Bivalent iron-containing catalysts, methods of making and using the same, and methods of producing nitrile compounds by ammoxidation of lower olefins

Abstract

This invention relates to a catalyst containing divalent iron, its preparation method and application, and a method for producing nitrile compounds by the ammoxidation reaction of low-carbon olefins. The catalyst comprises a support and an active component containing the following general formula: Mo 11.0 Bi b Fe c D d E e F f O x In the formula, D is selected from at least one of Li, Na, K, Rb, and Cs; E is selected from at least one of rare earth elements La, Pr, Nd, Sm, and Eu; F is selected from at least one of Ca, Mg, Zr, Te, Sb, Ni, Cr, W, and Nb; wherein b ranges from 0.1 to 5.0; c ranges from 0.1 to 5.0; d ranges from 0.1 to 5.0; e ranges from 0.1 to 5.0; f ranges from 0.1 to 15.0; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst; the catalyst crystal structure contains a divalent iron phase. The catalyst of this invention is applied to the ammoxidation of propylene to acrylonitrile, and has the characteristics of high propylene conversion rate and acrylonitrile selectivity.

Description

Technical Field

[0001] This invention relates to a catalyst containing divalent iron, its preparation method and application, and a method for producing nitrile compounds by ammoxidation of low-carbon olefins. Background Technology

[0002] Currently, the industrial production of unsaturated nitriles by propylene ammoxidation generally adopts the fluidized bed ammoxidation process. As one of the core technologies of this process, the research and improvement of catalysts have always been emphasized. At present, there are two main types of catalysts for the industrial ammoxidation of propylene to acrylonitrile: Mo-Bi-based and Sb-based. Among them, Mo-Bi-based catalysts dominate, accounting for 95% of the olefin ammoxidation market, and previous research and exploration have mainly focused on Mo-Bi-based catalysts.

[0003] The activity of a catalyst can be improved by introducing metal components with variable valence states, such as Fe and Ce. Metal elements with ionic radii greater than 0.8 nm and less than 0.8 nm, such as Cr, Ni, Mg, Mn, Zn, and Al, can act as structural and electronic promoters, improving the structure and stability of the catalyst. The introduction of rare earth elements can increase the number of lattice oxygens in the catalyst, thereby improving its catalytic performance. The introduction of elements such as Cs, Rb, P, B, and Al can modify the surface of the catalyst and adjust its acidity and basicity, thereby improving its selectivity and activity.

[0004] US 8455388 reports a Mo containing Ce. 12 Bi a Fe b A c D d E e F f G g Ce hOx compounds, wherein A is at least one of sodium, potassium, rubidium, and cesium; D is at least one of nickel, cobalt, magnesium, zinc, manganese, calcium, strontium, cadmium, and barium; E is at least one of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium, and tellurium; F is at least one of titanium, zirconium, hafnium, niobium, tantalum, thallium, and germanium; and G is at least one of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum, and mercury. The proportions of each atom are restricted to 0.05≤a≤7, 0.1≤b≤7, 0.01≤c≤5, 0.1≤d≤12, 0≤e≤5, 0≤f≤5, 0≤g≤0.2, and 0.01≤h≤5, wherein 0.15≤(a+h) / d≤1 and 0.8≤h / b≤5. The X-ray peak intensity at 2θ = 28 ± 0.3° and the Y-ray peak intensity at 2θ = 26.5 ± 0.3° in the XRD pattern are selected, with the X / Y ratio equal to or greater than 0.7. When 0.2 ≤ (a + h) / d ≤ 0.6 and 1 ≤ h / b ≤ 3, the X / Y ratio is equal to or greater than 0.8; when 0.3 ≤ (a + h) / d ≤ 0.5 and 1.5 ≤ h / b ≤ 2, the X / Y ratio is equal to or greater than 0.9. It only states that the catalyst contains Fe, but does not provide a detailed explanation of the phase in which Fe exists. Summary of the Invention

[0005] The technical problem to be solved by this invention is to improve the feed conversion rate and target product selectivity of ammonia oxidation catalysts.

[0006] It is generally believed that Fe exists primarily as ferric molybdate Fe2(MoO4)3 in fresh Mo-Bi catalysts after calcination. During the redox reaction, Fe2(MoO4)3 is reduced to ferrous molybdate FeMoO4 by the reducing agent, and then FeMoO4 is oxidized back to Fe2(MoO4)3 by oxygen supplementation with air. In the reaction, Fe... 3+ / Fe 2+ The presence of electron pairs plays a crucial role in promoting the rapid migration of oxygen in oxide lattices. However, this invention has found that the ease of FeMoO4 phase formation and the role of Fe in redox cycles are influenced by factors such as the degree of Fe... 3+ / Fe 2+ The number of electron pairs has a significant impact on the oxygen migration ability of oxide lattices, the activity and stability of catalysts.

