A method for direct synthesis of hydrogen peroxide aqueous solution from hydrogen and oxygen

Abstract

A method for directly synthesizing hydrogen peroxide aqueous solution from hydrogen and oxygen, characterized in that a mixed gas of reaction raw material gas and dilution gas is introduced into a liquid phase reaction medium in which a catalyst is dispersed to perform a contact reaction under hydrogen peroxide generation conditions to obtain product hydrogen peroxide; wherein the reaction raw material gas is oxygen and hydrogen, and the dilution gas is carbon dioxide.

Description

Technical Field

[0001] This invention relates to the field of hydrogen peroxide preparation, and specifically to a method for directly synthesizing an aqueous solution of hydrogen peroxide from hydrogen and oxygen. Background Technology

[0002] Hydrogen peroxide is an important inorganic chemical raw material and a green basic chemical, listed as one of the world's 100 most important chemicals. It is widely used in industries such as chemical, textile, papermaking, food, electronics, and medical. Hydrogen peroxide only produces water or oxygen during its reaction, without generating any environmentally polluting byproducts, making it a recognized green chemical. In recent years, with increasing demands for green and environmentally friendly economics and the need for products such as propylene oxide, the market demand for hydrogen peroxide has been continuously rising.

[0003] Currently, the main industrial production method for hydrogen peroxide is the anthraquinone process, accounting for over 95% of global production. This process includes four steps: anthraquinone hydrogenation, anthraquinone oxidation, hydrogen peroxide extraction, and working solution post-treatment. While the technology is mature, it suffers from drawbacks such as large equipment investment, complex process flow, and high energy consumption. In particular, the extensive use and periodic replacement of organic solvents during production leads to a series of product and environmental pollution problems.

[0004] The method of directly synthesizing hydrogen peroxide using hydrogen and oxygen as reactants in the presence of a metal catalyst offers advantages such as high atom economy and good environmental benefits, even though the only byproduct is water. It also aligns with green chemistry and clean production requirements. However, thermodynamic data shows that hydrogen peroxide formation is thermodynamically unfavorable. Under the action of a catalyst, the hydrogen peroxide produced by this method may undergo further decomposition into water and oxygen, or further hydrogenation to produce water, which severely affects the concentration and formation efficiency of the hydrogen peroxide solution, and also impacts the selectivity of hydrogen.

[0005] The methods disclosed in US patents US 4009252 and US4681751 introduce acidic media such as sulfuric acid, phosphoric acid, and hydrochloric acid, along with halide ions, as stabilizers for hydrogen peroxide. This approach aims to inhibit the degradation reaction of hydrogen peroxide to a certain extent, thereby increasing the final concentration and selectivity of the product. However, this method has several drawbacks. First, the addition of acidic media and halide ions leads to the precipitation of active metal components from the catalyst, significantly reducing catalyst lifespan and resulting in high catalyst loss costs. Second, the precipitated metal residues remain in the hydrogen peroxide aqueous solution, not only exacerbating further degradation of hydrogen peroxide but also affecting product quality. Subsequent separation operations further increase operating costs. Furthermore, the halogen-containing liquid solvents cause severe corrosion to the metal reactor, hindering long-term stable operation of the equipment.

[0006] To reduce the amount of acidic stabilizers and halogens added, many patents modify catalysts with acids or halogens or functionalize them to achieve halogen and acid immobilization. EP504741 discloses the use of a peracidic metal oxide to support the active component palladium. EP978316 discloses the use of acidic substances such as activated carbon with sulfonic acid groups as catalyst supports. EP492064 discloses the use of a catalyst based on palladium supported on a halogen-functionalized resin to suppress the degradation side reaction of hydrogen peroxide; however, stabilizers are still needed to improve catalyst activity. To improve catalyst activity and stability, CN1011602259A discloses a method for preparing hydrogen peroxide, which improves the selectivity of hydrogen peroxide at low acid concentrations by adding alkyl sulfate esters; however, this method still requires hydrohalic acids or alkali metal halide salts to improve the selectivity of hydrogen peroxide generation.

