CN110152733B - A kind of catalyst and its preparation method and the application of catalyzing the reaction of glycerol and urea - Google Patents

Abstract

The invention discloses a catalyst, a preparation method thereof and an application of catalyzing the reaction of glycerol and urea, and belongs to the field of novel catalysts. The preparation method is as follows: the heteropolyacid is reacted with potassium salt to obtain potassium heteropolyacid; the potassium heteropolyacid powder is immersed in a zinc material solution and then dried to remove the solvent to obtain a supported catalyst. Further, calcination is carried out at 300°C-700°C for 3 hours-5 hours to decompose the zinc species in the supported catalyst to obtain zinc oxide, thereby obtaining a composite catalyst. The prepared supported catalyst is used for synthesizing glycerol carbonate by reacting glycerol and urea, the conversion rate of glycerol can reach 94.8%, and the yield of glycerol carbonate can reach 85.8%. The zinc-based composite heteropolyacid salt catalyst disclosed in the invention has the advantages of high catalytic activity, easy recovery, green environmental protection, good thermal stability, and no corrosion and damage to equipment.

Description

A kind of catalyst and its preparation method and the application of catalyzing the reaction of glycerol and urea

technical field

The invention belongs to the field of novel catalysts, in particular, to a catalyst and a preparation method thereof and the application of catalyzing the reaction of glycerol and urea, and more particularly, to a zinc-based composite hybrid compound used for the reaction of glycerol and urea to synthesize glycerol carbonate Polyacid catalyst and preparation method and application thereof.

Background technique

Glycerol carbonate is an important high value-added glycerol derivative with the characteristics of non-toxicity, rapid biodegradation, good water solubility, high flash point (fp 165.9°C) and boiling point (bp 353.9°C). Has a wide range of uses. Glycerol carbonate can be used as high boiling point solvent, cleaning agent, lithium ion battery fluid component and surfactant component, as well as polymerization monomer, reaction intermediate, and preparation of gas separation membrane, etc. It has a very promising market. broad. At present, the synthesis of glycerol carbonate from glycerol is a research hotspot in the field of chemical industry. The glycerol used in the synthesis process is a by-product of the biodiesel production process. With the increase of biodiesel production capacity around the world year by year, the production of glycerol has also increased sharply, resulting in a serious market surplus. Therefore, converting glycerol into glycerol carbonate can not only significantly increase the added value of glycerol, but also increase the economic profit of biodiesel manufacturers, thereby promoting the development of the biodiesel industry.

At present, the methods for synthesizing glycerol carbonate from glycerol mainly include the reaction method of glycerol and dimethyl carbonate, the reaction method of glycerol and carbon dioxide, and the reaction method of glycerol and urea. Although the reaction method of glycerol and dimethyl carbonate has the advantages of mild reaction conditions and high conversion rate, the price of organic carbonates such as dimethyl carbonate itself is high, which reduces the economy of the process of producing glycerol carbonate. The reaction method of glycerol and carbon dioxide has high atom economy and can effectively utilize the greenhouse gas carbon dioxide, which has both economic and environmental benefits. It is an attractive method, but because carbon dioxide is a highly stable molecule, it is difficult to Therefore, the synthesis method has harsh reaction conditions and low conversion rate of reactants, which limits its industrialization process. In comparison, the glycerol and urea reaction method has the following advantages: (1) urea is actually a derivative of carbon dioxide, and the ammonia gas produced by the reaction can react with carbon dioxide to generate urea again, so this method can indirectly consume carbon dioxide; ( 2) The physical and chemical properties of urea are more active than carbon dioxide. Therefore, compared with the carbon dioxide reaction method, the reaction conditions of the urea reaction method are milder and easier to carry out; (3) The source of urea is wide and the price is low, so that the raw material cost of the product is significantly reduced, and the economy is economical. The benefits are obvious. Therefore, the reaction method of glycerol and urea has a good industrialization prospect. The reaction equation is:

