PREPARATION METHOD OF Cu-Pd-CeO2/GAMMA-Al2O3@NP CATALYST AND SYNTHESIS METHOD OF BENZOPYRAZINE COMPOUNDS

Abstract

A preparation method of Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst and a synthesis method of benzopyrazine compounds. The preparation method of the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst comprises the following steps: (1) preparing a CeO.sub.2/γ-Al.sub.2O.sub.3 carrier; (2) preparing a CeO.sub.2/γ-Al.sub.2O.sub.3@NP carrier; (3) preparing the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst by impregnation method. A one-pot method for synthesizing benzopyrazine compounds of formula (III) includes using an o-nitroaniline compound of formula (I) and an aliphatic diol compound of formula (II) as raw materials, carrying out the one-pot synthesis of the benzopyrazine compound of formula (III) under solvent-free condition and under the combined action of the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst prepared by the method and an alkali. The Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst increases the number of basic sites by doping N and P, and meanwhile loads CeO.sub.2 to assist in the extraction of protons, thereby improving the dehydrogenation activity and product selectivity.

Claims

1. A preparation method of a Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst, in the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst, the total loading amounts of N and P is 1.2%˜4.8%, the loading amount of Cu is 0.5%˜5 wt %, the loading amount of Pd is 0.5%˜5 wt %, and the loading amount of Ce is 5%˜15 wt %; the preparation method comprises the following steps: (1) mixing a certain amount of γ-Al.sub.2O.sub.3 with deionized water, stirring the mixture to obtain a slurry, heating the slurry to 70-90° C., then adding a corresponding amount of a solution of cerium-containing compound, subjecting the mixture to stirring and impregnation at a constant temperature of 70-90° C. for 2˜6 h, adding ammonia water dropwise to adjust the pH value of the solution to 9˜10, continuing to stir the resulting solution at the constant temperature for 2˜6 h, cooling it to room temperature and filtering it, washing the filter cake with deionized water until the filtrate becomes neutral, drying it at 80˜120° C. for 5˜9 h in the air, and then calcining it at 600˜800° C. for 2˜4 h in the air to obtain a CeO.sub.2/γ-Al.sub.2O.sub.3 carrier; (2) mixing a certain amount of the CeO.sub.2/γ-Al.sub.2O.sub.3 carrier with an aqueous solution of ammonium phosphate, subjecting the mixture to stirring and impregnation at 30˜50° C. for 1˜3 h, then drying it at 80˜120° C. for 5˜9 h in the air, and then calcining the dried product at 400˜600° C. for 1˜3 h in the air to obtain a CeO.sub.2/γ-Al.sub.2O.sub.3@NP carrier; (3) mixing a certain amount of the CeO.sub.2/γ-Al.sub.2O.sub.3@NP carrier with deionized water, stirring the mixture to obtain a slurry, heated it to 60˜100° C., then adding certain amounts of a palladium-containing compound solution and a copper-containing compound solution, subjecting the mixture to stirring and impregnation at the constant temperature for 3˜7 h; cooling it to room temperature, adding an alkaline solution dropwise to adjust the pH value to 8˜10, stirring the resulting solution at the constant temperature for 0.5˜1.5 h, filtering it, washing the filter cake with deionized water until the filtrate becomes neutral; dry it at 80˜120° C. in the air for 5˜9 h; then calcining the dried product at 200˜300° C. for 2˜6 h in the air, and finally reducing the calcined product with hydrogen at 200˜300° C. for 1˜3 h, thereby obtaining the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst.

2. The preparation method of claim 1, wherein: in the Cu—Pd—CeO2/γ-Al2O3@NP catalyst, the loading amount of Pd is 1-5 wt %; the loading amount of Cu is 1-5 wt %; and the loading amount of Ce is 10%.

3. The preparation method of claim 2, wherein: in the Cu—Pd—CeO2/γ-Al2O3@NP catalyst, the loading amount of Pd is 5 wt %.

