acetic acid synthesis:

1. Acetaldehyde oxidation method

The acetaldehyde oxidation method is completed in two steps. First, under the action of PdCl2 · CuCl2 catalyst, ethylene reacts and oxidizes to form acetaldehyde at a temperature of 100-150℃ and a pressure of 0.3MPa; the role of acetaldehyde in manganese acetate catalyst Under liquid phase conditions, it is oxidized with pure oxygen, enriched oxygen or air to generate acetic acid. Due to the simple process, high yield and wide source of raw materials, it became the main acetaldehyde production method in the 1960s.

2. Methanol carbonylation method

1) BASF high-pressure process: In 1913, BASF first discovered the methanol carbonylation reaction, but it was not until the appearance of corrosion-resistant nickel/molybdenum alloy in the late 1950s that the first pilot plant was built, and the first methanol carbonyl was built in 1960 The pilot plant for chemical production of acetic acid, the catalyst is cobalt iodide (CoI2), the reaction temperature of BASF synthesis process is about 250℃, the pressure is as high as 6.89MPa, and the selectivity of acetic acid is 90% and 70% based on methanol and CO, respectively. It passes through five towers. Distillation can obtain an acetic acid product with a purity of 99.8%.
2)(Monsanto)/BP process: In the mid-1970s, the development of a highly active rhodium catalyst for methanol carbonylation was a milestone in the process of preparing C2 chemicals from C1 raw materials. The Monsanto process uses a rhodium-based metal homogeneous catalyst with iodide added. The reaction is carried out at a lower temperature of 180°C and a pressure of 3.5MPa, and a high selectivity can be obtained, which is greater than 99% based on methanol and greater than 70% based on CO .
3)Celanese low water content process: This process adds high concentration of inorganic iodide (mainly lithium iodide) to the rhodium-based catalyst to enhance the stability of the catalyst system. After adding lithium iodide and methyl iodide promoters, it is allowed The water content in the reactor is greatly reduced while at the same time it can stably maintain a high reaction rate, so that the separation cost of the new process can be greatly reduced.
4) BP Chemical’s CATIVA process: The CATIVA process uses metal iridium as the main catalyst and adds a Part of rhenium, ruthenium and osmium are used as promoters. Among them, rhenium and ruthenium are the best promoter metals. Similar to the traditional rhodium-based catalytic process, the new iridium catalyst has higher reaction speed and target product selectivity under appropriate pressure and temperature. Compared with the traditional Monsanto/BP process, the advantages of CATIVA are: the activity of the iridium catalyst system is higher than that of the rhodium catalyst system; there are few by-products; and it can be operated with low water content (≤8%). If these technologies are used in the transformation of existing equipment, the production capacity of the equipment can be increased with a lower investment. Moreover, the low water content also brings about a drop in steam consumption and an improvement in CO conversion.
5) UOP/ChiyodaAcetica process: using methanol and CO as raw materials, using an additive with methyl iodide Rhodium-based catalyst supported by polyvinylpyridine resin. It is said that the heterogeneous catalyst can obtain high yield and improve the performance of the rhodium-based catalyst. The yield of acetic acid is higher than 99% based on methanol. The process synthesis reactor can be operated under low water content conditions. The HI concentration in the reactor is low, the corrosion problem is small, and compared with the traditional process, the new process has fewer by-products and high product purity. Another major feature of this process is that the reactor uses a bubble column, which eliminates the sealing problem of a stirred tower reactor. The operating pressure can be increased to 6.2MPa. In order to maintain the optimal CO partial