Catalyst for preparing acrylonitrile by propylene ammoxidation, preparation method therefor, and use thereof

Abstract

A catalyst for preparing acrylonitrile by propylene ammoxidation, a preparation method therefor, and a use thereof. The catalyst comprises an active component and a carrier, and the active component comprises Mo, Bi, Fe, at least one rare earth element, at least one alkali metal element, and at least one alkaline earth metal element. The catalyst has a molybdate crystal plane distribution index RQ of 0.65-0.98, where RQ = (R'+Q') / (R+Q).

Description

Catalyst for preparing acrylonitrile by ammoxidation of propylene, preparation method and application thereof Technical Field

[0001] The present invention relates to the field of catalysis, and more particularly to a highly stable catalyst for preparing acrylonitrile through propylene ammoxidation, and a preparation method and application thereof. Background Art

[0002] Acrylonitrile (AN) is a raw monomer used in the synthetic fiber acrylic. It is also a raw material for thermoplastic synthetic resins such as ABS and SAN, nitrile rubber, adiponitrile, acrylamide, and other derivatives. It is a key product in the petrochemical industry. The process technology for producing AN by ammoxidation of propylene has become increasingly mature, and the development of high-performance AN catalysts is a hot topic in the AN industry.

[0003] Currently, the industrial production of unsaturated nitriles by olefin ammoxidation still generally utilizes the fluidized bed ammoxidation process. As one of the core technologies of this process, catalysts have received significant attention for their research and improvement. Currently, there are two main types of catalysts for the industrial ammoxidation of propylene to acrylonitrile: Mo-Bi and Sb. Mo-Bi catalysts dominate, accounting for 95% of the olefin oxidation market, and previous research and exploration has primarily focused on Mo-Bi catalysts. The introduction of metal components with variable valence states, such as Fe and Ce, into the catalyst improves the redox performance of the catalyst and accelerates the recovery of the active components. Metal elements with ionic radii greater than or less than 0.8 nm, such as Cr, Ni, Mg, Mn, Zn, and Al, act as structural and electronic additives, improving the catalyst's structure and stability. Rare earth elements increase the lattice oxygen content of the catalyst, improving its catalytic performance. Surface modification and acid-base adjustments, such as Cs, Rb, P, B, and Al, improve the catalyst's selectivity and activity. Patent CN110557941A proposes that by controlling the composition and state of the specific peaks in the X-ray diffraction analysis, this catalyst has higher ammonia conversion and improves the yield of acrylonitrile and hydrogen cyanide as acrylonitrile ammoxidation product. In addition, patent CN113692315A proposes that by controlling the composition of the specific phase in the X-ray analysis, the yield of hydrogen cyanide can be improved while suppressing the reduction of the yield of acrylonitrile. However, the above phases with the catalyst are not analyzed, and the variation of the phase closely related to the catalyst activity in the reaction process is not further analyzed. The catalyst of the prior art has much room for improvement in terms of long-term stable operation and obtaining high propylene conversion. Therefore, it is necessary to analyze the phases of the catalyst, and then prepare the catalyst that shows the high propylene conversion in the long-term operation process.

[0004] Summary of the Invention

[0005] In view of the defects existing in the prior art, the object of the present invention is to provide a highly stable catalyst for the ammoxidation of propylene to acrylonitrile, which has the advantage of showing a high propylene conversion rate during long-term operation of the catalyst.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A catalyst, preferably a catalyst for the ammoxidation of propylene to acrylonitrile, comprising an active component and a carrier, wherein the active component comprises Mo, Bi, Fe, at least one rare earth element, at least one alkali metal element, and at least one alkaline earth metal element; the catalyst having a molybdate crystal plane distribution index RQ of 0.65-0.98, preferably 0.70-0.98; wherein: RQ = (R'+Q') / (R+Q,

[0008] Wherein, the R and Q are determined as follows:

[0009] Take a certain amount of catalyst and measure the peak areas of the catalyst's X-ray diffraction at 22.8°±0.2 (R) and 25.5°±0.2 (Q), and

[0010] The R' and Q' were determined as follows:

[0011] Under anaerobic conditions, a certain amount of catalyst was taken and propylene and nitrogen were introduced, wherein the gas molar ratio of propylene to nitrogen was 0.25, the reaction temperature was 430°C, and the catalyst weight space velocity was 0.18h - 1 , residence time 0.3s, thus completing one pulse reduction, and repeating the pulse reduction after an interval of 10min, for a total of 10 times, the peak areas of 2θ located at 22.8°±0.2 (R') and 25.5°±0.2 (Q') in the X-ray diffraction of the catalyst after 10 pulse reductions were measured.

[0012] In actual operation, in order to respectively determine the R and Q, and R' and Q', preferably, a certain amount (eg, 1-5 g) of catalyst can be taken and divided into two equal parts, one for determining the R and Q, and the other for determining the R' and Q'.

[0013] It will be understood by those skilled in the art that for the purpose of the present invention, when a "peak" is mentioned as being located at a certain 2θ position, it actually means that the peak top of the peak is located at this position.

[0014] The catalyst of the present invention has a bulk-enriched structure of Fe element, wherein the Fe element has an Fe distribution index D between the bulk and the surface of 10-40%, for example, 10-30%. Fe ,in:

[0015] D Fe =(C 整体Fe -C 表面Fe ) / C 整体Fe ;

[0016] wherein the C 整体Fe Represents the total Fe content of the catalyst as a whole;

[0017] The C 表面Fe Represents the Fe content on the catalyst surface.

[0018] The catalyst of the present invention has a molybdate crystal phase ratio index T / R of 2-5, wherein T is the peak area of ​​2θ located near 28.2°±0.2 in the X-ray diffraction of the catalyst.

[0019] The present invention also provides a method for preparing the catalyst of the present invention, wherein the amounts of active components including Mo and the carrier are determined, and the method comprises the following steps performed in sequence:

[0020] (1) adding a solvent to form a solution of the entire amount of the Fe element source, the entire amount of the source of at least one rare earth element, and a portion of the Mo element source in the active component, mixing these solutions and adding a dispersant to form a mixed solution I, and heat-treating the mixed solution I;

[0021] (2) adding a solvent to the remaining amount of the Mo element source to form a solution, and mixing it with the entire amount of the carrier source to form a mixed solution II;

[0022] (3) mixing all amounts of sources of other active ingredients other than the active ingredients used in steps (1) and (2) and adding a solvent to form a solution III;

[0023] (4) adding the mixed solution I to the mixed solution II to mix them to form a mixed solution IV;

[0024] (5) adding solution III to mixed solution IV to form slurry V;

[0025] (6) heat-treating the slurry V and then drying it to obtain granules;

[0026] (7) optionally calcining the particles to obtain the catalyst in the form of particles;

[0027] Wherein, the partial amount of Mo element source added in step (1) accounts for 40-80% of the total Mo element source. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 shows the XRD patterns of the catalyst of Example 1 measured with respect to R and Q, and R′ and Q′. DETAILED DESCRIPTION

[0029] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0030] In the present invention, unless otherwise specified, descriptions of dosage, content and related ratios are all based on “weight” unless it is obviously inconsistent with the common understanding in the art.

[0031] In the present invention, unless otherwise specified, the terms "comprises", "includes", "contains", "has" and similar expressions represent open-ended descriptions, but should also be understood as explicitly disclosing closed-ended situations at the same time. For example, "comprises" means that other elements that are not listed may also be included, but it also explicitly discloses the situation of only including the listed elements. In addition, as used herein, "comprises / comprising" is interpreted as explicitly stating the presence of the mentioned features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof. In addition, the term "comprising" is intended to include embodiments encompassed by the terms "essentially consisting of" and "consisting of". Similarly, the term "essentially consisting of" is intended to include embodiments encompassed by the term "consisting of".

