Iron-based mesoporous molecular sieve catalyst, its preparation method and application

Abstract

The application provides an iron-based mesoporous molecular sieve catalyst and a preparation method and application thereof. The catalyst comprises 10-35 parts by weight of Fe element oxide, 5-25 parts by weight of transition metal element oxide, 2-15 parts by weight of group IIIB element oxide and 30-75 parts by weight of modified HMS molecular sieve. The iron-based mesoporous molecular sieve catalyst provided by the application is used for preparing low-carbon olefins by a Fischer-Tropsch one-step method, and has high CO conversion rate and low-carbon olefin selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical catalysts, and further relates to an iron-based mesoporous molecular sieve catalyst, a preparation method and application thereof. BACKGROUND

[0002] Low carbon olefins are important basic raw materials in modern industry, which are widely used in the production of various plastics, solvents, medicines and the like, and have a large demand. At present, the source of low carbon olefins still mainly depends on petroleum resources, and petroleum resources are non-renewable resources. A large amount of exploitation and use force people to constantly seek and explore new renewable energy sources.

[0003] Fischer-Tropsch synthesis is a process in which synthesis gas is used to generate various liquid fuels and straight-chain alkanes and olefins through heterogeneous catalytic hydrogenation of CO on a catalyst. In the process of using Fischer-Tropsch synthesis to produce various fuels and chemicals, the catalyst is an important factor affecting the selectivity of the product.

[0004] At present, the catalyst for preparing low carbon olefins by Fischer-Tropsch synthesis is mainly an iron-based catalyst. For example, patent CN105195169A discloses a catalyst for preparing low carbon olefins by Fischer-Tropsch synthesis, a preparation method and application thereof. The catalyst is prepared by using a metal Mg-Al composite oxide as a carrier, Fe, K and Mn elements as precursors, and loading the Fe, K and Mn elements on the metal Mg-Al composite oxide through impregnation or complex precipitation. The catalyst has simple preparation process, mild conditions and good controllability, but the activity and selectivity of the catalyst for low carbon olefins are low. Under the evaluation conditions, the highest CO conversion rate is 82.08%, and the highest selectivity of low carbon olefins is 31.98%. Therefore, it is necessary to further explore the catalyst with higher activity and selectivity of low carbon olefins. SUMMARY

[0005] To solve the above problems, the present application provides an iron-based mesoporous molecular sieve catalyst and a preparation method thereof. The catalyst provided by the present application has high CO conversion rate and low carbon olefin selectivity in the reaction of Fischer-Tropsch one-step method for preparing low carbon olefins.

[0006] First, one of the purposes of the present application is to provide an iron-based mesoporous molecular sieve catalyst.

[0007] Specifically, the catalyst is prepared from raw materials including the following components, and the total weight of each component is 100 parts, including the following components:

[0008]

[0009] Preferably, the weight of each component is as follows:

[0010]

[0011] More preferably, the components are expressed in parts by weight as follows:

[0012]

[0013] Preferably, the ratio of the total pore volume to the average pore diameter of the iron-based mesoporous molecular sieve catalyst of the present invention is 0.1 to 0.3.

[0014] Preferably, the transition metal oxide is derived from at least one of Group IVB and Group IIB metal oxides; more preferably, it is derived from one or a combination of Zn and Zr oxides; more preferably, the Zn and Zr oxides are derived from zinc nitrate hexahydrate and scandium nitrate hydrate, respectively, and are obtained by calcination.

[0015] Preferably, the group IIIB element oxides are derived from one or a combination of Sc and Y element oxides; more preferably, the Sc and Y element oxides are derived from scandium nitrate hydrate and yttrium nitrate hexahydrate, respectively, and are obtained by calcination.

[0016] Preferably, the modified HMS molecular sieve is prepared by loading a modifier onto the HMS molecular sieve. The modifier can adjust the pore size and pore volume of the HMS molecular sieve. The modified HMS molecular sieve has a more suitable pore size and pore structure, which is more conducive to the timely diffusion of low-carbon olefins away from the active center and improves the selectivity of low-carbon olefins.

[0017] Preferably, the modifier is derived from a group VB metal element; more preferably, the group VB metal element is derived from one or a combination of Nb and V elements; even more preferably, Nb and V elements are derived from ammonium niobate oxalate hydrate and ammonium metavanadate, respectively, and are loaded onto the HMS molecular sieve in the form of oxides after calcination.

[0018] Preferably, the loading of the modifier element oxide is 1-10% of the mass of the modified HMS molecular sieve; more preferably 3-7%.

