CN115433055A - Treatment method of trifluoromethane - Google Patents

Abstract

The invention discloses a method for disposing trifluoromethane, which belongs to the technical field of resource conversion of trifluoromethane, and comprises the following steps: the method is characterized in that a solvent, chloride and trifluoromethane are reacted in a liquid phase reactor with stirring to prepare chloroform, the solvent is one or a mixture of more of alkyl halide, DMF, alcohols and ammonium, the chloride is chlorinated metal salt, the reaction temperature of the liquid phase reactor is 0-150 ℃, and the reaction pressure of the liquid phase reactor is-1.0-3.0 MPa.

Description

Treatment method of trifluoromethane

Technical Field

The invention relates to the technical field of resource conversion of trifluoromethane, in particular to a treatment method of trifluoromethane.

Background

Trifluoromethane (HFC 23), because its greenhouse effect potential value (GWP) is 14800 times that of carbon dioxide, belongs to super strong greenhouse gas, is a variety of ' carbon peak carbon neutralization ' and ' super high GWP which is of great concern, international and national concern are about the generation, use, recovery and destruction of trifluoromethane, and a related policy is specially issued for the single variety, the environmental protection department is specially entitled trifluoromethane atmosphere letter No. 2021/432, notification about the control of emission of by-product trifluoromethane, trifluoromethane (HFC 23) is a by-product of industrial production of chlorodifluoromethane (HCFC-22, R22), and due to its high temperature chamber effect potential value, the by-product cannot be directly discharged to the atmosphere, and needs to be treated. In general, trifluoromethane (HFC 23) is industrially treated by incineration to completely decompose it into hydrogen fluoride, carbon dioxide, and the like by calcination. However, the incineration treatment needs special incineration equipment, the investment is large, and the decomposition product hydrogen fluoride is easy to corrode. If trifluoromethane (HFC 23) can be recycled to convert other useful compounds, the method has important social and economic benefits. The resource conversion of trifluoromethane (HFC 23) is reported less, wherein a representative conversion method is to utilize trifluoromethane (HFC 23) to co-crack with methane and oxygen to synthesize important monomer vinylidene fluoride (CH 2= CF 2) for producing polyvinylidene fluoride and fluororubber. Methane and trifluoromethane (HFC 23) have high stability and hardly react at a high temperature of 700 ℃ without adding a catalyst. The literature Greenhouse gases, science and technology7 (5) (2017) 891-902, improved upon, and reported that the synthesis of vinylidene fluoride by co-cracking trifluoromethane (HFC 23) with methane and oxygen using rare earth metal oxides as a catalyst, the selectivity of vinylidene fluoride at 700 ℃ is 50% and the methane conversion is 5%. Although this method enables trifluoromethane (HFC 23) to react with methane and oxygen at a temperature of 700 ℃, the target product, vinylidene fluoride, has low selectivity and low yield, and the catalyst must be pretreated with trifluoromethane (HFC 23) at a high temperature before use. In order to improve the activity of the catalyst, the reaction temperature is increased to 800 ℃ in the method, and when the reaction temperature is 800 ℃, although the activity of the catalyst is improved to a certain extent, the thermal stability of the catalyst is poor; patent CN111217669A reports that improvement of a method for preparing vinylidene fluoride by resource conversion of trifluoromethane (HFC 23) requires a complete cracking and purifying device, has large investment and lower yield, and is not beneficial to industrial production; patent cn20171126421.X describes the conversion of trifluoromethane (HFC 23) to tetrafluoromethane, which is also a high GWP to be eliminated. The international organization "montreal protocol on ozone depleting substances" sets forth a list of HFC-23 destruction technologies approved by the bang: 1. gas or flue gas oxidation 2, liquid jet type incineration 3, cracking in a reaction furnace 4, rotary kiln incineration 5, argon plasma arc 6, nitrogen plasma arc 7, chemical reaction with hydrogen and carbon dioxide 8, and a superheated steam reactor; however, these methods are basically incineration treatment, and have complex process, high energy consumption, large corrosion of equipment and a lot of pollutants. In view of the above disposal methods, whether incineration or conversion, the disposal of the trifluoromethane produced by matching a set of 2 ten thousand/aHCFC 22 needs tens of millions to hundreds of millions, even hundreds of millions of economic investment, and also generates more new problems of energy consumption, environmental protection and safety, and no other method has real application except incineration; therefore, the invention provides a method which is convenient, has small investment (hundreds of thousands) and is easy to control, and has great significance for carrying out resource utilization on HFC23 and converting the HFC23 into chloroform and villiaumite which are used as raw materials of HCFC22, greatly reducing three wastes and energy consumption and being safe.

