Method for isomerizing cis-2-pentenenitrile to 3-pentenenitrile

Abstract

The present invention provides a method for isomerizing cis-2-pentenenitrile to 3-pentenenitrile. The method comprises: in a supercritical fluid, subjecting cis-2-pentenenitrile to an isomerization reaction under the action of a catalyst and a ligand to generate 3-pentenenitrile, wherein the catalyst is a rare earth metal oxide or a rare earth metal halide, and the ligand is a monodentate phosphite or a multidentate phosphite. The present invention uses the rare earth metal oxide or the rare earth metal halide in combination with the specific monodentate phosphite or multidentate phosphite to catalyze the isomerization of cis-2-pentenenitrile in the supercritical fluid to generate 3PN. The catalytic process has a high starting material conversion rate and a high 3PN selectivity, and enables efficient conversion of cis-2-pentenenitrile into 3PN in the second hydrocyanation step of an industrial process for preparing adiponitrile by a butadiene hydrocyanation method, thereby eliminating the poisoning effect on the catalyst, improving the process efficiency, saving costs, and improving economic benefits.

Description

A method for isomerizing cis-2-pentenenitrile into 3-pentenenitrile TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a method for isomerizing cis-2-pentenenitrile into 3-pentenenitrile. BACKGROUND

[0002] Adiponitrile is an important chemical raw material, and has extremely wide application value in many important fields such as plastics, rubber, fiber, etc., and plays a key role in promoting the development of modern industry. At present, the main production methods of adiponitrile in industry are propylene nitrile electrolysis dimerization method, adipic acid catalytic amination method and butadiene hydrocyanation method. Among them, the butadiene hydrocyanation method has high atom economy, short process route, high yield and small pollution, and has become the mainstream of industrialized preparation method of adiponitrile.

[0003] The reaction process of butadiene hydrocyanation method for preparing adiponitrile mainly includes three parts: (1) one-step hydrocyanation, that is, butadiene and hydrocyanic acid (HCN) generate 3-pentenenitrile (3PN) under the action of catalyst and ligand, and by-product branched 2-methyl-3-butenenitrile (2M3BN) is generated; (2) isomerization reaction, the by-product 2M3BN is isomerized into straight-chain 3PN under the action of catalyst; (3) two-step hydrocyanation, that is, 3PN and HCN react to obtain product adiponitrile under the action of catalyst and Lewis acid. As shown in the following reaction formula:

[0004] In the two-step hydrocyanation reaction, cis-2-pentenenitrile is by-produced, which not only means the loss of adiponitrile yield, but also the accumulation of cis-2-pentenenitrile will cause excess of hydrocyanic acid in the reaction system, and the excess of hydrocyanic acid reacts with the catalyst to generate cyanide, which deactivates the catalyst and reduces the production efficiency of adiponitrile.

[0005] The by-product cis-2-pentenenitrile has a boiling point close to that of 3PN, and is difficult to separate by distillation; therefore, cis-2-pentenenitrile is preferably isomerized into 3PN, so as to continue to participate in the two-step hydrocyanation. Patent CN1914164A discloses that alumina extrudate is used as catalyst to isomerize cis-2-pentenenitrile into 3PN through reaction distillation, but the required temperature is high, which is easy to produce oligomers, or the isomerization efficiency is low at low temperature for a long time. Patent USA5070202 uses primary amines and secondary amines and other amine substances to catalyze the isomerization of cis-2-pentenenitrile into 3PN, but there are still problems such as low conversion rate and poor selectivity. SUMMARY

[0006] To address the shortcomings of existing technologies, this invention discloses a method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile. This method can catalyze the efficient and selective isomerization of cis-2-pentenonitrile to obtain 3-pentenonitrile. Furthermore, this method is highly operable and applicable to isomerization reactions of mixtures containing 3PN and cis-2-pentenonitrile, thus possessing significant industrial application value.

[0007] To achieve the above technical objectives, this invention proposes a method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile. The method includes an isomerization reaction of cis-2-pentenonitrile in a supercritical fluid under the action of a catalyst and a ligand to generate 3-pentenonitrile. The catalyst is a rare earth metal oxide and / or a rare earth metal halide, and the ligand is a monodentate phosphite or a polydentate phosphite.

[0008] Based on extensive experimental findings, the research team of this invention discovered that, under supercritical fluid conditions, compared with existing technologies that use oxides such as alumina and zinc oxide as catalysts, the above-mentioned technical solution, using rare earth metal oxides or rare earth metal halides as catalysts, significantly improves the conversion rate and 3PN selectivity of cis-2-pentenonitrile isomerization. Furthermore, in the above-mentioned technical solution, monodentate or multidentate phosphites are used as catalyst ligands. Combined with specific catalyst types and supercritical fluid conditions, the synergistic effect of the three further improves the conversion rate and 3PN selectivity of cis-2-pentenonitrile, and the reaction conditions are relatively mild, with a significantly shortened reaction time.

