A Ti x Zr1O y Preparation method of composite oxide catalyst and its application in the oxygen-free dehydrogenation reaction of propane

Abstract

The application discloses a Ti x Zr1O y A preparation method of a composite oxide catalyst, the Ti x Zr1O y The composite oxide catalyst comprises multiple crystal forms, and the preparation method comprises the following steps: preparing a mixed aqueous solution of a Ti metal salt, a Zr metal salt and a precipitant; performing low-temperature precipitation on the mixed aqueous solution to obtain a precipitate; and then washing and drying the precipitate to obtain a Ti, Zr-containing composite hydroxide; and the Ti, Zr-containing composite hydroxide is topologically transformed into a Ti x Zr1O y Composite oxide through high-temperature calcination. Through the method, the prepared catalyst has the characteristics of low cost, non-toxicity and harmlessness, and the catalyst has good propane aerobic dehydrogenation activity, reaction regeneration stability and selectivity, and has an industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of industrial catalysis technology, and particularly relates to a Ti x Zr1O y Preparation method of composite oxide catalyst and its application in the oxygen-free dehydrogenation reaction of propane. Background Technology

[0002] Propylene, as an important chemical raw material, can be processed into various value-added products, primarily polypropylene. The expansion of various propylene production processes is rapid, with meltblown nonwoven fabric, the core material for face masks, using polypropylene as its main raw material. Dow Chemical released a global trend forecast in 2016, predicting that propylene demand will grow at an average annual rate of 2% to 3% by 2035, exceeding production capacity between 2016 and 2035. In short, propylene, as a crucial petrochemical product, plays a vital role in the national economy and is an important indicator of a country's economic development level. We need to further develop economical and environmentally friendly catalysts to optimize propylene production technologies.

[0003] Traditional propylene production processes include fluidized bed catalytic cracking and steam cracking of naphtha and light diesel oil. However, both methods heavily rely on fossil fuels and emit large amounts of carbon dioxide, polluting the environment. Furthermore, these methods have low propylene selectivity and cannot meet the growing demand for propylene. Therefore, given these circumstances, there is an urgent need for a scientifically sound and economically efficient propylene production method. In recent years, several propylene production technologies have developed rapidly, such as propane dehydrogenation (PDH), methanol-to-olefins (MTO), and Fischer-Tropsch (FT) processes. Currently, propylene produced as a byproduct of catalytic cracking accounts for 23%, steam cracking for 36%, propane dehydrogenation or mixed dehydrogenation for 21%, and MTO for 20%.

[0004] Propane dehydrogenation (PDH) refers to the technology of dehydrogenating propane to propylene under the action of a catalyst. Compared with other industrial processes for producing propylene, the main advantages of propane dehydrogenation are its low investment cost, low carbon emissions, environmental friendliness, readily available and economically valuable propane, and easy separation of the propylene product. Propane dehydrogenation to propylene technology mainly includes oxygen-free dehydrogenation and propane oxidation. Oxygen-free dehydrogenation technology has already been industrialized, while oxidative dehydrogenation technology is still in the research and development stage. Most propane oxygen-free dehydrogenation reactions use precious metals (Pt) or environmentally hazardous chromium (Cr) as the active center for the dehydrogenation reaction. Although these catalysts have good dehydrogenation activity, the high cost of precious metal catalysts, the tendency for active components to sinter, and the high toxicity and environmental pollution of Cr-based catalysts necessitate the development of inexpensive, low-toxicity, or even non-toxic propane oxygen-free dehydrogenation catalysts.

