Catalyst Separation Process

Abstract

A process for separating a catalyst component from a catalyst-containing slurry by centrifugation, comprising separating the catalyst component from a mother liquor of the catalyst-containing slurry using a stacked disc centrifuge equipped with a self-draining function, wherein solids discharge from the stacked disc centrifuge is enhanced by adding a wash liquid to the bowl and solids discharge chute of the stacked disc centrifuge.

Description

[Technical field]

[0001] The present invention relates to a process for separating and washing a catalyst from a mother liquor using a stacked disc centrifuge equipped with self-draining capabilities. [Background technology]

[0002] Introduction The type of centrifuge most commonly known in the prior art and used to perform separation of hard to filter catalyst from mother liquor is a laboratory-scale spin tube centrifuge. A problem with the prior art process of separating such hard to filter catalyst from mother liquor using a laboratory-scale spin tube centrifuge is that the volume of the spin tube is limited to a few liters at most, and the resulting separated catalyst must be removed manually, further limiting the throughput. This results in a longer separation time per gram of material. For example, by using a laboratory-scale disk centrifuge instead of a spin tube centrifuge in the present application, the separation time per gram of material is reduced by at least two times. In addition, laboratory-scale spin tube centrifuges are not suitable for use at pilot plant scale and commercial plant scale. Therefore, there is a need for a centrifuge process for catalyst separation from mother liquor in which the time to separate catalyst from mother liquor, especially non-filterable or hard to filter catalyst, is reduced, and the process is viable for use at pilot and / or commercial scale. Based on the particle size of the catalyst, especially when the catalyst is less than 5 micrometers in particle size, traditional filtration techniques such as vacuum and pressure filtration cannot be used because the flux through the filter media is very low due to the high resistance of the deposited cake.

[0003] So far, very little has been revealed in the prior art related to catalysts and centrifugation. In the article "Chemical Interesterification of Palm, Palm Kernel and Coconut Oils" by Laning, Steven J., J. Am. Oil Chem. SOC. 1985, 62(2), 400-404, a general description is given of the neutralization of the catalyst with water, followed by subjecting the catalyst to a centrifugation and drying operation.

[0004] In another paper by Inoue, T., Gunjishima, I., and Okamoto, A., "Synthesis of Diameter-Controlled Carbon Nanotubes Using Centrifugally Classified Nanoparticle Catalysts," Carbon, 2007, 45 2164-2170, the use of centrifuges is briefly mentioned for the synthesis of carbon nanotubes.

[0005] In the above two documents, the type of centrifuge used was not disclosed, but the common and well-known centrifuge used at the time of the above two documents and for the type of separation described in the above references is the aforementioned laboratory spin tube centrifuge. For example, CN Patent No. 107252740(A) discloses a centrifuge for processing architectural coating catalysts, the centrifuge being a laboratory scale spin tube centrifuge. CN Patent No. 107252740(A) does not disclose the use of a pilot scale or industrial (commercial) production scale centrifuge.

[0006] In the paper "Optimization of Biodiesel Production Over Chicken Egg Shell Derived CaO Catalyst in a Continuous Centrifugal Contactor Separator" by Fayyazi et al., Ind. Eng. Chem. Res. 2018, 57, 12742-12755, a continuous centrifugal contactor separator for heterogeneous catalytic liquid-liquid reactions is mentioned. In this case, the separation involves the separation of one liquid phase from another and does not involve solid particles. In addition, such centrifugal contactor separators disclosed in the above paper are a different type of equipment / technology than centrifuges.

[0007] Korean Patent No. 1241429(B1) discloses a method for producing an electrocatalyst for use in a fuel cell, which method is suitable for mass production of the catalyst by applying post-catalyst production process steps including centrifugation and washing steps. The above reference does not specify the type of centrifuge used. However, in line

[0037] on page 7 of Korean Patent No. 1241429(B), there is a reference to the use of a continuous centrifuge with 3,000 G force to 150,000 G force and a water washing step of 40 L / hour. From the vague description of the centrifuge in Korean Patent No. 1241429(B), a person skilled in the art can understand that the centrifuge used in the above referenced process relates to a tubular type centrifuge (e.g., a centrifuge used for nuclear isotope separation), which is very different from a disc centrifuge, and in which the liquid discharge is continuous but the solid removal is a manual operation.

