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CN114920632B - Method for preparing p-methylbenzaldehyde by utilizing wood chips - Google Patents

Method for preparing p-methylbenzaldehyde by utilizing wood chips Download PDF

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CN114920632B
CN114920632B CN202210568041.5A CN202210568041A CN114920632B CN 114920632 B CN114920632 B CN 114920632B CN 202210568041 A CN202210568041 A CN 202210568041A CN 114920632 B CN114920632 B CN 114920632B
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catalyst
reaction
rich
paraxylene
tolualdehyde
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CN114920632A (en
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李全新
杨明宇
何雨婷
罗月会
范明慧
张焰华
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University of Science and Technology of China USTC
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Abstract

The application provides a method for preparing p-methylbenzaldehyde by utilizing wood chips, which comprises the following steps: s1) taking wood dust as a raw material, and carrying out catalytic pyrolysis reaction in a protective atmosphere to obtain an intermediate rich in paraxylene; s2) in the presence of a ferroferric oxide modified chromium hydroxide magnetic catalyst, the intermediate rich in paraxylene is subjected to catalytic oxidation reaction in a hydrogen peroxide atmosphere to obtain the paramethylbenzaldehyde. The invention improves the yield and selectivity of the p-tolualdehyde by innovative design of the catalyst and the like, and effectively realizes the aim of directionally synthesizing the p-tolualdehyde by the wood chip biomass. The adopted heterogeneous catalyst is prepared by magnetic design, so that the difficulty in separating the catalyst from reaction products is solved. The invention converts the wood chip raw material which is rich in resources, low in price and renewable into chemicals with high added value, thereby realizing the high-valued comprehensive utilization of biomass resources, having simple and convenient method, easy separation of products and good economic and environmental benefits.

Description

Method for preparing p-methylbenzaldehyde by utilizing wood chips
Technical Field
The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing p-methylbenzaldehyde by utilizing wood chips.
Background
Para-methylbenzaldehyde is an important high value-added fine chemical, and is mainly used for the production of polyesters, plasticizers, medicines and fragrances. In industry, p-tolualdehyde is usually prepared by catalytic oxidation of p-xylene by using a homogeneous catalyst (Co/Mn/Br catalyst), but the method has the defects of complex process, large pollutant discharge amount, difficult product separation and the like (documents: wanna WH, janmachi D, thiyagarajan N, ramu R, tsai YF, yu SSF, selective Oxidation of Simple Aromatics Catalyzed by Nano-Biomimetic MetalOxide Catalysts: A Mini review. Front chem.,2020,8,589178). The preparation of aldehyde chemicals by selective oxidation of hydrocarbons has important application value in the chemical industry. Several suitable alkyl aromatic hydrocarbon oxidation catalysts have been studied, such as metal oxide catalysts or metal complex catalysts (literature: wanna WH, janmachi D, thiyagarajan N, ramu R, tsai YF, yu SSF, selective Oxidation of Simple Aromatics Catalyzed by Nano-Biomimetic Metal Oxide Catalysts: A Mini review. Front chem.,2020,8,589178); in comparison to a homogeneously catalyzed oxidation process, the catalyst is easily separated from the product in a heterogeneously catalyzed process.
In view of the demand for carbon abatement and sustainable development, the preparation of bio-based chemicals using renewable biomass resources has significant development prospects. Lignocellulosic biomass is the most abundant renewable resource, consisting mainly of cellulose, lignin and hemicellulose. In order to effectively utilize lignocellulose, it is necessary to develop related bio-based chemicals according to the composition and structure of lignocellulose.
Cellulose is the most abundant component of lignocellulose, which consists mainly of glucose units and is a polymer linked by beta-1, 4-glycosidic bonds. At present, developments have been reported in relation to cellulose-based chemicals, such as cellulose synthesis aromatics, furans, furfurals, 5-hydroxymethylfurals, valerolactones, levulinic acid, polyols and lactic acid (literature: ma J, shi S, jia X, XIa F, ma H, gao J, xu J, advances in catalytic conversion of lignocellulose to chemicals and liquid fuels, J.energy chem.,2019,36,74-86). Among them, catalytic cracking of cellulose is an effective method for preparing aromatic chemicals (literature: bayu A, abudula A, guan G, reaction pathways and selectivity in chemo-catalytic conversion of biomass-derived carbohydrates to high-value chemicals: A review. Fuel Process technology, 2019,196,106162). Furthermore, cellulose is useful for the preparation of high value-added chemicals such as valerolactone and levulinic acid (literature: maJ, shi S, jia X, xia F, ma H, gao J, xu J, advances in catalytic conversion of lignocellulose to chemicals and liquid fuels, J.energy chem.,2019,36,74-86); cellulose can be catalytically converted to sorbitol using noble metal catalysts (literature: wang D, niu W, tan M, wu M, zheng X, li Y, tsibaki, NPtnanocatalysts supported on reduced graphene oxide for selective conversion of cellulose or cellobiose to corbitol. Chemsuschem,2014,7,1398-1406).
Lignin is the second largest component in lignocellulosic biomass, accounting for about 20-30% of lignocellulose (literature: ma J, shi S, jia X, xia F, ma H, gao J, xu J, advances in catalytic conversion of lignocellulose to chemicals and liquid fuels, J. Energy chem.,2019,36,74-86). Lignin is an aromatic polymer with a three-dimensional network structure, and lignin mainly consists of three phenylpropane units and is linked through carbon-carbon bonds and ether bonds. Unlike cellulose, lignin has an aromatic ring structure and is rich in methoxy groups and other reactive groups. In view of the structural features of lignin, the preparation of phenolic compounds or aromatic chemicals from lignin is a promising conversion route (literature: liu Y, nie Y, lu X, zhang X, he H, pan F, zhou L, liu X, ji X, zhang S, cascade utilization of lignocellulosic biomass to high-value products.Green chem.,2019,21,3499-3535).
However, the reaction pathways and intermediates in the catalytic conversion of lignocellulose tend to be complex; the use of lignocellulose for the directed production of aromatic aldehyde chemicals has remained a challenging technological challenge to date. To our knowledge, the process of selectively preparing p-methylbenzaldehyde from lignocellulosic biomass has not been reported.
