A method for directly converting synthesis gas into polycarbon aldehydes and ketones

Abstract

The present invention provides a method for synthesizing polycarbon aldehydes and ketones with high selectivity from synthesis gas, wherein the method comprises the following steps: the method comprises the following steps: the method comprises the following steps: the method comprises the following steps: the method comprises the following steps: cat ), under the reaction conditions of H2 / CO molar ratio of 0.5 to 8.0, a high-selective synthesis of polycarbon aldehydes and ketones from syngas occurs under the action of an iron-based catalyst. The iron-based catalyst is composed of active components Fe5C2, Fe, alkali metal components and other components Fe3O4, Fe2C, etc. In this method, syngas can be highly selectively converted to generate polycarbon aldehydes and ketones at 150-210°C, and the selectivity of polycarbon aldehydes and ketones can be controlled to be more than 40%. Polycarbon aldehydes and ketones account for more than 99% of the aldehyde and ketone products, and the aldehyde and ketone mass ratio in the aldehyde and ketone products can be regulated in the range of 0.5-4.5. The present invention opens up a new route for the high-selective conversion of syngas to synthesize polycarbon aldehydes and ketones.

Description

Technical Field

[0001] The invention relates to a method for directly converting synthesis gas into polycarbon aldehydes and ketones, and in particular to a method for converting synthesis gas into polycarbon aldehydes and ketones with high selectivity over an iron-based catalyst. Background Art

[0002] Multi-carbon aldehydes and ketones refer to aldehyde and ketone compounds containing two or more carbon atoms. As high-value chemicals, they can be widely used in medicine, resins, solvents, coatings, dyes, rubber, chemicals, fine chemicals and other fields. At present, the production of multi-carbon aldehydes mostly adopts the hydroformylation of high-carbon olefins, and the production of multi-carbon ketones mostly adopts the isopropylbenzene process. Due to the high price of raw materials, the production of multi-carbon aldehydes and ketones is limited. Therefore, it is undoubtedly of great significance for my country to develop new production technologies for multi-carbon aldehydes and ketones.

[0003] The direct synthesis of polycarbon aldehydes and ketones from syngas has the advantage of a wide range of readily available raw materials, which meets the requirements of sustainable development in today's society and is a new green and economical synthesis route. The yield of polycarbon aldehydes and ketones in the current process is relatively low, which is related to the low selectivity of polycarbon aldehydes and ketones in the catalyst system currently under study. The research on highly selective catalysts is the focus of the research on this process. The low selectivity of polycarbon aldehydes and ketones produced by this process is related to the need for effective synergistic catalysis of the two active sites of the catalyst in this process. These two active sites include: (1) CO dissociation adsorption active site, which produces CH x *active species; (2) CO non-dissociative adsorption active sites, which adsorb CO and produce CO*active species. x * undergoes CO* insertion reaction to generate multi-carbon aldehydes and ketones. How to achieve efficient catalytic synergy of the two active sites of the catalyst is a challenging problem in the current research of this process and is also a key research direction of this process. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing multi-carbon aldehydes and ketones by directly converting syngas into syngas with high selectivity, in order to solve the problems existing in the prior art such as low selectivity of synthesizing multi-carbon aldehydes and ketones by directly converting syngas into syngas. 5 C 2 Active species CH x * and Fe active components to form active species CO*, CH x * and CO* can be effectively combined on the catalyst of the present invention to form multi-carbon aldehydes and ketones with high selectivity.

[0005] The present invention provides a method for synthesizing polycarbon aldehydes and ketones from synthesis gas, the method being characterized in that the synthesis gas raw material is introduced into a reactor containing an iron-based catalyst to react at 150-210°C to generate polycarbon aldehydes and ketones; the iron-based catalyst is at least composed of Fe 5 C2 , Fe and alkali metals, the mass content of each component is: active component Fe 5 C 2 The content is 23-55% (preferably 29-52%), the active component Fe content is 15-40% (preferably 20-38%), the alkali metal component content is 0.05-5% (preferably 0.5-5%), and the other components are Fe 3 O 4 and Fe 2 C (mass ratio is 0.9~1.1:1).

[0006] The synthesis gas is a raw gas containing carbon monoxide and hydrogen, wherein H 2 The molar ratio of CO to CO is 0.5-8, optimized to 2-5; the raw gas does not contain or may contain CO 2 , CH 4 , C 2 H 6 、N 2 , Ar and other impurity gases, and the content of the impurity gases shall not exceed 30% of the volume of the raw gas.

