System and method for preparing ketone through hydrogen peroxide mediated alkane conversion and application

Abstract

The invention relates to a system and method for preparing ketone through hydrogen peroxide mediated alkane conversion and application. The system comprises a two-step electrocatalytic reaction tank and a one-step thermocatalytic fixed bed reaction tank. The electro-catalytic reaction tank is composed of a zero-gap membrane electrode tank and an improved flow electrochemical tank, hydrogen and oxygen are generated by the electro-catalytic reaction tank through water electrolysis, and then the hydrogen and the oxygen are respectively introduced into the electro-catalytic reaction tank for oxidation reduction to prepare hydrogen peroxide; generated hydrogen peroxide is directly mixed with alkane gas through a tee joint and then enters a thermocatalytic fixed bed reactor, and a ketone product can be prepared. Compared with the prior art, the method has excellent ketone selectivity and production efficiency, and is a more efficient and stable reaction system compared with the currently reported electro-catalysis or thermocatalysis technology.

Description

Technical Field

[0001] This invention belongs to the field of alkane conversion to ketone, and particularly relates to a hydrogen peroxide-mediated system, method and application for alkane conversion to ketone. Background Technology

[0002] The preparation of ketones from alkanes is of great significance in industrial production. Currently, the main methods for producing ketones are based on oxidation, including high-temperature oxidation and organic matter-mediated oxidation. The main problems with these methods are the high energy consumption due to the high energy requirements of the high-temperature conditions, and the fact that organic matter-mediated oxidation typically yields a mixture of ketones and alcohols, requiring additional separation costs. Among various ketone products, acetone and butanone account for 22% and 7% of the market respectively, representing two typical examples of ketone preparations from the oxidation of straight-chain alkanes.

[0003] Acetone, an important chemical, has an annual production exceeding 2 million tons, but my country still relies on imports for a portion of its acetone demand. Currently, over 90% of industrial acetone production depends on the cumene process, which involves a multi-step process: first, propane is dehydrogenated to produce propylene, a process requiring high temperature and pressure conditions exceeding 773 K and 30–70 MPa; subsequently, the resulting propylene reacts with benzene at 473 K and 2–4 MPa to produce cumene, which further reacts to produce acetone and phenol; finally, these two products are separated and purified through a multi-stage distillation process. This process requires high temperature and pressure conditions, uses precious metal catalysts, and easily generates carbon dioxide emissions and large amounts of wastewater.

[0004] Butyl ketone (MEK) is also an important chemical product, mainly used in the production of adhesives. As of 2022, my country's MEK production was approximately 500,000 tons, with some exported. Industrial production of MEK primarily employs the n-butene hydration process, where n-butene is first added to form sec-butanol, followed by oxidative dehydrogenation to obtain MEK. This process suffers from drawbacks such as high temperature, long reaction time leading to low yield, high emissions of waste, and the need for butene concentration technology in addition to the hydration process.

[0005] Patent CN201510129021.8 discloses a method for simultaneously producing propylene oxide and acetone. In the presence of oxygen, propylene and isopropanol are catalyzed by titanium silicate molecular sieve (TS-1) to produce propylene oxide and acetone products. However, acetone is mainly a co-product obtained by the oxidation of isopropanol. The entire reaction system requires relatively high temperature and pressure conditions (40-160℃, 1-5MPa).

[0006] Patent application CN118108575A discloses a method for preparing acetone by low-temperature oxidation of propane. Using oxygen as an oxidant, propane is converted into acetone by high pressure (0.5-1 MPa) in a medium containing organic solvent at 200°C. This method produces a variety of oxygen-containing products (such as acetone, acetic acid, formic acid, isopropanol, etc.), resulting in a selectivity of less than 60% for acetone.

[0007] Utilizing renewable electricity as a driving force for a series of catalytic conversions is currently one of the mainstream technological routes for reducing energy consumption and waste emissions. Based on green electro-oxidation processes, directly synthesizing corresponding ketone products from propane or butane during conversion represents a revolutionary new route for reducing energy consumption and achieving carbon emission reduction. However, currently reported high-selectivity electrocatalytic oxidation current densities for propane and other alkanes are all below 10 mA / cm². 2 This is far lower than the current density (300 mA / cm²) required for industrial applications. 2 This is because as the current density increases, the potential rises, leading to excessive oxidation of alkanes such as propane, which in turn forms carbon dioxide, resulting in a decrease in product selectivity. Summary of the Invention

[0008] The purpose of this invention is to overcome the defects of the prior art by providing a system, method and application for hydrogen peroxide-mediated conversion of alkane to ketone, which has high selectivity, high electron utilization efficiency and high stability.

