CN109485543B - Method for preparing ethylene glycol and 1, 2-propylene glycol from cellulose in one step and catalyst thereof - Google Patents

Abstract

The invention discloses a method for preparing ethylene glycol and 1,2-propylene glycol from cellulose in one step and a catalyst thereof. The method comprises reacting cellulose and hydrogen in the presence of a catalyst in a reactor, wherein water, alkane, An alcohol or a combination thereof is used as a solvent, and the catalyst is a heterogeneous catalyst consisting of a metal oxide as a support and a hydrogenation metal supported on the support. By using the method and catalyst of the present invention, ethylene glycol and 1,2-propylene glycol can be prepared from cellulose in one step, wherein the conversion rate of raw cellulose can reach 100%, and the total yield of ethylene glycol and 1,2-propylene glycol is equal to It can reach more than 95%, thus providing a new way for one-step catalytic production of ethylene glycol and 1,2-propanediol directly from cellulosic biomass raw materials. In addition, the method of the invention has the advantages of simple process, simple reaction equipment, simple operation, mild reaction conditions, and cheap and easily available catalysts, so it is more suitable for industrial production and has very broad application prospects.

Description

Method for preparing ethylene glycol and 1,2-propanediol in one step from cellulose and its catalyst

technical field

The present invention relates to a method for preparing ethylene glycol and 1,2-propanediol from cellulose in one step and a catalyst thereof.

Background technique

Biomass is the only renewable source of organic carbon and is ideal for the production of fuels and chemicals as an alternative to petroleum. Therefore, the development of new routes and methods for converting biomass to fuels and chemicals is an important goal for the development of sustainable energy systems in the future. The main part of biomass is cellulose. Cellulose is a polymer formed by the polymerization of glucose through glycosidic bonds. Converting them into other useful chemicals is a feasible way to convert cellulose.

At present, polyols such as ethylene glycol and 1,2-propanediol are important energy liquid fuels and also very important polyester raw materials. The industry mainly adopts the petroleum route, that is, ethylene and propylene are epoxidized to obtain ethylene glycol, 1, 2-Propanediol. The method has high technical difficulty, low efficiency, high energy consumption and serious pollution.

At present, the hydrolysis and hydrogenation of biomass to prepare ethylene glycol and 1,2-propanediol is regarded as a new utilization method for cellulose conversion. This method can not only open up a new synthesis path, but also achieve high economic value products from cheap cellulose. , and in the conversion process, the hydroxyl groups of glucose units in cellulose are largely retained, and the atomic economy of the whole process is high, showing a strong industrial application prospect. In the early days, Zhang Tao's research group pioneered the use of Ni-W ₂ C/AC catalyst to convert renewable cellulose resources into ethylene glycol, and the ethylene glycol yield reached 61% (see Direct Catalytic Conversion of Cellulose into Ethylene Glycol Using Nickel-Promoted Tungsten CarbideCatalysts , Angew.Chem.2008, 120, 8638-8641), the development of this technology can replace the conversion of fossil resources into ethylene glycol. Liu Haichao's group directly catalyzed cellulose, ethylene glycol and 1,2 _- propanediol with a total yield of 56.3% by using Ru/AC+WO catalyst (Tungsten trioxide promoted selective conversion of cellulose into propylene glycol and ethylene glycol on a ruthenium catalyst, Angew. Chem. Int. Ed. 2012, 51, 3249-3253). Recently, Zhang Tao's group used a two-step thermochemical catalytic conversion of cellulose and converted cellulose to ethylene glycol (see Chemocatalytic conversion of cellulosicbiomass to methyl glycolate, ethylene glycol, and ethanol, ChemSusChem, 2017, 10, 1390-1394) , the two-step method avoids effectively avoiding the coking of intermediates and improves the yield of ethylene glycol. However, the depolymerization of cellulose in this method needs to be completed under relatively high temperature and multi-step reaction conditions, the reaction process is relatively complicated, and the economic cost is relatively high. In addition, among the reported catalysts, tungsten oxide supported catalysts are mainly used, and noble metal or non-precious metal Ni is mainly used as the active metal. On the one hand, the conversion efficiency of such catalysts is not high (for example, only about 80% conversion is reached), on the other hand, considering the cost and catalyst stability issues, catalysts prepared for metal oxide supported hydrogenation metals need to have low cost as well as higher catalytic stability and conversion efficiency.

