Fe3O4@FeMgAl-LDH magnetic catalyst, preparation method thereof and application thereof in catalyzing condensation reaction of furfural and acetone

Abstract

The application discloses a Fe3O4@FeMgAl-LDH magnetic catalyst, which comprises FeMgAl-LDH and Fe3O4; the FeMgAl-LDH is prepared by using solution A and solution B as raw materials through a coprecipitation reaction; the solution A is a mixed aqueous solution of Fe 3+ , Al 3+ and Mg 2+ , and the solution B is a mixed aqueous solution of OH ‑ and CO3 2‑ . The addition of the magnetic Fe3O4 increases the specific surface of the catalyst, improves the dispersibility and catalytic activity of the catalyst, significantly increases the conversion rate of raw materials and the yield of products, and is helpful to the recycling and reuse of the catalyst. The application discloses application of the Fe3O4@FeMgAl-LDH magnetic catalyst in a condensation reaction of furfural and acetone. Under the optimal reaction condition, the conversion rate of the furfural reaches 100%, and the total yield of the monocondensation product FAc and the di-condensation product F2Ac is above 99.8%.

Description

Technical Field

[0001] The invention belongs to the field of green catalysis and biomass resource application, and relates to a Fe3O4@FeMgAl-LDH magnetic catalyst and a preparation method thereof, and application of the catalyst in catalyzing the condensation reaction of furfural and acetone. Background Art

[0002] Energy has always been a hot topic in global development. As non-renewable resources decrease with the passage of time, the search for new energy sources plays a crucial role in future technological development. The use of fossil fuels leads to the production of large amounts of greenhouse gases and other harmful gases. It is widely recognized worldwide that the research of new energy sources, such as bioenergy, is the trend of the times.

[0003] Biomass, with its abundant sources and large reserves, is the only renewable organic carbon resource. Efficient conversion and utilization of biomass can alleviate dependence on fossil resources. Straw is an important biomass resource with high economic value. However, most straw is not properly processed, and some is even directly burned, producing greenhouse gases such as carbon dioxide and methane. Converting straw into fuel is a method to alleviate energy and environmental issues. By converting straw into biomass feedstock, many high-value-added industrial chemicals, such as furfural, levulinic acid, and 5-hydroxymethylfurfural, can be produced. Biomass furfural, a platform compound for biorefining, can be produced by catalytic conversion of hemicellulose- and cellulose-rich feedstocks (such as corn cobs, sugarcane bagasse, and wheat straw). Furfural serves as a bridge between biomass feedstock and biorefining, attracting widespread attention from academia and industry. Catalysts are key to achieving furfural resource utilization. Although homogeneous catalysts offer high catalytic performance, separation between the homogeneous catalyst and the product is expensive, and prolonged use can lead to corrosion of the equipment. The development of heterogeneous catalysts is of great significance for catalyst recovery and cost savings.

[0004] Patent CN115611831A prepares a magnesium-aluminum composite oxide (MgAl-LDO) catalyst for the condensation reaction of furfural and acetone. After a reaction temperature of 120°C for 2 hours, the furfural conversion rate reached 99%. Patent CN109759046A prepares a CaO / MgAl-LDO catalyst for the condensation reaction of furfural and acetone. Under optimal conditions, the furfural conversion rate reached 99%, and the total yield of furfurylideneacetone and difurfurylideneacetone reached 93.2%. However, the product yield and catalyst recovery of these catalysts still need to be improved. Furthermore, the CaO is fixed to the MgAl-LDO by a supported method and is easily dislodged by immersion or stirring. Therefore, to address the issues of catalyst selectivity and recovery, the development of more economical, green, efficient, and easily recyclable catalysts is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a magnetic nano-layered metal hydroxide catalyst (Fe3O4@FeMgAl-LDH magnetic catalyst) to address the above-mentioned problems of the prior art.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A Fe3O4@FeMgAl-LDH magnetic catalyst comprises FeMgAl-LDH (ferromagnesium aluminum hydrotalcite) and Fe3O4.

[0008] The Fe3O4@FeMgAl-LDH magnetic catalyst is prepared by wrapping FeMgAl-LDH on the surface of Fe3O4.

[0009] The FeMgAl-LDH is prepared by coprecipitation reaction using solution A and solution B as raw materials.

[0010] The Fe3O4@FeMgAl-LDH magnetic catalyst is prepared by the following method: adding solution A and solution B simultaneously to Fe3O4 aqueous dispersion to perform coprecipitation reaction, followed by aging, and the obtained precipitate is Fe3O4@FeMgAl-LDH magnetic catalyst; wherein, the solution A is Fe 3+ 、Al 3+ and Mg 2+ A mixed aqueous solution, wherein the solution B is OH - and CO3 2- of a mixed aqueous solution.

[0011] Preferably, the solution A is Fe 3+ A nitrate, hydrochloride or sulfate of Mg 2+ A nitrate, hydrochloride or sulfate of Al 3+ A mixed aqueous solution of one of nitrate, hydrochloride or sulfate.

[0012] Preferably, the Fe3O4 aqueous dispersion is prepared by mixing Fe3O4 and water in a dosage ratio of 0.2:20 to 1:20 g / mL.