[0019] Secondly, a second objective of this invention is to provide a method for preparing an iron-based mesoporous molecular sieve catalyst, which is one of the objectives of this invention, comprising the following steps:

[0020] Step 1: Prepare the modifier into solution A, immerse solution A on HMS molecular sieve, dry it first, and then calcine it to obtain the modified HMS molecular sieve.

[0021] Step 2: Prepare a mixed solution B by combining compounds of Fe, transition metals, and group IIIB elements. Impregnate the mixed solution B onto the modified HMS molecular sieve prepared in Step 1 to obtain a catalyst precursor. After drying and calcining the catalyst precursor, an iron-based mesoporous molecular sieve catalyst is obtained.

[0022] Preferably, in step one, the solvent for solution A is deionized water. The concentration of solution A is not limited, as long as it is sufficient to fully dissolve the solute.

[0023] Preferably, in step one, the modifier is a group VB metal element compound; preferably, the group VB metal element compound is a water-soluble compound; more preferably, it is one or a combination of ammonium niobate oxalate hydrate and ammonium metavanadate.

[0024] Preferably, in step one, the roasting temperature is 450–650°C, more preferably 480–620°C; and the roasting time is 3–12 h, more preferably 5–10 h.

[0025] Preferably, in step two, the solvent for mixed solution B is deionized water. The concentration of solution B is not limited, as long as it is sufficient to fully dissolve the solute.

[0026] Preferably, in step two, the solutes in the mixed solution B are all water-soluble compounds; more preferably, they are one or a combination of ferric nitrate nonahydrate, zinc nitrate hexahydrate, zirconium nitrate pentahydrate, scandium nitrate hydrate, and yttrium nitrate hexahydrate.

[0027] Preferably, in step two, the mixed solution B is impregnated onto the modified HMS molecular sieve under a vacuum of 1–80 kPa, more preferably 40–80 kPa.

[0028] Preferably, in step two, the roasting temperature is 350–600℃, more preferably 400–550℃; the roasting time is 6–24 h, more preferably 10–20 h.

[0029] Furthermore, a third objective of this invention is to provide the application of the iron-based mesoporous molecular sieve catalyst, which is one of the objectives of this invention, in the Fischer-Tropsch one-step process for the preparation of low-carbon olefins.

[0030] The Fischer-Tropsch one-step process for preparing low-carbon olefins includes using syngas as a raw material, which reacts with an iron-based mesoporous molecular sieve catalyst, one of the objectives of this invention, to generate low-carbon olefins.

[0031] It is worth mentioning that, in the Fischer-Tropsch one-step process for preparing low-carbon olefins of the present invention, the application conditions of the catalyst are as follows:

[0032] Preferably, the molar ratio of H2 to CO in the synthesis gas is 1.0 to 3.5.

[0033] Preferably, the reaction temperature is 260–480°C.

[0034] Preferably, the reaction pressure is 0.5 to 4.0 MPa.

[0035] Preferably, the volumetric space velocity of the feed gas is 1000–11000 h⁻¹. -1 .

[0036] Those skilled in the art will understand that the catalyst of the present invention preferably undergoes an online reduction process before being used in the Fischer-Tropsch one-step process for the preparation of low-carbon olefins. Specific reduction conditions can be reasonably selected by those skilled in the art without requiring inventive effort; for example, but not limited to, the reduction conditions are:

[0037] Preferably, the reduction temperature is 360–560°C;

[0038] Preferably, the reducing agent is H2 and / or CO;

[0039] Preferably, the reduction pressure is atmospheric pressure to 1.5 MPa (gauge pressure);

[0040] Preferably, the volume hourly space velocity of the reducing agent is 1000–11000 hr. -1 ;

[0041] Preferably, the reduction time is 12 to 72 hours.

[0042] For ease of comparison, the reduction conditions in the embodiments of this invention are all as follows:

[0043] Temperature 440℃

[0044] reducing gas H2

[0045] Pressure at normal pressure

[0046] Catalyst loading volume 3ml

[0047] The volume hourly space velocity of the reducing agent is 6000 h⁻¹. -1

[0048] Restoration time: 54 hours.

[0049] The iron-based mesoporous molecular sieve catalyst of the present invention is used in the Fischer-Tropsch one-step process for the preparation of low-carbon olefins, wherein the CO conversion rate can reach 96.5% and the low-carbon olefin selectivity can reach 72%. Detailed Implementation

[0050] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0051] In the following examples and comparative examples, the raw materials were all commercially available products.

