Catalyst with high activity, high stability and carbon deposition resistance under weak oxygen condition, preparation method of catalyst and application of catalyst in preparation of styrene through ethylbenzene dehydrogenation

Abstract

The invention discloses a high-activity, high-stability and anti-carbon-deposition catalyst under a weak oxygen condition, a preparation method and an application in styrene preparation through ethylbenzene dehydrogenation, and belongs to the technical field of catalysts. According to the catalyst, Al2O3 serves as a carrier and is loaded with Pt, Fe and Zr, Al2O3 with the proper thickness is deposited on the outer layer through atomic vapor deposition or a hydrothermal method, an impregnation method and other liquid phase coating technologies, the stability of the metal valence state in the reaction process is effectively maintained through cooperation of the sandwich type structural design and the element formula, and the activity of the catalyst can be remarkably improved through cooperation of Pt and Fe; the Zr element can effectively inhibit carbon deposition and improve the carbon deposition resistance of the catalyst; the Zr element has a synergistic effect on internal regulation and control of the active components of the catalyst and external protection of aluminum oxide coated on the surface, so that the stability of valence states of all the elements can be maintained to a great extent, carbon deposition is further inhibited, the stability of the catalyst is further maintained, and the catalytic activity and stability of the catalyst are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions, a preparation method and application in the dehydrogenation of ethylbenzene to produce styrene. Background Art

[0002] Styrene, a crucial building block in the modern petrochemical industry, is a key monomer in the synthesis of various polymer materials, such as polystyrene and styrene-butadiene rubber. Current industrial production primarily uses potassium-containing iron oxide as a catalyst, catalyzing the direct dehydrogenation (DDH) of ethylbenzene with steam co-feed. This process requires the introduction of large amounts of superheated steam (water / hydrocarbon molar ratio of 7-15:1) to the reaction for three main purposes: to provide heat for the reaction, to remove carbon deposits on the surface of the potassium-containing iron oxide catalyst, and to dilute the reaction system to increase equilibrium conversion. The extensive use of superheated steam not only increases process energy consumption but also contributes to high carbon emissions through the reaction of water vapor with carbon deposits, generating large amounts of CO2. Therefore, reducing or completely eliminating the use of water vapor is beneficial in terms of both energy consumption and environmental impact. Furthermore, in a water vapor environment, the potassium in the potassium-containing iron oxide catalyst is prone to migration from high-temperature to low-temperature zones or from the edges of the catalyst particles to the center, resulting in reduced catalyst stability. In summary, the high energy consumption, high carbon emissions and catalyst instability caused by the use of steam in the process of ethylbenzene dehydrogenation to produce styrene are not conducive to the healthy development of the ethylbenzene dehydrogenation industry.

[0003] Oxidative dehydrogenation of ethylbenzene (ODH) can generate water by reacting oxygen with hydrogen produced by oxidative dehydrogenation of ethylbenzene, thus promoting the forward reaction. It is another process besides direct dehydrogenation of ethylbenzene under water vapor. During the operation, the ratio of oxygen to ethylbenzene (EB) has a great influence on catalytic activity and operational safety. Theoretically, the O2:EB molar ratio for complete conversion of ethylbenzene is 0.5:1. If the gasification of carbon deposits is to be promoted, it needs to be higher than this value. Because excessive oxygen content not only poses an explosion risk, but also leads to deep oxidation to produce CO x , resulting in lower selectivity; while too low an oxygen content will reduce the conversion rate of ethylbenzene and make it difficult to eliminate carbon deposits. Therefore, weak oxygen conditions (such as an O2:EB molar ratio of 0.5 to 1.2:1 and an oxygen content of <10%) can be selected for the oxidative dehydrogenation of ethylbenzene. Within this range, the key to the oxidative dehydrogenation of ethylbenzene lies in the development of catalysts with high activity, high selectivity and high stability. That is, for this type of catalyst, while achieving a high conversion rate of ethylbenzene, it can also prevent excessive oxidation of ethylbenzene to ensure styrene selectivity; at the same time, it can also maintain the stability of the catalyst to prevent the catalyst from deactivating due to carbon deposition or loss of active components.

