CN106669655B - Preparation method of solid acid catalyst for preparing 5-hydroxymethylfurfural from biomass - Google Patents

Abstract

The present invention relates to a preparation method of a solid acid catalyst for preparing 5-hydroxymethyl furfural from biomass. The solid acid catalyst is a composite of carbon and niobium pentoxide and has an amorphous structure. The preparation method comprises: using sugar compounds and the like as carbon sources, niobium tartrate, niobium oxalate, niobium citrate, niobium pentachloride or other niobium salts as niobium sources, inorganic or organic acids as catalysts, using hydrothermal or solvothermal methods The composite is prepared by the method, and then carbonized at high temperature under nitrogen to obtain a niobium-carbon solid acid catalyst. The solid acid catalyst is used for the dehydration reaction of sugars and cellulose, the yield of the product 5-hydroxymethyl furfural is high, the catalyst recycling performance is good, and it is a kind of very good biomass catalytic conversion to prepare 5-hydroxymethyl furfural catalyst.

Description

A kind of preparation of solid acid catalyst for preparing 5-hydroxymethyl furfural from biomass method

technical field

The invention relates to a preparation method of a solid acid catalyst for preparing 5-hydroxymethylfurfural from biomass, and relates to the fields of catalytic chemistry and biomass resource utilization.

Background technique

With the rapid growth of the world economy, the resources of fossil fuels (especially oil) have become increasingly scarce, and their utilization has also brought a series of social and environmental problems to human society. The research on synthetic fuels and fine chemicals from substances and their derivatives has become one of the hotspots of domestic and foreign scientists. Because biomass has the advantages of sustainability and wide sources, and 5-hydroxymethylfurfural is an important class of furan compounds, it can be used to prepare liquid fuel 2,5-dimethylfuran, long-chain alkanes, pharmaceutical intermediates 2,5-diformylfuran, polyester monomer 2,5-furandicarboxylic acid, etc. Therefore, the conversion of biomass and its derivatives into 5-hydroxymethylfurfural through dehydration reaction is an important factor for efficient utilization of biomass way.

At present, inorganic liquid acid is usually used as a catalyst for the reaction of dehydrating biomass or its derivatives to synthesize 5-hydroxymethylfurfural, which has problems such as difficult product separation, serious equipment corrosion and environmental pollution. It was found that 70% HMF yield can be obtained by converting glucose into 5-hydroxymethylfurfural (HMF) using ionic liquid and chloro-1-methyl-3-ethylimidazole as the reaction medium (Science, 2007, 316). , 1597); when converting cellulose, the yield of 5-hydroxymethylfurfural was 58% (GreenChem, 2011, 13, 1503). However, the current cost of ionic liquids is too high, and the catalysts used at the same time are mostly CrCl ₃ , and chromium pollutes the environment seriously, so its industrial application is greatly restricted. However, as a new trend in the development of catalysts, solid acid catalysts have the advantages of easy separation and recovery, reuse, and environmental friendliness compared to liquid acid catalysts, so they are widely used in biomass conversion. For example, Antonio Jiménez-López et al. use Al-MCM-41 to catalyze glucose to prepare HMF, and the yield can reach 63%, but the catalyst has poor stability. , 164, 70–76.). Du Yuguang's research group used WO ₃ -Ta ₂ O ₅ to catalyze the conversion of carbohydrates to prepare HMF, and obtained HMF with high yield and high stability (patent number: CN201110435929.3), but the tantalum source (tantalum chloride) in the material preparation process. , tantalum ethoxide, etc.) are expensive and not suitable for large-scale industrial production. Therefore, on this basis, we need to find a stable, efficient and economical solid acid catalyst for the preparation of HMF from biomass.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a preparation method of a solid acid catalyst, and to apply the method to the reaction of preparing 5-hydroxymethylfurfural from biomass.

In order to achieve the above object, the concrete technical scheme of the present invention is as follows:

A method for preparing a solid acid catalyst for preparing 5-hydroxymethyl furfural from biomass, characterized in that: one or more of saccharide compounds and a niobium precursor are hydrothermally heated at a certain temperature in the presence of an acid catalyst Or solvent heat treatment for a period of time, after washing with deionized water, suction filtration, drying, grinding, and further carbonization for a certain period of time under nitrogen atmosphere and certain temperature conditions to obtain niobium-carbon solid acid catalyst. The obtained niobium-carbon solid acid catalyst can be used in the reaction for preparing 5-hydroxymethylfurfural from biomass.

The carbohydrate compound includes one or more of glucose, sucrose, maltose, fructose, galactose, lactose, cellobiose, raffinose and the like.

The niobium precursor is niobium tartrate, niobium pentachloride, niobium oxalate, niobium citrate, niobium ethoxide, niobium n-propoxide, niobium n-butoxide or other niobium salts.

The acid catalyst is one or more of phosphoric acid, sulfuric acid, formic acid, acetic acid, p-toluenesulfonic acid, citric acid, tartaric acid, oxalic acid, and the like.

