CN103242270A - Method for preparing furfural compounds from biomass - Google Patents

Abstract

The invention relates to a method for preparing furfural compounds from biomass, specifically including the preparation of solid acid catalyst and its reaction process, and the method of the invention can also be used for derivatives of biomass. It includes the following steps: adding biomass or its derivatives and a solid acid catalyst into the reactor, filling it with protective gas, adopting an organic solvent/saturated inorganic salt solution two-phase reaction system, and obtaining furfural, 5-Hydroxymethylfurfural. The advantage of the present invention is that after the reaction, the generated furfural and 5-hydroxymethylfurfural are efficiently extracted into the upper organic phase, and the solid acid catalyst and unreacted substrate remain in the bottom water phase, which can be achieved by simple separation The obtained furfural, 5-hydroxymethylfurfural or a mixture thereof can be used as a reaction intermediate to prepare fine chemicals and liquid fuels; the catalyst used is non-polluting and recyclable, and has good industrial application prospects.

Description

A method for preparing furfural compounds from biomass

technical field

The invention belongs to the fields of catalytic chemistry, organic chemistry and industrial fine chemical synthesis, and particularly relates to a solid acid catalyst and a reaction process for preparing furfural compounds from biomass, and more specifically relates to a catalyst for preparing furfural from biomass Catalyst and reaction process with 5-hydroxymethylfurfural.

Background technique

Today, fossil fuels such as coal, oil and natural gas are still the most important fuel sources worldwide. But fossil fuels are one-time non-renewable energy, and it is predicted that fossil fuels will be exhausted in the next century. Because of a series of advantages such as sustainability, cleanliness, wide range of sources, and safety, the research on the production of energy and fine chemicals from biomass resources has become a hot issue in the field of energy research. In this series of studies, the sugar dehydration reaction is one of the important reactions in biomass utilization, and the products furfural, 5-hydroxymethylfurfural, levulinic acid, lactic acid, formic acid, etc. are also commercial platforms with specific structures and properties compound. Among these platform compounds, furfural and 5-hydroxymethylfurfural are an important class of furan compounds, which can be used to prepare liquid fuel 2-methylfuran, 2,5-dimethylfuran, long-chain alkanes, and pharmaceutical intermediates 2,5-diformylfuran, polyester monomer 2,5-furandicarboxylic acid, etc. Therefore, developing a practical and efficient solid acid catalyst and its reaction process to prepare furfural and 5-hydroxymethylfurfural with high yield is an important way for the effective utilization of biomass.

Professor Dumesic and others at the University of Wisconsin in the United States found that when hydrochloric acid was used to catalyze the dehydration of fructose, the yield of the product 5-hydroxymethylfurfural could be as high as 70% or more (Science, 2006, 312, 1933). Chheda et al. found that in a water/organic biphasic system comprising water, dimethyl sulfoxide (DMSO) and 7:3 methyl isobutyl ketone (MIBK)/2-butanol, the use of inorganic acids (hydrochloric acid, When sulfuric acid or phosphoric acid) is used as a catalyst, it can effectively catalyze the dehydration reaction of carbohydrates such as sucrose, starch and cellobiose, and prepare 5-hydroxymethylfurfural with high selectivity (Green Chemistry, 2007, 9, 342). Chinese patent CN102617524 has prepared 5-hydroxymethylfurfural in a two-phase system composed of water and an organic solvent by using the acid salt of sulfuric acid and the normal salt of sulfuric acid as a catalyst; 5-Hydroxymethylfurfural was prepared in a two-phase system composed of water and organic solvent. However, when inorganic acids or soluble salts are used as catalysts, it is difficult to separate the catalysts from the products, and the inorganic acids of the catalysts severely corrode the reaction equipment and pollute the environment. The Davis research group of the University of California in the United States adopted a two-phase system, and under low pH conditions, the solid catalyst Sn-Beta molecular sieve was used to convert glucose into 5-hydroxymethylfurfural, and the selectivity and yield were 70% and 57% ( ACS Catalysis, 2011, 1, 408). However, in this reaction, the solid catalyst Sn-Beta mainly plays the role of isomerizing glucose to fructose, and when fructose is dehydrated to 5-hydroxymethylfurfural, it is still necessary to add inorganic acid (such as hydrochloric acid), so it is difficult to avoid inorganic acid Introduced disadvantages. Zhao et al. used glucose as a raw material, ionic liquid 1-methyl-3-ethylimidazole chloride as a reaction medium, and _CrCl as a catalyst to obtain HMF with a yield of about 70% (Science, 2007, 316, 1597). Zhang et al. also used ionic liquid as a medium and _CrCl3 as a catalyst under the condition of microwave heating to realize the conversion of corn stalks, rice straw and pine wood. The yields of 5-hydroxymethylfurfural and furfural were 45-45%. 52% and 23-31% (Tetrahedron Letters, 2009, 50, 5403). Chinese patent CN102321055A discloses a method for preparing 5 _- hydroxymethylfurfural from _cellulose -rich biomass. The yield of furfural can reach 52%. However, the current production cost of ionic liquid is too high, and its application as a reaction medium is limited to laboratory research, which does not have the advantage of low cost; at the same time, the chromium salt used is in a free state, which is harmful to the environment and difficult to separate from ionic liquid. The advantage of environmental protection limits its further industrial application. How to convert biomass effectively and pollution-free into 5-hydroxymethylfurfural or furfural has not yet been effectively solved.