[0007] According to a first aspect of the present invention, a catalyst containing divalent iron is provided, the catalyst comprising a support and an active component containing the following general formula:

[0008] Mo 11.0 Bi b Fe c D d E e F f O x,

[0009] In the formula, D is selected from at least one of Li, Na, K, Rb and Cs;

[0010] E is selected from at least one of the rare earth elements La, Pr, Nd, Sm and Eu;

[0011] F is selected from at least one of Ca, Mg, Zr, Te, Sb, Ni, Cr, W, and Nb;

[0012] in,

[0013] The value of b ranges from 0.1 to 5.0; the value of c ranges from 0.1 to 5.0; the value of d ranges from 0.1 to 5.0; the value of e ranges from 0.1 to 5.0; the value of f ranges from 0.1 to 15.0; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst; the catalyst crystal structure contains a divalent iron phase.

[0014] According to a second aspect of the present invention, the present invention provides a method for preparing the divalent iron catalyst of the present invention, the method comprising:

[0015] (a) Dissolve the Mo source to obtain molybdenum-containing solution I;

[0016] (b) Dissolve the Fe source, organic acid additive and E source to obtain iron-containing solution II;

[0017] (c) Dissolve the remaining active component sources to obtain active component solution III;

[0018] (d) Mix the required amount of carrier source with molybdenum-containing solution I and divide it into two portions by volume, labeled as molybdenum-supported solution I′ and molybdenum-supported solution I″.

[0019] (e) Iron-containing solution II is mixed with molybdenum-supported solution I′ to form coprecipitate slurry II′, and its pH value is adjusted to 1.0-8.0 with an alkaline substance; active component solution III is mixed with molybdenum-supported solution I′ to form coprecipitate slurry III′;

[0020] (f) Subsequently, the coprecipitated slurry II′ and coprecipitated slurry III′ were mixed and matured, and then dried and calcined to obtain the catalyst.

[0021] According to a third aspect of the present invention, the present invention provides the application of the catalyst described herein in an ammonia oxidation reaction, preferably in the ammonia oxidation reaction of low-carbon olefins, more preferably in the low-carbon olefins being propylene and / or isobutylene.

[0022] According to a fourth aspect of the present invention, the present invention provides a method for producing nitrile compounds by ammoxidation of low-carbon olefins, the method comprising: performing an ammoxidation reaction using low-carbon olefins, ammonia, and air as raw materials.

[0023] In the catalyst of this invention, the coexistence of divalent and trivalent iron phases facilitates the rapid migration of lattice oxygen at lower reaction temperatures, resulting in better catalyst performance, particularly better ammonia oxidation performance, especially for the ammonia oxidation of low-carbon olefins.

[0024] The key technology of this invention is that in the catalyst preparation process, Fe source and organic acid additives are used in combination with other technologies of this invention. Through the co-precipitation method of this invention and by adjusting its pH value, compared with the direct use of iron raw materials with nitrates and the slurry without pH adjustment, the catalyst is characterized by oxygen programmed temperature rise oxidation (i.e. O2-TPO) after calcination. The detection of oxygen consumption peak indicates that there are low-valence compounds in the catalyst that can be oxidized. XRD detection shows that there is a divalent iron phase in the crystal structure.

[0025] This invention effectively solves the problem of low propylene conversion and acrylonitrile yield in existing catalysts for ammonia oxidation, such as the ammonia oxidation of propylene to acrylonitrile. The catalyst of this invention, when applied to the ammonia oxidation to acrylonitrile, has the characteristics of high conversion rate and acrylonitrile selectivity. Attached Figure Description

[0026] Figure 1 This is the XRD pattern of Example 1;

[0027] Figure 2 These are the O2-TPO diagrams for Example 1 and Comparative Example 1. Detailed Implementation

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] This invention provides a catalyst containing divalent iron, the catalyst comprising a support and an active component represented by the following general formula:

[0030] Mo 11.0 Bi b Fe c D d E e F f O x ,

[0031] In the formula, D is selected from at least one of Li, Na, K, Rb and Cs;

[0032] E is selected from at least one of the rare earth elements La, Pr, Nd, Sm and Eu;

[0033] F is selected from at least one of Ca, Mg, Zr, Te, Sb, Ni, Cr, W, and Nb;

[0034] in,

[0035] The values ​​of b range from 0.1 to 5.0; the values ​​of c range from 0.1 to 5.0; the values ​​of d range from 0.1 to 5.0; the values ​​of e range from 0.1 to 5.0; the values ​​of f range from 0.1 to 15.0; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst; the crystal structure of the catalyst contains a divalent iron phase.