At present, the catalysts used for the reaction of glycerol and urea mainly include homogeneous catalysts and heterogeneous catalysts. Among them, the homogeneous catalyst mainly includes some zinc salts (such as zinc chloride, zinc bromide, zinc iodide, zinc sulfate, etc.) and zinc oxide. Park et al. investigated the catalytic activities of zinc salts such as zinc chloride, zinc bromide, and zinc iodide, and found that among these zinc salt catalysts, zinc chloride had the highest activity. 80.4% glycerol conversion and 80.2% glycerol carbonate yield were obtained by reacting at 150°C for 2 hours (Park J H, Choi J S, Woo S K, et al. Isolation and characterization of intermediate catalytic species in the Zn-catalyzed glycerolysis of urea). [J]. Applied Catalysis A: General, 2012, 433-434:35-45.). Although the homogeneous catalyst has high activity, it is difficult to separate and purify the product after the reaction, and the catalyst is also difficult to recover and reuse. Heterogeneous catalysts mainly include metal oxide catalysts (such as magnesium oxide, calcium oxide, lanthanum oxide, etc.), supported ionic liquid catalysts, supported metal nanoparticle catalysts (such as Au/MgO nanoparticle catalysts), hydrotalcite catalysts, etc. . Chinese Patent (Application Publication No. CN102794189A) discloses a catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is supported by magnesium oxide and other metal oxides (such as zinc oxide, calcium oxide, etc.) on hydroxyapatite composition above. When the catalyst is used to catalyze the reaction of glycerol and urea, the yield of glycerol carbonate can reach up to 78.0%, but the reaction process requires acetonitrile as a solvent, which increases the difficulty of product separation and purification. Although the above heterogeneous catalysts are easy to be recycled and reused, the catalyst activity is relatively low, the preparation process is relatively complicated, and the cost of metal nanoparticle catalysts and ionic liquid catalysts is also high, which is not conducive to industrial application.

酸性，可作为酸、氧化双功能催化剂。杂多酸(盐)在催化反应方面具有反应条件温和、无毒、不腐蚀设备、结构稳定、热稳定性高等优点，受到了越来越多的关注。Heteropolyacids (salts), as a new class of green solid acid catalysts, have definite compositions and structures and are stronger than inorganic acids (sulfuric acid, hydrochloric acid).

Acidic, can be used as acid and oxidation bifunctional catalyst. Heteropolyacids (salts) have the advantages of mild reaction conditions, non-toxicity, non-corrosive equipment, stable structure, and high thermal stability in catalytic reactions, and have received more and more attention.

At present, there is no relevant report on the use of zinc-based composite heteropoly acid salts as catalysts for the synthesis of glycerol carbonate by reacting glycerol with urea.

SUMMARY OF THE INVENTION

The invention solves the technical problems in the prior art that the catalyst for catalyzing the reaction of urea and glycerol has low catalytic activity and the catalyst is difficult to recycle. In the present invention, the zinc material system is immersed in the heteropolyacid salt solution to obtain a complex of the zinc material system and the heteropolyacid salt. When the composite is used to catalyze the reaction of urea and glycerol, the catalytic activity is high, the cost is low, and the complex is easy to be recycled and reused, so as to solve the technical problems of low activity, difficult recovery and high cost of the existing catalyst.

According to a first aspect of the present invention, a preparation method of a catalyst is provided, comprising the following steps:

(1) the heteropolyacid is dissolved in water, obtains the heteropolyacid solution, in this heteropolyacid solution, drips the potassium salt aqueous solution, makes the described heteropolyacid and the potassium salt react to obtain the heteropolyacid potassium;

(2) the potassium heteropolyacid obtained in step (1) is dried and ground successively to obtain powdery potassium heteropolyacid;

(3) dissolving a zinc material system in a solvent with a boiling point less than or equal to water, where the zinc material system is zinc nitrate, zinc acetate or basic zinc carbonate, to obtain a zinc material system solution; adding the zinc material system solution to the zinc material system For the powdered potassium heteropolyacid described in step (2), the potassium heteropolyacid is immersed in the zinc material system solution, and then the solvent is removed by drying to obtain a supported catalyst of the zinc material system and the potassium heteropolyacid.

Preferably, after the step (3), the method further comprises calcining the obtained supported catalyst at 300° C. to 700° C. for 3 hours to 5 hours, so as to decompose the zinc species in the supported catalyst to obtain zinc oxide, The zinc oxide is re-coordinated with the ligand atoms in the potassium heteropolyacid to form an inorganic salt to obtain a composite catalyst.

Preferably, the heteropolyacid is phosphotungstic acid, phosphomolybdic acid or silicotungstic acid.

Preferably, the potassium salt is potassium chloride, potassium oxalate or potassium acetate.

Preferably, step (2) also includes a process of roasting the powdered potassium heteropolyacid to remove crystal water; the solvent in step (3) is ethanol, methanol or distilled water; the immersion time in step (3) is 5 hours - 12 hours.

According to another aspect of the present invention, a catalyst prepared by any of the methods is provided.

According to another aspect of the present invention, the application of the catalyst for catalyzing the reaction of glycerol and urea to synthesize glycerol carbonate is provided.

Preferably, after the catalytic reaction, the catalyst is recovered by filtration, and the reaction of glycerol and urea is catalyzed again; preferably, the number of times of the re-catalysis is less than or equal to 5 times;

Preferably, the mass ratio of catalyst to glycerol is (0.01-0.1):1.