[0008] As illustrated above, various catalyst, centrifugation, and washing processes have been used in the past, with the most commonly used centrifuge type being the laboratory spin tube centrifuge. However, while stacked disc centrifuges are commercially available for production scale use, the prior art has not specifically focused on catalytic centrifugation processes or the use of stacked disc centrifuges for catalyst separation. Therefore, it would be desirable to provide a process for catalyst separation using a stacked disc centrifuge. Summary of the Invention

[0009] One embodiment of the present invention is directed to a process of separating catalyst from mother liquor using a stacked disc centrifuge equipped with self-draining capability. The stacked disc centrifuge discharges isolated solids at well-defined intervals in a short time span (e.g., 0.1 s to 10 s), thereby avoiding manual catalyst recovery and centrifuge washing. For example, in one preferred embodiment, a stacked disc centrifuge is used to separate catalyst present in a slurry (e.g., double metal cyanide (DMC) slurry) by providing the required centrifugal force (e.g., 8,000 G to 15,000 G) and having self-draining capability. The stacked disc centrifuge has been successfully used at pilot scale and can be easily scaled up to production scale. The resulting centrate produced from centrifugation using the stacked disc centrifuge is visually clear with a total suspended solids content of <0.2 wt.%. The entire amount of slurry can be processed without opening the centrifuge bowl of the stacked disc centrifuge, thereby allowing for substantially continuous operation.

[0010] Another embodiment of the invention is directed to a process for separating fine catalyst particles (e.g., particle size <5 μm) from a slurry using a stacked disk centrifuge and then washing the fine catalyst particles. In this embodiment, the process includes injecting a small amount (e.g., <0.5 L to 1 L) of wash liquid into the centrifuge to allow the cake to drain more easily. It is well known that after centrifugation, catalyst solids remaining in the centrifuge mix with the residual liquid and form a thick paste that is difficult to flow and drain from the centrifuge. The process of the invention beneficially improves the ability of the thick paste to drain from the centrifuge. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic perspective view of a stacked disc centrifuge. [Diagram 2] FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1. [Diagram 3] FIG. 1 is a schematic flow diagram of the process of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] By "slurry" herein is meant a mixture of solid catalyst particles and a solvent liquid.

[0013] As used herein, "automatic solids discharge feature" means a timer controlled operation which effects the discharge of wet cake containing catalyst solids from the stacked disc bowl.

[0014] By "centrate" herein is meant the liquid exiting the stacked disc bowl after most of the catalyst solid particles have been removed.

[0015] By "wet cake" herein is meant a cake that contains primarily catalyst solids and some mother liquor or solvent.

[0016] "Mother liquor" herein refers to the solvent mixture used in the catalyst synthesis process. It is the portion of the solution that remains after the catalyst particles have settled.

[0017] As used herein, "defludge" and "defludging" refer to the discharge of the catalyst solids cake from the stacked disc bowl.

[0018] As used throughout this specification, the following abbreviations have the following meanings unless the context clearly dictates otherwise: "=" means "equal to," @ means "at," "<" means "less than," ">" means "greater than," "≧" means "greater than or equal to," "≦" means "less than or equal to," g = grams, mg = milligrams, kg = kilogram, L = liters, mL = milliliters, L / hr = liters per hour, mL / min = milliliters per minute, M W weight = molecular weight, m ​​= meters, m 3 / hr = cubic meters per hour, M N = number average molecular weight, M w / M n = molecular weight distribution, μm = micrometers, μL = microliter, mm = millimeter, cm = centimeter, min = minutes, s = seconds, hr = hours, °C = degrees Celsius, mPa.s = millipascal seconds, psig = pounds per square inch gauge, kPa = kilopascal, G-force = magnitude of gravity, % = percent, vol% = volume percent, and wt% = weight percent.

[0019] All percentages stated herein are weight percentages (wt %) unless otherwise indicated.

[0020] Temperatures are given in degrees Celsius (° C.) and "ambient temperature" means 20° C. to 25° C. unless otherwise specified.