[0005] With a large amount of Ti cusDefective TiO₂ with oxygen vacancies 2-x Nanomaterials are widely used in photocatalysis and have recently been studied as PDH catalysts. Xie et al. (ACS Catal. 2020, 10, 14678-14693) studied pure TiO2 (5-10 nm) nanoparticles and found that through in-situ reduction, they exhibited excellent propane dehydrogenation catalytic performance, with a propane conversion of 21% at 550 °C, a propylene selectivity as high as 94%, and an initial propylene formation rate of 0.07 mmol g. -1 min -1 At 600℃, the initial conversion of propane can reach 67%, the single-pass yield of propylene is 45%, and the initial propylene formation rate is 0.17 mmol g. -1 min -1 Han et al. (Catal. Sci. Technol. 2020, 10, 7046-7055) prepared a Zn-supported TiO2 catalyst by impregnation. After H2 pretreatment and reduction, the initial propylene formation rate at 550℃ was 0.35 mmol g. -1 min -1 It is 5 times that of pure TiO2. The VO2 prepared by Ji et al. (ACS Appl. Nano Mater. 2023, 6, 7, 6354–6364) x The propylene yield of doped TiO2 (~26 nm) nanoparticles was 0.342 mmol g under UV-Vis irradiation at 500 °C. -1 min -1 It is 4.89 times that of pure TiO2. However, V-based catalysts are still toxic, and further research is needed to find non-toxic, environmentally friendly metals for doping modification. Xu et al. (ACS Catal. 2023, 13, 9, 6104–6113) prepared highly dispersed TiO2 with a thickness of approximately 2 atomic layers using the sol-gel method. x Ultrathin nanosheet catalyst TiO x / Al2O3, propylene formation rate at 600℃: 0.175 mol g Ti -1 h -1 With a propylene steady-state selectivity of nearly 93% and a low deactivation rate constant (kd = 0.0126 h⁻¹), it exhibits excellent performance. -1 However, this catalyst not only has a long preparation time and complicated steps, but also uses highly toxic hexadecyltrimethylammonium bromide and easily explosive concentrated nitric acid, posing risks for industrial application. Shang et al. (Ind. Eng. Chem. Res. 2021, 60, 35, 12811–12820) synthesized 1.5Sc / TiO2 catalyst using a solvothermal method. x Catalyst, propylene formation rate at 600℃: 0.7 mmol g -1 min-1 However, the hydrated scandium nitrate used in this catalyst is not only expensive but also flammable and explosive. In addition, it uses highly toxic hexadecyltrimethylammonium bromide, which also poses risks for industrial application.

[0006] Zhang et al. (J Catal. 2019, 3, 313-324) prepared a series of ZrO2 catalysts composed of monoclinic or tetragonal phases using precipitation, hydrothermal, or thermal evaporation methods. Among them, the initial propylene formation rate of m-ZrO2_1 was 0.31 mmol g at a reaction temperature of 550 °C. -1 min -1 Qu et al. (ACS Sustainable Chem. Eng. 2021, 9, 38, 12755–12765) prepared a series of ZnZr... x O y The initial propylene formation rate at 550℃ for ZnZr₂O is 0.18 mmol g. -1 min -1 Zhang et al. (ACS Catal. 2020, 10, 11, 6377–6388) used 1 nm uniform Rh nanoparticles impregnated with monoclinic ZrO2, where the initial propylene formation rate at 550 °C was 1.2 mmol g / L with a 0.05 Rh / ZrO2 ratio. -1 min -1 However, the RhCl3·xH2O used to prepare this catalyst is toxic and expensive, which is not conducive to industrial applications. Alexander Zubkov et al. (Crystals. 2021, 11, 1435) prepared Cr using a simple co-precipitation method. 10 Zr 90 O x Catalyst, initial propylene formation rate at 600℃: 0.96 mmol g -1 min -1 Although compared to ZnZr x O y The activity was greatly improved, but Cr-based catalysts are toxic and pose risks for industrial applications. Feng et al. (AIChE J.2023,9,69(5):e18011) synthesized VO42-containing monoclinic (ZrO2-M), tetragonal (ZrO2-T), and binary monoclinic-tetragonal (ZrO2 MT) phases deposited on ZrO2 support by precipitation method. x Nanocatalysts. Among them, 4VO x / ZrO2-M 31 T 69 The initial propylene formation rate at 580℃ was 0.2 mmol g. -1 min -1Deactivation rate constant K d Only 0.22h -1 It is relatively stable. Zhang et al. (ACS Catal. 2023, 10, 13, 6893–6904) prepared a series of Ga-doped ZrO2 catalysts using a hydrothermal method, among which GaZrO2... x The yield of propylene at a reaction temperature of 550 °C was 0.14 mmol g. -1 min -1 However, Ga-based catalysts are expensive, and there is still a need to continue searching for inexpensive and easily prepared metals for doping modification. Han et al. (ACS Catal. 2020, 10, 15, 8933–8949) studied MZrO x (M=Ce,La,Ti or Y), where TiZrO x After CO pretreatment and reduction, the initial propylene formation rate at 550℃ was only 0.05 mmol g. -1 min -1 Its activity is not as good as that of pure ZrO2.

