Selective hydrogenation catalyst having a mixed alumina phase support

Abstract

The method for producing a selective hydrogenation catalyst involves approximately 30 to 60 square meters / gram (m²). 2 The method also includes forming a mixed-phase alumina support having a BET surface area in the range of / g), the mixed-phase alumina support comprising alpha-alumina and theta-alumina. The method further includes impregnating the mixed-phase alumina support with an impregnation solution having one or more metals selected from Group VIIIB, Group IB, or both of the periodic table to form an impregnated support; drying the impregnated support at a temperature in the range of approximately 100°C to 150°C to form a dried impregnated support; calcining the dried impregnated support at a temperature in the range of 350°C to approximately 500°C to form a calcined impregnated support; and reducing one or more metals on the calcined impregnated support in the presence of hydrogen at a temperature in the range of approximately 400°C to approximately 600°C to form a selective hydrogenation catalyst.

Description

[Technical Field]

[0001] This disclosure relates to a catalyst composition comprising bimetallic nanoparticles contained on a support, and a method for preparing the catalyst composition. The catalyst composition is useful for the selective hydrogenation of highly unsaturated hydrocarbons contained in a treatment stream of low-unsaturated hydrocarbons. [Background technology]

[0002] Steam cracking units and refinery cracking units provide the production of unsaturated hydrocarbon product streams used as feedstock for downstream processes and other applications. Steam cracking units typically crack low molecular weight saturated hydrocarbons, such as ethane, propane, and butane, or naphtha-boiling-point range hydrocarbons, to produce lighter alkenes, such as ethylene, propylene, and butylene. Refinery cracking units typically crack heavy hydrocarbon fractions to obtain multiple product streams, including light gaseous hydrocarbons with high concentrations of unsaturated hydrocarbons.

[0003] One problem with the light olefin product streams obtained from these decomposition devices is that the olefin product streams may contain unacceptable concentrations of more highly unsaturated hydrocarbons (e.g., diolefins, alkynes, aromatic compounds, etc.). For example, the ethylene product stream may contain contamination concentrations of acetylene, or the propylene product stream may contain contamination concentrations of methylacetylene (MA) and propadiene (PD). The acetylene contained in the ethylene product stream, and the methylacetylene and propadiene contained in the propylene product stream, need to be removed from these product streams in order to make them usable.

[0004] Therefore, highly unsaturated hydrocarbons such as diolefins and hydrocarbons with triple bonds (alkynes) need to be removed from low-unsaturated product streams such as ethylene or propylene product streams. Selective hydrogenation processes are typically used to remove undesirable highly unsaturated hydrocarbons (e.g., alkenes, alkynes, etc.) from low-unsaturated hydrocarbon streams (e.g., ethylene and propylene).

[0005] A selective hydrogenation process is a catalytic process. This process involves contacting an olefin flow having a higher concentration of more unsaturated hydrocarbons with a selective hydrogenation catalyst under suitable reaction conditions. The more unsaturated hydrocarbons are selectively hydrogenated to olefins, with minimal hydrogenation of the desired olefin (e.g., ethylene and / or propylene) in the olefin flow. Desirable characteristics of the selective hydrogenation catalyst include high activity for providing the described selective hydrogenation and a long operating life.

[0006] PCT Publication 2013 / 186789 describes one of these selective hydrogenation catalysts. This catalyst comprises an inorganic oxide support and so-called fine alloy particles of an active metal component and an accelerator component. The active metal is selected from palladium, platinum, and nickel, and the accelerator is selected from silver, gold, and copper. The fine alloy particles are dispersed on the surface of the inorganic oxide support by a co-dispersion process using equilibrium absorption impregnation of the inorganic oxide support by contacting the inorganic oxide support with a solution containing the fine alloy particles. Examples of inorganic supports used in this catalyst include alpha alumina, theta alumina, delta alumina, gamma alumina, and combinations thereof. However, there is no disclosure regarding the ratio or amount of different phases of alumina in the inorganic support. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2013 / 186789 [Overview of the Initiative]

[0008] In one embodiment, a method for producing a selective hydrogenation catalyst involves a volume of approximately 30 to approximately 60 square meters / gram (m²). 2 The method also includes forming a mixed-phase alumina support having a BET surface area in the range of / g), the mixed-phase alumina support comprising alpha-alumina and theta-alumina. The method further includes impregnating the mixed-phase alumina support with an impregnation solution having one or more metals selected from Group VIIIB, Group IB, or both of the periodic table to form an impregnated support; drying the impregnated support at a temperature in the range of approximately 100°C to 150°C to form a dried impregnated support; calcining the dried impregnated support at a temperature in the range of 350°C to approximately 500°C to form a calcined impregnated support; and reducing one or more metals on the calcined impregnated support in the presence of hydrogen at a temperature in the range of approximately 400°C to approximately 600°C to form a selective hydrogenation catalyst.

[0009] In another embodiment, approximately 30 to approximately 60 square meters / gram (m 2 A selective hydrogenation catalyst comprising a mixed-phase alumina support having a BET surface area in the range of / g) and containing alpha-alumina and theta-alumina. The alpha-alumina is present in an amount of 30% to 70% by volume, with the remainder being theta-alumina. The selective hydrogenation catalyst also comprises bimetallic nanoparticles having at least one metal selected from group VIIIB of the periodic table and at least one metal selected from group IB.

[0010] In a further embodiment, a method for the selective hydrogenation of acetylene comprises contacting a selective hydrogenation catalyst with an olefin stream having a contamination concentration of unsaturated hydrocarbons under selective hydrogenation reaction conditions. The selective hydrogenation catalyst is approximately 30 to approximately 60 square meters / gram (m²). 2The invention comprises a mixed-phase alumina support having alpha-alumina and theta-alumina, having a BET surface area in the range of / g), wherein alpha-alumina is present in an amount of 30% to 70% by volume and the remainder is theta-alumina, and bimetallic nanoparticles having at least one metal selected from Group VIIIB of the periodic table and a promoting metal from Group IB.

