阅读说明：本技术 一种用于烃类转化反应的催化剂 (Catalyst for hydrocarbon conversion reaction ) 是由 刘冬 许正跃 王玉 曹晶 蔡吉乡 耿祖豹 董喜恩 施祖伟 邱祥涛 李安宏 侯鹏飞 于 2019-12-03 设计创作，主要内容包括：本发明涉及一种用于烃类转化反应的催化剂,其特征在于所述催化剂由内外两种不同性质的物质结合组成,内部的第一层物质具有较低的孔隙率,外部的第二层物质具有第一类型孔和第二类型孔,所述第一类型孔的孔径分布的最大值在4～50nm之间,所述第二类型孔的孔径分布的最大值在100～1000nm之间。所述催化剂具有较低的贵金属第一层载体渗透率,有利于贵金属的回收,在长链烃类烃转化反应,特别是C-(10)～C-(15)长直链烷烃脱氢制取单烯烃、C-(10)～C-(15)长链双烯烃选择性加氢反应过程中具有突出的选择性和活性,同时具有较好的稳定性,可以显著提高选择性,减少副反应,延长催化剂使用寿命。(The invention relates to a catalyst for hydrocarbon conversion reaction, which is characterized in that the catalyst is formed by combining an inner substance and an outer substance with different properties, wherein the inner first layer substance has lower porosity, and the outer second layer substance has a first type of pores and a second type of poresThe pore size distribution of the first type of pores is between 4 and 50nm, and the pore size distribution of the second type of pores is between 100 and 1000 nm. The catalyst has low noble metal first layer carrier permeability, is favorable for recovering noble metal, and is used in long-chain hydrocarbon conversion reaction, especially C 10 ～C 15 Dehydrogenation of long straight-chain alkane to prepare mono-olefin and C 10 ～C 15 The selective hydrogenation reaction process of the long-chain diolefin has outstanding selectivity and activity, and simultaneously has good stability, so that the selectivity can be obviously improved, side reactions are reduced, and the service life of the catalyst is prolonged.)

1. A catalyst for hydrocarbon conversion reaction, characterized in that the catalyst comprises a carrier and at least one catalytic component loaded on the carrier, the carrier comprises at least a first layer carrier and a second layer carrier, the second layer carrier spatially coats the first layer carrier, the material of the first layer carrier is different from that of the second layer carrier, the second layer carrier is deposited with at least one catalytic component, the ratio of the thickness of the second layer carrier to the effective diameter of the first layer carrier is between 0.01 and 0.2, the second layer carrier is distributed with a first type of pores and a second type of pores, the maximum value of the pore size distribution of the first type of pores is between 4 and 50nm, and the maximum value of the pore size distribution of the second type of pores is between 100 and 1000 nm.

2. The catalyst according to claim 1, wherein the first type of pores have a pore size distribution with a maximum value between 10 and 20nm and the second type of pores have a pore size distribution with a maximum value between 150 and 500 nm.

3. The catalyst according to claim 1, wherein the porosity of the first layer carrier is less than that of the second layer carrier, the first layer carrier has a pore volume of 0.3ml/g or less and a BET specific surface area of 20m or less²/g。

4. The catalyst of claim 1 wherein the catalytic component comprises one or more first catalytic components comprising one or more platinum group metals, one or more second catalytic components comprising one or more group IIIA, group IVA, group IIB, transition metals, and one or more third catalytic components comprising one or more alkali metals, alkaline earth metals.

5. The catalyst of claim 4, characterized in that the first catalytic component is platinum, the second catalytic component is tin, and the third catalytic component is an alkali metal.

6. The catalyst according to claim 5, characterized in that the catalytic component comprises, in weight percent based on the total weight of the catalyst: 0.05-0.5% of platinum; 0.01 to 0.5 percent of tin; 0.01 to 0.5% of an alkali metal.

7. The catalyst of claim 4, wherein the third catalytic component further comprises one or more of iron, cobalt, and nickel, and the weight percentage of the third catalytic component is 0.01 to 1.5% of the total weight of the catalyst.

8. The catalyst of claim 7 wherein the third catalytic component is cobalt.

9. The catalyst of claim 1 wherein the hydrocarbon comprises C₃～C₂₀Of an alkaolefin, preferably C₁₀～C₁₅Long linear alkanes or alkenes, including dehydrogenation, alkylation, and hydrogenation.

Technical Field

The invention relates to a catalyst, in particular to a catalyst for hydrocarbons such as C₃～C₂₀Hydrocarbons of (2), especially C₁₀～C₁₅Catalysts for hydrocarbon conversion processes of long chain alkanes and alkenes (hereinafter referred to as alkadienes).

Background

Long-chain hydrocarbons, especially C, are involved in the production of synthetic detergents and various surfactants₁₀～C₁₅Hydrocarbon conversion process of long chain hydrocarbons.

There are many patents on catalysts for long-chain alkane-olefin hydrocarbon conversion reactions, such as long-chain alkane dehydrogenation, selective hydrogenation of long-chain diolefin, and alkylation of long-chain alkane-olefin, and most of these catalysts use porous activated alumina as a carrier and a group VIII metal as a main catalytic element. For dehydrogenation reaction of long-chain alkane, platinum is used as a first catalytic component, tin is used as a second catalytic component, and alkali metal or alkaline earth metal is used as a third catalytic component.

