A catalytic process for the synthesis of furanylene-cycloketone compounds, catalysts and methods for their preparation

Abstract

The application discloses a catalytic method for synthesizing furan alkenyl-cycloketone compounds, a catalyst and a preparation method thereof, relates to the technical field of chemical catalysis and organic synthesis, and the catalyst is a solid catalyst with variable mesopore diameters and containing acid-base double sites; the catalyst is composed of an acidic mesoporous carrier and basic metal hydroxide loaded on the carrier; the acidic mesoporous carrier is a composite of SiO2 and acidic metal oxides, and is prepared by hydrolysis and calcination of soluble precursors of acidic metals, tetraethyl orthosilicate and hydroxyl carboxylic acid pore-forming agents. The mesopore diameter of the catalyst is 3.41nm-11.2nm, the specific surface area is 172.4-869.6m 2 / g, the acid content is 0.180-0.973mmol / g, the base content is 0.016-0.125mmol / g, and the catalyst has the characteristics of recyclability, high temperature resistance, solution non-pollution and the like.

Description

Technical Field

[0001] This invention relates to the fields of chemical catalysis and organic synthesis technology, specifically to a catalytic method, catalyst, and preparation method for synthesizing furanene-cyclic ketone compounds. Background Technology

[0002] Because corn cobs, a byproduct of agriculture in northern China, can be extensively converted into furfural products, if furfural compounds derived from biomass (containing a large amount of furan rings) can be used as the main raw material, and products such as cyclopentanone and cyclohexanone derived from the hydrogenation of lignocellulosic biomass as auxiliary raw materials, and specific structural products can be synthesized through a special Aldol condensation catalysis method, the deficiency of limited value-added routes in biomass utilization can be overcome. The targeted synthesis of highly selective bicyclic compounds as pharmaceutical or aviation fuel intermediates will have certain commercial benefits. Currently, researchers' studies on the Aldol condensation of aldehydes and ketones to generate bicyclic products indicate that this reaction occurs in multiple steps with synergistic asynchronous catalysis. Taking furfural and the auxiliary raw material cyclohexanone as an example, the reaction involves three main steps: a) Cyclohexanone is activated and loses its α-H to generate a carbanion intermediate; this step is preferred for base catalysis. b) The furfural aldehyde group is activated, adsorbs, and attacks the carbanion intermediate, undergoing an aldol linkage reaction to generate an undehydrated bicyclic intermediate; this step is limited by the concentration kinetics of the intermediate in step a and is preferred for acid catalysis. c) The bicyclic intermediate is dehydrated to generate bicyclic or even polycyclic aldol condensation products linked by carbon-carbon double bonds; this step is also preferred for acid catalysis and is limited by the steric kinetics of the intermediate in step b. The final products are the bicyclic 2-furanenyl-cyclohexanone (CAS: 10496-51-2) and the tricyclic trimer 2,6-bisfuranenyl-cyclohexanone (CAS: 893-00-5). Currently, most research results can only obtain trimer or even polymer products or bicyclic-tricyclic mixtures, and cannot prepare pure bicyclic 2-furanenyl-cycloketones, nor can they obtain their high-purity chromatographic and NMR spectra.

[0003] Analysis reveals that the aforementioned reference catalytic technologies failed to achieve highly selective production of specific bicyclic products due to two main bottlenecks: a) their technology is limited by the use of ordinary soda ash or even strong base catalysts, making it impossible to controllably adjust the basic and acidic catalytic sites at the same catalytic interface; b) they cannot utilize steric hindrance to prevent further carbon growth of the bicyclic intermediate into trimers or polymers. Based on this analysis, if the three steps mentioned above can be implemented in series within the same type of porous solid catalyst, while ensuring the confinement and rate-limiting effect of the internal channels on the carbon chain growth side reactions of the bicyclic intermediate, the synthesis cost of polycyclic aldol condensation products can be significantly reduced and selectivity improved. This would specifically address the current situation in my country's fine chemical industry, which is heavily reliant on petrochemical resource production. Currently, research on Aldol reactive polymers in the field of chemical technology mainly focuses on three directions, all of which are narrow application areas with stringent separation conditions and complex catalyst systems. For example: 1. Using Aldol to condense and synthesize pharmaceutical precursors (such as CN110862364A, CN102115771B, etc.); 2. Using Aldol to condense and synthesize aviation fuel precursors (such as CN114891535B, CN110302789A, CN110550993B, etc.); 3. Condensing and synthesizing fuel precursors while simultaneously hydrogenating to synthesize aviation fuel (such as CN111218312B, CN107488457B, CN110511778A, CN112552949B, etc.). The aforementioned synthetic catalytic process has not yet solved the following problems: 1. The products are mixtures or non-bicyclic products, and there is no pure product analysis data; 2. Soluble or liquid ionic base / organic base catalysts are used, and some use low specific surface area alkaline earth metal oxides / hydrotalcite and other solid bases. The development of tunable mesoporous solid catalysts has not been involved, and catalyst recovery and regeneration are difficult; 3. The difficulty in adjusting the basicity leads to many subsequent side reactions, which are difficult to control thermodynamically or kinetically, and the selectivity of Aldol multi-step elementary reaction tandem dehydration is low; 4. Multicyclic products are difficult to separate, etc. All of the above problems have led to increased reaction and separation costs, making it impossible to enter the fine chemical trading market, thus narrowing the catalytic application field of Aldol condensation and preventing it from generating profits in related industries. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a catalytic method, catalyst, and preparation method for synthesizing furanene-cyclic ketone compounds. This method facilitates the Aldol condensation of furanaldehyde and cyclic ketones, enabling highly selective production of furanene-cyclic ketone compounds containing double bonds. By controlling the pore size and utilizing the kinetic differences arising from the acid-base dual-site tandem arrangement in the catalytic route, the selectivity for generating the bicyclic main product is significantly higher than that for subsequent polycyclic products. This allows for the directed catalytic synthesis of high-value-added products with specific bicyclic numbers and the achievement of preliminary purification, further enhancing the application prospects of this invention.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] One object of the present invention is to provide an acid-base dual-site catalyst for the synthesis of furanylene-cyclic ketone compounds. The catalyst is a solid catalyst with variable mesopore diameter and simultaneously containing acid-base dual sites. Its mesopore diameter is 3.41 nm-11.2 nm and can be directionally controlled and concentratedly distributed using a hydroxycarboxylic acid pore-forming agent, with a specific surface area of ​​172.4-869.6 m². 2 / g, acidity is 0.180-0.973mmol / g, and alkalinity is 0.016-0.125mmol / g;

