Benefits of MSA

MSA is well known for its useful properties as a catalyst for esterification. The advantages of MSA lead to a reduction of production costs in several ways

LOW MOLECULAR WEIGHT

MSA is the lowest molecular weight sulfonic acid commercially available. In most esterifications, 30% less MSA by weight than PTSA can give the same kinetics as illustrated in Figure 1.

LIMITED BY-PRODUCTS

Sulfuric acid is a strong dehydrating agent which leads to charring color and ether formation. As these ethers are recycled with the excess alcohol, they compromise the purity and resistivity of the final ester, imparting odor and taste. Sulfuric acid reacts irreversibly with excess alcohol to form the alkyl sulfate. Alkyl sulfates, when neutralized, form detergents which increases separation time and COD. Unlike other homogeneous catalysts, MSA limits the amount of by-products, solid residues and effluents, decreasing purification costs and increasing equipment capacity.

HIGH THERMAL STABILITY

MSA has a higher thermal stability than PTSA. This reduces formation of decomposition products which can further react with the final product or starting materials imparting corrosion and color. MSA can operate over a wider range of temperatures, usually from 80°C to 150°C. Energy costs can be saved since MSA catalyzes esterifications at lower temperatures than titanates.

RECYCLABLE

Since MSA is water miscible, the cost of the catalyst can be noticeably reduced by recycling. More than 80% of introduced MSA can be recovered in some cases by washing the reaction medium with a small amount of water.

BIODEGRADABLE

As other acids, due to its acidity, MSA is toxic to aquatic organisms. Effluents have to be neutralized before being released into the environment. When neutralized, Methane Sulfonic Acid is considered readily biodegradable with respect to BOD₂₀ based on an OECD 301D Closed Bottle Test. After 20 days of incubation, biodegradability values of 77% were found in the range of 2 to 11 mg/I of MSA.

Laboratory simulation of an aerobic activated sludge treatment plant with non-neutralized MSA at a concentration of 160mg/I shows that MSA was biodegraded at 83% ± 12%.

Tests conducted by Arkema on effluent from DOP synthesis showed that effluent after reaction can have a lower COD than other sulfonic acid catalysts:

Since MSA can berecycled, less alkaline is needed to neutralize the residual acidity. Fewer salts and less effluent are formed which have become more difficult to eliminate.

LESS CORROSIVE THAN SULFURIC ACID

Corrosion testing was performed by Arkema with MSA 70% on stainless steels used for storage tanks and transfer lines. The results are as follows:

Lined mild steel is therefore preferred for storage tanks. H₂SO₄ is known to be 10-20 times more corrosive than MSA.