[0011] Additional features and advantages of exemplary implementations of the present disclosure are described below, some of which will be evident from the description or may be acquired by implementing such exemplary implementations. Such features and advantages may be realized and acquired by means and combinations specifically indicated in the appended claims. These and other features will be more fully evident from the following description and the appended claims or may be acquired by implementing the exemplary implementations described below. [Brief explanation of the drawing]

[0012] The advantages of this disclosure may become apparent by reading the detailed description below and referring to the drawings. [Figure 1] This is a flowchart of a method for producing a selective hydrogenation catalyst having a mixed-phase alumina support, in which the mixed-phase alumina support is impregnated in one step, according to an embodiment of the present disclosure. [Figure 2] This is a flowchart of a method for producing a selective hydrogenation catalyst having a mixed-phase alumina support having a two-step impregnation process, according to embodiments of the present disclosure. [Figure 3] This is a plot of catalyst selectivity / reactor temperature as a function of time for the catalytic performance of the catalyst and comparative catalyst of the present invention according to embodiments of the present disclosure. [Figure 4] This is a plot of the mass of green oil (GO) as a function of flow time for the catalyst and comparative catalyst of the present invention according to embodiments of the present disclosure. [Figure 5]A bar graph showing the amount of GO trapped in a cold trap during the selective hydrogenation process when using the catalyst of the present invention and a comparative catalyst according to an embodiment of the present disclosure.

Mode for Carrying Out the Invention

[0013] One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the technology disclosed in the present application. Further, in order to provide a concise description of these embodiments, not all features of the actual implementation forms may be described herein. As is the case in any engineering or design project, in the development of any such actual implementation form, it should be understood that numerous implementation form-specific decisions are made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which may vary from implementation form to implementation form. Further, although such development efforts may be complex and time-consuming, it should be understood that they are routine work in design, fabrication, and manufacturing for those skilled in the art who benefit from the present disclosure.

[0014] When introducing elements of various embodiments of the present disclosure, the articles "a", "an", and "the" are intended to mean that one or more of the elements exist. The terms "comprising", "including", and "having" are intended to be inclusive and mean that additional elements other than the recited elements may exist. In addition, it should be understood that references to "one embodiment" or "an embodiment" of the present disclosure are not intended to be construed as excluding the existence of additional embodiments that also incorporate the recited features.

[0015] As used herein, the terms "about", "approximately", and "substantially" represent an amount close to the stated amount that still performs the desired function or achieves the desired result. For example, the terms "about", "approximately", and "substantially" may refer to an amount within less than 10%, within less than 5%, within less than 1%, within less than 0.1%, and within less than 0.01% of the stated amount.

[0016] As mentioned above, selective hydrogenation for removing unsaturated hydrocarbons such as acetylene, methylacetylene, and propadiene is a catalytic process. In certain existing catalysts used for the selective hydrogenation of unsaturated hydrocarbons, the hydrogenation activity decreases over time due to degradation. For example, during selective hydrogenation, undesirable byproducts (e.g., heavy wax and green oil) resulting from the hydrogenation of unsaturated hydrocarbons are formed and accumulate on the catalyst surface. The accumulation of these undesirable byproducts over time causes catalyst degradation and deactivation, thereby reducing the overall performance of the selective hydrogenation catalyst. Therefore, it would be advantageous to develop a selective hydrogenation catalyst for removing unsaturated hydrocarbons from olefin streams that mitigates the formation of undesirable byproducts and has improved performance and stability compared to existing catalysts.

[0017] Selective hydrogenation catalysts are generally supported catalysts containing one or more precious metals (e.g., platinum, palladium, gold, silver, etc.). For example, a selective hydrogenation catalyst may contain a support (or carrier) containing one or more precious metals such as palladium (Pd), with an adjuvant amount of silver (Ag) impregnated onto the support. Supports used in existing catalysts are alumina-based, with a density of approximately 20 square meters / gram (m²). 2 / g) It has the following BET surface area. These alumina-based supports are mostly composed of alpha alumina. For example, the alumina-based supports of existing catalysts can have more than 90% alpha alumina. However, as described above, during the selective hydrogenation of an olefin stream having a large amount of unsaturated hydrocarbons (e.g., more than approximately 1 volume % (vol%)), undesirable by-products are formed that cause catalyst degradation and performance decline. Therefore, the reaction temperature is increased so that a desired amount of selective conversion of unsaturated hydrocarbons to smaller unsaturated C2 and / or C3 hydrocarbons can be achieved. Surprisingly, it has been found that by using a support having a mixed-phase alumina, the formation of undesirable by-products is reduced. Thereby, catalyst degradation can be alleviated and the desired catalyst performance is maintained. For example, as discussed in more detail below, the selective hydrogenation catalyst of the present disclosure includes a support having a mixture of theta (θ) alumina and alpha (α) alumina, which reduces the formation of undesirable by-products (e.g., wax and gas oil) during the selective hydrogenation process and improves the overall performance of the catalyst.

[0018] In addition to the selective hydrogenation catalyst, the present disclosure includes contacting an olefin process stream, which may have a certain concentration of highly unsaturated hydrocarbons (e.g., unsaturated hydrocarbons), with the catalyst under suitable reaction conditions. The catalyst provides for the selective hydrogenation of highly unsaturated hydrocarbons (e.g., unsaturated hydrocarbons having 6 or more carbon atoms) to low-unsaturated hydrocarbons, i.e., olefins, while the amount of undesirable hydrogenation of the olefins in the olefin process stream is minimal (e.g., less than 5%). In fact, as used herein, when referring to the selective hydrogenation catalyst disclosed herein, it means that the catalyst provides for the hydrogenation of highly unsaturated hydrocarbons such as alkynes and polyolefins contained in the olefin stream without hydrogenating a significant amount of olefins (e.g., alkenes) in the olefin stream to saturated hydrocarbons (e.g., alkanes).

