Double-metal cyanide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a double-metal cyanide catalyst as well as a preparation method and application thereof, and belongs to the technical field of double-metal cyanide catalysts. The preparation method of the double-metal cyanide catalyst comprises the following steps: S1, mixing a metal salt aqueous solution and a metal cyanide aqueous solution, and reacting to obtain double-metal cyanide slurry; and S2, adding acid into the double-metal cyanide slurry, aging, centrifuging and drying to obtain the double-metal cyanide catalyst, the weight ratio of the double metal cyanide slurry to the acid in the step S2 is 1: (0.001-0.004); the metal cyanide in the metal cyanide aqueous solution comprises cobalt element. When the double metal cyanide catalyst is used for preparing polyether, the chromaticity of the polyether can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of double metal cyanide catalysts, and in particular relates to a double metal cyanide catalyst and a preparation method and application thereof. Background Art

[0002] Double metal cyanide catalyst (DMC) is a commonly used catalyst for polyether synthesis. Research has been conducted abroad since the 1960s. In the 1990s, the catalytic efficiency of DMC was greatly improved. The use of 30-100ppm in the synthesis can efficiently complete the polymerization, thus achieving large-scale commercialization. The polyether synthesized using DMC catalyst has the advantages of low unsaturation, high functionality, and good molecular regularity.

[0003] However, when the existing cobalt-containing DMC is used in the preparation of polyether, it often exhibits a cobalt pink color, which affects the use of the polyether. Summary of the invention

[0004] Therefore, the present invention provides a double metal cyanide catalyst and a preparation method and application thereof, which can reduce the chromaticity of polyether when used as a catalyst to prepare polyether.

[0005] To this end, the present invention provides the following technical solutions.

[0006] In a first aspect, the present invention provides a method for preparing a double metal cyanide catalyst, comprising the following steps:

[0007] S1, mixing and reacting a metal salt aqueous solution and a metal cyanide aqueous solution to obtain a double metal cyanide slurry;

[0008] S2, adding acid to the double metal cyanide slurry, aging, centrifuging, and drying to obtain the double metal cyanide catalyst;

[0009] The weight ratio of the double metal cyanide slurry to the acid in S2 is 1:(0.001-0.004);

[0010] The metal cyanide in the metal cyanide aqueous solution includes cobalt element.

[0011] In one possible embodiment, the acid comprises an organic acid;

[0012] Preferably, the organic acid contains 2 to 7 carbons;

[0013] Preferably, the organic acid comprises at least one of lactic acid, glycolic acid, citric acid and adipic acid.

[0014] In a possible implementation manner, the aging time is 0.3 to 1.5 hours.

[0015] In a possible implementation, in S1, the metal salt aqueous solution and the metal cyanide aqueous solution are mixed and reacted while being stirred and ground;

[0016] Optionally, the mixed and reacted slurry in S1 is centrifuged to obtain a first slurry and a second slurry, wherein the particle size of the second slurry is greater than the particle size of the first slurry; the first slurry is used as a double metal cyanide slurry for S2, and the second slurry is stirred and ground again;

[0017] Optionally, based on the total mass of the double metal cyanide in the double metal cyanide slurry, the mass content of the double metal cyanide with a particle size of 1 to 100 μm is greater than 90%.

[0018] In one possible embodiment, the reactor A used in S1 includes a grinding stirring reactor and a centrifugal device;

[0019] Optionally, the material outlet of the grinding and stirring reactor is connected to the material inlet of the centrifugal device;

[0020] Optionally, the grinding and stirring reactor includes a metal salt aqueous solution feed inlet, a metal cyanide aqueous solution feed inlet and a circulating slurry inlet; the centrifugal device includes a first slurry outlet and a second slurry outlet, and the second slurry outlet is connected to the circulating slurry inlet.

[0021] In a possible embodiment, the reactor B used for aging is a plug flow reactor;

[0022] Optionally, the height-to-diameter ratio of the plug flow reactor is ≥10 / 1, preferably (20-100) / 1.

