CN111389395A

CN111389395A - Ruthenium iridium catalyst, preparation method thereof and application of ruthenium iridium catalyst in hydrogenolysis reaction of 5-hydroxymethylfurfural

Info

Publication number: CN111389395A
Application number: CN202010373283.XA
Authority: CN
Inventors: 方文浩; 王英浩; 曹秋娥
Original assignee: Yunnan University YNU
Current assignee: Yunnan University YNU
Priority date: 2020-05-06
Filing date: 2020-05-06
Publication date: 2020-07-10
Anticipated expiration: 2040-05-06
Also published as: CN111389395B

Abstract

The invention discloses a ruthenium-iridium catalyst, a preparation method thereof and application of the ruthenium-iridium catalyst in 5-hydroxymethylfurfural hydrogenolysis reaction, wherein a ruthenium-iridium catalyst carrier is activated carbon, and supported metals are ruthenium and iridium. The catalyst does not use any corrosive acid solution in the catalytic reaction, can efficiently, cheaply, environmentally, safely and stably convert 5-hydroxymethylfurfural into 2, 5-dimethylfuran, the conversion rate of a reactant 5-hydroxymethylfurfural reaches 100%, the yield of a target product 2, 5-dimethylfuran reaches 97%, and a byproduct only contains trace corrosive substances.

Description

Ruthenium iridium catalyst, preparation method thereof and application of ruthenium iridium catalyst in hydrogenolysis reaction of 5-hydroxymethylfurfural

Technical Field

The invention relates to a catalyst, in particular to a ruthenium iridium catalyst, a preparation method thereof and application thereof in 5-hydroxymethylfurfural hydrogenolysis reaction.

Background

The stable supply of energy is crucial to the development of economic society, and at present, the main energy of human beings still comes from non-renewable fossil raw materials such as crude oil, coal, natural gas and the like. However, the large amount of fossil raw materials produced and burned worldwide has caused problems of environmental pollution, energy shortage, global warming, and the like. In recent years, the real pressure of environmental pollution and energy shortage has prompted worldwide researchers to look for new green renewable energy sources. Lignin biomass is a sustainable, renewable source of chemical energy, with the ability to be converted into a variety of important liquid fuels and high value-added chemicals and the potential to replace traditional fossil feedstock, with huge reserves in nature sufficient to meet the growing energy needs. 5-hydroxymethylfurfural obtained from lignin biomass is one of the most important platform compounds in the field of lignin biomass conversion. It can be used for preparing various high-quality liquid fuels, such as 2, 5-dimethylfuran, 5-ethoxymethylfurfural, levulinic acid, 2, 5-furandimethanol, 2, 5-furandicarbaldehyde, ethyl levulinate and the like. The 5-hydroxymethyl furfural can be used for producing 2, 5-dimethylfuran which has a promising application prospect, so that the method is widely concerned.

Compared with the current biofuel ethanol, the 2, 5-dimethylfuran has the advantages of 1, higher energy density (31.5 MJ/L) which is basically close to gasoline, 2, higher boiling point (92-94 ℃) and low volatility, 3, higher octane number (119) and better explosion-proof performance, 4, insolubility in water and easiness in transportation and storage, 5, lower energy consumption in the separation process and lower production cost, and the 2, 5-dimethylfuran gradually becomes an excellent liquid biofuel source and is a renewable liquid fuel which is more suitable and has better development prospect than the mainstream ethanol liquid fuel.

The research work for preparing 2, 5-dimethylfuran by hydrogenolysis reaction of 5-hydroxymethylfurfural is still in the beginning stage, is one of the hot problems of research of numerous scientists in the field of biomass energy at home and abroad, but has many problems to be overcome:

1. 5-hydroxymethylfurfural is used for synthesizing 2, 5-dimethylfuran, and corrosive acid solutions such as sulfuric acid, hydrochloric acid, formic acid and the like and low-toxicity organic solvents such as methanol, dioxane and the like are required to be added into a part of a catalytic system. These acid solutions and organic solvents cause environmental pollution and harm to the personal safety of reaction operators, so that acid-resistant, corrosion-resistant and highly-closed reaction equipment is required, and the cost is increased.

