Method for preparing phenol from bio-oil

Abstract

The invention discloses a method for preparing phenol from bio-oil, and belongs to the field of organic material preparation. The method comprises the following steps: reacting bio-oil in the presence of a first catalyst metal molecular sieve composite catalyst to obtain an intermediate rich in benzene; the intermediate rich in benzene is subjected to a catalytic oxidation reaction in the atmosphere of a second catalyst and hydrogen peroxide, and phenol is obtained, the second catalyst comprises a ferroferric oxide carrier and a copper-containing substance loaded on the ferroferric oxide carrier. The preparation method provided by the invention has relatively high selectivity and yield on phenol, and is low in cost and environment-friendly. According to the method, the used raw material is the bio-oil, the raw material has the advantages of being rich in resource, environmentally friendly, renewable and the like, a terminal product is a biomass-based high-added-value chemical taking phenol as a main component, and high-value comprehensive utilization of biomass resources is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of organic material preparation, and particularly relates to a method for preparing phenol using bio-oil. Background Art

[0002] Phenol is a key intermediate in the chemical industry and can be used to produce various key chemicals and intermediates, such as phenolic resins, caprolactam, bisphenol A, salicylic acid, picric acid, pentachlorophenol, 2,4-D, adipic acid, phenolphthalein n-acetylethoxyaniline, etc. It has important uses in industries such as chemical raw materials, alkylphenols, synthetic fibers, plastics, synthetic rubbers, pharmaceuticals, pesticides, fragrances, dyes, coatings, and oil refining. In addition, phenol can also be used as a solvent, experimental reagent, and disinfectant. The aqueous solution of phenol can separate the protein and DNA on the chromosome in plant cells, facilitating the staining of DNA. In the medical field, phenol can also be used for instrument disinfection, excrement treatment, and skin sterilization and itching relief, etc. Phenol is usually produced by the cumene process worldwide, generally including: propylene and benzene react to form cumene under the catalysis of aluminum trichloride, it is oxidized to cumene hydroperoxide, and then decomposed with a cation exchange resin to obtain phenol. However, this method has disadvantages such as high pollution, high energy consumption, cumbersome process, and low phenol selectivity.

[0003] The above production process involves an oxidation step, and oxidation plays a crucial role in the energy conversion and synthesis of high-value fine chemicals, pesticides, and pharmaceutical intermediates. Traditional thermochemical methods usually require high temperatures, which easily lead to poor product selectivity. Therefore, selective oxidation under mild conditions remains a key challenge.

[0004] Due to the low reactivity of carbon-hydrogen bonds, the direct hydroxylation of benzene to prepare phenol is one of the most difficult selective oxidation reactions. Currently, there are literature reports on using various metal-modified catalysts to directly oxidize benzene to phenol, and these catalysts include palladium membranes, titanium silicate, vanadium-substituted catalysts, metal-modified activated carbon, metal-modified g-C3N4, and metal-modified zeolites, etc. Among these catalysts, iron-based catalysts relatively have advantages such as good stability, high selectivity, and low toxicity. Although significant progress has been made in the direct hydroxylation of benzene to prepare phenol using iron-containing solids, their catalytic performance is still limited by the inherent defects of iron materials. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing phenol using bio-oil. The preparation method of the present invention has high selectivity and yield for phenol, low cost, and is environmentally friendly.

[0006] The present invention provides a method for preparing phenol using bio-oil, comprising the following steps:

[0007] S1. Using bio-oil as raw material, react in the presence of a first catalyst to obtain an intermediate rich in benzene; the first catalyst is a metal molecular sieve composite catalyst, and the metal element therein is zinc; the molar content of benzene in the intermediate rich in benzene is above 70%;

[0008] S2. Catalytically oxidize the intermediate rich in benzene in an atmosphere of a second catalyst and hydrogen peroxide to obtain phenol; the second catalyst includes a ferric oxide carrier and a copper-containing substance supported thereon.

[0009] Preferably, in step S1, the bio-oil is a liquid biomass derivative produced by pyrolysis of lignocellulosic biomass; the water content in the bio-oil is 30 - 55%.

[0010] Preferably, in step S1, the mass fraction of zinc in the first catalyst is 1 - 3%; the molecular sieve component in the first catalyst is one or more of HY molecular sieve, Hβ molecular sieve, and HZSM-5 molecular sieve components.

[0011] Preferably, in step S1, the preparation of the first catalyst includes: adding a molecular sieve to an aqueous solution of a zinc salt, drying first at 100 - 150 °C, and then sintering at a temperature of 500 - 600 °C to obtain it.

[0012] Preferably, the reaction in step S1 is carried out in a protective atmosphere, and the reaction temperature is 500 - 610 °C.

[0013] Preferably, in step S2, the mass ratio of the second catalyst to the intermediate rich in benzene is 1:8 - 11; the mass content of the ferric oxide carrier in the second catalyst is 75 - 80%.

[0014] Preferably, in step S2, the second catalyst has a nanoparticle morphology;

[0015] The preparation of the second catalyst includes:

[0016] Mix ferric oxide nanoparticles and a copper-based metal salt solution, adjust the pH value to be alkaline, and carry out a hydrothermal reaction at a temperature of 100 - 180 °C, and separate to obtain a precipitate; the copper-based metal salt solution includes a copper-based metal salt, water, alcohol, and alkyl ammonium halide (mainly cetyltrimethylammonium bromide);

[0017] Dry the precipitate first at 150 - 250 °C, and then calcine it at 500 - 600 °C and in a protective atmosphere to obtain a powder sample.

[0018] Preferably, in the preparation of the second catalyst in step S2, it further includes:

[0019] The powder sample obtained by the calcination is reduced by hydrazine hydrate to obtain a second catalyst.

[0020] Preferably, in the preparation of the second catalyst in the step S2, the mass ratio of the hydrazine hydrate to the powder sample is 0.5-2.0:1.

[0021] Preferably, in the step S2, the catalytic oxidation reaction is carried out in a liquid-phase reaction kettle at a temperature of 60-80 °C and at atmospheric pressure.

