阅读说明：本技术 一种水滑石基催化剂在高浓度糖转化到1,2-丙二醇中的应用 (Application of hydrotalcite-based catalyst in conversion of high-concentration sugar to 1, 2-propylene glycol ) 是由 庞纪峰 郑明远 姜宇 赵宇 张涛 于 2019-10-24 设计创作，主要内容包括：本发明提供了一种水滑石基催化剂在高浓度糖转化到1,2-丙二醇中的应用,属于能源化工技术领域。采用共沉淀法制备水滑石前驱体,然后利用浸渍、吸附、交换法引入金属,通过焙烧、还原得到金属促进的金属-复合氧化物催化剂,此催化剂在高浓度糖催化转化到1,2-丙二醇的反应中表现出较高的选择性。本发明所提供的催化剂具有合成简单、催化剂活性高、稳定性好等优点,此反应具有原料为可再生资源、原子经济性高的特点。此外,与其他的以生物质为原料制1,2-丙二醇的技术相比较,本过程具有反应过程简单、时空收率高、便于工业化生产等优点。(The invention provides an application of a hydrotalcite-based catalyst in conversion of high-concentration sugar into 1, 2-propylene glycol, belonging to the technical field of energy and chemical industry. The method comprises the steps of preparing a hydrotalcite precursor by adopting a coprecipitation method, introducing metal by utilizing an impregnation, adsorption and exchange method, and roasting and reducing to obtain a metal-composite oxide catalyst promoted by the metal, wherein the catalyst shows higher selectivity in the reaction of catalyzing and converting high-concentration sugar to 1, 2-propylene glycol. The catalyst provided by the invention has the advantages of simple synthesis, high catalyst activity, good stability and the like, and the reaction has the characteristics of renewable resources as raw materials and high atom economy. In addition, compared with other technologies for preparing 1, 2-propylene glycol by taking biomass as a raw material, the process has the advantages of simple reaction process, high space-time yield, convenience for industrial production and the like.)

1. A hydrotalcite-based catalyst characterized by: the hydrotalcite-based catalyst comprises a component A and a component B; the component A is a noble metal; the component B is M with a layered hydrotalcite structure_xMg_yC₁O; the M is at least one of divalent metals; c is trivalent goldBelongs to; the x is the molar ratio of the divalent metal M to the trivalent metal C; y is the molar ratio of the metal Mg to the trivalent metal C;

the divalent metal iron, cobalt, nickel, copper and zinc, and the trivalent metal ions are aluminum, chromium, gallium and iron;

the noble metal is at least one of ruthenium, rhodium, palladium, iridium and platinum; the noble metal is present in metallic form; in the hydrotalcite-based catalyst, the mass ratio of the noble metal is 0.1-10 wt%; the mass ratio of the metal M is 2-70 wt%; the metal M exists in a metal state and an oxide form, and the mass ratio of the metal M existing in the metal state is 1-30%.

2. A method for preparing the hydrotalcite-based catalyst according to claim 1, comprising the steps of:

(1) dissolving divalent metal salt, Mg salt and trivalent metal salt in deionized water to prepare mixed salt solution a; dissolving alkali and carbonate in deionized water to prepare an alkali solution a;

(2) dropwise adding the mixed salt solution a into the alkali solution a at 20-70 ℃, stirring, obtaining a suspension after dropwise adding, adjusting the pH of the suspension to 8-12 with an alkali solution b, and stirring and crystallizing for 3-36h at 30-100 ℃; after the reaction is finished, carrying out suction filtration and washing, and drying for 1-48 hours at the temperature of 80-150 ℃ to obtain the layered hydrotalcite material;

(3) preparing a salt solution b from noble metal salt, adding the layered hydrotalcite material into the salt solution b, soaking or adsorbing or exchanging for 1-24 hours at 25-70 ℃, and then directly drying for 1-24 hours at 30-150 ℃ or drying for 1-24 hours at 30-150 ℃ after filtering;

(4) roasting the solid obtained in the step (3) at the temperature of 200-800 ℃ for 0.5-8h, and reducing the solid at the temperature of 150-600 ℃ for 0.1-5h in a hydrogen atmosphere to obtain the hydrotalcite-based catalyst.

3. The preparation method according to claim 2, wherein the alkali in the step (1) is at least one of hydroxide of lithium, sodium and potassium, and ammonia water; (ii) a The carbonate in the step (1) is one of carbonates of lithium, sodium, potassium and ammonia; in the alkali solution a, the mol ratio of alkali to carbonate is 5:1-1: 5; the alkali solution b in the step (2) is hydroxide solution of lithium, sodium and potassium or ammonia water, and the concentration of the alkali solution b is 0.1-3 mol/L.