[0019] <你提供的原始文本中此标签对应的内容为空,我按照原样保留> The disclosed catalyst is highly selective, particularly when used for the selective hydrogenation of acetylene contained in ethylene process streams. The catalyst is also remarkably stable, with a significantly lower rate of decline in its selectivity and activity due to time-on-stream (TOS) compared to other comparative catalysts. For example, the disclosed catalyst exhibits a decline in its selectivity and activity due to TOS approximately 5-6 times lower than that of existing catalysts. This means that the cycle length of the catalyst in use is significantly longer than that of other comparative catalysts. In fact, the catalyst disclosed herein can provide more than twice the cycle length of other catalysts.

[0020] The unexpectedly high selectivity characteristic of the disclosed catalyst means that when the catalyst is used in a selective hydrogenation process, undesirable unsaturated C 4+ It provides a much lower yield (e.g., less than approximately 50%) of hydrocarbon and / or green oil byproducts. As used herein, the term “green oil” refers to a mixture of compounds produced by side reactions during the selective hydrogenation of alkynes and diolefins contained in an olefin process stream. These side reactions form dimers, trimers, and other oligomers of alkynes and diolefins. Green oil oligomer compounds may have up to 24 or more carbon atoms per molecule.

[0021] The disclosed catalyst composition is a selective hydrogenation catalyst or selective hydrogenation catalyst precursor that can provide the numerous benefits discussed herein. The composition comprises a mixed alumina phase support / carrier containing impregnated bimetallic nanoparticles. The bimetallic nanoparticles contain one or more noble metal components, such as a silver component and a palladium component. These bimetallic nanoparticles have a silver-rich outer surface.

[0022] The alumina support used to prepare the catalyst compositions disclosed herein significantly contributes to their special properties. For example, existing selective hydrogenation catalysts use a support composed of more than 90% alpha-alumina, and 20m 2It has a BET surface area of less than 20 m² / g. In contrast, the support of the selective hydrogenation catalyst of the present disclosure has approximately 70% or less of alpha alumina. In particular, the disclosed catalyst has approximately 30% to approximately 70% of alpha alumina. In addition to alpha alumina, the support also has theta alumina. The theta alumina is present in an amount of approximately 30% to approximately 70%. For example, in an embodiment where the alpha alumina in the support is 70%, the theta alumina constitutes 30% of the total alumina in the support. In one embodiment, the ratio of alpha alumina to theta alumina in the support is 1:1. In this particular example, alpha alumina and theta alumina each constitute 50% of the total alumina in the support.

[0023] As described above, the surface area of the support in existing selective hydrogenation catalysts is approximately 20 m² / g or less in terms of BET surface area. However, unlike existing catalysts, the surface area of the support used in the catalysts disclosed herein is approximately 30 - 60 m² / g in terms of BET surface area. The surface area of the mixed-phase alumina support is affected by the ratio of alpha alumina to theta alumina. It has been found that by having theta alumina in the range of approximately 30% to approximately 70%, the desired surface area of the mixed-phase alumina can be achieved. 2 As described above, the surface area of the support in existing selective hydrogenation catalysts is less than 20 m² / g in terms of BET surface area. However, unlike existing catalysts, the surface area of the support used in the catalysts disclosed herein is approximately 30 - 60 m² / g in terms of BET surface area. The surface area of the mixed-phase alumina support is affected by the ratio of alpha alumina to theta alumina. It has been found that by having theta alumina in the range of approximately 30% to approximately 70%, the desired surface area of the mixed-phase alumina can be achieved. 2 / g in terms of BET surface area. The surface area of the mixed-phase alumina support is affected by the ratio of alpha alumina to theta alumina. It has been found that by having theta alumina in the range of approximately 30% to approximately 70%, the desired surface area of the mixed-phase alumina can be achieved.

[0024] By using a mixed-phase alumina support in the selective hydrogenation catalysts disclosed herein, catalyst degradation can be reduced and the overall performance can be improved compared to existing catalysts. For example, as will be discussed in more detail below, the selective hydrogenation catalysts of the present disclosure can form heavy waxes and green oils that accumulate on the catalyst surface and have an undesirable effect on performance, such as heavy even-carbon by-products (e.g., C6, C8, C 10+ ) to form less.

[0025] In addition to the mixed-phase alumina support, other features of the selective hydrogenation catalyst disclosed herein exist, which contribute to its unexpected properties and performance. These include the relative amounts of noble metals (e.g., silver and palladium) contained in the catalyst. For example, the ratio of silver to palladium can be an important factor in the selectivity of the catalyst. In all cases, the molar ratio of palladium to silver in the bimetallic nanoparticles should be in the range of 0.01:1 to 1:10. However, it may be desirable for silver and palladium to be present such that the molar ratio of palladium to silver is in a much narrower range. In particular, in certain embodiments, the molar ratio of palladium to silver in the bimetallic nanoparticles is in the range of 1:6.

[0026] Bimetallic nanoparticles have a total diameter of approximately 4 nanometers (nm) or less. For example, bimetallic nanoparticles may have a total diameter of 1, 2, 3, or 4 nm. As can be understood, not all bimetallic nanoparticles on a support have a diameter of 4 nm. Bimetallic nanoparticles on any given support may have different diameters within a desired range. In a preferred embodiment, bimetallic nanoparticles have a total diameter in the range of approximately 2 nm to approximately 3 nm.