Preferably, the temperature of glycerol and urea reaction is 120 ℃-160 ℃, the time of reaction is 1 hour-5 hour, the ratio of the amount of glycerol and urea substance is 2:(1-4), and the pressure of reaction is 2kPa- 3kPa.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) adopt heteropolyacid and potassium salt metathesis reaction to generate heteropolyacid potassium in the preparation method of the present invention, because the heteropolyacid salt thermal stability of potassium exchange is good; The homogeneous catalyst is easy to recover after the reaction; at the same time, the potassium salt required for the preparation of potassium heteropolyacid is cheap and widely available. In the present invention, the prepared supported catalyst is calcined, and the zinc species in the supported catalyst is decomposed to obtain zinc oxide. During the high-temperature calcination process, the zinc oxide (hydroxyl group on the surface) produced by calcination is strongly formed with the heteropolyacid structure. The interaction leads to the cleavage of the heteropolyacid structure into different units, in which a new phase is formed between a large number of coordination units and Zn-O, and a new inorganic zinc salt is stably formed.

(2) The catalyst prepared by the present invention has high catalytic activity, and the catalyst can be reused for many times. The catalyst prepared by the invention is used for synthesizing glycerol carbonate by reacting glycerol and urea, and has high catalytic activity. The uncalcined supported catalyst can catalyze the reaction of glycerol and urea to achieve a glycerol carbonate yield of 85.8%, which is higher than that of single nitric acid. The activities of zinc and potassium heteropolyacid are improved; and the calcined composite catalyst can also achieve a glycerol carbonate yield of 73.5%, and its catalytic activity is higher than that of the homogeneous catalyst zinc sulfate. At the same time, after the uncalcined supported catalyst is recycled for 5 times, the glycerol conversion rate of 96.5% and the glycerol carbonate yield of 69.5% can still be obtained. The excellent catalytic performance of the calcined composite catalyst is attributed to the co-assistance of Lewis acidic sites and Lewis basic sites. The active components of the composite catalyst after calcination are mainly ZnWO ₄ or ZnMoO ₄ , in which Zn ions can act as Lewis acid sites to activate the carbonyl group of urea, while WO ₄ ^2- and MoO ₄ ^2- can act as Lewis basic sites, The hydroxyl group of glycerol is activated, thereby activating the two raw materials and catalyzing the reaction.

(3) The catalyst prepared by the present invention is easy to recover. The catalyst prepared by the invention is a heterogeneous catalyst, the active component is less dissolved, exists in a solid form in the reaction process, and can be recovered and reused by simple methods such as filtration.

(4) The catalyst prepared by the present invention is environmentally friendly and does not corrode and damage equipment. The catalyst prepared by the invention is a green and environment-friendly catalyst, and will not cause corrosion and damage to the reactor during the reaction process.

(5) In the preparation method of the present invention, the raw materials are cheap, the sources are wide, the catalyst preparation process is simple, and the cost is low. The precursors of the catalyst active species of the present invention are common zinc salts and heteropoly acid salts, the raw materials are cheap, the sources are wide, the preparation method is an impregnation method, and the process is simple and easy to implement.

Description of drawings

1 is the XRD spectrum of the zinc-based composite potassium phosphotungstate catalyst prepared in Example 1.

FIG. 2 is the FT-IR spectra of the zinc-based composite potassium phosphotungstate catalysts prepared in Example 1 and Example 2. FIG.

3 is the FT-IR spectra of the zinc-based composite potassium phosphotungstate catalysts prepared in Example 1, Example 3 and Example 4.

FIG. 4 is the FT-IR spectra of the zinc-based composite potassium heteropolyacid catalysts prepared in Example 1 and Example 8. FIG.

5 is a schematic diagram of the reaction mechanism of the zinc-based composite potassium phosphotungstate catalyst prepared in Example 1.

FIG. 6 is an XRD pattern of the zinc-based composite potassium phosphomolybdate catalyst prepared in Example 7. FIG.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The invention provides a catalyst for synthesizing glycerol carbonate by reacting glycerol and urea. The catalyst is composed of a zinc material system supported on a heteropoly acid salt, the zinc material system precursor is zinc nitrate, zinc acetate or basic zinc carbonate, and the heteropoly acid salt is potassium phosphotungstate, phosphomolybdic acid Potassium or potassium silicotungstate. The mass of the zinc system is 20% to 70% of the mass of the heteropolyacid salt (calculated by the mass of the zinc oxide completely generated by the calcination of the zinc system relative to the potassium heteropolyacid).