[0036] The catalyst of this invention, after calcination, was analyzed by XRD, and a divalent iron phase was found in its crystal structure.

[0037] In this invention, the range of selectable contents of the support and active component is relatively wide, and commonly used content ranges can be used in this invention. For this invention, it is preferred that the support, calculated as oxide, is 30-65% of the catalyst weight and the active component is 35-70% of the catalyst weight.

[0038] The catalyst of the present invention contains low-valence compounds that can be oxidized. That is, after the catalyst is calcined at high temperature, it is subjected to oxygen programmed temperature oxidation (i.e., O2-TPO characterization) and low-valence compounds that can be oxidized are detected.

[0039] In this invention, there are no special requirements for the preparation method of the catalyst; as long as a catalyst with the aforementioned characteristics can be prepared, the purpose of this invention can be achieved. According to a preferred embodiment of this invention, a method for preparing the catalyst containing divalent iron is provided, the method comprising:

[0040] (a) Dissolve the Mo source to obtain molybdenum-containing solution I;

[0041] (b) Dissolve the Fe source, organic acid additive and E source to obtain iron-containing solution II;

[0042] (c) Dissolve the remaining active component sources to obtain active component solution III;

[0043] (d) Mix the required amount of carrier source with molybdenum-containing solution I and divide it into two portions by volume, labeled as molybdenum-supported solution I′ and molybdenum-supported solution I″.

[0044] (e) Iron-containing solution II is mixed with molybdenum-supported solution I′ to form coprecipitate slurry II′, and the pH value of coprecipitate slurry II′ is controlled to 1.0-8.0; active component solution III is mixed with molybdenum-supported solution I′ to form coprecipitate slurry III′;

[0045] (f) Subsequently, coprecipitated slurry II′ and coprecipitated slurry III′ were mixed and matured, and then dried and calcined to obtain the catalyst.

[0046] In this invention, the Fe element is used as a Fe source and an organic acid auxiliary as raw materials, and is applied to the catalyst preparation process in a timely manner through a co-precipitation method.

[0047] In this invention, dissolution is achieved by heating as needed, which is well known to those skilled in the art and will not be described in detail here.

[0048] The key technology of this invention lies in the use of Fe source and organic acid additives as raw materials in the catalyst preparation process, combined with other techniques of this invention, including co-precipitation and pH adjustment. Compared to directly using iron raw materials with nitrates without pH adjustment, the catalyst, after calcination, is characterized by oxygen programmed temperature oxidation (O2-TPO). This reveals the presence of oxidizable reducing compounds in the catalyst, and XRD analysis shows the presence of divalent iron phases in the crystal structure. The coexistence of divalent and trivalent iron phases in the catalyst facilitates the rapid migration of lattice oxygen at lower reaction temperatures, resulting in better catalyst reactivity.

[0049] In this invention, the volume ratio of molybdenum-supported solution I′ to molybdenum-supported solution I″ can be selected within a wide range. For this invention, the preferred volume ratio of molybdenum-supported solution I′ to molybdenum-supported solution I″ is 1:0.5 to 5, and more preferably 1:1 to 3. Dividing the molybdenum-supported solution into two parts allows for batch co-precipitation with iron-containing solutions II and III.

[0050] In this invention, the range of types of organic acid auxiliaries is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the organic acid auxiliaries are one or more of tartaric acid, citric acid, and oxalic acid, preferably oxalic acid, and more preferably oxalic acid dihydrate.

[0051] In this invention, the range of selectable amounts of organic acid additives is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the molar ratio of organic acid additives to Fe ions in the iron source is 0.5 to 5.0, preferably 1.0 to 2.5, including but not limited to 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, etc.

[0052] In this invention, the range of Fe sources is relatively wide, and commonly used Fe sources can all achieve the purpose of this invention. For this invention, ferric nitrate, ferric sulfate, and ferric citrate are preferred, with ferric citrate being the most preferred.