[0007] In the above method, in the presence of an alkali metal in the iron-based catalyst, CO and H are activated. 2 Formation of CH x The active component Fe 5 C 2 It can synergistically catalyze the active component Fe that activates CO to form CO* to produce multi-carbon aldehydes and ketones.

[0008] The multi-carbon aldehydes and ketones refer to multi-carbon aldehydes or multi-carbon ketones having 2 to 16 carbon atoms and containing a single carbonyl group (—C═O).

[0009] The iron-based catalyst may contain a structural additive, which includes SiO 2 、Al 2 O 3 One or two of the additives and the iron-based compounds (Fe 5 C 2 , Fe, alkali metals, Fe 3 O 4 and Fe 2 C) the total mass ratio is 0-0.25:1 (preferably 0-0.05:1); the structural additive is added to the iron-based catalyst by mixing and grinding with the iron-based compound, or the additive is added to the iron-based catalyst by adding the solution to the precipitation process of preparing the iron-based compound by precipitation method.

[0010] The iron-based catalyst can be prepared by the following method A or method B:

[0011] A. Commercial iron oxide (including ferroferric oxide and / or ferric oxide) pretreatment impregnation method

[0012] The steps are as follows: (1) pre-treating commercial iron oxide powder (particle size range 10-500nm, preferably 10-200nm) in an air atmosphere at 300-500°C (preferably 350-480°C) for 3-10 hours (preferably 4-8 hours) to remove impurities on the surface of the iron oxide; (2) preparing a soluble salt solution of an alkali metal, wherein the concentration of the alkali metal ion in the soluble salt solution is 0.01-3.0 mol / L (preferably 0.1-2.5 mol / L); (3) adding the salt of step (2) to the mixture; The solution is impregnated with the pretreated iron oxide of step (1) at 10-60° C. for 2-24 hours, dried at 60-120° C. for 4-24 hours, and calcined at 350-550° C. (preferably 350-500° C.) in air and / or inert atmosphere for 2-18 hours (preferably 4-10 hours); (2) the calcined sample obtained in step (3) is pretreated at 270-500° C. (preferably 320-480° C.) in a hydrogen flowing atmosphere for 2-50 hours (preferably 6-32 hours) for reduction; (3) the H 2 / CO synthesis gas (H 2 / CO molar ratio = 0.5-8) 150-220° C. (preferably 180-210° C.) for 1-5 hours (preferably 2-4 hours) to complete the carbonization of the iron active component to obtain an iron-based catalyst;

[0013] B. Precipitation method

[0014] The method comprises the following steps: (1) preparing a soluble iron salt solution, wherein the iron ion concentration of the iron salt solution is 0.02 to 2.0 mol / L (preferably 0.05 to 1.0 mol / L); (2) preparing an alkaline alkali metal solution, wherein the alkali metal ion concentration is 0.5 to 5 mol / L (preferably 1 to 3 mol / L); (3) gradually adding the alkali metal solution of step (2) to the iron salt solution of step (1) until the pH value of the solution changes to 9 to 10; stirring for 30 to 90 minutes, and separating the obtained product by centrifugation or filtration. The precipitated product is washed with distilled water until the pH value of the washing solution changes by 7-8, and the washed precipitated product is dried at 60-120° C. for 6-24 h; (4) the dried precipitated product is pretreated in an air atmosphere at 300-500° C. (preferably 350-450° C.) for 3-10 h (preferably 4-8 h) to remove impurities on the surface of the iron oxide; (5) the precipitated product is pretreated in a hydrogen flowing atmosphere at 270-450° C. (preferably 320-400° C.) for 2-50 h (preferably 4-30 h) for reduction; (6) the precipitated product is dried at 60-120° C. for 6-24 h; (7) the precipitated product is pretreated in an air atmosphere at 300-500° C. (preferably 350-450° C.) for 3-10 h (preferably 4-8 h) to remove impurities on the surface of the iron oxide; (8) the precipitated product is pretreated in a hydrogen flowing atmosphere at 270-450° C. (preferably 320-400° C.) for 2-50 h (preferably 4-30 h) for reduction; (9) the precipitated product is dried at 60-120° C. for 6-24 h; (10) the precipitated product is dried at 60-120° C. for 6-24 h; (11) the precipitated product is pretreated in an air atmosphere at 300-500° C. (preferably 350-450° C.) for 3-10 h (preferably 4-8 h) to remove impurities on the surface of the iron oxide; (12) the preci 2 / CO synthesis gas (H 2 / CO molar ratio = 0.5-8) 150-210°C (preferably 180-200°C) for 1-5 hours (preferably 2-4 hours) to complete the carbonization of the iron active components to obtain an iron-based catalyst.