[0052] In the test methods of the following embodiments, the total pore volume and average pore size of the catalyst were measured by cryogenic liquid nitrogen adsorption BET method and calculated by BJH model.

[0053] Example 1

[0054] 1. Preparation of modified HMS molecular sieves

[0055] Weigh out 5 parts by weight of ammonium oxalate hydrate of Nb2O5 and dissolve it in 40 g of deionized water to prepare solution A; impregnate the above solution A onto 95 parts by weight of HMS molecular sieve to obtain a mixture; dry the mixture at 100°C and then calcine it at 550°C for 6 h. After cooling, press it into tablets, crush and sieve it to 40-80 mesh to obtain the modified HMS molecular sieve.

[0056] 2. Catalyst Preparation

[0057] Weigh out 20 parts by weight of ferric nitrate nonahydrate (Fe2O3), 15 parts by weight of zinc nitrate hexahydrate (ZnO), and 10 parts by weight of scandium nitrate hydrate (Sc2O3), and dissolve them in 30 g of deionized water to prepare solution B. Under a vacuum of 80 kPa, the above solution B is impregnated onto 55 parts by weight of modified HMS molecular sieve to obtain a catalyst precursor. The catalyst precursor is dried at 110 °C and then calcined at 500 °C for 12 h to obtain an iron-based mesoporous molecular sieve catalyst.

[0058] The catalyst prepared in this embodiment contains the following components by weight percentage: 20% Fe2O3, 15% ZnO, 10% Sc2O3, and 55% modified HMS (containing 5% Nb2O5).

[0059] 2. Evaluation of catalysts

[0060] The evaluation criteria for catalysts are as follows:

[0061] The reaction conditions are:

[0062] millimeter fixed bed reactor

[0063] Reaction temperature 370℃

[0064] Reaction pressure 2.2 MPa

[0065] Catalyst loading volume 3ml

[0066] Catalyst loading 4500h -1

[0067] Raw material ratio (moles): H2 / CO = 2.5 / 1.

[0068] The specific evaluation results of the catalyst in this embodiment are detailed in Table 1.

[0069] Example 2

[0070] 1. Preparation of modified HMS molecular sieves

[0071] Weigh out 2 parts by weight of ammonium metavanadate (V2O5) and dissolve it in 35 g of deionized water to prepare solution A. Immerse 98 parts by weight of HMS molecular sieve to obtain a mixture. Dry the mixture at 105°C and then calcine it at 450°C for 12 h. After cooling, press it into tablets, crush and sieve it to 40-80 mesh to obtain the modified HMS molecular sieve.

[0072] 2. Catalyst Preparation

[0073] Weigh out 33 parts by weight of ferric nitrate nonahydrate (Fe2O3), 20 parts by weight of zinc nitrate hexahydrate (ZnO), and 7 parts by weight of yttrium nitrate hexahydrate (Y2O3), and dissolve them in 50 g of deionized water to prepare solution B. Under a vacuum of 60 kPa, the above solution B is impregnated onto 40 parts by weight of modified HMS molecular sieve to obtain a catalyst precursor. The catalyst precursor is dried at 100 °C and then calcined at 400 °C for 20 h to obtain an iron-based mesoporous molecular sieve catalyst.

[0074] The catalyst prepared in this embodiment contains the following components by weight percentage: 33% Fe2O3, 20% ZnO, 7% Y2O3, and 40% modified HMS (containing 2% V2O5).

[0075] 2. Catalyst Evaluation

[0076] The evaluation conditions for the catalyst in this embodiment are the same as in Example 1.

[0077] The specific evaluation results of the catalyst in this embodiment are detailed in Table 1.

[0078] Example 3

[0079] 1. Preparation of modified HMS molecular sieves

[0080] Weigh out 10 parts by weight of ammonium oxalate hydrate of Nb2O5 and dissolve it in 50 g of deionized water to prepare solution A; impregnate 90 parts by weight of HMS molecular sieve to obtain a mixture; dry the mixture at 100°C and then calcine it at 580°C for 5 h. After cooling, press it into tablets, crush and sieve it to 40-80 mesh to obtain the modified HMS molecular sieve.

[0081] 2. Catalyst Preparation

[0082] Weigh out 15 parts by weight of ferric nitrate nonahydrate (Fe2O3), 10 parts by weight of zirconium nitrate pentahydrate (ZrO2), and 5 parts by weight of scandium nitrate hydrate (Sc2O3), and dissolve them in 35 g of deionized water to prepare solution B. Under a vacuum of 40 kPa, the above solution B is impregnated onto 70 parts by weight of modified HMS molecular sieve to obtain a catalyst precursor. The catalyst precursor is dried at 110 °C and then calcined at 550 °C for 15 h to obtain an iron-based mesoporous molecular sieve catalyst.