[0023] In a possible embodiment, the metal salt in the metal salt aqueous solution includes one or more of zinc chloride, ferric chloride, ferrous chloride, nickel chloride, cobalt chloride, zinc bromide, ferric bromide, ferrous bromide, ferrous sulfate, zinc acetate, zinc acetylacetonate, and nickel acetylacetonate; preferably zinc chloride and zinc bromide;

[0024] and / or

[0025] The metal cyanide includes one or more of potassium hexacyanocobaltate and sodium hexacyanocobaltate.

[0026] In a possible embodiment, the metal salt aqueous solution includes an organic ligand, and the organic ligand includes alcohol and / or ether;

[0027] Preferably, the organic complexing agent includes one or more of ethanol, n-propanol, isopropanol, glycerol, diglycerol, polyglycerol, ethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, n-butanol, isobutanol, tert-butanol, dioxane, dioxolane, tetrahydrofuran, butyl ether, ethyl propyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol monomethyl ether.

[0028] In a possible implementation, the grinding and stirring reactor further includes: a shell, a stirring shaft, a dynamic grinding sheet, and a static grinding sheet.

[0029] In a possible embodiment, the outer diameter of the movable grinding plate is a disc-shaped structure of 40-1200 mm, preferably 60-800 mm; each movable grinding plate is provided with 10-1000, preferably 15-100 first channel holes; the total flow area of ​​all first channel holes 11 is preferably 8-600 mm 2 , more preferably 10-400mm 2 ; The radial distance from the outermost edge of the dynamic grinding plate to the inner wall of the reaction channel is 1-20mm, preferably 1-10mm.

[0030] In a possible embodiment, the shape of the static grinding plate is not particularly limited, but is preferably a ring with an outer diameter of 40-1200 mm, preferably 60-800 mm; each static grinding plate is provided with 10-1000, preferably 15-100 second channel holes; the total flow area of ​​the second channel holes is preferably 8-600 mm 2 , more preferably 10-400mm 2 .

[0031] In a possible implementation, the shape of the disc is not particularly limited, but is preferably a disc with an outer diameter of 50-2000 mm, preferably 120-500 mm. Each disc is provided with 4-20, preferably 6-12 third channel holes, and the cross-sectional shape of the third channel holes is circular, triangular, rectangular, rhombus, trapezoidal, polygonal or elliptical, etc., preferably circular; the opening ratio of the third channel holes relative to the disc area is 10-80%, preferably 20-70%.

[0032] In a possible implementation, the stirring shaft in the centrifugal device may not be connected to the stirring shaft in the grinding agitator, but may be a separately arranged stirring shaft. In this case, the rotation speed of the stirring shaft in the centrifugal device may be adjusted automatically.

[0033] In a possible embodiment, a metal salt aqueous solution and a metal cyanide aqueous solution are continuously added to a reactor A at a certain ratio under a temperature condition of 20 to 50° C., and the reaction liquid is sheared and mixed under the mutual movement of the dynamic grinding plate and the static grinding plate of the grinding and stirring reactor, so that the catalyst particles become uniform and fine, and the large particle catalyst returns to the reactor A from the bottom through the delivery pump, and the small particle catalyst enters the reactor B with the liquid, and is aged and crystallized in the presence of acid, and then centrifuged and dried to finally obtain a double metal cyanide catalyst. The delivery pump can be a centrifugal pump, a rotor pump or a diaphragm pump.

[0034] In a possible implementation, the mass ratio of the metal salt to the metal cyanide in the metal salt aqueous solution and the metal cyanide aqueous solution is 1 to 10, preferably 1.64 to 6.55.

[0035] The method has simple process, short production cycle, saves electricity and water, and has low production cost. At the same time, the prepared catalyst has high activity and still has high activity after long-term storage.

[0036] The metal salt aqueous solution and the cyanide aqueous solution are fed into the grinding and stirring reactor A through their respective feeding ports at a rate.

[0037] The mass ratio of the metal salt in the metal salt aqueous solution to the metal cyanide in the metal cyanide aqueous solution is 0.5 to 10 / 1, preferably (1.5 to 6.5) / 1.