US patent US4551574 discloses a catalyst for dehydrogenation of hydrocarbons, which comprises a porous support having uniformly distributed thereon a platinum group component, a tin component, an indium component, an alkali metal or alkaline earth metal component, wherein the atomic ratio of the indium component to the platinum group component is greater than 1.0. The catalyst is particularly useful in C₁₀～C₁₅Paraffin is dehydrogenated to olefins.

Chinese patent CN101612583A discloses a method for preparing saturated hydrocarbons such as C₃～C₂₀For dehydrogenation of alkanes, alkylaromatics, especially for C₁₀～C₁₅The dehydrogenation of long-chain paraffin to prepare saturated paraffin dehydrogenation catalyst with non-uniformly distributed active component of monoolefine. Wherein, the active components of the catalyst are distributed on the surface layer of the carrier, which can shorten the reaction diffusion path and improve the selectivity and stability of the reaction. The catalyst uses alumina pellets as a carrier, and adopts an impregnation method to carry various catalytic components on the carrier in a non-uniform way, wherein platinum metal as an active component is mainly distributed on the surface of the carrier, and tin, alkaline metal and VIII group metal as an auxiliary agent are uniformly distributed in the carrier as a whole.

Chinese patent CN1018619B discloses a surface impregnated dehydrogenation catalyst particle comprising a catalyst particle having a composition comprising a platinum group metal component, a promoter metal component selected from tin, germanium, rhenium and mixtures thereof, an optional alkali metal or alkaline earth metal or mixtures thereof and an optional halogen component on a solid refractory oxide support having a nominal equivalent diameter of at least 850 μm. The novel catalyst system is particularly useful as a hydrocarbon dehydrogenation catalyst. The catalyst is believed to confine the surface impregnated catalytic components entirely within a 400 μm deep shell on the outer surface of the catalyst support, making the catalytic sites more accessible, allowing the hydrocarbon reactants and products to have shorter diffusion paths, and reducing the residence time of the reactants and products in the catalyst particles due to the shortened diffusion paths, thereby reducing undesirable side effects due to secondary reactions.

During the hydrocarbon conversion process, hydrocarbons enter the pore channels of the catalyst, and a series of reactions occur on the surface of the active center. Compared with short-chain hydrocarbons, long-chain hydrocarbons have large mass transfer resistance in pore channels of the catalyst and long retention time due to long carbon chains, so deep side reactions are easy to occur, the selectivity of the hydrocarbon conversion process is reduced, and the service life of the catalyst is also short. The above reported techniques each adopt different methods to reduce the occurrence of side reactions, but the effect is still not satisfactory.

Disclosure of Invention

The invention relates to a hydrocarbon conversion catalyst different from the prior art, which solves the problems of large mass transfer resistance, low selectivity and short service life of the catalyst in the hydrocarbon conversion reaction of macromolecular long-chain alkane and olefin, reduces the degree of the first catalytic component of the catalyst permeating into the first layer of carrier of the catalyst, and improves the utilization efficiency of the first catalytic component of the catalyst.

In one embodiment of the present application, a catalyst is provided, the catalyst comprises a carrier and at least one catalytic component loaded on the carrier, the carrier comprises at least a first layer carrier and a second layer carrier, the second layer carrier spatially coats the first layer carrier, the material of the first layer carrier is different from the material of the second layer carrier, the second layer carrier has at least one catalytic component deposited thereon, the ratio of the thickness of the second layer carrier to the effective diameter of the first layer carrier is between 0.01 and 0.2, the second layer carrier has a first type of pores and a second type of pores distributed therein, the maximum value of the pore size distribution of the first type of pores is between 4 and 50nm, and the maximum value of the pore size distribution of the second type of pores is between 100 and 1000 nm.

Optionally, the maximum of the pore size distribution of the first type of pores is between 10 and 20nm, and the maximum of the pore size distribution of the second type of pores is between 150 and 500 nm.

Optionally, the porosity of the first layer of carrier is less than that of the second layer of carrier, the pore volume of the first layer of carrier is less than or equal to 0.3ml/g, and the BET specific surface area is less than or equal to 20m²/g。

Optionally, the catalytic components include one or more first catalytic components, one or more second catalytic components, and one or more third catalytic components.

In one embodiment of the present application, the first catalytic component comprises one or more platinum group metals, the second catalytic component comprises one or more group IIIA, group IVA, group IIB, transition metals, and the third catalytic component comprises one or more alkali, alkaline earth metals.

Optionally, the first catalytic component is platinum, the second catalytic component is tin, and the third catalytic component is an alkali metal.

Optionally, the weight percentage of the catalytic component in the total weight of the catalyst is: 0.05-0.5% of platinum; 0.01 to 0.5 percent of tin; 0.01 to 0.5% of an alkali metal.

Optionally, the third catalytic component further comprises one or more of iron, cobalt and nickel, and the weight percentage of the third catalytic component in the total weight of the catalyst is 0.01-1.5%.

Optionally, the third catalytic component is cobalt.

Optionally, the hydrocarbon comprises C₃～C₂₀Of an alkaolefin, preferably C₁₀～C₁₅Long linear alkanes or alkenes, including dehydrogenation, alkylation, and hydrogenation.

