A rhodium-based composite catalyst for higher alcohols, its preparation method and application

Abstract

The present invention provides a rhodium-based composite catalyst for higher alcohols, its preparation method, and application, relating to the field of catalyst technology. The rhodium-based composite catalyst for higher alcohols comprises a first active metal, a second active metal, and an aminosilanized acidic support. The first active metal is Rh, and the second active metal is one or more of Fe, Mn, K, or Cs. The acidic support is ZrO2 or H-ZSM-5. This catalyst addresses the problems of existing rhodium-based catalysts, such as poor selectivity for higher alcohols (C6+), susceptibility to sintering and deactivation, and high cost.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a rhodium-based composite catalyst for higher alcohols, a preparation method thereof, and applications thereof. Background Art

[0002] Higher alcohols (C6+ alcohols) are an important class of chemical raw materials with broad application prospects. For example, they are used in detergents, high-end cosmetics and fragrances, advanced emulsifiers and dispersants, plasticizers, and alcohol fuel additives. Currently, higher alcohols are mainly produced through processes such as petroleum cracking and olefin carbonylation. Direct production of higher alcohols from synthesis gas has the advantages of a shorter process, lower energy consumption, and avoids dependence on petroleum resources. However, the current products obtained from the Fischer-Tropsch reaction of synthesis gas generally have a low content of higher alcohols, and the selectivity of the by-products CH4 and CO2 are both >30%. The main reason for this is the lack of suitable catalysts.

[0003] Currently, researchers have developed several catalyst systems for the synthesis of higher alcohols from syngas, including modified Rh-based catalysts, Mo-based catalysts, modified methanol synthesis catalysts, and modified Fischer-Tropsch synthesis catalysts. Among them, rhodium-based catalysts have the following problems: ① They tend to produce methane and short-chain alkanes (such as C1-C4) rather than higher alcohols (C 6+ ), especially at high temperatures, the side reactions are exacerbated. The main reason is that CO dissociates on the Rh surface to form C* species, which are easily over-hydrogenated to form alkanes, rather than inserting with CO to form alcohols, resulting in low selectivity. ② Rhodium nanoparticles are prone to agglomeration (sintering) in high-temperature reactions (>250°C), resulting in a reduction in active sites, leading to easy sintering and deactivation. ③ Sulfur (S), chlorine (Cl - ) and other impurities can easily poison the active sites of rhodium, leading to catalyst deactivation. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a rhodium-based composite catalyst for higher carbon alcohols, which solves the problems of poor selectivity for higher carbon alcohols (C6+), easy sintering and deactivation, and high cost of existing rhodium-based catalysts.

[0005] The first aspect of the present invention provides a rhodium-based composite catalyst for higher alcohols, comprising a first active metal, a second active metal, and an aminosilanized acidic support.

[0006] The first active metal is Rh, the second active metal is one or more of Fe, Mn, K or Cs, and the acidic carrier is ZrO2 or H-ZSM-5.

[0007] The rhodium-based composite catalyst for high-carbon alcohols in this application reduces costs by introducing metals such as Fe, Mn, K or Cs to form alloys with Rh. At the same time, Fe and Mn can weaken the dissociation ability of Rh for CO through the electron-donating effect, promote the insertion of CO to generate high-carbon alcohols (C6+), while K or Cs can enhance the non-dissociative adsorption of CO and improve the selectivity of C6+ alcohols. The selection of an acidic carrier (ZrO2 or H-ZSM-5) can, on the one hand, promote the adsorption and dissociation of CO through the Lewis acid sites, which can promote the insertion of CO and improve the selectivity of C6+ alcohols. On the other hand, the acidic surface forms a strong metal-support interaction with Rh, which can inhibit sintering and improve sulfur and chlorine tolerance. The present invention further introduces basic site amino groups by using an amino-silanized acidic carrier, which can further weaken the dissociative adsorption of Rh for H2 through the electronic effect, reduce short-chain by-products such as methane, and at the same time, the alkaline environment can further enhance the non-dissociative adsorption of CO and promote the reaction of CO with CH x Coupling to form higher carbon alcohols (C6+)

[0008] Optionally, by mass fraction, the first active metal comprises 0.5 wt% to 10 wt%, the second active metal comprises 0.5 wt% to 8 wt%, and the acidic support comprises 85 wt% to 98 wt%. Optionally, the first active metal may comprise 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, or any value or range therebetween.