[0032] In the present invention, the active component and support of a catalyst each have meanings known in the art. For example, the active component can be understood as the form in which the active element in the catalyst exerts a catalytic effect (including a promoting catalytic effect) exists, while the support is a component used to support the active component, which may, for example, be reaction-inert. Those skilled in the art will appreciate that, for ease of description, the term "active component" may also be used herein to describe the active element itself, as appropriate.

[0033] The present invention provides a catalyst, preferably a catalyst for preparing acrylonitrile by ammoxidation of propylene, comprising an active component and a carrier, wherein the active component comprises Mo, Bi, Fe, at least one rare earth element, at least one alkali metal element, and at least one alkaline earth metal element; the catalyst has a molybdate crystal plane distribution index RQ of 0.65-0.98, preferably 0.70-0.98; wherein:

[0034] RQ=(R'+Q') / (R+Q),

[0035] Wherein, the R and Q are determined as follows:

[0036] Take a certain amount of catalyst and measure the peak areas of the catalyst's X-ray diffraction at 22.8°±0.2 (R) and 25.5°±0.2 (Q), and

[0037] The R' and Q' were determined as follows:

[0038] Under anaerobic conditions, a certain amount of catalyst was taken and propylene and nitrogen were introduced, wherein the gas molar ratio of propylene to nitrogen was 0.25, the reaction temperature was 430°C, and the catalyst weight space velocity was 0.18h - 1 , residence time 0.3s, thus completing one pulse reduction, and repeating the pulse reduction after an interval of 10min, for a total of 10 times, the peak areas of 2θ located at 22.8°±0.2 (R') and 25.5°±0.2 (Q') in the X-ray diffraction of the catalyst after 10 pulse reductions were measured.

[0039] The present invention provides the above-mentioned specific determination method for R' and Q'; however, it is understood by those skilled in the art that the specific determination method is exemplary and that the determination method can have reasonable flexibility, so that consistent or substantially consistent measurement results can be obtained within a certain range of measurement conditions. For example, a certain amount of catalyst can be taken, and propylene and nitrogen can be introduced under anaerobic conditions, wherein the gas molar ratio of propylene to nitrogen is 0.20-0.30, the reaction temperature is 430-440°C, the catalyst weight space velocity is 0.15-0.20h-1, and the residence time is 0.2-0.5s. Thus, a pulse reduction is completed. The pulse reduction is repeated after an interval of 5-15 minutes, and after a total of 10 times, the peak area of ​​2θ located at 22.8°±0.2 (R') and 25.5°±0.2 (Q') in the X-ray diffraction of the catalyst after 10 pulse reductions is measured.

[0040] The peak area described in this embodiment has a meaning known in the art and can be determined by a person skilled in the art based on the knowledge known in the art and by known techniques; for example, the peak area can be the area of ​​the region enclosed by the Gaussian function curve and the baseline whose mean is within the specified 2θ angle range after peak fitting of the spectrum within the 2θ angle range ±1° specified by the XRD diffraction pattern using a Gaussian function.

[0041] The baseline is a line connecting the points without peaks in the XRD diffraction pattern.

[0042] It should be noted that the "peakless point" mentioned above refers to a point on the so-called baseline in a graph in which the vertical axis represents the diffracted X-ray intensity and the horizontal axis represents 2θ in XRD measurement, indicating a point where no peak exists. Since XRD measurements typically include a certain degree of noise, even peakless (diffraction-free) areas will exhibit a certain degree of diffracted X-ray intensity. Therefore, a line where the diffracted X-ray intensity is substantially zero is mechanically determined by calculation using the measurement instrument, i.e., by calculating the noise and background based on the overall analysis results, and this line is used as the baseline.

[0043] When the baseline is significantly tilted relative to the X-axis representing 20, the peak area can be calculated by appropriately correcting the graph using the analysis software included with the XRD device used in the measurement so that the baseline is parallel to the X-axis.

[0044] The peak fitting refers to the process of using analytical software attached to the XRD device or other data processing software capable of curve fitting to identify the peaks of the spectral curve obtained by XRD measurement and perform curve fitting using the Gaussian function through the least squares method.

[0045] The catalyst of the present invention has a bulk-enriched structure of Fe element, wherein the Fe element has an Fe distribution index D of 10-40% between the bulk and the surface. Fe , where: D Fe =(C 整体Fe -C 表面Fe ) / C 整体Fe ;

[0046] wherein the C 整体Fe Represents the total Fe content of the catalyst as a whole;

[0047] The C 表面Fe Represents the Fe content on the catalyst surface.

[0048] In the context of the present invention, X-ray photoelectron spectroscopy (XPS) is used to determine the surface Fe content of the catalyst particles. 表面Fe Here, "surface" refers to the depth range of the catalyst surface that can be measured by XPS (generally <10 nm). As an example, in the context of the present invention, the equipment used for XPS measurement can be an AXIS Ultra DLD X-ray photoelectron spectrometer from Kratos Analytical Ltd.; during the sample preparation stage, the catalyst powder is directly fixed (for example, using double-sided tape) on a copper sheet and then placed on the sample stage; before testing, the vacuum in the sample analysis chamber is ensured to be better than 1.0 x 10 -8mbar before the X-ray source can be turned on. As an example, the specific test steps can be as follows: use CCTV to roughly adjust the sample position, adjust the test position to the clearest imaging position and the center mark position of the imaging position; use Mg Kα excitation light source with a current of 40mA to pre-scan the full spectrum to determine the sample element content, position and the position of the strongest peak; at the strongest peak position, adjust the sample height to the strongest signal; collect and save the sample spectrum information; after obtaining the XPS spectrum line, correct it with the C 1s spectrum line of contaminated carbon; calculate the molar percentage of surface Fe element as the C of the catalyst particles based on the ratio of these peak areas. 表面Fe .

[0049] In the context of the present invention, X-ray fluorescence analysis is used to determine the "overall Fe content (C 整体Fe )". As an example, the S4Pioneer X-ray fluorescence spectrometer of the German Bruker company can be used to determine the Fe content of the catalyst. For example, in the sample preparation stage, 3g of catalyst and 3g of boric acid are mixed, then ball-milled in a ball mill for 1.5 minutes, and then pressed into tablets; X-rays are used as the excitation light source, and the intensity of the secondary X-rays generated by the sample is measured, and then compared with the intensity of the secondary X-rays generated by the standard sample to determine the molar percentage of Fe in the sample, which is used as the C of the catalyst particles. 整体Fe .

[0050] Accordingly, in the context of the present invention, when referring to the distribution of elements or components on a catalyst, the "bulk phase" refers to the entire catalyst, excluding the "surface", for the purpose of the present invention.

[0051] In the context of the present invention, an X-ray powder diffractometer is used to determine the phase of the catalyst particles. As an example, a D8AdvanceSS X-ray powder diffractometer from Bruker, Germany, can be used to determine the phase of the catalyst; a Cu target is used, and the light source wavelength is At room temperature and normal pressure, the sample is ground into 200 mesh powder and placed in the sample cell for measurement.

[0052] Furthermore, the catalyst of the present invention has a molybdate crystal phase ratio index T / R of 2-5, wherein T is the peak area of ​​2θ located near 28.2°±0.2 in the X-ray diffraction of the catalyst.

