Method and catalyst for sustainable preparation of pyrrole compound

Abstract

The present invention provides a method and a catalyst for the green sustainable preparation of a pyrrole compound. The pyrrole compound is prepared by means of the dehydrogenation and cross condensation of an alcohol molecule and a 2-amino alcohol molecule, wherein the alcohol molecule comprises ethanol, propanol, isopropanol, butanol and a high-carbon fatty alcohol, and the amino alcohol comprises 2-aminoethanol and a substituted 2-amino alcohol. The catalyst is composed of composite oxide loaded metal nanoparticles, wherein the metal nanoparticles are mainly composed of one or more of Ni, Co and Cu; and the composite oxide is composed of two or three of nickel oxide, cobalt oxide, magnesium oxide, aluminum oxide, zinc oxide and zirconium oxide. By means of the catalyst, a pyrrole compound is prepared from an alcohol molecule and a 2-amino alcohol molecule for the first time under the condition of no additional alkali, and the highest yield can reach 99%.

Description

A sustainable method for preparing pyrrole compounds and catalyst Technical Field

[0001] The present invention relates to the fields of chemistry and catalysts, and in particular to a method for preparing pyrrole compounds by efficiently catalyzing the dehydrogenation and cross-condensation of alcohol molecules and 2-amino alcohol molecules and a catalyst thereof. Background Art

[0002] Pyrroles, as highly important five-membered nitrogen-containing heterocyclic compounds, are widely used in medicine due to their antitumor and antibacterial activities. For example, they serve as key building blocks for the synthesis of sumatinib and atorvastatin, drugs for treating gastric cancer and hypercholesterolemia. Pyrrole is also a key structural unit of chlorophyll in green plants and heme in human hemoglobin. Polypyrrole, a pyrrole-based monomer, is a high-molecular-weight conductive polymer used in batteries and capacitors. Therefore, exploring the green and sustainable preparation of pyrrole compounds is of great significance and value.

[0003] In industry, the earliest industrial production method of pyrrole is to use Pd, Ru and other catalysts to react 1,4-butynediol with ammonia, with a yield of more than 65%. Later, the production of pyrrole by MoO under high temperature was gradually developed. x , VO x The traditional industrial route for preparing pyrrole compounds is characterized by the raw materials mainly coming from petrochemicals, requiring high temperature and pressure, harsh reaction conditions, and high loadings of precious metals as active centers, resulting in high catalyst costs.

[0004] In laboratory preparation, the synthesis of pyrroles is primarily categorized into the Knorr reaction, which involves the condensation of α-halomethyl ketones, β-ketoesters, and ammonia; the Paal-Knorr reaction, which involves the condensation of 1,4-diketones with primary amines or ammonia; the Barton–Zard reaction, which involves the reaction of nitroolefins with α-isocyanatoacetic esters under alkaline conditions to produce pyrrole derivatives; and the Hantzsch reaction, which involves the condensation of α-aminoketones with carbonyl compounds containing electron-withdrawing groups at the α-position. However, these numerous pyrrole synthesis methods often require the addition of an equivalent amount of strong acid or base, the formation of environmentally hazardous halides, and the prior synthesis of specific reaction substrates. Therefore, the development of green and sustainable methods for the preparation of pyrrole compounds, without the need for the addition of strong acid or base, using renewable, inexpensive, and readily available reaction substrates, holds great scientific and industrial significance.