[0007] In summary, it is very meaningful to propose a catalyst system for propane dehydrogenation that uses inexpensive raw materials, is simple and quick to prepare, and is suitable for industrial production. Summary of the Invention

[0008] The present invention aims to solve one of the technical problems existing in the prior art or related technologies.

[0009] In view of this, on the one hand, the present invention proposes a Ti x Zr1O y A method for preparing a composite oxide catalyst, wherein the Ti x Zr1O y The composite oxide catalyst includes various crystal forms, and the preparation method includes the following steps:

[0010] Prepare a mixed aqueous solution of Ti metal salt, Zr metal salt and precipitant;

[0011] The mixed aqueous solution was subjected to low-temperature precipitation to obtain a precipitate;

[0012] The precipitate was then washed and dried to obtain a hydroxide containing Ti and Zr complex.

[0013] The hydroxide containing Ti and Zr complex undergoes topological transformation to Ti upon high-temperature calcination. x Zr1O y Composite oxides;

[0014] Preferably, the Ti metal salt is one or more of titanium chloride and titanium sulfate; the Zr metal salt is one or more of zirconium nitrate and zirconium oxychloride; and the precipitant is one or more of ammonium hydroxide solution, ethylenediamine, sodium hydroxide, and ammonia water.

[0015] Preferably, the above preparation method includes: dissolving Ti metal salt and Zr metal salt in deionized water to prepare solution A under a constant temperature ice-water bath below 0°C, and using precipitant solution B; slowly and uniformly adding solution B to solution A under vigorous stirring in a constant temperature ice-water bath below 0°C, then aging at room temperature for 0-24 hours, filtering and washing the product, and drying it at 60-100°C for 0-12 hours to obtain Ti and Zr composite hydroxide, which is then calcined in a muffle furnace at 550-750°C to obtain composite metal oxide catalysts with different crystal forms.

[0016] Preferably, the molar ratio of Ti to Zr in the Ti metal salt and Zr metal salt is 1:9-9:1;

[0017] Preferably, titanium sulfate and zirconium oxychloride octahydrate are added to 100 ml of deionized water, mixed and stirred for half an hour to form solution A, which is then placed in an ice-water bath. Under constant temperature ice-water bath below 0°C, the mixture is stirred continuously and precipitated in a mixed solution of ammonia solution with a concentration of 15wt%-25wt%, and the pH value is adjusted to 9-10. The solution is filtered, washed with deionized water until no chloride ions are present, and then washed twice with anhydrous ethanol. The solution is dried at 60-100°C for 0-12 hours to obtain the oxide precursor. The oxide precursor is calcined in flowing air at 500-750°C at 2°C / min for 4 hours to obtain TixZr1Oy composite oxides with different crystal forms.

[0018] On the other hand, the present invention provides a Ti x Zr1O y The application of composite oxide catalysts can be used in the oxygen-free dehydrogenation reaction of propane.

[0019] Preferably, the catalyst is used for the dehydrogenation process of low-carbon alkanes, and the application conditions are: reaction temperature of 525–600°C and space velocity of 0.5–4 ml g. -1 min -1 Reduction atmosphere: CO, H2, NH3, methane, ethane, propane, air; reduction time: 5 min-5 h; reduction temperature: 400-700℃.

[0020] This invention proposes a Ti x Zr1O yThe method for preparing composite oxide catalysts not only produces catalysts that are low in cost and non-toxic, but also uses conventional reagents such as Ti salt, Zr salt, and ammonia water, which are all inexpensive.