[0083] The catalyst prepared in this embodiment contains the following components by weight percentage: 15% Fe2O3, 10% ZrO2, 5% Sc2O3, and 70% modified HMS (containing 10% Nb2O5).

[0084] 2. Catalyst Evaluation

[0085] The evaluation conditions for the catalyst in this embodiment are the same as in Example 1.

[0086] The specific evaluation results of the catalyst in this embodiment are detailed in Table 1.

[0087] Example 4

[0088] 1. Preparation of modified HMS molecular sieves

[0089] Weigh out 7 parts by weight of ammonium metavanadate (V2O5) and dissolve it in 45 g of deionized water to prepare solution A. Immerse 93 parts by weight of HMS molecular sieve to obtain a mixture. Dry the mixture at 110°C and then calcine it at 500°C for 10 h. After cooling, press it into tablets, crush and sieve it to 40-80 mesh to obtain the modified HMS molecular sieve.

[0090] 2. Catalyst Preparation

[0091] Weigh out 25 parts by weight of ferric nitrate nonahydrate (Fe2O3), 12 parts by weight of zirconium nitrate pentahydrate (ZrO2), and 13 parts by weight of yttrium nitrate hexahydrate (Y2O3), and dissolve them in 50 g of deionized water to prepare solution B. Under a vacuum of 60 kPa, the above solution B is impregnated onto 50 parts by weight of modified HMS molecular sieve to obtain a catalyst precursor. The catalyst precursor is dried at 100 °C and then calcined at 550 °C for 10 h to obtain an iron-based mesoporous molecular sieve catalyst.

[0092] The catalyst prepared in this embodiment contains the following components by weight percentage: 25% Fe2O3, 12% ZrO2, 13% Y2O3, and 50% modified HMS (containing 7% V2O5).

[0093] 2. Catalyst Evaluation

[0094] The evaluation conditions for the catalyst in this embodiment are the same as in Example 1.

[0095] The specific evaluation results of the catalyst in this embodiment are detailed in Table 1.

[0096] Comparative Example 1

[0097] Weigh out 20 parts by weight of ferric nitrate nonahydrate (Fe2O3), 15 parts by weight of zinc nitrate hexahydrate (ZnO), and 10 parts by weight of scandium nitrate hydrate (Sc2O3), and dissolve them in 30 g of deionized water to prepare solution B. Under a vacuum of 80 kPa, the above solution B is impregnated onto 55 parts by weight of SiO2 to obtain a catalyst precursor. The catalyst precursor is dried at 110 °C and then calcined at 500 °C for 12 h to obtain the catalyst.

[0098] The catalyst prepared in this comparative example contains the following components by weight percentage: 20% Fe2O3, 15% ZnO, 10% Sc2O3, and 55% SiO2.

[0099] 2. Catalyst Evaluation

[0100] The evaluation conditions for this comparative catalyst are the same as those in Example 1.

[0101] The specific evaluation results of this comparative catalyst are detailed in Table 1.

[0102] Comparative Example 2

[0103] Weigh out 20 parts by weight of ferric nitrate nonahydrate (Fe2O3), 15 parts by weight of zinc nitrate hexahydrate (ZnO), and 10 parts by weight of scandium nitrate hydrate (Sc2O3), and dissolve them in 30 g of deionized water to prepare solution B. Under a vacuum of 80 kPa, the above solution B is impregnated onto 55 parts by weight of HMS molecular sieve to obtain a catalyst precursor. The catalyst precursor is dried at 110 °C and then calcined at 500 °C for 12 h to obtain the catalyst.

[0104] The catalyst prepared in this comparative example contains the following components by weight percentage: 20% Fe2O3, 15% ZnO, 10% Sc2O3, and 55% HMS.

[0105] 2. Catalyst Evaluation

[0106] The evaluation conditions for this comparative catalyst are the same as those in Example 1.

[0107] The specific evaluation results of this comparative catalyst are detailed in Table 1.

[0108] Table 1 shows the total pore volume, CO conversion, and selectivity for C2-C4 low-carbon olefins of the catalysts prepared in Examples 1-4 and Comparative Examples 1-2.

