CN111644194B

CN111644194B - Recycling Application of Pd/mpg-C3N4 Catalyst in HBIW Hydrogenolysis

Info

Publication number: CN111644194B
Application number: CN202010568290.5A
Authority: CN
Inventors: 陈锟; 刘伟; 黎胜富; 陈树森; 金韶华; 李丽洁; 束庆海; 陈煜�
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2020-06-19
Filing date: 2020-06-19
Publication date: 2021-05-28
Anticipated expiration: 2040-06-19
Also published as: CN111644194A

Abstract

The invention relates to Pd/mpg-C₃N₄A method for circularly applying a catalyst in HBIW hydrogenolysis reaction belongs to the technical field of noble metal catalysis. The invention loads common palladium metal to a novel carrier mpg-C₃N₄In the catalyst, the metal palladium has higher dispersity and stability, and the catalyst has a graphite phase mesoporous structure and unsaturated-NH and-NH₂The group increases the adsorptivity of the catalyst to the HBIW, improves the transfer efficiency of the HBIW in the catalyst, realizes the high-efficiency hydrogenation of the HBIW under the low-pressure condition, can be recycled, overcomes the problem of inactivation of the catalyst after use in the HBIW hydrogenolysis in the industry at present, greatly reduces the production cost of the CL-20, and has very high application prospect.

Description

Pd/mpg-C3N4Cyclic application method of catalyst in HBIW hydrogenolysis reaction

Technical Field

The invention relates to mesoporous graphite phase carbon nitride supported palladium (Pd/mpg-C)₃N₄) The catalyst is circularly applied to the hydrogenolysis reaction of Hexabenzylhexaazaisowurtzitane (HBIW), belonging to the technical field of noble metal catalysis.

Background

Hexanitrohexaazaisowurtzitane (CL-20) is a cage-shaped high-energy high-density material and is a fourth-generation explosive widely applied worldwide at present. At present, CL-20 is mainly synthesized by hydrogenolysis and nitration of Hexabenzylhexaazaisowurtzitane (HBIW), but the HBIW is unstable in cage structure after being debenzylated, so that hydrogenolysis is often carried out at normal temperature, and an acetyl reagent is adopted to protect the cage structure in the hydrogenolysis process, so that the catalyst is required to have higher catalytic activity. Catalysis widely used at presentThe agent is mainly Pd/C and Pd (OH)₂The catalyst has two kinds of catalyst (US 6147209A, WO9720785A1), palladium-based bimetal supported on silica and other carrier may be also used in HBIW hydrogenolysis, and the use amount of noble metal palladium is reduced to lower CL-20 production cost (CN 106946894A).

However, these catalysts tend to suffer from deactivation after use, because ethylbenzene, an impurity generated during hydrogenation, and insoluble products generated during hydrogenation, adhere to the surface of palladium metal, thus deactivating the catalysts. The noble metal in the deactivated catalyst is recovered by an incineration method and then is loaded on the carrier again, and the process is complex and the requirement on equipment is strict (CN201911086661. X). The catalyst accounts for 20-30% of the production cost of the CL-20 due to the disposable use of the catalyst, and the production cost of the CL-20 is greatly increased, so that the catalyst has great value in realizing the cyclic application of the catalyst.

Disclosure of Invention

The invention aims to solve the problem that the catalyst in the prior art is deactivated after use, and provides a cyclic application method of a Pd/mpg-C3N4 catalyst in HBIW hydrogenolysis reaction.

The purpose of the invention is realized by the following technical scheme.

The invention adopts mesoporous graphite phase carbon nitride (mpg-C)₃N₄) As a carrier of metallic palladium (Pd), the structural formula of the carrier is as follows:

the carrier is a carbon-nitrogen polymer, and has stable structure and acid and alkali resistance; the carrier has a 'nitrogen ring' consisting of six nitrogen atoms, and can generate strong coordination with palladium, so that the metal palladium is uniformly and stably attached to the mpg-C₃N₄Furthermore, the catalytic activity is greatly improved; at Pd/mpg-C₃N₄Presence of incompletely polymerized-NH and-NH on the surface₂The group can generate hydrogen bond with N in HBIW, so that the adsorption of the catalyst on a substrate HBIW is promoted, and the hydrogenation efficiency on HBIW is further improved; Pd/mpg-C₃N₄The catalyst also has a graphite phase structure and a mesoporous structure, so that the transfer and reaction of a substrate HBIW in the catalyst are promoted, and the high substance transfer efficiency is also favorable for easily removing impurities adsorbed in the catalyst and recovering the activity of the catalyst.

