CN112250856B

CN112250856B - Double metal cyanide complex catalyst, preparation method thereof and preparation method of polypropylene glycol

Info

Publication number: CN112250856B
Application number: CN202011090285.4A
Authority: CN
Inventors: 顾正桂; 茅启帆; 汪凯军; 曹晓艳
Original assignee: Nanjing Normal University
Current assignee: Nanjing Normal University
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2023-06-20
Anticipated expiration: 2040-10-13
Also published as: CN112250856A

Abstract

The invention discloses a double metal cyanide complex catalyst, a preparation method thereof and a preparation method of polypropylene glycol, wherein the catalyst meets the following requirementsThe following general formula: MCM@M ¹ _a [M ² _b (CN) _c ] _d ·vM ¹ (X) _e ·wL·xH ₂ O.yP.zS. The catalyst is a double metal cyanide catalyst modified by transition metal salts, organic ligands and co-complexing agents which grows on a mesoporous molecular sieve in situ through a synchronous dropping method, and is obtained through repeated pulping, washing and drying. The preparation method of the polypropylene glycol comprises the steps of adding the catalyst into raw materials for reaction, wherein the addition amount is 100-1000 ppm of the addition amount of the raw materials. The prepared catalyst is in an amorphous state, has extremely low crystallinity and large specific surface area, and has extremely high catalytic activity when the content of active components is low. The invention also provides a method for synthesizing polypropylene glycol by using the catalyst, and the obtained polypropylene glycol has narrower molecular weight distribution and lower aldehyde value, thus having wide application prospect.

Description

Double metal cyanide complex catalyst, preparation method thereof and preparation method of polypropylene glycol

Technical Field

The present invention relates to a catalyst, a method for preparing the same and a method for preparing polypropylene glycol, and particularly relates to a double metal cyanide complex catalyst, a method for preparing the same and a method for preparing polypropylene glycol.

Background

Polyether polyol, also called polyoxyalkylene polyol, is synthesized by homo-polymerization or copolymerization of various compounds containing active hydrogen or amine as initiator with alkylene oxide ring-opening polymerization. In the polyurethane industry, polyether polyol is the polyol raw material with the largest dosage in the plastic foam industry, commonly called as white material, and is a very important nonionic surfactant. The catalysts used for synthesizing polyether polyol at present mainly comprise the following components: (1) The polyether polyol is synthesized by homogeneous catalysis by taking alkali metal hydroxides such as metal Na, K, csOH, KOH and the like or alkaline earth metal hydroxides such as Ba (OH) 2, sr (OH) 2 and the like as catalysts. (2) The heterogeneous catalysis is carried out by taking alkaline earth metal oxide BaO and hydrotalcite composite metal compound as catalyst to synthesize polyether polyol. (3) Polyether polyol is synthesized by novel catalysts such as metalloporphyrin complex, phosphazene catalyst, macrocyclic complex catalyst and the like. (4) Polyether polyol is synthesized by coordination polymerization with double metal cyanide catalyst.

Double metal cyanide complexes were a class of highly efficient heterogeneous catalysts reported for the homopolymerization of propylene oxide to polyether polyols by the general tire rubber company in 1966 U.S. patent No. 3278457. The polyether product produced by the prior double metal cyanide catalyst has the characteristics of low unsaturation degree, high catalytic activity and the like compared with the traditional KOH catalysis, but the polyether product has some problems to be solved urgently: for example, DMC catalysts (double metal cyanide complex catalysts) are difficult to initiate directly small molecule initiators, and possible reasons are that small molecule initiators with two or more functionalities have multiple adjacent hydroxyl groups, which are relatively strongly bound to the active center, difficult to initiate by monomer chain insertion, and have some steric hindrance between adjacent hydroxyl groups. In addition, it is currently accepted that tertiary butanol has the highest catalytic activity when being used as an organic ligand, but the polyether synthesized by tertiary butanol when being used as a ligand tends to have wider molecular weight distribution, and tertiary butanol is easy to be dissolved in a polymerization system to be used as an initiator to form a monofunctional polymer during the reaction, so that the functionality of a product is reduced, and the next application of the product is seriously influenced.

