Pd-Te / TiO2 catalyst for reaction of preparing acetone through propylene gas phase oxidation as well as preparation method and application of Pd-Te / TiO2 catalyst

Abstract

The invention discloses a Pd-Te / TiO2 catalyst for preparing acetone through propylene gas phase oxidation as well as a preparation method and application of the Pd-Te / TiO2 catalyst. The Pd-Te / TiO2 catalyst is prepared from the following elements in percentage by weight: 0.5 to 3.0 percent of Pd and 0.03 to 0.07 percent of Te. The catalyst provided by the invention can oxidize propylene into acetone in one step at a lower reaction temperature by taking molecular oxygen as an oxidizing agent, has high atom utilization rate and does not pollute the environment. The Pd-Te / TiO2 catalyst is prepared by adopting an equivalent-volume impregnation method, the target product selectivity is high, meanwhile, the preparation method is simple and easy to implement, industrialization is easy to realize, and the Pd-Te / TiO2 catalyst is a simple and efficient catalyst for preparing acetone through propylene oxidation.

Description

TECHNICAL FIELD

[0001] The present application relates to a catalyst for catalyzing propylene gas phase one-step oxidation to prepare acetone and a preparation method thereof, in particular, a low-content Pd-Te bimetallic catalyst supported on a TiO2 carrier for a reaction process of propylene gas phase one-step oxidation to prepare acetone with molecular oxygen as an oxidant. BACKGROUND

[0002] Acetone is an important organic synthesis raw material, which is mainly used as an organic solvent in the industries of organic glass, explosives, pesticides, plastics, leather-making, rubber, fiber, oil, paint spraying, medicine, etc., and can also be used as an important chemical raw material for synthesizing polyisoprene rubber, bisphenol A, acetone cyanohydrin, methyl methacrylate (MMA), hexanediol, methyl ethyl ketone, methyl isobutyl ketone, propiopyl ketone enone, epoxy resin, acetic anhydride, organic glass, polycarbonate, iodoform, methacrylic acid, methyl ester, chloroform, etc., and is an important chemical intermediate. Initially, acetone was produced by fermentation and isopropanol dehydrogenation. The fermentation method has a complex process, low yield, great difficulty in separation and purification, and high cost, and is difficult to be large-scale industrialized. The isopropanol dehydrogenation method needs high-temperature conditions for dehydrogenation reaction, has great energy consumption, and has low yield, limited catalyst life, and frequent regeneration, which increases the production cost and operational complexity. Later, the cumene method replaced the above methods. After the industrialization of the cumene method, the production of acetone has been increasing year by year, and the cumene method has become the main method for producing acetone. However, the cumene method has a complex process flow, involves multiple reaction steps and separation processes, has large equipment investment, and has many by-products, which requires complex separation and purification means.

[0003] The propylene oxidation method is a new process for producing acetone, and the reaction principle is that propylene is adsorbed on the surface of the catalyst, and then undergoes incomplete oxidation reaction with oxygen under the action of the catalyst to generate the target product acetone. Compared with the traditional acetone production process, the raw material source of the propylene oxidation method is more extensive, propylene is an important basic raw material in petroleum chemical industry, has large output, relatively stable price, and is easy to obtain, has lower procurement cost and transportation cost. In terms of process conditions, the process flow of the propylene oxidation method is simpler, has fewer reaction steps, the reaction is usually carried out at lower temperature and pressure, the requirements for equipment are relatively low, the equipment investment and operating cost are reduced. At the same time, the propylene oxidation method produces less waste and pollutants in the production process, and has less impact on the environment. However, various by-products such as propylene aldehyde and propylene acid are easily generated in the propylene oxidation process, which reduces the selectivity of acetone. Therefore, how to optimize the catalyst and reaction conditions to obtain higher acetone selectivity and reduce the generation of by-products is the main problem currently faced.

