An iron-based metal composite oxide catalyst and its preparation and application

Abstract

The present invention provides an iron-based metal composite oxide catalyst, which comprises an active component and an auxiliary agent; the auxiliary agent is loaded on the active component; the active component is generally represented by FeM x O y , wherein M is one or more of alkaline earth metals Mg, Ca, Sr and Ba; the auxiliary agent is one or more of alkali metals Na, K and Rb. The present invention also provides a method for preparing the catalyst and a method for preparing the catalyst in the presence of CO or CO 2 The present invention aims at the application of iron-based catalysts in the hydrogenation reaction of CO or CO 2 In order to solve the problems of easy aggregation and poor stability of active components in hydrogenation reactions, an iron-based metal composite oxide catalyst with excellent chemical stability and thermal stability was designed and prepared by doping alkaline earth metals into iron oxides, which greatly improved the long-term stability of the catalyst and was beneficial to the industrial application of the catalyst.

Description

Technical Field

[0001] The present invention relates to the field of catalysis technology, and more particularly to a method for preparing a CO or CO 2 An iron-based metal composite oxide catalyst for hydrogenating olefins, and a preparation method and application thereof. Background Art

[0002] Olefins are important chemical raw materials. 2 ＝ –C 3 ＝ , ethylene, propylene) are often used as raw materials for other important monomers, such as vinyl chloride, vinyl acetate, styrene and ethylene glycol. 4+ ＝ , containing olefins with four carbon atoms or more), especially α-olefins (monoolefins with double bonds at the ends of the molecular chain), which have a wide range of uses and high added value. They are intermediates in the production of various fine chemicals such as synthetic comonomers, detergents, lubricants, plasticizer alcohols, etc.

[0003] With the continuous development of human society, the use of fossil energy has increased dramatically, and the amount of CO in the atmosphere has 2 The increasing content of carbon dioxide not only exacerbates the greenhouse effect, but also causes a huge waste of carbon resources. 2 To reduce greenhouse gas emissions, we need to optimize the energy structure dominated by fossil energy and vigorously develop new energy and renewable energy industries. 2 "Green hydrogen" produced from renewable energy or industrial hydrogen-rich conversion to produce high-value chemicals such as olefins can provide new strategies for achieving "carbon peak and carbon neutrality", which is of great significance for alleviating the energy crisis and climate crisis and achieving sustainable development.

[0004] In addition, in many industrial CO 2 and H 2 There is also a certain proportion of CO gas in the resources, such as methanol synthesis purge gas and coal-to-hydrogen desorption gas. If a method can be developed that can simultaneously convert CO and CO 2 The catalytic technology of co-conversion, without the need to separate CO in advance, can save separation costs and improve the economy of the technology and process.

[0005] CO 2 Hydrocarbons can be synthesized via direct and indirect routes. The direct route is usually considered to be CO 2The reverse water gas shift reaction is used to reduce CO to CO and the generated CO is then hydrogenated to generate hydrocarbon compounds through the Fischer-Tropsch synthesis reaction; the indirect route is usually carried out in several different reactors, and the intermediate products of the reaction include CO and / or methanol. Iron-based catalysts show high activity for both the reverse water gas shift and Fischer-Tropsch synthesis reactions, are inexpensive, and produce olefins as the main target product, so they are widely used in CO / CO 2 The hydroconversion research has attracted extensive attention.

[0006] Due to CO / CO 2 Hydrogenation reactions are often carried out under high temperature and high pressure, and the water vapor generated in the process will have a significant impact on the stability of the catalyst. In addition, the physical phase of the iron-based catalyst will undergo multiple transformations from oxidation phase, elemental phase and carbonization phase in different atmospheres during the calcination, reduction and reaction processes; and currently, most of the iron-based catalysts with better olefin synthesis performance are unsupported and have low strength, which will seriously affect the performance of the catalyst in the long-term catalytic reaction process. Therefore, the current iron-based catalysts have problems such as easy agglomeration of active components and poor stability during long-term reactions, making it difficult to meet the requirements of real industrial processes. Therefore, CO / CO 2 The direct preparation of olefins by hydrogenation is extremely challenging. Constructing an efficient and stable Fe-based catalyst that can achieve multi-active site synergistic catalysis is the key to achieving this process. Summary of the invention

[0007] In view of the iron-based catalyst in the prior art in CO or CO 2 The invention provides an iron-based metal composite oxide catalyst and a preparation method thereof as well as a method for preparing the catalyst in the presence of CO or CO 2 Application in hydrogenation to olefins.

