CN109485543B

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

Info

Publication number: CN109485543B
Application number: CN201811441236.3A
Authority: CN
Inventors: 张颖; 李闯; 傅尧
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2018-11-29
Filing date: 2018-11-29
Publication date: 2020-08-25
Anticipated expiration: 2038-11-29
Also published as: CN109485543A

Abstract

The present invention discloses a method for preparing ethylene glycol and 1, 2-propylene glycol from cellulose in one step and a catalyst therefor, the method comprising reacting cellulose with hydrogen in the presence of a catalyst 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 composed of a metal oxide as a carrier and a hydrogenation metal supported on the carrier. By utilizing the method and the catalyst, the ethylene glycol and the 1, 2-propylene glycol can be prepared from the cellulose in one step, wherein the conversion rate of the raw material cellulose can reach 100 percent, and the total yield of the ethylene glycol and the 1, 2-propylene glycol can reach more than 95 percent, thereby providing a brand new way for one-step catalytic production of the ethylene glycol and the 1, 2-propylene glycol from the cellulose biomass raw material. In addition, the method has the advantages of simple process, simple reaction equipment, simple and convenient operation, mild reaction conditions and cheap and easily-obtained used catalyst, thereby being more suitable for industrial production and having very wide application prospect.

Description

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

Technical Field

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

Background

Biomass is the only renewable organic carbon resource and is an ideal alternative to petroleum-derived fuels and chemicals. Therefore, the development of new routes and new methods for preparing fuels and chemicals by biomass conversion is an important target for the development of sustainable energy systems in the future. The major part of biomass is cellulose, which is a polymer formed by polymerization of glucose through glycosidic bonds, and its conversion to other useful chemicals is a viable route to cellulose conversion.

At present, polyhydric alcohols such as ethylene glycol and 1, 2-propylene glycol are important energy source liquid fuels and are also very important polyester raw materials, and the industry mainly adopts a petroleum route, namely ethylene glycol and 1, 2-propylene glycol are obtained by post-hydration of ethylene and propylene. The method has the advantages of high technical difficulty, low efficiency, high energy consumption and serious pollution.

At present, the method for preparing ethylene glycol and 1, 2-propylene glycol by hydrolysis and hydrogenation from biomass is regarded as a novel utilization way for cellulose conversion, a new synthesis path can be developed by the method, a product with high economic value can be obtained from cheap cellulose, in addition, in the conversion process, a large amount of hydroxyl of a glucose unit in the cellulose is reserved, the atom economy in the whole process is higher, and a stronger industrial utilization prospect is shown. The early billow task group initiated the use of Ni-W₂The C/AC catalyst converts renewable cellulose resources into Ethylene Glycol, the yield of the Ethylene Glycol reaches 61% (see Direct catalyst Conversion of cellulose to Ethylene Glycol Using Nickel-protein Tungsten Carbodes, Angew. chem.2008,120,8638-8641), and the development of the technology can replace fossil resources to convert into the Ethylene Glycol. The Liuhai super subject group is prepared by using Ru/AC + WO₃The catalyst directly catalyzes the total yield of cellulose, ethylene glycol and 1, 2-propylene glycol to be 56.3% (transition trioxide driven selective conversion of cellulose and ethylene glycol on a ruthenium catalyst, Angew. chem. int. Ed.2012,51, 3249-3253). Recently, the Zuotao group has used a two-step method of thermochemically catalytically converting cellulose and converting cellulose to ethylene glycol (see Chemocatalytic conversion of cellulose to methyl glycol, ethylene glycol, and ethanol, ChemSusChem,2017,10,1390-Yield of diol. However, the process of depolymerizing cellulose needs to be completed under the conditions of higher temperature and multiple steps of reaction, the reaction process is more complex, and the economic cost is higher. In addition, among the reported catalysts, a tungsten oxide supported catalyst is mainly used, and a noble metal or non-noble metal Ni is mainly used as an active metal. On the one hand, such catalysts are not efficient at conversion (e.g., only up to about 80% conversion), and on the other hand, catalysts prepared with metal oxide supported hydrogenation metals need to have lower cost and higher catalytic stability and conversion efficiency in view of cost and catalyst stability issues.

