Method for reducing small pores of catalyst support

Abstract

The present invention provides methods in which small pores having a size less than 0.3 microns are substantially reduced by utilizing caustic solution. In some embodiments, the reduction of small pores having a size less than 0.3 microns is achieved by treating the preformed catalyst support with hot caustic solution. In other embodiments, the reduction of small pores having a size less than 0.3 microns is achieved by adding caustic solution to the support composition during the preparation / molding of the catalyst support. The caustic solution treated catalyst support exhibits a positive / upward shift in the small pore size distribution.

Description

[0001] Cross-reference to related applications This invention claims the benefit of U.S. Provisional Patent Application No. 63 / 562,963, filed March 8, 2024, the entire contents and disclosure of which are incorporated herein by reference. Background Technology

[0002] This disclosure relates to a catalyst support (or catalyst carrier), and more specifically to a method for reducing the pore size (i.e., pores with a diameter of less than 0.3 micrometers) of the catalyst support.

[0003] Catalysts for the commercial-scale gas-phase oxidation of ethylene using molecular oxygen to produce ethylene oxide (EO) typically require high activity, high selectivity, and high durability (i.e., long catalyst lifetime). Various studies have been conducted to improve the activity and / or selectivity and / or durability of EO catalysts. Efforts have been made in this regard to improve the reaction promoters and / or supports for EO catalysts.

[0004] The supports used for EO catalysts are typically α-alumina supports. However, there are still many aspects of existing α-alumina supports used for EO catalysts that require further clarification and improvement. For example, the physical properties of α-alumina supports (such as specific surface area, pore diameter, pore distribution, pore volume, and porosity) and the chemical properties of these support materials need further refinement for optimization.

[0005] In EO catalysis, a pore size distribution smaller than 0.3 micrometers in the support is generally undesirable because such small pores negatively impact EO catalyst performance, particularly EO selectivity. In existing technologies, the pore size distribution of the support is largely determined by the available alumina feedstock (i.e., the alumina source) used to shape the support, and this pore size distribution is not easily controlled. Therefore, there is a need to provide methods for reducing the pore volume percentage of pores smaller than 0.3 micrometers in EO catalyst supports. Summary of the Invention

[0006] Several methods are provided in which the pore volume percentage of pores smaller than 0.3 micrometers is substantially reduced by utilizing a caustic solution. In some embodiments, the reduction of pores smaller than 0.3 micrometers is achieved by treating a preformed catalyst support with a hot caustic solution. In other embodiments, the reduction of pores smaller than 0.3 micrometers is achieved by adding a caustic solution to the support composition (i.e., the support formulation) during the preparation / forming of the catalyst support. The catalyst support treated with the caustic solution exhibits a positive / upward shift in the pore size distribution.

[0007] In one aspect of this disclosure, a method for reducing the small pore size distribution of a catalyst support is provided. In one embodiment, the method includes contacting a preformed catalyst support having a pore size distribution of less than 0.3 micrometers with a caustic solution to provide an admixture of the caustic solution and the preformed catalyst support. The admixture is then heated to a temperature of approximately 70°C or higher to provide a caustic solution-treated preformed catalyst support. The caustic solution-treated preformed catalyst support is then cooled to nominal room temperature and subsequently dried. The dried caustic solution-treated preformed catalyst support is then calcined at a temperature of approximately 1200°C or higher, and after calcination, the calcined caustic solution-treated preformed catalyst support is washed to provide a catalyst support with a reduced percentage of pore volume having pores smaller than 0.3 micrometers compared to the preformed catalyst support.

[0008] In another aspect of this disclosure, a method for molding a catalyst support is provided. In one embodiment, the method includes adding a caustic solution to a support composition (i.e., a formulation) to provide a blend of the support composition and the caustic solution. The blend is then molded into a molded body and subsequently calcined at a temperature greater than about 1200°C to convert the molded body into a catalyst support. The catalyst support formed using the caustic solution has a reduced pore volume percentage having pores with a pore size less than 0.3 micrometers compared to an equivalent catalyst support made without the caustic solution. Attached Figure Description

[0009] Figure 1 This is a graph showing the pore size distribution of catalyst support 1 before and after NaOH treatment.

[0010] Figure 2 This is a graph showing the pore size distribution of catalyst support 2 before and after NaOH treatment.

[0011] Figure 3 This is a graph showing the pore size distribution of catalyst support 3 before and after NaOH treatment.

[0012] Figures 4A-4B The images shown are scanning electron micrographs (SEMs) illustrating the morphology of catalyst support 1 before and after NaOH treatment.

[0013] Figures 5A-5B The images shown are scanning electron micrographs (SEMs) depicting the morphology of catalyst support 2 before and after NaOH treatment.

[0014] Figures 6A-6B The images shown are scanning electron micrographs (SEMs) illustrating the morphology of catalyst support 3 before and after NaOH treatment.

[0015] Figure 7 The graph shows the pore size distribution of catalyst support 4 prepared without NaOH, catalyst support 4A prepared with 0.3 wt.% NaOH, catalyst support 4B prepared with 0.6 wt.% NaOH, and catalyst support 4C prepared with 1.2 wt.% NaOH.