Therefore, there is a need in the art to develop a new process that can efficiently depolymerize cellulose to obtain ethylene glycol and 1,2-propanediol under mild conditions and with a simple reaction process, and develop new supported hydrogenation metals to prepare simple, Catalysts with stable performance and high conversion efficiency are of great significance, especially the application of catalysts with non-tungsten oxides as carriers supporting base metal Cu or Co as hydrogenation metals in the field of catalytic cellulose depolymerization has not been reported before.

SUMMARY OF THE INVENTION

The purpose of the present invention is to achieve high-efficiency one-step preparation of ethylene glycol and 1,2-propanediol from cellulose under mild conditions, and to develop a catalyst with higher catalytic activity for this process.

To this end, in one aspect, the present invention provides a method for preparing ethylene glycol and 1,2-propanediol from cellulose in one step, the method comprising reacting cellulose with hydrogen in the presence of a catalyst in a reactor to Ethylene glycol and 1,2-propanediol are produced using water, alkane, alcohol, or a combination thereof as a solvent, and the catalyst is a heterogeneous composition consisting of a metal oxide as a support and a hydrogenation metal supported on the support catalyst.

In a preferred embodiment, the method uses cellulose powder obtained after grinding as a raw material.

In a preferred embodiment, in the catalyst, the hydrogenation metal is Co or Cu, and the metal oxide is one or more selected from CeOx, MoOx and LaOx; The hydrogen metal is Co, and the metal oxide is CeOx or LaOx.

In a preferred embodiment, the reaction temperature of the reaction is 100-300°C, preferably 180-280°C, more preferably 200-260°C.

In a preferred embodiment, the hydrogen pressure of the reaction is 0.1-10 MPa, preferably 1-6 MPa.

In a preferred embodiment, the reaction time of the reaction is 1-24h, preferably 4-12h.

In another aspect, the present invention provides a catalyst for catalyzing the hydrogenation of cellulose to produce ethylene glycol and 1,2-propanediol in one step, the catalyst is composed of a metal oxide as a carrier and a hydrogenation catalyst supported on the carrier A heterogeneous catalyst composed of metals, wherein the hydrogenation metal is Co or Cu, and the metal oxide support is one or more selected from CeOx, MoOx and LaOx.

In a preferred embodiment, the hydrogenation metal is Co and the metal oxide is CeOx or LaOx.

In a preferred embodiment, the mass content of the hydrogenation metal is 0.1-30% based on the total mass of the catalyst.

In a preferred embodiment, the hydrogenation metal is supported on the support by impregnation or precipitation methods.

By utilizing the method and catalyst of the present invention, ethylene glycol and 1,2-propanediol can be prepared from cellulose in one step, wherein the conversion rate of raw cellulose reaches 100%, and the yield of ethylene glycol and 1,2-propylene glycol can reach 95% % or more, thus providing a new way for one-step catalytic production of ethylene glycol and 1,2-propanediol directly from cellulosic biomass raw materials. In addition, the method of the invention has the advantages of simple process, simple reaction equipment, simple operation and mild reaction conditions, and at the same time, the catalyst of the invention is cheap and easy to obtain, has a simple structure, is more suitable for industrial production, and has a very broad application prospect.

Description of drawings

Figure 1 is the X-ray of a 10% Co/CeO _X catalyst prepared according to an embodiment of the present invention (with CeO ₂ as the carrier to support hydrogenation metal cobalt, and based on the total mass of the catalyst, the cobalt content is 10%) and the pure CeO ₂ carrier. Diffraction (XRD) was used to characterize the spectrum.