4. The production method according to claim 3, wherein the divalent metal salt, Mg salt and trivalent metal salt are nitrate, chloride or sulfate salts of the corresponding metal ions; the molar ratio of the total metal amount in the divalent metal salt and the Mg salt to the metal amount in the trivalent metal ion salt is 1:3-6: 1; in the mixed salt solution a, the concentration of divalent metal and Mg is 0.1-10 mol/L.

5. The preparation method according to claim 2, wherein the precious metal precursor used in the impregnation method is at least one of ruthenium chloride, rhodium chloride, palladium chloride, chloroiridic acid, chloroplatinic acid, potassium hexacyanoplatinate, ruthenium nitrosyl nitrate, palladium nitrate, ammonium chloropalladate; in the salt solution b in the step (3), the concentration of the noble metal is 0.01-5 g/ml.

6. The application of the hydrotalcite-based catalyst according to claim 1 or 2, wherein the hydrotalcite-based catalyst is used in a reaction for obtaining 1, 2-propanediol by catalytic conversion of high-concentration sugar, and the catalytic hydrogenation reaction is carried out in a closed high-pressure reaction kettle or a continuous tubular reactor in a hydrogen atmosphere by taking sugar as a reaction raw material.

7. The use according to claim 6,

when the reactor is a high-pressure reaction kettle, adding the hydrotalcite-based catalyst sugar solution into the high-pressure reaction kettle for reaction at the temperature of 180-350 ℃, under the temperature of 25 ℃, under the hydrogen pressure of 1-6MPa, and for the reaction time of 10-180 minutes; the closed high-pressure reaction kettle can perform middle high-pressure sampling, so that the sugar solution continuously enters the reaction kettle, the 1, 2-propylene glycol solution is timely removed out of the reaction system, and the pressure and the temperature are kept unchanged in the reaction process;

when the reactor is a continuous tubular reactor, adding a hydrotalcite-based catalyst, and activating for 0.5-2h at the temperature of 200-500 ℃ in the continuous tubular reactor; then cooling, filling water into the system, adjusting the reaction temperature to 160-300 ℃ under the reaction condition, and the hydrogen pressure to 1-20MPa, and finally, feeding the sugar solution by a pump for a residence time of 0.1 second-10 minutes.

8. Use according to claim 6, characterized in that: the high-concentration sugar is at least one of glucose, xylose, arabinose, fructose, starch, straw hydrolysis sugar and industrial sugar raw materials, the concentration of the sugar solution is 5-50 wt%, the solvent is water, the content of impurities in the sugar solution is lower than 5 wt%, the content of inorganic salt is lower than 1 wt%, and the pH value of the sugar solution is 4-10.

9. Use according to claim 6, characterized in that: the conversion rate of raw materials is more than 90%, the selectivity of 1, 2-propylene glycol is more than 45%, and the molar ratio of the 1, 2-propylene glycol to the ethylene glycol is more than 3.

Technical Field

The invention belongs to the technical field of energy and chemical engineering, and particularly relates to an application of a hydrotalcite-based catalyst in conversion of high-concentration sugar to 1, 2-propylene glycol.

Background

With the shortage of fossil resources and the increase of environmental pollution, the development of new renewable carbon resource utilization has become a very urgent issue. Biomass is a renewable resource with abundant sources, and its conversion into high value-added chemicals has attracted extensive attention. Carbohydrates are the core of biorefineries, which can be obtained from biomass hydrolysis (enzymatic, acid hydrolysis) by heterogeneous catalysis. The process for producing glucose from starch has been industrialized since a long time ago, and the hydrolysis technology of lignocellulose has been developed greatly in recent years. The national renewable energy laboratory of America adopts a countercurrent shrinkage hydrolysis reactor, and the yield of glucose in the cellulose hydrolysate can reach 84%. On the other hand, sugar is a key raw material for preparing important chemical products through catalytic conversion, and a series of green compounds can be prepared through chemical reactions such as hydrogenation, dehydrogenation, deoxidation, oxidation and the like.