[0016] Figures 8A-8D The images shown are scanning electron micrographs (SEMs) illustrating the morphologies of catalyst support 4 prepared without NaOH, catalyst support 4A prepared with 0.3 wt.% NaOH, catalyst support 4B prepared with 0.6 wt.% NaOH, and catalyst support 4C prepared with 1.2 wt.% NaOH. Detailed Implementation

[0017] The present disclosure will now be described in more detail with reference to the following discussion and the accompanying drawings. In the following description, numerous specific details, such as particular structures, components, materials, dimensions, processing steps, and techniques, are set forth in order to provide an understanding of various embodiments of the present disclosure. However, those skilled in the art will understand that various embodiments of the present disclosure can be implemented without these specific details. As used throughout the present disclosure, the term “about” generally means a difference from a numerical value not exceeding ±10%, ±5%, ±2%, ±1%, or ±0.5%. When a range in the present disclosure is expressed as a range from one numerical value to another (e.g., 20 to 40), the present disclosure covers any numerical value falling within that range (i.e., 22, 24, 26, 28.5, 31, 33.5, 35, 37.7, 39, or 40) or any quantity defined by any two numerical values ​​that may exist within that range (e.g., 28.5-35).

[0018] The terminology used herein is for describing particular embodiments only and is not intended to limit this disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” are intended to include the plural forms as well. It should also be understood that when the terms “comprising” and / or “including” are used in this disclosure, they mean the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0019] Several methods are provided in which the pore volume percentage of pores smaller than 0.3 micrometers is substantially reduced by utilizing a caustic solution. In some embodiments, the reduction of pores smaller than 0.3 micrometers is achieved by treating a preformed catalyst support with a hot caustic solution. In other embodiments, the reduction of pores smaller than 0.3 micrometers is achieved by adding a caustic solution to the support composition (i.e., the catalyst formulation) during the preparation / forming of the catalyst support. In this disclosure, the catalyst support treated with the caustic solution exhibits a positive / upward shift in the pore size distribution. These aspects of this disclosure will now be described in more detail.

[0020] Preformed catalyst support treated with caustic solution In some embodiments, the reduction of pores smaller than 0.3 micrometers is achieved by treating a preformed catalyst support with a pore size distribution smaller than 0.3 micrometers using a hot caustic solution. In this embodiment, the preformed catalyst support treated with the hot caustic solution exhibits a positive / upward shift in pore size distribution from a value smaller than 0.3 micrometers. The term "preformed catalyst support" refers to a catalyst support that has been manufactured / shaped / calcined using any known catalyst support preparation / forming process. The catalyst support preparation / forming process may include providing a support composition (i.e., formulation) comprising at least one alumina source (i.e., alumina powder), shaping the support composition into a molded body, and calcining the molded body. The alumina source is typically α-alumina powder.

[0021] Preformed catalyst supports typically contain at least about 85 wt.%, more typically at least about 90 wt.%, and even more typically at least about 95 wt.%. The remaining components of the preformed catalyst support may include inorganic oxides other than α-alumina, such as silica, alkali metal oxides (e.g., sodium oxide), and trace amounts of other metal-containing or metal-free additives or impurities.

[0022] The preformed catalyst supports that can be used in this disclosure typically have a pore volume of about 0.3 mL / g to about 1.2 mL / g. The pore volumes reported in this disclosure can be measured by mercury porosimetry according to ASTM D4284. More typically, the pore volumes of the preformed catalyst supports that can be used in this disclosure are about 0.35 mL / g to about 0.9 mL / g. In some embodiments, the water absorption rate of the preformed catalyst supports that can be used in this disclosure is about 30% to about 90%, more typically in the range of about 35% to about 70%. The water absorption rate reported in this disclosure can be measured by a method similar to ASTM C373-18. The surface area of ​​the preformed catalyst supports that can be used in this disclosure is typically about 0.1 m². 2 / g to approximately 5.0m 2 / g, more typically about 0.3m 2 / g to approximately 4.5m2 / gm. The surface area reported in this disclosure is measurable according to ASTM D3663-20.

[0023] The preformed catalyst supports used in this disclosure typically have multimodal pore size distributions, such as bimodal distributions. The preformed catalyst support includes at least one pore mode with a pore size distribution less than 0.3 micrometers. The at least one pore mode with a pore size distribution less than 0.3 micrometers may account for at least about 50% or less of the total pore volume of the preformed catalyst support. More typically, the at least one pore mode with a pore size distribution less than 0.3 micrometers may account for about 10% to about 40% of the total pore volume of the preformed catalyst support. Even more typically, the at least one pore mode with a pore size distribution less than 0.3 micrometers may account for about 20% to about 30% of the total pore volume of the preformed catalyst support. In some embodiments, the preformed catalyst support contains at least about 90% of the pore volume, the pore volume of the preformed catalyst originating from pores with a pore size of about 20 micrometers or smaller. In yet another embodiment of this disclosure, at least about 85% of the pore volume of the preformed catalyst support originates from pores with a size of about 1 micrometer to about 6 micrometers. In yet another embodiment of this disclosure, less than about 15%, preferably less than about 10%, of the pore volume of the preformed catalyst support originates from pores with a size of less than about 1 micrometer. In yet another embodiment of this disclosure, at least about 80% of the pore volume of the preformed catalyst support originates from pores with a size of about 1 to 10 micrometers.

[0024] In one embodiment, the preformed catalyst support used in this disclosure may be bimodal, having a first set of pores of about 0.01 micrometers to about 1 micrometer and a second set of pores of greater than about 1 micrometer to about 10 micrometers. In such embodiments, the first set of pores may account for less than about 15% of the total pore volume of the preformed catalyst support of this disclosure, while the second set of pores may account for more than 85% of the total pore volume of the porous body. In yet another embodiment, the first set of pores may account for less than about 10% of the total pore volume of the preformed catalyst support of this disclosure, while the second set of pores may account for more than about 90% of the total pore volume of the preformed catalyst support of this disclosure.