[0004] Au-based catalysts have been widely used in studies of the gas-phase epoxidation of propylene to propylene oxide (PO). For example, as reported in the literature (Catalysis Communications, 90, 2017, 87–90), in the epoxidation of propylene to propylene oxide catalyzed by the Au / TS-1 catalyst, propylene oxide is the major product (98% selectivity) at a relatively low temperature (164 °C) in the presence of H2 and O2, while acetone is a byproduct with very low selectivity. Therefore, a simple strategy for the high-yield acetone production by the gas-phase oxidation of propylene using the Au / TS-1 catalyst remains difficult to achieve. The literature (Current Organic Synthesis, 2020, 17, 685-690) reports that an Au / TS-1 catalyst prepared by a deposition-precipitation method can synthesize acetone via the gas-phase oxidation of propylene in the presence of H2 and O2, achieving a selectivity of 70.6% for acetone at 280 °C. While the Au-based catalysts reported in the aforementioned literature can improve the acetone selectivity of the gas-phase epoxidation of propylene to acetone, they all require the presence of both H2 and O2 to complete the reaction. The use of H2 increases raw material costs, and its utilization efficiency is also high during the reaction. Therefore, there is a need to develop a more efficient, simpler, and higher-yield method for acetone synthesis. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a Pd-Te / TiO2 catalyst with high activity, high stability, simple process and no environmental pollution for catalyzing the gas-phase oxidation of propylene to acetone, as well as its preparation method and application.

[0006] The objective of this invention can be achieved through the following technical solution: a Pd-Te / TiO2 catalyst for catalyzing the gas-phase epoxidation of propylene to acetone, the catalyst comprising the following components by weight percentage:

[0007] Pd 0.5–3.0%,

[0008] Te 0.03~0.07%.

[0009] Furthermore, the Pd-Te / TiO2 catalyst was prepared by an equal-volume impregnation method.

[0010] This invention also provides a method for preparing a Pd-Te / TiO2 catalyst for the gas-phase oxidation of propylene to acetone, comprising the following steps:

[0011] TeCl4 and PdCl2 solutions were added dropwise to deionized water and stirred until homogeneous. Then, a certain amount of TiO2 support was added, stirred at room temperature, and impregnated by equal volume for 6 hours. After that, it was dried at 110℃ for 12 hours and calcined at 300℃ in a hydrogen atmosphere (80 mL / min, concentration of 10%, with N2 as the equilibrium gas) for 2 hours to finally obtain the Pd-Te / TiO2 catalyst.

[0012] The present invention also provides an application of a Pd-Te / TiO2 catalyst for catalyzing the gas-phase oxidation of propylene to acetone, wherein the catalyst is used for one-step gas-phase oxidation of propylene to acetone.

[0013] Furthermore, the conditions for the catalytic oxidation reaction are: a quartz tube fixed-bed reactor, a reaction temperature of 180–260 °C, and a reaction space velocity of 3000 mL·g⁻¹. -1 ·h -1 The volume ratio of propylene to oxygen is 2:1.

[0014] This invention employs an equal-volume impregnation method to prepare a Pd-Te / TiO2 catalyst. During preparation, the atomic ratio of Pd to Te is adjusted by varying the Te content. Since Te has a weak adsorption and activation capacity for O2-containing species on the catalyst surface, it has a blocking and dispersing effect on the continuous Pd sites on the catalyst surface. Therefore, the addition of a small amount of Te can prevent excessive activation of O2 by Pd on the catalyst, inhibit O2 dissociation, thereby suppressing the complete oxidation of propylene to generate byproducts and promoting the epoxidation of propylene to acetone, thus improving product selectivity.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The catalyst has a low loading of active components and is easy to prepare. The raw material gas does not need H2 in the reaction process. O2 is used as the oxidant, and acetone is produced by gas-phase one-step oxidation. It has low cost and high atom utilization rate, which is beneficial to industrial production.