[0053] In this invention, the range of alkaline substances is relatively wide, and commonly used alkaline substances can achieve the purpose of this invention. For this invention, the alkaline substance is preferably an inorganic alkali, such as one or more of potassium hydroxide, sodium hydroxide, and ammonia water, and ammonia water is particularly preferred.

[0054] In this invention, the pH value of the co-precipitation slurry II′ is preferably 3.0 to 7.0, including but not limited to 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, and 6.5. This can further improve the performance of the catalyst.

[0055] In this invention, the range of curing conditions is relatively wide. For this invention, in the preferred step (f), the curing conditions include: a temperature of 40-150°C, preferably 50-120°C, and preferably 80-100°C.

[0056] In this invention, the preferred curing conditions in step (f) include: a curing time of 10 minutes to 10.0 hours, preferably 30 minutes to 5 hours, and more preferably 1 to 3 hours.

[0057] In this invention, the range of drying conditions is relatively wide, and commonly used drying methods and steps are all applicable to this invention. For this invention, in step (f), the drying conditions in the oven include: a temperature of 80 to 160°C, preferably 90 to 150°C.

[0058] For the present invention, the drying time is determined as needed. The following is an illustrative description, but it is not limited to the scope of the present invention. For the present invention, in the preferred step (f), the oven drying conditions include: a time of 5.0 to 24.0 hours, preferably 8.0 to 12.0 hours.

[0059] In this invention, the range of selectable calcination conditions is relatively wide, and commonly used calcination conditions can all be used in this invention. For this invention, in the preferred step (f), the calcination conditions include: the calcination environment adopts an air atmosphere, or a mixed atmosphere of trace reducing gas and air. Preferably, in the mixed atmosphere, the volume percentage of reducing gas is 0.01-3.0%, more preferably 0.5-2.5%. There are many types of reducing gases. In this invention, ammonia is used as an example to illustrate the advantages of this invention.

[0060] In this invention, the range of selectable roasting temperatures is relatively wide. For this invention, the preferred roasting temperature is 550–650°C.

[0061] In this invention, the roasting time is determined according to the requirements. For this invention, the roasting time is 0.5 to 2.5 hours.

[0062] In this invention, there are no special requirements for the concentration of each solution. The preferred embodiments of this invention are described below, but they do not limit the scope of this invention.

[0063] For the present invention, the preferred concentration of Mo in the molybdenum-containing solution I is 2.0–8.0 mol / L, more preferably 2.5–5.5 mol / L, including but not limited to 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, and 5.4 mol / L.

[0064] For the present invention, the total metal ion concentration of iron-containing solution II is preferably 1.0 to 5.0 mol / L, more preferably 2.5 to 4.2 mol / L, including but not limited to 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0 mol / L, etc.

[0065] For the present invention, the total metal ion concentration of active component solution III is preferably 3.0 to 14.0 mol / L, more preferably 4.0 to 6.0 mol / L.

[0066] In this invention, the range of carrier sources that can be selected is relatively wide, and commonly used carrier sources can all be used in this invention. The preferred embodiments of this invention are described below, but this does not limit the scope of this invention.

[0067] For the present invention, the preferred carrier source is selected from silica sol, preferably wherein the silica weight content is 25-50%, more preferably 30-40%, for example, silica sol with a silica content of 30%, 40% or 45%.

[0068] This invention provides the application of the catalyst described herein in ammonia oxidation reactions, preferably in the ammonia oxidation reactions of low-carbon olefins, and more preferably in the low-carbon olefins being propylene and / or isobutylene.

[0069] This invention provides a method for producing nitrile compounds by ammoxidation of low-carbon olefins. The method includes: ammoxidation of low-carbon olefins, ammonia, and air as raw materials. In this invention, the range of selectable reaction conditions is relatively wide, and commonly used reaction conditions can be used in this invention. The preferred embodiments of this invention are described below, but they do not limit the scope of this invention.

[0070] For the present invention, the preferred raw material molar ratio is: propylene / ammonia / air = 1:(1.05~1.3):(9.2~9.8).

[0071] For the present invention, the preferred reaction temperature is 420–440°C.

[0072] For the present invention, the preferred reaction pressure is 0 to 0.14 MPa.

[0073] For the present invention, the preferred olefin feedstock loading (WWH) of the catalyst is 0.06–0.10 h. -1 .

[0074] In this invention, low-carbon olefin feedstocks can undergo ammoxidation reaction to produce nitrile compounds under the conditions described for the presence of a catalyst. The low-carbon olefin feedstocks are propylene and isobutylene, and the nitrile compounds produced are acrylonitrile and methacrylonitrile.