A method for recycling a Pd/mpg-C3N4 catalyst in an HBIW hydrogenolysis reaction comprises the following steps: sequentially adding HBIW, DMF, Pd/mpg-C in the hydrogen atmosphere at low temperature₃N₄Adding a catalyst, bromobenzene and acetic anhydride into a reactor, raising the temperature for first-stage hydrogenation, then continuing raising the temperature for second-stage hydrogenation, finally filtering, extracting a filtrate with a solvent, carrying out rotary evaporation on an extracting solution, drying to obtain a target product, washing the catalyst after solvent extraction to be neutral, drying and recovering.

Wherein the reaction formula of the catalytic hydrogenolysis of HBIW is shown as follows:

the mass ratio of palladium to HBIW is preferably 0.002-0.02, more preferably 0.003-0.01, and most preferably 0.005.

The hydrogen pressure is 1 bar;

the low temperature is lower than 10 ℃, and the first-stage hydrogenation method is to react for 1-2 hours at the temperature of 16-19 ℃; the second-stage hydrogenolysis method is to react for 8-10 h at 45-60 ℃.

The Pd/mpg-C₃N₄The preparation method of the catalyst comprises the following steps: mp-C₃N₄Uniformly stirring and dispersing in the water solution, adding the palladium salt solution into the carrier solution, stirring, adding the reducing agent solution, stirring, filtering, washing and drying to obtain Pd/mpg-C₃N₄A catalyst. The mass ratio of the palladium to the carrier is 10-20%;

the palladium salt comprises palladium chloride and palladium perchlorate;

the stirring time after the palladium salt solution is added is preferably 1-4 hours, and most preferably 3 hours;

the reducing agent comprises sodium borohydride and hydrazine hydrate.

The concentration of the palladium salt water solution is 50mg/ml, and the concentration of the reducing agent solution is 2 mg/ml;

the stirring time after the reducing agent is added is preferably 0.5-2 hours, and most preferably 1 hour.

The drying is preferably carried out at 70 ℃ for 10h under vacuum.

The solvent used for solvent extraction is chloroform.

The solvent used for washing the catalyst solvent is preferably formic acid, ethanol and water in sequence.

Advantageous effects

1. The invention relates to Pd/mpg-C₃N₄Cyclic application method of catalyst in HBIW hydrogenolysis reaction, Pd/mpg-C₃N₄The catalyst realizes the high-efficiency catalytic hydrogenolysis of HBIW under the low pressure of hydrogen, and increases the safety of hydrogenolysis on the premise of ensuring the catalytic effect; compared with Pd/C, Pd (OH)₂/C、Pd/Al₂O₃Isocatalytic, Pd/mpg-C₃N₄The catalyst overcomes the problems of catalyst deactivation caused by agglomeration and falling of metal palladium in application, difficult impurity adsorption and the like, improves the adsorption of the catalyst to HBIW, and realizes Pd/mpg-C₃N₄The catalyst can effectively reduce the industrial cost by the high-efficiency catalysis of the HBIW and the cyclic application of the catalyst, and has good application prospect.

2. The invention relates to Pd/mpg-C₃N₄Cyclic application method of catalyst in HBIW hydrogenolysis reaction, Pd/mpg-C₃N₄The catalyst has excellent activity and stability, is not easy to inactivate, can be put into reaction again after simple post-treatment, realizes the cyclic application of the catalyst in HBIW hydrogenolysis, greatly reduces the production cost and has good application prospect.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

Pd/mpg-C₃N₄Preparation of the catalyst

1g of mpg-C₃N₄Dispersing in 100ml deionized water, stirring for 15min, adding 3.4ml PdCl₂Aqueous solution (50mg/ml), stirred for 3h, then 4.2ml NaBH was added₄The solution (2mg/ml) is stirred for 1h, filtered, washed to neutrality with water and dried in vacuum at 70 ℃ for 10h to obtain Pd/mpg-C with 4.91 percent of palladium content₃N₄A catalyst.

Hydrogenolysis of hexabenzylhexaazaisowurtzitane

3.4g of HBIW, 346mg of 4.91 percent Pd/mpg-C₃N₄The catalyst and 6ml DMF were added to a reaction flask, the temperature was maintained at < 10 ℃ in a cold water bath, the gas in the flask was replaced with nitrogen three times, then the gas in the flask was replaced with hydrogen three times, 0.06ml bromobenzene and 6ml acetic anhydride were added, the reaction was started with stirring, and hydrogen was continuously supplied with a hydrogen balloon. Heating to 18 ℃ for reaction for 1h, then heating to 45 ℃ for reaction for 8h, cooling to room temperature after the reaction is finished, filtering, extracting the solid with trichloromethane, and carrying out rotary evaporation and drying on the extracting solution to obtain the hydrogenolysis product. Washing the catalyst after chloroform extraction with formic acid and ethanol in sequence, finally washing with water to neutrality, and recovering for later use.