[0021] Furthermore, the catalyst prepared in this invention exhibits excellent propane oxygen-free dehydrogenation activity, Ti x Zr1O y The composite oxide catalyst exhibits a higher initial propylene production rate than most reported TiO2 and ZrO2 catalysts. Furthermore, the TiO2 catalyst with altered crystal structure... x Zr1O y Composite oxides compared to reported commercial TiZrO x The initial rate of propylene production is greatly improved; at the same time, it has good reaction regeneration stability and selectivity, thus also having good prospects for industrial application.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the present invention. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 These are the XRD diffraction patterns of catalysts with a Ti to Zr molar ratio ranging from 1:1 to 5:1 in the embodiments of this invention.

[0026] Figure 2 This is a TEM image of the Ti3Zr1 catalyst in the embodiments of the present invention;

[0027] Figure 3 These are the XRD diffraction patterns of the catalyst with a Ti to Zr molar ratio of 3:1 in the embodiments of the present invention at different temperatures;

[0028] Figure 4 The propane conversion (a) and propylene selectivity (b) of the catalyst with a Ti to Zr molar ratio of 3:1 at different temperatures in the embodiments of the present invention (550°, total flow rate 20 ml / min, N2:C3H8:H2=8:1:1);

[0029] Figure 5 The examples of this invention show the initial rate of propylene formation and propylene selectivity of the catalyst with a Ti to Zr molar ratio of 3:1 under different reducing atmospheres and reduction times.

[0030] Figure 6 The initial rate of propylene formation and propylene selectivity in the cyclic regeneration of the catalyst with a Ti to Zr molar ratio of 3:1 in the embodiments of the present invention are shown.

[0031] Figure 7 The examples in this invention show the initial propylene production rate and propylene selectivity of the 3:1 Ti to Zr molar ratio catalyst under different pretreatment and reaction conditions. Detailed Implementation

[0032] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0033] On the one hand, this implementation plan proposes a Ti x Zr1O y A method for preparing a composite oxide catalyst, wherein the Ti x Zr1O y The composite oxide catalyst includes various crystal forms, and the preparation method includes the following steps:

[0034] Prepare a mixed aqueous solution of Ti metal salt, Zr metal salt and precipitant;

[0035] The mixed aqueous solution was subjected to low-temperature precipitation to obtain a precipitate;

[0036] The precipitate was then washed and dried to obtain a hydroxide containing Ti and Zr complex.

[0037] The hydroxide containing Ti and Zr complex undergoes topological transformation to Ti upon high-temperature calcination. x Zr1O y Composite oxides;

[0038] Preferably, the Ti metal salt is one or more of titanium chloride and titanium sulfate; the Zr metal salt is one or more of zirconium nitrate and zirconium oxychloride; and the precipitant is one or more of ammonium hydroxide solution, ethylenediamine, sodium hydroxide, and ammonia water.

[0039] Preferably, the above preparation method includes: dissolving Ti metal salt and Zr metal salt in deionized water to prepare solution A under a constant temperature ice-water bath below 0°C, and using precipitant solution B; slowly and uniformly adding solution B to solution A under vigorous stirring in a constant temperature ice-water bath below 0°C, then aging at room temperature for 0-24 hours, filtering and washing the product, and drying it at 60-100°C for 0-12 hours to obtain Ti and Zr composite hydroxide, which is then calcined in a muffle furnace at 550-750°C to obtain composite metal oxide catalysts with different crystal forms.

[0040] Preferably, the molar ratio of Ti to Zr in the Ti metal salt and Zr metal salt is 1:9-9:1;

[0041] Preferably, titanium sulfate and zirconium oxychloride octahydrate are added to 100 ml of deionized water to prepare solutions. The solutions are mixed and stirred for half an hour to obtain solution A, which is then placed in an ice-water bath. Under constant temperature ice-water bath conditions below 0°C, the solution is continuously stirred to precipitate a mixture of 15 wt%-25 wt% ammonia solution, and the pH is adjusted to 9-10. The solution is filtered, washed with deionized water until no chloride ions are present (tested with 0.1 mol / L AgNO3 solution), and then washed twice with anhydrous ethanol. The precursor is dried at 60-100°C for 0-12 hours to obtain the oxide precursor. The precursor is calcined in flowing air at 500-750°C for 4 hours at 2°C / min to obtain TixZr1Oy composite oxides with different crystal forms.