[0007] Because hydrogen has a wide explosive range, gaseous mixtures of hydrogen and oxygen pose an explosion risk when present at a molar concentration of 4%-94% under standard temperature and pressure conditions. For safety and operability reasons, inert and / or non-inert dilution gases (e.g., 70-95% by volume nitrogen or argon) need to be added during the direct synthesis of hydrogen peroxide from hydrogen and oxygen to avoid system explosion.

[0008] In summary, existing technologies suffer from problems such as low hydrogen peroxide yield, equipment corrosion, easy loss of active catalyst components affecting catalyst lifespan, and safety hazards due to the wide explosion limit of hydrogen causing direct contact between hydrogen and oxygen during the reaction process, which limits its large-scale industrial application. Summary of the Invention

[0009] The inventors discovered that using carbon dioxide as a diluent for the direct synthesis of hydrogen peroxide from hydrogen and oxygen not only allows the reactants to participate in the reaction in proportions outside the flammable range, reducing the risk of combustion and explosion from direct contact between hydrogen and oxygen and improving the safety of the reaction system, but also, during the reaction, carbon dioxide reacts with the liquid-phase reaction medium to generate an in-situ acid stabilizer, making the solution weakly acidic and effectively stabilizing the generated hydrogen peroxide. Furthermore, the pressure reduction in the reaction system after the reaction allows the gas to be removed from the liquid-phase reaction medium, preventing the introduction of impurities into the reaction system. Based on these findings, this invention was developed.

[0010] Therefore, the purpose of this invention is to address the problems existing in the direct synthesis of hydrogen peroxide from hydrogen and oxygen technologies, such as difficulties in product separation processes due to the addition of additional acids and halogen promoters, easy catalyst deactivation, and safety concerns. The invention provides a method for the direct synthesis of hydrogen peroxide from hydrogen and oxygen into an aqueous solution that not only improves the safety of the reaction system but also enhances the direct synthesis performance of hydrogen peroxide without the addition of additional stabilizers such as acids and halogens.

[0011] To achieve the above objectives, the present invention provides a method for directly synthesizing hydrogen peroxide aqueous solution from hydrogen and oxygen, characterized in that, under hydrogen peroxide generation conditions, a mixed gas of reactant gas and dilution gas is introduced into a liquid-phase reaction medium containing a dispersed catalyst to carry out a contact reaction to obtain the product hydrogen peroxide; wherein, the reactant gas is oxygen and hydrogen, and the dilution gas is carbon dioxide.

[0012] In this invention, the mixed gas of reactant gas and dilution gas includes a mixed gas I of hydrogen and dilution gas and a mixed gas II of oxygen and dilution gas; in mixed gas I, the hydrogen volume fraction is 1-15%; in mixed gas II, the oxygen volume fraction is 15-40%. Preferably, in mixed gas I, the hydrogen volume fraction is 5-10%; and in mixed gas II, the oxygen volume fraction is 20-30%.

[0013] In the mixture of reactant gas and dilution gas, the proportion of dilution gas is >50% by volume, preferably >55% by volume, and more preferably >60% by volume.

[0014] In the reaction feed gas, the molar ratio of hydrogen to oxygen is 0.01 to 2.5, preferably 0.5 to 1.0.

[0015] The mixture of reactant gas and dilution gas is introduced into a liquid reaction medium in which the catalyst is dispersed for contact reaction, which can be carried out in various reactors, such as in a high-pressure reactor.

[0016] The liquid-phase reaction medium is a solvent with good solubility in the reactant gas or low viscosity and low surface tension. The liquid-phase reaction medium can be water and one or more mixtures of methanol, ethanol, isopropanol, 1,4-dioxane, etc. Preferably, the liquid-phase reaction medium is water and / or methanol, which can better facilitate the dissolution of the reactant gas, better overcome the reaction mass transfer problem, and improve the reaction efficiency.

[0017] In this invention, the catalyst is a supported catalyst composed of one or more metals from Group 1 and / or Group 8 of the periodic table. For example, the metal element is selected from at least one of gold, silver, copper, ruthenium, palladium, platinum, rhodium, cobalt, nickel, and iridium.

[0018] In the supported catalyst, the support material is at least one of activated carbon, silica, titanium dioxide, alumina, cerium oxide, and titanium silicate molecular sieve. The loading amount of the metal element is preferably 0.01-10 wt%.