[0009] The objective of this invention can be achieved through the following technical solution: a system for preparing ketones by alkane conversion mediated by hydrogen peroxide, comprising an electrocatalytic reaction tank and a thermocatalytic fixed-bed reactor (7). The electrocatalytic reaction tank comprises a first electrocatalytic reaction tank (1) and a second electrocatalytic reaction tank (2). The first electrocatalytic reaction tank (1) generates hydrogen and oxygen by electrolyzing water, which are then introduced into the second electrocatalytic reaction tank (2) for oxidation-reduction to obtain hydrogen peroxide. The generated hydrogen peroxide is directly mixed with alkane gas through a three-way valve (6) and then introduced into the thermocatalytic fixed-bed reactor (7) for catalytic reaction to obtain ketones.

[0010] Furthermore, the electrocatalytic reaction cell is a zero-gap membrane electrode cell, comprising one or more membrane electrode assemblies and an electrolyte, wherein each membrane electrode assembly includes a proton exchange membrane and an anode catalyst and a cathode catalyst disposed on both sides thereof.

[0011] Furthermore, the electrolyte in the first electrocatalytic reaction cell (1) is water;

[0012] The electrolyte in the second electrocatalytic reaction tank (2) is a mixed solution of 0.01-1M H2SO4 and 0.01-0.5M Na2SO4 or 0.01-0.5M K2SO4.

[0013] Furthermore, the thermocatalytic fixed-bed reactor (7) is a pipe with an inner diameter of 3.5-10 mm and a length of 100-500 mm, and its interior is filled with a mixture of titanium silicate molecular sieve and quartz sand in a mass ratio of (0.05-0.8):2.5.

[0014] Furthermore, the Si / Ti ratio of the titanium-silicon molecular sieve ranges from 25 to 60:1, and the particle size of the quartz sand ranges from 20 to 200 mesh.

[0015] The present invention also provides a method for preparing ketones by hydrogen peroxide-mediated alkane conversion using the aforementioned system, comprising the following steps:

[0016] Water is fed into the first electrocatalytic reaction tank (1) and electrolyzed into oxygen and hydrogen, which are then fed into the second electrocatalytic reaction tank (2). The electrolyte is fed into the second electrocatalytic reaction tank (2) by a peristaltic pump. Hydrogen and oxygen are oxidized and reduced in the second electrocatalytic reaction tank (2) to prepare hydrogen peroxide. The hydrogen peroxide is mixed with alkane that is directly fed into the three-way valve (6) and fed into the thermocatalytic fixed bed reactor (7) to carry out a catalytic reaction to prepare ketone.

[0017] Furthermore, the current density applied to the first electrocatalytic reaction cell (1) is controlled to be 500–2000 mA / cm². 2 ;

[0018] The current density applied to the second electrocatalytic reaction cell (2) is controlled to be 100–1000 mA / cm². 2 ;

[0019] The electrolyte flow rate is 0.05-2 mL / min, measured with a 1 bar pressure gauge.

[0020] Furthermore, the gas flow rate introduced into the thermocatalytic fixed-bed reactor (7) is 0.1-50 mL / min.

[0021] The present invention also provides an application of the system, namely, using the system for the conversion of alkane to prepare ketone.

[0022] Furthermore, the alkane includes propane or butane.

[0023] Compared with the prior art, the present invention has the following superior effects:

[0024] (1) This invention utilizes renewable electricity to achieve efficient acetone production through electrocatalytic conversion. It primarily involves synthesizing hydrogen peroxide as an oxidant using two electrochemical reactors, followed by a reaction with propane under mild conditions to produce acetone. Unlike existing electrocatalytic systems, this invention utilizes the interaction between the electrosynthesized hydrogen peroxide and the titanium-silicon molecular sieve TS-1 to construct a Ti2(OOH)2 active oxygen species with moderate oxidizing power. This species can not only effectively oxidize propane but also further inhibit the over-oxidation of acetone products, thereby achieving highly selective acetone production. Through the implementation of this scheme, this invention achieves 1A cm -2 At current densities of up to 92%, the selectivity of acetone reaches approximately 92%, and the electron utilization efficiency is approximately 70%, while at 500 mA cm⁻¹... -2 Under these conditions, the system operated stably for 185 hours, consistently maintaining an acetone selectivity greater than 90% and an electron utilization efficiency of approximately 60%. This is comparable to existing electrocatalytic systems (current density below 10 mA cm⁻¹). -2 Compared to acetone selectivity of less than 50% and electron utilization of less than 1%, the performance has achieved a significant breakthrough.