[0042] This invention uses a modified co-precipitation method to prepare Ti x Zr1O y The composite oxide catalyst was prepared by slowly and uniformly adding the precipitant dropwise into a solution containing different proportions of Ti and Zr salts, followed by stirring in an ice-water bath for 1-2 hours. Compared to the hydrothermal method, this significantly reduced the preparation time and increased the yield, while maintaining consistent crystal structure even after scale-up. After filtration and drying, the Ti was calcined to obtain Ti. x Zr1O y Composite oxide catalysts. The preparation process is simple, easy to operate, and suitable for industrial production.

[0043] On the other hand, the present invention provides a Ti x Zr1O y The application of composite oxide catalysts is for catalyzing the dehydrogenation process of low-carbon alkanes such as propane.

[0044] Preferably, the catalyst is used for the dehydrogenation process of low-carbon alkanes, and the application conditions are: reaction temperature of 525–600°C and space velocity of 0.5–4 ml g. -1 min -1 Reduction atmosphere: CO, H2, NH3, methane, ethane, propane, air; reduction time: 5 min-5 h; reduction temperature: 400-700℃.

[0045] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore only examples, not intended to limit the scope of protection of the present invention.

[0046] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0047] Unless otherwise specified, all experimental materials used in the following examples were purchased from conventional reagent stores.

[0048] Example 1

[0049] The molar ratio of Ti to Zr ranges from 1:9 to 9:1. According to the mass values ​​in Table 1, weigh titanium sulfate and zirconium oxychloride octahydrate and add them separately to 100 ml of deionized water to prepare solutions. Mix and stir for half an hour to obtain solution A, and place it in an ice-water bath. Under constant temperature ice-water bath below 0℃, continuously stir to precipitate the mixture of 15wt%-25wt% ammonia solution, adjusting the pH to 9-10. Filter, wash with deionized water until no chloride ions are present (tested with 0.1 mol / L AgNO3 solution), and then wash twice with anhydrous ethanol. Dry at 80℃ for 10 h to obtain the oxide precursor. Calcine at 650℃ in flowing air at 2℃ / min for 4 h to obtain Ti with different crystal forms. x Zr1O y Composite oxides, such as Figure 1 As shown in the XRD pattern, a transition of three main crystalline phases occurs from Ti5Zr1 to Ti1Zr1: TiO2, Ti2ZrO6, and ZrTiO4. With the incorporation of Zr, the TiO2 crystalline phase is gradually suppressed. Figure 2 This is a TEM image of Ti3Zr1, showing Ti prepared by a modified simple precipitation method. x Zr1O y Ti and Zr elements are uniformly dispersed in nanoparticles (2-25nm).

[0050] This application example evaluated the propane oxygen-free dehydrogenation activity of samples prepared in the examples with Ti:Zr molar ratios ranging from 1:1 to 5:1. The catalyst performance evaluation was conducted on a micro fixed-bed reactor. After the reaction, the composition of the gas was quantitatively analyzed online using a gas chromatograph (SP-3420, Beijing Analytical Instrument Factory). The reactor was a transparent fixed-bed quartz reaction tube with an inner diameter of 8 mm and a wall thickness of 1 mm. The catalyst was placed in the isothermal section of the heating furnace and fixed with quartz wool above and below. A precise temperature controller was used to control the temperature during the experiment, and the heating furnace used a programmed temperature control system. The catalyst loading was 0.2 g, and the total feed gas flow rate was 40 mL / min. -1(C3H8:N2:H2 = 2:2:1, volume ratio), the reaction gas pressure was atmospheric pressure, and the particle size of the catalyst sample was 40 to 80 mesh. The activity test results are shown in Table 2, with a space velocity of 1 ml g / L. -1 min -1 Initial production rates of propylene with different molar ratios of titanium and zirconium at temperatures ranging from 525 to 600°C.