Disclosure of Invention
The invention aims to provide a method for preparing p-tolualdehyde by utilizing wood chips, which can realize the directional synthesis of the p-tolualdehyde by utilizing wood chip biomass, has higher yield and selectivity, has simple process and easy separation of products, and can realize the high-value comprehensive utilization of biomass resources.
The invention provides a method for preparing p-methylbenzaldehyde by utilizing wood chips, which comprises the following steps:
s1) taking wood dust as a raw material, and carrying out catalytic pyrolysis reaction in a protective atmosphere to obtain an intermediate rich in paraxylene;
s2) in the presence of a heterogeneous catalyst, the intermediate rich in paraxylene is subjected to catalytic oxidation reaction in a hydrogen peroxide atmosphere to obtain paramethylbenzaldehyde;
the heterogeneous catalyst is a ferroferric oxide modified chromium hydroxide magnetic catalyst.
Preferably, the content of chromium hydroxide in the heterogeneous catalyst is 40-50 wt%, and the content of ferroferric oxide is 50-60 wt%
Preferably, the heterogeneous catalyst is a ferroferric oxide modified chromium hydroxide magnetic catalyst obtained by a hydrothermal synthesis mode of ferroferric oxide and chromium salt.
Preferably, the mass ratio of the heterogeneous catalyst to the para-xylene-rich intermediate is 1:9 to 10; the para-xylene concentration in the para-xylene enriched intermediate is above 30 wt%.
Preferably, the mass ratio of the hydrogen peroxide to the intermediate rich in paraxylene is 4-6: 1, wherein the temperature of the catalytic oxidation reaction is 70-85 ℃.
Preferably, the para-xylene concentration in the para-xylene-enriched intermediate is from 30.5 to 60.5 weight percent.
Preferably, the catalyst adopted in the catalytic pyrolysis reaction in the step S1) is one or more of an HMOR molecular sieve catalyst and an oxide modified HMOR molecular sieve magnetic catalyst; further preferred are HMOR molecular sieve magnetic catalysts co-modified with yttria and ferroferric oxide.
Preferably, in the step S1), the particle size of the raw wood chips is 0.2-1 mm; the protective atmosphere includes a nitrogen atmosphere and/or a rare gas atmosphere.
Preferably, in step S1), the catalytic cracking reaction is performed at a temperature of 450 to 480 ℃ for 25 to 35 minutes.
Preferably, in step S2), the yield of p-tolualdehyde reaches 50.7%, and the selectivity of p-tolualdehyde reaches 68.3%.
Compared with the prior art, the invention provides a novel method for directionally preparing the p-tolualdehyde by utilizing wood chips (a typical lignocellulose raw material): the method can use a molecular sieve magnetic catalyst modified by yttrium oxide and ferric oxide together to selectively catalyze and crack wood dust into an intermediate rich in paraxylene, and selectively oxidize the intermediate rich in paraxylene into the paramethylbenzaldehyde under the action of a chromium hydroxide magnetic catalyst modified by the ferric oxide. The invention improves the yield and selectivity of the p-tolualdehyde through innovative design of the catalyst and the like, and effectively realizes the aim of directionally synthesizing the p-tolualdehyde by the wood chip biomass. Experiments show that the yield of the p-tolualdehyde can reach 50.7%, and the selectivity of the p-tolualdehyde can reach 68.3%. And the adopted heterogeneous catalyst is subjected to magnetic design preparation, so that the difficulty in separating the catalyst from reaction products is solved. The method provided by the invention converts the wood chip raw material which is abundant in resources, low in cost and renewable into the chemical p-methylbenzaldehyde with high added value, thereby realizing the high-value comprehensive utilization of biomass resources, being simple and convenient, being easy to separate products and having good economic and environmental benefits.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a method for preparing p-methylbenzaldehyde by utilizing wood chips, which comprises the following steps:
s1) taking wood dust as a raw material, and carrying out catalytic pyrolysis reaction in a protective atmosphere to obtain an intermediate rich in paraxylene;
s2) under the action of a heterogeneous catalyst with magnetism, the intermediate rich in paraxylene is subjected to catalytic oxidation reaction in a hydrogen peroxide atmosphere to obtain the paramethylbenzaldehyde.
The method provided by the invention uses wood chip biomass to selectively synthesize the p-tolualdehyde, and has the characteristics of higher yield and selectivity, simple and convenient process, easy separation of products and the like.
In the method provided by the embodiment of the invention, the step S1) specifically includes: and (3) carrying out catalytic pyrolysis reaction on raw wood dust in the presence of a catalyst in a protective atmosphere to obtain an intermediate rich in paraxylene. In the step S1), wood chips are used as raw materials, belong to lignocellulose raw materials, and mainly comprise cellulose (more than 40%), lignin (20-30%) and hemicellulose; the biomass raw material has wide sources and low cost. The wood chip raw material is usually in the form of a particulate powder, and the particle diameter is preferably 0.2 to 1mm, more preferably 0.2 to 0.4mm.
In the method provided by the embodiment of the present invention, the catalyst adopted in step S1) is denoted as a first catalyst (wood chip catalytic cracking catalyst), which may be one or more molecular sieve catalysts of HMOR molecular sieve catalysts and oxide modified HMOR molecular sieve magnetic catalysts, preferably a molecular sieve magnetic catalyst modified by yttrium oxide and ferric oxide together. In some preferred embodiments, the first catalyst Fe 3 O 4 @Y 2 O 3 HMOR, specific surface area of 199-200m 2 Per gram, pore volume of 0.12cm 3 And/g, the average particle size is 25-30nm.