1, 2-propylene glycol is an important organic chemical raw material and is widely applied to the fields of producing unsaturated polyester, epoxy resin, alkyd resin and the like. Meanwhile, the 1, 2-propylene glycol is widely applied in the industries of essence and spice, cosmetics, medicine, cigarette and the like. At present, the industrial production technology of 1, 2-propylene glycol at home and abroad is mainly a direct propylene oxide hydration method based on a petroleum route, and the production process is obviously influenced by the productivity and price of raw materials and has long process flow, large investment and high energy consumption.

At present, the technology of preparing polyols from carbohydrates (document 1: Process for the preparation of low molecular polymeric alcohols, patent, No. US 5107018; document 2: a new Process for producing ethylene glycol, CN 200610068869.5; document 3: a Process for producing diols and polyols by cracking sorbitol, CN200510008652.0) generally comprises three steps: (1) starch is gelatinized, enzymolyzed and saccharified to obtain glucose (2), and the glucose is hydrogenated by a noble metal ruthenium or nickel catalyst to obtain sorbitol (3), and the sorbitol is hydrogenolyzed at high temperature and high pressure to generate product polyhydric alcohols, mainly 1, 2-propylene glycol, glycerol and ethylene glycol. The product of the process is complex and has poor selectivity, which increases the difficulty of subsequent separation.

The other way is to prepare 1, 2-propylene glycol by hydrogenation of glycerol. For example, (document 4: a high selectivity catalyst for producing 1, 2-propanediol, CN 107774271A) zirconia, copper oxide and zinc oxide employed in the patent document are active components, and conversion of glycerin to 1, 2-propanediol with high selectivity is achieved. However, in the process, raw material glycerol is greatly influenced by biodiesel, the glycerol has wide application range, and the method has the defects of high raw material value, limited yield and the like.

The development of a process route for producing a large number of chemical products by taking glucose as a raw material replaces the traditional process route taking non-renewable petroleum resources as raw materials, and has particularly important significance for future development of China. (document 5: a process for producing ethylene glycol and 1, 2-propanediol by continuous hydrocracking of cellulose, CN 102643164B; document 6: a process for producing ethylene glycol and 1, 2-propanediol in one step from cellulose and a catalyst therefor, CN 109485543A; document 7: a process for producing ethylene glycol and 1, 2-propanediol, CN 101768050B) in documents 5 to 7, lignocellulose or sugar is used for catalytic conversion to polyhydric alcohol, but the main product is ethylene glycol, and the selectivity of 1, 2-propanediol is generally low. Even with the fructosyl starting material Jerusalem artichoke (ref 8: ChemUSchem 2012,5, 932-938), the yield of 1, 2-propanediol is less than 40%, so that the catalytic conversion of sugars into 1, 2-propanediol is still more difficult.

In recent years, (document 9: a method for preparing 1, 2-propanediol by metal hydrothermal reduction of carbohydrate, CN 104557461B, document 10: a method for synthesizing 1, 2-propanediol by using glucose, CN 104961625A) the preparation of 1, 2-propanediol by catalytic conversion of sugar has been greatly improved, but the defects of poor product selectivity, multi-step reaction and the like exist, and the production of 1, 2-propanediol is severely restricted.

Disclosure of Invention

The invention aims to provide an application of a hydrotalcite-based catalyst in conversion of high-concentration sugar into 1, 2-propylene glycol. The saccharide compound is catalytically converted into 1, 2-propylene glycol at high speed through a one-step catalytic hydrogenation degradation process on a hydrotalcite-based catalyst.

In order to achieve the purpose, the invention adopts the technical scheme that:

one aspect of the present invention provides a hydrotalcite-based catalyst comprising an active component a and a component B; the component is a noble metal; the component B is M with a layered hydrotalcite structure_xMg_yC₁O; the M is a divalent metal; c is trivalent metal ion; said M having a layered hydrotalcite structure_xMg_yC₁O is precipitated by divalent metal cations, trivalent cations, hydroxide anions and carbonate, the divalent metal M is at least one of iron, cobalt, nickel, copper and zinc, and the trivalent metal is at least one of aluminum, chromium, gallium and iron; the noble metal is at least one of ruthenium, rhodium, palladium, iridium and platinum; the noble metal is present in metallic form; the loading amount of the noble metal is 0.1-10 wt%; the loading amount of the metal M is 2-70 wt%; the metal M exists in a metal state and an oxide form, and the loading amount of the metal M existing in the metal state is 1-30%. After the catalyst is reduced, the noble metal and part of the metal M can be reduced to be in a metal state, and the content of the noble metal is 0.1-50 wt% of the metal M.