Therefore, there is a need in the art to develop a new process capable of efficiently depolymerizing cellulose under mild conditions and in a simple reaction process to obtain ethylene glycol and 1, 2-propanediol, and to develop a new supported hydrogenation metal to prepare a catalyst with simple structure, stable performance and high conversion efficiency.

Disclosure of Invention

The invention aims to realize the high-efficiency one-step preparation of ethylene glycol and 1, 2-propylene glycol from cellulose under mild conditions and simultaneously develop a catalyst with higher catalytic activity for the process.

To this end, in one aspect, the present invention provides a method for producing ethylene glycol and 1, 2-propanediol in one step from cellulose, the method comprising reacting cellulose with hydrogen in the presence of a catalyst in a reactor to produce ethylene glycol and 1, 2-propanediol, wherein water, an alkane, an alcohol or a combination thereof is used as a solvent, and the catalyst is a heterogeneous catalyst composed of a metal oxide as a carrier and a hydrogenation metal supported on the carrier.

In a preferred embodiment, the process uses as starting material a cellulose powder obtained after grinding.

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; preferably, the hydrogenation metal is Co and the metal oxide is CeOx or LaOx.

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

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

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

In another aspect, the present invention provides a catalyst for catalytic hydrogenation of cellulose to produce ethylene glycol and 1, 2-propanediol in one step, the catalyst being a heterogeneous catalyst composed of a metal oxide as a carrier and a hydrogenation metal supported on the carrier, wherein the hydrogenation metal is Co or Cu, and the metal oxide carrier 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 to 30% based on the total mass of the catalyst.

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

By utilizing the method and the catalyst, the ethylene glycol and the 1, 2-propylene glycol can be prepared from the cellulose in one step, wherein the conversion rate of the raw material cellulose reaches 100 percent, and the yield of the ethylene glycol and the 1, 2-propylene glycol can reach more than 95 percent, thereby providing a brand new way for the one-step catalytic production of the ethylene glycol and the 1, 2-propylene glycol from the cellulose biomass raw material. In addition, the method has the advantages of simple process, simple reaction equipment, simple and convenient operation, mild reaction conditions, cheap and easily-obtained catalyst, simple composition, suitability for industrial production and very wide application prospect.

Drawings

FIG. 1 is a schematic view of10% Co/CeO prepared by the embodiment of the invention_XCatalyst (with CeO)₂The carrier is loaded with hydrogenation metal cobalt, and the cobalt content is 10 percent based on the total mass of the catalyst) and pure CeO₂The X-ray diffraction (XRD) characterization spectrum of the support.

FIG. 2 is 10% Co/CeO prepared according to an embodiment of the present invention_XTransmission Electron Microscopy (TEM) characterization spectra of the catalyst, with magnification of 50000 x.

Detailed Description

As a result of intensive and extensive studies, the inventors of the present invention have obtained a novel process capable of realizing the preparation of ethylene glycol and 1, 2-propanediol by depolymerizing cellulose under mild conditions and in a simple reaction process with high efficiency, and have obtained a catalyst for the process having high catalytic activity.

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

In the process of the present invention, the reactor is not particularly limited as long as catalytic hydrogenation of the cellulose raw material can be achieved in a hydrogen atmosphere, and preferably, the reactor used may be a reaction tank such as a high-pressure reaction tank.

In the method of the present invention, cellulose as a raw material is not particularly limited, and may be cellulose of any origin, preferably cellulose of biomass origin, such as corn stover, sorghum stover, wheat straw, sugarcane residue, and the like, which can be easily obtained or purchased. More preferably, the cellulose is pulverized into a cellulose powder (e.g., < 140 mesh) by a grinder before use and then added to a reactor as a raw material to carry out a reaction.