[0009] Optionally, the second active metal can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt% or any value and range therebetween.

[0010] Optionally, the aminosilanized acidic carrier can be 85wt%, 86wt%, 87wt%, 88wt%, 89wt%, 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt% or any value and range therebetween.

[0011] In this application, Rh is a precious metal. A high loading (>10%) will significantly increase the cost and easily lead to particle agglomeration. A low loading may lead to insufficient active sites. In this application, a certain proportion of a second active metal is added to form an alloy with Rh. By adjusting the electronic structure, excessive dissociation of CO is suppressed and CC coupling is promoted. ZrO2 and H-ZSM-5 are used as acidic carriers. Their acidity will affect the adsorption of reactants and the stability of intermediates. By introducing a certain proportion of amino-silanized acidic carriers, acid-base dual functions are achieved, forming a strong metal-carrier interaction with Rh, further improving the selectivity of higher carbon alcohols, and at the same time, it can inhibit sintering, improve sulfur and chlorine tolerance, and ensure the stability of the catalyst.

[0012] Optionally, aminosilanization treatment of ZrO2 comprises the following steps:

[0013] a1: Clean ZrO2 with acid and then calcine it at 400-550°C; for example, dilute nitric acid can be used to clean it to remove impurities on the ZrO2 surface and increase the hydroxyl density and active sites.

[0014] a2: Add the ZrO2 calcined in step a1 to a solution of 3-aminopropyltriethoxysilane and toluene, and carry out a reflux reaction at 75-85° C.; then wash to remove the unreacted 3-aminopropyltriethoxysilane.

[0015] a3: calcining the ZrO2 after the reflux reaction in step a2 at 250-350°C in an inert atmosphere to obtain aminosilanized ZrO2.

[0016] Optionally, aminosilanization treatment is performed on ZrO2 to reduce its pore size to 5-10 nm, which is beneficial for the subsequent Rh dispersion.

[0017] Optionally, the mass ratio of 3-aminopropyltriethoxysilane to ZrO2 is 5%-10% to avoid pore blockage caused by excessive APTES.

[0018] Optionally, aminosilanization treatment of H-ZSM-5 comprises the following steps:

[0019] b1. Immerse the H-ZSM-5 in an alkaline solution at 70-80°C; for example, immerse the H-ZSM-5 in a 0.1-0.5 M sodium hydroxide solution to partially dissolve the silica-alumina framework and generate mesopores. Optionally, the pore size of the H-ZSM-5 after alkaline treatment is enlarged to 2-5 nm, facilitating the subsequent entry of 3-aminopropyltriethoxysilane into the pores.

[0020] b2. The H-ZSM-5 treated with alkali in step b1 is acid-cleaned, and then dried and calcined in sequence to obtain activated H-ZSM-5; for example, the expanded H-ZSM-5 can be cleaned with 0.1-0.3M dilute nitric acid to remove residual alkali and increase the surface hydroxyl density.

[0021] b3 Immerse the activated H-ZSM-5 in a solution of 3-aminopropyltriethoxysilane and toluene, and conduct a reflux reaction at 75-85°C to fully graft the silane. Then, dry and heat-treat in an inert atmosphere to obtain aminosilanized H-ZSM-5.

[0022] Optionally, the calcination temperature in step b2 is 450-550°C.

[0023] Optionally, the heat treatment temperature under inert atmosphere in step b3 is 140-160°C.

[0024] Optionally, the mass ratio of 3-aminopropyltriethoxysilane to H-ZSM-5 is 5%-15%.

[0025] A second aspect of the present invention provides a method for preparing a rhodium-based composite catalyst for higher alcohols, the preparation method comprising the following steps:

[0026] (1) According to the proportion of the first active metal and the second active metal in the total mass of the catalyst, the corresponding soluble salt and the acidic carrier are weighed respectively, and the soluble salt of the first active metal is mixed with a first solvent to obtain a first solution; and the soluble salt of the second active metal is mixed with a second solvent to obtain a second solution; optionally, the first solvent can be dilute hydrochloric acid, and the second solvent can be deionized water or propanol, however, the present invention is not limited thereto.