[0021] In a broad embodiment, the present invention provides a process for extracting catalyst components from a catalyst-containing suspension or slurry by separating the catalyst components (solid phase) from the mother liquor or solvent (liquid phase) of the slurry using a stacked disk centrifuge equipped with self-draining capabilities. The catalyst-containing suspension or slurry (herein "catalyst slurry") comprises a mixture of (a) at least one catalyst compound and (b) at least one liquid component, and may contain (c) one or more dissolved or undissolved components. For example, in one embodiment, the catalyst present in the catalyst slurry may be a single catalyst or a combination of two or more catalysts, and the liquid component present in the catalyst slurry may be one or more liquid components. In a preferred embodiment, the liquid component is an aqueous solution. Optional components may also be added to the catalyst slurry, if desired.

[0022] Any catalyst that is more dense than the mother liquor used in combination with the catalyst can be used in the present invention.For example, the catalyst present in the catalyst slurry can include one or more different catalyst compounds, including, for example, double metal cyanide (DMC), multimetal cyanide, aluminum compound, and mixtures thereof.In one preferred embodiment, the catalyst compound present in the catalyst slurry can include DMC catalyst.

[0023] Examples of useful aluminum compounds include trialkylaluminum compounds such as trimethylaluminum, triethylaluminum, tributylaluminum, tribenzylaluminum, and the like; aluminum alkoxides such as aluminum trimethoxide, aluminum triethoxide, aluminum triisopropoxide, aluminum triisopropoxide, aluminum tri-t-butoxide, aluminum tri-sec-butoxide, and the like; aluminum aryloxides such as aluminum phenoxide and aluminum phenoxide, where one or more of the phenoxide groups are ring-substituted with one or more of alkyl, CF3, cyano, COCH3, halogen, hydroxyl, alkoxyl, and the like; aluminum oxide, aluminum formate, aluminum acetate, aluminum propionate, aluminum 2-ethylhexanoate, aluminum benzoate, and the like. aluminum carboxylates, such as aluminum carboxylates where one or more of the benzoic acid groups are ring-substituted with one or more of alkyl, CF3, cyano, COCH3, halogen, hydroxyl, alkoxyl, etc., aluminum salicylate, aluminum amides, such as aluminum tris(dimethylamide), aluminum tris(diethylamide), aluminum tris(diphenylamide), aluminum tris(di(trimethylsilyl)amide), aluminum acetylacetonate, aluminum t-butylacetylacetonate, and alkyl aluminum oxides, such as diethylaluminum ethoxide, dimethylaluminum ethoxide, diethylaluminum isopropoxide, dimethylaluminum isopropoxide, methylaluminoxane, tetraethyldialuminoxane, and alkoxides.

[0024] The amount of catalyst compound present in the catalyst slurry of the present invention can be, for example, in one embodiment, from 0.01 wt.% to 15 wt.%, in another embodiment, from 0.5 wt.% to 10 wt.%, and in yet another embodiment, from 1 wt.% to 6 wt.%. Higher than 15 wt.% catalyst solids can result in (1) a faster accumulation of solids in the stacked disc bowl than the bowl can be drained, and (2) a high loss of solids to the centrate, both results that are undesirable.

[0025] The liquid component present in the catalyst slurry of the present invention may include one or more liquid compounds including, for example, water, t-butanol, 2-butanol, and polyether polyols, and mixtures thereof. The liquid component present in the catalyst slurry may be a single aqueous phase component, a biphasic system, or a system containing an organic phase component, and mixtures thereof, so long as the catalyst has a higher specific gravity than the liquid components used in the present invention.

[0026] In one preferred embodiment, the liquid compound other than water is VORANOL™ P4000 (4,000M W Polyether polyols, herein "P4000" (available from The Dow Chemical Company), as well as mixtures of P4000 with other liquid compounds.

[0027] The amount of liquid compound present in the slurry of the present invention can be, for example, in one embodiment, 85% to 99.99% by weight, in another embodiment, 90% to 99.5% by weight, and in yet another embodiment, 94% to 99% by weight.