[0004] Currently reported catalysts for the ethylbenzene ODH reaction primarily include metal catalysts and non-metallic catalysts. A search of published patents reveals that most non-metallic catalysts are currently in the laboratory research stage, including nanodiamonds (CN106316749A), boron carbide materials (CN109126843A), boron-, nitrogen-, and phosphorus-modified nanodiamonds (CN112717972A), and boron nitride (Chin. J. Chem. 2021, 39, 2563-2569). However, non-metallic materials exhibit low styrene selectivity in an oxygen atmosphere, and long-term operation can easily lead to oxidation and reduced activity. Metal catalysts for the ethylbenzene ODH reaction primarily include V-Mg-O (Catal. Today 2003, 81, 413-424) and Cu-Co-Fe2O4 (Catal. Lett. 2003, 91, 217-224). The main problem with metal catalysts such as Pt and Fe in weak oxygen conditions is that they are prone to carbon deposition, resulting in poor stability (Ind. Eng. Chem. Res. 2007, 46, 8722-8728). Therefore, developing a catalyst with high activity and high resistance to carbon deposition in weak oxygen conditions is of great significance for energy conservation and consumption reduction in the ethylbenzene dehydrogenation industry. Summary of the Invention

[0005] In view of the problem that the current dehydrogenation of ethylbenzene under weak oxygen conditions has poor stability due to poor anti-carbon deposition performance of the catalyst, the present invention proposes a catalyst with high activity, high stability and anti-carbon deposition under weak oxygen conditions, a preparation method and application in the dehydrogenation of ethylbenzene to produce styrene.

[0006] The catalyst (Al / Pt-Fe-Zr / Al) with high activity, high stability and carbon deposition resistance under weak oxygen conditions of the present invention is composed of the following components, with Al calculated as Al2O3, Zr calculated as ZrO2, Fe calculated as Fe2O3, and Pt calculated as PtO, based on 100 parts by mass:

[0007] 85.5 to 95.5 parts of Al2O3, preferably 90 to 95 parts;

[0008] 2 to 10 parts of ZrO2, preferably 3 to 7 parts;

[0009] 0.5 to 5 parts of Fe2O3, preferably 1 to 3 parts;

[0010] 0.1 to 1.0 parts of PtO, preferably 0.2 to 0.7 parts.

[0011] The preparation method of a catalyst (Al / Pt-Fe-Zr / Al) with high activity, high stability and carbon deposition resistance under weak oxygen conditions of the present invention comprises the following steps:

[0012] Step 1: Loading of Pt, Fe and Zr on the surface of Al2O3 carrier to obtain catalyst precursor

[0013] 1) Based on 100 parts by mass of the product, Al is calculated as Al2O3, Zr is calculated as ZrO2, Fe is calculated as Fe2O3, and Pt is calculated as PtO. Fe and Zr salts are weighed in a ratio of 85.5 to 95.5 parts by mass of Al2O3, 2 to 10 parts by mass of ZrO2, 0.5 to 5 parts by mass of Fe2O3, and 0.1 to 1.0 parts by mass of PtO, and the mixtures are dissolved in deionized water or alcohol, and then a water or alcohol solution of the Pt salt is added to obtain a mixed solution;

[0014] 2) adding an Al2O3 carrier to the mixed solution obtained in step 1), and obtaining a catalyst precursor after impregnation, drying and calcination;

[0015] In step 1), there is no restriction on the crystal form, specific surface area and size of the Al2O3 carrier;

[0016] In step 1), the Pt, Fe and Zr salts are one or two of nitrate, chloride, bromide, acetate, oxychloride and ethanolate;

[0017] In step 2), the immersion time is 10 to 18 hours, and the immersion temperature is not particularly required; the drying temperature is 50 to 100°C, and the drying time is not particularly required; the roasting temperature is 600 to 900°C, and the roasting time is 2 to 5 hours; the concentration ranges of Pt, Fe, and Zr salts in the mixed solution are 6×10 -3 ~1.2×10 -2 mol / L, 0.08-0.18 mol / L, 0.1-0.2 mol / L, the volume (mL) and mass (g) ratio of the mixed solution to the Al2O3 carrier is 2-3:1;

[0018] Step 2: Coat the catalyst precursor with Al2O3 to obtain the catalyst

[0019] 1) Atomic layer deposition (ALD) is performed using ultrapure Ar as a carrier gas and a purge gas, subjecting the catalyst precursor obtained in the first step to a cycle of "exposing to an aluminum precursor - purging" and "exposing to ultrapure water - purging" for 20 to 120 times, thereby forming an Al2O3 deposition layer on the catalyst precursor surface;

[0020] 2) calcining the catalyst precursor coated with the Al2O3 deposition layer obtained in step 1) to obtain the high-activity, high-stability and carbon deposition-resistant catalyst (Al / Pt-Fe-Zr / Al).