[0027] (2) impregnating the support with the first solution, drying it, and then reducing it at a certain temperature to obtain an acidic support loaded with the first active metal;

[0028] (3) impregnating the acidic support loaded with the first active metal with the second solution, drying, and then calcining to obtain the acidic support loaded with the second active metal;

[0029] (4) The acidic carrier loaded with the second active metal is subjected to reduction treatment at a certain temperature, and then subjected to passivation and calcination qualitative treatment in sequence to obtain a rhodium-based composite catalyst for high-carbon alcohols.

[0030] Optionally, the soluble salt of the first active metal is one of rhodium chloride or rhodium nitrate.

[0031] Optionally, the soluble salt of the second active metal is one or more of ferric nitrate, ferrous sulfate, manganese nitrate, manganese sulfate, potassium nitrate, cesium nitrate, and cesium chloride.

[0032] Optionally, the reduction treatment temperature in step (2) is 250-300° C. Optionally, the Rh particles are less than 5 nm, and Rh is reduced below 300° C. to inhibit particle agglomeration.

[0033] Optionally, the calcination temperature in step (3) is 350-450°C.

[0034] Optionally, in step (4), the reduction treatment temperature is 300-350°C, and the calcination qualitative treatment temperature is 400-550°C.

[0035] A third aspect of the present invention provides use of a rhodium-based composite catalyst for higher alcohols in the direct preparation of higher alcohols from synthesis gas.

[0036] Optionally, the catalyst is pre-reduced and then used in the synthesis of higher alcohols from syngas at a reduction temperature of 300-400°C, using hydrogen, CO or a mixture of the two at a space velocity of 2000-8000 h -1 , the reduction treatment time is 5-10h.

[0037] Optionally, in the reaction of directly converting synthesis gas into higher alcohols, the molar ratio of H2 to CO in the synthesis gas is 0.5-5, the reaction temperature is 200-400°C, and the reaction space velocity is 3000-6000h -1 , the reaction pressure is 3-9MPa.

[0038] Optionally, the reactor in the reaction of directly converting synthesis gas into higher alcohols is a fixed bed reactor, a fluidized bed reactor or a slurry bed reactor, and its specific structure and form are not specifically limited in the present invention.

[0039] Compared with the prior art, the present invention achieves at least one of the following beneficial effects:

[0040] (1) The rhodium-based composite catalyst for higher carbon alcohols of the present invention solves the problems of poor selectivity for higher carbon alcohols (C6+), easy sintering and deactivation, and high cost of existing rhodium-based catalysts.

[0041] (2) In the rhodium-based composite catalyst for higher carbon alcohols of the present invention, a second active metal is added in a certain proportion to form an alloy with Rh. By adjusting the electronic structure, the excessive dissociation of CO is suppressed and CC coupling is promoted. ZrO2 and H-ZSM-5 are used as acidic carriers. Their acidity affects the adsorption of reactants and the stability of intermediates. By introducing a certain proportion of amino-silanized acidic carriers, acid-base dual functions are realized, and a strong metal-carrier interaction is formed with Rh, thereby further improving the selectivity of higher carbon alcohols. At the same time, sintering can be suppressed, sulfur and chlorine tolerance can be improved, and the stability of the catalyst can be ensured.

[0042] (3) The rhodium-based composite catalyst for high-carbon alcohols of the present invention uses 3-aminopropyltriethoxysilane to treat ZrO2 to achieve acid-base dual functions, laying the foundation for the subsequent formation of a strong metal-support interaction with Rh.

[0043] (4) The rhodium-based composite catalyst for high-carbon alcohols of the present invention uses 3-aminopropyltriethoxysilane to treat H-ZSM-5 and graft amino groups to achieve acid-base dual functions, which is suitable for high-temperature and high-pressure synthesis gas to produce high-carbon alcohols. DETAILED DESCRIPTION

[0044] In order to more clearly illustrate the overall concept of the present invention, a detailed description is given below with reference to examples.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0046] Example 1

[0047] In one embodiment of the present invention, the rhodium-based composite catalyst for higher alcohols contains 1 wt% Rh, 1 wt% Fe, and 98 wt% ZrO2 as an acidic carrier.

