Alkali metal modified catalyst as well as preparation method and application thereof

Abstract

The invention provides an alkali metal modified catalyst as well as a preparation method and application thereof, alkali metal is used for modifying metal oxide with a spinel structure, the alkali metal affects the oxygen vacancy property in the spinel structure, non-dissociation adsorption of CO is promoted, formation of long-chain alpha-olefin and enhigher alcohol is facilitated, and the catalyst has the advantages of being simple in preparation process and low in cost. The catalyst is high in selectivity of long-chain olefin and high-carbon alcohol, high in CO conversion rate and low in selectivity of by-products (CH4 and the like). The preparation process of the alkali metal catalyst is simple, convenient and efficient, firstly, Prussian blue PB is synthesized, then PB serves as a template agent and reacts with other metal salts to synthesize nanocubic metal oxide MFe2O4, M can be Co, Mn, Zn, Mg and the like, and then dipping modification is conducted through alkaline metal. The alkali metal oxide prepared by the method disclosed by the invention is used as a catalyst, shows relatively excellent enol selectivity and reaction stability in a reaction for synthesizing enol through CO hydrogenation, and has a potential industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesis gas conversion, and further to an alkali metal modified catalyst and a preparation method and application thereof. Background Art

[0002] Long-chain α-olefins refer to olefins with more than five carbon atoms and unsaturated bonds at the end of the hydrocarbon chain. They are widely used as olefin comonomers, surfactants, plasticizers, etc. In the production process of α-olefins, the method of preparing α-olefins from synthesis gas has the characteristics of short process route and good product economy. It can not only produce even-carbon α-olefins but also odd-carbon α-olefins. As the requirements for raw materials in industries such as polyolefins, lubricants and detergents gradually increase, the market prospects for long-chain α-olefins are very promising. Mixed alcohols (mixtures of low-carbon alcohols of C1 to C5 and C 6+ The main use of low-carbon alcohols is as an additive for clean gasoline or directly as a fuel to replace lead-containing additives. Its main function is to increase the oxygen content, promote the clean combustion of fuel, and improve the octane number of fuel. 11 High carbon alcohols can be used to produce plasticizers, C 12 ~C 18 High carbon alcohols can be used to produce surfactants, which subsequently have important applications in the fields of textiles, papermaking, food, medicine, leather, etc. The demand for high carbon alcohols and their derivative products is also gradually increasing.

[0003] In this context, it is becoming more important to use coal and natural gas as raw materials and convert coal, natural gas or biomass into liquid fuel or high value-added chemical products through Fischer-Tropsch synthesis under the action of catalysts. Traditional Fischer-Tropsch synthesis catalysts are mainly based on Fe and Co metal oxides, but these catalysts are not ideal in terms of activity, selectivity, stability, etc. There are still many problems to be solved, and the development of new catalysts with high activity, high selectivity and high stability is crucial. Summary of the invention

[0004] In view of the problems of low activity and poor ene alcohol selectivity in existing Fischer-Tropsch synthesis catalysts, the purpose of the present invention is to provide an alkali metal modified catalyst and a preparation method and application thereof. The alkali metal modifies a metal oxide with a spinel structure, regulates the distribution of tetrahedrons and octahedrons in the spinel structure, modifies the microstructure of M-Fe spinel, regulates the formation of an alloy of metal M and Fe during reduction of MFe2O4, facilitates the formation of various metal carbides during reduction and carbonization, promotes the formation of multiple active sites, plays a role in synergistic catalysis and mutual stabilization, and improves the selectivity for olefins and alcohols. The alkali metal modification further affects the oxygen vacancy properties of the spinel metal oxide, promotes the non-dissociative adsorption of CO, and facilitates the formation of long-chain olefins and high-carbon alcohols. Moreover, the preparation process of the alkali metal modified catalyst is simple and efficient. The alkali metal modified catalyst not only shows a high CO conversion rate, but also significantly reduces the selectivity of by-products such as CH4. In the synthesis gas reaction, mixed alcohols and olefins, especially long-chain α-olefins, can be directly synthesized in one step with high selectivity.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] An alkali metal modified catalyst, wherein the catalyst is alkali metal modified MFe2O4, the MFe2O4 has a spinel structure, and M is any one or more of Co, Mn, Zn, Mg, and Ca.