[0053] It is readily and fully understood by those skilled in the art that a substance is generally determined by both its components and structure, and either of these can lead to significant changes in the physicochemical properties of the substance. In particular, for catalysts, in addition to the catalyst components, their structure also greatly affects the various behaviors of the catalyst. For example, for multi-component catalysts, there are a variety of commonly used structures in the art, such as blending, surface coating, pore loading, as well as the bulk enrichment structure and core-shell structure used in the present invention; and even for core-shell structures, there is still the issue of how the various components are distributed in the core and shell.

[0054] The present invention aims to provide a catalyst for the ammoxidation of propylene to acrylonitrile. It is well known to those skilled in the art that such catalysts experience reducing conditions during the reaction process; therefore, such catalysts preferably have good reduction resistance, thereby exhibiting high stability during long-term operation of the catalyst. For example, for a catalyst of a given composition, a simple approach for the components that may be reduced is to completely or partially encapsulate the components; however, it is readily understood that such encapsulation may prevent the active sites from being fully exposed, resulting in an undesirable reduction in catalytic activity. Therefore, the art seeks to impart desirable reduction resistance to the catalyst through appropriate structures while achieving as high a catalytic performance as possible.

[0055] The catalyst of the present invention contains active elements such as Mo, Bi, and Fe. It is known in the art that such propylene ammoxidation to acrylonitrile catalysts typically form molybdates, such as iron molybdate, during the preparation process. The inventors of the present invention unexpectedly discovered that appropriately distributing the active elements, such as Mo, Bi, and / or Fe, and the corresponding molybdates formed, within the bulk and surface of the catalyst to create a bulk-enriched structure is particularly advantageous for achieving the highest possible catalytic performance while imparting the catalyst with desirable reduction resistance. It is known in the art that such propylene ammoxidation to acrylonitrile catalysts contain a crystalline structure, and lattice oxygen plays an important role in the catalytic process.

[0056] Without being bound by any known theory, it is believed that when the specific catalyst components selected in the present invention are used, the specific preparation steps described in the present invention, particularly, for example, the stepwise addition of the Mo source rather than a single addition, the mixing and processing of specific components in each step, and the specific mixing order of the resulting mixtures from each step, optionally combined with specific processing conditions, result in the active Fe element being primarily concentrated within the crystals and having a specific crystal face, crystal phase composition, and distribution. This facilitates achieving the highest possible catalytic performance while imparting the catalyst with desirable reduction resistance. Based on extensive research and experimental verification, and without being bound by any known theory, it is believed that the specific element distribution, crystal face, and crystal phase distribution of the catalyst prepared by the specific method of the present invention can be represented by, for example, the molybdate crystal face distribution index RQ and the molybdate crystal phase ratio index T / R.

[0057] It is understood by those skilled in the art that the present invention prepares a catalyst having a specific structure by the specific method; however, those skilled in the art can adjust the steps or their sequence, conditions and / or raw materials of the method based on specific circumstances and professional skills, as long as a catalyst having the molybdate crystal plane distribution index RQ, molybdate crystal phase ratio index T / R, etc. can be obtained.

[0058] In the present invention, the active Fe element is mainly enriched in the interior of the crystal, which can be determined by the Fe distribution index D Fe To reflect: D Fe =(C 整体Fe -C 表面Fe ) / C 整体Fe ;

[0059] Among them, the C 整体Fe The total Fe content in the catalyst bulk phase represented by is the total Fe content of the entire catalyst measured by the X-ray fluorescence analysis method; and the C 表面Fe The Fe content on the catalyst surface represented by is the Fe content measured by the XPS analysis. A person skilled in the art will understand that according to the principle and test method of XPS analysis, it can be used to characterize the Fe content on the surface of the test object; the C 整体Fe and C 表面Fe All are based on the total weight of the test subject catalyst.

[0060] The catalyst of the present invention was subjected to a reduction treatment, and the ratio of the sum of the peak areas at 2θ near 22.8°±0.2 and 25.5°±0.2 in X-ray diffraction before and after reduction was examined, thereby determining the influence of composition changes of the key active phase in the catalyst during the reduction process on the catalyst activity and stability. During the research, the inventors found that when the (R'+Q') / (R+Q) ratio of the catalyst of the present invention is 0.65-0.98, preferably 0.70-0.98, the catalyst of the present invention can operate stably for a long time and provide a high propylene conversion rate in the reaction of propylene ammoxidation to acrylonitrile.

[0061] The reduction treatment conditions of the above catalyst are as follows: in situ pulse reduction of the catalyst in a propylene and nitrogen atmosphere under oxygen-free conditions;

[0062] Preferably, the in-situ pulse reduction conditions are:

[0063] Under anaerobic conditions, 1 g of catalyst was pulse reduced by introducing propylene and nitrogen at a molar ratio of 0.25, a reaction temperature of 430 ° C, and a catalyst load (weight space velocity) of 0.18 h -1, residence time 0.3s, interval 10min, continue pulse reduction, repeat 10 times in total, and the catalyst sample after pulse reduction is obtained.

[0064] The pulse reduction method can be reasonably flexible, so that consistent or substantially consistent measurement results can be obtained within a certain range of measurement conditions. For example, a certain amount of catalyst can be taken, and propylene and nitrogen can be introduced under anaerobic conditions, where the molar ratio of propylene to nitrogen is 0.20-0.30, the reaction temperature is 430-440°C, and the catalyst weight space velocity is 0.15-0.20h -1 , the residence time is 0.2-0.5s, thereby completing one pulse reduction, and repeating the pulse reduction after an interval of 5-15min, for a total of 10 times.

[0065] In a preferred technical solution of the present invention, the rare earth element is selected from at least one of La, Ce, Pr, Nd, and Sm, preferably at least one of La, Ce, and Nd; and / or,

[0066] The alkali metal element is selected from at least one of Li, Na, K, Rb and Cs, preferably K and Rb; and / or,

[0067] The alkaline earth metal element is selected from at least one of Be, Mg, Ca, Sr and Ba, preferably Mg or Ca; and / or

[0068] The element A is selected from at least one of W, V, Zr, P, Nb, Ni, Co, Cr, Mn, Tl, Au, Ag, Pt, Ru, Rh, Pd, Ti, Sb, In, Sn and Te, and is preferably at least one of W, Zr, P, Nb, Ni, Co, Cr, Ag, Mn and In.

[0069] The carrier used in the present invention can be a commonly used carrier in the art, preferably a neutral or substantially neutral carrier. Accordingly, the carrier is preferably silicon dioxide.

[0070] In a preferred technical solution of the present invention, based on the weight of the catalyst, the active component, calculated as oxide, has a content of 30%-90%, preferably 50-70%; the carrier content is 10%-70%, preferably 30-50%.

[0071] Furthermore, in the above technical solution, the active components, based on the weight of the catalyst particles, are:

[0072] The weight content of the Mo element calculated as MoO3 is 15%-55%, preferably 20%-45%;

[0073] The weight content of the Bi element calculated as Bi2O3 is 0.5%-3.5%, preferably 1.0%-3.5%;

[0074] The weight content of the Fe element calculated as Fe2O3 is 1%-12%, preferably 1.5%-11%;

[0075] The weight content of the rare earth element in the form of rare earth element oxide is 1.5%-8.5%, preferably 2.5%-5.0%;

[0076] The weight content of the alkali metal element calculated as oxide is 0.01%-0.60%, preferably 0.05%-0.55%;

[0077] The weight content of the alkaline earth metal calculated as oxide is 0.01%-4.0%, preferably 0.5%-3.5%;

[0078] The weight content of the element A calculated as oxide is 0.01%-15%, preferably 0.05%-14%.