[0008] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0009] An iron-based metal composite oxide catalyst, the catalyst comprising an active component and an auxiliary agent;

[0010] The auxiliary agent is loaded on the active component;

[0011] The active component is generally represented by FeM x O y , wherein M is one or more of the alkaline earth metals Mg, Ca, Sr and Ba, the molar number x of M is in the range of 0.1-10, and the molar number y of O is in the range of 1-12;

[0012] The auxiliary agent is one or more of alkali metals Na, K and Rb, and the content of the auxiliary agent accounts for 0.1-10% of the total mass of the catalyst.

[0013] Preferably, the alkaline earth metal M in the active component is one or both of Sr and Ba, the molar number x of M is preferably in the range of 1:(0.25-4), and the molar number y of O is preferably in the range of 1-6.

[0014] Preferably, the auxiliary agent is one or both of Na and K, and the content of the auxiliary agent accounts for 0.5-5% of the total mass of the catalyst.

[0015] Optionally, the catalyst is prepared by a coprecipitation method, which at least comprises:

[0016] According to the composition ratio of the catalyst, iron salt and alkaline earth metal salt are mixed to form a salt solution, and then an alkaline precipitant is added to gradually adjust the pH value of the solution to alkaline. After the addition is completed, the solution is aged, the product is separated from the solid and liquid, the solid is washed, dried, and calcined to obtain the catalyst.

[0017] Optionally, the auxiliary agent can come from the alkali metal remaining in the added alkali solution (by controlling the number of washing times and the amount of washing water), or can be added by impregnating the alkali metal salt solution after drying or roasting.

[0018] Optionally, the iron salt is selected from ferric iron salts;

[0019] The ferric iron salt is selected from at least one or more of ferric chloride, ferric sulfate, ferric acetate and ferric nitrate.

[0020] Optionally, the alkaline earth metal salt is selected from at least one or more of chlorides, nitrates and acetates of alkaline earth metals.

[0021] Optionally, the alkaline precipitant is selected from an alkaline solution capable of adjusting the pH value of the solution.

[0022] Preferably, the alkaline precipitant is selected from NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , at least one or more of ammonia water.

[0023] Optionally, the adding of the alkaline precipitant is carried out at 30-90°C.

[0024] Optionally, the aging time is 1-10h.

[0025] Optionally, the calcination temperature is 200-800° C., and the calcination time is 1-24 hours.

[0026] Optionally, the impregnation is an equal volume impregnation.

[0027] Optionally, the alkali metal salt is selected from at least one or more of chlorides, nitrates, acetates and carbonates of alkaline earth metals.

[0028] Optionally, the catalyst is used to convert CO and / or CO 2 , and H 2 The mixed raw gas passes through a fixed bed reactor containing the catalyst to react and obtain the olefin.

[0029] Optionally, the reaction conditions are:

[0030] H 2 and (CO+CO 2 ) is 1-8:1, the reaction temperature is 240-400°C, the reaction pressure is 0.1-10MPa, and the space velocity is 1000-30000mL / (h·g cat ).

[0031] Preferably, H 2 and (CO+CO 2 ) molar ratio is 2-4:1, reaction temperature is 280-340℃, reaction pressure is 1-4MPa, space velocity is 2000-8000mL / (h·g cat ).

[0032] Optionally, the H 2 and (CO+CO 2 ) is independently selected from any value among 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or any range therebetween.

[0033] Optionally, the reaction temperature is independently selected from any value of 240°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C or any range therebetween.

[0034] Optionally, the reaction pressure is independently selected from any value among 0.1 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, or any range between two values.

[0035] Optionally, the space velocity is independently selected from 1000 mL / (h·g cat )、2000mL / (h·g cat )、4000mL / (h·g cat )、6000mL / (h·g cat )、8000mL / (h·g cat )、10000mL / (h·g cat )、20000mL / (h·g cat )、30000mL / (h·g cat) or any range of values ​​between them.