[0005] In 2013, Kempe et al. first reported an Ir-PNP complex that catalyzed the reaction of aromatic and aliphatic secondary alcohols with substituted 2-aminoethanol in the presence of 1.1 equiv. of KOt Bu to produce 1,4-disubstituted pyrroles in yields ranging from 42% to 97%. Subsequently, Saito's group reported the synthesis of pyrroles from aromatic and aliphatic secondary alcohols with substituted 2-amino alcohols using *CpRuCl(PPh3)2 as a catalyst in the presence of 10 mol% KOt Bu, with yields ranging from 59% to 89%. Subsequently, the use of RuHCl(CO)(PPh3)3 and [(OC5H3N-CO-C5H3N-C5H4N)Ru(PPh3)2(CO)]Cl as catalysts was further developed. - Although it is a catalyst, the substrates are still limited to the reaction of aromatic and aliphatic secondary alcohols with substituted 2-amino alcohols, and the addition of a strong organic base, KOtBu, is also required; otherwise, pyrrole compounds cannot be obtained. In 2016, Milstein et al. reported that Co-PNN pincer chelates catalyzed the reaction of aliphatic secondary diols with aromatic and aliphatic long-chain primary amines in the presence of 5 mol% KOtBu to synthesize N-substituted 1,4-disubstituted pyrroles in yields of 22-93%. It is worth noting that 1,4-butanediol can also undergo this reaction, but this is only a single case with a primary diol, and the reaction of other primary diols has not been reported. Subsequently, in 2019, Banerjee's group reported that a complex formed by NiBr2 and phenanthroline ligands, in the presence of 1.0 equiv. KOtBu, catalyzed the reaction of aromatic secondary alcohols with substituted 2-aminoethanol to produce 1,4-disubstituted pyrroles in yields of 31-60%. In 2014, Kempe et al. reported the first heterogeneous catalytic synthesis of pyrroles. Using an equivalent amount of KOtBu and 1.27 wt% Ir / SiCN, they achieved yields of up to 90% for the reaction of aromatic and aliphatic secondary alcohols with substituted 2-amino alcohols. In 2016, Shimizu achieved a 92% yield for the synthesis of pyrroles from alcohols with amino alcohols using an equivalent amount of KOtBu and 5 wt% Pt / C, but the substrates were limited to reactions between secondary alcohols and substituted 2-amino alcohols.

[0006] However, the synthesis of pyrrole compounds reported in existing literature is limited to the reaction of aromatic and aliphatic secondary alcohols with substituted 2-amino alcohols. It is difficult to synthesize aromatic or aliphatic primary alcohols derived from green and renewable biomass resources, such as ethanol, propanol, butanol, furanol, and aromatic alcohols. Furthermore, existing systems require the addition of an equivalent amount of the strong organic base KOtBu, resulting in harsh reaction conditions, high production equipment requirements, and complex product separation and purification. Developing biomass-derived primary alcohols to prepare pyrrole compounds is a green and sustainable process with significant research and industrial value.

[0007] Summary of the Invention

[0008] The present invention provides a green and sustainable method for preparing pyrrole compounds, the route of which is shown in Formula I. The pyrrole compounds are prepared by dehydrogenating and cross-condensing biomass-derived alcohols with 2-amino alcohol molecules, with a yield of up to 99%. The alcohol molecules include ethanol, propanol, isopropanol, butanol, and higher-carbon aliphatic alcohols, and the amino alcohols include 2-aminoethanol and substituted 2-amino alcohols.

[0009]

[0010] The technical solutions of the present invention are as follows:

[0011] The catalytic reaction is carried out under a certain temperature, pressure and atmosphere by adding a certain amount of alcohol molecules, 2-amino alcohol molecules and a certain amount of catalyst into a certain type of reactor, reacting for a period of time. After the reaction is completed, the temperature is cooled, and a certain amount of product is taken. The yield of the pyrrole compound is determined by gas chromatography and nuclear magnetic resonance spectroscopy analysis.

[0012] Furthermore, the R1 and R2 groups in the alcohol molecule can be composed of one or more of H, methyl, ethyl, propyl, phenyl, furyl and the like.

[0013] Furthermore, the R3 and R4 groups of the 2-amino alcohol molecule can be composed of one or more groups such as H, methyl, ethyl, propyl, phenyl, and furyl.

[0014] Furthermore, the selected reactor is one of a glass tube reactor, a stainless steel reactor with a polytetrafluoroethylene lining, and a fixed bed reactor.

[0015] Furthermore, the molar ratio of the alcohol molecules to the 2-amino alcohol molecules is (2-100):1.

[0016] Furthermore, the selected reaction temperature is 50-250°C.

[0017] Furthermore, the selected reaction pressure is 0.1-2.0 MPa.

[0018] Furthermore, the selected reaction atmosphere is one of air, nitrogen, argon, etc.

[0019] Furthermore, the reaction time is 0.5-30h.

[0020] Furthermore, the added amount of the catalyst is 1-90% of the molar number of 2-amino alcohol molecules.

