A method for photochemical preparation of H2 from benzyl compounds

Abstract

This invention belongs to the field of hydrogen production and relates to a method for photochemically producing H2 from benzyl compounds. The method includes the following steps: S1, loading the benzyl compound into a reactor and setting the reaction system as an oxygen-free system; S2, irradiating the oxygen-free system in step S1 with a light source containing ultraviolet light; after the reaction is complete, extracting H2. This invention uses benzyl compounds as the hydrogen source and does not use a photocatalyst. It achieves H2 production through photochemical irradiation, avoiding the unavoidable drawbacks of photocatalytic hydrogen production technology that rely on photocatalysts. This simplifies the process, improves economic efficiency, enhances the economic and environmental friendliness of H2 production, and reduces energy consumption and production costs.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen preparation technology and relates to a method for photochemical preparation of H2 from benzyl compounds. Background Technology

[0002] Hydrogen energy is a renewable and clean new energy source with advantages such as high energy density, high stability, zero carbon emissions, and no secondary pollution. It is also storable and transportable, making it an ideal energy source to replace fossil fuels. It has great potential in solving the global energy and environmental crisis and is an important breakthrough for the future global energy revolution.

[0003] Currently, hydrogen production methods mainly include fossil fuel hydrogen production, water electrolysis hydrogen production, photocatalytic hydrogen production, and biomass hydrogen production. Among these, fossil fuel cracking accounts for 95% or more of the total H2 production, primarily sourced from the partial combustion and reforming of valuable non-renewable resources such as coal, oil, and natural gas. However, due to the non-renewable nature and limited storage of the main raw materials, and the unavoidable generation of large amounts of toxic CO gas during the hydrogen production process, this method is currently mainly used for producing chemical feedstocks, with hydrogen as a byproduct. Water electrolysis accounts for about 4% of the total H2 production, but its hydrogen production half-reaction kinetics are slow, requiring a large driving overpotential. The hydrogen production process consumes a large amount of electrical energy, involves secondary energy conversion, and is costly. Furthermore, the electrocatalysts are mostly expensive precious metal catalysts such as platinum and ruthenium oxide, and their oxidation, sulfidation, nitridation, and phosphorus oxidation processes. The research and development costs of materials such as compounds and transition metal-organic frameworks (MOFs) limit the large-scale industrial development of water electrolysis. In my country, biomass hydrogen production is a relatively recent field, mainly involving biomass thermal conversion and microbial preparation. The preparation processes are not yet mature, and further optimization research is needed for large-scale application. Photochemical methods can convert light energy into chemical energy, which is an effective measure to solve the energy crisis and environmental pollution. The photolysis of water can overcome the 237kJ energy barrier to decompose 1 mol of water into oxygen and hydrogen. The external energy can be provided by sunlight, which is theoretically feasible. Therefore, photocatalytic photolysis of water / alcohols to produce hydrogen is considered a renewable and environmentally friendly ideal method for hydrogen production.

[0004] Photocatalytic H2 production mainly involves the following steps: (1) photocatalyst light absorption to generate photogenerated electron-hole pairs; (2) separation and surface migration of photogenerated holes and electrons; and (3) hole oxidation and electron reduction on the catalyst surface. Current research focuses on the preparation of stable and efficient photocatalysts and the enhancement of photocatalytic processes, aiming to reduce the band gap, improve carrier mobility and photogenerated charge separation rate, and ultimately improve the efficiency of photocatalytic hydrogen production {see JNZhang, WPHu, S.Cao and L.Y.Piao., Recent progress for hydrogen production by photocatalytic naturalor simulated seawater splitting[J]. NANO RESEARCH 2020, 13(9), 2313-2322}.

