A process for the production of pentanoate esters by mixed butene carbonylation

Abstract

This invention provides a method for preparing valerate esters by carbonylation of mixed butenes, relating to the field of valerate ester preparation technology. The invention involves pre-preparing a catalyst precursor, ligand, mixed butenes, and an organic solvent with carbon monoxide in a pre-preparation device. The pre-prepared catalyst stream is then continuously fed into a reactor along with mixed butenes, an alcohol, and carbon monoxide for a hydrogen esterification reaction. Simultaneously, a separator separates the valerate ester product, recovers the alcohol, and recycles the catalyst solution. This method achieves efficient and continuous preparation of valerate esters from mixed butenes under mild conditions, offering advantages such as high raw material utilization, long catalyst lifespan, low production cost, and broad prospects for industrial application.

Description

Technical Field

[0001] This invention relates to the field of valerate preparation technology, and more particularly to a method for preparing valerate by carbonylation of mixed butenes. Background Technology

[0002] Valerate esters are an important class of fine chemical products and organic synthesis intermediates, used in fragrances, food additives, pharmaceutical intermediates, lubricants, plasticizers, and other fields. Some valerates also have good potential applications as fuels or fuel blending components. With the development of related downstream industries, higher requirements are being placed on the production cost, product purity, and greening of valerate ester processes. Therefore, developing efficient, economical, and continuously operable valerate ester preparation processes is of great significance.

[0003] Currently, valerate esters are mainly obtained by esterification of valerate acid with the corresponding alcohol under acidic catalysts. However, valerate acid feedstock often requires further conversion via oxidation of pentaldehyde or pentanol, olefin carbonylation, etc., resulting in a relatively long overall process with numerous separation steps and high raw material and operating costs. In recent years, there have also been reports of technologies for preparing valerate esters using biomass platform compounds as feedstocks. This type of route has certain advantages in resource renewability, but it usually involves multiple steps such as hydrogenation, ring opening, and esterification, placing high demands on catalyst performance, reaction conditions, and process integration. Further cost reduction and process stability improvements are still needed for industrial-scale promotion.

[0004] Mixed butenes are common C4 byproducts in petroleum refining, steam cracking, and coal chemical processes. They typically contain 1-butene, cis-2-butene, trans-2-butene, isobutene, and small amounts of butadiene and alkane components. Directly converting mixed butenes into valerate esters not only enhances the utilization value of C4 resources but also shortens the valerate ester preparation route, reducing intermediate oxidation and esterification steps, thus demonstrating good raw material economy and process development value.

[0005] Patents CN 200710098848.2, CN 202011363293.1, and CN 202310008346.5 disclose a technical route for producing valeral from mixed butene via hydroformylation. This method uses a complex catalyst composed of the noble metal Rh and complex ligands, resulting in low reactivity. Furthermore, oxidation and esterification processes are required to obtain valerate esters, leading to a long process, low yield, and high production costs. Patent CN 202210647264.0 discloses a method for producing valerate esters from butene using Pd chelated with bidentate phosphine ligands as a catalyst, achieving a selectivity of over 95% for valerate esters. However, catalyst recovery is difficult and stability is poor, hindering industrial application.

[0006] Therefore, it is still necessary to develop a method for the continuous preparation of valerate esters under relatively mild conditions using mixed butene as a direct raw material and carbon monoxide and alcohol as reaction components, so as to better meet the needs of industrial production of valerate esters and high-value utilization of C4 resources. Summary of the Invention

[0007] In view of this, the present invention provides a method for preparing valerate by carbonylation of mixed butene. The present invention pre-prepares a catalyst by reacting a catalyst precursor, ligand, mixed butene, and organic solvent with carbon monoxide in a pre-preparation device. The pre-prepared catalyst stream is then continuously fed into a reactor along with mixed butene, alcohol, and carbon monoxide for hydrogen esterification. Simultaneously, a separator separates the valerate product, recovers the alcohol, and recycles the catalyst solution. This method achieves efficient and continuous preparation of valerate from mixed butene under mild conditions, offering advantages such as high raw material utilization, long catalyst life, low production cost, and broad prospects for industrial application.