[0021] In step 1), the aluminum precursor is one or two of aluminum salts (such as aluminum chloride), aluminum alkoxides (such as aluminum isopropoxide and aluminum ethoxide), and aluminum alkyls (such as trimethylaluminum (TMA), tris(dimethylamino)aluminum, tris(diethylamino)aluminum, dimethylisopropoxyaluminum (DMCl), and 3-dimethylaminopropylaluminum (DMAD)).

[0022] In step 1), the deposition temperature of the ALD technology is 120-220° C. In each cycle, the catalyst precursor is exposed to the aluminum precursor for 0.01-1 second, removed and purged with Ar for 10-40 seconds, then exposed to H2O for 0.01-1 second, removed and purged with Ar for 10-40 seconds;

[0023] In step 1), the thickness of the Al2O3 deposited layer obtained is 2 to 12 nm;

[0024] In step 2), the calcination temperature is 600-900° C. and the calcination time is 2-8 hours;

[0025] In the second step, ALD is only one of the techniques for coating the Al2O3 deposited layer. This invention protects ALD technology because it can produce optimal catalysts. However, this does not exclude other liquid-phase coating techniques, such as hydrothermal and impregnation. These liquid-phase coating techniques can achieve coating effects similar to those of this invention through process optimization.

[0026] The impregnation method is a common method, widely reported in the literature. The impregnation coating process involves dissolving a certain proportion of aluminum salt in water or ethanol, adding a catalyst precursor, impregnating, drying, and calcining to obtain the catalyst. The aluminum salt is selected from aluminum nitrate, aluminum sulfate, or aluminum chloride. The mass ratio of the coated Al2O3 deposit to the catalyst precursor is 0.01 to 0.06:1. The impregnation time is 10 to 18 hours, with no specific requirements for the impregnation temperature. The drying temperature is 50 to 100°C, with no specific requirements for the drying time. The calcination temperature is 500 to 900°C, with a calcination time of 1 to 4 hours.

[0027] The hydrothermal method is a commonly used method and has been reported in many public literature. The steps of the hydrothermal coating method are as follows: dissolve a certain proportion of aluminum salt and alkaline substance in water, add alkaline solution dropwise to the aluminum salt solution (the molar ratio of alkaline substance to aluminum salt is 7-15:1), stir evenly, add catalyst precursor, transfer to a hydrothermal kettle for hydrothermal reaction, and then filter, wash, dry, and calcine to obtain the catalyst. The aluminum salt is one of aluminum nitrate, aluminum sulfate, and aluminum chloride, and the alkaline substance is one of sodium hydroxide, ammonium bicarbonate, and urea. The mass ratio of the coated Al2O3 deposit layer to the catalyst precursor is 0.01-0.06:1. The stirring time is 0.5-3 hours, the hydrothermal reaction time is 24-72 hours, and the hydrothermal reaction temperature is 80-180°C. The drying temperature is 50-100°C, and there is no special requirement for the drying time. The calcination temperature is 500-900°C and the calcination time is 1-4 hours.

[0028] The high-activity, high-stability and carbon deposition-resistant catalyst (Al / Pt-Fe-Zr / Al) prepared by the present invention can be used in the dehydrogenation of ethylbenzene to produce styrene. The catalyst can be used in the continuous and stable reaction of ethylbenzene dehydrogenation (ODH) to produce styrene under weak oxygen conditions (reaction conditions: the volume space velocity of the ODH reaction is 1000-8000 mL / g cat h, the molar ratio of oxygen to ethylbenzene is 0.5 to 1.2:1, and the reaction temperature is 550 to 650°C), or it can be applied to the continuous and stable reaction of ethylbenzene direct dehydrogenation (DDH) to styrene under anhydrous and oxygen-free conditions supplemented by intermittent air roasting and regeneration, that is, the cycle of "DDH-air in-situ roasting and regeneration-DDH" (reaction conditions: the volume space velocity of the DDH reaction is 1000 to 4000 mL / g cat h, the volume content of ethylbenzene in the carrier gas is 10-20%; the reaction temperature is 550-650°C; the volume space velocity of air regeneration is 3000-8000 mL / g cat h, ethylbenzene is not passed during air regeneration, and the roasting regeneration temperature is 500-800℃).

