CN1403194A

CN1403194A - Catalyst for catalytic hydrogenolysis of unsym-dimethylhydrazine and its prepn

Info

Publication number: CN1403194A
Application number: CN 01131291
Authority: CN
Inventors: 林培滋; 丁云杰; 罗洪原
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2001-09-05
Filing date: 2001-09-05
Publication date: 2003-03-19
Anticipated expiration: 2021-09-05
Also published as: CN1136970C

Abstract

THe catalyst for catalytic hydrogenolysis of unsym-dimethylhydrazine (UDMH) is one kind of improved loaded rhodium catalyst. The improved catalyst has added assistant, which is VIII element and alkali metal oxide. With the said improved catalyst and in the reaction conditions including temperature 100-300 deg.C, normal pressure, molar ratio between H2 and UDMH 1-10 and UDMH liquid space velocity 0.5-8 ml/ml catalyst, Hr, UDMH is converted to produce dimethylamine and ammonia. The said catalyst has simple preparation process, high reaction conversion rate and makes it possible to minimize the reaction apparatus.

Description

Catalyst for catalytic hydrogenolysis of unsym-dimethylhydrazine and preparation method thereof

Technical Field

The invention provides a catalyst and a method for producing ammonia and dimethylamine by catalytic hydrogenolysis of unsym-dimethylhydrazine.

Background

1, 1-dimethylhydrazine, also known as unsymmetrical dimethylhydrazine, is a colorless liquid with an irritating odor. In air, unsymmetrical dimethylhydrazine is easily oxidized slowly and fuming to turn yellow. At present, unsymmetrical dimethylhydrazine is mainly produced by a chloramine method, and is produced by taking sodium hypochlorite, ammonia water and dimethylamine as raw materials.

The main use of unsymmetrical dimethylhydrazine is as propellant for rockets. Unsymmetrical dimethylhydrazine stored for a long time is slowly oxidized by air to generate a part of hydrazone.

Such oxidized unsymmetrical dimethylhydrazine cannot be reused as a rocket propellant. Its disposal is a difficult problem. Because the unsymmetrical dimethylhydrazine has high nitrogen content, a large amount of NO can be generated when the unsymmetrical dimethylhydrazine is used as fuel for combustion_XCausing serious air pollution. And as unsymmetrical dimethylhydrazine is flammable, explosive and toxic, the unsymmetrical dimethylhydrazine is difficult to be transported to a production plant for treatment in a long distance. However, a catalyst capable of effectively hydrogenolyzing unsymmetrical dimethylhydrazine and a preparation method thereof have not been searched.

Disclosure of Invention

The invention aims to provide a catalyst for the reaction of unsymmetrical dimethylhydrazine catalyzed hydrogenolysis to useful ammonia and dimethylamine and a preparation method of the catalyst. In addition, the method for carrying out the unsymmetrical dimethylhydrazine catalytichydrogenolysis reaction by using the catalyst is simple, the equipment can be miniaturized, and a device with unsymmetrical dimethylhydrazine processing capacity of 300 tons/year can be arranged on an automobile. This process of the invention differs from catalytic decomposition in that the reaction uses hydrogen. The use of hydrogen gas can increase the yield of ammonia and dimethylamine. The reaction is represented by the following formula:

。

specifically, the catalyst used in the invention consists of a main active component, an auxiliary agent component and a carrier, wherein the main active component is metal rhodium, the auxiliary agent is added on the supported rhodium catalyst, and the auxiliary agent is mainly selected from VIII group elements in the periodic table of elements such as Fe, Co, Ni, Ru, Pd, Ir or Pt or oxides of alkali metals such as Li, Na or K, and the like. The supporter can be selected from alumina, silica, active carbon or diatomite, etc. The metal rhodium content of the catalyst is preferably from 0.5 to 5% by weight, and the promoter content is preferably from 0.05 to 1% by weight.

The new catalyst used in the present invention is prepared by impregnating the carrier with a solution of metal rhodium and soluble salts of the auxiliary agents, such as nitrates, chlorides, etc. The impregnated catalyst can be used for reduction after being dried, and can also be used for reduction after being calcined at the temperature of 300-500 ℃. The catalyst was reduced with hydrogen before use at a temperature of 300-500 ℃.