[0022] Lignocellulosic biomass is the most abundant and cheapest sustainable carbon source and can be used as a raw material for the production of renewable fuels and high-value chemicals. Among them, lignocellulosic biomass can produce bio-oil products with a content of up to 70% through fast pyrolysis, which is considered an ideal platform compound for the production of renewable biofuels or high-value chemicals. Compared with solid biomass raw materials, bio-oil has more convenient advantages in terms of raw material storage and transportation, and also has equipment compatible with the existing petroleum resource infrastructure. However, due to the high oxygen content, high viscosity and acidity, poor stability and low calorific value of bio-crude oil, its wide application is restricted. So far, converting the complex oxygen-containing compounds in bio-oil into high-value chemical substances with a single target is still a formidable challenge. The research so far has shown that when using single pathways such as pyrolysis, catalytic cracking, catalytic oxidation and catalytic hydrogenation, there are bottleneck problems of poor selectivity and low yield of the target product to varying degrees, and it is necessary to construct a coupling reaction system for the selective cracking of biomass and the selective conversion of intermediates oriented to the target product.

[0023] In addition to overcoming the limitations of existing catalysts such as iron-based catalysts, the present invention provides a method for preparing phenol from bio-oil. In the method of the present invention, first is the catalytic cracking step of bio-oil, which uses a specific metal molecular sieve composite catalyst to obtain an intermediate rich in benzene through reactions such as the catalytic cracking of bio-oil; then, the present invention uses a catalyst with copper-containing substances supported on iron trioxide (which can be called a copper-based magnetic composite catalyst) as the second catalyst, which can realize the selective conversion of the intermediate rich in benzene converted from bio-oil into biomass-based high-value chemicals mainly composed of phenol. The raw material used in the present invention is bio-oil, which has the advantages of rich resources, environmental friendliness and renewability, and the end product is biomass-based high-value chemicals mainly composed of phenol, which is conducive to the high-value comprehensive utilization of biomass resources. When some examples use the reduced copper-based magnetic composite catalyst, the benzene conversion rate can reach 35.5%, and the selectivity of phenol can reach 95.9%. The preparation method of the present invention has high phenol selectivity, high yield and low cost, and is conducive to large-scale popularization and application. Detailed implementation mode

[0024] In order to more clearly understand the technical features, objectives, and effects of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0025] The present invention provides a method for preparing phenol from bio-oil, comprising the following steps:

[0026] S1. Using bio-oil as a raw material, reacting in the presence of a first catalyst to obtain an intermediate rich in benzene; the first catalyst is a metal molecular sieve composite catalyst, and the metal element therein is zinc; the molar content of benzene in the intermediate rich in benzene is above 70%.

[0027] S2. Carrying out a catalytic oxidation reaction on the intermediate rich in benzene in an atmosphere of a second catalyst and hydrogen peroxide to obtain phenol; the second catalyst comprises a ferric oxide carrier and a copper-containing substance supported thereon.

[0028] The method for preparing phenol provided by the present invention has high selectivity and yield, low cost, and is environmentally friendly.

[0029] In an embodiment of the present invention, the raw material bio-oil can be placed in a fixed-bed reactor and reacted in the presence of a first catalyst and a protective atmosphere to obtain an intermediate rich in benzene; the first catalyst is a metal molecular sieve composite catalyst, and the metal element therein is zinc.

[0030] In an embodiment of the present invention, the bio-oil is specifically a solid biomass (i.e., lignocellulosic biomass), a biomass derivative liquid produced by rapid pyrolysis in a circulating fluidized bed reactor; the present invention has no special limitation on the source of the solid biomass, and plant biomass materials well-known to those skilled in the art can be used, such as straw biomass, rice husk biomass, peanut shell biomass, etc. The present invention preferably uses the bio-oil produced by rapid pyrolysis of straw in a circulating fluidized bed reactor as a raw material; according to the differences in different biomass raw materials, the water content in the bio-oil can be 30-55%, preferably 40-51%.

[0031] The first catalyst in the embodiment of the present invention can be a metal / molecular sieve composite catalyst, comprising a metal zinc element and a molecular sieve component. Among them, the mass fraction of zinc in the first catalyst is preferably 1-3%, more preferably 1-1.5%; the mass fraction of the molecular sieve component can be 97-99%.

[0032] Preferably, the molecular sieve component in the first catalyst is one or more of HY molecular sieve, Hβ molecular sieve, and HZSM-5 molecular sieve component, and more preferably the HZSM-5 molecular sieve component. In a specific embodiment of the present invention, the first catalyst with the following composition can be used: a Zn / HZSM-5 metal molecular sieve composite catalyst composed of 1.0 wt% zinc and 99.0 wt% HZSM-5 molecular sieve.

[0033] In an embodiment of the present invention, the mass ratio of the first catalyst to the bio-oil is preferably (2-4):1, and more preferably 3:1.

[0034] The embodiment of the present invention preferably uses the impregnation method and prepares the first catalyst according to the following steps:

[0035] First, mix a metal zinc salt with water (which can be deionized water) to prepare an aqueous solution of the zinc salt;

[0036] Then add the molecular sieve to the aqueous solution of the zinc salt, stir evenly, dry, and finally sinter, grind, and screen to obtain the product.

[0037] In an embodiment of the present invention, the zinc salt is preferably a water-soluble salt of zinc, such as zinc nitrate; the molecular sieve uses a conventional product, and the zinc salt and the molecular sieve are proportioned according to the amounts of zinc element and molecular sieve described above. The present invention has no special limitation on the amount of deionized water used, as long as it can completely dissolve the zinc salt and does not cause too much burden on subsequent drying. According to the different molecular ratios of silicon oxide and aluminum oxide, the types of molecular sieves include Y (sodium Y type), 13Z (sodium Z type), 4A (sodium A type), etc.; their space pores are divided into α, β, γ, hexagonal column, faujasite, etc. The Y-type molecular sieve has a twelve-membered oxygen ring, the ten-membered oxygen ring includes ZSM-5, ZSM-11, etc., and the eight-membered oxygen ring includes the A-type molecular sieve. The ZSM-5 molecular sieve is a zeolite molecular sieve containing organic amine cations, and its relative crystallinity of the H type is greater than 95%.