Disclosure of Invention

The invention aims to: a first object of the present invention is to provide a double metal cyanide complex catalyst which is highly catalytically active and capable of initiating a small molecule initiator;

a second object of the present invention is to provide a method for preparing a double metal cyanide complex catalyst;

the third object of the present invention is to provide a method for preparing polypropylene glycol.

The technical scheme is as follows: the double metal cyanide complex catalyst of the present invention satisfies the following general formula:

MCM@M ¹ _a [M ² _b (CN) _c ] _d ·vM ¹ (X) _e ·wL·xH ₂ O·yP·zS

wherein, MCM is mesoporous molecular sieve, M ¹ Is a divalent metal ion; m is M ² Is a transition metal ion; x is Cl ^- 、SO ₄ ^2- One of them; a. b, c, d, e is a positive number; l is an organic ligand, P is a co-complexing agent, S is a transition metal salt; v=0.5 to 3,w =0.1 to 2, x=0.1～2，y＝0～0.1，z＝0～0.01。

Preferably, the organic ligand is an ether and/or an ester; wherein the ethers are selected from ethylene glycol butyl ether and/or propylene glycol butyl ether, and the esters are selected from methyl acetoacetate and/or ethyl acetoacetate.

Preferably, the co-complexing agent is selected from polyoxypropylene ethylene oxide copolymer polyols having a molecular weight of 2000-8000.

Preferably, the transition metal salt is La (NO ₃ ) ₃ ·6H ₂ O、Cr(NO ₃ ) ₃ 9H2O or Ce (NO) ₃ ) ₃ ·6H ₂ At least one of O.

Preferably, the transition metal ion is selected from Co ³⁺ And/or Fe ²⁺ 。

The preparation method of the double metal cyanide complex catalyst comprises the following steps:

(1) Preparing a metal cyanide complex salt aqueous solution, which is named as solution A; adding transition metal salt and organic ligand into zinc salt water solution, named solution B;

(2) Mixing a mesoporous molecular sieve carrier with an organic ligand solution, and naming the mixture as a solution C;

(3) Under the condition of stirring, synchronously dripping the solution A and the solution B into the solution C, then adding an organic ligand and a co-complexing agent, and continuously stirring to obtain catalyst slurry;

(4) And filtering, separating, washing and drying the catalyst slurry to obtain the double metal cyanide complex catalyst.

Preferably, in the step (1), the metal cyanide complex salt is potassium cobalt cyanide, potassium ferricyanide or potassium nickel cyanide, and the zinc salt is zinc chloride, zinc sulfate, zinc acetate or zinc bromide.

Preferably, in the step (1), the addition amount of the transition metal salt is 0.5-3% of the mass of the zinc salt aqueous solution.

Preferably, in the step (2), the mass ratio of the mesoporous molecular sieve carrier to the zinc salt aqueous solution is 1:5-15.

Preferably, in the step (3), the mass ratio of the co-complexing agent to the zinc salt aqueous solution is 1:3 to 10.

Preferably, in the step (2), in the organic ligand solution, the volume ratio of the solution to the organic ligand L is 1-3: 1, a step of; among them, water is preferable as the solution.

Preferably, in the step (1), the concentration of the metal cyanide complex salt aqueous solution is 0.05-0.3 mol/L; the concentration of the zinc salt aqueous solution is 2-6 mol/L;

preferably, in the step (2), the solution A and the solution B are synchronously added into the solution C in an oil bath at the temperature of 30-90 ℃ in a dropwise manner under stirring; the synchronous dripping time of the solution A and the solution B is 20-60 min, and the stirring rotating speed is controlled at 2000-5000 r/min; stirring is continued for 0.5 to 2 hours;

preferably, in the step (3), the catalyst slurry is filtered and separated to obtain a catalyst filter cake, the catalyst filter cake is washed for 3-5 times by using mixed dissolved slurry of the organic ligand and water, and the proportion of the organic ligand in the mixed solution is gradually increased until the catalyst filter cake is washed by using pure organic ligand L for dissolving slurry to obtain a final catalyst filter cake; and (3) drying the final catalyst filter cake in vacuum at 50-80 ℃ to constant weight, and grinding to obtain catalyst powder.