[0079] In a preferred technical solution of the present invention, among the active components:

[0080] The atomic ratio of Bi / Mo is 0.008-0.25, preferably 0.01-0.20;

[0081] The atomic ratio of Fe / Bi is 1.0-12.0, preferably 1.5-11.0;

[0082] The atomic ratio of the sum of rare earth elements, alkali metal elements and alkaline earth metal elements to Mo is 0.05-0.4, preferably 0.10-0.35; and / or,

[0083] The atomic ratio of the elements A / Mo is 0.01-1.0, preferably 0.02-0.9. The above specific ratio range is conducive to the formation of a phase with better catalytic activity in the catalyst.

[0084] Another object of the present invention is to provide a method for preparing a catalyst for the ammoxidation of propylene to acrylonitrile having high stability, comprising the following steps performed in sequence:

[0085] (1) adding a solvent to form a solution of the entire amount of the Fe element source, the entire amount of the source of at least one rare earth element, and a portion of the Mo source in the active component, mixing these solutions and adding a dispersant to form a mixed solution I, and heat-treating the mixed solution I;

[0086] (2) adding a solvent to the remaining amount of the Mo element source to form a solution, and mixing it with the entire amount of the carrier source to form a mixed solution II;

[0087] (3) mixing all amounts of sources of other active ingredients other than the active ingredients used in steps (1) and (2) and adding a solvent to form a solution III;

[0088] (4) adding the mixed solution I to the mixed solution II to mix them to form a mixed solution IV;

[0089] (5) adding solution III to mixed solution IV to form slurry V;

[0090] (6) heat-treating the slurry V and then drying it to obtain granules;

[0091] (7) optionally calcining the particles to obtain the catalyst in the form of particles;

[0092] Wherein, the partial amount of Mo element source added in step (1) accounts for 40-80% of the total Mo element source.

[0093] It is understood that, although the steps involved in the method of the present invention are "performed in sequence" is an important feature for the purpose of the present invention, the emphasis is mainly on the steps in the method that have an obvious process relationship; for example, step (4) requires adding mixed solution I to mixed solution II. Therefore, step (4) should not and cannot be performed before step (1) of forming mixed solution I or before step (2) of forming mixed solution II. However, for some steps whose process relationship is not obvious, those skilled in the art can adjust or exchange the order of the steps as appropriate. For example, based on the above-described steps (1)-(7):

[0094] - Steps (1), (2) and (3) can be interchanged in any order to form, for example, the following order: steps (1), (3) and (2); steps (2), (1) and (3); steps (2), (3) and (1); steps (3), (1) and (2); or steps (3), (2) and (1);

[0095] - steps (3) and (4) may be interchanged to form the order of steps (1), (2), (4) and (3); and

[0096] - Steps (1) and (2) can be interchanged in order, and steps (3) and (4) can be interchanged in order to form the order of steps (2), (1), (4) and (3).

[0097] In the above discussion on adjusting or exchanging the order of steps, steps not specifically mentioned indicate that the original order of steps remains unchanged.

[0098] It is understood that, in the present invention, the "source" of various elements / components has a meaning known in the art, which may, for example, refer to various substances added as raw materials for the introduction of various active components / elements into the catalyst of the present invention. It is understood by those skilled in the art that the form of the target element / component to be introduced in the source may be different from that in the catalyst. For example, the support of the catalyst of the present invention may preferably be in the form of silica, while the source may preferably be in the form of silica sol.

[0099] It is understood that, in the present invention, "solubility" refers to the respective corresponding solvents. In the present invention, there is no particular limitation on the types of various solvents, and any conventional solvent in the art can be used in the present invention. For example, the solvent of the present invention can be independently selected from at least one of water, methanol, ethanol and ethyl acetate, preferably water.

[0100] In the steps (1) and (2), there is no particular restriction on the order of adding and mixing the various materials, as long as the mixed solutions I and II can be formed respectively. However, without being limited to any known theory, it is believed that in the step (4), the method of adding the mixed solution I to the mixed solution II for mixing is more advantageous than other mixing methods, such as adding the mixed solution II to the mixed solution I, for obtaining the catalyst particles required by the present invention. For this reason, preferably, the rate at which the mixed solution I is added to the mixed solution II is controlled, for example, the mixed solution I is added to the mixed solution II at a uniform speed within 5-15 minutes. Similarly, in the step (5), the method of adding the solution III to the mixed solution IV is particularly advantageous for obtaining the catalyst particles required by the present invention. For this reason, preferably, the rate at which the mixed solution III is added to the mixed solution IV is controlled, for example, the mixed solution III is added to the mixed solution IV at a uniform speed within 5-15 minutes.

[0101] This method can further stabilize the active phase during the reaction. As previously described, the Mo source is added in steps rather than all at once, with specific components mixed and processed in each step, and the mixtures obtained in each step have a specific mixing order. During the co-precipitation process, a source of at least one of Fe and rare earth elements such as La and Ce and a portion of the Mo source first form a mixed solution. By adding a dispersant and optionally performing a heat treatment, a eutectic structure with a stable active phase can be formed in the mixed solution, which is then added to the mixed solution formed by the other elements and the remaining amount of the Mo source. The above treatment and precipitation process is conducive to the formation of a uniform active phase in the catalyst and improves the stability of the highly active crystalline phase, which is conducive to maintaining good stability of the catalyst during the reduction process of the reaction.

[0102] In the above technical solution, the source of the active component is a compound containing an active component element, and the compound is preferably a water-soluble compound, more preferably a water-soluble salt; for example, nitrate, sulfate, hydrochloride, oxalate, etc.

[0103] In the above technical solution, the solvent of the mixed liquid and / or solution may preferably be water. The concentration of the mixed liquid and / or solution is not particularly limited, as long as the active component source and the carrier source are sufficiently mixed and dissolved. Preferably, for the present invention, the solutions formed by the various active component sources are each saturated solutions of the active component source. Without being limited by any known theory, it is believed that practicing the present invention with saturated solutions of the respective active component sources is particularly advantageous for obtaining the catalyst particles desired by the present invention, particularly, for example, with a desired distribution of various elements / components.

[0104] As previously mentioned, adding the Mo source in stages rather than all at once is particularly advantageous for forming the desired catalyst of the present invention. Accordingly, in a preferred embodiment of the present invention, the amount of the Mo source added in step (1) accounts for 40-80%, preferably 50-75%, of the total Mo source.

[0105] As previously mentioned, the mixing and processing of specific components in each step of the present invention, as well as the specific mixing order between the mixtures obtained in each step, are particularly advantageous for forming the desired catalyst of the present invention. Accordingly, in steps (1) and (2) of the method of the present invention, the sources of various elements / components are first formed into solutions and then mixed to form a mixture solution I. In contrast, for steps (1) or (2), the present invention does not recommend first mixing two or more sources of the elements / components and then forming a solution; nor does the present invention recommend first forming a solution of a source of one element / component and then adding the source of another element / component to the solution.

[0106] As described above, the present invention is particularly advantageous for forming the desired catalyst according to the present invention in combination with specific processing conditions. For example, for step (1), as described above, the amount of solvent added and thus the concentration of the mixed solution I may not be particularly limited; thus, in this step (1), the dispersibility of the sources of various elements / components in their respective solutions and the mixed solution I can be appropriately varied as needed by adjusting the concentration. However, the applicant unexpectedly discovered that, in step (1), the addition of a dispersant during the formation of the mixed solution I is particularly advantageous for forming the desired catalyst according to the present invention. Without being bound by any known theory, it is believed that the addition of a dispersant in step (1) is particularly advantageous for the implementation of the various steps subsequent to step (1) in the method according to the present invention, thereby smoothly obtaining the desired catalyst according to the present invention. Accordingly, in a preferred embodiment of the present invention, the dispersant in step (1) is selected from at least one of citric acid, acetic acid, oxalic acid, urea, aqueous ammonia, and ethanolamine; and / or, the amount of the dispersant added in step (1) is 0.01-0.2%, preferably 0.01-0.15%, of the total weight of the catalyst.