FIG. 2 is a transmission electron microscope (TEM) characterization spectrum of a 10% Co/CeO _X catalyst prepared according to an embodiment of the present invention, wherein the magnification is 50000×.

Detailed ways

After in-depth and extensive research, the inventors of the present invention have obtained a new process capable of efficiently depolymerizing cellulose to obtain ethylene glycol and 1,2-propanediol under mild conditions and with a simple reaction process, and obtained a new process for A catalyst with high catalytic activity for the process.

In some embodiments, the present invention provides a process for the production of ethylene glycol and 1,2-propanediol from high-yield hydrogenation of cellulose, comprising reacting cellulose and hydrogen in the presence of a cellulose hydrogenation catalyst in a reactor to produce high-yield Rate hydrogenation to produce ethylene glycol and 1,2-propanediol.

In the method of the present invention, the reactor is not particularly limited, as long as the catalytic hydrogenation of the cellulose raw material can be achieved in a hydrogen atmosphere. Preferably, the reactor used may be a reactor such as an autoclave.

In the method of the present invention, the cellulose used as a raw material is not particularly limited, and it can be any source of cellulose, preferably biomass-derived cellulose, such as corn stover, sorghum stover, wheat stover, sugarcane residue, etc., These cellulosic raw materials are readily available or commercially available. More preferably, before use, the cellulose is pulverized into cellulose powder (eg <140 mesh) by a mill and then added to the reactor as a raw material for the reaction.

In the method of the present invention, water, alkanes, alcohols, or combinations thereof are used as solvents. Here, the water used as the solvent may be, for example, distilled water or deionized water. The alkane-based solvent is preferably a liquid alkane-based solvent at room temperature, such as a linear, branched or cyclic alkane having 5 to 30 carbon atoms, preferably 6 to 18, more preferably 6 to 15, such as hexane, Dodecane, bicyclohexane, etc. The alcohol solvent is preferably a liquid alcohol solvent at room temperature, such as a linear, linear or cyclic monohydric or polyhydric alcohol having 1 to 12, preferably 1 to 10, more preferably 1 to 8 carbon atoms, For example, methanol, ethanol, propanol, butanol, butanediol, amyl alcohol, hexylene glycol, heptanediol, octanol, and the like. In the present invention, these solvents may be used alone or in combination of a plurality of them. In particular, in the reaction of the present invention, it is particularly preferable to use a mixture of water and alkane or alcohol and alkane as a solvent, because the inventors unexpectedly found that in such a mixed solvent, the efficiency and rate of the hydrogenation reaction are higher, which is not affected by the Without any theoretical limitation, the inventors believe this may be due to hydrogen being more readily dissolved in alkanes or alcohols.

In the present invention, the catalyst used is a heterogeneous catalyst consisting of a metal oxide as a support and a hydrogenation metal supported on the support.

In the catalyst of the present invention, the hydrogenation metal used is Co or Cu. In view of the fact that the catalysts in the prior art usually all use noble metals, and there are no related catalysts that only use Co or Cu or both as hydrogenation metals, the catalyst cost of the present invention is significantly lower than that of the prior art. More preferably, from the viewpoint of catalyst activity and cost, based on the total mass of the catalyst, the mass content of the hydrogenation metal is 0.1-30%, preferably 0.5-10%.

In the catalyst of the present invention, the metal oxide as the carrier is one or more selected from cerium oxide (CeOx), molybdenum oxide (MoOx) and lanthanum oxide (LaOx). For these oxides CeOx, MoOx or LaOx, it should be noted that x in the chemical formula does not represent any specific value, but is only used to indicate that the metal oxide is metal cerium (Ce), molybdenum (Mo) or lanthanum (La ), ie they are respectively in the form of oxides, for example CeOx in them can be in particular in the form of CeO ₂ or other oxides, or in the form of mixtures of these oxides. Unexpectedly, the inventors of the present invention have found that, compared with catalysts using noble metal or non-precious metal Ni in the prior art, the catalyst composed of the specific support of the present invention and the hydrogenation metal has higher catalytic activity, conversion efficiency and stability.