[0009] As can be seen from the embodiments and comparative examples of the present invention, the above technical solution can achieve high conversion rate and high selectivity, high process efficiency, and is suitable for industrial production.

[0010] In a further example of the invention, the type of catalyst is optimized. Optionally, the rare earth metal oxide includes at least one of lanthanum oxide, actinium oxide, samarium oxide, praseodymium oxide, cerium oxide, and neodymium oxide, and is further selected as lanthanum oxide; the rare earth metal halide is selected as a chloride, and is further selected as at least one of lanthanum chloride, cerium chloride, and europium chloride. This exploration process is illustrated in the embodiments of the invention.

[0011] In a further example of the invention, the amount of catalyst used was explored. Optionally, the molar ratio of the cis-2-pentenonitrile to the catalyst was (10-200):1, and more preferably (20-100):1, thereby improving the raw material conversion rate, saving costs, and improving product quality.

[0012] In a further example of the invention, the type and amount of supercritical fluid were optimized.

[0013] Optionally, the supercritical fluid includes at least one of supercritical carbon dioxide, supercritical nitrogen dioxide, supercritical sulfur dioxide, and supercritical ammonia, preferably supercritical carbon dioxide. The optimization process is shown in the embodiments of the present invention.

[0014] Optionally, the mass ratio of the supercritical fluid to the cis-2-pentenonitrile is (0.2-20):1, preferably (0.5-5):1. By controlling the supercritical fluid, the conversion rate of cis-2-pentenonitrile and the selectivity of 3PN in the overall reaction can be improved.

[0015] The types and amounts of ligands were explored in further examples of the present invention.

[0016] Optionally, the monodentate phosphite ligand includes at least one of triethyl phosphite, triphenyl phosphite, tri-p-toluene phosphite, tri-m-toluene phosphite, tri-o-toluene phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tris(2-phenylphenyl) phosphite, phenyl diisooctyl phosphite, triisooctyl phosphite, and diisodecyl phosphite, preferably triphenyl phosphite.

[0017] Optionally, the multidentate phosphite ligand is selected from 2,2'-biphenyl diphenyl phosphite, 2,2'-biphenyl dimethyl phosphite, 2,2'-biphenyl di(2,2'-biphenyl) phosphite, [1,1'-biphenyl]-2,2'-diyltetraphenyl phosphite, [1,1'-binaphthyl]-2,2'-diyltetraphenyl phosphite, tetraphenyl(3,3',5,5'-tetramethyl-[1,1'-biphenyl]-2,2'-diyl)phosphite, [1, At least one of the following: [1'-biphenyl]-2,2'-diyltetra-o-methyl bisphosphite, 3,3',5-trimethyl-[1,1'-biphenyl]-2,2'-diyl)bis(phosphite), 3,3',5,5'-tetra-tert-butyl-2,2'-biphenol bisphosphite di(2,2'-biphenol) ester, and 3,3',-di-tert-butyl-5,5'-dimethoxy-2,2'-biphenol bisphosphite di(2,2'-biphenol) ester; preferably 2,2'-biphenol bisphosphite diphenyl ester. Examples of the present invention illustrate the results of isomerization reactions of cis-2-pentenonitrile with different ligand catalysts.

[0018] Optionally, the molar ratio of the ligand to the catalyst is (1-20):1, preferably (2-10):1. Optimizing the amount of ligand can enhance the catalyst performance.

[0019] In a further example of the present invention, the control conditions of the isomerization reaction are optimized. Optionally, the temperature of the isomerization reaction is 20–200°C, preferably 40–80°C; optionally, the pressure of the isomerization reaction is 2–30 MPa, preferably 5–20 MPa. The control conditions of the isomerization reaction section of the present invention are relatively mild compared with the prior art and have strong operability; optionally, the time of the isomerization reaction is 0.5–20 h, preferably 2–10 h. The technical solution of the present invention can shorten the reaction time, thereby significantly improving production efficiency.