[0051] Table 1. Mass of metal salts used for different Ti and Zr molar ratios.

[0052] Ti / Zr molar ratio <![CDATA[Mass of TiSO4 / g]]> <![CDATA[Mass of ZrOCl2·8H2O / g]]> 1:1 2.4 3.22 1:3 0.80 3.22 1:5 0.48 3.22 1:7 0.34 3.22 1:9 0.27 3.22 2:1 2.4 1.61 3:1 2.4 1.07 4:1 2.4 0.81 5:1 2.4 0.64 7:1 2.4 0.46 9:1 2.4 0.36

[0053] Table 2. Initial propylene production rates at different temperatures for catalysts with Ti:Zr molar ratios from 1:1 to 5:1.

[0054]

[0055] Example 2

[0056] According to Table 1, with a Ti to Zr molar ratio of 3:1, titanium sulfate and zirconium oxychloride octahydrate were weighed and added to 100 ml of deionized water to prepare solutions. The mixture was stirred for half an hour to obtain solution A, which was then placed in an ice-water bath. Under constant temperature (below 0°C) in the ice-water bath, the mixture was continuously stirred to precipitate the 15 wt%–25 wt% ammonia solution, and the pH was adjusted to 9–10. The solution was filtered, washed with deionized water until no chloride ions were found (tested with 0.1 mol / L AgNO3 solution), and then washed twice with anhydrous ethanol. The precursor was dried at 80°C for 10 hours to obtain the oxide precursor. Calcination at 550, 600, 650, 700, and 750°C in flowing air at 2°C / min for 4 hours yielded different crystal forms of the same composite oxide. Figure 3 .

[0057] In this application example, the propane oxygen-free dehydrogenation reaction activity of the Ti / Zr molar ratio 3:1 sample prepared in Example 2 was evaluated. The catalyst performance evaluation was conducted on a micro fixed-bed reactor. After the reaction, the composition of the gas was quantitatively analyzed online using a gas chromatograph (SP-3420, Beijing Analytical Instrument Factory). The reactor was a transparent fixed-bed quartz reaction tube with an inner diameter of 8 mm and a wall thickness of 1 mm. The catalyst was placed in the isothermal section of the heating furnace and fixed with quartz wool above and below. A precise temperature controller was used to control the temperature during the experiment, and the heating furnace was programmed for temperature rise. The catalyst loading was 0.2 g, and the total feed gas flow rate was 20 mL / min. -1 (C3H8:N2:H2 = 1:8:1, volume ratio), the reaction gas pressure is atmospheric pressure, and the catalyst sample particle size is 40 to 80 mesh. Activity test results are as follows: Figure 4 As shown, the air velocity is 1 mlg.-1 min -1 The Ti3Zr1 catalyst calcined at 650℃ achieved a maximum propane conversion of 16.5% at 550℃, while also exhibiting the highest propylene selectivity (around 97.7%) and good stability (k). d =0.04h -1 ).

[0058] Example 3

[0059] In this application example, the propane oxygen-free dehydrogenation reaction activity of the Ti / Zr molar ratio 3:1 sample prepared in Example 1 was evaluated. The catalyst performance evaluation was conducted on a micro fixed-bed reactor. After the reaction, the composition of the gas after the reaction was quantitatively analyzed online using a gas chromatograph (SP-3420, Beijing Analytical Instrument Factory). The reactor was a transparent fixed-bed quartz reaction tube with an inner diameter of 8 mm and a wall thickness of 1 mm. The catalyst was placed in the isothermal section of the heating furnace and fixed above and below with quartz wool. A precise temperature controller was used to control the temperature during the experiment, and the heating furnace used a programmed temperature control system. The catalyst loading was 0.05 g, and the total feed gas flow rate was 40 mL / min. -1 (C3H8:N2:H2 = 2:2:1, volume ratio), the reaction gas pressure is atmospheric pressure, and the particle size of the catalyst sample is 40 to 80 mesh. Activity test results are as follows... Figure 5 As shown, the space velocity is 1 ml g -1 min -1 At a reaction temperature of 550℃, the Ti3Zr1 catalyst achieved a peak initial propylene conversion rate of 0.62 mmol g after 1 h of H2 reduction. -1 min -1 The highest initial propylene conversion rate of 0.66 mmol g was reached after 15 minutes of CO reduction. -1 min -1 CO has a higher reducing power than H2. In the same reduction time, it will consume more lattice oxygen and generate more oxygen vacancies and coordinated unsaturated metal-oxygen acid-base pairs.

