Regulation and control method for catalyzing transfer hydrogenation and etherification of biomass-based aldehydes

Abstract

The invention discloses a regulation and control method for catalyzing transfer hydrogenation and etherification of biomass-based aldehydes, which comprises the following steps: synthesizing a mesoporous molecular sieve carrier by a hydrothermal method, preparing a catalyst loading 5-20wt% of Zr by an equivalent-volume impregnation method, and regulating selective transfer hydrogenation and etherification of a biomass-based aldehyde compound in an alcohol solvent by controlling temperature programming, calcining and activating of the catalyst. And selective distribution of hydrogenation products and etherification products is realized. Taking furfural and cinnamyl aldehyde as examples, under the condition of reaction for 2-12 hours at 100-180 DEG C in an alcohol solvent, an unactivated catalyst can catalyze complete conversion of a substrate, and the selectivity of hydrogenated products furfuryl alcohol and cinnamyl alcohol can reach 94% and 85%; after the temperature of the catalyst is raised to 100-500 DEG C for activation, the main product is changed from alcohol to ether, and the selectivity of furfuryl ether and cinnamyl ether of etherification products can reach 65% and 60%; the selectivity of hydrogenation and etherification reactions can be further improved by regulating and controlling reaction conditions.

Description

Technical Field

[0001] This invention relates to the fields of chemical engineering and energy, specifically to biomass-based aldehyde transfer hydrogenation and etherification reaction processes, applicable to the heterogeneous catalytic conversion and high-value utilization of biomass-based platform compounds. Background Technology

[0002] Biomass resources are the fourth largest carbon-containing resource, and their high-value utilization is an important direction for alleviating the energy crisis and achieving green and sustainable development. Biomass resources such as corn cobs, sugarcane bagasse, and citrus peels, as well as agricultural and forestry wastes, can be catalytically converted to yield a series of biomass-based platform compounds, such as furfural and 5-hydroxymethylfurfural, and unsaturated organic aldehydes and ketones, such as cinnamaldehyde and citral. These unsaturated aldehydes and ketones can be further converted into high-value-added compounds, such as polycondensable unsaturated alcohol ether monomers or high-boiling-point, high-calorific-value saturated alcohol ethers, through reactions such as hydrogenation and etherification. This represents an extension and expansion of the biomass refining pathway. On the one hand, biomass-based unsaturated aldehydes are abundant, and developing green, low-cost, high-value conversion pathways is of practical significance for achieving fuel and chemical substitution under the "dual carbon" background. On the other hand, biomass-based unsaturated aldehydes simultaneously possess aromatic benzene or furan rings, olefin double bonds, and aldehyde carbon-oxygen double bonds, and can undergo various competing reactions such as oxidation, reduction, disproportionation, condensation, and polymerization under the influence of multiple sites in acids, bases, and metals. Studying its selective transfer hydrogenation and etherification reaction mechanisms can provide common rules for the efficient and selective catalytic transformation of other bio-based platform compounds, and promote the development of the "precise bond breaking / bonding" catalytic concept in biomass conversion.