The invention also provides a set of process flow for carrying out reaction by utilizing the catalyst and a corresponding device for preparing ammonia and dimethylamine by catalytic hydrogenolysis of unsym-dimethylhydrazine. The process conditions are as follows: the reaction temperature is 100 ℃ and 300 ℃, the reaction pressure is normal pressure, H2/UDMH is 1-10 (molecular ratio), and the liquid volume space velocity is 1-10 hours^-1. The device consists of an unsymmetrical dimethylhydrazine storage tank (1), an unsymmetrical dimethylhydrazine pump (2), a hydrogen production machine (7), a vaporization mixer (3), a reactor (4), a cooler (5) and a separator (6). The new unsymmetrical dimethylhydrazine catalytic hydrogenolysis catalyst is placed in the reactor (4). The device can be miniaturized, and the device with the unsymmetrical dimethylhydrazine processing capacity of 300 tons/year can be integrally installed on an automobile.

The reactors used as described above may be used in one or more reactors connected in parallel or in series, or switched. The reactor may be tubular reactor, which may be operated under isothermal or near isothermal condition, with catalyst inside the tubes and heat conducting medium between the tubes.

The process operation of the invention is illustrated as follows: quantitatively conveying the unsymmetrical dimethylhydrazine in the storage tank into a vaporization mixer by a pump, wherein the temperature of the vaporization mixer is generally maintained at 100-200 ℃ to vaporize the unsymmetrical dimethylhydrazine, simultaneously, hydrogen from a hydrogen production machine also enters the vaporization mixer to be mixed with the vaporized unsymmetrical dimethylhydrazine, mixed gas enters a reactor through a pipeline, the temperature of the reactor is generally maintained at 100-300 ℃, the gaseous unsymmetrical dimethylhydrazine and the hydrogen are contacted with a catalyst in the reactor and carry out catalytic hydrogenolysis reaction to generate products such as ammonia, dimethylamine and the like, and the products are cooled to realize the separation of the ammonia and the dimethylamine in a separation tank. The whole reaction process is a normal pressure process and can also be carried out under the condition of pressure.

FIG. 1 is a simplified flow diagram of an apparatus for the catalytic hydrogenolysis of unsym-dimethylhydrazine to ammonia and dimethylamine having one reactor.

In summary, the present invention converts unsymmetrical dimethylhydrazine to ammonia and dimethylamine over a novel catalyst. The new catalyst is prepared with metal rhodium as main active component and through adding assistant to obtain high activity, selectivity and load. The device can be miniaturized, and the device with the unsymmetrical dimethylhydrazine treatment capacity of 300 tons/year can be integrally installed on a vehicle (8300mm multiplied by 2500mm multiplied by 3200 mm).

Detailed Description

The following is further illustrated by examples. Example 1

49.72 g of carrier silica was weighed out, an aqueous solution containing 0.51 g of rhodium chloride and 0.0514 g of ruthenium trichloride was prepared, and the prepared aqueous solution was used for silica, and then dried at 120 ℃. Then, the catalyst was reduced at 300 ℃ under a hydrogen stream to obtain a catalyst. Example 2

Weighing 48.75 g of alumina carrier, preparing an aqueous solution containing 2.032 g of rhodium chloride and 1.24 g of nickel nitrate hexahydrate, impregnating the carrier with the prepared solution, standing, drying at 120 ℃, and roasting at 300 ℃. Then the catalyst is prepared by reduction under the hydrogen flow at 400 ℃. Example 3

Weighing 48.5 g of carrier silicon dioxide, preparing an aqueous solutioncontaining 2.032 g of rhodium trichloride and 1.34 g of chloroiridic acid, impregnating the silicon dioxide with the prepared aqueous solution, standing, drying at 120 ℃, and roasting at 400 ℃. Then, the catalyst was obtained by reduction under a hydrogen stream at 300 ℃. Example 4

Weighing 47.4 g of carrier aluminum oxide, preparing an aqueous solution containing 5.08 g of rhodium trichloride and 0.05 g of potassium nitrate, soaking the carrier by the prepared aqueous solution, standing, drying at 120 ℃, roasting at 400 ℃, and reducing the roasted catalyst at 300 ℃ in hydrogen flow to obtain the catalyst. Example 5

Weighing 49 g of carrier aluminum oxide, preparing an aqueous solution containing 1.02 g of rhodium trichloride and 1.15 g of lithium nitrate, soaking the carrier by the prepared aqueous solution, standing, drying at 120 ℃, roasting at 500 ℃, and reducing the roasted catalyst at 500 ℃ under hydrogen flow to obtain the catalyst. Example 6

The catalytic decomposition of unsymmetrical dimethylhydrazine was carried out using the experimental equipment shown in the attached drawing. The reaction pressure was normal pressure, the reaction temperature was 200 ℃, the catalyst was the catalyst prepared in example 1, the amount of the catalyst used was 100 ml, the feed rate of unsymmetrical dimethylhydrazine was 500 ml/h, the hydrogen flow rate was 25 l/min, and the experimental results are shown in table 1. Example 7