[0075] In this invention, the catalyst is used in the ammoxidation reaction of low-carbon olefins to produce nitrile compounds. Preferably, propylene, ammonia, and air are used as raw materials for the ammoxidation reaction to produce acrylonitrile, wherein the molar ratio of the raw materials is propylene / ammonia / air = 1 / 1.05–1.3 / 9.2–9.8, the preferred reaction temperature is 420–440°C, the preferred reaction pressure is 0–0.14 MPa, and the preferred propylene loading (WWH) of the catalyst is 0.06–0.10 h⁻¹. -1 .

[0076] The activity evaluation of the catalyst of this invention was carried out in a fixed-bed reactor with an inner diameter of 6 mm. The catalyst loading was 0.5 g, the reaction temperature was 430 °C, the propylene / ammonia / air molar ratio was 1:1.25:9.7, the reaction pressure was atmospheric pressure, and the reaction load (WWH) was 0.085 h⁻¹. -1 Under these conditions, better results were achieved.

[0077] In this invention, propylene conversion, acrylonitrile selectivity, and single-pass yield are defined as follows:

[0078]

[0079]

[0080]

[0081] XRD testing conditions, instrument: D8 ADVANCE, CuK α Source, scanning speed 0.5° / minute;

[0082] O2-TPO detection conditions: Instrument: Bio-Tech PCA-1200S chemisorption analyzer, catalyst loading 0.08 g, 10% O2 / He flow rate 50 ml / min, heating rate 10℃ / min.

[0083] The present invention will be further illustrated below with specific embodiments, but the present invention is not limited to the following embodiments.

[0084] Example 1

[0085] Weigh out 98.5 grams of (NH4)6Mo7O 24 ·4H2O

[0086] Add 105 g of water and heat to dissolve to obtain solution (Ⅰ), in which the molar concentration of Mo ions is 5.0 mol / L.

[0087] 36.4 g of ferric citrate (FeC6H5O7), 18.8 g of oxalic acid dihydrate, 5.2 g of Pr(NO3)3·6H2O, and 3.3 g of Nd(NO3)3·6H2O were weighed and dissolved in 40 g of water by heating to obtain solution (II). The total molar concentration of Fe, Pr, and Nd ions was 3.5 mol / L, and the molar ratio of oxalic acid to Fe ions was 1.0.

[0088] 43.2 g of Bi(NO3)3·5H2O, 23.1 g of Mg(NO3)2·6H2O, 6.7 g of RbNO3, 136.8 g of Ni(NO3)2·6H2O, and 1.2 g of CrO3 were weighed and dissolved in 60 g of water by heating to obtain solution (III). The total molar concentration of Bi, Mg, Rb, Ni, and Cr ions was 5.5 mol / L.

[0089] Weigh 172 grams of silica sol with a silica content of 40% by weight, mix it with solution I, and divide it into two portions at a volume ratio of 1:3. These portions are labeled as solution I′ and solution I″, with the smaller portion being solution I′.

[0090] Solution II and solution I′ are mixed to form coprecipitate slurry II′, and its pH is adjusted to 5.0 with 10% (v / v) dilute ammonia. Solution III and solution I′ are mixed to form coprecipitate slurry III′.

[0091] Slurry II′ and slurry III′ were mixed and stirred, then matured at 90°C for 1.0 hour, followed by drying in an oven at 120°C for 8 hours, and finally calcined at 600°C for 1.5 hours in a muffle furnace with an air atmosphere containing 0.5% (by volume) ammonia to obtain a product with the composition Mo. 11.0 Bi 1.8 Fe 2.9 Pr 0.2 Nd 0.1 Mg 1.8 Ni 9.3 Rb 0.9 Cr 0.2 O x The catalyst, wherein the support accounts for 30.0% by weight.

[0092] XRD patterns as follows Figure 1 As shown in the figure, in addition to Fe2(MoO4)3, the calcined catalyst also contains the FeMoO4 phase. The O2-TPO diagram is shown below. Figure 2 As shown in the figure, the calcined catalyst exhibits oxygen consumption peaks at 537℃ and 630℃, indicating the presence of oxidizable low-valence compounds in the catalyst.

[0093] Example 2

[0094] Weigh out 104.7 grams of (NH4)6Mo7O 24 · 4H2O was added to 150g of water and heated to dissolve, resulting in solution (Ⅰ), in which the molar concentration of Mo ions was 3.8mol / L.