[0027] With the foregoing in mind, Figure 1 is a block diagram of Method 10 for preparing a selective hydrogenation catalyst disclosed herein. Method 10 includes forming a mixed-phase alumina support (block 12). For example, to form a mixed-phase alumina support, an alumina precursor is placed in a calcination furnace (e.g., a rotary calcination furnace) and calcined at a temperature of approximately 1000°C to approximately 1200°C for approximately 2 to approximately 6 hours, thereby forming a mixed-phase alumina support. In a preferred embodiment, the alumina precursor is calcined at a temperature of 1075°C to 1100°C for 3 to 5 hours. The alumina precursor may be boehmite, gamma alumina, theta alumina, alpha alumina, gibbsite, diaspore, or any other suitable alumina mixture resulting in an alumina mixture having both alpha and theta phases. The alumina precursor may be of any preferred size and shape. For example, the alumina precursor may be in the form of tablets, pellets, extruded products, or any other suitable shape, and may have a size of 0.5 mm to 20 mm.

[0028] By calcining an alumina precursor at a temperature exceeding 1000°C, the phases of the alumina precursor are converted to different phases. In particular, the phases of the alumina precursor are converted to alpha and theta phases. The resulting mixed-phase alumina support disclosed herein contains approximately 30% to 70% by weight of alpha alumina, with the remainder being theta alumina. For example, in one embodiment, the mixed-phase alumina support contains 30% by weight of alpha alumina and 70% by weight of theta alumina. In another embodiment, the mixed-phase alumina support contains 70% by weight of alpha alumina and 30% by weight of theta alumina. In a preferred embodiment, the mixed-phase alumina support contains 50% by weight of alpha alumina and 50% by weight of theta alumina. The amounts of alpha alumina and theta alumina in the resulting mixed-phase alumina support can be controlled by the calcination temperature and calcination time.

[0029] Alumina precursors can be formed into structures of desired shapes by any known preferred method. Extruded structures are typically prepared by mixing the desired alumina powder with water and one or more additives to form a plastic mixture, and then forming this mixture into an extruded product by any known extrusion method. The formed extruded products may be cylindrical, lobe-shaped, or twisted, having a nominal extruded diameter in the range of 0.5 mm to 25 mm and an extruded length in the range of 1 mm to 50 mm.

[0030] Spherical structures or balls of alumina precursors can be produced by applying any known granulation method, which uses an inclined rotating disk or pan to supply inorganic oxide particles while simultaneously spraying an agglomerating slurry onto the particles. By this method, the particles are formed into spherical particles. The spherical carrier particles have a diameter in the range of 0.5 mm to 25 mm.

[0031] Dry tableting can also be used to prepare molded alumina precursor structures. In this method, cylindrical pellets or pills of alumina precursor are produced by pressing dry alumina powder, which is optionally mixed with additives such as lubricants and binders, between two punches of a tableting press. The alumina precursor particles, which are cylindrical pellets, have a pellet diameter in the range of 0.5 mm to 25 mm and a pellet length in the range of 1 mm to 50 mm. The molded alumina precursor is calcined as described above.

[0032] The calcined molded alumina precursor has a surface area and pore volume that allows the mixed-phase alumina support to be impregnated with metal nanoparticles or a metal salt solution. The mixed-phase alumina support of this disclosure is 30 m 2 / g~70m 2 / g, preferably 40m 2 / g~60m 2 / g, most preferably 50m 2It has a surface area in the range of / g (determined by the BET method using N2, ASTM test method D3037) and a bulk density in the range of 0.7 to 0.8 grams / cubic centimeter (g / cc). It has been found that the surface area of ​​the molded alumina precursor can be adjusted based on the amount of theta alumina present in the mixed-phase alumina support. In particular, it has been found that by having theta alumina in the range of approximately 30% to 70%, the surface area of ​​the mixed-phase support can be increased by 2 to 3 times compared to a support having alpha alumina as the sole alumina phase. Compared to alumina supports of existing catalysts, the higher surface area of ​​the mixed-phase alumina support provides improved hydrogenation activity, partly due to the increased metal surface area of ​​the catalyst as a whole in this disclosure.

[0033] The mixed-phase alumina support obtained from the action of block 12 has a bimodal pore size distribution with pore radii in the range of approximately 5 nanometers (nm) to 150 nm. The pore volume of the mixed-phase alumina support is in the range of 0.40 cubic centimeters / gram (cc / g) to 0.65 cc / g. Preferably, the pore volume is in the range of 50 cc / g to 55 cc / g. The references herein to the pore size distribution and pore volume of the calcined molded particles are for properties such as those determined by mercury intrusion porosimetry, ASTM test method D4284. The measurement of the pore size distribution of the calcined molded particles is performed at 25°C with a mercury surface tension of 474 dynes / cm, and 140 o The contact angle is used and measured by any suitable measuring device.

[0034] Method 10 includes preparing a metal salt impregnation solution (block 16). The metal salt impregnation solution can be prepared by any preferred technique. For example, the metal salt may be dissolved in a desired volume of water. Examples of metal salts used to prepare the impregnation solution include, but are not limited to, noble metal salts such as palladium salts and silver salts. As a non-limiting example, the palladium salt used to prepare the impregnation solution is selected from the group of palladium salts consisting of palladium nitrate, palladium halide, palladium carbonate, palladium phosphate, palladium acetate, palladium oxide, and palladium sulfate, and the silver salt used to prepare the impregnation solution is selected from the group of silver salts consisting of silver nitrate, silver halide, silver carbonate, silver phosphate, silver acetate, silver hydroxide, silver oxide, and silver sulfate. A preferred palladium salt is palladium nitrate, and a preferred silver salt is silver nitrate.

