A preparation method of a palladium-based homogeneous catalyst and its application in the synthesis of isophytol

Abstract

The invention relates to the technical field of chemistry, and discloses a method for preparing a palladium-based homogeneous catalyst. The catalyst is prepared by complexing a PEG-modified PAMAM dendritic macromolecule PAMAM-PEG as a ligand and palladium as an active component. The catalyst is easily soluble in ethanol, has good selectivity, and the active component is not easy to fall off, and has high activity. The invention also provides an application of the palladium-based homogeneous catalyst in the synthesis of isophytol, thereby realizing the recycling of the catalyst, saving the catalyst cost, realizing the full hydrogenation of dehydrogenated isophytol, and effectively reducing the system waste rate and the content of perhydrogenated isophytol.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for preparing a palladium-based homogeneous catalyst and application of the palladium-based homogeneous catalyst in the synthesis of isophytol. Background Art

[0002] Isophytol is a diterpene-type unsaturated tertiary alcohol composed of four isoprene molecules connected end to end. Pure isophytol is a colorless oily liquid that is flammable, insoluble in water, and easily soluble in organic solvents such as alcohol and ketone. It is the main raw material for producing vitamin E. The existing synthesis method of isophytol is generally: dehydrogenated isophytol is selectively hydrogenated under the heterogeneous catalysis of Lindlar catalyst, and then filtered to recover the catalyst, and the reaction liquid is distilled to obtain isophytol.

[0003] The existing process routes for synthesizing isophytol have the following shortcomings: poor continuity and stability of intermittent reactions, high rates of overhydrogenation and waste in the reaction products; low activity of heterogeneous catalysts, and the main catalyst is easily detached and deactivated, and has a short lifespan; if a homogeneous catalyst is used instead, there is a problem of difficulty in separating and recovering the catalyst, and it is necessary to screen or develop an efficient separation system.

[0004] Therefore, how to provide a homogeneous catalyst and a continuous synthesis route for preparing isophytol using the homogeneous catalyst is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing a palladium-based homogeneous catalyst, and applies the palladium-based homogeneous catalyst to the synthesis of isophytol, so as to solve the problems of poor stability and low efficiency of the existing isophytol synthesis process, as well as low catalyst activity and difficulty in recycling.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a method for preparing a palladium-based homogeneous catalyst, wherein the catalyst is prepared by a complex reaction using PEG-modified PAMAM dendrimer PAMAM-PEG as a ligand and palladium as an active component.

[0008] Preferably, in the preparation method of the above-mentioned palladium-based homogeneous catalyst, the following steps are included:

[0009] (1) dissolving the PAMAM-PEG ligand in an organic solvent, performing magnetic stirring and condensation reflux to obtain a ligand solution;

[0010] (2) adding a PbCl2 solution dropwise to the ligand solution to carry out a complexation reaction, and after the reaction is completed, cooling, filtering, and washing the reaction mixture to obtain a crystalline product;

[0011] (3) Drying the crystalline product to obtain a palladium-based homogeneous catalyst.

[0012] Preferably, in the preparation method of the above-mentioned palladium-based homogeneous catalyst, the mass ratio of PAMAM-PEG ligand to palladium chloride is (1-1.2):(0.2-0.5).

[0013] Preferably, in the preparation method of the above palladium-based homogeneous catalyst, the organic solvent in step (1) is anhydrous methanol, and the ratio of the PAMAM-PEG ligand to the organic solvent is (0.5-1.5) g:25 ml.

[0014] Preferably, in the above-mentioned method for preparing the palladium-based homogeneous catalyst, the magnetic stirring in step (1) is carried out under the protection of an inert gas, and the stirring temperature is 20-50° C., and the stirring time is 5-20 min.

[0015] Preferably, in the above-mentioned method for preparing the palladium-based homogeneous catalyst, the PbCl2 solution is prepared by dissolving palladium chloride in an organic solvent;

[0016] Further preferably, the organic solvent is anhydrous methanol, and the ratio of palladium chloride to the organic solvent is (0.1-0.5) g:25 ml.