[0021] Furthermore, the catalyst is composed of composite oxide-supported metal nanoparticles, the metal nanoparticles are composed of one or more of Ni, Co, and Cu, and the composite oxide is composed of one or more of nickel oxide, cobalt oxide, copper oxide, magnesium oxide, aluminum oxide, iron oxide, zinc oxide, and zirconium oxide, wherein:

[0022] The loading amount of the metal nanoparticles is 5-30% based on the mass of the composite oxide.

[0023] Furthermore, the preparation method of the catalyst comprises the following steps:

[0024] Step 1) Preparation of composite metal oxide

[0025] Precipitating and calcining two or more of a divalent metal, a trivalent metal, and a tetravalent metal to form a composite metal oxide;

[0026] Step 2) Reduction of composite metal oxides

[0027] The composite metal oxide is reduced to obtain composite oxide-supported metal nanoparticles, namely the catalyst.

[0028] Furthermore, in step 1), the divalent metal is composed of one or more of Ni, Co, Cu, Mg, and Zn.

[0029] Furthermore, in step 1), the trivalent metal is one or two of Al and Fe.

[0030] Furthermore, in step 1), the tetravalent metal is composed of one or two of Zr and Ga.

[0031] Furthermore, in step 1), the molar ratio of the divalent metal oxide to the trivalent metal oxide or the tetravalent metal oxide is (2-4):1, wherein when the divalent metal oxide, the trivalent metal oxide and the tetravalent metal oxide are composited, the molar ratio of the trivalent metal oxide to the tetravalent metal oxide is (5-20):1.

[0032] Furthermore, in step 1), the precursors of the divalent, trivalent and tetravalent metals are composed of one or more of nitrates, sulfates, chlorides and organic salts of the divalent or trivalent metals.

[0033] Furthermore, in step 1), the pH value of the divalent, trivalent and tetravalent metal precipitation is 8.0-11.

[0034] Furthermore, in step 1), the metal salt precipitation time is 0.5-5h.

[0035] Furthermore, in step 1), the condition for the metal salt to form a precipitate is to control the pH of the precipitate by adding an inorganic base or organic base such as sodium hydroxide, potassium hydroxide, lithium hydroxide, urea, or hexamethylenetetramine.

[0036] Furthermore, in step 1), the drying temperature of the formed metal precipitate is 60-120° C., and the drying time is 2-24 hours.

[0037] Furthermore, in step 1), the metal precipitate is calcined at a temperature of 300-800° C. for 0.01-5 hours, and then cooled to room temperature.

[0038] Furthermore, in step 1), the atmosphere for calcining the metal precipitate is one of air, nitrogen and argon.

[0039] Furthermore, in step 2), the metal nanoparticles are composed of one or more of Ni, Co, and Cu.

[0040] Furthermore, in step 2), a certain amount of the composite metal oxide is weighed and placed in a tube furnace, and the temperature is raised to 300-800° C. in a hydrogen atmosphere and maintained for 0.01-5 hours to obtain the composite oxide-supported metal nanoparticles.

[0041] Furthermore, in step 2), the solid powder of the composite metal oxide is spread flat on the bottom of a porcelain boat, and then the porcelain boat is placed in the constant temperature zone in the center of the quartz tube of a tube furnace, and the tube furnace is gradually heated at a heating rate of 1-20°C / min. When the temperature of the constant temperature zone in the center of the quartz tube reaches 300-800°C, it is maintained for 0.01-5h, and then cooled to room temperature to obtain the metal nanoparticles loaded with the composite oxide.

[0042] The beneficial effects of the present invention are:

[0043] 1. The catalyst of the present invention can, for the first time, achieve the efficient synthesis of pyrrole compounds by dehydrogenation and cross-condensation of alcohol molecules and 2-amino alcohol molecules without the addition of an external base. It also expands the substrate alcohol from the previously reported limited aromatic primary or secondary alcohols to aliphatic primary alcohols for the first time, providing a greener and more sustainable method for preparing pyrrole compounds.