[0035] The amount of water used to dissolve the precious metal salt is equal to the pore volume of the mixed-phase alumina support (so-called incipient wetness). The relative amounts of palladium salt and silver salt in the impregnation solution are such that the catalyst of this disclosure has approximately 0.01% by weight and 0.1% by weight of palladium and approximately 0.03% to 0.5% by weight of silver.

[0036] After preparing the impregnation solution according to the actions of block 16, method 10 includes impregnating a mixed-phase alumina support with the impregnation solution to form an impregnated support (block 18). For example, the impregnation solution may be sprayed onto the mixed-phase alumina support at ambient temperature so that the pores of the mixed-phase alumina support are filled with the first impregnation solution. However, any other suitable impregnation technique may be used, for example, initial wet impregnation and wet impregnation.

[0037] Method 10 also includes drying and firing the impregnated support to form a fired impregnated support (block 20). For example, the impregnated support is dried in air at a temperature of approximately 100°C to approximately 150°C for 5 to 30 minutes. The resulting dried support is further fired in air at a temperature of approximately 350°C to approximately 500°C for 1 to 5 hours, thereby forming a fired impregnated support.

[0038] After drying and calcining the impregnated support according to Block 20, the noble metal in the calcined impregnated support is reduced to form a selective hydrogenation catalyst (Block 24). For example, the calcined impregnated support is heat-treated in a hydrogen-containing atmosphere at a temperature of approximately 400°C to approximately 600°C for 1 to 6 hours. The hydrogen-containing atmosphere may have more than 20% hydrogen and the remainder nitrogen. In a preferred embodiment, the calcined impregnated support is heat-treated at a temperature of 500°C. By reducing the noble metal at a temperature in the range of approximately 400°C to approximately 500°C, the bimetallic nanoparticles may have a silver-rich outer surface. The silver-rich outer surface of the bimetallic nanoparticles is beneficial for the stability and activity of the selective hydrogenation catalyst of the present disclosure.

[0039] Figure 2 is a flow chart of Method 30, which may also be used to prepare a selective hydrogenation catalyst of the present disclosure. In Method 30, a mixed alumina support is prepared in the same manner as in Method 10 (Block 12). However, instead of impregnating the mixed alumina support with a single impregnation solution containing both a palladium salt and a silver salt, Method 30 impregnates the palladium salt and the silver salt separately. For example, Method 30 includes preparing a first impregnation solution and a second impregnation solution (Block 32). The impregnation solutions may be prepared by dissolving a metal salt in a desired volume of water. Examples of metal salts used to prepare each impregnation solution include, but are not limited to, palladium salts and silver salts. As a non-limiting example, the palladium salt used to prepare the first impregnation solution is selected from the group of palladium salts consisting of palladium nitrate, palladium halide, palladium carbonate, palladium phosphate, palladium acetate, palladium oxide, and palladium sulfate. A preferred palladium salt is palladium nitrate. The silver salt used in the preparation of the second impregnation solution is selected from the group of silver salts consisting of silver nitrate, silver halide, silver carbonate, silver phosphate, silver acetate, silver hydroxide, silver oxide, and silver sulfate. The preferred silver salt is silver nitrate.

[0040] After preparing the impregnation solution according to the actions of block 32, method 30 includes impregnating a mixed-phase alumina support with the first impregnation solution to form a first impregnated support (block 36), drying and calcining the first impregnated support to form a first calcined impregnated support (block 38), and reducing the calcined impregnated support to form a reduced metal impregnated support (block 40). The actions of blocks 36, 38, and 40 are carried out in the same manner as the actions of blocks 18, 20, and 24, respectively.

[0041] Method 30 further includes impregnating a reducing metal-impregnated support with a second impregnation solution to form a second impregnated support (block 42). Similar to the action in block 18 of Method 10, the second impregnation solution can be sprayed onto the reducing metal-impregnated support at ambient temperature so that the second impregnation solution coats the reducing metal particles in the pores of the reducing metal-impregnated support. The noble metal salt in the second impregnation solution may be either a palladium salt or a silver salt, depending on which noble metal is desired to be the outermost metal. In a preferred embodiment, the metal salt in the second impregnation solution is a silver salt.

[0042] The second impregnated support is dried to remove water and calcined to form a second calcined impregnated support (block 48), and the remaining second metal salt on the second calcined impregnated support is reduced in the same manner as in the actions of blocks 20 and 24, respectively (block 50), thereby forming the selective hydrogenation catalyst of the present disclosure.

[0043] The selective hydrogenation catalyst compositions of the present disclosure have a total silver content in the range of 0.03% to 0.5% by weight and a total palladium content in the range of 0.01% to 1% by weight. Preferably, the total silver content is in the range of 0.04% to 0.3% by weight. Preferably, the total palladium content of the selective hydrogenation catalyst composition is in the range of 0.015% to 0.09% by weight, more preferably 0.02% to 0.08% by weight. The weight percentage of silver is based on the total weight of the catalyst composition, assuming that silver is a metal regardless of its actual form. The weight percentage of palladium is based on the total weight of the catalyst composition, assuming that palladium is a metal regardless of its actual form.

[0044] As described above, the selective hydrogenation catalysts of the present disclosure can be used for the selective hydrogenation of acetylene and other highly unsaturated hydrocarbons. Surprisingly, catalysts such as those of the present disclosure have a lifespan of 20m 2It has been found that a selective hydrogenation catalyst having a mixed-phase alumina support in combination with a surface area exceeding / g reduces the formation of undesirable by-products that lead to catalyst degradation and have an undesirable impact on performance. Therefore, at least in part, the reduction of undesirable by-products makes the disclosed catalyst more stable and improves overall performance compared to existing catalysts. The selective hydrogenation process can be carried out in a single reactor or in two or more reactors connected in any preferred flow configuration. When two or more reactors are used, the reactors can be arranged in parallel flow, series flow, or a combination of the two flow configurations. Each reactor defines a reaction zone containing a certain volume of selective hydrogenation catalyst. Each reactor is provided with a feed inlet means for receiving a feed flow and introducing it into its reaction zone, which is operated under selective hydrogenation reaction conditions. Each reactor is also provided with a reactor effluent outlet means for withdrawing reactor effluent from its reaction zone.