[0003] Catalytic transfer hydrogenation plays a crucial role in fine chemicals and organic synthesis. Compared to hydrogen reduction, which is mostly carried out under high temperature and pressure, it allows for the hydrogenation reduction of substrates under relatively mild conditions. Currently, catalytic transfer hydrogenation of biomass-based unsaturated aldehydes such as furfural, 5-hydroxymethylfurfural, and cinnamaldehyde often uses alcohols (such as methanol, ethylene glycol, and isopropanol) as both hydrogen sources and green solvents. During the reaction, aldehydes can be hydrogenated to corresponding alcohols such as furfuryl alcohol, furanyl dimethyl alcohol, and cinnamyl alcohol, or further etherified to corresponding etherified products such as alkoxyfurfural ether and cinnamyl ether. The selective control of hydrogenation and etherification remains challenging. Some studies report combined statistics of furfuryl alcohol and its etherified products as data on the activity and selectivity of transfer hydrogenation. While hydrogenation is relatively easy to achieve, it still suffers from selective instability and poor cycle life. Research on highly selective etherification is relatively limited, requiring harsh reaction conditions, typically high temperature and pressure. Some studies still achieve hydrogenation and etherification in a hydrogen atmosphere. For example, when using furfural as a substrate, Zhang Zongchao et al., in patent CN202110505144.2, used a 15% Ni-5% Fe / ZrO2 catalyst in isopropanol solvent, under a H2 pressure of 4 MPa, to catalyze the reaction of furfural at 230°C for 4 hours, achieving a difurfuryl ether yield of 90%. Under the same isopropanol and hydrogen conditions, Yang Jinghe et al., in patent CN202310059148.1, used a 4.5 wt% Cu / SiO2 catalyst to catalyze the reaction of furfural at 150°C for 8 hours, achieving a conversion rate of 99.7%, mainly yielding isopropyl furfuryl ether with a selectivity of 80.3%. When using 5-hydroxymethylfurfural as a substrate, Qi Haisong et al. in patent CN201811538975.4 used Zr / LS as a catalyst and reacted in isopropanol at 120℃ for 8 hours, achieving a conversion rate of 95% and obtaining 5-isopropoxymethyl-2-furan methanol with a selectivity of 90%. Hu Lei et al. in patent CN202211453137.3 used sulfonated Zr-BDC-SO3H-2 as a catalyst and reacted in the same solvent and temperature for 3 hours, obtaining 2,5-diisopropoxymethylfuran with a selectivity and yield of 96.9%.

[0004] In summary, the hydrogenation and etherification of biomass-based aldehydes still exhibit significant selectivity differences. On the one hand, achieving highly selective hydrogenation and etherification requires stringent reaction condition control and specific catalyst types. On the other hand, under the same reaction conditions, different substrates and catalysts result in significantly different products, leading to poor universality and difficulty in extending the application to other biomass-based aldehydes to obtain target products with corresponding selectivity. Therefore, to address the limitations of existing technologies regarding the selectivity differences in the transfer hydrogenation and etherification of aldehydes, this invention provides a method for controlling the selective transfer hydrogenation and etherification of biomass-based aldehydes. This method employs a hydrothermal synthesis of mesoporous molecular sieve supports, prepares a catalyst supported on 5-20 wt.% Zr using an equal-volume impregnation method, and controls the selective transfer hydrogenation and etherification of biomass-based aldehydes in alcohol solvents by controlling the programmed temperature calcination activation of the catalyst, thereby achieving a selective distribution of hydrogenation and etherification products. Taking furfural and cinnamaldehyde as examples, under the conditions of reaction in alcohol solvent at 100-180℃ for 2-12 h, the unactivated catalyst can catalyze the complete conversion of the substrate, and the selectivity of the hydrogenation products furfuryl alcohol and cinnamaldehyde can reach 94% and 85%, respectively. After the catalyst is activated by temperature programmed increase of 100-500℃, the main product changes from alcohol to ether, and the selectivity of the etherification products furfuryl ether and cinnamaldehyde can reach 65% and 60%, respectively. By adjusting the reaction conditions, the selectivity of the hydrogenation and etherification reactions can be further improved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for selectively transferring hydrogenation and etherification of biomass-based aldehydes. This method provides a target product-oriented selective catalytic conversion pathway for the catalytic conversion of existing biomass-based aldehyde compounds such as furfural and cinnamaldehyde, and realizes a green control strategy for converting biomass-based alcohols and ethers from sustainable and renewable raw materials into high-value-added chemical biomass-based alcohols and ethers.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: Mesoporous molecular sieve supports were synthesized using a hydrothermal method, and catalysts loaded with 5-20 wt.% Zr were prepared using an equal-volume impregnation method. By controlling the programmed temperature calcination activation of the catalyst, the selective transfer hydrogenation and etherification of biomass-based aldehydes in alcohol solvents were regulated, achieving selective distribution of hydrogenation and etherification products. Taking furfural and cinnamaldehyde as examples, under conditions of reaction at 100-180℃ for 2-12 h in alcohol solvents, the unactivated catalyst could catalyze the complete conversion of the substrate, with selectivities of 94% and 85% for the hydrogenation products furfuryl alcohol and cinnamaldehyde, respectively. After catalyst activation at a programmed temperature of 100-500℃, the main product changed from alcohol to ether, with selectivities of 65% and 60% for the etherification products furfuryl ether and cinnamaldehyde, respectively. Adjusting the reaction conditions could further improve the selectivity of the hydrogenation and etherification reactions.