[0044] 2. In the catalyst of the present invention, since the metal nanoparticles are loaded on the acid-base bifunctional composite oxide support to form a synergistic catalytic effect, in the reaction of catalyzing alcohol molecules and 2-amino alcohol molecules to prepare pyrroles, the metal cations on the acid-base bifunctional composite oxide support act as Lewis bases to promote the activation of the OH bond in the alcohol / 2-amino alcohol, thereby generating corresponding alkoxy species. The alkoxy species are then adsorbed on the metal nanoparticles, and Cα-H activation occurs to generate a C=O bond. The generated carbonyl compound undergoes cross-condensation with the amine on the acid-base bifunctional composite oxide support, wherein the acid center on the composite oxide can activate the C=O bond and the base center activates the NH bond, thereby promoting the condensation and dehydration of the two to generate imine compounds, which then continue to undergo intramolecular dehydration and cyclization on the composite oxide to generate pyrrole compounds.

[0045] 3. By using the catalyst of the present invention, the yield of pyrrole compounds is 30-99%. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] Example 1 Highly Selective Synthesis of Pyrrole from Ethanol and 2-Aminoethanol Catalyzed by Supported Ni Catalyst

[0048] Catalyst preparation: Weigh 0.02 mol, 0.009 mol, and 0.001 mol of nickel nitrate, aluminum nitrate, and zirconium nitrate, respectively, and fully dissolve them in 150 mL of deionized water. Then weigh 0.06 mol of sodium hydroxide and fully dissolve it in 150 mL of deionized water. At the same time, weigh 0.005 mol of sodium carbonate and dissolve it in a four-necked flask filled with 150 mL of deionized water. The metal salt solution and sodium hydroxide solution are added dropwise to the four-necked flask at the same time. After the metal salt solution is added dropwise, the four-necked flask is transferred to a constant temperature water bath at 60 ° C and stirred for crystallization for 24 hours. Filter under reduced pressure, wash with deionized water until neutral, then wash once with anhydrous ethanol, filter, and dry in an oven. The precursor prepared above is reduced in hydrogen to prepare a supported Ni catalyst.

[0049] Catalytic Reaction: Accurately weigh 3.0 mL of ethanol, 0.5 mmol of 2-aminoethanol, and 30 mg of catalyst into a 20 mL glass reaction tube. The glass tube reactor was then placed in an oil bath at 120°C and allowed to react for 24 hours. After the reaction, the reactor was quickly cooled to room temperature. The liquid product was analyzed by gas chromatography. The conversion of 2-aminoethanol was greater than 99%, and the yield of pyrrole was 93.3%.

[0050] Example 2 Highly Selective Synthesis of 3-Methylpyrrole by Catalyzing Propanol and 2-Aminoethanol with Supported Ni Catalyst

[0051] Catalyst preparation: Weigh 0.02 mol, 0.009 mol, and 0.001 mol of nickel nitrate, aluminum nitrate, and zirconium nitrate, respectively, and fully dissolve them in 150 mL of deionized water. Then weigh 0.06 mol of sodium hydroxide and fully dissolve it in 150 mL of deionized water. At the same time, weigh 0.005 mol of sodium carbonate and dissolve it in a four-necked flask filled with 150 mL of deionized water. Add the metal salt solution and sodium hydroxide solution dropwise into the four-necked flask at the same time. After the metal salt solution is added dropwise, transfer the four-necked flask to a constant temperature water bath at 60°C and continue stirring and crystallizing for 24 hours. Filter under reduced pressure, wash with deionized water until neutral, then wash once with anhydrous ethanol, filter, and dry in an oven. The precursor prepared above is reduced in hydrogen to prepare a supported Ni catalyst.

[0052] Catalytic Reaction: Accurately weigh 3.0 mL of propanol, 0.5 mmol of 2-aminoethanol, and 30 mg of catalyst into a 20 mL glass reaction tube. The glass tube reactor was then placed in an oil bath at 120°C and allowed to react for 24 hours. After the reaction, the reactor was quickly cooled to room temperature. The liquid product was analyzed by gas chromatography. The conversion of 2-aminoethanol was greater than 99%, and the yield of 3-methylpyrrole was 89.2%.