[0109] Table 1

[0110]

[0111] As can be seen from the results in Table 1, compared with the catalysts of Comparative Examples 1 to 2, the catalysts of Examples 1 to 4 of the present invention significantly improved the CO conversion and C2-C4 low-carbon olefin selectivity in the Fischer-Tropsch one-step process for the preparation of low-carbon olefins.

[0112] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An iron-based mesoporous molecular sieve catalyst, comprising the following components in 100 parts by weight of all components: 10-35 parts by weight of Fe element oxide; 5-25 parts by weight of transition metal oxides; 2-15 parts by weight of oxides of Group IIIB elements; 30-75 parts by weight of modified HMS molecular sieve; The transition metal oxides include at least one of group IVB metal oxides and group IIB metal oxides; The modified HMS molecular sieve is an HMS molecular sieve loaded with at least one group VB metal element oxide. The content of group VB metal element oxides in the modified HMS molecular sieve is 1-10% of the mass of the modified HMS molecular sieve.

2. The iron-based mesoporous molecular sieve catalyst according to claim 1, characterized in that, The components are in parts by weight as follows: 15-35 parts by weight of Fe element oxide; 10-20 parts by weight of transition metal oxides; 5-15 parts by weight of oxides of Group IIIB elements; 30-70 parts by weight of modified HMS molecular sieve.

3. The iron-based mesoporous molecular sieve catalyst according to claim 1, characterized in that, The transition metal oxides include one or a combination of Zn and Zr oxides; and / or, The group IIIB element oxides include one or a combination of Sc and Y element oxides; and / or, The group VB metal oxide is at least one of Nb and V oxides.

4. The iron-based mesoporous molecular sieve catalyst according to claim 1, characterized in that, The content of group VB metal oxides in the modified HMS molecular sieve is 3-7% of the mass of the modified HMS molecular sieve.

5. The iron-based mesoporous molecular sieve catalyst according to claim 1, characterized in that, The ratio of the total pore volume to the average pore diameter of the catalyst is 0.1–0.3 cm. 3 / g / nm.

6. The method for preparing the iron-based mesoporous molecular sieve catalyst according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: Step 1: Prepare the modifier into solution A, immerse solution A on HMS molecular sieve, dry it first, and then calcine it to obtain the modified HMS molecular sieve; the modifier is the group VB metal element compound; Step 2: Prepare a mixed solution B by combining the Fe-containing compound, the transition metal compound, and the group IIIB compound. Impregnate the mixed solution B onto the modified HMS molecular sieve obtained above to obtain a catalyst precursor. After drying and calcining the catalyst precursor, an iron-based mesoporous molecular sieve catalyst is obtained.

7. The method for preparing the iron-based mesoporous molecular sieve catalyst according to claim 6, characterized in that, In step one, The solvent for solution A is deionized water; and / or, The group VB metal compound is a water-soluble compound; and / or, The calcination temperature is 450–650°C; and / or, The roasting time is 3 to 12 hours.

8. The method for preparing the iron-based mesoporous molecular sieve catalyst according to claim 7, characterized in that, In step one, The group VB metal compound is one or a combination of ammonium niobate oxalate hydrate and ammonium metavanadate; and / or, The calcination temperature is 480~620℃; and / or, The roasting time is 5-10 hours.

9. The method for preparing the iron-based mesoporous molecular sieve catalyst according to claim 6, characterized in that, In step two, The solvent for the mixed solution B is deionized water; and / or, The solutes in the mixed solution B are all water-soluble compounds.

10. The method for preparing the iron-based mesoporous molecular sieve catalyst according to claim 9, characterized in that, In step two, the solute in the mixed solution B is a combination of ferric nitrate nonahydrate, zinc nitrate hexahydrate and / or zirconium nitrate pentahydrate, scandium nitrate hydrate and / or yttrium nitrate hexahydrate.

11. The method for preparing the iron-based mesoporous molecular sieve catalyst according to claim 6, characterized in that, In step two, Under a vacuum of 1~80 kPa, the mixed solution B is impregnated on a modified HMS molecular sieve; and / or, The calcination temperature is 350–600℃; and / or, The roasting time is 6 to 24 hours.

12. The method for preparing the iron-based mesoporous molecular sieve catalyst according to claim 11, characterized in that, In step two, Under a vacuum of 40-80 kPa, the mixed solution B is impregnated onto a modified HMS molecular sieve; and / or, The calcination temperature is 400~550℃; and / or, The roasting time is 10-20 hours.

13. The application of the iron-based mesoporous molecular sieve catalyst according to any one of claims 1 to 5, characterized in that, The catalyst is used in the Fischer-Tropsch one-step process for the preparation of low-carbon olefins.

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