The invention provides a kind of preparation method of the catalyst used for glycerol and urea reaction synthesis glycerol carbonate, comprises the following steps:

(1) Phosphotungstic acid crystal hydrate (H ₃ PW ₁₂ O ₄₀ · _X H ₂ O) was calcined at 110° C. for 2 hours to remove most of the crystal water, and ground to obtain a solid powder.

(2) dissolve the phosphotungstic acid solid powder of step (1) gained in a small amount of distilled water, stir to dissolve it, obtain a clear transparent phosphotungstic acid solution, and dissolve the potassium chloride of the stoichiometric ratio in distilled water to make a solution , and then slowly drop the potassium chloride solution into the phosphotungstic acid solution, while vigorously stirring, a white precipitate will gradually form during the reaction. .

(3) centrifuging the mixture obtained in step (2), washing the obtained solid with distilled water for several times until no Cl exists ⁱⁿ the solution, drying and grinding, and calcining at 300° C. for 2 hours to obtain a white powdery sample phosphorus Potassium tungstate, recorded as K3PW.

(4) Dissolving a certain amount of zinc precursor in an appropriate amount of solvent, adding the K3PW obtained in step (3) under stirring, stirring and immersing at room temperature for 12 hours, then drying the obtained mixture for 12 hours, and grinding to obtain a supported type catalyst precursor. The zinc precursor is zinc nitrate, zinc acetate or basic zinc carbonate, preferably zinc nitrate; the solvent is distilled water or absolute ethanol, preferably distilled water.

(5) The dried catalyst precursor is placed in a muffle furnace and calcined at 100° C. to 700° C. for 3 to 5 hours, and the obtained white solid material is denoted as ZnO/K PW, which is the reaction of glycerol and urea to synthesize glycerol carbonate catalyst.

The catalyst for synthesizing glycerol carbonate by the reaction of glycerol and urea provided by the invention, its catalytic reaction temperature is between 120 DEG C and 160 DEG C, the reaction time is between 1 hour and 5 hours, and the molar ratio of glycerol and urea is 2: Between 1 and 1:2, the reaction pressure is between 2kPa and 3kPa, and the mass ratio of catalyst to glycerol is between 1% and 10%.

The reaction mechanism of the calcined composite catalyst is shown in FIG. 5 . The excellent catalytic performance of the composite catalyst is attributed to the co-assistance of its Lewis acidic sites and Lewis basic sites. The active components of the calcined composite catalyst are mainly ZnWO ₄ or ZnMoO ₄ , in which Zn ions can act as Lewis acid sites to activate the carbonyl group of urea, and WO ₄ ^2- can act as Lewis basic sites to activate the hydroxyl groups of glycerol, thereby The two raw materials are activated to catalyze the reaction.

Example 1

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of zinc material system supported on a heteropoly acid salt, the zinc material system precursor is zinc nitrate, and the heteropoly acid salt is phosphorus Potassium Tungstate. Wherein zinc nitrate is 50% of the mass of potassium phosphotungstate (calculated by the mass of zinc oxide completely generated by calcination of zinc system relative to potassium phosphotungstate), and the calcination temperature of the catalyst is 500°C.

Described zinc material series composite heteropolyacid salt catalyst, and its preparation method comprises the following steps:

(1) Phosphotungstic acid crystal hydrate (H ₃ PW ₁₂ O ₄₀ · _X H ₂ O) was calcined at 110° C. for 2 hours to remove most of the crystal water, and ground to obtain a solid powder.

(2) dissolve the phosphotungstic acid solid powder of step (1) gained in a small amount of distilled water, stir to dissolve it, obtain a clear transparent phosphotungstic acid solution, and dissolve the potassium chloride of the stoichiometric ratio in distilled water to make a solution , and then slowly drop the potassium chloride solution into the phosphotungstic acid solution, while vigorously stirring, a white precipitate will gradually form during the reaction. .

(3) centrifuging the mixture obtained in step (2), washing the obtained solid with distilled water for several times until no Cl exists ⁱⁿ the solution, drying and grinding, and calcining at 300° C. for 2 hours to obtain a white powdery sample phosphorus Potassium tungstate, recorded as K3PW.

(4) Dissolving a quantitative amount of zinc nitrate in an appropriate amount of distilled water, adding the K3PW obtained in step (3) under stirring, stirring and immersing at room temperature for 12 hours, then drying the obtained mixture for 12 hours, and grinding to obtain a supported catalyst precursor.

(5) The dried catalyst precursor is placed in a muffle furnace and fired at 500° C. for 4 hours, and the obtained white solid material is denoted as ZnO/K PW, which is the catalyst for synthesizing glycerol carbonate by reacting glycerol and urea.