[0007] In some embodiments, the alkali metal is any one or more of Li, Na, K, Rb, and Cs.

[0008] The present invention also provides a method for preparing an alkali metal modified catalyst, comprising dispersing Prussian blue, metal acetate and alkali metal salt in a solvent for reaction, and then drying and calcining the mixture in sequence to obtain the alkali metal modified catalyst; or dispersing Prussian blue and metal acetate in a solvent for reaction, immersing the generated precursor in an alkali metal salt solution, and then drying and calcining the mixture in sequence to obtain the alkali metal modified catalyst.

[0009] In some embodiments, the reaction temperature is 20-60°C, and the reaction time is 12-36h; and / or the drying temperature is 20-60°C, and the drying time is 10-30h; and / or the calcination temperature is 350-750°C, and the calcination time is 2-6h; and / or the molar ratio of the Prussian blue to the metal acetate is 2:1-1:2; and / or the amount of the alkali metal salt added is 0.1-5wt%.

[0010] In some embodiments, the preparation steps of the Prussian blue include: dispersing polyvinyl pyrrolidone in a hydrochloric acid solution to prepare a mixed solution, adding the mixed solution to a potassium ferrocyanide solution or a potassium ferrocyanide solution for reaction, and then centrifuging, washing, and vacuum drying in sequence to obtain the Prussian blue; the molar ratio of the polyvinyl pyrrolidone to the potassium ferrocyanide or the potassium ferrocyanide is 5:1 to 1:5; the concentration of the hydrochloric acid solution is 0.05 to 0.5 mol / L; or, dissolving an iron salt in deionized water to prepare a mixed solution, adding the mixed solution to a potassium ferrocyanide solution or a potassium ferrocyanide solution for reaction, and then centrifuging, washing, and vacuum drying in sequence to obtain the Prussian blue; the molar ratio of the iron salt to the potassium ferrocyanide or the potassium ferrocyanide is 2:1 to 1:2.

[0011] In some embodiments, the reaction temperature is 50-90°C, the reaction time is 12-36 hours, and the vacuum drying temperature is 30-80°C.

[0012] In some embodiments, the metal acetate is any one or more of manganese acetate, cobalt acetate, zinc acetate, and nickel acetate; and / or the alkali metal salt is any one or more of sodium nitrate, potassium nitrate, lithium nitrate, rubidium nitrate, cesium nitrate, sodium carbonate, and potassium carbonate.

[0013] The present invention also provides an application of an alkali metal modified catalyst, wherein the alkali metal modified catalyst or the alkali metal modified catalyst prepared by the above preparation method is sequentially reduced and carbonized and then used to catalyze the hydrogenation of synthesis gas to synthesize enol.

[0014] In some embodiments, the reduction conditions are: the reducing gas is pure hydrogen, the reducing temperature is 250-450°C, the reducing pressure is 0.1-1.0 MPa, the heating rate is 1-2°C / min, and the volume space velocity is 2000-4000h -1 , constant temperature time is 8 to 22 hours; and / or, the carbonization treatment conditions are: the carbonization atmosphere is synthesis gas, the carbonization temperature is 200 to 350°C, the carbonization pressure is 0.1 to 1.0 MPa, and the air velocity is 2000 to 4000 h -1 , the carbonization time is 20 to 60 hours.

[0015] In some embodiments, the reaction conditions for catalytic synthesis gas hydrogenation to synthesize enol are: the reaction gas is synthesis gas, and the volume space velocity is 2000-6000h -1 ; The molar ratio of H2 to CO in the synthesis gas is 0.5-3, the reaction temperature is 200-350°C, and the reaction pressure is 0.1-3.5MPa.