[0015] In the catalyst preparation method, the alkali metal of the iron-based catalyst refers to one or more of Li, Na, K, Rb, and Cs, optimized to one or more of Na, K, Rb, and Cs, and optimally K; the soluble salt of the alkali metal refers to a salt compound that can be dissolved in water, preferably one or more of nitrate, carbonate, and acetate; the inert atmosphere gas is one or more of nitrogen and argon; the soluble iron salt in the precipitation method refers to an iron salt compound that can be dissolved in water, preferably one or more of nitrate, carbonate, and acetate; the alkali metal solution in step (2) of the precipitation method refers to one or more of alkali metal hydroxide, carbonate solution, acetate, and propionate; in step (3) of the precipitation method, the alkali metal content of the washed precipitated product is controlled by controlling the amount of distilled water used and the number of washing times.

[0016] The catalyst preparation method is characterized in that: the reduction step conditions are: normal pressure, H 2 :600~3000mL / (h·g cat ), 270~450℃, time: 2~50h; carbonization step conditions: 1.0~7.0MPa, synthesis gas: 500~8000mL / (h·g cat ), H in the synthesis gas 2 / CO molar ratio = 0.5-8, may or may not contain CO 2 , CO 2 It accounts for 0-10% of the synthesis gas.

[0017] The method for directly converting synthesis gas into multi-carbon aldehydes and ketones has a reaction temperature of 150-210° C. (preferably 170-200° C.), a reaction pressure of 1.0-7.0 MPa (preferably 2.0-5.0 MPa), and a raw gas space velocity of 500-8000 mL / (h·g cat ) preferably 1000 to 4000 mL / (h·g cat )).

[0018] The method for directly converting synthesis gas to prepare multi-carbon aldehydes and ketones can realize the low-temperature direct conversion of synthesis gas to synthesize multi-carbon aldehydes and ketones, the selectivity of aldehyde and ketone products can reach more than 40%, the multi-carbon aldehydes and ketones account for more than 99% of the aldehyde and ketone products, and the aldehyde-ketone mass ratio in the aldehyde and ketone products can be regulated in the range of 0.5-4.5; the multi-carbon aldehydes and ketones refer to multi-carbon aldehydes or multi-carbon ketones with a carbon number of 2-16 and a single carbonyl group (-C=O).

[0019] The present invention has the following characteristics:

[0020] (1) The catalyst used in the present invention is a single element Fe active component, and the catalyst preparation is simple, the selectivity is high, and the stability is good;

[0021] (2) The present invention can realize the low-temperature and high-selectivity conversion of synthesis gas into multi-carbon aldehydes and ketones, with a simple reaction device and a short process flow;

[0022] In the method, when the syngas conversion rate is lower than 210°C, high-selectivity conversion and synthesis of multi-carbon aldehydes and ketones can be achieved, the selectivity of multi-carbon aldehydes and ketones can be controlled to be above 40%, the multi-carbon aldehydes and ketones account for more than 99% of the aldehyde and ketone products, and the aldehyde-ketone mass ratio in the aldehyde and ketone products can be regulated within the range of 0.5-4.5. The present invention opens up a new route for the high-selectivity conversion and synthesis of multi-carbon aldehydes and ketones from syngas. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Distribution diagram of organic products from direct synthesis of multi-carbon aldehydes and ketones from syngas. In the diagram, hydrocarbon compounds refer to olefins and alkanes with carbon numbers of 1-18, alcohol compounds refer to monohydroxy alcohol compounds with carbon numbers of 1-13, and aldehyde and ketone compounds refer to monocarbonyl aldehyde compounds and ketone compounds with carbon numbers of 3-16. DETAILED DESCRIPTION

[0024] The technical details of the present invention are described in detail by the following examples. It should be noted that the examples are only used to further illustrate the technical features of the present invention, rather than to limit the present invention.