Invention content:

The purpose of the present invention is to provide a simple and direct catalytic conversion of biomass and its derivatives into furfural and 5-hydroxymethylfurfural. High, high energy consumption, high requirements for reaction equipment, and the catalyst cannot be recycled and reused.

To achieve the above object, the technical solution adopted in the present invention is:

酸性位，可以催化生物质及其衍生物的直接转化。在有机溶剂/饱和无机盐水溶液的双相体系中，80～240℃的温度下反应0.5-48小时，糠醛和5-羟甲基糠醛的收率分别在8～80％范围内变动。The invention provides a solid acid catalyst for efficiently catalytically converting biomass to prepare furfural and 5-hydroxymethylfurfural. The catalyst has two acid sites, Lewis acid site and

Acid sites, which can catalyze the direct conversion of biomass and its derivatives. In the two-phase system of organic solvent/saturated inorganic salt solution, react at a temperature of 80-240 DEG C for 0.5-48 hours, and the yields of furfural and 5-hydroxymethylfurfural vary in the range of 8-80%.

酸起到水解和脱水作用。该种催化剂是过渡金属的氧化物、磷酸盐、硫酸盐，也可以是经过过渡金属离子交换的分子筛或粘土矿物。其中过渡金属的氧化物、磷酸盐、硫酸盐可以通过沉淀法、溶胶-凝胶法和水热合成法制备；所述过渡金属离子交换的分子筛和粘土矿物是通过过渡金属的氯化物、硝酸盐、醋酸盐、溴化物与分子筛和粘土矿物交换而得，所述分子筛或矿物为ZSM-5、Beta、MCM-41、SBA-15、5A、13X、Ca-蒙脱土、Na-蒙脱土；所述的过渡金属包括Ti、Zr、Hf、V、Nb、Ta、Cr、Mo、W、Sn、Zn、Fe、Co以及其中的一种或多种的混合物。The solid acid catalyst used has both Lewis acidic sites and Acidic sites, where the Lewis acid plays the role of isomerization,

Acid acts on hydrolysis and dehydration. The catalyst is transition metal oxide, phosphate, sulfate, or molecular sieve or clay mineral exchanged by transition metal ions. Wherein transition metal oxides, phosphates, and sulfates can be prepared by precipitation, sol-gel, and hydrothermal synthesis; the transition metal ion-exchanged molecular sieves and clay minerals are prepared by transition metal chlorides, nitrates , acetate, bromide exchanged with molecular sieves and clay minerals, the molecular sieves or minerals are ZSM-5, Beta, MCM-41, SBA-15, 5A, 13X, Ca-montmorillonite, Na-montmorillonite Earth; the transition metals include Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Sn, Zn, Fe, Co and a mixture of one or more thereof.

The biomass is corn stalks, bagasse, rice hulls, sawdust, wood sticks, cellulose, hemicellulose; the carbohydrates are starch, sucrose, glucose, inulin, fructose, and xylose.

The reaction system adopted is a two-phase reaction system of organic solvent/saturated aqueous inorganic salt solution, where the inorganic salts include LiCl, KCl, NaCl, CsCl, CaCl ₂ , MgCl ₂ , LiBr, NaBr, KBr, Na ₂ SO ₄ and their arbitrary proportions The mixture; the organic solvent is tetrahydrofuran, toluene, hexane, acetone, methyl isobutyl ketone, 1,4-dioxane, 1-butanol, 2-butanol and their mixtures in any proportion.

For water-soluble carbohydrates, the reaction can also be carried out continuously in a fixed-bed reactor, the saturated inorganic salt solution of carbohydrates and the organic solvent are fed separately, the temperature is controlled at 100-200°C, and the space velocity is controlled at 0.5-60h ^-1 .