[0095] 44.6 g of ferric citrate (FeC6H5O7), 28.7 g of oxalic acid dihydrate, and 7.8 g of Nd(NO3)3·6H2O were weighed and dissolved in 66 g of water by heating to obtain solution (II). The total molar concentration of Fe and Nd ions was 2.6 mol / L, and the molar ratio of oxalic acid to Fe ions was 1.2.

[0096] 51.7 g of Bi(NO3)3·5H2O, 30.2 g of Mg(NO3)2·6H2O, 8.9 g of RbNO3, 159.2 g of Ni(NO3)2·6H2O, and 3.5 g of Ca(NO3)2·4H2O were weighed and dissolved in 105 g of water by heating to obtain solution (Ⅲ). The total molar concentration of Bi, Mg, Rb, Ni, and Ca ions was 4.5 mol / L.

[0097] Weigh 217 grams of silica sol with a silica content of 40% by weight, mix it with solution I, and divide it into two portions at a volume ratio of 1:2, labeled as solution I′ and solution I″ respectively, with the smaller volume being solution I′.

[0098] Solution II and solution I′ are mixed to form coprecipitate slurry II′, and its pH is adjusted to 3.0 with 10% (v / v) dilute ammonia. Solution III and solution I′ are mixed to form coprecipitate slurry III′.

[0099] Slurry II′ and slurry III′ were mixed and stirred, then matured at 100°C for 2 hours, followed by drying in an oven at 110°C for 12 hours, and finally calcined at 630°C for 2.0 hours in a muffle furnace with an air atmosphere containing 1.5% (by volume) ammonia to obtain a product with the composition Mo. 11.0 Bi 2.0 Fe 3.4 Nd 0.3 Mg 2.2 Ni 10.2 Rb 1.1 Ca 0.3 O x The catalyst, wherein the support accounts for 32.6% by weight.

[0100] The XRD pattern and O2-TPO pattern are similar to those in Example 1.

[0101] Example 3

[0102] Weigh out 89.6 grams of (NH4)6Mo7O 24170 g of 4H2O was added and heated to dissolve the solution to obtain solution (Ⅰ), in which the molar concentration of Mo ions was 2.9 mol / L.

[0103] Weigh out 53.6 g of ferric citrate (FeC6H5O7), 38.6 g of oxalic acid dihydrate, and 8.9 g of Pr(NO3)3·6H2O, add 80 g of the solution, and heat to dissolve to obtain solution (II). The total molar concentration of Fe and Pr ions is 2.6 mol / L, and the molar ratio of oxalic acid to Fe ions is 1.4.

[0104] 48.9 g of Bi(NO3)3·5H2O, 28.6 g of Mg(NO3)2·6H2O, 5.1 g of CsNO3, 138.4 g of Ni(NO3)2·6H2O, 4.2 g of Zr(NO3)4·5H2O, and 1.2 g of CrO3 were weighed and dissolved in 76 g of water by heating to obtain solution (Ⅲ). The total molar concentration of Bi, Mg, Cs, Ni, Zr, and Cr ions was 4.9 mol / L.

[0105] Weigh 295 grams of silica sol with a silica content of 30% by weight, mix it with solution I, and divide it into two equal portions at a volume ratio of 1:1, which are labeled as solution I′ and solution I″ respectively.

[0106] Solution II and solution I′ are mixed to form coprecipitate slurry II′, and its pH is adjusted to 6.5 with 10% (v / v) dilute ammonia. Solution III and solution I′ are mixed to form coprecipitate slurry III′.

[0107] Slurry II′ and slurry III′ were mixed and stirred, then matured at 80°C for 3 hours, followed by drying in an oven at 100°C for 10 hours, and finally calcined at 610°C for 0.5 hours in a muffle furnace with an air atmosphere containing 2.5% (by volume) ammonia to obtain a product with the composition Mo. 11.0 Bi 2.2 Fe 4.7 Pr 0.4 Mg 2.4 Ni 10.3 Cs 0.6 Z r0.2 Cr 0.3 O x The catalyst, wherein the support accounts for 35.1% by weight.

[0108] The XRD pattern and O2-TPO pattern are similar to those in Example 1.

[0109] Example 4

[0110] The method is the same as in Example 1, except that "after mixing the silica sol and solution I, it is divided into two parts at a volume ratio of 1:3" is replaced with "after mixing the silica sol and solution I, it is divided into two parts at a volume ratio of 1:4, with the smaller volume being the molybdenum-supported solution I′". The other steps are the same as in Example 1.