Example 2

1g of mpg-C₃N₄Dispersing in 100ml deionized water, stirring for 15min, adding 5ml PdCl₂Aqueous solution (50mg/ml), stirred for 3h, then 6.2ml NaBH was added₄The solution (2mg/ml) was stirred for 1h, filtered, washed to neutrality with water and dried under vacuum at 70 ℃ for 10h to give Pd/mpg-C with a palladium content of 7.44%₃N₄A catalyst.

Hydrogenolysis of hexabenzylhexaazaisowurtzitane

3.4g of HBIW, 228mg of 7.44 percent Pd/mpg-C₃N₄The catalyst and 6ml DMF were added to a reaction flask, the temperature was maintained at < 10 ℃ in a cold water bath, the gas in the flask was replaced with nitrogen three times, then the gas in the flask was replaced with hydrogen three times, 0.06ml bromobenzene and 6ml acetic anhydride were added, the reaction was started with stirring, and hydrogen was continuously supplied with a hydrogen balloon. Heating to 18 ℃ for reaction for 1h, then heating to 45 ℃ for reaction for 8h, cooling to room temperature after the reaction is finished, filtering, extracting the solid with trichloromethane, and carrying out rotary evaporation and drying on the extracting solution to obtain the hydrogenolysis product. Mixing trichloro nailThe catalyst after the alkane extraction is washed by formic acid and ethanol in sequence, and finally washed to be neutral by water, the catalyst is recovered and repeatedly applied to HBIW hydrogenolysis reaction for two times, and the activity is not obviously reduced.

Example 3

1g of mpg-C₃N₄Dispersing in 100ml deionized water, stirring for 15min, adding 6.7ml PdCl₂Aqueous solution (50mg/ml), stirred for 3h, then 8.3ml NaBH was added₄The solution (2mg/ml) was stirred for 1h, filtered, washed to neutrality with water and dried under vacuum at 70 ℃ for 10h to give Pd/mpg-C with a palladium content of 11.13%₃N₄A catalyst.

Hydrogenolysis of hexabenzylhexaazaisowurtzitane

3.4g of HBIW, 153mg of 11.13% Pd/mpg-C₃N₄Adding catalyst and 6ml DMF into a reaction flask, maintaining the temperature of a cold water bath at less than 10 ℃, replacing gas in the reaction flask by nitrogen for three times, then replacing gas in the reaction flask by hydrogen for three times, adding 0.06ml bromobenzene and 6ml acetic anhydride, starting stirring reaction, and continuously providing hydrogen by using a hydrogen balloon. Heating to 18 ℃ for reaction for 1h, then heating to 45 ℃ for reaction for 8h, cooling to room temperature after the reaction is finished, filtering, extracting the solid with trichloromethane, carrying out rotary evaporation on the extracting solution, and drying to obtain the hydrogenolysis product. Washing the catalyst after chloroform extraction with formic acid and ethanol in sequence, finally washing with water to neutrality, and recovering for later use.

Example 4

Example Pd/mpg-C₃N₄The catalyst preparation operation and parameters were the same as in example 2.

Hydrogenolysis of hexabenzylhexaazaisowurtzitane

3.4g of HBIW, 228mg of 7.44 percent Pd/mpg-C₃N₄The catalyst and 6ml DMF were added to a reaction flask, the temperature was maintained at < 10 ℃ in a cold water bath, the gas in the flask was replaced with nitrogen three times, then the gas in the flask was replaced with hydrogen three times, 0.06ml bromobenzene and 6ml acetic anhydride were added, the reaction was started with stirring, and hydrogen was continuously supplied with a hydrogen balloon. Heating to 18 deg.C for reaction for 1h, heating to 25 deg.C for reaction for 8h, cooling to room temperature after reaction, filtering, extracting solid with chloroform, rotary evaporating the extractive solution, and drying to obtain hydrogenAnd (4) decomposing the product. Washing the catalyst after chloroform extraction with formic acid and ethanol in sequence, finally washing with water to neutrality, and recovering for later use.

Comparative example 1

The catalyst used in this comparative example was purchased as 10% Pd/C.

