CN111234197A - Method for preparing biomass-based polytetrahydrofuran from furfural - Google Patents

Abstract

The application discloses a method for preparing biomass-based polytetrahydrofuran from furfural, which comprises the following steps: converting furfural into tetrahydrofurfuryl alcohol (step 1), decarbonylating the tetrahydrofurfuryl alcohol to convert the tetrahydrofurfuryl alcohol into tetrahydrofuran (step 2), and polymerizing the tetrahydrofuran to generate polytetrahydrofuran (step 3). Its advantages are: the problems of reactant polymerization, catalyst coking inactivation and the like caused by the direct decarbonylation of furfural to generate furan are avoided, so that the reaction is terminated, the economical efficiency of a reaction route and the industrial operability of continuous reaction are greatly improved, and the great breakthrough of the preparation of the biomass-based high polymer material is realized. The method is more environment-friendly and efficient, radically solves the problems of polymerization of a reaction system, catalyst inactivation and the like in the decarbonylation of the furfural, and improves the environment-friendliness and efficiency of the reaction, so that the method is easier to implement industrially on a large scale, and lays a foundation for the development of an environment-friendly reaction process for preparing the biomass-based high polymer material from the furfural.

Description

A kind of method for preparing biomass-based polytetrahydrofuran from furfural

technical field

The present application relates to the field of chemical technology, in particular to a method for preparing biomass-based polytetrahydrofuran from furfural.

Background technique

Polytetrahydrofuran (PTHF) is a polymer produced by ring-opening polymerization of tetrahydrofuran. It is mainly used as a soft segment of block polyurethane or block polyether polyester (thermoplastic elastomer). It can be used as tires, transmission belts, gaskets, etc. Can be used in coatings, artificial leather, films, etc. In addition, PTHF has good application prospects in polyurethane products such as protective materials, infusion tubes, blood belts, etc., and can be used as medical polymer materials.

Tetrahydrofuran, as the basic raw material for the synthesis of polytetrahydrofuran, is currently mainly obtained by the petroleum method and the furfural method. Methods based on petrochemical feedstocks include 1,4-butanediol method, butadiene method and maleic anhydride method, but with the large consumption of non-renewable energy petroleum, biomass has attracted much attention as a sustainable energy source. Hemicellulose can be extracted from biomass resources such as corncob, and furfural can be obtained by acid-catalyzed hydrolysis to xylose and dehydration.

The preparation of tetrahydrofuran from renewable biomass furfural is of great significance in solving the oil crisis and deep processing of furfural. Its current main process route is to first obtain furan through metal-catalyzed decarbonylation of furfural, and then obtain tetrahydrofuran through metal hydrogenation. Chinese patent (CN 1308986A) reported the use of alkali metal oxides (K ₂ O, CaO, MgO, BaO, Cs ₂ O) as auxiliary agents, loading 0.4%-0.7% Pt, and Al ₂ O ₃ -TiO ₂ as composite The oxide-supported catalyst realizes gas-phase decarbonylation of furfural to produce furan at normal pressure and 280°C, with a conversion rate of 80% to 97% and a selectivity of 85% to 92%. The Chinese patent (CN 107970928 A) reported the addition of a co-active moiety Ga-Ga ₂ O ₃ (Ga is partially reduced by Ga ₂ O ₃ , and the reduction degree is 10%-70%). The catalyst uses 0.05-0.4% Pd as the main active part, and Al ₂ O ₃ as the carrier for furfural decarbonylation to prepare furan. The decarbonylation process has high activity and selectivity, but the aldehyde group of furfural is unstable and easy to polymerize, and the coking of noble metal catalyst leads to rapid deactivation, and the cost of noble metal is high and the recycling rate is not high, which is not conducive to industrial expansion of large-scale production. .

In the process of hydrogenation of furan to obtain tetrahydrofuran in the second step, Li Ping et al. reported (Applied Science and Technology, 2008, 35(7), 65-68) that Raney Ni was used as a catalyst (the dosage was 8% to 12%), and the hydrogen pressure was Under the reaction conditions of 2.0-5.0 MPa, the conversion rate of furan can reach 99%, and the yield of tetrahydrofuran is about 70%. In addition, Wang Chengxue et al. (Natural Gas Chemical Industry (C1 Chemistry and Chemical Industry), 2010 (02), 79-82) discussed the preparation of tetrahydrofuran by hydrogenating furan with Pd/C as a catalyst, in which the conversion rate of furan can reach 92%, and the yield of tetrahydrofuran The rate is about 90%.