[0060] Example 4

[0061] In an application example, the propane oxygen-free dehydrogenation reaction activity of the Ti / Zr molar ratio 3:1 sample prepared in Example 1 was tested for reaction regeneration stability. Catalyst performance evaluation was conducted on a micro fixed-bed reactor. After the reaction, the composition of the gas after the reaction was quantitatively analyzed online using a gas chromatograph (SP-3420, Beijing Analytical Instrument Factory). The reactor was a transparent fixed-bed quartz reaction tube with an inner diameter of 8 mm and a wall thickness of 1 mm. The catalyst was placed in the isothermal section of the heating furnace and fixed above and below with quartz wool. A precise temperature controller was used to control the temperature during the experiment, and the heating furnace used a programmed temperature control system. The catalyst loading was 0.2 g, and the total feed gas flow rate was 20 mL / min. -1 (C3H8:N2:H2 = 1:8:1, volume ratio), the reaction gas pressure is atmospheric pressure, and the catalyst sample particle size is 40 to 80 mesh. Regeneration conditions are: 550℃ with air only (flow rate 10 ml / min) for 30 min, followed by nitrogen (flow rate 10 ml / min) for 5 min, before the next round of testing. The total flow rate of the feed gas is 20 mL / min. -1 (C3H8:N2:H2 = 1:8:1, volume ratio). The initial yield decreases with continuous catalyst regeneration, but the stability is excellent; the deactivation rate constant K remains constant in the fifth cycle. d =0.0077h -1 This is superior to the aforementioned studies on catalysts for TiO2 and ZrO2.

[0062] It can be seen that different crystal forms of Ti x Zr1O y Within the composite oxide system, different titanium-zirconium molar ratios affect the crystal structure of the composite oxide, significantly influencing its propane dehydrogenation catalytic performance. Different pretreatment conditions (reducing atmosphere, time, and temperature) also affect the propane dehydrogenation catalytic performance.

[0063] Comparative Example

[0064] The propane dehydrogenation activity of the Ti / Zr molar ratio 3:1 sample prepared in Example 1 under different pretreatment and reaction conditions was evaluated. Catalyst performance evaluation was conducted on a micro fixed-bed reactor. After the reaction, the composition of the gas was quantitatively analyzed online using a gas chromatograph (SP-3420, Beijing Analytical Instrument Factory). The reactor was a transparent fixed-bed quartz reaction tube with an inner diameter of 8 mm and a wall thickness of 1 mm. The catalyst was placed in the isothermal section of the heating furnace and fixed with quartz wool. A precise temperature controller was used to control the temperature during the experiment, and the heating furnace was programmed for temperature rise. The catalyst loading was 0.05 g, and the total feed gas flow rate was 40 mL / min. -1(C3H8:N2:H2 = 2:2:1, volume ratio), the reaction gas pressure is atmospheric pressure, and the particle size of the catalyst sample is 40 to 80 mesh. Activity test results are as follows... Figure 7 As shown, the pretreatment conditions had a significant impact on the reaction activity. After pretreatment with H2 reducing gas, the initial propylene formation rate at 550℃ was 0.45 mmol g. -1 min -1 The initial propylene formation rate at 550℃ was 0.66 mmol g after CO reducing gas pretreatment, which was 1.7 times that of the untreated rate. -1 min -1 The yield was 2.5 times that of the untreated product. Furthermore, the reducing gas in the reaction process also affected the catalytic activity; similarly, after H2 reducing gas pretreatment, the initial propylene formation rate at 550℃ with added H2 was 0.62 mmol g / L. -1 min -1 It is 1.4 times the initial propylene formation rate without the addition of reducing gas.