[0025] (2) This invention utilizes a cascaded electro-thermal catalytic system constructed with a zero-gap membrane electrode cell, an improved flow electrolytic cell, and a micro fixed-bed reactor to achieve efficient preparation of acetone or butanone via hydrogen peroxide-mediated alkane oxidation. Compared to current industrial production processes, acetone production costs are reduced by approximately 50%, with an estimated cost below US$800 per ton. With the rapid growth in demand and current supply shortages in the acetone sector, this field is poised for significant growth and development opportunities, especially with the commissioning of large-scale phenol-acetone plants in China, which will greatly enhance the competitiveness of the acetone market and maintain a stable growth trend in industry output. The butanone market is also showing a positive development trend. This technical solution employs a low-energy-consumption, zero-carbon-emission, and high-efficiency ketone product preparation technology, offering significant advantages in economic feasibility and technological superiority compared to current ketone products (especially acetone). The development of this technology is expected to alleviate the dependence on external sources for acetone production and break the current supply shortage.

[0026] (3) This invention first uses green electricity to decompose water in a membrane electrode system to produce green hydrogen and oxygen; then, hydrogen and oxygen are introduced into the anode and cathode of an improved flow electrolytic cell, respectively, to facilitate the electrosynthesis of hydrogen peroxide; finally, the produced hydrogen peroxide and propane are mixed through a three-way valve and directly fed into a fixed-bed reactor to prepare acetone. All the energy required for the entire reaction system comes from green electricity, the raw materials are only propane and water, and no pollutants such as carbon dioxide are produced, making it very green and energy-efficient. Theoretical calculations combined with a series of in-situ spectroscopic experiments show that the binuclear Ti active center in the TS-1 catalyst readily forms Ti2(OOH)2 active species with hydrogen peroxide, significantly reducing the reaction energy barrier of the first step of alkane dehydrogenation and facilitating the second step of dehydrogenation to produce ketone products. Simultaneously, the weaker acidity inhibits further peroxidation. Through the implementation of this scheme, a maximum of 1000 mA / cm² can be achieved. 2 At the given current density, this system achieves an electron utilization efficiency exceeding 70%, with an acetone selectivity reaching 92% at 500 mA / cm². 2 Operating under these conditions for 185 hours, the system consistently maintained an acetone selectivity of over 90% and an electron utilization efficiency of approximately 60%, making it the most advanced and efficient propane-selective oxidation system for acetone production reported to date. Attached Figure Description

[0027] Figure 1 A cascaded electro-thermal catalytic reaction system for the conversion of propane to acetone;

[0028] Figure 2 This invention provides a performance comparison with previously reported techniques for the selective electro-oxidation of propane to produce acetone.

[0029] Figure 3 Selectivity and yield of propane selective oxidation to prepare acetone at different current densities;

[0030] Figure 4 Electron utilization efficiency and hydrogen peroxide utilization rate at different current densities for the selective oxidation of propane;

[0031] Figure 5 The electron utilization efficiency and propane single-pass conversion efficiency of selective propane oxidation at different flow rates;

[0032] Figure 6 The selectivity, electron utilization efficiency, and yield of butane oxidation to butanone were evaluated. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] This invention constructs a cascaded electro-thermal catalytic system, comprising a two-step electrocatalytic reaction tank and a one-step thermocatalytic fixed-bed reactor. The electrocatalytic reaction tank consists of a zero-gap membrane electrode cell and a modified flow electrochemical cell. In the first electrocatalytic reaction tank, hydrogen and oxygen are generated by electrolyzing water. These are then introduced into the second electrocatalytic reaction tank for oxidation-reduction to produce hydrogen peroxide. The generated hydrogen peroxide is directly mixed with alkane gas through a three-way valve and then introduced into the thermocatalytic fixed-bed reactor to produce ketones.

[0035] Specifically, such as Figure 1 As shown, the two-step electrocatalytic reaction tank includes a first electrocatalytic reaction tank 1 and a second electrocatalytic reaction tank 2. Both electrocatalytic reaction tanks are composed of zero-gap membrane electrode cells. Each zero-gap membrane electrode cell includes one or more membrane electrode assemblies. Each membrane electrode assembly includes an anode, a cathode, a proton exchange membrane, and an electrolyte. The anode and cathode are attached to both sides of the proton exchange membrane to form a zero-gap membrane electrode. The electrolyte in the first electrocatalytic reaction tank 1 is water. Electricity is passed through the anode and cathode to electrolyze the water. The second electrocatalytic reaction tank 2 uses a mixed solution of 0.01–1 M H₂SO₄ and 0.01–0.5 M Na₂SO₄ or 0.01–0.5 M K₂SO₄ as the electrolyte. The electrolyte is introduced into the second electrocatalytic reaction tank 2 via a peristaltic pump, and the flow rate of the electrolyte is controlled at 0.05–2 mL / min, preferably 1 mL / min.