In the method of the present invention, preferably, the reaction temperature is 100-300°C, preferably 180-280°C, more preferably 200-260°C.

In the method of the present invention, preferably, the hydrogen pressure in the reaction system is 0.1-10 MPa, preferably 1-6 MPa.

In the method of the present invention, preferably, the reaction time is 1-24h, preferably 4-12h.

The catalyst of the present invention can be obtained by supporting a hydrogenation metal on a metal oxide support by a conventional impregnation method or precipitation method. For example, using _CeO2 as an example, the catalyst of the present invention can be prepared by the following general impregnation method:

Dissolve a soluble salt containing carrier metal Ce ions, such as cerium nitrate, in distilled water, and add a dilute aqueous ammonia solution dropwise to precipitate the resulting aqueous cerium nitrate solution until the Ce metal is completely precipitated, for example, stirring at 25-80°C 12-24h, and after suction filtration and washing, drying at 20-100°C for 6-12h, and calcining at 400-600°C for 2-4h to obtain the desired CeO ₂ carrier. MoOx or LaOx supports can be prepared similarly.

A soluble nitrate, chloride or sulfate containing metal ion of a hydrogenated metal such as Co or Cu is mixed in distilled water with optional co-agent such as a surfactant (eg cetyltrimethylammonium bromide) , to obtain an aqueous solution of hydrogenated metal ions;

Then, the obtained aqueous solution of hydrogenated metal ions is added to the dispersion liquid of the above-mentioned carrier CeO ₂ , MoOx or LaOx dispersed in a suitable solvent such as water, for example, at 25-80° C. under stirring, for example, for more than 12-24 h; then, for example, The solvent is removed by distillation under reduced pressure on a rotary evaporator, and the catalyst precursor is obtained, for example, by drying in a drying oven at 20-100° C. for 6-12 h;

Finally, the catalyst precursor is subjected to reduction treatment under a hydrogen atmosphere at 300-600°C. After this reduction treatment process, the metal state of the hydrogenation metal such as Co or Cu is a metal element, and the metal oxides CeO ₂ , The metal state in MoOx or LaOx remains in the oxide state, thereby obtaining the heterogeneous catalyst required by the present invention.

Without being bound by any theory, the hydrogenation metal in the heterogeneous catalyst obtained by the present invention and the two metal species in the support metal oxide promote the dispersion of each other, so that the hydrogenation metal particles are uniformly dispersed on the metal oxide support. Therefore, in the reaction process of catalyzing hydrogenation of cellulose to prepare ethylene glycol and 1,2-propanediol, the heterogeneous catalyst of the present invention has high catalytic activity. In addition, due to the mild reaction temperature of the method of the present invention, the saccharides or small molecular compounds obtained by the hydrogenation reaction of the raw material cellulose are not easily polymerized, which also leads to the high catalytic activity of the catalyst of the present invention, and at the same time, the conversion rate of the raw material and the product are improved. The yields of ethylene glycol and 1,2-propanediol are high. Taking the Co/CeOx catalyst composed of the hydrogenation metal as Co and the carrier as CeOx as an example, the inventors of the present invention have unexpectedly found that in the art, it is generally believed that CeOx contains a large amount of low-valence Ce ³⁺ to provide Lewis bases The site conducts an efficient retro-aldol condensation reaction on the substrate, and at the same time, the Ce species undergoes electron transfer behavior to Co, and the low-valence Co has a higher electron cloud density, showing a higher catalytic hydrogenation. active. Similarly, the use of hydrogenated metal Cu and supports MoOx or LaOx is also the case.

In the method of the present invention, preferably, the catalyst used is a powdered catalyst that has been ground by a grinder to increase the contact area of the reaction, thereby accelerating the reaction.

Although not particularly limited, preferably, in the reactor, the mass ratio of the catalyst to cellulose used may be 1:1-100, more preferably 1:1-20.

