Composite iron catalysts, methods for their preparation and use

Abstract

The present application relates to the technical field of catalyst, in particular to a composite iron catalyst, a preparation method and application thereof. The catalyst comprises the following components by weight: a) 40-70 parts of iron element and / or oxide of iron element; b) 25-45 parts of at least one of copper element, oxide of copper element, indium element and oxide of indium element; c) 5-15 parts of at least one of lanthanide element and oxide of lanthanide element; and the average particle size of the catalyst is 350-700 nm. The composite iron catalyst provided by the present application has an average particle size of 350-700 nm, and has the advantages of high carbon monoxide conversion rate and high selectivity of low-carbon olefins in the reaction of synthesizing low-carbon olefins from synthesis gas.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a composite iron catalyst, its preparation method, and its application. Background Technology

[0002] Ethylene, propylene, and other low-carbon olefins are important basic raw materials in modern chemical industry. The traditional route for producing ethylene and propylene is through naphtha cracking, which is constrained by petroleum resources. However, my country's petroleum resources are relatively scarce. Therefore, developing technology to directly produce low-carbon olefins from syngas using natural gas, coal, and renewable resources is of significant strategic importance. Fischer-Tropsch catalysts are primarily iron-based catalysts; different additives and preparation methods can modulate the catalyst structure and improve the selectivity for low-carbon olefins.

[0003] CN110433812A discloses a catalyst and preparation method for a one-step synthesis of low-carbon olefins from syngas. Fe was synthesized via a stepwise precipitation method and an impregnation method using iron, zirconium, sodium, potassium, magnesium, manganese, and zinc salt solutions. 100 Zr x B y O z A catalyst, wherein B is selected from at least one of K, Na, Mg, Mn, and Zn, is used in the one-step synthesis of low-carbon olefins from syngas. It exhibits high CO conversion but low selectivity for low-carbon olefins. At a mass hourly space velocity (mass space velocity) of 2NLCO·gFe... -1 ·h -1 Under reaction conditions of 300℃, 1.5MPa, and an H2:CO molar ratio of 2, the catalyst achieved a CO conversion rate of 96.3%, but the selectivity for low-carbon olefins was only 55.8%. Currently, there is a need to develop a highly efficient catalyst for the production of low-carbon olefins from syngas, exhibiting high selectivity for these olefins. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low carbon monoxide conversion and low selectivity for low-carbon olefins in the syngas-to-low-carbon olefins reaction in the prior art, and to provide a composite iron catalyst, its preparation method, and its application. This catalyst has a small average particle size and, when used in the syngas-to-low-carbon olefins reaction, exhibits the advantages of high carbon monoxide conversion and high selectivity for low-carbon olefins.

[0005] To achieve the above objectives, a first aspect of the present invention provides a composite iron catalyst, comprising, by weight, the following components:

[0006] a) 40–70 parts, iron and / or iron oxides;

[0007] b) 25 to 45 parts, of at least one of copper, copper oxide, indium, and indium oxide;

[0008] c) 5 to 15, at least one of the lanthanides and lanthanide oxides;

[0009] The catalyst has an average particle size of 350-700 nm.

[0010] A second aspect of the present invention provides a method for preparing the composite iron catalyst of the present invention, the method comprising:

[0011] (1) Dissolve the soluble salts of the elements in components a), b) and c) in water to prepare solution A;

[0012] (2) Dissolve urea in a C2-C3 diol to prepare solvent B;

[0013] (3) Mix solution A and solvent B to prepare mixture C; after performing a solvothermal reaction on mixture C, separate, wash and dry to obtain precipitate D;

[0014] (4) The precipitate D is roasted in an oxygen-containing atmosphere.

[0015] A third aspect of the present invention provides the application of the aforementioned composite iron catalyst in the direct production of low-carbon olefins from syngas.

[0016] Through the above technical solution, the composite iron catalyst provided by the present invention has an average particle size of 350-700 nm. The small average particle size gives it the advantages of high carbon monoxide conversion and high selectivity for low-carbon olefins when used in the synthesis of low-carbon olefins from syngas.