[0005] In the existing technology, the photocatalytic method for producing H2 has the following unavoidable bottleneck problems: (1) The photocatalytic process has quantum efficiency limitations and mass transfer limitations due to the recombination of photogenerated carriers: the recombination of photogenerated carriers in photocatalysts is unavoidable, and solid heterogeneous catalysts have gas-liquid-solid three-phase mass transfer limitations in the hydrogen ion oxidation process of photocatalytic hydrogen production, resulting in kinetic limits; (2) The photocatalyst's light shielding problem: the photocatalysts for water splitting are mainly solid catalysts such as TiO2, CdS, SrTiO3, and g-C3N4, which are easily dispersed in water to form suspensions. The light shielding effect limits the limited amount of catalyst that can be added, making it difficult to increase H2 production by increasing the amount of photocatalyst; (3) The photocorrosion and separation and recovery problems of photocatalysts: photocatalysts exhibit photocorrosion during use, and their performance degrades with repeated use. Furthermore, the separation of nanoparticles consumes a lot of energy. Using a loading form can alleviate the current separation situation to some extent, but it is difficult to solve the problems of weak light transmission, poor mass transfer, low recovery rate, and high separation and recovery costs. The above problems limit the large-scale application of photocatalysis in the field of hydrogen production and are difficult to overcome in the short term. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for the photochemical preparation of H2 from benzyl compounds. Using benzyl compounds as the hydrogen source, this method eliminates the need for photocatalysts and produces H2 through illumination. This photochemical method avoids the unavoidable drawbacks of photocatalytic hydrogen production (bottlenecks such as difficulties in catalyst use and separation / recovery) inherent in photocatalytic hydrogen production. It also circumvents the low economic efficiency and energy losses associated with electrocatalytic H2 production, simplifies the process, improves economics, and facilitates small-scale or large-scale H2 production. The raw materials are readily available and the process is simple, exhibiting characteristics of green and economical chemistry.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0008] This invention provides a method for the photochemical preparation of H2 from benzyl compounds, comprising the following preparation steps:

[0009] S1. The benzyl compound is loaded into the reactor, and the reaction system is set as an anaerobic system;

[0010] S2. Irradiate the oxygen-free system in step S1 with a light source containing ultraviolet light. After the reaction is complete, extract H2.

[0011] Preferably, the benzyl compound is one of benzyl ether compounds, benzylamine compounds, benzyl alkane compounds, benzyl alcohol compounds, benzyl aldehyde compounds, benzyl acid compounds, and benzyl ketone compounds.

[0012] Specifically, the benzyl ether compound is benzyl methyl ether, dibenzyl ether, or isocyanate, etc.

[0013] Alternatively, the benzylamine compound may be benzylamine, phenethylamine, amphetamine, or N,N-dimethylbenzylamine, etc.

[0014] Alternatively, the benzyl alkane compound may be toluene, ethylbenzene, propylbenzene, o-xylene, p-xylene, m-xylene, styrene, or styrene, etc.

[0015] Alternatively, the benzyl alcohol compound may be benzyl alcohol, α-phenylethanol, β-phenylethanol, phenylpropanol, or p-methoxybenzyl alcohol, etc.

[0016] Alternatively, the benzyl aldehyde compound may be benzaldehyde, phenylacetaldehyde, or phenylpropionaldehyde, etc.

[0017] Alternatively, the benzyl acid compound may be benzoic acid, phenylacetic acid, or terephthalic acid, etc.

[0018] Alternatively, the benzyl ketone compound may be benzylacetone or indene, etc.

[0019] Preferably, in step S1, the method for setting up the anaerobic system is to introduce an inert gas into the reactor.

[0020] Preferably, the inert gas is at least one of helium, nitrogen, and argon.

[0021] Preferably, in step S2, the ultraviolet light source is one of a xenon lamp, a mercury lamp, or sunlight.

[0022] Preferably, in step S2, the reaction temperature is controlled within the range of ≥20℃ and less than the boiling point of the benzyl compound, and the reaction time is at least 10 min.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention uses a light source containing ultraviolet light as the energy driving force. Benzyl compounds form large molecular clusters, which absorb energy and reach an excited state in an anaerobic reaction system. In the system, a large number of active benzyl hydrogen clusters attract each other to spontaneously generate H2. This solves the bottleneck problems of difficult catalyst use and separation and recovery in photocatalytic H2 production, avoids the high pollution and non-renewable resources of fossil fuel cracking for H2 production, and avoids the low economic efficiency and energy loss of electrocatalytic H2 production. It has the characteristics of green chemistry and economic chemistry.