[0007] The catalyst consists of an acidic mesoporous support and an alkaline metal hydroxide supported on the support;

[0008] The acidic mesoporous support is a composite of SiO2 and acidic metal oxide, which is prepared by hydrolysis and calcination of a soluble precursor of acidic metal, tetraethyl silicate and hydroxycarboxylic acid pore-forming agent; the acidic metal is selected from one of Al, V, Zr, Nb, Mo and W.

[0009] The alkaline metal hydroxide is selected from one of the hydroxides of Mg, Ca, Sr, Ba, Li, Na, and K.

[0010] Furthermore, based on a SiO2 mass of 100wt% in the acidic mesoporous support, the mass fraction of the acidic metal oxide is 5wt%-30wt%; based on a total catalyst mass of 100wt%, the mass fraction of the alkaline metal hydroxide is 0.5wt%-10wt%.

[0011] Furthermore, the soluble precursor of the acidic metal is one of aluminum sec-butoxide, zirconium nitrate, niobium oxalate, ammonium molybdate, ammonium metavanadate, and ammonium tungstate; the alkaline metal hydroxide is one of magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0012] Another object of the present invention is to provide a method for preparing the above-mentioned catalyst, specifically comprising the following steps:

[0013] S1: Preparation of acidic mesoporous carrier: A soluble precursor of acidic metal, tetraethyl silicate, deionized water and hydroxycarboxylic acid pore-forming agent are mixed in a corrosion-resistant glass or metal container and stirred at 85°C to generate an acidic gel. Then, the mixture is dried at 60°C and calcined at 550°C for 6 hours to decompose and volatilize the hydroxycarboxylic acid pore-forming agent, thus obtaining the acidic mesoporous carrier.

[0014] S2: Alkaline component loading: An aqueous solution of alkaline metal hydroxide is loaded onto the acidic mesoporous support obtained in step S1 using an equal-volume impregnation method, wherein the loading amount of the alkaline metal hydroxide is such that the mass fraction of the alkaline metal hydroxide in the final catalyst is 0.5wt%-10wt%; after baking at 80°C for 12 hours, it is calcined in air at 400°C for 4 hours to obtain an acid-base dual-site catalyst.

[0015] Further, in step S1, the hydroxycarboxylic acid pore-forming agent is one or a mixture of two of glycolic acid, citric acid, tartaric acid, lactic acid, and 2-hydroxyisobutyric acid; when two hydroxycarboxylic acid pore-forming agents are mixed in a certain proportion, the pore size of the obtained acidic carrier is between that obtained when using these two pore-forming agents alone.

[0016] The mass ratio of the soluble precursor of the acidic metal, tetraethyl silicate, deionized water and hydroxycarboxylic acid pore-forming agent is (1.10-3.42):17.6:30:(8-24).

[0017] The soluble precursor of the acidic metal is one of aluminum sec-butoxide, zirconium nitrate, niobium oxalate, ammonium molybdate, ammonium metavanadate, and ammonium tungstate.

[0018] Further, in step S2, the alkaline metal hydroxide is one of magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0019] Another objective of this invention is to provide a catalytic method for synthesizing furanene-cyclic ketone compounds, comprising the following steps: loading cyclic ketone compounds and furanaldehyde compounds as reactants into a reactor, adding an acid-base dual-site catalyst and mixing in a solvent, and carrying out an Aldol condensation reaction under liquid-phase heating conditions at a reaction temperature of 110-130°C for 12 hours; after the reaction, performing hot solution separation (standing / centrifugation / filtration / vacuum filtration) and recovering the catalyst to obtain a reaction solution; subjecting the reaction solution to cooling and freezing treatment (-10°C to -35°C) to separate the precipitated polycyclic byproducts into crystals, and concentrating and cooling recrystallizing or vacuum distilling the remaining liquid (since the solubility of the reaction products in organic solvents varies greatly with temperature, the hot solution can be directly separated by cooling recrystallization or purified by distillation using highly selective physical methods, without the need for complex purification steps), to obtain furanene-cyclic ketone compounds of the general formula (I):

[0020] (I);

[0021] In the formula, the -R group is one of -H, -OH, -CHO, -CH2OH, -COOH, -CH3 or -C2H5;

[0022] The mass ratio of the catalyst to the furanaldehyde compound, the cyclic ketone compound, and the solvent is (0.1-1.5):(0.5-10):(0.5-5):(10-40).