[0008] The present invention provides a method for preparing valerate by carbonylation of mixed butenes, comprising the following steps: S1. The catalyst precursor, ligand, mixed butene and organic solvent are put into a high-pressure catalyst preformer, and carbon monoxide is introduced to carry out the catalyst preformation reaction to obtain a liquid stream containing a highly active catalyst. S2. The catalyst stream from the preformer is continuously fed into the reactor along with the mixed butene and alcohol in a specific ratio, and carbon monoxide is introduced to maintain the system pressure. Under the reaction conditions, the hydrogen esterification reaction of the olefin is carried out. S3. The reaction liquid continues to flow into the separator, distilling off the generated valerate ester. The organic solvent solution of the catalyst is returned to the catalyst preformer for recycling, replenishing the liquid phase stream from step S1. The recovered alcohol is returned to the reactor to participate in the reaction again.

[0009] Preferably, in step S1, the mixed butene contains 40-100 wt% butene and 0-60 wt% alkanes.

[0010] Preferably, in step S1, the butene is at least one of 1-butene, cis-2-butene, trans-2-butene, isobutene, and butadiene.

[0011] Preferably, in step S1, the mixed butene contains 10-40 wt% 1-butene, 5-50 wt% cis-2-butene, 5-50 wt% trans-2-butene, 1-10 wt% isobutene and 0-5 wt% butadiene, with the balance being alkanes.

[0012] Preferably, in step S1, the catalyst precursor is at least one selected from cobalt acetate, cobalt chloride, cobalt acetylacetonate, cobalt carbonate, cobalt sulfate, cobalt nitrate, cobalt carbonyl, and cobalt oxalate.

[0013] Preferably, in step S1, the ligand is at least one selected from pyridine, hydroxypyridine, hydroxymethylpyridine, aminopyridine, alkylpyridine, phenylpyridine, bipyridine, and carboxypyridine.

[0014] Preferably, in step S1, the organic solvent is at least one selected from 1,4-dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, toluene, 1,2-dichloroethane, DMF, xylene, and cyclohexane.

[0015] Preferably, in step S1, the mass fraction of the catalyst precursor entering the preformer is 1-30 wt%, the mass fraction of the mixed butene is 0-50 wt%, the molar ratio of the catalyst precursor to the ligand is 0.5-5:1, and the balance is an organic solvent.

[0016] Preferably, in step S1, the pressure of carbon monoxide in the catalyst preform is 0.5~15 MPa and the temperature is 120~200℃.

[0017] Preferably, in step S2, the molar ratio of the alcohol to the mixed butene introduced into the reactor is (1~10):1, and the molar ratio of the cobalt content in the catalyst stream to the mixed butene is (0.05~1):1.

[0018] Preferably, in step S2, the alcohol is at least one selected from methanol, ethanol, propanol, butanol, hexanol, cyclopentanol, cyclohexanol, and benzyl alcohol.

[0019] Preferably, in step S2, the pressure of carbon monoxide in the reactor is 0.5~15 MPa and the temperature is 120~200℃.

[0020] Preferably, in step S2, the reactor has two or more reactors connected in series. More preferably, the reactor includes a first reactor and a second reactor, wherein the catalyst stream from the preformer first enters the first reactor and then the second reactor, and the mixed butene and alcohol enter the first reactor.

[0021] Preferably, in step S3, the separator is a series molecular distillation device with a distillation temperature of 40~100℃ and a pressure of 10 Pa~100 kPa.

[0022] Preferably, in step S3, the reacted material first flows through a first separator to recover the alcohol and allows the recovered alcohol to enter the reactor, then flows through a second separator to collect the generated valerate product, and the remaining heavy components are recycled back to the preformer as a catalyst solution.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention uses cobalt salts or cobalt compounds as catalyst precursors, combined with nitrogen-containing ligands, to pre-prepare the catalyst under a carbon monoxide atmosphere. This allows the catalytically active component to form in situ within the reaction system and maintain high activity. Compared to catalytic systems relying on noble metals and complex phosphine ligands, the catalyst raw materials used in this invention are relatively readily available and cost-effective. Furthermore, the coordinated operation of the pre-preparator and reactor reduces the risk of catalyst deactivation during storage, transfer, and recycling, thus improving the conversion rate and selectivity of the carbonylation of mixed butenes to prepare valerate.