[0017] The preparation method described in this invention uses urea and C2-C3 diols as composite solvents, and the composite solvothermal preparation method results in smaller co-precipitated catalyst particles. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The first aspect of this invention provides a composite iron catalyst, comprising, by weight, the following components:

[0020] a) 40–70 parts, iron and / or iron oxides;

[0021] b) 25 to 45 parts, of at least one of copper, copper oxide, indium, and indium oxide;

[0022] c) 5 to 15 parts, at least one of lanthanides and lanthanide oxides;

[0023] The catalyst has an average particle size of 350-700 nm. The catalyst of the present invention has an even smaller average particle size.

[0024] According to a preferred embodiment of the present invention, the lanthanide element is selected from thulium and / or ytterbium.

[0025] According to a preferred embodiment of the present invention, the content of component c) in the catalyst is 7 to 13 parts.

[0026] According to a preferred embodiment of the present invention, the average particle size of the catalyst is 400-600 nm;

[0027] Composite iron catalysts possessing the aforementioned characteristics of this invention can all achieve the objectives of this invention, and their preparation methods are not particularly required. Regarding this invention, according to a preferred embodiment of this invention, this invention provides a method for preparing the composite iron catalyst described herein, the method comprising:

[0028] (1) Dissolve the compounds of elements in components a), b) and c) in water to prepare solution A;

[0029] (2) Dissolve urea in a C2-C3 diol to prepare solvent B;

[0030] (3) Mix solution A and solvent B to prepare mixture C; after performing a solvothermal reaction on mixture C, separate, wash and dry to obtain precipitate D;

[0031] (4) The precipitate D is calcined in an oxygen-containing atmosphere. In the preparation method of the present invention, urea and C2-C3 diols are used as composite solvents, and the composite solvothermal preparation method results in smaller co-precipitated catalyst particles.

[0032] In this invention, steps (1) and (2) are only used to differentiate the preparation of different solutions, and there is no particular limitation on the order of steps (1) and (2).

[0033] In this invention, the mass fraction of urea in solvent B can be selected from a wide range. According to a preferred embodiment of this invention, the mass fraction of urea is 5-20%.

[0034] According to a preferred embodiment of the present invention, the C2-C3 diol is selected from ethylene glycol and / or propylene glycol, preferably a mixture of ethylene glycol and propylene glycol, and more preferably a mass ratio of ethylene glycol to propylene glycol of 1:0.2-5.

[0035] In this invention, the ratio of the amounts of solution A and solution B can be selected over a wide range. According to a preferred embodiment of this invention, the mass ratio of component a) iron in solution A to the mass ratio of urea in solvent B is 1:0.3-1.8.

[0036] In this invention, there are no particular limitations on the separation method of the product after solvothermal treatment. For example, conventional separation methods in the art, such as filtration, vacuum filtration, and centrifugation, can all achieve the purpose of this invention.

[0037] In this invention, there are no particular limitations on the washing method or washing solvent. As long as excess urea, glycol, etc. are removed, it is acceptable. Water washing is preferred.

[0038] In this invention, there are no particular limitations on the conditions of the solvothermal reaction in step (3). According to a preferred embodiment of this invention, the solvothermal reaction conditions include: a temperature of 140-220°C, and the reaction time can be reasonably adjusted according to actual needs. Preferably, the time is 2-36 hours.

[0039] In this invention, there are no particular limitations on the drying conditions in step (3). According to a preferred embodiment of this invention, the drying conditions include: a temperature of 40 to 90°C, and the reaction time can be reasonably adjusted according to actual needs. Preferably, the time is 6 to 48 hours.

[0040] In this invention, the range of selectable calcination conditions in step (4) is relatively wide. According to a preferred embodiment of this invention, the calcination conditions include: a temperature of 300 to 500°C, and the reaction time can be reasonably adjusted according to actual needs. Preferably, the time is 2 to 8 hours.

[0041] In this invention, there is no particular limitation on the types of soluble compounds of components a), b), and c), as long as they are soluble in water. According to a preferred embodiment of the invention, the soluble compound of component a) is selected from at least one of iron nitrates, sulfates, and chlorides; the soluble compound of component b) is selected from at least one of copper or indium nitrates, sulfates, and chlorides; and the soluble compound of component c) is selected from soluble salts of lanthanides, preferably at least one of thulium or ytterbium nitrates, sulfates, and chlorides.