[0019] The mass ratio of the liquid-phase reaction medium to the supported catalyst is 100–1000. Preferably, the ratio is 400–700. From the perspective of minimizing the decomposition of hydrogen peroxide, preferably, the supported catalyst is a catalyst supported on activated carbon or titanium dioxide with one or more of gold, palladium, and platinum as a carrier. More preferably, it is an activated carbon catalyst supported on gold and palladium.

[0020] In this invention, the hydrogen peroxide generation conditions are as follows: reaction temperature -10-30℃, reaction pressure 1.0-10.0 MPa, and hydrogen to oxygen molar ratio 0.01-2.5; preferably, the hydrogen peroxide generation conditions are as follows: reaction temperature 0-10℃, reaction pressure 3.0-6.0 MPa, and hydrogen to oxygen molar ratio 0.5-1.0.

[0021] Preferably, the method of the present invention achieves better technical results without adding halogen stabilizers to the reaction liquid medium.

[0022] The method of the present invention also includes rapidly cooling the temperature of the reaction system to the temperature required for the direct synthesis of hydrogen peroxide from hydrogen and oxygen using a constant temperature water bath.

[0023] The present invention has the following beneficial effects:

[0024] (1) Using carbon dioxide as a dilution gas for the direct synthesis of hydrogen peroxide from hydrogen and oxygen allows the reaction to occur outside of combustion and explosion, thus avoiding the safety issues associated with direct contact between hydrogen and oxygen and effectively increasing the safety of the reaction system.

[0025] (2) Carbon dioxide dilution gas dissolves in the liquid reaction medium to form carbonic acid, which acts as a stabilizer for the hydrogen peroxide produced, thereby increasing the selectivity of hydrogen (indicating the percentage of hydrogen peroxide produced from the consumed hydrogen) and inhibiting the decomposition of hydrogen peroxide.

[0026] (3) In the preferred embodiment of the present invention, it is not necessary to add stabilizers such as acids and halogens to the liquid reaction medium. This can avoid the corrosion of the reaction device by the liquid reaction medium after the addition of stabilizers, and also avoid the separation of stabilizers and hydrogen peroxide after the reaction, which greatly simplifies the process flow.

[0027] (4) By detecting the metal concentration in the liquid solvent after the reaction, it was found that this method can effectively avoid the loss of active components of supported metal catalysts, improve the service life of catalysts, and reduce the cost of catalyst use.

[0028] (5) Compared with traditional acid stabilizers, the method of the present invention uses carbon dioxide as an in-situ acid stabilizer, which will not cause the dissolution of catalyst metal components and reactor corrosion during the reaction process. It is removed from the reaction system under reduced pressure after the reaction, and there is no subsequent separation problem. It significantly extends the service life of the catalyst, reduces the process cost, and simplifies the process flow. Attached Figure Description

[0029] Figure 1 A flowchart of the method provided by the present invention.

[0030] Figure 2 The laboratory apparatus for the method of this invention is shown in the figure. 1—hydrogen cylinder; 2—oxygen cylinder; 3, 5—pressure gauges; 4—feed inlet; 6—electric stirring rod; 7—thermocouple; 8—tail gas discharge valve; 9—inner liner; 10, 11—condensate; 12—condensation box; 13—gas chromatograph; 14—computer. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. The embodiments described are merely some embodiments of the present invention, not all embodiments, and do not limit the present invention.

[0032] Figure 1 The reaction process of this invention is explained. Figure 1 In the reactor, a hydrogen / dilution gas mixture and an oxygen / dilution gas mixture are thoroughly mixed and contacted in a liquid-phase reaction medium, and react with a catalyst to obtain the product hydrogen peroxide. The tail gas after the reaction is analyzed by gas chromatography to obtain the hydrogen conversion rate, and the reaction liquid phase is filtered and analyzed using the cerium titration method to obtain the hydrogen peroxide concentration in the product.

[0033] Figure 2 The laboratory reaction apparatus of the present invention is described. Figure 2 In this reactor, a high-pressure reaction vessel is installed, equipped with a PTFE-lined tube, a constant-temperature water bath, and a mechanical stirrer. The reaction catalyst and liquid reaction medium are contained within the vessel. A mixture of hydrogen / dilution gas and oxygen / dilution gas is introduced through the inlet pipe at the reactor head, entering the liquid reaction medium and reacting fully with the catalyst. The reaction exhaust gas is collected from the exhaust port at the reactor head and analyzed by gas chromatography. The key feature of this reactor is the computer-controlled flow rate and stirring rate of the coolant, enabling rapid cooling to the required reaction temperature and maintaining a stable reaction temperature throughout the entire reaction process.