[0029] The catalyst of the present invention has the following technical advantages over existing catalysts:

[0030] (1) The catalyst of the present invention has both high activity and high resistance to carbon deposition; the styrene selectivity (S ST ) is greater than the value reported in the existing industry, and the amount of styrene generated per unit carbon deposition (Y ST ) is higher than the value in currently available reports;

[0031] (2) The catalyst of the present invention does not contain toxic metals and has environmental advantages;

[0032] (3) The catalyst of the present invention can operate for a long time under the conditions of no water vapor and weak oxygen, and has the advantages of low energy consumption and high safety.

[0033] The technical principle achieved by the catalyst of the present invention is:

[0034] (1) The catalyst of the present invention is unique in its design and has a sandwich-like structure. Specifically, the alumina support substrate is first loaded with Pt, Fe, and Zr components, then coated with alumina of appropriate thickness and calcined at high temperature to strengthen the structure.

[0035] (2) The catalyst of the present invention is characterized by its unique formulation; specifically, the combination of Pt, Fe, Zr, and alumina;

[0036] (3) In the catalyst of the present invention, Pt and Fe can synergistically significantly improve the catalyst activity;

[0037] (4) In the catalyst described in the present invention, the Zr element can effectively inhibit carbon deposition and improve the catalyst's anti-carbon deposition performance; the internal regulation of the catalyst's active components by the Zr element, in synergistic effect with the external protection of the surface-coated aluminum oxide, can maintain the stability of the valence states of each element to a large extent, thereby inhibiting carbon deposition and maintaining the stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The XPS spectra of the catalysts of Example 1 and Comparative Example 5 before and after the reaction are as follows: the total spectrum (a), O1s spectrum (b), Al 2p spectrum (c), Pt 4d 5 / 2 spectrum (d), Fe 2p spectrum (e), and Zr 3d spectrum (f);

[0039] Figure 2 TG curves of the catalysts of Example 1 and Comparative Example 5 after the reaction;

[0040] Table 1 Element content data of the catalysts of Example 1 and Comparative Example 5 calculated by XPS before and after the reaction

[0041]

[0042]

[0043] Depend on Figure 1 As can be seen from Table 1, after the reaction, Fe 2+ / Fe 3+ The ratio of Fe in Example 1 increased significantly compared to that before the reaction. 2+ / Fe 3+It is relatively stable, which shows that the Al2O3 layer deposited by ALD technology can effectively maintain the valence state of Fe element. 4+ The chemical shift is relatively stable, changing only 0.1eV, indicating that the electrons of Al and Zr in the catalyst are relatively stable; while the chemical shifts of Al and Zr in the catalyst of Comparative Example 5 decreased significantly after the reaction (0.4-0.5eV), indicating that the chemical environment of the catalyst changed significantly after the reaction, and the Al 3+ 、Zr 4+ Electrons were obtained. The O1s spectrum is divided into two peaks near 530.5-530.9eV and 531.5-531.9eV, respectively attributable to O=Al and OH species. The chemical shifts of both characteristic peaks in Comparative Example 5 decreased after the reaction, while the O=Al in Example 1 remained unchanged, indicating that the chemical environment of Al2O3 in Example 1 is more stable. The chemical shift of the OH species in Example 1 increased after the reaction, which may be attributed to the reduction in the content of OH species after the reaction.

[0044] Figure 2 It can be seen that the catalyst of Example 1 runs stably for 140 hours longer than the catalyst of Comparative Example 5, but the carbon deposit content only increases by 2.7%. This shows that the catalyst of Example 1 has a stronger ability to resist carbon deposition.