[0048] The preparation method of the rhodium-based composite catalyst for higher alcohols comprises the following steps:

[0049] (1) According to the rhodium-based composite catalyst for higher carbon alcohols, the mass percentage of Rh component is 1wt%, the mass percentage of Fe component is 1wt%, and the mass percentage of acidic carrier ZrO2 is 98wt%. Rhodium chloride, ferric nitrate and ZrO2 are weighed, rhodium chloride is added to 0.1M dilute hydrochloric acid to prepare a rhodium chloride solution with a concentration of 1M, and ferric nitrate is added to ethanol to prepare a ferric nitrate solution with a concentration of 1M.

[0050] The ZrO2 is subjected to aminosilanization treatment, comprising the following steps: a1: washing the ZrO2 with 0.1M dilute nitric acid, and then calcining it at 400°C for 2h to stabilize the structure;

[0051] a2: Add the ZrO2 calcined in step a1 to a solution of 3-aminopropyltriethoxysilane and toluene, wherein the volume ratio of 3-aminopropyltriethoxysilane to toluene is 1:10, and reflux the solution at 80°C for 5 hours. Centrifuge to remove unreacted 3-aminopropyltriethoxysilane, and dry the solution; wherein the mass ratio of 3-aminopropyltriethoxysilane to ZrO2 is 5%.

[0052] a3: The ZrO2 after the reflux reaction in step a2 is calcined at 250°C in a nitrogen atmosphere to form a stable Si-O-Zr bond to obtain aminosilanized ZrO2. The average pore size of the aminosilanized ZrO2 is 6 nm.

[0053] (2) The aminosilanized ZrO2 carrier was impregnated with rhodium chloride solution, and after drying, it was reduced with hydrogen at 300°C for 3h to obtain ZrO2 loaded with rhodium nanoparticles.

[0054] (3) ZrO2 loaded with rhodium nanoparticles was impregnated with ferric nitrate solution, dried, and calcined at 400 °C for 3 h to obtain Rh-Fe / ZrO2.

[0055] (4) Rh-Fe / ZrO2 was reduced at 300°C for 2 h in a hydrogen atmosphere, and then a 1% O2 / N2 mixed gas was introduced to passivate the surface to prevent the oxidation and inactivation of Rh nanoparticles. Finally, it was calcined at 500°C for 2 h to enhance the mechanical strength, thereby obtaining a rhodium-based composite catalyst for high-carbon alcohols.

[0056] Example 2

[0057] In one embodiment of the present invention, the rhodium-based composite catalyst for higher alcohols contains 8wt% Rh, 5wt% Fe, and 87wt% ZrO2 as an acidic carrier.

[0058] The preparation method of the rhodium-based composite catalyst for higher alcohols comprises the following steps:

[0059] (1) According to the rhodium-based composite catalyst for higher carbon alcohols, the mass percentage of Rh component is 8wt%, the mass percentage of Fe component is 5wt%, and the mass percentage of acidic carrier ZrO2 is 87wt%. Rhodium nitrate, ferric chloride and ZrO2 are weighed, and rhodium nitrate is added to 0.1M dilute hydrochloric acid to prepare a 1M rhodium nitrate solution. Ferric chloride is added to ethanol to prepare a 1M ferric chloride solution.

[0060] The ZrO2 is subjected to aminosilanization treatment, comprising the following steps: a1: washing the ZrO2 with 0.1M dilute nitric acid, and then calcining it at 500°C for 2h to stabilize the structure;

[0061] a2: Add the ZrO2 calcined in step a1 to a solution of 3-aminopropyltriethoxysilane and toluene, wherein the volume ratio of 3-aminopropyltriethoxysilane to toluene is 1:10, and reflux the solution at 75°C for 6 hours. Centrifuge to remove unreacted 3-aminopropyltriethoxysilane, and dry the solution; wherein the mass ratio of 3-aminopropyltriethoxysilane to ZrO2 is 10%.

[0062] a3: The ZrO2 after the reflux reaction in step a2 is calcined at 350°C in a nitrogen atmosphere to form a stable Si-O-Zr bond to obtain aminosilanized ZrO2. The average pore size of the aminosilanized ZrO2 is 7 nm.

[0063] (2) The aminosilanized ZrO2 carrier was impregnated with rhodium nitrate solution, dried, and then reduced with hydrogen at 250°C for 3 h to obtain ZrO2 loaded with rhodium nanoparticles, with Rh particles <5 nm.

[0064] (3) The ZrO2 loaded with rhodium nanoparticles was impregnated with ferric chloride solution, dried, and calcined at 350 °C for 3 h to obtain Rh-Fe / ZrO2.