[0036] Optionally, the catalyst further comprises an activation step before use;

[0037] Preferably, the reduction conditions are: in-situ reduction at 300-500° C. for 2-50 h in a reducing atmosphere;

[0038] Specifically, the reduction conditions are: at 0.1 MPa, pure H 2 , temperature is 350℃, space velocity is 1500mL / (h·g cat ), restoration time 8h.

[0039] Preferably, the reducing atmosphere is selected from H 2 , CO at least one.

[0040] In the present application, "olefin" refers to a monoolefin having 2 to 25 carbon atoms, such as ethylene, propylene, butene, pentene, hexene, heptene, octene, and the like.

[0041] The beneficial effects of this application include:

[0042] The present application provides an iron-based metal composite oxide catalyst. The raw materials used to prepare the catalyst are cheap, the preparation process is simple, and it is suitable for industrial production. The prepared catalyst is applied to 2 The feed gas hydrogenation reaction has high olefin selectivity and exhibits excellent long-term stability. It still maintains a high catalytic activity after 2000 hours of reaction, so it has good industrial application prospects.

[0043] The present invention also provides a method for preparing the catalyst and a method for preparing the catalyst in a process containing CO or CO 2 The present invention aims at the application of iron-based catalyst in the hydrogenation reaction of CO or CO 2 In order to solve the problems of easy aggregation and poor stability of active components in hydrogenation reactions, an iron-based metal composite oxide catalyst with excellent chemical stability and thermal stability was designed and prepared by doping alkaline earth metals into iron oxides, which greatly improved the long-term stability of the catalyst and was beneficial to the industrial application of the catalyst. DETAILED DESCRIPTION

[0044] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0045] Unless otherwise specified, the raw materials in the examples of this application were purchased from commercial sources. Unless otherwise specified, the test methods all adopted conventional methods, and the instrument settings all adopted the settings recommended by the manufacturer.

[0046] The analysis method in the examples of this application is as follows:

[0047] In the examples of this application, the raw material conversion rate and product selectivity are calculated as follows:

[0048] In the embodiments of the present application, CO or CO 2 Conversions and product selectivities were calculated on a carbon molar basis.

[0049] CO or CO 2 The conversion rate calculation formula is as follows:

[0050]

[0051] Product hydrocarbon C i The selectivity calculation formula is as follows:

[0052]

[0053] In the above formula, CO xin and CO xout Represents the CO inlet and outlet of the reactor, respectively. x The mole fraction, C i is a hydrocarbon with i carbon atoms.

[0054] Example 1

[0055] Catalyst preparation: 18.2 g Fe(NO 3 ) 3 .9H 2 O and 9.5gSr(NO 3 ) 2 , press Fe 3+ :Sr 2+ =1:1 molar ratio to form a salt solution with a metal ion concentration of about 3 mol / L. At 80°C and stirring, add 50 mL of 5 mol / L NaOH solution at a uniform rate to adjust the pH value of the solution to about 10. After the addition is complete, keep stirring for 4 hours at the same temperature and finally cool to room temperature. After the reaction is completed, the deposited product is centrifuged and washed twice with 800 mL of deionized water. The product is then dried at 120°C and calcined at 500°C for 3 hours to obtain a catalyst sample. Through ICP-OES characterization test, the residual Na in the sample was analyzed and measured to be 2wt%. The active component corresponding to this sample is FeSrO 2.5 , recorded as catalyst #1.

[0056] Example 2

[0057] The operation is the same as in Example 1, except that Sr(NO 3 ) 2 Replaced by Ba(NO 3 )2 The rest of the operations were the same, and the obtained product was 2wt% Na-FeBaO 2.5 , recorded as catalyst #2.

[0058] Example 3

[0059] The operation is the same as in Example 1, except that Sr(NO 3 ) 2 Replaced by Mg(NO 3 ) 2 The rest of the operations were the same, and the obtained product was 2wt% Na-FeMgO 2.5 , recorded as catalyst #3.

[0060] Example 4

[0061] The operation is the same as in Example 1, except that Sr(NO 3 ) 2 Replaced by Ca(NO 3 ) 2 The rest of the operations were the same, and the obtained product was 2wt% Na-FeCaO 2.5 , recorded as catalyst #4.

[0062] Example 5

[0063] The operation is the same as in Example 1, except that NaOH is replaced by KOH. The other operations are the same, and the obtained product is 2wt% K-FeSrO 2.5 , recorded as catalyst #5.