[0038] The present invention adopts a stirred grinding reactor for preparation, and the rotation speed of the stirring shaft is 80-10000r / min, preferably 100-5000r / min.

[0039] The feed solution obtained in step B is centrifuged for dehydration, and dried to constant weight under vacuum conditions at 40-50° C. to obtain a double metal cyanide catalyst.

[0040] In a second aspect, the present invention provides a double metal cyanide catalyst prepared according to the method.

[0041] In a third aspect, the present invention provides an application of a double metal cyanide catalyst in polyether synthesis.

[0042] The technical solution of the present invention has the following advantages:

[0043] 1. The preparation method of the double metal cyanide catalyst of the present invention comprises the following steps: S1, mixing and reacting a metal salt aqueous solution and a metal cyanide aqueous solution to obtain a double metal cyanide slurry; S2, adding an acid to the double metal cyanide slurry, aging, centrifuging, and drying to obtain the double metal cyanide catalyst; the weight ratio of the double metal cyanide slurry to the acid in S2 is 1: (0.001-0.004); the metal cyanide in the metal cyanide aqueous solution includes cobalt element.

[0044] The double metal cyanide slurry of the present invention is aged after adding acid, which can avoid the secondary aggregation and enlargement of the double metal cyanide particles in the slurry, maintain the original particle size, and help improve the activity of the catalyst. It can also help reduce the chromaticity of the DMC polyether in the subsequent catalytic preparation of polyether, and avoid the obtained polyether showing the pink color of cobalt. In addition, the amount of acid used must also meet the dosage range of the present invention. Too little acid has a poor effect, and too much acid increases the cost and has the risk of damaging the double metal cyanide to decompose it and produce hydrocyanic acid.

[0045] The polyether synthesized by using the catalyst has the advantages of high activity and low unsaturation, and the content of high molecular byproducts in the prepared polyether polyol is less than 4%.

[0046] 2. The aging time is 0.3 to 1.5 hours. Aging time within this range can keep the particle size of the catalyst within an appropriate range, making it easy to separate and having higher catalytic activity.

[0047] 3. In S1, the metal salt aqueous solution and the metal cyanide aqueous solution are mixed and reacted while being stirred and ground; based on the total mass of the double metal cyanide in the double metal cyanide slurry, the mass content of the double metal cyanide with a particle size of 1 to 100 μm is greater than 90%.

[0048] Stirring and grinding during the mixing reaction can further pulverize the product and make the catalyst particle size uniform. The mass content of the obtained double metal cyanide with a particle size of 1 to 100 μm is greater than 90%, which helps to further improve the activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 It is a flow chart of the preparation method of the present invention;

[0051] Figure 2It is a schematic diagram of the structure of reactor A;

[0052] Figure 3 It is a top view schematic diagram of the dynamic grinding sheet;

[0053] Figure 4 It is a top view schematic diagram of a static grinding sheet;

[0054] Figure 5 A schematic diagram of a disc viewed from above;

[0055] Figure 6 It is a top view of the disc fixing sleeve;

[0056] Figure 7 This is the AA section view of the disc fixing sleeve;

[0057] Figure 8 Schematic diagram of the angle between the disc busbar and the axial direction.

[0058] Reference numerals:

[0059] 1-shell; 2-metal salt aqueous solution feed port; 3-circulating slurry inlet; 4-metal cyanide aqueous solution feed port; 5-stirring shaft; 6-dynamic grinding disc; 7-static grinding disc; 8-small particle slurry discharge port; 9-large particle slurry discharge port; 10-disc; 11-first channel hole; 12-second channel hole; 13-disc fixing sleeve. DETAILED DESCRIPTION

[0060] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0061] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0062] Polypropylene glycol: number average molecular weight 2000, Wanhua Chemical Group Co., Ltd.

[0063] Propylene oxide: Wanhua Chemical Group Co., Ltd.

[0064] Polyoxypropylene triol: A700, number average molecular weight 700, Wanhua Chemical Group Co., Ltd.

[0065] Example 1

[0066] This embodiment provides a method for preparing a double metal cyanide catalyst, using a device such as Figure 1 As shown, it includes: reactor A, reactor B, centrifuge and dryer.