[0020] It is worth noting that the research team further discovered through numerous experiments that this invention is also applicable to the isomerization process of mixtures containing cis-2-pentenonitriles with 3PN, exhibiting excellent conversion rates and product selectivity. Therefore, the technical solution of this invention has significant industrial application value. The embodiments of this invention illustrate experimental results for the catalytic isomerization of mixtures containing cis-2-pentenonitriles with 3PN.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention selects rare earth metal oxides or rare earth metal halides, combined with specific monodentate or polydentate phosphites, to catalyze the isomerization of cis-2-pentenonitrile to generate 3PN in supercritical fluid. This catalytic process has high feed conversion rate and high 3PN selectivity. It can efficiently convert cis-2-pentenonitrile to 3PN in the two-step hydrocyanation process of butadiene to adiponitrile in the industrial process, thereby eliminating its poisoning effect on the catalyst, improving process efficiency, saving costs, and enhancing economic benefits. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 shows the gas chromatography results of the reacted material in Example 1 of the present invention.

[0024] Figure 2 shows the gas chromatography results of the reacted material in Comparative Example 3.1 of the present invention. Detailed Implementation

[0025] To facilitate understanding of the present invention, a more comprehensive description will be provided below, along with preferred embodiments. However, it should be understood that these embodiments are merely for more detailed explanation and should not be construed as limiting the invention in any way, i.e., not intended to limit the scope of protection of the invention.

[0026] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] In the following embodiments, the catalyst used needs to be calcined at high temperature to remove moisture before use and transferred to the reactor in an inert gas atmosphere; then the ligand and cis-2-pentenonitrile are added sequentially, the reactor is then sealed, a vacuum is drawn, and carbon dioxide gas (or nitrogen dioxide, sulfur dioxide, etc.) is introduced; by controlling the temperature and pressure of the reactor, the gas reaches a supercritical state for the reaction; after the reaction is completed, the temperature is lowered and the pressure is reduced; then gas chromatography is used for analysis. The inert gas refers to a gas that does not chemically interact with the reactants, such as nitrogen and gases of Group 0 elements in the periodic table (such as argon).

[0029] The monodentate and polydentate phosphites used in the embodiments of the present invention can be obtained commercially or prepared using existing publicly available technologies.

[0030] In the following examples, the conversion rate is based on the reactant cis-2-pentenonitrile, that is, the proportion of cis-2-pentenonitrile that has reacted to the initial feed; selectivity is the proportion of the target product 3-pentenonitrile to the amount of reactant that has decreased.

[0031] Example 1

[0032] A method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile is disclosed. Specifically, in this embodiment, 1 mol of lanthanum oxide catalyst, 5 mol of triphenyl phosphite as a ligand, and 100 mol of cis-2-pentenonitrile are added sequentially to a reaction vessel in an inert gas atmosphere. The reaction vessel is then sealed, evacuated, and carbon dioxide gas is introduced. The reaction vessel temperature is controlled at 40°C, the pressure at 10 MPa, and the reaction time is 3 h. Quantitative analysis is performed using gas chromatography (Figure 1). The conversion rate is based on the reactant cis-2-pentenonitrile, i.e., the proportion of cis-2-pentenonitrile reacted relative to the initial feed. Selectivity represents the proportion of the target product 3-pentenonitrile to the amount of reactants reduced. The results are shown in Table 1.

[0033] Comparative Example 1

[0034] Comparative Example 1 includes Comparative Examples 1.1, 1.2, 1.3, and 1.4. The operation process and control conditions are the same as those in Example 1, except that the catalysts used are aluminum oxide, zinc oxide, and tin oxide, respectively. The reaction results are shown in Table 1.

[0035] Comparative Example 2

[0036] The procedure for this comparative example is as follows: Under a nitrogen atmosphere, 1 mol of lanthanum oxide catalyst, 5 mol of triphenyl phosphite as a ligand, 100 mol of cis-2-pentenonitrile, and 100 mol of organic solvent were added sequentially to the reactor. The reactor was then sealed, purged with nitrogen, and the temperature was controlled at 80℃, the pressure at 1 MPa, and the reaction time at 3 h. Quantitative analysis was performed using gas chromatography after the reaction. This comparative example includes Comparative Example 2.1 and Comparative Example 2.2, the difference being the solvents used: toluene and cyclohexane, respectively. The reaction results are shown in Table 1.

[0037] Comparative Example 3

[0038] Comparative Example 1 includes Comparative Example 3.1 and Comparative Example 3.2. The operation process and control conditions are the same as those in Example 1. The difference is that the ligand used in Comparative Example 3.1 is triphenylphosphine, while no ligand is added in Comparative Example 3.2. The reaction results are shown in Table 1, and the gas chromatogram of Comparative Example 3.1 is shown in Figure 2.

