A selective hydrogenation catalyst for alkynes and its preparation method and application

Abstract

The present invention provides an alkyne selective hydrogenation catalyst and a preparation method thereof. The alkyne selective hydrogenation catalyst provided by the present invention is obtained by improving the alumina carrier preparation method. During the preparation process of the alumina carrier, a certain amount of α-Al2O3 powder is added, and the particle size, impurity content, etc. of the α-Al2O3 powder used must meet certain conditions. The prepared alumina carrier has the advantages of low bulk density, large water absorption, large pore volume and average pore size. Due to the increase in pore volume and water absorption of the alumina carrier, the active metal Pd can be more evenly distributed on the surface of the alumina carrier, thereby forming a highly dispersed Pd catalyst. At the same time, due to the increase in pore size, the olefins generated by the selective hydrogenation of alkynes can diffuse faster, avoiding excessive hydrogenation to alkanes, and having better selectivity.

Description

Technical Field

[0001] The present invention belongs to the field of catalysts, and in particular relates to an alkyne selective hydrogenation catalyst and a preparation method and application thereof. Background Art

[0002] In ethylene production plants, cracked gas undergoes distillation to produce a C2 fraction rich in ethylene, ethane, and acetylene, and a C3 fraction rich in propane, propylene, propyne, and propadiene (often collectively referred to as MAPD). Acetylene, propyne, and propadiene are impurities in the C2 and C3 fractions, increasing catalyst consumption in subsequent polymerization reactions and affecting polymer product performance. Industrially, hydrogenation is used to remove these alkynes, increasing olefin production and improving resource utilization.

[0003] Typically, alkyne selective hydrogenation catalysts are supported metal catalysts, consisting of a support, a primary active component, and a co-active component. Common supports are alumina with varying structures and specific surface areas. The primary active component is palladium (Pd), a metal with hydrogenation catalytic activity, and co-active components are often selected from metals such as Cu, Ag, and Au. These catalysts are often prepared using an impregnation-calcination method, where a solution containing the active component (mostly a salt solution) is brought into contact with a prepared support to load the active component onto the support. After drying, the catalyst is calcined at high temperature to decompose the metal salt into its corresponding oxide. The active component in the calcined catalyst typically exists as an oxide, which is then reduced with hydrogen and used in the hydrogenation reaction.

[0004] During catalyst preparation, the physical properties and microstructure of the alumina support significantly influence catalyst performance, leading to extensive research. Chinese patent CN101062483A discloses a method for preparing a catalyst using a porous metal support. After forming a dense oxide layer on the porous metal surface, a sol of an inorganic oxide is coated, dried, and calcined to form an intermediate support layer, which is then loaded with the metal active component. Because the porous metal substrate is used, the catalyst exhibits excellent thermal conductivity, rapidly dissipating the reaction heat and preventing overheating of the catalyst bed.

[0005] Chinese patent CN106669850A discloses a method for preparing an alumina support. This method uses chloroaluminate-modified pseudo-boehmite as a raw material, along with boric acid or phosphoric acid compounds, alkyl chlorides, and a binder. After uniform mixing, the mixture is extruded, shaped, dried, and calcined to produce a macroporous alumina support. This method produces a support with large pore sizes and volumes, exhibiting a dual pore distribution.

[0006] U.S. Patent No. 6,794,552 discloses a method for modifying an alumina support. The method involves impregnating a hot alumina support with molten zinc nitrate or magnesium nitrate to form a Zn-Al or Mg-Al spinel structure on the surface of the alumina support. The structure is then loaded with metal active components such as Pd. Due to the special surface structure of the alumina support, the prepared catalyst exhibits good selectivity for the selective hydrogenation of alkynes.

[0007] Existing technologies for improving the performance of alkyne selective hydrogenation catalysts by optimizing the preparation of alumina supports are long and complex preparation processes, resulting in high production costs. Furthermore, the physical properties of the alumina supports vary from batch to batch, leading to inconsistent catalyst performance. There is a need to develop alkyne selective hydrogenation catalysts with simpler preparation methods, less performance fluctuations, and improved selectivity. Summary of the Invention

[0008] In order to solve the above-mentioned technical problems, the present invention proposes a selective hydrogenation catalyst for alkynes, which is obtained by improving the preparation method of an alumina carrier. During the preparation process of the alumina carrier, a certain amount of α-Al2O3 powder is added, and the particle size, impurity content, etc. of the α-Al2O3 powder used must meet certain conditions. The prepared alumina carrier has the advantages of low bulk density, high water absorption, large pore volume and average pore size. Due to the increase in pore volume and water absorption of the alumina carrier, the active metal Pd can be more evenly distributed on the surface of the alumina carrier, thereby forming a highly dispersed Pd catalyst. At the same time, due to the increase in average pore size, the olefins generated by the selective hydrogenation of alkynes can diffuse faster, avoiding excessive hydrogenation to alkanes, and having better selectivity.

[0009] One of the objects of the present invention is to provide an alkyne selective hydrogenation catalyst, comprising a main active component Pd, an optional co-metal active component and an alumina support, wherein the alumina support has a water absorption rate of 40 to 70%, a pore volume of 0.6 to 0.9 ml / g, and a most probable pore diameter of 0.100 to 0.300 μm.