[0013] The Fe3O4, Fe 3+ 、Al 3+ and Mg 2+ The ratio of the total amount of substance to the amount of substance of Fe3O4 is 100:2.5~100:11.2.

[0014] Preferably, the Fe3O4, Fe 3+ 、Al 3+ and Mg 2+The ratio of the total amount of substance to the amount of substance of Fe3O4 is 100:4.5 to 100:5.6.

[0015] Most preferably, the Fe3O4, Fe 3+ 、Al 3+ and Mg 2+ The ratio of the total amount of substance to the amount of substance of Fe3O4 is 100:5.5~100:5.6.

[0016] The Fe 3+ Mg 2+ 、Al 3+ The molar ratio of substances is (0.1~0.4):2:1.

[0017] Preferably, the Fe 3+ Mg 2+ 、Al 3+ The molar ratio of substances is (0.3~0.4):2:1.

[0018] Most preferably, the Fe 3+ Mg 2+ 、Al 3+ The molar ratio of substances is 0.4:2:1.

[0019] Preferably, the solution B is a mixed aqueous solution of NaOH and Na2CO3.

[0020] The OH - and CO3 2- The amount of substances satisfy:

[0021]

[0022] in, Mg 2+ the amount of substance; Al 3+ and Fe 3+ The total amount of substance.

[0023] Preferably, the OH - and CO3 2- The amount of substances satisfy:

[0024]

[0025] The Fe of the present invention 3+ It is made of Fe 3+ One of the nitrates, hydrochlorides or sulfates provided, Mg 2+ It is composed of Mg 2+ A nitrate, hydrochloride or sulfate of Al 3+By Al 3+ One of the nitrate, hydrochloride or sulfate salts is provided.

[0026] A second object of the present invention is to provide a method for preparing the Fe3O4@FeMgAl-LDH magnetic catalyst, comprising: heating an Fe3O4 aqueous dispersion solution to a coprecipitation reaction temperature, simultaneously adding solution A and solution B dropwise under stirring, maintaining the pH of the mixed solution at 9 to 10 during the addition process, and aging the mixture under stirring after the addition is completed. The resulting precipitate is the Fe3O4@FeMgAl-LDH magnetic catalyst.

[0027] The temperature of the coprecipitation reaction is 55-65°C, preferably 60°C.

[0028] The pH of the coprecipitation reaction is controlled at 9-10.

[0029] The aging temperature is 55-65°C, preferably 60°C.

[0030] The aging time is 6 to 10 hours, preferably 12 hours.

[0031] As a further preferred technical solution of the preparation method of the Fe3O4@FeMgAl-LDH magnetic catalyst of the present invention, it also includes: after aging is completed, filtering is performed, and the filter cake is washed, filtered, dried, and ground in sequence.

[0032] Preferably, the washing is to wash the filter cake with deionized water until the pH value of the filtrate is 7.

[0033] Preferably, the drying temperature is 80-110° C., the drying time is 12-24 hours, and the drying equipment is a drying oven or an oven.

[0034] The third object of the present invention is to provide the use of the Fe3O4@FeMgAl-LDH magnetic catalyst in catalyzing the condensation reaction of furfural and acetone.

[0035] A method for preparing furfurylideneacetone (FAc) and difurfurylideneacetone (F2Ac) through a condensation reaction of furfural and acetone, comprising: using an Fe3O4@FeMgAl-LDH magnetic catalyst to catalyze a condensation reaction of furfural and acetone to generate furfurylideneacetone (FAc) and difurfurylideneacetone (F2Ac).

[0036] The molar ratio of furfural to acetone is 1:2 to 1:12, preferably 1:8 to 1:10, and most preferably 1:10.

[0037] The added amount of the Fe3O4@FeMgAl-LDH catalyst is 1 to 10 wt% of the total amount of furfural and acetone, preferably 5 wt%.

[0038] The condensation reaction time is 1 to 140 minutes, preferably 120 minutes.

[0039] The temperature of the condensation reaction is 80-160°C, preferably 160°C.

[0040] Catalytic mechanism:

[0041] The mechanism of the condensation reaction of furfural and acetone is shown in the figure Figure 1 As shown in the figure, the polyhydroxy structure of Fe3O4@FeMgAl-LDH provides a large number of basic sites for catalysis. 3+ After the hydroxide is formed, trace amounts of oxides are formed during the aging process, providing certain acidic sites. The entire catalytic process is dominated by alkalinity, supplemented by acidity. Under the action of base, the α-carbon of acetone loses a proton to form a carbon anion, enhancing its nucleophilicity. Under the action of the acidic site, the furfural molecule protonates the carbonyl oxygen atom, enhancing the electrophilicity of the carbonyl carbon, promoting the formation of furfurylideneacetone (FAc). FAc is then dehydrated under the dominance of alkalinity to form difurfurylideneacetone (F2Ac).

[0042] The beneficial effects of the present invention are:

[0043] (1) The Fe3O4@FeMgAl-LDH magnetic catalyst of the present invention is a magnetic nano-hydrotalcite, which has a layered structure and a large specific surface area.