[0007] The specific process is as follows: The catalyst support of this invention is a mesoporous molecular sieve, including MCM-41, MCM-48, and SBA-15 molecular sieves; the supported metal precursor is ZrO(NO3)2; the loading amount is 5 wt.% ~ 20 wt.% (g Zr / g molecular sieve). An equal-volume impregnation method is used, utilizing water with the saturated water absorption capacity of the molecular sieve to prepare an equal volume of ZrO(NO3)2 precursor impregnation solution. The corresponding amount of support is added during stirring to ensure uniform mixing. The mixture is stirred for 5 min, ultrasonically treated for 1-3 min, covered with filter paper, allowed to stand for 24 h, and then dried in an oven at 110℃ for 12 h.

[0008] The mesoporous molecular sieve of the present invention is synthesized by hydrothermal method. Taking MCM-41 as an example: the template agent hexadecyltrimethylammonium bromide is added to distilled water and stirred to dissolve. The pH is adjusted to 11 with ammonia water. After adding tetraethyl orthosilicate, the mixture is stirred for 1 hour. The mixture is then transferred to a polytetrafluoroethylene hydrothermal reactor and hydrothermally crystallized at 100°C for 10 hours. After cooling and filtration, the filter cake is washed until neutral and dried at 80°C for 10 hours. Then, it is placed in a tube furnace and calcined at 550°C for 2 hours with a programmed temperature increase of 5°C / min to remove the template agent and obtain the carrier powder.

[0009] The catalyst programmed temperature calcination activation process of the present invention involves placing 0.2-0.5 g of the catalyst according to claim 4 in a calcination tube, introducing N2, adjusting the gas flow rate to 0.5-10 mL / min, setting the temperature program as follows: initial temperature 30℃, heating rate 5℃ / min, final temperature 100-500℃, holding at that temperature for 120 min, cooling down after completion, and then using it immediately.

[0010] The experimental apparatus described in this invention is a high-temperature, high-pressure reactor with a polytetrafluoroethylene liner, a magnetic stirrer, and a temperature control device. Before the reaction, it is purged with nitrogen and sealed. In the process conditions, the biomass-based aldehyde compound can be one of unsaturated aldehyde compounds such as furfural, 5-hydroxymethylfurfural, cinnamaldehyde, and citral. Taking furfural and cinnamaldehyde as examples, the substrate concentration is 0.5–35 wt.%, preferably 5–20 wt.%; the alcohol solvent is one of methanol, ethanol, and isopropanol, preferably isopropanol; the catalyst-to-substrate mass ratio is 5%–50 wt.%, preferably 10–25 wt.%; and the reaction temperature is 120–170 °C. o C, preferably 130-160 o C; The reaction time is 2~10 h, preferably 2~8 h.

[0011] Compared with existing technologies, the method of this invention has the following characteristics: 1. The method of this invention is a green pathway for the sustainable and renewable biomass-based aldehyde compounds to produce high-value-added chemicals such as biomass-based alcohols and ethers, and is a means to realize the deep processing of biomass resources and further green fine chemical industry.

[0012] 2. This invention utilizes a simple and effective programmed temperature calcination method to activate Zr-based catalysts supported on mesoporous molecular sieves, enabling the regulation of unsaturated aldehyde transfer hydrogenation and etherification, as well as the selective distribution of hydrogenation and etherification products. This provides a target product-oriented selective catalytic conversion regulation strategy for the efficient conversion of existing biomass resources. Detailed Implementation

[0013] The following examples will help to understand the present invention, but the scope of the present invention is not limited thereto.