[0025] 2. This invention employs a benzyl compound oxygen-free system for photochemical reaction, eliminating the need for a photocatalyst, thus saving production costs. Furthermore, it avoids the reaction mechanism bottlenecks inherent in photocatalyst systems, such as the recombination problem of photogenerated carriers, the efficiency of photogenerated carrier transfer to the catalyst surface, and the mass transfer limitations of heterogeneous catalysts in gas-liquid-solid three-phase systems. Traditional photocatalytic hydrogen production methods typically have hydrogen yields of only μmol·h⁻¹. -1 Taking benzyl methyl ether as an example, the hydrogen production rate in this invention is 159.70 mmol·h. -1 The hydrogen production rate is increased by orders of magnitude, the reaction process is simplified, and the hydrogen production rate is high.

[0026] 3. The benzyl compound clusters of the present invention, after being irradiated by a light source containing ultraviolet light, have hydrogen atoms that combine in pairs to form hydrogen gas. The free carbon atoms after dehydrogenation and carbon-carbon coupling produce products with high economic value. Taking toluene, 1,2-hydroxyanisole, and 1,3-hydroxyanisole as examples, toluene dehydrogenates to produce 1,2-diphenylethane, which is more expensive than toluene. 1,2-hydroxyanisole and 1,3-hydroxyanisole dehydrogenates form dendrobine by benzylation in pairs. The photoreaction method of the present invention can obtain a series of high-value byproducts in addition to clean energy hydrogen gas.

[0027] 4. The product hydrogen gas and the reaction system of the method of the present invention are two phases of gas and liquid, which can be directly separated, making it easy to obtain hydrogen gas and also easy to recover and utilize the reactants after dehydrogenation, thus facilitating application and promotion. Attached Figure Description

[0028] Figure 1 This is a bar chart of hydrogen production at different times in Embodiment 1 of the present invention;

[0029] Figure 2 This is a bar chart showing the hydrogen production at different times in Embodiment 2 of the present invention;

[0030] Figure 3 This is a bar chart showing the hydrogen production of Examples 6, 7 and 8 of the present invention.

[0031] Figure 4 This is a bar chart showing the hydrogen production of Example 1 and Comparative Examples 1, 2, and 3 of the present invention. Detailed Implementation

[0032] The principles and features of the present invention are described below (in conjunction with the accompanying drawings). The examples given are for illustrative purposes only and are not intended to limit the scope of the invention.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] Some of the raw materials used in this invention, including toluene, phenylethane, isopropylbenzene, styrene or phenylpropene benzyl alcohol, α-phenylethanol, p-methoxybenzyl alcohol, benzylacetone, indene, benzaldehyde, phenylacetaldehyde, benzyl methyl ether, dibenzyl ether, isochloromethane, phenylacetic acid, benzylamine, phenethylamine, and N,N-dimethylbenzylamine, are analytical grade and purchased from the market.

[0035] This invention provides a method for the photochemical preparation of H2 from benzyl compounds, comprising the following preparation steps:

[0036] S1. The benzyl compound is loaded into the reactor, and the reaction system is set as an anaerobic system;

[0037] S2. Irradiate the oxygen-free system in step S1 with a light source containing ultraviolet light. After the reaction is complete, extract H2.

[0038] The reaction mechanism of this invention is as follows: benzyl compound molecules readily form macromolecular clusters with surrounding molecules in solution through weak hydrogen bonding (HH). The H atoms of two adjacent benzyl compounds in the cluster attract each other. The benzyl compound macromolecular clusters are excited to an excited state by ultraviolet light. The macromolecular system is activated through the photoexcitation process, which strengthens the interaction between two adjacent benzyl compounds in the cluster. The benzyl H atoms are activated in large quantities under the action of the cluster. Finally, a large number of active benzyl hydrogen atoms in the system attract each other to generate H2.

[0039] Preferably, the benzyl compound is one of benzyl ether compounds, benzylamine compounds, benzyl alkane compounds, benzyl alcohol compounds, benzyl aldehyde compounds, benzyl acid compounds, and benzyl ketone compounds.