The prepared catalyst is used for synthesizing glycerol carbonate by reacting glycerol and urea, and the reaction conditions are as follows: the reaction temperature is 140° C., the reaction time is 4 hours, the molar ratio of glycerol and urea is 1:1, the reaction pressure is 3kPa, the catalyst and glycerol are The mass ratio is 5%. After the reaction, the reaction product was taken out, and the composition of the product was analyzed by gas chromatography. The conversion rate of glycerol was 86.4%, and the yield of glycerol carbonate could reach 73.5%.

Catalyst characterization, as shown in Figure 1, XRD analysis shows that the main component of the catalyst is zinc tungstate, and a small amount of zinc oxide exists, and no obvious characteristic peaks of potassium phosphotungstate species are seen in the XRD spectrum . The zinc tungstate species in the XRD pattern were formed from zinc nitrate and potassium phosphotungstate during the calcination process.

Example 2

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of a zinc material system supported on a heteropoly acid salt, the zinc material system is zinc nitrate, and the heteropoly acid salt is phosphotungstic acid Potassium. Wherein, zinc nitrate is 50% of the mass of potassium phosphotungstate (calculated in terms of the mass of zinc oxide completely generated by calcination of zinc system relative to potassium phosphotungstate)).

The preparation method of the zinc-based supported heteropoly acid salt catalyst is the same as that in Example 1, and the drying temperature used in step (4) is 100° C., excluding step (5). The prepared catalyst is used for synthesizing glycerol carbonate by reacting glycerol and urea. The reaction conditions are the same as those in Example 1. After the reaction, the reaction product is taken out, and the composition of the product is analyzed by gas chromatography. The yield can reach 85.8%. The catalyst was recovered, washed with methanol for 3 times, and used directly for the next reaction. According to the above conditions, the catalyst was recycled 5 times, and the product composition was analyzed by gas chromatography. After the fifth reaction, the conversion rate of glycerol was 96.5%. The yield of glycerol carbonate was 69.5%.

In this embodiment, the drying temperature described in step (4) is 100° C. The influence of the amount of the supported catalyst prepared in step (4) on the reaction activity of urea and glycerol is shown in Table 1, and the supported catalyst prepared in step (4) is shown in Table 1. The influence of the reaction time for catalyzing urea and glycerol on the reaction activity is shown in Table 2, and the supported catalyst prepared by step (4) is used for catalyzing the influence of urea and glycerol reaction temperature on the reaction activity and is shown in Table 3, and the step (4) is prepared When the supported catalyst catalyzes the reaction of urea and glycerol, the effect of the ratio of the amount of glycerol to urea substances on the reaction activity is shown in Table 4.

Table 1 The effect of catalyst dosage on the reactivity of urea and glycerol

Table 2 Effect of reaction time on reactivity

Table 3 Influence of reaction temperature on reactivity

The effect of the ratio of the amount of table 4 glycerol to urea substances on the reactivity

Example 3

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of a zinc material system supported on a heteropoly acid salt, the zinc material system precursor is zinc acetate, and the heteropoly acid salt is phosphorus Potassium Tungstate. Wherein, zinc acetate is 50% of the mass of potassium phosphotungstate (calculated by the mass of zinc oxide completely generated by calcination of zinc system relative to potassium phosphotungstate), and the calcination temperature of the catalyst is 500°C.

The preparation method of the zinc-based composite heteropoly acid salt catalyst is the same as that of Example 1, but the zinc-based precursor is changed to zinc acetate. The prepared catalyst was used for synthesizing glycerol carbonate by reacting glycerol and urea, and the reaction conditions were the same as those in Example 1. After the reaction was completed, the reaction product was taken out, and the product composition was analyzed by gas chromatography. The glycerol conversion rate was 85.6%, and the glycerol carbonate The yield was 67.3%.

Example 4

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of a zinc material system supported on a heteropoly acid salt, the zinc material system precursor is basic zinc carbonate, and the heteropoly acid salt It is potassium phosphotungstate. Wherein basic zinc carbonate is 50% of the mass of potassium phosphotungstate (in terms of the mass of zinc oxide completely generated by calcination of zinc system relative to potassium phosphotungstate), and the calcination temperature of the catalyst is 500°C.

The preparation method of the zinc-based composite heteropoly acid salt catalyst is the same as that in Example 1, but the zinc-based precursor is changed to basic zinc carbonate. The prepared catalyst was used for glycerol and urea to react to synthesize glycerol carbonate. The reaction conditions were the same as those of Example 1. After the reaction, the reaction product was taken out, and the product composition was analyzed by gas chromatography. The glycerol conversion rate was 84.6%, and the glycerol carbonate The ester yield was 60.6%.