[0039] Table 1

[0040] As can be verified by Table 1, existing technologies use oxides such as alumina and zinc oxide as catalysts to catalyze the isomerization reaction of cis-2-pentenonitrile, but the isomerization effect is not obvious (e.g., Comparative Example 3.3), resulting in low conversion rate of cis-2-pentenonitrile and low 3PN selectivity. After introducing supercritical fluid, the conversion rate of cis-2-pentenonitrile and the 3PN selectivity are improved (e.g., Comparative Examples 1.1-1.4), but the reaction time is still relatively long. In Example 1 of this invention, under supercritical fluid conditions, through optimization of the catalyst type and ligands, the conversion rate of cis-2-pentenonitrile and the 3PN selectivity are significantly improved, while the reaction time is also shortened.

[0041] Example 2

[0042] Based on the method for isomerization of cis-2-pentenonitrile to 3-pentenonitrile shown in Example 1, this example explores the types of catalysts used. Specifically, the parameters and control conditions in this example are the same as in Example 1, except that the type of catalyst used is different. The control conditions and reaction results are shown in Table 2.

[0043] Table 2

[0044] As can be confirmed by Table 2, the catalyst of the present invention is a rare earth metal oxide or a rare earth metal halide. The rare earth metal oxide may be selected from at least one of lanthanum oxide, actinium oxide, samarium oxide, praseodymium oxide, cerium oxide, and neodymium oxide, and may further be selected from lanthanum oxide. The rare earth metal halide may be selected from chlorides, and may further be selected from at least one of lanthanum chloride, cerium chloride, and europium chloride.

[0045] Example 3

[0046] Based on the method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile shown in Example 1, this example explores the type of supercritical fluid used. Specifically, the parameters and control conditions in this example are the same as in Example 1, except that the type of supercritical fluid used is different. The control conditions and reaction results are shown in Table 3.

[0047] Table 3

[0048] As can be verified from Table 3, the supercritical fluid in the technical solution of the present invention can be selected from at least one of supercritical carbon dioxide, supercritical nitrogen dioxide, supercritical sulfur dioxide, and supercritical ammonia, and can be further selected from supercritical carbon dioxide.

[0049] Example 4

[0050] Based on the method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile shown in Example 1, this example explores the types of monodentate or polydentate ligands used. Specifically, the parameters and control conditions in this example are the same as in Example 1, except that the types of ligands used are different. The control conditions and reaction results are shown in Table 4.

[0051] Table 4

[0052] As can be confirmed by Table 4, the monodentate phosphite ligand used in the technical solution of the present invention can be selected from at least one of triethyl phosphite, triphenyl phosphite, tri-p-toluene phosphite, tri-m-toluene phosphite, tri-o-toluene phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tris(2-phenylphenyl) phosphite, phenyl diisooctyl phosphite, triisooctyl phosphite, and diisodecyl phosphite, and may be further selected from triphenyl phosphite. The multidentate phosphite ligand may be selected from 2,2'-biphenyl diphenyl phosphite, 2,2'-biphenyl dimethyl phosphite, 2,2'-biphenyl di(2,2'-biphenyl) phosphite, [1,1'-biphenyl]-2,2'-diyltetraphenyl phosphite, [1,1'-binaphthyl]-2,2'-diyltetraphenyl phosphite, tetraphenyl(3,3',5,5'-tetramethyl-[1,1'-biphenyl]-2,2'-diyl)phosphite, [1,1'-binaphthyl]-2,2'-diyltetraphenyl phosphite, etc. At least one of [1,1'-biphenyl]-2,2'-diyltetra-o-methyl bisphosphite, 3,3',5-trimethyl-[1,1'-biphenyl]-2,2'-diyl)bis(phosphite), 3,3',5,5'-tetra-tert-butyl-2,2'-biphenol bisphosphite di(2,2'-biphenol) ester, and 3,3',-di-tert-butyl-5,5'-dimethoxy-2,2'-biphenol bisphosphite di(2,2'-biphenol) ester; further optionally, 2,2'-biphenol bisphosphite diphenyl ester.

[0053] Example 5

[0054] Based on the method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile shown in Example 1, this example explores the control conditions for the isomerization reaction. The control conditions and reaction results are shown in Table 5.

[0055] Table 5

[0056] As can be confirmed from Table 5, the molar ratio of the cis-2-pentenonitrile to the catalyst is (10-200):1, and more preferably (20-100):1; the mass ratio of the supercritical fluid to the cis-2-pentenonitrile is (0.2-20):1, preferably (0.5-5):1; and the molar ratio of the ligand to the catalyst is (1-20):1, preferably (2-10):1.

[0057] Furthermore, in the technical solution of the present invention, the temperature of the isomerization reaction can be selected from 20 to 200°C, and more preferably from 40 to 80°C; the pressure of the isomerization reaction can be selected from 2 to 30 MPa, and more preferably from 5 to 20 MPa; optionally, the time of the isomerization reaction is 0.5 to 20 h, preferably 2 to 10 h.

