Mature acetic acid production processes include acetylene acetaldehyde, ethanol acetaldehyde, ethylene acetaldehyde, butane oxidation and methanol low-pressure carbonyl synthesis. Acetylene acetaldehyde method has been eliminated because of serious mercury pollution; Due to the backward production technology and high cost, the ethanol acetaldehyde method has been eliminated abroad, and there is still a small amount of production in China. Ethylene acetaldehyde method has been eliminated abroad because of consuming ethylene resources and high product cost, but it is still the main production process in China. Butane oxidation method is only applicable to areas rich in light oil, and is not popularized. At present, the widely used method is methanol low-pressure carbonyl synthesis. According to different catalyst systems, each company has developed its own unique low-pressure carbonylation technology for methanol:
★ BP active process
BP Company changed the rhodium-based catalyst in the traditional process technology into iridium-based catalyst, namely BP catalytic method. Rare metals such as rhenium, ruthenium and osmium are used as cocatalysts, and the catalytic activity of iridium catalyst is obviously higher than that of rhodium catalyst. When the water content is low, the iridium catalyst has high stability, low energy consumption and few by-products such as propylene, and can be operated at the water content ≤5%(Vol, the same below), which can greatly improve the traditional methanol carbonylation process and reduce the production cost and investment. In addition, due to the reduction of water content, the utilization efficiency of co is improved and the steam consumption is reduced. Cative process was successfully applied in the acetic acid plant of Samsung Company for the first time, and it is planned to be applied in Chongqing Yang Zijiang Acetyl Chemical Co., Ltd. and Nanjing at present.
★ Celanese AO Plus process
1980 the AO Plus process (acid optimization method) was introduced by Celanese company in the United States. In this process, high concentration of inorganic iodine (mainly lithium iodide) was added to change the composition of the catalyst, so that the reactor was operated at a low water content of 4% ~ 5%, and the yield and refining capacity of carbonylation reaction were improved. Using special patented technology, the yield of acetic acid can reach 99%, and the reaction speed is very fast. The total iodine content of the product is less than 5× 10- 12.
★ Celanese Silver Guard Technology
Celanese company developed Silverguard process, which overcame the defects of corrosion of AO Plus process equipment, high iodine residue in products and poisoning of downstream catalyst. The process uses silver ion exchange resin as rhodium catalyst; However, by the traditional method, the iodine residue in the product is generally 65438±00μg/g/g.
★ Chiyoda vinegar technology
Chiyoda Company developed Acetica process in 1997. This process combines heterogeneous rhodium catalyst with polyvinyl pyridine resin to form a phase carrier catalyst system, which can improve the catalytic activity of rhodium and make the yield of acetic acid exceed 99%. With methyl iodide as co-catalyst, the solid rhodium-based composite catalyst (supported on a special material sphere) was suspended, and the reaction was carried out in a closed bubble column reactor at 65438 075℃ and 2.8MPa. The final product was obtained after flash evaporation, dehydration and refining, and the methanol conversion rate was ≥99%.
Technology of producing acetic acid by ethane and ethylene raw material route
★ Selective catalytic oxidation of ethane
The selective catalytic oxidation process of ethane was developed by United Carbon Company in 1980s, which is called ethylene process. The main feature of this process is that besides acetic acid, a certain proportion of ethylene is also produced. There is no industrialization at present. Saudi Arabia Basic Industries Company has developed a new process for co-production of acetic acid and ethylene with ethane as raw material and phosphorus modified molybdenum niobium vanadate catalyst. Ethane reacts with air (15:85) at 260℃ and 1.38MPa. When the ethane conversion is 53.3%, the selectivity of acetic acid and ethylene is 49.9% and 10.5% respectively.
★ Direct oxidation of ethylene
Showa Electric Company of Japan developed the process of direct oxidation of ethylene to acetic acid, and built an acetic acid plant with a production capacity of 65438+ 10,000 t/a in Chiba factory in 1997. In this process, palladium catalyst was used to react in a fixed bed reactor at150 ~160℃ and about 0.9MPa. The once-through conversion of ethylene was 7.4%, and the selectivity of acetic acid, acetaldehyde and CO2 were 86.4%, 8. 1% and 5. 1% respectively. The process is very simple, and the wastewater discharge is only110 of the ethylene acetaldehyde method.
Domestic low-pressure carbonyl synthesis technology of methanol
★ Senenin industrialization process
After more than 20 years, Southwest Research Institute of Chemical Technology has completed the technical development of 654.38+100000 t/a methanol low-pressure carbonylation to acetic acid. The process adopts two reactors in series, and the second reactor can make the unreacted raw materials in the first reactor fully react, improve the reaction efficiency and reduce the load of refining and tail gas recovery system. In order to solve the problem of catalyst precipitation, Southwest Research Institute of Chemical Technology adopted measures such as increasing converters and reducing the water content of reaction solution, which improved the reaction conversion rate and the heat resistance of rhodium-based catalyst. When producing crude acid, evaporation process can greatly increase the content of acetic acid in crude acetic acid, reduce the circulation of mother liquor and reduce the load of separation section; Compared with acetic acid as absorbent, methanol absorbent has better absorption effect, less consumption and less corrosion to equipment. After technical appraisal by experts organized by the former State Bureau of Petrochemical Industry, it is considered that the process has high conversion rate and selectivity, few by-products, less "three wastes" emission and the product quality has reached the world advanced level. The process was industrialized in June1998+1October 65438, and obtained the national patent in June 1999.