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Methanol gas-phase dehydration method (two-step process): Methanol vapor passes through a solid catalyst to undergo gas-phase dehydration and produce BME. Reaction equation: 2CH3OH → CH3OCO3 + H2O. ZSM-5 molecular sieve catalysts made from γ-Al2O3/SiO2 are widely used both domestically and internationally. In this reaction, choosing different process conditions for various catalysts is of great significance for both the methanol conversion rate and DME selectivity. The typical production process consists of vaporization under pressure (0.8–1.0 MPa), catalytic dehydration, and four-column distillation; the product quality meets the requirements for propellants in aerosol products: dimethyl ether ≥ 99.9% (wt, the same below) ； Methanol ≤10 ppm ； Light components (CO, H2, C1–C5 light hydrocarbons, etc.) < 0.1% ； Water ≤50ppm ； Residues ≤ 10 ppm. The methanol conversion rate for this process is 60%–80%, the dimethyl ether selectivity is 99%, and the optimal reaction temperature is 280–330ºC. Its advantage is that the manufacturing technology is mature, allowing for easy large-scale production. Although the process flow is short and the investment per ton of production capacity is low, there is less reaction heat and less by-product steam. However, both the vaporization of the raw material and the purification and separation of the product require large amounts of steam, and the high price of methanol as a raw material results in higher production costs for this process. Therefore, this process is generally suitable for small-scale investment and implementation by enterprises that do not produce syngas, with the dimethyl ether produced being mainly used for internal consumption. The total capacity of the plant using this technology is approximately 5,000 tons per year.