Process for the catalytic hydroesterification of long chain olefins to carboxylic acid esters using oxide supported ruthenium catalysts and halide salts

Abstract

The present application relates to the technical field of heterogeneous catalysis, and in particular to a method for preparing carboxylic acid ester by catalyzing long-chain alkene hydroesterification with the aid of oxide-supported ruthenium catalyst and halogen salt. The oxide carrier is immersed in a ruthenium precursor solution, and after removing the solvent, an oxide loaded with a ruthenium precursor is obtained. The ruthenium ion in the oxide loaded with a ruthenium precursor is reduced to ruthenium clusters or ruthenium nanoparticles by using a liquid-phase reduction method or a gas-phase reduction method, and an oxide-supported ruthenium catalyst is obtained. The oxide-supported ruthenium catalyst of the present application is used together with halogen salt to catalyze long-chain alkene hydroesterification to prepare carboxylic acid ester, which not only improves the hydroesterification reaction rate, but also inhibits the isomerization, hydrogenation and polymerization side reactions of long-chain alkene. In addition, the present application realizes efficient heterogeneous hydroesterification of long-chain alkene, CO and organic alcohol under mild conditions, and overcomes the problems existing in the prior art.

Description

Technical Field

[0001] This invention relates to the field of heterogeneous catalysis technology, specifically to a method for the hydrogen esterification of long-chain olefins to prepare carboxylic acid esters using oxide-supported ruthenium catalysts and halogen salt-assisted catalysis. Background Technology

[0002] Long-chain carboxylic esters (≥5 carbon atoms) have significant industrial application value and are widely used in plasticizers, lubricants, and surfactants. Especially against the backdrop of increasingly stringent environmental regulations, these compounds are seen as green alternatives to phthalate plasticizers and mineral-based lubricants, leading to continuously growing market demand. Traditionally, the synthesis of long-chain carboxylic esters mainly relies on "olefin hydroformylation-oxidation-esterification" or "olefin hydrocarboxylation-esterification" processes, which are cumbersome, energy-intensive, and involve equipment corrosion and environmental pollution due to the use of strong acids. In contrast, long-chain carboxylic esters prepared by direct hydrogen esterification of long-chain olefins, carbon monoxide, and organic alcohols not only achieve 100% atom economy but also utilize greener and milder reaction conditions, significantly simplifying the process.

[0003] Conventional hydrogen esterification reactions of long-chain olefins typically employ homogeneous catalytic systems catalyzed by palladium (Pd). For example, patents CN100417635A, CN101003456A, CN1075805A, CN1221516A, and CN119977809A disclose various methods for preparing long-chain carboxylic esters. However, these methods all require the addition of phosphine ligands and acidic auxiliaries, leading to complex and energy-intensive separation processes for the subsequent high-boiling-point carboxylic ester products. Furthermore, homogeneous Pd catalysts are difficult to recover, and acidic media pose a corrosive problem to reaction equipment, hindering industrial applications.

[0004] Existing research has yielded heterogeneous Pd catalysts (such as patents CN118106030A and CN119978027A) by coordinating N, P, and S coordinating atoms on an insoluble support with Pd salts, achieving the recovery of Pd substances. However, in most applications, these catalyst systems still require the addition of acidic promoters and phosphine ligands to maintain high carbonylation reaction activity.