[0016] Compared with the prior art, the alkali metal modified catalyst provided by the present invention and its preparation method and application have the following beneficial effects:

[0017] 1. The catalyst provided by the present invention is a metal oxide with a spinel structure modified with an alkali metal. While achieving excellent CO conversion rate, it also has a low selectivity for CH4 byproducts, and can also achieve high selectivity for mixed long-chain olefins and mixed alcohols in the product. The selectivity of olefins and alcohols in the product is ≥70%, and the proportion of long-chain olefins and alcohols in the liquid phase product is ≥80%. It is worth noting that in the alcohol product, C 2+ Alcohol distribution ratio ≥ 90%, C 6+ Alcohol distribution ratio ≥50%;

[0018] 2. The metal oxide provided by the present invention is a spinel-type oxide with a special cubic structure. The modification of the alkali metal additive regulates the distribution of tetrahedrons and octahedrons in the spinel structure through its cationic characteristics, modifies the microstructure of the M-Fe spinel, regulates the formation of the alloy of metal M and Fe during the reduction of the MFe2O4 oxide, and is conducive to the formation of various metal carbides during reduction and carbonization, promotes the formation of multiple active sites, plays a synergistic catalytic and mutual stabilizing role in the reaction process, and improves the selectivity for olefins and alcohols; at the same time, the spinel-type oxide modified by the alkali metal can also affect the oxygen vacancy properties in the spinel structure, promote the non-dissociative adsorption of CO, promote the growth of the carbon chain, and facilitate the formation of long-chain olefins and high-carbon alcohols;

[0019] 3. The alkali metal modified catalyst of the present invention is easy to prepare and has good reproducibility, which is conducive to industrial mass production. In addition, different composition catalysts can be selected according to market conditions, and the product can be regulated in different proportions between long-chain olefins and high-carbon alcohols, thereby improving market adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The preferred implementation modes will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0021] Figure 1 This is a SEM image of the alkali metal modified catalyst 001-CoFeK provided in Example 4 of the present invention;

[0022] Figure 2 This is a SEM image of the alkali metal modified catalyst 002-MnFeK provided in Example 5 of the present invention;

[0023] Figure 3 This is a SEM image of the catalyst comparison-CoFeZrNa provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0025] In order to simplify the drawings, only the parts related to the invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0026] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0027] In this document, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In addition, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0029] Example 1

[0030] The invention provides an alkali metal modified catalyst, which is alkali metal modified MFe2O4, the MFe2O4 has a spinel structure, and M is any one or more of Co, Mn, Zn, Mg and Ca.

[0031] The above-mentioned M is preferably any one or more of Zn, Mn, Co and Mg.

[0032] Spinel transition metal oxides (AB2O4) are different from ordinary mixed metal oxides. There are strong interactions between the metal elements inside, which can form a good redox pair, which is beneficial to enhance the redox ability of the catalyst. At the same time, AB2O4 spinel is mainly composed of AO tetrahedron and BO octahedron, and the structure mainly includes normal spinel, reverse spinel and mixed spinel. In the normal spinel, metal A occupies the tetrahedral coordination center (A = Co, Cu, Mg, Fe, Ni, Zn, etc.), and metal B occupies the octahedral coordination center (B = Mn, Al, Co, Fe, In, Ga, Ni, etc.). The structure of spinel can be regulated by replacing the A and B positions of spinel with atoms of different valence states, thereby achieving structural regulation.

[0033] Furthermore, the alkali metal mentioned above is any one or more of Li, Na, K, Rb, and Cs.

[0034] The alkali metal is preferably Na or K.

[0035] Example 2

[0036] Based on Example 1, this example provides a method for preparing the above-mentioned alkali metal modified catalyst, including two methods:

[0037] Method 1: Prussian blue, metal acetate and alkali metal salt are dispersed in a solvent for reaction, and then dried and calcined in sequence to obtain an alkali metal modified catalyst.

