A method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw

Abstract

The invention discloses a method for producing furfural and 5-hydroxymethylfurfural simultaneously by utilizing metal-rich straw, wherein the method mixes the crushed metal-rich straw with water, adjusts the pH value of the mixture to acidity, then performs hydrothermal pretreatment, adds persulfate for activation pretreatment after cooling, adds an extraction phase, performs catalytic reaction, and obtains furfural and 5-hydroxymethylfurfural. The method of the invention uses the metal elements in the metal-rich straw as transition metal activators, does not require additional activation means, has obvious cost advantages, and has simple process, high yield, and short time consumption. It is suitable for the safe treatment of large-scale metal-rich biomass and the value-added treatment of plant repair biomass and biomass collected in polluted areas, and has good market prospects.

Description

Technical Field

[0001] The invention belongs to the field of chemical technology and agricultural waste resource utilization, relates to a biorefining scheme, and specifically relates to a method for simultaneously producing furfural and 5-hydroxymethylfurfural by utilizing metal-rich straw. Background Art

[0002] Phytoremediation technology is an effective and widely used soil remediation method. However, the safe disposal of hyperaccumulators that have completed the remediation task has become a problem. For the two sources of metal-rich biomass mentioned above, traditional methods of waste biomass treatment, such as direct disposal, incineration, and returning to the field, will cause metal elements to be released back into the environment, causing secondary pollution. Therefore, exploring a green and effective treatment strategy will open up a new direction for the application of phytoremediation technology and the sustainable utilization of metal-rich biomass.

[0003] At present, the research on obtaining value-added chemicals from biomass has attracted people's attention. Furfural and 5-hydroxymethylfurfural are potential components for the production of various industrially important organic parts, and are listed by the U.S. Department of Energy as the top ten multifunctional platform chemicals that can be made from lignocellulose. The traditional production of 5-hydroxymethylfurfural and furfural usually requires the isomerization and dehydration of sugars under acidic conditions, such as glucose, fructose, and xylose, and requires the addition of exogenous metal salts or acid catalysts, which increases the production cost and hinders market promotion. Generally speaking, furfural is produced from the hemicellulose part of lignocellulosic biomass, while 5-hydroxymethylfurfural is obtained by catalytic conversion of the cellulose part. In the production process using lignocellulosic biomass as raw material, cellulose and hemicellulose are first depolymerized into small sugar molecules under acidic hydrothermal conditions, and then these sugars undergo dehydration reactions to produce corresponding furan chemicals. However, the structure of lignocellulosic biomass is complex, and the conversion rate of the target product is not high. Efficient pretreatment methods are often required to destroy the lignocellulose structure to release cellulose and hemicellulose. In most current studies, the higher yields of furfural and 5-hydroxymethylfurfural are calculated based on cellulose, hemicellulose, and sugars, while the yields based on the original biomass conversion are concentrated at 5-10%. At the same time, there are few studies on the efficient production of furfural and 5-hydroxymethylfurfural using wood cellulosic biomass. In view of this, how to directly produce high-value furfural and 5-hydroxymethylfurfural chemicals simultaneously through metal-rich biomass and reduce production costs is of great significance for improving the utilization rate of such biomass. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for simultaneously producing furfural and 5-hydroxymethylfurfural by utilizing metal-rich straw with high catalytic efficiency, relatively high yield and low cost.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw comprises the following steps:

[0007] The crushed metal-rich straw is mixed with water in a ratio of 1 g: 10 mL to 50 mL, the pH value of the obtained mixture is adjusted to 2 to 6, and a hydrothermal pretreatment is performed at 140° C. to 200° C. After cooling, persulfate is added for activation pretreatment, wherein the concentration of the persulfate in the hydrothermal pretreatment product is 10 mmol / L to 90 mmol / L, and then an extraction phase is added, and a catalytic reaction is performed at 140° C. to 220° C. to obtain furfural and 5-hydroxymethylfurfural.

[0008] In the above method of using metal-rich straw to simultaneously produce furfural and 5-hydroxymethylfurfural, preferably, the volume ratio of the extraction phase to water is 1:1-2.

[0009] In the above method of simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw, preferably, the metal elements contained in the metal-rich straw include one or more of Fe, Mn, Cu, Zn and Cr.

[0010] In the above method of simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw, preferably, the metal-rich straw includes one or more of rice straw, soybean straw and corn straw, but is not limited thereto.

[0011] In the above method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw, preferably, the extraction phase comprises one or more of methyl isobutyl ketone, dimethyl sulfoxide and methanol.

[0012] In the above method of using metal-rich straw to simultaneously produce furfural and 5-hydroxymethylfurfural, preferably, the persulfate is potassium hydrogen persulfate or potassium persulfate.

[0013] In the above method of using metal-rich straw to simultaneously produce furfural and 5-hydroxymethylfurfural, preferably, the activation pretreatment time is 10 minutes to 30 minutes.

[0014] In the above method of using metal-rich straw to simultaneously produce furfural and 5-hydroxymethylfurfural, preferably, the hydrothermal pretreatment time is 0.5h to 2h.