[0024] This invention employs a continuous feeding, continuous reaction, continuous separation, and catalyst solution recycling process. After the reaction liquid is separated by a separator, the valerate product is collected, unreacted alcohol is recovered to the reactor, and the heavy component solution containing the catalyst is returned to the pretreatment unit to continue the recycling process. This process can reduce the fluctuations caused by batch operation, improve product quality stability and raw material utilization, while reducing catalyst replenishment and separation load, making it suitable for further scale-up applications.

[0025] This invention can also adjust the coordination environment of the catalytic active center by regulating the type and amount of ligands, thereby controlling the ratio of straight-chain to branched products in the valerate ester product. This catalytic system exhibits good adaptability to 1-butene, cis-2-butene, trans-2-butene, isobutene, and a small amount of butadiene in mixed butenes, improving the comprehensive utilization efficiency of complex C4 feedstocks and demonstrating good feedstock adaptability and industrial application potential.

[0026] The catalytic reaction system provided by this invention can efficiently convert 1-butene and isobutene, which have high activity in mixed butene feedstocks, into valerate esters, and also exhibits very high catalytic activity for cis-2-butene, trans-2-butene, and a small amount of butadiene, which have low activity in the feedstocks. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings.

[0028] Figure 1 This is a schematic diagram of the process flow for the preparation of valerate by carbonylation of mixed butene according to the present invention. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to 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.

[0030] Unless otherwise stated, all experiments were repeated three times, and the results are expressed as averages.

[0031] Example 1: A method for preparing valerate by carbonylation of mixed butenes, comprising the following steps: The specific composition of the mixed butene used in this embodiment is: 25wt% 1-butene, 30wt% cis-2-butene, 35wt% trans-2-butene, 5wt% isobutene, 2wt% butadiene, and the balance is n-butane; In a 2 L catalyst preformer, 300.4 g of cobalt acetate (10% cobalt), 200 g of mixed butene, 322.8 g of 4-hydroxypyridine and 176.8 g of 1,4-dioxane were added as solvent. After nitrogen purging three times, the temperature was raised to 150 °C, the stirring speed was 600 rpm, and the carbon monoxide pressure was increased to 8 MPa. First stage: 380 g of methanol and 133 g of mixed butene were added to a 2 L reactor; similarly, 380 g of methanol and 133 g of mixed butene were added to a 2 L reactor. After three nitrogen purgings, the temperature was raised to 150 °C, the stirring speed was 600 rpm, and the carbon monoxide pressure was increased to 8 MPa and kept stable. After the preformer reached the set temperature, it reacted for 10 h, and then the product was fed into the first reactor at a rate of 20 g / h. After the first reactor ran for 20 h, the product was fed into the second reactor at a rate of 20 g / h. After the second reactor ran for 20 h, the product was discharged to the separator, the remaining methanol was distilled off and returned to the first reactor, the generated valerate product was collected, and the remaining catalyst solution was recycled back to the preformer. Second stage: After all feed and discharge are normal, methanol and mixed butene are introduced into the first reactor at feed rates of 54.3 g / h and 19 g / h, respectively. No more feed is introduced into the second reactor. The discharge rate is controlled to keep the total mass of material in the first and second reactors constant. The third stage: In a nitrogen gas stream, the reaction material first flows through the first separator, where methanol is recovered to the alcohol storage tank of the first reactor at 70°C and 100 kPa. Then it flows through the second separator, where the generated valerate product is collected at 40°C and 1000 Pa. The remaining recombinant material is divided into catalyst solution and recycled back to the preformer.

[0032] After running stably under the above process conditions for 200 hours, samples were taken for analysis and a 1000-hour life test was carried out. The results are shown in Table 1.

[0033] Table 1 Results of 1000 h life test

[0034] As shown in Table 1, the total conversion rate of mixed butene remained between 94.1% and 96.6%; it was 95.8% at 200 h and still 95.2% at 1000 h, without showing a significant downward trend with the extension of the running time. This indicates that the continuous reaction system can maintain a high feed conversion capacity and good catalyst activity during long-term operation.