The invention forms a catalyst carrier which is internally and externally anisotropic and comprises a first layer carrier and a second layer carrier by selecting different substances, and provides two different types of holes by adjusting the pore structure of the second layer carrier of the catalyst, wherein the first type of holes provides high specific surface area and active center required by reaction, so that the reaction activity of the catalyst is improved; the second type holes are used as diffusion channels of reactants and products, so that the diffusion process of the reactants and the products is greatly improved, the occurrence of deep side reaction is reduced, the reaction selectivity is improved, and the service life of the catalyst is prolonged. Meanwhile, the first layer of carrier with low porosity prevents the infiltration of active elements of the catalyst, improves the utilization efficiency of the first catalytic component of the catalyst, reduces the difficulty of recovering noble metals from the waste catalyst after the catalyst is inactivated and replaced, prevents reactants and products from diffusing into the first layer of carrier, and shortens the diffusion distance of the reactants and the products in the catalyst, thereby further reducing the occurrence of side reactions and enabling the reaction to obtain higher selectivity.

Detailed Description

Long chain alkalkenes, especially C₁₀～C₁₅The molecular volume of the linear alkane olefin is larger. Compared with some low-carbon-number micromolecular hydrocarbons, the long-chain alkane has larger diffusion resistance and long retention time in the catalyst, so that deep side reaction is easier to occur, the selectivity of a target product is low, the carbon deposition of the catalyst is serious, and the service life is short. The catalyst related by the invention is formed by combining two substances with different properties, namely a first layer carrier and a second layer carrier, catalytic reaction active centers are only distributed on the second layer carrier positioned on the outer layer, so that the diffusion distance of reactants and products in the catalyst is greatly shortened, the second layer carrier provides two different types of holes, and the first type of holes with smaller sizes (the maximum value of the hole diameter distribution is between 4 and 50 nm) provide high specific surface area and active centers required by the reaction, so that the reaction activity of the catalyst is improved; the second type of large-size pores (the maximum value of pore size distribution is between 100 and 1000 nm) are used as diffusion channels of reactants and products, so that the diffusion time of the reactants and the products is greatly shortened, the diffusion process of the reactants and the products is improved, the diffusion resistance of the reactants and the products is reduced, the retention time in the catalyst is reduced, the occurrence of side reactions is reduced, the selectivity of target products is improved, the reaction efficiency of the catalyst is effectively improved, the generation and accumulation of carbon deposition are reduced, and the service life of the catalyst is prolonged. The catalyst of the present invention can be used for hydrocarbons such as C₃～C₂₀Of alkanes, especially for C₁₀～C₁₅Dehydrogenation of long linear alkanesPreparation of mono-olefins, C₁₀～C₁₅Selective hydrogenation of long-chain diolefins, C₁₀～C₁₅Alkylation of long chain olefins, and the like.

The catalyst comprises a first layer carrier with low porosity and a second layer carrier with a porous structure coated on the first layer carrier, wherein various catalytic components are loaded on the second layer carrier with the porous structure.

The carrier of the catalyst provided by the invention is provided with a first type of holes and a second type of holes, wherein the maximum value of the pore size distribution of the first type of holes is between 4 and 50nm, and the maximum value of the pore size distribution of the second type of holes is between 100 and 1000 nm.

The catalyst carrier is formed by combining a first layer carrier and a second layer carrier which are respectively formed by two substances with different properties inside and outside. The material of the first layer carrier may include, but is not limited to, a-alumina, silicon carbide, mullite, cordierite, zirconia, titania, a mixture of one or more of the metals. The first layer of carrier material can be shaped into different shapes, such as spheres, strips, sheets, rings, gears, cylinders, etc., as desired. A preferably spherical first layer carrier, which may have a diameter of 0.5mm to 10mm, preferably 1.2mm to 2.5 mm. When the first layer carrier is spherical, the diameter refers to the actual diameter of the first layer carrier; when the first layer carrier is non-spherical, the diameter refers to the "effective diameter", i.e., the diameter of the first layer carrier when it is formed into a spherical shape. The carrier forming method of the first layer can be selected from carrier forming methods known in the field according to the characteristics of materials, such as compression molding, extrusion molding, rolling ball forming, dropping ball forming, granulation molding, melt molding and the like. According to different materials forming the first layer of carrier, the raw material powder is added with one or more of inorganic acids or organic acids and a small amount of water, wherein the inorganic acids or organic acids are 2-20% of the weight of the raw material powder, the inorganic acids or organic acids are fully mixed and then formed, the formed first layer of carrier is placed in a closed space at the temperature of 40-90 ℃ to continue to react for 5-24 hours under the conditions of constant temperature and constant humidity, the humidity environment is kept at a proper temperature to promote the crystal structure to be fully converted, and then the first layer of carrier is formedThen drying the mixture at 100 to 150 ℃ for 2 to 8 hours. The dried first layer of carrier needs to be fired and shaped at a certain temperature to finally form a structure with low porosity, the firing temperature is at least higher than the using temperature of the catalyst and is generally 450-1700 ℃ according to the characteristics of different materials. The first layer of the carrier is a low-porosity substance, specifically, the pore volume is less than or equal to 0.3ml/g, the BET specific surface area is less than or equal to 20m²Material/g. In one embodiment of the present application, the material comprising the first layer of support is a low porosity substance, which prevents infiltration of the catalytic component. In the catalyst containing a noble metal such as platinum, in order to reduce the cost, the noble metal supported on the waste catalyst is recovered and used after the catalyst is deactivated and replaced, and the recovery process requires that the waste catalyst is completely dissolved by an acid or an alkali to precipitate the supported noble metal into a solution and then recover the noble metal. The substance constituting the second layer carrier can be dissolved completely by an acid or a base in general, and the noble metal component supported in the second layer carrier can be recovered relatively easily. However, the material constituting the first layer carrier is often not completely dissolved by the acid and alkali, and if the noble metal permeates into the first layer carrier to a large extent, it is difficult to completely recover the noble metal by the chemical process, and the recovered first layer carrier still contains a large amount of noble metal, resulting in a low noble metal recovery rate, so that it is advantageous to reduce the amount of the noble metal contained in the first layer carrier as much as possible. The first layer carrier with low porosity prevents the infiltration of catalytic components, has extremely low content of noble metals, improves the utilization efficiency of the catalytic components, and reduces the difficulty of recovering the noble metals from the waste catalyst. Meanwhile, the lower porosity of the first layer of carrier prevents inward diffusion of reactants and products, shortens the diffusion distance of the reactants and the products in the catalyst and reduces the occurrence of side reactions.