[0065] (4) Rh-Fe / ZrO2 was reduced at 350°C for 2 h in a hydrogen atmosphere, and then a 1% O2 / N2 mixed gas was introduced to passivate the surface to prevent the oxidation and inactivation of Rh nanoparticles. Finally, it was calcined at 400°C for 2 h to enhance the mechanical strength, thereby obtaining a rhodium-based composite catalyst for higher carbon alcohols.

[0066] Example 3

[0067] In one embodiment of the present invention, the rhodium-based composite catalyst for higher alcohols contains 6wt% Rh, 5wt% Fe, and 89wt% ZrO2 as an acidic carrier.

[0068] The preparation method of the rhodium-based composite catalyst for higher alcohols comprises the following steps:

[0069] (1) According to the rhodium-based composite catalyst for high-carbon alcohols, the mass percentage of Rh component is 6wt%, the mass percentage of Fe component is 5wt%, and the mass percentage of acidic carrier ZrO2 is 89wt%. Rhodium chloride, ferric nitrate and ZrO2 are weighed, rhodium chloride is added to 0.1M dilute hydrochloric acid to prepare a rhodium chloride solution with a concentration of 1M, and ferric nitrate is added to ethanol to prepare a ferric nitrate solution with a concentration of 1M.

[0070] The ZrO2 is subjected to aminosilanization treatment, comprising the following steps: a1: washing the ZrO2 with 0.1M dilute nitric acid, and then calcining it at 450°C for 2h to stabilize the structure;

[0071] a2: Add the ZrO2 calcined in step a1 to a solution of 3-aminopropyltriethoxysilane and toluene, wherein the volume ratio of 3-aminopropyltriethoxysilane to toluene is 1:10, and reflux the solution at 80°C for 5 hours. Centrifuge to remove unreacted 3-aminopropyltriethoxysilane, and dry the solution; wherein the mass ratio of 3-aminopropyltriethoxysilane to ZrO2 is 7%.

[0072] a3: The ZrO2 after the reflux reaction in step a2 is calcined at 300°C in a nitrogen atmosphere to form a stable Si-O-Zr bond to obtain aminosilanized ZrO2. The average pore size of the aminosilanized ZrO2 is 7nm.

[0073] (2) The aminosilanized ZrO2 carrier was impregnated with rhodium chloride solution, dried, and then reduced with hydrogen at 250°C for 3 h to obtain ZrO2 loaded with rhodium nanoparticles. The Rh particles were less than 5 nm.

[0074] (3) ZrO2 loaded with rhodium nanoparticles was impregnated with ferric nitrate solution, dried, and calcined at 400 °C for 3 h to obtain Rh-Fe / ZrO2.

[0075] (4) Rh-Fe / ZrO2 was reduced at 320°C for 2 h in a hydrogen atmosphere, and then a 1% O2 / N2 mixed gas was introduced to passivate the surface to prevent the oxidation and inactivation of Rh nanoparticles. Finally, it was calcined at 500°C for 2 h to enhance the mechanical strength, thereby obtaining a rhodium-based composite catalyst for higher carbon alcohols.

[0076] Example 4

[0077] In one embodiment of the present invention, the rhodium-based composite catalyst for higher alcohols contains 6wt% Rh, 5wt% Fe, and 89wt% of the acidic carrier H-ZSM-5.

[0078] The preparation method of the rhodium-based composite catalyst for higher alcohols comprises the following steps:

[0079] (1) According to the rhodium-based composite catalyst for high-carbon alcohols, the mass percentage of Rh component is 6wt%, the mass percentage of Fe component is 5wt%, and the mass percentage of acidic carrier H-ZSM-5 is 89wt%. Rhodium chloride, ferric nitrate and H-ZSM-5 are weighed, rhodium chloride is added to 0.1M dilute hydrochloric acid to prepare a 2M rhodium chloride solution, and ferric nitrate is added to ethanol to prepare a 2M ferric nitrate solution.

[0080] The H-ZSM-5 is subjected to aminosilanization treatment, including the following steps: b1. The H-ZSM-5 is immersed in a 0.2M sodium hydroxide solution at 70°C to partially dissolve the silica-alumina skeleton and generate mesopores. The pore size of the H-ZSM-5 after the alkali treatment is enlarged to 2-5 nm.