[0038] In the process of preparing the first catalyst in the embodiments of the present invention, the temperature of stirring during the addition of the molecular sieve is preferably 50-80°C, more preferably 60-70°C; the stirring time is preferably 5-10 hours, more preferably 6-8 hours. The drying temperature is preferably 100-150°C, more preferably 120-130°C; the drying time is preferably 8-20 hours, more preferably 9-18 hours, further preferably 10-15 hours or 12-15 hours. The sintering temperature is preferably 500-600°C, more preferably 550-560°C; the sintering time is preferably 1-10 hours, more preferably 3-8 hours or 4-8 hours, further preferably 5-6 hours. The present invention preferably performs sintering in a muffle furnace, and the metal molecular sieve composite catalyst is obtained by grinding and sieving.

[0039] The catalytic reaction of the bio-oil in the embodiments of the present invention is carried out under a protective atmosphere. The protective atmosphere is preferably an inert gas such as nitrogen or argon that does not participate in the reaction and isolates active gases such as oxygen, and more preferably nitrogen. In some embodiments, the flow rate of nitrogen during the reaction is preferably 100-200 mL / min, more preferably 150 mL / min.

[0040] In a specific embodiment of the present invention, the bio-oil preferably enters the reactor at a feeding rate of 10 g / h. The first catalyst is placed in a fixed-bed reactor and the reaction is carried out under a protective atmosphere. The bio-oil undergoes catalytic cracking, deoxygenation, aromatization, alkylation, dealkylation and other reactions under the action of the first catalyst to obtain an intermediate rich in benzene (aromatic hydrocarbons). In addition, there is a certain amount of methanol in the reactor; the addition of methanol can increase the H / Ceff ratio in the reactants and reduce the formation of by-products such as coke and polycyclic aromatic hydrocarbons (such as naphthalene and indene) in the products. At the same time, it can effectively promote the alkylation reaction and significantly increase the carbon molar yield of aromatic hydrocarbons.

[0041] The reactions catalyzed by the first catalyst in the embodiments of the present invention include one or more of catalytic cracking reaction, deoxygenation reaction, aromatization reaction, alkylation reaction and dealkylation reaction. The reaction temperature is preferably 500-610°C, more preferably 550-600°C, further preferably 560-580°C; the reaction pressure is atmospheric pressure, and the reaction time is preferably 0.5-3 hours, more preferably 1-2 hours. After the bio-oil undergoes catalytic cracking and other reactions, an intermediate rich in benzene is obtained; the molar content of benzene in the intermediate rich in benzene is above 70%, and it also contains a small amount of aromatic hydrocarbon substances such as toluene and xylene.

[0042] In the embodiments of the present invention, the product obtained in the first step reaction (i.e., the benzene-rich intermediate) can be mixed with a second catalyst in a liquid-phase reaction kettle, and an aromatic hydrocarbon selective oxidation reaction is carried out under the conditions of a hydrogen peroxide atmosphere and stirring to obtain biomass-based high-value-added chemicals mainly composed of phenol.

[0043] The second catalyst described in the present invention includes: a copper-containing substance and a magnetite magnetic carrier (which can be a copper-based substance and Fe3O4 nanoparticles). As a catalyst for the catalytic oxidation of aromatic hydrocarbon intermediates, the copper-based substance is the active center for the activation and oxidation of the carbon-hydrogen bond of aromatic hydrocarbons. While the magnetic carrier (Fe3O4 nanoparticles) plays a role in the bimetallic synergistic effect, it is beneficial to improve the product yield and the separation and recovery of the catalyst. Traditionally, supported copper catalysts have also been used, but it is difficult to directly introduce hydroxyl functional groups into benzene molecules; at the same time, it is difficult to separate and recover the catalyst from the product.

[0044] The copper-containing substance in the second catalyst includes copper-based phases such as elemental copper, copper oxide, and cuprous oxide, and is preferably a copper-based magnetic catalyst after a certain reduction. In specific embodiments of the present invention, the second catalyst is preferably Cu@Fe3O4, Cu@Fe3O4-0.5, Cu@Fe3O4-1.0, Cu@Fe3O4-2.0; the numbers therein represent the mass ratio of the reducing agent hydrazine hydrate to the copper-based catalyst before reduction.

[0045] In the embodiments of the present invention, the hydrothermal method can be adopted, and preferably the second catalyst is prepared according to the following steps:

[0046] First, provide magnetite nanoparticles: preferably, an iron salt (such as ferric chloride hexahydrate) is mixed with ethanol, cetyltrimethylammonium bromide, and water (which can be deionized water), the pH value is adjusted to alkaline, stirred, hydrothermally treated, magnetically separated, and dried to obtain magnetic nanoparticles, which are used as the catalyst carrier;

[0047] Then, the magnetic nanoparticles are mixed with a copper-based metal salt solution, the pH value is adjusted to alkaline, stirred, hydrothermally treated, magnetically separated, dried, and calcined to prepare a copper-based magnetic catalyst; the copper-based metal salt solution is mainly a mixed solution of a copper-based metal salt, water, ethanol, and cetyltrimethylammonium bromide (CTAB).

[0048] Finally, preferably, the copper-based magnetic catalyst is added to a prepared 0.3 mol / L aqueous solution of hydrazine hydrate (N2H4·H2O), stirred, reduced, washed, and dried to obtain the second catalyst (the reduced copper-based magnetic catalyst).

[0049] Specifically, the weighed ferric chloride hexahydrate can be dissolved in a mixed solution formed by deionized water, ethanol, and cetyltrimethylammonium bromide (CTAB). Mechanically stir at 95 - 98 °C, preferably add ammonia water to adjust the pH value of the solution to 8 - 10, and then mechanically stir at 60 - 70 °C until evenly mixed. Subsequently, the obtained mixed solution can be subjected to a hydrothermal reaction in a high-pressure reactor at 120 - 150 °C; after cooling the separated precipitate to room temperature, it is collected by magnetic separation and washed alternately with ethanol and deionized water 3 - 5 times. Finally, magnetic iron oxide nanoparticles are prepared by drying at 110 - 120 °C.

[0050] In the embodiments of the present invention, the copper-based metal salt is preferably nitrate, such as copper nitrate. The magnetic nanoparticles are preferably dissolved in a mixed solution of copper nitrate, water, ethanol, and CTAB, and can be stirred at room temperature; the stirring time is preferably 5 - 10 hours. The hydrothermal temperature is preferably 130 - 180 °C, more preferably 140 - 150 °C; the hydrothermal time is preferably 5 - 15 hours, more preferably 8 - 13 hours, and most preferably 10 - 11 hours. The present invention preferably performs the hydrothermal treatment in an oven.

