CN112569996B - Catalyst for preparing perhaloethylene, preparation method and application thereof - Google Patents

Abstract

The invention relates to a catalyst for catalyzing and producing perhalogenated ethylene, which at least comprises nitrides and/or carbides of VIII group and/or VIB group and/or IIB group metals as catalyst active components, and the preparation method comprises the steps of (1) preparing a metal oxide precursor; step (2), temperature programming, reducing, nitriding and/or carbonizing; and (3) passivating to obtain the catalyst.

Description

Catalyst for preparing perhaloethylene and its preparation method and application

technical field

The present application relates to a catalyst and a preparation method thereof, in particular to a catalyst for preparing perhaloethylene and a preparation method thereof.

Background technique

CTFE is an important commercial monomer in the production of fluorine-containing polymers, and can be used to prepare a series of fluorine coatings, fluorine resins, fluorine rubber and fluorine-chlorine lubricants. These fluorine-containing materials have excellent chemical inertness and weather resistance, and are widely used in cutting-edge technology, military aerospace, and electronics industries. Various methods have been used to prepare CTFE. The existing production processes mainly include: trifluorotrichloroethane metal zinc powder reductive dechlorination method, trifluorotrichloroethane catalytic hydrodechlorination method, ethylene and oxygen participation Trifluorotrichloroethane catalytic dechlorination method, trifluorotrichloroethane electrochemical reduction method, tetrafluorochloroethane cracking method and other methods.

EP0459463A discloses the impact of carrier performance on the process of preparing chlorotrifluoroethylene by catalytic hydrogenation. When alumina is used as carrier, the conversion rate of trifluorotrichloroethane is lower than 50%. They compared Pd-Hg/Al The activity of ₂ O ₃ and Pd-Hg/C, the catalyst dosage of the former is 1.3g, the Pd loading is 0.5%, the conversion rate is 54.7%, the latter catalyst dosage is 0.6g, the Pd loading is 2%, the conversion The rate is 63.9%.

US5089454 discloses that active carbon, alumina, titanium oxide and other materials are used as carriers, one or more of alkali metal and alkaline earth metal salts are used as auxiliary agents, and group VIII metals are used as catalyst active components. When the reaction temperature is 200-300 ° C , the conversion rate of chlorotrifluoroethylene is above 40%.

CN1460549A discloses a catalyst for preparing chlorotrifluoroethylene and trifluoroethylene by catalytic hydrodechlorination of 1,1,2-trifluoro-2,2,1-trichloroethane, which is characterized in that the precious metal palladium and metal Copper is the main active component, alkali metal lithium and rare earth metal or metal lanthanum are added as modification aids, and coconut shell activated carbon is used as the carrier; the amount of precious metal palladium used is 0.5% to 0.4% of the total weight of the catalyst; the metal used Copper is used in an amount of 1% to 12% of the total weight of the catalyst; the amount of lithium metal used is 0.2% to 2% of the total weight of the catalyst; the amount of rare earth metal or metal lanthanum used is 0.5% to 2% of the total weight of the catalyst. 4%. The raw material conversion rate can reach 100%, and the CTFE selectivity can reach up to 84.7%.

CN105457651A discloses a hydrodechlorination catalyst consisting of a main catalyst, an auxiliary agent and a carrier; the main catalyst is Pd and Cu; the auxiliary agent is selected from one of Mg, Ca, Ba, Co, Mo, Ni, Sm and Ce One, two or more combinations; the main catalyst and auxiliary agent are loaded on the activated carbon carrier. Its preparation method: add activated carbon into acid or alkali solution, reflux treatment in water bath at 60-90°C for 2-4 hours, wash and dry; use the soluble salt solution of main catalyst and auxiliary agent to separate under vacuum or normal pressure Step impregnation or co-impregnation of pretreated activated carbon; drying the impregnated activated carbon at a drying temperature of 90-120°C; reducing the dried activated carbon to obtain a catalyst. A metal alloy phase is formed on the surface of the carrier between the selected first active component and the second active component, and the activity is moderate, which is beneficial to improving product selectivity and prolonging catalyst life. The raw material conversion rate can reach 97.8%, and the CTFE selectivity can reach 96.2%.