The first catalyst of the embodiment of the invention enables the raw material system to carry out pyrolysis reaction by using the catalytic reaction system. For the preferred first catalyst (Fe 3 O 4 @Y 2 O 3 @HMOR), yttria (Y) 2 O 3 ) The content in the first catalyst is preferably 15 to 18wt%, and may be specifically 15.0wt%, 15.5wt%, 16.0wt%, 16.5wt%, 17.0wt%, 17.5wt% or 18.0wt%; ferroferric oxide (Fe) 3 O 4 ) The content in the first catalyst is preferably 5 to 8wt%, and may be specifically 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt% or 8.0wt%; the HMOR molecular sieve is preferably present in the first catalyst in an amount of from 74 to 80wt%, and may specifically be present in an amount of 74.0wt%, based on the weight of the catalyst, 74.5wt%, 75.0wt%, 75.5wt%, 76.0wt%, 76.5wt%, 77.0wt%, 77.5wt% or 80.0wt%.
In the method provided by the embodiment of the invention, the first catalyst used in the step S1) is preferably obtained by modifying a molecular sieve by a rare earth salt and an iron source through a hydrothermal synthesis method; the preparation method comprises the following steps:
a) Adding HMOR molecular sieve into aqueous solution containing yttrium chloride, and stirring at room temperature for 1-2 hours; b) Sintering the obtained precipitate at 400-500 ℃ for 4-6 hours to obtain an yttrium oxide modified HMOR molecular sieve precursor; c) Adding the yttrium oxide modified HMOR molecular sieve precursor into an aqueous solution containing ferric chloride, adding ammonia water into the mixed solution, adjusting the pH value to 9-11, and stirring for 1-2 hours at room temperature; the dosage proportion of the HMOR molecular sieve, the yttrium chloride and the ferric chloride is determined according to the content of the HMOR molecular sieve, the yttrium oxide and the ferric oxide in the first catalyst to be finally prepared, and the HMOR molecular sieve, the yttrium oxide and the ferric oxide are not limited independently; d) The mixed solution is reacted for 10 to 12 hours at the temperature of about 100 ℃ in a stainless steel autoclave, the precipitate after the reaction is respectively washed for 3 times by water and ethanol, and is dried for 10 to 12 hours at the temperature of 100 to 110 ℃; e) Sintering the dried precipitate for 10-12 hours at 300-400 ℃ to obtain the molecular sieve magnetic catalyst jointly modified by yttrium oxide and ferroferric oxide; the specific surface area of the catalyst can be 199.8m 2 Per gram, pore volume of 0.12cm 3 And/g, the average particle diameter is 25.8nm.
In the method provided by the embodiment of the present invention, preferably, the mass ratio of the first catalyst to the wood chips is 2:1, the temperature of the catalytic cracking reaction is preferably 450-480 ℃, more preferably 470 ℃; the catalytic cracking reaction time may be 25 to 35 minutes, preferably 30 minutes. The protective atmosphere can comprise nitrogen atmosphere and/or rare gas atmosphere, and the pressure of the reaction system is normal pressure.
The catalytic pyrolysis of the wood chip raw material in the embodiment of the invention can be performed in a fixed bed reactor, and specific operation steps are as follows: introducing inert gas nitrogen into the fixed bed reactor, heating the fixed bed reactor to the reaction temperature by using an external heating mode, mixing the first catalyst and the wood dust, then injecting the mixture into a central constant temperature area of the catalytic reactor for catalytic cracking reaction, and collecting the obtained liquid product which is an intermediate rich in paraxylene in a condensing tank through condensation.
In the embodiment of the invention, the main component of the intermediate rich in paraxylene is paraxylene, and generally contains aromatic hydrocarbon substances such as benzene, toluene and the like; in the present invention, the paraxylene concentration is preferably 30wt% or more, more preferably 30.5 to 60.5wt%, and still more preferably 58.5 to 60.5wt%.
After obtaining the intermediate rich in paraxylene, the embodiment of the invention carries out selective catalytic oxidation on the intermediate in a liquid phase reaction kettle. Namely, step S2) is specifically: and the intermediate rich in paraxylene is subjected to catalytic oxidation reaction in a hydrogen peroxide atmosphere under the action of a second catalyst (heterogeneous catalyst and ferroferric oxide modified chromium hydroxide magnetic catalyst) to obtain the paramethylbenzaldehyde.
In the method provided by the embodiment of the invention, in the step S2), the second catalyst is a ferroferric oxide modified chromium hydroxide magnetic catalyst (Cr (OH) 3 @Fe 3 O 4 ) The method comprises the steps of carrying out a first treatment on the surface of the Chromium hydroxide (Cr (OH) 3 ) The content in the second catalyst is preferably 40 to 50wt%, and may be specifically 40.0wt%, 42.0wt%, 44.0wt%, 46.0wt%, 48.0wt% or 50.0wt%. And, the content of the ferroferric oxide in the second catalyst is preferably 50 to 60wt%, and specifically may be 50.0wt%, 52.0wt%, 54.0wt%, 56.0wt%, 58.0wt% or 60.0wt%. In some specific examples, the specific surface area of the second catalyst may be at 310m 2 Above/g, such as 310-315m 2 /g; pore volume of 0.45cm 3 And/g, the average particle diameter is 15-20nm, such as 18-19nm.
In the method provided by the invention, the second catalyst used in the step S2) is preferably obtained from ferroferric oxide and chromium salt by a hydrothermal synthesis method; the preparation method comprises the following steps:
a) Adding ferroferric oxide into aqueous solution containing chromium nitrate, stirring at room temperatureStirring for 1-2 hours; b) Adding ammonia water into the mixed solution, adjusting the pH value to 9-11, and stirring for 1-2 hours at room temperature; the dosage proportion of the ferroferric oxide to the chromium nitrate is determined according to the content of the ferroferric oxide and the chromium hydroxide in the second catalyst to be finally prepared, and is not limited independently; c) Reacting the mixed solution in a stainless steel autoclave at 170-190 ℃ for at least 24 hours; d) Washing the precipitate with water and ethanol for 3 times, and drying at 100-110deg.C for 10-12 hr; e) Sintering the dried precipitate at 300-400 ℃ for 10 hours to obtain the ferroferric oxide modified chromium hydroxide magnetic catalyst; its specific surface area can be 310.4m 2 Per gram, pore volume of 0.45cm 3 And/g, the average particle diameter is 18.7nm.