The second layer of support material may be selected from, but is not limited to, a mixture of one or more of gamma alumina, delta alumina, eta alumina, theta alumina, zeolites, non-zeolitic molecular sieves, titania, zirconia, ceria. Gamma-alumina, delta-alumina, zeolites, non-zeolitic molecular sieves are preferred. The material forming the second layer carrier is porous substance and has two different types of pore channel structures at the same time, the first layer carrier is made of porous materialThe maximum value of the pore size distribution of the first type of pores is between 4 and 50nm, and the maximum value of the pore size distribution of the second type of pores is between 100 and 1000 nm. The total volume of the two types of pores is at least 0.5ml/g, preferably at least 1.0 ml/g. The two types of pores each provide a ratio of pore volume between 1:9 and 9:1, preferably between 3:7 and 7: 3. The BET specific surface area of the second layer of support material is at least 50m²A/g, preferably of at least 100m²/g。

The combination of the second layer carrier and the first layer carrier can be achieved by first forming a slurry of the second layer carrier material and then using the prior art methods of dipping, spraying, coating, etc., but is not limited to the above methods. The preparation of the second layer carrier material slurry usually includes a peptization process, in which the second layer carrier material with a porous structure is mixed with water according to a certain proportion and stirred, and usually a certain amount of peptizing agent, such as nitric acid, hydrochloric acid or organic acid, is added, and the amount of peptizing agent is 0.01% -5% of the total amount of the slurry. The thickness of the second layer support can be controlled by the amount of second layer support material slurry used. The invention finds that the thickness of the second layer carrier is not a certain value, and changes along with the diameter of the first layer carrier, so as to obtain the optimal catalyst reaction performance, and particularly, the ratio of the thickness of the second layer carrier to the effective diameter of the first layer carrier is between 0.01 and 0.2.

The second layer support material having two types of pores may be made of a single porous substance (as in example 1), for example, by applying a slurry of the second layer support material having two types of pores (the maximum values of the pore size distribution are 10 to 20nm and 150 to 300nm, respectively) to the first layer support; or, according to the pore structure of the selected second layer carrier material itself, a certain amount of pore-forming agent may be selectively added, so that the final catalyst has two different types of pore structures (as in example 2), for example, the pore-forming agent is added to the slurry of the second layer carrier material having one type of pores (the maximum value of the pore size distribution is 15 to 30nm), and the slurry of the second layer carrier material to which the pore-forming agent is added is coated on the first layer carrier. The pore-forming agent is selected from sesbania powder, methyl cellulose, polyvinyl alcohol, carbon black and other materials according to the required pore diameter, but is not limited to the materials, and the adding amount is controlled to be 5-50% of the mass of the second layer of the carrier material. The pore structure of the finally prepared catalyst is characterized in that the maximum value of the pore size distribution of the first type of pores is between 4 and 50nm, the maximum value of the pore size distribution of the second type of pores is between 100 and 1000nm, the pore volume provided by the first type of pores accounts for 10 to 90 percent, preferably 30 to 70 percent, of the total pore volume, and the pore volume provided by the second type of pores accounts for 90 to 10 percent, preferably 70 to 30 percent, of the total pore volume.

The combination of the second layer of carrier and the first layer of carrier can be completed only by high-temperature roasting. Specifically, the first layer of carrier coated with the second layer of carrier material slurry is dried at 60-200 ℃ for 0.5-10 hours, and then is baked at 300-900 ℃ for a sufficient time, for example, 2-15 hours, so as to obtain the carrier.

The first catalytic component of the catalyst of the present invention is a platinum group metal selected from the group consisting of platinum, palladium, osmium, iridium, ruthenium, rhodium and mixtures thereof, preferably platinum. The second catalytic component is selected from the group consisting of tin, germanium, lead, indium, lanthanum, cerium, zinc and mixtures thereof, preferably tin and lanthanum, particularly preferably tin. The third catalytic component is selected from alkali metals and alkaline earth metals, wherein the alkali metals and the alkaline earth metals are selected from at least one of lithium, sodium, potassium, magnesium, calcium and strontium, preferably sodium and magnesium, particularly preferably sodium, and the weight of the third catalytic component accounts for 0.01-0.5% of the total weight of the catalyst; the third catalytic component can also contain at least one of iron, cobalt and nickel, particularly preferably cobalt, and the weight of the third catalytic component accounts for 0.01-1.5% of the total weight of the catalyst.