[0025] The preformed catalyst supports that can be used in this disclosure typically have an average flat-plate crushing strength of about 10 N to about 150 N, where N is Newton. More typically, the average flat-plate crushing strength of the preformed catalyst supports that can be used in this disclosure is about 40 N to about 105 N. The crushing strength reported herein is the average flat-plate crushing strength that can be measured according to ASTM 4179-22.

[0026] In some embodiments, the preformed catalyst support used in this disclosure has an initial low alkali metal content. "Low alkali metal content" means that the preformed catalyst support contains about 2000 ppm or less, typically about 30 ppm to about 300 ppm of alkali metal. A preformed catalyst support containing a low alkali metal content can be obtained by substantially avoiding the addition of alkali metal during the support manufacturing process. "Substantially avoiding the addition of alkali metal" means that in the manufacturing process of the preformed catalyst support used in this disclosure, only trace amounts of alkali metal in the form of impurities from other components of the preformed catalyst support are used. In another embodiment, a preformed catalyst with a low alkali metal content can be obtained by performing various washing steps. Washing steps may include washing in an alkali, acid, water, or another solvent.

[0027] Preformed catalyst supports suitable for use in this disclosure can be prepared using conventional support manufacturing methods well known to those skilled in the art. While not limited to the specific compositions and formulations contained herein, more information regarding support compositions and methods for preparing catalyst supports can be found, for example, in U.S. Patent Publication No. 2007 / 0037991.

[0028] After providing the preformed catalyst support, the preformed catalyst support is subjected to a hot caustic solution treatment. The hot caustic solution treatment of the preformed catalyst support involves contacting the preformed catalyst support with a caustic solution to provide a caustic solution-treated preformed catalyst support. In this disclosure, the caustic solution that can be used in the contacting step includes a base present in the solution with a pH of about 10 or greater. Illustrative examples of such bases that can be used as components of the caustic solution include, but are not limited to, LiOH, NaOH, KOH, or CsOH. The solution is typically water, but not always. In embodiments, the molar concentration of the caustic solution used to treat the preformed catalyst support is from about 0.1 M to about 2 M, more typically from about 0.3 M to about 1 M. In this disclosure, molar concentration represents a measure of the concentration of a solute (here, for example, a base) in a solution (e.g., water), expressed as the number of moles of substance per liter of solution.

[0029] In this disclosure, the contact includes adding a caustic solution to a preformed catalyst support to provide a blend of the caustic solution and the preformed catalyst support. The amount of caustic solution added to the preformed catalyst support is typically from about 2 ml to about 10 ml per gram of preformed catalyst support. More typically, the amount of caustic solution added to the preformed catalyst support is from about 3 ml to about 5 ml per gram of preformed catalyst support. The contact can be carried out in the presence of stirring. The stirring can be continuous or intermittent, after a certain amount of caustic solution has been added to the preformed catalyst support.

[0030] After providing the caustic solution and the blend of the preformed catalyst support, the blend is heated to a temperature of about 70°C or higher, more typically a contact temperature of about 80°C to about 90°C. The duration of the heating step can vary. In one embodiment, the heating step is performed over a period of about 1 to about 5 hours. The heating step can be performed in the presence of stirring. The stirring can be continuous or intermittent. Heating provides the preformed catalyst support treated with the caustic solution.

[0031] The caustic solution-treated preformed catalyst support is then cooled to nominal room temperature, after which the cooled caustic solution-treated preformed catalyst support can be decanted and dried. In this disclosure, the term "nominal room temperature" means a temperature of about 18°C ​​to about 25°C. Cooling can be performed in air or under vacuum. Drying can also be performed in air or under vacuum and may include any drying method, such as air drying, oven drying, or drying under a heat lamp. The drying step removes water from the caustic solution-treated preformed catalyst support.

[0032] The dried, caustic solution-treated preformed catalyst support is then subjected to a calcination step. The calcination step can be carried out at a temperature of about 1200°C or higher, more typically at a calcination temperature of about 1250°C to about 1550°C. The calcination step can be carried out in air, an inert environment, or any combination thereof. In one embodiment, the calcination step can be carried out in flowing air. After the calcination step, the resulting calcined, caustic solution-treated preformed catalyst support is cooled to nominal room temperature. The heating and cooling rates can be in the range of 1°C / min to 5°C / min. Other heating and cooling rates in the range of 0.5°C / min to 20°C / min may also be used in this disclosure.

[0033] Following calcination, the calcined preformed catalyst support treated with a caustic solution is washed to provide a catalyst support with reduced residual caustic impurities and a reduced pore volume percentage of pores smaller than 0.3 micrometers compared to the preformed catalyst support before caustic solution treatment. In this disclosure, the washing step includes washing in deionized water. Washing can be a single wash or multiple washes.