[0040] Specifically, the benzyl ether compound is benzyl methyl ether, dibenzyl ether, or isocyanate, etc.

[0041] Alternatively, the benzylamine compound may be benzylamine, phenethylamine, amphetamine, or N,N-dimethylbenzylamine, etc.

[0042] Alternatively, the benzyl alkane compound may be toluene, ethylbenzene, propylbenzene, o-xylene, p-xylene, m-xylene, styrene, or styrene, etc.

[0043] Alternatively, the benzyl alcohol compound may be benzyl alcohol, α-phenylethanol, β-phenylethanol, phenylpropanol, or p-methoxybenzyl alcohol, etc.

[0044] Alternatively, the benzyl aldehyde compound may be benzaldehyde, phenylacetaldehyde, or phenylpropionaldehyde, etc.

[0045] Alternatively, the benzyl acid compound may be benzoic acid, phenylacetic acid, or terephthalic acid, etc.

[0046] Alternatively, the benzyl ketone compound may be benzylacetone or indene, etc.

[0047] Preferably, in step S1, the method for setting up the anaerobic system is to introduce an inert gas into the reactor.

[0048] Preferably, the inert gas is at least one of helium, nitrogen, and argon.

[0049] Preferably, in step S2, the ultraviolet light source is one of a xenon lamp, a mercury lamp, or sunlight.

[0050] Preferably, in step S2, the reaction temperature is controlled within the range of ≥20℃ and less than the boiling point of the benzyl compound, and the reaction time is at least 10 min.

[0051] If the reaction temperature is below 20℃, the reactants will solidify, which is not conducive to the reaction and reduces the efficiency of hydrogen production.

[0052] The present invention will now be described in detail with reference to embodiments and experimental data.

[0053] Example 1

[0054] In this embodiment, nitrogen is used as the oxygen source, toluene as the free hydrogen atom source, and a xenon lamp as the ultraviolet light source. The steps are as follows:

[0055] S1. 5 mL of toluene is placed into 4 reactors respectively. Nitrogen gas is introduced into the reactors at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, the reactors are sealed.

[0056] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 1 h, 2 h, 3 h, and 4 h under xenon lamp irradiation and stirring. The system was in a closed state throughout the reaction. After the reaction, the reactor gas was extracted, and the hydrogen production at each reaction time was quantitatively analyzed by gas chromatography. The results of the hydrogen production change over time are shown below. Figure 1 As shown.

[0057] from Figure 1As can be seen, the concentration of H2 in the resulting system increases with increasing reaction time. After reacting at 20℃ for 4 hours, the H2 concentration was 287.33 mmol, and the H2 yield was 71.83 mmol·h. -1 .

[0058] The structure of the organic phase was confirmed by nuclear magnetic resonance and high-resolution mass spectrometry analysis, which showed that the organic phase contained 1,2-diphenylethane with a toluene dehydrobenzyl structure.

[0059] Example 2

[0060] This embodiment uses compressed nitrogen as the oxygen source, phenylethane as the free hydrogen atom source, and a xenon lamp as the ultraviolet light source. The steps are as follows:

[0061] S1. 5 mL of phenyl ethane is loaded into 4 reactors respectively. Nitrogen gas is introduced into the reactors at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 30 min. After the oxygen is removed, the reactors are sealed.

[0062] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 1 h, 2 h, 3 h, and 4 h under xenon lamp irradiation and stirring. The system was in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production at each reaction time was quantitatively analyzed by gas chromatography. The results of the hydrogen production change over time are shown below. Figure 2 As shown.

[0063] from Figure 2 It can be seen that the concentration of H2 in the resulting system increases with the increase of reaction time. After reacting at 20℃ for 4 h, the H2 concentration is 367.71 mmol, and the H2 yield is 91.93 mmol·h. -1 .

[0064] Example 3

[0065] In this embodiment, helium is used as the oxygen source, isopropylbenzene as the free hydrogen atom source, and a xenon lamp as the ultraviolet light source. The steps are as follows:

[0066] S1. Add 5 mL of isopropylbenzene to the reactor, and introduce nitrogen into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0067] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The mixture was reacted at 20°C for 4 hours under the irradiation and stirring of the xenon lamp. The system was kept in a closed state throughout the reaction. After the reaction time was up, a product containing H was obtained. 2In this system, reactor gas was extracted, and hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 157.89 mmol, and the H2 yield was 39.47 mmol·h⁻¹. -1 .