[0010] Preferably, the metal-assisted active component is selected from at least one of Ag, Bi, Cu, Au, Pb, Zn, and Ga, preferably at least one of Ag, Bi, Zn, and Ga;

[0011] In terms of mass percentage, in the catalyst, the content of the main active component Pd is 0.02-0.3%, and the content of the auxiliary metal active component is 0-0.6%, preferably 0-0.3%;

[0012] The alumina carrier has a water absorption rate of 50-65%, a pore volume of 0.63-0.8 ml / g, and a most probable pore diameter of 0.120-0.250 μm;

[0013] The specific surface area of ​​the alumina carrier is 5 to 120 m2 / g, bulk density of 0.3-0.9g / ml, strength of 20-200Nm; preferably, the specific surface area of ​​the alumina carrier is 20-100m 2 / g, bulk density is 0.5-0.8g / ml, strength is 30-100Nm;

[0014] The alumina carrier also contains 0.01-1 wt% of alkali metal elements, alkaline earth metal elements, and / or rare earth metal elements to further improve its strength, specific surface area, pore volume, etc. The alkali metal element is selected from at least one of Na, K, and Li; the alkaline earth metal element is selected from at least one of Mg and Ca; and the rare earth metal element is selected from at least one of La, Ce, Pr, and Y, preferably at least one of La and Ce.

[0015] A second object of the present invention is to provide a method for preparing the above-mentioned alkyne selective hydrogenation catalyst, comprising loading components including the main active component Pd and the co-metal active component on the alumina carrier to obtain the alkyne selective hydrogenation catalyst. Preferably, the preparation method specifically comprises: immersing the components including the alumina carrier in a metal compound solution containing a Pd compound and a co-metal compound, and drying and calcining to obtain the alkyne selective hydrogenation catalyst.

[0016] Specifically,

[0017] The Pd compound is selected from soluble compounds of metal Pd, preferably at least one selected from palladium nitrate, palladium chloride, and palladium acetate;

[0018] The auxiliary metal compound is selected from at least one of chlorides, nitrates, and acetates of Ag, Bi, Cu, Au, Pb, Zn, and Ga, and is preferably selected from at least one of chlorides and nitrates of Ag, Bi, Zn, and Ga;

[0019] Based on the saturated water absorption rate of the alumina support, the amount of the metal compound solution used is 40 to 90%, preferably 40 to 70%, of the saturated water absorption rate of the alumina support.

[0020] In the above preparation method, the metal compound solution can be loaded onto the support using the impregnation method commonly used in the art, such as spraying, equal volume impregnation, or supersaturated impregnation. When loading multiple metalloid active components, a one-step loading method or a step-by-step loading method can be used. The one-step loading method is to prepare two or more metalloid active components into a mixed solution, and then load them onto the support in a single step; the step-by-step loading method is to prepare several active component precursors into solutions and load them onto the support separately. After each loading, it needs to be dried and calcined before the next loading.

[0021] In the above preparation method, there are no special requirements for the drying and calcination conditions, and the drying and calcination conditions commonly used in the art can be adopted. Preferably, the drying temperature is 40-150°C, and the drying time is 4-48 hours; preferably, the drying temperature is 50-120°C, and the drying time is 8-24 hours; the calcination time varies according to the content of the metal active component. As the content of the metal active component increases, the calcination time can be increased accordingly. Specifically, the calcination time is 2-15 hours, preferably 3-9 hours; the calcination temperature is 300-500°C.

[0022] In the above preparation method, the preparation method of the alumina support includes the steps of powder mixing, kneading and forming, and drying and calcining, and specifically includes the following steps:

[0023] Step 1: uniformly mix the components including alumina powder and additives to obtain a powder to be kneaded;

[0024] Step 2: adding the acidic aqueous solution to the powder to be kneaded and kneading into a shape;

[0025] Step 3: Dry and calcine the kneaded product to obtain the alumina support.

[0026] In the above step 1, the alumina powder includes pseudo-boehmite powder, α-Al2O3 powder, and optionally alumina trihydrate powder and / or fast-deoxidizing alumina powder.

[0027] The pseudo-boehmite powder can be commonly used pseudo-boehmite. Preferably, the specific surface area of ​​the pseudo-boehmite powder is 200 to 300 m 2 / g, pore volume 0.5~1.2ml / g, bulk density 0.2~0.4g / ml.

[0028] The α-Al2O3 powder can be obtained by calcining high-purity aluminum hydroxide at a temperature greater than 1300°C. A fluorine-containing compound can be added during the calcination process to form flaky aluminum oxide particles. In this case, the F content in the α-Al2O3 powder is no more than 0.1%. The α-Al2O3 powder can also be obtained by calcining pseudo-boehmite powder used for molding at a temperature greater than 1300°C. Preferably, the α-Al2O3 content in the α-Al2O3 powder is greater than 95%, the particle size of the powder is 2 to 100 μm, and the mass content of Na, Fe, and Si is less than 0.1%. The α-Al2O3 powder accounts for 5 to 30% by weight of the total weight of the alumina powder, preferably 5 to 20% by weight.