[0034] Compared to the preformed catalyst support before treatment with a caustic solution, the catalyst support provided after the above-described treatment with a hot caustic solution has a reduced pore size distribution. Notably, compared to the preformed catalyst support before treatment with a caustic solution, the catalyst support provided after the above-described treatment with a caustic solution has a reduced percentage of pore volume with pores smaller than 0.3 micrometers. Using the above-described hot caustic solution treatment method, a reduction in the volume of small-sized pores from about greater than 3% to about less than 1.2% can be achieved. In embodiments of this application, the small-sized pore size distribution of less than 0.3 micrometers is shifted upwards. In some embodiments, the upward shift is from a small-sized pore size distribution of less than 0.3 micrometers to a larger pore size distribution of greater than 0.6 micrometers. In some embodiments, the upward shift is from a small-sized pore size distribution of less than 0.3 micrometers to a larger pore size distribution of greater than 0.6 micrometers.

[0035] In embodiments of this disclosure, compared to an equivalent untreated preformed catalyst support, the caustic solution-treated preformed catalyst support also exhibits a reduction in surface area, water absorption, and pore volume. Furthermore, in embodiments of this disclosure, compared to an untreated preformed catalyst support, the caustic solution-treated preformed catalyst support also exhibits an increase in average flat plate crush resistance.

[0036] II. Preparation of catalyst supports including caustic solutions In some embodiments, the reduction of pores smaller than 0.3 micrometers is achieved by adding a caustic solution to the support composition during the preparation / forming of the catalyst support. In such embodiments, the support composition comprises any conventional support composition wherein at least one alumina source (i.e., alumina powder) is used to form the catalyst support. In some embodiments, the support composition comprises at least one α-alumina powder, a non-silicate binder, a primary loss-on-burning material, a solvent, and a lubricant. An example of a non-silicate binder is boehmite (γ-AlOOH). Typically, the non-silicate binder is dispersed in deionized water or another solvent. In this disclosure, the α-alumina powder used in the catalyst composition can be milled α-alumina powder, unmilled α-alumina powder, or a combination of milled and unmilled α-alumina powder. In some embodiments, the α-alumina powder is milled α-alumina powder with a particle size of about 0.1 micrometers to about 6 micrometers.

[0037] When using unground α-alumina powder, the unground α-alumina powder used in this disclosure may have an average particle size of about 10 micrometers to about 100 micrometers. When unground α-alumina powder is used in conjunction with ground α-alumina powder, the weight ratio of ground α-alumina powder to unground α-alumina powder may be about 1:10 to about 10:1.

[0038] The primary burnout material that can be used includes any conventional burnout material with a particle size of about 1 micrometer to about 10 micrometers. Some examples of primary burnout materials that can be used include cellulose, substituted cellulose such as methylcellulose, ethylcellulose and carboxyethylcellulose, stearates (e.g., organic stearates such as methyl or ethyl stearates), waxes, granular polyolefins (e.g., polyethylene and polypropylene), walnut shell powder, etc., which burn out at the sintering temperature used to prepare the catalyst support. An auxiliary burnout material may optionally be used. When used, the auxiliary burnout material has a larger particle size than the primary burnout material described above. The auxiliary burnout material may be the same as or different from the primary burnout material. In one embodiment, graphite with a particle size of about 3 micrometers to about 10 micrometers can be used as the auxiliary burnout material. In another embodiment, paraffin or PTFE with a particle size of about 1 micrometer to about 9 micrometers can be used as the auxiliary burnout material. When an auxiliary burnout material is used, the weight ratio of the primary burnout material to the auxiliary burnout material can be in the range of about 1 to 5.

[0039] As described above, the catalyst support composition may contain a lubricant. When present, the lubricant may include conventional lubricants, such as petroleum jelly. The amount of lubricant that can be added at this stage of the invention may include the total amount or a portion of the lubricant used to form the catalyst support of this application.

[0040] The remaining components of the composition may include inorganic oxides other than α-alumina, such as silica, alkali metal oxides (e.g., sodium oxide), and trace amounts of other metal-containing or metal-free additives or impurities. While not limited to the specific compositions and formulations contained herein, more information on support compositions and methods for preparing catalyst supports can be found, for example, in U.S. Patent Publication No. 2007 / 0037991.

[0041] Regardless of the type of support composition used, a caustic solution is added to the support composition. In this embodiment, the caustic solution that can be added to the support composition is the same as that mentioned in the previous embodiment, in which the preformed catalyst support was treated with a hot caustic solution. In this disclosure, the caustic solution is added to the support composition in an amount of about 0.5 wt.% to about 2.5 wt.% based on the total weight of the alumina source present in the support composition. More generally, the amount of caustic solution added to the support composition is about 1 wt.% to about 1.5 wt.% based on the total weight of the alumina source present in the support composition. The addition can be carried out in the presence of continuous or intermittent stirring.

[0042] The carrier composition (i.e., the blend) with the added caustic solution is then molded into a molded body. The shape formed by the molding step can vary and can be selected according to the desired application of the resulting catalyst support. The molding of the blend is typically carried out by pressing, extrusion, molding, casting, etc. In one embodiment of this disclosure, extrusion can be performed using an extrusion die capable of producing a hollow cylindrical shape, which can then be cut into substantially equal-length segments. The cut extrudate is then dried using any conventional drying method.

[0043] After the molded article is formed, it undergoes a calcination step. The calcination step can be carried out at a temperature of about 1200°C or higher, more typically at a calcination temperature of about 1250°C to about 1550°C. The calcination step can be carried out in air, an inert environment, or any combination thereof. In one embodiment, the calcination step can be carried out in flowing air. After the calcination step, the resulting catalyst support is cooled to nominal room temperature. The heating and cooling rates can be in the range of 1°C / min to 5°C / min. Other heating and cooling rates in the range of 0.5°C / min to 20°C / min may also be used in this disclosure.