[0051] After magnetic separation, the drying temperature is preferably 100 - 150 °C, more preferably 120 - 130 °C; the drying time is preferably 8 - 20 hours, more preferably 10 - 18 hours, and most preferably 12 - 15 hours. The calcination temperature is preferably 500 - 600 °C, more preferably 550 - 560 °C; the calcination time is preferably 1 - 10 hours, more preferably 3 - 8 hours, and most preferably 5 - 6 hours. The present invention preferably performs the calcination in a muffle furnace.

[0052] In the preferred embodiment of the present invention, hydrazine hydrate reduction is also carried out, and the reaction can be stirred for 1 - 2 hours and then dried conventionally to obtain the reduced copper-based magnetic catalyst.

[0053] Regarding the dosages of the copper-based substance, the magnetic nanoparticle carrier, water, and hydrazine, the mass ratio of hydrazine hydrate to the copper-based magnetic substance is preferably 0.5 - 2.0:1, more preferably 0.5 - 1.5:1, and most preferably 0.5 - 1.0:1; in the specific embodiments of the present invention, it can be 1.0 (i.e., 1:1). The mass fraction of the copper-based substance is preferably 15 - 25%, more preferably 17 - 21%, and most preferably 19 - 20%. Specifically, in the embodiments of the present invention, it can be 20%. And the mass content of the iron oxide carrier in the second catalyst can be 75 - 80%.

[0054] Specifically, in the embodiments of the present invention, a second catalyst having the following components can be used: a reduced copper-based magnetic catalyst composed of hydrazine hydrate reducing copper-based magnetic substance (the ratio of hydrazine hydrate to copper-based magnetic substance is 1:2); a reduced copper-based magnetic catalyst composed of hydrazine hydrate reducing copper-based magnetic substance (the ratio of hydrazine hydrate to copper-based magnetic substance is 1:1); a reduced copper-based magnetic catalyst composed of hydrazine hydrate reducing copper-based magnetic substance (the ratio of hydrazine hydrate to copper-based magnetic substance is 2:1).

[0055] In the present invention, the mass ratio of the second catalyst to the aromatic intermediate is preferably 1:(8 - 11), more preferably 1:(9 - 10), and in specific embodiments of the present invention, it can be 1:10.

[0056] The selective catalytic oxidation of the aromatic intermediate described in the embodiments of the present invention is carried out in a liquid-phase reaction kettle. After heating the mixture of the aromatic intermediate and the second catalyst to the reaction temperature, hydrogen peroxide (in the atmosphere of hydrogen peroxide) is introduced, and the catalytic oxidation reaction is carried out under stirring conditions. The temperature of the catalytic oxidation reaction is preferably 70 - 90 °C, more preferably 70 - 80 °C, and the reaction pressure is normal pressure; the time of the catalytic oxidation reaction is preferably 3 - 6 hours, more preferably 4 - 5 hours. The molar ratio of the hydrogen peroxide to the aromatic intermediate is preferably 2 - 5:1, more preferably 3 - 4:1.

[0057] The method for preparing phenol from bio-oil in the embodiments of the present invention uses bio-oil as a raw material, and under the action of a composite catalyst, through bio-oil catalytic cracking reaction and selective catalytic oxidation reaction of aromatic intermediates, etc., high-value chemicals mainly composed of phenol are obtained. This new controllable conversion process is achieved by coupling the selective catalytic pyrolysis of bio-oil to prepare benzene-rich intermediates and the subsequent catalytic hydroxylation process. This study uses renewable bio-oil resources to direct the synthesis of bio-based phenol, which has important scientific significance and potential application value in promoting the efficient utilization of renewable biomass resources and the development of high-value bio-based chemicals.

[0058] To better illustrate the present invention, further examples are given below through embodiments, but it should not be construed as a limitation to the protection scope of the present invention. In the embodiments, all original reagents and materials are commercially available, and the experimental methods without specific experimental conditions are conventional methods and conditions well-known in the art.

[0059] Among them, the carbon molar yield Y l (C-mol%) formula is as follows:

[0060]

[0061] Conversion rate C conv. (C-mol%) formula is as follows:

[0062]

[0063] The selectivity S of the product i (C - mol%) is calculated by the following formula:

[0064]

[0065] In the following example study, the bio - oil (straw biomass pyrolysis oil) generated by the fast pyrolysis of straw in a circulating fluidized bed reactor was used as the experimental raw material. The elemental and component analysis is shown in Table 1 below.

[0066] Table 1 Characteristics of the bio - oil used a

[0067] Component analysis wt% Elemental analysis wt% Acid 21.4 C 42.1 Aldehydes 14.8 H 7.5 Ketone 17.2 <![CDATA[O a > 50.2 Alcohols 4.7 N 0.2 Phenols 11.7 S ＜0.1 Furan 9.1 Unknown substances <![CDATA[21.1 a >

[0068] a According to the differences in different biomass raw materials, the water content in the bio - oil used in this study is 50.7 wt%.

[0069] Example 1

[0070] In this example, the effect of using a Zn / HZSM - 5 metal molecular sieve composite catalyst for the catalytic cracking of straw biomass pyrolysis oil to prepare benzene - rich aromatic intermediates was investigated. The Zn / HZSM - 5 metal molecular sieve composite catalyst used was prepared by the conventional impregnation method: Weigh 4.6 g of zinc nitrate, add 400 mL of deionized water to form an aqueous zinc nitrate solution. Then add 100 g of HZSM - 5 molecular sieve powder to the zinc nitrate solution, stir at 60 °C for 8 hours, dry in an oven at 120 °C for 12 hours, and finally sinter in a muffle furnace at 550 °C for 6 hours, grind and sieve (40 - 60 mesh) to obtain a Zn / HZSM - 5 metal molecular sieve composite catalyst composed of 1.0 wt% zinc and 99.0 wt% HZSM - 5 molecular sieve.