3.4g of HBIW, 170mg of 10% Pd/C catalyst and 6ml of DMF were charged into a reaction flask, the temperature was maintained at < 10 ℃ by means of a cold water bath, the gas in the reaction flask was replaced with nitrogen three times, then the gas in the reaction flask was replaced with hydrogen three times, hydrogen was continuously supplied with a hydrogen balloon, 0.06ml of bromobenzene and 6ml of acetic anhydride were added, and the reaction was started with stirring. Heating to 18 ℃ for reaction for 1h, then heating to 45 ℃ for reaction for 8h, cooling to room temperature after the reaction is finished, filtering, extracting the solid with trichloromethane, carrying out rotary evaporation on the extracting solution, and drying to obtain the hydrogenolysis product. Washing the catalyst after chloroform extraction with formic acid and ethanol in sequence, finally washing with water to neutrality, and recovering for later use.

Comparative example 2

The catalyst used in this comparative example was 10% Pd/C recovered in comparative example 1.

1.7g of HBIW, 85mg of 10% recovered palladium/C catalyst and 3ml of DMF were charged into a reaction flask, the temperature was maintained at < 10 ℃ by a cold water bath, the gas in the reaction flask was replaced with nitrogen three times, then the gas in the reaction flask was replaced with hydrogen three times, 0.03ml of bromobenzene and 3ml of acetic anhydride were added, the reaction was started with stirring, and hydrogen was continuously supplied with a hydrogen balloon. Heating to 18 ℃ for reaction for 1h, then heating to 45 ℃ for reaction for 8h, cooling to room temperature after the reaction is finished, filtering, extracting the solid with trichloromethane, carrying out rotary evaporation on the extracting solution, and drying to obtain the hydrogenolysis product.

The yields of the HBIW hydrogenolysis products in the examples and comparative examples are shown in Table 1:

TABLE 1

The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. a Pd/mpg-C ₃ N ₄ catalyzer in HBIW hydrogenolysis reaction cycle application method, it is characterized in that: under low temperature, hydrogen atmosphere environment, successively HBIW, DMF, Pd/mpg-C ₃ N ₄ The catalyst, bromobenzene and acetic anhydride are added to the reactor, the temperature is raised to carry out one-stage hydrogenation, then the temperature is continued to be raised to carry out two-stage hydrogenation, and finally the target product is obtained by filtration, solvent extraction of the filtrate, rotary evaporation of the extract, and drying. The catalyst was washed to neutrality and recovered by drying; due to the presence of incompletely polymerized -NH and _-NH2 groups _on the surface of Pd/mpg _- C3N4, the groups could generate hydrogen bonds with N in HBIW, promoting The adsorption of the substrate HBIW by the catalyst improves the hydrogenation efficiency of HBIW; Pd/mpg-C ₃ N ₄ also has a graphitic phase structure and a mesoporous structure, which promotes the transfer and reaction of the substrate HBIW in the catalyst; mpg _- _C3N4 can be recycled in this reaction.

2. The method of claim 1, wherein the mass ratio of the palladium to HBIW is 0.002 to 0.02.

3. The method of claim 2, wherein the mass ratio of the palladium to HBIW is 0.003 to 0.01.

4. method as claimed in claim 2 or 3, is characterized in that: the mass ratio of described palladium and HBIW is 0.005.

5. The method according to claim 1, characterized in that: the hydrogen pressure is 1 bar; the low temperature is that the temperature is lower than 10°C, and the first-stage hydrogenation method is to react at 16～19°C for 1～2h ; The second-stage hydrogenation method is to react at 45 to 60 ° C for 8 to 10 h.

6. The method according to claim 1, wherein: the preparation method of the Pd/mpg-C ₃ N ₄ catalyst is: the mpg-C ₃ N ₄ is uniformly dispersed in the aqueous solution by stirring, and the palladium salt solution is Add to the carrier solution, add the reducing agent solution after stirring, stir, filter, wash and dry to obtain a Pd/mpg-C ₃ N ₄ catalyst; the mass ratio of the palladium to the carrier is 10-20%.

7. method as claimed in claim 6 is characterized in that: described palladium salt comprises palladium chloride and palladium perchlorate; described reducing agent comprises sodium borohydride and hydrazine hydrate; described solvent extraction uses The solvent is chloroform; the solvents used for washing the catalyst solvent are formic acid, ethanol and water in sequence.

8. The method according to claim 6, wherein the stirring time after adding the palladium salt solution is preferably 1-4h; the stirring time after adding the reducing agent is preferably 0.5-2h .

9. The method of claim 6, wherein the concentration of the palladium salt aqueous solution is 50 mg/mL, and the concentration of the reducing agent solution is 2 mg/mL.

10 . The method of claim 6 , wherein the drying is preferably vacuum drying at 70° C. for 10 h. 11 .