FIG. 2 is the FT-IR spectra of the zinc-based composite potassium phosphotungstate catalysts prepared in Example 1 and Example 2. FIG. Curve (a) in Fig. 2 is the FT-IR spectrum of the zinc-based composite potassium phosphotungstate catalyst prepared in Example 1. It can be seen that the absorption peaks obviously belong to zinc tungstate, and the 877cm ^-1 and 834cm ^-1 peaks belong to Zn- The vibration absorption peaks of OW, 705cm ^-1 and 633cm ^-1 peaks belong to the vibration absorption peaks of WO, and the 538cm ^-1 and 472cm ^-1 peaks belong to the vibration absorption peaks of Zn-O. Curve (b) in Fig. 2 is the FT-IR spectrum of the zinc-based supported potassium phosphotungstate catalyst obtained in Example 2, and it can be seen that the absorption peak belonging to potassium phosphotungstate is obviously, and the wavelength in the fingerprint region is 1081 cm ^-1 , The peaks at 986cm ^-1 , 890cm ^-1 and 803cm ^-1 belong to the characteristic peaks of potassium phosphotungstate, and the absorption peak at 1387cm ^-1 indicates the existence of NO ₃ ^- .

FIG. 3 is the FT-IR spectra of the zinc-based composite potassium phosphotungstate catalysts prepared in Example 1, Example 3 and Example 4. FIG. Curve (a) in FIG. 3 is the FT-IR spectrum of the zinc-based composite potassium phosphotungstate catalyst prepared in Example 1. Curve (b) in Fig. 3 is the FT-IR spectrum of the zinc-based composite potassium phosphotungstate catalyst prepared in Example 3. It can be seen that the absorption peaks obviously belong to zinc tungstate, and the peaks at 877 cm ^-1 and 834 cm ^-1 belong to Zn -OW vibration absorption peaks, 705cm ^-1 and 633cm ^-1 peaks belong to WO vibration absorption peaks, 538cm ^-1 and 472cm ^-1 peaks belong to Zn-O vibration absorption peaks. These characteristic peaks are basically consistent with the characteristic peaks of the sample in Example 1. Curve (c) in Fig. 3 is the FT-IR spectrum of the zinc-based composite potassium phosphotungstate catalyst prepared in Example 4. It can be seen that the absorption peaks obviously belong to zinc tungstate, and the peaks at 877 cm ^-1 and 834 cm ^-1 belong to Zn -OW vibration absorption peaks, 705cm ^-1 and 633cm ^-1 peaks belong to WO vibration absorption peaks, 538 and 472cm ^-1 peaks belong to Zn-O vibration absorption peaks. These characteristic peaks are basically consistent with the characteristic peaks of the sample of Example 1 and the characteristic peak of the sample of Example 3.

Example 5

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of zinc material system supported on a heteropoly acid salt, the zinc material system precursor is zinc nitrate, and the heteropoly acid salt is phosphorus Potassium Tungstate. Wherein, zinc nitrate is 50% of the mass of potassium phosphotungstate (calculated based on the mass of zinc oxide completely generated by calcination of zinc system relative to potassium phosphotungstate).

The preparation method of the zinc-based composite heteropoly acid salt catalyst is the same as that in Example 1, but the calcination temperature is changed to 300°C-700°C. The prepared catalyst was used for glycerol and urea to react to synthesize glycerol carbonate, and the reaction conditions were the same as those in Example 1. After the reaction, the reaction product was taken out, and the product composition was analyzed by gas chromatography. Its catalytic performance is shown in Table 5.

Table 5 Effects of calcination temperature on catalytic activity of catalysts

Example 6

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of zinc material system supported on a heteropoly acid salt, the zinc material system precursor is zinc nitrate, and the heteropoly acid salt is phosphorus Potassium Tungstate.

The preparation method of the zinc compound type composite heteropoly acid salt catalyst is the same as that in Example 1, but the mass percentage of zinc nitrate relative to potassium phosphotungstic acid is changed (the zinc oxide that is completely generated by the zinc system roasting is relative to phosphotungstic acid). potassium mass meter). The prepared catalyst was used for glycerol and urea to react to synthesize glycerol carbonate, and the reaction conditions were the same as those in Example 1. After the reaction, the reaction product was taken out, and the product composition was analyzed by gas chromatography. Its catalytic performance is shown in Table 6.