[0025] Example 1

[0026] Commercial Iron Oxide Pretreatment Impregnation Method

[0027] First, the ferroferric oxide with a particle size of 10-30 nm purchased from Shanghai Pantian Powder Material Co., Ltd. was pretreated in an air atmosphere at 500°C for 8 hours to remove impurities on the surface of the ferroferric oxide; secondly, KNO 3 Solution, KNO 3 The concentration in the solution is 0.5 mol / L; then 5 ml of KNO 3 The solution was immersed in 4.9 g of pretreated ferroferric oxide at 30 °C for 12 hours, dried at 80 °C for 12 hours, and calcined at 350 °C in air for 6 hours. 1.0 g of the calcined sample was placed in a hydrogen flowing atmosphere (normal pressure, H 2 :600mL / (h·g cat )) pre-treated for 20 h for reduction; switching the molar ratio H 2 / CO=2 synthesis gas (7.0MPa, 500mL / (h·g cat )) After the iron active component was carbonized at 200°C for 5 hours, an iron-based catalyst was obtained, which was labeled as catalyst A and has a composition shown in Table 6.

[0028] Catalyst A was loaded into a fixed bed reactor to test the performance of direct synthesis of polycarbon aldehydes and ketones from syngas. The reaction conditions were: the molar ratio of the raw gas to H2 / CO=2.0, temperature is 170-210℃ (specific values ​​are shown in Table 1), pressure is 4.0MPa, and the feed gas space velocity is 2400mL / (h·g cat The results of the reaction performance evaluation of direct synthesis of multi-carbon aldehydes and ketones from synthesis gas are listed in Table 1.

[0029] Table 1 Reaction performance of direct synthesis of multi-carbon aldehydes and ketones from syngas over catalyst A

[0030]

[0031] Note: Aldehydes and ketones in the table refer to aldehydes or ketones containing a single carbonyl group; other oxides refer to other oxygen-containing organic products (mainly alcohol compounds with carbon numbers of 1-13, trace amounts of ether compounds with carbon numbers of 2-10 and organic carboxylic acids); multi-carbon aldehydes and ketones refer to multi-carbon aldehydes or multi-carbon ketones with carbon numbers of 2-16 and a single carbonyl group (-C=O); aldehyde-ketone ratio refers to the mass ratio of multi-carbon aldehydes to multi-carbon alcohols. The meanings are the same as in the subsequent Tables 2-5, and will not be explained one by one.

[0032] It can be seen from the results in Table 1 that within the temperature range investigated, Catalyst A exhibits good performance in the conversion of syngas to multi-carbon aldehydes and ketones, especially at temperatures below 190°C, the selectivity of aldehydes and ketones in the product remains above 40%. As the reaction temperature increases, the CO conversion rate increases, and the results show that the optimal reaction temperature of Catalyst A is 180°C.

[0033] Example 2

[0034] Preparation of iron-based catalysts by precipitation method and their catalytic performance

[0035] First, 0.04 mol Fe(NO 3 ) 3 ˙9H 2 O was dissolved in 50 ml of water to prepare Fe salt solution; secondly, sodium carbonate solution was prepared. + The concentration is 1 mol / L; then, the prepared sodium carbonate solution is gradually added to the prepared Fe salt solution until the pH value of the solution changes to 9. Stir for 30 minutes, filter and separate the precipitate, wash twice with 100 ml of distilled water until the pH value is 8, dry the washed product at 80°C for 8 hours; calcine the dried precipitate at 350°C in air atmosphere for 6 hours; then calcine at 400°C in hydrogen flowing atmosphere (normal pressure, H 2 :3000mL / (h·g cat )) for 10 h for reduction; switching the molar ratio H 2 / CO=2 synthesis gas (1.0MPa, 8000mL / (h·g cat)) After the iron active component was carbonized at 190°C for 4 hours, an iron-based catalyst was obtained, which was labeled as catalyst B and has a composition shown in Table 6.

[0036] Catalyst B was loaded into a fixed bed reactor to test the performance of direct synthesis of polycarbon aldehydes and ketones from syngas. The reaction conditions were: the molar ratio of the raw gas to H 2 / CO=2.0, temperature is 190℃, pressure is 1.0-7.0MPa (specific values ​​are shown in Table 1), feed gas space velocity is 2400mL / (h·g cat The results of the reaction performance evaluation of direct synthesis of multi-carbon aldehydes and ketones from synthesis gas are listed in Table 2.