[0067] Reactor A includes a grinding agitator and a centrifuge. Figure 2 As shown, the grinding and stirring reactor comprises: a shell 1, a metal salt aqueous solution feed port 2, a circulating slurry inlet 3, an annular metal cyanide aqueous solution feed port 4, a stirring shaft 5, a dynamic grinding sheet 6 and a static grinding sheet 7. The shell 1 is coaxially arranged with the stirring shaft 5, the dynamic grinding sheet 6 and the static grinding sheet 7 are arranged spaced apart from each other along the axial direction of the stirring shaft 5, the dynamic grinding sheet 6 is fixed on the stirring shaft, and the static grinding sheet 7 is fixed on the inner wall of the shell 1, the dynamic grinding sheet 6 is provided with a first channel hole 11, and the static grinding sheet 7 is provided with a second channel hole 12 (such as Figure 3 , Figure 4 shown).

[0068] One or more dynamic grinding plates 6 are provided, and one or more static grinding plates 7 are provided, and the dynamic grinding plates and static grinding plates are arranged in stages according to the flow direction of the material; and the first stage contacted by the material is the static grinding plate.

[0069] The dynamic grinding plate 6 also has a central hole, so that the stirring shaft 5 passes through the central hole, and the dynamic grinding plate 6 is fixed on the stirring shaft 5 and is located in the reaction channel. The number of stages of the dynamic grinding plates 6 arranged from top to bottom is 2-6, preferably 2-4, and the dynamic grinding plates 6 and the stirring shaft 5 rotate together; each dynamic grinding plate 6 is provided with a first channel hole 11, and the cross-sectional shape of the first channel hole 11 is circular, triangular, rectangular, rhombus, trapezoidal, polygonal or elliptical, etc., preferably circular, rectangular, triangular; the first channel holes 11 on the dynamic grinding plate 6 can be evenly distributed, for example, distributed at equal distances in the circumferential direction, or can be unevenly distributed, but preferably evenly distributed. The ratio of the total area of ​​the first channel holes 11 to the total area of ​​the dynamic grinding plate 6 is the opening rate of the dynamic grinding plate, which is 10-80%, preferably 20-70%.

[0070] The static grinding sheet 7 also has a central hole, through which the stirring shaft 5 passes, and the static grinding sheet 7 is fixed on the inner wall of the reactor shell and located in the reaction channel. The number of static grinding sheets 7 arranged from top to bottom is 1-6, preferably 2-4; the axial distance between each level of static grinding sheet 7 and the dynamic grinding sheet 6 of the adjacent level is 1-50mm, preferably 1-30mm, more preferably 1-25mm, and most preferably 2-15mm; the static grinding sheet 7 is provided with a second channel hole 12, and the cross-sectional shape of the second channel hole 12 is circular, triangular, rectangular, rhombus, trapezoidal, polygonal or elliptical, etc., preferably circular, rectangular, triangular; the second channel holes 12 can be evenly distributed on the static grinding sheet 7, for example, distributed at equal distances in the radial or circumferential direction of the ring, or can be non-uniformly distributed, preferably evenly distributed. The ratio of the second channel holes 12 to the total area of ​​the static grinding sheet 7 is the static grinding sheet opening rate, which is 10-80%, preferably 20-70%. The radial distance from the innermost edge of the static grinding plate 7 to the outermost edge of the stirring shaft 5 is 1-10 mm, preferably 1-5 mm.

[0071] The centrifugal device includes a small particle slurry outlet 8, a large particle slurry outlet 9 and a disc 10; the small particle slurry outlet 8 is arranged above the centrifugal device, and the large particle slurry outlet is arranged at the bottom of the centrifugal device. The slurry feed port of the centrifugal device is connected to the discharge port of the grinding stirrer. The large particle slurry outlet 9 is connected to the circulating slurry inlet 3 of the grinding stirrer through an external circulation pipeline, and a circulation pump is arranged on the external circulation pipeline.