[0107] As previously mentioned, the present invention is particularly advantageous for forming the desired catalyst in conjunction with specific processing conditions. For example, the heat treatment conditions for the mixed solution I in step (1) are: heat treatment at 80-150°C and maintaining the temperature for 10-30 minutes; preferably, the heat treatment heating rate is 10-20°C / min.

[0108] In a preferred technical solution of the present invention, the carrier source in step (2) is silica sol, the solid content of the silica sol is 20 wt%-50 wt% in terms of silicon dioxide, and the average particle size is 10-35 nm.

[0109] As previously mentioned, the present invention is particularly advantageous for forming the desired catalyst in conjunction with specific processing conditions. For example, in a preferred embodiment of the present invention, the heat treatment temperature for forming the slurry in step (6) is 60-150°C and maintained at this temperature for 5-20 minutes; preferably, the heat treatment heating rate is 8-25°C / min.

[0110] In a preferred embodiment of the present invention, the various solutions are mixed in each step of the method of the present invention at a temperature at which they are completely dissolved. Accordingly, for example, after heat treatment of mixed solution I in step (1), it is cooled to room temperature and then mixed with mixed solution II in step (4).

[0111] In a preferred embodiment of the present invention, the drying in step (6) is performed by spray drying, wherein the conditions include, for example, a drying temperature of 250-350°C, preferably 300-350°C; and / or a drying time of 0.1-2.0 hours, preferably 0.2-1.0 hours; and / or an average diameter of the spray droplets of 20-200 μm, preferably 40-180 μm. The drying heat source for the spray drying is a drying heat source commonly used in the prior art, such as air.

[0112] In a preferred embodiment of the present invention, the calcination conditions of step (7) include: a calcination temperature of 250-700°C; a calcination time of 30-300 minutes; preferably, the temperature is increased to 250-400°C at a calcination heating rate of 5-20°C / min, held for 10-60 minutes, and then further increased to 400-700°C at a calcination heating rate of 5-20°C / min, held for 20-90 minutes. The calcination atmosphere is the common atmosphere used in catalyst preparation processes in the prior art, such as air.

[0113] Another object of the present invention is to provide an application of the catalyst for the reaction of propylene ammoxidation to acrylonitrile, preferably, the reaction conditions include: a molar ratio of propylene / ammonia / air (in terms of O2) of 1:(1.1-1.35):(1.8-2.5), a reaction temperature of 420-440°C, a reaction pressure of 0.03-0.14 MPa (in terms of gauge pressure), and a weight hourly space velocity (catalyst loading) of 0.04-0.10 h -1 .

[0114] Beneficial effects of the present invention:

[0115] The catalyst of the present invention has a more stable active phase, which is conducive to maintaining relatively stable reaction performance during the reaction process. When the catalyst of the present invention is used in the reaction of propylene ammoxidation to produce acrylonitrile, it can achieve a high propylene conversion rate.

[0116] Example

[0117] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0118] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0119] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the scope of protection of the present invention.

[0120] Reagent sources: All reagents are commercially available.

[0121] In the embodiment, the R and Q are respectively measured as follows:

[0122] Take 1g of the catalyst and measure the peak areas at 22.8°±0.2 and 25.5°±0.2 in the X-ray diffraction of the catalyst, and

[0123] The method for determining R' and Q' in the catalyst pulse reduction experiment is:

[0124] Under anaerobic conditions, 1 g of catalyst was added to the reactor for pulse reduction. Propylene and nitrogen were introduced, with a molar ratio of propylene to nitrogen of 0.25, a reaction temperature of 430 ° C, and a catalyst load (weight space velocity) of 0.18 h -1 , residence time 0.3s, interval 10min, repeat the pulse reduction, a total of 10 times, the sample after the pulse reduction experiment.

[0125] For R and Q, as well as R' and Q', the sample XRD was performed using an X-ray powder diffractometer from Bruker, Germany, with a Cu-K target radiation, a wavelength of 0.15406 nm, a scanning range of 5-80°, and a scanning rate of 5° / min.

[0126] The compositions of the catalysts in the following examples and comparative examples are calculated based on the theoretical proportions of the feed amounts.

[0127] Example 1

[0128] 581.7 g (NH4)6Mo7O 24 ·4H2O was dissolved in water, 795.5 g of Fe(NO3)3·9H2O, 77.1 g of Pr(NO3)3·6H2O and 42.6 g of La(NO3)3·6H2O were added and mixed, and 0.5 g of urea was added to form a mixed solution I. The mixed solution I was heat treated at 80°C with a heating rate of 10°C / min and kept at a constant temperature for 10 minutes. 3.63 g of KOH, 173.2 g of Bi(NO3)3·5H2O, 524.4 g of Ni(NO3)2·6H2O and 137.3 g of Mg(NO3)2·6H2O were added to water and dissolved to obtain solution III. 241.7 g of (NH4)6Mo7O 244H2O was dissolved in water, and 2750 g of silica sol (average particle size 25 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution II was formed. After 5 minutes, the mixed solution I was added at a uniform rate and stirred to form a mixed solution IV. After 5 minutes, solution III was added at a uniform rate to form a slurry V. The slurry V was heated to 150°C at a rate of 10°C / min and kept at a constant temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer with a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, it was calcined in an air atmosphere, and the calcination heating rate was controlled at 5°C / min to 300°C, and the temperature was kept for 30 minutes. Then, the temperature was raised to 550°C at a rate of 20°C / min and the temperature was kept for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0129] 50%K 0.15 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 La 0.3 Bi 1.0 Mo 13 O x +50%SiO2

[0130] FIG1 is an XRD pattern of R and Q, and R' and Q' measured in Example 1, wherein the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) is 0.85. The ratio T / R of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 is 4.4, D Fe It is 36%.

[0131] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0. After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 99.3%, and the reaction remained stable.

[0132] Example 2

[0133] 524.0 g (NH4)6Mo7O 24·4H2O was dissolved in water, 803.6 g of Fe(NO3)3·9H2O, 78.3 g of Nd(NO3)3·6H2O and 42.9 g of La(NO3)3·6H2O were added and mixed, and 1.0 g of urea was added to form a mixed solution I. The mixed solution I was heat treated at 100°C with a heating rate of 15°C / min and kept at a constant temperature for 15 minutes. 3.66 g of KOH, 87.5 g of Bi(NO3)3·5H2O, 128.4 g of Mn(NO3)2, 524.7 g of Co(NO3)2·6H2O, 138.7 g of Mg(NO3)2·6H2O and 6.09 g of AgNO3 were added to water and dissolved to obtain solution III. 307.8 g of (NH4)6Mo7O 24 4H2O was dissolved in water, and 2750 g of silica sol (average particle size 20 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution II was formed. After 6 minutes, the mixed solution I was added at a uniform rate and stirred to form a mixed solution IV. After 10 minutes, solution III was added at a uniform rate to form slurry V. The slurry V was heated to 120°C at a rate of 10°C / min and kept at a constant temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer with a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, it was calcined in an air atmosphere, and the calcination heating rate was controlled at 10°C / min to 300°C, and the temperature was kept for 30 minutes. Then, the temperature was increased to 550°C at a rate of 20°C / min and the temperature was kept for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0134] 50% Ag 0.1 K 0.15 Fe 5.46 Co 5.0 Mn 1.0 Mg 1.5 Nd 0.5 La 0.3 Bi 0.5 Mo 13 O x +50%SiO2

[0135] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.88. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 4.1, D Fe It is 38%.

