1 c 1 |, L4 l & ampP2 p, f4 u- s 1.2 The high-sand solid methionine production process [4 ~ 6] mainly uses hydrocyanic acid instead of sodium cyanide for hydantoin reaction, and the by-products of ammonia, carbon dioxide and potassium bicarbonate are recycled, which greatly reduces waste discharge and effectively solves the problem of environmental protection. )y，T) G9 `, @9 ~3 S
1.3 production process of liquid methionine in high-altitude sand [7] The main reaction of liquid methionine sodium salt in high-altitude sand is similar to the production process of solid methionine, and sodium hydroxide can replace potassium carbonate for hydrolysis.
2 U7 o$ h4 v' Z8 L 1.4 Monsanto liquid methionine production technology [8 ~ 9] Compared with other production technologies, Monsanto liquid MHA production technology is the simplest. The main raw materials are β-methylthiopropionaldehyde, hydrocyanic acid and sulfuric acid. The yield is very high, only one kind of waste is produced, which reduces the reaction steps and environmental protection treatment costs, and is the production process with the lowest operating cost.
5 @ * B； e9？ ) g$ g7 V 1.5 Methylthiol production process The conventional production method of methyl mercaptan is that methanol and hydrogen sulfide are converted into methyl mercaptan at about 290℃ under the action of acidic catalyst, and the reaction is almost quantitative, and the reaction adopts a fixed bed [10]. The recent patent documents put forward the technical scheme of preparing methyl mercaptan from synthesis gas on molybdenum-containing catalyst, the main purpose of which is to reduce the production cost of methyl mercaptan by replacing methanol with cheap synthesis gas [1 1 ~ 12]. 3 E. d: E: d 1 z
The production process of 1.6 β- methylthiopropionaldehyde [13 ~ 14]β- methylthiopropionaldehyde is prepared by the addition of methyl mercaptan and acrolein. This reaction is similar to the hydration of acrolein to 3- hydroxypropionaldehyde. Weak acid cation exchange resin can be used as catalyst, and the reaction selectivity can reach above 95%. The main side reaction is the polymerization of acrolein.