 2 hours, then stir at 80°C for 1.5 hours, the stirring speed is 600 rpm, and then stir at 120°C The obtained solid was dried in an oven for 12 hours, and the obtained solid was calcined in flowing air at 500°C for 4 hours to prepare a catalyst material with a molar ratio of Fe and Cr of 50:50, referred to as FeCr ₅₀ .

Weigh 200 mg of FeCr ₅₀ catalyst into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% H ₂ /Ar gas mixture with a flow rate of 20 ml/min, and a gas space velocity of 12000 h ^-1 , The catalyst was reduced at 500°C for 2 hours, then the temperature was lowered to 280°C, and the HMF aqueous solution with a concentration of 12.6mg/ml was injected into the reaction tube with a syringe pump, the injection rate was 1ml/h, the weight hourly space velocity was 0.063h ^-1 , and the carrier gas H ₂ /Ar (50vol%) of 20ml/min, after 1.5h of reaction, the condensed liquid phase product was collected and analyzed by gas chromatography, the conversion rate of HMF was 100%, and the selectivity of 5-MF was 45.1% , the yield of 5-MF was 45.1%.

Example 7

Referring to the method in Example 6, chromium nitrate was replaced by manganese nitrate to prepare a catalyst material with a molar ratio of Fe and Mn of 50:50, referred to as FeMn ₅₀ .

Weigh 200 mg of FeMn ₅₀ catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% H ₂ /Ar gas mixture with a flow rate of 20 ml/min, and a gas space velocity of 12000 h ^-1 , The catalyst was reduced at 500°C for 2 hours, then the temperature was lowered to 280°C, and the HMF aqueous solution with a concentration of 12.6mg/ml was injected into the reaction tube with a syringe pump, the injection rate was 1ml/h, the weight hourly space velocity was 0.063h ^-1 , and the carrier gas Be the hydrogen of 20ml/min, after reacting 1.5h, collect the liquid phase product after the condensation and use the gas chromatograph to analyze, the conversion rate of HMF is 54.1%, the selectivity of 5-MF is 46.4%, 5-MF productive rate is 25.1%.

Example 8

Referring to the method in Example 6, chromium nitrate was replaced by nickel nitrate to prepare a catalyst material with a molar ratio of Fe and Ni of 50:50, referred to as FeNi ₅₀ .

Weigh 200 mg of FeNi ₅₀ catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% H ₂ /Ar gas mixture with a flow rate of 20 ml/min, and a gas space velocity of 12000 h ⁻¹ . The catalyst was reduced at 500°C for 2 hours, then the temperature was lowered to 280°C, and the HMF aqueous solution with a concentration of 12.6mg/ml was injected into the reaction tube with a syringe pump, the injection rate was 1ml/h, the weight hourly space velocity was 0.063h ^-1 , and the carrier gas Be the hydrogen of 20ml/min, after reacting 1.5h, collect the liquid phase product after the condensation and use gas chromatograph to analyze, the transformation rate of HMF is 61.2%, the selectivity of 5-MF is 34.0%, 5-MF productive rate is 20.8%.

Example 9

Referring to the method in Example 6, chromium nitrate was replaced with zinc nitrate to prepare a catalyst material with a molar ratio of Fe and Zn of 50:50, referred to as FeZn ₅₀ .

Weigh 200 mg of FeZn ₅₀ catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 20vol% _H2 /Ar mixed gas with a flow rate of 20ml/min, and the gas space velocity is 12000h ^-1 , the The catalyst was reduced at 500°C for 2 hours, then lowered to 300°C, and the HMF aqueous solution with a concentration of 12.6mg/ml was injected into the reaction tube with a syringe pump, the injection rate was 1ml/h, the weight hourly space velocity was 0.063h ^-1 , and the carrier gas Be the hydrogen of 20ml/min, collect the liquid phase product after the reaction 1.5h and use the gas chromatograph to analyze, the conversion rate of HMF is 91.2%, the selectivity of 5-MF is 60.1%, and the 5-MF productive rate is 54.8%.

Example 10

Referring to the method in Example 6, chromium nitrate was replaced by aluminum nitrate to prepare a catalyst material with a molar ratio of Fe and Al of 50:50, referred to as FeAl ₅₀ .

Weigh 200 mg of FeAl ₅₀ catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% H ₂ /Ar mixed gas with a flow rate of 20 ml/min, and a gas space velocity of 12000 h ^-1 , The catalyst was reduced at 500°C for 2 hours, then the temperature was lowered to 280°C, and the HMF aqueous solution with a concentration of 12.6mg/ml was injected into the reaction tube with a syringe pump, the injection rate was 1ml/h, the weight hourly space velocity was 0.063h ^-1 , and the carrier gas Be the hydrogen of 20ml/min, after reacting 1.5h, collect the liquid phase product after the condensation and use gas chromatograph to analyze, the transformation rate of HMF is 100%, the selectivity of 5-MF is 42.2%, and the 5-MF yield is 42.2%.

