Heterogeneous Chemistry of Acetone in Sulfuric Acid Solutions:  Implications for the Upper Troposphere

The uptake of acetone vapor by liquid sulfuric acid has been investigated over the range of 40−87 wt % H2SO4 and between the temperatures 198 and 300 K. Studies were performed with a flow-tube reactor, using a quadrupole mass spectrometer for detection. At most concentrations studied (40−75 wt %), acetone was physically absorbed by sulfuric acid without undergoing irreversible reaction. However, at acid concentrations at or above 80 wt %, reactive uptake of acetone was observed, leading to products such as mesityl oxide and/or mesitylene. From time-dependent uptake data and liquid-phase diffusion coefficients calculated from molecular viscosity, the effective Henry's law solubility constant (H*) was determined. The solubility of acetone in liquid sulfuric acid was found to increase with increasing acid concentration and decreasing temperature. In the 75 wt % and 230 K range, the value for H* was found to be ∼2 × 106 M/atm. This value suggests that acetone primarily remains in the gas phase rather than absorbing into sulfate aerosols under atmospheric conditions.