[0015] In the above method of using metal-rich straw to simultaneously produce furfural and 5-hydroxymethylfurfural, preferably, the catalytic reaction time is 1 hour to 3 hours.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] (1) The present invention provides a method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw, thereby achieving the purpose of catalytically producing high-value furan chemicals directly from agricultural and forestry waste straw, and avoiding the use of high-cost raw materials and reagents. In the present invention, metal-rich straw grown from metal-contaminated areas is collected as raw material, and hydrothermal pretreatment is used to promote the migration of metal elements enriched in the straw to the liquid phase, thereby obtaining a mixed solution containing exuded metals, which acts as a transition metal activator to cooperate with persulfate to further destroy the structure of lignocellulosic biomass, thereby better achieving the transformation from "straw → pentose / hexose → 5-hydroxymethylfurfural / furfural". The hydrothermal synergistic persulfate oxidation technology can directly catalyze the metal-rich straw to produce high-value furfural and 5-hydroxymethylfurfural. Compared with the existing synthesis methods of furfural and 5-hydroxymethylfurfural, the method of the present invention using metal-rich straw to simultaneously produce furfural and 5-hydroxymethylfurfural has the advantages of low raw material cost, simple operation, short time consumption, no need for additional addition of metal catalysts, and simultaneous production of two furan chemicals with high yield. It is suitable for the safe treatment of large-scale metal-rich biomass and the value-added treatment of plant restoration biomass and biomass collected in polluted areas, and has a good market prospect.

[0018] (2) In the method of the present invention, Fe, Mn, Cu, Zn, and Cr in the metal-rich straw are partially transferred to the solution during the hydrothermal pretreatment process, playing the role of transition metal activators, avoiding the use of additional activators, and having certain cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a graph showing the influence of different solid-liquid ratios on the yields of furfural and 5-hydroxymethylfurfural in Example 1 of the present invention.

[0020] Figure 2 The figure is a graph showing the effect of different pH values ​​on the yields of furfural and 5-hydroxymethylfurfural in Example 1 of the present invention.

[0021] Figure 3 This is a graph showing the effect of different hydrothermal pretreatment temperatures on the yields of furfural and 5-hydroxymethylfurfural in Example 1 of the present invention.

[0022] Figure 4 The figure is a graph showing the influence of different persulfate concentrations on the yields of furfural and 5-hydroxymethylfurfural in Example 1 of the present invention.

[0023] Figure 5 The figure is a graph showing the influence of different reaction temperatures on the yields of furfural and 5-hydroxymethylfurfural in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0025] Embodiment 1:

[0026] A method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw of the present invention, specifically catalyzing the metal-rich straw to simultaneously generate furfural and 5-hydroxymethylfurfural by hydrothermal coordinated persulfate oxidation technology, comprises the following steps:

[0027] 1g of crushed rice straw is mixed with 40mL of water (preferably ultrapure water), and the metal content in the rice straw is: Fe573.5mg / kg, Mn 293.2mg / kg, Cu 35.1mg / kg, Zn 135.8mg / kg, Cr 55.6mg / kg, and the resulting mixture is adjusted to pH 3, and the mixture is hydrothermally pretreated at 180°C for 1h and then cooled, and KHSO5 is added to make the concentration of KHSO5 30mM, and the activation pretreatment is performed for 30min. 20mL of methyl isobutyl ketone is added as an extraction phase, so that 5-hydroxymethylfurfural and furfural in the aqueous phase can be effectively extracted and stored during the thermal catalytic reaction, and then the catalytic reaction is carried out at 200°C for 2h. After the reaction is completed, solid-liquid separation is performed by a circulating vacuum pump to obtain furfural and 5-hydroxymethylfurfural. The concentrations of furfural and 5-hydroxymethylfurfural in the solution obtained by solid-liquid separation were detected by high performance liquid chromatography, and the results showed that the yields of furfural and 5-hydroxymethylfurfural were 22.5wt% and 18.6wt%, respectively. 5-hydroxymethylfurfural and furfural in the organic phase can be separated by extraction with dichloromethane.

[0028] The effects of different reaction parameters on the yields of furfural and 5-hydroxymethylfurfural were investigated, specifically using a method substantially the same as in Example 1, except that:

[0029] (1) Different solid-liquid ratios

[0030] 1g of crushed rice straw was mixed with 10, 20, 30, 40, and 50mL of water, respectively, and the pH was adjusted to 3 before hydrothermal pretreatment at 180°C for 1h, and then 30mM KHSO5 was added for persulfate oxidation pretreatment for 30min. After adding 20mL of methyl isobutyl ketone as the extraction phase, the catalytic reaction was carried out at a reaction temperature of 200°C for 2h. After the reaction was completed, solid-liquid separation was carried out by a circulating vacuum pump, and the concentrations of furfural and 5-hydroxymethylfurfural in the solution obtained by solid-liquid separation were detected.