[0038] Method 2: Prussian blue and metal acetate are dispersed in a solvent for reaction, the generated precursor is immersed in an alkali metal salt solution, and then dried and calcined in sequence to obtain an alkali metal modified catalyst.

[0039] The above solvent is preferably anhydrous ethanol, and may also be ethanol aqueous solution of different concentrations.

[0040] The metal acetate is any one or more of manganese acetate, cobalt acetate, zinc acetate and nickel acetate.

[0041] The alkali metal salt is any one or more of sodium nitrate, potassium nitrate, lithium nitrate, rubidium nitrate, cesium nitrate, sodium carbonate and potassium carbonate.

[0042] Furthermore, the molar ratio of Prussian blue to metal acetate is 2:1 to 1:2, preferably 1:1.

[0043] Furthermore, in the final catalyst system, the amount of alkali metal salt added is 0.1 to 5 wt%, preferably 0.5 to 2.5 wt%.

[0044] In the above method 1 and method 2, the reaction temperature is 20-60°C, and the reaction time is 12-36 hours. Preferably, the reaction temperature is 40-60°C, and the reaction time is 20-30 hours.

[0045] In the above method 1 and method 2, the drying temperature is 20-60° C., and the drying time is 10-30 hours. Preferably, the drying temperature is 40-60° C., and the drying time is 15-25 hours.

[0046] The calcination temperature is 350-750°C, and the calcination time is 2-6 hours. Preferably, the calcination temperature is 400-700°C, and the calcination time is 2-4 hours.

[0047] In some embodiments, the steps of preparing the precursor in method 2 are:

[0048] A certain amount of Prussian blue and metal acetate are dispersed in an ethanol solution and reacted for a period of time, and then the product is dried to obtain the precursor.

[0049] Subsequently, a certain amount of alkali metal salt is dissolved in an ethanol solution to prepare a modified solution, and an equal volume of the modified solution is impregnated into the above precursor for 12 to 24 hours, followed by drying and calcination in sequence to obtain an alkali metal modified catalyst.

[0050] The reaction temperature of the Prussian blue and the metal acetate is 20-60°C, and the reaction time is 12-36 hours. Preferably, the reaction temperature is 40-60°C, and the reaction time is 20-30 hours.

[0051] The precursor is dried at a temperature of 20 to 60° C. and for a drying time of 10 to 30 hours.

[0052] In some embodiments, the present invention also provides two methods for preparing Prussian blue PB, the first method comprising the steps of:

[0053] A certain amount of polyvinyl pyrrolidone (PVP) is dispersed in a hydrochloric acid solution to prepare solution A, a certain amount of potassium ferrocyanide or potassium ferrocyanide is dispersed in deionized water to prepare solution B, solution B is added to solution A, and reacted at 50-90° C. for 12-36 hours, and then centrifuged, washed, and dried in sequence to obtain Prussian blue.

[0054] Furthermore, the molar ratio of polyvinylpyrrolidone PVP to potassium ferrocyanide or potassium ferrocyanide is 5:1 to 1:5, preferably 2:1 to 1:2.

[0055] The concentration of the hydrochloric acid solution is 0.05 to 0.5 mol / L, preferably 0.1 to 0.3 mol / L.

[0056] The drying temperature is 30 to 80°C, preferably 50 to 60°C.

[0057] Ethanol is used in the above washing step.

[0058] The above reaction temperature is preferably 60-80° C., and the reaction time is preferably 20-30 h.

[0059] In some embodiments, the steps of the second method of Prussian Blue PB include:

[0060] A certain amount of iron salt is dissolved in deionized water to prepare solution C, and a certain amount of potassium ferrocyanide or potassium ferrocyanide is dissolved in deionized water to prepare solution D. Solution D is slowly added to solution C, stirred, reacted at 50-80°C for 12-24h, and then centrifuged, washed, and dried in sequence to obtain Prussian blue.