2. The requirements for the catalyst support are high: part of the catalyst support requires the use of high cost graphene or carbon nanotubes. The expensive price of graphene and carbon nanotubes (several hundreds to thousands yuan per gram) causes huge cost burden and reduces economic benefit, which is not beneficial to industrial mass production.

3. Most catalytic systems require harsh conditions such as:

the high efficiency of the catalyst depends on supporting expensive noble metals: at present, the basic research and development of the catalytic reaction mainly focuses on loading expensive noble metals such as platinum, palladium and the like; the loading required for such catalysts is also relatively high, and basically the mass fraction of the noble metal loading needs to be around 3-10%. Thus resulting in a substantial increase in the cost of the catalyst.

If non-noble metals such as copper, zinc and nickel with low cost are used as the active components of the catalyst, the reaction needs to be kept at high temperature, high pressure and long time to ensure the reaction is complete. The metal waste liquid generated during the reaction can pollute the water body, and the catalyst has large dosage and low economic benefit. The reaction temperature is higher: generally 180 ℃ to 240 ℃, the energy consumption is higher, and the reduction of the reaction temperature is compensated by adding acid solution or organic solvent or increasing the pressure of hydrogen; the reaction time is longer: most of the catalytic reactions need to be carried out for about 18-24 hours, so that the deep reduction of 5-hydroxymethylfurfural is easily caused, and byproducts are generated; the reaction pressure is higher: most catalytic reactions need to be carried out under the hydrogen pressure of 3-6MPa, which is easy to cause waste of hydrogen and potential danger.

The defects make the existing catalyst not beneficial to practical application, influence economic benefits, and have potential safety hazards in high pressure, high temperature, corrosive and low-toxicity reaction solutions in the production process.

In addition, the 5-hydroxymethylfurfural molecule is an active organic substance, the molecule contains an aldehyde group and a hydroxymethyl group, the degree of the hydrogenation reduction reaction of the two functional groups is difficult to control, the product distribution is complex, and a large number of byproducts are produced. The double bond of the furan ring of the target product 2, 5-dimethylfuran is often deeply reduced to generate 2, 5-dimethyltetrahydrofuran, or the furan ring is opened to produce a chain compound. Resulting in low yield of the target product 2, 5-dimethylfuran and extremely difficult separation and purification.

Therefore, the key to realizing breakthrough in this field lies in developing a catalyst capable of efficiently, cheaply, environmentally, safely and stably converting 5-hydroxymethylfurfural into 2, 5-dimethylfuran.

Disclosure of Invention

The invention aims to provide a ruthenium iridium catalyst, a preparation method thereof and application of the ruthenium iridium catalyst in 5-hydroxymethylfurfural hydrogenolysis reaction, and solves the problems that the cost of noble metal used by the existing catalyst is high, or the activity of catalysts loaded with copper, zinc, nickel and the like is not high, the target yield is low, and the pollution of waste liquid to the environment is serious.

In order to solve the technical problems, the invention adopts the following technical scheme:

a ruthenium-iridium catalyst has active carbon as carrier and ruthenium and iridium as supported metals.

Preferably, the theoretical loading of iridium is 0.1 to 2.0 wt% and the theoretical loading of ruthenium is 0.1 to 8.0 wt%.

Preferably, a solution containing ruthenium ions and iridium ions is prepared, the pH value of the solution is adjusted to be 4-9, then polyvinylpyrrolidone or polyvinyl alcohol with the molecular weight of 5000-30000 and activated carbon are sequentially added for reaction in a dark place, and after the reaction is finished, a solid phase is separated and dried and reduced to obtain the ruthenium-iridium catalyst.

Preferably, the mass ratio of the polyvinylpyrrolidone or the polyvinyl alcohol to the activated carbon is 9: 300-400.

Preferably, the reaction time is 4 to 8 hours.

Preferably, after the reaction is finished, the reaction solution is filtered by suction, then water with the temperature of 80-100 ℃ is used for suction filtration and washing until the filtrate becomes colorless transparent liquid, and the solid phase on the filter membrane is dried, wherein the filter membrane used for suction filtration is an organic phase filter membrane with the specification of 50mm × 0.08.08 um-50mm × 0.2.2 um.

Preferably, the drying temperature is 80-100 ℃ and the drying time is 10-24 h.