SUMMARY OF THE INVENTION

The present application provides a method for preparing biomass-based polytetrahydrofuran from furfural.

This application adopts the following technical solutions:

Furfural is converted into tetrahydrofurfuryl alcohol (step 1), tetrahydrofurfuryl alcohol is converted to tetrahydrofuran by decarbonylation (step 2), and tetrahydrofuran is polymerized to generate polytetrahydrofuran (step 3). The synthetic route is shown below.

A preparation method of polytetrahydrofuran, the preparation method comprises the following steps:

Step 1, furfural generates tetrahydrofurfuryl alcohol through full hydrogenation

The furfural, the catalyst and the solvent are added into the autoclave, the active center of the catalyst in this step is one or more of Pt, Ru, Pd, Ni, Rh, and Co, the reaction kettle is sealed, and N is _introduced to replace The air in the reaction kettle is fed with H ₂ , and the temperature of the reaction kettle is raised to 100-150° C. After the reaction is completed, the H ₂ is released after the reaction kettle is cooled, and the catalyst is filtered and the solvent is removed by rotary evaporation to obtain tetrahydrofurfuryl alcohol;

Step 2, decarbonylation of tetrahydrofurfuryl alcohol to prepare tetrahydrofuran

The catalyst is loaded into the fixed-bed reactor for reduction under H atmosphere. _The active center of the catalyst in this step is one or more of Pd, Pt, Ru, Ni, Au, Co, and Fe. After the reduction is completed, The tetrahydrofurfuryl alcohol is pumped into the fixed _- bed reactor, reacted under H atmosphere, and the reaction solution is taken out from the distillate pipe for each reaction period of time;

Step 3, ring-opening polymerization of tetrahydrofuran to prepare polytetrahydrofuran

Add catalyst and tetrahydrofuran into the reaction flask, the catalyst in this step is liquid acid, AlCl ₃ , FeCl ₃ , PW ₁₂ /SiO ₂ , PMo ₂ /SiO ₂ , SiW ₁₂ /Al ₂ O ₃ , SiMo ₁₂ /Al ₂ O ₃ One or more of , ZSM-5 molecular sieve, MCM-42 molecular sieve, H-Beta molecular sieve, HUSY molecular sieve, SiO ₂ -TiO ₂ , SiO ₂ -ZrO ₂ , TiO ₂ -ZrO ₂ , SiO ₂ -Al ₂ O ₃ After being heated to 25-60 ℃, slowly drip the initiator with a constant pressure dropping funnel, the initiator in this step is ethylene oxide, propylene oxide, epoxy chloroethylene, oxetane, cyclic One or more of oxychloropropane and acetic anhydride are introduced into N ₂ for protection, and after the reaction is completed, ethanol is added to terminate the reaction, filtered, the kettle liquid is concentrated, and vacuum-dried to obtain polytetrahydrofuran.

The carrier of the catalyst in step 1 is one or more of all-silicon molecular sieve, diatomaceous earth, carbon material, Al ₂ O ₃ and SiO ₂ .

The solvent in step 1 is one or more of water, ethanol, alkane, and cycloalkane.

The volume ratio of furfural to solvent in step 1 is 10:1-1:10.

The _H2 pressure in step 1 is 2.0-6.0MPa, and the reaction time is 1-8h.

In step 2, the reduction temperature of the catalyst under _H2 atmosphere is 400-800 °C, and the reduction time is 5-10 h.

The carrier of the catalyst in step 2 is one or more of SiO ₂ , Al ₂ O ₃ and C.

In step 2, the reaction temperature is 300-400°C, the reaction time is 1-4h, the H ₂ pressure is 2-4MPa, and the gas inlet velocity is 15-200mL/min.

The reaction time in step 3 is 2-8h.