After the reaction is over, stand still, and the generated furfural and 5-hydroxymethylfurfural are efficiently extracted into the upper organic phase, while the solid acid catalyst, inorganic salt and unreacted substrate remain in the bottom water phase, which can be achieved by simple separation Obtain an organic solution of furfural, 5-hydroxymethylfurfural or a mixture thereof; the obtained organic phase can be directly used in the preparation of liquid fuel, or the obtained organic phase can be distilled and dried under reduced pressure to prepare high-purity furfural and 5-hydroxymethylfurfural base furfural.

The present invention has the following advantages:

1. Compared with the method for preparing furfural and 5-hydroxymethylfurfural by dehydration of traditional protonic acid catalyst, the solid acid catalyst used in the present invention is simple to prepare, low in cost and high in activity, and can directly convert biomass without adding other inorganic acids, In particular, complex biomass such as starch or cellulose is efficiently catalytically converted into 5-hydroxymethylfurfural, which is environmentally friendly, does not easily cause equipment corrosion, and is easy to separate.

2. The reaction adopts a two-phase system. The yield of furfural and 5-hydroxymethylfurfural is high, and the reaction process is green and pollution-free. Furfural can be extracted into the organic phase in time, while promoting the dehydration of sugar in the water phase to prepare furfural and 5-hydroxymethylfurfural, it can also avoid furfural and 5-hydroxymethylfurfural in the water phase. Carbohydrates are further reacted to form humin, which reduces the deactivation of the catalyst while increasing the selectivity, and improves the service life of the catalyst and the yield of furfural and 5-hydroxymethylfurfural.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention enumerates the following examples, but the examples are only used to help understand the present invention, and should not be regarded as specific limitations to the present invention.

Examples 1-8

Catalyst preparation by ion exchange method: Weigh a certain mass of molecular sieves or clay minerals and metal chlorides, nitrates, acetates or bromides, and then add them to a beaker containing 300mL of water, and perform ion exchange at a specific temperature After a period of time, the catalyst in the beaker was taken out, filtered and washed, and dried overnight at a temperature of 100°C.

In eight reactors of the same type, 10 mL of an aqueous solution of methyl isobutyl ketone and saturated potassium chloride with a volume ratio of 7: 3 was added, then 0.5 g of glucose was added, and 0.1 g of the catalysts of Examples 1-8 were added respectively. , tighten the screws of the reactor, fill with nitrogen protective gas, place in eight different heating mantles respectively, raise the heating mantles to 160°C respectively, keep the temperature constant, stir, and stop the reaction after 3 hours of reaction. The reaction system was cooled to room temperature, and the catalyst was separated by centrifugation. The reaction solution was analyzed by high-performance liquid chromatography, and the results obtained from the reactions of different catalysts are shown in Table 1.

Table 1 Different catalysts catalyze the yield of 5-hydroxymethylfurfural from glucose

Example serial number Metal species for ion exchange Molecular sieve Yield of 5-Hydroxymethylfurfural (%) 1 Ti ZSM-5 20.3 2 Cr Beta 25.4 3 Fe MCM-41 23.2 4 Zn Na-montmorillonite 32.2 5 ZnSn Ca-montmorillonite 49.8 6 MoFe SBA-15 18.7 7 CoNbTa 5A 21.1 8 wxya 13X 20.9

Examples 9-17

In nine reactors of the same model, add 10 mL of saturated aqueous solution of methyl isobutyl ketone and different inorganic salts with a volume ratio of 7:3, then add 0.5 g of glucose and 0.1 g of the catalyst of Example 5 respectively, and tighten the reaction The screw of the device was filled with nitrogen protective gas, and placed in nine different heating mantles respectively. The heating mantles were raised to 160°C, kept at constant temperature, stirred, and the reaction was stopped after 3 hours of reaction. The reaction system was cooled to room temperature, and the catalyst was separated by centrifugation. The reaction solution was detected by high performance liquid chromatography, and the results obtained from the reaction under different saturated inorganic salt solutions are shown in Table 2.