Example

In order to further illustrate the present invention, the present invention will be described in detail below with reference to the embodiments and accompanying drawings. Those skilled in the art understand that these examples are not intended to limit the scope of the invention.

In the following examples, unless otherwise specified, the methods used are conventional methods in the art, and the materials, reagents, etc. used can be obtained from commercial sources.

catalyst preparation

Example 1

Preparation of 10%Co/CeOx Heterogeneous Catalyst

According to the general method described above, 3 g of cerium nitrate salt was dissolved in 100 mL of water to obtain an aqueous cerium nitrate solution. A 2.5% aqueous ammonia solution was added dropwise to precipitate the obtained aqueous cerium nitrate solution until the pH was 10, stirred at 40 °C for 15 h, and after suction filtration and washed with distilled water, dried at 60 °C for 8 h, and then heated at 550 °C for 15 h. calcined at ℃ for 2.5 h, thereby obtaining a CeO ₂ carrier. 596.6 mg of Co(NO ₃ ) ₂ ·6H ₂ O was dissolved in 20 g of distilled water to obtain a Co(NO ₃ ) ₂ aqueous solution, and 1.2 g of the CeO ₂ carrier obtained above was only ball milled and dispersed in distilled water to obtain a _CeO dispersion. Then, the obtained Co(NO ₃ ) ₂ aqueous solution was added to the obtained CeO ₂ dispersion, and after stirring at 60° C. for 15 h, the solvent was removed by rotary evaporation, and then dried at 100° C. for 8 h. A catalyst precursor is obtained. Finally, the obtained catalyst precursor was reduced in a hydrogen atmosphere at 600 °C for 2 h to obtain the desired heterogeneous catalyst.

By elemental analyzer, it was determined that the mass content of metallic Co in the obtained heterogeneous catalyst was 10%, that is, a 10% Co/CeOx heterogeneous catalyst was obtained.

In order to explore the existence state of each species, especially each metal species in the obtained catalyst, the obtained heterogeneous catalyst was characterized by XRD. For comparison, pure CeO ₂ was also characterized by XRD, and the results are shown in Figure 1. As can be seen from Fig. 1, in the obtained 10%Co/CeOx heterogeneous catalyst, only characteristic peaks corresponding to pure CeOx species were observed, but not any oxides of metallic Co, indicating that Co metal It exists in the form of metal element instead of oxide, and it is very uniformly dispersed on the surface of CeOx carrier.

In addition, in order to further determine the existence state of each species in the obtained catalyst, the obtained 10%Co/CeOx heterogeneous catalyst was characterized by TEM, and FIG. 2 shows the 10%Co/CeOx prepared according to Example 1 of the present invention. TEM characterization spectra of heterogeneous catalysts. It can be seen from Figure 2 that in the obtained 10% Co/CeOx heterogeneous catalyst, the metal particles are uniformly dispersed on the metal oxide support. Without being bound by a particular theory, it is believed that this may also be one of the reasons for the greatly increased activity of the catalyst of the present invention in catalyzing the one-step production of ethylene glycol and 1,2-propanediol from cellulose.

Example 2

The heterogeneous catalysts shown in Table 1 below were prepared and obtained by the same preparation and characterization procedures as in Example 1, except that the types and amounts of hydrogenation metal and support oxide were changed. Also, the results by XRD characterization and TEM characterization (spectra not shown) were similar to those of Example 1 above.

Catalyst application

Example 3

In a 50 mL autoclave, 100 mg of ground corn stover cellulose powder was added, and 100 mg of the 10% Co/CeOx heterogeneous catalyst prepared in Example 1 was added. 10 mL of distilled water was added to the reaction kettle as a solvent, and the hydrogen pressure was kept at 3 MPa, and then heated to 245° C. by a heating mantle and reacted under magnetic stirring for 6 h. After the reaction was completed, the reaction vessel was cooled to room temperature and the reactor was emptied, and then filtered to separate the catalyst from the reaction solution. The reaction solution was diluted with methanol to prepare a sample for analysis, and analyzed by gas chromatography. Based on the results of the gas chromatographic analysis, the conversion rate of the cellulose raw material and the total yield of the target products ethylene glycol and 1,2-propanediol were calculated, and the average value of the experimental results repeated three times is shown in Experiment No. 1 of Table 1.