[0045] Table 2 Preparation conditions of catalysts in Examples and Comparative Examples

[0046]

[0047]

[0048] Table 3 Reaction type, reaction time, reaction temperature and catalytic activity (C) of the catalysts of Examples and Comparative Examples coke 、X EB 、S ST and Y ST )data

[0049]

[0050] DETAILED DESCRIPTION

[0051] The catalyst prepared under the above conditions was evaluated for ethylbenzene dehydrogenation activity in a fixed-bed reactor. The process was as follows: Ethylbenzene feedstock was introduced into the reactor via a bubbling method. The ethylbenzene concentration was controlled by controlling the N2 flow rate and the ethylbenzene tank heating temperature. 0.4 g of catalyst was loaded into the reaction tube and heated to 600°C under a 12 mL / min N2 atmosphere. The feed gas was split into two streams: one at 12 mL / min and 14.1 vol% EB / N2, and the other at 30 mL / min and 5 vol% O2 / N2, either air or no gas flow. The outlet product was cooled in a thermostatic water bath and collected with anhydrous ethanol. The outlet product was analyzed using a Shimadzu GC-2010 Plus gas chromatograph equipped with an FID detector.

[0052] Under the condition of similar styrene selectivity, the carbon deposit content of the catalyst with low ethylbenzene conversion and short reaction time is also low. It is not comprehensive to judge the anti-carbon deposition performance of the catalyst by simply using the carbon deposit content. Therefore, this application uses the styrene production corresponding to unit carbon deposition (Y ST ) is used to indicate the activity and anti-carbon deposition performance of the catalyst. Ethylbenzene conversion rate (X EB ), styrene selectivity (S ST ), the carbon deposit content of the catalyst (C coke ) and Y ST Calculate using the following formula:

[0053]

[0054] In the present invention, the catalyst XPS test was performed using an X-ray photoelectron spectrometer (PHIQuantera II, Ulvac-Phi, Japan). The excitation source was monochromatized Al-Kα radiation with an energy of 1486.7 eV, and the C1s binding energy peak (286.8 eV) was used as the internal standard for calibration. The catalyst TG test was performed on a Perkin-Elmer TGA 7 instrument in the temperature range of 50-800°C and a heating rate of 10°C min. -1 .

[0055] The catalyst preparation conditions, reaction types, reaction times and catalytic activity results in various examples of the present invention are shown in Tables 2 and 3.

[0056] Example 1

[0057] 1) Weigh 0.087 g of FeCl₃ and 0.197 g of ZrOCl₂·8H₂O and dissolve them in 3 mL of deionized water. Then add 1 mL of a 0.0375 mol / L aqueous solution of H₂PtCl₄ to obtain a mixed solution.

[0058] 2) adding 1.5 g of commercial Al2O3 powder with a particle size of 100-150 mesh to the mixed solution obtained in step 1), soaking for 12 hours, removing and drying at 60°C, and then calcining in a muffle furnace at a heating rate of 5°C / min to 800°C for 3 hours to obtain a catalyst precursor;

[0059] 3) using ALD technology (chamber model MNT-C100) with ultrapure Ar as carrier gas and purge gas, the catalyst precursor A obtained in step 2) was exposed to TMA and ultrapure water alternately for 80 cycles at 150° C.; each ALD cycle consisted of exposure to TMA for 0.02 s, Ar purge for 20 s, and exposure to H2O for 0.02 s, Ar purge for 25 s; thereby, an Al2O3 layer with a thickness of 8 nm was deposited on the surface of the catalyst precursor to obtain an intermediate;

[0060] 4) calcining the intermediate obtained in step 3) at 800° C. for 6 h in a muffle furnace at a heating rate of 5° C. / min to obtain a powder catalyst with a thickness of 8 nm;

[0061] 0.4 g of the above catalyst was used for ethylbenzene oxidative dehydrogenation evaluation. After heating to 600 ° C in a 12 mL / min N2 atmosphere, the mixed feed gas was switched to 12 mL / min, 14.1 vol% EB / N2 and 30 mL / min, 5 vol% O2 / N2. The catalyst could operate stably for 196 h. The highest X EB and S ST , C of the catalyst after 196h of reaction coke and Y ST See Tables 2 and 3.

[0062] Example 2

[0063] The preparation process of the catalyst is different from that of Example 1, except that the number of ALD deposition cycles is 50 and the deposition thickness is 5 nm. Other parameters and operation processes are the same as those of Example 1. The evaluation method of the catalyst is the same as that of Example 1. The catalyst can operate stably for 74 hours. The maximum X EB and S ST , C of the catalyst after 74h reaction coke and Y ST See Tables 2 and 3.