[0064] Example 6

[0065] The operation is the same as in Example 1, except that NaOH is replaced with ammonia water, and the sample is then immersed in NaNO 3 solution to obtain 2wt% Na-impregnated FeSrO 2.5 Catalyst, denoted as catalyst #6.

[0066] Example 7

[0067] The operation was the same as in Example 6, except that 2 wt% Na was replaced with 0.5 wt% Na. The rest of the operation was the same, and the obtained product was 0.5 wt% Na-FeSrO 2.5 , recorded as catalyst #7.

[0068] Example 8

[0069] The operation is the same as in Example 6, except that 2wt% Na is replaced by 5wt% Na. The rest of the operation is the same, and the obtained product is 5wt% Na-FeSrO 2.5 , recorded as catalyst #8.

[0070] Example 9

[0071] The operation is the same as in Example 1, except that 18.2 g Fe(NO 3 ) 3 .9H 2 O and 9.5gSr(NO 3 ) 2 " is replaced by "29.1gFe(NO 3 ) 3 .9H 2 O and 3.8gSr(NO 3 ) 2 The rest of the operations were the same, and the obtained product was 2wt% Na-FeSr 0.25 O 1.75 , recorded as 9# catalyst.

[0072] Example 10

[0073] The operation is the same as in Example 1, except that 18.2 g Fe(NO 3 ) 3 .9H 2 O and 9.5gSr(NO 3 ) 2 " is replaced by "9.1gFe(NO 3 ) 3 .9H 2 O and 14.3gSr(NO 3 ) 2 The rest of the operations were the same, and the obtained product was 2wt% Na-FeSr 3 O 4.5 , recorded as catalyst #10.

[0074] Embodiment 11

[0075] The operation is the same as in Example 1, except that "calcination at 400°C for 3 h" is replaced by "calcination at 600°C for 3 h". The rest of the operation is the same. Under this condition, 2 wt% Na-FeSrO 2.5 The product is recorded as catalyst #11.

[0076] Comparative Example 1

[0077] The operation is the same as in Example 1, except that 18.2 g Fe(NO 3 ) 3 .9H 2 O and 9.5gSr(NO 3 ) 2 ” is replaced by “36.4gFe(NO 3 ) 3 .9H 2O", the rest of the operations were the same, and only 2wt% Na-modified Fe 2 O 3 The product is recorded as D1# catalyst.

[0078] Comparative Example 2

[0079] The operation is the same as in Example 1, except that 18.2 g Fe(NO 3 ) 3 .9H 2 O and 9.5gSr(NO 3 ) 2 " is replaced by "24.2gFe(NO 3 ) 3 .9H 2 O and 8.7gCo(NO 3 ) 2 ”, and obtain 2wt%Na-modified FeCo 0.5 O 2 The product is recorded as sample D2#.

[0080] Comparative Example 3

[0081] The operation is the same as in Comparative Example 1, except that the Fe modified by 2 wt% Na is obtained. 2 O 3 The product was then impregnated with an equal volume of Sr(NO 3 ) 2 The solution was modified with 2wt% Na and 10wt% Sr. 2 O 3 The product is recorded as sample D3#.

[0082] In order to investigate the effects of catalysts and reaction conditions on the catalytic effect, the catalysts in the examples and comparative examples were evaluated under certain reaction conditions. The evaluation results are shown in Table 1. The amount of catalyst was 1.0 g, and the catalysts were pre-reduced in situ before use. The reduction conditions were: 0.1 MPa, pure H 2 The temperature is 350°C and the space velocity is 1500 mL / (h·g cat ), reduction time 8h. Reaction conditions: H 2 / CO 2 =2.0-4.0, temperature 280-360°C, pressure 1.0-5.0MPa, space velocity 2000-12000mL / (h·g cat ), and the catalyst performance was investigated.

[0083] Table 1 CO under different catalysts and reaction conditions 2 Hydrogenation reaction performance

[0084]

[0085] Example 12

[0086] Weigh 1.0 g of catalyst particles #1 prepared by the method of Example 1 and load them into the reactor. Switch the feed gas to one containing CO and / or CO 2 The mixed gas of CO on the catalyst was investigated. x Hydrogenation synthesis of olefins. Reduction conditions: normal pressure, pure H 2 (25 mL / min), 350 °C reduction time 8 h. Reaction conditions: H 2 / (CO+CO 2 )=2.0, temperature is 320℃, pressure is 3.0MPa, space velocity is 8000mL / (h·g cat The results (see Table 2) show that the catalyst has good 2 The reactions using 2-nitropropene as raw materials all showed excellent performance in synthesizing olefins.