[0061] Furthermore, the molar ratio of the iron salt to potassium ferrocyanide or potassium ferrocyanide is 2:1 to 1:2.

[0062] The above reaction temperature is preferably 60-80° C., and the reaction time is preferably 15-20 h.

[0063] Ethanol is used in the above washing step.

[0064] Example 3

[0065] On the basis of Examples 1 and 2, this example provides an application of an alkali metal modified catalyst, wherein the alkali metal modified catalyst is sequentially reduced and carbonized and then used to catalyze the hydrogenation of synthesis gas to synthesize enol.

[0066] In some embodiments, the reduction conditions are:

[0067] The reducing gas is pure hydrogen, the reducing temperature is 250~450℃, the reducing pressure is 0.1~1.0MPa, the heating rate is 1~2℃ / min, and the volume space velocity is 2000~4000h -1 , constant temperature time is 8 to 22 hours.

[0068] In some embodiments, the conditions of the carbonization treatment are:

[0069] The carbonization atmosphere is synthesis gas, the carbonization temperature is 200-350°C, the carbonization pressure is 0.1-1.0 MPa, and the air velocity is 2000-4000 h -1 , the carbonization time is 20 to 60 hours.

[0070] In some embodiments, the reaction conditions for the catalytic synthesis gas hydrogenation to synthesize enol are: the reaction gas is synthesis gas, and the volume space velocity is 2000-6000h -1 .

[0071] The molar ratio of H2 to CO in the synthesis gas is 0.5-3, the reaction temperature is 200-350°C, and the reaction pressure is 0.1-3.5MPa.

[0072] The above reaction is carried out in a fixed bed reactor.

[0073] The technical solution of the present invention is described below by specific examples:

[0074] Example 4

[0075] (1) Preparation of Prussian Blue PB: 15.2 g of PVP K30 (K30 refers to a specific type of polyvinyl pyrrolidone (PVP) with a K value of about 30) was dispersed in 200 mL of 0.1 M HCl solution and stirred for 10 min to obtain a colorless solution A.

[0076] Then add 0.3429g K3Fe(CN)6 and stir for 10min. The solution is bright yellow. After reacting in an oil bath at 80℃ for 24h, the color turns to dark blue. Then centrifuge and wash with anhydrous ethanol for 3 times. Then vacuum dry at 25℃ for 12h to obtain a blue solid, numbered PB-1.

[0077] (2) Preparation of alkali metal modified catalyst: 2 g PB-1, 2.81 g Co(AC)2·4H2O and 0.102 g KNO3 were dispersed in 50 mL anhydrous ethanol and stirred magnetically for 24 h. The solution gradually turned dark blue. The catalyst was dried at 60 °C in vacuum for 16 h and calcined at 700 °C for 2 h at a heating rate of 2 °C / min to obtain an alkali metal modified catalyst, numbered 001-CoFeK. Figure 1 Shown is the SEM image of the 001-CoFeK alkali metal modified catalyst.

[0078] (3) Application: The mesh size of 001-CoFeK catalyst is 20-40 mesh, and the dosage is 4.0 g. Quartz sand of the same mesh size is taken, mixed in a mass ratio of 1:4, and then loaded into a fixed bed reaction tube.

[0079] The reduction conditions are: reduction pressure of 0.2 MPa, reduction temperature of 300 °C, H2 reduction for 5 h, and space velocity of 6600 h -1 .

[0080] After the reduction, the carbonization was carried out with synthesis gas (H2 / CO=1), the carbonization temperature was 265°C, the carbonization time was 24h, the carbonization pressure was 0.5MPa, and the carbonization space velocity was 4000h -1 .

[0081] After carbonization, the reaction was switched to synthesis conditions. The reaction conditions were: H2 / CO in the synthesis gas = 2, the reaction pressure was 0.5 MPa, the reaction temperature was 265 °C, and the volume space velocity was 2000 h -1 .