In the process 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 solvent is preferably an alkane solvent which is liquid at room temperature, for example, a linear, branched or cyclic alkane having 5 to 30, preferably 6 to 18, more preferably 6 to 15 carbon atoms, for example, hexane, dodecane, bicyclohexane or the like. The alcohol solvent is preferably an alcohol solvent which is liquid at room temperature, for example, a linear, straight-chain 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, pentanol, hexanediol, heptanediol, octanol or the like. In the present invention, these solvents may be used alone or in a mixture of plural kinds. In particular, in the reaction of the present invention, it is particularly preferable to use water and an alkane or a mixture of an alcohol and an alkane as the solvent, because the inventors have unexpectedly found that the efficiency and rate of the hydrogenation reaction are higher in such a mixed solvent, without being limited by any theory, which the inventors believe may be due to hydrogen being more easily dissolved in the alkane or alcohol.

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

In the catalyst of the present invention, the hydrogenation metal used is Co or Cu. The catalyst cost of the present invention is significantly lower than the prior art, since the prior art catalysts typically use precious metals, and there is no associated catalyst that uses only Co or Cu or both as hydrogenation metals. More preferably, the hydrogenation metal is contained in an amount of 0.1 to 30% by mass, preferably 0.5 to 10% by mass, based on the total mass of the catalyst, from the viewpoint of catalyst activity and cost.

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). It should be noted that, for these oxides CeOx, MoOx or LaOx, x in the chemical formula does not represent any specific value, but is merely used to indicate that the metal oxide is an oxide of cerium (Ce), molybdenum (Mo) or lanthanum (La), i.e. they are present in the form of an oxide, respectively, for example, wherein CeOx may be specifically CeO₂Or in the form of other oxides, or in the form of mixtures of these oxides. Unexpectedly, the inventors of the present invention have found thatCompared with the catalyst using noble metal or non-noble metal Ni in the prior art, the catalyst composed of the specific carrier and the hydrogenation metal has higher catalyst activity, conversion efficiency and stability.

In the process of the present invention, the reaction temperature is preferably 100-.

In the process of the present invention, it is preferred that the hydrogen pressure in the reaction system is from 0.1 to 10MPa, preferably from 1 to 6 MPa.

In the process of the present invention, the reaction time is preferably from 1 to 24h, preferably from 4 to 12 h.

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 a precipitation method. For example, to use CeO₂As an example of a support, the catalyst of the invention can be prepared by the following general impregnation method:

dissolving soluble salt containing carrier metal Ce ion such as cerous nitrate in distilled water, adding diluted ammonia water solution dropwise to precipitate the obtained cerous nitrate water solution until Ce metal is completely precipitated, e.g. stirring at 25-80 deg.C for 12-24h, filtering and washing, drying at 20-100 deg.C for 6-12h, and calcining at 400-600 deg.C for 2-4h to obtain desired CeO₂And (3) a carrier. MoOx or LaOx supports can be prepared similarly.

Mixing soluble nitrate, chloride salt or sulfate of metal ions containing a hydrogenation metal such as Co or Cu with an optional adjuvant such as a surfactant (e.g., cetyltrimethylammonium bromide) in distilled water to obtain an aqueous solution of the hydrogenation metal ions;

the aqueous solution of the hydrogenated metal ions thus obtained is then added to the above-mentioned carrier CeO dispersed in a suitable solvent such as water₂MoOx or LaOx, for example, at 25-80 ℃ for 12-24 hours or more; followed by distillation under reduced pressure, for example by a rotary evaporator, to remove the solvent and drying, for example, in a drying oven at 20 to 100 ℃ for 6 to 12 hours to obtain a catalyst precursor;

finally, the catalyst precursor is subjected toReducing at 300-₂The metal state in MoOx or LaOx is maintained as an oxide state, whereby the heterogeneous catalyst required in the present invention can be obtained.