[0014] Example 1: Synthesis method of mesoporous molecular sieve MCM-41 catalyst support: 1.5g of cetyltrimethylammonium bromide was added to 65mL of distilled water and stirred to dissolve. The pH was adjusted to 11 with ammonia water. 5g of tetraethyl orthosilicate was added and stirred for 1h. The mixture was then transferred to a hydrothermal reactor with a polytetrafluoroethylene liner and hydrothermally crystallized at 100℃ for 10h. After cooling and filtration, the filter residue was washed until neutral and dried at 80℃ for 10h. The residue was then placed in a tube furnace and calcined at 550℃ for 2h with a programmed temperature increase of 5℃ / min to remove the template agent, resulting in a powder support.

[0015] Example 2: Synthesis method of catalyst support mesoporous molecular sieve MCM-48: Take a round-bottom flask, add 7.643g hexadecyltrimethylammonium bromide, 0.645g NaOH, 0.123g NH4F and 36mL water, stir to dissolve, react in a water bath at 35℃ for 3 h, add about 8.98g tetraethyl orthosilicate and stir for 3 h, then transfer to a hydrothermal reactor with a polytetrafluoroethylene liner, crystallize at 100℃ for 12 h, cool and filter, wash with deionized water until neutral, dry at 100℃, and remove the template agent in the same way as above.

[0016] Example 3: Synthesis method of SBA-15 mesoporous molecular sieve supported by catalyst: Take a 100 mL beaker, add 2.00 g P123, 10 mL concentrated hydrochloric acid and 53 mL deionized water, stir to form a homogeneous solution, and slowly add 4.3 mL tetraethyl orthosilicate. Continue stirring at 40 °C for 5 h. Transfer to a reaction vessel lined with polytetrafluoroethylene, crystallize at 100 °C for 12 h, cool and filter, wash with deionized water until neutral, and dry at 100 °C. The method for removing the template agent is the same as above.

[0017] Example 4: Preparation of supported Zr catalyst: Taking 10wt.% Zr / MCM-41 as an example: Take 0.25g ZrO(NO3)2 hydrate (i.e. containing 0.1g Zr) in a beaker, add an appropriate amount of distilled water to dissolve and grind Amberlyst-15 (unsieved) in a small beaker, add a small amount of distilled water to obtain zirconium oxynitrate solution, then add 0.90g of uniformly calcined MCM-41 support, stir and impregnate to form a uniform slurry mixture, let stand for 24h, and then put it into an oven to dry at 100℃.

[0018] Example 5: Catalyst temperature-programmed activation: 0.5 g of catalyst was placed in a calcination tube, N2 was introduced, the temperature controller was turned on and the temperature-programmed activation was set. The initial temperature was 30°C, the activation temperature was 100°C-600°C, and the temperature was increased to the activation temperature at a rate of 5°C / min. The temperature was held for 120 min. After the activation was completed, the temperature program was stopped, and the catalyst was taken out after cooling to room temperature.

[0019] Example 6: Furfural Hydrogenation and Etherification: In a polytetrafluoroethylene-lined tube, 20 mL of isopropanol was used as the solvent, and 0.2 g of furfural and 0.1 g of catalyst were added. A stir bar was placed inside (600 rpm), the tube was sealed, and the air was purged with nitrogen. The temperature was increased to 150 °C at a rate of 10 °C / min for 4 hours. After the reaction, the reaction solution was filtered and stored. 0.2 mL of the reaction solution, 0.1 mL of 20 mg / mL n-pentanol, and 0.1 mL of isopropanol were mixed to prepare a 0.4 mL solution for gas chromatography detection. Single-point quantification and area normalization methods were used to qualitatively and quantitatively analyze the residual substrate and product in the reaction solution.