[0017] Further preferably, the organic solvent is anhydrous methanol, the complexation reaction time in step (2) is 12-36 hours, and the reaction temperature is 20-50°C.

[0018] Preferably, in the preparation method of the above-mentioned palladium-based homogeneous catalyst, the drying in step (3) is performed by vacuum drying at 50-80°C for 5-15h, followed by freeze drying at (-10)-(-30)°C for 15-32h;

[0019] Further preferably, the drying in step (3) is performed by vacuum drying at 60°C for 10 h and then freeze drying at -20°C for 24 h.

[0020] On the other hand, the present invention also provides an application of the palladium-based homogeneous catalyst prepared by the above method in the synthesis of isophytol, comprising the following steps:

[0021] S1. Dehydrogenated isophytol dissolved in an organic solvent is used as a raw material, the palladium-based homogeneous catalyst and the sulfide inhibitor are added, and after being fully mixed, the mixture is continuously hydrogenated in a multi-tank series reactor;

[0022] S2. After the continuous hydrogenation reaction is completed, the reaction liquid is subjected to membrane separation treatment.

[0023] Preferably, in the application of the above-mentioned palladium-based homogeneous catalyst in the synthesis of isophytol, the addition amount of the palladium-based homogeneous catalyst is 0.5%-2% of the mass of dehydroisophytol; the addition amount of the thioether inhibitor (containing 1%wt thioether) is 2-5 times the mass of the catalyst, and the thioether content in the thioether inhibitor is 1%.

[0024] Preferably, in the application of the above-mentioned palladium-based homogeneous catalyst in the synthesis of isophytol, the continuous hydrogenation reaction is carried out at a rotation speed of 600-800 r / min, and the reaction temperature is 80-100° C., and the residence time is 8-15 h.

[0025] Preferably, in the application of the above-mentioned palladium-based homogeneous catalyst in the synthesis of isophytol, in step S2, the membrane separation process uses a highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer.

[0026] Preferably, in the application of the above-mentioned palladium-based homogeneous catalyst in the synthesis of isophytol, the twisted structure monomer is

[0027] Preferably, in the application of the above-mentioned palladium-based homogeneous catalyst in the synthesis of isophytol, the method for preparing the highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer comprises the following steps:

[0028] A. After the polysulfone-based membrane is soaked and then blown dry, the polysulfone-based membrane is hydrophilically modified using tannic acid-iron modification liquid to obtain mPSF;

[0029] B. adding the twisted structure monomer into an aqueous solution of methylpiperidinium dithiocarbamate, stirring and dissolving, to obtain an mPIP solution;

[0030] C. Pour the mPIP solution onto the surface of the mPSF to soak it and then blow it dry. Continue to pour the n-hexane solution of trimesoyl chloride onto the membrane surface to react. After the reaction is completed, wash and dry to obtain the polypiperazineamide nanofiltration membrane.

[0031] Furthermore, the hydrophilic modification in step A is to pour the tannic acid-iron modification liquid on the surface of the polysulfone-based membrane and deposit it for 5-20 minutes;

[0032] and / or the pH value of the methylpiperidinium dithiocarbamate aqueous solution in step B is 12-13;

[0033] And / or in step C, the infiltration time is 1-5 minutes, the reaction time is 30-80 seconds, and the drying is heat treatment in an oven at 30-80° C. for 1-5 minutes.

[0034] Preferably, in the application of the above-mentioned palladium-based homogeneous catalyst in the synthesis of isophytol, after membrane separation treatment in step S2, isophytol passes through the membrane, and the palladium-based homogeneous catalyst, a small amount of hydrogenation and by-products such as heaps are retained, and the retained liquid is refluxed to the initial stage of the reaction to continue the catalytic reaction.