In the method provided by the embodiment of the present invention, in step S2), the mass ratio of the second catalyst to the intermediate rich in paraxylene is preferably 1:9 to 10, more preferably 1:10.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared heterogeneous catalyst and the intermediate rich in paraxylene into a liquid phase reaction kettle, heating the reactor under a protective atmosphere, adding hydrogen peroxide into the reaction kettle by using a syringe pump, and carrying out selective oxidation reaction on the aromatic hydrocarbon intermediate obtained by catalytic pyrolysis of wood chips under the action of a specific heterogeneous catalyst under the preferential stirring condition, wherein the obtained product is the paramethylbenzaldehyde after a certain period of reaction.
In the embodiment of the invention, the mass ratio of the hydrogen peroxide to the intermediate rich in paraxylene is preferably 4-6:1, more preferably 5:1, a step of; the catalytic oxidation reaction temperature is preferably 70-85 ℃, more preferably 80 ℃; the time of the catalytic oxidation reaction is preferably 5 to 8 hours, more preferably 6 hours. According to the embodiment of the invention, the selective catalytic oxidation reaction can be carried out to obtain the chemical mainly containing the p-methylbenzaldehyde, and the selectivity can reach 68.3%.
According to the method provided by the invention, firstly, the wood chip biomass raw material is catalytically cracked into the intermediate rich in paraxylene, and then the paramethylbenzaldehyde is synthesized through catalytic oxidation. The method provided by the invention has at least the following advantages and beneficial technical effects:
the invention preferentially utilizes the molecular sieve magnetic catalyst modified by the ferroferric oxide and the yttrium oxide together as the catalyst for catalytic cracking reaction, can realize the selective preparation of the intermediate rich in paraxylene by wood dust, and has the paraxylene selectivity of 60.3 percent and the paraxylene yield of 21.3 percent. After that, the invention uses the ferroferric oxide modified chromium hydroxide magnetic catalyst as the catalyst of the selective oxidation reaction, and the intermediate rich in paraxylene prepared by the catalytic pyrolysis of wood dust is selectively converted into biomass-based high-value chemicals mainly containing paramethylbenzaldehyde, the selectivity of the paramethylbenzaldehyde reaches 68.3%, and the yield of the paramethylbenzaldehyde reaches 50.7%.
In addition, the magnetic catalyst is utilized in the catalytic reaction process, so that the separation of the catalyst and reaction products after the reaction is facilitated. The raw material used in the invention is wood chip biomass, and the raw material has the advantages of abundant resources, low price, reproducibility and the like, and the end product is a bio-based high-added value chemical product mainly comprising p-tolualdehyde, thereby being beneficial to the high-value comprehensive utilization of biomass resources.
For clarity, the following examples are provided in detail. The wood chips used in the examples were derived from the wood processing plant of the Synectar city of Anhui province and consisted of 41.9wt% cellulose, 29.6wt% lignin and 19.3wt% hemicellulose; the elemental composition comprises 46.2wt% C, 6.0wt% H and 44.2wt% O; the particle size of the ground wood dust is 0.2-0.4 mm.
Example 1
In this example, a molecular sieve magnetic catalyst co-modified with yttria and ferroferric oxide (Y 2 O 3 @Fe 3 O 4 @ HMOR) as a first catalyst, the wood chip feedstock is catalytically cracked to obtain an effect of para-xylene-rich aromatic intermediates.
Using Y 2 O 3 @Fe 3 O 4 @ HMOR catalystThe preparation method adopts a conventional hydrothermal synthesis method and comprises the following steps of: a) 10g of HMOR molecular sieve was added to an aqueous solution comprising yttrium chloride (4.0 g) and deionized water (100 g) and stirred at 25℃for 2 hours at room temperature; b) Sintering the precipitate at 450 ℃ for 5 hours to obtain an HMOR molecular sieve precursor modified by yttrium oxide; c) Adding an yttrium oxide modified HMOR molecular sieve precursor into an aqueous solution containing ferric trichloride (1.6 g) and deionized water (50 g), adding ammonia water into the mixed solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; d) Reacting the mixed solution in a stainless steel autoclave for 10 hours at 100 ℃, respectively washing the precipitate after the reaction with deionized water and ethanol for 3 times, and drying at 110 ℃ for 12 hours; e) And sintering the dried precipitate for 10 hours at 350 ℃ to obtain the molecular sieve magnetic catalyst modified by yttrium oxide and ferroferric oxide together. In the obtained catalyst, the content of yttrium oxide is 17.5 weight percent, the content of ferroferric oxide is 5.5 weight percent, and the content of HMOR molecular sieve is 77.0 weight percent; the specific surface area of the catalyst was 199.8m 2 Per gram, pore volume of 0.12cm 3 And/g, the average particle diameter is 25.8nm.
In this example, the wood chip catalytic cracking is performed in a fixed bed reactor under the following reaction conditions: the weight ratio of the catalyst to the wood chip raw material is 2:1, the carrier gas is nitrogen, the pressure is normal pressure, and the temperature is 470 ℃; the catalytic cracking reaction time was 30 minutes.
The specific operation steps of the wood chip catalytic cracking are as follows: introducing inert gas nitrogen (the flow rate is 100 mL/min) into the fixed bed reactor; heating the fixed bed reactor to 470 ℃ by using an external heating mode; the Fe is mixed with 3 O 4 @Y 2 O 3 Mixing the @ HMOR magnetic catalyst and wood dust (with the particle size range of 0.2-0.4 mm) according to the mass ratio of 2:1, and then injecting the mixture into a central constant temperature area of a catalytic reactor for catalytic cracking reaction; the liquid product obtained by the catalytic pyrolysis of the wood chips is collected in a condensing tank through condensation, and after the reaction is carried out for 30 minutes, the collected product components are quantitatively analyzed by utilizing gas chromatography-mass spectrometry.
In this example, a co-modified fraction of yttria and ferroferric oxide was usedSub-sieve magnetic catalyst (Fe) 3 O 4 @Y 2 O 3 @ HMOR) for catalytic pyrolysis of wood chips, the selectivity of p-xylene was 60.3%, and the yield of p-xylene was 21.3%, and the specific results are shown in table 1.