[0044] After calcination, the catalyst support can be washed to provide a catalyst support with a reduced pore volume percentage of pores smaller than 0.3 micrometers compared to an equivalent catalyst support prepared without the addition of a caustic solution. In this disclosure, the washing step includes washing in deionized water. The washing can be a single wash or multiple washes.

[0045] Catalyst supports formed by adding caustic solutions typically contain at least about 85 wt.%, more typically at least about 90 wt.%, and even more preferably at least about 95 wt.%. The remaining components of catalyst supports formed by adding caustic solutions may include inorganic oxides other than α-alumina, such as silica, alkali metal oxides (e.g., sodium oxide), and trace amounts of other metal-containing or metal-free additives or impurities.

[0046] Catalyst supports formed by adding caustic solutions typically have a pore volume of about 0.2 mL / g to about 0.8 mL / g, more typically about 0.3 mL / g to about 0.5 mL / g. In some embodiments, the catalyst supports formed by adding caustic solutions have a water absorption rate of about 20% to about 80%, more typically in the range of about 30% to about 50%. The catalyst supports formed by adding caustic solutions typically have a pore volume of about 0.3 mL / g. 2 / g to approximately 3.0m 2 The surface area per gram is typically about 0.5 m². 2 / g to approximately 1.2m 2 / g of surface area.

[0047] Catalyst supports formed by adding caustic solutions typically have a multimodal pore size distribution, such as bimodal. A catalyst support formed by adding caustic solutions may include at least one modal pore size distribution with a pore size distribution less than 0.3 micrometers. The at least one modal pore size distribution with a pore size distribution less than 0.3 micrometers may account for at least about 60% or less of the total pore volume of the preformed catalyst support. More typically, the at least one modal pore size distribution with a pore size distribution less than 0.3 micrometers may account for about 1% to about 40% of the total pore volume of the preformed catalyst support. Even more typically, the at least one modal pore size distribution with a pore size distribution less than 0.3 micrometers may account for about 10% to about 30% of the total pore volume of the preformed catalyst support. In some embodiments, the catalyst support formed by adding caustic solutions contains at least about 90% of the pore volume, with the pore volume of the porous body originating from pores with a pore size of about 20 micrometers or smaller. In yet another embodiment of this disclosure, at least about 85% of the pore volume of the preformed catalyst support originates from pores with a size of about 1 micrometer to about 6 micrometers. In yet another embodiment of this disclosure, less than about 15%, preferably less than about 10%, of the pore volume of the preformed catalyst support originates from pores with a size of less than about 1 micrometer. In yet another embodiment of this disclosure, at least about 80% of the pore volume of the preformed catalyst support originates from pores with a size of about 1 to 10 micrometers.

[0048] In some embodiments, the catalyst support formed by adding a caustic solution has an initial low alkali metal content. A catalyst support formed by adding a caustic solution with a low alkali metal content can be obtained by substantially avoiding the addition of alkali metals during the support manufacturing process. In another embodiment, a catalyst support formed by adding a caustic solution with a low alkali metal content can be obtained by performing various washing steps. Washing steps may include washing in an alkali, acid, water, or another solvent.

[0049] In one embodiment of this disclosure, the catalyst support formed by adding a caustic solution may have a silica content of less than about 0.5 wt.%, preferably less than about 0.3 wt.%, based on SiO2, and a sodium content of less than about 0.2 wt.%, preferably less than about 0.1 wt.%, based on Na2O. In some embodiments, the catalyst support formed by adding a caustic solution may have an acid-leached sodium content of 40 ppm or less.

[0050] III. Catalysts comprising catalyst supports with reduced pore size In another embodiment, the catalyst support described above may contain one or more catalytically active materials, typically metals, on or within the support. That is, a catalyst support formed by treating a pre-formed catalyst support with a hot caustic solution, or a catalyst support intentionally made by adding a caustic solution during the support manufacturing process, may contain one or more catalytically active materials. These one or more catalytically active materials can catalyze specific reactions and are well known in the art. In some embodiments, the catalytically active materials include one or more transition metals and / or lanthanides from Groups 3-14 of the periodic table. In such applications, one or more promoters (i.e., substances that contribute to a specific reaction) may also be provided on or within the catalyst support of this disclosure. These one or more promoters may be, for example, alkali metals, alkaline earth metals, transition metals, and / or elements from Groups 15-17 of the periodic table.

[0051] In embodiments where the catalyst support of this disclosure (or a catalyst support formed by treating a pre-formed catalyst support with a hot caustic solution, or a catalyst support intentionally made by adding a caustic solution during the manufacture of the support) is used as a support in silver-based epoxidation catalysis, the catalyst support of this disclosure includes silver on and / or in the support. Silver can be incorporated on or in the catalyst support in ways well known in the art, for example by impregnation with a silver salt followed by heat treatment (which is well known in the art), as described, for example, in U.S. Patent Nos. 4,761,394, 4,766,105, 4,908,343, 5,057,481, 5,187,140, ​​5,102,848, 5,011,807, 5,099,041, and 5,407,888, all of which are incorporated herein by reference. The concentration of the silver salt in solution is typically in the range of about 0.1 wt.% to the maximum value allowed by the solubility of the particular silver salt in the solubility solvent used. More typically, the concentration of silver salt is from about 0.5 wt.% to 45 wt.% based on silver, and even more typically, from about 5 wt.% to 35 wt.% based on the weight of the catalyst support. These amounts are usually also the weight amounts in the catalyst after heat treatment. For suitability as an ethylene epoxidation catalyst, the amount of silver should be catalytically effective for ethylene epoxidation, and it can be any of the amounts mentioned above.