Example 4

The one-step preparation of ethylene glycol and 1,2-propanediol from cellulose was carried out in the same procedure as in Example 3 except that different catalysts and different reaction conditions were used as shown in Experiment Nos. 2-34 of Table 1, and the resulting cellulose The conversion rates of the starting materials and the total yields of ethylene glycol and 1,2-propanediol are shown in Experiment Nos. 2-34 in Table 1, respectively.

Table 1

As can be seen from the reaction results in Table 1 above, the present invention obtains a heterogeneous catalyst supported by a hydrogenation metal on a metal oxide carrier. Using the catalyst in the presence of water, alkanes, alcohols or a combination thereof as a solvent, the catalyst can be It is realized that ethylene glycol and 1,2-propanediol can be prepared from catalyzed raw cellulose with high conversion rate and high yield under mild reaction conditions.

Moreover, the catalyst used has a very good catalytic effect in this reaction, wherein the depolymerization of cellulose feedstock can be converted at high conversion (up to 100%) and in high yield (>95%) under the catalysis of this catalyst The target diol products are obtained, namely ethylene glycol and 1,2-propanediol.

In addition, in the method of the present invention, the preferred reaction conditions are as follows: the reaction temperature is 100-300°C, more preferably 200-280°C; the hydrogen pressure is 0.1-10MPa, more preferably 1-6MPa; the reaction time is 1-24h. Under such reaction conditions, ethylene glycol and 1,2-propanediol products can be prepared from cellulose catalytic hydrogenation in one step with high cellulose conversion rate and high total yield of target products ethylene glycol and 1,2-propanediol.

In addition, in the method of the present invention, the sources of cellulose raw materials are wide and biomass-derived cellulose raw materials can be used, and waste utilization can be realized.

In addition, in the present invention, by utilizing a catalyst with a simple and efficient composition and preparation process, a new method for the next step of catalytic conversion of cellulose under milder conditions to prepare ethylene glycol and 1,2-propanediol with high selectivity is obtained; The method of the invention has the advantages of simple process, simple reaction equipment and simple operation, can better meet the requirements of industrial application, and has a very broad application prospect.

The above embodiments are only used to help understand the method and the core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (10)

1. A method for preparing ethylene glycol and 1,2-propanediol in one step from cellulose, the method comprising reacting cellulose with hydrogen in the presence of a catalyst to generate ethylene glycol and 1,2-propanediol in a reactor, wherein Water, an alkane, an alcohol, or a combination thereof is used as a solvent, and the catalyst is a heterogeneous catalyst consisting of a metal oxide as a support and a hydrogenation metal supported on the support, the hydrogenation metal being Co, so The metal oxide is one or more selected from CeOx, MoOx and LaOx, and the mass content of the hydrogenation metal is 0.1-30% based on the total mass of the catalyst. 2 . The method according to claim 1 , wherein the method uses the cellulose powder obtained after grinding as a raw material. 3 . 3. The method of claim 1, wherein the metal oxide is CeOx or LaOx. 4. The method according to claim 1, wherein the reaction temperature of the reaction is 100-300°C. 5. The method according to claim 1, wherein the reaction temperature of the reaction is 180-280°C. 6. The method according to claim 1, wherein the reaction temperature of the reaction is 200-260°C. 7. The method according to claim 1, wherein the hydrogen pressure of the reaction is 0.1-10 MPa. 8. The method according to claim 1, wherein the hydrogen pressure of the reaction is 1-6 MPa. 9. method according to claim 1 is characterized in that, the reaction time of described reaction is 1-24h. 10. The method according to claim 1, wherein the reaction time of the reaction is 4-12h.

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