Preferably, the reduction treatment is to reduce the catalyst for 30-120min under a hydrogen flow at 400 ℃ and 250 ℃.

An application of ruthenium iridium catalyst in 5-hydroxymethylfurfural hydrogenolysis reaction is characterized in that 5-hydroxymethylfurfural, catalyst and solvent are placed in a reaction kettle, air in the reaction kettle is discharged, hydrogen is filled in the reaction kettle, and 5-hydroxymethylfurfural hydrogenolysis reaction is carried out.

Preferably, the mass ratio of the catalyst to the solvent to the 5-hydroxymethylfurfural is 45: 300-600: 100-150 ℃, the hydrogen pressure is 1.5-2.5MPa, the reaction time is 3-20h, and the reaction temperature is 140-200 ℃.

Compared with the prior art, the invention has the beneficial effects that:

the catalyst does not use any corrosive acid solution in the catalytic reaction, has small harm to reaction operators, and can neglect environmental pollution.

The carrier used by the catalyst is low-cost, non-toxic and harmless activated carbon powder, so that the product is easy to separate and the catalyst is easy to recover.

The catalyst is an activated carbon-loaded ruthenium-iridium alloy nanoparticle reported for the first time. Ruthenium-iridium is used as catalytic active metal, the price and the acquisition difficulty of the carrier and the metal are low, the total load mass fraction is only 1.5%, the cost is low compared with noble metals such as platinum, palladium and the like, and the catalytic efficiency is higher compared with non-noble metals such as copper, zinc, nickel and the like.

The preparation method optimizes the preparation conditions of the catalyst, and the influence of the ruthenium-iridium bimetallic ratio on the reaction is adjusted; microscopically high dispersion of the metal nanoparticles is achieved and the reaction achieves optimal conversion and yield.

The catalyst can improve the reaction speed, reduce the reaction temperature and pressure, and ensure the relatively safe and efficient reaction.

The method optimizes the metal ratio of ruthenium to iridium and the preparation method of the catalyst, and improves the activity of the catalyst. The conversion rate of the reactant 5-hydroxymethylfurfural reaches 100%, the yield of the target product 2, 5-dimethylfuran reaches 97%, and the byproduct has only trace corrosive substances.

Drawings

FIG. 1 is a diagram of the reaction route and reaction intermediates for the preparation of 2, 5-dimethylfuran from 5-hydroxymethylfurfural;

FIG. 2 is a transmission electron micrograph of 0.5% Ir-1% Ru/C catalyst;

FIG. 3 is a graph of the particle size distribution of the corresponding iridium-ruthenium alloy nanoparticles in a 0.5% Ir-1% Ru/C catalyst;

FIG. 4 is a graph of energy dispersive X-ray-line scanning spectral signals for 0.5% Ir-1% Ru/C catalyst.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The chemical reagents and solvents used in the examples of the present application are analytically pure; the stirring mode adopts a magnetic stirrer. The electrochemical determination conditions are all within the potential range of 0.0-1.0V.

Example 1:

the preparation process of the target catalyst is 0.5% Ir-1% Ru/C:

firstly, RuCl with 1m L concentration of 5mg/m L is added₃·3H₂O solution and IrCl with concentration of 1m L of 2.5mg/m L₃·xH₂Pouring O solution into a 250ml round bottom flask, pouring 100ml deionized water, stirring uniformly, dropwise adding NaOH solution with the concentration of 1mg/m L in the stirring process until the pH value of the solution is about 5, continuously adding 18mg polyvinylpyrrolidone with the average molecular weight of 10000, stirring for 15min, then adding 492.5mg activated carbon to ensure that the theoretical metal loading proportion is 0.5 percent of iridium to 1 percent of ruthenium, stirring for 6 h under the condition of keeping out of the sun, carrying out suction filtration on the solution, carrying out suction filtration and washing by using deionized water with the temperature of 1.5L and the temperature of 90 ℃ until filtrate is colorless transparent liquid, using a filter membrane for suction filtration, wherein the filter membrane is an organic phase filter membrane with the specification of 50mm × 0.08.08 um, then putting the catalyst powder on the filter paper into an 80 ℃ oven for drying overnight, carrying out hydrogen reduction treatment after drying, reducing the catalyst for 30min under the hydrogen flow of 350 ℃, drying and storing the catalyst for later use。