The yield of 5-hydroxymethylfurfural under different saturated inorganic salt solutions of table 2

Example serial number Inorganic salt type 5-Hydroxymethylfurfural yield (%) 9 LiCl 51.9 10 Na ₂ SO ₄ 41.9 11 NaCl 51.8 12 CsCl 51.4 13 _CaCl2 37.2 14 MgCl ₂ 33.0 15 LiBr 51.7 16 NaBr 51.6 17 KBr 51.8

Examples 18-27

In ten reactors of the same model, add different organic solvents and saturated potassium chloride solution with a volume ratio of 7: 3, then add 0.5 g of glucose and 0.1 g of the catalyst of Example 5 respectively, tighten the screw of the reactor, and be full of nitrogen Protective gas was placed in ten different heating mantles respectively, and the heating mantles were raised to 160° C., kept at constant temperature, stirred, and reacted for 3 hours to stop the reaction. The reaction system was cooled to room temperature, and the catalyst was separated by centrifugation. The reaction solution was detected by high-performance liquid chromatography, and the results obtained in different organic solvents are shown in Table 3.

The yield of 5-hydroxymethylfurfural under different organic solvents of table 3

Example serial number Organic solvents 5-Hydroxymethylfurfural yield (%) 18 Hexane 23.5 19 toluene 25.4 20 acetone 38.5 twenty one 1,4-dioxane 49.6 twenty two 2-butanol 50.2 twenty three Tetrahydrofuran 51.2 twenty four 1-butanol 48.3 25 Tetrahydrofuran + 1-butanol 51.8 26 Methyl isobutyl ketone+2-butanol 50.7 27 Acetone+1,4-dioxane 45.4

Examples 28-36

Add the methyl isobutyl ketone organic solvent and the aqueous solution of saturated potassium chloride that volume ratio is 7:3 in nine reactors of the same model, then add respectively the catalyst 0.1 of the biomass of 0.5g other kinds and embodiment 5 g. Tighten the screws of the reactor, fill it with nitrogen protective gas, place it in eleven different heating mantles, raise the heating mantles to 160°C respectively, keep the temperature constant, stir, and stop the reaction after 3 hours of reaction. The reaction system was cooled to room temperature, and the catalyst was separated by centrifugation. The reaction solution was detected by high performance liquid chromatography, and the results obtained from the reaction under different biomass raw materials are shown in Table 4.

Table 4 different biomass or its derivatives are used as the yield of raw material furfural and 5-hydroxymethylfurfural

Example serial number Biomass type Furfural yield (%) 5-Hydroxymethylfurfural yield (%) 28 fructose 0 77.6 29 sucrose 25.6 44.8 30 Inulin 0.7 56.4 31 starch 0 40.6 32 Bagasse 13.0 16.8 33 Corn stalks 11.0 15.9 34 pine wood 12.3 10.2 35 Xylose 52.0 0 36 Cellulose 1.9 38.5

Example 37

We choose xylose as the model substrate and use NbOPO ₄ as the catalyst to carry out the continuous conversion of water-soluble carbohydrates in a fixed-bed reactor. The saturated inorganic salt solution of xylose and the THF organic solvent are fed separately. The volume ratio is controlled at 1:4, the total space velocity is controlled at 40h ^-1 , the catalyst mass is 1g, the particle size is 40-60 mesh, the reaction temperature is controlled at 160°C, the bed pressure is controlled at 2.2MPa, and the N ₂ flow rate is controlled at 30mL/min. Samples were taken at different time periods, and the reaction solution was detected by high performance liquid chromatography. The yield of furfural can reach about 67%, and the catalyst has a long service life. After continuous reaction for 50 hours, the yield of furfural remains stable.

Examples 38-42

Preparation of catalyst by sol-gel method: use transition metal nitrate, acetate, alkoxide as raw material, citric acid or its ammonium salt as chelating agent, use sol-gel method to synthesize transition metal with mesoporous and macroporous structure Oxides, phosphates and sulfates and mixtures thereof.

In five reactors of the same type, 10 mL of methyl isobutyl ketone organic solvent and saturated potassium chloride aqueous solution with a volume ratio of 7:3 were added, then 0.5 g of glucose was added, and 0.1 g of the catalysts of Examples 37-41 were added respectively. g. Tighten the screws of the reactor, fill it with nitrogen protective gas, place it in eight different heating mantles respectively, raise the heating mantles to 160° C., keep the temperature constant, stir, and stop the reaction after 3 hours of reaction. The reaction system was cooled to room temperature, and the catalyst was separated by centrifugation. The reaction solution was detected by high-performance liquid chromatography, and the results obtained by reacting with different catalysts are shown in Table 5.