[0052] In addition to silver, the silver-based epoxidation catalyst of this disclosure may further comprise a promoting amount of one or more promoting substances. The one or more promoting substances may be introduced into the catalyst support of this disclosure before, during, or after silver deposition. As used herein, the “promoting amount” of a component of the catalyst refers to the amount by which that component effectively provides one or more improvements in the catalyst’s catalytic performance compared to a catalyst without said component.

[0053] For example, silver-based epoxidation catalysts may contain promoting amounts of Group 1 alkali metals or mixtures of two or more Group 1 alkali metals. Suitable Group 1 alkali metal promoters include, for example, lithium, sodium, potassium, rubidium, cesium, or combinations thereof. Cesium is generally preferred, and combinations of cesium with other alkali metals are also preferred. The amount of alkali metal (based on alkali metal content) is typically from about 10 ppm to about 3000 ppm of the total catalyst, more typically from about 15 ppm to about 2000 ppm, more typically from about 20 ppm to about 1500 ppm, and even more typically from about 50 ppm to about 1000 ppm.

[0054] Silver-based epoxidation catalysts may also contain a promoting amount of a Group 2 alkaline earth metal or a mixture of two or more Group 2 alkaline earth metals. Suitable alkaline earth metal promoters include, for example, beryllium, magnesium, calcium, strontium, and barium, or combinations thereof. The amount of alkaline earth metal promoter is similar to that of the alkali metal promoters described above.

[0055] The silver-based epoxidation catalyst may also contain a promoting amount of a main group element or a mixture of two or more main group elements. Suitable main group elements include any element from Group 13 (Boron Group) to Group 17 (Halogen Group) of the periodic table. In one embodiment, a promoting amount of one or more sulfur compounds, one or more phosphorus compounds, one or more boron compounds, or combinations thereof may be used.

[0056] Silver-based epoxidation catalysts may also contain a promoting amount of transition metal or a mixture of two or more transition metals. Suitable transition metals may include, for example, elements from Group 3 (scandium), Group 4 (titanium), Group 5 (vanadium), Group 6 (chromium), Group 7 (manganese), Groups 8-10 (iron, cobalt, nickel), and Group 11 (copper) of the periodic table, as well as combinations thereof. More generally, the transition metal is an early transition metal selected from Groups 3, 4, 5, 6, or 7 of the periodic table, such as hafnium, yttrium, molybdenum, tungsten, rhenium, chromium, titanium, zirconium, vanadium, tantalum, niobium, or combinations thereof.

[0057] In one embodiment of this disclosure, the silver-based epoxidation catalyst comprises silver, cesium, and rhenium. In another embodiment of this disclosure, the silver-based epoxidation catalyst comprises silver, cesium, rhenium, and one or more substances selected from Li, K, W, Zn, Mo, Mn, and S.

[0058] Silver-based epoxidation catalysts may also contain a promoting amount of rare earth metals or a mixture of two or more rare earth metals. Rare earth metals include any element with atomic numbers 57-71, yttrium (Y), and scandium (Sc). Some examples of these elements include lanthanum (La), cerium (Ce), and samarium (Sm).

[0059] Transition metal or rare earth metal promoters are typically present in a total catalyst amount of about 0.1 μmol / g to about 10 μmol / g, more typically about 0.2 μmol / g to about 5 μmol / g, and even more typically about 0.5 μmol / g to about 4 μmol / g, on a metal basis. All of the above-mentioned promoters, except for alkali metals, can be in any suitable form, including, for example, zero-valent metal or high-valent metal ions.

[0060] Silver-based epoxidation catalysts may also contain a certain amount of rhenium (Re), which is known as a particularly effective promoter for highly selective ethylene epoxidation catalysts. The rhenium component in the catalyst can be in any suitable form, but more typically in one or more rhenium-containing compounds (e.g., rhenium oxides) or complexes. Rhenium can be present, for example, in amounts from about 0.001 wt.% to about 1 wt.%. More typically, rhenium is present, for example, in amounts from about 0.005 wt.% to about 0.5 wt.%, and even more typically, based on the weight of the total catalyst, including the support, and expressed as rhenium metal, in amounts from about 0.01 wt.% to about 0.05 wt.%. All these promoters, except for alkali metals, can be in any suitable form, including, for example, zero-valent or high-valent metal ions.

[0061] After impregnation with silver and any accelerator, the impregnated catalyst support of this disclosure is removed from the solution and calcined for a sufficient time to reduce the silver component to metallic silver and remove volatile decomposition products from the silver-containing support. Calcination is typically accomplished by heating the impregnated catalyst support (preferably at a gradually increasing rate) to a temperature in the range of about 200°C to about 600°C, more typically about 200°C to about 500°C, more typically about 250°C to about 500°C, more typically about 200°C or 300°C to about 450°C, at a reaction pressure in the range of about 0.5 to about 35 bar. Generally, the higher the temperature, the shorter the required calcination time. Various heating time periods for the heat treatment of impregnated supports have been described in the art. See, for example, U.S. Patent No. 3,563,914, which shows heating for less than 300 seconds, and U.S. Patent No. 3,702,259, which discloses heating at temperatures from 100°C to 375°C for 2 to 8 hours to reduce silver salts in a catalyst. Continuous or stepwise heating procedures can be used for this purpose. During calcination, the impregnated catalyst support is typically exposed to a gaseous atmosphere containing an inert gas (e.g., nitrogen). The inert gas may also contain a reducing agent.