The vacuum drying in step 3 is drying in a vacuum drying oven at 100° C. for 24 hours.

The above-mentioned at least one technical solution adopted in this application can achieve the following beneficial effects:

The present application uses furfural biomass as raw material, and converts it into polytetrahydrofuran polymer through a new reaction path, that is, three steps of complete hydrogenation, de-CH ₂ OH, and ring-opening polymerization. The new route of the present application avoids the problems of reactant polymerization and catalyst coking and deactivation caused by direct decarbonylation of furfural to furan, thereby terminating the reaction, greatly improving the economy of the reaction route and the industrial operability of the continuous reaction, and realizing production A major breakthrough in the preparation of substance-based polymer materials. The new route of the present application is not only more green and efficient, but also solves the problems of polymerization of the reaction system and catalyst deactivation in the decarbonylation of furfural from the root, improves the greenness and efficiency of the reaction, and makes it easier to implement large-scale industrially. , laying the foundation for the development of green reaction process for furfural to prepare biomass-based polymer materials.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below with reference to the specific embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

Example 1

(1) Hydrogenation of furfural to prepare tetrahydrofurfuryl alcohol

Weigh 2g of activated carbon powder into a 100mL flask, add 30mL of Pd standard solution (concentration of 0.0027g Pd/mL), stir at room temperature for 24h, rotate at 60°C until the water is completely evaporated, and the obtained precursor is dried overnight in a 100°C oven. After calcination at 350 °C in _N2 for 4 h, reduction was performed at 350 °C in a high-purity _H2 atmosphere for 4 h, and after complete cooling, a 5:1 ratio of _N2 and air was used for aging for later use.

0.2 g of the prepared Pd/C catalyst was added to the reaction kettle, and 3 g of furfural and 50 mL of ethanol were added. The reaction kettle was sealed, and H ₂ was introduced to replace the air in the reaction kettle; 4 MPa of H ₂ was introduced into the reaction kettle, the temperature of the reaction kettle was raised to 120° C., and the reaction was carried out for 3 h. After the reaction is completed, it is cooled to release H ₂ , the reaction solution is obtained by opening the kettle, and tetrahydrofurfuryl alcohol is obtained by distillation.

The results of chromatographic analysis showed that the yield of tetrahydrofurfuryl alcohol was 98%.

(2) Decarbonylation of tetrahydrofurfuryl alcohol to prepare tetrahydrofuran

15.2 g of nickel nitrate hexahydrate and 15.86 g of gold chloride were dissolved in 500 mL of deionized water. Then, the 500 mL mixed solution of nickel nitrate and gold chloride was divided into two parts, and 400 mL of one part was transferred to the flask, 2 g of Al ₂ O ₃ was added, and the mixture was heated and stirred in an oil bath at 70°C. 7 g of sodium carbonate was added to another 100 mL of the nickel salt solution, and then the 100 mL of the mixed solution was added dropwise to the flask. After the dropwise addition, the temperature of the oil bath of the whole system was raised to 120°C. After 24 hours of reaction, the mixture was cooled, then suction filtered, and the green powder was washed to neutrality. The obtained precursor was dried in an oven at 100 °C overnight, and calcined at 300 °C in air for 4 hours before use.

Use acetone to clean the fixed bed, put 2g of catalyst into the fixed bed bed casing, fill it with quartz sand, pass H ₂ into the fixed bed, reduce the catalyst at 500 ℃ for 4 hours, and cool down the temperature to 300 ℃ after reduction, The tetrahydrofurfuryl alcohol was pumped at a sampling rate of _0.07mL /min, the pressure of H was adjusted to 2MPa, the flow rate was adjusted to 78mL/min, the reaction solution was taken out from the distillate tube every 3h of reaction, and tetrahydrofuran was obtained by distillation.

Chromatographic analysis showed that the yield of tetrahydrofuran was 90%.