[0031] (2) Different pH

[0032] 1g of crushed rice straw was mixed with 40mL of aqueous solution, and the pH was adjusted to 2, 3, 4, 5, and 6, and then hydrothermally pretreated at 180°C for 1h, and then 30mM KHSO5 was added for persulfate oxidation pretreatment for 30min. After adding 20mL of methyl isobutyl ketone as the extraction phase, the catalytic reaction was carried out at a reaction temperature of 200°C for 2h. After the reaction was completed, solid-liquid separation was carried out by a circulating vacuum pump, and the concentrations of furfural and 5-hydroxymethylfurfural in the solution obtained by solid-liquid separation were detected.

[0033] (3) Different hydrothermal temperatures

[0034] 1g of crushed rice straw was mixed with 40mL of aqueous solution, and the pH was adjusted to 3 before hydrothermal pretreatment at 140, 160, 180, and 200°C for 1h, and then 30mM KHSO5 was added for persulfate oxidation pretreatment for 30min. After adding 20mL of methyl isobutyl ketone as the extraction phase, the catalytic reaction was carried out at a reaction temperature of 200°C for 2h. After the reaction was completed, solid-liquid separation was performed by a circulating vacuum pump, and the concentrations of furfural and 5-hydroxymethylfurfural in the solution obtained by solid-liquid separation were detected.

[0035] (4) Different peroxymonosulfate concentrations

[0036] 1g of crushed rice straw was mixed with 40mL of aqueous solution, and the pH was adjusted to 3 before hydrothermal pretreatment at 180℃ for 1h, and then 10, 30, 50, 70, and 90mM KHSO5 was added for persulfate oxidation pretreatment for 30min. After adding 20mL of methyl isobutyl ketone as the extraction phase, the catalytic reaction was carried out at a reaction temperature of 200℃ for 2h. After the reaction was completed, solid-liquid separation was carried out by a circulating vacuum pump, and the concentrations of furfural and 5-hydroxymethylfurfural in the solution obtained by solid-liquid separation were detected.

[0037] (5) Different reaction temperatures

[0038] 1 g of crushed rice straw was mixed with 40 mL of aqueous solution, and the pH was adjusted to 3 before hydrothermal pretreatment at 180 ° C for 1 h, and then 30 mM KHSO5 was added for persulfate oxidation pretreatment for 30 min. After adding 20 mL of methyl isobutyl ketone as the extraction phase, the catalytic reaction was carried out at reaction temperatures of 140, 160, 180, 200, and 220 ° C for 2 h. After the reaction was completed, solid-liquid separation was performed by a circulating vacuum pump, and the concentrations of furfural and 5-hydroxymethylfurfural in the solution obtained by solid-liquid separation were detected.

[0039] Figures 1 to 5 : is the influence change diagram of different reaction parameters on the yield of furfural and 5-hydroxymethylfurfural in this Example 1, wherein: Figure 1 The effect of different solid-liquid ratios on the yield, Figure 2 The effect of different pH on the yield is shown in Figure 2. Figure 3The effect of different hydrothermal pretreatment temperatures on the yield, Figure 4 The effect of different persulfate concentrations on the yield, Figure 5 It can be seen from the figure that under the conditions of solid-liquid ratio of 1g:40mL, pH of 3, hydrothermal temperature of 180°C, persulfate concentration of 30mM, and reaction temperature of 200°C, the yields of furfural and 5-hydroxymethylfurfural can reach 22.5wt% and 18.6wt% respectively.

[0040] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw, characterized in that: The following steps are involved: The crushed metal-rich straw is mixed with water in a ratio of 1g:10mL-50mL, wherein the metal contents of the metal-rich straw are 573.5mg / kg of Fe, 293.2mg / kg of Mn, 35.1mg / kg of Cu, 135.8mg / kg of Zn and 55.6mg / kg of Cr, the pH value of the obtained mixture is adjusted to 2-6, and a hydrothermal pretreatment is performed at 140°C-200°C, and after cooling, persulfate is added for activation pretreatment, wherein the concentration of the persulfate in the hydrothermal pretreatment product is 10mmol / L-90mmol / L, and then an extraction phase is added, and a catalytic reaction is performed at 140°C-220°C to obtain furfural and 5-hydroxymethylfurfural.

2. The method for simultaneously producing furfural and 5-hydroxymethylfurfural by utilizing metal-rich straw according to claim 1, characterized in that: The volume ratio of the extraction phase to water is 1:1-2.

3. The method for simultaneously producing furfural and 5-hydroxymethylfurfural by utilizing metal-rich straw according to claim 1, characterized in that: The metal-rich straw includes one or more of rice straw, soybean straw and corn straw.

4. The method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw according to any one of claims 1 to 3, characterized in that: The extraction phase includes one or more of methyl isobutyl ketone, dimethyl sulfoxide and methanol.

5. The method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw according to any one of claims 1 to 3, characterized in that: The persulfate is potassium hydrogen persulfate or potassium persulfate.

6. The method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw according to any one of claims 1 to 3, characterized in that: The activation pretreatment time is 10 min to 30 min.

7. The method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw according to any one of claims 1 to 3, characterized in that: The time of the hydrothermal pretreatment is 0.5h to 2h.

8. The method for simultaneously producing furfural and 5-hydroxymethylfurfural using metal-rich straw according to any one of claims 1 to 3, characterized in that: The catalytic reaction time is 1 h to 3 h.

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