CN117024238A - Method for synthesizing polycyclic alkane from lignin-derived phenols through one-pot two-step method - Google Patents

Abstract

The application discloses a method for synthesizing polycyclic alkane from lignin-derived phenols by a one-pot two-step method. 1) In the first step of reaction, lignin-derived phenolic compounds are firstly converted into ketone compounds under the action of a hydrogenation catalyst, and then the ketone compounds are rapidly subjected to aldol condensation under the action of solid acid to generate aviation kerosene precursors; 2) In the second reaction step, the reaction condition is directly enhanced without separating the product in the first step, and the aviation kerosene precursor directly realizes complete hydrodeoxygenation to generate polycyclic alkane under the action of a hydrogenation catalyst and solid acid in the first step; lignin-derived phenolic compounds are synthesized into multi-ring aviation kerosene in a reaction vessel by changing reaction conditions. Compared with the traditional chain aviation kerosene, the density and the heat value of the aviation kerosene are high, and the aviation kerosene can be used as a substitute of the traditional aviation fuel. The catalyst and the raw materials used in the application have rich sources, low price and easy separation; the whole production process is simple and convenient to operate.

Description

A method for synthesizing polycyclic alkanes from phenols derived from lignin through a one-pot and two-step process

Technical field

A method for synthesizing polycyclic alkanes from phenolic compounds derived from lignin through a one-pot and two-step process. The method of the invention involves two processes in one pot. The first process is the hydrogenation of phenolic compounds derived from lignin to generate ketone compounds. Subsequently, the ketone compounds undergo aldol condensation under the action of solid acid and at the same time the carbon-carbon double bonds are saturated. off; the second process is complete hydrodeoxygenation reaction.

Background technique

Biomass energy has the advantages of abundant reserves, renewable nature, and _CO2 neutrality. Therefore, using biomass resources to produce aviation fuel components or chemicals to partially replace the fuel or chemicals obtained from traditional oil refining can not only reduce China's oil consumption It is highly dependent on foreign countries and is in line with the current green development concept. Lignin is the second largest biomass resource in nature after cellulose, and it is also the only clean non-petroleum resource in nature that can provide renewable aromatic compounds. The biomass oil obtained by pyrolysis of lignin contains more benzene ring structural units and is a cheap and clean resource that can be converted into high-energy aromatic hydrocarbons and naphthenes. It is one of the most potential petroleum supplementary energy sources.

Cyclohexanone and its derivatives are an important biomass platform compound, which can be obtained by hydrogenation of lignin-derived phenols ([CN103724174B]; Sheng, X.; Wang, C.; Wang, W. Organic Process Research&Development 2021,25(11),2425-2431; Xu, G.Y.; Guo, J.H.; Zhang, Y.; Fu, Y.; Chen, J.Z.; Ma, L.L.; Guo, Q. -2492.). Cyclohexanone and its derivatives can undergo aldol condensation, followed by hydrodeoxygenation to obtain polycycloalkanes. However, this process involves multiple reaction processes, many separation steps, and high energy consumption. Therefore, compared with the step-by-step synthesis strategy, it is more attractive to directly convert lignin-derived phenols into polycyclic alkanes through a single-kettle series reaction.

Contents of the invention

The present invention uses easily separated solid acid catalysts and hydrogenation catalysts to convert lignin-derived phenols into oxygen-containing jet fuel precursors under mild conditions, and then continues to use the catalysts and solvents used in the previous step to simply increase the temperature and reaction After pressure, liquid fuel is obtained with high yield through a two-step process; the catalyst in the present invention has the characteristics of solvent-free, easy separation, simple operation process, low energy consumption, low cost, etc., and provides a synthesis of phenolic compounds derived from lignin. New routes for high-density polycyclic aviation kerosene.

The present invention is achieved through the following technical solutions:

The reaction process is realized through a one-pot two-step reaction process.