[0028] In addition to the above components (a) and (b) of the slurry, the slurry may also include other additional optional compounds, additives, agents, or components (c), which may be added to the slurry mixture in combination with any one of components (a) or (b), or in combination with both components (a) and (b), or the optional components may be added as separate additions. Optional additives or agents that may be used in the present invention may include one or more optional compounds known in the art for their use or function. For example, optional additives, agents, or components may include aluminum sec-butoxide, aluminum isopropoxide, aluminum oxide, and mixtures thereof.

[0029] The amount of the optional compound used to be added to the slurry mixture can be, for example, from 0 wt % to 5 wt % in one embodiment, from 0.01 wt % to 2 wt % in another embodiment, and from 0.5 wt % to 1.0 wt % in yet another embodiment.

[0030] In the manufacturing process for producing the catalyst, typically the resulting product formed is a catalyst-containing slurry in which undissolved solid particles are present in the liquid phase. Generally, the process of the present invention involves adding other compounds, such as water, to the catalyst-containing slurry to form an aqueous catalyst slurry that can be subjected to a centrifugation process step. For example, components (a)-(c) are mixed together to form a slurry, which is then introduced into a centrifuge. For example, the components that make up the catalyst slurry composition can be mixed together by any known mixing process and equipment. The order of mixing of the components is not important, and the remaining components may be added after two or more compounds are mixed together. The mixing of the components can be carried out at a temperature of from 10° C. to 80° C. in one embodiment, from 15° C. to 60° C. in another embodiment, and from 20° C. to 40° C. in yet another embodiment.

[0031] As an example of the present invention, but not limited thereto, the DMC catalyst slurry can be prepared by mixing an aqueous zinc chloride solution with a solution containing potassium hexacyanocobaltate (KHCC), tert-butanol (t-BuOH), and water to form a mixture in a reaction vessel. Propylene oxide polyol can then be added to the mixture in the reaction vessel. The process temperature in the reaction vessel can be controlled at a desired temperature, such as 30° C. The resulting mixture is the DMC catalyst slurry.

[0032] One of the advantageous properties exhibited by the resulting catalyst slurry produced according to the above process includes, for example, that the slurry is pumpable and can be pumped using conventional pumps without any special equipment or process conditions.

[0033] In a typical embodiment, the centrifugation process of the present invention for treating a catalyst slurry and separating the catalyst from the mother liquor of the slurry comprises using a stacked disc centrifuge equipped with self-draining capability. The stacked disc centrifuge (also known as a "disk bowl centrifuge") used in the present invention can be any disc bowl centrifuge known in the centrifuge industry, for example, as described in Perry's Chemical Engineers' Handbook.

[0034] Referring to Figure 1, there is shown a stacked disc centrifuge, generally designated as reference numeral 10. The centrifuge 10 is operatively connected to a motor, generally designated by reference numeral 40, and both pieces of the equipment (centrifuge 10 and motor 40) are positioned on a base or platform, generally designated by reference numeral 50. The centrifuge 10 includes a housing 11 for housing an internal rotating assembly, generally designated by reference numeral 20, as shown in cross-sectional view in Figure 2. The centrifuge 10 also includes an inlet conduit 12 for introducing a supply of slurry 32 into the centrifuge 10, and the centrifuge 10 includes an outlet conduit 13 for discharging a centrate stream 33 from the centrifuge 10. In addition, the centrifuge 10 includes an outlet conduit 14 for discharging a sludge stream 34 from the centrifuge 10.

[0035] 2, there is shown a cross-sectional view of the internal elements of a rotating assembly 20 contained by the housing 11 of the stacked disc centrifuge 10. The rotating assembly 20 includes, for example, an upper bowl body 21, a lower bowl body 22, and a plurality of disc members 23. The rotating assembly 20 also includes a rotatable shaft or rod 24 integral with the body 22 for rotating the centrifuge body 21, the centrifuge body 22, and the disc members 23 in the direction indicated by the directional arrow 31.

[0036] Referring again to FIG. 2, there is shown an opening or inlet 25 positioned in the upper body 21 for feeding slurry 32 to the centrifuge 10 and the rotating assembly 20, an outlet or discharge 26 positioned in the upper body 21 for discharging a centrate flow 33, and an outlet or discharge orifice 27 positioned towards the lower body 22 for discharging a sludge flow 35 which exits the centrifuge 10 via the rotating assembly 20 through orifice 27 and conduit 14 when the centrifuge 10 is in operation.