[0044] (2) The magnetic core of the Fe3O4@FeMgAl-LDH magnetic catalyst of the present invention is Fe3O4. 3+ Mg 2+ 、Al 3+ Combined with the constituent hydrotalcite, the magnetic core Fe3O4 is directly wrapped in the hydrotalcite, and the layer structure of the hydrotalcite will not be destroyed due to the combination with the magnetic core, avoiding the problem of the magnetic core Fe3O4 being easily detached due to stirring when directly loaded on the hydrotalcite, which is beneficial to the recovery of the catalyst.

[0045] (3) The preparation process of the Fe3O4@FeMgAl-LDH magnetic catalyst of the present invention is simple and inexpensive, and has high economic benefits.

[0046] (4) The addition of magnetic Fe3O4 makes the Fe3O4@FeMgAl-LDH magnetic catalyst of the present invention magnetic. After catalyzing the condensation reaction of furfural and acetone, the catalyst can be separated by magnetic attraction and is easy to recover. This simplifies the steps of separating the product and the catalyst, greatly saves the raw material cost of the catalyst, and has certain industrial practical value.

[0047] (5) The addition of magnetic Fe3O4 increases the specific surface area of ​​the catalyst, improves the dispersibility and catalytic activity of the catalyst, allows more acetone to be adsorbed on the catalyst, increases the probability of carbon anions contacting furfural, and thus increases the raw material conversion rate and product selectivity. The Fe3O4@FeMgAl-LDH magnetic catalyst of the present invention is used to catalyze the condensation reaction of furfural and acetone. Under optimal conditions, the conversion rate of furfural is 100%, and the total yield of the monocondensation product FAc (furfurylideneacetone) and the dicondensation product F2Ac (difurfurylideneacetone) is above 99.8%. Moreover, the catalytic activity does not change significantly after the catalyst is reused 5 times, and the product yield can still be maintained above 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the mechanism diagram of the condensation of furfural and acetone catalyzed by Fe3O4@FeMgAl-LDH magnetic catalyst.

[0049] Figure 2 3 are SEM images of FeMgAl-LDH and Fe3O4@FeMgAl-LDH catalysts (Example 1); wherein, a is the SEM image of FeMgAl-LDH, and b is the SEM image of Fe3O4@FeMgAl-LDH catalyst.

[0050] Figure 3 Figure 2 is the XRD pattern of Fe3O4@FeMgAl-LDH catalysts with different Fe contents.

[0051] Figure 4 FT-IR images of Fe3O4@FeMgAl-LDH catalysts with different Fe contents.

[0052] Figure 5 The adsorption-desorption curves of Fe3O4@FeMgAl-LDH catalysts with different Fe contents. DETAILED DESCRIPTION

[0053] The technical solutions of the present invention are described in more detail below with reference to the embodiments, but these embodiments do not limit the protection scope of the present invention.

[0054] Example 1

[0055] According to the molar ratio of the metal elements iron, magnesium, and aluminum of 0.4:2:1, 1.62g Fe(NO3)3·9H2O (0.004mol), 5.13g Mg(NO3)2·6H2O (0.02mol), and 3.75g Al(NO3)3·9H2O (0.01mol) were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0056] According to the formula Calculate the amount of NaOH and Na2CO3 respectively, take 2.176g NaOH and 2.97g Na2CO3 and dissolve them in 100mL deionized water to prepare a mixed alkaline aqueous solution, recorded as solution B.

[0057] About 20 mL of deionized water was pre-added to a four-necked flask, and 0.5 g of Fe3O4 (0.002 mol) was added and uniformly dispersed to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solution A and solution B were simultaneously added dropwise to the four-necked flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued at 60°C for 12 hours. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The filtrate was dried in an oven at 105°C for 24 hours to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 5.5% Fe3O4@FeMgAl, and ground into powder for later use.

[0058] According to the preparation method of Fe3O4@FeMgAl-LDH magnetic catalyst in this embodiment, the difference is that the Fe3O4 aqueous dispersion is replaced with an equal volume of deionized water, and the iron magnesium aluminum hydrotalcite FeMgAl-LDH is prepared by coprecipitation method, which is recorded as FeMgAl-0.4:2:1 (Comparative Example 4). The SEM shows Figure 2 a. From Figure 2 It can be seen that FeMgAl-LDH presents a typical hydrotalcite-like layered structure, consisting of metal oxide sheets, which are connected by excess positive charges generated by anion neutralization. Its grains are hexagonal and the grain size is less than 500nm, indicating that the co-precipitation method can prepare nano-sized hydrotalcite. The SEM image of the prepared 5.5% Fe3O4@FeMgAl is shown in Figure 1. Figure 2 As shown in b. Figure 2 b It can be seen that the nano-FeMgAl-LDH shell is wrapped on the surface of the Fe3O4 magnetic core and forms a spherical structure, but the morphology of the FeMgAl-LDH on the surface is similar, and the shell still presents a hexagonal sheet structure.