4. The preparation method of claim 2, wherein: in the Cu—Pd—CeO2/γ-Al2O3@NP catalyst, the loading amount of Cu is 3.5%.

5. The preparation method of claim 1, wherein: the palladium-containing compound is H.sub.2PdCl.sub.4, Pd(CH.sub.3COO).sub.2 or Pd(NO.sub.3).sub.2; the copper-containing compound is Cu(NO.sub.3).sub.2 or CuCl.sub.2; and the cerium-containing compound is CeCl.sub.3 or Ce(OH).sub.3.

6. The preparation method according to claim 1, wherein: in step (1), the feeding ratio of γ-Al.sub.2O.sub.3 to deionized water is 5 g: 35-45 mL, and the concentration of the cerium-containing compound solution calculated as the concentration of Ce is 0.04-0.06 g/mL.

7. The preparation method of claim 1, wherein in step (2), the concentration of the aqueous solution of ammonium phosphate is 0.002-0.0025 g/mL.

8. The preparation method of claim 1, wherein: in step (3), the feeding ratio of the CeO.sub.2/γ-Al.sub.2O.sub.3@NP carrier to deionized water calculated as the feeding ratio of γ-Al.sub.2O.sub.3 to deionized water is 5 g:35-45 mL, the concentration of the palladium-containing compound solution is 0.04-0.05 g/mL in terms of the concentration of Pd, and the concentration of the copper-containing compound solution is 0.04-0.05 g/mL in terms of the concentration of Cu.

9. The preparation method according to claim 1, wherein: in step (3), the alkaline solution is 0.05-0.15 g/ml NaOH aqueous solution, 0.05-0.15 g/ml NaHCO.sub.3 aqueous solution or 0.05-0.15 g/ml Na.sub.2CO.sub.3 aqueous solution.

10. A one-pot method for synthesizing benzopyrazine compounds of formula (III), which comprises: using an o-nitroaniline compound of formula (I) and an aliphatic diol compound of formula (II) as raw materials, carrying out the one-pot synthesis of the benzopyrazine compound of formula (III) under solvent-free condition and under the combined action of the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst prepared by the method of claim 1 and an alkali; ##STR00002## wherein, X.sub.1, X.sub.2, X.sub.3, X.sub.4 are each independently hydrogen, methyl, ethyl or methoxy; R.sub.1, R.sub.2 are each independently hydrogen, methyl or ethyl.

11. The method of claim 10, wherein: the mass ratio of the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalyst to the o-nitroaniline compound is 1:5˜20; and the molar ratio of the o-nitroaniline compound:the aliphatic diol compound:the alkali is 1:5˜15:0.5˜2.

12. The method of claim 10, wherein the reaction temperature is 70-90° C.; and the reaction time is 6-12 hours.

13. The method of claim 12, wherein the reaction temperature is 75-85° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0035] The following specific examples illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto.

[0036] Examples 1 to 3 are examples of preparing supported metal solid catalysts:

Example 1

[0037] 5 g of γ-Al.sub.2O.sub.3 (aladdin #A102091) were mixed with 35 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 70° C. in a water bath, 6.25 ml of Ce(OH).sub.3 solution (0.04 g Ce/ml) were added dropwise, the mixture was subjected to stirring and impregnation at 70° C. for 2 h, then ammonia water (25-28%) was added dropwise to adjust the pH value to between 9 and 10, then the temperature of the solution was maintained and the solution was stirred for another 2 hours; then the resulting reaction mixture was cooled to room temperature and filtered, and the filter cake was washed with deionized water until the filtrate became neutral; then the filter cake was dried in air atmosphere at 80° C. for 5 h and then calcined at 600° C. for 2 h in air atmosphere to obtain CeO25 wt %/γ-Al.sub.2O.sub.3; CeO25 wt %/γ-Al.sub.2O.sub.3 was then added into 40 ml of 0.002 g/ml ammonium phosphate aqueous solution, the mixture was subjected to stirring and impregnation at 30° C. for 1 h and then dried at 80° C. for 5 h, and the dried product was calcined at 400° C. for 1 h to obtain a CeO25 wt %/γ-Al.sub.2O.sub.3@NP carrier; CeO25 wt %/γ-Al.sub.2O.sub.3@NP was then mixed with 35 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 60° C. in a water bath, 4.375 ml of Pd(C.sub.2H.sub.3O.sub.2).sub.2 solution (0.04 g Pd/ml) and 1.875 ml of CuCl.sub.2 solution (0.04 g Cu/ml) were added dropwise respectively, the mixture was subjected to stirring and impregnation at a constant temperature of 60° C. for 3 h, cooled to 25° C., then added dropwise with 0.1 g/ml NaHCO.sub.3 aqueous solution to adjust the pH value to between 8 and 10, then stirred for 0.5 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 80° C. for 5 h in air atmosphere, calcined at 200° C. for 2 h in air atmosphere, and finally reduced in hydrogen atmosphere at 200° C. for 1 h to obtain a Cu1.5 wt %-Pd3.5 wt %-CeO25 wt %/γ-Al.sub.2O.sub.3@NP catalyst.