In the first process, in the first step of the reaction, phenolic compounds derived from lignin are first selectively hydrogenated into ketones under the action of a hydrogenation catalyst in a hydrogen atmosphere, and then the ketone compounds are rapidly Under the action of solid acid catalyst, aldol condensation occurs to generate jet fuel precursor, which is an unsaturated organic substance containing multiple carbon numbers;

The reaction is carried out in a batch reactor. The molar ratio of lignin-derived phenols to the active components in the hydrogenation catalyst is 1:0.0002~0.005. The mass ratio of the amount of solid acid catalyst to the reaction substrate is 0.2~1 The reaction temperature is between 80 and 120°C, the reaction time is between 2 and 12 hours, and the reaction pressure is between 0.5MPa and 2MPa.

The second process continues using the catalyst and solvent from the first step. After step 1 is completed, the hydrogen reaction pressure is directly rushed to 3MPa~5MPa without opening the kettle, the temperature is raised to 180~240°C, and the reaction time is 4h-12h. In the first step, the hydrogenation catalyst and solid acid directly achieve complete hydrodeoxygenation of the jet fuel precursor to generate polycycloalkanes.

Further, in the above technical solution, the above two-step reactions are both in a hydrogen atmosphere.

Further, in the above technical solution, the hydrogenation catalyst described in the first step is a supported catalyst A/X, which includes a metal active site A and a carrier X supported on a carrier. _{The carrier _ _ _} One or more than two kinds, wherein the loading amount of the catalyst is between 0.1wt% and 15wt%.

Further, in the above technical solution, the solid acid catalyst described in the first step is Nafion-212, Amberlyst-15, Amberlyst-36, TiP ₂ , CeP ₂ , AlP ₂ , ZrP _0.5 , ZrP ₁ , ZrP ₂ , ZrP ₃ At least one; among them, the solid acids Nafion-212, Amberlyst-15, and Amberlyst-36 are commercially purchased, and other solid acids are prepared by co-precipitation method. TiP ₂ , CeP ₂ , AlP ₂ , etc. are prepared by mixing and stirring the metal precursor nitrate solution and ammonium dihydrogen phosphate solution at a certain molar ratio at 50°C, and then adding concentrated ammonia drop by drop to adjust the pH value to 8 to 10. Continue stirring for 4 to 8 hours, filter and wash, dry at 80°C overnight, and calcine at 350 to 650°C for 5 to 8 hours. Zirconium phosphate ( _ZrP to neutrality, then dried at 120°C overnight, and roasted at 400°C for 4 hours.

Through the above steps, we successfully synthesized high-density aviation fuel with a multi-ring structure.

The structure of the product polycycloalkane is:

The present application uses a method that combines a cheap and easily available solid acid catalyst and a noble metal hydrogenation catalyst to achieve the desired series process. This process can be divided into two steps. Under the conditions of unchanged catalyst and solvent, the first step is to achieve hydrogenation of phenolic compounds and subsequent aldol condensation to obtain an oxygen-containing jet fuel precursor. The second step is to strengthen the reaction conditions. Achieve complete hydrodeoxygenation of oxygenated jet fuel precursor, and finally obtain polycycloalkanes.

Description of the drawings

Figure 1 is the mass spectrum of the product of Example 64;

Figure 2 is the mass spectrum of the product of Example 67;

Figure 3 is the mass spectrum of the product of Example 68;

Figure 4 is the mass spectrum of the product of Example 69;

Figure 5 is a product distribution mass spectrum of the raw material phenol in the first step reaction process of Example 64;

Figure 6 is a mass spectrum of the target product during the first step of the reaction of the raw material phenol in Example 64.

Detailed ways

The present invention will be described below with specific examples, but the protection scope of the present invention is not limited to these examples.

Sources of catalysts in the following examples: The hydrogenation catalyst described in the first step is a supported catalyst A/X, which includes a metal active site A and a carrier X supported on a carrier. _{The carrier _ _ _} One or two or more types of catalysts, wherein the catalyst loading is between 0.1% and 15%.