In this example, the chromium hydroxide catalyst modified with ferroferric oxide (Cr (OH) 3 @Fe 3 O 4 ) When the aromatic hydrocarbon obtained by the catalytic pyrolysis of the wood chips is used as a raw material, the effect of preparing the p-tolualdehyde by the selective catalytic oxidation of the aromatic hydrocarbon intermediate is carried out.
Cr (OH) used 3 @Fe 3 O 4 The catalyst is prepared by adopting a conventional hydrothermal reaction method and comprises the following specific steps: a) 10g of a ferroferric oxide magnetic carrier was added to an aqueous solution containing chromium nitrate (16.5 g) and deionized water (200 g), and stirred at room temperature at 25℃for 2 hours; b) Adding ammonia water into the mixed solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; c) Reacting the mixed solution in a stainless steel autoclave at 180 ℃ for 24 hours; d) Washing the precipitate after reaction with deionized water and ethanol for 3 times respectively, drying at 110 ℃ for 12 hours, e) sintering the dried precipitate at 350 ℃ for 10 hours, and obtaining the ferroferric oxide modified chromium hydroxide magnetic catalyst. In the catalyst obtained, ferroferric oxide (Fe 3 O 4 ) 55.5 wt.% of a chromium hydroxide component (Cr (OH) 3 ) Is 44.5wt%; the specific surface area of the catalyst was 310.4m 2 Per gram, pore volume of 0.45cm 3 And/g, the average particle diameter is 18.7nm.
The conditions for the selective catalytic oxidation of the intermediate employed in this example were: ferroferric oxide modified Cr (OH) 3 The mass ratio of the catalyst to the intermediate rich in paraxylene is 1:10; the mass ratio of the hydrogen peroxide oxidant to the intermediate rich in paraxylene is 5:1, the catalytic oxidation reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In this example, when the aromatic hydrocarbon intermediate was subjected to selective catalytic oxidation to prepare p-tolualdehyde using a chromium hydroxide catalyst modified with ferroferric oxide, the selectivity of p-tolualdehyde was 68.3%, and the yield of p-tolualdehyde was 50.7%. The specific results are shown in Table 2.
Example 2
In this example, a molecular sieve catalyst modified with yttria (Y 2 O 3 @ HMOR) as a catalyst, the wood chip feedstock is catalytically cracked to obtain an effect of para-xylene-rich intermediate.
Using Y 2 O 3 The @ HMOR catalyst is prepared by adopting a conventional hydrothermal synthesis method and comprises the following steps of: a) 10g of HMOR molecular sieve was added to an aqueous solution comprising yttrium chloride (3.9 g) and deionized water (100 g) and stirred at 25℃for 2 hours at room temperature; b) Reacting the mixed solution in a stainless steel autoclave for 10 hours at 180 ℃, respectively washing the precipitate after the reaction with deionized water and ethanol for 3 times, and drying at 110 ℃ for 12 hours; c) Sintering the precipitate at 450 ℃ for 5 hours to obtain the yttrium oxide modified HMOR molecular sieve. The catalyst obtained had a yttria content of 17.8wt% and an HMOR molecular sieve content of 82.0wt%.
In this example, the wood chip catalytic cracking is performed in a fixed bed reactor under the following reaction conditions: the weight ratio of the catalyst to the wood chip raw material is 2:1, the carrier gas is nitrogen, the pressure is normal pressure, and the temperature is 470 ℃; the catalytic cracking reaction time was 30 minutes.
The specific operation steps of the wood chip catalytic cracking are as follows: introducing inert gas nitrogen (the flow rate is 100 mL/min) into the fixed bed reactor; heating the fixed bed reactor to 470 ℃ by using an external heating mode; by mixing the above Y 2 O 3 @ HMOR catalyst and woodMixing scraps (the grain diameter range is 0.2-0.4 mm) according to the mass ratio of 2:1, and then injecting the mixture into a central constant temperature area of a catalytic reactor for catalytic cracking reaction; the liquid product obtained by the catalytic pyrolysis of the wood chips is collected in a condensing tank through condensation, and after the reaction is carried out for 30 minutes, the collected product components are quantitatively analyzed by utilizing gas chromatography-mass spectrometry.
In this example, a yttria modified molecular sieve catalyst (Y 2 O 3 @ HMOR) for catalytic pyrolysis of wood chips, the selectivity of p-xylene was 58.2%, and the yield of p-xylene was 18.9%, and the specific results are shown in table 1.
The chromium hydroxide catalyst modified with ferroferric oxide (Cr (OH) was examined below 3 @Fe 3 O 4 ) The aromatic hydrocarbon obtained by the catalytic pyrolysis of the wood chips is used as a raw material, and the effect of preparing the p-tolualdehyde by the selective catalytic oxidation of an aromatic hydrocarbon intermediate is carried out.
In this example, a ferroferric oxide modified chromium hydroxide catalyst (Cr (OH) 3 @Fe 3 O 4 ) The preparation method and composition thereof were the same as in example 1.
The conditions for the selective catalytic oxidation of the intermediate employed in this example were: ferroferric oxide modified Cr (OH) 3 The mass ratio of the catalyst to the intermediate rich in paraxylene is 1:10; the mass ratio of the hydrogen peroxide oxidant to the intermediate rich in paraxylene is 5:1, the catalytic oxidation reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In this example, when the aromatic hydrocarbon intermediate was subjected to selective catalytic oxidation to prepare p-tolualdehyde using a chromium hydroxide catalyst modified with ferroferric oxide, the selectivity of p-tolualdehyde was 61.9%, and the yield of p-tolualdehyde was 43.6%. The specific results are shown in Table 2.
Example 3
In this example, the effect of catalytic cracking of wood chip feedstock to yield para-xylene rich aromatic intermediates using HMOR molecular sieves as catalysts was first examined.
In this example, the HMOR catalyst used was from the university of se south opening catalyst factory. The wood chip catalytic cracking is carried out in a fixed bed reactor, and the reaction conditions are as follows: the weight ratio of the catalyst to the wood chip raw material is 2:1, the carrier gas is nitrogen, the pressure is normal pressure, and the temperature is 470 ℃; the catalytic cracking reaction time was 30 minutes.