Example 2

[0038] 5 g of γ-Al.sub.2O.sub.3 (aladdin #A102091) were mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 10 ml of CeCl.sub.3 solution (0.05 g Ce/ml) were added dropwise, the mixture was subjected to stirring and impregnation at 80° C. for 4 hours, then ammonia water (25-28%) was added dropwise to adjust the pH value to between 9 and 10, then the temperature of the solution was maintained and the solution was stirred for another 4 hours; then the resulting reaction mixture was cooled to room temperature and filtered, and the filter cake was washed with deionized water until the filtrate became neutral; then the filter cake was dried in air atmosphere at 100° C. for 7 h and then calcined at 700° C. for 3 h in air atmosphere to obtain CeO10 wt %/γ-Al.sub.2O.sub.3; CeO10 wt %/γ-Al.sub.2O.sub.3 was then added into 32 ml of 0.0025 g/ml ammonium phosphate aqueous solution, the mixture was subjected to stirring and impregnation at 40° C. for 2 h and then dried at 100° C. for 7 h, and the dried product was calcined at 500° C. for 2 h to obtain a CeO10 wt %/γ-Al.sub.2O.sub.3@NP carrier; CeO10 wt %/γ-Al.sub.2O.sub.3@NP was mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 5 ml of H.sub.2PdCl.sub.4 solution (0.05 g Pd/ml) and 3.5 ml of Cu(NO.sub.3).sub.2 solution (0.05 g Cu/ml) were added dropwise respectively, the mixture was subjected to stirring and impregnation at a constant temperature of 80° C. for 5 h, cooled to 25° C. and then added dropwise with 0.1 g/ml Na.sub.2CO.sub.3 aqueous solution to adjust the pH value to between 8 and 10, then the mixture was stirred for 1 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 100° C. for 7 h in air atmosphere, calcined at 250° C. for 4 h in air atmosphere, and finally reduced in hydrogen atmosphere at 250° C. for 2 h to obtain a Cu3.5 wt %-Pd5 wt %-CeO.sub.210 wt %/γ-Al.sub.2O.sub.3@NP catalyst.