[0081] b2: The H-ZSM-5 treated with alkali in step b1 is washed with 0.2M dilute nitric acid, and then dried and calcined at 500°C for 2h to stabilize the structure and remove adsorbed water to obtain activated H-ZSM-5.

[0082] b3 Immerse the activated H-ZSM-5 in a solution of 3-aminopropyltriethoxysilane and toluene and ultrasonically treat it for 30 minutes to promote diffusion. The volume ratio of 3-aminopropyltriethoxysilane and toluene is 1:20. Reflux reaction is carried out at 80°C for 10 hours to fully graft the silane. Then, centrifugation, washing and drying are carried out in sequence, and heat treatment is carried out at 150°C in a nitrogen atmosphere for 2 hours to obtain aminosilanized H-ZSM-5.

[0083] (2) The rhodium chloride solution was impregnated into aminosilanized H-ZSM-5, which was then dried and reduced with hydrogen at 250°C for 3 h to obtain H-ZSM-5 loaded with rhodium nanoparticles. The Rh particles were less than 5 nm.

[0084] (3) The H-ZSM-5 loaded with rhodium nanoparticles was impregnated with ferric nitrate solution, dried, and calcined at 400 °C for 3 h to obtain Rh-Fe / H-ZSM-5.

[0085] (4) Rh-Fe / H-ZSM-5 was reduced at 320 °C for 2 h in a hydrogen atmosphere, and then a 1% O2 / N2 mixed gas was introduced to passivate the surface to prevent the oxidation and inactivation of Rh nanoparticles. Finally, it was calcined at 500 °C for 2 h to enhance the mechanical strength, thereby obtaining a rhodium-based composite catalyst for high-carbon alcohols.

[0086] Example 5

[0087] In one embodiment of the present invention, the rhodium-based composite catalyst for higher alcohols contains 6wt% Rh, 5wt% Fe, 2wt% K, and 87wt% of the acidic carrier H-ZSM-5.

[0088] The preparation method of the rhodium-based composite catalyst for higher alcohols comprises the following steps:

[0089] (1) According to the rhodium-based composite catalyst for high-carbon alcohols, the mass percentage of Rh component is 6wt%, the mass percentage of Fe component is 5wt%, the mass percentage of K component is 2wt%, and the mass percentage of acidic carrier H-ZSM-5 is 87wt%. Rhodium chloride, ferric nitrate, potassium nitrate and H-ZSM-5 are weighed, and rhodium chloride is added to 0.1M dilute hydrochloric acid to prepare a 2M rhodium chloride solution. Ferric nitrate and potassium nitrate are added to deionized water to prepare a 2M ferric nitrate solution and potassium nitrate solution.

[0090] The H-ZSM-5 is subjected to aminosilanization treatment, including the following steps: b1. The H-ZSM-5 is immersed in a 0.2M sodium hydroxide solution at 70°C to partially dissolve the silica-alumina skeleton and generate mesopores. The pore size of the H-ZSM-5 after the alkali treatment is enlarged to 2-5 nm.

[0091] b2: The H-ZSM-5 treated with alkali in step b1 is washed with 0.2M dilute nitric acid, and then dried and calcined at 500°C for 2h to stabilize the structure and remove adsorbed water to obtain activated H-ZSM-5.

[0092] b3 Immerse the activated H-ZSM-5 in a solution of 3-aminopropyltriethoxysilane and toluene and ultrasonically treat it for 30 minutes to promote diffusion. The volume ratio of 3-aminopropyltriethoxysilane and toluene is 1:20. Reflux reaction is carried out at 80°C for 10 hours to fully graft the silane. Then, centrifugation, washing and drying are carried out in sequence, and heat treatment is carried out at 150°C in a nitrogen atmosphere for 2 hours to obtain aminosilanized H-ZSM-5.

[0093] (2) Rhodium chloride solution and ferric nitrate were mixed, and aminosilanized H-ZSM-5 was added dropwise. Ultrasonic assistance was used for 30 minutes to ensure uniform penetration. The mixture was allowed to stand at room temperature for 15 hours and dried at 90°C for 12 hours to obtain Rh-Fe / H-ZSM-5.

[0094] (3) Rh-Fe / H-ZSM-5 was impregnated with potassium nitrate solution, dried, and calcined at 400 °C for 4 h to obtain Rh-Fe-K / H-ZSM-5.