[0111] The XRD pattern and O2-TPO pattern are similar to those in Example 1.

[0112] Example 5

[0113] The method is the same as in Example 1, except that "18.8 g of oxalic acid dihydrate" is replaced with "17.5 g of tartaric acid", the molar ratio of tartaric acid to Fe ions is 0.8, and the other steps are the same as in Example 1.

[0114] The XRD pattern and O2-TPO pattern are similar to those in Example 1.

[0115] Example 6

[0116] The method is the same as in Example 1, except that "cooking at 90°C for 1.0 hour" is replaced with "cooking at 40°C for 15 minutes", and the other steps are the same as in Example 1.

[0117] The XRD pattern and O2-TPO pattern are similar to those in Example 1.

[0118] Example 7

[0119] The method is the same as in Example 1, except that the calcination is carried out in an ammonia-free air atmosphere, while the other steps are the same as in Example 1.

[0120] The XRD pattern and O2-TPO pattern are similar to those in Example 1.

[0121] Comparative Example 1

[0122] The method is the same as in Example 1, except that oxalic acid was not added in step (b) and the coprecipitated slurry II′ was not pH adjusted; the other steps are the same as in Example 1. The O2-TPO diagram is shown below. Figure 2 As shown in the figure, there are no obvious oxygen consumption peaks at around 530℃ and 600℃, indicating that there are relatively few low-valence compounds in the catalyst that can be oxidized.

[0123] Comparative Example 2

[0124] The method was followed in Example 1, except that the molybdenum-supported solution was not divided into two portions, oxalic acid was not added in step (b), and all solutions were directly mixed uniformly to form a coprecipitate slurry. Furthermore, the coprecipitate slurry was not pH-adjusted and was calcined in air. Other steps and processing conditions were the same as in Example 1. The O2-TPO diagram is shown below. Figure 2As shown in the figure, there are no obvious oxygen consumption peaks at around 530℃ and 600℃, indicating that there are relatively few low-valence compounds in the catalyst that can be oxidized.

[0125] The catalysts prepared in the examples and comparative examples were subjected to the reaction of propylene ammoxidation to acrylonitrile under the following reaction conditions, and the results are shown in Table 1.

[0126] φ6 mm fixed bed reactor

[0127] Reaction temperature 430℃

[0128] Reaction pressure: atmospheric pressure

[0129] Catalyst loading: 0.5 grams

[0130] Catalyst propylene loading (WWH) 0.085h -1

[0131] Raw material ratio (moles): Propylene / Ammonia / Air = 1 / 1.25 / 9.7

[0132] Table 1

[0133]

[0134]

[0135] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst containing divalent iron, characterized in that, The catalyst comprises a support and an active component represented by the following general formula: Mo 11.0 Bi b Feb c D d HAVE BEEN e F f O x , In the formula, D is selected from at least one of Li, Na, K, Rb and Cs; E is selected from at least one of the rare earth elements La, Pr, Nd, Sm and Eu; F is selected from at least one of Ca, Mg, Zr, Te, Sb, Ni, Cr, W, and Nb; in, The value of b ranges from 0.1 to 5.0; the value of c ranges from 0.1 to 5.0; the value of d ranges from 0.1 to 5.0; the value of e ranges from 0.1 to 5.0; the value of f ranges from 0.1 to 15.0; and x is the total number of oxygen atoms required to satisfy the oxidation states of each element in the catalyst. The catalyst crystal structure contains a divalent iron phase.

2. The catalyst according to claim 1, wherein, Based on oxides, the support comprises 30-65% of the catalyst weight, and the active component comprises 35-70% of the catalyst weight; and / or The catalyst contains low-valence compounds that can be oxidized.

3. The method for preparing the catalyst containing divalent iron according to claim 1 or 2, characterized in that, The method includes: (a) Dissolve the Mo source to obtain molybdenum-containing solution I; (b) Dissolve the Fe source, organic acid additive and E source to obtain iron-containing solution II; (c) Dissolve the remaining active component sources to obtain active component solution III; (d) Mix the required amount of carrier source with molybdenum-containing solution I and divide it into two portions by volume, labeled as molybdenum-supported solution I′ and molybdenum-supported solution I″. (e) Iron-containing solution II is mixed with molybdenum-supported solution I′ to form coprecipitate slurry II′, and the pH value of coprecipitate slurry II′ is controlled at 1.0~8.0; active component solution III is mixed with molybdenum-supported solution I′ to form coprecipitate slurry III′; (f) Subsequently, coprecipitated slurry II′ and coprecipitated slurry III′ were mixed and matured, and then dried and calcined to obtain the catalyst.