Example 3

[0039] 5 g of γ-Al.sub.2O.sub.3 (aladdin #A102091) were mixed with 45 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 90° C. in a water bath, 12.5 ml of CeCl.sub.3 solution (0.06 g Ce/ml) were added dropwise, the mixture was subjected to stirring and impregnation at 90° C. for 6 hours, then ammonia water (25-28%) was added dropwise to adjust the pH value to between 9 and 10, then the temperature of the solution was maintained and the solution was stirred for another 6 hours; then the resulting reaction mixture was cooled to room temperature and filtered, and the filter cake was washed with deionized water until the filtrate became neutral; then the filter cake was dried in air atmosphere at 120° C. for 9 h and then calcined at 800° C. for 4 h in air atmosphere to obtain CeO15 wt %/γ-Al.sub.2O.sub.3; CeO10 wt %/γ-Al.sub.2O.sub.3 was then added into 32 ml of 0.0025 g/ml ammonium phosphate aqueous solution, the mixture was subjected to stirring and impregnation at 50° C. for 3 h and then dried at 120° C. for 9 h, and the dried product was calcined at 600° C. for 3 h to obtain a CeO15 wt %/γ-Al.sub.2O.sub.3@NP carrier; CeO15 wt %/γ-Al.sub.2O.sub.3@NP was then mixed with 45 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 100° C. in a water bath, 5 ml of Pd(NO.sub.3).sub.2 solution (0.05 g Pd/ml) and 5 ml of Cu(NO.sub.3).sub.2 solution (0.05 g Cu/ml) were added dropwise respectively, the mixture was subjected to stirring and impregnation at a constant temperature of 100° C. for 7 h, cooled to 25° C. and then added dropwise with 0.1 g/ml NaOH aqueous solution to adjust the pH value to between 8 and 10, then the mixture was stirred for 1.5 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 120° C. for 9 h in air atmosphere, calcined at 300° C. for 6 h in air atmosphere, and finally reduced in hydrogen atmosphere at 300° C. for 3 h to obtain a Cu5 wt %-Pd5 wt %-CeO.sub.215 wt %/γ-Al.sub.2O.sub.3@NP catalyst.

[0040] Examples 4-14 used the Cu—Pd—CeO.sub.2/γ-Al.sub.2O.sub.3@NP catalysts obtained by the above-mentioned preparation methods for the synthesis of benzopyrazine compounds:

Examples 4-6

[0041] Examples 4-6 investigated the reaction results of one-pot synthesis of benzopyrazine compounds from o-nitroaniline and various aliphatic diols.

[0042] 0.2 g of the catalyst prepared in Example 2 (Cu3.5 wt %-Pd5 wt %-CeO210 wt %/γ-Al.sub.2O.sub.3@NP), 2 g of o-nitroaniline, 8 ml of an aliphatic diol and 0.8 g of potassium hydroxide were put into a three-necked flask reactor. The mixture was heated to 80° C. and started to stir (1000 r/min), after stirred at the constant temperature for 6 h, the reaction was stopped, and the reaction solution was cooled to room temperature and filtered to separate the catalyst. The filtrate was extracted and then analyzed by gas chromatography, and the experimental results are shown in Table 1.

TABLE-US-00001 TABLE 1 The experimental results of one-pot reaction of o-nitroaniline and different aliphatic diols conversion example aliphatic diol rate (%) product selectivity (%) 4 ethanediol 100 benzopyrazine 98.3 5 1,2-propanediol 100 2-methyl 94.7 benzopyrazine 6 2,3-butanediol 100 2,3-dimethyl 93.1 benzopyrazine

Example 7

[0043] Example 7 investigated the effect of increasing the amount of catalyst to improve the yield of benzopyrazine.

[0044] 0.4 g of the catalyst prepared in Example 2 (Cu3.5 wt %-Pd5 wt %-CeO210 wt %/γ-Al2O3@NP), 2 g of o-nitroaniline, 8 ml of ethanediol and 0.8 g of potassium hydroxide were put into a three-necked flask reactor. The mixture was heated to 80° C. and started to stir (1000 r/min), after stirred at the constant temperature for 6 h, the reaction was stopped, and the reaction solution was cooled to room temperature and filtered to separate the catalyst. The filtrate was extracted and then analyzed by gas chromatography, and the conversion rate of o-nitroaniline was 100%, the selectivity of the target product benzopyrazine is 97.5%.

Examples 8-10

[0045] Examples 8-10 investigated the reaction results of one-pot synthesis of benzopyrazine compounds with ethanediol and different o-nitroaniline compounds.