The method for synthesizing polypropylene glycol by using the double metal cyanide complex catalyst comprises the following steps: putting the catalyst and the initiator in the reactor, introducing inert gas into the reactor, and adding propylene oxide monomer into the kettle, wherein the mass ratio of the alkylene oxide to the initiator is 5-20:1; the addition amount of the catalyst is 100-1000 ppm of the addition amount of the raw materials.

Preferably, after polymerization reaction for 5-10 hours under the conditions of controlling the initial pressure to 0.1-1 Mpa, the temperature to 100-140 ℃ and the rotating speed to 250-550 r/min, unreacted monomers are removed, and the polypropylene glycol product is obtained by filtering and separating the product and the catalyst, wherein the molecular weight distribution of the polypropylene glycol product is narrower and the aldehyde value is lower.

The beneficial effects are that: compared with the prior art, the invention has the following remarkable effects: 1. the mesoporous molecular sieve is loaded with active component double metal cyanide, the crystallinity of the catalyst is low, and the catalyst has higher catalytic activity when the content of the active component is low; 2. the method is applied to the synthesis of polypropylene glycol products, and has narrower molecular weight distribution and lower aldehyde content. 3. The catalyst of the invention is easy to initiate a small molecular initiator, on one hand, because the catalyst of the invention has high catalytic activity, and on the other hand, the catalyst of the invention weakens the difference of coordination ability between the initiator and a polymerization monomer through the modification of an electron-donating organic ligand, thereby being capable of successfully initiating the small molecular initiator. 4. The polypropylene glycol prepared by the coordination polymerization system has the advantages of narrow molecular weight distribution, low catalyst consumption, mild reaction conditions, less propylene oxide isomerization phenomenon and less oxidation reaction under the nitrogen atmosphere, so that the prepared polypropylene glycol product has the advantages of narrow molecular weight distribution and lower aldehyde value.

Drawings

FIG. 1 is an SEM image of the DMC-1 catalyst prepared in example 1, wherein FIGS. 1 (a) and 1 (b) are each an SEM image at 15000 and 8000 magnification, respectively;

FIG. 2 is a Zn preparation of comparative example 1 ₃ [Co(CN) ₆ ] ₂ ·12H ₂ XRD patterns of O and the catalyst DMC-1 prepared in example 1;

FIG. 3 is Zn prepared in comparative example 1 ₃ [Co(CN) ₆ ] ₂ ·12H ₂ FTIR spectra of O and of the catalyst DMC-1 prepared in example 1;

FIG. 4 is a graph of the local FTIR spectrum of the catalyst DMC-1 prepared in example 1;

FIG. 5 is an FTIR chart of the polypropylene glycol samples prepared in example 2 and example 3 and the standard samples;

FIG. 6 is a sample of polypropylene glycol prepared in example 3 ¹ HNMR diagram.

Detailed Description

The invention is described in further detail below with reference to the drawings.

Example 1

The embodiment discloses a preparation method of a novel double metal cyanide complex catalyst carried by a mesoporous molecular sieve, wherein an organic ligand L is ethyl acetoacetate; the co-complexing agent P is polyoxypropylene ethylene oxide copolymer polyol with molecular weight of 3000, and is prepared byCommercially available; la (NO) is selected as transition metal salt S ₃ ) ₃ ·6H ₂ O; the specific preparation steps of the catalyst are as follows:

(1) Will be 3X 10 ^-3 A solution A was prepared by dissolving mol of potassium cobalt cyanide in 18ml of water. Will be 2.5X10 ^-2 Dissolving mol zinc chloride in 5ml water to obtain zinc chloride aqueous solution, and weighing La (NO) 1% of the mass of the zinc chloride aqueous solution ₃ ) ₃ ·6H ₂ O and half of the water volume of ethyl acetoacetate are dissolved in zinc chloride water solution to prepare solution B. 0.8g of mesoporous molecular sieve MCM-41 is added into 30ml of water and ethyl acetoacetate mixed solution, wherein the mixed solution comprises the following components: 60% of water and 40% of ethyl acetoacetate; stirring uniformly to obtain solution C.