[0036] The cathode and anode are prepared by the following method:

[0037] Titanium felt was used as the supporting electrode and immersed in an aqueous solution of iridium chloride at a pH of 7-8 for 30 minutes. It was then calcined in air at 300-400℃ for 2-4 hours. The iridium loading was 0.1 mg / cm³. 2 The titanium felt-supported iridium oxide prepared was used as the anode.

[0038] The cathode of the first electrocatalytic reaction cell 1 is prepared by dispersing 20 mg of 50% Pt / 50% C in 1.5 mL of water and 1.5 mL of ethanol, adding 100 μL of Nafion solution, and ultrasonically dispersing the mixture to obtain an electrocatalyst slurry. The slurry is then sprayed layer by layer onto hydrophilic / hydrophobic carbon paper and vacuum dried at room temperature. The Pt / C loading is controlled at 1 mg / cm³. -2 / 2mg cm -2 (Calculated based on the total amount of catalyst).

[0039] The cathode of the second electrocatalytic reaction cell 2 is prepared by dispersing 40 mg of BP2000 in 4 mL of isopropanol and 1 mL of methanol, adding 80 μL of Nafion solution, and then sonicating under ultrasonic conditions to obtain a uniformly dispersed electrocatalyst slurry. This slurry is then sprayed layer by layer onto hydrophobic carbon paper and vacuum dried at room temperature. The BP2000 loading is controlled at 2 mg / cm³. 2 (Calculated based on the total amount of catalyst).

[0040] Water from storage tank 3 enters the first electrocatalytic reaction tank 1, and the current density applied to the first electrocatalytic reaction tank 1 is controlled to be 500–2000 mA / cm². 2 Electrolysis of water produces oxygen and hydrogen. The oxygen is separated in a gas-liquid separator 4, and the separated water is returned to the storage tank 3. The separated oxygen enters the second electrocatalytic reaction tank 2, and the hydrogen directly enters the second electrocatalytic reaction tank 2. The electrolyte in the electrolyte tank 5 is fed into the second electrocatalytic reaction tank 2 via a peristaltic pump. The current density applied to the second electrocatalytic reaction tank 2 is controlled to be 100–1000 mA / cm². 2 Hydrogen and oxygen are redox-induced to produce hydrogen peroxide in the second electrocatalytic reaction tank 2. The hydrogen peroxide is then transported to the three-way valve 6 and mixed with alkane (propane) that is directly introduced into the three-way valve. The mixture then enters the thermal catalytic fixed-bed reactor 7. The gas flow rate into the thermal catalytic fixed-bed reactor 7 is controlled to be 0.1-50 mL / min, and the electrolyte flow rate is controlled to be 0.05-2 mL / min, measured with a 1 bar pressure gauge.

[0041] The thermocatalytic fixed-bed reactor 7 is a pipe with an inner diameter of 3.5-10 mm and a length of 100-500 mm. It is filled with a mixture of titanium silicate molecular sieve and quartz sand in a mass ratio of (0.05-0.8):2.5. The thermocatalytic conditions include: reaction temperature of 30-80℃, no external pressure, and the Si / Ti ratio of the titanium silicate molecular sieve is in the range of 25-60. The pipe is made of stainless steel, glass or quartz. The particle size of the quartz sand is in the range of 20-200 mesh and the mass range is 0.5-10 g.

[0042] The gas and liquid from the reaction in the thermocatalytic fixed-bed reactor 7 are separated by a gas-liquid separator 8. The gas is unreacted alkanes, and the final ketone product is collected in the liquid. The ketone is concentrated after distillation, and the remaining solution is returned to the second electrocatalytic reaction tank 2.