The catalytic hydrogenolysis of unsymmetrical dimethylhydrazine was carried out using the experimental setup as shown in the figure. The reaction pressure was normal pressure, the reaction temperature was 100 ℃, the catalyst was the catalyst prepared in example 2, the amount of the catalyst was 100 ml, the feed rate of unsymmetrical dimethylhydrazine was 800 ml/hr, the hydrogen flow rate was 19 l/min, and theexperimental results are shown in table 1. Example 8

The catalytic decomposition of unsymmetrical dimethylhydrazine was carried out using the experimental equipment shown in the attached drawing. The reaction pressure was normal pressure, the reaction temperature was 300 ℃, the catalyst was the catalyst prepared in example 3, the amount of the catalyst used was 100 ml, the feed rate of unsymmetrical dimethylhydrazine was 1000 ml/hour, the hydrogen flow rate was 5 l/min, and the experimental results are shown in table 1. Example 9

The catalytic decomposition of unsymmetrical dimethylhydrazine was carried out using the experimental equipment shown in the attached drawing. The reaction pressure was normal pressure, the reaction temperature was 150 ℃, the catalyst was the catalyst prepared in example 4, the amount of the catalyst used was 100 ml, the feed rate of unsymmetrical dimethylhydrazine was 200 ml/hr, the hydrogen flow rate was 5 l/min, and the experimental results are shown in table 1. Example 10

The catalytic decomposition of unsymmetrical dimethylhydrazine was carried out using the experimental equipment shown in the attached drawing. The reaction pressure was normal pressure, the reaction temperature was 150 ℃, the catalyst was the catalyst prepared in example 5, the amount of the catalyst used was 100 ml, the feed rate of unsymmetrical dimethylhydrazine was 500 ml/h, the hydrogen flow rate was 15 l/min, and the experimental results are shown in table 1.

TABLE 1 results of the experiments

Example number	LHSV	H2/UDM H (mol/mol)	Reaction temperature (℃)	Unsym-dimethyl hydrazine for preparing N-methyl hydrazine Chemical conversion rate (mol％)	Yield of ammonia (mol％)	Yield of dimethylamine (mol％)
Example number	LHSV	H2/UDM H (mol/mol)	Reaction temperature (℃)		Yield of ammonia (mol％)	Yield of dimethylamine (mol％)	6	5	10	200	100	75	59
7	8	5	100	100	73	63	6	5	10	200	100	75	59
7	8	5	100	100	73	63	8	10	1	300	100	76	62
9	2	5	150	100	77	61	8	10	1	300	100	76	62
9	2	5	150	100	77	61	10	5	5	150	100	72	66

From the results of the above examples, it can be seen that the catalyst provided by the present invention has the advantages of simple preparation method, low precious metal content, high hydrogenolysis activity for the unsymmetrical dimethylhydrazine catalyst, and capability of realizing the miniaturization and the motorization of equipment, and the device with the unsymmetrical dimethylhydrazine processing capacity of 300 ton/year can be used for the vehicle-carrying of large trucks.

Claims

1. A catalyst for the catalytic hydrogenolysis of unsym-dimethylhydrazine to ammonia and dimethylamine,comprising: the catalyst consists of main active component of metal rhodium, assistant component of VIII family element or alkali metal oxide, and carrier of alumina, silica, active carbon or diatomite, with the metal rhodium content of 0.5-5 wt% and the assistant content of 0.05-1 wt%.

2. A preparation method of a catalyst for producing ammonia and dimethylamine by unsymmetrical dimethylhydrazine catalytic hydrogenolysis is characterized by comprising the following steps: the carrier is impregnated by the water solution of soluble salts of metal rhodium and auxiliary elements, and the carrier is reduced by hydrogen after being dried, wherein the reduction temperature is 300-500 ℃.

3. The method of claim 2, wherein: the soluble salts of the metal rhodium and the auxiliary agent are nitrates or chlorides.

4. The method of claim 3, wherein: the catalyst is roasted at 300-500 deg.c before reduction.

5. A method for producing ammonia and dimethylamine by unsymmetrical dimethylhydrazine catalytic hydrogenolysis is characterized in that: (1) using the catalyst of claim 1; (2) the process conditions are as follows: 100 ℃ and 300 ℃, reaction pressure: atmospheric pressure, H2(mol)/udmh (mol) 1-10, liquid space velocity of unsymmetrical dimethylhydrazine: 1-10 ml/ml catalyst/h.