[0046] 0.2 g of the catalyst prepared in Example 2 (Cu3.5 wt %-Pd5 wt %-CeO.sub.210 wt %/γ-Al.sub.2O.sub.3@NP), 2 g of an o-nitroaniline compound, 8 ml of ethanediol and 0.8 g of potassium hydroxide were put into a three-necked flask reactor. The mixture was heated to 80° C. and started to stir (1000 r/min), after stirred at the constant temperature for 6 h, the reaction was stopped, and the reaction solution was cooled to room temperature and filtered to separate the catalyst. The filtrate was extracted and then analyzed by gas chromatography, and the experimental results are shown in Table 2.

TABLE-US-00002 TABLE 2 The experimental result of one-pot reaction of ethylene glycol and different o-nitroaniline compounds o-nitroaniline conversion selectivity example compound rate (%) product (%)  8 4-methyl-2- 100 6-methyl- 90.9 nitroaniline quinoxaline  9 4-ethyl-2- 100 6-ethyl- 89.6 nitroaniline quinoxaline 10 3-methyl-2- 100 5-methyl- 86.2 nitroaniline quinoxaline

Examples 11-14

[0047] Examples 11-14 investigated the reaction results of one-pot synthesis of benzopyrazine from ethanediol and o-nitroaniline under the action of different catalysts.

[0048] A catalyst, 2 g of o-nitroaniline, 8 ml of ethanediol and 0.8 g of potassium hydroxide were put into a three-necked flask reactor, wherein the catalyst is respectively the catalyst prepared by Example 1, 2 or 3 and the catalyst recovered after the reaction of Example 4, and the amount of the catalyst is 0.2 g. The mixture was heated to 80° C. and started to stir (1000 r/min), after stirred at the constant temperature for 6 h, the reaction was stopped, and the reaction solution was cooled to room temperature and filtered to separate the catalyst. The filtrate was extracted and then analyzed by gas chromatography, and the experimental results are shown in Table 3, where the target product is benzopyrazine.

TABLE-US-00003 TABLE 3 The experimental results of one-pot reaction of ethanediol and o-nitroaniline under the action of different catalysts conversion example catalyst rate (%) selectivity (%) 11 example 1 100 94.5 12 Example 2 100 98.3 13 Example 3 100 96.1 14 catalyst recovered from Example 4 100 97.2

Comparative Example 1

[0049] 5 g of γ-Al2O3 (aladdin #A102091) were mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 5 ml of H.sub.2PdCl.sub.4 solution (0.05 g Pd/ml) and 3.5 ml of Cu(NO.sub.3).sub.2 solution (0.05 g Cu/ml) were added dropwise respectively, the mixture was subjected to stirring and impregnation at a constant temperature of 80° C. for 5 h, cooled to 25° C. and then added dropwise with 0.1 g/ml Na.sub.2CO.sub.3 aqueous solution to adjust the pH value to between 8 and 10, then the mixture was stirred for 1 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 100° C. for 7 h in air atmosphere, calcined at 250° C. for 4 h in air atmosphere, and finally reduced in hydrogen atmosphere at 250° C. for 2 h to obtain a Cu3.5 wt %-Pd5 wt %/γ-Al.sub.2O.sub.3 catalyst.

Comparative Example 2

[0050] 5 g of γ-Al.sub.2O.sub.3 (aladdin #A102091) were mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 10 ml of CeCl.sub.3 solution (0.05 g Ce/ml) were added dropwise, the mixture was subjected to stirring and impregnation at 80° C. for 4 hours, then ammonia water (25-28%) was added dropwise to adjust the pH value to between 9 and 10, then the temperature of the solution was maintained and the solution was stirred for another 4 hours; then the resulting reaction mixture was cooled to room temperature and filtered, and the filter cake was washed with deionized water until the filter liquor became neutral; then the filter cake was dried in air atmosphere at 100° C. for 7 h and then calcined at 700° C. for 3 h in air atmosphere to obtain CeO10 wt %/γ-Al.sub.2O.sub.3; CeO.sub.210 wt %/γ-Al.sub.2O.sub.3 was then mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 5 ml of H.sub.2PdCl.sub.4 solution (0.05 g Pd/ml) and 3.5 ml of Cu(NO.sub.3).sub.2 solution (0.05 g Cu/ml) were added dropwise respectively, the mixture was subjected to stirring and impregnation at a constant temperature of 80° C. for 5 h, cooled to 25° C. and then added dropwise with 0.1 g/ml Na.sub.2CO.sub.3 aqueous solution to adjust the pH value to between 8 and 10, then the mixture was stirred for 1 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 100° C. for 7 h in air atmosphere, calcined at 250° C. for 4 h in air atmosphere, and finally reduced in hydrogen atmosphere at 250° C. for 2 h to obtain the Cu3.5 wt %-Pd5 wt %-CeO.sub.210 wt %/γ-Al.sub.2O.sub.3 catalyst.