[0034] In the examples and comparative examples, the hydrogen peroxide generation efficiency is the amount of hydrogen peroxide produced per unit time per unit catalyst. The concentration of H2O2 in the reaction products was determined using the cerium titration method, and the hydrogen peroxide generation efficiency was calculated accordingly. A certain amount of the post-reaction filtrate was weighed into an Erlenmeyer flask, a small amount of acidic stabilizer was added, and titration was performed using Ce(SO4)2 as a standard solution and ferrophenoneroline ion solution as an indicator. The titration endpoint was considered when the orange-red color turned blue. The reaction equation and calculation formula are as follows:

[0035] 2Ce(SO4)2+H2O2→2Ce2(SO4)3+2H2SO4+O2↑

[0036] The concentration of the standard solution is denoted as C, the volume of standard solution consumed in the titration is denoted as V, and T is the reaction time, m. catalysts Based on the mass of the catalyst and the quantitative relationship of the reaction, the hydrogen peroxide formation efficiency is calculated according to the following formula:

[0037]

[0038] The hydrogen conversion rate calculation formula in the examples and comparative examples is as follows:

[0039]

[0040] In the formula, A i0 : Peak area of ​​component i (H2) before reaction; A i : Peak area of ​​component i (H2) after reaction; A st0 : Peak area of ​​the internal standard before reaction; A st : Peak area of ​​the internal standard after reaction; fi and f st These are the corresponding molar correction factors for the substances; ni and n st These represent the amounts of the corresponding substances. The reaction tail gas was analyzed using a Varian 3800 gas chromatograph with a thermal conductivity detector (TCD). The analytical conditions were as follows: a 3m × 0.3mm Porapak Q column, held at 30℃ for 22 min. Quantitative analysis of the products was performed using the internal standard method.

[0041] Example 1

[0042] 1.7 mol of methanol, 1.6 mol of water, and 0.2 g of AuPd / C catalyst were added sequentially to the reactor. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with carbon dioxide dilution gas to obtain mixed gas I; oxygen was mixed with carbon dioxide dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / carbon dioxide mixed gas I and oxygen / carbon dioxide mixed gas II were introduced respectively. The molar ratios of hydrogen, oxygen, and dilution gas were consistently controlled at 4%, 4%, and 92%, respectively, with a total pressure of 3.0 MPa. The reaction temperature was controlled at 2°C, the stirring speed at 1200 rpm, and the reaction time at 30 min.

[0043] After the reaction, the solution was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration. The hydrogen peroxide generation efficiency was found to be 165 mol / L. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 65.1% by GC analysis of the collected gas after the reaction.

[0044] Method for determining the amount of active metal in the catalyst: The above synthesis reaction was performed using 0.5 g of catalyst. After the experiment, the catalyst sample was filtered and recovered, and dried in a vacuum drying oven at 30 °C for 17 h. The sample was collected and the activity was evaluated again according to the standard experiment. The operation was repeated 10 times. The supernatant after the reaction was characterized and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The degree of dissolution of the metal was expressed as the percentage of the total amount of the metal in the reaction, as shown in Table 1.

[0045] Table 1

[0046]

[0047] Table 1 shows that the active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, which was 0.21 μg / L. -1 It accounts for 0.6% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 3.88 μg / L. -1 It accounts for 11.1% of the active component Pd in ​​the catalyst.

[0048] Comparative Example 1

[0049] 1.7 mol methanol, 1.6 mol water, and 0.2 g AuPd / C catalyst were added sequentially to the reactor. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with nitrogen dilution gas to obtain the first premixed gas; oxygen was mixed with nitrogen dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / nitrogen mixed gas I and oxygen / nitrogen mixed gas II were introduced respectively. The molar ratio of hydrogen / oxygen / dilution gas was always controlled at 4%:4%:92%, the total pressure was 3.0 MPa, and the reaction temperature was controlled by computer at 2℃, the stirring speed at 1200 r / m, and the reaction time at 30 min.