[0023] This method achieves highly selective synthesis and efficient separation of bicyclic products. The condensation product contains a unique structure where a furan ring (or tetrahydrofuran ring) and a cyclic ketone molecule are linked at the α-position of the ketone group by a double-bonded alkenyl group (furan—C=cyclic ketone), making it suitable for the synthesis of specific pharmaceuticals or fine chemicals. Furthermore, the ketones or solvents in the product solution can be recovered and reused. The novel catalytic process in this invention, when used for directed condensation reactions to generate bicyclic products, does not require complex reaction equipment, nor does it need to consider complex separation issues or equipment corrosion resistance. The reaction start-up conditions are mild; therefore, this process can be considered novel and economically feasible, with promising industrial application prospects.

[0024] Further, the cyclic ketone compound is one of cyclobutanone, cyclopentanone, 1,3-cyclopentanedione, cyclohexanone, 1,2-cyclohexanedione, 1,3-cyclohexanedione, 1,4-cyclohexanedione, or cycloheptanone; the furanaldehyde compound is one of furfural, tetrahydrofurfural, 5-hydroxymethylfurfural, 5-methylfurfural, 5-ethylfurfural, 2,5-furandicarboxaldehyde, 2,5-dicarboxytetrahydrofuran, or 5-formyl-2-furancarboxylic acid.

[0025] Further, the solvent is one or more of methanol, ethanol, isopropanol, n-butanol, cyclohexanol, cyclopentanol, ethyl acetate, tetrahydrofuran, dioxane, dioxacyclopentacyclo, benzene, alkylbenzene, n-hexane, cyclohexane, n-quinane, dodecane, methyl levulinate, ethyl levulinate, and gama-valerolactone; or, the cyclic ketone compound can be used directly as both a reactant and a solvent. When the compound itself is used as both a reactant and an excess solvent, the solubility of the polycyclic product can change significantly with temperature while maintaining solution stability, facilitating recrystallization to separate impurities and achieving a solvent-free reaction. Since the catalytic temperature required for ketone-ketone self-condensation in cyclic ketone solvents is higher than that for aldehyde-ketone condensation, the reaction can be thermodynamically controlled without additional solvent consumption.

[0026] Furthermore, when the reaction temperature is 110-130℃ and the reaction time is 12h, in the Aldol condensation reaction, the conversion rate of furanaldehyde compound is 72.5%-99.8%, the selectivity of furanene-cycloketone compound is 55.2-95.8%, and the selectivity of tricyclic and polycyclic by-products is less than 2.01-2.11%.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. Using furanaldehyde and cyclic ketones derived from some lignocellulosic biomass, starch, sugars, etc. as raw materials, a specific Aldol condensation reaction can be carried out in one batch to selectively prepare bicyclic furanene-cyclic ketone products containing double bonds for use in fine chemicals, pharmaceuticals, and other fields, thus expanding the application areas of biomass and Aldol condensation.

[0029] 2. Since the pore size of the catalyst suitable for the bicyclic main reaction and the polycyclic side reaction can be directionally controlled, the catalyst can regulate the rate of a series of side reactions related to polycyclic compounds through the principle of reaction kinetics, thereby directionally improving the selectivity of bicyclic products to a maximum of 95.8% (yield 92.2%), which basically solves the problems of low selectivity and polycyclic product mixture.

[0030] 3. The catalyst used in this invention has both acid-base amphoteric sites, which can catalyze the reaction of high-concentration raw materials at low temperatures with high reaction efficiency. Under the optimal synthesis conditions, the furfural conversion rate can reach 97.0%, and under other synthesis conditions, the furfural conversion rate can be higher than 99.8%, which reduces the purification difficulty and eliminates the problem of carbon buildup during high-temperature polymerization.

[0031] 4. When it is necessary to synthesize bicyclic compounds with specific structures, a suitable system can be directly selected for thermal synthesis and then cooled for crystallization or distillation to purify the product (the catalyst is separated from the hot solution in advance). There is no need to use liquid catalysts that are difficult to separate or easily mixed with impurities, nor is it necessary to use complex separation steps such as multi-stage extraction, which basically solves the purification and separation problem.

[0032] 5. The porous solid alkali catalyst synthesized in this invention is easy to separate and recover, resistant to high-temperature calcination, recyclable, does not easily lose alkali ions, is not easily blocked by mesopores, and has a simple synthesis process, thus improving the problem of catalyst usage cost.

[0033] Because this invention directly synthesizes the target product in a single batch at a relatively low temperature, without intermediate steps and with almost no other byproducts, the target product can be obtained simply by cooling and crystallizing the centrifuged reaction liquid and distilling it, thus increasing economic efficiency. Furthermore, the compounds obtained from this reaction can be used directly as solvents after appropriate hydrogenation, and ketone raw materials can also be used as solvents. Unreacted ketones, furanaldehydes, and other compounds can be recycled and reused. Combined with the advantages of the catalyst, this process does not cause environmental pollution. The bicyclic product exhibits high selectivity, mild operation, simple process, high safety, and is environmentally friendly. It has promising industrial applications in polymer precursors, fuel precursors, and pharmaceutical precursors, and provides valuable supplementary technology to the development of my country's chemical industry. Attached Figure Description

[0034] Figure 1The GC-total ion chromatogram of the purified bicyclic product 2-furanenyl-cyclohexanone (11.9 min) is shown.

[0035] Figure 2 High-resolution mass spectrum of the purified bicyclic product 2-furanenyl-cyclohexanone;

[0036] Figure 3 Mass spectrometry data of the purified bicyclic product 2-furanenyl-cyclohexanone, matched with the Agilent NIST library;

[0037] Figure 4 The purified bicyclic product 2-furanenyl-cyclohexanone 1 H NMR spectrum;

[0038] Figure 5 A tandem reaction mechanism diagram for the highly selective catalytic condensation of Aldol to 2-furanenyl-cyclohexanone using an acid-base dual-site catalyst. Detailed Implementation

[0039] To make the objectives and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0040] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.