The performance test operation process of the 0.5 percent Ir-1 percent Ru/C catalyst comprises the following steps:

the method comprises the steps of pouring 90mg of catalyst, 10m of L tetrahydrofuran solvent, 2mmol of 5-hydroxymethylfurfural and stirring magnetons into a polytetrafluoroethylene lining of a high-pressure reaction kettle in sequence, blowing the mixture for three times by using 0.5MPa of argon gas after the reaction kettle is installed, pumping residual gas in the kettle by using a high-pressure pump, connecting the kettle with a hydrogen steel cylinder, blowing the hydrogen gas for three times by using 0.5MPa of hydrogen gas, raising the hydrogen pressure to 2.0MPa, keeping the aeration process for about 1 minute, finally putting the reaction kettle into a high-temperature magnetic stirring oil bath kettle with the preset temperature of 170 ℃, setting the rotating speed of magnetic stirring to be 800rpm, reacting for 18 hours, putting the reaction kettle into ice water to cool for 5-10 minutes after the reaction is finished for 18 hours, releasing the gas in the kettle, sucking the reaction liquid in the kettle by using an injector, filtering by using a 0.45nm filter head to obtain filtrate, quantitatively analyzing the filtrate by using a 1310 Raf trap type gas chromatograph, and the gas chromatograph is provided with a TR-5 column and.

The catalyst in the application catalyzes a reactant 5-hydroxymethylfurfural to carry out hydrogenolysis reaction to obtain a target product 2, 5-dimethylfuran, and the reaction mechanism is shown as a path 2 in fig. 1. The structure and the particle size of the catalyst obtained in example 1 are characterized, and the results are shown in fig. 2 and fig. 3, and it is clear from fig. 2 and fig. 3 that the metal particles of the catalyst have a diameter of 2-6nm, are uniformly supported on the surface of the activated carbon support, and are nano-sized catalyst. The EDS test of the catalyst obtained in example 1 shows that the concentration signals of ruthenium and iridium are superposed in the same position range, and the result is shown in figure 4, which indicates that the ruthenium-iridium bimetallic nanoparticles on the catalyst exist on the activated carbon carrier in the form of alloy.

In order to examine the influence of the catalyst obtained in this example on the progress of the reaction, the progress of the reaction was monitored to obtain the relationship between the progress of the reaction and the time, as shown in table 1.

Table 1: relationship between reaction progress and time

The reaction results in table 1 show that: after 9 hours of reaction, a conversion of 78% has been reached, exhibiting a very high efficiency of the present catalyst, after 18 hours a conversion of 100% has been reached. In the reaction process, intermediate products are generated: 5-methylfurfural and 5-methylfurfuryl alcohol. The intermediate product exists in the initial stage of the reaction, and the intermediate product is quickly converted into the target product 2, 5-dimethylfuran by the high-efficiency catalyst along with the reaction.

In order to investigate the effect of gas pressure on the catalytic performance of the catalyst obtained in this example, parameters such as the conversion of the raw material and the yield of the target product were measured under different hydrogen pressures, and the results are shown in table 2.

Table 2: effect of gas pressure on catalytic Performance

The reaction results in table 2 show that: when the hydrogen pressure in the reaction kettle is 2MPa, the catalyst shows the best catalytic effect, and the excessive pressure does not have great promotion effect on the conversion rate and the selectivity. When the hydrogen pressure is less than 2MPa, the selectivity and conversion rate of the reaction are greatly reduced. The reaction was not found to proceed if hydrogen was replaced with argon, indicating that the reaction required hydrogen as a source of hydrogen. Therefore, a hydrogen pressure of 2MPa is selected as the most suitable gas pressure for the reaction.

In order to examine the influence of the quality of the catalyst on the catalytic performance, parameters such as the conversion of the raw material and the yield of the objective product were measured for different amounts of the catalyst, and the results are shown in Table 3.

Table 3: effect of catalyst quality on catalytic Performance

Table 3 the reaction results show that: after 18 hours of reaction, the conversion of the reactants reached 100% only if the catalyst mass was equal to or greater than 90 mg. There was substantially no difference in the reaction results between the catalyst used at 120mg and 90 mg. Therefore, 90mg was selected as the most suitable catalyst mass for the reaction.