[0059] The XRD pattern of the prepared 5.5% Fe3O4@FeMgAl is shown in Figure 3 As shown. Figure 3 As can be seen in the figure, the strong peaks at lower diffraction angles of 11.5°, 24°, and 35° are attributed to diffraction from the d003, d006, and d102 basal planes, while the less intense peaks appearing at higher diffraction angles of 39°, 46°, 61°, and 62° are assigned to diffraction from the d105, d108, d110, and d113 basal planes. These patterns clearly show the crystal structure of the hydrotalcite, demonstrating the successful synthesis of the Fe3O4 / FeMgAl-LDH.

[0060] The FT-IR image of the prepared 5.5% Fe3O4@FeMgAl is shown in Figure 4 As shown in the figure, 5.5% Fe3O4@FeMgAl has a -1 There is a strong and broad absorption band near 1650 cm, which is the hydrogen bond and OH stretching vibration peak of water molecules on the surface and between the octahedral layers. -1 Another absorption band corresponding to water deformation was found at 1358 and 1380 cm -1 CO3 appears around 2- The asymmetric vibration peak of 400-900 cm-1 indicates that half of the interlayer carbonate ions are replaced by hydroxyl ions. -1 The vibration peaks are the stretching vibration and bending vibration of MO and M-OH (M = Mg, Al), 560 cm -1 All these indicate that hydrotalcite was successfully synthesized.

[0061] The N2 adsorption-desorption curve of the prepared 5.5% Fe3O4@FeMgAl is shown in Figure 5 As shown in the figure, its N2 adsorption-desorption curve belongs to the H3 type isotherm, indicating that 5.5%Fe3O4@FeMgAl is a typical mesoporous material. The specific surface area (S BET ), pore volume and pore size are shown in Table 1, and its specific surface area reaches 152.64m 2 / g.

[0062] Catalyst performance evaluation: 0.89g of 5.5% Fe3O4@FeMgAl catalyst was placed in a 50mL reactor, and 2.3g of furfural and 15.6g of acetone were added. The reactor was sealed and heated. After heating to 160°C, stirring and reacting for 120 minutes were started. After the reaction was completed, samples were taken and tested by gas chromatography. The results showed that the conversion rate of furfural was 100%, the total selectivity of the product was 99.8%, and the yield was 99.8%. In order to evaluate the repeatability of the catalyst, after each experiment, the catalyst was recovered with a magnet, washed with ethanol, and dried in a vacuum drying oven for the next reaction. The catalyst was reused 5 times, and the conversion rate of furfural remained at around 99.1%, the activity of the catalyst did not decrease significantly, and the product yield remained at 96.6%; after being reused 5 times, the XRD pattern of 5.5% Fe3O4@FeMgAl was as follows Figure 3 As shown in the FT-IR diagram Figure 4As shown in FIG, there is no obvious change in the structure of the catalyst after being reused 5 times, indicating that the present invention directly encapsulates the magnetic core Fe3O4 in the hydrotalcite, avoiding the problem of the magnetic core Fe3O4 being easily detached due to stirring when directly loaded on the hydrotalcite, which is beneficial to the recovery of the catalyst.

[0063] Example 2

[0064] The preparation of 6.1% Fe3O4@FeMgAl is the same as that in Example 1, except that the molar ratio of the metal elements Fe, Mg, and Al is 0.1:2:1.

[0065] According to the molar ratio of metal elements iron, magnesium and aluminum of 0.1:2:1, 0.40g Fe(NO3)3·9H2O, 5.13g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0066] According to the formula Calculate the amount of NaOH and Na2CO3 respectively, take 1.99g NaOH and 2.33g Na2CO3 and dissolve them in 100mL deionized water to prepare a mixed alkaline aqueous solution, recorded as solution B.

[0067] About 20 mL of deionized water was added to a four-necked flask in advance, and 0.5 g of Fe3O4 was added and dispersed evenly to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solution A and solution B were simultaneously added dropwise to the four-necked flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued and the mixture was aged at 60°C for 12 h. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The mixture was dried in an oven at 105°C for 24 h to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 6.1% Fe3O4@FeMgAl, and ground into powder for later use.

[0068] The XRD pattern of the prepared 6.1% Fe3O4@FeMgAl is shown in Figure 3 As shown. Figure 3 As can be seen in the figure, the strong peaks at lower diffraction angles of 11.5°, 24°, and 35° are attributed to diffraction from the d003, d006, and d102 basal planes, while the less intense peaks appearing at higher diffraction angles of 39°, 46°, 61°, and 62° are assigned to diffraction from the d105, d108, d110, and d113 basal planes. These patterns clearly show the crystal structure of hydrotalcite, which also proves that Fe3O4 / FeMgAl-LDH was successfully synthesized.

[0069] The FT-IR image of the prepared 6.1% Fe3O4@FeMgAl is shown in Figure 2. Figure 4 As shown in the figure, 6.1%Fe3O4@FeMgAl has a -1 There is a strong and broad absorption band near 1650 cm, which is the hydrogen bond and OH stretching vibration peak of water molecules on the surface and between the octahedral layers. -1 Another absorption band corresponding to water deformation was found at 1358 and 1380 cm -1 CO3 appears around 2- The asymmetric vibration peak of 400-900 cm-1 indicates that half of the interlayer carbonate ions are replaced by hydroxyl ions. -1 The vibration peaks are the stretching vibration and bending vibration of MO and M-OH (M = Mg, Al), 560 cm -1 All these indicate that hydrotalcite was successfully synthesized.