[0029] The alumina trihydrate and the fast-dehydrating alumina can both be selected from commonly used components. For example, the alumina trihydrate powder can be selected from at least one of gibbsite, bayerite, and norhydrite. The fast-dehydrating alumina powder is obtained by rapid dehydration of aluminum hydroxide, wherein the mass content of Na and Fe is less than 0.1%; the mass of the alumina trihydrate powder accounts for 0 to 10% of the total mass of the alumina powder; the mass of the fast-dehydrating alumina powder accounts for 0 to 10% of the total mass of the alumina powder.

[0030] In step 1 above, the additive is selected from at least one of a silicon-containing compound and a forming and pore-forming aid, and the amount of the additive is 0-20%, preferably 0-10%, of the total mass of the alumina support. The silicon-containing compound is selected from water-insoluble silicon-containing compounds, preferably at least one selected from dry silica gel, nano-silicon oxide, and silicon carbide; the nano-silicon oxide and dry silica gel preferably have an average particle size of less than 120 nm. The forming and pore-forming aid is selected from at least one of natural organic matter, a high molecular weight polymer, and a decomposable alkaline compound, preferably at least one selected from sesbania powder, starch, methylcellulose, hydroxypropyl methylcellulose, sodium hydroxymethylcellulose, polyethylene microspheres, polystyrene, polyethylene oxide, polyethylene glycol, polyvinyl alcohol, sodium polyacrylate, polyethylene glycol, polyacrylate acrylic acid, urea, methylamine, ethylenediamine, ammonium carbonate, and ammonium bicarbonate. Those skilled in the art can select one or more forming and pore-forming aids based on experience.

[0031] In step 2 above, the acid in the acidic aqueous solution is selected from at least one of an organic acid, an inorganic acid, and an acidic salt compound, preferably selected from at least one of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, oxalic acid, citric acid, and ammonium dihydrogen phosphate; the mass percentage concentration of the acid in the acidic aqueous solution is 0.1-10%, preferably 0.1-5%. The weight ratio of the acidic aqueous solution to the powder to be kneaded is 0.5-5:1, preferably 0.6-2:1. Those skilled in the art can adjust the amount of acid in the acidic aqueous solution based on the plasticity of the billet after kneading and the specific surface area, strength, and bulk density of the carrier after high-temperature calcination.

[0032] A soluble additive is also added to the acidic aqueous solution. The soluble additive is selected from at least one of an alkali metal compound, an alkaline earth metal compound, and a rare earth metal compound. The alkali metal compound is selected from inorganic salt compounds of metals Na, K, and Li, preferably at least one of nitrates and chlorides of the metals Na, K, and Li; the alkaline earth metal compound is selected from inorganic salt compounds of metals Mg and Ca, preferably at least one of nitrates and chlorides of the metals Mg and Ca; and the rare earth metal compound is selected from soluble rare earth metal salt compounds, preferably at least one of nitrates and chlorides of La, Ce, Pr, and Y, more preferably at least one of nitrates and chlorides of La and Ce. The metal in the soluble additive accounts for 0-1.35% of the total amount of the alumina powder, preferably 0-0.9%, based on the mass percentage of the metal element.

[0033] In the above step 3, the drying temperature is 60-150°C, and the drying time is 3-48 hours; the roasting temperature is 800-1200°C, and the roasting time is 3-48 hours; during the roasting process, when the temperature is below 500°C, the heating rate is 30-150°C / h, and when the temperature is above 500°C, the heating rate is 100-280°C / h.

[0034] A third object of the present invention is to provide the above-mentioned alkyne selective hydrogenation catalyst or the alkyne selective hydrogenation catalyst prepared by the above-mentioned preparation method for use in alkyne hydrogenation reactions.

[0035] According to a specific embodiment of the present invention, the catalyst is reduced before use. Preferably, the reduction conditions are: a reducing atmosphere with a hydrogen content of not less than 50%, a reduction reaction temperature of 80 to 200° C., and a reduction reaction time of 2 to 12 hours;

[0036] When the catalyst is used for the selective hydrogenation reaction of carbon distillate, the acetylene content in the carbon distillate is 1.0-5.0%, the reaction temperature is 20-120°C, and the reaction space velocity is 3000-12000h -1 ;or,

[0037] When the catalyst is used for the selective hydrogenation reaction of C3 fraction, the percentage of propyne and propadiene in the C3 fraction is 1.0-5.0%, the reaction temperature is 30-70°C, and the reaction space velocity is 20-120h -1 .

[0038] In the present invention, α-Al2O3 powder is added during the preparation of the alumina support to produce an alumina support with increased pore volume, pore diameter, and water absorption, and a lower bulk density. This alumina support is loaded with the active component Pd and co-active components such as Ag, Au, and Zn. After appropriate drying and calcination steps, a stable and highly selective alkyne selective hydrogenation catalyst is obtained. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0040] The test instruments and test conditions used in the examples are as follows:

[0041] The specific surface area was measured using the nitrogen physical adsorption BET method;

[0042] The bulk density was calculated by measuring the mass of 100 mL of alumina support, and the average value was obtained after three measurements for each sample;

[0043] The pore volume and the most probable pore diameter were measured by mercury intrusion method, which was carried out according to the general pore volume measurement method of alumina support.