[0095] (4) Rh-Fe-K / H-ZSM-5 was reduced at 320 °C for 2 h in a hydrogen atmosphere, and then a 1% O2 / N2 mixed gas was introduced to passivate the surface to prevent the oxidation and inactivation of Rh nanoparticles. Finally, it was calcined at 500 °C for 2 h to enhance the mechanical strength, thereby obtaining a rhodium-based composite catalyst for high-carbon alcohols.

[0096] Example 6

[0097] Based on Example 5, the main differences are that the rhodium-based composite catalyst for higher alcohols contains 6wt% of Rh, 5wt% of Mn, 2wt% of K, and 87wt% of the acidic carrier H-ZSM-5.

[0098] In the preparation method, ferric nitrate was replaced by manganese nitrate, and the other steps were the same as those in Example 5.

[0099] Example 7

[0100] Based on Example 5, the main difference is that the acidic support H-ZSM-5 is replaced by the acidic support ZrO2, and the higher alcohol is treated with 6wt% Rh, 5wt% Fe, 2wt% K, and 87wt% ZrO2 in a rhodium-based composite catalyst. The aminosilanization step of ZrO2 is the same as in Example 3, and the other steps are the same as in Example 5.

[0101] Example 8

[0102] The main differences from Example 6 are that the rhodium-based composite catalyst for higher alcohols contains 6 wt % Rh, 5 wt % Mn, and 2 wt % Cs, and the acidic support H-ZSM-5 contains 87 wt %. In the preparation method, potassium nitrate is replaced with cesium nitrate. The other steps are the same as in Example 6.

[0103] Example 9

[0104] Based on Example 1, the main difference is that N-aminoethyl-3-aminopropylmethyldimethoxysilane is used to carry out aminosilanization treatment on ZrO2. Other steps are the same as those in Example 1.

[0105] Example 10

[0106] Based on Example 1, the main difference is that the second active metal is 12 wt %. Other steps are the same as Example 1.

[0107] Example 11

[0108] Based on Example 1, the main difference is that the first active metal is 0.2 wt %.

[0109] Comparative Example 1

[0110] The main difference from Example 1 is that the acidic support is not subjected to aminosilanization treatment.

[0111] Comparative Example 2

[0112] The main difference from Example 1 is that no second active metal is added.

[0113] Test Case

[0114] The rhodium-based composite catalyst for higher alcohols prepared in the above examples and comparative examples was applied to the reaction of preparing higher alcohols from synthesis gas. Before the reaction of directly preparing higher alcohols from synthesis gas, the catalyst was first subjected to reduction pretreatment. The rhodium-based composite catalyst for higher alcohols prepared in the examples and comparative examples was loaded into a fixed bed reactor for reduction pretreatment: the reduction temperature was 400° C., the reducing gas was a mixture of hydrogen and CO, and the space velocity was 8000 h / min. -1 , the reduction treatment time is 6h.

[0115] When the synthesis gas is reacted, the molar ratio of H2 to CO in the synthesis gas is 2, and the reaction space velocity is 4000h -1 The reaction temperature was 300°C and the reaction pressure was 6 MPa. After the reaction, the types and contents of the components in the product were analyzed by gas chromatography. The conversion rate and selectivity of the reaction were calculated accordingly. The results are shown in Table 1.

[0116] Table 1

[0117]

[0118] As shown in Table 1, the rhodium-based composite catalyst for higher carbon alcohols of the present invention can be used to prepare higher carbon alcohols from synthesis gas. When the synthesis gas reaction is carried out at a relatively high temperature (300°C) and pressure, the CO conversion rate is not less than 25%, and the C6+ alcohol selectivity is not less than 25%. The rhodium-based composite catalyst for higher carbon alcohols prepared by the present invention has high (C6+) selectivity.

[0119] Stability test: The molar ratio of H2 to CO in the synthesis gas is 2, and the reaction space velocity is 4000h -1 The reaction temperature was 300°C, the reaction pressure was 6 MPa, and the operation was continuous for 300 hours. The stability of the rhodium-based composite catalyst for higher alcohols prepared in the above example was tested. After 300 hours, the fluctuation rate of CO conversion rate changed by about 6%, and the fluctuation rate of C6+ alcohol selectivity changed by about 4%. Compared with the existing Rh-based catalyst (which sintered and deactivated after 300 hours of operation), the rhodium-based composite catalyst for higher alcohols prepared in this application has improved stability and good resistance to sintering and poisoning.