[0072] The stirring shaft 5 is divided into two sections, the upper section is fixed to the dynamic grinding disc, and the lower section is connected to the disc fixing sleeve 13. The disc fixing sleeve is a sleeve-type cylindrical structure. The top view of the disc fixing sleeve is as shown in FIG. Figure 6 As shown, Figure 6 The AA section is as follows Figure 7 As shown, the stirring shaft 5 passes through the inner wall of the disc fixing sleeve and is fixed to the stirring shaft 5 at the upper and lower top ends. The disc fixing sleeve is a hollow structure with openings at the upper and lower ends, and the material can enter the bottom of the reactor A through the openings at the upper and lower ends. The outer wall of the disc fixing sleeve is connected and fixed to the disc 10, and the disc 10 can rotate with the stirring shaft 5.

[0073] The angle α between the disc busbar and the axial direction is 30 to 60° (e.g. Figure 8 As shown in FIG. 1 , the number of discs arranged from top to bottom is 4-12, preferably 6-9. The discs 10 rotate together with the stirring shaft 5; each disc 10 is provided with a third channel hole (as shown in FIG. Figure 5As shown), the third channel hole is located at the outer edge of the disc, and the ratio of the distance from the center of the third channel hole to the center of the stirring shaft 5 to the radius of the disc is 0.5-0.9, preferably 0.6-0.7. The third channel holes can be evenly distributed on the disc, for example, equidistantly distributed in the circumferential direction, or non-uniformly distributed, but preferably evenly distributed.

[0074] The material of the reactor A provided by the present invention is a conventional material in the art, including but not limited to steel, glass, ceramic, alloy, silicon carbide or enameled steel.

[0075] The grinding stirrer of this embodiment is alternately provided with four static grinding plates and three dynamic grinding plates from top to bottom, the spacing between the dynamic and static grinding plates is 5 mm, the diameter of the dynamic grinding plate is 96 mm, the inner edge of the static grinding plate is 2 mm away from the outer side of the stirring shaft, the first channel hole 11 on the dynamic grinding plate 6 and the second channel hole 12 on the static grinding plate 7 are both circular, with a diameter of 10 mm and are evenly distributed. The porosity of the dynamic grinding plate and the porosity of the static grinding plate are both 30%, and the inner diameter of the reactor A is 100 mm; 8 levels of discs are evenly distributed in the centrifugal device, the vertical distance between adjacent discs is 8 mm, and 8 third channel holes with a diameter of 20 mm are evenly distributed on each disc. The ratio of the distance from the center of the third channel hole to the center of the stirring shaft 5 to the radius of the disc is 0.65.

[0076] Reactor B is a plug flow reactor with a diameter of 160 mm and a length of 12000 mm.

[0077] The preparation method of the double metal cyanide catalyst of this embodiment includes:

[0078] A metal salt aqueous solution is prepared, which includes, by mass percentage, 60.5% water, 7.9% zinc chloride, and 31.6% tert-butyl alcohol; and a metal cyanide aqueous solution is prepared, which includes, by mass percentage, 95% water and 5% potassium hexacyanocobaltate.

[0079] The speed of the grinding stirrer was adjusted to 400 rpm. Since the centrifugal device was coaxial with the grinding stirrer, its speed was also 400 rpm, and it was kept stable for 3 minutes. The metal salt aqueous solution and the metal cyanide aqueous solution were pumped into the grinding stirrer from the metal salt aqueous solution feed port 2 and the metal cyanide aqueous solution feed port 4 at a feed rate of 6 L / min, respectively, and the mass ratio of zinc chloride to potassium hexacyanocobaltate was 1.58 / 1. Keep the small particle slurry outlet 8 closed, and allow the liquid to return to the circulating slurry inlet 3 through the large particle slurry outlet 9. After the grinding agitator, the centrifugal equipment and the external circulation pipeline are filled with liquid, turn on the circulation pump and open the small particle slurry outlet 8 at the same time. The large particle slurry at the bottom of the centrifugal equipment is recirculated into the grinding agitator, and the small particle slurry begins to transfer backward to the reactor B. At the inlet of the reactor B, lactic acid is pumped in at a flow rate of 12 g / min (the sum of the feed materials of the reactor A (i.e., the metal salt aqueous solution and the metal cyanide aqueous solution) is also the feed amount of the reactor B, that is, the mass ratio of the slurry entering the reactor B to the lactic acid is 1:0.001), and aged in the reactor B. It can be calculated by the volume and feed amount of the reactor B that the aging time of the material in the reactor B is 0.33h (i.e., the residence time in the reactor B). Samples are taken at the outlet of the reactor B to measure the particle size. The white slurry liquid passing through reactor B is treated by a centrifuge to remove the solvent, and the solid is washed with a mixed solution of water, tert-butyl alcohol, and polypropylene glycol (mass ratio 89.3 / 8.9 / 1.8) until the potassium ion in the system is less than 5 ppm. The solid is dried under vacuum at 50° C. to constant weight to obtain a white powder solid, which is a double metal cyanide catalyst.