[0070] The N2 adsorption-desorption curve of the prepared 6.1% Fe3O4@FeMgAl is shown in Figure 5 As shown in Figure 1, its N2 adsorption-desorption curve belongs to the H3 type isotherm, indicating that 6.1%Fe3O4@FeMgAl is a typical mesoporous material. The specific surface area, pore volume and pore size of 6.1%Fe3O4@FeMgAl-LDH catalyst are shown in Table 1.

[0071] The performance evaluation of the catalyst was the same as in Example 1, and the conversion rate of furfural was 84.9%, the total selectivity of the product was 98.8%, and the yield was 83.9%.

[0072] Example 3

[0073] The preparation of 5.9% Fe3O4@FeMgAl is the same as that in Example 1, except that the molar ratio of the metal elements Fe, Mg, and Al is 0.2:2:1.

[0074] According to the molar ratio of metal elements iron, magnesium and aluminum of 0.2:2:1, 0.81g Fe(NO3)3·9H2O, 5.13g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0075] According to the formula Calculate the amount of NaOH and Na2CO3 respectively, take 2.05g NaOH and 2.54g Na2CO3 and dissolve them in 100mL deionized water to prepare a mixed alkaline aqueous solution, recorded as solution B.

[0076] About 20 mL of deionized water was pre-added into a four-necked flask, and 0.5 g of Fe3O4 was added and dispersed uniformly to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solutions A and B were simultaneously added dropwise into the four-necked flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued and the mixture was aged at 60°C for 12 h. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The mixture was then dried in an oven at 105°C for 24 h to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 5.9% Fe3O4@FeMgAl, which was ground into powder for later use.

[0077] The XRD pattern of the prepared 5.9% Fe3O4@FeMgAl is shown in Figure 3 As shown. Figure 3 As can be seen in the figure, the strong peaks at lower diffraction angles of 11.5°, 24°, and 35° are attributed to diffraction from the d003, d006, and d102 basal planes, while the less intense peaks appearing at higher diffraction angles of 39°, 46°, 61°, and 62° are assigned to diffraction from the d105, d108, d110, and d113 basal planes. These patterns clearly show the crystal structure of hydrotalcite, which also proves that Fe3O4 / FeMgAl-LDH was successfully synthesized.

[0078] The FT-IR image of the prepared 5.9% Fe3O4@FeMgAl is shown in Figure 4 As shown in the figure, 5.9%Fe3O4@FeMgAl at 3439cm -1 There is a strong and broad absorption band near 1650 cm, which is the hydrogen bond and OH stretching vibration peak of water molecules on the surface and between the octahedral layers. -1 Another absorption band corresponding to water deformation was found at 1358 and 1380 cm -1 CO3 appears around 2- The asymmetric vibration peak of 400-900 cm-1 indicates that half of the interlayer carbonate ions are replaced by hydroxyl ions. -1 The vibration peaks are the stretching vibration and bending vibration of MO and M-OH (M = Mg, Al), 560 cm -1 All these indicate that hydrotalcite was successfully synthesized.

[0079] The N2 adsorption-desorption curve of the prepared 5.9% Fe3O4@FeMgAl is shown in Figure 5As shown in Figure 1, its N2 adsorption-desorption curve belongs to the H3 type isotherm, indicating that 5.9%Fe3O4@FeMgAl is a typical mesoporous material. The specific surface area, pore volume and pore size of 5.9%Fe3O4@FeMgAl-LDH catalyst are shown in Table 1.

[0080] The performance evaluation of the catalyst was the same as in Example 1, and the furfural conversion was 89.2%, the total product selectivity was 99.3%, and the yield was 88.6%.

[0081] Example 4

[0082] The preparation of 5.7% Fe3O4@FeMgAl is the same as that in Example 1, except that the molar ratio of the metal elements Fe, Mg, and Al is 0.3:2:1.

[0083] According to the molar ratio of metal elements iron, magnesium and aluminum of 0.3:2:1, 1.22g Fe(NO3)3·9H2O, 5.13g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0084] According to the formula Calculate the amount of NaOH and Na2CO3 respectively, take 2.11g NaOH and 2.76g Na2CO3 and dissolve them in 100mL deionized water to prepare a mixed alkaline aqueous solution, recorded as solution B.

[0085] About 20 mL of deionized water was added to a four-necked flask in advance, and 0.5 g of Fe3O4 was added and dispersed evenly to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solutions A and B were simultaneously added dropwise to the four-necked flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued and the mixture was aged at 60°C for 12 h. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The mixture was then dried in an oven at 105°C for 24 h to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 5.7% Fe3O4@FeMgAl, and ground into powder for later use.

[0086] The XRD pattern of the prepared 5.7% Fe3O4@FeMgAl is shown in Figure 3 As shown. Figure 3As can be seen in the figure, the strong peaks at lower diffraction angles of 11.5°, 24°, and 35° are attributed to diffraction from the d003, d006, and d102 basal planes, while the less intense peaks appearing at higher diffraction angles of 39°, 46°, 61°, and 62° are assigned to diffraction from the d105, d108, d110, and d113 basal planes. These patterns clearly show the crystal structure of hydrotalcite, which also proves that Fe3O4 / FeMgAl-LDH was successfully synthesized.