[0037] The stacked disk centrifuge 10 can provide a centrifugal force of 4,000 G-force to 14,000 G-force in one embodiment, 5,000 G-force to 12,000 G-force in another embodiment, and 6,000 G-force to 10,000 G-force in yet another embodiment. Based on the centrifugal force provided in the process, the separation time can be significantly reduced. For example, the total processing time of the process, which can include filling, separation, solids discharge, and equipment cleaning, can be reduced, for example, by up to 50% in one embodiment, 10% to 40% in another embodiment, and 20% to 30% in yet another embodiment.

[0038] Stacked disc centrifuges are ideally suited to separate particles having a particle size of 0.05 μm to 100 μm in one typical embodiment, 0.1 μm to 50 μm in another embodiment, and 0.5 μm to 10 μm in yet another embodiment. Stacked disc centrifuges are also ideally suited to separate particles having a concentration of 0.01% to 15% by weight in one typical embodiment, 0.5% to 10% by weight in another embodiment, and 1% to 6% by weight in yet another embodiment.

[0039] The capacity of a stacked disc centrifuge useful in the present invention can depend on various factors such as the size of the disc bowl and how easily / difficult the particles can be separated. For example, as an illustration of a stacked disc centrifuge with intermittent self-cleaning bowl in the present invention, but not limited thereby, the stacked disc centrifuge can be a Westfalia SA-1. This centrifuge has a maximum capacity of, for example, 0.001 L / hr to 300 L / hr in one typical embodiment, 0.020 L / hr to 50 L / hr in another embodiment, and 0.030 L / hr to 0.2 L / hr in yet another embodiment. In other embodiments, different centrifuge models have different capacities.

[0040] As previously mentioned, the stacked disc centrifuge used in the present invention is equipped with an automatic solids discharge feature for separating the catalyst solids from the mother liquor of the slurry. For example, referring to Figure 3, there is shown a schematic flow diagram of one broad embodiment of the catalyst separation process of the present invention, generally designated by reference numeral 60, and including the following steps: Step (a): Providing a stacked disc centrifuge equipped with automatic solids discharge, as indicated by numeral 61. Step (b): Providing a catalyst-containing slurry, as indicated by the numeral 62. Step (c): Feeding the catalyst containing slurry into a stacked disc centrifuge, as indicated by numeral 63. Step (d): centrifuging the catalyst containing slurry in a stacked disc centrifuge to form a cake and centrate, as indicated by the numeral 64, and removing the centrate from the stacked disc centrifuge substantially continuously during the centrifugation step. Step (e): Automatically removing cake material from the stacked disc centrifuge at preset intervals with the assistance of a portion of the wash fluid as indicated by numeral 65. Step (f): Optionally, adding additional wash fluid to the drained catalyst to complete the wash, as indicated by numeral 66.

[0041] A preferred embodiment of the catalyst separation process of the present invention comprises the following steps. Step (1): Providing a stacked disc centrifuge equipped with an automatic solids discharge function, which step (1) may further include setting the operating parameters of the centrifuge of step (1), for example, by setting a feed and separation duration timer on the centrifuge control panel to a time period between 10 minutes and 50 minutes, and setting a bowl open duration timer on the centrifuge control panel to a time period between 0.1 seconds and 1.0 seconds.

[0042] The bowl opening / closing is hydraulically actuated, i.e. the operating water pressure lines to the centrifuge are set at 21 psig (144.8 kPa) to 36 psig (248.2 kPa).

[0043] Step (2): Providing a catalyst-containing slurry.

[0044] Step (3): Supplying power to the centrifuge and allowing the centrifuge to reach its maximum bowl speed. For example, as an illustration of a stacked disc centrifuge useful in the present invention, but not limited thereby, the stacked disc centrifuge may be an SA-1 model. For the SA-1 model, the maximum speed of the centrifuge corresponds to, for example, a centrifugal force of 8,000 G, and the maximum speed of the centrifuge is reached in, for example, a period of 300 seconds. In other embodiments, different centrifuge models have different maximum G forces and different acceleration times.