(3) Preparation of polytetrahydrofuran by polymerization of tetrahydrofuran

Weigh 0.82 g of the activated MCM-42 catalyst and 100 ml of tetrahydrofuran into a reaction flask, replace the air in the reaction flask with nitrogen, and ensure that the polymerization reaction is carried out in _N2 . The magnetic stirring was turned on, the temperature was raised to 60°C, and the initiator propylene oxide was slowly added dropwise with a constant pressure dropping funnel, and the viscosity of the polymerization system increased with the progress of the polymerization reaction. After 2.5 hours of reaction, ethanol was added to the polymerization system to terminate the reaction, and the polymerization system was milky white. The mixture was extracted and separated three times, and water, ethanol and other volatile organic compounds were removed by rotary evaporator. The obtained polytetrahydrofuran was transferred to a vacuum drying oven, dried at 100° C. for 24 h, water and residual organic matter were completely removed, and a white waxy solid was obtained. The yield (%) was calculated by the following formula to obtain polytetrahydrofuran in 85% yield.

Example 2

(1) Hydrogenation of furfural to prepare tetrahydrofurfuryl alcohol

Weigh 2g Al ₂ O ₃ powder into a 100mL flask, add 30mL Ni standard solution (concentration is 0.0027g Ni/mL), stir at room temperature for 24h, rotate at 60°C until the water is completely evaporated, the obtained precursor is placed in a 100°C oven It was dried overnight, calcined at 350 °C for 4 h in the air, reduced in a high-purity _H2 atmosphere at 350 °C for 4 h, and after complete cooling, aged with a 5:1 ratio of _N2 and air for later use.

0.2 g of the prepared Ni/Al ₂ O ₃ catalyst was added to the reaction kettle, and 3 g of furfural and 50 mL of ethanol were added. The reaction kettle was sealed, and H ₂ was introduced to replace the air in the reaction kettle; 4 MPa of H ₂ was introduced into the reaction kettle, the temperature of the reaction kettle was raised to 120° C., and the reaction was carried out for 3 h. After the reaction is completed, it is cooled to release H ₂ , the reaction solution is obtained by opening the kettle, and tetrahydrofurfuryl alcohol is obtained by distillation.

The results of chromatographic analysis showed that the yield of tetrahydrofurfuryl alcohol was 87%.

(2) Decarbonylation of tetrahydrofurfuryl alcohol to prepare tetrahydrofuran

17.3 g of ruthenium chloride were dissolved in 500 mL of deionized water. Then, the 500 mL ruthenium chloride solution was divided into two portions, and 400 mL of one portion was transferred to a flask, 2 g CeO ₂ was added, and the mixture was placed in an oil bath at 70° C. with heating and stirring. To another 100 mL of the ruthenium salt solution, 7 g of sodium carbonate was added, and then the 100 mL of the mixed solution was added dropwise to the flask. After the dropwise addition, the temperature of the oil bath of the whole system was raised to 120°C. After 24 hours of reaction, the mixture was cooled, then suction filtered, and the green powder was washed to neutrality. The obtained precursor was dried in an oven at 100 °C overnight, and calcined at 300 °C in air for 4 hours before use.

Use acetone to clean the fixed bed, put 2 g of catalyst into the fixed-bed bed casing, and fill it with quartz sand, pass H into the fixed bed to reduce the catalyst at 500 °C for ₄ h, and reduce the temperature to 300 °C after the reduction. The tetrahydrofurfuryl alcohol was pumped at a sampling rate of _0.07mL /min, the pressure of H was adjusted to 2MPa, and the flow rate was adjusted to 78mL/min. The reaction solution was taken out from the distillate tube every 3h of reaction, and tetrahydrofuran was obtained by distillation.

Chromatographic analysis showed that the yield of tetrahydrofuran was 70%.

(3) Preparation of polytetrahydrofuran by polymerization of tetrahydrofuran

Weigh 0.82 g of the activated SiW ₁₂ /Al ₂ O ₃ catalyst and 100 ml of tetrahydrofuran into a reaction flask, and replace the air in the reaction flask with nitrogen to ensure that the polymerization reaction is carried out in N ₂ . The magnetic stirring was turned on, the temperature was raised to 60°C, and the initiator acetic anhydride was slowly added dropwise with a constant pressure dropping funnel, and the viscosity of the polymerization system increased with the progress of the polymerization reaction. After 2.5 hours of reaction, sodium hydroxide was added to the polymerization system to terminate the reaction, and the polymerization system was milky white. The mixture was extracted and separated three times, and water, ethanol and other volatile organic compounds were removed by rotary evaporator. The obtained polytetrahydrofuran was transferred to a vacuum drying oven, dried at 100° C. for 24 h, water and residual organic matter were completely removed, and a white waxy solid was obtained. The yield (%) was calculated by the following formula to obtain polytetrahydrofuran in 80% yield.