[0044] The strength was measured using a universal particle strength measuring instrument, and the average value of the measurement results of 20 carrier particles was taken;

[0045] The water absorption rate is obtained by taking 20 g of the alumina carrier, soaking it in water for 10 minutes, taking it out and draining the surface water, and measuring the weight increase.

[0046] Example 1

[0047] Preparation method of alumina carrier: Weigh 180g pseudo-boehmite powder, 20g α-Al2O3 powder, 8g sesbania powder, and 10g starch, mix them evenly in a mixer, and transfer them to a kneader. The pseudo-boehmite powder has a specific surface area of ​​252.4m 2 / g, pore volume 0.944ml / g, and bulk density 0.33g / ml; α-Al2O3 powder obtained from this pseudo-boehmite is calcined at 1400°C. It has an α-Al2O3 content of 98.0%, an average particle size of 5μm, and Na, Fe, and Si mass contents of less than 0.01%. 2.00g of concentrated nitric acid, 2.00g of acetic acid, and 1.517g of lanthanum nitrate are weighed and added to 200g of deionized water to prepare a mixed solution. This mixed solution is added to the uniformly mixed powder, thoroughly kneaded, and then extruded and pelletized to produce spherical particles with a particle size of 4-6mm. After drying at 120°C for 12 hours, the powder is calcined at 1175°C for 6 hours, with the heating rate controlled at 100°C / hr below 600°C and 200°C / hr above 500°C. This produces an alumina carrier with a La loading of 0.35%.

[0048] Active metal loading method: 0.079 g of silver nitrate was added to 5 mL of palladium nitrate solution containing 10 mg Pd / mL. The solution was diluted to 58 mL with deionized water and sprayed onto a 100 g alumina support. The sprayed sample was dried at 120°C for 6 hours and calcined at 500°C for 8 hours to obtain catalyst S1, which had a Pd content of 0.05% by mass and an Ag content of 0.05% by mass.

[0049] Example 2

[0050] Preparation method of alumina carrier: Weigh 150g pseudo-boehmite powder, 50g α-Al2O3 powder, 6g sesbania powder, 5g starch, and 3g cross-linked polyethylene microspheres with a particle size of about 40 microns, mix them evenly in a mixer, and transfer them to a kneader. The pseudo-boehmite powder has a specific surface area of ​​252.4m 2 / g, pore volume 0.944ml / g, bulk density 0.33g / ml; α-Al2O3 powder obtained from this pseudo-boehmite by calcining at 1500°C, with an α-Al2O3 content of 99.5%, an average particle size of 12μm, and Na, Fe, and Si mass contents less than 0.01%. 3.00g of concentrated nitric acid and 1.745g of cerium nitrate were weighed and added to 200g of deionized water to prepare a mixed solution. The mixed solution was added to the uniformly mixed powder, thoroughly kneaded, and then extruded and pelletized to obtain spherical particles with a particle size of 4-6mm. The drying conditions were the same as in Example 1, and the calcination temperature was the same as in Example 1, at 1165°C, to obtain an alumina carrier with a Ce loading of 0.40%.

[0051] Active metal loading method: 5 mL of palladium nitrate solution containing 10 mg Pd / mL was measured, diluted to 58 mL with deionized water, and sprayed onto 100 g of alumina support. The solution was dried at 120°C for 6 h and calcined at 500°C for 8 h to obtain a Pd-containing catalyst precursor. 0.110 g of silver nitrate and 0.045 g of zinc nitrate were weighed and prepared into 58 mL of solution with deionized water. The solution was sprayed onto 100 g of the Pd-containing catalyst precursor prepared above. The solution was dried at 120°C for 6 h and calcined at 500°C for 8 h to obtain catalyst S2, which had a Pd content of 0.05% by mass, an Ag content of 0.07% by mass, and a Zn content of 0.01% by mass.

[0052] Example 3:

[0053] Preparation method of alumina carrier: Weigh 170g pseudo-boehmite powder, 20g α-Al2O3 powder, 10g alumina trihydrate powder, 6g sesbania powder, and 5g urea, mix them evenly in a mixer, and transfer them to a kneader. The specific surface area of ​​the pseudo-boehmite powder is 257.9m 2 / g, pore volume 1.16ml / g, bulk density 0.23g / ml; α-Al2O3 powder is obtained by calcining high-purity aluminum hydroxide at 1500℃, with an average particle size of 75μm, α-Al2O3 content of 99.5%, and Na, Fe, and Si mass contents of about 0.05%. Same as Example 1. Weigh 2.00g concentrated nitric acid, 1g acetic acid, and 1.517g lanthanum nitrate, add 190g deionized water to prepare a mixed solution. Add the above mixed solution to the evenly mixed powder, knead thoroughly, and then extrude and granulate to obtain spherical particles with a particle size of 4-6mm. The drying conditions are the same as in Example 1, and the calcination procedure is the same as in Example 1, with a calcination temperature of 1180℃ to obtain an alumina carrier with a La loading of 0.35%.