[0043] The above system can be used in the electrothermal catalytic conversion of alkanes to ketones. This invention primarily utilizes this system to achieve a clean, efficient, stable, and continuous electrothermal catalytic conversion of alkanes to ketones. By employing a cascaded electrothermal catalytic system, a current density as high as 1 ampere per square centimeter is achieved, with an electron utilization efficiency of approximately 70% and a ketone selectivity as high as 92%. Operating at 500 milliamperes per square centimeter for 185 hours, the system consistently maintains a ketone selectivity greater than 90% and an electron utilization efficiency of approximately 60%. Figure 2 The diagram illustrates the current research status of direct anodic electro-oxidation and indirect cathodic electro-oxidation of alkanes, particularly including direct anodic electro-oxidation of propane to acetone and cathodic oxygen-mediated reduction indirect oxidation of propane to acetone. A comparison of this invention with existing reported techniques for selective propane electro-oxidation to acetone shows that, at a maximum A / cm², [the technology can achieve] [the desired results]. 2 At the specified current density, the system of this invention achieves an electron utilization efficiency exceeding 70%, while previously reported current densities for the selective electro-oxidation of propane to acetone are all below 10 mA / cm². 2 .

[0044] Unless otherwise specified, the raw materials and equipment used in this invention are all commercially available or commonly used equipment.

[0045] Example 1

[0046] The selective oxidation of propane to acetone via electrothermal coupling involves the following steps:

[0047] (1) Preparation of the anode catalyst: Titanium felt was used as the supporting electrode and impregnated in an aqueous solution of iridium chloride at a pH of 7-8 for 30 minutes. It was then calcined in air at 400℃ for 4 hours. The iridium loading was 0.1 mg / cm³. 2 The titanium felt-supported iridium oxide prepared was used as the anode catalyst.

[0048] (2) Preparation of the cathode catalyst for the first electrocatalytic reaction cell 1: 20 mg of 50% Pt / C (i.e., 10 mg Pt, 10 mg C) was dispersed in 1.5 mL of water and 1.5 mL of ethanol, and 100 μL of Nafion solution was added. The mixture was then ultrasonically dispersed to obtain a uniform cathode slurry. The cathode slurry was then sprayed layer by layer onto hydrophilic carbon paper and vacuum dried at room temperature. The Pt / C loading (i.e., the coating amount of the cathode slurry) was controlled at 1 mg / cm³. 2 The cathode catalyst was obtained.

[0049] (3) Construction of the first electrocatalytic reaction cell 1: The anode catalyst obtained in step (1) and the cathode catalyst of the first electrocatalytic reaction cell 1 obtained in step (2) are pressed onto both sides of the proton exchange membrane to form a membrane electrode. The membrane electrode is sandwiched between two conductive plates to form the first electrocatalytic reaction cell 1. Pure water is used as the electrolyte for both the cathode and the anode.

[0050] (4) Preparation of the cathode catalyst for the second electrocatalytic reaction cell 2 (i.e., the improved flow electrolyzer):

[0051] 40 mg of BP2000 was dispersed in 4 mL of isopropanol and 1 mL of methanol, and 80 μL of Nafion solution was added. The mixture was then sonicated until uniformly dispersed. The electrocatalyst was then sprayed layer by layer onto hydrophobic carbon paper and dried under vacuum at room temperature. The BP2000 loading was controlled at 2 mg / cm³. 2 (Calculated based on the total amount of catalyst).

[0052] (5) Construction of the second electrocatalytic reaction cell 2:

[0053] The anode catalyst and proton exchange membrane prepared in step (1) are bonded together. A liquid flow channel is added between the cathode catalyst and proton exchange membrane in the second electrocatalytic reaction cell 2 prepared in step (4) to serve as the cathode electrolyte flow channel. The cathode electrolyte is a mixture of 0.1M H2SO4 and 0.5M Na2SO4. The hydrogen and oxygen generated by the cathode and anode of the first electrocatalytic cell are respectively introduced into the anode and cathode of the second catalytic reaction cell.

[0054] (6) Electrothermal coupling of propane selective oxidation to acetone

[0055] Connect the conductive plate of the first electrocatalytic reaction cell 1 to a power source and control the application of 1000 mA / cm. 2 At a current density of 1, hydrogen and oxygen are obtained at the cathode and anode of the first electrocatalytic reaction cell 1, respectively.

[0056] The resulting hydrogen and oxygen were then introduced into the anode and cathode of the improved flow electrolyzer (i.e., the second electrocatalytic reaction cell 2), respectively. The flow rate of the cathode electrolyte in the second electrocatalytic reaction cell 2 was controlled at 1 mL / min, and an applied current of 300 mA / cm² was maintained. 2 The current density.