4. The preparation method according to claim 3, wherein, The volume ratio of molybdenum-supported solution I′ to molybdenum-supported solution I″ is 1:0.5~5.

5. The preparation method according to claim 4, wherein, The volume ratio of molybdenum-supported solution I′ to molybdenum-supported solution I″ is 1:1~3.

6. The preparation method according to claim 3, wherein, In step (b), The organic acid auxiliaries are one or more of tartaric acid, citric acid, and oxalic acid; and / or The molar ratio of organic acid additives to Fe ions in the iron source is 0.5~5.

0.

7. The preparation method according to claim 6, wherein, In step (b), The organic acid auxiliaries are oxalic acid; and / or The molar ratio of organic acid additives to Fe ions in the iron source is 1.0~2.

5.

8. The preparation method according to claim 7, wherein, In step (b), the organic acid auxiliary is oxalic acid dihydrate.

9. The preparation method according to claim 3, wherein, In step (b), the Fe source is one or more of ferric nitrate, ferric sulfate, and ferric citrate.

10. The preparation method according to claim 9, wherein, In step (b), the Fe source is ferric citrate.

11. The preparation method according to claim 3, wherein, In step (e), The alkaline substance is an inorganic base; The pH value of coprecipitated slurry II′ is 3.0 ~ 7.

0.

12. The preparation method according to claim 11, wherein, In step (e), the alkaline substance is one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

13. The preparation method according to claim 12, wherein, In step (e), the alkaline substance is ammonia.

14. The preparation method according to claim 3, wherein, In step (f), The conditions for ripening include: a temperature of 40~150℃; and / or The time ranges from 10 minutes to 10.0 hours.

15. The preparation method according to claim 14, wherein, In step (f), The conditions for ripening include: a temperature of 50~120℃; and / or The time ranges from 30 minutes to 5.0 hours.

16. The preparation method according to claim 3, wherein, In step (f), Drying conditions include a temperature of 80~160℃; The time is 5.0 to 24.0 hours.

17. The preparation method according to claim 16, wherein, In step (f), Drying conditions include a temperature of 90~150℃; The time is 8.0~12.0 hours.

18. The preparation method according to claim 3, wherein, In step (f), the calcination conditions include: the calcination environment is an air atmosphere, or a mixture of trace reducing gas and air; The roasting temperature is 550~650℃, and the time is 30 minutes to 2.5 hours.

19. The preparation method according to claim 18, wherein, In the mixed atmosphere, the volume percentage of the reducing gas is 0.01~3.0%, and the reducing gas is ammonia.

20. The preparation method according to claim 19, wherein, In the mixed atmosphere, the volume percentage of reducing gas is 0.5% to 2.5%.

21. The preparation method according to claim 3, wherein, The concentration of Mo in molybdenum-containing solution I is 2.0–8.0 mol / L; and / or The total metal ion concentration of iron-containing solution II is 1.0–5.0 mol / L; and / or The total metal ion concentration of active component solution III is 3.0–14.0 mol / L; and / or The carrier source is selected from silica sol, wherein the weight content of silica is 25-50%.

22. The preparation method according to claim 21, wherein, The concentration of Mo in molybdenum-containing solution I is 2.5–5.5 mol / L; and / or The total metal ion concentration of iron-containing solution II is 2.5–4.2 mol / L; and / or The total metal ion concentration of active component solution III is 4.0–6.0 mol / L; and / or The carrier source is selected from silica sol, wherein the weight content of silica is 30-40%.

23. The use of the catalyst according to claim 1 or 2 in the ammonia oxidation reaction.

24. The application according to claim 23, wherein, Application of the catalyst in the ammoxidation reaction of low-carbon olefins.

25. The application according to claim 24, wherein, The low-carbon olefin is propylene and / or isobutylene.

26. A method for producing nitrile compounds by ammoxidation of low-carbon olefins, characterized in that, The method comprises: in the presence of the catalyst described in claim 1 or 2, carrying out an ammonia oxidation reaction using low-carbon olefins, ammonia, and air as raw materials.

27. The method according to claim 26, wherein, The raw material molar ratio is: propylene / ammonia / air = 1 : (1.05~1.3) : (9.2~9.8); and / or The reaction temperature is 420~440℃; and / or The reaction pressure is 0~0.14 MPa; and / or The olefin feedstock loading of the catalyst is 0.06~0.10 h. -1 .

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