Comparative Example 3

[0051] 5 g of γ-Al.sub.2O.sub.3 (aladdin #A102091) were mixed with 32 ml of 0.0025 g/ml ammonium phosphate aqueous solution, the mixture was subjected to stirring and impregnation at 40° C. for 2 h and dried at 100° C. for 7 h, and the dried product was calcined at 500° C. for 2 h to obtain a γ-Al.sub.2O.sub.3@NP carrier; γ-Al.sub.2O.sub.3@NP was then mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 5 ml of H.sub.2PdCl.sub.4 solution (0.05 g Pd/ml) and 3.5 ml of Cu(NO.sub.3).sub.2 solution (0.05 g Cu/ml) were added dropwise respectively, the mixture was subjected to stirring and impregnation at a constant temperature of 80° C. for 5 h, cooled to 25° C. and then added dropwise with 0.1 g/ml Na.sub.2CO.sub.3 aqueous solution to adjust the pH value to between 8 and 10, then the mixture was stirred for 1 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 100° C. for 7 h in air atmosphere, calcined at 250° C. for 4 h in air atmosphere, and finally reduced in hydrogen atmosphere at 250° C. for 2 h to obtain a Cu3.5 wt %-Pd5 wt %/γ-Al.sub.2O.sub.3@NP catalyst.

Comparative Example 4

[0052] 5 g of γ-Al.sub.2O.sub.3 (aladdin #A102091) were mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 10 ml of CeCl.sub.3 solution (0.05 g Ce/ml) were added dropwise, the mixture was subjected to stirring and impregnation at 80° C. for 4 hours, then ammonia water (25-28%) was added dropwise to adjust the pH value to between 9 and 10, and the temperature of the solution was maintained and stirred for another 4 hours; then the resulting reaction mixture was cooled to room temperature and filtered, and the filter cake was washed with deionized water until the filtrate became neutral; then the filter cake was dried in an air atmosphere at 100° C. for 7 h and then calcined at 700° C. for 3 h in an air atmosphere to obtain CeO10 wt %/γ-Al.sub.2O.sub.3, CeO10 wt %/γ-Al.sub.2O.sub.3 was then added into 32 ml of 0.0025 g/ml ammonium phosphate aqueous solution, the mixture was subjected to stirring and impregnation at 40° C. for 2 h and dried at 100° C. for 7 h, and the dried product was calcined at 500° C. for 2 h to obtain a CeO10 wt %/γ-Al.sub.2O.sub.3@NP carrier, CeO10 wt %/γ-Al.sub.2O.sub.3@NP was then mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 5 ml of H.sub.2PdCl.sub.4 solution (0.05 g Pd/ml) were added dropwise, the mixture was subjected to stirring and impregnation at a constant temperature of 80° C. for 5 h, cooled to 25° C. and then added dropwise with 0.1 g/ml Na.sub.2CO.sub.3 aqueous solution to adjust the pH value to between 8 and 10, then the mixture was stirred for 1 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 100° C. for 7 h in air atmosphere, calcined at 250° C. for 4 h in air atmosphere, and finally reduced in hydrogen atmosphere at 250° C. for 2 h to obtain a Pd5 wt %-CeO.sub.210 wt %/γ-Al.sub.2O.sub.3@NP catalyst.