[0005] Currently, oxide-supported ruthenium-based heterogeneous catalysts have shown good application potential in olefin hydrogen esterification reactions, especially in achieving this conversion under acid-free conditions. For example, patents CN108003023A, CN108003024A, and CN114621089A report methods for catalyzing the hydrogen esterification of ethylene to prepare methyl propionate using such catalysts. Subsequent studies have further developed oxide-supported ruthenium-based bimetallic catalytic systems (such as CN114618519A and CN114618521A), but the olefins applicable to these systems are still mainly limited to ethylene and styrene, and the heterogeneous hydrogen esterification process of long-chain olefins has not yet been achieved. However, compared with ethylene and styrene, long-chain olefins are more prone to isomerization, hydrogenation, and polymerization side reactions. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for the hydrogen esterification of long-chain olefins to carboxylic acid esters using oxide-supported ruthenium catalysts and halogen salt-assisted catalysis. This invention employs a "ruthenium precursor impregnation-chemical reduction" method to obtain the oxide-supported ruthenium catalyst. Using a specific halogen salt as a promoter, this invention significantly enhances the hydrogen esterification reaction rate while suppressing side reactions such as isomerization, hydrogenation, and polymerization of long-chain olefins through the synergistic effect of the promoter and the ruthenium active center of the oxide-supported ruthenium catalyst. This achieves highly efficient heterogeneous hydrogen esterification reactions of long-chain olefins, CO, and organic alcohols under mild conditions. Furthermore, the oxide-supported ruthenium catalyst of this invention can be recycled without phosphine ligands and acid promoters, exhibits stable activity, and the products are easily separated. The process is green and environmentally friendly, thus overcoming the problems of ligand dependence, equipment corrosion, high energy consumption, and difficult catalyst recovery in existing technologies. This provides a promising new approach for the green, economical, and efficient production of long-chain carboxylic acid esters.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first objective of this invention is to provide a method for preparing an oxide-supported ruthenium catalyst, comprising the following steps: S1. The oxide support is immersed in a ruthenium precursor solution, and after removing the solvent, an oxide loaded with ruthenium precursor is obtained.

[0008] S2. Use liquid-phase reduction or gas-phase reduction to reduce ruthenium ions in the oxide of the supported ruthenium precursor to ruthenium clusters or ruthenium nanoparticles to obtain oxide-supported ruthenium catalyst.

[0009] Preferably, the ruthenium loading in the oxide of the ruthenium precursor is 0.1 wt% to 10 wt%; more preferably, the ruthenium loading in the oxide of the ruthenium precursor is 0.2 wt% to 5 wt%.

[0010] Preferably, the impregnation conditions are: stirring at 30℃~110℃ for 1h~12h.

[0011] Preferably, the drying conditions for the oxide supported on the ruthenium precursor are: drying at 40℃~120℃ for 1h~12h.

[0012] Preferably, the liquid-phase reduction method is operated as follows: using hydrazine hydrate, sodium borohydride, ascorbic acid or sodium citrate as reducing agents, the reducing agents are mixed with oxides of ruthenium-supported precursors and a reduction reaction is carried out; wherein, the molar ratio of the reducing agent to ruthenium in the precursor is 1~100:1; the conditions for the reduction reaction are: stirring at 0℃~150℃ for 1h~10h.

[0013] Preferably, the operation of the gas-phase reduction method is as follows: using H2, CO, Ar or N2 as the reducing atmosphere, calcining at 30℃ to 800℃ for 0.5h to 24h at a heating rate of 3℃ / min to 20℃ / min; wherein the flow rate of the reducing atmosphere gas is 10mL / min to 200mL / min; more preferably, calcining at 100℃ to 450℃ for 2h to 14h.

[0014] Preferably, in the ruthenium precursor solution, the ruthenium precursor is selected from at least one of ruthenium trichloride, dodecacarbonyl ruthenium, ruthenium acetate, ruthenium nitrite sulfate, ruthenium nitrite nitrate, ammonium ruthenium chloride, ruthenium acetylacetone, cyclooctadiene ruthenium dichloride, bis(ethylcyclopentadiene)ruthenium, bis-(2-methylallyl)cyclooct-1,5-diene ruthenium, tris(triphenylphosphine) ruthenium dichloride, and hexaammine ruthenium chloride.

[0015] Preferably, the oxide support is selected from metal oxide supports, silica-containing supports, metal oxide supports loaded with metal oxides, or silica supports loaded with metal oxides.

[0016] Preferably, the metal oxide support is selected from CeO2, La2O3, and Pr6O. 11 WO3, Al2O3, TiO2, ZrO2, Nb2O5 or MgO.

[0017] Preferably, the silica-containing carrier is selected from silica, all-silica molecular sieve, diatomaceous earth, white carbon black or silica gel.

[0018] More preferably, all-silicon molecules are screened from SBA-15 or Silicalite-1.

[0019] A second objective of this invention is to provide an oxide-supported ruthenium catalyst prepared by the above-described method.