Example 2:

the preparation process of the target catalyst is 0.5% Ir-0.5% Ru/C:

firstly, 0.5m L RuCl with the concentration of 5mg/m L₃·3H₂O solution and IrCl with concentration of 1m L of 2.5mg/m L₃·xH₂Pouring the O solution into a 250ml round-bottom flask, pouring 100ml deionized water, stirring uniformly, dropwise adding a NaOH solution with the concentration of 1mg/m L in the stirring process until the pH value of the solution is about 4, continuously adding 12mg polyvinylpyrrolidone with the average molecular weight of 20000, stirring for 15min, then adding 492.5mg activated carbon to ensure that the theoretical metal loading proportion is 0.5 percent of iridium to 0.5 percent of ruthenium, stirring for 6 h under the condition of keeping out of the sun, carrying out suction filtration on the solution, carrying out suction filtration and washing by using deionized water with the temperature of 1.5L and the temperature of 90 ℃ until the filtrate is colorless transparent liquid, using a filter membrane for suction filtration, wherein the filter membrane is an organic phase filter membrane with the specification of 50mm × 0.08um, then placing the catalyst powder on the filter paper into a 90 ℃ oven for drying for 15h, carrying out hydrogen reduction treatment after drying, reducing the catalyst under the hydrogen flow of 350 ℃ for 30min, and drying and storing for later.

Example 3:

the preparation process of the target catalyst is 0.5% Ir-4% Ru/C:

firstly, RuCl with the concentration of 4m L of 5mg/m L is added₃·3H₂O solution and IrCl with concentration of 1m L of 2.5mg/m L₃·xH₂Pouring the O solution into a 250ml round-bottom flask, pouring 100ml deionized water, stirring uniformly, dropwise adding a NaOH solution with the concentration of 1mg/m L in the stirring process until the pH value of the solution is about 6, continuously adding 54mg polyvinylpyrrolidone with the average molecular weight of 30000, stirring for 15min, then adding 477.5mg activated carbon to ensure that the theoretical metal loading proportion is 0.5 percent of iridium to 4 percent of ruthenium, stirring for 6 h under the condition of keeping out of the sun, carrying out suction filtration on the solution, carrying out suction filtration and washing by using the deionized water with the temperature of 1. 1.5L and the temperature of 100 ℃ until the filtrate is colorless transparent liquid, using a filter membrane for suction filtration, wherein the filter membrane is an organic phase filter membrane with the specification of 50mm × 0.1um, then placing the catalyst powder on the filter paper into an oven with the temperature of 100 ℃ for drying for 10The catalyst was reduced under a hydrogen stream at 400 ℃ for 30 min. And after the catalyst is prepared, drying and storing in dark for later use.

Example 4:

the preparation process of the target catalyst is 0.5% Ir-8% Ru/C:

firstly, RuCl with 8m L concentration of 5mg/m L is added₃·3H₂O solution and IrCl with concentration of 1m L of 2.5mg/m L₃·xH₂Pouring the O solution into a 250ml round-bottom flask, pouring 100ml deionized water, stirring uniformly, dropwise adding a NaOH solution with the concentration of 1mg/m L in the stirring process until the pH value of the solution is about 9, continuously adding 100mg polyvinylpyrrolidone with the average molecular weight of 5000, stirring for 15min, then adding 457.5mg activated carbon to ensure that the theoretical metal loading proportion is 0.5% of iridium to 8% of ruthenium, stirring for 8h under a dark condition, carrying out suction filtration on the solution, carrying out suction filtration and washing by using deionized water with the temperature of 1.5L and the temperature of 80 ℃ until the filtrate is colorless transparent liquid, carrying out suction filtration by using an organic phase filtration membrane with the specification of 50mm × 0.2.2 um, then putting the catalyst powder on an 80 ℃ oven for drying overnight, carrying out hydrogen reduction treatment after drying, reducing the catalyst for 120min under the hydrogen flow of 250 ℃, drying and storing the catalyst for later use.