[0087] The FT-IR image of the prepared 5.7% Fe3O4@FeMgAl is shown in Figure 2. Figure 4 As shown in the figure, 5.7%Fe3O4@FeMgAl has a -1 There is a strong and broad absorption band near 1650 cm, which is the hydrogen bond and OH stretching vibration peak of water molecules on the surface and between the octahedral layers. -1 Another absorption band corresponding to water deformation was found at 1358 and 1380 cm -1 CO3 appears around 2- The asymmetric vibration peak of 400-900 cm-1 indicates that half of the interlayer carbonate ions are replaced by hydroxyl ions. -1 The vibration peaks are the stretching vibration and bending vibration of MO and M-OH (M = Mg, Al), 560 cm -1 All these indicate that hydrotalcite was successfully synthesized.

[0088] The N2 adsorption-desorption curve of the prepared 5.7% Fe3O4@FeMgAl is shown in Figure 5 As shown in Figure 1, its N2 adsorption-desorption curve belongs to the H3 type isotherm, indicating that 5.7%Fe3O4@FeMgAl is a typical mesoporous material. The specific surface area, pore volume and pore size of 5.7%Fe3O4@FeMgAl-LDH catalyst are shown in Table 1.

[0089] The performance evaluation of the catalyst was the same as in Example 1, and the furfural conversion was 93.5%, the total product selectivity was 99.1%, and the yield was 92.7%.

[0090] Example 5

[0091] The preparation of 2.5% Fe3O4@FeMgAl was the same as in Example 1, except that the amount of Fe3O4 added as the magnetic core was 0.2 g.

[0092] According to the molar ratio of metal elements iron, magnesium and aluminum of 0.4:2:1, 1.62g Fe(NO3)3·9H2O, 5.13g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0093] According to the formula Calculate the amount of NaOH and Na2CO3 respectively, take 2.18g NaOH and 2.97g Na2CO3 and dissolve them in 100mL deionized water to prepare a mixed alkaline aqueous solution, recorded as solution B.

[0094] About 20 mL of deionized water was pre-added into a four-necked flask, and 0.2 g of Fe3O4 was added and dispersed uniformly to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solutions A and B were simultaneously added dropwise to the flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued. The mixture was aged at 60°C for 12 h. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The mixture was then dried in an oven at 105°C for 24 h to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 2.5% Fe3O4@FeMgAl, and ground into powder for later use.

[0095] The performance evaluation of the catalyst was the same as in Example 1, and the furfural conversion was 85.3%, the total product selectivity was 98.3%, and the yield was 83.9%.

[0096] Example 6

[0097] The preparation of 4.8% Fe3O4@FeMgAl was the same as in Example 1, except that the amount of Fe3O4 added as the magnetic core was 0.4 g.

[0098] According to the molar ratio of metal elements iron, magnesium and aluminum of 0.4:2:1, 1.62g Fe(NO3)3·9H2O, 5.13g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0099] The preparation of mixed alkaline solution B is the same as in Example 5.

[0100] About 20 mL of deionized water was pre-added into a four-necked flask, and 0.4 g of Fe3O4 was added and dispersed uniformly to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solutions A and B were simultaneously added dropwise to the flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued and the mixture was aged at 60°C for 12 h. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The mixture was then dried in an oven at 105°C for 24 h to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 4.8% Fe3O4@FeMgAl, and ground into powder for later use.

[0101] The performance evaluation of the catalyst was the same as in Example 1, and the furfural conversion was 96.5%, the total product selectivity was 96.7%, and the yield was 93.3%.

[0102] Example 7

[0103] The preparation of 9.1% Fe3O4@FeMgAl was the same as in Example 1, except that the amount of Fe3O4 added as the magnetic core was 0.8 g.

[0104] According to the molar ratio of metal elements iron, magnesium and aluminum of 0.4:2:1, 1.62g Fe(NO3)3·9H2O, 5.13g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0105] The preparation of mixed alkaline solution B is the same as in Example 5.

[0106] About 20 mL of deionized water was added to a four-necked flask in advance, and 0.8 g of Fe3O4 was added and dispersed evenly to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solutions A and B were simultaneously added dropwise to the flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued and the mixture was aged at 60°C for 12 h. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. It was then dried in an oven at 105°C for 24 h to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 9.1% Fe3O4@FeMgAl, and ground into powder for later use.

[0107] The performance evaluation of the catalyst was the same as in Example 1, and the furfural conversion was 94.7%, the total product selectivity was 94.2%, and the yield was 89.2%.

[0108] Example 8

[0109] The preparation of 11.2% Fe3O4@FeMgAl was the same as in Example 1, except that the amount of Fe3O4 added as the magnetic core was 1 g.

[0110] According to the molar ratio of metal elements iron, magnesium and aluminum of 0.4:2:1, 1.62g Fe(NO3)3·9H2O, 5.13g Mg(NO3)2·6H2O and 3.75g Al(NO3)3·9H2O were weighed and dissolved in 100mL deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0111] The preparation of mixed alkaline solution B is the same as in Example 5.