[0045] In a selective hydrogenation process, an olefin feed is introduced into a reaction zone containing a selective hydrogenation catalyst as disclosed herein. The olefin feed is an alkene product stream containing monounsaturated hydrocarbons, which is brought into contact with the catalyst within the reaction zone under selective hydrogenation reaction conditions. A preferred monounsaturated hydrocarbon product stream may be any product stream of ethylene, propylene, or butylene, or a combination of these low molecular weight olefins.

[0046] The olefin feed or alkene product streams treated by the selective hydrogenation process of the present disclosure may also contain contamination concentrations of highly unsaturated hydrocarbons such as alkynes, e.g., acetylene or methylacetylene, and polyunsaturated hydrocarbons such as diolefins, e.g., propadiene. The selective hydrogenation catalysts disclosed herein provide selective hydrogenation of the highly unsaturated hydrocarbons contained in the olefin feed to their respective monosaturated hydrocarbons, i.e., olefins, with minimal hydrogenation of the olefins in the olefin feed to saturated hydrocarbons (e.g., ethane).

[0047] Preferred uses of selective hydrogenation catalysts include the selective hydrogenation of acetylene contained in an ethylene product stream, or the selective hydrogenation of methylacetylene and propadiene contained in a propylene product stream. Of these two processes, the selective hydrogenation catalysts of the present disclosure are particularly useful in the selective hydrogenation of acetylene contained in an ethylene product stream.

[0048] The ethylene product feed to a selective acetylene hydrogenation process can typically have an acetylene concentration between 2 mol% and 100 parts per million moles (ppmm). The selective hydrogenation process can reduce the concentration of acetylene in the ethylene product feed, resulting in a reactor effluent or treated ethylene product with a reduced acetylene concentration, typically significantly below 100 ppm. This process is highly selective in the hydrogenation of acetylene. The selectivity is typically greater than 70%, more typically greater than 72%, and even greater than 74%. Ethylene selectivity is defined as the difference between the volume of ethylene in the reactor inlet feed and the volume of ethylene in the reactor outlet feed, divided by the difference between the acetylene in the reactor inlet feed and the acetylene in the reactor outlet feed, and multiplied by 100. Selective hydrogenation of acetylene is an ethylene flow for forming ethylene and is typically carried out as a gas-phase process with a space velocity of gaseous ethylene flow ranging from 500 v / vh to 15,000 v / vh based on catalyst volume, a temperature ranging from 10°C to 250°C, and a pressure ranging from 0.01 bar to 90 bar. The molar ratio of hydrogen to acetylene in the feed contacted with the selective hydrogenation catalyst is typically in the range of 0.8 to 1.8.

[0049] The selective hydrogenation of methylacetylene and propadiene contained in a propylene stream for the formation of propylene can be carried out as a gas-phase or liquid-phase process. In the case of a gas-phase process, the space velocity of the propylene stream is typically in the range of 1,500 v / vh to 5,000 v / vh, based on the catalyst volume. The reaction temperature is in the range of 50°C to 180°C, and the pressure may be in the range of 10 bar to 35 bar. The molar ratio of hydrogen to methylacetylene and propadiene in the propylene stream in the feed that is contacted with the selective hydrogenation catalyst is typically in the range of 0.8 to 2.

[0050] The following examples are provided to illustrate the unexpectedly improved performance of the selective hydrogenation catalysts of the present disclosure, but they should not be construed as limiting them in any way. For each sample, the depth of the deposited precious metals on the catalyst was determined using an electron probe microanalyzer (EPMA). The EPMA provides information on the chemical composition of the sample surface using an electron beam coupled with a wavelength-dispersive X-ray spectrometer (WDX). A cross-section of the catalyst is prepared by polishing the sample. Point measurements at predetermined positions along the cross-section (typically in 50 μm steps) are performed by moving an electric sample stage under a non-moving electron beam. This results in a line scan of various dots. The impregnation thickness can then be determined by the concentration along the line position across the cross-section.

[0051] Example 1-1 Step Impregnation This Example 1 describes the preparation of catalyst 1, which represents the catalyst of the present invention.

[0052] A 5 mm bullet of gamma alumina is calcined at approximately 1100°C for 3-5 hours to form a mixed-phase alumina support having 50% alpha alumina and 50% theta alumina. The impregnation solution is prepared by dissolving a certain amount of palladium nitrate (Pd(NO3)2) and silver nitrate (AgNO3) in a volume of water equal to the pore volume of the mixed-phase alumina support, resulting in approximately 0.03% Pd and 0.18% Ag on the final catalyst. The impregnation solution is sprayed onto the mixed-phase alumina support at ambient temperature. The impregnated mixed-phase alumina support is dried in air at 120°C for 2 hours. The dried impregnated mixed-phase alumina support is calcined in air at 500°C for 3 hours. After calcination, the resulting impregnated mixed-phase alumina support is heated at 400°C for 1 hour in a hydrogen-containing atmosphere with >20% hydrogen to reduce the palladium and silver metals and form selective hydrogenation catalyst 1. In the resulting catalyst 1, 95% of the Pd metal is deposited on the outer 100 micrometers (μm) of the mixed alumina phase support.

[0053] Example 2-2 Step Impregnation This Example 2 describes the preparation of catalyst 2, which represents the catalyst of the present invention.