[0057] The cathode electrolyte obtained from the reaction in the second electrocatalytic reaction tank 2 is mixed with propane through a three-way valve and then introduced into the thermocatalytic fixed-bed reactor 7. The propane gas flow rate is 3 mL / min, the cathode electrolyte flow rate is 0.1 mL / min, and the titanium-silicon molecular sieve in the thermocatalytic fixed-bed reactor 7 has a Si / Ti ratio of 30, a mass of 200 mg, and quartz sand with a particle size of 26 mesh and a mass of 2.5 g. The thermocatalytic fixed-bed reactor 7 has an inner diameter of 4.6 mm, is made of stainless steel, and is heated at 60℃.

[0058] The gas and solution obtained from the reaction in the thermocatalytic fixed-bed reactor 7 are separated by a gas-liquid separator 8. The obtained gas is propane gas, and the obtained solution is returned to the cathode liquid storage container of the improved flow electrolyzer after purifying acetone.

[0059] (7) Performance testing

[0060] The hydrogen peroxide obtained from the second electrocatalytic reaction tank 2 is mainly detected using an ultraviolet analyzer. Specifically, cerium sulfate is used as the reaction reagent. The amount of hydrogen peroxide produced within a certain time period can be calculated by the amount of cerium sulfate consumed. The Faraday efficiency (FE) of the hydrogen peroxide can be calculated using Equation 1:

[0061] FE=(nFZ) / Q (1)

[0062] Where n is the amount of hydrogen peroxide obtained based on ultraviolet testing, F is the Faraday constant, Z is the number of electrons transferred from oxygen reduction to hydrogen peroxide, and Q is the total charge consumed within a certain time.

[0063] For the thermocatalytic fixed-bed reactor 7, after a certain reaction time, the gaseous and liquid products of propane oxidation were detected by gas chromatography and nuclear magnetic resonance spectroscopy, respectively. The concentration of the gaseous products could be calculated from a standard curve, and then the amount of substance could be determined using the ideal gas law. For the liquid products, dimethyl sulfoxide was used as an internal standard. Based on the peak areas of the internal standard and the product, as well as the number of protons in the groups carried by the internal standard and the product, the product concentration (ppm) was first calculated, and then the amount of substance of the product was obtained using Equation 2.

[0064] For example, acetone:

[0065] Amount of acetone (mol) = Acetone concentration (ppm) × Liquid volume (mL) / 18 × 10 -6 (2)

[0066] In the fixed-bed reactor system, the utilization rate of hydrogen peroxide can be calculated using Equation 3:

[0067] Hydrogen peroxide utilization rate =

[0068] (Amount of hydrogen peroxide consumed to generate acetone in a certain time / Amount of hydrogen peroxide entering the fixed bed in a certain time) × 100% (3)

[0069] Based on the above detection and analysis, it can be concluded that:

[0070] Selectivity of acetone products = (Amount of propane required to produce acetone / Amount of propane required to produce all products) × 100%

[0071] Acetone yield = Amount of acetone produced per unit time / Mass of catalyst used

[0072] Electron utilization efficiency = Hydrogen peroxide Faraday efficiency × Hydrogen peroxide utilization rate × Acetone selectivity × 100%

[0073] The selectivity, yield, and electron utilization efficiency of the obtained products are as follows: Figure 3 and Figure 4 As shown, it is at 300mA cm -2 The data was obtained by detection at current density. Figure 3 It can be seen that the selectivity of acetone products exceeds 90%, while the yield reaches 1 mmol / g. catalyst -1 h -1 That's all. Thanks to the high efficiency of hydrogen peroxide utilization, from Figure 4 It can be seen that the electron utilization efficiency reaches over 80%.

[0074] Figure 5 Electron utilization efficiency and propane single-pass conversion efficiency at different flow rates for the selective oxidation of propane; from Figure 5 It can be seen that at higher propane flow rates, the single-pass conversion efficiency and electron utilization efficiency of propane are both low due to the shortened residence time. At an appropriate propane flow rate, excess propane can maximize the conversion of hydrogen peroxide and obtain a relatively high electron utilization efficiency, but at the cost of sacrificing the single-pass efficiency of propane. By further reducing the propane flow rate, the single-pass conversion efficiency of propane can be increased to ~50% while ensuring that the electron utilization efficiency reaches more than 50%.

[0075] In summary, at 300mA cm -2 At the specified current density, the selectivity and yield of acetone were 90% and 1.98 mmol g, respectively. catalyst -1 h -1 The electron utilization efficiency can reach 82%.