[0062] On the other hand, this disclosure relates to a method for producing ethylene oxide in the gas phase by converting ethylene to ethylene oxide in the presence of oxygen using the aforementioned silver-based epoxidation catalyst. Typically, the ethylene oxide production process is carried out by continuously contacting an oxygen-containing gas with ethylene in the presence of a catalyst at temperatures ranging from about 180°C to about 330°C, more typically from about 200°C to about 325°C, and more typically from about 225°C to about 270°C, with pressures varying from about atmospheric pressure to about 30 atmospheres depending on the desired mass rate and yield. Pressures typically range from about atmospheric pressure to about 500 psi. However, higher pressures can be used within the scope of this disclosure. Residence times in large reactors are typically on the order of about 0.1 to about 5 seconds. Typical methods for the oxidation of ethylene to ethylene oxide involve oxidizing the ethylene gas phase with molecular oxygen in a fixed-bed tubular reactor in the presence of the catalyst of this invention. Conventional commercial fixed-bed ethylene oxide reactors are typically in the form of multiple parallel elongated tubes (within a suitable shell). In one embodiment, the tube has an outer diameter of approximately 0.7 to 2.7 inches, an inner diameter of 0.5 to 2.5 inches, a length of 15 to 45 feet, and is filled with catalyst.

[0063] In some embodiments, the silver-based epoxidation catalyst described above exhibits high selectivity in the oxidation of ethylene with molecular oxygen to ethylene oxide. For example, selectivity values ​​of at least about 83 mol% to about 93 mol% can be achieved. In some embodiments, the selectivity is about 87 mol% to about 93 mol%. The conditions for carrying out this oxidation reaction in the presence of the silver-based epoxidation catalyst generally include those described in the prior art. This applies to, for example, suitable temperature, pressure, residence time, diluent material (e.g., nitrogen, carbon dioxide, steam, argon, and methane), the presence of a modifier to control the catalytic activity (e.g., 1,2-dichloroethane, vinyl chloride, or ethyl chloride), whether it is desirable to employ a cyclic operation or to apply continuous conversion in different reactors to increase the ethylene oxide yield, and any other specific conditions that can be selected in the method for preparing ethylene oxide.

[0064] In ethylene oxide production, the reactant feed mixture typically contains about 0.5% to about 45% ethylene and about 3% to about 15% oxygen, with the balance consisting of relatively inert materials, including substances such as nitrogen, carbon dioxide, methane, ethane, and argon. Typically, only a portion of the ethylene reacts with each pass through the catalyst. After separating the desired ethylene oxide product and removing appropriate purge streams and carbon dioxide to prevent uncontrolled accumulation of inert products and / or byproducts, the unreacted material is usually returned to the oxidation reactor.

[0065] The following examples are given to further illustrate this disclosure. The scope of this disclosure should not be limited to the examples given herein.

[0066] Example 1 In this embodiment, three pre-formed catalyst supports, namely catalyst supports 1, 2, and 3, were used to study the effect of NaOH treatment. The NaOH treatment involved immersing each of catalyst supports 1, 2, and 3 in 1M NaOH. Immersion was carried out at 80°C for 3 hours. After immersion, each NaOH-treated catalyst support was decanted, dried, and then subjected to a first calcination at 700°C. Subsequently, each NaOH-treated catalyst support was washed with deionized water, dried, and subjected to a second calcination at 1550°C. The pore size distribution and other properties listed in Table 1 of the untreated and NaOH-treated catalyst supports were analyzed. Figure 1-3 This is a graph illustrating the pore size distribution of catalyst supports 1, 2, and 3 before and after NaOH treatment.

[0067] The data in Table 1 show that, for each NaOH-treated catalyst support, compared to an equivalent untreated catalyst support, the surface area, water absorption rate, and pore volume are reduced, and the number of pores smaller than 0.3 micrometers is also reduced. Furthermore, the data in Table 1 indicate that, for each NaOH-treated catalyst support, compared to an equivalent untreated catalyst support, the average flat plate crush resistance is increased, and the modal pore size exhibits an upward / positive shift. The upward / positive shift of the modal pore size can be described in the following sections of this disclosure. Figure 1-3 As seen in Table 1, the data illustrates that the NaOH treatment according to this disclosure can lead to a reduction in pores smaller than 0.3 micrometers in preformed catalyst supports containing such small-sized pores.

[0068] The effect of NaOH treatment on the morphology of each of catalyst supports 1, 2, and 3 is shown in the figure. Figures 4A-4B , Figures 5A-5B and Figures 6A-6B In the SEM shown. It is worth noting that, Figure 4A , 5A The SEM images shown in Figures 6A and 6A respectively display the morphologies of catalyst supports 1, 2, and 3 before NaOH treatment. Figure 4B , 5B The SEM images shown in Figures 6B and 6B respectively show the morphology of catalyst supports 1, 2 and 3 after NaOH treatment.

[0069] Table 2 includes XRF analyses of catalyst support 1, both untreated and treated with NaOH. XRF analysis showed that the impurities in untreated and NaOH-treated catalyst supports 1 were similar, and no significant increase in Na₂O was observed between the NaOH-treated and untreated catalyst supports.