[0058] Example 6

[0059] A method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile is disclosed. Specifically, in this embodiment, 1 mol of lanthanum oxide catalyst, 5 mol of triphenyl phosphite as a ligand, and 100 mol of cis-2-pentenonitrile material (containing 20% ​​molar percentage of 3PN) are sequentially added to a reaction vessel under an inert gas atmosphere. The reaction vessel is then sealed, evacuated, and purged with carbon dioxide gas. The reaction temperature is controlled at 40°C, the pressure at 10 MPa, and the reaction time at 4 h. Quantitative analysis using gas chromatography after the reaction shows that the conversion rate of cis-2-pentenonitrile remains 100%, and the selectivity for 3-pentenonitrile is 99.5%, verifying that this invention can be used to catalyze the isomerization of cis-2-pentenonitrile to 3PN in a mixture containing cis-2-pentenonitrile and 3PN. Therefore, the technical solution of this invention can be applied to the isomerization process of mixtures containing cis-2-pentenonitrile and 3PN, and has significant industrial application value.

[0060] It should be noted that the above description is a further detailed explanation of the present invention in conjunction with specific embodiments, and should not be construed as limiting the specific implementation of the present invention to these descriptions; the dimensional data in this embodiment do not necessarily limit the technical solution, but merely illustrate one specific working condition. For those skilled in the art, various simple improvements and modifications can be made without departing from the concept of the present invention, and all such improvements and modifications should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile, characterized in that, The method includes an isomerization reaction of cis-2-pentenonitrile in a supercritical fluid under the action of a catalyst and a ligand to generate 3-pentenonitrile; wherein the catalyst is a rare earth metal oxide and / or a rare earth metal halide, and the ligand is a monodentate phosphite or a polydentate phosphite.

2. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The rare earth metal oxide includes at least one of lanthanum oxide, actinium oxide, samarium oxide, praseodymium oxide, cerium oxide, and neodymium oxide, with lanthanum oxide being preferred.

3. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The rare earth metal halide is a chloride, preferably at least one of lanthanum chloride, cerium chloride, and europium chloride.

4. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The molar ratio of the cis-2-pentenonitrile to the catalyst is (10-200):1, preferably (20-100):

1.

5. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The supercritical fluid includes at least one of supercritical carbon dioxide, supercritical nitrogen dioxide, supercritical sulfur dioxide, and supercritical ammonia, preferably supercritical carbon dioxide.

6. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The mass ratio of the supercritical fluid to the cis-2-pentenonitrile is (0.2-20):1, preferably (0.5-5):

1.

7. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The monodentate phosphite ligand includes at least one of triethyl phosphite, triphenyl phosphite, tri-p-toluene phosphite, tri-m-toluene phosphite, tri-o-toluene phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tris(2-phenylphenyl) phosphite, diisooctyl phosphite, triisooctyl phosphite, and diisodecyl phosphite, preferably triphenyl phosphite.

8. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The multidentate phosphite ligand is selected from 2,2'-biphenyl diphenyl phosphite, 2,2'-biphenyl dimethyl phosphite, 2,2'-biphenyl di(2,2'-biphenyl) phosphite, [1,1'-biphenyl]-2,2'-diyltetraphenyl phosphite, [1,1'-binaphthyl]-2,2'-diyltetraphenyl phosphite, tetraphenyl(3,3',5,5'-tetramethyl-[1,1'-biphenyl]-2,2'-diyl)phosphite, [1,1'- At least one of [1,1'-biphenyl]-2,2'-diyltetra-o-methyl bisphosphite, 3,3',5-trimethyl-[1,1'-biphenyl]-2,2'-diyl)bis(phosphite), 3,3',5,5'-tetra-tert-butyl-2,2'-biphenol bisphosphite di(2,2'-biphenol) ester, and 3,3',-di-tert-butyl-5,5'-dimethoxy-2,2'-biphenol bisphosphite di(2,2'-biphenol) ester; preferably 2,2'-biphenol bisphosphite diphenyl ester.

9. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The molar ratio of the ligand to the catalyst is (1-20):1, preferably (2-10):

1.

10. The method for isomerizing cis-2-pentenonitrile to 3-pentenonitrile according to claim 1, characterized in that, The isomerization reaction is carried out at a temperature of 20–200°C, preferably 40–80°C. Preferably, the pressure of the isomerization reaction is 2-30 MPa, more preferably 5-20 MPa; Preferably, the isomerization reaction takes 0.5 to 20 hours, and more preferably 2 to 10 hours.

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