[0136] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 99.0%, and the reaction remained stable.

[0137] Example 3

[0138] 743.5 g (NH4)6Mo7O 24 ·4H2O was dissolved in water, 1140.1 g of Fe(NO3)3·9H2O, 66.6 g of Ce(NO3)3·6H2O and 101.6 g of La(NO3)3·6H2O were added and mixed, and 1.5 g of urea was added to form a mixed solution I. The mixed solution I was heat treated at 120°C with a heating rate of 20°C / min and kept at a constant temperature for 30 minutes. 11.32 g of RbNO3, 124.1 g of Bi(NO3)3·5H2O, 744.5 g of Co(NO3)2·6H2O, 181.2 g of Ca(NO3)2·6H2O, 5.17 g of Cr2O3 and 4.32 g of AgNO3 were added to water and dissolved to obtain solution III. 436.6 g of (NH4)6Mo7O 24 4H2O was dissolved in water, and 1650 g of silica sol (average particle size 25 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution II was formed. After 7 minutes, the mixed solution I was added at a uniform rate and stirred to form a mixed solution IV. After 12 minutes, solution III was added at a uniform rate to form a slurry V. The slurry V was heated to 100°C at a rate of 10°C / min and kept at a constant temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer with a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, it was calcined in an air atmosphere, and the calcination heating rate was controlled at 20°C / min to 300°C, and the temperature was kept for 30 minutes. Then, the temperature was raised to 550°C at a rate of 20°C / min and the temperature was kept for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0139] 70% Ag 0.05 Rb 0.15 Fe 5.46 Co 5.0 Cr 0.1 Ca 1.5 La 0.5 Ce 0.3 Bi0.5 Mo 13 O x +30%SiO2

[0140] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.90. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 3.8, D Fe It is 28%.

[0141] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 98.5%, and the reaction remained stable.

[0142] Example 4

[0143] 638.9 g (NH4)6Mo7O 24 ·4H2O was dissolved in water, 979.7 g of Fe(NO3)3·9H2O, 38.3 g of Sm(NO3)3·6H2O and 52.4 g of La(NO3)3·6H2O were added and mixed, and 0.5 g of citric acid was added to form a mixed solution I. The mixed solution I was heat treated at 80°C with a heating rate of 10°C / min and kept at a constant temperature for 10 minutes. 9.73 g of RbNO3, 106.6 g of Bi(NO3)3·5H2O, 645.8 g of Ni(NO3)2·6H2O, 169.1 g of Mg(NO3)2·6H2O, 4.44 g of Cr2O3 and 11.15 g of AgNO3 were added to water and dissolved to obtain solution III. 375.2 g of (NH4)6Mo7O 244H2O was dissolved in water, and 2200 g of silica sol (average particle size 25 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution II was formed. After 5 minutes, the mixed solution I was added at a uniform rate and stirred to form a mixed solution IV. After 8 minutes, solution III was added at a uniform rate to form a slurry V. The slurry V was heated to 150°C at a rate of 20°C / min and kept at a constant temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer with a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, it was calcined in an air atmosphere, and the calcination heating rate was controlled at 20°C / min to 300°C, and the temperature was kept for 20 minutes. Then, the temperature was increased to 550°C at a rate of 20°C / min and the temperature was kept for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0144] 60% Ag 0.15 Rb 0.15 Fe 5.46 Ni 5.0 Cr 0.1 Mg 1.5 Sm 0.5 La 0.3 Bi 0.5 Mo 13 O x +40%SiO2

[0145] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.81. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 3.5, D Fe It is 29%.

[0146] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 98.9%, and the reaction remained stable.

[0147] Example 5

[0148] 644.6 g (NH4)6Mo7O 24·4H2O was dissolved in water, 988.4 g of Fe(NO3)3·9H2O, 38.7 g of Sm(NO3)3·6H2O and 38.5 g of Ce(NO3)3·6H2O were added and mixed, and 0.5 g of oxalic acid was added to form a mixed solution I. The mixed solution I was heat treated at 80°C with a heating rate of 10°C / min and kept constant at that temperature for 10 min. 9.81 g of RbNO3, 107.6 g of Bi(NO3)3·5H2O, 651.5 g of Ni(NO3)2·6H2O, 170.6 g of Mg(NO3)2·6H2O, 4.48 g of Cr2O3 and 6.64 g of In(NO3)3 were added to water and dissolved to obtain solution III. 378.5 g of (NH4)6Mo7O 24 4H2O was dissolved in water, and 2200 g of silica sol (average particle size 25 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution II was formed. After 5 minutes, the mixed solution I was added at a uniform rate and stirred to form a mixed solution IV. After 8 minutes, solution III was added at a uniform rate to form a slurry V. The slurry V was heated to 120°C at a rate of 20°C / min and kept at a constant temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer with a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, it was calcined in an air atmosphere, and the calcination heating rate was controlled at 20°C / min to 300°C, and the temperature was kept for 10 minutes. Then, the temperature was increased to 550°C at a rate of 20°C / min and the temperature was kept at 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0149] 60%In 0.05 Rb 0.15 Fe 5.46 Ni 5.0 Cr 0.1 Mg 1.5 Sm 0.5 Ce 0.2 Bi 0.5 Mo 13 O x +40%SiO2

[0150] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.83. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 4.1, D Fe It is 38%.

[0151] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 98.8%, and the reaction remained stable.

[0152] Example 6

[0153] 640.1 g (NH4)6Mo7O 24 ·4H2O was dissolved in water, 981.5 g of Fe(NO3)3·9H2O, 94.9 g of Pr(NO3)3·6H2O and 35 g of La(NO3)3·6H2O were added and mixed, and 1.0 g of ammonia water (50%) was added to form a mixed solution I. The mixed solution I was heat treated at 80°C with a heating rate of 10°C / min and kept constant for 10 min. 6.5 g of RbNO3, 106.8 g of Bi(NO3)3·5H2O, 647 g of Ni(NO3)2·6H2O, 156 g of Ca(NO3)2·6H2O, 4.45 g of CrO3 and 13.18 g of In(NO3)3 were added to water and dissolved to obtain solution III. 375.9 g of (NH4)6Mo7O 24 4H2O was dissolved in water, and 2200 g of silica sol (average particle size 25 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution II was formed. After 5 minutes, the mixed solution I was added at a uniform rate and stirred to form a mixed solution IV. After 8 minutes, solution III was added at a uniform rate to form a slurry V. The slurry V was heated to 100°C at a rate of 20°C / min and kept at a constant temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer with a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, it was calcined in an air atmosphere, and the calcination heating rate was controlled at 20°C / min to 300°C, and the temperature was kept for 20 minutes. Then, the temperature was raised to 550°C at a rate of 20°C / min and the temperature was kept for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0154] 60%In 0.1 Rb 0.10 Fe 5.46 Ni 5.0 Cr 0.1 Ca 1.5 Pr 0.5 La 0.2 Bi0.5 Mo 13 O x +40%SiO2

[0155] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.75. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 4.7, D Fe It is 32%.

[0156] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 99.0%, and the reaction remained stable.