[0070] Table 1: Examples of NaOH Treatment Table 2: XRF analysis of catalyst support 1 before and after NaOH treatment Example 2 In this embodiment, the effect of adding NaOH during the catalyst support preparation / forming process was investigated. Notably, and in this embodiment, catalyst supports 4 were prepared using the same support preparation process and support composition, with and without the addition of NaOH, in increments of NaOH (0.3 wt.%, 0.6 wt.%, and 1.2 wt.%). Catalyst support 4 is an α-alumina support, prepared by providing a support composition containing at least one alumina source, forming the support composition into a molded body, and then calcining the molded body at 1550°C. Catalyst support 4A was prepared using the same catalyst support preparation / forming process and support composition as catalyst support 4, except that 0.3 wt.% NaOH was added before the molding step. Catalyst support 4B was prepared using the same catalyst support preparation / forming process and support composition as catalyst support 4, except that 0.6 wt.% NaOH was added before the molding step. Catalyst support 4C was prepared using the same catalyst support preparation / molding process and support composition as catalyst support 4, except that 1.2 wt.% NaOH was added before the molding step. The physical properties of each of catalyst supports 4, 4A, 4B, and 4C listed in Table 3 were then determined.

[0071] As shown in Table 3, the catalyst supports prepared with increased NaOH levels exhibit a significant impact on support properties, particularly the micropore size (0.3 μm) distribution. The increased NaOH also reduces the surface area of ​​the catalyst support. This example illustrates that the method of adding NaOH during the catalyst support preparation / forming process of this disclosure can be used to increase and control the micropore size distribution of the support. Micropore size distribution shifts can be addressed within the framework of this disclosure. Figure 7 It can be clearly seen in the middle. Figure 8A (Catalyst support 4 without NaOH) Figure 8B (Catalyst support 4A prepared with 0.3 wt. % NaOH) Figure 8C (Catalyst support 4B prepared with 0.6 wt. % NaOH) and Figure 8D The SEM image shown in (catalyst support 4C prepared with 1.2 wt. % NaOH) reveals visible variations in the morphology, particle size, and porosity of the catalyst support with varying NaOH levels.

[0072] Table 3: Effect of NaOH on the pore size distribution of the support While this disclosure has been specifically shown and described with reference to its preferred embodiments, those skilled in the art will understand that foregoing and other changes in form and detail may be made without departing from the spirit and scope of this disclosure. Therefore, it is expected that this disclosure is not limited to the precise form and detail described and illustrated, but falls within the scope of the appended claims.

Claims

1. A method for reducing the small pore size distribution of a catalyst support, comprising: A preformed catalyst support having a pore size distribution of less than 0.3 micrometers is contacted with a caustic solution to provide a mixture of the caustic solution and the preformed catalyst support. The blend is heated to about 70°C or higher to provide a preformed catalyst support treated with a caustic solution; The preformed catalyst support treated with caustic solution was cooled to nominal room temperature; The preformed catalyst support treated with caustic solution is dried and cooled; The dried, caustic solution-treated preformed catalyst support is calcined at approximately 1200°C or higher. as well as The calcined preformed catalyst support treated with caustic solution is washed to provide a catalyst support with a reduced pore volume having pores smaller than 0.3 micrometers compared to the preformed catalyst support.

2. The method of claim 1, wherein the caustic solution comprises an alkali with a pH of about 13 or greater and water.

3. The method of claim 2, wherein the molar concentration of the caustic solution is from about 0.1 M to about 2 M.

4. The method of claim 3, wherein the molar concentration of the caustic solution is from about 0.5 M to about 1 M.

5. The method of claim 1, wherein the contact comprises adding the caustic solution to the preformed catalyst carrier in an amount of about 2 ml to about 20 ml per gram of the preformed catalyst carrier used.

6. The method of claim 5, wherein the contact comprises adding the caustic solution to the preformed catalyst carrier in an amount of about 5 ml to about 10 ml per gram of the preformed catalyst carrier used.

7. The method of claim 1, wherein the caustic solution is NaOH.

8. The method of claim 1, wherein the heating temperature is from about 50°C to about 90°C.

9. The method of claim 1, further comprising adding a catalytically effective amount of silver to the catalyst support.

10. The method of claim 1, further comprising adding a promoting amount of a transition metal or a mixture of two or more transition metals to the catalyst support.

11. A method for forming a catalyst support, comprising: Add a caustic solution to the carrier composition to provide a mixture of the carrier composition and the caustic solution; The mixture is molded into a molded body; as well as The molded body is calcined at a temperature of about 1200°C or higher to convert it into a catalyst support.

12. The method of claim 11, wherein the caustic solution comprises an alkali with a pH of about 13 or greater and water.

13. The method of claim 12, wherein the molar concentration of the caustic solution is from about 0.1 M to about 2 M.

14. The method of claim 13, wherein the molar concentration of the caustic solution is from about 0.5 M to about 1 M.

15. The method of claim 11, wherein, Based on the total amount of alumina source present in the carrier composition, the amount of caustic solution added is from about 10 wt.% to about 50 wt.%.

16. The method of claim 15, wherein, Based on the total amount of alumina source present in the carrier composition, the amount of caustic solution added is from about 20 wt.% to about 30 wt.%.

17. The method of claim 11, wherein the caustic solution is NaOH.

18. The method of claim 11, wherein the molding comprises extrusion.

19. The method of claim 11, further comprising adding a catalytically effective amount of silver to the catalyst support.

20. The method of claim 19, further comprising adding a promoting amount of a transition metal or a mixture of two or more transition metals to the catalyst support.

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