[0071] In this example, the catalytic cracking of straw biomass pyrolysis oil is carried out in a fixed-bed reactor. The reaction conditions are as follows: the weight ratio of the first catalyst to the biomass pyrolysis oil raw material is 3, the carrier gas is nitrogen, the pressure is atmospheric pressure, and the temperature is 570 °C. The specific operation steps of the catalytic cracking of straw biomass pyrolysis oil are as follows: the upper layer of the quartz tube reactor is the pyrolysis zone (quartz sand), and the lower layer is the catalytic zone (15 g of catalyst). Before the reaction starts, an inert gas, nitrogen (flow rate: 150 ml / min), is introduced into the fixed-bed reactor to purge the reactor for 2 hours, and the fixed-bed reactor is heated to 570 °C by an external heating method to remove the water adsorbed on the device and the catalyst. After the reaction temperature is stabilized, the reactants (the mass ratio of biomass pyrolysis oil / methanol is 2) are pushed into the central constant-temperature zone of the reactor at a feeding rate of 10 g / h. The liquid products obtained from the catalytic cracking of straw biomass pyrolysis oil are collected in a condensation tank by liquid nitrogen condensation, and the components of the collected products are quantitatively analyzed by gas chromatography-mass spectrometry. When using the Zn / HZSM-5 metal molecular sieve composite catalyst, the results of the catalytic cracking of biomass pyrolysis oil are shown in Table 2. The selectivity of benzene is 77.7%, and the yield of benzene reaches 34.4%.

[0072] In this example, in order to optimize the catalytic system for phenol synthesis, the effect of selectively catalytic oxidation for preparing phenol was investigated using a copper-based magnetic catalyst (Cu@Fe3O4-1.0) reduced by hydrazine hydrate with benzene as the standard substrate. The preparation method of the second catalyst used is as follows:

[0073] 8.1 g of ferric chloride hexahydrate was weighed and dissolved in a mixed solution formed by 50 ml of deionized water, 12 ml of ethanol, and 0.2 g of cetyltrimethylammonium bromide (CTAB). Mechanical stirring was carried out at 96 °C, and ammonia water was added to adjust the pH value of the solution to 10.0. Mechanical stirring was carried out at 70 °C for 1 hour until evenly mixed. Subsequently, the mixed solution was subjected to a hydrothermal reaction in a high-pressure reactor at 150 °C for 10 hours. After the precipitate was cooled to room temperature, it was collected by magnetic separation and washed alternately with ethanol and deionized water 3 - 5 times. Finally, magnetic iron oxide nanoparticles were prepared by drying at 120 °C for 12 hours, which can be used as a comparative catalyst.

[0074] Weigh 3.8 g of copper nitrate and add it to a mixed solution containing 500 ml of deionized water, 120 ml of ethanol, and 2.0 g of cetyltrimethylammonium bromide (CTAB) to completely dissolve it. Subsequently, add 100 g of magnetic support (Fe3O4 nanoparticles) to the mixed solution, adjust the pH of the solution to 9.0 with ammonia water (25 wt%), and stir for 5 hours at room temperature. Subsequently, perform a hydrothermal reaction at 150 °C for 10 hours in a high-pressure reactor. After cooling to 25 °C, wash the precipitate three times alternately with ethanol and deionized water. Dry it at 120 °C for 12 hours. Finally, calcine the dried precipitate at 550 °C for 5 hours under nitrogen protection to obtain a copper-based magnetic catalyst (denoted as Cu@Fe3O4) composed of 20.4 wt% of typical copper-based metal oxides and 80.0 wt% of magnetic iron oxide nanoparticles.

[0075] Weigh 50 g of the copper-based magnetic catalyst Cu@Fe3O4 powder, add it to 3.3 L of the prepared 0.3 mol / L aqueous hydrazine (N2H4·H2O) solution, stir for 1 hour, and then wash it 3 - 5 times alternately with ethanol and deionized water. Finally, dry it at 80 °C for 12 hours to obtain the Cu@Fe3O4-1.0 catalyst.

[0076] In this example, the selective catalytic oxidation of benzene (model compound) is carried out in a liquid-phase reaction kettle. The reaction conditions for the selective catalytic oxidation of benzene used in this example are: the weight ratio of the second catalyst to benzene is 1:10, the molar ratio of hydrogen peroxide to the reaction substrate is 3:1, the pressure is atmospheric pressure, and the temperature is 70 °C. The operation steps for the benzene catalytic oxidation reaction are as follows: First, add the prepared Cu@Fe3O4-1.0 catalyst and benzene to the liquid-phase reaction kettle respectively. The amount of the catalyst used is 10 g, and the amount of the benzene reactant used is 100 g; heat the reactor to 70 °C; then push the reactants into the central constant-temperature zone of the reactor at a feeding rate of 10 g / h of hydrogen peroxide. Turn on the stirrer in the reaction kettle to stir the reactants, so that benzene undergoes a further selective oxidation reaction of aromatic hydrocarbons under the action of the second catalyst; after reacting for 4 hours, the product is quantitatively analyzed by a chromatograph-mass spectrometer.

[0077] When using the reduced copper-based magnetic catalyst Cu@Fe3O4-1.0, the results of the selective catalytic oxidation of benzene to prepare phenol are shown in Table 3. The benzene conversion rate reaches 35.5%, and the selectivity of phenol reaches 95.9%.

[0078] Comparative Example 1

[0079] In this comparative example, the effect of catalytic cracking of bio-oil to prepare benzene-rich aromatic intermediates using a Re-HY rare earth molecular sieve composite catalyst was investigated. The Re-HY rare earth molecular sieve composite catalyst used was prepared by the impregnation method: Weigh 4.4 g of sodium perrhenate, add 400 mL of deionized water to form an aqueous solution, then add 100 g of HY molecular sieve powder to the aqueous solution, stir at 60 °C for 8 hours, then dry in an oven at 120 °C for 12 hours, and finally sinter in a muffle furnace at 550 °C for 6 hours. After grinding and sieving, a Re-HY catalyst composed of 3.0 wt% rhenium and 97.0 wt% HY molecular sieve was obtained.

[0080] The reaction conditions and operation steps for the catalytic cracking of bio-oil in this comparative example were the same as those in Example 1; the results of the catalytic cracking of bio-oil using the Re-HY rare earth molecular sieve composite catalyst are shown in Table 2. The benzene selectivity was 92.6%, and the benzene yield reached 21.9%.