[0065] This invention utilizes titanium and zirconium, elements abundant in the Earth's crust, and employs a modified co-precipitation method to prepare a highly active propane oxygen-free dehydrogenation catalyst. After a simple reduction pretreatment, it can be directly used for the oxygen-free dehydrogenation of propane to olefins. Specifically, Ti catalysts with different Ti / Zr ratios are prepared using the co-precipitation method. x Zr1O y Composite oxides were synthesized, and the crystal phase was controlled by adjusting the calcination temperature. Reduction pretreatment (reduction atmosphere, time, and temperature) was applied to the aforementioned Ti. x Zr1O y The composite oxides were found to exhibit a volcanic relationship between their reducing power and propane dehydrogenation catalytic performance. Among them, Ti3Zr1O... y After H2 reduction pretreatment with the composite oxide catalyst, the initial propane-propylene formation rates at 550 and 600 °C were 0.62 and 1.71 mmol g, respectively. -1 min -1 propylene selectivity was 97.6%. Meanwhile, Ti... x Zr1O y The stability of the composite oxide catalyst increases after continuous regeneration, and the deactivation rate constant k d Only 0.0077h -1 This high-efficiency propane dehydrogenation catalyst is comparable to industrial Pt-based catalysts. It boasts advantages such as low cost, simple preparation, and non-toxicity, making it a promising candidate for industrial application.

[0066] This invention provides a cheaper and non-toxic alternative to the propane dehydrogenation catalysts currently used in industry. The catalyst has excellent conversion rate, selectivity and stability, and has significant technical and economic benefits, thus having broad application value.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these changes and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A Ti x Zr1O y The application of composite oxide catalysts is characterized by, The Ti x Zr1O y Composite oxide catalysts include various crystal forms; The Ti x Zr1O y The preparation method of the composite oxide catalyst includes the following steps: Prepare a mixed aqueous solution of Ti metal salt, Zr metal salt and precipitant; The mixed aqueous solution was subjected to low-temperature precipitation to obtain a precipitate; The precipitate was then washed and dried to obtain a hydroxide containing Ti and Zr complex. The hydroxide containing Ti and Zr complex undergoes topological transformation to Ti upon high-temperature calcination. x Zr1O y Composite oxides; The molar ratio of Ti to Zr in the Ti metal salt and Zr metal salt is 1:9-9:1; Add titanium sulfate and zirconium oxychloride octahydrate to 100 ml of deionized water respectively, mix and stir for half an hour to make solution A, and place it in an ice water bath; Precipitation was carried out in a mixed solution of ammonia solution with a concentration of 15wt%-25wt% under constant temperature ice-water bath below 0 °C with continuous stirring, and the pH value was adjusted to 9-10. The solution was filtered, washed with deionized water until no chloride ions were found, and then washed twice with anhydrous ethanol. The precursor was dried at 60-100 °C for 0-12 h to obtain the oxide precursor. The oxide precursor was calcined in flowing air at 500-750 °C at 2 °C / min for 4 h to obtain Ti with different crystal forms. x Zr1O y Composite oxides; The Ti x Zr1O y The composite oxide catalyst was applied to the oxygen-free dehydrogenation reaction of propane. The dehydrogenation process was carried out at a reaction temperature of 525–600 °C, a space velocity of 0.5–4 ml g⁻¹ min⁻¹, a reducing atmosphere of CO, H₂, NH₃, methane, ethane, or propane, a reduction time of 5 min–5 h, and a reduction temperature of 400–700 °C.

2. A Ti according to claim 1 x Zr1O y The application of composite oxide catalysts is characterized by, The Ti metal salt is one or more of titanium chloride and titanium sulfate; the Zr metal salt is one or more of zirconium nitrate and zirconium oxychloride; the precipitant is one or more of ammonium hydroxide solution, ethylenediamine, sodium hydroxide, and ammonia water.

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