[0082] Example 5

[0083] (1) Preparation of Prussian blue PB: Dissolve 51.1 g of anhydrous FeCl3 in 500 mL of deionized water and stir to obtain solution C.

[0084] Take 51.9g K3Fe(CN)6 and dissolve it in 200mL deionized water, stir evenly, and obtain solution D, which is yellow-green. Slowly add solution D to the third solution C, and the color of the solution immediately changes to dark green. The addition time is about 10min, and it is vigorously stirred for 10min, and then kept in a 60℃ oven for 19h, and the color changes to dark dark blue. Then centrifuge, wash once with anhydrous ethanol / deionized water = 1 / 1 (volume ratio), and then vacuum dry at 60℃ for 12h to obtain a blue solid, numbered PB-2.

[0085] (2) Preparation of alkali metal modified catalyst: 5 g PB-2, 5 g Mn(AC)2 and 0.142 g KNO3 were dispersed in 150 mL anhydrous ethanol and stirred magnetically for 30 h. The solution gradually turned dark blue. The catalyst was dried at 60 °C in vacuum for 16 h and calcined at 500 °C for 2 h at a heating rate of 2 °C min to obtain an alkali metal modified catalyst, numbered 002-MnFeK. Figure 2 Shown is the SEM image of the 002-MnFeK alkali metal modified catalyst.

[0086] (3) Application: The mesh size of 002-MnFeK catalyst is 20-40 mesh, and the dosage is 4.0 g. Quartz sand of the same mesh size is taken, mixed in a mass ratio of 1:4, and then loaded into a fixed bed reaction tube.

[0087] The reduction conditions are: reduction pressure of 0.5 MPa, reduction temperature of 280°C, H2 reduction for 5 h, and space velocity of 8000 h -1 .

[0088] After the reduction, the carbonization was carried out with synthesis gas (H2 / CO=1), the carbonization temperature was 250°C, the carbonization time was 36h, the carbonization pressure was 0.5MPa, and the carbonization space velocity was 8000h -1 .

[0089] After carbonization, the reaction was switched to synthesis conditions. The reaction conditions were: H2 / CO in the synthesis gas = 2, the reaction pressure was 3.0 MPa, the reaction temperature was 280 °C, and the volume space velocity was 2000 h -1 .

[0090] Example 6

[0091] (1) Preparation of alkali metal modified catalyst: Prussian blue was prepared using PB-1 synthesized in Example 4. 10 g PB-1, 9 g Zn(AC)2 and 0.239 g NaNO3 were added to 120 mL anhydrous ethanol and stirred under magnetic stirring for 20 h. The solution gradually turned into dark blue. The catalyst was dried at 50 °C in vacuum for 16 h and calcined at 550 °C for 4 h at a heating rate of 2 °C / min to obtain an alkali metal modified catalyst, numbered 003-ZnFeNa.

[0092] (2) Application: The mesh size of 003-ZnFeNa catalyst is 20-40 mesh, and the dosage is 4.0 g. Quartz sand of the same mesh size is taken, mixed in a mass ratio of 1:4, and then loaded into a fixed bed reaction tube.

[0093] The reduction conditions are: reduction pressure of 0.2 MPa, reduction temperature of 350°C, H2 reduction for 10 h, and space velocity of 2000 h -1 .

[0094] After the reduction, the carbonization was carried out with synthesis gas (H2 / CO=2), the carbonization temperature was 280°C, the carbonization time was 48h, the carbonization pressure was 0.5MPa, and the carbonization space velocity was 6000h -1 .

[0095] After carbonization, the reaction was switched to synthesis conditions. The reaction conditions were: H2 / CO in the synthesis gas = 2, the reaction pressure was 1.5 MPa, the reaction temperature was 300 °C, and the volume space velocity was 3600 h -1 .