[0035] The overall selectivity of valerate remained between 96.0% and 98.1% throughout the testing period, indicating that side reactions were effectively suppressed and the reaction system exhibited high selectivity for the target valerate product. At 1000 h, the overall selectivity of valerate was still 97.1%, indicating that catalyst recycling and separation / recovery processes did not significantly adversely affect the selectivity of the target product.

[0036] The product regioselectivity ratio fluctuated between 4.0:1 and 4.5:1, with relatively small overall variation, indicating that the regioselectivity of the catalytic system remained relatively stable during long-term operation. This suggests that the pre-prepared catalyst system and continuous recycling process can not only maintain high conversion and selectivity, but also maintain a relatively stable ratio of straight-chain (methyl valerate) to branched-chain (methyl 2-methylbutyrate) products.

[0037] As can be seen from the data in Table 1, the process of this invention exhibits good stability during 1000 h of continuous operation: the total conversion rate of mixed butene remains at approximately 95% for a long period, the total selectivity of valerate esters remains at approximately 97% for a long period, and the product positive-to-iso ratio remains stable at approximately 4.2:1. These results demonstrate that the catalyst of this invention has a long service life, stable catalyst recycling, feasible continuous preparation of valerate esters, and high product selectivity. They also further illustrate that the combination of the preformer, series reactors, and separation and recovery system helps to improve the catalyst activity retention capacity and process stability.

[0038] Example 2 The difference from Example 1 is that a mixture of butenes with a specific content of 10 wt% 1-butene, 30 wt% cis-2-butene, 50 wt% trans-2-butene, 1 wt% isobutene, 5 wt% butadiene, and the balance being n-butane is used instead of the mixed butenes in Example 1.

[0039] The initial feed of the preformer in Example 1 was replaced with 661 g of cobalt chloride (30% cobalt), 202.2 g of pyridine and 136.8 g of tetrahydrofuran.

[0040] In the first stage, 450 g of ethanol and 54 g of mixed butene were used instead of the feed amount in the reactor of Example 1.

[0041] In the second stage, the feed rates of ethanol (47 g / h) and mixed butene (5.7 g / h) were replaced with those of Example 1.

[0042] The reaction pressure in both the preformer and the reactor is 15 MPa, and the reaction temperature is 120℃.

[0043] In the third stage, ethanol is recovered to an alcohol storage tank at 80°C and 100 kPa, and the generated valerate product is collected at 65°C and 1000 Pa.

[0044] Example 3 The difference from Example 1 is that a mixture of butenes with a specific content of 40wt% 1-butene, 50wt% cis-2-butene, 5wt% trans-2-butene, 1wt% isobutene, and the balance being n-butane is used instead of the mixed butenes in Example 1.

[0045] The initial feed of the preformer in Example 1 was replaced with 60.4 g cobalt acetylacetonate (1% cobalt), 92.6 g 4-hydroxymethylpyridine, 500 g mixed butene and 377 g ethylene glycol dimethyl ether.

[0046] In the first stage, 260 g of n-propanol and 240 g of mixed butene were used instead of the feed amount in the reactor of Example 1.

[0047] In the second stage, the feed rates of n-propanol and mixed butene were replaced by 4.1 g / h and 3.8 g / h, respectively, instead of the feed rates of both in Example 1.

[0048] The reaction pressure in both the preformer and the reactor is 0.5 MPa, and the reaction temperature is 200℃.

[0049] In the third stage, n-propanol is recovered to an alcohol storage tank at 100°C and 100 kPa, and the generated valerate product is collected at 70°C and 1000 Pa.

[0050] Example 4 The difference from Example 1 is that the mixed butene in Example 1 is replaced with a mixed butene with a specific content of 25wt% 1-butene, 5wt% cis-2-butene, 50wt% trans-2-butene, 10wt% isobutene, 2wt% butadiene, and the balance being n-butane.

[0051] The initial feed of the preformer in Example 1 was replaced with 202 g cobalt carbonate (10% cobalt), 319.4 g 4-aminopyridine, 200 g mixed butene and 278.6 g toluene.

[0052] In the first stage, 440 g of n-butanol and 67 g of mixed butene were used instead of the feed amount in the reactor of Example 1.