CN105944734A discloses a catalyst for preparing chlorotrifluoroethylene by catalytic hydrodechlorination of trifluorotrichloroethane, comprising a first catalyst, a second catalyst, an auxiliary agent and a carrier, wherein the first catalyst is selected from cobalt or rhodium A kind of, its dosage is 0.1%～15% of the total mass of the catalyst, the second catalyst is selected from one of chromium or manganese, and its consumption is 0.5%～22% of the total catalyst mass, and the auxiliary agent is selected from alkali Metal potassium or rare earth metal rhenium is used in an amount of 0.1% to 5% of the total mass of the catalyst. The catalyst of the present invention shows very high activity in the reaction of trifluorotrichloroethane hydrodechlorination to prepare chlorotrifluoroethylene, and the reaction conditions are mild, the operation is stable and good, and it is suitable for the reaction of trifluorotrichloroethane Process for the preparation of chlorotrifluoroethylene by hydrodechlorination.

These catalysts all suffer from certain disadvantages such as consumption of expensive materials, low product yields, poor stability, etc. Applicants have recognized that there is a continuing need in the art for further improvements in catalysts for the production of CTFE. The invention provides a catalyst with good selectivity, conversion rate and stability for the production of vinyl halides (such as CTFE, etc.) and a preparation method thereof.

Contents of the invention

The invention provides a catalyst for producing perhalogenated vinyl (such as CTFE) and a preparation method thereof, and simultaneously provides a method for producing halogenated vinyl.

The raw material perhalogenated ethane that the present invention adopts is the perhalogenated ethane that meets following formula:

CF _a Cl _b -CF _d Cl _f

Wherein, a is 0-3, b is 1-3, and a+b=3; d is 0-3, f is 1-3, and d+f=3; and b+f is 2-6.

Preferred perhaloethanes are 1,2-dichlorotetrafluoroethane (fluorocarbon 114) or 1,1,2-trichloro-1,2,2-trifluoroethane (fluorocarbon 113) , of which 1,1,2-trichloro-1,2,2-trifluoroethane is particularly preferred.

The product is a perhaloethylene according to the formula:

CF _m Cl _n = CF _x Cl _y

Wherein, m is 0-2, n is 0-2, and m+n=2; and x is 0-2, y is 0-2, and x+y=2. The preferred product is chlorotrifluoroethylene.

The catalyst for producing perhalogenated vinyl provided by the present invention at least includes nitrides and/or carbides of Group VIII and/or Group VIB and/or Group IIB metals as catalyst active components.

Further, the catalyst for the production of perhaloethylene provided by the present invention also includes a carrier, with nitrides and/or carbides of Group VIII and/or Group VIB and/or Group IIB metals as catalyst active components. Preferably, the content of the catalyst active component is 0.5-30wt%. More preferably, the content of the active component is 1-20wt%, or 2-15wt%, or 5-15wt%.

Preferably, the active component is a composition of at least two nitrides, a composition of at least two carbides, a composition of at least two nitrogen/carbides, a double metal nitride or a double metal carbide, nitrogen/carbide The carbide means a metal compound containing both nitrides and carbides of metal elements.

Preferably, the active component is selected from at least two of cobalt nitride, molybdenum nitride, nickel nitride, zinc nitride, titanium nitride, iron nitride, and tungsten nitride.

Preferably, the active components are cobalt nitride and molybdenum nitride, or molybdenum nitride and nickel nitride, or cobalt nitride and nickel nitride, or cobalt nitride and zinc nitride, or molybdenum nitride and zinc nitride, or nickel nitride and zinc nitride, or iron nitride and tungsten nitride, or nickel nitride and molybdenum nitride, the molar ratio of the two nitrides is 1:0.1-10, preferably 1:0.2-5 or 1:0.5-2.