In an embodiment of the present application, the weight percentages of the components in the catalyst are: 0.05-0.5% of platinum; 0.01 to 0.5 percent of tin; 0.01 to 0.5% of alkali metal; 0.01-1.5% of cobalt, and the balance of a carrier.

In the invention, the atomic ratio of the content of the tin and platinum metals has a large influence on the performance of the catalyst, and the performance of the catalyst is reduced due to the excessively high or excessively low atomic ratio of the tin and platinum metals. The tin/platinum atomic ratio is generally 1 to 5, and the most preferable value is 1 to 2.

The catalytic components may be supported on the aforementioned support by impregnation. One method is to prepare each catalytic component into a mixed solution and contact the mixed solution with a carrier; another method is to contact the solutions of the catalytic components individually with the support. Drying the carrier impregnated with the catalytic component at 80-150 ℃, then roasting at 250-650 ℃ for 2-8 hours at constant temperature, introducing water vapor for continuous treatment for 0.5-4 hours, and then reducing with hydrogen at 100-600 ℃ for 0.5-10 hours to obtain a catalyst product.

The catalyst is especially suitable for the hydrocarbon conversion process of long-chain alkane olefin, such as long-chain alkane dehydrogenation reaction, long-chain diolefin selective hydrogenation reaction, preferably C₁₀～C₁₅Linear alkaolefins of (a).

Example 1 preparation of catalyst A

In the embodiment, one alumina powder with two types of pores (the pore diameter distribution ranges of the two types of pores are respectively 10-20 nm and 150-300 nm) is used for preparing the second layer of carrier, mullite is used as the first layer of carrier, the carrier containing an inner layer and an outer layer is obtained by effective combination, and the catalyst is prepared.

500 g of high-purity Al is taken₂O₃Powder, 196 g of high-purity SiO₂Mixing the powder, 70 g of water and 10 g of 10% nitric acid, kneading for 1 hour, pressing into pellets, placing in a closed space at 70 ℃ under the conditions of constant temperature and constant humidity, continuing to react for 10 hours, drying at 150 ℃ for 2 hours, and roasting at 1450 ℃ for 1 hour to obtain a first layer of carrier pellets with the diameter of 2.0 mm. XRD analysis showed mullite crystal form.

50 g of alumina powder (with two types of holes, the pore diameter distribution ranges of the two types of holes are respectively 10-20 nm and 150-300 nm), 20 g of 20% nitric acid and 600 g of water are mixed and stirred for 2 hours to prepare alumina slurry. The slurry was sprayed with a spray gun onto a first layer of carrier pellets 2.0mm in diameter. Drying the pellets coated with the slurry at 100 ℃ for 6 hours, and then roasting at 500 ℃ for 6 hours to obtain a carrier containing an inner layer and an outer layer. Analysis showed the second layer support to have a thickness of 150 μm and a ratio to the first layer support diameter of 0.075.

Soaking the prepared carrier in a mixed solution containing chloroplatinic acid, tin chloride and sodium chloride for 10 minutes to fully adsorb, heating and vacuumizing until no liquid residue exists, drying at 120 ℃ for 0.5 hour, then roasting at 450 ℃ for 4 hours, introducing water vapor for treatment for 1 hour, and reducing with hydrogen at 500 ℃ for 2 hours to obtain the finished product catalyst A. Elemental analysis shows that the mass contents of the metal components are Pt0.21%, Sn0.15% and Na0.23% respectively based on the whole catalyst.

The catalyst is characterized by adopting a mercury intrusion method (ISO 15901-1Evaluation of pore size distribution and location of solid materials by means of mercury condensation and gas adsorption), a curve (namely a pore volume-pore size curve) with the abscissa as pore size and the ordinate as pore volume is generated, two types of pores exist in the second layer of the catalyst carrier, the maximum value of the pore size distribution of the first type of pores (namely the pore size value corresponding to the first peak in the curve, the same below) is 13nm, the maximum value of the pore size distribution of the second type of pores (namely the pore size value corresponding to the second peak in the curve, the same below) is 165nm, and the first type of pores have the volume of 0.7ml/g, the second type of pores have the volume of 0.88ml/g and the total pore volume of 1.58ml/g only by taking the mass of the second layer of the carrier as a base number.

Example 2 preparation of catalyst B

In the embodiment, alumina powder with one type of pores (the pore size distribution range is 15-30 nm) is added with a pore-forming agent methyl cellulose to prepare a second-layer carrier with two types of pores, mullite is used as a first-layer carrier, carriers containing an inner layer and an outer layer are obtained by effective combination, and the catalyst is prepared.

The first layer carrier was prepared according to the method of example 1.

50 g of alumina powder (with a type of hole and the pore diameter distribution range of 15-30 nm), 20 g of 20% nitric acid, 12 g of methylcellulose and 600 g of water are mixed and stirred to prepare alumina slurry. The mixture was shaped according to the method of example 1 to obtain a carrier having two layers, an inner layer and an outer layer. Analysis showed that the second layer support had a thickness of 110 μm and a ratio to the first layer support diameter of 0.055.

Catalyst B was obtained according to the catalyst preparation method of example 1. Elemental analysis shows that the mass contents of the metal components are Pt0.20%, Sn0.14% and Na0.23% respectively based on the whole catalyst.