[0017] (2) The Pd-Te / TiO2 catalyst prepared by the equal volume impregnation method can significantly inhibit the complete oxidation of propylene, improve the selectivity of acetone, the product of epoxidation reaction, and has good stability. It is an economical and efficient catalyst for the gas-phase oxidation of propylene to acetone. Attached Figure Description

[0018] Figure 1 For Pd 150 -Activity diagram of Te1 / TiO2 catalyst for the gas-phase epoxidation of propylene to acetone at different temperatures;

[0019] Figure 2Comparison of propylene conversion rates for propylene gas-phase epoxidation to acetone using Pd-Te / TiO2 series catalysts with different Pd / Te atomic ratios;

[0020] Figure 3 A comparison of acetone selectivity of Pd-Te / TiO2 series catalysts with different Pd / Te atomic ratios for the gas-phase epoxidation of propylene to acetone;

[0021] Figure 4 Pd at different airspeeds 100 -Activity diagram of Te1 / TiO2 catalyst for the gas-phase epoxidation of propylene to acetone;

[0022] Figure 5 Pd at 200℃ 100 -Stability of the Te1 / TiO2 catalyst for the gas-phase epoxidation of propylene to acetone. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments, but this is by no means a limitation on the scope of protection of the present invention.

[0024] Example 1

[0025] Pd 150 Preparation of the Te1 / TiO2 catalyst: 9.6 g of PdCl2 solution (Pd mass fraction 0.625%) and 0.096 g of TeCl4 solution (Te mass fraction 0.5%) were dropwise added to deionized water and stirred until homogeneous. 2 g of TiO2 support was added, and the mixture was stirred at room temperature for 6 hours of equal-volume impregnation. Then, it was dried at 110 °C for 12 hours and calcined at 300 °C in a hydrogen atmosphere (80 mL / min, concentration 10%, with N2 as the equilibrium gas) for 2 hours.

[0026] The atomic ratio of Pd to Te is adjusted by changing the Te content. In this embodiment, the atomic ratio of Pd to Te is 150:1.

[0027] Example 2

[0028] The mass of the added TeCl4 solution was changed to 0.142 g, and the rest was the same as in Example 1, to obtain Pd. 100 -Te1 / TiO2 catalyst, in this embodiment the atomic ratio of Pd to Te is 100:1.

[0029] Example 3

[0030] The mass of the added TeCl4 solution was changed to 0.284 g, and the rest was the same as in Example 1, to obtain Pd. 50 -Te1 / TiO2 catalyst, in this embodiment the atomic ratio of Pd to Te is 50:1.

[0031] Comparative Example 1

[0032] Preparation of Pd / TiO2 catalyst: 9.6 g of PdCl2 solution (Pd mass fraction 0.625%) was added dropwise to deionized water and stirred until homogeneous. 2 g of TiO2 support was added, and the mixture was stirred at room temperature for 6 hours of equal volume impregnation. Then, it was dried at 110 °C for 12 hours and calcined at 300 °C in a hydrogen atmosphere (80 mL / min, concentration 10%, with N2 as the equilibrium gas) for 2 hours.

[0033] Performance Evaluation

[0034] The catalytic performance evaluation conditions were as follows: 0.4 g of the catalysts prepared in Examples 1-3 and the comparative example were placed in a quartz tube fixed-bed reactor, respectively, with oxygen as the oxidant and a total flow rate of 20 mL·min⁻¹ for the reaction feed gas. -1 The nitrogen:propylene:oxygen ratio was 7:2:1, and the reaction space velocity was 3000 mL·g⁻¹. -1 ·h -1 The reaction was carried out under the specified conditions, and the reaction tail gas was detected by packed column gas chromatography.

[0035] 1. Effect of reaction temperature on the catalytic performance of propylene gas-phase epoxidation to acetone

[0036] Pd 150 The activity test results of the Te1 / TiO2 catalyst are as follows: Figure 1 As shown, from Figure 1 As the reaction temperature increases, the conversion rate of propylene gradually increases, while the selectivity of the product acetone gradually decreases. At 200℃, the conversion rate of propylene is 5.6%, and the selectivity of acetone is 21.7%.