[0035] The present invention provides a preparation method of a palladium-based homogeneous catalyst and application of the catalyst in the synthesis of isophytol. Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention provides a new homogeneous hydrogenation catalyst to replace the traditional heterogeneous palladium carbon catalyst. The palladium-based homogeneous catalyst is prepared with PEG-modified PAMAM dendrimer as a ligand and palladium as an active component. The product yield reaches about 85%. It is easily soluble in ethanol, has good selectivity, and the active component is not easy to fall off, and has high activity.

[0037] (2) In the process of synthesizing isophytol, the present invention adopts multi-reactor series continuous hydrogenation to replace the traditional intermittent reactor hydrogenation, thereby improving the stability and efficiency of the reaction and reducing the over-hydrogenation and waste material rates;

[0038] (3) The present invention adopts a new highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer to achieve selective separation of homogeneous catalysts and products. The rigidity and twisted structure of the modified monomer endow the membrane with good selectivity, flux and service life; the membrane separation technology is used to purify isophytol to replace the traditional complex post-processing device, thereby simplifying the process flow;

[0039] (4) The present invention realizes the recycling of the catalyst, saves the catalyst cost, and the method of reacting and passing through the membrane can achieve the full hydrogenation of dehydrogenated isophytol, effectively reducing the system sizing rate and the content of hydrogenated isophytol. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the synthesis process of the palladium-based homogeneous catalyst of the present invention;

[0041] Figure 2 It is a schematic structural diagram of a twisted structure monomer of the present invention;

[0042] Figure 3 Schematic diagram of the synthesis mechanism of the highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer of the present invention;

[0043] Figure 4 It is a schematic diagram of the synthesis process of the highly selective polypiperazineamide nanofiltration membrane modified by a twisted structure monomer of the present invention. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing a palladium-based homogeneous catalyst, comprising the following steps:

[0047] (1) 1.1 g of PAMAM-PEG ligand was dissolved in 25 ml of anhydrous methanol, added to a three-necked round-bottom flask, magnetically stirred and refluxed, and stirred at 30 ° C under nitrogen protection for 10 min to obtain a ligand solution;

[0048] (2) 0.333 g of palladium chloride was dissolved in 25 ml of anhydrous methanol to obtain a PbCl2 solution, which was then slowly added dropwise into a three-necked round-bottom flask using a constant pressure dropping funnel. After reacting for 24 hours, the reaction mixture was immediately placed in a low-temperature cooling tank, filtered, and washed several times with a small amount of anhydrous methanol to obtain a crystalline product;

[0049] (3) The crystalline product is dried under vacuum at 60° C. and then freeze-dried to obtain a brown-gray solid, which is the palladium-based homogeneous catalyst A.

[0050] Example 2

[0051] This embodiment provides a method for preparing a palladium-based homogeneous catalyst, comprising the following steps:

[0052] (1) 1.2 g of PAMAM-PEG ligand was dissolved in 25 ml of anhydrous methanol, added to a three-necked round-bottom flask, magnetically stirred and refluxed, and stirred at 30 ° C under nitrogen protection for 10 min to obtain a ligand solution;

[0053] (2) 0.5 g of palladium chloride was dissolved in 25 ml of anhydrous methanol to obtain a PbCl2 solution, which was then slowly added dropwise into a three-necked round-bottom flask using a constant pressure dropping funnel. After reacting for 12 h, the reaction mixture was immediately placed in a low-temperature cooling tank, filtered, and washed several times with a small amount of anhydrous methanol to obtain a crystalline product;

[0054] (3) The crystalline product is dried under vacuum at 60° C. and then freeze-dried to obtain a brown-gray solid, which is the palladium-based homogeneous catalyst B.