[0042] A third aspect of this invention provides the application of the composite iron catalyst described herein in the direct production of low-carbon olefins from syngas. For example, specific application conditions may include:

[0043] A method for directly producing low-carbon olefins from syngas includes: using syngas as a raw material, reacting the raw material with the composite iron catalyst described in this invention to produce low-carbon olefins.

[0044] According to a preferred embodiment of the present invention, the molar ratio of H2 to CO in the synthesis gas is preferably 0.5 to 4.

[0045] According to a preferred embodiment of the present invention, the contact reaction conditions include a temperature of 300–450°C.

[0046] According to a preferred embodiment of the present invention, the contact reaction conditions include a pressure of 0.1 to 3.0 MPa.

[0047] According to a preferred embodiment of the present invention, the volumetric space velocity of the feed gas is 1000–12000 h⁻¹. -1 .

[0048] 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 direct production of low-carbon olefins from syngas. Specific reduction conditions can be reasonably selected by those skilled in the art without requiring inventive effort; for example, but not limited to, reduction conditions include:

[0049] The reduction temperature is 300–600℃;

[0050] The reducing agent is H2 and / or CO;

[0051] The reduction pressure is atmospheric pressure to 3 MPa (gauge pressure);

[0052] The volume hourly space velocity of the reducing agent is 1000–8000 hr. -1 ;

[0053] The restoration time is 6 to 48 hours.

[0054] Using the composite iron catalyst described in this invention, the CO conversion rate can reach 97.0%, and the selectivity of low-carbon olefins in hydrocarbons can reach 72.9%, achieving good technical results.

[0055] The present invention will be described in detail below through embodiments.

[0056] In the following examples, the reduction conditions for the composite iron catalyst are as follows:

[0057] Temperature 400℃

[0058] Pressure 0.5MPa

[0059] Catalyst loading volume 3ml

[0060] The volume hourly space velocity of the reducing agent is 4000 h⁻¹. -1

[0061] reducing gas H2

[0062] Restoration time is 24 hours.

[0063] In the following examples, the particle size of the composite iron catalyst was measured using a ZETASIZERNano-ZS laser nanoparticle size analyzer from Malvern Instruments Ltd.

[0064] Example 1

[0065] (1) Weigh out 55.0 parts by weight of ferric nitrate nonahydrate (molecular formula: Fe(NO3)3·9H2O), 36.0 parts by weight of copper nitrate trihydrate (molecular formula: Cu(NO3)2·3H2O), and 9.0 parts by weight of thulium nitrate hexahydrate (molecular formula: Tm(NO3)3·6H2O), and dissolve them in 80 ml of deionized water. After complete dissolution, solution A is obtained.

[0066] (2) Dissolve urea in ethylene glycol to prepare a composite solvent B with a urea mass fraction of 12%;

[0067] (3) Under stirring conditions, a composite solvent B containing 35.0 parts by weight of urea was added to solution A, and the mixture was stirred until homogeneous to obtain mixture C. Mixture C was transferred to an autoclave, heated to 180°C and maintained for 24 hours. After heating was completed, it was naturally cooled to room temperature, centrifuged, and the precipitate was repeatedly washed with distilled water and anhydrous ethanol. It was then vacuum dried at 70°C for 36 hours to obtain precipitate D.

[0068] (4) The precipitate D was roasted in air at a temperature of 400°C for 5 hours.

[0069] The catalyst evaluation conditions are as follows:

[0070] φ8 mm fixed bed reactor

[0071] Reaction temperature 360℃

[0072] Reaction pressure 2.5 MPa

[0073] Catalyst loading volume 3ml

[0074] Catalyst loading 4000 hours -1

[0075] Raw material ratio (moles): H2 / CO = 3.0 / 1.

[0076] For ease of comparison, the composition, average particle size and evaluation results of the catalyst in this embodiment are listed in Table 1.