[0037] 2. Effect of Pd / Te atomic ratio on catalytic performance of propylene gas-phase oxidation to acetone

[0038] The effect of Pd / Te atomic ratio on catalytic performance, such as Figure 2 and Figure 3 As shown, from Figure 2 and Figure 3 It can be seen that the Pd / TiO2 catalyst has the highest propylene conversion rate, but it mainly undergoes a complete oxidation reaction to generate the byproduct CO2, thus exhibiting the lowest selectivity. The addition of Te significantly reduces the conversion rate, but significantly increases the selectivity for the epoxidized product acetone. With increasing Te content, the selectivity for acetone first increases and then decreases, while the trend in propylene conversion is opposite to that of selectivity. The highest selectivity is achieved when the Pd / Te atomic ratio is 100, reaching 35.3% acetone selectivity at 200℃, at which point the propylene conversion rate is 2.5%.

[0039] 3. Effect of space velocity on the catalytic performance of propylene gas-phase oxidation to acetone

[0040] The reaction space velocity (OSV) for the gas-phase oxidation of propylene to acetone was changed from 3000 mL·g⁻¹. -1 ·h -1 Gradually increase to 12000 mL·g -1 ·h -1 The remaining catalytic performance evaluation conditions remain unchanged, and the activity test results are as follows: Figure 4 As shown, from Figure 4 As the reaction space velocity increases, the conversion rate of propylene gradually decreases, while the selectivity of the product acetone decreases slightly but remains essentially unchanged. Low space velocity conditions are conducive to the contact and adsorption of reactants and catalysts, thereby enhancing the reaction activity.

[0041] 4. Stability of Pd-Te / TiO2 catalyst in the gas-phase oxidation of propylene to acetone

[0042] Pd 100 The stability test results of the Te1 / TiO2 catalyst for the gas-phase oxidation of propylene to acetone are as follows: Figure 5 As shown, from Figure 5 As can be seen, the conversion rate of propylene remained at around 2.5% throughout the 12-hour reaction period, while the selectivity of the product acetone decreased slightly, remaining between 33% and 35%. Therefore, this catalyst exhibits excellent long-term catalytic stability.

[0043] from Figures 1-5 It can be seen that the addition of Te effectively improved the product selectivity of propylene gas-phase oxidation to acetone. With increasing reaction temperature, the conversion rate of propylene gradually increased, while the selectivity of acetone gradually decreased. With increasing Te content, the selectivity of acetone first increased and then decreased, reaching its highest point when the Pd / Te atomic ratio was 100. Meanwhile, Pd... 100 The Te1 / TiO2 catalyst exhibits good stability, with no significant decrease in activity during a 12-hour reaction period.

Claims

1. A Pd-Te / TiO2 catalyst for catalyzing the gas-phase oxidation of propylene to acetone, characterized in that, The catalyst comprises the following components by weight percentage: Pd 0.5–3.0%, Te 0.03~0.07%.

2. The Pd-Te / TiO2 catalyst for catalyzing the gas-phase oxidation of propylene to acetone according to claim 1, characterized in that, The Pd-Te / TiO2 catalyst was prepared by an equal-volume impregnation method.

3. The method for preparing a Pd-Te / TiO2 catalyst for catalyzing the gas-phase oxidation of propylene to acetone according to claim 1, characterized in that, The Pd-Te / TiO2 catalyst was prepared by the following method: TeCl4 and PdCl2 solutions were added dropwise to deionized water and stirred until homogeneous. Then, a certain amount of TiO2 support was added, stirred at room temperature, and impregnated by equal volume for 6 hours. After that, it was dried at 110℃ for 12 hours and calcined at 300℃ in a hydrogen atmosphere (80 mL / min, concentration of 10%, with N2 as the equilibrium gas) for 2 hours to finally obtain the Pd-Te / TiO2 catalyst.

4. The application of the Pd-Te / TiO2 catalyst according to any one of claims 1-3 for catalyzing the gas-phase oxidation of propylene to acetone, characterized in that, The catalyst was used to catalyze the one-step gas-phase oxidation of propylene to acetone.

5. The application of the Pd-Te / TiO2 catalyst according to claim 4 for catalyzing the gas-phase oxidation of propylene to acetone, characterized in that, The conditions for the catalytic oxidation reaction were: a quartz tube fixed-bed reactor, a reaction temperature of 180–260 °C, and a reaction space velocity of 3000–12000 mL·g. -1 ·h -1 The volume ratio of propylene to oxygen is 2:1.

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