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The gas-phase catalytic dehydrochlorination of 1,1,2-trichloroethane to produce 1,1-dichloroethylene: Traditionally, 1,1,2-trichloroethane is saponified to obtain dichloroethylene; this production method is outdated, generates many by-products, results in high costs, and causes significant environmental pollution. This process features a short route; it does not require the use of NaOH solution. Instead, 1,1,2-trichloroethane gas undergoes catalytic dehydrochlorination in a gas phase environment using a catalyst, and 1,1-dichloroethylene is obtained through direct condensation and distillation. The selectivity and conversion rate of the target product are both greater than 90%, while the overall yield of the target product is around 85%. Moreover, this production process does not generate any industrial waste such as wastewater or exhaust gas. The production cost is about 500 yuan/ton lower compared to the traditional saponification method. Below is a cost analysis comparison of the two processes along with an introduction to the simple process flow. 1,1,2-Trichloroethane is used, along with the NaOH saponification method, to prepare 1,1-dichloroethylene. In this process, the raw materials consumed are vinyl chloride/chlorine/catalyst, and NaOH solution; the products are 1,1-dichloroethylene along with a residual mixture of NaCl and excess NaOH. The mixed residue can be used for exhaust gas absorption, and after simple treatment, it can be sold at a low price. The current market prices of the three raw materials are shown in the table below: Price (yuan/ton): Vinyl chloride, Chlorine, Trichloroethane; 32% Sodium hydroxide – 4,800, 800, 3,700, 800. The current market price of vinylidene chloride is shown in the table below: Price (yuan/ton): Vinylidene chloride, Sodium chloride residue – 7,000, 0–50. The cost of this production process can be estimated as follows: based on the production of 1 ton of vinylidene chloride, with expenses such as utilities, labor costs, and equipment depreciation excluded. As shown in the data in the table above, we can conclude that the profit from producing one ton of vinylidene chloride using the saponification method is currently approximately 1,097.303 yuan. However, from an industrial perspective, this process generates a large amount of wastewater (mixed residues of NaCl/NaOH/sodium hypochlorite, etc.); approximately 3 tons of industrial wastewater are produced for every ton of vinylidene chloride manufactured. 2: The simplified flow diagram for the gas-phase catalytic HCl removal process using 1,1,2-trichloroethane to produce 1,1-dichloroethylene is shown below. Process description: 1,1,2-trichloroethane with a purity of around 98% is fed into Vaporizer No. 1 via Pump No. 1; after vaporization, it enters a sulfidation bed where gas-phase catalytic reaction takes place to remove HCl. The gas mixture after the reaction is condensed into a liquid mixture in a condenser, and then purified 1,1-dichloroethylene is separated out through two distillation columns (with a yield of about 85% for 1,1-dichloroethylene), while 1-trans-1,2-dichloroethylene is obtained as a by-product (with a conversion rate of 5–8%). The residue is the content