Without being bound by any theory, the two metal species in the hydrogenation metal and in the support metal oxide in the heterogeneous catalyst obtained by the present invention promote dispersion with each other, so that the hydrogenation metal particles are uniformly dispersed on the metal oxide support. Therefore, the heterogeneous catalyst of the present invention has high catalytic activity in the reaction process of catalytically hydrogenating cellulose to produce ethylene glycol and 1, 2-propanediol. In addition, because the reaction temperature of the method is mild, the saccharides or small molecular compounds obtained by the hydrogenation reaction of the raw material cellulose are not easy to polymerize, which also leads to high catalytic activity of the catalyst of the invention and simultaneously leads to high conversion rate of the raw material and high yield of the products of ethylene glycol and 1, 2-propylene glycol. Taking the example of a Co/CeOx catalyst comprising a hydrogenation metal as Co and a support as CeOx, the inventors of the present invention have unexpectedly discovered that CeOx is generally believed to contain a significant amount of Ce in its lower valence state in the art³⁺A Lewis base site is provided to carry out efficient retro-aldol (retro-aldol) condensation reaction on a substrate, meanwhile, Ce species carry out electron transfer behavior on Co, and low-valence Co has higher electron cloud density and shows higher catalytic hydrogenation activity. Similarly, the same is true for the hydrogenation metal Cu and the support MoOx or LaOx.

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

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

Examples

In order to further illustrate the present invention, the following detailed description of the invention is given in conjunction with examples and the accompanying drawings. Those skilled in the art will appreciate that these examples are not intended to limit the scope of the present invention.

In the following examples, unless otherwise specified, the methods used are all conventional in the art, and the materials, reagents and the like used are commercially available.

Catalyst preparation

Example 1

Preparation of 10% Co/CeOx heterogeneous catalyst

According to the general method described above, 3g of cerium nitrate salt was dissolved in 100mL of water to obtain an aqueous cerium nitrate solution. The resulting cerium nitrate aqueous solution was precipitated by dropwise addition of a 2.5% aqueous ammonia solution to a pH of 10, stirred at 40 ℃ for 15 hours, and after suction filtration and washing with distilled water, dried at 60 ℃ for 8 hours, followed by calcination at 550 ℃ for 2.5 hours, thereby obtaining CeO₂And (3) a carrier. 596.6mg of Co (NO)₃)₂·6H₂O was dissolved in 20g of distilled water to obtain Co (NO)₃)₂An aqueous solution, and 1.2g of the above-obtained CeO₂The carrier was pulverized by a ball mill only and dispersed in distilled water to obtain CeO₂And (3) dispersing the mixture. Then, the obtained Co (NO) is subjected to₃)₂An aqueous solution was added to the obtained CeO₂After stirring the dispersion at 60 ℃ for 15 hours, the solvent was removed by rotary evaporation, followed by drying at 100 ℃ for 8 hours, thereby obtaining a catalyst precursor. Finally, the resulting catalyst precursor was reduced in a hydrogen atmosphere at 600 ℃ for 2h to obtain the desired heterogeneous catalyst.

The obtained heterogeneous catalyst was determined to have a metallic Co content of 10% by mass by an elemental analyzer, i.e., a 10% Co/CeOx heterogeneous catalyst was obtained.

In order to investigate the presence of the various species, in particular the various metal species, in the obtained catalyst, XRD characterization was carried out on the obtained heterogeneous catalyst. Wherein for comparison, pure CeO is used₂XRD characterization was also performed and the results are shown in figure 1. As can be seen from FIG. 1, in the 10% Co/CeOx heterogeneous catalyst obtained, only the characteristic peak corresponding to the pure CeOx species was observed, while the characteristic peak of any oxide of metallic Co could not be observed, indicating that the Co metal is in the form of the elemental metal and not in the form of oxidationIn the form of a matrix and dispersed very uniformly on the surface of the CeOx support.

In addition, in order to further confirm the existence state of each species in the obtained catalyst, the obtained 10% Co/CeOx heterogeneous catalyst was subjected to TEM characterization, and fig. 2 shows a TEM characterization spectrum of the 10% Co/CeOx heterogeneous catalyst prepared according to example 1 of the present invention. As can be seen from fig. 2, in the obtained 10% Co/CeOx heterogeneous catalyst, the metal particles were in a uniformly dispersed state on the metal oxide support. Without being bound to a particular theory, it is believed that this may also be one of the reasons why the catalyst of the present invention has a greatly improved activity in catalyzing the reaction of cellulose to produce ethylene glycol and 1, 2-propanediol in one step.