[0157] Comparative Example 1

[0158] 795.5 g of Fe(NO3)3·9H2O, 77.1 g of Pr(NO3)3·6H2O, 42.6 g of La(NO3)3·6H2O, 3.63 g of KOH, 173.2 g of Bi(NO3)3·5H2O, 524.4 g of Ni(NO3)2·6H2O, and 137.3 g of Mg(NO3)2·6H2O were added to water and dissolved to obtain solution III. 823.4 g of (NH4)6Mo7O 24 4H2O was dissolved in water, and 2750 g of silica sol (average particle size 25 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution I was formed. Solution III was added to form slurry V. The slurry V was heated to 150°C at a rate of 10°C / min and kept at this temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer at a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, the mixture was calcined in an air atmosphere, and the calcination heating rate was controlled at 5°C / min to 300°C, and the temperature was kept for 30 minutes. Then, the temperature was increased to 550°C at a rate of 20°C / min and the temperature was kept at this temperature for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0159] 50%K 0.15 Fe 5.46 Ni5.0 Mg 1.5 Pr 0.5 La 0.3 Bi 1.0 Mo 13 O x +50%SiO2

[0160] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.60. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 6.1, D Fe It is 6%.

[0161] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 94.1%.

[0162] Comparative Example 2

[0163] 803.6 g of Fe(NO3)3·9H2O, 78.3 g of Nd(NO3)3·6H2O, 42.9 g of La(NO3)3·6H2O, 3.66 g of KOH, 87.5 g of Bi(NO3)3·5H2O, 128.4 g of Mn(NO3)2, 524.7 g of Co(NO3)2·6H2O, 138.7 g of Mg(NO3)2·6H2O, and 6.09 g of AgNO3 were added to water and dissolved to obtain solution III. 831.8 g of (NH4)6Mo7O 244H2O was dissolved in water, and 2750 g of silica sol (average particle size 20 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution I was formed. Solution III was added to form slurry V. The slurry V was heated to 150°C at a rate of 10°C / min and kept at this temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer at a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, the mixture was calcined in an air atmosphere, and the calcination heating rate was controlled at 10°C / min to 300 degrees, and the temperature was kept at 30 minutes. Then, the temperature was raised to 550°C at a rate of 20°C / min and the temperature was kept at this temperature for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0164] 50% Ag 0.1 K 0.15 Fe 5.46 Co 5.0 Mn 1.0 Mg 1.5 Nd 0.5 La 0.3 Bi 0.5 Mo 13 O x +50%SiO2

[0165] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.62. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 5.5, D Fe 8%.

[0166] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 95.7%.

[0167] Comparative Example 3

[0168] 581.7 g (NH4)6Mo7O 24·4H2O was dissolved in water, and 795.5 g of Fe(NO3)3·9H2O, 77.1 g of Pr(NO3)3·6H2O and 42.6 g of La(NO3)3·6H2O were added and mixed to form a mixed solution I. 3.63 g of KOH, 173.2 g of Bi(NO3)3·5H2O, 524.4 g of Ni(NO3)2·6H2O and 137.3 g of Mg(NO3)2·6H2O were added to water and dissolved to obtain solution III. 241.7 g of (NH4)6Mo7O 24 4H2O was dissolved in water, and 2750 g of silica sol (average particle size 25 nm) with a weight concentration of 40% was added. After stirring for 30 minutes, a mixed solution II was formed. After adding the mixed solution I and stirring, a mixed solution IV was formed. Solution III was continued to be added to form a slurry V. The slurry V was heated to 150°C at a rate of 10°C / min and kept at a constant temperature for 15 minutes. The prepared slurry was formed into microspheres in a spray dryer with a drying temperature of 300°C, a drying time of 0.5h, and an average diameter of the spray droplets of 100μm to obtain particles. Finally, it was calcined in an air atmosphere, and the calcination heating rate was controlled at 5°C / min to 300°C, and stayed for 30 minutes, and then raised to 550°C at 20°C / min and stayed for 45 minutes. The composition of the catalyst obtained according to the above steps is expressed as follows:

[0169] 50%K 0.15 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 La 0.3 Bi 1.0 Mo 13 O x +50%SiO2

[0170] According to the XRD measurements of R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.63. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 5.9, D Fe It is 5.5%.

[0171] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 95.4%.

[0172] Comparative Example 4

[0173] 581.7 g (NH4)6Mo7O 24 ·4H2O was dissolved in water, and 795.5 g of Fe(NO3)3·9H2O, 77.1 g of Pr(NO3)3·6H2O and 42.6 g of La(NO3)3·6H2O were added and mixed to form a mixed solution I. 3.63 g of KOH, 173.2 g of Bi(NO3)3·5H2O, 524.4 g of Ni(NO3)2·6H2O and 137.3 g of Mg(NO3)2·6H2O were added to water and dissolved to obtain solution III. 241.7 g of (NH4)6Mo7O 24 Dissolve 4H2O in water, add 2750 g of 40% silica sol (average particle size 25 nm), and add 0.5 g of urea to form mixed solution II. Heat-treat mixed solution II at 80°C at a heating rate of 10°C / min and maintain the temperature for 10 minutes. Add mixed solution I to mixed solution II and stir to form mixed solution IV. Continue adding solution III to form slurry V. Heat slurry V at a heating rate of 10°C / min to 150°C and maintain the temperature for 15 minutes. Form microspheres from the prepared slurry in a spray dryer at a drying temperature of 300°C for 0.5 hours, with an average spray droplet diameter of 100 μm, to obtain particles. Finally, calcinate in air at a controlled heating rate of 5°C / min to 300°C, hold for 30 minutes, then heat at 20°C / min to 550°C and hold for 45 minutes. The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0174] 50%K 0.15 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 La 0.3 Bi 1.0 Mo 13 O x +50%SiO2

[0175] According to the XRD patterns measured for R and Q, and R' and Q', the ratio of the peak areas R' and Q' at 2θ near 22.8°±0.2 and 25.5°±0.2 to the peak areas R and Q in the fresh agent (R'+Q') / (R+Q) was 0.64. The ratio of the peak areas T and R at 2θ near 28.2°±0.2 and 22.8°±0.2 was 6.0, D FeIt is 4.9%.

[0176] The reaction conditions for the ammoxidation of propylene to produce acrylonitrile using the catalyst obtained above are: a φ38 mm fluidized bed reactor, a catalyst particle size of 50 μm, a reaction temperature of 430°C, a reaction pressure of 0.084 MPa, a catalyst loading of 300 g, and a catalyst propylene load (weight hourly space velocity) of 0.085 h -1 ; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 2.0 After 1000 hours of operation, the reaction results were as follows: the propylene conversion rate was 95.3%.

[0177] Table 1 Composition and evaluation results of the catalysts obtained in each embodiment and comparative example Note: O in the above catalyst composition X The X value is the coordination value that satisfies the oxidation state of other elements.

[0178] The data from the 4-hour and 1000-hour runs of the catalysts above demonstrate that the catalyst of the present invention has a more stable active phase, thereby facilitating relatively stable reaction performance during the reaction. The catalyst of the present invention can achieve high propylene conversion when used in the ammoxidation of propylene to acrylonitrile.