[0041] Example 1 Catalyst Preparation

[0042] This embodiment helps technicians understand the preparation and synthesis method of acid-base dual-site mesoporous catalysts. Specifically, it includes the following steps:

[0043] S1: Preparation of acidic mesoporous support: A soluble precursor of acidic metal (aluminum sec-butoxide, zirconium nitrate, niobium oxalate, ammonium molybdate, ammonium metavanadate or ammonium tungstate), tetraethyl silicate, deionized water and hydroxycarboxylic acid pore-forming agent (glycolic acid, citric acid, tartaric acid, lactic acid or 2-hydroxyisobutyric acid) are mixed in a mass ratio of (1.10-3.42):17.6:30:(8-24), stirred at 85°C to generate acidic gel, dried at 60°C, and then calcined at 550°C for 6 h to obtain acidic mesoporous support;

[0044] S2: Alkaline component loading: Prepare a quantitative amount of alkaline metal hydroxide aqueous solution, and load the alkaline metal hydroxide (magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide) aqueous solution onto the acidic mesoporous support obtained in step S1 using an equal volume impregnation method. The loading amount of alkaline metal hydroxide is such that the mass fraction of alkaline metal hydroxide in the final catalyst is 0.5wt%-10wt%. After drying at 80℃, calcine in air at 400℃ for 4h to obtain an acid-base dual-site catalyst.

[0045] The mesopore size of the catalyst in this embodiment, as determined by the BET method, ranges from 3.41 nm to 11.2 nm, and the specific surface area is adjustable from 172.4 to 869.6 nm. 2 / g. It should be noted that the proportions of different elements are adjustable within the allowable range of the loaded mass fraction and need to be determined according to the actual reaction requirements. Depending on the amount added, the composition of some catalysts is shown in Table 1, and their specific surface area, pore size, and other parameters are shown in Table 2.

[0046] Table 1 shows the mass composition of acid-base dual-site catalysts synthesized with different precursor usage amounts.

[0047] ,

[0048]

[0049] The surface parameters of the acid-base dual-site catalysts in the above table are shown in Table 2 after analysis by BET instrument.

[0050] Table 2. Internal surface parameters of acid-base dual-site mesoporous catalysts synthesized with different acidic supports.

[0051] ,

[0052]

[0053] Example 2: Regulation of catalyst pore size

[0054] This embodiment helps technicians understand the impact of the type and amount of pore-forming agent on the control of catalyst pore size parameters.

[0055] This embodiment uses the KOH / Al-Si (molar ratio Al:Si=1:6, mass ratio AlO) method used in Example 1. x Preparation parameters of the catalyst (SiO2 = 14.2wt%: 100wt%). Some of the raw materials and steps were the same as in Example 1. The acidic metal precursor used was 3.42g of aluminum sec-butoxide, and the basic precursor used was potassium hydroxide. The difference was that different types and quantities of pore-forming agents were used.

[0056] The final internal surface parameters of the acid-base dual-site catalyst, analyzed using a BET instrument, are shown in Table 3. The data indicate that the type and amount of hydroxycarboxylic acid pore-forming agent affect the catalyst pore size. Furthermore, when two hydroxycarboxylic acid pore-forming agents with different characteristic pore sizes are mixed, the resulting catalyst pore size may fall between the two. Therefore, technicians can fine-tune the support pore size based on the proportion of hydroxycarboxylic acid pore-forming agents used in the mixture.

[0057] Table 3 Internal surface parameters of acid-base dual-site catalysts prepared with different amounts of pore-forming agent

[0058]

[0059] Example 3: Preliminary Synthesis of Furanide-Cyclokes

[0060] This embodiment helps technicians understand the preliminary synthesis process of furanene-cycloketones. Specifically, it includes the following steps:

[0061] Cyclic ketones and furan aldehydes undergo Aldol condensation under acid-base catalysis to generate furanene-cyclic ketones with specific structures. The entire process is carried out in a single reactor using a single catalyst. During operation, the aldehyde / ketone reactants to be condensed are loaded into the reactor, and a novel catalyst is added. The mass ratio of catalyst to aldehyde, ketone reactants, and solvent is (0.1-1.5):(0.5-10):(0.5-15):(10-40). The liquid phase is heated to induce Aldol condensation at 110°C for 12 hours. The resulting mixture is then subjected to hot solution centrifugation in a high-speed centrifuge, or allowed to settle at a controlled temperature, or filtered / vacuum filtered at a controlled temperature to separate the catalyst from the supernatant, allowing for complete catalyst recovery. Gas chromatography-mass spectrometry analysis of the supernatant reveals that the molecular structure of the furanene-cyclic ketone condensation product is one (highly selective main product) or several (one main product and a small amount of byproducts):

[0062]

[0063] In the formula, the substituent R in the molecular formula refers to one of -H (hydrogen atom), -OH (hydroxyl group), -CHO (aldehyde group), -CH2OH (hydroxymethyl), -COOH (carboxyl group), -CH3 (methyl), or -C2H5 (ethyl). The cyclic ketone compound is one of cyclobutanone, cyclopentanone, 1,3-cyclopentanedione, cyclohexanone, 1,2-cyclohexanedione, 1,3-cyclohexanedione, 1,4-cyclohexanedione, or cycloheptanone (also known as cork ketone). The furanaldehyde compound is one of furfural, tetrahydrofurfural, 5-hydroxymethylfurfural, 5-methylfurfural, 5-ethylfurfural, 2,5-furandicarboxaldehyde, 2,5-dicarboxytetrahydrofuran, or 5-formyl-2-furancarboxylic acid, used to achieve Aldol aldehyde-ketone condensation. The solvent is one or more of methanol, ethanol, isopropanol, n-butanol, cyclohexanol, cyclopentanol, ethyl acetate, tetrahydrofuran, dioxane, dioxane, benzene, alkylbenzene, n-hexane, cyclohexane, n-quinane, dodecane, methyl levulinate, ethyl levulinate, and gama-valerolactone; or, the cyclic ketone compound is used directly as both a reactant and a solvent.