Example 2

In the same preparation and characterization procedures as in example 1, except for changing the kinds and amounts of the hydrogenation metal and the support oxide, heterogeneous catalysts shown in table 1 below were prepared and obtained. Also, the results of characterization by XRD and characterization by TEM (spectrum not shown) are similar to those of example 1 described above.

Catalyst application

Example 3

100mg of ground corn stover cellulose powder was added to a 50mL autoclave, and 100mg of the 10% Co/CeOx heterogeneous catalyst prepared in example 1 was added. To the reaction kettle, 10mL of distilled water was added as a solvent, and the hydrogen pressure was maintained at 3MPa, after which it was heated to 245 ℃ by a heating mantle and reacted for 6h under magnetic stirring. After the reaction was completed, it was cooled to room temperature and the reaction vessel was vented, followed by filtration 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 chromatography 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 of three repetitions is shown in experiment No. 1 of table 1.

Example 4

The production of ethylene glycol and 1, 2-propanediol from cellulose in one step was carried out in the same procedure as in example 3 except that different catalysts and different reaction conditions as shown in experiment numbers 2 to 34 of table 1 were used, and the conversion of the obtained cellulose raw material and the total yields of ethylene glycol and 1, 2-propanediol were respectively shown in experiment numbers 2 to 34 of table 1.

TABLE 1

As can be seen from the reaction results of table 1 above, the present invention obtains a heterogeneous catalyst in which a hydrogenation metal is supported on a metal oxide carrier, and by using the catalyst in the presence of water, alkanes, alcohols or a combination thereof as a solvent, it is possible to produce ethylene glycol and 1, 2-propylene glycol at high conversion and high yield by catalyzing raw material cellulose under mild reaction conditions.

Moreover, the catalyst used has a very good catalytic effect in this reaction, where the depolymerization of the cellulosic feedstock under the catalytic action of the catalyst can be converted with high conversion (up to 100%) and the target diol products, i.e. ethylene glycol and 1, 2-propylene glycol, are obtained in high yields (> 95%).

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

In addition, in the method of the present invention, the cellulose raw material is widely available and a biomass-derived cellulose raw material can be used, and waste utilization can be achieved.

In addition, in the invention, by utilizing the catalyst with simple composition and preparation process and high efficiency, a new method for preparing the ethylene glycol and the 1, 2-propylene glycol in high selectivity by performing catalytic conversion on the cellulose in one step under mild conditions is obtained; meanwhile, the method has the advantages of simple process, simple reaction equipment and simple and convenient operation, can better meet the requirements of industrial application, and has very wide application prospect.

The above embodiments are only intended to help the understanding of the method of the present invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims

1. A process for producing ethylene glycol and 1, 2-propanediol in one step from cellulose, which comprises reacting cellulose with hydrogen in the presence of a catalyst in a reactor to produce ethylene glycol and 1, 2-propanediol, wherein water, an alkane, an alcohol or a combination thereof is used as a solvent, and the catalyst is a heterogeneous catalyst composed of a metal oxide as a carrier and a hydrogenation metal supported on the carrier, the hydrogenation metal being Co, the metal oxide being one or more selected from CeOx, MoOx and LaOx, and the mass content of the hydrogenation metal being 0.1 to 30% based on the total mass of the catalyst.

2. The method according to claim 1, characterized in that the method uses cellulose powder obtained after grinding as a raw material.

3. The method of claim 1, wherein the metal oxide is CeOx or LaOx.

4. The method as claimed in claim 1, wherein the reaction temperature of the reaction is 100-300 ℃.

5. The method as claimed in claim 1, wherein the reaction temperature of the reaction is 180-280 ℃.

6. The method as claimed in claim 1, wherein the reaction temperature of the reaction is 200-260 ℃.

7. The process according to claim 1, wherein the hydrogen pressure of the reaction is 0.1 to 10 MPa.

8. The process according to claim 1, wherein the hydrogen pressure of the reaction is 1 to 6 MPa.

9. The process according to claim 1, wherein the reaction time is 1 to 24 hours.

10. The process according to claim 1, wherein the reaction time is 4 to 12 hours.