Preferably, the active components are nitrogen/cobalt carbide and nitrogen/molybdenum carbide, or nitrogen/molybdenum carbide and nitrogen/nickel carbide, or nitrogen/cobalt carbide and nitrogen/nickel carbide, or nitrogen/cobalt carbide and nitrogen/nickel carbide Zinc carbide, or nitrogen/molybdenum carbide and nitrogen/zinc carbide, or nitrogen/nickel carbide and nitrogen/zinc carbide, or nitrogen/iron carbide and nitrogen/tungsten carbide, or nitrogen/nickel carbide and nitrogen/molybdenum carbide ; The molar ratio of the two nitrogen/carbides is 1:0.1-10, preferably 1:0.2-5 or 1:0.5-2.

Preferably, the active component is nickel-molybdenum double-metal nitride or cobalt-molybdenum double-metal nitride.

Preferably, the carrier is alumina, titania, silica, molecular sieve.

The preparation method of the catalyst for the production of perhaloethylene provided by the present invention comprises step (1) preparation of metal oxide precursor; step (2) temperature-programmed reduction nitriding and/or carbonization; step (3) passivation, That is the catalyst.

Preferably, step (1) is to weigh a certain amount of salt containing active metal components, roast at high temperature for 2-6 hours in an air atmosphere, and obtain a precursor metal oxide by pressing and sieving; or impregnate the carrier in a certain In the first metal salt solution with the highest concentration, after standing overnight at room temperature, dry at 80-160° C. for 2-10 hours in an air atmosphere, calcinate for 2-6 hours in an air atmosphere, cool down and dry to obtain a precursor metal oxide. Preferably, after cooling and drying, the second metal salt solution is impregnated, and the precursor metal oxide is obtained through the same treatment as the first impregnation. Preferably, the calcination temperature is 400-800°C, more preferably 400-600°C.

Preferably, step (2) is to carry out temperature-programmed reduction nitriding and/or carbonization of the precursor metal oxide in a vacuum heating furnace. Reducing gas for nitriding and/or carbonization; preferably, the temperature is raised to 300-400°C at 8-15°C/min, and then to the final temperature of 600-800°C at 0.3-5°C/min, preferably 650°C-750°C Or 700° C., kept at a constant temperature for 2-5 hours; preferably, the nitriding and/or carbonizing is at normal pressure.

In a specific embodiment, the reducing gas is ammonia, a mixed gas of ammonia and hydrogen, organic amine, a mixed gas of ammonia and organic amine; more preferably, the reducing gas is a mixed gas of ammonia and hydrogen, and ammonia The gas and hydrogen gas mixture volume ratio is 1:0.5-4 or 1:1-3.

In a specific embodiment, the reducing gas is ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, ethylenediamine, monoethanolamine, One or more in diethanolamine; Preferably, reducing gas is one or more in ammonia, diethylamine, diethanolamine; Most preferably reducing gas is the mixed gas of ammonia and diethylamine, mixed volume The ratio is 1:0.2-5 or 1:0.4-3 or 1:0.5-2.

In a specific embodiment, when the reducing gas is methane, ethane, or propane, it is used for carbonization.

Preferably, in step (3), after the nitriding and/or carbonizing is completed, the temperature is lowered to room temperature in a reducing gas atmosphere, and then passivated by a mixed gas of O ₂ and N ₂ . Preferably, the volume ratio of O ₂ and N ₂ is 1:99; the passivation time is 5-20h.

The invention also provides the application of the catalyst in the catalytic preparation of perhaloethylene, especially the application in the preparation of chlorotrifluoroethylene.

The present invention also provides a process for the production of perhaloethylenes, the process comprising dechlorinating one or more haloethanes in the gas phase in the presence of a catalyst and at least one compound, the at least one The compound will react with chlorine from the dechlorination reaction in the gaseous reaction mixture in the presence of a catalyst.

detailed description

The present invention will be further described below in conjunction with specific examples, but the present invention is not limited to these specific implementations. Those skilled in the art will realize that the present invention covers all alternatives, modifications and equivalents as may be included within the scope of the claims.