[0050] After the reaction, the solution was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration. The hydrogen peroxide generation efficiency was found to be 102 mol / L. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 54.7% by GC analysis of the collected gas after the reaction.

[0051] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method described in Example 1, as shown in Table 2.

[0052] Table 2

[0053]

[0054] The results in Table 2 show that, in the comparative method using nitrogen as the diluent, the catalyst active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, amounting to 0.19 μg / L. -1 It accounts for 0.54% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 4.02 μg / L. -1 It accounts for 11.4% of the active component Pd in ​​the catalyst.

[0055] Example 2

[0056] 1.7 mol methanol, 1.6 mol water, and 0.2 g AuPd / C catalyst were added sequentially to the reactor. 0.1 mol hydrochloric acid (37% by mass) was added as an acid and halogen stabilizer. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with carbon dioxide dilution gas to obtain mixed gas I; oxygen was mixed with carbon dioxide dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / carbon dioxide mixed gas I and oxygen / carbon dioxide mixed gas II were introduced respectively. The molar ratio of hydrogen / oxygen / dilution gas was consistently maintained at 4%:4%:92%, the total pressure at 3.0 MPa, and the reaction temperature was controlled by computer at 2°C, the stirring speed at 1200 rpm, and the reaction time at 30 min.

[0057] After the reaction, the solution was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration. The hydrogen peroxide generation efficiency was found to be 124 mol. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 55.9% by GC analysis of the collected gas after the reaction.

[0058] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method in Example 1, as shown in Table 3.

[0059] Table 3

[0060]

[0061] The results in Table 3 show that the active component Au did not dissolve in any of the multiple reactions, while the amount of Pd dissolved after one reaction was 4.7 μg / L. -1 It accounts for 13.7% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 15.57 μg / L. -1 It accounts for 44.5% of the active component Pd in ​​the catalyst.

[0062] Comparative Example 2

[0063] 1.7 mol methanol, 1.6 mol water, and 0.2 g AuPd / C catalyst were added sequentially to the reactor. 0.1 mol hydrochloric acid (37% by mass) was added as an acid and halogen stabilizer. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with nitrogen dilution gas to obtain mixed gas I; oxygen was mixed with nitrogen dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / nitrogen mixed gas I and oxygen / nitrogen mixed gas II were introduced respectively. The molar ratio of hydrogen / oxygen / dilution gas was consistently maintained at 4%:4%:92%, the total pressure at 3.0 MPa, and the reaction temperature was controlled by computer at 2°C, the stirring speed at 1200 rpm, and the reaction time at 30 min.

[0064] After the reaction, the solution was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration. The hydrogen peroxide generation efficiency was found to be 136 mol. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 59.7% by GC analysis of the collected gas after the reaction.

[0065] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method described in Example 1, as shown in Table 4.

[0066] Table 4

[0067]

[0068] The results in Table 4 show that the active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, amounting to 4.3 μg / L. -1 It accounts for 12.2% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 12.7 μg / L. -1 It accounts for 36.4% of the active component Pd in ​​the catalyst.

[0069] Example 3

[0070] 1.7 mol of methanol, 1.6 mol of water, and 0.2 g of AuPd / C catalyst were added sequentially to the reactor. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with carbon dioxide dilution gas to obtain mixed gas I; oxygen was mixed with carbon dioxide dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / carbon dioxide mixed gas I and oxygen / carbon dioxide mixed gas II were introduced respectively. The molar ratios of hydrogen, oxygen, and dilution gas were consistently controlled at 4%, 4%, and 92%, respectively, with a total pressure of 3.0 MPa. The reaction temperature was controlled by computer at 10°C, the stirring speed at 1200 rpm, and the reaction time at 30 min.

[0071] After the reaction, the solution was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration. The hydrogen peroxide generation efficiency was found to be 142 mol. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 67.7% by GC analysis of the collected gas after the reaction.

[0072] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method described in Example 1, as shown in Table 5.

[0073] Table 5

[0074]

[0075] Table 5 shows that the active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, which was 0.16 μg / L. -1 It accounts for 0.51% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 3.43 μg / L. -1 It accounts for 10.9% of the active component Pd in ​​the catalyst.