[0064] Example 3

[0065] The preparation process of the catalyst is different from that of Example 1, except that the commercial Al2O3 particle size is 20-40 mesh; the evaluation method of the catalyst is the same as that of Example 1; the catalyst can operate stably for 146 hours; the highest X EB and S ST , C of the catalyst after 146h of reaction coke and YST See Tables 2 and 3.

[0066] Example 4

[0067] The preparation process of the catalyst is compared with that of Example 1, except that the amount of FeCl3 used is 0.13g and the amount of ZrOCl2·8H2O used is 0.394g; the evaluation method of the catalyst is the same as that of Example 1; the catalyst can be stably operated for 120h; the maximum X EB and S ST , C of the catalyst after 120h of reaction coke and Y ST See Tables 2 and 3.

[0068] Example 5

[0069] The preparation process of the catalyst is the same as that of Example 1; the evaluation method of the catalyst is different from that of Example 1, except that the reaction temperature is 580°C; the catalyst can operate stably for 135h; the maximum X EB and S ST , C of the catalyst after 135h of reaction coke and Y ST See Tables 2 and 3.

[0070] Example 6

[0071] The catalyst preparation process was similar to that in Example 1, except that the commercial Al2O3 particle size was 20-40 mesh. Al2O3 was deposited on the catalyst precursor using an impregnation method. The procedure was as follows: 0.15 g of Al(NO3)3·9H2O was dissolved in 3 mL of deionized water, 1.0 g of the catalyst precursor was added, and the mixture was impregnated overnight. After drying at 60°C, the mixture was calcined in a muffle furnace at 600°C for 2 h at a heating rate of 2°C / min to obtain a powdered catalyst. Note: The thickness of the Al2O3 deposit obtained by the impregnation method could not be measured; the deposited amount was 2 wt% (of the catalyst precursor).

[0072] The evaluation method of the catalyst is the same as that of Example 1; the catalyst can operate stably for 128 hours; the highest X EB and S ST , C of the catalyst after 128h of reaction coke and Y ST See Tables 2 and 3.

[0073] Example 7

[0074] The catalyst preparation process is different from that in Example 1, except that the commercial Al2O3 particle size is 20-40 mesh. The catalyst precursor is hydrothermally deposited using the following procedure: 0.15g of Al(NO3)3·9H2O and 0.22g of CO(NH2)2 are weighed and dissolved in 20mL of deionized water, and then the CO(NH2)2 solution is added dropwise to the Al(NO3)3 solution. After stirring for 1h, 1.0g of the catalyst precursor is added and then transferred to a 100mL hydrothermal reactor for hydrothermal reaction. After a hydrothermal reaction at 100°C for 48h, the mixture is filtered and washed with water until neutral. After drying at 60°C, the mixture is calcined in a muffle furnace at 600°C for 2h at a heating rate of 2°C / min to obtain a hydrothermally deposited powder catalyst. Note: The thickness of the Al2O3 deposition could not be measured, and the deposition amount is 2wt% (of the catalyst precursor).

[0075] The evaluation method of the catalyst is the same as that of Example 1; the catalyst can operate stably for 112 hours; the highest X EB and S ST , C of the catalyst after 112h of reaction coke and Y ST See Tables 2 and 3.

[0076] Example 8

[0077] The preparation process of the catalyst is the same as that of Example 1; the evaluation method of the catalyst is different from that of Example 1, except that the reaction is carried out in a cycle of "direct dehydrogenation of ethylbenzene (oxygen-free) - catalyst air regeneration - direct dehydrogenation of ethylbenzene", first reacting in an oxygen-free state for 20 hours, then shutting off the ethylbenzene and introducing 30 mL / min of air into the reactor for 1 hour to regenerate the catalyst, and then reintroducing ethylbenzene after the regeneration is completed; the catalyst can operate stably for 100 hours; the maximum X EB and S ST , C of the catalyst after 100h of reaction coke and Y ST See Tables 2 and 3.

[0078] Comparative Example 1

[0079] The catalyst used was a commercial Fe-K catalyst for ethylbenzene oxidative dehydrogenation with a particle size of 20 to 40 meshes. The catalyst evaluation method was different from that in Example 1, except that the reaction type was DDH, the feed gas contained only 12 mL / min and 14.1 vol% EB / N2; the highest X EB and S ST , C of the catalyst after 10h of reaction coke and Y ST See Tables 2 and 3.