[0064] Example 4 Purification of furanene-cycloketone

[0065] This embodiment helps technicians understand the purification process of furanylene-cyclic ketones. Specifically, it includes the following steps:

[0066] The hot supernatant obtained after the reaction is cooled and frozen to below -15°C to remove trace amounts of polycyclic (tricyclic and above) byproduct organic crystals, yielding a high-purity product solution. The solvent is removed by vacuum distillation using a rotary evaporator or vacuum distillation apparatus at 5-30 k absolute pressure (vacuum degree ≥70%) and temperature ≥90°C, yielding a preliminary furanylene-cyclic ketone product. This preliminary product is washed repeatedly with water to remove trace amounts of furanaldehyde, cyclic ketones, and other small molecules, and then dried to obtain a high-purity product. The solvent is reused for the reaction, crystallization separation, or returned to a pure solvent storage device. The separated high-purity product organic crystals can be used for mass spectrometry (MS) or nuclear magnetic resonance (NMR). 1 HNMR analysis that meets the standards can be used for quantitative analysis of standard samples or other extended uses permitted in industry.

[0067] Taking the condensation of furfural and cyclohexanone as an example, a solution of 1.5g furfural and 15g cyclohexanone was prepared and catalytically reacted at 110℃ to obtain 16.5g of solution, containing approximately 2.25g of 2-furanenyl-cyclohexanone, 13.7g of cyclohexanone, 0.23g of polycyclic byproducts, and trace amounts of unreacted furfural. After freezing, approximately 0.2g of polycyclic byproduct organic crystals were separated from the solution; after rotary evaporation under reduced pressure, approximately 2.2g of solid was separated from the solution, of which 2-furanenyl-cyclohexanone had a purity ≥95%, preliminarily reaching chemical purity. The results of chromatographic GC analysis, mass spectrometry MS analysis, and nuclear magnetic resonance NMR analysis are shown below. Figure 1-4 . Figure 1 The image shows the chromatogram of the purified 2-furanenyl-cyclohexanone. Peak area analysis showed that the peak area of ​​this product accounted for ≥95%, while the peak area of ​​the remaining molecules accounted for ≤5%. Figure 2 The mass spectrum of purified 2-furanenylcyclohexanone obtained from mass spectrometry analysis using an Agilent 5973N is shown. Figure 3 The standard mass spectrum of 2-furanenyl-cyclohexanone provided by the Agilent NIST database can be used by technicians for research and comparison. Figure 4 The purified 2-furanenyl-cyclohexanone 1 The 1H NMR spectrum shows no obvious impurity peaks, and the hydrogen atom position analysis is accurate, proving that the product purity is up to standard. Figure 2 Combined analysis proves that the molecular structure of the product was correctly determined.

[0068] Example 5 Catalyst Screening (Part 1)

[0069] This example helps technicians understand the effect of novel catalysts synthesized from different acidic or basic metal precursors on the yield of Aldol condensation reactions.

[0070] When 1.5 g furfural (0.0156 mol) and 15 g cyclohexanone (0.153 mol) were used as reaction raw materials, the reaction temperature was 110 °C, the reaction time was 12 h, and 0.5 g of solid catalyst was added. After the separation process in Example 4, the yields of bicyclic and polycyclic products were obtained as follows, as shown in Table 4.

[0071] Table 4. Maximum yields and selectivity of the reaction products of cyclohexanone and furfural

[0072] (The bicyclic product is 2-furanenyl-cyclohexanone, and the polycyclic product is 2,5-bisfuranenyl-cyclohexanone.)

[0073] ,

[0074]

[0075] In the table above, the Al:Si molar ratio of the Al-Si support is 1:6, and the content of the remaining acidic metal (denoted by M) oxide supports is recorded as a mass fraction: MO. xThe SiO2 ratio is 20wt%:100wt%. The equivalent 2% LiOH and KOH are interpreted as the same amount of hydroxide as the 0.5g supported catalyst, calculated as 0.5g × 2% LiOH / Al-Si = 0.5g × 0.02 = 0.01g LiOH. The data shows that a higher product yield is obtained when basic hydroxides are supported on a silica-alumina support. Furthermore, pure acidic supports and pure hydroxides can also catalyze the reaction, but the yield is inferior to that of acid-base dual-site catalysts. Besides silica-alumina acidic supports, acidic element supports such as niobium, molybdenum, tungsten, zirconium, and vanadium can also be used to catalyze this reaction, but due to their relatively large atomic masses leading to a lower total molar mass and a reduced molar mass of acidic sites, the reaction performance is inferior to that of silica-alumina supports.

[0076] Example 6 Catalyst Screening (II)

[0077] This embodiment helps technicians understand the effect of acidic silica-alumina supports with different acid concentrations as pure acid catalysts on the yield of Aldol condensation reaction.