The solid acid catalyst is at least one of Nafion-212, Amberlyst-15, Amberlyst-36, TiP ₂ , CeP ₂ , AlP ₂ , ZrP _0.5 , ZrP ₁ , ZrP ₂ and ZrP ₃ ; among them, the solid acid Nafion-212, Amberlyst-15 , Amberlyst-36 was purchased commercially, and other solid acids were prepared by co-precipitation method. TiP ₂ , CeP ₂ , AlP ₂ , etc. are prepared by mixing and stirring the metal precursor nitrate solution and ammonium dihydrogen phosphate solution at a certain molar ratio at 50°C, and then adding concentrated ammonia drop by drop to adjust the pH value to 8 to 10. Continue stirring for 4 to 8 hours, filter and wash, dry at 80°C overnight, and calcine at 350 to 650°C for 5 to 8 hours. Zirconium phosphate ( _ZrP to neutrality, then dried at 120°C overnight, and roasted at 400°C for 4 hours.

Example 1:

The following reaction formula is the reaction route of the present invention, and the reaction conditions in Example 2 are adopted.

Examples 2 to 10:

1) In the first step of the reaction, add 0.4g phenol (or other phenols) and a certain amount of catalyst into the reaction kettle. At the same time, add 40ML cyclohexane as the solvent, and react for a period of time at a certain temperature and pressure. Details The reaction results are shown in Table 1.

Table 1 Reaction conditions and results of hydrogenation and aldol condensation of phenol and its derivatives.

It can be seen from Table 1 that the conversion activities of different lignin-derived phenols are related to their structures. Among them, phenol is easy to undergo hydrogenation and aldol condensation reaction. The conversion activity of para-substituted alkylphenols is similar to that of phenol, followed by meta-substituted alkylphenols. Substituted alkylphenols and ortho-substituted alkylphenols; at the same time, the type of substituents also affects the transformation activity of phenolic derivatives.

2) The influence of different combinations of catalysts on the first step reaction.

Add 0.4g of phenol and catalyst (including hydrogenation catalyst and solid acid) into a 100ML batch reactor and add 40ML of cyclohexane as solvent, and react under certain conditions; see Table 2 for detailed reaction results.

Table 2 Reaction results of phenol using different catalyst combinations in the first step reaction.

As can be seen from Table 2, phenol has different conversion activities under different catalyst combinations, and the catalytic performance affects the hydrogenation of phenol into ketones and further conversion into aldol condensation products. Overall, precious metals have better hydrogenation properties, but different precious metals have different selective hydrogenation effects on phenol. Some precious metals promote excessive hydrogenation, which will affect the subsequent aldol condensation reaction. At the same time, different solid acids also show different effects of aldol condensation ability. The strong aldol condensation ability of solid acids can also inhibit the excessive hydrogenation of cyclohexanone into alcohol to a certain extent. The amount of metal loading also has an important influence on the selective hydrogenation catalysis of phenol.

3) The effect of reaction conditions on the selective hydrogenation and aldol condensation reaction of phenol.

Add 0.4g phenol and 40 40ML cyclohexane into a 100ML batch reactor, add a certain amount of combined catalyst, and react under different conditions for a period of time; the results are shown in Table 3.

Table 3 Reaction results of phenol under different reaction conditions

As can be seen from Table 3, the reaction conditions have a certain impact on the distribution of the product. Metal hydrogenation catalysts are mainly used in the hydrogenation of phenol to form ketones or alcohols. If the amount of hydrogenation catalyst is too low, the reaction of phenol will be incomplete, and if the amount of hydrogenation catalyst is too high, the selectivity of ketones will be reduced. Temperature and pressure also have the same impact on the hydrogenation process. ; Solid acid catalysts mainly act on the aldol condensation of ketones. However, excess acid will lead to a decrease in carbon balance. It may be that excess acid causes the hydrogenation of alcohols into alkanes. After optimizing the reaction conditions, we can harvest 89% of the oxygen-containing jet fuel precursors, which will be directly hydrodeoxygenated into alkanes in the second step.

4) A one-pot two-step synthesis of polycycloalkanes from phenols derived from lignin

The first step of the reaction is to add 0.4g of the substrate in Example 2-10 and the amount of 1wt% Pd/MgAl-HT catalyst and ZrP ₂ catalyst in Table 4 into the reaction kettle, and at the same time add 40ML of cyclohexane as the solvent , react at a hydrogen pressure of 100 Psi and a temperature of 120°C for 12 hours.