[0068] Example 4

[0069] In this embodiment, argon is used as the oxygen removal source, styrene as the free hydrogen atom source, and a xenon lamp as the ultraviolet light source. The steps are as follows:

[0070] S1. Add 5 mL of styrene to the reactor, and introduce nitrogen into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0071] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 696.19 mmol, and the H2 yield was 174.05 mmol·h. -1 .

[0072] Example 5

[0073] This embodiment uses compressed nitrogen as the oxygen source, styrene as the free hydrogen atom source, and a xenon lamp as the ultraviolet light source. The steps are as follows:

[0074] S1. Add 5 mL of styrene to the reactor and introduce nitrogen into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0075] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 368.86 mmol, and the H2 yield was 39.47 mmol·h. -1 .

[0076] Example 6

[0077] In this embodiment, compressed nitrogen is used as the oxygen source, benzyl alcohol is used as the free hydrogen atom source, and a xenon lamp is used as the ultraviolet light source. The steps are as follows:

[0078] S1. Add 5 mL of benzyl alcohol to the reactor, and introduce nitrogen into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0079] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 731.98 mmol, and the H2 yield was 232.03 mmol·h. -1 The hydrogen production results are as follows: Figure 3 As shown.

[0080] Example 7

[0081] In this embodiment, helium is used as the oxygen removal source, α-phenylethanol is used as the free hydrogen atom source, and a xenon lamp is used as the ultraviolet light source. The steps are as follows:

[0082] S1. Add 5 mL of α-phenylethanol to the reactor, and introduce nitrogen into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0083] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 797.32 mmol, and the H2 yield was 199.33 mmol·h. -1 The hydrogen production results are as follows: Figure 3 As shown.

[0084] Example 8

[0085] In this embodiment, compressed nitrogen is used as the oxygen source, p-methoxybenzyl alcohol is used as the free hydrogen atom source, and a xenon lamp is used as the ultraviolet light source. The steps are as follows:

[0086] S1. Add 5 mL of p-methoxybenzyl alcohol to the reactor, and introduce nitrogen gas into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0087] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 928.12 mmol, and the H2 yield was 182.99 mmol·h. -1 The hydrogen production results are as follows: Figure 3 As shown.

[0088] from Figure 3 It can be seen that as the methylene carbon chain in the benzyl functional group of benzyl alcohols increases, the concentration of H2 in the resulting system increases, and the influence on hydrogen production is: methoxy > ethylidene > methylene.

[0089] Example 9

[0090] In this embodiment, nitrogen is used as the oxygen source, p-methoxybenzyl alcohol is used as the free hydrogen atom source, and sunlight is used as the ultraviolet light source. The steps are as follows:

[0091] S1. Add 5 mL of p-methoxybenzyl alcohol to the reactor, and introduce nitrogen gas into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0092] S2. The reaction was carried out at 20°C for 4 hours under natural sunlight and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 489.06 mmol, and the H2 yield was 122.27 mmol·h⁻¹. -1 .

[0093] Example 10

[0094] In this embodiment, nitrogen is used as the oxygen source, benzylacetone as the free hydrogen atom source, and sunlight as the ultraviolet light source. The steps are as follows:

[0095] S1. Add 5 mL of p-benzylacetone to reactor 3, and introduce nitrogen into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0096] S2. The reaction was carried out at 20°C for 4 hours under natural sunlight and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 572.14 mmol, and the H2 yield was 143.04 mmol·h⁻¹. -1 .

[0097] Example 11

[0098] In this embodiment, helium is used as the oxygen removal source, benzylacetone is used as the free hydrogen atom source, and sunlight is used as the light source containing ultraviolet light. The steps are as follows:

[0099] S1. Add 5 mL of p-benzylacetone to reactor 3, and introduce helium gas into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0100] S2. The reaction was carried out at 20°C for 4 hours under natural sunlight and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 572.12 mmol, and the H2 yield was 143.03 mmol·h⁻¹. -1 .