[0037] Table 2 Reaction performance of direct synthesis of polycarbon aldehydes and ketones from syngas over catalyst B

[0038]

[0039] It can be seen from the results in Table 2 that within the pressure range investigated, Catalyst B exhibits good performance in the conversion of syngas to multi-carbon aldehydes and ketones, and the selectivity of aldehydes and ketones in the product remains above 20%. With increasing pressure, the CO conversion rate increases, and it can be seen from the results that the optimal reaction pressure of Catalyst B is 3.0 MPa.

[0040] Example 3

[0041] The steps of catalyst preparation and evaluation were the same as those in Example 1, except that KNO 3 The solution was replaced with potassium acetate solution, K + The concentration of was modified to 2.5 mol / L, the obtained iron-based catalyst was marked as catalyst C, and the reaction conditions evaluated were replaced by: the molar ratio of the feed gas H 2 / CO=1.0, temperature is 200℃, pressure is 5.0MPa, raw gas space velocity is 1000~7000mL / (h·g cat ) (Specific values ​​are shown in Table 1). The evaluation results of the reaction performance of direct synthesis of multi-carbon aldehydes and ketones from synthesis gas over Catalyst C are listed in Table 3, and its composition is shown in Table 6.

[0042] Table 3 Reaction performance of direct synthesis of multi-carbon aldehydes and ketones from syngas over catalyst C

[0043]

[0044] From the results in Table 3, it can be seen that within the investigated space velocity range, Catalyst C exhibits good reaction performance for the conversion of syngas to multi-carbon aldehydes and ketones, and the selectivity of aldehydes and ketones in the product can reach up to 47.5%. As the reaction space velocity increases, the CO conversion rate decreases. From the results, it can be seen that the optimal reaction space velocity of Catalyst C is 1000 mL / (h·g cat ).

[0045] Example 4.

[0046] The steps of catalyst preparation and evaluation were the same as those in Example 2, except that 0.04 mol Fe(NO 3 ) 3 ˙9H 2 O was replaced by 0.04 mol Fe(NO 3 ) 2 ˙6H 2 O, the obtained iron-based catalyst is marked as catalyst D, and its composition is shown in Table 6. The reaction conditions evaluated were replaced by: the raw gas molar ratio H 2 / CO=2.0, temperature is 190℃, pressure is 4.0MPa, space velocity is 2000mL / (h·g cat The evaluation results of the reaction performance of direct synthesis of multi-carbon aldehydes and ketones from synthesis gas over catalyst D are listed in Table 4.

[0047] Example 5.

[0048] The steps of catalyst preparation and evaluation were the same as those of Example 2, except that the precipitate after drying in the preparation step was calcined at 350°C in an air atmosphere for 6 hours; and then heated at 400°C in a hydrogen flowing atmosphere (normal pressure, H 2 :3000mL / (h·g cat )) for 10 h for reduction; switch to synthesis gas (1.0 MPa, 8000 mL / (h·g cat )) After the iron active component is carbonized at 190°C for 4 hours to obtain an iron-based catalyst" is replaced by "the precipitated product after drying is calcined at 500°C in an air atmosphere for 3 hours; then calcined at 300°C in 10% hydrogen / N 2 Flowing atmosphere (normal pressure, H 2 :2000mL / (h·g cat )) Pre-treatment for 15h for restoration; switch H 2 / CO synthesis gas (3.0MPa, 3000mL / (h·g cat )) 200°C for 2 hours", the prepared iron-based catalyst is marked as catalyst E, and its composition is shown in Table 6. The reaction conditions evaluated are replaced by: the raw gas molar ratio H 2 / CO=3.0, temperature is 200℃, pressure is 4.0MPa, space velocity is 500mL / (h·g cat The evaluation results of the reaction performance of direct synthesis of multi-carbon aldehydes and ketones from synthesis gas over catalyst E are listed in Table 4.

[0049] Example 6.