[0081] Comparative Example 2

[0082] In this comparative example, the effect of catalytic cracking of straw biomass pyrolysis oil to prepare aromatic intermediates using an Hβ catalyst without added metal components was investigated; the reaction conditions and operation steps for the catalytic cracking of straw biomass pyrolysis oil were the same as those in Example 1. The results of the catalytic cracking of bio-oil using the Hβ catalyst are shown in Table 2. The benzene selectivity was 86.7%, and the benzene yield reached 28.9%.

[0083] Comparative Example 3

[0084] In this comparative example, the effect of catalytic cracking of straw biomass pyrolysis oil to prepare aromatic intermediates using an HZSM-5 catalyst without added metal components was investigated; the reaction conditions and operation steps for the catalytic cracking of straw biomass pyrolysis oil were the same as those in Example 1. The results of the catalytic cracking of bio-oil using the HZSM-5 catalyst are shown in Table 2. The benzene selectivity was 77.9%, and the benzene yield reached 30.8%.

[0085] Table 2 Results of preparing benzene-rich intermediates from bio-oil using different first catalysts

[0086]

[0087] The benzene-rich intermediate was obtained by the co-catalytic conversion of bio-oil and methanol (where the mass ratio of bio-oil to methanol was 2:1) using a Zn@HZSM-5 catalyst at 570 °C. The composition of a typical benzene-rich intermediate was as follows: benzene (77.7 C-mol%), toluene (11.4 C-mol%), xylene (4.9 C-mol%), trimethylbenzene (0.4 C-mol%), indene (0.6 C-mol%), naphthalene series (4.6 C-mol%), others (0.4 C-mol%).

[0088] Example 2

[0089] In this example, the effect of selectively catalytic oxidation of benzene to prepare phenol using a copper-based magnetic (Fe₃O₄ nanoparticles) catalyst was investigated. The catalyst used was prepared by a conventional hydrothermal method: 3.8 g of copper nitrate was weighed and added to a mixed solution containing 500 ml of deionized water, 120 ml of ethanol, and 2.0 g of cetyltrimethylammonium bromide (CTAB) to completely dissolve it. Subsequently, 100 g of a magnetic support (Fe₃O₄ nanoparticles) was added to the mixed solution, and the pH of the solution was adjusted to 9.0 with ammonia water (25 wt%), and it was stirred at room temperature for 5 hours. Subsequently, a hydrothermal reaction was carried out in a high-pressure reactor at 150 °C for 10 hours. After cooling to 25 °C, the precipitate was washed alternately with ethanol and deionized water three times. It was dried at 120 °C for 12 hours. Finally, under nitrogen protection, the dried precipitate was calcined at 550 °C for 5 hours to obtain a copper-based magnetic catalyst (Cu@Fe₃O₄) composed of 20.4 wt% of a typical copper-based metal oxide and 80.0 wt% of Fe₃O₄ magnetic nanoparticles.

[0090] In this example, the benzene selective catalytic oxidation reactor, reactants, reaction conditions, and operating procedures used were the same as those in Example 1. The results of selectively catalytic oxidation of benzene to prepare phenol using the copper-based magnetic catalyst are shown in Table 3. The benzene conversion rate reached 20.3%, and the selectivity of phenol reached 96.1%.

[0091] Example 3

[0092] In this example, the effect of selectively catalytic oxidation of benzene to prepare phenol using a copper-based magnetic catalyst (Cu@Fe₃O₄-0.5) reduced by hydrazine hydrate was investigated. The preparation method of the catalyst used was as follows: 67 g of copper-based magnetic catalyst Cu@Fe₃O₄ powder (prepared as in Example 2) was weighed and added to 2.2 L of a prepared 0.3 mol / L hydrazine hydrate (N₂H₄·H₂O) aqueous solution and stirred for 1 hour, and then washed alternately with ethanol and deionized water 3 - 5 times. Finally, it was dried at 80 °C for 12 hours to obtain the Cu@Fe₃O₄-0.5 catalyst.

[0093] In this example, the benzene selective catalytic oxidation reactor, reactants, reaction conditions, and operating procedures used were the same as those in Example 1. The results of selectively catalytic oxidation of benzene to prepare phenol using the reduced copper-based magnetic catalyst Cu@Fe₃O₄-0.5 catalyst are shown in Table 3. The benzene conversion rate reached 30.1%, and the selectivity of phenol reached 98.9%.

[0094] Example 4

[0095] In this example, the effect of preparing phenol by selective catalytic oxidation of benzene using a copper-based magnetic catalyst (Cu@Fe3O4-2.0) reduced by hydrazine hydrate was investigated. The preparation method of the catalyst used is as follows: Weigh 34 g of copper-based magnetic catalyst Cu@Fe3O4 powder (the preparation is shown in Example 2), add it to 4.4 L of a prepared 0.3 mol / L hydrazine hydrate (N2H4·H2O) aqueous solution, stir for 1 hour, and then wash it alternately with ethanol and deionized water 3 - 5 times. Finally, dry it at 80 °C for 12 hours to obtain the Cu@Fe3O4-2.0 catalyst.

[0096] In this example, the reactor for selective catalytic oxidation of benzene, the reactants, the reaction conditions, and the operation steps are the same as those in Example 1. When using the reduced copper-based magnetic catalyst Cu@Fe3O4-2.0 catalyst, the results of preparing phenol by selective catalytic oxidation of benzene are shown in Table 3. The benzene conversion rate reaches 39.1%, and the selectivity of phenol reaches 87.7%.

[0097] Comparative Example 4

[0098] In this comparative example, the effect of preparing phenol by selective catalytic oxidation of benzene using a magnetic iron oxide nanoparticle support catalyst was investigated. The catalyst used was prepared by a conventional hydrothermal method: Weigh 8.1 g of ferric chloride hexahydrate and dissolve it in a mixed solution formed by 50 ml of deionized water, 12 ml of ethanol, and 0.2 g of cetyltrimethylammonium bromide (CTAB). Stir mechanically at 96 °C, and add ammonia water to adjust the pH value of the solution to 10.0. Stir mechanically at 70 °C for 1 hour until evenly mixed. Subsequently, the mixed solution was subjected to a hydrothermal reaction in a high-pressure reactor at 150 °C for 10 hours. After the precipitate was cooled to room temperature, it was collected by magnetic separation and washed alternately with ethanol and deionized water 3 - 5 times. Finally, a magnetic iron oxide nanoparticle catalyst was prepared by drying at 120 °C for 12 hours.