[0055] Example 3

[0056] This embodiment provides a method for preparing a palladium-based homogeneous catalyst, comprising the following steps:

[0057] (1) Dissolve 1 g of PAMAM-PEG ligand in 25 ml of anhydrous methanol, add the mixture into a three-necked round-bottom flask, perform magnetic stirring and condensation reflux, and stir at 30 °C under nitrogen protection for 10 min to obtain a ligand solution;

[0058] (2) 0.2 g of palladium chloride was dissolved in 25 ml of anhydrous methanol to obtain a PbCl2 solution, which was then slowly added dropwise into a three-necked round-bottom flask using a constant pressure dropping funnel. After reacting for 24 hours, the reaction mixture was immediately placed in a low-temperature cooling tank, filtered, and washed several times with a small amount of anhydrous methanol to obtain a crystalline product;

[0059] (3) The crystalline product is dried under vacuum at 60° C. and then freeze-dried to obtain a brown-gray solid, which is the palladium-based homogeneous catalyst C.

[0060] Example 4

[0061] This embodiment provides a method for synthesizing isophytol using the above-mentioned palladium-based homogeneous catalyst, comprising the following steps:

[0062] S1. Mix dehydroisophytol and ethanol by weight, add 1% of the weight of dehydroisophytol to dissolve the palladium-based homogeneous catalyst A, and then add 3 times the weight of the catalyst to the sulfide inhibitor. After the raw material liquid is fully mixed in a mixer, it enters a multi-tank series reactor for continuous hydrogenation. Hydrogen is introduced from the bottom of the tower. At 80°C and a stirring speed of 600r / min, a continuous reaction is carried out for a residence time of 10h, and the resulting reaction liquid is subjected to subsequent membrane separation treatment;

[0063] S2. The reaction liquid enters the membrane separation device. The membrane is a highly selective polypiperazineamide nanofiltration membrane modified with twisted structure monomers. Driven by a pressure of 1 MPa, isophytol passes through the membrane, while the catalyst and a small amount of by-products such as hydrogenation and heels are retained. The retained liquid flows back to the initial reaction stage to continue the catalytic reaction.

[0064] Specifically, Figure 4 As shown in the figure, a highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer was prepared by the following method: a polysulfone PSF base membrane was soaked in deionized water overnight to wet and clean the membrane pores, and then the PSF base membrane was fixed to a plate frame and dried with an air knife; a TA-Fe modification solution (TA: 0.3 mg / mL; FeCl3·6H2O: 0.2 mg / mL) was prepared, and it was poured on the surface of the PSF base membrane and deposited for 10 minutes for hydrophilic modification, which was recorded as mPSF;

[0065] Prepare a 0.5% w / v PIP aqueous solution, adjust the pH to 13 with a 1 mol / L NaOH aqueous solution, then take 0.025 g of the twisted structure monomer and add it to the PIP aqueous solution with a pH of 13, stir well to dissolve, and obtain an mPIP solution;

[0066] The base membrane was fixed on the plate frame and blown dry with an air knife. Subsequently, the mPIP solution was poured on the surface of the base membrane and soaked for 3 minutes. The aqueous phase was then poured out and blown dry with an air knife. A 0.5% w / v TMC n-hexane solution was poured on the membrane surface to react for 50 seconds. The organic phase was then poured out and rinsed with n-hexane to remove the unreacted organic phase monomers on the surface. The prepared nanofiltration membrane was heat-treated in an oven at 60°C for 2 minutes to obtain a highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer, which was stored in deionized water.

[0067] like Figure 3 The figure shows a schematic diagram of the synthesis mechanism of a highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer. During the membrane preparation process, a certain amount of a twisted structure monomer is added to the aqueous solution, and the aqueous solution and the organic solution are subjected to interfacial polymerization to form a membrane. The rigidity and twisted structure of the monomer give the membrane good selectivity, flux and service life.