[0050] The steps of catalyst preparation and evaluation were the same as those in Example 1, except that the ferroferric oxide was replaced by purchased α-iron oxide with a particle size of 10-100 nm. The prepared iron-based catalyst was marked as F, and its composition is shown in Table 6. The reaction conditions for evaluation were replaced by the raw gas molar ratio H 2 / CO=5.0,10%CO 2 , temperature is 180℃, pressure is 2.0MPa, space velocity is 8000mL / (h·g cat ), the reaction performance evaluation results of direct synthesis of multi-carbon aldehydes and ketones from synthesis gas over catalyst F are listed in Table 4.

[0051] Example 7.

[0052] The steps of catalyst preparation and evaluation were the same as those in Example 1, except that the ferroferric oxide was replaced by purchased α-iron oxide with a particle size of 10-100 nm and Al2O3 with a particle size of 50-500 nm. 2 O 3 , where Al 2 O 3 The mass ratio of α-iron oxide to α-iron oxide was 1:4. The prepared iron-based catalyst was marked as G, and its composition is shown in Table 6. The reaction conditions evaluated were replaced by the raw gas molar ratio H 2 / CO=5.0,3%CO 2 , temperature 180℃, pressure 3.0MPa, space velocity 2000mL / (h·g cat ), the reaction performance evaluation results of direct synthesis of multi-carbon aldehydes and ketones from synthesis gas over catalyst G are listed in Table 4.

[0053] Example 8.

[0054] The steps of catalyst preparation and evaluation were the same as those in Example 2, except that 0.10 g SiO was added during the precipitation process in the preparation step. 2 (Before adding sodium carbonate solution to Fe salt solution, 0.01g SiO 2 The prepared iron salt solution was added, and then the prepared sodium carbonate solution was gradually added to the prepared Fe salt solution until the pH value of the solution changed to 9). The prepared iron-based catalyst was marked as H, and its composition is shown in Table 6. The reaction conditions evaluated were replaced by the raw gas molar ratio H 2 / CO=2.0,3%CO 2 , temperature 180℃, pressure 4.0MPa, space velocity 1000mL / (h·g cat ), the reaction performance evaluation results of direct synthesis of multi-carbon aldehydes and ketones from syngas over catalyst H are listed in Table 4.

[0055] Table 4 Reaction performance of direct synthesis of polycarbon aldehydes and ketones from syngas over iron-based catalysts

[0056]

[0057] From the results in Table 4, it can be seen that catalyst DH exhibits good performance in the conversion of syngas to multi-carbon aldehydes and ketones, and the selectivity of aldehydes and ketones in the product can reach up to 40.2%. Among them, the selectivity of aldehydes and ketones of the iron-based catalyst modified by K is relatively high. 2 and Al 2 O 3 The carrier has a certain hydrogenation capacity, which leads to an increase in the CO conversion rate.

[0058] Example 9.

[0059] Under the following evaluation conditions: the raw gas molar ratio H 2 / CO=2.0, temperature is 180℃, pressure is 4.0MPa, space velocity is 4000mL / (h·g cat ) was investigated for the stability of the reaction performance of catalyst A for direct synthesis of multi-carbon aldehydes and ketones from synthesis gas, and the evaluation results are listed in Table 5.

[0060] Table 5 Stability of direct synthesis of polycarbon aldehydes and ketones from syngas over iron-based catalysts

[0061]

[0062] It can be seen from the results in Table 5 that catalyst A exhibits good reaction stability for converting syngas to multi-carbon aldehydes and ketones, the selectivity of aldehyde and ketone compounds in the product remains above 45%, and the selectivity of multi-carbon aldehydes and ketones in the product remains at 100%.

[0063] Example 10

[0064] Catalysts A and H were characterized by X-ray diffraction and Mössbauer spectra to determine the phase composition of the catalysts. The results are listed in Table 6. Table 6 Phase composition of iron-based catalysts

[0065]

[0066] It can be seen from Table 6 that the composition of the prepared iron-based catalyst is Fe 5 C 2 and Fe crystal phase, and Fe 5 C 2 Responsible for the dissociation of CO into CH x , synergistically with the Fe sites responsible for the non-dissociative adsorption of CO, promoted the direct and highly selective synthesis of multi-carbon aldehydes and ketones from syngas. In addition, compared with the crystalline phase composition of the Na-modified Fe-based catalyst, the Fe crystalline phase content of the K-modified catalyst was higher.