The specific operation steps of the wood chip catalytic cracking are as follows: introducing inert gas nitrogen (the flow rate is 100 mL/min) into the fixed bed reactor; heating the fixed bed reactor to 470 ℃ by using an external heating mode; mixing the HMOR catalyst and wood dust (with the particle size range of 0.2-0.4 mm) according to the mass ratio of 2:1, and then injecting the mixture into a central constant temperature area of a catalytic reactor for catalytic cracking reaction; the liquid product obtained by the catalytic pyrolysis of the wood chips is collected in a condensing tank through condensation, and after the reaction is carried out for 30 minutes, the collected product components are quantitatively analyzed by utilizing gas chromatography-mass spectrometry.
In this example, when the HMOR molecular sieve catalyst was used for catalytic pyrolysis of wood chips, the selectivity for paraxylene was 30.9%, and the yield of paraxylene was 11.3%, and the specific results are shown in table 1.
The chromium hydroxide catalyst modified with ferroferric oxide (Cr (OH) was examined below 3 @Fe 3 O 4 ) The aromatic hydrocarbon obtained by the catalytic pyrolysis of the wood chips is used as a raw material, and the effect of preparing the p-tolualdehyde by the selective catalytic oxidation of an aromatic hydrocarbon intermediate is carried out.
In this example, a ferroferric oxide modified chromium hydroxide catalyst (Cr (OH) 3 @Fe 3 O 4 ) The preparation method and composition thereof were the same as in example 1.
Intermediate Selectivity employed in this example The catalytic oxidation reaction conditions are: ferroferric oxide modified Cr (OH) 3 The mass ratio of the catalyst to the intermediate rich in paraxylene is 1:10; the mass ratio of the hydrogen peroxide oxidant to the intermediate rich in paraxylene is 5:1, the catalytic oxidation reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In this example, when a chromium hydroxide catalyst modified with ferroferric oxide was used to prepare p-tolualdehyde by selective catalytic oxidation of an aromatic hydrocarbon intermediate, the selectivity of p-tolualdehyde was 45.6%, and the yield of p-tolualdehyde was 31.0%. The specific results are shown in Table 2.
TABLE 1 results of catalytic cracking of wood chips to para-xylene enriched intermediates
Figure BDA0003659041450000121
As can be seen from table 1, the wood chip biomass is subjected to catalytic cracking, deoxidization, aromatization, isomerization and other reactions under the action of a catalyst to obtain an intermediate mainly comprising paraxylene. Of all the first catalysts examined (wood chip catalytic cracking catalysts), the jointly modified molecular sieve magnetic catalyst of yttria and ferroferric oxide gave the greatest para-xylene yield.
In addition, the use of a catalyst having magnetic properties facilitates separation of the catalyst from the reaction products after the reaction.
Example 4
In this example, the modification of chromium hydroxide magnetic catalysis with ferroferric oxide was examinedChemical agent (Cr (OH) 3 @Fe 3 O 4 -I) effect of selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediate to para-methylbenzaldehyde using para-xylene-rich intermediate derived from catalytic pyrolysis of wood chips in example 1 as a raw material.
In this example, cr (OH) was used 3 @Fe 3 O 4 -I catalysts prepared by conventional hydrothermal reaction, comprising the following specific steps: a) 10g of a ferroferric oxide magnetic carrier was added to an aqueous solution containing chromium nitrate (14.5 g) and deionized water (200 g), and stirred at room temperature at 25℃for 2 hours; b) Adding ammonia water into the mixed solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; c) Reacting the mixed solution in a stainless steel autoclave at 180 ℃ for 24 hours; d) Washing the precipitate after reaction with deionized water and ethanol for 3 times respectively, drying at 110 ℃ for 12 hours, e) sintering the dried precipitate at 350 ℃ for 10 hours, and obtaining the ferroferric oxide modified chromium hydroxide magnetic catalyst. In the catalyst obtained, ferroferric oxide (Fe 3 O 4 ) 59.9 wt.% of chromium hydroxide component (Cr (OH) 3 ) The mass fraction of (2) was 40.1wt%.
In this example, the selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates was carried out in a liquid phase reaction vessel, and the aromatic hydrocarbon selective catalytic oxidation reactants were derived from para-xylene-rich intermediates obtained by catalytic pyrolysis of wood chips in example 1 (see table 1).
The conditions for the selective catalytic oxidation of the aromatic hydrocarbon intermediate employed in this example were: cr (OH) 3 @Fe 3 O 4 -I the mass ratio of catalyst to para-xylene-rich intermediate is 1:10; the mass ratio of the oxidant hydrogen peroxide to the aromatic hydrocarbon intermediate rich in paraxylene is 5:1, the catalytic reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In the present embodiment, cr (OH) is used 3 @Fe 3 O 4 When the magnetic catalyst is used for preparing the p-methylbenzaldehyde by carrying out the selective catalytic oxidation on the aromatic hydrocarbon intermediate, the selectivity of the p-methylbenzaldehyde reaches 65.7%, the yield of the p-methylbenzaldehyde reaches 46.8%, and the specific results are shown in Table 2.
Example 5
In this example, a chromium hydroxide magnetic catalyst modified with ferroferric oxide (Cr (OH) 3 @Fe 3 O 4 -II) effect of selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediate to para-methylbenzaldehyde using para-xylene-rich intermediate derived from catalytic pyrolysis of wood chips in example 1 as a raw material.
In this example, cr (OH) was used 3 @Fe 3 O 4 -II catalysts prepared by conventional hydrothermal reaction, comprising the following specific steps: a) 10g of a ferroferric oxide magnetic carrier was added to an aqueous solution containing chromium nitrate (18.0 g) and deionized water (200 g), and stirred at room temperature at 25℃for 2 hours; b) Adding ammonia water into the mixed solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; c) Reacting the mixed solution in a stainless steel autoclave at 180 ℃ for 24 hours; d) Washing the precipitate after reaction with deionized water and ethanol for 3 times respectively, drying at 110 ℃ for 12 hours, e) sintering the dried precipitate at 350 ℃ for 10 hours, and obtaining the ferroferric oxide modified chromium hydroxide magnetic catalyst. In the catalyst obtained, ferroferric oxide (Fe 3 O 4 ) Is 50.7 wt.% of chromium hydroxide component (Cr (OH) 3 ) The mass fraction of (2) was 49.3wt%.
