Does corrosion in low-temperature methanol washing produce iron carbonyl [Fe(CO)5]?

Iron carbonyl can be formed under certain conditions!

It may not be the main corrosion product. Source: http://bbs.hcbbs.com/viewthread.php?tid=70304&extra=&highlight=shell&page=1. Carbonyl iron powder was first invented by Germans; during World War II, German factories were seized by the United States, and since then the U.S. has also begun to produce carbonyl iron powder. Currently, Germany’s BASF company owns the world’s largest and most advanced production line for iron carbide powder. Ferrocene powder is obtained by reacting CO with iron under high temperature and pressure to produce a ferrocene oil-like substance, which is then separated under low pressure to yield the final product. It can be shipped after annealing for oxidation prevention. At a temperature of 200°C and a pressure of 200 bar, the carbonylation reaction proceeds as follows: Fe + 5CO → Fe(CO)5. At 300°C and 1 bar, Fe(CO)5 decomposes into Fe and CO: Fe(CO)5 → Fe + 5CO. During this decomposition process, since Fe acts as a catalyst for the reaction between CO and CO2, NH3 is typically used as a protective gas to suppress this reaction. As a result, the iron carbonyl powder inevitably contains nitrogen. The product collected from the cyclone collector generally has an iron content of around 97%, with the contents of C and N both being less than 1%. Due to the presence of impurities such as Fe2O3 and Fe3N, and because iron powder also exhibits a certain degree of adsorption for CO and NH3 gases, these factors result in the iron powder having a relatively high hardness; it is therefore commonly referred to as hard powder. By reducing the iron powder with H2 gas for 1 hour, the iron content can be increased to around 99.0%, while the contents of other elements will also decrease significantly. This reduced iron carbonyl powder has a slightly lower hardness and is also known as soft powder. Ferrous carbonyl powder is highly reactive; under normal conditions, after being left for a period of time, it will aggregate spontaneously due to an increase in entropy. The agglomeration of iron powder leads to an increase in particle size and makes the particles sticky, which has a significant impact on injection molding applications. The highest-quality iron carbide powder currently available on the market is produced by the German company BASF. Cobalt iron powder has very high requirements regarding the manufacturing process; a temperature change of 3 degrees during the decomposition of 5-cobalt iron, or an increase in gas flow of 5%, can significantly affect the particle size and carbon content of the cobalt iron powder.

Yes. The protective bed before the Topsox process claims to be able to remove impurities such as iron carbonyl generated by low-temperature methanol washing, in addition to desulfurization and other functions

The appearance of iron carbonyl during the low-temperature methanol washing process seems unreasonable! Iron carbonyl generally forms in conversion systems; one reason is that the temperature and pressure are suitable, and the other is that the medium contains high levels of CO as well as high water content! The low-temperature methanol washing system operates at temperatures of over -60 degrees; the water content in this system is very low. Although the CO concentration is also high, the temperature conditions are not suitable! The situation described above is likely caused by iron carbonyl resulting from the transformation process! This is just my personal opinion for reference only; feel free to give your feedback!

I think these hydroxide iron compounds are generated in the transformation section. The general conditions for the hydroxide iron reaction are: 200 degrees, 5-20 Mpa. In methanol, the following reaction also occurs: 3Fe3(CO)12 + nCH3OH → [Fe(CH3OH)n][Fe3(CO)11] + 5Fe(CO)5. Fe(CO)5 is a yellow oily liquid with a melting point of –21°C and a boiling point of 102.8°C℃ ； Insoluble in water, soluble in alkalis, concentrated sulfuric acid, alcohols, benzene, and petroleum ether. I think it’s the hydroxyl-iron generated during the transformation that enters the methanol wash, where it is absorbed by methanol. It then goes to the regeneration tower, but since it isn’t completely removed, it is carried back to the top of T1; trace amounts of hydroxyl-iron end up in the methanol synthesis process along with the process gas! This post was last edited by z880347730 on 2009-3-17 21:48]

Carbonyl iron and carbonyl nickel are generated in the low-temperature methanol wash heat regeneration tower; it is possible to consider installing a filter at the bottom of the tower to remove them