Complete hydrohydrodeoxygenation of different oxygenated jet fuel precursors.

After the first step of reaction is completed, it is first lowered to room temperature, then hydrogen gas is injected to 4MPa and the temperature is raised for reaction. The reaction conditions are shown in Table 4. The raw materials in Examples 64-72 respectively correspond to the target products after the substrates in Examples 2-10 in Step 1 are reacted for 12 hours in the first step. These target products will be directly hydrodeoxygenated in the second step to obtain the corresponding bicyclo Alkane fuel.

The above two-step reactions are performed in a hydrogen atmosphere.

Table 4 Bicycloalkanes finally synthesized from different lignin-derived phenols in a one-pot two-step process

As can be seen from Table 4, after series reactions, we can directly obtain polycycloalkanes in one pot. The process is simple and does not require separation, which is beneficial to chemical production.

Claims (8)

1. A method for synthesizing polycyclic alkane from lignin-derived phenols by a one-pot two-step method is characterized in that:

1) In the first step of reaction, lignin-derived phenolic compounds are firstly subjected to selective hydrogenation to ketone under the action of a hydrogenation catalyst in a hydrogen atmosphere, and then the ketone compounds are rapidly subjected to aldol condensation under the action of a solid acid catalyst to generate unsaturated organic matters with multiple carbon numbers from aviation kerosene precursors;

2) In the second reaction step, the reaction condition is directly enhanced without separating the product in the first step, the hydrogen pressure is increased to 3 MPa-5 MPa, the temperature is increased to 180-240 ℃, and the reaction time is 4-12 h; the aviation kerosene precursor directly realizes complete hydrodeoxygenation to generate polycyclic alkane under the action of a hydrogenation catalyst and solid acid in the first step.

2. The method according to claim 1, characterized in that:

the lignin-derived phenolic compounds in step 1) are phenol, o-cresol, m-cresol, p-ethylphenol, p-propylphenol, guaiacol, methylguaiacol, o-diphenol lignin-derived phenolic compounds.

3. The method according to claim 1, characterized in that:

the hydrogenation catalyst in the steps 1 and 2) is a supported catalyst A/X, and comprises a metal active component A and a carrier X which are supported on a carrier; the carrier X is SiO ₂ 、TiO ₂ 、CeO ₂ 、Al ₂ O ₃ At least one of MgAl-HT, mgO, liAl-HT; the metal active component A is one or more than two of Pt, pd, ru, ir, rh, ni, fe, cu, wherein the metal active component loading of the catalyst is between 0.1wt% and 15 wt%.

4. The method according to claim 1, characterized in that:

the solid acid catalyst in step 1 and 2) is Nafion-212, amberlyst-15, amberlyst-36, tiP, ceP, alP, zrP _0.5 ，ZrP ₁ ，ZrP ₂ ，ZrP ₃ At least one kind.

5. The method according to claim 1, characterized in that:

the molar ratio of lignin-derived phenols to active component on the hydrogenation catalyst support is 1:0.0002 to 0.005, the mass ratio of the solid acid catalyst to the reaction substrate is between 0.2 and 1.

6. The method according to claim 1 or 2, characterized in that:

in the step 1), the hydrogenation and aldol condensation reaction are carried out in a batch kettle type reactor, the reaction temperature is between 80 and 180 ℃, the reaction time is between 2 and 12 hours, the reaction pressure is between 0.5 and 2MPa, and the hydrogenation catalyst and the solid acid are required to be added simultaneously in the reaction process.

7. The method according to claim 1 or 2, characterized in that:

the hydrodeoxygenation in step 2) is performed on the basis of step 1. After the step 1 is completed, the reaction pressure is directly flushed to 3 MPa-5 MPa without opening a kettle, the temperature is increased to 180-240 ℃, and the reaction time is 4-12 h.

8. The process according to claim 1 or 2, characterized in that the product polycycloalkane has the structure