[0099] In this comparative example, the selective catalytic oxidation of benzene was carried out in a liquid-phase reaction kettle. The reaction conditions for the selective catalytic oxidation of benzene used in this comparative example are: the weight ratio of the catalyst to benzene is 1:10, the molar ratio of hydrogen peroxide to the reaction substrate is 3:1, the pressure is atmospheric pressure, and the temperature is 70 °C.

[0100] The operation steps for the catalytic oxidation reaction of benzene are as follows: First, add the above-prepared magnetic iron oxide nanoparticle catalyst and benzene to the liquid-phase reaction kettle respectively. The amount of the catalyst used is 10 g, and the amount of the benzene reactant used is 100 g; heat the reactor to 70 °C; then push the reactants into the central constant-temperature zone of the reactor at a feeding rate of 10 g / h of hydrogen peroxide. Turn on the stirrer in the reaction kettle to stir the reactants, so that benzene undergoes further aromatic hydrocarbon selective oxidation reaction under the action of the second catalyst; after reacting for 4 hours, the product is quantitatively analyzed by a gas chromatography-mass spectrometer.

[0101] When using a magnetic iron oxide nanoparticle catalyst, the results of the selective catalytic oxidation of benzene to prepare phenol are shown in Table 3. The conversion rate of benzene reaches 10.8%, and the selectivity of phenol reaches 72.7%.

[0102] Comparative Example 5

[0103] In this comparative example, the effect of using different supported copper-based metal oxide catalysts (CuO@SiO2) as carriers on the selective catalytic oxidation of benzene to prepare phenol was investigated. The catalyst used was prepared by a conventional hydrothermal method: 3.8 g of copper nitrate was weighed and added to a mixed solution containing 500 ml of deionized water, 120 ml of ethanol, and 2.0 g of cetyltrimethylammonium bromide (CTAB) to completely dissolve it. Subsequently, 100 g of silica was added to the mixed solution, and the pH of the solution was adjusted to 9.0 with ammonia water (25 wt%), and stirred at room temperature for 5 hours. Subsequently, a hydrothermal reaction was carried out in a high-pressure reactor at 150 °C for 10 hours. After cooling to 25 °C, the precipitate was washed three times alternately with ethanol and deionized water. It was dried at 120 °C for 12 hours. Finally, under nitrogen protection, the dried precipitate was calcined at 550 °C for 5 hours to obtain a supported copper-based catalyst (denoted as CuO@SiO2) composed of 20.0 wt% of a typical copper-based metal oxide and 80.0 wt% of silica.

[0104] In this comparative example, the reactor, reactants, reaction conditions, and operating procedures used for the selective catalytic oxidation of benzene were the same as those in Example 1. When using the supported copper-based catalyst CuO@SiO2, the results of the selective catalytic oxidation of benzene to prepare phenol are shown in Table 3. The conversion rate of benzene reaches 16.0%, and the selectivity of phenol reaches 92.2%.

[0105] Comparative Example 6

[0106] In this comparative example, when investigating different supported copper-based metal oxide catalysts (CuO@MCM-41) as carriers, the effect of the selective catalytic oxidation of benzene to prepare phenol was examined. The catalysts used were prepared by a conventional hydrothermal method: 3.8 g of copper nitrate was weighed and added to a mixed solution containing 500 ml of deionized water, 120 ml of ethanol, and 2.0 g of cetyltrimethylammonium bromide (CTAB) to completely dissolve it. Subsequently, 100 g of MCM-41 was added to the mixed solution, and the pH of the solution was adjusted to 9.0 with ammonia water (25 wt%), and the mixture was stirred at room temperature for 5 hours. Subsequently, a hydrothermal reaction was carried out in a high-pressure reactor at 150 °C for 10 hours. After cooling to 25 °C, the precipitate was washed alternately with ethanol and deionized water three times. It was dried at 120 °C for 12 hours. Finally, under nitrogen protection, the dried precipitate was calcined at 550 °C for 5 hours to obtain a supported copper-based catalyst (denoted as CuO@MCM-41) composed of 20.0 wt% of a typical copper-based metal oxide and 80.0 wt% of MCM-41.

[0107] In this comparative example, the reactor for the selective catalytic oxidation of benzene, the reactants, the reaction conditions, and the operation steps were the same as those in Example 1. When using the supported copper-based catalyst CuO@MCM-41, the results of the selective catalytic oxidation of benzene to prepare phenol are shown in Table 3. The benzene conversion reached 26.1%, and the selectivity for phenol reached 95.7%.

[0108] The results of the catalytic oxidation of benzene using different catalysts are shown in Table 3.

[0109] Table 3 Effects of the catalytic oxidation of benzene to prepare phenol using different second catalysts

[0110]

[0111] As can be seen from this table, benzene undergoes a catalytic oxidation reaction under the action of the reduced copper-based magnetic catalyst, and the obtained product is mainly phenol; among the second catalysts, the regulation of the copper valence state by hydrazine reduction increases the benzene conversion and phenol selectivity; among the investigated copper-based magnetic catalysts with different ratios of hydrazine to copper, the Cu@Fe3O4-1.0 catalyst has good benzene oxidation activity and phenol selectivity, with a benzene conversion of 35.5% and a phenol selectivity of 95.9%.

[0112] Meanwhile, the catalyst with a magnetic support exhibits excellent magnetic separation and recycling performance during the catalytic hydroxylation process.

[0113] Example 5

[0114] In this example, the effect of the selective catalytic oxidation of benzene-rich aromatics obtained by catalytic cracking of bio-oil to prepare phenol was investigated using a copper-based magnetic catalyst (Cu@Fe3O4-1.0) reduced by hydrazine hydrate. The reactants for the selective catalytic oxidation of benzene-rich aromatics were derived from the aromatic intermediates obtained by catalytic cracking of straw biomass pyrolysis oil using the Zn / HZSM-5 metal molecular sieve composite catalyst in Example 1 (see Table 2).