[0054] A 5 mm gamma alumina bullet is calcined at approximately 1100°C for 3-5 hours to form a mixed-phase alumina support containing 50% alpha alumina and 50% theta alumina. The palladium (Pd) impregnation solution is prepared by dissolving palladium nitrate (Pd(NO3)2) in a volume of water equal to the pore volume of the mixed-phase alumina support. The amount of Pd(NO3)2 dissolved in the water is such that it produces approximately 0.03 wt% Pd. Similarly, the silver (Ag) impregnation solution is prepared by dissolving AgNO3 in a volume of water equal to the pore volume of the mixed-phase alumina support. The amount of AgNO3 dissolved in this volume of water is such that it produces approximately 0.18 wt% Ag on the final catalyst. The Pd impregnation solution is sprayed onto the mixed-phase alumina support at ambient temperature. The Pd-impregnated mixed-phase alumina support is dried in air at 120°C for 2 hours. A dried Pd-impregnated mixed-phase alumina support is calcined in air at a temperature of 500°C for 3 hours. After calcination, the resulting Pd-impregnated mixed-phase alumina support is heated at 150°C for 1 hour in a hydrogen-containing atmosphere with >20% hydrogen to reduce the palladium metal.

[0055] After the reduction of palladium metal, the Pd-impregnated mixed-phase alumina support is impregnated with an Ag-impregnated solution at ambient temperature. The Pd and Ag-impregnated mixed-phase alumina support is dried in air at 120°C for 2 hours. The dried Pd-impregnated mixed-phase alumina support is calcined in air at 500°C for 3 hours. After calcination, the resulting Pd and Ag-impregnated mixed-phase alumina support is heated at 400°C for 1 hour in a hydrogen-containing atmosphere with >20% hydrogen to reduce the palladium metal. In the resulting catalyst 2, 95% of the Pd and Ag metals are deposited on the outer 200 micrometers (μm) of the mixed alumina support.

[0056] Example 3 - Comparative Example This Example 3 describes the preparation of catalyst 3, which represents a comparative catalyst.

[0057] 400 grams (g) of 4 x 4 mm tablets of aluminum alpha oxide support were impregnated with a 2% hydrazine aqueous solution. The volume of the hydrazine aqueous solution corresponded to 35% of the pore volume of the aluminum alpha oxide support. Aqueous solutions of Pd(NO3)2 and AgNO3 were prepared so that the yields of Pd and Ag content in the catalyst were 0.035% by weight and 0.025% by weight, respectively. The support was impregnated with the Pd and Ag aqueous solutions in volumes corresponding to 65% of the pore volume of the support. The resulting impregnated support was dried and calcined at 630°C for 5 hours under a nitrogen atmosphere to obtain a comparative catalyst.

[0058] Table 1 below shows the characteristics of the selective hydrogenation catalysts of Examples 1 to 3 above.

[0059] [Table 1]

[0060] Example 4 This Example 4 describes the performance tests performed to characterize the catalyst compositions of Examples 1 and 3.

[0061] The experimental conditions were selected to be very similar to those of the first terminal reactor in a steam cracking apparatus.

[0062] An experimental reactor was packed in five layers with 15 cc of catalyst diluted with 85 cc of α-alumina spheres. A feed having the composition shown in Table 2 was supplied to the reactor at a rate that provided 4,000 v / vh GHSV. The reactor was operated at a pressure of 10 bar and a temperature adjusted and maintained to provide an acetylene conversion rate of at least 55%, i.e., an acetylene concentration of 9,000 ppm at the reactor outlet.

[0063] [Table 2]

[0064] Figure 3 shows plot 54 of the selectivity and stability of the selective hydrogenation catalyst of Example 1 compared to Example 3. As shown in plot 54, the selectivity data 56 and reactor temperature 58 when using catalyst 1 of the present disclosure show improved stability and selectivity of the catalyst when used for hydrogenation of acetylene in flow for more than 400 hours compared to the comparative catalyst. Catalyst 1 of the present invention maintained a selectivity for ethylene greater than 70% after 450 hours. Furthermore, the reactor temperature 58 did not need to be increased to maintain an acetylene conversion rate greater than 55% after 450 hours. In contrast, as shown by the selectivity and temperature data 60, 62 respectively, the selectivity of comparative catalyst 3 decreased after approximately 100 hours, falling to less than 70%, and the selectivity of comparative catalyst 3 did not improve even after increasing the reactor temperature to maintain a conversion rate of at least 55%. Instead, the selectivity 60 of comparative catalyst 3 continued to decrease. Therefore, based on the data shown in plot 54, catalyst 1 of the present invention provides significantly better acetylene conversion selectivity for ethylene than comparative catalyst 3. Thus, the ethylene yield is higher with catalyst 1 compared to comparative catalyst 3. The selectivity of the catalyst is calculated as follows: [(ethylene outlet concentration - ethylene inlet concentration) / (acetylene inlet concentration - acetylene outlet concentration)] * 100.

[0065] Furthermore, in the test using catalyst 1, the temperature 58 was decreased rather than increased to maintain a 55% conversion rate. In stark contrast, the temperature 62 used in the test of comparative catalyst 3 was increased after 100 hours and continued to increase to maintain a 55% conversion rate. After 200 hours, comparative catalyst 3 was unable to maintain a 55% conversion rate, even after the temperature was increased.

[0066] Another measure of the improved acetylene conversion selectivity for the catalysts of this disclosure to ethylene is the amount of green oil produced during the hydrogenation process. Green oil is a substance in which more than eight carbon atoms (C) condense under hydrogenation reaction conditions. 8+Green oil is a mixture of hydrocarbons having ) . Green oil can condense on the catalyst and on the pores of the reactor. Condensation of green oil on and within the catalyst pores has an undesirable effect on the catalyst's performance. In other words, green oil contributes to catalyst degradation and reduces the selectivity for acetylene conversion to ethylene. Figures 4 and 5 show plots 68 and bar graphs 70 of green oil generated over time during the hydrogenation process and collected on the catalyst and in the cold trap, respectively. As shown in Figure 4, comparative catalyst 3 produced more than 1 g of green oil in 300 hours and continued to increase to 1.5 g in 600 hours, while catalyst 1 produced less than approximately 0.6 g in 300 hours. Furthermore, as shown in Figure 5, catalyst 1 accumulated less green oil on its surface compared to comparative catalyst 3, and less green oil was collected in the cold trap when catalyst 1 was used than when comparative catalyst 3 was used. Therefore, the yield of green oil is lower when using the catalysts of this disclosure than when using the comparative catalysts.