[0080] The present invention realizes rapid mixing and rapid reaction of multiple streams of materials, avoids flocculation or aggregation of catalyst slurry particles, and further avoids embedding or accumulation of impurity ions (such as potassium ions) on the catalyst.

[0081] Example 2

[0082] This embodiment provides a method for preparing a double metal cyanide catalyst. The device used is the same as that of Embodiment 1 except that the reactor B has a diameter of 300 mm and a length of 10000 mm. The preparation method comprises:

[0083] Prepare a metal salt aqueous solution with a mass concentration of 60.5% water, 7.9% zinc chloride, and 31.6% tert-butyl alcohol;

[0084] A metal cyanide aqueous solution is prepared with a mass concentration of 95% water and 5% potassium hexacyanocobaltate.

[0085] The speed of the grinding stirrer was adjusted to 200 rpm. Since the centrifugal device was coaxial with the grinding stirrer, its speed was also 200 rpm and stabilized for 3 minutes. The metal salt aqueous solution and the metal cyanide aqueous solution were pumped into the grinding stirrer from the metal salt aqueous solution feed port 2 and the metal cyanide aqueous solution feed port 4 at a feed rate of 6 L / min and 3 L / min, respectively, and the mass ratio of zinc chloride to potassium hexacyanocobaltate was 3.16 / 1. Keep the small particle slurry outlet 8 closed, and allow the liquid to return to the circulating slurry inlet 3 through the large particle slurry outlet 9. After the grinding agitator, the centrifugal device and the external circulation pipeline are filled with liquid, turn on the circulation pump and open the small particle slurry outlet 8 at the same time. The large particle slurry at the bottom of the centrifugal device is recirculated into the grinding agitator, and the small particle slurry begins to transfer backward to the reactor B. At the inlet of the reactor B, the hydroxyacetic acid solution (based on the total mass of the hydroxyacetic acid solution, including 30% hydroxyacetic acid, 60% water, and 10% tert-butanol) is pumped in at a flow rate of 60 g / min, that is, the amount of hydroxyacetic acid added is 18 g / min, and the ratio of the slurry entering the reactor B to the hydroxyacetic acid is 1:0.002. Aging is carried out in the reactor B for an aging time of 1.31 h. Samples are taken at the outlet of the reactor B to measure the particle size. The white slurry liquid passing through reactor B is treated by a centrifuge to remove the solvent, and the solid is washed with a mixed solution of water, tert-butyl alcohol, and polypropylene glycol (mass ratio 89.3 / 8.9 / 1.8) until the potassium ion in the system is less than 5 ppm. The solid is dried under vacuum at 50° C. to constant weight to obtain a white powder solid, which is a double metal cyanide catalyst.

[0086] Example 3

[0087] This embodiment provides a method for preparing a double metal cyanide catalyst. The device used is the same as that in Example 1. The preparation method includes:

[0088] Prepare a metal salt aqueous solution with a mass concentration of 60.5% water, 7.9% zinc chloride, and 31.6% tert-butyl alcohol;

[0089] A metal cyanide aqueous solution is prepared with a mass concentration of 95% water and 5% potassium hexacyanocobaltate.