[0045] Step (4): Feed the slurry into the centrifuge, for example, by setting the slurry feed pump speed at a rate of 1.2 L / hr to 12.0 L / hr. After the bowl is completely filled, clear centrate is observed exiting through the centrifuge outlet line and collected in a carboy. A total suspended solids analysis is performed on this centrate, and the solids content is 0.001% to 0.02% by weight.

[0046] The centrifuge may be run at temperatures up to 170° C. in one embodiment, between 10° C. and 100° C. in another embodiment, and between 20° C. and 50° C. in yet another embodiment. At centrifugation temperatures below 10° C., the liquid may become too viscous to flow, and at centrifugation temperatures above 170° C., the seals and motors that spin the centrifuge may not be able to maintain heat and the motors may stop working.

[0047] The wet cake obtained after separation is reslurried in a washing solution containing at least water and t-BuOH, and optional other liquids such as P4000, to remove any undesired compounds. Generally, a typical catalyst synthesis process involves a total of three washing and four centrifugation steps. The reslurry steps are carried out at 20°C to 40°C under an inert atmosphere.

[0048] Step (5): Desludge the catalyst solids from the centrifuge after the centrifugation period. For example, after 10 minutes of centrifugation, the centrifuge bowl is opened for 0.5 seconds while the catalyst solids are desludged (discharged) from the centrifuge into a receiving vessel. Step (5) desludge is carried out at ambient temperature under an inert atmosphere.

[0049] Step (6): Running the pump continuously and feeding the slurry to the centrifuge so that the separation is a substantially continuous operation. By "substantially continuous" it is meant that the bowl is opened for a very short duration resulting in the discharge of the continuously fed slurry, but not in a significant amount (e.g., in this application, less than 0.3% of the total catalyst slurry). In one embodiment, the following washing solution is used to rinse the bowl and discharge chute after a certain number of deslaggings to remove any excess solids adhering to the bowl, bowl walls, and discharge chute. For example, after 5-10 deslaggings.

[0050] Step (7): Recovering the wet cake discharged from the centrifuge and further washing to remove undesirable compounds from the catalyst. The wet cake is collected at ambient temperature under an inert atmosphere.

[0051] Step (8): Repeating the centrifugation and washing steps of steps (4) to (7) a predetermined number of times, for example, 1 to 3 times, to form a final catalyst wet cake. The catalyst solids loss in each centrate and cake discharge are listed in Table I below. Losses are measured as a percentage of total solids.

[0052] Some of the advantageous properties exhibited by the resulting catalytic solids separated according to the processes described above may include, for example, (1) activity for propoxylation, (2) activity for ethoxylation, and (3) activity for propoxylation and ethoxylation, and any combination thereof.

[0053] The catalyst is a desired component of the present invention, and the catalyst is separated from the centrate after the centrifugation process. The centrate produced by the process of the present invention can either (1) be directed to a flash distillation unit where the solvent mixture can be recovered, or (2) be sent to a waste treatment facility. The recovered solvent can be reused in the catalyst synthesis process and / or in the cleaning step of the centrifugation process. For example, when the centrate contains t-BuOH, water, KCl, ZnCl2, supported DMC particles, and mixtures thereof, if desired, the centrate can be distilled to remove salts and the resulting t-BuOH and water azeotrope can be recycled back to the DMC synthesis process and / or the azeotrope can be used to clean stacked disk centrifuges. EXAMPLES

[0054] The following inventive and comparative examples are presented to further illustrate the present invention, but should not be construed as limiting the scope of the claims. Unless otherwise indicated, all parts and percentages are by weight.