[0020] The third objective of this invention is to provide a method for preparing carboxylic acid esters by halogen salt-assisted catalytic hydrogen esterification of long-chain olefins, comprising the following steps: Using long-chain olefins, CO, and organic alcohols as raw materials, and halogen salts as auxiliaries, long-chain olefins, CO, and organic alcohols undergo hydrogen esterification reactions under the catalysis of oxide-supported ruthenium catalysts to obtain carboxylic acid esters.

[0021] The long-chain olefins are selected from olefins with ≥4 carbon atoms, including straight-chain olefins and branched-chain olefins. The number of double bonds in the olefins is ≥1, such as 1-hexene, 2-hexene, 1-octene, 1-heptene, 1-dodecene, butadiene, isoprene, methyl pentenoate, and 4-phenyl-1-butene. The olefins of the present invention can also be selected from ethylene or propylene.

[0022] Organic alcohols are selected from C1 to C2. 20 Alkyl alcohols, C1~C 20 Alkyl alcohols include straight-chain alcohols and branched-chain alcohols, such as methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, and n-octanol.

[0023] The structure of a halide salt is Y + X; X - Selected from F - Cl - ,Br - Or I - ;Y + Selected from alkali metal ions, imidazoles, triazoles, quaternary ammonium compounds, pyridines, or quaternary phosphines.

[0024] Preferably, the alkali metal ion is selected from Li + Na + or K + Imidazoles are selected from Quaternary ammonium compounds are selected from Pyridines are selected from Quaternary phosphines are selected from Triazoles are selected from Among them, R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 and R 19 Selected independently from C1 to C 20 alkyl or aryl; R 2 R9 R 10 R 11 R 12 and R 13 They were also selected independently from H.

[0025] Preferably, the conditions for the hydrogen esterification reaction are: under a CO atmosphere of 0.1 MPa to 4 MPa, the reaction is carried out at 80°C to 200°C for 3 to 20 hours.

[0026] Preferably, the molar ratio of oxide-supported ruthenium catalyst, halide salt and long-chain olefin is 0.5~5:10~1000:100.

[0027] Preferably, in the process of catalytic hydrogen esterification of long-chain olefins to prepare carboxylic acid esters, a stable internal standard compound that does not participate in the reaction and is not a reaction byproduct is also added. The internal standard compound is selected from mesitylene, biphenyl, cyclohexane, chlorobenzene, or toluene. The internal standard compound is used to quantitatively calculate the conversion rate of hydrogen in the long-chain olefins and the yield of the carboxylic acid esters during the catalytic hydrogen esterification of long-chain olefins to prepare carboxylic acid esters.

[0028] Preferably, a high-pressure reactor is used in the process of catalytic hydrogen esterification of long-chain olefins to prepare carboxylic acid esters.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a method for preparing an oxide-supported ruthenium catalyst. The method involves impregnating an oxide in a ruthenium precursor solution, followed by solid-liquid separation to obtain the ruthenium-supported oxide. The ruthenium-supported oxide is then reduced to obtain the oxide-supported ruthenium catalyst. This oxide-supported ruthenium catalyst is applicable to various oxide supports and metal chemical reduction methods, avoiding the limitations of supports and chemical reduction treatments in existing catalyst preparation methods.

[0030] 2. To catalyze the hydrogen esterification of long-chain olefins to prepare carboxylic acid esters, this invention uses a specific halogen salt as a promoter. Under the catalytic action of an oxide-supported ruthenium catalyst, the synergistic effect of the promoter and the ruthenium active center of the oxide-supported ruthenium catalyst enables a highly efficient heterogeneous hydrogen esterification reaction of long-chain olefins, CO, and organic alcohols to prepare carboxylic acid esters. The presence of the halogen salt can regulate the chemical environment (composition and electrons) of the oxide and ruthenium, promote the dissociation of organic alcohols, accelerate the hydrogen esterification reaction rate, and simultaneously inhibit the side reactions of isomerization, hydrogenation, and polymerization of long-chain olefins, thereby improving the selectivity of long-chain olefin hydrogen esterification. Furthermore, the oxide-supported ruthenium catalyst of this invention has good applicability to various long-chain olefins, and its activity does not significantly decrease after multiple cycles of use. Attached Figure Description

[0031] Figure 1 This is a transmission electron microscope (TEM) image of the Ru-CeO2 catalyst from Example 1. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased on the market or prepared by existing methods.