The mercury intrusion method is adopted for characterization, and the two types of pores exist in the second layer of the catalyst carrier, the maximum value of the pore size distribution of the first type of pores is 19nm, the maximum value of the pore size distribution of the second type of pores is 252nm, and the volume of the first type of pores is 0.9ml/g, the volume of the second type of pores is 0.6ml/g and the total pore volume is 1.50ml/g only by taking the mass of the second layer of the carrier as a base number.

Example 3 preparation of catalyst C

In the embodiment, one alumina powder with two types of pores (the pore diameter distribution ranges of the two types of pores are respectively 8-18 nm and 200-500 nm) is used for preparing the second layer of carrier, mullite is used as the first layer of carrier, the carrier containing an inner layer and an outer layer is obtained by effective combination, and the catalyst is prepared.

The first layer carrier was prepared according to the method of example 1.

50 g of alumina powder (with two types of holes, the pore diameter distribution ranges of the two types of holes are respectively 8-18 nm and 200-500 nm), 20 g of 20% nitric acid and 600 g of water are mixed and stirred for 2 hours to prepare alumina slurry. The mixture was shaped according to the method of example 1 to obtain a carrier having two layers, an inner layer and an outer layer. Analysis showed a second layer carrier thickness of 240 μm, with a ratio of 0.12 to the first layer carrier diameter.

Catalyst C was obtained according to the catalyst preparation method of example 1. Elemental analysis shows that the mass contents of the metal components are Pt0.22%, Sn0.15% and Na0.24% respectively based on the whole catalyst.

The mercury intrusion method is adopted for characterization, and the two types of pores exist in the second layer of the catalyst carrier, the maximum value of the pore size distribution of the first type of pores is 11nm, the maximum value of the pore size distribution of the second type of pores is 383nm, and the volume of the first type of pores is 0.68ml/g, the volume of the second type of pores is 0.97ml/g and the total pore volume is 1.65ml/g only by taking the mass of the second layer of the carrier as a base number.

Example 4 preparation of catalyst D

In the embodiment, one alumina powder with two types of pores (the pore diameter distribution ranges of the two types of pores are respectively 8-15 nm and 50-200 nm) is used for preparing the second layer of carrier, mullite is used as the first layer of carrier, the carrier containing an inner layer and an outer layer is obtained by effective combination, and the catalyst is prepared.

The first layer carrier was prepared according to the method of example 1.

50 g of alumina powder (with two types of holes, the pore diameter distribution ranges of the two types of holes are respectively 8-15 nm and 50-200 nm), 20 g of 20% nitric acid and 600 g of water are mixed and stirred for 2 hours to prepare alumina slurry. The mixture was shaped according to the method of example 1 to obtain a carrier having two layers, an inner layer and an outer layer. Analysis showed a second layer of support having a thickness of 70 μm and a ratio to the first layer of support diameter of 0.035.

Catalyst D was obtained according to the catalyst preparation method of example 1. Elemental analysis shows that the mass contents of the metal components are Pt0.20%, Sn0.15% and Na0.23% respectively based on the whole catalyst.

The mercury intrusion method is adopted for characterization, and the two types of pores exist in the second layer of the catalyst carrier, the maximum value of the pore size distribution of the first type of pores is 9nm, the maximum value of the pore size distribution of the second type of pores is 120nm, and the volume of the first type of pores is 0.58ml/g, the volume of the second type of pores is 0.82ml/g and the total pore volume is 1.40ml/g only by taking the mass of the second layer of the carrier as a base number.

EXAMPLE 5 preparation of catalyst E

In the embodiment, one alumina powder with two types of pores (the pore diameter distribution ranges of the two types of pores are respectively 8-18 nm and 200-500 nm) is used for preparing the second layer of carrier, mullite is used as the first layer of carrier, the carrier containing an inner layer and an outer layer is obtained by effective combination, and the catalyst is prepared.

The first layer carrier was prepared according to the method of example 1.

The mixture was shaped according to the procedure of example 3 to obtain a carrier having two layers, an inner layer and an outer layer. Analysis showed a second layer support thickness of 200 μm, with a ratio of 0.1 to the first layer support diameter.

Soaking the prepared carrier in a mixed solution containing chloroplatinic acid, tin chloride, cobalt chloride and sodium chloride for 10 minutes to fully adsorb, heating and vacuumizing until no liquid remains, drying at 120 ℃ for 0.5 hour, then roasting at 450 ℃ for 4 hours, introducing water vapor for 1 hour, and reducing with hydrogen at 500 ℃ for 2 hours to obtain the finished product catalyst E. Elemental analysis shows that the mass contents of the metal components are Pt0.21%, Sn0.15%, Co0.11% and Na0.23% respectively based on the whole catalyst.

The mercury intrusion method is adopted for characterization, and the two types of pores exist in the second layer of the catalyst carrier, the maximum value of the pore size distribution of the first type of pores is 11nm, the maximum value of the pore size distribution of the second type of pores is 410nm, and the volume of the first type of pores is 0.65ml/g, the volume of the second type of pores is 0.98ml/g and the total pore volume is 1.63ml/g only by taking the mass of the second layer of the carrier as a base number.

