Catalytic conversion of lactic acid to 2,3-pentanedione over sodium salts and base on low surface area silica support has been studied. Yield and selectivity toward 2,3-pentanedione are optimal at around 300 °C, 3−4 s residence time, and 0.5 MPa total pressure. Anions of initial salt catalysts used do not participate in lactic acid condensation to 2,3-pentanedione once steady-state conditions have been achieved; instead, sodium lactate has been identified by postreaction FTIR spectroscopy as the primary, stable species on the support during reaction. Sodium lactate is believed to be an intermediate in 2,3-pentanedione formation. Conversion of a sodium salt to sodium lactate is greatest when the salt used has a low melting point and a volatile conjugate acid; the extent of conversion depends weakly on reaction time and temperature within experimental conditions. At high temperature (∼350 °C), sodium lactate decomposes to sodium propanoate and sodium acetate, which may explain reduced 2,3-pentanedione yields at higher temperatures.

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The catalytic conversion of lactic acid over various sodium salt catalysts and support materials has been carried out to identify potential catalyst/support combinations for 2,3-pentanedione and acrylic acid production. Low surface area, pure silica is the best support for suppressing undesirable side reactions to acetaldehyde and propanoic acid, which are favored over high surface area (microporous) or surface acidic materials. The best catalysts for 2,3-pentanedione and acrylic acid formation are the sodium salts of group IV and group V oxides, with sodium arsenate giving a 2,3-pentanedione yield of 25% and combined selectivity to acrylic acid and 2,3-pentanedione of 83% at 300 °C and 0.5 MPa total pressure.

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The influence of the aromatic hydrocarbons in gasoline on the fuel distillation parameter, as well as the particle number (PN), black carbon (BC), and other regulated gaseous emissions from a passenger car (PC) and light-duty truck (LDT), was assessed by operating two vehicles fueled with U.S. Environmental Protection Agency Tier 3 certification gasoline and two gasoline test fuels over two standard drive cycles. The two gasoline test fuels represent a range of commercial motor gasoline, with one containing less naphthalenes and lower heavy fraction volatility (T80, T90, and final boiling point) than the other. Observations showed that various gasolines have minor impact on both vehicles on regulated gaseous emissions and fuel consumption. Particulate emissions from both vehicles showed similar trends with fuel type, with lower naphthalene containing gasoline produced lower PN and BC emissions. In addition, the effect of fuel on particle emissions varied with vehicle type, drive cycle, and power to weight ratio. Results also showed that lowering the naphthalenes in gasoline produces smaller sized particles. The real-time particle emission time series from both vehicles suggested that the composition and volatility of the gasoline fuels are sensitive parameters in influencing particulate matter emissions. These results could support one possible explanation of the large variations in emission factors reported in the literature when using different gasolines in the same type of vehicle and driving conditions.