[0112] About 20 mL of deionized water was pre-added into a four-necked flask, and 1 g of Fe3O4 was added and uniformly dispersed to obtain an Fe3O4 aqueous dispersion. The Fe3O4 aqueous dispersion was heated to 60°C, and solutions A and B were simultaneously added dropwise to the flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued. The mixture was aged at 60°C for 12 h. After the aging was completed, the mixture was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The mixture was dried to obtain a Fe3O4@FeMgAl-LDH magnetic catalyst, recorded as 11.2% Fe3O4@FeMgAl, and ground into powder for later use.

[0113] The performance evaluation of the catalyst was the same as in Example 1, and the furfural conversion was 84.6%, the total product selectivity was 98.4%, and the yield was 83.2%.

[0114] Comparative Example 1

[0115] According to the molar ratio of metal elements magnesium and aluminum being 2:1, 5.13 g Mg(NO3)2·6H2O (0.02 mol) and 3.75 g Al(NO3)3·9H2O (0.01 mol) were weighed and dissolved in 100 mL of deionized water to prepare a mixed salt solution, which was recorded as solution A.

[0116] According to the formula Calculate the amount of NaOH and Na2CO3 respectively, take 1.92g NaOH and 2.12g Na2CO3 and dissolve them in 100mL deionized water to prepare a mixed alkaline aqueous solution, recorded as solution B.

[0117] About 20 mL of deionized water was added to a four-necked flask in advance, and solution A and solution B were simultaneously added dropwise to the four-necked flask under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued at 60°C for 12 hours. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The filtrate was dried in an oven at 105°C for 24 hours to obtain the MgAl-LDH catalyst, which was then ground into powder for later use.

[0118] The catalyst performance evaluation was the same as in Example 1, except that the catalyst was MgAl-LDH. The furfural conversion rate was 22.6%, the total product selectivity was 97.9%, and the yield was 22.1%.

[0119] Comparative Example 2

[0120] The MgAl-LDH prepared in Comparative Example 1 was placed in a muffle furnace and calcined at 450° C. for 3 h to prepare MgAl-LDO.

[0121] The catalyst performance evaluation was the same as that of Comparative Example 1, except that the catalyst was MgAl-LDO. The furfural conversion rate was 45.0%, the total product selectivity was 91.1%, and the yield was 41.0%.

[0122] Comparative Example 3

[0123] According to the molar ratio of metal elements calcium, magnesium, and aluminum of 1:2:1, 2.36 g Ca(NO3)2·4H2O (0.01 mol), 5.13 g Mg(NO3)2·6H2O (0.02 mol), and 3.75 g Al(NO3)3·9H2O (0.01 mol) were weighed and dissolved in 100 mL of deionized water to prepare a mixed brine solution, which was recorded as solution A.

[0124] According to the formula Calculate the amount of NaOH and Na2CO3 respectively, take 2.56g NaOH and 2.12g Na2CO3 and dissolve them in 100mL deionized water to prepare a mixed alkaline aqueous solution, recorded as solution B.

[0125] About 20 mL of deionized water was added to a four-necked flask in advance, and solution A and solution B were added dropwise to the four-necked flask simultaneously under stirring. The pH of the mixed solution was always maintained at 9-10 during the addition. After the addition was completed, stirring was continued at 60°C for 12 hours. After the aging was completed, the mixed solution was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The filter cake was dried in an oven at 105°C for 24 hours to obtain the CaMgAl-LDH catalyst, which was then ground into powder for later use.

[0126] The catalyst performance evaluation was the same as in Example 1, except that the catalyst was CaMgAl-LDH. The conversion of furfural was 44.2%, the total selectivity of the products was 95.1%, and the yield was 42.0%.

[0127] Comparative Example 4

[0128] Referring to the preparation of FeMgAl-LDH (denoted as FeMgAl-0.4:2:1) as in Example 1, except that the Fe304 aqueous dispersion was replaced with the same volume of deionized water. The SEM image of the prepared FeMgAl-LDH is shown in Figure 2a, and its specific surface, pore volume and pore size are shown in Table 1. Figure 2 a, and its specific surface, pore volume and pore size are shown in Table 1.

[0129] The catalyst performance evaluation was the same as in Example 1, except that the catalyst was FeMgAl-LDH. The conversion of furfural was 81.2%, the total selectivity of the products was 97.1%, and the yield was 78.8%.

[0130] Table 1. Specific surface and pore volume and pore size of materials

[0131]

Claims

1. Application of Fe3O4@FeMgAl-LDH magnetic catalyst in catalyzing the condensation reaction of furfural and acetone, characterized by: Fe3O4@FeMgAl-LDH magnetic catalyst includes FeMgAl-LDH and Fe3O4; the FeMgAl-LDH is prepared by coprecipitation reaction with solution A and solution B as raw materials; the solution A is Fe 3+ 、Al 3+ and Mg 2+ A mixed aqueous solution, wherein the solution B is OH - and CO3 2- The Fe3O4@FeMgAl-LDH magnetic catalyst is prepared by the following method: solution A and solution B are simultaneously added dropwise to the Fe3O4 aqueous dispersion for a coprecipitation reaction, followed by aging to obtain a precipitate that is the Fe3O4@FeMgAl-LDH magnetic catalyst.