[0034] In existing technologies, the hydrogen esterification of long-chain olefins mainly relies on homogeneous palladium catalytic systems, requiring the addition of phosphine ligands and acidic promoters to maintain catalytic activity. This leads to difficulties in product separation, high energy consumption, severe equipment corrosion, and challenges in catalyst recovery and reuse. Although some studies have attempted to develop heterogeneous palladium catalysts, they still cannot escape dependence on phosphine ligands and acidic promoters. Furthermore, the catalytic systems exhibit poor adaptability to long-chain olefins, are prone to isomerization, hydrogenation, and polymerization side reactions, and suffer from low reaction selectivity, making it difficult to achieve efficient conversion under mild conditions. In addition, existing oxide-supported ruthenium catalysts are only suitable for short-chain olefins such as ethylene or styrene and cannot effectively catalyze the hydrogen esterification of long-chain olefins, exhibiting significant substrate limitations.

[0035] To address the problems of the existing technologies, this invention designs a heterogeneous catalyst with an oxide support and ruthenium as the active center, and combines it with a halide salt as an auxiliary agent. This achieves a synergistic catalytic effect between the ruthenium active center and halide ions, which not only significantly improves the hydrogen esterification reaction rate but also effectively suppresses the isomerization, hydrogenation, and polymerization side reactions of long-chain olefins. Simultaneously, this invention optimizes the catalyst preparation process parameters (such as support type, ruthenium precursor, reduction method, and loading), broadening the substrate applicability range of the catalytic system. It achieves highly efficient heterogeneous hydrogen esterification reactions of long-chain olefins with CO and organic alcohols under mild conditions (80℃~200℃, 0.1MPa~4MPa CO). Furthermore, the oxide-supported ruthenium catalyst of this invention can be stably recycled without phosphine ligands and acid auxiliary agents, the products are easy to separate, and the process is green and environmentally friendly. This overcomes the key defects of existing technologies, such as ligand dependence, equipment corrosion, high energy consumption, difficulty in catalyst recovery, and poor substrate adaptability.

[0036] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will provide a detailed description in conjunction with specific embodiments: (1) Investigate the effect of the type of oxide on the performance of the 1-hexene hydrogen esterification reaction: Example 1 The preparation method of oxide-supported ruthenium catalyst includes the following steps: 16.0 mg of RuCl3 was dissolved in 10 mL of deionized water and sonicated until completely dissolved to obtain a RuCl3 solution. 1 g of CeO2 was dispersed in 25 mL of deionized water, and the RuCl3 solution was slowly added under stirring. The mixture was stirred at 30 °C for 12 h, and then the solvent was removed by vacuum distillation. The resulting solid was dried at 120 °C for 6 h to obtain an oxide of the supported ruthenium precursor. The oxide of the supported ruthenium precursor was calcined at 270 °C for 2 h in a H2 atmosphere to obtain an oxide-supported ruthenium catalyst, denoted as the Ru-CeO2 catalyst. The heating rate was controlled at 3 °C / min, and the gas flow rate was 30 mL / min. The ruthenium loading in the oxide-supported ruthenium catalyst was determined by ICP to be 0.7 wt%.

[0037] Figure 1 The results demonstrate that Ru clusters were successfully loaded onto cerium oxide.

[0038] Example 2 The preparation steps are the same as in Example 1, except that CeO2 is replaced with an equimolar amount of Al2O3.

[0039] Example 3 The preparation steps are the same as in Example 1, except that CeO2 is replaced with an equimolar amount of WO3.

[0040] Example 4 The preparation steps are the same as in Example 1, except that CeO2 is replaced with an equimolar amount of SBA-15.

[0041] Example 5 The preparation steps are the same as in Example 1, except that CeO2 is replaced with an equimolar amount of Silicalite-1.

[0042] Example 6 The preparation steps are the same as in Example 1, except that CeO2 is replaced with an equimolar amount of SBA-15-loaded CeO2. The SBA-15-loaded CeO2 is prepared according to the following steps: 1g of SBA-15 is dispersed in 10mL of 1mol / L cerium nitrate aqueous solution, followed by the addition of ammonia water for polar precipitation (pH 11), centrifugation, washing with deionized water, and drying at 80°C; after drying, it is calcined at 400°C for 4h to obtain SBA-15-loaded CeO2.