Comparative Example 5

[0053] 5 g of γ-Al.sub.2O.sub.3 (aladdin #A102091) were mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 10 ml of CeCl.sub.3 solution (0.05 g Ce/ml) were added dropwise, the mixture was subjected to stirring and impregnation at 80° C. for 4 hours, then ammonia water (25-28%) was added dropwise to adjust the pH value to between 9 and 10, and the temperature of the solution was maintained and the solution was stirred for another 4 h; then the resulting reaction mixture was cooled to room temperature and filtered, and the filter cake was washed with deionized water until the filtrate became neutral; then the filter cake was dried in an air atmosphere at 100° C. for 7 h and then calcined at 700° C. for 3 h in an air atmosphere to obtain CeO10 wt %/γ-Al.sub.2O.sub.3, CeO10 wt %/γ-Al.sub.2O.sub.3 was added into 32 ml of 0.0025 g/ml ammonium phosphate aqueous solution, the mixture was subjected to stirring and impregnation at 40° C. for 2 h and dried at 100° C. for 7 h, and the dried product was calcined at 500° C. for 2 h to obtain a CeO10 wt %/γ-Al.sub.2O.sub.3@NP carrier; CeO10 wt %/γ-Al.sub.2O.sub.3@NP was then mixed with 40 mL of deionized water and stirred to obtain a slurry, the slurry was heated to 80° C. in a water bath, 3.5 ml of Cu(NO.sub.3).sub.2 solution (0.05 g Cu/ml) were added dropwise respectively, the mixture was subjected to stirring and impregnation at a constant temperature of 80° C. for 5 h, cooled to 25° C. and then added dropwise with 0.1 g/ml Na.sub.2CO.sub.3 aqueous solution to adjust the pH value to between 8 and 10, then the mixture was stirred for 1 h and filtered, and the filter cake was washed with deionized water until the filtrate became neutral, dried at 100° C. for 7 h in air atmosphere, calcined at 250° C. for 4 h in air atmosphere, and finally reduced in hydrogen atmosphere at 250° C. for 2 h to obtain a Cu3.5 wt %-CeO.sub.210 wt %/γ-Al.sub.2O.sub.3@NP catalyst.

[0054] The catalysts prepared by the above-mentioned comparative examples 1-5 were respectively used in the following reactions:

[0055] 2 g of o-nitroaniline, 8 ml of ethanediol, 0.8 g of potassium hydroxide and a catalyst were put into a three-necked flask reactor. The mixture was heated to 80° C. and started to stir (1000 r/min), after stirred at the constant temperature for 6 h, the reaction was stopped, and the reaction solution was cooled to room temperature and filtered to separate the catalyst. The filtrate was extracted and analyzed by gas chromatography, and the experimental results are shown in Table 4, wherein the target product is benzopyrazine.

TABLE-US-00004 TABLE 4 Experimental results of one-pot reaction with ethanediol and o-nitroaniline under the action of different catalysts comparative conversion selectivity example catalyst rate (%) (%) 1 0.2 g Cu3.5 wt %-Pd5 wt %/ 100 85.4 γ-Al.sub.2O.sub.3 2 0.2 g Cu3.5 wt %-Pd5 wt %- 100 91.2 CeO.sub.210 wt %/γ-Al.sub.2O.sub.3 3 0.2 g Cu3.5 wt %-Pd5 wt %/ 100 88.3 γ-Al.sub.2O.sub.3@NP 4 0.2 g Pd5 wt %-CeO.sub.210 50.1 96.8 wt %/γ-Al.sub.2O.sub.3@NP 5 0.2 g Cu3.5 wt %-CeO.sub.210 0 0 wt %/γ-Al.sub.2O.sub.3@NP 6 0.2 g 5 wt % Pd-CeO.sub.210 wt %/ 59.7 92.0 γ-Al.sub.2O.sub.3@NP + 0.2 g 3.5 wt % Cu-CeO.sub.210 wt %/γ-Al.sub.2O.sub.3@NP 7 0.2 g 3.5 wt % Cu-Pd5 wt %- 100 98.3 CeO.sub.210 wt %/γ-Al.sub.2O.sub.3@NP