[0101] Example 12

[0102] This embodiment uses helium as the oxygen removal source, indene as the free hydrogen atom source, and sunlight as the ultraviolet light source. The steps are as follows:

[0103] S1. Add 5 mL of indene to reactor 3, and introduce helium into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0104] S2. The reaction was carried out at 20°C for 4 hours under natural sunlight and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 3157.64 mmol, and the H2 yield was 789.4 mmol·h⁻¹. -1 .

[0105] Example 13

[0106] In this embodiment, helium is used as the oxygen source, benzaldehyde as the free hydrogen atom source, and a mercury lamp as the ultraviolet light source. The steps are as follows:

[0107] S1. Add 5 mL of benzaldehyde to reactor 3, and introduce helium gas into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0108] S2, 300W mercury lamp, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under the irradiation and stirring of the mercury lamp. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 627.79 mmol, and the H2 yield was 156.95 mmol·h. -1.

[0109] Example 14

[0110] In this embodiment, argon gas is used as the oxygen removal source, phenylacetaldehyde is used as the free hydrogen atom source, and sunlight is used as the light source containing ultraviolet light. The steps are as follows:

[0111] S1. Add 5 mL of phenylacetaldehyde to reactor 3, and introduce argon gas into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0112] S2. The reaction was carried out at 20°C for 4 hours under natural sunlight and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 731.47 mmol, and the H2 yield was 182.87 mmol·h. -1 .

[0113] Example 15

[0114] In this embodiment, argon is used as the oxygen removal source, benzyl methyl ether is used as the free hydrogen atom source, and a xenon lamp is used as the ultraviolet light source. The steps are as follows:

[0115] S1. Add 5 mL of benzyl methyl ether to reactor 3, and introduce argon gas into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The gas introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0116] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 638.79 mmol, and the H2 yield was 159.70 mmol·h. -1 .

[0117] Example 16

[0118] In this embodiment, compressed argon gas is used as the oxygen removal source, dibenzyl ether is used as the free hydrogen atom source, and a xenon lamp is used as the ultraviolet light source. The steps are as follows:

[0119] S1. Add 5 mL of dibenzyl ether to reactor 3, and introduce argon gas into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The gas introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0120] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 845.31 mmol, and the H2 yield was 211.33 mmol·h. -1 Analysis using nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HMS) revealed that the organic phase contained benzaldehyde (a dehydrogenated dibenzyl ether), benzoic acid, benzyl benzoate, and benzoin.

[0121] Example 17

[0122] In this embodiment, compressed nitrogen is used as the oxygen source, a heterochromatic lamp is used as the free hydrogen atom source, and a xenon lamp is used as the light source containing ultraviolet light. The steps are as follows:

[0123] S1. Fill reactor 3 with 5 mL of the different color, and introduce nitrogen into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0124] S2, Xenon lamp 300W, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under xenon lamp irradiation and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 953.75 mmol, and the H2 yield was 238.44 mmol·h. -1 .

[0125] Example 18

[0126] In this embodiment, nitrogen is used as the oxygen source, phenylacetic acid is used as the free hydrogen atom source, and sunlight is used as the light source containing ultraviolet light. The steps are as follows:

[0127] S1. Add 5 mL of phenylacetic acid to reactor 3, and introduce nitrogen gas into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0128] S2. The reaction was carried out at 20°C for 4 hours under natural sunlight and stirring. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 794.41 mmol, and the H2 yield was 198.60 mmol·h⁻¹. -1 .

[0129] Example 19

[0130] In this embodiment, helium is used as the oxygen source, benzoylamine is used as the free hydrogen atom source, and a mercury lamp is used as the light source containing ultraviolet light. The steps are as follows:

[0131] S1. Add 5 mL of aniline to reactor 3, and introduce helium gas into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0132] S2, 300W mercury lamp, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under the irradiation and stirring of the mercury lamp. The system was kept in a closed state throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 529.24 mmol, and the H2 yield was 132.31 mmol·h⁻¹. -1 .