[0077] Example 2

[0078] (1) Weigh out 42.0 parts by weight of ferric nitrate nonahydrate, 45.0 parts by weight of copper nitrate trihydrate, and 13.0 parts by weight of thulium nitrate hexahydrate, and dissolve them in 80 ml of deionized water. After complete dissolution, solution A is obtained.

[0079] (2) Add urea to propylene glycol to prepare a composite solvent B with a mass fraction of 5%;

[0080] (3) Under stirring conditions, a composite solvent B containing 39.0 parts by weight of urea was added to solution A, and the mixture was stirred until homogeneous to form mixture C. Mixture C was transferred to an autoclave and heated to 220°C for 10 hours. After heating, it was allowed to cool naturally to room temperature and centrifuged. The precipitate was washed repeatedly with distilled water and anhydrous ethanol and dried under vacuum at 70°C for 36 hours to obtain precipitate D.

[0081] (4) The precipitate D was roasted in air at a temperature of 400°C for 5 hours.

[0082] Example 3

[0083] (1) Weigh out 68.0 parts by weight of ferric nitrate nonahydrate, 25.0 parts by weight of indium nitrate monohydrate (molecular formula: In(NO3)3·H2O) equivalent to 25.0 parts by weight of indium nitrate monohydrate (molecular formula: In(NO3)3·H2O) equivalent to 7.0 parts by weight of ytterbium nitrate hexahydrate (molecular formula: Yb(NO3)3·6H2O) equivalent to 7.0 parts by weight of Yb2O3, and dissolve them in 80 ml of deionized water in sequence. After complete dissolution, solution A is obtained.

[0084] (2) Add urea to ethylene glycol to prepare a composite solvent B with a urea mass fraction of 20%;

[0085] (3) Under stirring conditions, a composite solvent B containing 25.0 parts by weight of urea was slowly added to solution A. After stirring until homogeneous, mixture C was prepared. Mixture C was transferred to an autoclave and heated to 150°C for 36 hours. After heating, it was allowed to cool naturally to room temperature. The mixture was then centrifuged, and the precipitate was repeatedly washed with distilled water and anhydrous ethanol. The precipitate was then vacuum dried at 70°C for 36 hours to obtain precipitate D.

[0086] (4) The precipitate D was roasted in air at a temperature of 400°C for 5 hours.

[0087] Example 4

[0088] The method of Example 1 was followed, except that a mixture of ethylene glycol and propylene glycol in a mass ratio of 1:3 was used instead of ethylene glycol. All other conditions were the same as in Example 1. The results are shown in Table 1.

[0089] Example 5

[0090] The method is the same as in Example 1, except that the weight proportions of Fe and Tm elements in step (1) are different from those in Example 1, specifically:

[0091] (1) Weigh out 49.0 parts by weight of ferric nitrate nonahydrate (Fe2O3), 36.0 parts by weight of copper nitrate trihydrate (CuO), and 15.0 parts by weight of thulium nitrate hexahydrate (Tm2O3), and dissolve them in 80 ml of deionized water. After complete dissolution, solution A is obtained. The remaining conditions are the same as in the example. The results are shown in Table 1.

[0092] Example 6

[0093] The method is the same as in Example 1, except that the weight proportions of Fe and Tm elements in step (1) are different from those in Example 1, specifically:

[0094] (1) Weigh out 59.0 parts by weight of ferric nitrate nonahydrate (Fe2O3), 36.0 parts by weight of copper nitrate trihydrate (CuO), and 5.0 parts by weight of thulium nitrate hexahydrate (Tm2O3), and dissolve them in 80 ml of deionized water. After complete dissolution, solution A is obtained. The remaining conditions are the same as in the example. The results are shown in Table 1.

[0095] Example 7

[0096] The method is the same as in Example 1, except that in step (1), the lanthanide element is thulium nitrate hexahydrate equivalent to 5.0 parts by weight of Tm2O3, and the ytterbium nitrate hexahydrate equivalent to 4.0 parts by weight of Yb2O3 is specifically:

[0097] (1) Weigh out 55.0 parts by weight of ferric nitrate nonahydrate (Fe2O3), 36.0 parts by weight of copper nitrate trihydrate (CuO), 5.0 parts by weight of thulium nitrate hexahydrate (Tm2O3), and 4.0 parts by weight of ytterbium nitrate hexahydrate (Yb2O3), and dissolve them sequentially in 80 ml of deionized water. After complete dissolution, solution A is obtained; the remaining conditions are the same as in the example. The results are shown in Table 1.