[0053] In the second stage, the feed rates of n-butanol (125.6 g / h) and mixed butene (19 g / h) were replaced with those of both in Example 1.

[0054] In the third stage, n-butanol is recovered to an alcohol storage tank at 80°C and 1000 Pa, and the generated valerate product is collected at 70°C and 100 Pa.

[0055] Example 5 The difference from Example 1 is that the mixed butene used is the same as in Example 1.

[0056] The initial feed of the preformer in Example 1 was replaced with 263 g cobalt sulfate (10% cobalt), 316 g 4-methylpyridine, 200 g mixed butene and 221 g 1,2-dichloroethane.

[0057] In the first stage, 385 g of n-hexanol and 122 g of mixed butene were used instead of the feed amount in the reactor of Example 1.

[0058] In the second stage, the feed rates of n-hexanol (60.2 g / h) and mixed butene (19 g / h) were replaced with those of both in Example 1.

[0059] In the third stage, n-hexanol is recovered to an alcohol storage tank at 80°C and 500 Pa, and the generated valerate product is collected at 80°C and 100 Pa.

[0060] Example 6 The difference from Example 1 is that the mixed butene used is the same as in Example 1.

[0061] The initial feed of the preformer in Example 1 was replaced with 310.4 g cobalt nitrate (10% cobalt), 263.4 g 4-phenylpyridine, 200 g mixed butene and 226.2 g DMF.

[0062] In the first stage, 450 g of cyclopentanol and 59 g of mixed butene were used instead of the feed amount in the reactor of Example 1.

[0063] In the second stage, the feed rates of cyclopentanol and mixed butene were replaced with 146 g / h and 19 g / h respectively in Example 1.

[0064] In the third stage, cyclopentanol is recovered to an alcohol storage tank at 90°C and 500 Pa, and the generated valerate product is collected at 90°C and 50 Pa.

[0065] Example 7 The difference from Example 1 is that the mixed butene used is the same as in Example 1.

[0066] The initial feed of the preformer in Example 1 was replaced with 290.1 ​​g of cobalt octacarbonyl (10% cobalt), 265 g of 2,2'-bipyridine, 200 g of mixed butene and 244.9 g of xylene.

[0067] In the first stage, 394 g of cyclohexanol and 110 g of mixed butene were used instead of the feed amount in the reactor of Example 1.

[0068] In the second stage, the feed rates of cyclohexanol (67.9 g / h) and mixed butene (19 g / h) were replaced with those of both in Example 1.

[0069] In the third stage, cyclohexanol is recovered to an alcohol storage tank at 90°C and 100 Pa, and the generated valerate product is collected at 100°C and 50 Pa.

[0070] Example 8 The difference from Example 1 is that the mixed butene used is the same as in Example 1.

[0071] The initial feed of the preformer in Example 1 was replaced with 249.4 g cobalt oxalate (10% cobalt, 146.95 g cobalt), 417.8 g 2-pyridinecarboxylic acid, 200 g mixed butene and 132.8 g cyclohexane.

[0072] In the first stage, 430 g of benzyl alcohol and 74 g of mixed butene were used instead of the feed amount in the reactor of Example 1.

[0073] In the second stage, the feed rates of benzyl alcohol and mixed butene were replaced with 109 g / h and 19 g / h respectively, instead of the feed rates of both in Example 1.

[0074] In the third stage, benzyl alcohol is recovered to an alcohol storage tank at 100°C and 100 Pa, and the generated valerate product is collected at 100°C and 10 Pa.

[0075] Comparative Example 1 The difference from Example 1 is that an intermittent high-pressure reactor is used for the reaction.

[0076] The mixed butene used was the same as in Example 1. In a 2 L high-pressure reactor, 66.4 g of cobalt acetate (0.1 times butene, 177.02 g), 71.3 g of 4-hydroxypyridine (2 times Co, 95.1 g), 600 g of methanol, 210 g of mixed butene, and 190 g of 1,4-dioxane were added as solvent. After three nitrogen purgings, the temperature was raised to 150 °C, the stirring speed was 600 rpm, and the carbon monoxide pressure was maintained at 8 MPa for 50 h. The reaction was then stopped, and samples were taken for analysis. The total conversion rate of the mixed butene was 76.4%, the total selectivity of valerate was 84.0%, and the product positive-to-iso ratio was 4.2:1.