Comparative example 1 preparation of catalyst F

In the embodiment, one alumina powder with two types of pores (the pore diameter distribution ranges of the two types of pores are respectively 10-20 nm and 150-300 nm) is used for preparing the second layer of carrier, mullite is used as the first layer of carrier, the carrier containing an inner layer and an outer layer is obtained by effective combination, and the catalyst is prepared.

500 g of high-purity Al is taken₂O₃Powder, 196 g of high-purity SiO₂The powder, 70 g of water and 10 g of 10% nitric acid were mixed, kneaded for 1 hour, pressed into pellets, dried at 150 ℃ for 2 hours, and then calcined at 1450 ℃ for 1 hour to obtain first layer carrier pellets with a diameter of 2.0 mm. XRD analysis showed mullite crystal form.

The mixture was shaped according to the method of example 1 to obtain a carrier having two layers, an inner layer and an outer layer. Analysis showed the second layer support to have a thickness of 150 μm and a ratio to the first layer support diameter of 0.075.

Catalyst F was obtained according to the catalyst preparation method of example 1. Elemental analysis shows that the mass contents of the metal components are Pt0.20%, Sn0.15% and Na0.23% respectively based on the whole catalyst.

The mercury intrusion method is adopted for characterization, and the two types of pores exist in the second layer of the catalyst carrier, the maximum value of the pore size distribution of the first type of pores is 13nm, the maximum value of the pore size distribution of the second type of pores is 165nm, and the volume of the first type of pores is 0.7ml/g, the volume of the second type of pores is 0.88ml/g and the total pore volume is 1.58ml/g only by taking the mass of the second layer of the carrier as a base number.

Comparative example 2 preparation of catalyst G

In the embodiment, alumina powder with one type of pores (the pore size distribution range is 8-15 nm) is used for preparing a second-layer carrier, mullite is used as a first-layer carrier, the carrier containing an inner layer and an outer layer is obtained through effective combination, and the catalyst is prepared.

The first layer carrier was prepared according to the method of example 1.

The mixture was shaped according to the method of example 1 to obtain a carrier having two layers, an inner layer and an outer layer. Analysis showed that the thickness of the second layer support was 100 μm, which is a ratio of 0.05 to the diameter of the first layer support.

Catalyst G was obtained according to the catalyst preparation method of example 1. Elemental analysis shows that the mass contents of the metal components are Pt0.20%, Sn0.15% and Na0.23% respectively based on the whole catalyst.

Using the mercury intrusion method for characterization, it was found that there was one type of pores in the second layer of the catalyst support, the maximum value of the pore size distribution was 10nm, and the pore volume was 1.05ml/g based on the mass of the second layer support alone.

Comparative example 3 preparation of catalyst H

This example prepares a radially uniform composition alumina spherical support with two types of pores and prepares a catalyst.

50 g of alumina powder, 20 g of 20% nitric acid and 200 g of water are mixed and stirred to prepare alumina slurry. And preparing the slurry into pellets by an oil column molding method, drying the pellets for 6 hours at 100 ℃, and roasting the pellets for 6 hours at 500 ℃ to obtain the radial uniform carrier.

Catalyst H was obtained according to the catalyst preparation method of example 1. Elemental analysis shows that the mass contents of the metal components are Pt0.45%, Sn0.76% and Na0.5% respectively based on the whole catalyst.

By adopting the mercury intrusion method for characterization, two types of pores exist in the catalyst, the maximum value of the pore size distribution of the first type of pores is 11nm, the pore volume of the first type of pores is 0.66ml/g, the maximum value of the pore size distribution of the second type of pores is 380nm, the pore volume of the second type of pores is 0.94ml/g, and the total pore volume is 1.6 ml/g.

Comparative example 4 preparation of catalyst I

In the embodiment, one alumina powder with two types of pores (the pore diameter distribution ranges of the two types of pores are respectively 10-20 nm and 150-300 nm) is used for preparing the second layer of carrier, mullite is used as the first layer of carrier, the carrier containing an inner layer and an outer layer is obtained by effective combination, and the catalyst is prepared.

The first layer carrier was prepared according to the method of example 1.

50 g of alumina powder (with two types of holes, the pore diameter distribution ranges of the two types of holes are respectively 10-20 nm and 150-300 nm), 20 g of 20% nitric acid and 600 g of water are mixed and stirred for 2 hours to prepare alumina slurry. The slurry was sprayed with a spray gun onto a first layer of carrier pellets 1.3mm in diameter. Drying the pellets coated with the slurry at 100 ℃ for 6 hours, and then roasting at 500 ℃ for 6 hours to obtain a carrier containing an inner layer and an outer layer. Analysis showed a second layer carrier thickness of 350 μm, with a ratio of 0.27 to the first layer carrier diameter.

Catalyst I was obtained according to the catalyst preparation method of example 1. Elemental analysis shows that the mass contents of the metal components are Pt0.22%, Sn0.16% and Na0.23% respectively based on the whole catalyst.

The mercury intrusion method is adopted for characterization, and the two types of pores exist in the second layer of the catalyst carrier, the maximum value of the pore size distribution of the first type of pores is 13nm, the maximum value of the pore size distribution of the second type of pores is 165nm, and the volume of the first type of pores is 0.72ml/g, the volume of the second type of pores is 0.89ml/g and the total pore volume is 1.61ml/g based on the mass of the second layer of the catalyst carrier.