In the preparation process, the saccharide compound and the niobium precursor are added to the solvent in a mass ratio of 10:1-1:1, preferably 5:1-2:1.

In the hydrothermal or solvothermal synthesis, the solvent may be one of organic solvents such as water, methanol, ethanol or ethylene glycol.

The hydrothermal or solvothermal temperature is 140-260°C, preferably 160-220°C; and the time is 4-48h, preferably 6-24h.

The carbonization temperature is 300°C-800°C, preferably 400°C-600°C; the time is 2-10h, preferably 4-8h.

In the reaction of preparing 5-hydroxymethylfurfural from the biomass, the biomass raw material is one of cellulose, glucose, fructose, sucrose, inulin, starch, etc.; Catalyst, 0.2g biomass raw material, 6ml tetrahydrofuran, and 2ml saturated aqueous sodium chloride solution were put into a high-pressure magnetic stirring reaction kettle, and the reaction was stirred for 8 hours at 180°C under 0.5MPa nitrogen conditions. The purpose of filling nitrogen was to ensure that the reaction was in the liquid phase system. in progress.

The present invention has the following advantages:

The invention provides a simple preparation method of a solid acid catalyst, which is applied to the reaction of biomass conversion to prepare 5-hydroxymethylfurfural, and has stable structure, good water resistance and can be industrialized. Mass production. In addition, this method can be used to synthesize solid acid catalysts with different acid amounts and acid strengths by adjusting different carbon sources, types of niobium precursors and their ratios.

Glucose, fructose, sucrose, inulin and starch were purchased from Sinopharm Chemical Reagent Co., Ltd.; cellulose was purchased from Aladdin Chemical Reagent Co., Ltd.

The reaction solution was analyzed by high performance liquid chromatography, using Agilent 1200 HPLC analysis, the chromatographic column was XDB-C18 chromatographic column (4.5 μm, 250 mm, Eclipse USA), and the chromatographic column was kept constant at 35 ^oC . The LC was equipped with an Agilent G1329A autosampler to increase the reproducibility of the injection. The product HMF was detected by an Agilent G1314B UV detector (VWD) with a UV wavelength of 254 nm. The mobile phase was a mixture of methanol and pure water with a volume ratio of 20:80 and a flow rate of 0.6 mL/min.

Quantitative analysis of the product was carried out using the external standard method. Prepare standard solutions of known product standard samples with different concentrations, measure the peak area of liquid chromatography, and make a standard curve based on the relationship between concentration and peak area. The standard curve formula of the product HMF is: A=2318557.1x; wherein, A is the peak area value of the HMF signal directly given by the chromatography; x is the mass concentration of HMF. The mass fraction of niobium pentoxide in the solid acid catalyst was measured on a PerkinElmer Pyris Diamond type TGA thermogravimeter, air was introduced, the flow rate was 50 ml/min, and the heating rate was 10 °C/min.

The total acid content of the solid acid catalyst was measured by acid-base titration. The specific operation steps were as follows: Accurately weigh 0.25 g of niobium-carbon solid acid catalyst and evenly disperse it in 30 mL of NaOH solution with a concentration of 0.05 mol·L ^-1 . Ultrasonic dispersion treatment was carried out for 1 hour at room temperature. After the reaction, the reaction solution was centrifuged, the supernatant was taken out, and titrated with 0.05 mol·L ^-1 hydrochloric acid solution. Using phenolphthalein as an indicator, the total acid content of the solid acid catalyst was obtained by calculation.

The X-ray diffraction (XRD) spectrum of the solid acid catalyst was measured on a Bruker diffractometer (D8 Focus) X-ray diffractometer using a Cu target Kα (λ=0.154056 nm) source, the test voltage was 40 kV, and the test current was 40 mA, the scanning range is 10-80°, and the scanning speed is 6°/min. According to the XRD pattern, it is judged whether the obtained catalyst has an amorphous structure.

The specific surface area and average pore size of solid acid catalysts were measured on a Micromeritics ASAP2020M static nitrogen adsorption instrument. The samples were pretreated under vacuum at 180 °C. After pretreatment, they were analyzed at liquid nitrogen temperature (77 K). Nitrogen was used as the adsorbate to determine the pore structure and specific surface area of the catalyst.

Description of drawings

Accompanying drawing 1 is the XRD spectrum of the niobium-carbon solid acid catalyst prepared in Example 1.

Accompanying drawing 2 is the niobium-carbon solid acid catalyst synthesized under different conditions in Table 1.

Accompanying drawing 3 is the physical properties of different niobium-carbon solid acid catalysts in Table 2 and their performance of catalyzing cellulose to prepare 5-hydroxymethyl furfural.

Accompanying drawing 4 is table 3 different biomass raw material as reaction substrate.

Figure 5 shows the cycle stability of the reaction of Example 49 niobium-carbon solid acid catalyst for cellulose hydrolysis and dehydration to prepare HMF.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention sets forth the following examples, but the examples are only used to help the understanding of the present invention, and should not be regarded as a specific limitation of the present invention.