The invention also provides a preparation method of the catalyst, which comprises the following steps:

(1) dissolving divalent metal salt, Mg salt and trivalent metal salt in deionized water to prepare mixed salt solution a; dissolving alkali and carbonate in deionized water to prepare an alkali solution a;

(2) dropping the mixed salt solution a into the alkali solution a at the temperature of 20-70 ℃, vigorously stirring, obtaining a suspension after dropping is finished, adjusting the pH of the suspension to 8-12 by using an alkali solution b, and stirring and crystallizing for 3-36 hours at the temperature of 30-100 ℃; after the reaction is finished, carrying out suction filtration and washing, and drying for 1-48 hours at the temperature of 80-150 ℃ to obtain the layered hydrotalcite material;

(3) noble metal is introduced by at least one of impregnation, adsorption and exchange methods, and the method specifically comprises the following steps: preparing a salt solution b from noble metal salt, adding the hydrotalcite into the salt solution b, soaking or adsorbing or exchanging for 1-24 hours at 25-70 ℃, and then directly drying for 1-24 hours at 30-150 ℃ or drying for 1-24 hours at 30-150 ℃ after filtering.

(4) Roasting the solid obtained in the step (3) at the temperature of 200-800 ℃ for 0.5-8h, and reducing the solid at the temperature of 150-600 ℃ for 0.1-5h in a hydrogen atmosphere to obtain the hydrotalcite-based catalyst.

Based on the technical scheme, preferably, the alkali in the step (1) is at least one of hydroxides of lithium, sodium and potassium and ammonia water; the amount of base is the theoretical amount to neutralize the divalent and trivalent cations to neutrality; the carbonate in the step (1) is one of carbonates of lithium, sodium, potassium and ammonia; in the alkali solution a, the mol ratio of alkali to carbonate is 5:1-1: 5; the alkali solution b in the step (2) is hydroxide solution of lithium, sodium and potassium or ammonia water, and the concentration of the alkali solution b is 0.1-3 mol/L.

Based on the technical scheme, preferably, the divalent metal precursor and the trivalent metal precursor are nitrate, chloride or sulfate of corresponding metal ions; the molar ratio of the total metal amount in the divalent metal salt and the Mg salt (the total amount of the divalent metal Mg) to the metal in the trivalent metal ion salt is 1:3-6: 1; in the mixed salt solution a, the concentration of divalent metal and metal Mg is 0.1-10 mol/L.

Based on the technical scheme, preferably, the precious metal precursor used in the impregnation method is at least one of ruthenium chloride, rhodium chloride, palladium chloride, chloroiridic acid, chloroplatinic acid, potassium hexacyanoplatinate, ruthenium nitrosyl nitrate, palladium nitrate and ammonium chloropalladate; in the salt solution b in the step (3), the concentration of the noble metal is 0.01-5 g/ml.

The invention also provides an application of the hydrotalcite-based catalyst, wherein the hydrotalcite-based catalyst is used in a reaction for obtaining 1, 2-propylene glycol through catalytic conversion of high-concentration sugar, and the catalytic hydrogenation reaction is carried out in a closed high-pressure reaction kettle or a continuous tubular reactor in a hydrogen atmosphere by taking sugar as a reaction raw material.

Based on the technical scheme, preferably, the sugar is used as a reaction raw material, and the catalytic hydrogenation reaction is carried out in a closed high-pressure reaction kettle or a continuous tubular reactor, wherein the reaction kettle or the continuous tubular reactor is filled with hydrogen in the reaction process, the reaction temperature is more than or equal to 160 ℃, and the reaction time is more than 0.1 second and less than 180 minutes;

when the reactor is a high-pressure reaction kettle, adding the hydrotalcite-based catalyst sugar solution into the high-pressure reaction kettle for reaction, and adding the sugar solution into the catalyst solution under the protection of hydrogen; the reaction temperature is 180 ℃ and 350 ℃, the hydrogen pressure is 1-6MPa at 25 ℃, and the reaction time is 10-180 minutes; the closed high-pressure reaction kettle can perform middle high-pressure sampling, so that the sugar solution continuously enters the reaction kettle, the 1, 2-propylene glycol solution is timely removed out of the reaction system, and the pressure and the temperature are kept unchanged in the reaction process;

when the reactor is a continuous tubular reactor, adding a hydrotalcite-based catalyst, and activating for 0.5-2h at the temperature of 200-500 ℃ in the continuous tubular reactor; then cooling, filling water into the system, adjusting the reaction temperature to 160-300 ℃ under the reaction condition, and adjusting the hydrogen pressure to 1-20MPa, finally, feeding sugar solution by a pump, wherein the retention time is 0.1 second-10 minutes, the catalyst bed layer is filled with water when the reaction starts, and the sugar solution is gradually introduced until the steady state.