[0098] Comparative Example 1

[0099] The method is the same as in Example 1, except that ammonia water is used for co-precipitation to prepare the catalyst, specifically:

[0100] (1) Weigh out 55.0 parts by weight of ferric nitrate nonahydrate, 36.0 parts by weight of copper nitrate trihydrate, and 9.0 parts by weight of thulium nitrate hexahydrate, and dissolve them in 50 ml of deionized water. After complete dissolution, solution A is obtained.

[0101] (2) Under stirring conditions, a 25w% ammonia solution was slowly added to solution A, the pH value was kept at 8.0, and after stirring evenly, the solution was centrifuged. The precipitate was washed repeatedly with distilled water and anhydrous ethanol, and then vacuum dried at 70°C for 36 hours to obtain the precipitate.

[0102] (3) Finally, the precipitate was roasted in air at a temperature of 400°C for 5 hours.

[0103] The catalyst, by weight percentage, contains the following components: 55% Fe2O3, 36% CuO, and 9% Tm2O3.

[0104] The catalyst evaluation conditions were the same as in Example 1, and the results are shown in Table 1.

[0105] Table 1

[0106]

[0107] As can be seen from the results in Table 1, the catalysts of Examples 1-6 of the present invention have the advantages of high carbon monoxide conversion and high selectivity for low-carbon olefins when used in the synthesis gas to produce low-carbon olefins reaction.

[0108] 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. The application of composite iron catalysts in the direct production of low-carbon olefins from syngas, characterized in that, The catalyst comprises the following components in parts by weight: a) 40–70 parts, iron and / or iron oxides; b) 25 to 45 parts, of at least one of copper, copper oxide, indium, and indium oxide; c) 5 to 15 parts of at least one of a lanthanide element and a lanthanide oxide, wherein the lanthanide element is selected from thulium and / or ytterbium; The catalyst has an average particle size of 350–700 nm; the preparation method of the composite iron catalyst includes: (1) Dissolve the soluble compounds of elements in components a), b) and c) in water to prepare solution A; (2) Dissolve urea in a C2-C3 diol to prepare solvent B; (3) Mix solution A and solvent B to prepare mixture C; after performing a solvothermal reaction on mixture C, separate, wash and dry to obtain precipitate D; (4) The precipitate D is roasted in an oxygen-containing atmosphere.

2. The application according to claim 1, wherein, In the catalyst, the content of component c) is 7–13 parts; and / or The average particle size of the catalyst is 400–600 nm.

3. The application according to claim 1, wherein, In solvent B, the mass fraction of urea is 5-20%.

4. The application according to claim 1, wherein, The C2-C3 diols are selected from ethylene glycol and / or propylene glycol.

5. The application according to claim 4, wherein, The C2-C3 diol is a mixture of ethylene glycol and propylene glycol, and the mass ratio of ethylene glycol to propylene glycol in the C2-C3 diol is 1:0.2-5.

6. The application according to claim 1, wherein, The mass ratio of iron in solution A to urea in solvent B is 1:0.3-1.

8.

7. The application according to claim 1, wherein, In step (3), the solvothermal reaction conditions include: a temperature of 140–220°C and a time of 2–36 hours; and / or Drying conditions include: a temperature of 40–90°C and a time of 6–48 hours; and / or In step (4), the roasting conditions include: a temperature of 300-500℃ and a time of 2-8 hours.

8. The application according to claim 1, wherein, The soluble compound of component a) is selected from at least one of iron nitrates, sulfates, and chlorides; and / or The soluble compound of component b) is selected from at least one of nitrates, sulfates, and chlorides; and / or The soluble compounds in component c) are selected from soluble salts of lanthanides.

9. The application according to claim 8, wherein, The soluble compound of component c) is at least one of the nitrate, sulfate and chloride of thulium or ytterbium.

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