[0133] Example 20

[0134] In this embodiment, helium is used as the oxygen source, phenylethylamine is used as the free hydrogen atom source, and a mercury lamp is used as the light source containing ultraviolet light. The steps are as follows:

[0135] S1. Add 5 mL of phenylethylamine to reactor 3, and introduce helium gas into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0136] S2, 300W mercury lamp, luminous power density 500mW / cm² 2 The reaction was carried out at 20°C for 4 hours under irradiation and stirring with a mercury lamp. The system was kept closed throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 87.24 mmol, and the H2 yield was 21.81 mmol·h⁻¹. -1

[0137] Example 21

[0138] In this embodiment, compressed helium is used as the oxygen source, N,N-dimethylbenzylamine is used as the free hydrogen atom source, and a mercury lamp is used as the light source containing ultraviolet light. The steps are as follows:

[0139] S1. Add 5 mL of N,N-dimethylbenzylamine to reactor 3, and introduce helium gas into the reactor at a flow rate of 50 mL / min to form an oxygen-free reaction system. The introduction time is 15 min. After the oxygen is purged, seal the reactor.

[0140] S2, 300W mercury lamp, luminous power density 500mW / cm² 2The reaction was carried out at 20°C for 4 hours under irradiation and stirring with a mercury lamp. The system was kept closed throughout the reaction. After the reaction, a system containing H2 was obtained. The reactor gas was extracted, and the hydrogen production was quantitatively analyzed by gas chromatography. The H2 concentration was 4578.86 mmol, and the H2 yield was 1144.71 mmol·h⁻¹. -1 .

[0141] The following experimental examples illustrate the beneficial effects of the present invention. Experimental methods not specifying particular conditions in the following examples are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, standard conditions, or conditions recommended by the manufacturer shall be followed.

[0142] Experimental Example

[0143] I. Determination of Hydrogen Production

[0144] Hydrogen production was determined in Examples 1-21: Hydrogen production was quantitatively analyzed by gas chromatography. The specific analytical method was as follows: 1 mL of hydrogen was injected into a gas chromatograph (FULI GC9790-Ⅱ) for analysis. The gas chromatography used a thermal conductivity detector (TCD), a 5A molecular sieve column, and argon (99.999%) as the carrier gas. The measurement results are shown in Table 1 below:

[0145] Table 1. Results of Hydrogen Production and Rate

[0146]

[0147]

[0148] As shown in Table 1, the hydrogen yield of benzyl compounds is in the mmol level. Examples 1 and 2 show that the hydrogen yield from the photoreaction of benzyl compounds increases with time. The hydrogen production method of this invention can achieve a maximum hydrogen production rate of 1144.71 mmol·h. -1 .

[0149] II. The effect of catalyst presence and reaction temperature on hydrogen production

[0150] Comparative Example 1: 1.2 g of Na₂S solid was weighed into 250 ml of water, and 3 g of CdS catalyst was added. A photocatalytic hydrogen production reaction was carried out using a closed-loop system. The system was evacuated for 20 min, then irradiated with light (420 nm filter, 300 W Xe lamp, 20 A). The generated H₂ was detected by gas chromatography, and the results are as follows: Figure 4 As shown.

[0151] Comparative Example 2: 0.6 g of NiO catalyst was added to 600 mL of water, along with 0.05 mol / L of oxalic acid sacrificial agent. The mixture was then irradiated (400-700 nm, 250 W Xe lamp) in a reactor purged with nitrogen. The generated H2 was detected by gas chromatography, and the results are as follows: Figure 4 As shown.

[0152] Comparative Example 3: 5 mL of toluene was added to reactor 3. Helium gas was introduced into the reactor at a flow rate of 50 mL / min to form an anaerobic reaction system for 15 min. After oxygen removal, the reactor was sealed, and the reaction temperature was adjusted to 10℃, 20℃, 30℃, and 40℃, respectively, and then irradiated with light (300W xenon lamp, light power density 500mW / cm²). 2 After reacting for 4 hours, the hydrogen production was quantitatively analyzed by gas chromatography. The results are as follows: Figure 4 As shown.