Table 6 Effects of different ZnO/K3PW on the catalytic activity of catalysts

Example 7

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of zinc material system supported on a heteropoly acid salt, the zinc material system precursor is zinc nitrate, and the heteropoly acid salt is phosphorus Potassium Molybdate. Wherein, zinc nitrate is 50% of the mass of potassium phosphomolybdate (calculated by the mass of zinc oxide completely generated by calcination of zinc system relative to potassium phosphomolybdate), and the calcination temperature of the catalyst is 500°C.

Said zinc-based composite heteropoly acid salt catalyst, and its preparation method, comprising the following steps:

(1) Phosphomolybdic acid crystal hydrate (H ₃ PMo ₁₂ O ₄₀ · _X H ₂ O) was calcined at 110° C. for 2 hours to remove most of the crystal water, and ground to obtain a solid powder.

(2) the phosphomolybdic acid solid powder of step (1) gained is dissolved in a small amount of distilled water, stir to dissolve it, obtain a transparent phosphomolybdic acid solution, the potassium chloride of the stoichiometric ratio is dissolved in distilled water to make a solution, Then the potassium chloride solution was slowly added dropwise to the phosphomolybdic acid solution, and at the same time, the solution was vigorously stirred, and a precipitate would gradually form during the reaction.

(3) centrifuging the mixture obtained in step (2), washing the obtained solid with distilled water for several times until no Cl exists ⁱⁿ the solution, drying and grinding, calcining at 300° C. for 2 hours to obtain a yellow powdery sample phosphorus Potassium molybdate, denoted as K3PMo.

(4) Dissolving a quantitative amount of zinc nitrate in an appropriate amount of distilled water, adding the K3PMo obtained in step (3) under stirring, stirring and dipping at room temperature for 12 hours, then drying the obtained mixture for 12 hours, and grinding to obtain a supported catalyst precursor.

(5) The dried catalyst precursor was placed in a muffle furnace and calcined at 500° C. for 4 hours, and the light yellow substance obtained by taking out was denoted as ZnO/K PMo, which was the catalyst for synthesizing glycerol carbonate by reacting glycerol and urea.

The prepared catalyst is used for synthesizing glycerol carbonate by reacting glycerol and urea, and the reaction conditions are as follows: the reaction temperature is 140° C., the reaction time is 4 hours, the molar ratio of glycerol and urea is 1:1, the reaction pressure is 3kPa, the catalyst and glycerol are The mass ratio is 5%. After the reaction, the reaction product was taken out, and the composition of the product was analyzed by gas chromatography. The conversion rate of glycerol was 91.1%, and the yield of glycerol carbonate could reach 74.6%.

FIG. 6 is an XRD pattern of the zinc-based composite potassium phosphomolybdate catalyst prepared in Example 7. FIG. The bottom spectrum in Figure 6 is the standard XRD spectrum card JCPDS72-1846 belonging to zinc molybdate (ZnMoO ₄ ), and the upper spectrum belongs to the catalyst spectrum of zinc compound potassium phosphomolybdate, through the comparison of characteristic peaks , it can be confirmed that the composite catalyst prepared in Example 7 clearly contains the active material system ZnMoO ₄ .

Example 8

A catalyst for synthesizing glycerol carbonate by reacting glycerol and urea, the catalyst is composed of zinc material system supported on a heteropoly acid salt, the zinc material system precursor is zinc nitrate, and the heteropoly acid salt is silicon Potassium Tungstate. Wherein, zinc nitrate is 50% of the mass of potassium silicotungstate (calculated by the mass of zinc oxide completely generated by calcination of zinc system relative to potassium silicotungstate), and the calcination temperature of the catalyst is 500°C.

Said zinc-based composite heteropoly acid salt catalyst, and its preparation method, comprising the following steps:

(1) silicotungstic acid crystal hydrate (H ₄ SiW ₁₂ O ₄₀ · _X H ₂ O) was calcined at 110° C. for 2 hours to remove most of the crystal water, and ground to obtain a solid powder.

(2) dissolving the silicotungstic acid solid powder of step (1) gained in a small amount of distilled water, stirring to dissolve it, obtaining a clear and transparent silicotungstic acid solution, dissolving the potassium chloride of the stoichiometric ratio in distilled water and making up solution, and then slowly drop the potassium chloride solution into the silicotungstic acid solution while stirring vigorously.

(3) place the clear solution obtained in step (2) in an oven to dry the moisture, and the white solid obtained after removing the moisture is ground and calcined at 300 ° C for 2 hours to obtain a white powdery sample potassium silicotungstate, denoted as K SiW .

(4) Dissolving a quantitative amount of zinc nitrate in an appropriate amount of distilled water, adding the K4SiW obtained in step (3) under stirring, stirring and immersing at room temperature for 12 hours, then drying the obtained mixture for 12 hours, and grinding to obtain a supported catalyst precursor.