Example 11

Referring to the preparation method of Example 9, the addition amount of iron nitrate was changed to 4 mmol, and the addition amount of zinc nitrate was changed to 1 mmol to prepare a catalyst material with a molar ratio of Fe and Zn of 80:20, referred to as FeZn ₂₀ .

Weigh 200 mg of FeZn ₂₀ catalyst into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% H ₂ /Ar gas mixture with a flow rate of 20 ml/min, and a gas space velocity of 12000 h ^-1 . The catalyst was reduced at 500°C for 2 hours, then the temperature was lowered to 280°C, and the HMF aqueous solution with a concentration of 12.6mg/ml was injected into the reaction tube with a syringe pump, the injection rate was 1ml/h, the weight hourly space velocity was 0.063h ^-1 , and the carrier gas Be the hydrogen of 20ml/min, collect the liquid phase product after the reaction 1.5h and use the gas chromatograph to analyze, the conversion rate of HMF is 98.8%, the selectivity of 5-MF is 78.2%, and the 5-MF yield is 77.3%.

Example 12

Referring to the preparation method of Example 9, the addition amount of iron nitrate was changed to 4.5 mmol, and the addition amount of zinc nitrate was changed to 0.5 mmol to prepare a catalyst material with a molar ratio of Fe and Zn of 90:10, referred to as FeZn ₁₀ .

Weigh 200 mg of FeZn ₁₀ catalyst into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed a 50 vol% H ₂ /Ar gas mixture with a flow rate of 20 ml/min, and a gas space velocity of 12000 h ^-1 , The catalyst was reduced at 500°C for 2 hours, then the temperature was lowered to 280°C, and the HMF aqueous solution with a concentration of 12.6mg/ml was injected into the reaction tube with a syringe pump, the injection rate was 1ml/h, the weight hourly space velocity was 0.063h ^-1 , and the carrier gas Be the hydrogen of 20ml/min, collect the liquid phase product after the reaction 1.5h and use the gas chromatograph to analyze, the conversion rate of HMF is 97.7%, the selectivity of 5-MF is 75.8%, 5-MF productive rate is 74.1%.

Example 13

Weigh 200 mg of iron oxide catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed 50 vol% H ₂ /Ar mixed gas with a flow rate of 20 ml/min, and the gas space velocity is 12000 h ^-1 , put the catalyst Restore at 500°C for 2 hours, then lower the temperature to 300°C, inject HMF aqueous solution with a concentration of 60mg/ml into the reaction tube with a syringe pump, the injection rate is 1ml/h, the weight hourly space velocity is 0.3h ^-1 , and the carrier gas is 20ml /min of hydrogen, after the reaction of 1.5h, the condensed liquid phase product was collected and analyzed using a gas chromatograph. The conversion rate of HMF was 32.8%, the selectivity of 5-MF was 65.9%, and the 5-MF yield was 21.6%. .

Example 14

Weigh 200 mg of iron oxide catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed 50 vol% H ₂ /Ar mixed gas with a flow rate of 20 ml/min, and the gas space velocity is 12000 h ^-1 , put the catalyst Restore at 500°C for 2 hours, then lower the temperature to 300°C, inject HMF aqueous solution with a concentration of 1mg/ml into the reaction tube with a syringe pump, the injection rate is 3ml/h, the weight hourly space velocity is 0.015h ^-1 , and the carrier gas is 20ml /min of hydrogen, after the reaction of 1.5h, the condensed liquid phase product was collected and analyzed by a gas chromatograph. The conversion rate of HMF was 96.8%, the selectivity of 5-MF was 72.7%, and the 5-MF yield was 70.4%. .

Example 15

Weigh 200 mg of iron oxide catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed 50 vol% H ₂ /Ar mixed gas with a flow rate of 20 ml/min, and the gas space velocity is 12000 h ^-1 , put the catalyst Restore at 500°C for 2 hours, then lower the temperature to 300°C, inject HMF aqueous solution with a concentration of 12.6mg/ml into the reaction tube with a syringe pump, the injection rate is 1ml/h, the weight hourly space velocity is 0.063h ^-1 , and the carrier gas is 20ml/min of hydrogen, take a sample every 1 hour, after 8 hours of reaction, stop injecting the HMF solution, and reheat the temperature to 500°C to reduce the catalyst for 2 hours; after the treatment, cool down to 300°C and inject HMF aqueous solution, Thus, the next round of catalytic reaction cycle is entered; a total of five cycles are performed, and the condensed liquid phase product is collected during the reaction and analyzed by a gas chromatograph. The cycle life test results are shown in Figure 1.

