Upgrading of diesel fuels and mixtures of hydrocarbons by means of oxygen low pressure plasmas: a comparative study☆

Oxidative Functionalization of Long-Chain Liquid Alkanes by Pulsed Plasma Discharges at Atmospheric Pressure

“…Early reports on plasma oxidation of liquid hydrocarbons applied plasma discharges to various hydrocarbon species including olefins and aromatic compounds. − However, the partial oxidation of saturated hydrocarbons is of high interest due to the non-reactive nature of secondary C–H bonds. For saturated hydrocarbons in particular, plasma oxidation has been studied mostly for small molecules, such as the catalytic methane oxidation to methanol and other valuable chemicals. , Among early studies on plasma oxidation of larger saturated alkanes, Suhr et al applied a low pressure oxygen plasma in contact with 2,2,4-trimethylpentane and found 2,4,4-trimethylpentan-2-ol, 2,4,4-trimethylpentan-3-ol, and 2,2,4-trimethylpentan-3-one as main products.…”

“…The functionalization of long-chain saturated hydrocarbons is of high interest due to their use in multiple applications. Long-chain alcohols and ketones are valuable precursors in the production of surfactants and lubricants, especially in biomass-derived chemicals. − Oxygenated long-chain hydrocarbons also add value to diesel fuels by improving their efficiency and decreasing particulate emissions. ,, This paper investigated the oxidative functionalization of a large, saturated hydrocarbon, n -octadecane, into oxygenated products (alcohols, ketones, and aldehydes) by oxygen radical attack. Reaction products were determined by gas chromatography, mass spectrometry (GC–MS), nuclear magnetic resonance (NMR) spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy.…”

“…For saturated hydrocarbons in particular, plasma oxidation has been studied mostly for small molecules, such as the catalytic methane oxidation to methanol and other valuable chemicals. , Among early studies on plasma oxidation of larger saturated alkanes, Suhr et al applied a low pressure oxygen plasma in contact with 2,2,4-trimethylpentane and found 2,4,4-trimethylpentan-2-ol, 2,4,4-trimethylpentan-3-ol, and 2,2,4-trimethylpentan-3-one as main products. Patiño and co-workers extensively investigated the application of a low-pressure oxygen plasma on the surface of liquid saturated hydrocarbons cooled down close to the freezing point. ,− Results indicated that oxidation of n -hexane, n -heptane, n -dodecane, and n -tridecane occurred only on secondary carbons, yielding almost exclusively secondary alcohols and ketones. Oxidation of branched molecules like 4-methyl-heptane and squalene confirmed this observation, as only secondary and tertiary alcohols were formed along with ketones.…”

Biphasic Plasma Microreactor for Oxyfunctionalization of Liquid Hydrocarbons

“…This can be attributed in part to visible plasma instabilities in the microreactor in single compound experiments due to the possible extensive evaporation of C 10 , which leads to a decreased plasma intensity as these gaseous C 10 molecules compete for electron dissociation. 34 The presence of other compounds may promote evaporation of more volatile alkanes due to faster diffusion to the interface (this is probably not as important given the weak dependence of diffusivity on molecular weight and the small volume of liquids) and lower cooling induced by evaporation of smaller amounts of lighter hydrocarbons when mixtures are used while maintaining plasma stability and homogeneity. The preferential reactivity of smaller alkanes at different gas-to-liquid flow ratios is reaffirmed in a binary mixture of n-C 12 and n-C 16 (Figure S11a−c).…”

“…This is due to high gas-phase alkane concentrations that cause plasma instabilities and decreased intensities due to competition for electron dissociation. 34 Overall, higher vapor pressures (due to the hydrocarbon size or higher temperatures) can enhance evaporation and mass transfer at the plasma-liquid interface, inducing higher conversions. However, too extreme vapor pressures cause plasma instabilities, therefore impeding higher conversions.…”