[0078] In this embodiment, the operating conditions and reactants are the same as in Example 5, except that the amount of acidic metal precursor is changed, resulting in a different molar ratio of acidic metal atoms to silicon atoms. Since traditional silicon-aluminum molecular sieves often use the silicon-aluminum molar ratio as a characteristic parameter, the silicon-aluminum support is calculated using integer multiples of the silicon-aluminum molar ratio during preparation, while other acidic metal supports are calculated using integer multiples of their mass ratio. The yields of bicyclic and polycyclic products obtained by using acidic supports synthesized with different molar and mass ratios as catalysts for this reaction are shown in Table 5. The data shows that acidic supports cannot achieve high selectivity in this reaction, and increasing the acidity does not always benefit the reaction; the highest yield range is found at an aluminum-silicon molar ratio of 1:6. If transition metals such as niobium and tungsten are used as strong acidic site supports, their larger atomic masses result in a much lower molar ratio than aluminum-silicon supports. Therefore, their catalytic effect is slightly better than that of silicon-aluminum supports in the range of 1:10 to 1:8, but the catalytic effect decreases when the molar ratio is less than 1:10.

[0079] Table 5. Yields of bicyclic and polycyclic products synthesized under acidic support catalysis with different molar and mass ratios.

[0080]

[0081] Example 7 Catalyst Screening (Part 3)

[0082] This example helps technicians understand the effects of different strengths of basicity and acid-base synergy on the yield of furanene-cyclohexanone bicyclic products.

[0083] The operating conditions and reactants in this embodiment are the same as in Example 5, except that different amounts of alkaline hydroxide are used in pure alkaline catalysts and strong base-weak acid catalysts. The yields of bicyclic and polycyclic products obtained by catalyzing this reaction with different alkaline or strong base-weak acid catalysts are shown in Table 6. In the catalyst data, the mass of pure LiOH and KOH alkaline catalysts used is equal to the loaded mass on 0.5g of a strong base-weak acid supported catalyst. For example, when using 0.5g of 10wt% LiOH / SiO2 catalyst, the internal loaded lithium hydroxide mass is 0.5g × 10wt% = 0.05g, which corresponds to 0.05g of pure alkaline catalyst (10% LiOH). The data shows that even pure alkaline catalysts cannot achieve high selectivity for dimers; when the alkalinity is significantly increased, the trimer C… 16 The yield of the product (2,5-bisfuranenylcyclohexanone) increases, but the overall yield is still below 70%. When hydroxide is impregnated on a silica support, the silica support itself is weakly acidic, so it can be regarded as a strong base-weak acid catalyst. In this case, the yield of the bicyclic product is slightly higher than that of a pure basic catalyst, showing a site synergistic effect, but the yield is still lower than that of a strong acid-weak base catalyst impregnated on a silica-alumina support.

[0084] Table 6 Yields of bicyclic (furanene-cyclohexanone) and polycyclic products under soda ash and soda ash catalysts

[0085]

[0086] Example 8: The Necessity of a Specific Loading Ratio in the Preparation of a Weak Base-Supported Strong Acid Catalyst

[0087] This example helps technicians understand the effect of catalysts loaded with different amounts of weak bases on a strong acid support on the yield of furanene-cyclohexanone bicyclic products.

[0088] In this example, the operating conditions and reactants are the same as in Example 5, except that a weak base-supported strong acid catalyst (strong acid, weak base) was synthesized using a strong acid-type silica-alumina support (aluminum-silicon molar ratio 1:6). The yields of the bicyclic and polycyclic products are shown in Table 7. The data in the table show that when the loading of the weak basic hydroxide is below 5%, both weak basic and strong acid sites coexist on the catalyst surface. The optimal loading is 0.5%-3%, and the optimal reaction yield can reach 92.9%. When the loading increases to about 5%, the weak basic and strong acid sites neutralize each other, resulting in the worst catalytic effect. Further increasing the loading to 10%, the weak basic hydroxide is in excess and completely covers the acid sites, and the catalytic effect returns to being dominated by basicity. The yield of furanylene-cyclohexanone increases again, but it is inferior to the yield of the catalyst with a 2% loading. Relevant catalyst acidity and basicity data are shown in Example 9. The detailed tandem mechanism of the highly selective catalytic reaction of this Aldol condensation reaction by the weak base-strong acid catalyst in this example is shown in... Figure 5 .

[0089] Table 7 Yields of bicyclic (furanene-cyclohexanone) and tricyclic products under strong acid-weak base catalysts

[0090]

[0091] Example 9: Acid-base dual-site catalyst acid-base properties

[0092] This embodiment helps technicians understand the effects of different impregnation loadings of weakly basic hydroxides on the acid and basic parameters of an acid-base dual-site catalyst.

[0093] This example illustrates the internal surface parameters and acid-base site parameters of the catalyst used in Example 8. The acid-base parameters of the impregnated strong acid-weak base catalyst (aluminum-silicon molar ratio 1:6) are shown in Table 8 after CO2-TPD and NH3-TPD analysis. The results show that the acid content is 0.180-0.973 mmol / g and the base content is 0.016-0.125 mmol / g, which can be directionally controlled. Because this catalyst possesses both acidic and basic sites, NH3-TPD and CO2-TPD signals can be measured simultaneously. The data in the table show that the optimal basic site content is achieved when the loading of the weak basic hydroxide is 2%, corresponding to the reaction effect in Example 8. The preparation method of the relevant catalyst is described in Example 1.