In this example, the selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates was carried out in a liquid phase reaction vessel, and the aromatic hydrocarbon selective catalytic oxidation reactants were derived from para-xylene-rich intermediates obtained by catalytic pyrolysis of wood chips in example 1 (see table 1).
The conditions for the selective catalytic oxidation of the aromatic hydrocarbon intermediate employed in this example were: cr (OH) 3 @Fe 3 O 4 -II the mass ratio of catalyst to para-xylene-rich intermediate is 1:10; the mass ratio of the oxidant hydrogen peroxide to the aromatic hydrocarbon intermediate rich in paraxylene is 5:1, the catalytic reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In the present embodiment, cr (OH) is used 3 @Fe 3 O 4 When the magnetic catalyst II is used for preparing the p-tolualdehyde by the selective catalytic oxidation of the aromatic hydrocarbon intermediate, the selectivity of the p-tolualdehyde reaches 68.0%, and the yield of the p-tolualdehyde reaches 50.3%. The specific results are shown in Table 2.
Comparative example 1
In this comparative example, the use of chromium hydroxide catalyst (Cr (OH) 3 ) The effect of selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates to para-methylbenzaldehyde was obtained using para-xylene-rich intermediates derived from catalytic pyrolysis of wood chips in example 1 as a raw material.
Cr (OH) used 3 The catalyst is prepared by adopting a conventional hydrothermal reaction method, and comprises the following specific steps: a) 40g of chromium nitrate was added to deionized water (200 g) and stirred at 25℃for 2 hours at room temperature; b) Adding ammonia water into the solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; c) Reacting the mixed solution in a stainless steel autoclave at 180 ℃ for 24 hours; d) Washing the precipitate with deionized water and ethanol for 3 timesThe mixture was dried at 110℃for 12 hours to obtain a chromium hydroxide catalyst sample.
In this comparative example, the selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates was carried out in a liquid phase reaction vessel, and the aromatic hydrocarbon selective catalytic oxidation reactants were derived from aromatic hydrocarbon intermediates obtained by catalytic pyrolysis of wood chips in example 1 (see table 1).
The conditions for the selective catalytic oxidation of the aromatic hydrocarbon intermediate employed in this comparative example were: cr (OH) 3 The mass ratio of the catalyst to the intermediate rich in paraxylene is 1:10; the mass ratio of the hydrogen peroxide oxidant to the aromatic hydrocarbon intermediate rich in paraxylene is 5:1, the catalytic oxidation reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In this comparative example, when p-methylbenzaldehyde was prepared by selective catalytic oxidation of an aromatic hydrocarbon intermediate using a chromium hydroxide catalyst, the selectivity of p-methylbenzaldehyde was 61.9%, and the yield of p-methylbenzaldehyde was 42.7%. The specific results are shown in Table 2.
Comparative example 2
In this comparative example, the use of a ferroferric oxide catalyst (Fe 3 O 4 ) The effect of selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates to para-methylbenzaldehyde was obtained using para-xylene-rich intermediates derived from catalytic pyrolysis of wood chips in example 1 as a raw material.
The ferroferric oxide catalyst is prepared by adopting a conventional hydrothermal reaction method, and comprises the following specific steps: a) 40g of ferric trichloride was added to 200g of deionized water and stirred at 25℃for 2 hours at room temperature; b) Adding ammonia water into the mixed solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; c) Reacting the mixed solution in a stainless steel autoclave at 100 ℃ for 24 hours; d) And washing the precipitate after the reaction with deionized water and ethanol for 3 times respectively, and drying at 110 ℃ for 12 hours to obtain a ferroferric oxide catalyst sample.
In this comparative example, the selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates was carried out in a liquid phase reaction vessel, and the aromatic hydrocarbon selective catalytic oxidation reactants were derived from aromatic hydrocarbon intermediates obtained by catalytic pyrolysis of wood chips in example 1 (see table 1).
The conditions for the selective catalytic oxidation of the aromatic hydrocarbon intermediate employed in this comparative example were: the mass ratio of the ferroferric oxide catalyst to the intermediate rich in paraxylene is 1:10; the mass ratio of the hydrogen peroxide oxidant to the aromatic hydrocarbon intermediate rich in paraxylene is 5:1, the catalytic reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In this comparative example, when a ferroferric oxide catalyst was used for the selective catalytic oxidation of an aromatic intermediate to prepare p-tolualdehyde, the selectivity of p-tolualdehyde was 48.2%, the yield of p-tolualdehyde was 9.7%, and the specific results are shown in Table 2.
Comparative example 3
In this comparative example, the use of a nickel hydroxide catalyst (Ni (OH) 2 ) The effect of selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates to para-methylbenzaldehyde was obtained using para-xylene-rich intermediates derived from catalytic pyrolysis of wood chips in example 1 as a raw material.
UsingNi (OH) 2 The catalyst is prepared by adopting a conventional hydrothermal reaction method, and comprises the following specific steps: a) 40g of nickel nitrate was added to deionized water (200 g) and stirred at 25℃for 2 hours at room temperature; b) Adding ammonia water into the solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; c) Reacting the mixed solution in a stainless steel autoclave at 180 ℃ for 24 hours; d) And washing the precipitate after the reaction with deionized water and ethanol for 3 times respectively, and drying at 110 ℃ for 12 hours to obtain a nickel hydroxide catalyst sample.
In this comparative example, the selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates was carried out in a liquid phase reaction vessel, and the aromatic hydrocarbon selective catalytic oxidation reactants were derived from aromatic hydrocarbon intermediates obtained by catalytic pyrolysis of wood chips in example 1 (see table 1).