Examples 1-18

Weigh a certain amount of carbon source and 2 grams of niobium source into a beaker, add 20 mL of acidic solution, and after continuous stirring for 2 hours, transfer the obtained solution to a stainless steel pressure kettle with a teflon lining, and crystallize at a certain temperature A dark brown solid was obtained after some time. After washing with deionized water, drying, and then placing in a tube furnace, carbonization for a certain period of time in a nitrogen atmosphere and a certain temperature, the required niobium-carbon solid acid catalyst (carbon source, niobium source, mass ratio , synthesis solvent, and the specific description of carbonization temperature are shown in Table 1, and the characterization results of physicochemical parameters of each solid acid catalyst are shown in Table 2).

0.2 g of catalyst, 0.2 g of cellulose, 6 mL of tetrahydrofuran, 2 mL of saturated aqueous sodium chloride solution were added to the high-pressure magnetic stirring batch reactor, filled with 0.5 MPa nitrogen, heated to 180 ^oC , and reacted at a constant temperature for 8 hours, and the reaction system was cooled to At room temperature (25°C), the catalyst was separated by centrifugation. The reaction solution was analyzed by high performance liquid chromatography, and the yield of 5-hydroxymethylfurfural was calculated, as shown in Table 2.

Examples 34-48

Add 0.2 g of the catalyst in the above embodiment, 0.2 g of biomass raw materials, 6 mL of tetrahydrofuran, 2 mL of saturated aqueous sodium chloride solution into the high-pressure magnetic stirring batch reactor, fill with 0.5 MPa nitrogen, heat to 180 ° C, and react at a constant temperature for 8 hours. , the reaction system was cooled to room temperature (25 °C), and the catalyst was separated by centrifugation. The reaction solution was analyzed by high performance liquid chromatography, and the yield of 5-hydroxymethylfurfural was calculated, as shown in Table 3.

Example 49

0.2 g of the catalyst of Example 1, 0.2 g of cellulose, 6 ml of tetrahydrofuran, 2 ml of saturated aqueous sodium chloride solution were added to the high-pressure magnetic stirring batch reaction kettle, filled with 0.5 MPa nitrogen, heated to 180° C., and reacted at a constant temperature for 8 hours. The reaction system was cooled to room temperature (25°C), and the catalyst was separated by centrifugation. The reaction solution was analyzed by high performance liquid chromatography, and the yield of 5-hydroxymethylfurfural was calculated. After the catalyst was washed with deionized water, it was put into the next reaction, and the reaction was repeated 8 times in total.

Claims (7)

1. a preparation method for preparing the solid acid catalyst of 5-Hydroxymethylfurfural from biomass, is characterized in that: One or more sugar compounds and niobium precursors are hydrothermally or solvothermally treated at a certain temperature for a period of time in the presence of an acid catalyst, washed with deionized water, filtered with suction, dried, and ground. Further carbonizing for a period of time under the temperature condition, to obtain a niobium-carbon solid acid catalyst, and the obtained niobium-carbon solid acid catalyst is used in the reaction of biomass for preparing 5-hydroxymethylfurfural; Wherein, the mass ratio of the carbohydrate compound to the niobium precursor is 10:1-1:1; The acid catalyst is one or more of phosphoric acid, sulfuric acid, formic acid, acetic acid, p-toluenesulfonic acid, citric acid, tartaric acid, and oxalic acid; The hydrothermal or solvothermal solvent is water, methanol, ethanol or ethylene glycol, the temperature is 140-260°C, and the time is 4-48h; The carbonization temperature is 300°C-800°C, and the time is 2-10h. 2 . The preparation method of solid acid catalyst according to claim 1 , wherein the carbohydrate compound comprises one of glucose, sucrose, maltose, fructose, galactose, lactose, cellobiose and raffinose. 3 . or more. 3. the preparation method of solid acid catalyst according to claim 1, is characterized in that: described niobium precursor is niobium tartrate, niobium pentachloride, niobium oxalate, niobium citrate, niobium ethoxide, niobium n-propoxide or n-propoxide Niobium butoxide. 4. The method for preparing a solid acid catalyst according to claim 1, wherein the mass ratio of the saccharide compound to the niobium precursor is 5:1-2:1. 5 . The method for preparing a solid acid catalyst according to claim 1 , wherein the hydrothermal or solvothermal temperature is 160-220° C. and the time is 6-24 h. 6 . 6 . The method for preparing a solid acid catalyst according to claim 1 , wherein the carbonization temperature is 400-600° C. and the time is 4-8 h. 7 . 7. the preparation method of solid acid catalyst according to claim 1, is characterized in that: gained niobium carbon solid acid catalyst is used in the reaction that biomass prepares 5-hydroxymethyl furfural, and described biomass raw material is cellulose , one or more of glucose, fructose, sucrose, inulin and starch.

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