[0094] Table 8. Acid-base parameters of different hydroxides supported on acid-base dual-site catalysts with strong acidity in silicon and aluminum.

[0095]

[0096] A comparison of data from Examples 5-9 shows that the yield of furanylene-cyclohexanone can only reach its maximum when both alkalinity and acidity are within a suitable range.

[0097] Example 10: Universality Study of Different Raw Materials

[0098] This embodiment helps technicians understand the effect of different furanaldehyde and ketone raw material structures on the yield of bicyclic products generated by the Aldol condensation reaction in this invention.

[0099] The reaction conditions and time in this example are the same as in Example 5, and the catalyst used is 2% LiOH / Al-Si (Al:Si molar ratio 1:6). The difference lies in the type of reactants and the structure of the bicyclic product. When 0.0155 mol furfural and 0.155 mol cyclic ketones are used as reactants, the different yields of bicyclic products obtained by the synthesis process in Example 9 and distillation separation are shown in Table 9. The data in the table show that when molecules containing diketone or dialdehyde groups are used as reactants, the yield of polymers is higher.

[0100] Table 9. Highest yields and selectivity of bicyclic (substituted furanene-cycloketone) products synthesized from different starting materials.

[0101]

[0102] Example 11 Effect of catalyst mesopore size optimization on the purity of furanene-cycloketone products

[0103] This embodiment helps technicians understand the effect of the mesoporous pore size confinement of different catalyst supports on the selectivity of Aldol condensation to generate bicyclic and tricyclic or higher-order products.

[0104] In this embodiment, the remaining conditions are the same as in Example 5, and the catalyst used is 2% KOH / Al-Si (Al:Si molar ratio 1:6). The difference lies in the different pore sizes of the catalyst support. The chromatographic analysis data for the different bicyclic / polycyclic selectivity changes are shown in Table 10. The data show that when the catalyst mesopore size gradually increases from 3 nm to 10 nm, C... 11 :C 16 The proportion gradually decreases. Therefore, the smaller the catalyst pore size, the more favorable its confinement effect is for the formation of C. 11 The separation of the bicyclic product, furanylene-cyclic ketone, is easier. Furthermore, since the bicyclic molecules generated from reactants with different structures have different sizes, technicians can fine-tune the process based on the data in Example 10 to achieve the goal of controlling reaction selectivity. The preparation methods for 2% KOH / Al-Si with different pore sizes are shown in Example 2.

[0105] Table 10 Yields and selectivity of bicyclic and polycyclic products using catalysts with different pore sizes

[0106]

[0107] Example 12 Reaction Temperature Optimization

[0108] This example helps technicians understand the effect of reaction temperature on the yield of furanene-cyclohexanone produced in the Aldol condensation reaction.

[0109] In this example, the operating conditions and reaction raw materials are the same as in Example 5, using 2% LiOH / Al-Si (Al:Si=1:6) as the catalyst. The difference lies in the reaction temperature. Yield data at different temperatures are shown in Table 11. The data indicate that the optimal synthesis temperature for furanylene-cyclohexanone is approximately 110-130℃.

[0110] Table 11 Yields and selectivity of bicyclic and polycyclic products at different reaction temperatures

[0111]

[0112] Example 13 Optimization of Reaction Time

[0113] This example helps technicians understand the effect of reaction time on the yield of furanene-cyclohexanone produced by the Aldol condensation reaction.

[0114] In this example, the reaction temperature and reactants are the same as in Example 5, using 2% LiOH / Al-Si (Al:Si=1:6) as the catalyst. The difference lies in the reaction time. Yield data at different times are shown in Table 12. The data shows that the optimal synthesis time for furanylene-cyclohexanone is approximately 12 hours. When the dimer concentration reaches its peak and the furanyl aldehyde feedstock is exhausted, furanylene-cyclohexanone will slowly convert to 2,5-bisfuranylene-cyclohexanone, i.e., C... 16 Trimer.

[0115] Table 12 Yields and selectivity of bicyclic and polycyclic products at different reaction times

[0116]

[0117] Example 14 Optimization of Reaction Feedstock, Solvent, and Catalyst

[0118] This example helps technicians understand the effects of reactant and catalyst concentrations on the yield of furanene-cyclohexanone produced in the Aldol condensation reaction.

[0119] In this example, the reaction temperature and time were the same as in Example 5, and 2% LiOH / Al-Si (molar ratio Al:Si = 1:6) was used as the catalyst. The difference lay in the amount of raw materials and catalyst fed. Yield data for different feed amounts are shown in Table 13. The data show that the reaction using a polar solvent (such as dioxane) to synthesize furanylene-cyclohexanone yields higher raw material conversion and bicyclic C... 11 The product yield was lower, but the total product mass was lower than that of the solvent-free system of 1.5g furfural + 15g cyclohexanone. Non-polar solvents (such as cyclohexane) have insufficient solubility for both the raw materials and products, resulting in a less efficient reaction compared to polar solvents. When the furfural:cyclohexanone feed ratio is greater than 1:10, polycyclic aromatic hydrocarbons (PAHs) are more abundant. 16 The product yield will increase significantly; when the catalyst feed amount is greater than 0.5g, the increased number of catalytic sites also leads to the formation of polycyclic C atoms. 16 The product yield increased, therefore, the composition of furfural (1.5g), cyclohexanone (15g), and catalyst (0.5g) was a bicyclic C. 11 Optimal feed size to maximize product yield.