[0053] Example 3 Highly Selective Synthesis of 3-Ethylpyrrole from Butanol and 2-Aminoethanol over Supported Ni Catalyst

[0054] Catalyst preparation: Weigh 0.02 mol, 0.009 mol, and 0.001 mol of nickel nitrate, aluminum nitrate, and zirconium nitrate, respectively, and fully dissolve them in 150 mL of deionized water. Then weigh 0.06 mol of sodium hydroxide and fully dissolve it in 150 mL of deionized water. At the same time, weigh 0.005 mol of sodium carbonate and dissolve it in a four-necked flask filled with 150 mL of deionized water. Add the metal salt solution and sodium hydroxide solution dropwise into the four-necked flask at the same time. After the metal salt solution is added dropwise, transfer the four-necked flask to a constant temperature water bath at 60°C and continue stirring and crystallizing for 24 hours. Filter under reduced pressure, wash with deionized water until neutral, then wash once with anhydrous ethanol, filter, and dry in an oven. The precursor prepared above is reduced in hydrogen to prepare a supported Ni catalyst.

[0055] Catalytic Reaction: Accurately weigh 3.0 mL of butanol, 0.5 mmol of 2-aminoethanol, and 30 mg of catalyst into a 20 mL glass reaction tube. The glass tube reactor was then placed in an oil bath at 120°C and allowed to react for 24 hours. After the reaction, the reactor was quickly cooled to room temperature. The liquid product was analyzed by gas chromatography. The conversion of 2-aminoethanol was greater than 99%, and the yield of 3-ethylpyrrole was 98.9%.

[0056] Example 4 Highly Selective Synthesis of 2-Methylpyrrole from Isopropanol and 2-Aminoethanol Catalyzed by Supported Ni Catalyst

[0057] Catalyst preparation: Weigh 0.02 mol, 0.009 mol, and 0.001 mol of nickel nitrate, aluminum nitrate, and zirconium nitrate, respectively, and fully dissolve them in 150 mL of deionized water. Then weigh 0.06 mol of sodium hydroxide and fully dissolve it in 150 mL of deionized water. At the same time, weigh 0.005 mol of sodium carbonate and dissolve it in a four-necked flask filled with 150 mL of deionized water. Add the metal salt solution and sodium hydroxide solution dropwise into the four-necked flask at the same time. After the metal salt solution is added dropwise, transfer the four-necked flask to a constant temperature water bath at 60°C and continue stirring and crystallizing for 24 hours. Filter under reduced pressure, wash with deionized water until neutral, then wash once with anhydrous ethanol, filter, and dry in an oven. The precursor prepared above is reduced in hydrogen to prepare a supported Ni catalyst.

[0058] Catalytic Reaction: Accurately weigh 3.0 mL of isopropanol, 0.5 mmol of 2-aminoethanol, and 30 mg of catalyst into a 20 mL glass reaction tube. Place the glass tube reactor in a 120°C oil bath and continue the reaction for 24 hours. After the reaction, quickly cool the reactor to room temperature. The liquid product is analyzed by gas chromatography. The yield of 2-methylpyrrole is 99%.

[0059] Example 5 Highly Selective Synthesis of Pyrrole from Ethanol and 2-Aminoethanol Catalyzed by Supported Co Catalyst

[0060] Catalyst preparation: Weigh 0.02 mol and 0.01 mol of cobalt nitrate and aluminum nitrate respectively and fully dissolve them in 150 mL of deionized water. Then weigh 0.06 mol of sodium hydroxide and fully dissolve it in 150 mL of deionized water. At the same time, weigh 0.005 mol of sodium carbonate and dissolve it in a four-necked flask filled with 150 mL of deionized water. Add the metal salt solution and sodium hydroxide solution dropwise into the four-necked flask at the same time. After the metal salt solution is added dropwise, transfer the four-necked flask to a constant temperature water bath at 60°C and continue stirring and crystallizing for 24 hours. Filter under reduced pressure, wash with deionized water until neutral, then wash once with anhydrous ethanol, filter, and dry in an oven. The precursor prepared above is reduced in hydrogen to prepare a supported Co catalyst.

[0061] Catalytic Reaction: Accurately weigh 3.0 mL of ethanol, 0.5 mmol of 2-aminoethanol, and 30 mg of catalyst into a 20 mL glass reaction tube. The glass tube reactor was then placed in an oil bath at 120°C and allowed to react for 24 hours. After the reaction, the reactor was quickly cooled to room temperature. The liquid product was analyzed by gas chromatography. The conversion of 2-aminoethanol was greater than 99%, and the yield of pyrrole was 44.2%.