[0076] Example 2

[0077] The only difference from Example 1 is:

[0078] The current density applied to the first electrocatalytic reaction cell 1 is 1000 mA / cm².2 ,

[0079] The applied current density in the second electrocatalytic reaction cell 2 is 500 mA / cm². 2 ,

[0080] The mass of titanium silicate molecular sieve in the thermocatalytic fixed-bed reactor 7 is 300 mg, and the mass of quartz sand is 2.5 g.

[0081] The rest is the same as in Example 1.

[0082] Example 3

[0083] The only difference from Example 1 is:

[0084] The current density applied to the first electrocatalytic reaction cell 1 is 2000 mA / cm². 2 ,

[0085] The applied current density in the second electrocatalytic reaction cell 2 is 1000 mA / cm². 2 ,

[0086] The mass of titanium silicate molecular sieve in the thermocatalytic fixed-bed reactor 7 is 600 mg, and the mass of quartz sand is 2.5 g.

[0087] The rest is the same as in Example 1.

[0088] Comparative Example 1

[0089] The only difference from Example 1 is that: the first electrocatalytic reaction tank 1 and the second electrocatalytic reaction tank 2 are not included. Commercially available hydrogen peroxide and propane gas are directly mixed through a three-way valve and then introduced into the thermocatalytic fixed bed reactor 7 for subsequent reactions.

[0090] The same testing method as in Example 1 was used to test the performance of Examples 2-3 and Comparative Example 1. The test results are as follows:

[0091] Example 1 Example 2 Example 3 Comparative Example 1 Acetone selectivity 90％ 95％ 92％ 87％ Acetone yield 1.98 mmol g -1 h -1 ]]> 1.27 mmol g -1 h -1 ]] <![CDATA[1.66mmol g -1 h -1 ]]> <![CDATA[1.02mmol g -1 h -1 ]]> Electron utilization efficiency 82％ 80.8％ 70％ 60％

[0092] As can be seen from the table above, the selectivity of acetone products exceeds 90% across the entire current density range, and the acetone yield remains above 1 mmol g. -1 h -1 The electron utilization efficiency can reach over 70%, and its performance is superior compared to commercially available hydrogen peroxide as a raw material, fully demonstrating the system's excellence and potential market application potential.

[0093] Example 4

[0094] The electrothermal coupling of butane selective oxidation to butanone involves the following steps:

[0095] A zero-gap membrane electrode was used as the electrocatalytic partial reaction device, with the same structure as in Example 1. A pressure of 1000 mA / cm was applied to the first electrocatalytic reaction cell 1. 2 The current density was adjusted to produce hydrogen and oxygen at the cathode and anode, respectively. The resulting hydrogen and oxygen were then fed into the second electrocatalytic reaction cell 2. The cathode electrolyte consisted of 0.1 M H₂SO₄ and 0.5 M Na₂SO₄, with a flow rate of 1 mL / min, and an applied current of 800 mA / cm² was maintained. 2 The current density was determined. The obtained cathode electrolyte was mixed with a pre-cooled butane-methanol mixture (butane + 95% v / v methanol) (pre-cooling temperature: -20-0℃, cooling time: 1-5h). Then, with butane continuously introduced at a gas velocity of 2 mL / min, the Si / Ti ratio of the titanium-silicon molecular sieve was 30, the mass was 50-800 mg, and the reaction temperature was 50-90℃. The resulting gas and solution were separated by a gas-liquid separator. The obtained gas was butane gas, and the obtained solution, after purification of butanone, was returned to the cathode electrolyte storage container of the improved flow electrolytic cell. The selectivity, electron utilization efficiency, and yield of the obtained butanone were as follows: Figure 6 As shown, at 800mA / cm 2 At the specified current density, the selectivity, electron utilization efficiency, and yield of butanone were 70%, 30%, and 2.69 mmol g, respectively. catalyst -1 h -1 This indicates that the system can be extended to the synthesis of other ketone products.

[0096] In summary, this invention proposes a spatially decoupled cascaded electrothermal catalytic reaction system for the conversion of alkanes to ketones: First, in a membrane electrode system, water is electrolyzed to produce green hydrogen and oxygen; then, hydrogen and oxygen are introduced into the anode and cathode of a modified flow electrolyzer, respectively, to facilitate the electrosynthesis of hydrogen peroxide; finally, the resulting hydrogen peroxide and propane are mixed through a three-way valve and directly fed into a fixed-bed reactor to produce acetone. The entire reaction system requires energy entirely from green electricity, uses only propane and water as raw materials, and produces no pollutants such as carbon dioxide, making it highly green and energy-efficient. Theoretical calculations combined with a series of in-situ spectroscopic experiments show that the binuclear Ti active sites in the TS-1 catalyst readily form Ti2(OOH)2 active species with hydrogen peroxide, significantly reducing the reaction energy barrier for the first-step dehydrogenation of alkanes and facilitating the second-step dehydrogenation to produce ketone products. Simultaneously, the weak acidity inhibits further peroxidation.