[0087] Table 2 CO of catalyst x Hydrogenation reaction performance

[0088]

[0089] Embodiment 13

[0090] 1.0 g of catalyst particles #1 prepared by the method of Example 1 were weighed and placed in the reactor for CO 2 Hydrogenation reaction. Reduction conditions: normal pressure, pure H 2 (25 mL / min), 350 °C reduction time 8 h. Reaction conditions: H 2 / CO 2 =3.0, temperature is 320°C, pressure is 3.0MPa, space velocity is 8000mL / (h·g cat ), the catalyst CO 2 The results (see Table 3) show that catalyst 1 always exhibits excellent CO stability over a reaction time of 2000 h. 2 Hydrogenation to olefins performance, the catalyst has no obvious deactivation phenomenon. However, after 500h reaction time, the activity of the comparative samples D1#, D2# and D3# decreased significantly compared with their initial activity (see Table 1), and the catalyst showed a certain degree of deactivation.

[0091] Table 3 CO on different catalysts 2 Hydrogenation reaction stability

[0092]

[0093]

[0094] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An iron-based metal composite oxide catalyst, characterized in that: The catalyst comprises an active component and an auxiliary agent; the auxiliary agent is loaded on the active component; the active component is generally represented by FeM x O y , wherein M is one or more of alkaline earth metals Ca, Sr and Ba, the molar number x of M is in the range of 0.1-10, and the molar number y of O is in the range of 1-12; the auxiliary agent is one or two of alkali metals Na and K, and the content of the auxiliary agent accounts for 0.1-10% of the total mass of the catalyst; The catalyst is prepared by a coprecipitation method, comprising: According to the composition ratio of the catalyst, iron salt and alkaline earth metal salt are mixed to form a salt solution, and then an alkaline precipitant is added to gradually adjust the pH value of the solution to alkaline. After the addition is completed, the solution is aged, the product is separated into solid and liquid, the solid is washed, dried, and roasted to obtain the catalyst. The auxiliary agent comes from the alkali metal remaining in the added alkaline precipitant, or is added by impregnating the alkali metal salt solution after drying or roasting.

2. The catalyst according to claim 1, characterized in that The alkaline earth metal M in the active component is one or both of Sr and Ba, the molar number x of M is 0.25-4, and the molar number y of O is 1-6.

3. The catalyst according to claim 1, characterized in that The content of the additive accounts for 0.5-5% of the total mass of the catalyst.

4. The catalyst according to claim 1, characterized in that The iron salt is selected from ferric iron salts; The ferric iron salt is selected from one or more of ferric chloride, ferric sulfate, ferric acetate and ferric nitrate; The alkaline earth metal salt is selected from one or more of chlorides, nitrates and acetates of alkaline earth metals; The alkaline precipitant is selected from an alkaline solution capable of adjusting the pH value of the solution, specifically one or more of NaOH, KOH, Na2CO3, K2CO3, and ammonia water; The alkali metal salt is selected from one or more of alkali metal chlorides, nitrates, acetates and carbonates.

5. Use of the catalyst according to any one of claims 1 to 4, characterized in that: Passing a mixed raw gas containing CO and / or CO2 and H2 through a fixed bed reactor containing the catalyst to react and obtain olefins; The reaction conditions are: the molar ratio of H2 to (CO+CO2) is 1-8:1, the reaction temperature is 240-400℃, the reaction pressure is 0.1-10 MPa, and the space velocity is 1000-30000 mL / (h∙g cat ).

6. The use of the catalyst according to claim 5, characterized in that: The reaction conditions are: the molar ratio of H2 to (CO+CO2) is 2-4:1, the reaction temperature is 280-340℃, the reaction pressure is 1-4MPa, and the space velocity is 2000-8000 mL / (h∙g cat ).

7. The use of the catalyst according to claim 5, characterized in that: The catalyst also includes an activation step before use; The activation conditions are: in-situ reduction at 300-500°C for 2-50 h in a reducing atmosphere; The reducing atmosphere is selected from one or both of H2 and CO.

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