[0055] General Procedure for Centrifugation of Catalyst Slurry A 50 L batch of double metal cyanide (DMC) catalyst slurry consisting of DMC solids in a mother liquor of P4000, t-BuOH, and water was processed in a stacked disk centrifuge equipped with automatic solids discharge to separate the DMC solids from the mother liquor. The process was carried out under an inert atmosphere (N2). The wet cake obtained after separation was reslurried, i.e., washed with a washing solution containing t-BuOH, water, and P4000 to remove the undesired potassium in the wet cake product. The resulting loss of solid content in the centrate is measured and the centrate is discarded. The washed wet cake, the catalyst product, is then recovered. Optionally, the DMC synthesis process can be subjected to any number of washing and centrifugation steps. For example, in one preferred embodiment, the DMC synthesis procedure of the present invention includes a total of three washing steps and four centrifugation steps.

[0056] Example 1 The DMC slurry described above was subjected to a stacked disc centrifuge equipped with automatic solids discharge and the DMC solids were separated from the mother liquor using the following process.

[0057] Step (1) - The bowl open timer and separation interval timer on the centrifuge control panel of the centrifuge unit were set to 0.5 seconds and 10 minutes, respectively. The bowl open / close of the centrifuge used was hydraulically driven and the operating water pressure line was 25 psig (172.4 kPa). The centrifuge unit was powered and allowed to reach maximum bowl speed, which corresponded to a centrifugal force of approximately 8,000 G.

[0058] Step (2) - The slurry feed pump speed was set at 9.0 L / hr. After the centrifuge bowl was completely filled, clear centrate was observed to exit through the drain line and the centrate was collected in a carboy. A total suspended solids analysis was performed on this centrate. The solids loss in the centrate is listed in Table I.

[0059] Step (3) - After 10 minutes of centrifugation, the bowl was opened for 0.5 seconds while the DMC solids were desludged (drained) from the centrifuge into a receiving vessel. The centrifuge bowl and solids discharge chute were rinsed with 1 L of the washing solution described in Example 2 to aid in the removal of solids adhering to the bowl.

[0060] Step (4) - The resulting wet cake product from step (3) above is collected and the loss of DMC solids in the centrate is set forth in Table I.

[0061] Example 2 The wet cake collected from the procedure of Example 1 was washed by reslurrying the wet cake with the same wash solution to remove any undesirable potassium present in the DMC slurry. The wash solution (26.6 kg) contained t-BuOH (49.7 wt%), water (49.7 wt%), and P4000 (0.6 wt%). The resulting DMC slurry after the above washes was then subjected to centrifugation using the same stacked disk centrifuge and the same steps (1)-(4) of Example 1. The loss of DMC solids in the centrate of this Example 2 is listed in Table I.

[0062] Example 3 The collected wet cake from Example 2 was used in this Example 3, and the centrifugation and washing steps of Example 2 were repeated to obtain yet another DMC wet cake. The washing solution (17.2 kg) contained t-BuOH (64.3 wt%), water (34.6 wt%), and P4000 (1.0 wt%). The solids loss in the centrate in this Example 3 is listed in Table I.

[0063] Example 4 The wet cake collected from Example 3 was used in this Example 4 to obtain another DMC wet cake by repeating the centrifugation and washing steps of Example 3. The washing solution (13.8 kg) contained t-BuOH (98.0 wt%), water (1.4 wt%), and P4000 (0.6 wt%). The solids loss in the centrate is listed in Table I.

[0064] [Table 1]