[0115] In this example, the selective catalytic oxidation reactor, reactants, reaction conditions, and operating procedures for the benzene-rich aromatics obtained by catalytic cracking of bio-oil were the same as those in Example 1. When using the reduced copper-based magnetic catalyst Cu@Fe3O4-1.0, the results of the selective catalytic oxidation of benzene-rich aromatics obtained by catalytic cracking of bio-oil to prepare phenol are shown in Table 4. The benzene conversion rate reached 38.1%, and the selectivity of phenol reached 73.6%. At the same time, a small amount of oxidation by-products were detected, including cresol, benzaldehyde, and benzoic acid, which can be attributed to the partial oxidation of toluene present in the bio-oil-derived aromatic intermediates. In addition, a small amount of xylene and naphthalene series found in the aromatic intermediates obtained from bio-oil will also lead to the production of by-products such as dimethylphenol, methylbenzaldehyde, methylbenzoic acid, and methylnaphthoquinone.

[0116] Example 6

[0117] In this example, in order to improve the selective production of bio-derived phenol, the effect of the selective catalytic oxidation of benzene-rich aromatics obtained by catalytic cracking of bio-oil after distillation treatment using a copper-based magnetic catalyst (Cu@Fe3O4-1.0) reduced by hydrazine hydrate was also investigated.

[0118] In this example, the selective catalytic oxidation reactor, reactants, reaction conditions, and operating procedures for the benzene-rich aromatics obtained by catalytic cracking of bio-oil after distillation treatment were the same as those in Example 1. When using the reduced copper-based magnetic catalyst Cu@Fe3O4-1.0, the results of the selective catalytic oxidation of benzene-rich aromatics obtained by catalytic cracking of bio-oil after distillation treatment to prepare phenol are shown in Table 4. The benzene conversion rate reached 39.1%, and the selectivity of phenol reached 91.8%.

[0119] Table 4 Hydroxylation of different bio-oil-derived intermediates to produce bio-based phenol over CuO@Fe3O4-1 catalyst

[0120]

[0121] As can be seen from the above embodiments, in the embodiments of the present invention, first is the step of catalytic cracking of bio-oil, which uses a specific metal molecular sieve composite catalyst to obtain an intermediate rich in benzene through reactions such as catalytic cracking of bio-oil; thereafter, the present invention uses a catalyst of iron oxide supported with copper-containing substances as the second catalyst to selectively convert the intermediate rich in benzene converted from bio-oil into biomass-based high-value chemicals mainly composed of phenol. The raw material used in the present invention is bio-oil, which has the advantages of rich resources, environmental friendliness and renewability, etc., and the end product is biomass-based high-value chemicals mainly composed of phenol, which is conducive to the high-value comprehensive utilization of biomass resources.

[0122] The above examples are only used to illustrate the technical features and implementation process of the present invention, rather than limiting the technical solution of the present invention. It should be noted that for those of ordinary skill in the art, the present invention can still be modified or equivalently replaced, and any modification or replacement that does not depart from the principle of the present invention is covered by the protection of the present invention.

Claims

1. A method for preparing phenol from bio-oil, characterized in that, It includes the following steps: S1. Using bio-oil as a raw material, reacting in the presence of a first catalyst to obtain an intermediate rich in benzene; the first catalyst is a metal molecular sieve composite catalyst, and the metal element therein is zinc; the molar content of benzene in the intermediate rich in benzene is above 70%; S2. Catalytically oxidizing the intermediate rich in benzene in an atmosphere of a second catalyst and hydrogen peroxide to obtain phenol; the second catalyst includes a magnetite carrier and a copper-containing substance supported thereon.

2. The method for preparing phenol from bio-oil according to claim 1, characterized in that, In step S1, the bio-oil is a liquid biomass derivative produced by pyrolysis of lignocellulosic biomass; the water content in the bio-oil is 30-55%.

3. The method for preparing phenol from bio-oil according to claim 1, wherein, In step S1, the mass fraction of zinc in the first catalyst is 1-3%; the molecular sieve component in the first catalyst is one or more of HY molecular sieve, Hβ molecular sieve, and HZSM-5 molecular sieve components.

4. The method for preparing phenol from bio-oil according to claim 3, wherein, In step S1, the preparation of the first catalyst includes: adding a molecular sieve to an aqueous solution of a zinc salt, drying first at 100-150 °C, and then sintering at a temperature of 500-600 °C to obtain it.

5. The method for preparing phenol from bio-oil according to any one of claims 1-4, characterized in that, The reaction in step S1 is carried out under a protective atmosphere, and the temperature of the reaction is 500-610 °C.

6. The method for preparing phenol from bio-oil according to any one of claims 1-4, characterized in that, In step S2, the mass ratio of the second catalyst to the intermediate rich in benzene is 1:8-11; the mass content of the magnetite carrier in the second catalyst is 75-80%.

7. The method for preparing phenol from bio-oil according to claim 6, characterized in that, In step S2, the second catalyst has a nanoparticle morphology; The preparation of the second catalyst includes: Mixing magnetite nanoparticles and a copper-based metal salt solution, adjusting the pH value to be alkaline, and carrying out a hydrothermal reaction at a temperature of 100-180 °C, and separating to obtain a precipitate; the copper-based metal salt solution includes a copper-based metal salt, water, an alcohol, and an alkyl ammonium halide; Drying the precipitate first at 150-250 °C, and then calcining at 500-600 °C and under a protective atmosphere to obtain a powder sample.

8. The method for preparing phenol from bio-oil according to claim 7, characterized in that, In the preparation of the second catalyst in step S2, it further includes: Reducing the powder sample obtained by calcination with hydrazine hydrate to obtain the second catalyst.

9. The method for preparing phenol from bio-oil according to claim 8, characterized in that, In the preparation of the second catalyst in step S2, the mass ratio of hydrazine hydrate to the powder sample is 0.5-2.0:

1.

10. The method for preparing phenol from bio-oil according to claim 9, characterized in that, In step S2, the catalytic oxidation reaction is carried out in a liquid-phase reaction kettle, the temperature is 60-80 °C, and the pressure is normal pressure.

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