[0054] Active metal loading method: 5 mL of a palladium nitrate solution containing 10 mg Pd / mL was diluted to 58 mL with deionized water, sprayed onto a 100 g alumina support, dried at 120°C for 6 h, and calcined at 500°C for 8 h to obtain a Pd-containing catalyst precursor. 0.146 g of chloroauric acid was weighed and prepared into 58 mL of a solution with deionized water. This solution was sprayed onto 100 g of the Pd-containing catalyst precursor prepared above, dried at 120°C for 6 h, and calcined at 500°C for 8 h to obtain catalyst S3, which had a Pd content of 0.05% by mass and an Au content of 0.07% by mass.

[0055] Example 4:

[0056] Preparation method for an alumina carrier: Weigh 170g of pseudo-boehmite powder, 20g of α-Al2O3 powder, 10g of fast-dealumina powder, 6g of sesbania powder, and 6g of starch, mix thoroughly in a mixer, and transfer to a kneader. The pseudo-boehmite powder has the same physical properties as in Example 1. The α-Al2O3 powder is obtained by calcining high-purity aluminum hydroxide at 1500°C. Ammonium fluoride is added during the calcination process. The resulting α-Al2O3 powder is flaky, with an average particle size of 51μm, an α-Al2O3 content of 99.5%, and approximately 0.05% by weight of Na, Fe, and Si. Weigh 2.00g of concentrated nitric acid, 1g of acetic acid, and 8.936g of magnesium nitrate and add them to 190g of deionized water to prepare a mixed solution. This mixed solution is added to the uniformly mixed powder, kneaded thoroughly, and then extruded and pelletized to produce spherical particles with a diameter of 4-6mm. The drying conditions were the same as those in Example 1, the calcination procedure was the same as in Example 1, and the calcination temperature was 1180° C. to obtain an alumina carrier with a Mg loading of 0.60%.

[0057] Active metal loading method: 5 mL of palladium nitrate solution containing 10 mg Pd / mL was measured and diluted to 58 mL with deionized water. 0.079 g of silver nitrate was added and sprayed onto 100 g of an alumina support. The solution was dried at 120°C for 6 h and calcined at 500°C for 8 h to obtain a Pd-containing catalyst precursor. 0.052 g of gallium nitrate was weighed and prepared into 58 mL of solution using deionized water. A small amount of dilute nitric acid may be added to promote dissolution. The solution was sprayed onto 100 g of the Pd-containing catalyst precursor prepared above. The solution was dried at 120°C for 6 h and calcined at 500°C for 8 h to obtain catalyst S4, which had a Pd content of 0.05% by mass, an Ag content of 0.04% by mass, and a Ga content of 0.01% by mass.

[0058] Comparative Example 1:

[0059] Preparation method of alumina carrier: Weigh 200g pseudo-boehmite powder, 8g sesbania powder, and 4g starch, mix them evenly in a mixer, and transfer them to a kneader. The specific surface area of ​​the pseudo-boehmite powder is 189.9m 2 / g, pore volume 0.804ml / g, bulk density 0.25g / ml. Weigh 2.80g of concentrated nitric acid and add it to 200g of deionized water to prepare a mixed solution. The mixed solution is added to the uniformly mixed powder, and after thorough kneading, it is extruded and granulated to obtain spherical particles with a particle size of 4-6mm. The drying conditions are the same as those in Example 1, and the calcination procedure is the same as in Example 1, at a calcination temperature of 1195°C, to obtain an alumina support.

[0060] Active metal loading method: 0.016 g of silver nitrate was added to 5 mL of palladium nitrate solution containing 10 mg Pd / mL. The solution was diluted to 58 mL with deionized water and sprayed onto a 100 g alumina support. The sprayed sample was dried at 120°C for 6 h and calcined at 500°C for 8 h to obtain catalyst D1, which had a Pd content of 0.05% by mass and an Ag content of 0.01% by mass.

[0061] Comparative Example 2:

[0062] Preparation method of alumina carrier: Weigh 190g of pseudo-boehmite powder, 10g of α-Al2O3 powder, 8g of sesbania powder, and 4g of starch, mix them evenly in a mixer, and transfer them to a kneader. The physical properties of the pseudo-boehmite powder are the same as those in Comparative Example 1. The α-Al2O3 powder is obtained by calcining ordinary aluminum hydroxide at 1300°C, with an average particle size of 4μm, an α-Al2O3 content of 93.9%, a Si mass content of 0.2%, and a Na and Fe mass content of approximately 0.1%. Weigh 2.80g of concentrated nitric acid and add it to 200g of deionized water to prepare a mixed solution. The above mixed solution is added to the evenly mixed powder, kneaded thoroughly, and then extruded into pellets to obtain spherical particles with a particle size of 4-6mm. The drying and calcination conditions are the same as those in Comparative Example 1 to obtain an alumina carrier.

[0063] Active metal loading method: same as Comparative Example 1.