[0068] Example 5

[0069] This embodiment provides a method for synthesizing isophytol using the above-mentioned palladium-based homogeneous catalyst, comprising the following steps:

[0070] S1. Mix dehydrogenated isophytol and ethanol in equal weight, add 0.5% of the weight of dehydrogenated isophytol to dissolve the palladium-based homogeneous catalyst B, and then add 3 times the weight of the catalyst to the sulfide inhibitor. After the raw material liquid is fully mixed in a mixer, it enters a multi-tank series reactor for continuous hydrogenation. Hydrogen is introduced from the bottom of the tower. At 100°C and a stirring speed of 600r / min, a continuous reaction is carried out for a residence time of 10h, and the resulting reaction liquid is subjected to subsequent membrane separation treatment;

[0071] S2. Same as Example 4.

[0072] Example 6

[0073] This embodiment provides a method for synthesizing isophytol using the above-mentioned palladium-based homogeneous catalyst, comprising the following steps:

[0074] S1. Mix dehydroisophytol and ethanol by weight, add 2% of the weight of dehydroisophytol to dissolve the palladium-based homogeneous catalyst C, and then add 4 times the weight of the catalyst to the sulfide inhibitor. After the raw material liquid is fully mixed in a mixer, it enters a multi-tank series reactor for continuous hydrogenation. Hydrogen is introduced from the bottom of the tower. After a continuous reaction with a residence time of 8h at 80°C and a stirring speed of 600r / min, the obtained reaction liquid is subjected to subsequent membrane separation treatment;

[0075] S2. Same as Example 4.

[0076] Example 7

[0077] This embodiment provides a method for synthesizing isophytol using the above-mentioned palladium-based homogeneous catalyst, comprising the following steps:

[0078] S1. Mix dehydroisophytol and ethanol by weight, add 1% of the weight of dehydroisophytol to dissolve the palladium-based homogeneous catalyst B, and then add 3 times the weight of the catalyst to the sulfide inhibitor. After the raw material liquid is fully mixed in a mixer, it enters a multi-tank series reactor for continuous hydrogenation. Hydrogen is introduced from the bottom of the tower. After a continuous reaction with a residence time of 8h at 80°C and a stirring speed of 600r / min, the obtained reaction liquid is subjected to subsequent membrane separation treatment;

[0079] S2. Same as Example 4.

[0080] Example 8

[0081] This embodiment provides a method for synthesizing isophytol using the above-mentioned palladium-based homogeneous catalyst, comprising the following steps:

[0082] S1. Mix dehydroisophytol and ethanol by weight, add 1% of the weight of dehydroisophytol to dissolve the palladium-based homogeneous catalyst C, and then add 3 times the weight of the catalyst to the sulfide inhibitor. After the raw material liquid is fully mixed in a mixer, it enters a multi-tank series reactor for continuous hydrogenation. Hydrogen is introduced from the bottom of the tower. At 80°C and a stirring speed of 600r / min, a continuous reaction is carried out for a residence time of 8h, and the resulting reaction liquid is subjected to subsequent membrane separation treatment;

[0083] S2. Same as Example 4.

[0084] Comparative Example 1

[0085] This comparative example provides a method for synthesizing isophytol, comprising the following steps:

[0086] Mix dehydroisophytol and ethanol in equal mass, add 0.5% of Lindlar catalyst by mass of dehydroisophytol, and then add 1% of thioether inhibitor by mass 3 times of the catalyst, intermittently hydrogenate in a high-pressure reactor at a pressure of 2.5 MPa, react for 6 hours at 80°C and a stirring speed of 600 r / min, and then discharge the material.

[0087] Relevant tests were conducted on the process of synthesizing isophytol in Examples 4-8 and Comparative Example 1, and the test results are shown in Table 1.

[0088] Table 1 Test results

[0089] Main content% Residue% Hydrogen permeability % Scrap rate % Comparative Example 1 93.4898 3.0710 0.5341 2.027 Example 4 96.4886 0.9365 0.2849 1.5432 Example 5 95.9532 1.5648 0.3654 1.9365 Example 6 96.2345 1.2549 0.3025 1.6521 Example 7 95.4321 0.6541 0.5014 1.8406 Example 8 95.5421 1.5234 0.4521 1.9416

[0090] It can be seen from the above table that compared with the traditional heterogeneous catalytic hydrogenation to prepare isophytol, the method of synthesizing isophytol using a palladium-based homogeneous catalyst in the present invention can effectively reduce the over-hydrogenation and waste material rates in the reaction products.

