Calcium magnesium acetate (CMA) is a deicer and can be used as an alternative to road salt. It is approximately as corrosive as normal

tap water Tap water (also known as faucet water, running water, or municipal water) is water supplied through a tap, a water dispenser valve. In many countries, tap water usually has the quality of drinking water. Tap water is commonly used for drinking, ...

, and in varying concentrations can be effective in stopping road ice from forming down to around (its

eutectic temperature A eutectic system or eutectic mixture ( ) is a homogeneous mixture that has a melting point lower than those of the constituents. The lowest possible melting point over all of the mixing ratios of the constituents is called the ''eutectic tempe ...

). CMA can also be used as an H₂S capture agent.

Production

CMA can be produced from a reaction of a magnesium/calcium compound with

glacial acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...

. If it is reacted with dolomite or dolomitic lime, acetic acid does not need to be concentrated to produce CMA. Acetic acid production requires the fermentation of organic material which must be carried out at a pH around 6.0. Separating agents used to recover acetic acid must therefore maintain a high capacity while within this pH range. Amberlite LA-2 in 1-octanol diluent maintains nearly full capacity up to a pH value of 6.0 and is readily regenerated by aqueous, slaked dolomitic lime to form CMA, making it a good acetic acid separating agent for CMA production.

Use as road deicer

Sodium chloride road salt costs less than $50 per ton to produce but is corrosive to metals in highway structures and increases the concentration of sodium in drinking water, which can lead to adverse health effects. Alternative deicing substances have been sought to alleviate these problems. CMA has been found to be an effective deicer and environmentally benign, though its production cost of $650 per ton is much greater than the cost of road salt. Using estimates based on New York State Data, a 1992 report in the ''Journal of Policy Analysis and Management'' concluded that $615 per ton would be saved in vehicle corrosion and that $75 per ton would be saved in aesthetic damage to roadside trees if the state highway agencies switched to using CMA as a deicer instead of sodium chloride rock salt, far outweighing its initial production cost. The report also warned that excessive federal subsidization of CMA could encourage its inefficient overuse.

Use for H₂S removal

CMA has the ability to form highly cenospheric oxide particles when heated to high temperatures, which contain thin, porous walls that are effective at capturing

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The und ...

from temperatures from 700 to 1100 °C up to 90%. Integrated gasification combined cycle (IGCC) systems are used to convert

coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...

into clean, usable fuel gas which is then used to run

gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...

systems for power generation. An essential step in this conversion process is the elimination of the environmentally harmful H₂S and COS from the gas that is formed from sulfur contained in the coal.

Desulfurization mechanism

CMA (CaMg₂(CH₃COO)₆) decomposes around 380-400 °C to produce the following products: CaCO₃, MgO, CH₃COCH₃, and CO₂. CaCO₃ further decomposes around 700 °C to CaO and CO₂. A sulfidation reaction then takes place when CaO is reacted with H₂S at reducing conditions in a gasifier, yielding CaS and H₂O. CaS is finally reacted with O₂ to produce inert CaSO₄ which can then be disposed of.

References

External links

Material safety data sheet