[0080] Comparative Example 2

[0081] The preparation process of the catalyst is different from that of Example 1, except that the commercial Al2O3 particle size is 20-40 mesh, does not contain FeCl3 and ZrOCl2·8H2O, and the ALD deposition technology and subsequent intermediate calcination step are not used. The evaluation method of the catalyst is different from that of Example 1, except that the reaction type is direct dehydrogenation of ethylbenzene (DDH), the feed gas contains only 12 mL / min and 14.1 vol% EB / N2; the catalyst has no stable operation section, and shows a trend of first increasing and then decreasing; the maximum X EB and S ST , C of the catalyst after 10h of reaction coke and Y ST See Tables 2 and 3.

[0082] Comparative Example 3

[0083] The preparation process of the catalyst is different from that of Example 1 in that the commercial Al2O3 particle size is 20-40 mesh, it does not contain ZrOCl2·8H2O, and the ALD deposition technology and subsequent intermediate calcination step are not used. The evaluation method of the catalyst is different from that of Example 1 in that the reaction type is DDH, the feed gas contains only 12 mL / min and 14.1 vol% EB / N2; the catalyst has no stable operation section and shows a trend of first increasing and then decreasing; the maximum X EB and S ST , C of the catalyst after 26h of reaction coke and Y ST See Tables 2 and 3.

[0084] Comparative Example 4

[0085] The catalyst preparation process is different from that in Example 1, except that the commercial Al2O3 particle size is 20-40 mesh, and the ALD deposition technology and subsequent intermediate calcination step are not used; the catalyst evaluation method is different from that in Example 1, except that the reaction type is DDH, the feed gas contains only 12 mL / min and 14.1 vol% EB / N2; the catalyst has no stable operation section, and shows a trend of first increasing and then decreasing; the maximum X EB and S ST , C of the catalyst after 26h of reaction coke and Y ST See Tables 2 and 3.

[0086] Comparative Example 5

[0087] The preparation process of the catalyst is different from that of Example 1, except that the commercial Al2O3 particle size is 20-40 mesh, and the ALD deposition technology and subsequent intermediate calcination step are not used; the evaluation method of the catalyst is the same as that of Example 1; the catalyst can be stably operated for 56 hours, with the highest X EB and S ST, C of the catalyst after 56h of reaction coke and Y ST See Tables 2 and 3.

[0088] Comparative Example 6

[0089] The preparation process of the catalyst is different from that of Example 1, except that FeCl3 and ZrOCl2·8H2O are not contained; the evaluation method of the catalyst is the same as that of Example 1; the catalyst can be stably operated for 32 hours, with a maximum X EB and S ST , C of the catalyst after 32h of reaction coke and Y ST See Tables 2 and 3.

[0090] Comparative Example 7

[0091] The preparation process of the catalyst is different from that of Example 1, except that H2PtCl4 and ZrOCl2·8H2O are not contained; the evaluation method of the catalyst is the same as that of Example 1; the catalyst can be stably operated for 34 hours, with a maximum X EB and S ST , C of the catalyst after 34h reaction coke and Y ST See Tables 2 and 3.

[0092] Comparative Example 8

[0093] The preparation process of the catalyst is different from that of Example 1, except that ZrOCl2·8H2O is not contained; the evaluation method of the catalyst is the same as that of Example 1; the catalyst can be stably operated for 50 hours, with a maximum X EB and S ST , C of the catalyst after 50h of reaction coke and Y ST See Tables 2 and 3.

[0094] Comparative Example 9

[0095] The preparation process of the catalyst is different from that of Example 1, except that the carrier is cordierite (20-40 mesh), the Al2O3 deposition method is the impregnation method, and the deposition process is the same as that of Example 6; the evaluation method of the catalyst is the same as that of Example 1; the catalyst can be stably operated for 32 hours, and the highest X EB and S ST , C of the catalyst after 32h of reaction coke and Y ST See Tables 2 and 3.

[0096] The comparative examples, examples, and accompanying characterization results demonstrate that the Pt-Fe bimetallic catalyst can enhance catalytic activity, that the addition of Zr contributes to carbon deposition resistance, that surface coating with a certain thickness of alumina can significantly enhance carbon deposition resistance, and that weak oxygen conditions extend the catalyst's stable reaction time. The present invention utilizes coating techniques such as ALD under these conditions to effectively maintain the stability of the metal valence state before and after the reaction, thereby enabling the catalyst of the present invention to exhibit enhanced catalytic activity, stability, and carbon deposition resistance in the oxidative dehydrogenation of ethylbenzene.