[0062] Example 6 Highly Selective Synthesis of Pyrrole from Ethanol and 2-Aminoethanol Catalyzed by Supported Cu Catalyst

[0063] Catalyst preparation: Weigh 0.005 mol, 0.02 mol, and 0.01 mol of copper nitrate, zinc nitrate, and aluminum nitrate, respectively, and fully dissolve them in 150 mL of deionized water. Then, weigh 0.06 mol of sodium hydroxide and fully dissolve it in 150 mL of deionized water. Simultaneously, weigh 0.005 mol of sodium carbonate and dissolve it in a four-necked flask containing 150 mL of deionized water. Add the metal salt solution and sodium hydroxide solution dropwise to the four-necked flask simultaneously. After the metal salt solution is added dropwise, transfer the four-necked flask to a 60°C constant-temperature water bath and continue stirring and crystallizing for 24 hours. Filter under reduced pressure, wash with deionized water until neutral, then wash once with anhydrous ethanol, filter, and dry in an oven. The precursor prepared above is reduced in hydrogen to prepare a supported Cu catalyst.

[0064] Catalytic Reaction: Accurately weigh 3.0 mL of ethanol, 0.5 mmol of 2-aminoethanol, and 30 mg of catalyst into a 20 mL glass reaction tube. The glass tube reactor was then placed in an oil bath at 120°C and allowed to react for 24 hours. After the reaction, the reactor was quickly cooled to room temperature. The liquid product was analyzed by gas chromatography. The conversion of 2-aminoethanol was greater than 99%, and the yield of pyrrole was 30%.

[0065] [Corrected on 20.02.2025 according to Rule 91] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A method for the sustainable preparation of pyrrole compounds, characterized in that: The raw materials are composed of abundant and readily available alcohol molecules and 2-amino alcohol molecules.

2. The method for preparing pyrrole compounds according to claim 1, characterized in that: The R1 and R2 groups in the alcohol molecules are composed of one or more of H, methyl, ethyl, propyl, phenyl, furyl and the like.

3. The method for preparing pyrrole compounds according to claim 1, characterized in that: The R1 and R2 groups of the 2-amino alcohol molecules are respectively composed of one or more of H, methyl, ethyl, propyl, phenyl, furyl and the like.

4. The method for preparing pyrrole compounds according to claim 1, characterized in that: The alcohol molecules are both reactants and reaction solvents, the molar ratio of the alcohol molecules to the 2-amino alcohol molecules is (2-100):1, the amount of catalyst added is 1-90% of the molar number of the 2-amino alcohol molecules added, the reaction temperature is 50-250°C, and the reaction time is 0.5-30h.

5. The method for preparing pyrrole compounds according to claim 1, characterized in that: Reaction temperature 50-250℃.

6. The method for preparing pyrrole compounds according to claim 1, characterized in that: The reaction time is 0.5-30h.

7. The method for preparing pyrrole compounds according to claim 1, characterized in that: The reactor is one of a glass tube reactor, a stainless steel reactor with a polytetrafluoroethylene lining and a fixed bed reactor.

8. The method for preparing pyrrole compounds according to claim 1, characterized in that: The reaction atmosphere is one of air, nitrogen, argon, etc., and the pressure is 0.1-2.0 MPa.

9. The method for preparing pyrrole compounds according to claim 4, characterized in that: The catalyst is composed of composite oxide-supported metal nanoparticles.

10. The method for preparing pyrrole compounds according to claim 9, characterized in that: The composite oxide is composed of two or three of nickel oxide, cobalt oxide, magnesium oxide, aluminum oxide, zinc oxide and zirconium oxide.

11. The method for preparing pyrrole compounds according to claim 10, characterized in that: The metal nanoparticles are mainly composed of one or more of Ni, Co and Cu.

12. The method for preparing pyrrole compounds according to claim 11, characterized in that: The composite oxide consists of a divalent metal oxide and a trivalent or tetravalent metal oxide.

13. The method for preparing pyrrole compounds according to claim 12, characterized in that: The molar ratio of the divalent metal oxide to the trivalent or tetravalent metal oxide is (2-4):1; wherein when the divalent metal oxide, the trivalent metal oxide and the tetravalent metal oxide are compounded, the molar ratio of the trivalent metal oxide to the tetravalent metal oxide is (5-20):1.

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