As can be seen from Fig. 1, in the first circulation process, when the reaction time is 2h, the conversion rate of HMF can reach 94.0%, the selectivity of 5-MF can reach 67.0%, and the productive rate of 5-MF at this moment is 63.0%; With the extension of the reaction time, the conversion rate of HMF and the selectivity of 5-MF showed a slow decline overall. When the reaction time was 8h, the conversion rate of HMF was 84.3%, and the selectivity of 5-MF was 59.1%. The yield was 49.8%.

The results of 5 cycles show that the conversion rate and selectivity slowly decline in each reaction cycle, but the reduction and regeneration of the catalyst can partially recover its conversion rate and selectivity. When the time is 2h, the conversion rate of HMF can still reach 89.7%, the selectivity of 5-MF is 61.2%, and the yield of 5-MF is 54.9%.

Example 16

Weigh 200 mg of iron oxide catalyst and put it into the middle section of the reaction tube, install the reaction tube in an electric heating furnace, feed 50 vol% H ₂ /Ar mixed gas with a flow rate of 20 ml/min, and the gas space velocity is 12000 h ^-1 , put the catalyst Restore at 500°C for 2 hours, then lower the temperature to 300°C, inject HMF aqueous solution with a concentration of 12.6mg/ml into the reaction tube with a syringe pump, the injection rate is 1ml/h, the weight hourly space velocity is 0.063h ^-1 , and the carrier gas is The air of 20ml/min, after reacting 1.5h, collect the condensed liquid phase product and use gas chromatography to analyze, the conversion rate of HMF is 100%, the selectivity of 5-MF is 6.4%, and the 5-MF productive rate is 6.4% %.

Comparative example 1

Referring to the preparation method of Example 9, only 5 mmol of zinc nitrate was added, and iron nitrate was not added to prepare a zinc oxide catalyst.

Weigh 200mg of zinc oxide catalyst and put it into a reaction tube plugged with an appropriate amount of quartz wool. The other end is also filled with an appropriate amount of quartz wool. The reaction tube is installed in a fixed bed reactor, and the flow rate is 20ml/min. H ₂ /Ar mixed gas, the gas space velocity is 12000h ^-1 , the catalyst is reduced at 500°C for 2 hours, and then the temperature is lowered to 300°C, and the HMF aqueous solution with a concentration of 12.6mg/ml is injected into the reaction tube with a syringe pump. The rate is 1ml/h, the weight hourly space velocity is 0.063h ^-1 , the carrier gas is hydrogen at 20ml/min, and the liquid phase product is collected after 1.5h of reaction and analyzed by gas chromatography. The conversion rate of HMF is 21.7%, 5- The selectivity to MF was 11.4%, and the yield of 5-MF was 2.5%.

Claims (9)

1. A method for preparing 5-methylfurfural by using an iron-based catalyst is characterized by comprising the following steps:

(1) And (3) reduction process: putting the iron-based catalyst into a reactor, and introducing reducing gas for reduction and activation treatment;

(2) The reaction process is as follows: introducing an aqueous solution containing 5-hydroxymethylfurfural into the reactor, and reacting to obtain an aqueous solution containing 5-hydroxymethylfurfural;

the metal element in the iron-based catalyst comprises an iron element and a doping element, wherein the doping element is one or more than two of V, cr, mn, co, ni, zn, cu, al and Mg elements.

2. The method according to claim 1, wherein the iron element is 50 to 100mol% based on the metal element.

3. The method for producing 5-methylfurfural according to claim 1 or 2, wherein the reducing gas contains H ₂ Or CO content of 20-100%, reducing temperature of 400-600 deg.c and reducing time of 2-4 hr.

4. The production process according to any one of claims 1 to 3, wherein the aqueous solution containing 5-hydroxymethylfurfural has a 5-hydroxymethylfurfural concentration of 1 to 60mg/ml and a reaction temperature of 220 to 300 ℃.

5. The production method according to any one of claims 1 to 4, wherein the reaction process comprises the steps of:

injecting 5-hydroxymethylfurfural aqueous solution into a reactor by using a sample injection pump, wherein the injection rate of the 5-hydroxymethylfurfural aqueous solution is 1-3 ml/h, and the weight hourly space velocity is 0.015-0.3 h ^-1 And introducing carrier gas, and reacting to obtain the product, namely the aqueous solution containing the 5-methylfurfural.

6. The method for producing 5-methylfurfural according to claim 5 wherein a carrier gas introduced during the reaction is a non-oxidizing gas.

7. The method according to claim 6, wherein the flow rate of the carrier gas used in the reaction process is 20 to 50ml/min.

8. An aqueous solution containing 5-methylfurfural, characterized by being produced by the method according to any one of claims 1 to 7.

9. The use of 5-methylfurfural according to claim 8 in the fields of medicine, agricultural chemicals, food or energy.

Images