(2) Under the oil bath condition of 80 ℃, slowly and synchronously dropwise adding the solution A and the solution B into the solution C with the speed of 3000r/min for 20min. Adding 10ml of mixed solution of water and ethyl acetoacetate and 1.25g of co-complexing agent P into the solution, and continuously stirring and mixing for 30min; wherein, in the mixed solution of water and ethyl acetoacetate: 30% of water and 70% of ethyl acetoacetate.

(3) After stirring, cooling the obtained slurry, filtering and separating to obtain a filter cake, washing the obtained filter cake with mixed dissolved slurry consisting of ethyl acetoacetate and water for 3 times, and gradually increasing the proportion of ethyl acetoacetate in the mixed solution until the filter cake of the final catalyst is obtained by washing the slurry with pure ethyl acetoacetate. The final filter cake was dried under vacuum at 50℃to constant weight and ground to give the catalyst, designated DMC-1.

Determination of catalyst composition: the contents of the components in the catalyst DMC-1 are determined by combining inductively coupled plasma emission spectroscopy ICP, an elemental analyzer EA and thermogravimetric analysis TGA as follows:

TABLE 1 catalyst DMC-1 composition Table

From Table 1 it is inferred that the approximate composition of DMC-1 is MCM-41@Zn ₃ [Co(CN) ₆ ] ₂ ·ZnCl ₂ ·0.70EAA·0.76H ₂ O·0.03P123·0.0006La(NO ₃ ) ₃ 。

Comparative example 1

Zinc cobalt cyanide Zn ₃ [Co(CN) ₆ ] ₂ ·12H ₂ Preparation of O:

Zn ₃ [Co(CN) ₆ ] ₂ ·12H ₂ o is synthesized without adding any organic ligand, co-complexing agent and transition metal salt. The preparation method comprises the following steps: 1g of potassium cobalt cyanide was dissolved in 18ml of water to prepare solution A. Solution B was prepared by dissolving 3.3g of zinc chloride in 5ml of water. Slowly dripping the solution A into the solution B to generate white precipitate, filtering, drying and grinding to obtain Zn ₃ [Co(CN) ₆ ] ₂ ·12H ₂ O。

Example 2

Synthesis of high molecular weight polypropylene glycol above PPG-1000:

in this example, a high molecular weight polypropylene glycol was synthesized using a low molecular weight polypropylene glycol having a Mn of 550 as an initiator, and the specific steps were as follows: the catalyst DMC-1 prepared in example 1 above was used to catalyze the synthesis of high molecular weight polypropylene glycols. Polypropylene glycol is synthesized in an autoclave, and the stirring speed and the temperature of the autoclave are controlled. 6g of a polypropylene glycol starter having Mn of 550 and 0.02g of the catalyst DMC-1 obtained in example 1 were charged into an autoclave, and after a plurality of times of substitution with nitrogen, 30g of propylene oxide was added to the autoclave. And (3) controlling the rotating speed to be 350r/min, starting the reaction for 6 hours under the pressure of 0.1Mpa, removing unreacted monomers, and filtering and separating the product from the catalyst to obtain the polypropylene glycol product. The effect of varying the reaction temperature on the properties of the polypropylene glycol product is shown in Table 2.

And (3) detecting products: and detecting the hydroxyl value, aldehyde value, conversion rate and PH value of the product. The induction time of the catalyst is recorded in the reaction process, and when the temperature of the reaction kettle rises to the reaction set temperature, the time is counted, and the induction time is counted when the phenomenon of 'temperature rise and pressure drop' or obvious pressure drop occurs. The hydroxyl number of the product was determined by the phthalic anhydride method. 2, 4-dinitrophenylhydrazine is used for carrying out pre-column derivatization, and the content of formaldehyde, acetaldehyde and acrolein in the polypropylene glycol is measured by a high performance liquid chromatography.