[0077] Comparative Example 2 The difference from Example 1 is that: after running stably under the process conditions of Example 1 for 200 h, the first reactor was sampled and analyzed. The total conversion rate of mixed butene was 82.9%, the total selectivity of valerate was 92.6%, and the product positive-to-iso ratio was 3.5:1.

[0078] Comparative Example 3 The difference from Example 1 is that: no high-pressure catalyst pre-formulator is set up, and no catalyst pre-formulation reaction is carried out; a mixed solution of 300.4 g cobalt acetate, 322.8 g 4-hydroxypyridine and 176.8 g 1,4-dioxane is directly added to the first reactor at a rate of 20 g / h; the first and second reactors are still operated according to the temperature, pressure and continuous feed and discharge mode of Example 1. After the reaction liquid enters the separator, product separation and alcohol recovery are carried out, and the remaining catalyst solution is recycled back to the mixed solution.

[0079] After 200 hours of stable operation, the total conversion rate of mixed butene was 85.1%, the total selectivity of valerate was 85.6%, and the product positive-to-iso ratio was 4.3:1.

[0080] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing valerate by carbonylation of mixed butenes, characterized in that, Includes the following steps: S1. The catalyst precursor, ligand, mixed butene and organic solvent are put into a high-pressure catalyst preformer, and carbon monoxide is introduced to carry out the catalyst preformation reaction to obtain a liquid stream containing a highly active catalyst. S2. The catalyst stream from the preformer is continuously fed into the reactor along with the mixed butene and alcohol in a specific ratio, and carbon monoxide is introduced to maintain the system pressure. Under the reaction conditions, the hydrogen esterification reaction of the olefin is carried out. S3. The reaction liquid continues to flow into the separator, distilling off the generated valerate ester. The organic solvent solution of the catalyst is returned to the catalyst preformer for recycling, replenishing the liquid phase stream from step S1. The recovered alcohol is returned to the reactor to participate in the reaction again.

2. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S1, the mixed butene contains 40-100 wt% butene and 0-60 wt% alkane, wherein the butene is at least one of 1-butene, cis-2-butene, trans-2-butene, isobutene, and butadiene.

3. The method for preparing valerate by carbonylation of mixed butenes according to claim 2, characterized in that, In step S1, the mixed butene contains 10-40 wt% 1-butene, 5-50 wt% cis-2-butene, 5-50 wt% trans-2-butene, 1-10 wt% isobutene and 0-5 wt% butadiene, with the balance being alkanes.

4. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S1, the catalyst precursor is at least one of cobalt acetate, cobalt chloride, cobalt acetylacetonate, cobalt carbonate, cobalt sulfate, cobalt nitrate, cobalt carbonyl, and cobalt oxalate.

5. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S1, the ligand is at least one selected from pyridine, hydroxypyridine, hydroxymethylpyridine, aminopyridine, alkylpyridine, phenylpyridine, bipyridine, and carboxypyridine.

6. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S1, the organic solvent is at least one selected from 1,4-dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, toluene, 1,2-dichloroethane, DMF, xylene, and cyclohexane.

7. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S1, the mass fraction of the catalyst precursor entering the preformer is 1-30 wt%, the mass fraction of the mixed butene is 0-50 wt%, the molar ratio of the catalyst precursor to the ligand is 0.5-5:1, and the remainder is an organic solvent.

8. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S2, the molar ratio of alcohol to mixed butene introduced into the reactor is (1~10):1, and the molar ratio of cobalt content to mixed butene in the catalyst stream is (0.05~1):

1.

9. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S3, there are two or more reactors connected in series; the separator is a series molecular distillation device with a distillation temperature of 40~100℃ and a pressure of 10 Pa~100 kPa.

10. The method for preparing valerate by carbonylation of mixed butenes according to claim 1, characterized in that, In step S3, the reacted material first flows through the first separator to recover the alcohol and then enters the reactor. It then flows through the second separator to collect the generated valerate product. The remaining heavy components are recycled back to the preformer as a catalyst solution.

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