Disclosure of Invention

The invention aims to provide a method for treating trifluoromethane, which aims to solve the problems that the equipment proposed in the background art is complicated, the investment is large, and great pollution is generated when trifluoromethane is converted.

In order to achieve the purpose, the invention provides the following technical scheme: a method for disposing of trifluoromethane, the method comprising the steps of:

chloroform is prepared by reacting solvent, chloride salt and trifluoromethane in a liquid phase reactor with stirring.

Preferably, the solvent is one or a mixture of alkyl halides, DMF, alcohols and ammonium.

Preferably, the chloride salt is a metal chloride salt.

Preferably, the reaction temperature of the liquid phase reactor is 0 to 150 ℃.

Preferably, the reaction pressure of the liquid phase reactor is-1.0-3.0 MPa.

Compared with the prior art, the invention has the beneficial effects that: compared with other conversion methods, the method for treating the trifluoromethane has the advantages of simple equipment, small investment, safety, environmental protection and low requirement on the purity of the trifluoromethane, does not need to carry out intentional rectification on the trifluoromethane, can convert HCFC22 and HCFC21 contained in the trifluoromethane into chloroform, is favorable for activating reaction and saves the energy consumption for rectifying HFC 23.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Compared with other conversion methods, the treatment method of the trifluoromethane provided by the invention has the advantages of simple equipment, small investment, safety, environmental protection, low requirement on the purity of the trifluoromethane, no need of deliberately rectifying the trifluoromethane, conversion of HCFC22 and HCFC21 contained in the trifluoromethane into chloroform, activation of reaction facilitated by HCFC22 and HCFC21 contained in the trifluoromethane, and energy consumption for rectifying HFC23 conservation, and comprises the following steps:

the chloroform is prepared by the reaction of solvent, chlorate and trifluoromethane in a liquid phase reactor with stirring, the trifluoromethane can contain inevitable impurities such as HCFC22, HCFC21 and the like, the energy consumption for purifying the HFC23 which is a byproduct in the previous process is reduced, and the produced villiaumite can be used as a catalyst for other reactions;

the chloride salt is converted into fluoride salt, and the reaction has a short induction period;

the general reaction formula is as follows: HFC23+ chloride-chloroform + fluorochloride-chloroform + fluoride salt;

the solvent is one or a mixture of more of alkyl halide, DMF, alcohol and ammonium, and preferably chloroform which is the same as the reaction product;

the chloride salt includes metal chloride salt, preferably aluminum chloride and other cheap salts;

the reaction temperature can be controlled between 0 ℃ and 150 ℃, preferably between 55 ℃ and 100 ℃, and the reaction speed can be increased due to high temperature;

the reaction pressure is-1.0-3.0 MPa, preferably-1.0-1.5 MPa;

example 1

Adding 266 g of anhydrous aluminum chloride (about 2 mol) into a 2L stainless steel reaction kettle with stirring, sealing, vacuumizing to gauge pressure of-0.1 MPa, sucking 800 g of carbon tetrachloride by using negative pressure, starting stirring for 1 hour, introducing 70 g of HFC23, heating to 60 ℃, stopping heating, continuing stirring, increasing the pressure to gauge pressure of 0.96MPa, continuously increasing the reaction temperature due to partial activation of the reaction, when the temperature is increased to 65 ℃, the reaction becomes very violent, rapidly increasing the temperature to about 97.5 ℃, rapidly reducing the pressure to 0.4MPa, returning the temperature to 55 ℃ after half an hour, reducing the pressure to 0.4MPa, continuously introducing 35 g of HFC23, controlling the pressure within 0.9MPa, finishing about 2 minutes, rapidly increasing the temperature to 98.5 ℃, beginning to reduce the pressure, when the pressure is reduced to 0.2MPa, naturally cooling the temperature to 40 ℃, and introducing 35 g of HFC23 again, wherein the process is the same as above; after the temperature naturally drops to the normal temperature, the pressure is already negative. And then, performing chromatographic analysis on the liquid phase in the kettle to form a product which mainly comprises chloroform and carbon tetrachloride, wherein HFC23 and theoretical transition products HCFC22 and HCFC21 cannot be detected, the almost complete conversion of HFC23 can be determined, and the conversion rate and the selectivity of HFC23 are close to 100 percent because the system is a closed system and can be calculated.