Catalyst test conditions: Feed the mixture of CF ₂ Cl-CFCl ₂ (R-113) and hydrogen into the reactor containing the catalyst bed (the reaction tube of the tubular reactor adopts an inner diameter of 12 mm and a length of 50 cm), and the contact time is 10 seconds, the feed molar ratio (R-113:H ₂ ) was 1:2, and the temperature was 500°C. The outlet gas of the reactor was collected and analyzed for composition. For the non-supported catalyst, it is made into 40-60 mesh catalyst particles and filled in the reaction tube.

1. Preparation of unsupported catalyst

Example 1

A certain amount of ammonium molybdate and cobalt nitrate were weighed, calcined at 500°C for 4 hours in an air atmosphere, pressed into tablets, and sieved to obtain precursor oxides. The precursor oxide is subjected to temperature-programmed reduction nitriding and/or carbonization in a vacuum heating furnace. Before nitriding and/or carbonizing, vacuumize and then pass nitrogen to purge. The reducing gas is ammonia gas purified by 3A molecular sieve and calcium oxide deoxygenation and dehydration. ℃, then raise the temperature at 0.3℃/min to the set final temperature of 600℃, and keep the temperature constant for 5h. Then the catalyst was passivated for 10 h at room temperature with a mixed gas with a volume ratio of O ₂ and N ₂ of 1:99.

Example 2-25

Example 1 was adjusted from the aspects of active ingredients and their content, nitriding final temperature, nitriding gas, etc., and the specific conditions are shown in Table 1. Wherein the nickel source is nickel nitrate, and the zinc source is zinc nitrate.

Example 26

The difference from Example 1 is that the reducing gas is methane.

Comparative example 1-6

The difference between Comparative Example 1 and Example 1 is that: without nitriding and/or carbonizing steps, what is obtained is a metal oxide catalyst.

The difference between Comparative Example 2 and Comparative Example 1 is that the active components are nickel and molybdenum.

The difference between Comparative Example 3 and Comparative Example 1 is that the active components are cobalt and nickel.

The difference between Comparative Example 4 and Comparative Example 1 is that the active ingredients are cobalt and zinc.

The difference between Comparative Example 5 and Comparative Example 1 is that the active components are molybdenum and zinc.

The difference between Comparative Example 6 and Comparative Example 1 is that the active ingredients are nickel and zinc.

Table 1: Unsupported catalyst components and test results

It can be seen that the combination of nitrides and/or carbides of cobalt, molybdenum, nickel, zinc and other metals shows good catalytic performance for the reaction process of R-113 synthesis of CTFE.

By comparing Examples 1-5, it can be seen that the performance of catalysts obtained at different nitriding final temperatures is not the same. Due to the different degrees of sintering and agglomeration of metal particles at different temperatures, the number of catalytic active sites is different, which will cause The catalytic activity is different; on the other hand, at different nitriding temperatures, the metals exhibit different valence states, and the metal nitrides sintered at a temperature of 700 ° C have higher catalytic activity. By comparing Examples 3 and 6-9, it can be seen that the combined reducing gas of organic amines, organic amines and ammonia can obtain catalyst products with better catalytic activity and selectivity, because the organic amines contain N and C element not only forms nitrides but also forms part of carbides in the process of temperature programming, and the formed nitrogen/carbides have better catalytic activity and selectivity.

2. Preparation of Supported Catalyst

Example 27

Basically the same as in Example 1, the preparation method of the precursor oxide is different: the carrier is immersed in the ammonium molybdate aqueous solution with a certain concentration according to the loading capacity set in the experiment, and after being aged overnight at room temperature, it is placed in an air atmosphere at 120°C Drying for 5 hours, calcination at 500°C for 4 hours in an air atmosphere; then impregnating the second component of cobalt nitrate according to the same procedure to obtain a precursor oxide, and then to prepare a catalyst. Wherein, the catalyst carrier is alumina (such as a commercially available alumina carrier).

Examples 28-52

Example 27 was adjusted from the aspects of active ingredients and their content, nitriding final temperature, nitriding gas, etc. The specific conditions are shown in Table 2. Wherein the nickel source is nickel nitrate, and the zinc source is zinc nitrate.