[0076] Example 4

[0077] 1.7 mol of ethanol, 1.6 mol of water, and 0.2 g of AuPd / C catalyst were added sequentially to the reactor. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with carbon dioxide dilution gas to obtain mixed gas I; oxygen was mixed with carbon dioxide dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / carbon dioxide mixed gas I and oxygen / carbon dioxide mixed gas II were introduced respectively. The molar ratios of hydrogen, oxygen, and dilution gas were consistently controlled at 4%, 4%, and 92%, respectively, with a total pressure of 3.0 MPa. The reaction temperature was controlled by computer at 2°C, the stirring speed at 1200 rpm, and the reaction time at 30 min. After the reaction, the mixture was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration, yielding a hydrogen peroxide generation efficiency of 115 mol / L. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 49.1% by GC analysis of the collected gas after the reaction.

[0078] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method described in Example 1, as shown in Table 6.

[0079] Table 6

[0080]

[0081] Table 6 shows that the active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, which was 0.18 μg / L. -1 It accounts for 0.51% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 3.78 μg / L. -1 It accounts for 10.8% of the active component Pd in ​​the catalyst.

[0082] Example 5

[0083] 1.7 mol of methanol, 1.6 mol of water, and 0.2 g of AuPd / C catalyst were added sequentially to the reactor. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with carbon dioxide dilution gas to obtain mixed gas I; oxygen was mixed with carbon dioxide dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / carbon dioxide mixed gas I and oxygen / carbon dioxide mixed gas II were introduced respectively. The molar ratios of hydrogen, oxygen, and dilution gas were consistently controlled at 4%, 7%, and 89%, respectively, with a total pressure of 3.0 MPa. The reaction temperature was controlled by computer at 2°C, the stirring speed at 1200 rpm, and the reaction time at 30 min. After the reaction, the mixture was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration, yielding a hydrogen peroxide generation efficiency of 154 mol / L. H2O2 kg cat-1 h -1 The hydrogen conversion rate was calculated to be 62.3% by GC analysis of the collected gas after the reaction.

[0084] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method in Example 1, as shown in Table 7.

[0085] Table 7

[0086]

[0087] Table 7 shows that the active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, which was 0.21 μg / L. -1 It accounts for 0.6% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 3.80 μg / L. -1 It accounts for 10.8% of the active component Pd in ​​the catalyst.

[0088] Example 6

[0089] 1.7 mol methanol, 1.6 mol water, and 0.2 g Pd / C catalyst were added sequentially to the reactor. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with carbon dioxide dilution gas to obtain mixed gas I; oxygen was mixed with carbon dioxide dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / carbon dioxide mixed gas I and oxygen / carbon dioxide mixed gas II were introduced respectively. The molar ratios of hydrogen, oxygen, and dilution gas were consistently controlled at 4%, 4%, and 92%, respectively, with a total pressure of 3.0 MPa. The reaction temperature was controlled by computer at 2°C, the stirring speed at 1200 rpm, and the reaction time at 30 min. After the reaction, the mixture was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration, yielding a hydrogen peroxide generation efficiency of 44 mol / L. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 67.6% by GC analysis of the collected gas after the reaction.

[0090] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method in Example 1, as shown in Table 8.

[0091] Table 8

[0092] Catalyst recycle number Pd leaching / pg L -1 ]] Pd leaching / % 1 0.27 0.78 10 4.01 11.5

[0093] Table 8 shows that the active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, which was 0.27 μg / L. -1It accounts for 0.78% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 4.01 μg / L. -1 It accounts for 11.5% of the active component Pd in ​​the catalyst.

[0094] Example 7

[0095] 1.7 mol methanol, 1.6 mol water, and 0.15 g AuPd / C catalyst were added sequentially to the reactor. The reactor was then sealed and the flanges reinforced. Hydrogen was mixed with carbon dioxide dilution gas to obtain mixed gas I; oxygen was mixed with carbon dioxide dilution gas to obtain mixed gas II. The reactor and pipelines underwent three gas purgings, during which hydrogen / carbon dioxide mixed gas I and oxygen / carbon dioxide mixed gas II were introduced respectively. The molar ratios of hydrogen, oxygen, and dilution gas were consistently controlled at 4%, 7%, and 89%, respectively, with a total pressure of 3.0 MPa. The reaction temperature was controlled by computer at 2°C, the stirring speed at 1200 rpm, and the reaction time at 30 min. After the reaction, the mixture was filtered to remove the catalyst, and a small amount of the filtrate was analyzed to determine the hydrogen peroxide concentration, yielding a hydrogen peroxide generation efficiency of 141 mol. H2O2 kg cat -1 h -1 The hydrogen conversion rate was calculated to be 60.7% by GC analysis of the collected gas after the reaction.