[0120] Table 13 Yields and selectivity of bicyclic and polycyclic products under different feedstock and catalyst feed rates

[0121]

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A catalyst for the synthesis of furanylenyl-cycloketone compounds, characterized by: The catalyst is a solid catalyst with variable mesopore diameter and containing both acid and base sites, having a mesopore diameter of 3.41-11.2 nm, a specific surface area of 172.4-869.6 m 2 / g, an acid amount of 0.180-0.973 mmol / g, and a base amount of 0.016-0.125 mmol / g. The catalyst is composed of an acidic mesoporous carrier and a basic metal hydroxide supported on the carrier; The acidic mesoporous carrier is a composite of SiO2 and an acidic metal oxide, and is prepared by hydrolysis and calcination of a soluble precursor of the acidic metal, tetraethyl orthosilicate and a hydroxyl carboxylic acid pore-forming agent; the acidic metal is selected from one of Al, V, Zr, Nb, Mo and W; The basic metal hydroxide is selected from one of hydroxides of Mg, Ca, Sr, Ba, Li, Na and K; The mass fraction of the acidic metal oxide is 5wt%-30wt% based on 100wt% of the mass of SiO2 in the acidic mesoporous carrier; and the mass fraction of the basic metal hydroxide is 0.5wt%-10wt% based on 100wt% of the total mass of the catalyst; The soluble precursor of the acidic metal is one of aluminum sec-butoxide, zirconium nitrate, niobium oxalate, ammonium molybdate, ammonium metavanadate and ammonium tungstate; and the basic metal hydroxide is one of magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, lithium hydroxide, sodium hydroxide and potassium hydroxide.

2. The method of claim 1, wherein the catalyst is prepared by the steps of: Specifically comprising the following steps: S1: Preparation of the acidic mesoporous carrier: mixing a soluble precursor of the acidic metal, tetraethyl orthosilicate, deionized water and a hydroxyl carboxylic acid pore-forming agent, stirring and reacting at 85℃ to generate an acidic gel, then drying at 60℃, and then calcining at 550℃ for 6h to obtain the acidic mesoporous carrier; S2: Loading of the basic component: using an equal-volume impregnation method, loading a basic metal hydroxide aqueous solution onto the acidic mesoporous carrier obtained in step S1, the loading amount of the basic metal hydroxide being calculated based on the mass fraction of the basic metal hydroxide in the final catalyst being 0.5wt%-10wt%; after baking at 80℃ for 12h, calcining at 400℃ in air for 4h to obtain the acid-base dual-site catalyst.

3. The method of claim 2, wherein: In step S1, the hydroxyl carboxylic acid pore-forming agent is one of glycolic acid, citric acid, tartaric acid, lactic acid, 2-hydroxyisobutyric acid or a mixture of two of them; The mass ratio of the soluble precursor of the acidic metal, tetraethyl orthosilicate, deionized water and the hydroxyl carboxylic acid pore-forming agent is (1.10-3.42):17.6:30:(8-24); The soluble precursor of the acidic metal is one of aluminum sec-butoxide, zirconium nitrate, niobium oxalate, ammonium molybdate, ammonium metavanadate and ammonium tungstate.

4. The method of claim 2, wherein: In step S2, the basic metal hydroxide is one of magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, lithium hydroxide, sodium hydroxide and potassium hydroxide.

5. A catalytic process for the synthesis of furanylenyl-cycloketone compounds, characterized by, Comprising the following steps: Mixing the cyclic ketone compound and the furan aldehyde compound with the catalyst of claim 1 in a solvent, and carrying out Aldol condensation reaction at a temperature of 110-130℃ for 12h; after the reaction is completed, separating and recovering the catalyst to obtain a reaction liquid; subjecting the reaction liquid to cooling and freezing treatment to separate and crystallize the polycyclic byproduct, and subjecting the remaining liquid to concentration and cooling recrystallization or reduced-pressure distillation treatment to obtain a furan alkenyl-cyclic ketone compound as shown in general formula (I): （I）； In the formula, the -R group is one of -H, -OH, -CHO, -CH2OH, -COOH, -CH3, or -C2H5; The mass ratio of the catalyst, the furan aldehyde compound, the cyclic ketone compound, and the solvent is (0.1-1.5):(0.5-10):(0.5-15):(10-40).

6. The catalytic process of claim 5, wherein: The cyclic ketone compound is one of cyclobutanone, cyclopentanone, 1,3-cyclopentanedione, cyclohexanone, 1,2-cyclohexanedione, 1,3-cyclohexanedione, 1,4-cyclohexanedione, or cycloheptanone; and the furan aldehyde compound is one of furfural, tetrahydrofurfural, 5-hydroxymethylfurfural, 5-methylfurfural, 5-ethylfurfural, 2,5-furandicarboxaldehyde, 2,5-diformyltetrahydrofuran, or 5-formyl-2-furoic acid.

7. The catalytic process of claim 5, wherein: The solvent is one or a mixture of multiple of methanol, ethanol, isopropanol, n-butanol, cyclohexanol, cyclopentanol, ethyl acetate, tetrahydrofuran, dioxane, dioxane, benzene, alkylbenzene, n-hexane, cyclohexane, n-quian, dodecane, methyl levulinic acid, ethyl levulinic acid, gama-valerolactone; or the cyclic ketone compound is directly used as the reaction raw material and the solvent.

8. The catalytic process of claim 5, wherein: In the Aldol condensation reaction, when the reaction temperature is 110-130℃ and the reaction time is 12h, the conversion rate of the furan aldehyde compound is 72.5%-99.8%, the selectivity of the furan alkenyl-cyclic ketone compound is 55.2-95.8%, and the selectivity of the tricyclic and polycyclic by-products is less than 2.01-2.11%.

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