Example 2

Adding 266 g of anhydrous aluminum chloride (about 2 mol) into a 2L stainless steel reaction kettle with stirring, sealing, vacuumizing to gauge pressure of-0.1 MPa, sucking 800 g of chloroform with the same product by using negative pressure, starting stirring for 1 hour, introducing 70 g of HFC23, heating to 50 ℃, stopping heating, continuing stirring, increasing the pressure to gauge pressure of 1.1MPa, continuously increasing the reaction temperature when the temperature is increased to 60 ℃, causing the reaction to be very violent, rapidly increasing the temperature to about 100 ℃, rapidly reducing the pressure to 0.7MPa, returning the temperature to 70 ℃ after half an hour, reducing the pressure to 0.4MPa, continuously introducing 70 g of HFC23, controlling the pressure within 1.0MPa, completing about 5 minutes, rapidly increasing the temperature to 110 ℃, and beginning to reduce the pressure, and naturally reducing the temperature to normal temperature when the pressure is already negative. The composition of the liquid phase in the kettle is analyzed by chromatography and is basically the same as the composition of chloroform which is put into the kettle in the early stage, HFC23 and theoretical transition products HCFC22 and HCFC21 can not be detected, almost complete conversion of HFC23 can be determined, and the conversion rate and the selectivity of HFC23 are close to 100 percent because the system is a closed system and can be calculated.

Example 3

50 g of the solid fluoride salt obtained in the example 2 and left in the kettle is added into a 2L stainless steel kettle, the kettle is vacuumized to-0.1 MPa at normal temperature, 1000 g of CFC113 is sucked in by vacuum, stirring and heating are started, the temperature is raised to 47 ℃, heating is stopped, and a reactant is sampled and analyzed after 3 hours, so that the gas phase mainly comprises CFC114a3.5%, CFC1130.2%, CFC113a93% and CFC112a2%, and the results are consistent with a CFC113 isomerization production device, which shows that the fluoride salt has high activity and can meet the use requirements for producing CFC113a and the like.

Example 4 in a2 liter stainless steel reaction kettle with stirring, 266 grams of anhydrous aluminum chloride (about 2 mol) is added, the kettle is sealed and vacuumized to the gage pressure of-0.1 MPa, 800 grams of dichloromethane is sucked by negative pressure, stirring is started for 1 hour, 50 grams of HFC23 is introduced, the temperature is raised to 50 ℃, heating is stopped and stirring is continued, the pressure is raised to the gage pressure of 0.82MPa, the reaction temperature is continuously raised because partial activation has been carried out on the reaction, the temperature is raised to 73.5 ℃, the pressure is rapidly reduced to 0.62MPa, the temperature is returned to 62 ℃ after half an hour, the pressure is reduced to 0.56MPa, 78 grams of HFC23 is continuously introduced, the pressure is controlled within 1.2MPa, the reaction is completed within about 60 minutes, the temperature is raised to 110 ℃, the pressure is reduced, and the temperature is naturally reduced to negative pressure. And then, performing chromatographic analysis on the liquid phase in the kettle to form the composition, wherein HFC23 and theoretical transition products HCFC22 and HCFC21 cannot be detected, almost complete conversion of HFC23 can be determined, and the conversion rate and selectivity of HFC23 can be calculated to be close to 100% because the system is a closed system.

Compared with other conversion methods, the method has the advantages of simple equipment, low investment, safety, environmental protection and contribution to popularization and application, the main source of the trifluoromethane is a byproduct of HCFC22 production, the trifluoromethane inevitably contains HCFC22 and HCFC21, the trifluoromethane is converted into chloroform and can be fed back to a production device as a raw material for HCFC22 production, the treatment environment is reduced, the conversion rate is high, the transition products HCFC22 and HCFC21 can not be almost detected, the purity requirement on the trifluoromethane is low, the trifluoromethane does not need to be rectified deliberately, the trifluoromethane contains HCFC22 and HCFC21 and can be converted into chloroform, the HCFC22 and HCFC21 are beneficial to activation reaction, the energy consumption for rectifying the trifluoromethane is saved, the feeding mode can be one time or multiple times, and the continuous feeding can also be carried out.

While the invention has been described above with reference to an embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the various features of the embodiments disclosed herein may be used in any combination, provided that there is no structural conflict, and the combinations are not exhaustively described in this specification merely for the sake of brevity and conservation of resources. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (5)

1. A method for handling trifluoromethane, comprising: the method for disposing the trifluoromethane comprises the following steps:

chloroform is prepared by reacting solvent, chloride salt and trifluoromethane in a liquid phase reactor with stirring.

2. A method of handling trifluoromethane according to claim 1, wherein: the solvent is one or a mixture of alkyl halide, DMF, alcohol and ammonium.

3. A method according to claim 2, characterized in that: the chloride salt is a chlorinated metal salt.

4. A method according to claim 3, characterized in that: the reaction temperature of the liquid phase reactor is 0-150 ℃.

5. A method according to claim 4, characterized in that: the reaction pressure of the liquid phase reactor is-1.0-3.0 MPa.