The conditions for the selective catalytic oxidation of the aromatic hydrocarbon intermediate employed in this comparative example were: ni (OH) 2 The mass ratio of the catalyst to the intermediate rich in paraxylene is 1:10; the mass ratio of the hydrogen peroxide oxidant to the aromatic hydrocarbon intermediate rich in paraxylene is 5:1, the catalytic oxidation reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In this comparative example, when the aromatic hydrocarbon intermediate was subjected to selective catalytic oxidation using a nickel hydroxide catalyst to prepare p-methylbenzaldehyde, the selectivity of p-methylbenzaldehyde was 41.9%, and the yield of p-methylbenzaldehyde was 23.3%. The specific results are shown in Table 2.
Comparative example 4
In this comparative example, the use of ferric hydroxide catalyst Fe (OH) was examined 3 The wood chips from example 1 were used to catalyze crackingWhen the intermediate rich in paraxylene obtained by decomposition is used as a raw material, the aromatic hydrocarbon intermediate rich in paraxylene has the effect of preparing the paramethylbenzaldehyde by selective catalytic oxidation.
Fe (OH) used 3 The catalyst is prepared by adopting a conventional hydrothermal reaction method, and comprises the following specific steps: a) 40g of ferric nitrate was added to deionized water (200 g) and stirred at 25℃for 2 hours at room temperature; b) Adding ammonia water into the solution, adjusting the pH value to 10, and stirring for 2 hours at the room temperature of 25 ℃; c) Reacting the mixed solution in a stainless steel autoclave at 180 ℃ for 24 hours; d) And washing the precipitate after the reaction with deionized water and ethanol for 3 times respectively, and drying at 110 ℃ for 12 hours to obtain a ferric hydroxide catalyst sample.
In this comparative example, the selective catalytic oxidation of para-xylene-rich aromatic hydrocarbon intermediates was carried out in a liquid phase reaction vessel, and the aromatic hydrocarbon selective catalytic oxidation reactants were derived from aromatic hydrocarbon intermediates obtained by catalytic pyrolysis of wood chips in example 1 (see table 1).
The conditions for the selective catalytic oxidation of the aromatic hydrocarbon intermediate employed in this comparative example were: ni (OH) 2 The mass ratio of the catalyst to the intermediate rich in paraxylene is 1:10; the mass ratio of the hydrogen peroxide oxidant to the aromatic hydrocarbon intermediate rich in paraxylene is 5:1, the catalytic oxidation reaction temperature is 80 ℃; the catalytic cracking reaction time was 6 hours.
The operation steps of the catalytic reaction of the aromatic hydrocarbon intermediate are as follows: firstly, respectively adding the prepared catalyst and aromatic hydrocarbon intermediate into a liquid phase reaction kettle, wherein the dosage of the catalyst is 10g, and the dosage of an aromatic hydrocarbon intermediate reactant is 100g; heating the reactor to 80 ℃ under an inert gas nitrogen atmosphere; slowly adding hydrogen peroxide (500 g) into the liquid phase reaction kettle by using a syringe pump; stirring reactants by opening a stirrer in the reaction kettle to perform selective oxidation reaction; after 6 hours of reaction, the product was quantitatively analyzed by chromatography-mass spectrometer.
In this comparative example, when p-methylbenzaldehyde was prepared by selective catalytic oxidation of an aromatic hydrocarbon intermediate using an iron hydroxide catalyst, the selectivity for p-methylbenzaldehyde was 46.8%, and the yield of p-methylbenzaldehyde was 15.2%. The specific results are shown in Table 2.
TABLE 2 results of catalytic oxidation of aromatic intermediates to p-methylbenzaldehyde
Figure BDA0003659041450000181
As can be seen from table 2, the intermediate rich in para-xylene obtained by catalytic pyrolysis of wood chips further undergoes catalytic oxidation reaction under the action of a catalyst to obtain a chemical mainly comprising para-tolualdehyde; among all the second catalysts examined (aromatic hydrocarbon oxidation catalysts), the ferroferric oxide modified chromium hydroxide magnetic catalyst had the best p-tolualdehyde selectivity and yield, the p-tolualdehyde yield reached 50.7% and the p-tolualdehyde selectivity reached 68.3%.
In addition, the use of a catalyst having magnetic properties facilitates separation of the catalyst from the reaction products after the reaction.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (5)

1. The method for preparing the p-tolualdehyde by utilizing the wood chips is characterized by comprising the following steps of:
s1) taking wood dust as a raw material, and carrying out catalytic pyrolysis reaction in a protective atmosphere to obtain an intermediate rich in paraxylene; the catalyst adopted in the step S1) for the catalytic pyrolysis reaction is one or more of an HMOR molecular sieve catalyst and an oxide modified HMOR molecular sieve magnetic catalyst; the concentration of the paraxylene in the paraxylene-rich intermediate is above 30 wt%;
s2) in the presence of a heterogeneous catalyst, the intermediate rich in paraxylene is subjected to catalytic oxidation reaction in a hydrogen peroxide atmosphere to obtain paramethylbenzaldehyde;
the heterogeneous catalyst is a ferroferric oxide modified chromium hydroxide magnetic catalyst; the content of chromium hydroxide in the heterogeneous catalyst is 40-50wt% and the content of ferroferric oxide is 50-60wt%; the heterogeneous catalyst is a ferroferric oxide modified chromium hydroxide magnetic catalyst obtained by utilizing a hydrothermal synthesis mode through ferroferric oxide and chromium salt.
2. The method for preparing p-tolualdehyde by utilizing wood chips according to claim 1, wherein the mass ratio of the heterogeneous catalyst to the intermediate rich in p-xylene is 1:9 to 10.
3. The method for preparing p-tolualdehyde by utilizing wood chips according to claim 2, wherein the mass ratio of the hydrogen peroxide to the intermediate rich in p-xylene is 4-6: 1, wherein the temperature of the catalytic oxidation reaction is 70-85 ℃.
4. A method for producing p-tolualdehyde using wood chips according to any one of claims 1 to 3, wherein the concentration of p-xylene in the p-xylene-rich intermediate is 30.5 to 60.5wt%.
5. The method for preparing p-tolualdehyde by utilizing wood chips according to claim 1, wherein the catalyst adopted in the catalytic pyrolysis reaction in the step S1) is an HMOR molecular sieve magnetic catalyst jointly modified by yttrium oxide and ferroferric oxide.
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