Example 6 catalyst first layer support Pt content analysis

The first layer support prepared according to example 1 was characterized by the mercury intrusion method described above and showed a pore volume of 0.11ml/g and a specific surface of 10m²/g。

The catalyst a obtained in example 1 was boiled with 15% HCl to dissolve the second layer carrier, and the Pt content of the remaining first layer carrier was analyzed by X-ray fluorescence spectroscopy (GB/T6609.30-2009), which revealed that the Pt content in the first layer carrier was 0.0012 wt%.

Comparative example 5 analysis of Pt content of first layer Carrier of catalyst

The first layer support prepared according to comparative example 1 was characterized by the mercury intrusion method described above, and the result showed that the first layer support had a pore volume of 0.42ml/g and a specific surface of 50m²/g。

The catalyst F obtained in comparative example 1 was boiled with 15% HCl to dissolve the second support, and the Pt content of the remaining first support was analyzed by X-ray fluorescence spectroscopy (GB/T6609.30-2009), which revealed that the Pt content in the first support was 0.015 wt%.

The first layer carrier is designed into a low-porosity substance, so that precious metals (such as platinum group metals) can be prevented from entering the first layer carrier, the recovery rate of the precious metals is improved, and the production cost is reduced.

As can be seen by comparing the data of comparative example 5 with that of example 6, the first layer carrier prepared by the method of example 1 has a pore volume of 0.11ml/g and a specific surface of 10m²Per g, very low porosity, whereas the first layer of support prepared by the method of comparative example 1 has a pore volume of 0.42ml/g and a specific surface of 50m²The porosity is higher. Meanwhile, as can be seen from the comparison data, after acid digestion, the content of the residual Pt in the catalyst a with the low porosity of the first layer carrier is far less than the content of the residual Pt in the catalyst F with the high porosity of the first layer carrier by 0.0012 wt%. The first layer carrier of the catalyst A is a substance with extremely low porosity, so that Pt is prevented from entering the first layer carrier, the catalyst A has higher Pt recovery rate, the noble metal use efficiency is higher, and the catalyst use cost is lower.

Example 7 dehydrogenation of Long-chain alkanes

The catalysts of examples 1-5 and comparative examples 1-4 were tested for long chain alkane dehydrogenation. The reactor is a stainless steel reaction tube with an inner diameter of 30mm and is filled with 5ml of catalyst. The reaction raw material is long straight-chain alkane, wherein the total normal alkane content is 99.47 percent, and C₁₀9.39% of component C₁₁29.29% of component C₁₂29.98% of component C₁₃26.61% of component C₁₄Component (C) 4.02%₁₅The component accounts for 0.18 percent, the content of non-normal alkane is 0.53 percent, the reaction temperature is 485 ℃, and the liquid hourly space velocity is 20h^-1,H₂The mol ratio of hydrocarbon is 6, and the reaction pressure is 0.1 MPa. And (2) continuously and constantly passing the reaction raw material mixture through a catalyst bed layer under the reaction condition to react to obtain a reaction product, wherein the reaction product contains the product monoolefin and other byproducts, and also contains unreacted raw material long straight-chain alkane.

The results of the dehydrogenation activity and selectivity of long-chain alkane of the catalyst of each example are shown in tables 1 and 2, wherein the long-chain alkane conversion rate (content of long-chain alkane in the raw material-content of long-chain alkane in the product)/content of long-chain alkane in the raw material is 100%, and the mono-olefin product selectivity is the content of mono-olefin in the product/(content of long-chain alkane in the raw material-content of long-chain alkane in the product) × 100%.

TABLE 1 catalytic dehydrogenation reaction conversion

TABLE 2 catalytic dehydrogenation reaction monoolefin selectivity

As shown in the data in tables 1 and 2, the five catalysts A, B, C, D, E with two-layer carriers and two types of pore channel distributions, prepared in examples 1 to 5 of the present invention, have significantly improved conversion rate and selectivity of reaction compared with the comparative catalyst G, H, wherein the catalyst E prepared by adding metal Co has the smallest reduction range with time, and has better stability and selectivity than the catalyst A, B, C, D without adding Co. The conversion and selectivity of catalyst a with the low porosity first layer support is higher than that of catalyst F with the higher porosity first layer support. The catalyst A, B, C, D, E with the ratio of the thickness of the second layer carrier to the effective diameter of the first layer carrier being 0.01-0.2 has higher conversion rate and selectivity than the catalyst I with the ratio of the thickness of the second layer carrier to the effective diameter of the first layer carrier not being 0.01-0.2.

The reactivity of the catalyst gradually decreases with the increase of the reaction time, and is shown as a decrease in the conversion of the catalyst (i.e., the conversion of the long linear alkane). For economic reasons, it is generally necessary to replace the catalyst when the conversion of the catalyst falls below a certain value, and the time the catalyst has been in use can be regarded as the life of the catalyst. Table 3 shows the time the catalyst has been in use when the conversion of long linear alkanes is reduced to 11.0%.

TABLE 3 Life of the catalyst (service time)

Catalyst and process for preparing same	Life (hours)
		A	291
B	295
		C	333
D	242
		E	390
F	228
		G	191
H	207
		I	211

As seen from the data in table 3, the five catalysts A, B, C, D, E of the present invention have significantly increased service time compared to catalyst F, G, H, I. Catalyst E, prepared with the addition of metallic Co, was used for a longer time than catalyst A, B, C, D without the addition of Co. The catalyst of the invention has better stability and longer service life.

Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the embodiments of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.