A Novel Application of Methanesulfonic Acid as Catalyst for the Alkylation of Olefins with Aromatics

Methanesulfonic acid (MSA) in clean processes and applications: a tutorial review

This Tutorial Review acquaints chemists and metallurgists with the properties and industrial applications of methanesulfonic acid (MSA, CH3SO3H). Over the past quarter-century, MSA has garnered increasing interest as a reagent for green chemistry due to its strong acidity, while circumventing many of the challenges associated with handling concentrated sulfuric acid, hydrochloric acid, or nitric acid. Concentrated MSA is a non-oxidizing reagent, exhibiting high chemical stability against redox reactions and hydrolysis, as well as high thermal stability and limited corrosivity towards construction materials. It is colorless, odorless, and possesses a very low vapor pressure. MSA combines commendable biodegradability with low toxicity. It is extensively utilized as a Brønsted acid catalyst for esterification or alkylation reactions, and is employed in biodiesel production. The high solubility of its metal salts, the high electrical conductivity of its concentrated solutions, coupled with the high electrochemical stability of MSA and its anion, make MSA-based electrolytes beneficial in electrochemical applications. Examples include the electrodeposition of tin-lead solder for electronic applications and the high-speed plating of tin on steel plate for food cans. MSA-based electrolytes are used in redox flow batteries (RFBs). MSA offers a much safer and environmentally friendlier alternative to electrolytes based on fluoroboric or fluorosilicic acid. A novel application area is as a strong acid in extractive metallurgy, where it may contribute to the development of circular hydrometallurgy. MSA is being explored in lithium-ion battery recycling flowsheets, as well as in other applications in the field of metal recovery and refining. However, this review is not solely about the advantages of MSA for green chemistry or clean technologies, as there are also some potential drawbacks. Apart from its higher price compared to regular strong acids, MSA has only minor advantages for applications where sulfuric acid performs well. Since methanesulfonate biodegrades into sulfate, the same emission restrictions as for sulfate should be considered. In conclusion, MSA is the acid of choice for applications where metal sulfates cannot be used due to poor solubility or where concentrated sulfuric acid is too reactive towards organics.

Activity of a Sulfonated Carbon-Based Catalyst Derived from Organosolv Lignin toward Esterification of Stearic Acid under Near-Critical Alcohol Conditions

In this study, an environmentally benign carbon-based catalyst derived from extracted bagasse lignin (EL) was successfully synthesized by solvothermal carbonization and sulfonation with methane sulfonic acid (MSA). Interestingly, the results indicated that the use of MSA as a sulfonation agent made a catalyst with higher thermal stability than conventional sulfuric acid. Thus, in comparison to the catalyst prepared by using sulfuric acid, the catalyst prepared by using MSA (EL-MSA) exhibited higher catalytic activity in the esterification of stearic acid under near-critical methanol conditions. Under optimum conditions (260 °C for 5 min, a 9:1 methanol-to-stearic-acid molar ratio, 5 wt % catalyst loading, and 10% v/v toluene), the esterification over the EL-MSA catalyst promoted a 91.1% methyl stearate yield. Moreover, the results also revealed that the high thermal stability of the EL-MSA catalyst not only affects its great catalytic activity, but it also prevents damage to the porous structure and decomposition of acidic surface oxygen-containing functional groups. It contributes to the excellent reusability of the catalyst. After the fifth run, a high yield of 82.8% was obtained. The effect of alcohol type on the catalyst performance was also studied. It was found that the EL-MSA catalyst also presented good performance toward esterification with ethanol and propanol, from which ethyl stearate and propyl stearate with a more than 80% ester yield can be achieved.

Specific-Ion Effects Unveil a Route for Modulating Oxidatively Triggered Acid Systems for Reservoir Applications

On-demand in situ preparation of industrially relevant organic acids, namely, methanesulfonic acid, triflic acid, and trifluoroacetic acid, is demonstrated in this study. Sodium and potassium bromate were found to selectively oxidize a series of ammonium salts NH₄X, where X = OMs, OTf, or OTFAc, with characteristic clock reaction behavior. The redox system undergoes rapid acid formation following an extended induction time at 150 °C and is identified as a potential candidate for high-temperature oil field chemistry applications where on-demand acid placement is required. Although the reaction kinetics for acid formation from NH₄X salts where X = Cl, Br, F, or SO₄^2- follows a pK_a trend, the rates of formation of the organic acids are much slower and deviate from this trend. Furthermore, we demonstrate that the rate of acid formation can be modulated by the addition of alkali metal salts, with the strongest effect observed from LiBr. Spectroscopic studies implicate the formation of lithium bromate ion pairs that slow or altogether inhibit the oxidation of NH₄⁺. Additionally, the presence of Br^- alters the reaction path, eliminating the clock behavior and creating a pathway for Li⁺ to strongly inhibit the redox reaction. From these studies, a method for slowing ammonium oxidation under reservoir conditions to sufficiently delay acid formation until the precursors are placed in the zone of interest is identified.

Acid-Modified Hierarchical Porous Rare-Earth-Containing Y Zeolite as a Highly Active and Stable Catalyst for Olefin Removal

Rare-earth-containing ultrastable Y zeolite (ReUSY) was modified by oxalic acid solution leaching treatment and applied in industrial units for catalytic olefin removal from aromatic hydrocarbons. The porous structure and amount of acidity of the modified ReUSY (denoted as ReUSY-x, where x indicated the amount of oxalic acid in solution) could be tuned by different concentrations of oxalic acid solution, and the ReUSY-x samples exhibited different catalytic performances. Based on the best catalytic performance of ReUSY-25, an industrial catalyst was prepared and applied in industrial units for catalytic olefin removal. The industrial catalyst exhibited excellent activity and regeneration stability with a long lifetime of about 2 years, which was about 13 times longer than that of activated clay.

Conductivity, Viscosity, Spectroscopic Properties of Organic Sulfonic Acid solutions in Ionic Liquids

Sulfonic acids in ionic liquids (ILs) are used as catalysts, electrolytes, and solutions for metal extraction. The sulfonic acid ionization states and the solution acid/base properties are critical for these applications. Methane sulfonic acid (MSA) and camphor sulfonic acid (CSA) are dissolved in several IL solutions with and without bis(trifluoromethanesulfonyl)imine (HTFSI). The solutions demonstrated higher conductivities and lower viscosities. Through calorimetry and temperature-dependent conductivity analysis, we found that adding MSA to the IL solution may change both the ion migration activation energy and the number of “free” charge carriers. However, no significant acid ionization or proton transfer was observed in the IL solutions. Raman and IR spectroscopy with computational simulations suggest that the HTFSI forms dimers in the solutions with an N-H-N “bridged” structure, while MSA does not perturb this hydrogen ion solvation structure in the IL solutions. CSA has a lower solubility in the ILs and reduced the IL solution conductivity. However, in IL solutions containing 0.4 M or higher concentration of HTFSI, CSA addition increased the conductivity at low CSA concentrations and reduced it at high concentrations, which may indicate a synergistic effect.