TABLE 2 influence of the reaction temperature on the product properties

Example 3

Synthesis of low molecular weight polypropylene glycols below PPG-1000:

in the embodiment, glycerin is used as an initiator to synthesize the low molecular weight polypropylene glycol, and the specific steps are as follows: the catalyst DMC-1 prepared in example 1 above was used in the synthesis of low molecular weight polypropylene glycols. The specific steps are that polypropylene glycol is synthesized in an autoclave, and the stirring speed and the temperature of the autoclave are controlled. 5g of glycerol initiator and 0.06g of DMC-1 catalyst obtained in example 1 were introduced into an autoclave, and after a plurality of replacements with nitrogen, 50g of propylene oxide was added to the autoclave. And (3) controlling the rotating speed to be 350r/min, starting the reaction for 6 hours under the pressure of 0.5Mpa, removing unreacted monomers, and filtering and separating the product from the catalyst to obtain the polypropylene glycol product. The effect of varying the reaction temperature on the properties of the polypropylene glycol product is shown in Table 3, and the product was tested in the same manner as in example 3.

TABLE 3 influence of the reaction temperature on the product properties

The effect of reaction temperature on various properties of the products was comprehensively analyzed by combining the results of tables 2 and 3. Experimental results show that when the temperature is lower than 100 ℃, the reaction is too slow, the induction period is longer, and the induction period gradually decreases along with the increase of the reaction temperature. The aldehyde content in the polypropylene glycol product increases with increasing reaction temperature. The excessive temperature can oxidize or generate side reaction in the synthesis process to generate aldehyde substances, and the disproportionation reaction rate of propylene oxide is obviously accelerated at high temperature, so that the aldehyde substances are generated. Along with the rise of temperature, the polymerization reaction rate is obviously accelerated, the molecular weight of the polypropylene glycol product is gradually increased, and the monomer conversion rate is gradually increased, but when the temperature is higher than 130 ℃, the polymerization reaction heat effect is serious, the reaction kettle is difficult to remove the reaction heat in time, and the side reaction is obviously increased, so that the monomer conversion rate is reduced, and the molecular weight of the product is reduced. In conclusion, when the reaction temperature is controlled to be 120-130 ℃, the catalyst provided by the invention has extremely high catalytic activity in the process of catalyzing and synthesizing the polypropylene glycol product, the induction period can be shortened to 10min, and the obtained polypropylene glycol product has narrower molecular weight distribution, lower aldehyde value and good color and luster, and is beneficial to the next application of the polypropylene glycol product.

Example 4

The basic procedure is the same as in example 1, except that: the organic ligand L is methyl acetoacetate; the molecular weight of the co-complexing agent P is 8000; the transition metal salt S is Cr (NO) ₃ ) ₃ ·9H ₂ O；

(1) Will be 9X 10 ^-4 A solution A was prepared by dissolving mol of potassium cobalt cyanide in 18ml of water. Will be 9X 10 ^-3 Dissolving mol zinc chloride in 4.5ml water to obtain zinc chloride aqueous solution, and weighing Cr (NO) equivalent to 0.5% of the mass of the zinc chloride aqueous solution ₃ ) ₃ ·9H ₂ O and half of the water volume of methyl acetoacetate are dissolved in zinc chloride aqueous solution to prepare solution B. Wherein, the mole ratio of cobalt potassium cyanide to zinc chloride is 1:10. 0.38g of mesoporous molecular sieve MCM-41 is added into 30ml of mixed solution of water and methyl acetoacetate, and the mixed solution is as follows: 50% of water and 50% of methyl acetoacetate; stirring uniformly to obtain solution C. The mass ratio of the mesoporous molecular sieve carrier MCM-41 to the zinc chloride aqueous solution is 1:15.

(2) Under the oil bath condition of 80 ℃, slowly and synchronously dropwise adding the solution A and the solution B into the solution C of 2000r/min for 20min. Adding 10ml of mixed solution of water and methyl acetoacetate and 0.57g of co-complexing agent P into the solution, and continuously stirring and mixing for 30min; wherein, in the mixed solution of water and methyl acetoacetate: 30% of water and 70% of methyl acetoacetate.