[0067] Embodiment 11

[0068] The steps of catalyst preparation and evaluation are the same as those in Example 1, except that the reaction conditions for evaluation are replaced by the raw gas molar ratio H 2 / CO=2.0, temperature is 190℃, pressure is 4.0MPa, space velocity is 2400mL / (h·g cat ), the product distribution results of direct synthesis of multi-carbon aldehydes and ketones from syngas over catalyst I are listed in Figure 1 .from Figure 1 It can be seen that the products of the prepared Fe-based catalyst are mainly oxygen-containing compounds, and the carbon numbers of multi-carbon aldehydes and ketones in the products are concentrated in the C 2 -C 13 .

Claims

1. A method for synthesizing polycarbon aldehydes and ketones from synthesis gas, characterized in that: The syngas feed gas is introduced into the reactor and contacts the iron-based catalyst therein to react at 150-210°C and 1.0-7.0 MPa to generate multi-carbon aldehydes and ketones; the feed gas space velocity is 500-8000 mL / (h∙g cat ); The iron-based catalyst is composed of at least Fe5C2, Fe and alkali metal, wherein the mass content of each component is: the active component Fe5C2 content is 23-55%, the active component Fe content is 15-40%, the alkali metal component content is 0.05-5%, and other components are Fe3O4 and Fe2C, and the mass ratio of Fe3O4 to Fe2C is 0.9-1.1:1; The synthesis gas is a raw gas containing carbon monoxide and hydrogen, wherein the molar ratio of H2 to CO is 0.5-8; the raw gas does not contain or contains one or more of CO2, CH4, C2H6, N2, Ar impurity gases, and the impurity gas content does not exceed 30% of the volume of the raw gas; The iron-based catalyst can be prepared by the following method A or method B: A. Commercial iron oxides, including pre-treatment impregnation of ferroferric oxide and / or ferric oxide Steps: (1) commercial iron oxide powder with a particle size range of 10-500nm is pretreated at 300-500℃ air atmosphere for 3-10 hours to remove impurities on the surface of the iron oxide; (2) a soluble salt solution of alkali metal is prepared, wherein the concentration of alkali metal ions in the soluble salt solution is 0.01-3.0 mol / L; (3) the salt solution of step (2) is impregnated with the pretreated iron oxide of step (1) at 10-60℃ for 2-24 hours, dried at 60-120℃ for 4-24 hours, and calcined at 350-550℃ in air and / or inert atmosphere for 2-18 hours; (2) the calcined sample obtained in step (3) is pretreated at 270-500℃ in hydrogen flowing atmosphere for 2-50h for reduction; (3) H2 / CO synthesis gas is switched, H2 / CO molar ratio = 0.5-8, and the iron-based catalyst is obtained after the iron active component is carbonized at 150-220℃ for 1-5 hours; B. Precipitation Method Steps: (1) preparing a soluble iron salt solution, wherein the iron ion concentration of the iron salt solution is 0.02-2.0 mol / L; (2) preparing an alkaline alkali metal solution, wherein the alkali metal ion concentration is 0.5-5 mol / L; (3) gradually adding the alkali metal solution of step (2) to the iron salt solution of step (1) until the pH value of the solution changes to 9-10; The mixture is stirred for 30 to 90 minutes, separated by centrifugation or filtration, and washed with distilled water until the pH value of the washing liquid changes by 7 to 8. The washed precipitate is dried at 60 to 120°C for 6 to 24 hours. (4) The dried precipitate is pretreated in an air atmosphere at 300 to 500°C for 3 to 10 hours to remove impurities on the surface of the iron oxide. (5) The precipitate is pretreated in a hydrogen flowing atmosphere at 270 to 450°C for 2 to 50 hours for reduction. (6) The H2 / CO synthesis gas is switched to a H2 / CO molar ratio of 0.5 to 8, and the iron-based catalyst is obtained by treating the precipitate at 150 to 210°C for 1 to 5 hours to complete the carbonization of the iron active component.