Claims

1. A method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions, comprising the following steps: Step 1: Loading of Pt, Fe and Zr on the surface of Al2O3 carrier to obtain catalyst precursor 1) Based on 100 parts by mass of the product, Al is calculated as Al2O3, Zr is calculated as ZrO2, Fe is calculated as Fe2O3, and Pt is calculated as PtO. Fe and Zr salts are weighed in a ratio of 85.5 to 95.5 parts by mass of Al2O3, 2 to 10 parts by mass of ZrO2, 0.5 to 5 parts by mass of Fe2O3, and 0.1 to 1.0 parts by mass of PtO, and the mixtures are dissolved in deionized water or alcohol, and then a water or alcohol solution of the Pt salt is added to obtain a mixed solution; 2) adding an Al2O3 carrier to the mixed solution obtained in step 1), and obtaining a catalyst precursor after impregnation, drying and calcination; Step 2: Coat the catalyst precursor with Al2O3 to obtain the catalyst 1) Using atomic layer deposition technology, with ultrapure Ar as the carrier gas and purge gas, the catalyst precursor obtained in the first step is subjected to a cycle of "exposure to an aluminum precursor - purge" and "exposure to ultrapure water - purge" 20 to 120 times to form an Al2O3 deposition layer on the catalyst precursor surface; 2) calcining the catalyst precursor coated with the Al2O3 deposition layer obtained in step 1) to obtain the high-activity, high-stability and carbon deposition-resistant catalyst.

2. The method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions according to claim 1, characterized in that: In step 1) of the first step, the Pt, Fe and Zr salts are one or two of nitrate, chloride, bromide, acetate, chloride oxide and ethanolate.

3. The method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions according to claim 1, characterized in that: In step 1) of the first step, Fe and Zr salts are weighed in a ratio of 90 to 95 parts by mass of Al2O3, 3 to 7 parts by mass of ZrO2, 1 to 3 parts by mass of Fe2O3 and 0.2 to 0.7 parts by mass of PtO, dissolved in deionized water or alcohol, and then a water or alcohol solution of the Pt salt is added to obtain a mixed solution.

4. The method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions according to claim 1, characterized in that: In step 2) of the first step, the immersion time is 10 to 18 hours, the drying temperature is 50 to 100°C, the calcination temperature is 600 to 900°C, and the calcination time is 2 to 5 hours; the concentration ranges of Pt, Fe, and Zr salts in the mixed solution are 6×10 -3 ~1.2×10 -2 mol / L, 0.08~0.18mol / L, 0.1~0.2mol / L, the volume and mass ratio of the mixed solution to the Al2O3 carrier is 2~3mL:1g.

5. The method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions according to claim 1, characterized in that: In step 1) of the second step, the aluminum precursor is one or two of aluminum chloride, aluminum isopropoxide, aluminum ethoxide, trimethylaluminum, tris(dimethylamino)aluminum, tris(diethylamino)aluminum, dimethylisopropoxyaluminum, and 3-dimethylaminopropylaluminum.

6. The method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions according to claim 1, characterized in that: In step 1) of the second step, the deposition temperature of the atomic layer deposition technology is 120-220°C; in each cycle operation, the catalyst precursor is exposed to the aluminum precursor for 0.01-1s, removed and purged with Ar for 10-40s, then exposed to H2O for 0.01-1s, removed and purged with Ar for 10-40s; the thickness of the obtained Al2O3 deposited layer is 2-12nm.

7. The method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions as claimed in claim 1, characterized in that: In step 2) of the second step, the calcination temperature is 600-900° C. and the calcination time is 2-8 hours.

8. The method for preparing a catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions as claimed in claim 1, characterized in that: In the second step 1), the atomic layer deposition technique is replaced by a hydrothermal method or an immersion method.

9. A catalyst with high activity, high stability and carbon deposition resistance under weak oxygen conditions, characterized by: The method is prepared by any one of claims 1 to 8.

10. Use of the catalyst of claim 9 that is highly active, highly stable and resistant to carbon deposition under weak oxygen conditions in the dehydrogenation of ethylbenzene to produce styrene.

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