The yield of 5-hydroxymethylfurfural under the catalytic action of different catalysts in table 5

Example serial number catalyst 5-Hydroxymethylfurfural yield (%) 38 NbOPO ₄ 50.4 39 ZrOSO ₄ 52.8 40 WO ₃ 45.7 41 Ta ₂ O ₅ 21.3 42 WO ₃ -ZrO ₂ 35.9

Examples 43-47

The reacted catalyst in Example 11 was centrifuged, washed three times with water and ethanol, and then dried in an oven at 100° C. for 2 hours. Catalyst is taken out to add in the reactor afterwards, add simultaneously the methyl isobutyl ketone organic solvent and saturated potassium chloride solution that volume ratio is 7: 3, and 0.5g glucose, tighten the screw of reactor, be full of nitrogen protection gas, place In the heating mantle, the heating mantle was raised to 160° C., kept at constant temperature, stirred, and reacted for 3 hours to stop the reaction. The reaction system was cooled to room temperature, and the catalyst was separated by centrifugation, and the reaction solution was detected by high performance liquid chromatography; the same method was used for subsequent cycles, and the cycle process was the same as in Example 43, and the cycle was repeated 5 times. The results are shown in Table 6.

Table 6 Catalyst recycling results

Example serial number Catalyst cycle times 5-Hydroxymethylfurfural yield (%) 11 0 51.8 43 1 50.3 44 2 50.8 45 3 50.5 46 4 51.1 47 5 49.8

It can be seen from the above examples that the present invention has prepared a solid acid catalyst containing two kinds of acid sites, and in a two-phase system composed of organic solvent/saturated inorganic salt solution, it can directly and rapidly realize the catalytic conversion of biomass to prepare Furfural and 5-hydroxymethylfurfural; this process is environmentally friendly, with mild conditions and low cost, and the catalyst can be recycled and reused. It is an ideal solid acid catalyst for preparing furfural compounds and has a good industrial application prospect.

Claims (6)

1. method for preparing the furfural compounds from biomass, it may further comprise the steps: will be dispersed or dissolved in the diphasic system of organic solvent/saturated inorganic salt solution through biomass or the carbohydrate of ball milling, add solid acid catalyst, under 80～240 ℃ of temperature, reacted 0.5～48 hour.

2. method according to claim 1, biomass are maize straw, bagasse, rice husk, wood chip, batten, Mierocrystalline cellulose, hemicellulose; Carbohydrate is starch, sucrose, glucose, synanthrin, fructose, wood sugar; Catalyzer is not only to have had the Lewis acidic site, but also have

The solid acid of acidic site; Organic solvent is tetrahydrofuran (THF), toluene, hexane, acetone, methyl iso-butyl ketone (MIBK), 1, the mixture of 4-dioxane, 1-butanols, 2-butanols and their arbitrary proportions; Inorganic salt are mixtures of halogenide and vitriol and their arbitrary proportions.

3. catalyzer according to claim 2 is characterized in that: such solid acid catalyst have simultaneously the Lewis acidic site and

Acidic site, wherein isomerization is played in Lewis acid,

Hydrolysis and dehydration are played in acid; This kind catalyzer is the oxide compound of transition metal, phosphoric acid salt, vitriol and the molecular sieve that gets through the transition metal ion exchange and the mixture of clay mineral and their arbitrary proportions.

4. according to the oxide compound of the described transition metal of claim 3, phosphoric acid salt, vitriol are by coprecipitation method, sol-gel method and hydrothermal synthesis method preparation; The molecular sieve of described transition metal ion exchange and clay mineral are that muriate, nitrate, acetate, bromide and molecular sieve and the clay mineral exchange by transition metal gets, and described molecular sieve or mineral are ZSM-5, Beta, MCM-41, SBA-15,5A, 13X, Ca-polynite, Na-polynite; Described transition metal comprises Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Sn, Zn, Fe, Co and one or more mixture wherein.

5. method according to claim 1, for water miscible carbohydrate, be reflected in the fixed-bed reactor and carry out continuously, saturated inorganic salt solution and the organic solvent of carbohydrate containing separate charging, temperature control is at 100～200 ℃, and air speed is controlled at 0.5-20h ^-1

6. method according to claim 1, it is characterized in that: after reaction finishes, static, the furfural that generates, 5 hydroxymethyl furfural efficiently are extracted in the upper organic phase, solid acid catalyst, inorganic salt and unreacted substrate are deposited in the bottom aqueous phase, can obtain the organic solution of furfural, 5 hydroxymethyl furfural or its mixture by simple separation; The gained organic phase can be directly used in the preparation of liquid fuel, also can prepare highly purified furfural and 5 hydroxymethyl furfural after the underpressure distillation of gained organic phase, the drying.