[0020] Example 7: Cinnamaldehyde Hydrogenation and Etherification: In a polytetrafluoroethylene-lined tube, 0.2 g of cinnamaldehyde and 0.1 g of catalyst were added to 20 mL of isopropanol as solvent, and a stir bar (600 rpm) was placed inside. After sealing, the air was purged with nitrogen, and the temperature was increased to 150 °C at a rate of 10 °C / min for 8 h. After the reaction, the reaction solution was filtered and stored. 0.1 mL of the reaction solution was mixed with 0.1 mL of a 10 mg / mL n-pentanol internal standard solution and used for gas chromatography detection. Single-point quantification and area normalization methods were used for qualitative and quantitative analysis of the residual substrate and product in the reaction solution.

[0021] Table 1. Mesoporous molecular sieve-supported Zr catalyst catalyzes the hydrogenation and etherification of furfural. Note: Experimental conditions were: 0.2g furfural, 0.1g catalyst, 20mL alcohol solvent, reaction at 150℃ for 4h, and stir bar speed of 600rpm; d 400 That is, the catalyst is calcined at 400℃.

[0022] The results of the transfer hydrogenation and etherification reactions of furfural catalyzed by Zr catalysts supported on mesoporous molecular sieves are shown in Table 1 above. The experimental results show that the unactivated catalyst can catalyze the highly selective conversion of furfural to furfuryl alcohol under the experimental conditions, with 10% Zr / MCM-48 catalyst yielding 94% furfuryl alcohol. The catalyst activated by calcination at 400℃, under the same conditions, mainly yields etherified products of furfural catalyzed by 10% Zr / SBA-15-d catalyst. 400The selectivity for catalyzing furfural to isopropoxyfurfuryl ether can reach 65%. In addition, although the activity of the unactivated catalyst in ethanol for the conversion of furfural is slightly lower than that in isopropanol solvent, it also shows a similar trend with high selectivity for hydrogenation products. 10% Zr / MCM-48 catalyzes 86% conversion of furfural, and the selectivity for furfuryl alcohol is 66%.

[0023] Table 2. Mesoporous molecular sieve-supported Zr catalyst catalyzes the hydrogenation and etherification of cinnamaldehyde. Note: Experimental conditions were: 0.2 g cinnamaldehyde, 0.1 g catalyst, 20 mL isopropanol, reaction time 4 h, stir bar speed 600 rpm; d 400 That is, the catalyst is calcined at 400℃.

[0024] The results of the catalytic hydrogenation and etherification reactions of cinnamaldehyde using Zr catalysts supported on mesoporous molecular sieves are shown in Table 2 above. The experimental results indicate that the unactivated catalyst can catalyze the highly selective conversion of cinnamaldehyde to cinnamyl alcohol under the experimental conditions, with 10% Zr / MCM-41 catalyst yielding 85% cinnamyl alcohol. The catalyst activated by calcination at 500℃ catalyzes furfural mainly to yield the etherification product under the same conditions, with 10% Zr / SBA-15-d catalyst showing the best results. 400 The selectivity for catalytic conversion of cinnamaldehyde alcohol to isopropoxycinnamyl ether can reach 60%.

[0025] In summary, this invention provides a method for controlling the transfer hydrogenation and etherification of biomass-based aldehydes. By controlling the programmed temperature calcination of the activated mesoporous molecular sieve-supported Zr catalyst, the selective transfer hydrogenation and etherification of aldehydes in alcohol solvents can be regulated, achieving selective distribution of hydrogenation and etherification products. Taking furfural and cinnamaldehyde as examples, under the condition of reaction at 100-180℃ for 2-12 h in alcohol solvents, the unactivated catalyst can catalyze the complete conversion of the substrate, with selectivity of 94% and 85% for the hydrogenation products furfuryl alcohol and cinnamaldehyde, respectively. After activation at a programmed temperature of 100-500℃, the main product changes from alcohol to ether, with selectivity of 65% and 60% for the etherification products furfuryl ether and cinnamaldehyde, respectively. This invention achieves selective control of biomass-based alcohols and ethers from sustainable and renewable raw materials to high-value-added chemicals, providing a target product-oriented selective catalytic conversion pathway and green control strategy for biomass catalytic conversion.