2. The method according to claim 1, characterized in that: The iron-based catalyst, wherein the mass content of each component is: the active component Fe5C2 content is 29-52%, the active component Fe content is 20-38%, and the alkali metal component content is 0.5-5%; The molar ratio of H2 to CO is 2-5; the impurity gas content does not exceed 10% of the raw gas volume; The iron-based catalyst can be prepared by the following method A or method B: A. Commercial iron oxides including ferroferric oxide and / or ferric oxide pre-impregnation Steps: (1) commercial iron oxide powder with a particle size range of 10-200nm is pretreated in an air atmosphere at 350-480℃ for 4-8 hours to remove impurities on the surface of the iron oxide; (2) a soluble salt solution of an alkali metal is prepared, wherein the concentration of alkali metal ions in the soluble salt solution is 0.1-2.5 mol / L; (3) the salt solution of step (2) is impregnated with the pretreated iron oxide of step (1) at 10-60℃ for 2-24 hours, dried at 60-120℃ for 4-24 hours, and calcined at 350-500℃ in air and / or inert atmosphere for 4-10 hours; (2) the calcined sample obtained in step (3) is pretreated in a hydrogen flowing atmosphere at 320-480℃ for 6-32h for reduction; (3) the iron-based catalyst is obtained after switching to H2 / CO synthesis gas at 180-210℃ for 2-4 hours to complete the carbonization of the iron active component; B. Precipitation Method Steps: (1) preparing a soluble iron salt solution, wherein the iron ion concentration of the iron salt solution is 0.05-1.0 mol / L; (2) preparing an alkaline alkali metal solution, wherein the alkali metal ion concentration is 1-3 mol / L; (3) gradually adding the alkali metal solution of step (2) to the iron salt solution of step (1) until the pH value of the solution changes to 9-10; Stir for 30 to 90 minutes, separate the precipitated product by centrifugation or filtration, wash with distilled water until the pH value of the washing solution changes by 7 to 8, and dry the washed precipitated product at 60 to 120°C for 6 to 24 hours; (4) pretreat the dried precipitated product in an air atmosphere at 350 to 450°C for 4 to 8 hours to remove impurities on the surface of the iron oxide; (5) pretreat the precipitated product in a hydrogen flowing atmosphere at 320 to 400°C for 4 to 30 hours for reduction; (6) switch to H2 / CO synthesis gas at 180 to 200°C for treatment for 2 to 4 hours to complete the carbonization of the iron active components to obtain an iron-based catalyst; The reaction temperature for the generation of multi-carbon aldehydes and ketones is 170-200°C, the reaction pressure is 2.0-5.0 MPa, and the feed gas space velocity is 1000-4000 mL / (h∙g cat ).

3. The method according to claim 1, characterized in that: The iron-based catalyst contains or does not contain a structural additive, which includes one or two of SiO2 and Al2O3, and the mass ratio of the additive to the total of Fe5C2, Fe, alkali metal, Fe3O4 and Fe2C in the catalyst is 0-0.25:

1.

4. The method according to claim 3, characterized in that: The mass ratio of the additive to the total of Fe5C2, Fe, alkali metal, Fe3O4 and Fe2C in the catalyst is 0-0.05:

1.

5. The method according to claim 1, characterized in that: The alkali metal of the iron-based catalyst refers to one or more of Li, Na, K, Rb, and Cs; The soluble salt of alkali metal in the impregnation method refers to one or more of nitrate, carbonate and acetate; The inert atmosphere gas is one or more of nitrogen and argon; The alkali metal solution in step (2) of the precipitation method refers to one or more of an alkali metal hydroxide solution, a carbonate solution, an acetate solution, and a propionate solution; In step (3) of the precipitation method, the alkali metal content of the washed precipitated product is controlled by controlling the amount of distilled water used and the number of washing times.

6. The method according to claim 5, characterized in that: The alkali metal of the iron-based catalyst refers to one or more of Na, K, Rb, and Cs; In the precipitation method, the soluble iron salt refers to one or more of nitrate, carbonate and acetate.

7. The method according to claim 1, characterized in that: Reduction step conditions: atmospheric pressure, H2: 600~3000 mL / (h·g cat ), 270~450℃, time: 2~50h; Carbonization step conditions: 1.0~7.0MPa, synthesis gas: 500~8000 mL / (h·g cat ), the H2 / CO molar ratio in the synthesis gas = 0.5~8; the synthesis gas contains or does not contain CO2, and CO2 accounts for 0~10% of the synthesis gas.

8. The method according to claim 7, characterized in that: The H2 / CO molar ratio in the synthesis gas is 2-5.

9. The method according to any one of claims 1 to 8, characterized in that: The multi-carbon aldehydes and ketones refer to multi-carbon aldehydes or multi-carbon ketones having a carbon number of 2 to 16 and containing a single carbonyl group.

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