Science Concentrates: ACS Meeting News CATALYSIS
Catalyst makes acetic acid from methane The team evaluated cataBy dotting the pores of a zeolysts with a range of rholite with individual rhodium dium concentrations by atoms, researchers have first dispersing them in come up with a catalyst water and then delivthat couples methane, ering the suspensions carbon monoxide, and to a reactor charged oxygen to produce with methane, CO, acetic acid at low temand oxygen at various perature. The findings, partial pressures. The which the team reported reactions produced a last week at the ACS namixture of acetic acid, tional meeting in New formic acid, and methOrleans, could lead to anol. By optimizing the a low-cost, low-energy Tucked inside the pores of a conditions, the team catalytic process for zeolite, this rhodium-based boosted the selectivity manufacturing the orcatalyst couples methane, CO, for acetic acid to 70% ganic acid. and oxygen to make acetic acid The chemical inat low temperature. (Rh = green; at just 150 °C. Under those conditions, the dustry produced about Al = gold; O = red; C = blue) anchored catalyst was 14 million metric tons more than 1,000 times as active as soluof acetic acid in 2017 for use as a reagent to make monomers and other compounds, tion-phase rhodium cations. To understand how the catalyst does as well as for use in the medical and food its job, the team used isotope labeling and industries. other experimental methods coupled with Manufacturers produce acetic acid computational analysis. The researchers through a number of commercial proproposed a complex 18-step mechanism, cesses, including methanol carbonylation, which generated a lively discussion at the which couples CO to the alcohol. Methapresentation. nol is typically produced from a mixture “The mechanism is quite convincing and of CO and hydrogen known as synthesis seems consistent with the data,” remarked gas, which in turn is made from coal or Aditya (Ashi) Savara, a methane. Some of those symposium coorganizer industrial processes run and catalysis specialist at temperatures as high at Oak Ridge National as 1,000 °C. Laboratory. “The seFranklin (Feng) Tao lectivities, activities, of the University of and reaction rates unKansas reported that he der those conditions and his coworkers used are surprising and a wet chemical process impressive.” and ion-exchange chemGeorgia Tech’s Meiistry to deposit isolatlin Liu also praised ed rhodium cations metric tons of acetic acid inside the micropores manufactured globally in 2017 the study, noting that rationally designed of ZSM-5, an aluminoSource: Mordor Intelligence catalysts like the ones silicate zeolite. On the basis of X-ray absorption spectroscopy and described by Tao may benefit other catalytic processes by considerably reducing other methods, the team concluded that energy consumption and cost.—MITCH the catalyst takes the form of anchored RhO5 species. JACOBY
~14 million
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C&EN | CEN.ACS.ORG | MARCH 26, 2018
C R E D I T: FRA N KL I N TAO/U. KA N SAS
Isolated metal ions drive coupling chemistry at low temperature
