Carbonylation technology for acetic anhydride production

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This post was last edited by jsshdw on 2016-10-12 at 18:42. Operational experience with acetate production using the liquid methanol carbonylation method has shown that the acetic anhydride production process developed in China is reliable. In the process for synthesizing acetic anhydride via carbonylation, the reactor consists of an esterifier and a carbonylation reactor; methanol and acetic acid react in the esterifier to produce methyl acetate, which then reacts with CO in the carbonylation reactor to form acetic anhydride. Due to the presence of water in the catalyst of this process, acetic anhydride is produced – while at the same time some acetic acid is also generated. When this process is primarily used for the production of acetic anhydride, its main raw materials are methanol, CO, and acetic acid. Additionally, this process can also directly produce acetic acid by reacting the raw materials CO and methanol in a carbonylation reactor, without the need for an esterifier. The production process is as follows: First, methanol and acetic acid react in the presence of a sulfuric acid catalyst to produce methyl acetate. The reaction takes place at atmospheric pressure, at a temperature of 65–85°C, with an acetic acid conversion rate of approximately 100%. Then, methyl acetate undergoes a carbonylation reaction with methanol and carbon monoxide in the presence of iodomethane and a rhodium-based catalyst or a nickel-based catalyst (rhodium-based catalysts are more commonly used industrially because their catalytic activity is 10 times that of nickel-based catalysts) to produce acetic anhydride as a by-product, along with acetic acid. The reaction pressure is around 25–45 MPa, and the reaction temperature is around 180°C. Its acetic anhydride/acetic acid ratio can be adjusted as needed. Based on years of experience in the development of acetic anhydride, the advantages of producing acetic anhydride via the carbonyl method are as follows: 1. Acetic acid is one of the most widely used organic acids; it is primarily used in the production of vinyl acetate, polyvinyl alcohol, terephthalic acid, ethyl acetate, butyl acetate, acetic anhydride, chloroacetic acid, acetate fibers, and various acetate derivatives. It can also be further processed into a wide range of products such as pesticides, pharmaceuticals, dyes, coatings, synthetic fibers, plastics, and adhesives. 2. The carbonylation method boasts advantages such as a short process flow, high product quality, low consumption, and reduced emissions of waste substances; it represents a major breakthrough in C1 chemistry and embodies the current advanced level of acetic acid production technology. 3. This technology utilizes a new generation of catalysts, which are rhodium complexes with excellent catalytic activity for methanol carbonylation; iodomethane and other catalysts are used in conjunction with these compounds. Such catalysts exhibit high stability, high activity, high selectivity, and good adaptability, which has enabled the rapid industrialization and application of the carbonylation process for acetic acid production. 4. In the engineering design, a pre-separation tower was added, and the light-component tower was specially designed to enhance the ability to capture and utilize catalysts; this improved the efficiency of separating light components as well as the utilization capacity of the equipment in the purification system. Due to the high corrosiveness of the medium, corrosion-resistant materials such as Hastelloy must be used, which helps to **extend the service life of the installation**. 5. High CO utilization rate, few reaction impurities, good product quality; product separation is simpler compared to traditional processes, with low energy consumption and less waste liquid. 6. PSA is used to recover CO from the exhaust gases, resulting in a significant reduction in exhaust emissions. I hope to exchange ideas and share technologies with everyone.