[0096] Example 7

[0097] (1) Preparation of alkali metal modified catalyst: Prussian blue was prepared using PB-2 synthesized in Example 5. 8 g PB-2, 8 g Mg(AC)2 and 0.142 g RbNO3 were added to 50 mL anhydrous ethanol and stirred for 30 h under magnetic stirring. The solution gradually turned into dark blue. The catalyst was dried at 55°C for 30 h and calcined at 450°C for 4 h at a heating rate of 2°C / min to obtain an alkali metal modified catalyst, numbered 004-MgFeRb.

[0098] (2) Application: The mesh size of 004-MgFeRb catalyst is 20-40 mesh, and the dosage is 4.0 g. Quartz sand of the same mesh size is taken, mixed in a mass ratio of 1:4, and then loaded into a fixed bed reaction tube.

[0099] The reduction conditions are: reduction pressure of 0.3 MPa, reduction temperature of 300 °C, H2 reduction for 20 h, and space velocity of 4000 h -1 .

[0100] After the reduction, the carbonization was carried out with synthesis gas (H2 / CO=0.5), the carbonization temperature was 300°C, the carbonization time was 12h, the carbonization pressure was 0.5MPa, and the carbonization space velocity was 8000h -1 .

[0101] After carbonization, the reaction was switched to synthesis conditions. The reaction conditions were: H2 / CO in the synthesis gas = 1.0, the reaction pressure was 2.5 MPa, the reaction temperature was 260 °C, and the volume space velocity was 6000 h -1 .

[0102] Comparative Example 1

[0103] In a 35°C water bath, 150 mL of deionized water and 5 g of ZrO2 were added to a three-necked flask. A mixed solution of metal nitrates of Co and Fe (Fe / Co=2 / 1) and a 2M NaOH solution were simultaneously added to the three-necked flask and co-precipitated. The pH value of the precipitation was 8.0, and the precipitation reaction lasted for 20 minutes. After the reaction, the temperature was raised to 85°C for aging for 2 hours. Afterwards, the filter was washed with water to control the conductivity. The filter cake was dried at 120°C for 24 hours, calcined at 450°C for 3 hours, and the heating rate was 1°C / min. The catalyst number obtained was Comparison-CoFeZrNa, Figure 3 Shown is a SEM image of the comparative-CoFeZrNa catalyst.

[0104] Comparative: The mesh size of the CoFeZrNa catalyst is 20-40 meshes, and the dosage is 4.0 g. Quartz sand of the same mesh size is taken, mixed in a mass ratio of 1:4, and then filled into the fixed bed reaction tube.

[0105] The reduction conditions are: reduction pressure of 0.2 MPa, reduction temperature of 300 °C, H2 reduction for 5 h, and space velocity of 6600 h -1 .

[0106] After the reduction, the carbonization was carried out with synthesis gas (H2 / CO=1), the carbonization temperature was 265°C, the carbonization time was 24h, the carbonization pressure was 0.5MPa, and the carbonization space velocity was 4000h -1 .

[0107] After carbonization, the reaction was switched to synthesis conditions. The reaction conditions were: H2 / CO in the synthesis gas = 2, the reaction pressure was 0.5 MPa, the reaction temperature was 265 °C, and the volume space velocity was 2000 h -1 .

[0108] The performance evaluation results and product distribution results of the catalysts prepared in Examples 4 to 7 and Comparative Example 1 are shown in Table 1.

[0109] Table 1 Reaction performance of the catalysts described in Examples 4 to 7 and Comparative Example 1

[0110]

[0111] Based on the results of Examples 4 to 7 and the result of Comparative Example 1, the alkali metal modified catalyst provided by the present invention further improves the selectivity of long-chain olefins in the product while maintaining a high alcohol selectivity; and the C 6+ The proportion of higher carbon alcohols is also significantly increased. The catalyst provided by the present invention can simultaneously produce a large amount of mixed higher carbon olefins and mixed higher carbon primary alcohols, and has higher atom economy and added value.

[0112] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An alkali metal modified catalyst, characterized in that The catalyst is alkali metal-modified MFe2O4, and the MFe2O4 has a spinel structure. M is any one or more of Co, Mn, Zn, Mg, and Ca.