[0090] The speed of the grinding stirrer was adjusted to 1000 rpm. Since the centrifugal device was coaxial with the grinding stirrer, its speed was also 1000 rpm and was kept stable for 3 minutes. The metal salt aqueous solution and the metal cyanide aqueous solution were pumped into the grinding stirrer from independent inlets at a feed rate of 4 L / min and 1 L / min, respectively, and the mass ratio of zinc chloride to potassium hexacyanocobaltate was 6.32 / 1. Keep the small particle slurry outlet 8 closed, and the other liquid returns to the circulating slurry inlet 3 through the large particle slurry outlet. After the grinding agitator, the centrifugal equipment and the external circulation pipeline are full of liquid, turn on the circulation pump and open the small particle slurry outlet 8 at the same time. The large particle slurry at the bottom of the centrifugal equipment recirculates into the grinding agitator, and the small particle slurry begins to transfer backward to the reactor B. At the inlet of the reactor B, citric acid solution (based on the total mass of the citric acid solution, including 30% citric acid, 60% water, and 10% tert-butanol) is pumped in at a flow rate of 66.7 g / min, that is, the actual amount of citric acid added is 20 g / min (the mass ratio of slurry to citric acid is 1:0.004), and aging is carried out in the reactor B for 0.8 h. Samples are taken at the outlet of the reactor B to measure the particle size. The white slurry liquid passing through reactor B is treated by a centrifuge to remove the solvent, and the solid is washed with a mixed solution of water, tert-butyl alcohol, and polypropylene glycol (mass ratio 89.3 / 8.9 / 1.8) until the potassium ion in the system is less than 5 ppm. The solid is dried under vacuum at 50° C. to constant weight to obtain a white powder solid, which is a double metal cyanide catalyst.

[0091] Comparative Example 1

[0092] This comparative example provides a method for preparing a double metal cyanide catalyst, which is basically the same as Example 1, except that lactic acid is not added to the reactor B to obtain the double metal cyanide catalyst.

[0093] Comparative Example 2

[0094] This comparative example provides a preparation method of a double metal cyanide catalyst, which is basically the same as Example 1, except that the double metal cyanide slurry obtained in reactor A does not enter reactor B for acid aging, but directly enters the subsequent centrifugation and drying process to obtain a double metal cyanide catalyst.

[0095] Test Case

[0096] (1) Particle size test method of double metal cyanide catalyst (DMC): 1 g of the slurry at the outlet of reactor B was dispersed in a mixture of 100 g of tert-butyl alcohol and 100 g of polyoxypropylene triol. After ultrasonic dispersion for 10 min, the particle size was tested using a Dandong BetterSize 2000 laser particle size analyzer.

[0097] The test results are shown in Table 1.

[0098] Table 1

[0099]

[0100] As can be seen from Table 1, the catalyst prepared in the present invention is mainly composed of small-sized particles, which avoids the secondary aggregation and enlargement of double metal cyanide particles in the slurry, and helps to improve the activity of the catalyst.

[0101] (2) Activity of DMC: Using the rate test method, 70 g of polyoxypropylene triol and 0.057 g of DMC (the concentration of the catalyst in the final synthesized polyether polyol is about 100 ppm) were added to a 1L reactor. After nitrogen replacement, the temperature was raised to 105°C and vacuum degassed for 1 hour under stirring. After nitrogen was pressurized to normal pressure, 10 g of propylene oxide (PO) was added at one time. The reaction pressure was monitored until the reaction pressure began to decrease, indicating that DMC was activated. The remaining 490 g of propylene oxide was gradually added to ensure that the reactor pressure was below 40 psi. After addition, the reactor was kept at 105°C for aging for 1 hour. After degassing and cooling, the final polyether polyol was obtained.

[0102] The activation time is the time from the one-time addition of 10 g of propylene oxide (PO) to the start of the reaction pressure drop.

[0103] The reaction rate is the slope of the plot of PO consumption (g) versus reaction time (min), and PO consumption (g) refers to the cumulative amount of propylene oxide added during the gradual addition of the remaining 490 g of propylene oxide.

[0104] (3) Color test of polyether polyols: A colorimeter, model ColorQuest XT, Hunterlab, was used to measure the A value of the polyether polyols (the larger the A value, the redder the color).