[0043] Example 7 The preparation steps are the same as in Example 1, except that CeO2 is replaced with an equimolar amount of Al2O3-loaded CeO2. The Al2O3-loaded CeO2 is prepared according to the following steps: 1g of alumina is dispersed in 10mL of 1mol / L cerium nitrate aqueous solution, followed by the addition of ammonia water for polar precipitation (pH 11), centrifugation, washing with deionized water, and drying at 80°C; after drying, it is calcined at 550°C for 4h to obtain Al2O3-loaded CeO2.

[0044] Evaluation method of oxide-supported ruthenium catalyst: In a high-pressure reactor with 30 mL of solvent and equipped with a temperature control system, 0.5 mmol of 1-hexene, oxide-supported ruthenium catalyst (1.5 mol% ruthenium), 84 mg of LiCl (2 mmol), 20 mg of cyclohexane, and 2 mL of methanol were added sequentially. After sealing the reactor, CO was introduced to a pressure of 0.5 MPa, and the system was heated to 165 °C and reacted for 14 h to obtain carboxylic acid esters. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was analyzed by gas chromatography. The results are shown in Table 1. Table 1 shows the results of 1-hexene hydroesterification catalyzed by different oxide-supported ruthenium catalysts. (2) Investigate the effect of the type of ruthenium precursor on the hydrogen esterification performance of 1-hexene: Example 8 The preparation steps are the same as in Example 1, except that RuCl3 is replaced with an equimolar amount of ammonium ruthenium chloride.

[0045] Example 9 The preparation steps are the same as in Example 1, except that RuCl3 is replaced with an equimolar amount of dodecacarbonylruthenium.

[0046] Example 10 The preparation steps are the same as in Example 1, except that RuCl3 is replaced with an equimolar amount of ruthenium nitrite.

[0047] Example 11 The preparation steps are the same as in Example 1, except that RuCl3 is replaced with an equimolar amount of ruthenium acetylacetone.

[0048] The evaluation methods for the oxide-supported ruthenium catalysts in Examples 8 to 11 are the same as those for the oxide-supported ruthenium catalyst in (1), and the results are shown in Table 2: Table 2 shows the catalytic hydrogenation results of 1-hexene using Ru-CeO2 catalysts obtained from different ruthenium precursors. (3) Investigate the effect of Ru-CeO2 catalysts prepared with different impregnation solvents on the hydrogen esterification performance of 1-hexene: Example 12 The preparation steps are the same as in Example 1, except that the solvent of the RuCl3 solution is replaced with an equal amount of methanol instead of deionized water.

[0049] Example 13 The preparation steps are the same as in Example 1, except that the solvent of the RuCl3 solution is replaced with an equal amount of ethanol instead of deionized water.

[0050] The evaluation methods for the oxide-supported ruthenium catalysts in Examples 12 and 13 are the same as those for the oxide-supported ruthenium catalysts in (1), and the results are shown in Table 3: Table 3 shows the results of 1-hexene hydrogen esterification catalyzed by Ru-CeO2 catalysts prepared with different impregnation solvents. (4) Investigate the effect of Ru-CeO2 catalysts prepared at different impregnation temperatures and times on the hydrogen esterification performance of 1-hexene: Example 14 The preparation steps are the same as in Example 1, except that the CeO2 impregnation time is changed from 12h to 1h.

[0051] Example 15 The preparation steps are the same as in Example 1, except that the CeO2 impregnation time is changed from 12h to 6h.

[0052] Example 16 The preparation steps are the same as in Example 1, except that the impregnation temperature of CeO2 is changed from 30°C to 70°C.

[0053] Example 17 The preparation steps are the same as in Example 1, except that the impregnation temperature of CeO2 is changed from 30°C to 110°C.

[0054] The evaluation methods for the oxide-supported ruthenium catalysts in Examples 14 to 17 are the same as those for the oxide-supported ruthenium catalysts in (1), and the results are shown in Table 4: Table 4 shows the results of 1-hexene hydrogen esterification catalyzed by Ru-CeO2 catalysts prepared at different impregnation temperatures and times. (5) Investigate the effect of different drying temperatures and times on the hydrogen esterification reaction performance of oxide-supported ruthenium catalyst: Example 18 The preparation steps are the same as in Example 1, except that the drying time of the resulting solid is changed from 6 hours to 1 hour.