[0064] Experimental Example 1:

[0065] The above-mentioned S1-S4 and D1-D2 catalysts were subjected to a C2 selective hydrogenation evaluation experiment, and the reaction conditions were as follows:

[0066] 5 ml of catalyst was loaded into a 316L stainless steel reaction tube. After nitrogen displacement, the reaction materials were introduced into the reactor. The reaction materials (molar fraction) were: 0.6% hydrogen, 0.4% acetylene, 6.56% ethane, and 92.44% ethylene. The reaction pressure was 1 MPa, the reaction temperature was 90°C, and the reaction space velocity was 8000 hr. -1 The experimental results are shown in Table 1.

[0067] Table 1. Catalytic reaction performance of the catalysts obtained in Examples 1 to 4 and Comparative Examples 1 to 2

[0068] Selectivity (%) Acetylene content at reactor outlet (μg / g) S1 53 55 S2 58 42 S3 47 60 S4 56 46 D1 35 79 D2 40 68

[0069] Example 5:

[0070] Alumina carrier preparation method: same as Example 1.

[0071] Active metal loading method: 25 mL of palladium nitrate solution containing 10 mg Pd / mL was diluted to 58 mL with deionized water and sprayed onto a 100 g alumina support. The sprayed sample was dried at 120°C for 6 h and calcined at 550°C for 8 h to obtain catalyst S5, which had a Pd content of 0.25% by mass.

[0072] Example 6:

[0073] Preparation method of alumina carrier: Weigh 188g pseudo-boehmite powder, 12g α-Al2O3 powder, 8g sesbania powder, 2g cellulose, 3g ammonium carbonate, mix them evenly in a mixer, and transfer them to a kneader. The pseudo-boehmite powder has a specific surface area of ​​245.7m 2 / g, pore volume 0.869ml / g, bulk density 0.22g / ml; α-Al2O3 powder is the same as in Example 1. 1.00g concentrated nitric acid, 3g acetic acid, and 0.365g potassium nitrate are weighed and added to 200g deionized water to prepare a mixed solution. This mixed solution is added to the uniformly mixed powder, thoroughly kneaded, and then extruded and pelletized to obtain spherical particles with a particle size of 4-6mm. Drying and calcination conditions are the same as in Example 1 to obtain an alumina carrier with a K loading of 0.10%.

[0074] Active metal loading method: 25 mL of palladium nitrate solution containing 10 mg Pd / mL was diluted to 58 mL with deionized water, sprayed onto 100 g of an alumina support, dried at 120°C for 6 h, and calcined at 550°C for 8 h to obtain a Pd-containing catalyst precursor. 0.209 g of chloroauric acid was weighed and prepared into 58 mL of solution with deionized water. This solution was sprayed onto 100 g of the Pd-containing catalyst precursor prepared above, dried at 120°C for 6 h, and calcined at 550°C for 8 h to obtain catalyst S6, which had a Pd content of 0.25% by mass and an Au content of 0.1% by mass.

[0075] Example 7:

[0076] Alumina carrier preparation method: same as Example 4.

[0077] Active metal loading method: 25 mL of palladium nitrate solution containing 10 mg Pd / mL was measured and diluted to 58 mL with deionized water. The solution was sprayed onto 100 g of an alumina support, dried at 120°C for 6 h, and calcined at 550°C for 8 h to obtain a Pd-containing catalyst precursor. 0.259 g of gallium nitrate was weighed and prepared into 58 mL of solution with deionized water. A small amount of dilute nitric acid may be added to promote dissolution. The solution was sprayed onto 100 g of the Pd-containing catalyst precursor prepared above. The solution was dried at 120°C for 6 h, and calcined at 500°C for 8 h to obtain catalyst S7, which had a Pd content of 0.25% by mass and a Ga content of 0.05% by mass.

[0078] Comparative Example 3:

[0079] Alumina carrier preparation method: same as Comparative Example 1.

[0080] Active metal loading method: 35 mL of palladium nitrate solution containing 10 mg Pd / mL was diluted to 58 mL with deionized water and sprayed onto a 100 g alumina support. The sprayed sample was dried at 120°C for 6 h and calcined at 550°C for 8 h to obtain catalyst D3, which had a Pd content of 0.35% by mass.

[0081] Experimental Example 2:

[0082] The catalysts S5-S7 and D3 were used in a sidestream experiment for the selective hydrogenation of propyne and propadiene from a C3 fraction. The reaction conditions were as follows: 92 ml of the catalyst was loaded into a stainless steel tube reactor. After nitrogen displacement, the reaction raw materials were hydrogenated and introduced into the reactor. The composition (molar fraction) of the reaction raw materials was 4.99% propane, 92.3% propylene, 1.19% propadiene, and 1.39% propyne. The hydrogen to alkyne ratio was approximately 1.4-1.6. The experimental space velocity was 70 h / min. -1 After 100 hours of reaction, the reaction results are shown in Table 2 below:

[0083] Table 2. Catalytic performance of the catalysts obtained in Examples 5 to 7 and Comparative Example 3

[0084] catalyst MAPD conversion rate (%) MAPD selectivity (%) S5 99.1 71 S6 98.7 74 S7 99.5 75 D3 97.4 63

[0085] The physical properties of the alumina supports used in the above examples and comparative examples are shown in Table 3 below:

[0086] Table 3. Physical properties of alumina supports in Examples and Comparative Examples

[0087]

[0088] According to the physical property data table of alumina carriers, the S1-S4 and S6 alumina carriers prepared by the method of the present invention have high water absorption, large pore volume and most probable pore diameter. The specific surface area of ​​the S1-S4 and S6 alumina carriers is 20-50 m 2 / g. The alkyne selective hydrogenation catalysts prepared based on these supports showed higher activity and selectivity in the selective hydrogenation of C2 fractions and C3 fractions.