[0120] The foregoing is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. A rhodium-based composite catalyst for higher alcohols, characterized in that: The rhodium-based composite catalyst for higher alcohols comprises a first active metal, a second active metal, and an aminosilanized acidic support. The first active metal is Rh, the second active metal is one or more of Fe, Mn, K or Cs, and the acidic support is ZrO2 or H-ZSM-5; The first active metal forms an alloy with the second active metal; Calculated by mass fraction, the first active metal is 0.5wt%-10wt%, the second active metal is 0.5wt%-8wt%, and the acidic carrier is 85wt%-98wt%.

2. The rhodium-based composite catalyst for higher alcohols according to claim 1, wherein The aminosilanization treatment of ZrO2 includes the following steps: a1: Wash ZrO2 with acid and then calcine at 400-550℃; a2: Add the ZrO2 calcined in step a1 to a solution of 3-aminopropyltriethoxysilane and toluene, and reflux the solution at 75-85°C. a3: calcining the ZrO2 after the reflux reaction in step a2 at 250-350°C in an inert atmosphere to obtain aminosilanized ZrO2.

3. The rhodium composite catalyst for higher alcohols according to claim 2, wherein Aminosilanization treatment of ZrO2 pore size 5-10nm; And / or the mass ratio of 3-aminopropyltriethoxysilane to ZrO2 is 5%-10%.

4. The rhodium-based composite catalyst for higher alcohols according to claim 1, wherein The aminosilanization treatment of H-ZSM-5 includes the following steps: b1: Immerse H-ZSM-5 in an alkaline solution and treat at 70-80°C; b2: acid-washing the H-ZSM-5 treated with alkali in step b1, followed by drying and calcining to obtain activated H-ZSM-5; b3: Immerse the activated H-ZSM-5 in a solution of 3-aminopropyltriethoxysilane and toluene, conduct a reflux reaction at 75-85°C, and then successively dry and heat-treat under an inert atmosphere to obtain aminosilanized H-ZSM-5.

5. The rhodium-based composite catalyst for higher alcohols according to claim 4, wherein The pore size of the H-ZSM-5 after alkali treatment in step b1 is 2-5 nm; and / or the calcination temperature in step b2 is 450-550°C; and / or the heat treatment temperature in the inert atmosphere in step b3 is 140-160° C.; And / or the mass ratio of 3-aminopropyltriethoxysilane to H-ZSM-5 is 5%-15%.

6. A method for preparing a rhodium-based composite catalyst for higher alcohols as claimed in any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) Weighing the corresponding soluble salt and acidic carrier according to the proportion of the first active metal and the second active metal in the total mass of the catalyst, mixing the soluble salt of the first active metal with a first solvent to obtain a first solution; and mixing the soluble salt of the second active metal with a second solvent to obtain a second solution; (2) impregnating the support with the first solution, drying it, and then reducing it at a certain temperature to obtain an acidic support loaded with the first active metal; (3) impregnating the acidic support loaded with the first active metal with the second solution, drying, and then calcining to obtain the acidic support loaded with the second active metal; (4) The acidic carrier loaded with the second active metal is subjected to reduction treatment at a certain temperature, and then subjected to passivation and calcination qualitative treatment in sequence to obtain a rhodium-based composite catalyst for high-carbon alcohols.

7. The preparation method according to claim 6, characterized in that The soluble salt of the first active metal is one of rhodium chloride or rhodium nitrate; And / or the soluble salt of the second active metal is one or more of ferric nitrate, ferrous sulfate, manganese nitrate, manganese sulfate, potassium nitrate, cesium nitrate, and cesium chloride.

8. The preparation method according to claim 6, characterized in that The reduction treatment temperature in step (2) is 250-300°C; and / or the calcination temperature in step (3) is 350-450°C; And / or in step (4), the reduction treatment temperature is 300-350°C, and the calcination qualitative treatment temperature is 400-550°C.

9. Use of the rhodium-based composite catalyst for higher alcohols as claimed in any one of claims 1 to 5 in the direct preparation of higher alcohols from synthesis gas.

Images