[0067] The technical benefits of using a mixed-phase alumina support for selective hydrogenation catalysts include improving the overall performance of these catalysts for the selective conversion of highly unsaturated hydrocarbons (e.g., alkynes, alkadienes, etc.) to low-unsaturated hydrocarbons such as ethylene and propylene. The mixed-phase alumina support used in these catalysts generally has both alpha-alumina and theta-alumina in a desired ratio, increasing the BET surface area of ​​the support by 2 to 3 times compared to existing selective hydrogenation catalysts having alumina supports with only alpha-phase. In particular, the mixed-phase alumina support has theta-alumina in the range of approximately 30% to 70%, with the remainder being alpha-alumina. The combination of theta-alumina, increased surface area, and bimodal pore size distribution of the catalysts of this disclosure provides improvements in the selective hydrogenation of acetylene and other highly unsaturated olefins for conversion to ethylene and other low-saturated olefins.

[0068] This disclosure can be embodied in other specific forms without departing from its spirit or essential features. The embodiments described should be considered in all respects to be illustrative and not limiting. Accordingly, the scope of this disclosure is indicated not by the foregoing description but by the appended claims. All modifications that fall within the meaning and scope of the equivalents of the claims are encompassed within that scope.

Claims

1. A method for producing a selective hydrogenation catalyst, Approximately 30 to 60 square meters / gram (m ２ A mixed-phase alumina support having a BET surface area in the range of / g), wherein the mixed-phase alumina support comprises alpha alumina and theta alumina, The mixed-phase alumina support is impregnated with an impregnation solution containing one or more metals selected from Group VIII, Group IB, or both of the periodic table to form an impregnated support. The impregnated support is dried at a temperature in the range of approximately 100°C to 250°C to form a dried impregnated support. The aforementioned dried impregnated support is fired at a temperature range of 350°C to approximately 550°C to form a fired impregnated support. A method comprising reducing one or more metals on the calcined and impregnated support at a temperature in the range of approximately 350°C to approximately 650°C in the presence of hydrogen to form the selective hydrogenation catalyst.

2. The method according to claim 1, wherein forming the mixed-phase alumina support comprises firing an alumina precursor at a temperature in the range of approximately 1075°C to approximately 1100°C, and the alumina precursor comprises boehmite or gamma alumina.

3. The method according to claim 1 or 2, wherein the mixed phase alumina has 30% to 70% alpha alumina and the remainder is theta alumina.

4. The method according to any one of claims 1 to 3, wherein the ratio of alpha alumina to theta alumina is 1:

1.

5. The method according to any one of claims 1 to 4, wherein the one or more metals selected from Group VIIIB is palladium, the one or more metals selected from Group IB is silver, and the palladium and silver metals are in the form of metal salts.

6. The method according to any one of claims 1 to 5, wherein impregnation of the mixed-phase alumina comprises a first impregnation step of impregnating the mixed-phase alumina support with a first impregnation solution containing palladium nitrate or silver nitrate to form a first impregnated support, and a second impregnation step of impregnating the first impregnated support with a second impregnation solution different from the first impregnation solution to form a second impregnated support, wherein the first impregnation solution and the second impregnation solution contain palladium nitrate or silver nitrate, the first impregnated support is dried, calcined and reduced before the second impregnation step to form a reduced impregnated support, and the second impregnated support is dried, calcined and reduced after the second impregnation step to form the catalyst.

7. The method according to any one of claims 1 to 6, wherein approximately 95% of at least one metal is located within a depth of 100 micrometers (μm) of the catalyst, and the depth extends from the outermost surface of the mixed-phase alumina support toward the innermost surface of the mixed-phase alumina support.

8. A selective hydrogenation catalyst, Approximately 30 to 60 square meters / gram (m ２ A mixed-phase alumina support comprising alpha-alumina and theta-alumina, having a BET surface area in the range of ( / g), wherein the alpha-alumina is present in an amount of 30% to 70% by volume, and the remainder is theta-alumina, A selective hydrogenation catalyst comprising bimetallic nanoparticles containing at least one metal selected from Group VIII of the periodic table and at least one metal selected from Group IB.

9. The catalyst according to claim 8, wherein the ratio of alpha alumina to theta alumina is 1:

1.

10. The catalyst according to claim 8 or 9, wherein the amount of alpha alumina and theta alumina is 50% by volume.

11. The catalyst according to any one of claims 8 to 10, comprising a bulk density in the range of approximately 0.7 grams / cubic centimeter (g / cc) to approximately 0.8 g / cc.

12. The catalyst according to any one of claims 8 to 11, wherein 95% of the bimetallic nanoparticles are located within a depth of 100 micrometers (μm) of the catalyst, and the depth extends from the outermost surface of the mixed-phase alumina support toward the innermost surface of the mixed-phase alumina support.

13. The catalyst according to any one of claims 8 to 12, wherein the at least one metal selected from Group VIIIB is palladium, and the at least one metal selected from Group IB is silver.

14. A method for the selective hydrogenation of acetylene, A method comprising contacting an olefin stream having a contamination concentration of unsaturated hydrocarbons with a selective hydrogenation catalyst according to any one of claims 8 to 13 under selective hydrogenation reaction conditions.

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