Based on the technical scheme, preferably, the high-concentration sugar is at least one of glucose, xylose, arabinose, fructose, starch, straw hydrolysis sugar and industrial sugar raw materials, the concentration of the sugar solution is 5-50 wt%, the solvent is water, the content of impurities in the sugar solution is lower than 5 wt%, the content of inorganic salts is lower than 1 wt%, and the pH of the sugar solution is 4-10.

Based on the technical scheme, preferably, the conversion rate of the raw materials is more than 90%, the selectivity of 1, 2-propylene glycol is more than 45%, and the ratio of the 1, 2-propylene glycol to ethylene glycol is more than 3.

The method provided by the invention takes sugars from different sources as reaction raw materials, and the sugars are directly and efficiently catalytically converted into the 1, 2-propylene glycol on a single catalyst. The reaction process is simple to operate, the catalyst is simple and easy to prepare, the cost is low, and the conversion efficiency is high. The process has the advantages of high operability and easy industrialization.

Advantageous effects

(1) The method adopts a coprecipitation method to prepare a hydrotalcite precursor, then introduces noble metal by at least one of impregnation, adsorption and exchange methods, and obtains a noble metal promoted metal-composite oxide catalyst by roasting and reduction, wherein the catalyst shows higher selectivity in the reaction of catalyzing and converting high-concentration sugar into 1, 2-propylene glycol.

(2) Compared with the prior art of preparing the 1, 2-propylene glycol by using a biomass as a raw material, the process has the advantages of simple reaction process, high space-time yield, convenience for industrial production and the like.

(3) After the carbohydrate is catalyzed and degraded, the carbon, hydrogen and oxygen atoms in the molecules of the raw materials are reserved to the greatest extent, and the raw materials are renewable resources and have high atom economy.

(4) The catalyst has the advantages of simple preparation process, convenient use, relatively high stability and good industrial application prospect.

The present invention will be described in detail with reference to specific examples, which are not intended to limit the scope of the present invention.

Detailed Description

Comparative example 1

Cu₁Mg₃Al₁Preparation of O:

0.01mol of copper nitrate, 0.03mol of magnesium nitrate and 0.01mol of aluminum nitrate are weighed and dissolved in deionized water to prepare a mixed salt solution A. And dissolving sodium carbonate and sodium hydroxide in deionized water in the molar ratio of 4 to 3 to prepare mixed alkali solution B. Dropping A into B in 40 deg.C constant temperature water bath, and controlling dropping speed to 3mL min with constant flow pump^-1And stirring vigorously during the dripping process. After the dropwise addition, the pH of the suspension is adjusted to 10 by using a 3M NaOH solution, and the suspension is continuously stirred and crystallized in a constant-temperature water bath kettle at the temperature of 70 ℃ for 18 hours to obtain a precipitate. Obtaining the hydrotalcite precursor with a layered structure through the steps of pumping filtration, washing and drying。

Roasting the precursor at 600 ℃, and reducing the precursor for 2 hours at 400 ℃ in a hydrogen atmosphere to obtain Cu₁Mg₃Al₁O catalyst, wherein the content of metallic copper in metallic state after reduction is 10%.

Comparative example 2

Ni₁Mg₄Al₁Preparation of O:

0.01mol of nickel nitrate, 0.04mol of magnesium nitrate and 0.01mol of aluminum nitrate are weighed and dissolved in deionized water to prepare a mixed salt solution A. And dissolving sodium carbonate and ammonia water in the molar ratio of 4 to 3 in deionized water to prepare mixed alkali solution B. Dropping A into B in 35 deg.C constant temperature water bath, and controlling dropping speed to 2mL min with constant flow pump^-1And stirring vigorously during the dripping process. After the dropwise addition, the pH of the suspension is adjusted to 10 by ammonia water, and the suspension is continuously stirred and crystallized for 18 hours in a constant-temperature water bath kettle at the temperature of 80 ℃ to obtain a precipitate. And carrying out suction filtration, washing and drying to obtain the hydrotalcite precursor with the layered structure.

Roasting the precursor at 500 ℃, and reducing the roasted precursor for 2 hours at 450 ℃ in a hydrogen atmosphere to obtain Ni₁Mg₄Al₁O catalyst, wherein the content of metallic nickel in metallic state after reduction is 12%.