[0179] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A catalyst comprising an active component and a carrier; the active component comprising Mo, Bi, Fe, at least one rare earth element, at least one alkali metal element, and at least one alkaline earth metal element; the catalyst having a molybdate crystal plane distribution index RQ of 0.65-0.98, preferably 0.70-0.98; wherein: RQ=(R'+Q') / (R+Q), Wherein, the R and Q are determined as follows: Take a certain amount of catalyst and measure the peak areas of the catalyst at 22.8°±0.2 and 25.5°±0.2 in X-ray diffraction, and The R' and Q' are determined as follows: Take a certain amount of catalyst, introduce propylene and nitrogen in the absence of oxygen, where the gas molar ratio of propylene to nitrogen is 0.25, the reaction temperature is 430°C, and the catalyst weight space velocity is 0.18h - 1 , residence time 0.3s, thus completing one pulse reduction, and repeating the pulse reduction after an interval of 10min. After a total of 10 times, the peak areas of 2θ located at 22.8°±0.2 and 25.5°±0.2 in the X-ray diffraction of the catalyst after 10 pulse reductions were measured.

2. The catalyst according to claim 1, characterized in that The catalyst has a bulk-enriched structure of Fe element, wherein the Fe element has an Fe distribution index D of 10-40% between the bulk phase and the surface. Fe , where: D Fe =(C 整体Fe -C 表面Fe ) / C 整体Fe ; Wherein C 整体Fe Represents the total Fe content of the catalyst; The C 表面Fe Represents the Fe content on the catalyst surface.

3. The catalyst according to claim 1, characterized in that The catalyst has a molybdate crystal phase ratio index T / R of 2-5, wherein T is the peak area of ​​2θ located near 28.2°±0.2 in the X-ray diffraction of the catalyst.

4. The catalyst according to claim 1, characterized in that Based on the weight of the catalyst, the active component is calculated as oxide and its content is 30%-90%, preferably 50-70%; the carrier content is 10%-70%, preferably 30-50%; preferably, the carrier is silicon dioxide.

5. The catalyst according to claim 1, characterized in that The rare earth element is selected from at least one of La, Ce, Pr, Nd and Sm, preferably at least one of La, Ce and Nd; and / or, The alkali metal element is selected from at least one of Li, Na, K, Rb and Cs, preferably K, Rb; and / or, The alkaline earth metal element is selected from at least one of Be, Mg, Ca, Sr and Ba, preferably Mg and Ca; and / or, The active component further comprises element A, which is selected from at least one of W, V, Zr, P, Nb, Ni, Co, Cr, Mn, Tl, Au, Ag, Pt, Ru, Rh, Pd, Ti, Sb, In, Sn and Te, preferably at least one of W, Zr, P, Nb, Ni, Co, Cr, Ag, Mn and In.

6. The catalyst according to claim 5, characterized in that The active components, based on the weight of the catalyst, The weight content of the Mo element, calculated as MoO3, is 15%-55%, preferably 20%-45%; and / or, The Bi element is calculated as Bi2O3, and its weight content is 0.5%-3.5%, preferably 1.0%-3.5%; and / or, The Fe element is calculated as Fe2O3, and its weight content is 1%-12%, preferably 1.5%-11%; and / or, The rare earth element, calculated as rare earth element oxide, has a weight content of 1.5% to 8.5%, preferably 2.5% to 5.0%; and / or, The alkali metal element, calculated as oxide, has a weight content of 0.01% to 0.60%, preferably 0.05% to 0.55%; and / or, The alkaline earth metal, calculated as oxide, has a weight content of 0.01% to 4.0%, preferably 0.5% to 3.5%; and / or, The weight content of the element A, calculated as oxide, is 0.01%-15%, preferably 0.05%-14%.

7. The catalyst according to any one of claims 1 to 6, characterized in that Among the active ingredients: The atomic ratio of Bi / Mo is 0.008-0.25, preferably 0.01-0.20; and / or, The atomic ratio of Fe / Bi is 1.0-12.0, preferably 1.5-11.0; and / or, The atomic ratio of the sum of rare earth elements, alkali metal elements and alkaline earth metal elements to Mo is 0.05-0.4, preferably 0.10-0.35; and / or, The active component further comprises element A, and the atomic ratio of element A / Mo is 0.01-1.0, preferably 0.02-0.

9.

8. A method for preparing a catalyst according to any one of claims 1 to 7, wherein: The amount of active components including Mo and the support is determined and includes the following steps in order: (1) adding a solvent to form a solution of the entire amount of the Fe element source, the entire amount of the source of at least one rare earth element, and a part of the Mo element source in the active component, mixing these solutions and adding a dispersant to form a mixed solution I, and heat treating the mixed solution I; (2) adding a solvent to the remaining amount of the Mo element source to form a solution, and mixing it with the entire amount of the carrier source to form a mixed solution II; (3) mixing all amounts of sources of other active components other than the active components used in steps (1) and (2) and adding a solvent to form a solution III; (4) adding the mixed solution I to the mixed solution II to mix them to form a mixed solution IV; (5) adding solution III to mixed solution IV to form slurry V; (6) heat-treating the slurry V and then drying it to obtain particles; (7) optionally calcining the particles to obtain the catalyst in particle form; Wherein, the partial amount of Mo element source added in step (1) accounts for 40-80% of the total Mo element source.

9. The method according to claim 8, characterized in that The partial amount of Mo element source added in step (1) accounts for 50-75% of the total Mo element source; and / or, The dispersant is selected from at least one of citric acid, acetic acid, oxalic acid, urea, ammonia water, and ethanolamine; and / or, The dispersant is added in an amount of 0.01-0.2% of the total weight of the catalyst, preferably 0.01-0.15%; and / or, The heat treatment conditions of the mixed solution I in step (1) are: heat treatment at 80-150° C. and maintaining the constant temperature for 10-30 min; preferably, the heat treatment heating rate is 10-20° C. / min.

10. The method according to claim 8, characterized in that In the step (6), the heat treatment temperature of the slurry is 60-150°C, and the constant temperature is maintained for 5-20 minutes; preferably, the heat treatment heating rate is 8-25°C / min.

11. The method according to claim 8, characterized in that The carrier source of step (2) is silica sol, the solid content of the silica sol is 20wt%-50wt% in terms of silicon dioxide, and the average particle size is preferably 10-35nm.

12. The method according to claim 8, characterized in that The solutions formed by the sources of the various active components are each saturated solutions of the sources of the active components.

13. The method according to claim 8 or 12, characterized in that: The sources of the various active components are the compounds containing the active elements, respectively, and the compounds are preferably water-soluble compounds, more preferably water-soluble salts; and / or, The solvent of the mixed liquid and / or solution is water.

14. The method according to claim 8, characterized in that The drying in step (6) is spray drying, and the conditions include: the drying temperature is 250-350°C; preferably 300-350°C; and / or, The drying time is 0.1-2.0 h, preferably 0.2-1.0 h; and / or, The average diameter of the spray droplets is 20-200 μm, preferably 40-180 μm.

15. The preparation method according to claim 8, characterized in that: The roasting conditions of step (7) include: a roasting temperature of 250-700°C; a roasting time of 30-300 min; preferably, the temperature is increased to 250-400°C at a roasting heating rate of 5-20°C / min, and the temperature is kept for 10-60 min; then the temperature is further increased to 400-700°C at a roasting heating rate of 5-20°C / min, and the temperature is kept for 20-90 min.

16. Use of the catalyst according to any one of claims 1 to 7 in the reaction of propylene ammoxidation to produce acrylonitrile.

17. A method for preparing acrylonitrile by ammoxidation of propylene, the method being carried out in the presence of a catalyst as claimed in any one of claims 1 to 7 under the following reaction conditions: a molar ratio of propylene / ammonia / air (in terms of O2) of 1:(1.1-1.35):(1.8-2.5), a reaction temperature of 420-440°C, a reaction pressure of 0.03-0.14 MPa in terms of gauge pressure, and a weight hourly space velocity of 0.04-0.10 h -1 .

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