Claims

1. A method for regulating the transfer hydrogenation and etherification of biomass-based aldehydes, characterized in that: Mesoporous molecular sieve supports were synthesized using a hydrothermal method, and catalysts loaded with 5-20 wt.% Zr were prepared using an equal-volume impregnation method. By controlling the programmed temperature rise and calcination activation of the catalyst, the selective transfer hydrogenation and etherification of biomass-based aldehydes in alcohol solvents were regulated, achieving selective distribution of hydrogenation and etherification products. Taking furfural and cinnamaldehyde as examples, under the condition of reaction at 100-180℃ for 2-12 h in alcohol solvent, the unactivated catalyst could catalyze the complete conversion of the substrate, with selectivity of 94% and 85% for the hydrogenation products furfuryl alcohol and cinnamaldehyde, respectively. After catalyst activation at a programmed temperature rise of 100-500℃, the main product changed from alcohol to ether, with selectivity of 65% and 60% for the etherification products furfuryl ether and cinnamaldehyde, respectively. Adjusting the reaction conditions can further improve the selectivity of hydrogenation and etherification reactions.

2. The method according to claim 1, characterized in that: The catalyst support is a mesoporous molecular sieve, including MCM-41, MCM-48 and SBA-15 molecular sieves; the supported metal precursor is ZrO(NO3)2; the loading amount is 5 wt.% ~ 20 wt.% (gZr / g molecular sieve).

3. The method according to claim 1, characterized in that: Mesoporous molecular sieves are synthesized by hydrothermal method. Taking MCM-41 as an example: the template agent hexadecyltrimethylammonium bromide is added to distilled water and stirred to dissolve. The pH is adjusted to 11 with ammonia water, tetraethyl orthosilicate is added and stirred for 1 hour. The mixture is then transferred to a polytetrafluoroethylene hydrothermal reactor and hydrothermally crystallized at 100°C for 10 hours. After cooling and filtration, the filter cake is washed until neutral and dried at 80°C for 10 hours. It is then placed in a tube furnace and calcined at 550°C for 2 hours with a programmed temperature increase of 5°C / min to remove the template agent and obtain the carrier powder.

4. The method according to claim 3, characterized in that: Using the equal-volume impregnation method, the carrier synthesized in claim 3 is used to prepare an equal amount of ZrO(NO3)2 precursor impregnation solution with water of its saturated water absorption capacity. The corresponding amount of carrier is added during stirring to make it evenly mixed. The mixture is stirred for 5 minutes, ultrasonically treated for 1 to 3 minutes, covered with filter paper, and allowed to stand for 24 hours. Then it is dried in an oven at 110°C for 12 hours.

5. The method according to claim 4, characterized in that: The catalyst programmed temperature calcination activation process involves placing 0.2-0.5 g of the catalyst from claim 4 in a calcination tube, introducing N2, adjusting the gas flow rate to 0.5-10 mL / min, setting the temperature program as follows: initial temperature 30℃, heating rate 5℃ / min, final temperature 100-500℃, holding at that temperature for 120 min, cooling down after completion, and using it immediately.

6. The method according to claim 1, characterized in that: The biomass-based aldehyde compound can be one of unsaturated aldehyde compounds such as furfural, 5-hydroxymethylfurfural, cinnamaldehyde, and citral. Taking furfural and cinnamaldehyde as examples, the substrate concentration is 0.5~35 wt.%; the alcohol solvent is one of low-carbon alcohols such as methanol, ethanol, and isopropanol; the catalyst to substrate feed mass ratio is 5%~50 wt.%; the reaction temperature is 100~180°C. o C; the reaction time is 2~12 h; the reaction apparatus is a high temperature and high pressure reactor with a magnetic stirrer and temperature control device and a polytetrafluoroethylene liner, which is purged and sealed with nitrogen before the reaction.

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