[0055] Example 19 The preparation steps are the same as in Example 1, except that the drying time of the resulting solid is changed from 6 hours to 12 hours.

[0056] Example 20 The preparation steps are the same as in Example 19, except that the drying temperature of the resulting solid is changed from 120°C to 40°C.

[0057] Example 21 The preparation steps are the same as in Example 19, except that the drying temperature of the resulting solid is changed from 120°C to 180°C.

[0058] The evaluation methods for the oxide-supported ruthenium catalysts in Examples 18 to 21 are the same as those for the oxide-supported ruthenium catalysts in (1), and the results are shown in Table 5: Table 5 shows the results of 1-hexene hydrogen esterification catalyzed by Ru-CeO2 catalysts prepared at different drying temperatures and times. (6) Investigate the effect of Ru-CeO2 catalysts prepared under different conditions by gas-phase reduction method on the performance of 1-hexene hydrogen esterification reaction: Example 22 The preparation steps are the same as in Example 1, except that the calcination temperature is changed from 270°C to 100°C.

[0059] Example 23 The preparation steps are the same as in Example 1, except that the calcination temperature is changed from 270°C to 450°C.

[0060] Example 24 The preparation steps are the same as in Example 1, except that the calcination atmosphere is changed from H2 to Ar.

[0061] Example 25 The preparation steps are the same as in Example 1, except that the calcination atmosphere is changed from H2 to CO.

[0062] Example 26 The preparation steps are the same as in Example 1, except that the calcination time is changed from 2 hours to 8 hours.

[0063] Example 27 The preparation steps are the same as in Example 1, except that the calcination time is changed from 2 hours to 14 hours.

[0064] Example 28 The preparation steps are the same as in Example 1, except that the heating rate in the calcination process is changed from 3°C / min to 10°C / min.

[0065] Example 29 The preparation steps are the same as in Example 1, except that the heating rate in the calcination process is changed from 3°C / min to 20°C / min.

[0066] Example 30 The preparation steps are the same as in Example 1, except that the gas flow rate is changed from 30 mL / min to 80 mL / min during the calcination process.

[0067] Example 31 The preparation steps are the same as in Example 1, except that the gas flow rate is changed from 30 mL / min to 130 mL / min during the calcination process.

[0068] The evaluation methods for the oxide-supported ruthenium catalysts in Examples 19 to 31 are the same as those for the oxide-supported ruthenium catalysts in (1), and the results are shown in Table 6: Table 6 shows the results of 1-hexene hydrogen esterification catalyzed by Ru-CeO2 catalysts prepared under different reduction conditions. (7) Investigate the effect of Ru-CeO2 catalysts prepared under different liquid-phase reduction conditions on the hydrogen esterification reaction performance of 1-hexene: Example 32 A method for preparing an oxide-supported ruthenium catalyst is the same as that for (1), except that the gas-phase reduction method is replaced by a liquid-phase reduction method, and includes the following steps: 16.0 mg of RuCl3 was dissolved in 10 mL of deionized water and sonicated until completely dissolved to obtain a RuCl3 solution. 1 g of CeO2 was dispersed in 25 mL of deionized water, and the RuCl3 solution was slowly added under stirring for 30 min to obtain a mixture. Hydrazine hydrate was dissolved in 20 mL of deionized water and then slowly added dropwise to the mixture. After reduction at 30 °C for 1 h, the solvent was removed by centrifugation, and the mixture was washed with deionized water and methanol and then vacuum dried at 120 °C for 6 h to obtain the Ru-CeO2 catalyst. The molar ratio of hydrazine hydrate to ruthenium atoms in the mixture was 5:1.

[0069] Example 33 The preparation steps are the same as in Example 32, except that the reducing agent is replaced with sodium borohydride instead of hydrazine hydrate.

[0070] Example 34 The preparation steps are the same as in Example 33, except that the molar ratio of sodium borohydride to ruthenium atoms in the mixture is changed from 5:1 to 2:1.

[0071] Example 35 The preparation steps are the same as in Example 33, except that the molar ratio of sodium borohydride to ruthenium atoms in the mixture is changed from 5:1 to 10:1.

[0072] Example 36 The preparation steps are the same as in Example 33, except that the reduction temperature is changed from 30°C to 60°C.