(3) After stirring, cooling the obtained slurry, filtering and separating to obtain a filter cake, washing the obtained filter cake with mixed dissolved slurry consisting of methyl acetoacetate and water for 3 times, and gradually increasing the proportion of the methyl acetoacetate in the mixed solution until the filter cake of the final catalyst is obtained by washing with pure methyl acetoacetate esterified slurry. The final filter cake was dried under vacuum at 80℃to constant weight and ground to give the catalyst, designated DMC-2. The mass ratio of the co-complexing agent P to the zinc chloride aqueous solution is 1:10.

example 5

The basic procedure is the same as in example 1, except that: the organic ligand L is propylene glycol butyl ether; the molecular weight of the co-complexing agent P is 5000, and the co-complexing agent P is obtained through the market; the transition metal salt S is Ce (NO) ₃ ) ₃ ·6H ₂ O；

(1) Will be 5.4X10 ^-3 The mol potassium ferricyanide was dissolved in 18ml of water to prepare solution A. Will be 2.16X10 ^-2 Dissolving mol zinc sulfate in 3.6ml water to obtain zinc sulfate aqueous solution, and weighing Ce (NO) with the mass of 3% of that of the zinc sulfate aqueous solution ₃ ) ₃ ·6H ₂ O and half of the water volume of propylene glycol butyl ether are dissolved in zinc sulfate aqueous solution to prepare solution B. Wherein, the mole ratio of potassium ferricyanide to zinc sulfate is 1:4. 1.41g of mesoporous molecular sieve MCM-41 is added into 30ml of water and propylene glycol butyl ether mixed solution, and the mixed solution is as follows: 75% of water and 25% of propylene glycol butyl ether; stirring uniformly to obtain solution C. The mass ratio of the mesoporous molecular sieve carrier MCM-41 to the zinc sulfate aqueous solution is 1:5.

(2) Under the oil bath condition of 80 ℃, slowly and synchronously dropwise adding the solution A and the solution B into the solution C with the speed of 5000r/min for 20min. Adding 10ml of mixed solution of water and propylene glycol butyl ether and 2.36g of co-complexing agent P into the solution, and continuously stirring and mixing for 30min; wherein, in the mixed solution of water and propylene glycol butyl ether: 30% of water and 70% of propylene glycol butyl ether.

(3) After stirring, cooling the obtained slurry, filtering and separating to obtain a filter cake, washing the obtained filter cake with mixed dissolved slurry consisting of propylene glycol butyl ether and water for 3 times, and gradually increasing the proportion of the propylene glycol butyl ether in the mixed solution until the filter cake is washed with pure propylene glycol butyl ether slurry to obtain a final catalyst filter cake. The final filter cake was dried under vacuum at 70℃to constant weight and ground to give the catalyst, designated DMC-2. The mass ratio of the co-complexing agent P to the zinc sulfate aqueous solution is 1:3.

example 6

The basic procedure is the same as in example 2, except that: 6g of starter polypropylene glycol (Mn=550) and 0.0036g of the catalyst DMC-1 obtained in example 1 were charged into an autoclave, and after a plurality of times of substitution with nitrogen, 30g of propylene oxide was added to the autoclave. The rotating speed is controlled at 250r/min, the initial pressure is 1Mpa, the unreacted monomers are removed after the reaction is carried out for 10 hours at the temperature of 100 ℃, and the polypropylene glycol product is obtained after the product and the catalyst are separated by filtration.

Example 7

The basic procedure is the same as in example 2, except that: 6g of starter polypropylene glycol (Mn=550) and 0.126g of the catalyst DMC-1 obtained in example 1 were charged into an autoclave, and after a plurality of replacements with nitrogen, 120g of propylene oxide was added to the autoclave. The rotation speed is controlled at 550r/min, the initial pressure is 0.5Mpa, unreacted monomers are removed after the reaction is carried out for 5 hours at 140 ℃, and the polypropylene glycol product is obtained after the product and the catalyst are separated by filtration.