[0097] Through the implementation of this scheme, a maximum of 1000 mA / cm² can be achieved. 2 At the given current density, this system achieves an electron utilization efficiency exceeding 70%, with an acetone selectivity reaching 92% at 500 mA / cm². 2Operating under these conditions for 185 hours, the system consistently maintained an acetone selectivity of over 90% and an electron utilization efficiency of approximately 60%, making it the most advanced and efficient propane-selective oxidation system for acetone production reported to date.

Claims

1. A system for preparing ketones by hydrogen peroxide-mediated alkane conversion, characterized in that, The reactor includes an electrocatalytic reaction tank and a thermocatalytic fixed-bed reactor (7). The electrocatalytic reaction tank includes a first electrocatalytic reaction tank (1) and a second electrocatalytic reaction tank (2). The first electrocatalytic reaction tank (1) generates hydrogen and oxygen by electrolyzing water. These are then introduced into the second electrocatalytic reaction tank (2) for oxidation-reduction to prepare hydrogen peroxide. The generated hydrogen peroxide is directly mixed with alkane gas through a three-way valve (6) and then introduced into the thermocatalytic fixed-bed reactor (7) for catalytic reaction to prepare ketones.

2. The system for preparing ketones from alkane via hydrogen peroxide-mediated conversion according to claim 1, characterized in that, The electrocatalytic reaction cell is a zero-gap membrane electrode cell, comprising one or more membrane electrode assemblies and an electrolyte. Each membrane electrode assembly includes a proton exchange membrane and an anode catalyst and a cathode catalyst disposed on both sides thereof.

3. The system for preparing ketones from alkane via hydrogen peroxide-mediated conversion according to claim 1, characterized in that, The electrolyte in the first electrocatalytic reaction cell (1) is water; The electrolyte in the second electrocatalytic reaction cell (2) is a mixed solution of 0.01-1M H2SO4 and 0.01-0.5M Na2SO4 or 0.01-0.5M M K2SO4.

4. The system for preparing ketones from alkane via hydrogen peroxide-mediated conversion according to claim 1, characterized in that, The thermocatalytic fixed-bed reactor (7) is a pipe with an inner diameter of 3.5-10 mm and a length of 100-500 mm, and its interior is filled with a mixture of titanium silicon molecular sieve and quartz sand with a mass ratio of (0.05-0.8):2.

5.

5. The system for preparing ketones by hydrogen peroxide-mediated alkane conversion according to claim 4, characterized in that, The Si / Ti ratio of the titanium-silicon molecular sieve ranges from 25 to 60:1, and the particle size of the quartz sand ranges from 20 to 200 mesh.

6. A method for preparing ketones from hydrogen peroxide-mediated alkane conversion using the system described in any one of claims 1-5, characterized in that, Includes the following steps: Water is fed into the first electrocatalytic reaction tank (1) and electrolyzed into oxygen and hydrogen, which are then fed into the second electrocatalytic reaction tank (2). The electrolyte is fed into the second electrocatalytic reaction tank (2) by a peristaltic pump. Hydrogen and oxygen are oxidized and reduced in the second electrocatalytic reaction tank (2) to prepare hydrogen peroxide. The hydrogen peroxide is mixed with alkane that is directly fed into the three-way valve (6) and fed into the thermocatalytic fixed bed reactor (7) to carry out a catalytic reaction to prepare ketone.

7. The method for preparing ketones by hydrogen peroxide-mediated alkane conversion according to claim 6, characterized in that, The current density applied to the first electrocatalytic reaction cell (1) is controlled to be 500–2000 mA / cm². 2 ; The current density applied to the second electrocatalytic reaction cell (2) is controlled to be 100–1000 mA / cm². 2 ; The electrolyte flow rate is 0.05-2 mL / min, measured with a 1 bar pressure gauge.

8. The method for preparing ketones by hydrogen peroxide-mediated alkane conversion according to claim 6, characterized in that, The gas flow rate introduced into the thermocatalytic fixed-bed reactor (7) is 0.1-50 mL / min.

9. An application of the system as described in any one of claims 1-4, characterized in that, The system was used to convert alkane into ketones.

10. The application according to claim 9, characterized in that, The alkane mentioned includes propane or butane.

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