[0073] Example 37 The preparation steps are the same as in Example 33, except that the reduction temperature is changed from 30°C to 90°C.

[0074] Example 38 The preparation steps are the same as in Example 33, except that the reduction time is changed from 1 hour to 5 hours.

[0075] Example 39 The preparation steps are the same as in Example 33, except that the reduction time is changed from 1 hour to 10 hours.

[0076] The evaluation methods for the oxide-supported ruthenium catalysts in Examples 32 to 39 are the same as those for the oxide-supported ruthenium catalysts in (1), and the results are shown in Table 7: Table 7 shows the results of 1-hexene hydrogen esterification catalyzed by Ru-CeO2 catalysts prepared under different reduction conditions. (8) Investigate the effect of different ruthenium loading on the hydrogen esterification reaction performance of 1-hexene: Example 40 The preparation steps are the same as in Example 1, except that the amount of RuCl3 added (5 mg) is changed and the ruthenium loading is replaced by 0.2 wt% instead of 0.7 wt%.

[0077] Example 41 The preparation steps are the same as in Example 1, except that the amount of RuCl3 added (35 mg) is changed and the ruthenium loading is replaced by 1.5 wt% instead of 0.7 wt%.

[0078] Example 42 The preparation steps are the same as in Example 1, except that the amount of RuCl3 added (125 mg) is changed and the ruthenium loading is replaced by 5 wt% instead of 0.7 wt%.

[0079] The evaluation methods for the oxide-supported ruthenium catalysts in Examples 40 to 42 are the same as those for the oxide-supported ruthenium catalysts in (1), and the results are shown in Table 8: Table 8 shows the results of 1-hexene hydrogen esterification catalyzed by Ru-CeO2 catalysts with different ruthenium loadings. (0) Investigate the effect of the molar ratio of ruthenium to 1-hexene in the oxide-supported ruthenium catalyst on the hydrogen esterification performance of 1-hexene: Taking the Ru-CeO2 catalyst of Example 1 as an example, the amount of Ru-CeO2 catalyst was changed, and the results are shown in Table 9: Table 9 shows the effect of different molar ratios of ruthenium to 1-hexene on the hydrogen esterification of 1-hexene. (10) Investigate the effect of the type of halide salt on the performance of 1-hexene hydrogen esterification reaction: Taking the Ru-CeO2 catalyst of Example 1 as an example, the results of changing the type of halide salt are shown in Table 10: Table 10 shows the effect of halide type on the hydrogen esterification of 1-hexene. (11) Investigate the effect of the molar ratio of halide salt to 1-hexene on the hydrogen esterification reaction performance of 1-hexene: Taking the Ru-CeO2 catalyst of Example 1 as an example, with LiCl as the halide salt, the molar ratio of LiCl to 1-hexene was changed, and the results are shown in Table 11: Table 11 shows the effect of halogen salt dosage on the hydrogen esterification of 1-hexene. (12) Investigate the effect of Ru-CeO2 catalyst on the reaction performance of different long-chain olefins: Taking the Ru-CeO2 catalyst of Example 1 as an example, the types of long-chain olefins were changed, and the results are shown in Table 12: Table 12 shows the effects of different olefin species on hydrogen esterification. (13) Investigate the effect of Ru-CeO2 catalyst on the reactivity of different organic alcohols: Taking the Ru-CeO2 catalyst of Example 1 as an example, the types of organic alcohols were changed, and the results are shown in Table 13: Table 13 shows the effects of 1-hexene and different organic alcohols on hydrogen esterification. (14) Investigate the effect of the amount of organic alcohol on the hydrogen esterification performance of 1-hexene: Taking the Ru-CeO2 catalyst of Example 1 as an example, with methanol as the organic alcohol, the amount of methanol was varied, and the results are shown in Table 14: Table 14 shows the effect of methanol dosage on the hydrogen esterification of 1-hexene. (15) Investigate the effect of reaction temperature on the hydrogen esterification performance of 1-hexene: Taking the Ru-CeO2 catalyst of Example 1 as an example, with methanol as the organic alcohol, the reaction temperature was changed, and the results are shown in Table 15: Table 15 shows the effect of reaction temperature on the hydrogen esterification of 1-hexene. (16) Investigate the effect of CO pressure on the hydrogen esterification performance of 1-hexene: Taking the Ru-CeO2 catalyst of Example 1 as an example, with methanol as the organic alcohol, the CO pressure was changed, and the results are shown in Table 16: Table 16 shows the effect of CO pressure on the hydrogen esterification of 1-hexene. (17) Investigate the effect of reaction time on the hydrogen esterification performance of 1-hexene: Taking the Ru-CeO2 catalyst of Example 1 as an example, with methanol as the organic alcohol, the hydrogen esterification reaction time was changed, and the results are shown in Table 17: Table 17 shows the effect of reaction time on the hydrogen esterification of 1-hexene. (18) Investigate the effect of not adding halogen salt additives on the cycling performance of 1-hexene hydrogen esterification: Taking the Ru-CeO2 catalyst of Example 1 as an example, with methanol as the organic alcohol and no halogen salt added, the conversion rate of 1-hexene is 98%, but the yield of carboxylic acid ester is only 18%, with most of it being isomerized olefins and hydrogenated hexane.