[0096] The amount of active metal components of the catalyst in the supernatant after the reaction was determined using the method in Example 1, as shown in Table 9.

[0097] Table 9

[0098]

[0099] Table 9 shows that the active component Au did not dissolve in any of the multiple reactions, while only a small amount of Pd dissolved after the first reaction, which was 0.13 μg / L. -1 It accounts for 0.51% of the active component Pd in ​​the catalyst, and the amount of Pd precipitated after the catalyst is reused 10 times is only 2.70 μg / L. -1 It accounts for 10.3% of the active component Pd in ​​the catalyst.

Claims

1. A method for directly synthesizing hydrogen peroxide aqueous solution from hydrogen and oxygen, characterized in that, Under hydrogen peroxide generation conditions, a mixture of reactant gas and dilution gas is introduced into a liquid-phase reaction medium containing a dispersed catalyst for contact reaction to obtain hydrogen peroxide as the product. The reactant gas is oxygen and hydrogen, with a hydrogen to oxygen molar ratio of 0.01–2.

5. The dilution gas is carbon dioxide. The proportion of the dilution gas in the mixture of reactant gas and dilution gas is >50% by volume. The liquid-phase reaction medium is selected from one or more of water, methanol, ethanol, isopropanol, and 1,4-dioxane. Under the hydrogen peroxide generation conditions, the reaction temperature is -10–30°C, and the reaction pressure is 1.0–10.0 MPa.

2. The method according to claim 1, characterized in that, The mixture of reactant gas and dilution gas includes a mixture of hydrogen and dilution gas I and a mixture of oxygen and dilution gas II; in mixture I, hydrogen accounts for 1 to 15% by volume; in mixture II, oxygen accounts for 15 to 40% by volume.

3. The method according to claim 2, characterized in that, In the gas mixture I, hydrogen accounts for 5-10% by volume; in the gas mixture II, oxygen accounts for 20-30% by volume.

4. The method according to claim 1, characterized in that, In the mixture of the reactant gas and the dilution gas, the proportion of the dilution gas is >55% by volume.

5. The method according to claim 1, characterized in that, In the mixture of the reactant gas and the dilution gas, the proportion of the dilution gas is >60% by volume.

6. The method according to claim 1, characterized in that, The molar ratio of hydrogen to oxygen in the reaction feed gas is 0.5 to 1.

0.

7. The method according to claim 1, characterized in that, The contact reaction is carried out in a high-pressure reactor.

8. The method according to claim 1, characterized in that, The liquid reaction medium is water and / or methanol.

9. The method according to claim 1, characterized in that, The catalyst is a supported catalyst consisting of one or more metals from Group 1 and / or Group 8 of the periodic table.

10. The method according to claim 9, characterized in that, The metallic element is selected from at least one of gold, silver, copper, ruthenium, palladium, platinum, rhodium, cobalt, nickel, and iridium.

11. The method according to claim 9, characterized in that, In the supported catalyst, the support material is at least one of activated carbon, silicon dioxide, titanium dioxide, aluminum oxide, cerium oxide, and titanium-silicon molecular sieve.

12. The method according to claim 9, characterized in that, The metal element loading is 0.01-10 wt%.

13. The method according to claim 9, characterized in that, The supported catalyst is an activated carbon catalyst supported on gold and palladium.

14. The method according to claim 1, characterized in that, The hydrogen peroxide generation conditions described above include a reaction temperature of 0-10℃ and a reaction pressure of 3.0-6.0 MPa.

15. The method according to claim 1, characterized in that, No halogen stabilizers are added to the reaction liquid medium in this method.

16. The method according to claim 1, characterized in that, The mass ratio of the liquid reaction medium to the catalyst is 100-1000.

17. The method according to claim 1, characterized in that, The mass ratio of the liquid reaction medium to the catalyst is 400-700.

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