Claims

1. A catalyst for selective hydrogenation of alkynes, comprising a main active component Pd, an optional co-metal active component and an alumina support, wherein: The water absorption rate of the alumina carrier is 40~70%, the pore volume is 0.6~0.9mL / g, and the most probable pore diameter is 0.100~0.300μm; the alumina powder used in the preparation method of the alumina carrier includes pseudo-boehmite powder, α-Al2O3 powder, and optional trihydrate alumina powder and / or fast-desorption alumina powder, and the α-Al2O3 powder is 5~30wt% of the total weight of the alumina powder; in terms of mass percentage, the content of the main active component Pd in ​​the catalyst is 0.02~0.3%.

2. The catalyst according to claim 1, characterized in that The metal-assisted active component is selected from at least one of Ag, Bi, Cu, Au, Pb, Zn, and Ga; and / or, Calculated by mass percentage, the content of the metal-assisted active component in the catalyst is 0-0.6%.

3. The catalyst according to claim 2, characterized in that The metal-supporting active component is selected from at least one of Ag, Bi, Zn, and Ga; and / or, Calculated by mass percentage, the content of the metal-assisted active component in the catalyst is 0-0.3%.

4. The catalyst according to claim 1, characterized in that The alumina support has a water absorption rate of 50-65%, a pore volume of 0.63-0.8 mL / g, and a most probable pore diameter of 0.120-0.250 μm; and / or, The specific surface area of ​​the alumina carrier is 5 to 120 m 2 / g, bulk density is 0.3~0.9g / mL, and strength is 20~200Nm.

5. The catalyst according to claim 4, characterized in that The specific surface area of ​​the alumina carrier is 20-100 m 2 / g, bulk density is 0.5~0.8g / mL, and strength is 30~100Nm.

6. The catalyst according to claim 1, characterized in that The alumina carrier further contains 0.01-1 wt% of alkali metal elements, alkaline earth metal elements and / or rare earth metal elements.

7. The catalyst according to claim 6, characterized in that The alkali metal element is selected from at least one of Na, K, and Li; the alkaline earth metal element is selected from at least one of Mg and Ca; and the rare earth metal element is selected from at least one of La, Ce, Pr, and Y.

8. A method for preparing the alkyne selective hydrogenation catalyst according to any one of claims 1 to 7, comprising loading components including the main active component Pd and the co-metal active component on the alumina carrier to obtain the alkyne selective hydrogenation catalyst.

9. The preparation method according to claim 8, characterized in that The preparation method specifically comprises: immersing components including an alumina carrier in a metal compound solution containing a Pd compound and a metal promoter compound, and drying and calcining the solution to obtain the alkyne selective hydrogenation catalyst.

10. The preparation method according to claim 9, characterized in that The Pd compound is selected from soluble compounds of metallic Pd; and / or, The auxiliary metal compound is selected from at least one soluble compound among chlorides, nitrates and acetates of Ag, Bi, Cu, Au, Pb, Zn and Ga; and / or, Based on the saturated water absorption rate of the alumina support, the amount of the metal compound solution used is 40-90% of the saturated water absorption rate of the alumina support.

11. The preparation method according to claim 10, characterized in that: The Pd compound is selected from at least one of palladium nitrate, palladium chloride, and palladium acetate; and / or, The metal-supporting compound is selected from at least one soluble compound of chlorides and nitrates of Ag, Bi, Zn, and Ga; and / or, Based on the saturated water absorption rate of the alumina support, the amount of the metal compound solution used is 40-70% of the saturated water absorption rate of the alumina support.

12. The preparation method according to claim 9, characterized in that The drying temperature is 40-150°C and the drying time is 4-48 hours; and / or, The calcination temperature is 300-500°C; and / or, The roasting time is 2 to 15 hours.

13. The preparation method according to claim 12, characterized in that The drying temperature is 50-120°C and the drying time is 8-24 hours; and / or, The roasting time is 3 to 9 hours.

14. The preparation method according to claim 9, characterized in that The preparation method of the alumina carrier includes the steps of powder mixing, kneading and molding, and drying and calcining.

15. The preparation method according to claim 14, characterized in that The preparation method of the alumina carrier specifically comprises the following steps: Step 1: uniformly mix the components including alumina powder and additives to obtain a powder to be kneaded; Step 2: adding the acidic aqueous solution to the powder to be kneaded and kneading into a shape; Step 3: Dry and calcine the kneaded product to obtain the alumina support.

16. The preparation method according to claim 15, characterized in that The additive is selected from at least one of a silicon-containing compound and a forming pore-forming aid; and / or, The acid in the acidic aqueous solution is selected from at least one of an organic acid, an inorganic acid, and an acidic salt compound; and / or, The mass percentage concentration of the acid in the acidic aqueous solution is 0.1-10%; and / or, The weight ratio of the acidic aqueous solution to the powder to be kneaded is 0.5 to 5:1; and / or, A soluble auxiliary agent is also added to the acidic aqueous solution.