FIG. 1 is an SEM image of the preparation of catalyst DMC-1 of example 1, wherein FIG. 1 (a) is a partial SEM image and FIG. 1 (b) is an overall SEM image, showing good bonding of the support to the active component. The carrier MCM-41 molecular sieve is formed by growing together in an agglomeration shape, the grain size is uniform, the arrangement is compact, and a plurality of petal-shaped double metal cyanide catalysts are grown on the molecular sieve.

FIG. 2 shows Zn prepared in comparative example 1 ₃ [Co(CN) ₆ ] ₂ ·12H ₂ The XRD patterns of O and the DMC-1 catalyst prepared in example 1 indicate that the DMC-1 catalyst prepared is in a state where an amorphous form and a monoclinic form coexist, and is mainly in an amorphous state and has extremely low crystallinity. The addition of molecular sieve carrier MCM-41, organic ligand L and co-complexing agent P123 inhibits the formation of catalyst crystals, so that DMC crystals are changed from cubic crystals to monoclinic crystals and amorphous states. This is because of Zn ²⁺ At the AND [ Co (CN) ₆ ] ^3- At the same time of binding, the organic ligand L and the complexing agent P123 react with anions on the surface of the molecular sieve to form chemical bonds, and the organic ligand L and the complexing agent P123 react with Zn ²⁺ Coordination is performed, and the coordination can destroy Zn ₃ [Co(CN) ₆ ] ₂ ·12H ₂ The structure of the O crystal, thereby inhibiting the growth of the catalyst crystal. In addition, la (NO) ₃ ) ₃ ·6H ₂ The addition of O makes the spectrum obviously wider and the crystallinity lower while the catalyst structure is not changed. Research shows that the lower the DMC crystallinity is, the higher the catalytic activity is, so the catalyst prepared by the invention has extremely high catalytic activity in the synthesis of polypropylene glycol.

FIG. 3 shows Zn prepared in comparative example 1 ₃ [Co(CN) ₆ ] ₂ ·12H ₂ O and FTIR spectra of catalyst DMC-1 prepared in example 1, zn is evident from the figure ₃ [Co(CN) ₆ ] ₂ ·12H ₂ The stretching vibration peak of-CN in O and the absorption peak of Co-CN bond have blue shift, which indicates Zn in the catalyst structure ²⁺ -CN-Co ³⁺ And (3) generating a structure. Co-CN and-CN peak position and Zn of prepared catalyst DMC-1 ₃ [Co(CN) ₆ ] ₂ ·12H ₂ O is different, and therefore it can be judged that the catalyst does not contain a cubic crystal structure. This is due to the addition of the organic ligand L and co-complexing agent P123 during the preparation process, which changes the catalyst from a cubic form to a form in which the amorphous structure and the monoclinic form coexist, which corresponds to XRD analysis.

FIG. 4 is a partial FTIR spectrum of the catalyst DMC-1 prepared in example 1, showing the successful reaction of the organic ligand ethyl acetoacetate with Zn ²⁺ Coordination to increase the content of Zn in the catalyst ²⁺ The number of coordinated oxygen atoms further increases the number of active centers and improves the catalytic activity. The added ketone ligand ethyl acetoacetate has tautomerism, and the absorption peak of the ligand ethyl acetoacetate existing in ketone form is 1724cm ^-1 The position of the absorption peak of the enol form is 1629cm ^-1 。

FIG. 5 is a FTIR chart of the polypropylene glycol samples prepared in example 2 (B) and example 3 (C) and the standard sample (A), showing that the synthesized polypropylene glycol samples are consistent with the standard sample. In the figure at 3400cm ^-1 The characteristic absorption peak of stretching vibration of terminal hydroxyl (-OH) appears, 2970cm ^-1 And 2873cm ^-1 With methyl (-CH) ₃ ) Is an antisymmetric and symmetrical telescopic vibration absorption peak of 1458cm ^-1 And 1375.1cm ^-1 Is methyl (-CH) ₃ ) Is not symmetrical in deformation vibrationDynamic and symmetric deformation vibration absorption peaks. At 1100cm ^-1 The strong absorption peak is an ether bond (C-O-C) antisymmetric telescopic vibration characteristic absorption peak, the repeated times of the group in the main chain of polyether are large, and the absorption intensity is high, so that the characteristic absorption band of polyether compounds is identified. At 945cm ^-1 The absorption peak is the symmetrical telescopic vibration absorption peak of ether bond. Furthermore, at 1647cm in the figure ^-1 A weaker absorption peak appears, indicating that the synthesized sample contains some unsaturation. This is caused by side reactions occurring during the course of the reaction. The absorption peak intensity of unsaturated double bond is relatively weak, which indicates that the content of double bond is low, and indicates that the prepared polypropylene glycol sample has low unsaturation degree.