[0105] The test results are shown in Table 2.

[0106] Table 2

[0107]

[0108] As shown in Table 2, the double metal cyanide catalyst prepared in the present invention has a short activation time and a fast reaction rate, indicating that the double metal cyanide catalyst prepared in the present invention has a higher catalytic efficiency. In addition, the A value of the present invention is significantly reduced, which can improve the catalytic efficiency while avoiding the cobalt pink color of the prepared polyether.

[0109] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing a double metal cyanide catalyst, characterized in that: The following steps are involved: S1, mixing and reacting a metal salt aqueous solution and a metal cyanide aqueous solution to obtain a double metal cyanide slurry; S2, adding acid to the double metal cyanide slurry, aging, centrifuging, and drying to obtain the double metal cyanide catalyst; The weight ratio of the double metal cyanide slurry to the acid in S2 is 1:(0.001-0.004); The metal cyanide in the metal cyanide aqueous solution includes cobalt element.

2. The method for preparing a double metal cyanide catalyst according to claim 1, characterized in that: The acid comprises an organic acid; Preferably, the organic acid contains 2 to 7 carbons; Preferably, the organic acid comprises at least one of lactic acid, glycolic acid, citric acid and adipic acid.

3. The method for preparing a double metal cyanide catalyst according to claim 1, characterized in that: The aging time is 0.3 to 1.5 hours.

4. The method for preparing a double metal cyanide catalyst according to claim 1, characterized in that: In S1, the metal salt aqueous solution and the metal cyanide aqueous solution are mixed and reacted while being stirred and ground; Optionally, the mixed and reacted slurry in S1 is centrifuged to obtain a first slurry and a second slurry, and the particle size of the second slurry is greater than the particle size of the first slurry; The first slurry is used as double metal cyanide slurry for S2, and the second slurry is stirred and ground again; Optionally, based on the total mass of the double metal cyanide in the double metal cyanide slurry, the mass content of the double metal cyanide with a particle size of 1 to 100 μm is greater than 90%.

5. The method for preparing a double metal cyanide catalyst according to claim 4, characterized in that: The reactor A used in S1 includes a grinding stirring reactor and a centrifugal device; Optionally, the material outlet of the grinding and stirring reactor is connected to the material inlet of the centrifugal device; Optionally, the grinding and stirring reactor comprises a metal salt aqueous solution feed inlet, a metal cyanide aqueous solution feed inlet and a circulating slurry inlet; The centrifugal device includes a first slurry outlet and a second slurry outlet, and the second slurry outlet is connected to the circulating slurry inlet.

6. The method for preparing a double metal cyanide catalyst according to any one of claims 1 to 5, characterized in that: The reactor B used for the aging is a plug flow reactor; Optionally, the height-to-diameter ratio of the plug flow reactor is ≥10 / 1, preferably (20-100) / 1.

7. The method for preparing a double metal cyanide catalyst according to any one of claims 1 to 5, characterized in that: The metal salt in the metal salt aqueous solution includes one or more of zinc chloride, ferric chloride, ferrous chloride, nickel chloride, cobalt chloride, zinc bromide, ferric bromide, ferrous bromide, ferrous sulfate, zinc acetate, zinc acetylacetonate, and nickel acetylacetonate; and / or The metal cyanide includes one or more of potassium hexacyanocobaltate and sodium hexacyanocobaltate.

8. The method for preparing a double metal cyanide catalyst according to any one of claims 1 to 5, characterized in that: The metal salt aqueous solution includes an organic ligand, and the organic ligand includes alcohol and / or ether; Preferably, the organic complexing agent includes one or more of ethanol, n-propanol, isopropanol, glycerol, diglycerol, polyglycerol, ethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, pentaerythritol, sorbitol, sucrose, n-butanol, isobutanol, tert-butanol, dioxane, dioxolane, tetrahydrofuran, butyl ether, ethyl propyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol monomethyl ether.

9. A double metal cyanide catalyst prepared according to the method according to any one of claims 1 to 8.

10. Use of the double metal cyanide catalyst according to claim 9 in polyether synthesis.

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