17. The preparation method according to claim 16, characterized in that The acid in the acidic aqueous solution is selected from at least one of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, oxalic acid, citric acid, and ammonium dihydrogen phosphate; and / or, The mass percentage concentration of the acid in the acidic aqueous solution is 0.1-5%; and / or, The weight ratio of the acidic aqueous solution to the powder to be kneaded is 0.6 to 2:1; and / or, The soluble auxiliary agent is selected from at least one of alkali metal compounds, alkaline earth metal compounds and rare earth metal compounds.

18. The preparation method according to claim 17, characterized in that: The specific surface area of ​​the pseudo-boehmite powder is 200-300m 2 / g, pore volume 0.5~1.2mL / g, bulk density 0.2~0.4g / mL; and / or, The α-Al2O3 powder has an α-Al2O3 content greater than 95%, a particle size of 2 to 100 μm, and a mass content of Na, Fe, and Si less than 0.1%; and / or The mass of the alumina trihydrate powder accounts for 0-10% of the total mass of the alumina powder; and / or, The mass of the quick-release alumina powder accounts for 0-10% of the total mass of the alumina powder; and / or, The silicon-containing compound is selected from water-insoluble silicon-containing compounds; and / or, Calculated by the mass percentage of Si element, the Si element in the silicon-containing compound is 0-1.35% of the total weight of the alumina powder; and / or, The forming and pore-forming aid is selected from at least one of natural organic matter, high molecular polymer, and decomposable alkaline compound; and / or, The amount of the forming pore-forming aid is 0-20% of the total mass of the alumina carrier; and / or, The acid in the acidic aqueous solution is selected from at least one of nitric acid, acetic acid, oxalic acid and citric acid; and / or, The alkali metal compound is selected from inorganic salt compounds of metals Na, K, and Li; and / or, The alkaline earth metal compound is selected from inorganic salt compounds of metals Mg and Ca; and / or, The rare earth metal compound is selected from soluble rare earth metal salt compounds; and / or, Calculated by the mass percentage of the metal element, the metal in the soluble additive accounts for 0-1.35% of the total amount of the alumina powder.

19. The preparation method according to claim 18, characterized in that The α-Al2O3 powder accounts for 5-20 wt% of the total weight of the alumina powder; and / or, The silicon-containing compound is selected from at least one of dry silica gel, nano silicon oxide, and silicon carbide; and / or, Calculated by the mass percentage of Si element, the Si element in the silicon-containing compound is 0-0.9% of the total weight of the alumina powder; and / or, The forming pore-forming aid is selected from at least one of sesbania powder, starch, methyl cellulose, hydroxypropyl methyl cellulose, sodium hydroxymethyl cellulose, polyethylene microspheres, polystyrene, polyethylene oxide, polyvinyl alcohol, sodium polyacrylate, polyethylene glycol, polyacrylate acrylic acid, urea, methylamine, ethylenediamine, ammonium carbonate, and ammonium bicarbonate; and / or, The amount of the forming pore-forming aid is 0-10% of the total mass of the alumina carrier; and / or, The alkali metal compound is selected from at least one of nitrates and chlorides of metals Na, K and Li; and / or The alkaline earth metal compound is selected from at least one of nitrates and chlorides of metal Mg and Ca; and / or The rare earth metal compound is at least one selected from the group consisting of nitrates and chlorides of La, Ce, Pr, and Y; and / or Calculated by the mass percentage of the metal element, the metal in the soluble additive accounts for 0-0.9% of the total amount of the alumina powder.

20. The preparation method according to claim 15, characterized in that The drying temperature is 60-150° C. and the drying time is 3-48 hours; and / or, The calcination temperature is 800-1200° C. and the calcination time is 3-48 hours; and / or, During the calcination process, when the temperature is below 500° C., the heating rate is 30-150° C. / h; when the temperature is above 500° C., the heating rate is 100-280° C. / h.

21. Use of the alkyne selective hydrogenation catalyst according to any one of claims 1 to 7 or the alkyne selective hydrogenation catalyst prepared by the preparation method according to any one of claims 8 to 20 in an alkyne selective hydrogenation reaction.

22. The use according to claim 21, characterized in that The catalyst is reduced before use.

23. The use according to claim 22, characterized in that The reduction conditions are as follows: a reducing atmosphere having a hydrogen content of not less than 50%, a reduction reaction temperature of 80-200° C., and a reduction reaction time of 2-12 hours.

24. The use according to claim 21, characterized in that When the catalyst is used for the selective hydrogenation reaction of carbon distillate, the acetylene content in the carbon distillate is 1.0-5.0%, the reaction temperature is 20-120°C, and the reaction space velocity is 3000-12000h -1 ;or, When the catalyst is used for the selective hydrogenation reaction of C3 fraction, the percentage of propyne and propadiene in the C3 fraction is 1.0-5.0%, the reaction temperature is 30-70°C, and the reaction space velocity is 20-120h -1 .

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