[0065] In each of the above examples, the slurry was advantageously continuously fed to the centrifuge using a slurry feed pump to provide a separation process that is nearly continuous operation. In general, the process of the present invention has at least two advantages: (1) the centrifuge allows for good catalyst recovery, and (2) the centrifuge allows for short processing times. For example, the process time for isolating DMC solids using a stacked disk centrifuge was reduced by up to 50% compared to a spin tube centrifuge. The self-draining function in conjunction with washing the solids using a rinse solution showed a reduction in process drain time from 2 hours to 10 seconds. Solids are lost in the centrate and / or stick to the centrifuge bowl, discharge chute, reactor walls, and agitator blades. The entire volume of the DMC slurry shown in Examples 1-4 was processed in the manner described above, and the results of the above examples illustrate that less than 0.02 wt.% of solids are lost in the centrate and the overall catalyst recovery is approximately 92.5%. The present specification includes the following aspects. Section 1. 1. A process for separating fine catalyst components from a catalyst-containing slurry by separating the catalyst components from a mother liquor of the catalyst-containing slurry, comprising: (a) providing a stacked disc centrifuge equipped with an automatic discharge feature; (b) providing a catalyst-containing slurry comprising a mixture of (i) at least one catalyst compound and (ii) at least one liquid component; (c) feeding the catalyst-containing slurry into the stacked disk centrifuge of step (a); (d) centrifuging the catalyst-containing slurry for a predetermined period of time to form a cake material of catalyst solids in the centrifuge and centrate, the centrate being substantially continuously removed from the centrifuge during the centrifugation step (d); (e) removing the cake material from the centrifuge after the centrifugation of step (d). Section 2. (f) during the step (e) of removing the cake material from the centrifuge, substantially simultaneously washing the cake material of step (e) with a washing solution to remove any undesirable components from the cake material. Section 3. Item 13. The process of item 1, wherein the at least one liquid component is water. Section 4. Item 10. The process of item 1, wherein the at least one catalyst compound is a double metal cyanide. Section 5. Item 3. The process of item 2, wherein the washing step of step (f) is carried out using water, butanol, polyether polyol, or a mixture thereof as the washing solution. Section 6. Item 1. The process of item 1, wherein the catalyst solids content in the cake material is between 10 weight percent and 40 weight percent. Section 7. Item 1. The process according to item 1, wherein the feed rate of the catalyst-containing slurry to the centrifuge is from 0.001 liters per hour to 300 liters per hour. Section 8. Item 1, the process further comprising operating the centrifuge at a centrifugal force of between 6,000 G and 14,000 G. Section 9. Item 1, comprising further discharging the isolated solids from the centrifuge at predetermined intervals over a period of 5 minutes to 60 minutes. Section 10. Item 1. The process of item 1, wherein the resultant centrate produced from the centrifugation is visually clear with a total suspended solids loss of 0.005 weight percent to 0.2 weight percent. Section 11. (g) after the centrifuging step (d) and before the removing step (e), injecting a wash fluid into the centrifuge. Section 12. Item 1. A catalyst product produced by the process described in item 1.

Claims

1. 1. A process for separating fine catalyst components from a catalyst-containing slurry by separating the catalyst components from a mother liquor of the catalyst-containing slurry, comprising: (a) providing a stacked disc centrifuge equipped with auto-drain; (b) providing a catalyst-containing slurry comprising a mixture of (i) at least one catalyst compound and (ii) at least one liquid component; (c) feeding the catalyst-containing slurry into the stacked disk centrifuge of step (a); (d) centrifuging the catalyst-containing slurry for a predetermined period of time to form a cake material of catalyst solids in the centrifuge and centrate, the centrate being substantially continuously removed from the centrifuge during the centrifuging step (d); (e) removing the cake material from the centrifuge after the centrifugation of step (d); (f) during said step (e) of removing said cake material from said centrifuge, substantially simultaneously washing said cake material of step (e) with a wash solution to remove any undesirable components therefrom.

2. The process of claim 1 , wherein the at least one liquid component is water.

3. 10. The process of claim 1, wherein the at least one catalyst compound is a double metal cyanide.

4. 2. The process of claim 1, wherein the washing step of step (f) is carried out using water, butanol, polyether polyol, or mixtures thereof as the washing solution.

5. 10. The process of claim 1, wherein the catalyst solids content in the cake material is from 10 weight percent to 40 weight percent.

6. 10. The process of claim 1, wherein the feed rate of the catalyst-containing slurry to the centrifuge is from 0.001 liters per hour to 300 liters per hour.

7. 10. The process of claim 1, further comprising operating the centrifuge at a centrifugal force of between 6,000 G-force and 14,000 G-force.

8. 10. The process of claim 1 further comprising discharging isolated solids from the centrifuge at predetermined intervals over a period of from 5 minutes to 60 minutes.

9. 10. The process of claim 1, wherein the resultant centrate produced from the centrifugation is visually clear with a total suspended solids loss of 0.005 weight percent to 0.2 weight percent.

10. 10. The process of claim 1, further comprising the step of: (g) injecting a wash fluid into the centrifuge after the centrifuging step (d) and before the removing step (e).

11. 13. A catalyst product produced by the process of claim 1.

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