## 2 Materials and Methods
### R134a Production Process  
At present, most manufacturers of R134a use heterogeneous catalysts to fluorinate trichloroetherline with hydrogen fluoride in the gas phase process to produce R134a. The direct input and output of the R134a production process are shown in Figure 2.  
The direct reaction to produce R134a is divided into two stages and is completed under the action of solid metal oxide catalyst under high temperature and high pressure:  
\[\text{CHCl}=\text{CCL}_{2}+4\text{HF}\rightarrow\text{CH}_{2}\text{FCF}_{3}+3 \text{HCl} \tag{4}\]  
The first-stage reactor fluorinates the intermediate material trichloroethylene into R133a, and the conversion can be completed at one time. R133a does not need to be separated and stored in the reactor to wait for the next reaction. In the second stage, when fluorine is used to replace the last remaining chlorine substituent, the chemical reaction equilibrium will be biased toward the raw material end, so hydrogen chloride, the reaction product, needs to be removed, so that the reaction moves toward the product end equilibrium. The entire reaction process is completely closed, the intermediate product remains in the reactor, and the amount released into the atmosphere is very small, so it is not included in the calculation of greenhouse gas emissions. All gases that may enter the atmosphere will undergo thermal oxidation treatment. The gas emitted after the process will not contain ozone-depleting substances. The main by-product of the reaction is hydrochloric acid, which can be sold directly. Other by-products that may be released into the environment are fluorinated volatile organic compounds (VOCs), including greenhouse gases and spent catalysts. The former  
Figure 2: The material and energy input of the direct reaction of the synthetic refrigerant R134a. is usually removed from the process exhaust gas stream by thermal oxidation treatment. Compared with the main raw materials, the amount of catalyst used in the reaction is very small, so it is not included in the calculation. In the direct reaction, the sources of carbon raw materials are crude oil and natural gas, and ethylene is produced by pyrolyzing natural gas and refined oil products. Ethylene reacts with chlorine to be chlorinated into dichloroethane, which is then further chlorinated into trichloro ethylene and tetrachloroethylene. Chlorine is produced by membrane electrolysis and mercury electrolysis in traditional chlor-alkali plants. The source of the fluorine raw material is fluorospar (a calcium fluoride mineral). Acid-grade fluorospar reacts with fuming sulfuric acid (a mixture of sulfuric acid and sulfur trioxide) to produce anhydrous hydrogen fluoride. Fuming sulfuric acid is made from mined sulfur ore. The production process of raw materials and intermediate products is shown in Figure 3. Materials and energy input are taken into consideration in the production of these intermediate products. In the literature, each ton of R134a requires about 1.3 tons of trichloroethylene and 0.8 tons of HF. It also requires electricity, heat (in the form of steam or natural gas), nitrogen, air, and water [15]. Operation mode. The average production of R134a per ton requires 1.2 MWh of electricity, 28 GJ of thermal energy (from various sources), 0.5 ton of nitrogen, and 13 m\({}^{3}\) of water. Different countries and factories have different production processes and raw material production methods and sources, resulting in certain differences in the energy consumption and carbon emissions of the final product. The source of the literature data referenced above is mainly [PERSON] in 2003 The research results, the data is relatively old, and the research results are based on the global raw material trade in developed countries such as Europe and the United States. Based on this, this article cooperates with a well-known domestic refrigerant manufacturer to analyze the raw material consumption and electricity and heat input of the factory's R134a refrigerant production workshop.