2. The use according to claim 1, characterized in that: The solution A is Fe 3+ A nitrate, hydrochloride or sulfate of Mg 2+ A nitrate, hydrochloride or sulfate of Al 3+ The solution B is a mixed aqueous solution of NaOH and Na2CO3.

3. The use according to claim 1, characterized in that: The Fe3O4, Fe 3+ 、Al 3+ and Mg 2+ The ratio of the total amount of substance of Fe3O4 to the amount of substance of Fe3O4 is 100:2.5 to 100:11.2; the Fe 3+ Mg 2+ 、Al 3+ The amount of substance ratio is (0.1-0.4):2:1; the OH - and CO3 2- The amount of substances satisfy: ； in, Mg 2+ the amount of substance; Al 3+ and Fe 3+ The total amount of substance.

4. The use according to claim 3, characterized in that: The Fe3O4, Fe 3+ 、Al 3+ and Mg 2+ The ratio of the total amount of substance of Fe3O4 to the amount of substance of Fe3O4 is 100:4.5 to 100:5.6; the Fe 3+ Mg 2+ 、Al 3+ The molar ratio of substances is (0.3~0.4):2:

1.

5. The use according to claim 4, characterized in that: The Fe3O4, Fe 3+ 、Al 3+ and Mg 2+ The ratio of the total amount of substance of Fe3O4 to the amount of substance of Fe3O4 is 100:5.5 to 100:5.6; the Fe 3+ Mg 2+ 、Al 3+ The molar ratio of substances is 0.4:2:

1.

6. The use according to claim 1, characterized in that: The Fe3O4@FeMgAl-LDH magnetic catalyst is prepared by the following method: the method comprises: heating an Fe3O4 aqueous dispersion solution to a coprecipitation reaction temperature, simultaneously adding solution A and solution B dropwise under stirring conditions, maintaining the pH of the mixed solution at 9 to 10 during the addition process, and aging the solution under stirring after the addition is completed. After the aging is completed, the obtained precipitate is the Fe3O4@FeMgAl-LDH magnetic catalyst.

7. The use according to claim 6, characterized in that: The temperature of the coprecipitation reaction is 55-65° C.; the temperature of the aging is 55-65° C.; and the aging time is 6-10 hours.

8. The use according to claim 6, characterized in that: The temperature of the coprecipitation reaction is 60°C.

9. The use according to claim 6, characterized in that: The aging temperature is 60°C.

10. The use according to claim 6, characterized in that: The aging time is 12 h.

11. The use according to claim 6, characterized in that: The preparation of the Fe3O4@FeMgAl-LDH magnetic catalyst further includes: filtering after aging, washing the filter cake, filtering, drying, and grinding in sequence.

12. The use according to claim 11, characterized in that: The washing step is to use deionized water to wash the filter cake until the pH value of the filtrate is 7; the drying temperature is 80-110° C., and the drying time is 12-24 h.

13. A method for preparing furfurylideneacetone and difurfurylideneacetone by condensation reaction of furfural and acetone, characterized in that: include: Fe3O4@FeMgAl-LDH magnetic catalyst was used to catalyze the condensation reaction of furfural and acetone to produce furfurylideneacetone and difurfurylideneacetone. The Fe3O4@FeMgAl-LDH magnetic catalyst comprises FeMgAl-LDH and Fe3O4; the FeMgAl-LDH is prepared by coprecipitation reaction using solution A and solution B as raw materials; the solution A is Fe 3+ 、Al 3+ and Mg 2+ A mixed aqueous solution, wherein the solution B is OH - and CO3 2- The Fe3O4@FeMgAl-LDH magnetic catalyst is prepared by the following method: solution A and solution B are simultaneously added dropwise to the Fe3O4 aqueous dispersion to perform a coprecipitation reaction, followed by aging to obtain a precipitate that is the Fe3O4@FeMgAl-LDH magnetic catalyst; The molar ratio of furfural to acetone is 1:2 to 1:12; The amount of the Fe3O4@FeMgAl-LDH catalyst added is 1-10 wt % of the total amount of furfural and acetone; The condensation reaction time is 1 to 140 minutes; The temperature of the condensation reaction is 80-160°C.

14. The method for preparing furfurylideneacetone and difurfurylideneacetone by condensation reaction of furfural and acetone according to claim 13, characterized in that: The molar ratio of furfural to acetone is 1:8 to 1:

10.

15. The method for preparing furfurylideneacetone and difurfurylideneacetone by condensation reaction of furfural and acetone according to claim 14, characterized in that: The molar ratio of furfural to acetone is 1:

10.

16. The method for preparing furfurylideneacetone and difurfurylideneacetone by condensation reaction of furfural and acetone according to claim 13, characterized in that: The added amount of the Fe3O4@FeMgAl-LDH catalyst is 5 wt% of the total amount of furfural and acetone.

17. The method for preparing furfurylideneacetone and difurfurylideneacetone by condensation reaction of furfural and acetone according to claim 13, characterized in that: The condensation reaction time is 120 min; the condensation reaction temperature is 160°C.

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