[0153] Depend on Figure 4 It can be seen that when a photocatalyst is added, the hydrogen production efficiency of traditional photocatalysts such as CdS is basically at the μM level (0.396 μmol / h), and very few, such as NiO, reach the mmol level (1.58 mmol / h). Their hydrogen production efficiency is much lower than that of the benzyl compound of this invention without a photocatalyst (71.83 mmol / h). When the reaction temperature is below 20 degrees, the fluidity of the benzyl compound is weakened and the hydrogen production rate is low. As the reaction temperature rises to room temperature and above, the hydrogen production capacity of the benzyl compound is significantly enhanced.

[0154] In summary, this invention does not use a photocatalyst, thus saving production costs. Furthermore, it avoids the reaction mechanism bottlenecks of photocatalyst systems, such as the recombination problem of photogenerated carriers, the efficiency of photogenerated carriers transferring to the catalyst surface, and the mass transfer limitation of heterogeneous catalysts in gas-liquid-solid three-phase systems. The reaction process is simplified, and the hydrogen production rate is high.

[0155] The benzyl compound clusters of the present invention, after being irradiated by a light source containing ultraviolet light, have hydrogen atoms that combine in pairs to form hydrogen gas. The carbon-carbon coupling products after dehydrogenation of the free carbon atoms have high economic value. Taking toluene, 1,2-hydroxyanisole, and 1,3-hydroxyanisole as examples, toluene dehydrogenates to form 1,2-diphenylethane, which is more expensive than toluene. 1,2-hydroxyanisole and 1,3-hydroxyanisole dehydrogenates form dendrobine by combining in pairs after dehydrogenation. The photoreaction method of the present invention can obtain a series of high-value byproducts in addition to clean energy hydrogen gas.

[0156] The product hydrogen gas of the method of the present invention is a gas-liquid two-phase system with the reaction system, which can be directly separated, making it easy to obtain hydrogen gas and also easy to recover and utilize the reactants after dehydrogenation, thus facilitating its application and promotion.

[0157] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for photochemical preparation of H2 from benzyl compounds, characterized in that, The preparation steps include the following: S1. Benzyl compound, isocyanate, styrene, styrene propene, α-phenylethanol, β-phenylethanol, phenylpropanol, benzaldehyde, benzoic acid or indene are loaded into the reactor, and the reaction system is set as an anaerobic system. S2. Irradiate the oxygen-free system in step S1 with a light source containing ultraviolet light. After the reaction is complete, extract H2. The reaction temperature is controlled within the range of ≥20℃ and less than the boiling point of the benzyl compound, and the reaction time is at least 10 min.

2. The method for photochemical preparation of H2 from a benzyl compound according to claim 1, characterized in that, The benzyl compound is one of the following: benzyl ether compounds, benzylamine compounds, benzyl alkane compounds, benzyl alcohol compounds, benzyl aldehyde compounds, benzyl acid compounds, and benzyl ketone compounds.

3. The method for photochemical preparation of H2 from a benzyl compound according to claim 2, characterized in that, The benzyl ether compound is benzyl methyl ether or dibenzyl ether; Alternatively, the benzylamine compound may be benzylamine, phenethylamine, amphetamine, or N,N-dimethylbenzylamine; Alternatively, the benzyl alkane compound may be toluene, ethylbenzene, propylbenzene, o-xylene, p-xylene, or m-xylene; Alternatively, the benzyl alcohol compound may be benzyl alcohol or p-methoxybenzyl alcohol; Alternatively, the benzyl aldehyde compound may be phenylacetaldehyde or phenylpropionaldehyde; Alternatively, the benzyl acid compound may be phenylacetic acid or terephthalic acid; Alternatively, the benzyl ketone compound may be benzylacetone.

4. The method for photochemical preparation of H2 from a benzyl compound according to claim 1, characterized in that, In step S1, the method for setting up the anaerobic system is to introduce an inert gas into the reactor.

5. The method for photochemical preparation of H2 from a benzyl compound according to claim 4, characterized in that, The inert gas is at least one of nitrogen and argon.

6. The method for photochemical preparation of H2 from a benzyl compound according to claim 1, characterized in that, In step S2, the ultraviolet light source is one of a xenon lamp, a mercury lamp, or sunlight.

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