The above descriptions are merely examples of the present application, and are not intended to limit the present application. Various modifications and variations of this application are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the scope of the claims of this application.

Claims (10)

1. A method for preparing polytetrahydrofuran, which is characterized by comprising the following steps:

step 1, furfural is subjected to full hydrogenation reaction to generate tetrahydrofurfuryl alcohol

Adding furfural, catalyst and solvent into a high-pressure reaction kettle, wherein the active center of the catalyst in the step is one or more of Pt, Ru, Pd, Ni, Rh and Co, sealing the reaction kettle, and introducing N₂Replacing air in the reaction kettle, and introducing H into the reaction kettle₂Raising the temperature of the reaction kettle to 100-150 ℃, and releasing H after the reaction kettle is cooled after the reaction is finished₂Filtering the catalyst and removing the solvent by rotary evaporation to obtain tetrahydrofurfuryl alcohol;

step 2, decarbonylation of tetrahydrofurfuryl alcohol to prepare tetrahydrofuran

Loading the catalyst into a fixed bed reactor for H₂Reducing under atmosphere, wherein the active center of the catalyst in the step is one or more of Pd, Pt, Ru, Ni, Au, Co and Fe, pumping tetrahydrofurfuryl alcohol into a fixed bed reactor after the reduction is finished, and carrying out reaction in the presence of H₂Reacting under atmosphere, and discharging reaction liquid from the fraction pipe every reaction period;

step 3, tetrahydrofuran ring-opening polymerization is carried out to prepare polytetrahydrofuran

Adding a catalyst and tetrahydrofuran into a reaction bottle, wherein the catalyst in the step is liquid acid and AlCl₃、FeCl₃、PW₁₂/SiO₂、PMo₂/SiO₂、SiW₁₂/Al₂O₃、SiMo₁₂/Al₂O₃ZSM-5 molecular sieve, MCM-42 molecular sieve, H-Beta molecular sieve, HUSY molecular sieve and SiO₂-TiO₂、SiO₂-ZrO₂、TiO₂-ZrO₂、SiO₂-Al₂O₃Heating to 25-60 deg.C, slowly dripping initiator (one or more of ethylene oxide, propylene oxide, ethylene oxide chloride, oxetane, epichlorohydrin and acetic anhydride) with constant pressure dropping funnel, and introducing N₂Protecting, adding ethanol after the reaction is finished to terminate the reaction, filtering, concentrating the kettle liquid, and drying in vacuum to obtain the polytetrahydrofuran.

2. The method according to claim 1, wherein the method of step 1The carrier of the catalyst is full-silicon molecular sieve, diatomite, carbon material and Al₂O₃、SiO₂One or more of (a).

3. The method according to claim 1, wherein the solvent in step 1 is one or more selected from water, ethanol, alkane, and cycloalkane.

4. The method according to claim 1, wherein the volume ratio of furfural to solvent in step 1 is 10: 1-1: 10.

5. the method of claim 1, wherein H in step 1 is₂The pressure is 2.0-6.0MPa, and the reaction time is 1-8 h.

6. The method of claim 1, wherein in step 2, the catalyst is in H₂The reduction temperature under the atmosphere is 400-800 ℃, and the reduction time is 5-10 h.

7. The method according to claim 1, wherein the carrier of the catalyst in the step 2 is SiO₂、Al₂O₃And C.

8. The method as claimed in claim 1, wherein the reaction temperature in step 2 is 300-400 ℃, the reaction time is 1-4H, and H is₂The pressure is 2-4MPa, and the air inlet speed is 15-200 mL/min.

9. The method of claim 1, wherein the reaction time in step 3 is 2 to 8 hours.

10. The method according to claim 1, wherein the vacuum drying in step 3 is drying in a vacuum oven at 100 ℃ for 24 hours.