Example 53

The difference from Example 27 is that the reducing gas is methane.

Comparative example 7-12

The difference between Comparative Example 7 and Example 27 is that: the metal oxide catalyst was obtained without nitriding and/or carbonizing steps.

The difference between Comparative Example 8 and Comparative Example 7 is that the active components are nickel and molybdenum.

The difference between Comparative Example 9 and Comparative Example 7 is that the active components are cobalt and nickel.

The difference between Comparative Example 10 and Comparative Example 7 is that the active ingredients are cobalt and zinc.

The difference between Comparative Example 11 and Comparative Example 7 is that the active ingredients are molybdenum and zinc.

The difference between Comparative Example 12 and Comparative Example 7 is that the active ingredients are nickel and zinc.

Table 2: Supported catalyst components and test results

It can be seen that the combination of nitrides and/or carbides of cobalt, molybdenum, nickel, zinc and other metals loaded on the carrier shows good catalytic performance for the reaction process of R-113 synthesis of CTFE. Its catalytic activity is significantly improved.

By comparing Examples 27-32, it can be seen that with the increase of the active ingredient content, the catalytic activity of the supported catalyst increases gradually, and there is a downward trend in the catalytic performance in the period exceeding 20wt%. Increase, the active sites of metal particles first increase and then decrease, after reaching a certain content, the degree of sintering and agglomeration increases, and the number of catalytic active sites decreases, resulting in a decline in catalytic activity; on the other hand, at different nitriding temperatures , the metals exhibit different valence states, and the metal nitrides sintered at 700 °C have higher catalytic activity. By comparing Examples 30, 33-36, it can be seen that the combined reducing gas of organic amines, organic amines and ammonia can obtain catalyst products with better catalytic activity and selectivity, which reflects the same law as that of non-supported catalysts. The same, but compared with non-supported catalysts, the catalytic activity and selectivity are higher. The reason is that the dispersibility of the carbides in the formation part is enhanced, and more active sites can be exposed to catalyze the reaction.

All documents mentioned in this patent application are incorporated by reference in this patent application as if each individual document was incorporated by reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (6)

1. The use of a catalyst for the production of perhalogenated ethylene, characterized in that: at least comprises at least two of cobalt nitride, molybdenum nitride, nickel nitride, zinc nitride, titanium nitride, iron nitride and tungsten nitride as catalyst active components, or at least comprises nitrogen/cobalt carbide and nitrogen/molybdenum carbide, or nitrogen/cobalt carbide and nitrogen/nickel carbide, or nitrogen/cobalt carbide and nitrogen/zinc carbide, or nitrogen/molybdenum carbide and nitrogen/zinc carbide, or nitrogen/nickel carbide and nitrogen/zinc carbide, or nitrogen/iron carbide and nitrogen/tungsten carbide, or nitrogen/nickel carbide and nitrogen/molybdenum carbide as catalyst active components;

at least one raw material is 1, 2-dichlorotetrafluoroethane or 1, 2-trichloro-1, 2-trifluoroethane;

at least one product is chlorotrifluoroethylene.

2. Use according to claim 1, characterized in that: the catalyst also comprises a carrier, and the content of the active components of the catalyst is 0.5-30wt%.

3. Use according to claim 1, characterized in that: the active components are cobalt nitride and molybdenum nitride, or cobalt nitride and nickel nitride, or cobalt nitride and zinc nitride, or molybdenum nitride and zinc nitride, or nickel nitride and zinc nitride, or iron nitride and tungsten nitride, or nickel nitride and molybdenum nitride, and the molar ratio of the two nitrides is 1.

4. Use according to claim 1, characterized in that: the molar ratio of the two nitrogen/carbides is 1.1-10.

5. Use according to any one of claims 1 to 4, characterized in that: the preparation method of the catalyst comprises the steps of (1) preparing a metal oxide precursor; step (2), temperature programming, reduction, nitridation and/or carbonization; and (3) passivating to obtain the catalyst.

6. Use according to any one of claims 1 to 4, for the preparation of chlorotrifluoroethylene.