[0080] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

Claims

1. A method for preparing carboxylic acid esters by halogen salt-assisted catalytic hydrogen esterification of long-chain olefins, characterized in that, Includes the following steps: Using long-chain olefins, CO, and organic alcohols as raw materials, and halogen salts as auxiliaries, long-chain olefins, CO, and organic alcohols undergo hydrogen esterification reactions under the catalysis of oxide-supported ruthenium catalysts to obtain carboxylic acid esters. Among them, long-chain olefins are selected from olefins with ≥4 carbon atoms; Organic alcohols are selected from C1 to C2. 20 Alkyl alcohols; The structural formula of a halide salt is Y + X - ;X - Selected from F - Cl - ,Br - Or I - ;Y + Selected from alkali metal ions, imidazoles, triazoles, quaternary ammonium compounds, pyridines, or quaternary phosphines; The oxide-supported ruthenium catalyst was prepared according to the following steps: The oxide support was immersed in a ruthenium precursor solution, and after removing the solvent, an oxide loaded with the ruthenium precursor was obtained; the ruthenium loading in the oxide was 0.1 wt% to 10 wt%. The ruthenium ions in the oxide of the supported ruthenium precursor were reduced to ruthenium clusters or ruthenium nanoparticles by liquid-phase reduction method to obtain oxide-supported ruthenium catalyst. The oxide support is selected from metal oxide supports, silica-containing supports, metal oxide supports loaded with metal oxides, or silica supports loaded with metal oxides. The liquid-phase reduction method is operated as follows: using hydrazine hydrate, sodium borohydride, ascorbic acid or sodium citrate as reducing agents, the reducing agents are mixed with oxides of ruthenium-supported precursors and a reduction reaction is carried out; wherein, the molar ratio of ruthenium in the reducing agent to that in the oxides of ruthenium-supported precursors is 1~100:1; The conditions for the reduction reaction are: stirring at 0℃~150℃ for 1h~10h.

2. The method for preparing carboxylic acid esters by halogen salt-assisted catalytic hydrogen esterification of long-chain olefins according to claim 1, characterized in that, Alkali metal ions are selected from Li + Na + or K + Imidazoles are selected from Quaternary ammonium compounds are selected from Pyridines are selected from Quaternary phosphines are selected from Triazoles are selected from ; Among them, R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 R 11 R 12 R 13 R 14 R 15 R 16 R 17 R 18 and R 19 Selected independently from C1 to C 20 alkyl or aryl; R 2 R 9 R 10 R 11 R 12 and R 13 They were also selected independently from H.

3. The method for preparing carboxylic acid esters by halogen salt-assisted catalytic hydrogen esterification of long-chain olefins according to claim 1, characterized in that, The molar ratio of ruthenium, halide salt and long-chain olefin in oxide-supported ruthenium catalyst is 0.5~5:10~1000:

100.

4. The method for preparing carboxylic acid esters by halogen salt-assisted catalytic hydrogen esterification of long-chain olefins according to claim 1, characterized in that, The conditions for the hydrogen esterification reaction are: under a CO atmosphere of 0.1 MPa to 4 MPa, the reaction is carried out at 80℃ to 200℃ for 3 to 20 hours.

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