FIG. 6 is a sample of polypropylene glycol prepared in example 3 ¹ HNMR diagram. The peaks in the figure can be divided into two regions, a first region (region I) at δ1.05-1.07 and a second region (region II) at δ2.8-3.9. The I region is an absorption peak of methyl protons on the epoxypropane chain segment, and the methyl groups are connected with the methine groups so that the peak cracking is divided into two peaks. The II region is the absorption peak of the rest protons in the polyether polyol molecule and comprises the methylene and hydrogen cores in the methyne on the epoxypropane chain segment, the methylene and hydrogen cores in the methyne on the terminal glycerin chain segment and the hydrogen cores in the terminal hydroxyl group.

Claims

1. A double metal cyanide complex catalyst characterized in that the catalyst satisfies the general formula:

MCM@M ¹ _a [M ² _b (CN) _c ] _d ·vM ¹ (X) _e ·wL·xH ₂ O·yP·zS

wherein MCM represents mesoporous molecular sieve, M ¹ Is a divalent metal ion; m is M ² Is a transition metal ion; x is Cl ^- 、SO ₄ ^2- One of them; a. b, c, d, e is a positive number; l is an organic ligand, P is a co-complexing agent, S is a transition metal salt; v=0.5 to 3,w =0.1 to 2, x=0.1 to 2, y=0.03 to 0.1, z=0.0006 to 0.01;

the co-complexing agent is polyoxypropylene ethylene oxide copolymer polyol with the molecular weight of 2000-8000;

the organic ligand is ethers and/or esters; the ethers are selected from ethylene glycol butyl ether and/or propylene glycol butyl ether, and the esters are selected from methyl acetoacetate and/or ethyl acetoacetate;

the transition metal salt is La (NO) ₃ ) ₃ ·6H ₂ O、Cr(NO ₃ ) ₃ ·9H ₂ O、Ce(NO ₃ ) ₃ ·6H ₂ At least one of O.

2. The double metal cyanide complex catalyst of claim 1, wherein the transition metal ion is selected from Co ³⁺ And/or Fe ²⁺ 。

3. A method for preparing the double metal cyanide complex catalyst of claim 1, comprising the steps of:

4. The method for producing a double metal cyanide complex catalyst according to claim 3, wherein in the step (1), the metal cyanide complex salt is potassium cobalt cyanide, potassium ferricyanide or potassium nickel cyanide, and the zinc salt is zinc chloride or zinc sulfate.

5. The method for producing a double metal cyanide complex catalyst according to claim 3, wherein in the step (1), the molar ratio of the metal cyanide complex salt to the zinc salt is 1:4 to 10.

6. The method for preparing a double metal cyanide complex catalyst according to claim 3, wherein in the step (2), the mass ratio of the mesoporous molecular sieve carrier to the zinc salt aqueous solution is 1:5-15.

7. The method for preparing a double metal cyanide complex catalyst according to claim 3, wherein in step (3), the mass ratio of the co-complexing agent to the zinc salt aqueous solution is 1:3 to 10.

8. A method for synthesizing polypropylene glycol using the double metal cyanide complex catalyst of claim 1, comprising the steps of:

the double metal cyanide complex catalyst as claimed in claim 1 and an initiator are put into a reactor, inert gas is introduced into the reactor, propylene oxide monomer is added into the reactor, and the mass ratio of the propylene oxide to the initiator is 5-20:1; the addition amount of the catalyst is 100-1000 ppm of the addition amount of the raw materials.