(5) The dried catalyst precursor is placed in a muffle furnace and calcined at 500° C. for 4 hours, and the obtained white substance is denoted as ZnO/K SiW, which is a catalyst for synthesizing glycerol carbonate by reacting glycerol and urea.

The prepared catalyst is used for synthesizing glycerol carbonate by reacting glycerol and urea, and the reaction conditions are as follows: the reaction temperature is 140° C., the reaction time is 4 hours, the molar ratio of glycerol and urea is 1:1, the reaction pressure is 3kPa, the catalyst and glycerol are The mass ratio is 5%. After the reaction is completed, the reaction product is taken out, and the composition of the product is analyzed by gas chromatography. The conversion rate of glycerol is 75.7%, and the yield of glycerol carbonate can reach 60.3%.

FIG. 4 is the FT-IR spectra of the zinc-based composite potassium heteropolyacid catalysts prepared in Example 1 and Example 8. FIG. Curve (a) in FIG. 4 is the FT-IR spectrum of the zinc-based composite potassium phosphotungstate catalyst prepared in Example 1. Curve (b) in Figure 4 is the FT-IR spectrum of the zinc-based composite potassium silicotungstate catalyst prepared in Example 8. It can be seen that the absorption peaks obviously belong to zinc tungstate, and the 885cm ^-1 and 818cm ^-1 peaks belong to Zn -OW vibration absorption peak, 720cm ^-1 and 610cm ^-1 peaks belong to WO vibration absorption peak, 472cm ^-1 peak belongs to Zn-O vibration absorption peak. These characteristic peaks are basically consistent with the characteristic peaks of the sample in Example 1.

Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (11)

1. a preparation method for the heterogeneous catalyst of catalyzing glycerol and urea reaction synthesis glycerol carbonate, is characterized in that, contains following steps: (1) the heteropolyacid is dissolved in water, obtains the heteropolyacid solution, in this heteropolyacid solution, drips the potassium salt aqueous solution, makes the described heteropolyacid and the potassium salt react to obtain the heteropolyacid potassium; (2) the potassium heteropolyacid obtained in step (1) is dried and ground successively to obtain powdery potassium heteropolyacid; (3) dissolving a zinc material system in a solvent with a boiling point less than or equal to water, wherein the zinc material system is zinc nitrate, zinc acetate or basic zinc carbonate, to obtain a zinc material system solution; adding the zinc material system solution to the zinc material system For the powdered potassium heteropolyacid in step (2), the potassium heteropolyacid is immersed in the zinc material system solution, and then the solvent is removed by drying to obtain a supported catalyst of the zinc material system and the potassium heteropolyacid. 2. The preparation method of catalyst as claimed in claim 1, is characterized in that, after described step (3), also comprises the supported catalyst obtained under 300 ℃-700 ℃ of conditions roasting 3 hours-5 hours, make The zinc species in the supported catalyst is decomposed to obtain zinc oxide, and the zinc oxide is re-coordinated with the ligand atoms in the potassium heteropolyacid to form an inorganic salt to obtain a composite catalyst. 3. The preparation method of a catalyst according to claim 1 or 2, wherein the heteropolyacid is phosphotungstic acid, phosphomolybdic acid or silicotungstic acid. 4. the preparation method of catalyst as claimed in claim 1 or 2, is characterized in that, described potassium salt is potassium chloride, potassium oxalate or potassium acetate. 5. the preparation method of catalyst as claimed in claim 1 or 2, is characterized in that, step (2) also comprises the process that described powdery potassium heteropolyacid is roasted to remove crystal water; The solvent described in step (3) It is ethanol, methanol or distilled water; the soaking time of step (3) is 5 hours-12 hours. 6. The catalyst prepared by the method of any one of claims 1-5. 7. The application of the catalyst as claimed in claim 6 for catalyzing the reaction of glycerol and urea to synthesize glycerol carbonate. 8. The application according to claim 7, characterized in that, after the catalytic reaction, the catalyst is recovered by filtration, and the reaction of glycerol and urea is catalyzed again. 9 . The application according to claim 8 , wherein the number of times of re-catalysis is less than or equal to 5 times. 10 . 10. application as claimed in claim 7 is characterized in that, the mass ratio of catalyst and glycerol is (0.01-0.1): 1. 11. application as claimed in claim 7, is characterized in that, the temperature of glycerol and urea reaction is 120 ℃-160 ℃, and the time of reaction is 1 hour-5 hour, and the ratio of the amount of substance of glycerol and urea is 2: (1-4), the reaction pressure is 2kPa-3kPa.

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