2. The alkali metal modified catalyst according to claim 1, characterized in that The alkali metal is any one or more of Li, Na, K, Rb, and Cs.

3. A method for preparing an alkali metal modified catalyst, characterized in that: Prussian blue, metal acetate and alkali metal salt are dispersed in a solvent for reaction, and then dried and calcined in sequence to obtain the alkali metal modified catalyst as claimed in any one of claims 1 to 2; or, Prussian blue and metal acetate are dispersed in a solvent for reaction, the generated precursor is immersed in an alkali metal salt solution, and then dried and calcined in sequence to obtain the alkali metal modified catalyst as claimed in any one of claims 1-2.

4. The preparation method according to claim 3, characterized in that: The reaction temperature is 20 to 60° C., and the reaction time is 12 to 36 hours; and / or, The drying temperature is 20 to 60° C., and the drying time is 10 to 30 hours; and / or, The calcination temperature is 350-750° C., and the calcination time is 2-6 hours; and / or, The molar ratio of the Prussian blue to the metal acetate is 2:1 to 1:2; and / or, The added amount of the alkali metal salt is 0.1-5 wt %.

5. The preparation method according to claim 3, characterized in that: The preparation steps of the Prussian blue include: Dispersing polyvinyl pyrrolidone in a hydrochloric acid solution to prepare a mixed solution, adding the mixed solution to a potassium ferrocyanide solution or a potassium ferrocyanide solution for reaction, and then centrifuging, washing, and drying in sequence to obtain the Prussian blue; The molar ratio of the polyvinyl pyrrolidone to the potassium ferrocyanide or the potassium ferrocyanide is 5:1 to 1:5; The concentration of the hydrochloric acid solution is 0.05-0.5 mol / L; or, Dissolving an iron salt in deionized water to prepare a mixed solution, adding the mixed solution to a potassium ferrocyanide solution or a potassium ferrocyanide solution for reaction, and then centrifuging, washing, and drying in sequence to obtain the Prussian blue; The molar ratio of the iron salt to the potassium ferrocyanide or the potassium ferrocyanide is 2:1 to 1:

2.

6. The preparation method according to claim 5, characterized in that: The reaction temperature is 50 to 90° C., and the reaction time is 12 to 36 hours; The drying temperature is 30-80°C.

7. The preparation method according to claim 3, characterized in that: The metal acetate is any one or more of manganese acetate, cobalt acetate, zinc acetate, and nickel acetate; and / or, The alkali metal salt is any one or more of sodium nitrate, potassium nitrate, lithium nitrate, rubidium nitrate, cesium nitrate, sodium carbonate and potassium carbonate.

8. An application of an alkali metal modified catalyst, characterized in that: The alkali metal modified catalyst according to any one of claims 1-2, or the alkali metal modified catalyst prepared by the preparation method according to any one of claims 3-7 is sequentially subjected to reduction and carbonization treatments and then used to catalyze the hydrogenation of synthesis gas to synthesize enol.

9. The use according to claim 8, characterized in that: The reduction conditions are: The reducing gas is pure hydrogen, the reducing temperature is 250~450℃, the reducing pressure is 0.1~1.0MPa, the heating rate is 1~2℃ / min, and the volume space velocity is 2000~4000h -1 , constant temperature time is 8 to 22 hours; and / or, The conditions of the carbonization treatment are: The carbonization atmosphere is synthesis gas, the carbonization temperature is 200-350°C, the carbonization pressure is 0.1-1.0 MPa, and the air velocity is 2000-4000 h -1 , the carbonization time is 20 to 60 hours.

10. The use according to claim 8, characterized in that: The reaction conditions for catalytic synthesis gas hydrogenation to enol are: The reaction gas is synthesis gas, and the volume space velocity is 2000~6000h -1 ; The molar ratio of H2 to CO in the synthesis gas is 0.5-3, the reaction temperature is 200-350°C, and the reaction pressure is 0.1-3.5MPa.

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