To understand the effect of the ruthenium-iridium composition on the catalytic performance of the catalysts obtained in examples 1-4, the catalytic performance of the 1.5% Ir/C catalyst and the 1.5% Ru/C catalyst were tested and the results are shown in Table 4.

Table 4: effect of ruthenium-iridium composition in catalysts on catalytic Performance

The reaction results in table 4 show that: in the catalyst, the iridium-ruthenium bimetallic synergistic effect greatly improves the conversion rate of 5-hydroxymethylfurfural, and when the iridium-ruthenium metal mass composition ratio is 0.5: 1, the best catalytic effect is achieved. The excessive loading of ruthenium can cause the selectivity of the catalyst to the target product 2, 5-dimethylfuran to be reduced, and a large amount of corrosive substances can be generated after the reaction is finished.

In addition, the application researches the conversion rate of 5-hydroxymethylfurfural under different reaction conditions of 45: 300-600: 100-150 of the mass ratio of the catalyst to the solvent to the 5-hydroxymethylfurfural, 1.5-2.5MPa of hydrogen pressure, 3-20h of reaction time, 140-200 ℃ of reaction temperature and the like, and the results show that the catalysts all have better catalytic effect, but the effects are better when the reaction conditions are 2.0mmol of 5-hydroxymethylfurfural, 10m L of tetrahydrofuran, 90mg of catalyst, 170 ℃, 2MPa of hydrogen pressure and 18h of reaction time.

Although the invention has been described herein with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More specifically, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, other uses will also be apparent to those skilled in the art.

Claims

1. A ruthenium iridium catalyst is characterized in that: the carrier is active carbon, and the supported metals are ruthenium and iridium.

2. A ruthenium iridium catalyst according to claim 1 wherein: the theoretical load proportion of iridium is 0.1-2.0 wt%, and the theoretical load proportion of ruthenium is 0.1-8.0 wt%.

3. A method for preparing a ruthenium iridium catalyst according to claim 1 or 2, wherein: preparing a solution containing ruthenium ions and iridium ions, adjusting the pH value of the solution to 4-9, then sequentially adding polyvinylpyrrolidone or polyvinyl alcohol and activated carbon with the molecular weight of 5000-30000, carrying out a light-resistant reaction, separating out a solid phase after the reaction is finished, and carrying out drying and reduction treatment to obtain the ruthenium-iridium catalyst.

4. The method for preparing a ruthenium iridium catalyst according to claim 1, wherein: the mass ratio of the polyvinylpyrrolidone or the polyvinyl alcohol to the activated carbon is 9: 250-410.

5. The method for preparing a ruthenium iridium catalyst according to claim 1, wherein: the reaction time is 4-8 h.

6. The method for preparing ruthenium iridium catalyst according to claim 1, wherein the reaction solution is filtered after the reaction is completed, and then the filtrate is filtered and washed with water at 80-100 ℃ until the filtrate turns into colorless transparent liquid, and the solid phase on the filter membrane is dried, wherein the filter membrane used for filtering is an organic phase filter membrane with the specification of 50mm × 0.08.08 um-50mm × 0.2.2 um.

7. The method for preparing a ruthenium iridium catalyst according to claim 1, wherein: the drying temperature is 80-100 ℃, and the drying time is 10-24 h.

8. The method for preparing a ruthenium iridium catalyst according to claim 1, wherein: the reduction treatment is to reduce the catalyst for 30-120min under the hydrogen flow at the temperature of 250-400 ℃.

9. Use of a ruthenium iridium catalyst according to claims 1 to 8 in the hydrogenolysis of 5-hydroxymethylfurfural, characterized in that: placing 5-hydroxymethylfurfural, a catalyst and a solvent in a reaction kettle, discharging air in the reaction kettle, and filling hydrogen into the reaction kettle to carry out hydrogenolysis reaction on the 5-hydroxymethylfurfural.

10. The use of a ruthenium iridium catalyst according to claim 9 in the hydrogenolysis of 5-hydroxymethylfurfural, characterized in that: the mass ratio of the catalyst to the solvent to the 5-hydroxymethylfurfural is 45: 300-600: 100-150 ℃, the hydrogen pressure is 1.5-2.5MPa, the reaction time is 3-20h, and the reaction temperature is 140-200 ℃.