[0091] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the scheme disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0092] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Application of a palladium-based homogeneous catalyst in the synthesis of isophytol, characterized in that: The palladium-based homogeneous catalyst is prepared by using a polyamide-amine dendritic macromolecule PAMAM-PEG modified with polyethylene glycol (PEG) as a ligand and palladium as an active component through a complex reaction; the steps include: (1) dissolving the PAMAM-PEG ligand in an organic solvent to obtain a ligand solution; (2) adding a PdCl2 solution dropwise to the ligand solution to carry out a complex reaction, and after the reaction is completed, cooling, filtering, and washing the reaction mixture to obtain a crystalline product; (3) drying the crystalline product to obtain a palladium-based homogeneous catalyst; The mass ratio of PAMAM-PEG ligand to palladium chloride is (1-1.2):(0.2-0.5).

2. The use of a palladium-based homogeneous catalyst in the synthesis of isophytol according to claim 1, characterized in that: In step (1), the magnetic stirring is carried out under the protection of an inert gas, and the stirring temperature is 20-50° C. and the stirring time is 5-20 min; The drying in step (3) is performed by vacuum drying at 50-80°C for 5-15h, followed by freeze drying at (-10)-(-30)°C for 15-32h.

3. The use of a palladium-based homogeneous catalyst in the synthesis of isophytol according to claim 2, characterized in that: include: S1. Dehydrogenated isophytol dissolved in an organic solvent is used as a raw material, a palladium-based homogeneous catalyst and a thioether inhibitor are added, and the mixture is fully mixed and then continuously hydrogenated in a multi-tank series reactor; S2. After the continuous hydrogenation reaction is completed, the reaction liquid is subjected to membrane separation treatment.

4. The use of the palladium-based homogeneous catalyst in the synthesis of isophytol according to claim 3, characterized in that: The added amount of the palladium-based homogeneous catalyst is 0.5%-2% of the mass of dehydroisophytol, and the added amount of the thioether inhibitor is 2-5 times of the mass of the catalyst. The continuous hydrogenation reaction is carried out at a rotation speed of 600-800 r / min, a reaction temperature of 80-100° C., and a residence time of 8-15 h.

5. The use of the palladium-based homogeneous catalyst in the synthesis of isophytol according to claim 3, characterized in that: In step S2, the membrane separation process uses a highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer, wherein the twisted structure monomer is 6. Use of the palladium-based homogeneous catalyst in the synthesis of isophytol according to claim 5, characterized in that: The method for preparing the highly selective polypiperazineamide nanofiltration membrane modified with a twisted structure monomer comprises the following steps: A. After the polysulfone-based membrane is soaked and then blown dry, the polysulfone-based membrane is hydrophilically modified using tannic acid-iron modification liquid to obtain mPSF; B. adding the twisted structure monomer into an aqueous solution of methylpiperidinium dithiocarbamate, stirring and dissolving, to obtain an mPIP solution; C. Pour the mPIP solution onto the surface of the mPSF to soak it and then blow it dry. Continue to pour the n-hexane solution of trimesoyl chloride onto the membrane surface to react. After the reaction is completed, wash and dry to obtain the polypiperazineamide nanofiltration membrane.

7. Use of the palladium-based homogeneous catalyst in the synthesis of isophytol according to claim 6, characterized in that: The hydrophilic modification in step A is to pour the tannic acid-iron modification liquid on the surface of the polysulfone-based membrane and deposit it for 5-20 minutes; The pH value of the methylpiperidinium dithiocarbamate aqueous solution in step B is 12-13; In step C, the infiltration time is 1-5 minutes, the reaction time is 30-80 seconds, and the drying is heat treatment in an oven at 30-80° C. for 1-5 minutes.

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